1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2017 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2017 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1043 @subsection Choosing Modes
1045 You can run @value{GDBN} in various alternative modes---for example, in
1046 batch mode or quiet mode.
1054 Do not execute commands found in any initialization file.
1055 There are three init files, loaded in the following order:
1058 @item @file{system.gdbinit}
1059 This is the system-wide init file.
1060 Its location is specified with the @code{--with-system-gdbinit}
1061 configure option (@pxref{System-wide configuration}).
1062 It is loaded first when @value{GDBN} starts, before command line options
1063 have been processed.
1064 @item @file{~/.gdbinit}
1065 This is the init file in your home directory.
1066 It is loaded next, after @file{system.gdbinit}, and before
1067 command options have been processed.
1068 @item @file{./.gdbinit}
1069 This is the init file in the current directory.
1070 It is loaded last, after command line options other than @code{-x} and
1071 @code{-ex} have been processed. Command line options @code{-x} and
1072 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1075 For further documentation on startup processing, @xref{Startup}.
1076 For documentation on how to write command files,
1077 @xref{Command Files,,Command Files}.
1082 Do not execute commands found in @file{~/.gdbinit}, the init file
1083 in your home directory.
1089 @cindex @code{--quiet}
1090 @cindex @code{--silent}
1092 ``Quiet''. Do not print the introductory and copyright messages. These
1093 messages are also suppressed in batch mode.
1096 @cindex @code{--batch}
1097 Run in batch mode. Exit with status @code{0} after processing all the
1098 command files specified with @samp{-x} (and all commands from
1099 initialization files, if not inhibited with @samp{-n}). Exit with
1100 nonzero status if an error occurs in executing the @value{GDBN} commands
1101 in the command files. Batch mode also disables pagination, sets unlimited
1102 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1103 off} were in effect (@pxref{Messages/Warnings}).
1105 Batch mode may be useful for running @value{GDBN} as a filter, for
1106 example to download and run a program on another computer; in order to
1107 make this more useful, the message
1110 Program exited normally.
1114 (which is ordinarily issued whenever a program running under
1115 @value{GDBN} control terminates) is not issued when running in batch
1119 @cindex @code{--batch-silent}
1120 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1121 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1122 unaffected). This is much quieter than @samp{-silent} and would be useless
1123 for an interactive session.
1125 This is particularly useful when using targets that give @samp{Loading section}
1126 messages, for example.
1128 Note that targets that give their output via @value{GDBN}, as opposed to
1129 writing directly to @code{stdout}, will also be made silent.
1131 @item -return-child-result
1132 @cindex @code{--return-child-result}
1133 The return code from @value{GDBN} will be the return code from the child
1134 process (the process being debugged), with the following exceptions:
1138 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1139 internal error. In this case the exit code is the same as it would have been
1140 without @samp{-return-child-result}.
1142 The user quits with an explicit value. E.g., @samp{quit 1}.
1144 The child process never runs, or is not allowed to terminate, in which case
1145 the exit code will be -1.
1148 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1149 when @value{GDBN} is being used as a remote program loader or simulator
1154 @cindex @code{--nowindows}
1156 ``No windows''. If @value{GDBN} comes with a graphical user interface
1157 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1158 interface. If no GUI is available, this option has no effect.
1162 @cindex @code{--windows}
1164 If @value{GDBN} includes a GUI, then this option requires it to be
1167 @item -cd @var{directory}
1169 Run @value{GDBN} using @var{directory} as its working directory,
1170 instead of the current directory.
1172 @item -data-directory @var{directory}
1173 @itemx -D @var{directory}
1174 @cindex @code{--data-directory}
1176 Run @value{GDBN} using @var{directory} as its data directory.
1177 The data directory is where @value{GDBN} searches for its
1178 auxiliary files. @xref{Data Files}.
1182 @cindex @code{--fullname}
1184 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1185 subprocess. It tells @value{GDBN} to output the full file name and line
1186 number in a standard, recognizable fashion each time a stack frame is
1187 displayed (which includes each time your program stops). This
1188 recognizable format looks like two @samp{\032} characters, followed by
1189 the file name, line number and character position separated by colons,
1190 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1191 @samp{\032} characters as a signal to display the source code for the
1194 @item -annotate @var{level}
1195 @cindex @code{--annotate}
1196 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1197 effect is identical to using @samp{set annotate @var{level}}
1198 (@pxref{Annotations}). The annotation @var{level} controls how much
1199 information @value{GDBN} prints together with its prompt, values of
1200 expressions, source lines, and other types of output. Level 0 is the
1201 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1202 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1203 that control @value{GDBN}, and level 2 has been deprecated.
1205 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1209 @cindex @code{--args}
1210 Change interpretation of command line so that arguments following the
1211 executable file are passed as command line arguments to the inferior.
1212 This option stops option processing.
1214 @item -baud @var{bps}
1216 @cindex @code{--baud}
1218 Set the line speed (baud rate or bits per second) of any serial
1219 interface used by @value{GDBN} for remote debugging.
1221 @item -l @var{timeout}
1223 Set the timeout (in seconds) of any communication used by @value{GDBN}
1224 for remote debugging.
1226 @item -tty @var{device}
1227 @itemx -t @var{device}
1228 @cindex @code{--tty}
1230 Run using @var{device} for your program's standard input and output.
1231 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1233 @c resolve the situation of these eventually
1235 @cindex @code{--tui}
1236 Activate the @dfn{Text User Interface} when starting. The Text User
1237 Interface manages several text windows on the terminal, showing
1238 source, assembly, registers and @value{GDBN} command outputs
1239 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1240 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1241 Using @value{GDBN} under @sc{gnu} Emacs}).
1243 @item -interpreter @var{interp}
1244 @cindex @code{--interpreter}
1245 Use the interpreter @var{interp} for interface with the controlling
1246 program or device. This option is meant to be set by programs which
1247 communicate with @value{GDBN} using it as a back end.
1248 @xref{Interpreters, , Command Interpreters}.
1250 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1251 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1252 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1253 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1254 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1255 @sc{gdb/mi} interfaces are no longer supported.
1258 @cindex @code{--write}
1259 Open the executable and core files for both reading and writing. This
1260 is equivalent to the @samp{set write on} command inside @value{GDBN}
1264 @cindex @code{--statistics}
1265 This option causes @value{GDBN} to print statistics about time and
1266 memory usage after it completes each command and returns to the prompt.
1269 @cindex @code{--version}
1270 This option causes @value{GDBN} to print its version number and
1271 no-warranty blurb, and exit.
1273 @item -configuration
1274 @cindex @code{--configuration}
1275 This option causes @value{GDBN} to print details about its build-time
1276 configuration parameters, and then exit. These details can be
1277 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1282 @subsection What @value{GDBN} Does During Startup
1283 @cindex @value{GDBN} startup
1285 Here's the description of what @value{GDBN} does during session startup:
1289 Sets up the command interpreter as specified by the command line
1290 (@pxref{Mode Options, interpreter}).
1294 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1295 used when building @value{GDBN}; @pxref{System-wide configuration,
1296 ,System-wide configuration and settings}) and executes all the commands in
1299 @anchor{Home Directory Init File}
1301 Reads the init file (if any) in your home directory@footnote{On
1302 DOS/Windows systems, the home directory is the one pointed to by the
1303 @code{HOME} environment variable.} and executes all the commands in
1306 @anchor{Option -init-eval-command}
1308 Executes commands and command files specified by the @samp{-iex} and
1309 @samp{-ix} options in their specified order. Usually you should use the
1310 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1311 settings before @value{GDBN} init files get executed and before inferior
1315 Processes command line options and operands.
1317 @anchor{Init File in the Current Directory during Startup}
1319 Reads and executes the commands from init file (if any) in the current
1320 working directory as long as @samp{set auto-load local-gdbinit} is set to
1321 @samp{on} (@pxref{Init File in the Current Directory}).
1322 This is only done if the current directory is
1323 different from your home directory. Thus, you can have more than one
1324 init file, one generic in your home directory, and another, specific
1325 to the program you are debugging, in the directory where you invoke
1329 If the command line specified a program to debug, or a process to
1330 attach to, or a core file, @value{GDBN} loads any auto-loaded
1331 scripts provided for the program or for its loaded shared libraries.
1332 @xref{Auto-loading}.
1334 If you wish to disable the auto-loading during startup,
1335 you must do something like the following:
1338 $ gdb -iex "set auto-load python-scripts off" myprogram
1341 Option @samp{-ex} does not work because the auto-loading is then turned
1345 Executes commands and command files specified by the @samp{-ex} and
1346 @samp{-x} options in their specified order. @xref{Command Files}, for
1347 more details about @value{GDBN} command files.
1350 Reads the command history recorded in the @dfn{history file}.
1351 @xref{Command History}, for more details about the command history and the
1352 files where @value{GDBN} records it.
1355 Init files use the same syntax as @dfn{command files} (@pxref{Command
1356 Files}) and are processed by @value{GDBN} in the same way. The init
1357 file in your home directory can set options (such as @samp{set
1358 complaints}) that affect subsequent processing of command line options
1359 and operands. Init files are not executed if you use the @samp{-nx}
1360 option (@pxref{Mode Options, ,Choosing Modes}).
1362 To display the list of init files loaded by gdb at startup, you
1363 can use @kbd{gdb --help}.
1365 @cindex init file name
1366 @cindex @file{.gdbinit}
1367 @cindex @file{gdb.ini}
1368 The @value{GDBN} init files are normally called @file{.gdbinit}.
1369 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1370 the limitations of file names imposed by DOS filesystems. The Windows
1371 port of @value{GDBN} uses the standard name, but if it finds a
1372 @file{gdb.ini} file in your home directory, it warns you about that
1373 and suggests to rename the file to the standard name.
1377 @section Quitting @value{GDBN}
1378 @cindex exiting @value{GDBN}
1379 @cindex leaving @value{GDBN}
1382 @kindex quit @r{[}@var{expression}@r{]}
1383 @kindex q @r{(@code{quit})}
1384 @item quit @r{[}@var{expression}@r{]}
1386 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1387 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1388 do not supply @var{expression}, @value{GDBN} will terminate normally;
1389 otherwise it will terminate using the result of @var{expression} as the
1394 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1395 terminates the action of any @value{GDBN} command that is in progress and
1396 returns to @value{GDBN} command level. It is safe to type the interrupt
1397 character at any time because @value{GDBN} does not allow it to take effect
1398 until a time when it is safe.
1400 If you have been using @value{GDBN} to control an attached process or
1401 device, you can release it with the @code{detach} command
1402 (@pxref{Attach, ,Debugging an Already-running Process}).
1404 @node Shell Commands
1405 @section Shell Commands
1407 If you need to execute occasional shell commands during your
1408 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1409 just use the @code{shell} command.
1414 @cindex shell escape
1415 @item shell @var{command-string}
1416 @itemx !@var{command-string}
1417 Invoke a standard shell to execute @var{command-string}.
1418 Note that no space is needed between @code{!} and @var{command-string}.
1419 If it exists, the environment variable @code{SHELL} determines which
1420 shell to run. Otherwise @value{GDBN} uses the default shell
1421 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1424 The utility @code{make} is often needed in development environments.
1425 You do not have to use the @code{shell} command for this purpose in
1430 @cindex calling make
1431 @item make @var{make-args}
1432 Execute the @code{make} program with the specified
1433 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1436 @node Logging Output
1437 @section Logging Output
1438 @cindex logging @value{GDBN} output
1439 @cindex save @value{GDBN} output to a file
1441 You may want to save the output of @value{GDBN} commands to a file.
1442 There are several commands to control @value{GDBN}'s logging.
1446 @item set logging on
1448 @item set logging off
1450 @cindex logging file name
1451 @item set logging file @var{file}
1452 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1453 @item set logging overwrite [on|off]
1454 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1455 you want @code{set logging on} to overwrite the logfile instead.
1456 @item set logging redirect [on|off]
1457 By default, @value{GDBN} output will go to both the terminal and the logfile.
1458 Set @code{redirect} if you want output to go only to the log file.
1459 @kindex show logging
1461 Show the current values of the logging settings.
1465 @chapter @value{GDBN} Commands
1467 You can abbreviate a @value{GDBN} command to the first few letters of the command
1468 name, if that abbreviation is unambiguous; and you can repeat certain
1469 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1470 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1471 show you the alternatives available, if there is more than one possibility).
1474 * Command Syntax:: How to give commands to @value{GDBN}
1475 * Completion:: Command completion
1476 * Help:: How to ask @value{GDBN} for help
1479 @node Command Syntax
1480 @section Command Syntax
1482 A @value{GDBN} command is a single line of input. There is no limit on
1483 how long it can be. It starts with a command name, which is followed by
1484 arguments whose meaning depends on the command name. For example, the
1485 command @code{step} accepts an argument which is the number of times to
1486 step, as in @samp{step 5}. You can also use the @code{step} command
1487 with no arguments. Some commands do not allow any arguments.
1489 @cindex abbreviation
1490 @value{GDBN} command names may always be truncated if that abbreviation is
1491 unambiguous. Other possible command abbreviations are listed in the
1492 documentation for individual commands. In some cases, even ambiguous
1493 abbreviations are allowed; for example, @code{s} is specially defined as
1494 equivalent to @code{step} even though there are other commands whose
1495 names start with @code{s}. You can test abbreviations by using them as
1496 arguments to the @code{help} command.
1498 @cindex repeating commands
1499 @kindex RET @r{(repeat last command)}
1500 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1501 repeat the previous command. Certain commands (for example, @code{run})
1502 will not repeat this way; these are commands whose unintentional
1503 repetition might cause trouble and which you are unlikely to want to
1504 repeat. User-defined commands can disable this feature; see
1505 @ref{Define, dont-repeat}.
1507 The @code{list} and @code{x} commands, when you repeat them with
1508 @key{RET}, construct new arguments rather than repeating
1509 exactly as typed. This permits easy scanning of source or memory.
1511 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1512 output, in a way similar to the common utility @code{more}
1513 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1514 @key{RET} too many in this situation, @value{GDBN} disables command
1515 repetition after any command that generates this sort of display.
1517 @kindex # @r{(a comment)}
1519 Any text from a @kbd{#} to the end of the line is a comment; it does
1520 nothing. This is useful mainly in command files (@pxref{Command
1521 Files,,Command Files}).
1523 @cindex repeating command sequences
1524 @kindex Ctrl-o @r{(operate-and-get-next)}
1525 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1526 commands. This command accepts the current line, like @key{RET}, and
1527 then fetches the next line relative to the current line from the history
1531 @section Command Completion
1534 @cindex word completion
1535 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1536 only one possibility; it can also show you what the valid possibilities
1537 are for the next word in a command, at any time. This works for @value{GDBN}
1538 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1540 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1541 of a word. If there is only one possibility, @value{GDBN} fills in the
1542 word, and waits for you to finish the command (or press @key{RET} to
1543 enter it). For example, if you type
1545 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1546 @c complete accuracy in these examples; space introduced for clarity.
1547 @c If texinfo enhancements make it unnecessary, it would be nice to
1548 @c replace " @key" by "@key" in the following...
1550 (@value{GDBP}) info bre @key{TAB}
1554 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1555 the only @code{info} subcommand beginning with @samp{bre}:
1558 (@value{GDBP}) info breakpoints
1562 You can either press @key{RET} at this point, to run the @code{info
1563 breakpoints} command, or backspace and enter something else, if
1564 @samp{breakpoints} does not look like the command you expected. (If you
1565 were sure you wanted @code{info breakpoints} in the first place, you
1566 might as well just type @key{RET} immediately after @samp{info bre},
1567 to exploit command abbreviations rather than command completion).
1569 If there is more than one possibility for the next word when you press
1570 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1571 characters and try again, or just press @key{TAB} a second time;
1572 @value{GDBN} displays all the possible completions for that word. For
1573 example, you might want to set a breakpoint on a subroutine whose name
1574 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1575 just sounds the bell. Typing @key{TAB} again displays all the
1576 function names in your program that begin with those characters, for
1580 (@value{GDBP}) b make_ @key{TAB}
1581 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1582 make_a_section_from_file make_environ
1583 make_abs_section make_function_type
1584 make_blockvector make_pointer_type
1585 make_cleanup make_reference_type
1586 make_command make_symbol_completion_list
1587 (@value{GDBP}) b make_
1591 After displaying the available possibilities, @value{GDBN} copies your
1592 partial input (@samp{b make_} in the example) so you can finish the
1595 If you just want to see the list of alternatives in the first place, you
1596 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1597 means @kbd{@key{META} ?}. You can type this either by holding down a
1598 key designated as the @key{META} shift on your keyboard (if there is
1599 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1601 If the number of possible completions is large, @value{GDBN} will
1602 print as much of the list as it has collected, as well as a message
1603 indicating that the list may be truncated.
1606 (@value{GDBP}) b m@key{TAB}@key{TAB}
1608 <... the rest of the possible completions ...>
1609 *** List may be truncated, max-completions reached. ***
1614 This behavior can be controlled with the following commands:
1617 @kindex set max-completions
1618 @item set max-completions @var{limit}
1619 @itemx set max-completions unlimited
1620 Set the maximum number of completion candidates. @value{GDBN} will
1621 stop looking for more completions once it collects this many candidates.
1622 This is useful when completing on things like function names as collecting
1623 all the possible candidates can be time consuming.
1624 The default value is 200. A value of zero disables tab-completion.
1625 Note that setting either no limit or a very large limit can make
1627 @kindex show max-completions
1628 @item show max-completions
1629 Show the maximum number of candidates that @value{GDBN} will collect and show
1633 @cindex quotes in commands
1634 @cindex completion of quoted strings
1635 Sometimes the string you need, while logically a ``word'', may contain
1636 parentheses or other characters that @value{GDBN} normally excludes from
1637 its notion of a word. To permit word completion to work in this
1638 situation, you may enclose words in @code{'} (single quote marks) in
1639 @value{GDBN} commands.
1641 The most likely situation where you might need this is in typing the
1642 name of a C@t{++} function. This is because C@t{++} allows function
1643 overloading (multiple definitions of the same function, distinguished
1644 by argument type). For example, when you want to set a breakpoint you
1645 may need to distinguish whether you mean the version of @code{name}
1646 that takes an @code{int} parameter, @code{name(int)}, or the version
1647 that takes a @code{float} parameter, @code{name(float)}. To use the
1648 word-completion facilities in this situation, type a single quote
1649 @code{'} at the beginning of the function name. This alerts
1650 @value{GDBN} that it may need to consider more information than usual
1651 when you press @key{TAB} or @kbd{M-?} to request word completion:
1654 (@value{GDBP}) b 'bubble( @kbd{M-?}
1655 bubble(double,double) bubble(int,int)
1656 (@value{GDBP}) b 'bubble(
1659 In some cases, @value{GDBN} can tell that completing a name requires using
1660 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1661 completing as much as it can) if you do not type the quote in the first
1665 (@value{GDBP}) b bub @key{TAB}
1666 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1667 (@value{GDBP}) b 'bubble(
1671 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1672 you have not yet started typing the argument list when you ask for
1673 completion on an overloaded symbol.
1675 For more information about overloaded functions, see @ref{C Plus Plus
1676 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1677 overload-resolution off} to disable overload resolution;
1678 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1680 @cindex completion of structure field names
1681 @cindex structure field name completion
1682 @cindex completion of union field names
1683 @cindex union field name completion
1684 When completing in an expression which looks up a field in a
1685 structure, @value{GDBN} also tries@footnote{The completer can be
1686 confused by certain kinds of invalid expressions. Also, it only
1687 examines the static type of the expression, not the dynamic type.} to
1688 limit completions to the field names available in the type of the
1692 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1693 magic to_fputs to_rewind
1694 to_data to_isatty to_write
1695 to_delete to_put to_write_async_safe
1700 This is because the @code{gdb_stdout} is a variable of the type
1701 @code{struct ui_file} that is defined in @value{GDBN} sources as
1708 ui_file_flush_ftype *to_flush;
1709 ui_file_write_ftype *to_write;
1710 ui_file_write_async_safe_ftype *to_write_async_safe;
1711 ui_file_fputs_ftype *to_fputs;
1712 ui_file_read_ftype *to_read;
1713 ui_file_delete_ftype *to_delete;
1714 ui_file_isatty_ftype *to_isatty;
1715 ui_file_rewind_ftype *to_rewind;
1716 ui_file_put_ftype *to_put;
1723 @section Getting Help
1724 @cindex online documentation
1727 You can always ask @value{GDBN} itself for information on its commands,
1728 using the command @code{help}.
1731 @kindex h @r{(@code{help})}
1734 You can use @code{help} (abbreviated @code{h}) with no arguments to
1735 display a short list of named classes of commands:
1739 List of classes of commands:
1741 aliases -- Aliases of other commands
1742 breakpoints -- Making program stop at certain points
1743 data -- Examining data
1744 files -- Specifying and examining files
1745 internals -- Maintenance commands
1746 obscure -- Obscure features
1747 running -- Running the program
1748 stack -- Examining the stack
1749 status -- Status inquiries
1750 support -- Support facilities
1751 tracepoints -- Tracing of program execution without
1752 stopping the program
1753 user-defined -- User-defined commands
1755 Type "help" followed by a class name for a list of
1756 commands in that class.
1757 Type "help" followed by command name for full
1759 Command name abbreviations are allowed if unambiguous.
1762 @c the above line break eliminates huge line overfull...
1764 @item help @var{class}
1765 Using one of the general help classes as an argument, you can get a
1766 list of the individual commands in that class. For example, here is the
1767 help display for the class @code{status}:
1770 (@value{GDBP}) help status
1775 @c Line break in "show" line falsifies real output, but needed
1776 @c to fit in smallbook page size.
1777 info -- Generic command for showing things
1778 about the program being debugged
1779 show -- Generic command for showing things
1782 Type "help" followed by command name for full
1784 Command name abbreviations are allowed if unambiguous.
1788 @item help @var{command}
1789 With a command name as @code{help} argument, @value{GDBN} displays a
1790 short paragraph on how to use that command.
1793 @item apropos @var{args}
1794 The @code{apropos} command searches through all of the @value{GDBN}
1795 commands, and their documentation, for the regular expression specified in
1796 @var{args}. It prints out all matches found. For example:
1807 alias -- Define a new command that is an alias of an existing command
1808 aliases -- Aliases of other commands
1809 d -- Delete some breakpoints or auto-display expressions
1810 del -- Delete some breakpoints or auto-display expressions
1811 delete -- Delete some breakpoints or auto-display expressions
1816 @item complete @var{args}
1817 The @code{complete @var{args}} command lists all the possible completions
1818 for the beginning of a command. Use @var{args} to specify the beginning of the
1819 command you want completed. For example:
1825 @noindent results in:
1836 @noindent This is intended for use by @sc{gnu} Emacs.
1839 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1840 and @code{show} to inquire about the state of your program, or the state
1841 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1842 manual introduces each of them in the appropriate context. The listings
1843 under @code{info} and under @code{show} in the Command, Variable, and
1844 Function Index point to all the sub-commands. @xref{Command and Variable
1850 @kindex i @r{(@code{info})}
1852 This command (abbreviated @code{i}) is for describing the state of your
1853 program. For example, you can show the arguments passed to a function
1854 with @code{info args}, list the registers currently in use with @code{info
1855 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1856 You can get a complete list of the @code{info} sub-commands with
1857 @w{@code{help info}}.
1861 You can assign the result of an expression to an environment variable with
1862 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1863 @code{set prompt $}.
1867 In contrast to @code{info}, @code{show} is for describing the state of
1868 @value{GDBN} itself.
1869 You can change most of the things you can @code{show}, by using the
1870 related command @code{set}; for example, you can control what number
1871 system is used for displays with @code{set radix}, or simply inquire
1872 which is currently in use with @code{show radix}.
1875 To display all the settable parameters and their current
1876 values, you can use @code{show} with no arguments; you may also use
1877 @code{info set}. Both commands produce the same display.
1878 @c FIXME: "info set" violates the rule that "info" is for state of
1879 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1880 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1884 Here are several miscellaneous @code{show} subcommands, all of which are
1885 exceptional in lacking corresponding @code{set} commands:
1888 @kindex show version
1889 @cindex @value{GDBN} version number
1891 Show what version of @value{GDBN} is running. You should include this
1892 information in @value{GDBN} bug-reports. If multiple versions of
1893 @value{GDBN} are in use at your site, you may need to determine which
1894 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1895 commands are introduced, and old ones may wither away. Also, many
1896 system vendors ship variant versions of @value{GDBN}, and there are
1897 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1898 The version number is the same as the one announced when you start
1901 @kindex show copying
1902 @kindex info copying
1903 @cindex display @value{GDBN} copyright
1906 Display information about permission for copying @value{GDBN}.
1908 @kindex show warranty
1909 @kindex info warranty
1911 @itemx info warranty
1912 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1913 if your version of @value{GDBN} comes with one.
1915 @kindex show configuration
1916 @item show configuration
1917 Display detailed information about the way @value{GDBN} was configured
1918 when it was built. This displays the optional arguments passed to the
1919 @file{configure} script and also configuration parameters detected
1920 automatically by @command{configure}. When reporting a @value{GDBN}
1921 bug (@pxref{GDB Bugs}), it is important to include this information in
1927 @chapter Running Programs Under @value{GDBN}
1929 When you run a program under @value{GDBN}, you must first generate
1930 debugging information when you compile it.
1932 You may start @value{GDBN} with its arguments, if any, in an environment
1933 of your choice. If you are doing native debugging, you may redirect
1934 your program's input and output, debug an already running process, or
1935 kill a child process.
1938 * Compilation:: Compiling for debugging
1939 * Starting:: Starting your program
1940 * Arguments:: Your program's arguments
1941 * Environment:: Your program's environment
1943 * Working Directory:: Your program's working directory
1944 * Input/Output:: Your program's input and output
1945 * Attach:: Debugging an already-running process
1946 * Kill Process:: Killing the child process
1948 * Inferiors and Programs:: Debugging multiple inferiors and programs
1949 * Threads:: Debugging programs with multiple threads
1950 * Forks:: Debugging forks
1951 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1955 @section Compiling for Debugging
1957 In order to debug a program effectively, you need to generate
1958 debugging information when you compile it. This debugging information
1959 is stored in the object file; it describes the data type of each
1960 variable or function and the correspondence between source line numbers
1961 and addresses in the executable code.
1963 To request debugging information, specify the @samp{-g} option when you run
1966 Programs that are to be shipped to your customers are compiled with
1967 optimizations, using the @samp{-O} compiler option. However, some
1968 compilers are unable to handle the @samp{-g} and @samp{-O} options
1969 together. Using those compilers, you cannot generate optimized
1970 executables containing debugging information.
1972 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1973 without @samp{-O}, making it possible to debug optimized code. We
1974 recommend that you @emph{always} use @samp{-g} whenever you compile a
1975 program. You may think your program is correct, but there is no sense
1976 in pushing your luck. For more information, see @ref{Optimized Code}.
1978 Older versions of the @sc{gnu} C compiler permitted a variant option
1979 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1980 format; if your @sc{gnu} C compiler has this option, do not use it.
1982 @value{GDBN} knows about preprocessor macros and can show you their
1983 expansion (@pxref{Macros}). Most compilers do not include information
1984 about preprocessor macros in the debugging information if you specify
1985 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1986 the @sc{gnu} C compiler, provides macro information if you are using
1987 the DWARF debugging format, and specify the option @option{-g3}.
1989 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1990 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1991 information on @value{NGCC} options affecting debug information.
1993 You will have the best debugging experience if you use the latest
1994 version of the DWARF debugging format that your compiler supports.
1995 DWARF is currently the most expressive and best supported debugging
1996 format in @value{GDBN}.
2000 @section Starting your Program
2006 @kindex r @r{(@code{run})}
2009 Use the @code{run} command to start your program under @value{GDBN}.
2010 You must first specify the program name with an argument to
2011 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2012 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2013 command (@pxref{Files, ,Commands to Specify Files}).
2017 If you are running your program in an execution environment that
2018 supports processes, @code{run} creates an inferior process and makes
2019 that process run your program. In some environments without processes,
2020 @code{run} jumps to the start of your program. Other targets,
2021 like @samp{remote}, are always running. If you get an error
2022 message like this one:
2025 The "remote" target does not support "run".
2026 Try "help target" or "continue".
2030 then use @code{continue} to run your program. You may need @code{load}
2031 first (@pxref{load}).
2033 The execution of a program is affected by certain information it
2034 receives from its superior. @value{GDBN} provides ways to specify this
2035 information, which you must do @emph{before} starting your program. (You
2036 can change it after starting your program, but such changes only affect
2037 your program the next time you start it.) This information may be
2038 divided into four categories:
2041 @item The @emph{arguments.}
2042 Specify the arguments to give your program as the arguments of the
2043 @code{run} command. If a shell is available on your target, the shell
2044 is used to pass the arguments, so that you may use normal conventions
2045 (such as wildcard expansion or variable substitution) in describing
2047 In Unix systems, you can control which shell is used with the
2048 @code{SHELL} environment variable. If you do not define @code{SHELL},
2049 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2050 use of any shell with the @code{set startup-with-shell} command (see
2053 @item The @emph{environment.}
2054 Your program normally inherits its environment from @value{GDBN}, but you can
2055 use the @value{GDBN} commands @code{set environment} and @code{unset
2056 environment} to change parts of the environment that affect
2057 your program. @xref{Environment, ,Your Program's Environment}.
2059 @item The @emph{working directory.}
2060 Your program inherits its working directory from @value{GDBN}. You can set
2061 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2062 @xref{Working Directory, ,Your Program's Working Directory}.
2064 @item The @emph{standard input and output.}
2065 Your program normally uses the same device for standard input and
2066 standard output as @value{GDBN} is using. You can redirect input and output
2067 in the @code{run} command line, or you can use the @code{tty} command to
2068 set a different device for your program.
2069 @xref{Input/Output, ,Your Program's Input and Output}.
2072 @emph{Warning:} While input and output redirection work, you cannot use
2073 pipes to pass the output of the program you are debugging to another
2074 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2078 When you issue the @code{run} command, your program begins to execute
2079 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2080 of how to arrange for your program to stop. Once your program has
2081 stopped, you may call functions in your program, using the @code{print}
2082 or @code{call} commands. @xref{Data, ,Examining Data}.
2084 If the modification time of your symbol file has changed since the last
2085 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2086 table, and reads it again. When it does this, @value{GDBN} tries to retain
2087 your current breakpoints.
2092 @cindex run to main procedure
2093 The name of the main procedure can vary from language to language.
2094 With C or C@t{++}, the main procedure name is always @code{main}, but
2095 other languages such as Ada do not require a specific name for their
2096 main procedure. The debugger provides a convenient way to start the
2097 execution of the program and to stop at the beginning of the main
2098 procedure, depending on the language used.
2100 The @samp{start} command does the equivalent of setting a temporary
2101 breakpoint at the beginning of the main procedure and then invoking
2102 the @samp{run} command.
2104 @cindex elaboration phase
2105 Some programs contain an @dfn{elaboration} phase where some startup code is
2106 executed before the main procedure is called. This depends on the
2107 languages used to write your program. In C@t{++}, for instance,
2108 constructors for static and global objects are executed before
2109 @code{main} is called. It is therefore possible that the debugger stops
2110 before reaching the main procedure. However, the temporary breakpoint
2111 will remain to halt execution.
2113 Specify the arguments to give to your program as arguments to the
2114 @samp{start} command. These arguments will be given verbatim to the
2115 underlying @samp{run} command. Note that the same arguments will be
2116 reused if no argument is provided during subsequent calls to
2117 @samp{start} or @samp{run}.
2119 It is sometimes necessary to debug the program during elaboration. In
2120 these cases, using the @code{start} command would stop the execution of
2121 your program too late, as the program would have already completed the
2122 elaboration phase. Under these circumstances, insert breakpoints in your
2123 elaboration code before running your program.
2125 @anchor{set exec-wrapper}
2126 @kindex set exec-wrapper
2127 @item set exec-wrapper @var{wrapper}
2128 @itemx show exec-wrapper
2129 @itemx unset exec-wrapper
2130 When @samp{exec-wrapper} is set, the specified wrapper is used to
2131 launch programs for debugging. @value{GDBN} starts your program
2132 with a shell command of the form @kbd{exec @var{wrapper}
2133 @var{program}}. Quoting is added to @var{program} and its
2134 arguments, but not to @var{wrapper}, so you should add quotes if
2135 appropriate for your shell. The wrapper runs until it executes
2136 your program, and then @value{GDBN} takes control.
2138 You can use any program that eventually calls @code{execve} with
2139 its arguments as a wrapper. Several standard Unix utilities do
2140 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2141 with @code{exec "$@@"} will also work.
2143 For example, you can use @code{env} to pass an environment variable to
2144 the debugged program, without setting the variable in your shell's
2148 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2152 This command is available when debugging locally on most targets, excluding
2153 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2155 @kindex set startup-with-shell
2156 @anchor{set startup-with-shell}
2157 @item set startup-with-shell
2158 @itemx set startup-with-shell on
2159 @itemx set startup-with-shell off
2160 @itemx show startup-with-shell
2161 On Unix systems, by default, if a shell is available on your target,
2162 @value{GDBN}) uses it to start your program. Arguments of the
2163 @code{run} command are passed to the shell, which does variable
2164 substitution, expands wildcard characters and performs redirection of
2165 I/O. In some circumstances, it may be useful to disable such use of a
2166 shell, for example, when debugging the shell itself or diagnosing
2167 startup failures such as:
2171 Starting program: ./a.out
2172 During startup program terminated with signal SIGSEGV, Segmentation fault.
2176 which indicates the shell or the wrapper specified with
2177 @samp{exec-wrapper} crashed, not your program. Most often, this is
2178 caused by something odd in your shell's non-interactive mode
2179 initialization file---such as @file{.cshrc} for C-shell,
2180 $@file{.zshenv} for the Z shell, or the file specified in the
2181 @samp{BASH_ENV} environment variable for BASH.
2183 @anchor{set auto-connect-native-target}
2184 @kindex set auto-connect-native-target
2185 @item set auto-connect-native-target
2186 @itemx set auto-connect-native-target on
2187 @itemx set auto-connect-native-target off
2188 @itemx show auto-connect-native-target
2190 By default, if not connected to any target yet (e.g., with
2191 @code{target remote}), the @code{run} command starts your program as a
2192 native process under @value{GDBN}, on your local machine. If you're
2193 sure you don't want to debug programs on your local machine, you can
2194 tell @value{GDBN} to not connect to the native target automatically
2195 with the @code{set auto-connect-native-target off} command.
2197 If @code{on}, which is the default, and if @value{GDBN} is not
2198 connected to a target already, the @code{run} command automaticaly
2199 connects to the native target, if one is available.
2201 If @code{off}, and if @value{GDBN} is not connected to a target
2202 already, the @code{run} command fails with an error:
2206 Don't know how to run. Try "help target".
2209 If @value{GDBN} is already connected to a target, @value{GDBN} always
2210 uses it with the @code{run} command.
2212 In any case, you can explicitly connect to the native target with the
2213 @code{target native} command. For example,
2216 (@value{GDBP}) set auto-connect-native-target off
2218 Don't know how to run. Try "help target".
2219 (@value{GDBP}) target native
2221 Starting program: ./a.out
2222 [Inferior 1 (process 10421) exited normally]
2225 In case you connected explicitly to the @code{native} target,
2226 @value{GDBN} remains connected even if all inferiors exit, ready for
2227 the next @code{run} command. Use the @code{disconnect} command to
2230 Examples of other commands that likewise respect the
2231 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2232 proc}, @code{info os}.
2234 @kindex set disable-randomization
2235 @item set disable-randomization
2236 @itemx set disable-randomization on
2237 This option (enabled by default in @value{GDBN}) will turn off the native
2238 randomization of the virtual address space of the started program. This option
2239 is useful for multiple debugging sessions to make the execution better
2240 reproducible and memory addresses reusable across debugging sessions.
2242 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2243 On @sc{gnu}/Linux you can get the same behavior using
2246 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2249 @item set disable-randomization off
2250 Leave the behavior of the started executable unchanged. Some bugs rear their
2251 ugly heads only when the program is loaded at certain addresses. If your bug
2252 disappears when you run the program under @value{GDBN}, that might be because
2253 @value{GDBN} by default disables the address randomization on platforms, such
2254 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2255 disable-randomization off} to try to reproduce such elusive bugs.
2257 On targets where it is available, virtual address space randomization
2258 protects the programs against certain kinds of security attacks. In these
2259 cases the attacker needs to know the exact location of a concrete executable
2260 code. Randomizing its location makes it impossible to inject jumps misusing
2261 a code at its expected addresses.
2263 Prelinking shared libraries provides a startup performance advantage but it
2264 makes addresses in these libraries predictable for privileged processes by
2265 having just unprivileged access at the target system. Reading the shared
2266 library binary gives enough information for assembling the malicious code
2267 misusing it. Still even a prelinked shared library can get loaded at a new
2268 random address just requiring the regular relocation process during the
2269 startup. Shared libraries not already prelinked are always loaded at
2270 a randomly chosen address.
2272 Position independent executables (PIE) contain position independent code
2273 similar to the shared libraries and therefore such executables get loaded at
2274 a randomly chosen address upon startup. PIE executables always load even
2275 already prelinked shared libraries at a random address. You can build such
2276 executable using @command{gcc -fPIE -pie}.
2278 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2279 (as long as the randomization is enabled).
2281 @item show disable-randomization
2282 Show the current setting of the explicit disable of the native randomization of
2283 the virtual address space of the started program.
2288 @section Your Program's Arguments
2290 @cindex arguments (to your program)
2291 The arguments to your program can be specified by the arguments of the
2293 They are passed to a shell, which expands wildcard characters and
2294 performs redirection of I/O, and thence to your program. Your
2295 @code{SHELL} environment variable (if it exists) specifies what shell
2296 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2297 the default shell (@file{/bin/sh} on Unix).
2299 On non-Unix systems, the program is usually invoked directly by
2300 @value{GDBN}, which emulates I/O redirection via the appropriate system
2301 calls, and the wildcard characters are expanded by the startup code of
2302 the program, not by the shell.
2304 @code{run} with no arguments uses the same arguments used by the previous
2305 @code{run}, or those set by the @code{set args} command.
2310 Specify the arguments to be used the next time your program is run. If
2311 @code{set args} has no arguments, @code{run} executes your program
2312 with no arguments. Once you have run your program with arguments,
2313 using @code{set args} before the next @code{run} is the only way to run
2314 it again without arguments.
2318 Show the arguments to give your program when it is started.
2322 @section Your Program's Environment
2324 @cindex environment (of your program)
2325 The @dfn{environment} consists of a set of environment variables and
2326 their values. Environment variables conventionally record such things as
2327 your user name, your home directory, your terminal type, and your search
2328 path for programs to run. Usually you set up environment variables with
2329 the shell and they are inherited by all the other programs you run. When
2330 debugging, it can be useful to try running your program with a modified
2331 environment without having to start @value{GDBN} over again.
2335 @item path @var{directory}
2336 Add @var{directory} to the front of the @code{PATH} environment variable
2337 (the search path for executables) that will be passed to your program.
2338 The value of @code{PATH} used by @value{GDBN} does not change.
2339 You may specify several directory names, separated by whitespace or by a
2340 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2341 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2342 is moved to the front, so it is searched sooner.
2344 You can use the string @samp{$cwd} to refer to whatever is the current
2345 working directory at the time @value{GDBN} searches the path. If you
2346 use @samp{.} instead, it refers to the directory where you executed the
2347 @code{path} command. @value{GDBN} replaces @samp{.} in the
2348 @var{directory} argument (with the current path) before adding
2349 @var{directory} to the search path.
2350 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2351 @c document that, since repeating it would be a no-op.
2355 Display the list of search paths for executables (the @code{PATH}
2356 environment variable).
2358 @kindex show environment
2359 @item show environment @r{[}@var{varname}@r{]}
2360 Print the value of environment variable @var{varname} to be given to
2361 your program when it starts. If you do not supply @var{varname},
2362 print the names and values of all environment variables to be given to
2363 your program. You can abbreviate @code{environment} as @code{env}.
2365 @kindex set environment
2366 @anchor{set environment}
2367 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2368 Set environment variable @var{varname} to @var{value}. The value
2369 changes for your program (and the shell @value{GDBN} uses to launch
2370 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2371 values of environment variables are just strings, and any
2372 interpretation is supplied by your program itself. The @var{value}
2373 parameter is optional; if it is eliminated, the variable is set to a
2375 @c "any string" here does not include leading, trailing
2376 @c blanks. Gnu asks: does anyone care?
2378 For example, this command:
2385 tells the debugged program, when subsequently run, that its user is named
2386 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2387 are not actually required.)
2389 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2390 which also inherits the environment set with @code{set environment}.
2391 If necessary, you can avoid that by using the @samp{env} program as a
2392 wrapper instead of using @code{set environment}. @xref{set
2393 exec-wrapper}, for an example doing just that.
2395 Environment variables that are set by the user are also transmitted to
2396 @command{gdbserver} to be used when starting the remote inferior.
2397 @pxref{QEnvironmentHexEncoded}.
2399 @kindex unset environment
2400 @anchor{unset environment}
2401 @item unset environment @var{varname}
2402 Remove variable @var{varname} from the environment to be passed to your
2403 program. This is different from @samp{set env @var{varname} =};
2404 @code{unset environment} removes the variable from the environment,
2405 rather than assigning it an empty value.
2407 Environment variables that are unset by the user are also unset on
2408 @command{gdbserver} when starting the remote inferior.
2409 @pxref{QEnvironmentUnset}.
2412 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2413 the shell indicated by your @code{SHELL} environment variable if it
2414 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2415 names a shell that runs an initialization file when started
2416 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2417 for the Z shell, or the file specified in the @samp{BASH_ENV}
2418 environment variable for BASH---any variables you set in that file
2419 affect your program. You may wish to move setting of environment
2420 variables to files that are only run when you sign on, such as
2421 @file{.login} or @file{.profile}.
2423 @node Working Directory
2424 @section Your Program's Working Directory
2426 @cindex working directory (of your program)
2427 Each time you start your program with @code{run}, it inherits its
2428 working directory from the current working directory of @value{GDBN}.
2429 The @value{GDBN} working directory is initially whatever it inherited
2430 from its parent process (typically the shell), but you can specify a new
2431 working directory in @value{GDBN} with the @code{cd} command.
2433 The @value{GDBN} working directory also serves as a default for the commands
2434 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2439 @cindex change working directory
2440 @item cd @r{[}@var{directory}@r{]}
2441 Set the @value{GDBN} working directory to @var{directory}. If not
2442 given, @var{directory} uses @file{'~'}.
2446 Print the @value{GDBN} working directory.
2449 It is generally impossible to find the current working directory of
2450 the process being debugged (since a program can change its directory
2451 during its run). If you work on a system where @value{GDBN} is
2452 configured with the @file{/proc} support, you can use the @code{info
2453 proc} command (@pxref{SVR4 Process Information}) to find out the
2454 current working directory of the debuggee.
2457 @section Your Program's Input and Output
2462 By default, the program you run under @value{GDBN} does input and output to
2463 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2464 to its own terminal modes to interact with you, but it records the terminal
2465 modes your program was using and switches back to them when you continue
2466 running your program.
2469 @kindex info terminal
2471 Displays information recorded by @value{GDBN} about the terminal modes your
2475 You can redirect your program's input and/or output using shell
2476 redirection with the @code{run} command. For example,
2483 starts your program, diverting its output to the file @file{outfile}.
2486 @cindex controlling terminal
2487 Another way to specify where your program should do input and output is
2488 with the @code{tty} command. This command accepts a file name as
2489 argument, and causes this file to be the default for future @code{run}
2490 commands. It also resets the controlling terminal for the child
2491 process, for future @code{run} commands. For example,
2498 directs that processes started with subsequent @code{run} commands
2499 default to do input and output on the terminal @file{/dev/ttyb} and have
2500 that as their controlling terminal.
2502 An explicit redirection in @code{run} overrides the @code{tty} command's
2503 effect on the input/output device, but not its effect on the controlling
2506 When you use the @code{tty} command or redirect input in the @code{run}
2507 command, only the input @emph{for your program} is affected. The input
2508 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2509 for @code{set inferior-tty}.
2511 @cindex inferior tty
2512 @cindex set inferior controlling terminal
2513 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2514 display the name of the terminal that will be used for future runs of your
2518 @item set inferior-tty [ @var{tty} ]
2519 @kindex set inferior-tty
2520 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2521 restores the default behavior, which is to use the same terminal as
2524 @item show inferior-tty
2525 @kindex show inferior-tty
2526 Show the current tty for the program being debugged.
2530 @section Debugging an Already-running Process
2535 @item attach @var{process-id}
2536 This command attaches to a running process---one that was started
2537 outside @value{GDBN}. (@code{info files} shows your active
2538 targets.) The command takes as argument a process ID. The usual way to
2539 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2540 or with the @samp{jobs -l} shell command.
2542 @code{attach} does not repeat if you press @key{RET} a second time after
2543 executing the command.
2546 To use @code{attach}, your program must be running in an environment
2547 which supports processes; for example, @code{attach} does not work for
2548 programs on bare-board targets that lack an operating system. You must
2549 also have permission to send the process a signal.
2551 When you use @code{attach}, the debugger finds the program running in
2552 the process first by looking in the current working directory, then (if
2553 the program is not found) by using the source file search path
2554 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2555 the @code{file} command to load the program. @xref{Files, ,Commands to
2558 The first thing @value{GDBN} does after arranging to debug the specified
2559 process is to stop it. You can examine and modify an attached process
2560 with all the @value{GDBN} commands that are ordinarily available when
2561 you start processes with @code{run}. You can insert breakpoints; you
2562 can step and continue; you can modify storage. If you would rather the
2563 process continue running, you may use the @code{continue} command after
2564 attaching @value{GDBN} to the process.
2569 When you have finished debugging the attached process, you can use the
2570 @code{detach} command to release it from @value{GDBN} control. Detaching
2571 the process continues its execution. After the @code{detach} command,
2572 that process and @value{GDBN} become completely independent once more, and you
2573 are ready to @code{attach} another process or start one with @code{run}.
2574 @code{detach} does not repeat if you press @key{RET} again after
2575 executing the command.
2578 If you exit @value{GDBN} while you have an attached process, you detach
2579 that process. If you use the @code{run} command, you kill that process.
2580 By default, @value{GDBN} asks for confirmation if you try to do either of these
2581 things; you can control whether or not you need to confirm by using the
2582 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2586 @section Killing the Child Process
2591 Kill the child process in which your program is running under @value{GDBN}.
2594 This command is useful if you wish to debug a core dump instead of a
2595 running process. @value{GDBN} ignores any core dump file while your program
2598 On some operating systems, a program cannot be executed outside @value{GDBN}
2599 while you have breakpoints set on it inside @value{GDBN}. You can use the
2600 @code{kill} command in this situation to permit running your program
2601 outside the debugger.
2603 The @code{kill} command is also useful if you wish to recompile and
2604 relink your program, since on many systems it is impossible to modify an
2605 executable file while it is running in a process. In this case, when you
2606 next type @code{run}, @value{GDBN} notices that the file has changed, and
2607 reads the symbol table again (while trying to preserve your current
2608 breakpoint settings).
2610 @node Inferiors and Programs
2611 @section Debugging Multiple Inferiors and Programs
2613 @value{GDBN} lets you run and debug multiple programs in a single
2614 session. In addition, @value{GDBN} on some systems may let you run
2615 several programs simultaneously (otherwise you have to exit from one
2616 before starting another). In the most general case, you can have
2617 multiple threads of execution in each of multiple processes, launched
2618 from multiple executables.
2621 @value{GDBN} represents the state of each program execution with an
2622 object called an @dfn{inferior}. An inferior typically corresponds to
2623 a process, but is more general and applies also to targets that do not
2624 have processes. Inferiors may be created before a process runs, and
2625 may be retained after a process exits. Inferiors have unique
2626 identifiers that are different from process ids. Usually each
2627 inferior will also have its own distinct address space, although some
2628 embedded targets may have several inferiors running in different parts
2629 of a single address space. Each inferior may in turn have multiple
2630 threads running in it.
2632 To find out what inferiors exist at any moment, use @w{@code{info
2636 @kindex info inferiors
2637 @item info inferiors
2638 Print a list of all inferiors currently being managed by @value{GDBN}.
2640 @value{GDBN} displays for each inferior (in this order):
2644 the inferior number assigned by @value{GDBN}
2647 the target system's inferior identifier
2650 the name of the executable the inferior is running.
2655 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2656 indicates the current inferior.
2660 @c end table here to get a little more width for example
2663 (@value{GDBP}) info inferiors
2664 Num Description Executable
2665 2 process 2307 hello
2666 * 1 process 3401 goodbye
2669 To switch focus between inferiors, use the @code{inferior} command:
2672 @kindex inferior @var{infno}
2673 @item inferior @var{infno}
2674 Make inferior number @var{infno} the current inferior. The argument
2675 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2676 in the first field of the @samp{info inferiors} display.
2679 @vindex $_inferior@r{, convenience variable}
2680 The debugger convenience variable @samp{$_inferior} contains the
2681 number of the current inferior. You may find this useful in writing
2682 breakpoint conditional expressions, command scripts, and so forth.
2683 @xref{Convenience Vars,, Convenience Variables}, for general
2684 information on convenience variables.
2686 You can get multiple executables into a debugging session via the
2687 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2688 systems @value{GDBN} can add inferiors to the debug session
2689 automatically by following calls to @code{fork} and @code{exec}. To
2690 remove inferiors from the debugging session use the
2691 @w{@code{remove-inferiors}} command.
2694 @kindex add-inferior
2695 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2696 Adds @var{n} inferiors to be run using @var{executable} as the
2697 executable; @var{n} defaults to 1. If no executable is specified,
2698 the inferiors begins empty, with no program. You can still assign or
2699 change the program assigned to the inferior at any time by using the
2700 @code{file} command with the executable name as its argument.
2702 @kindex clone-inferior
2703 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2704 Adds @var{n} inferiors ready to execute the same program as inferior
2705 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2706 number of the current inferior. This is a convenient command when you
2707 want to run another instance of the inferior you are debugging.
2710 (@value{GDBP}) info inferiors
2711 Num Description Executable
2712 * 1 process 29964 helloworld
2713 (@value{GDBP}) clone-inferior
2716 (@value{GDBP}) info inferiors
2717 Num Description Executable
2719 * 1 process 29964 helloworld
2722 You can now simply switch focus to inferior 2 and run it.
2724 @kindex remove-inferiors
2725 @item remove-inferiors @var{infno}@dots{}
2726 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2727 possible to remove an inferior that is running with this command. For
2728 those, use the @code{kill} or @code{detach} command first.
2732 To quit debugging one of the running inferiors that is not the current
2733 inferior, you can either detach from it by using the @w{@code{detach
2734 inferior}} command (allowing it to run independently), or kill it
2735 using the @w{@code{kill inferiors}} command:
2738 @kindex detach inferiors @var{infno}@dots{}
2739 @item detach inferior @var{infno}@dots{}
2740 Detach from the inferior or inferiors identified by @value{GDBN}
2741 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2742 still stays on the list of inferiors shown by @code{info inferiors},
2743 but its Description will show @samp{<null>}.
2745 @kindex kill inferiors @var{infno}@dots{}
2746 @item kill inferiors @var{infno}@dots{}
2747 Kill the inferior or inferiors identified by @value{GDBN} inferior
2748 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2749 stays on the list of inferiors shown by @code{info inferiors}, but its
2750 Description will show @samp{<null>}.
2753 After the successful completion of a command such as @code{detach},
2754 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2755 a normal process exit, the inferior is still valid and listed with
2756 @code{info inferiors}, ready to be restarted.
2759 To be notified when inferiors are started or exit under @value{GDBN}'s
2760 control use @w{@code{set print inferior-events}}:
2763 @kindex set print inferior-events
2764 @cindex print messages on inferior start and exit
2765 @item set print inferior-events
2766 @itemx set print inferior-events on
2767 @itemx set print inferior-events off
2768 The @code{set print inferior-events} command allows you to enable or
2769 disable printing of messages when @value{GDBN} notices that new
2770 inferiors have started or that inferiors have exited or have been
2771 detached. By default, these messages will not be printed.
2773 @kindex show print inferior-events
2774 @item show print inferior-events
2775 Show whether messages will be printed when @value{GDBN} detects that
2776 inferiors have started, exited or have been detached.
2779 Many commands will work the same with multiple programs as with a
2780 single program: e.g., @code{print myglobal} will simply display the
2781 value of @code{myglobal} in the current inferior.
2784 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2785 get more info about the relationship of inferiors, programs, address
2786 spaces in a debug session. You can do that with the @w{@code{maint
2787 info program-spaces}} command.
2790 @kindex maint info program-spaces
2791 @item maint info program-spaces
2792 Print a list of all program spaces currently being managed by
2795 @value{GDBN} displays for each program space (in this order):
2799 the program space number assigned by @value{GDBN}
2802 the name of the executable loaded into the program space, with e.g.,
2803 the @code{file} command.
2808 An asterisk @samp{*} preceding the @value{GDBN} program space number
2809 indicates the current program space.
2811 In addition, below each program space line, @value{GDBN} prints extra
2812 information that isn't suitable to display in tabular form. For
2813 example, the list of inferiors bound to the program space.
2816 (@value{GDBP}) maint info program-spaces
2820 Bound inferiors: ID 1 (process 21561)
2823 Here we can see that no inferior is running the program @code{hello},
2824 while @code{process 21561} is running the program @code{goodbye}. On
2825 some targets, it is possible that multiple inferiors are bound to the
2826 same program space. The most common example is that of debugging both
2827 the parent and child processes of a @code{vfork} call. For example,
2830 (@value{GDBP}) maint info program-spaces
2833 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2836 Here, both inferior 2 and inferior 1 are running in the same program
2837 space as a result of inferior 1 having executed a @code{vfork} call.
2841 @section Debugging Programs with Multiple Threads
2843 @cindex threads of execution
2844 @cindex multiple threads
2845 @cindex switching threads
2846 In some operating systems, such as GNU/Linux and Solaris, a single program
2847 may have more than one @dfn{thread} of execution. The precise semantics
2848 of threads differ from one operating system to another, but in general
2849 the threads of a single program are akin to multiple processes---except
2850 that they share one address space (that is, they can all examine and
2851 modify the same variables). On the other hand, each thread has its own
2852 registers and execution stack, and perhaps private memory.
2854 @value{GDBN} provides these facilities for debugging multi-thread
2858 @item automatic notification of new threads
2859 @item @samp{thread @var{thread-id}}, a command to switch among threads
2860 @item @samp{info threads}, a command to inquire about existing threads
2861 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2862 a command to apply a command to a list of threads
2863 @item thread-specific breakpoints
2864 @item @samp{set print thread-events}, which controls printing of
2865 messages on thread start and exit.
2866 @item @samp{set libthread-db-search-path @var{path}}, which lets
2867 the user specify which @code{libthread_db} to use if the default choice
2868 isn't compatible with the program.
2871 @cindex focus of debugging
2872 @cindex current thread
2873 The @value{GDBN} thread debugging facility allows you to observe all
2874 threads while your program runs---but whenever @value{GDBN} takes
2875 control, one thread in particular is always the focus of debugging.
2876 This thread is called the @dfn{current thread}. Debugging commands show
2877 program information from the perspective of the current thread.
2879 @cindex @code{New} @var{systag} message
2880 @cindex thread identifier (system)
2881 @c FIXME-implementors!! It would be more helpful if the [New...] message
2882 @c included GDB's numeric thread handle, so you could just go to that
2883 @c thread without first checking `info threads'.
2884 Whenever @value{GDBN} detects a new thread in your program, it displays
2885 the target system's identification for the thread with a message in the
2886 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2887 whose form varies depending on the particular system. For example, on
2888 @sc{gnu}/Linux, you might see
2891 [New Thread 0x41e02940 (LWP 25582)]
2895 when @value{GDBN} notices a new thread. In contrast, on other systems,
2896 the @var{systag} is simply something like @samp{process 368}, with no
2899 @c FIXME!! (1) Does the [New...] message appear even for the very first
2900 @c thread of a program, or does it only appear for the
2901 @c second---i.e.@: when it becomes obvious we have a multithread
2903 @c (2) *Is* there necessarily a first thread always? Or do some
2904 @c multithread systems permit starting a program with multiple
2905 @c threads ab initio?
2907 @anchor{thread numbers}
2908 @cindex thread number, per inferior
2909 @cindex thread identifier (GDB)
2910 For debugging purposes, @value{GDBN} associates its own thread number
2911 ---always a single integer---with each thread of an inferior. This
2912 number is unique between all threads of an inferior, but not unique
2913 between threads of different inferiors.
2915 @cindex qualified thread ID
2916 You can refer to a given thread in an inferior using the qualified
2917 @var{inferior-num}.@var{thread-num} syntax, also known as
2918 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2919 number and @var{thread-num} being the thread number of the given
2920 inferior. For example, thread @code{2.3} refers to thread number 3 of
2921 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2922 then @value{GDBN} infers you're referring to a thread of the current
2925 Until you create a second inferior, @value{GDBN} does not show the
2926 @var{inferior-num} part of thread IDs, even though you can always use
2927 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2928 of inferior 1, the initial inferior.
2930 @anchor{thread ID lists}
2931 @cindex thread ID lists
2932 Some commands accept a space-separated @dfn{thread ID list} as
2933 argument. A list element can be:
2937 A thread ID as shown in the first field of the @samp{info threads}
2938 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2942 A range of thread numbers, again with or without an inferior
2943 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2944 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2947 All threads of an inferior, specified with a star wildcard, with or
2948 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2949 @samp{1.*}) or @code{*}. The former refers to all threads of the
2950 given inferior, and the latter form without an inferior qualifier
2951 refers to all threads of the current inferior.
2955 For example, if the current inferior is 1, and inferior 7 has one
2956 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2957 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2958 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2959 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2963 @anchor{global thread numbers}
2964 @cindex global thread number
2965 @cindex global thread identifier (GDB)
2966 In addition to a @emph{per-inferior} number, each thread is also
2967 assigned a unique @emph{global} number, also known as @dfn{global
2968 thread ID}, a single integer. Unlike the thread number component of
2969 the thread ID, no two threads have the same global ID, even when
2970 you're debugging multiple inferiors.
2972 From @value{GDBN}'s perspective, a process always has at least one
2973 thread. In other words, @value{GDBN} assigns a thread number to the
2974 program's ``main thread'' even if the program is not multi-threaded.
2976 @vindex $_thread@r{, convenience variable}
2977 @vindex $_gthread@r{, convenience variable}
2978 The debugger convenience variables @samp{$_thread} and
2979 @samp{$_gthread} contain, respectively, the per-inferior thread number
2980 and the global thread number of the current thread. You may find this
2981 useful in writing breakpoint conditional expressions, command scripts,
2982 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2983 general information on convenience variables.
2985 If @value{GDBN} detects the program is multi-threaded, it augments the
2986 usual message about stopping at a breakpoint with the ID and name of
2987 the thread that hit the breakpoint.
2990 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2993 Likewise when the program receives a signal:
2996 Thread 1 "main" received signal SIGINT, Interrupt.
3000 @kindex info threads
3001 @item info threads @r{[}@var{thread-id-list}@r{]}
3003 Display information about one or more threads. With no arguments
3004 displays information about all threads. You can specify the list of
3005 threads that you want to display using the thread ID list syntax
3006 (@pxref{thread ID lists}).
3008 @value{GDBN} displays for each thread (in this order):
3012 the per-inferior thread number assigned by @value{GDBN}
3015 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3016 option was specified
3019 the target system's thread identifier (@var{systag})
3022 the thread's name, if one is known. A thread can either be named by
3023 the user (see @code{thread name}, below), or, in some cases, by the
3027 the current stack frame summary for that thread
3031 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3032 indicates the current thread.
3036 @c end table here to get a little more width for example
3039 (@value{GDBP}) info threads
3041 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3042 2 process 35 thread 23 0x34e5 in sigpause ()
3043 3 process 35 thread 27 0x34e5 in sigpause ()
3047 If you're debugging multiple inferiors, @value{GDBN} displays thread
3048 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3049 Otherwise, only @var{thread-num} is shown.
3051 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3052 indicating each thread's global thread ID:
3055 (@value{GDBP}) info threads
3056 Id GId Target Id Frame
3057 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3058 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3059 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3060 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3063 On Solaris, you can display more information about user threads with a
3064 Solaris-specific command:
3067 @item maint info sol-threads
3068 @kindex maint info sol-threads
3069 @cindex thread info (Solaris)
3070 Display info on Solaris user threads.
3074 @kindex thread @var{thread-id}
3075 @item thread @var{thread-id}
3076 Make thread ID @var{thread-id} the current thread. The command
3077 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3078 the first field of the @samp{info threads} display, with or without an
3079 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3081 @value{GDBN} responds by displaying the system identifier of the
3082 thread you selected, and its current stack frame summary:
3085 (@value{GDBP}) thread 2
3086 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3087 #0 some_function (ignore=0x0) at example.c:8
3088 8 printf ("hello\n");
3092 As with the @samp{[New @dots{}]} message, the form of the text after
3093 @samp{Switching to} depends on your system's conventions for identifying
3096 @kindex thread apply
3097 @cindex apply command to several threads
3098 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3099 The @code{thread apply} command allows you to apply the named
3100 @var{command} to one or more threads. Specify the threads that you
3101 want affected using the thread ID list syntax (@pxref{thread ID
3102 lists}), or specify @code{all} to apply to all threads. To apply a
3103 command to all threads in descending order, type @kbd{thread apply all
3104 @var{command}}. To apply a command to all threads in ascending order,
3105 type @kbd{thread apply all -ascending @var{command}}.
3109 @cindex name a thread
3110 @item thread name [@var{name}]
3111 This command assigns a name to the current thread. If no argument is
3112 given, any existing user-specified name is removed. The thread name
3113 appears in the @samp{info threads} display.
3115 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3116 determine the name of the thread as given by the OS. On these
3117 systems, a name specified with @samp{thread name} will override the
3118 system-give name, and removing the user-specified name will cause
3119 @value{GDBN} to once again display the system-specified name.
3122 @cindex search for a thread
3123 @item thread find [@var{regexp}]
3124 Search for and display thread ids whose name or @var{systag}
3125 matches the supplied regular expression.
3127 As well as being the complement to the @samp{thread name} command,
3128 this command also allows you to identify a thread by its target
3129 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3133 (@value{GDBN}) thread find 26688
3134 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3135 (@value{GDBN}) info thread 4
3137 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3140 @kindex set print thread-events
3141 @cindex print messages on thread start and exit
3142 @item set print thread-events
3143 @itemx set print thread-events on
3144 @itemx set print thread-events off
3145 The @code{set print thread-events} command allows you to enable or
3146 disable printing of messages when @value{GDBN} notices that new threads have
3147 started or that threads have exited. By default, these messages will
3148 be printed if detection of these events is supported by the target.
3149 Note that these messages cannot be disabled on all targets.
3151 @kindex show print thread-events
3152 @item show print thread-events
3153 Show whether messages will be printed when @value{GDBN} detects that threads
3154 have started and exited.
3157 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3158 more information about how @value{GDBN} behaves when you stop and start
3159 programs with multiple threads.
3161 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3162 watchpoints in programs with multiple threads.
3164 @anchor{set libthread-db-search-path}
3166 @kindex set libthread-db-search-path
3167 @cindex search path for @code{libthread_db}
3168 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3169 If this variable is set, @var{path} is a colon-separated list of
3170 directories @value{GDBN} will use to search for @code{libthread_db}.
3171 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3172 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3173 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3176 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3177 @code{libthread_db} library to obtain information about threads in the
3178 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3179 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3180 specific thread debugging library loading is enabled
3181 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3183 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3184 refers to the default system directories that are
3185 normally searched for loading shared libraries. The @samp{$sdir} entry
3186 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3187 (@pxref{libthread_db.so.1 file}).
3189 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3190 refers to the directory from which @code{libpthread}
3191 was loaded in the inferior process.
3193 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3194 @value{GDBN} attempts to initialize it with the current inferior process.
3195 If this initialization fails (which could happen because of a version
3196 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3197 will unload @code{libthread_db}, and continue with the next directory.
3198 If none of @code{libthread_db} libraries initialize successfully,
3199 @value{GDBN} will issue a warning and thread debugging will be disabled.
3201 Setting @code{libthread-db-search-path} is currently implemented
3202 only on some platforms.
3204 @kindex show libthread-db-search-path
3205 @item show libthread-db-search-path
3206 Display current libthread_db search path.
3208 @kindex set debug libthread-db
3209 @kindex show debug libthread-db
3210 @cindex debugging @code{libthread_db}
3211 @item set debug libthread-db
3212 @itemx show debug libthread-db
3213 Turns on or off display of @code{libthread_db}-related events.
3214 Use @code{1} to enable, @code{0} to disable.
3218 @section Debugging Forks
3220 @cindex fork, debugging programs which call
3221 @cindex multiple processes
3222 @cindex processes, multiple
3223 On most systems, @value{GDBN} has no special support for debugging
3224 programs which create additional processes using the @code{fork}
3225 function. When a program forks, @value{GDBN} will continue to debug the
3226 parent process and the child process will run unimpeded. If you have
3227 set a breakpoint in any code which the child then executes, the child
3228 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3229 will cause it to terminate.
3231 However, if you want to debug the child process there is a workaround
3232 which isn't too painful. Put a call to @code{sleep} in the code which
3233 the child process executes after the fork. It may be useful to sleep
3234 only if a certain environment variable is set, or a certain file exists,
3235 so that the delay need not occur when you don't want to run @value{GDBN}
3236 on the child. While the child is sleeping, use the @code{ps} program to
3237 get its process ID. Then tell @value{GDBN} (a new invocation of
3238 @value{GDBN} if you are also debugging the parent process) to attach to
3239 the child process (@pxref{Attach}). From that point on you can debug
3240 the child process just like any other process which you attached to.
3242 On some systems, @value{GDBN} provides support for debugging programs
3243 that create additional processes using the @code{fork} or @code{vfork}
3244 functions. On @sc{gnu}/Linux platforms, this feature is supported
3245 with kernel version 2.5.46 and later.
3247 The fork debugging commands are supported in native mode and when
3248 connected to @code{gdbserver} in either @code{target remote} mode or
3249 @code{target extended-remote} mode.
3251 By default, when a program forks, @value{GDBN} will continue to debug
3252 the parent process and the child process will run unimpeded.
3254 If you want to follow the child process instead of the parent process,
3255 use the command @w{@code{set follow-fork-mode}}.
3258 @kindex set follow-fork-mode
3259 @item set follow-fork-mode @var{mode}
3260 Set the debugger response to a program call of @code{fork} or
3261 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3262 process. The @var{mode} argument can be:
3266 The original process is debugged after a fork. The child process runs
3267 unimpeded. This is the default.
3270 The new process is debugged after a fork. The parent process runs
3275 @kindex show follow-fork-mode
3276 @item show follow-fork-mode
3277 Display the current debugger response to a @code{fork} or @code{vfork} call.
3280 @cindex debugging multiple processes
3281 On Linux, if you want to debug both the parent and child processes, use the
3282 command @w{@code{set detach-on-fork}}.
3285 @kindex set detach-on-fork
3286 @item set detach-on-fork @var{mode}
3287 Tells gdb whether to detach one of the processes after a fork, or
3288 retain debugger control over them both.
3292 The child process (or parent process, depending on the value of
3293 @code{follow-fork-mode}) will be detached and allowed to run
3294 independently. This is the default.
3297 Both processes will be held under the control of @value{GDBN}.
3298 One process (child or parent, depending on the value of
3299 @code{follow-fork-mode}) is debugged as usual, while the other
3304 @kindex show detach-on-fork
3305 @item show detach-on-fork
3306 Show whether detach-on-fork mode is on/off.
3309 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3310 will retain control of all forked processes (including nested forks).
3311 You can list the forked processes under the control of @value{GDBN} by
3312 using the @w{@code{info inferiors}} command, and switch from one fork
3313 to another by using the @code{inferior} command (@pxref{Inferiors and
3314 Programs, ,Debugging Multiple Inferiors and Programs}).
3316 To quit debugging one of the forked processes, you can either detach
3317 from it by using the @w{@code{detach inferiors}} command (allowing it
3318 to run independently), or kill it using the @w{@code{kill inferiors}}
3319 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3322 If you ask to debug a child process and a @code{vfork} is followed by an
3323 @code{exec}, @value{GDBN} executes the new target up to the first
3324 breakpoint in the new target. If you have a breakpoint set on
3325 @code{main} in your original program, the breakpoint will also be set on
3326 the child process's @code{main}.
3328 On some systems, when a child process is spawned by @code{vfork}, you
3329 cannot debug the child or parent until an @code{exec} call completes.
3331 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3332 call executes, the new target restarts. To restart the parent
3333 process, use the @code{file} command with the parent executable name
3334 as its argument. By default, after an @code{exec} call executes,
3335 @value{GDBN} discards the symbols of the previous executable image.
3336 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3340 @kindex set follow-exec-mode
3341 @item set follow-exec-mode @var{mode}
3343 Set debugger response to a program call of @code{exec}. An
3344 @code{exec} call replaces the program image of a process.
3346 @code{follow-exec-mode} can be:
3350 @value{GDBN} creates a new inferior and rebinds the process to this
3351 new inferior. The program the process was running before the
3352 @code{exec} call can be restarted afterwards by restarting the
3358 (@value{GDBP}) info inferiors
3360 Id Description Executable
3363 process 12020 is executing new program: prog2
3364 Program exited normally.
3365 (@value{GDBP}) info inferiors
3366 Id Description Executable
3372 @value{GDBN} keeps the process bound to the same inferior. The new
3373 executable image replaces the previous executable loaded in the
3374 inferior. Restarting the inferior after the @code{exec} call, with
3375 e.g., the @code{run} command, restarts the executable the process was
3376 running after the @code{exec} call. This is the default mode.
3381 (@value{GDBP}) info inferiors
3382 Id Description Executable
3385 process 12020 is executing new program: prog2
3386 Program exited normally.
3387 (@value{GDBP}) info inferiors
3388 Id Description Executable
3395 @code{follow-exec-mode} is supported in native mode and
3396 @code{target extended-remote} mode.
3398 You can use the @code{catch} command to make @value{GDBN} stop whenever
3399 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3400 Catchpoints, ,Setting Catchpoints}.
3402 @node Checkpoint/Restart
3403 @section Setting a @emph{Bookmark} to Return to Later
3408 @cindex snapshot of a process
3409 @cindex rewind program state
3411 On certain operating systems@footnote{Currently, only
3412 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3413 program's state, called a @dfn{checkpoint}, and come back to it
3416 Returning to a checkpoint effectively undoes everything that has
3417 happened in the program since the @code{checkpoint} was saved. This
3418 includes changes in memory, registers, and even (within some limits)
3419 system state. Effectively, it is like going back in time to the
3420 moment when the checkpoint was saved.
3422 Thus, if you're stepping thru a program and you think you're
3423 getting close to the point where things go wrong, you can save
3424 a checkpoint. Then, if you accidentally go too far and miss
3425 the critical statement, instead of having to restart your program
3426 from the beginning, you can just go back to the checkpoint and
3427 start again from there.
3429 This can be especially useful if it takes a lot of time or
3430 steps to reach the point where you think the bug occurs.
3432 To use the @code{checkpoint}/@code{restart} method of debugging:
3437 Save a snapshot of the debugged program's current execution state.
3438 The @code{checkpoint} command takes no arguments, but each checkpoint
3439 is assigned a small integer id, similar to a breakpoint id.
3441 @kindex info checkpoints
3442 @item info checkpoints
3443 List the checkpoints that have been saved in the current debugging
3444 session. For each checkpoint, the following information will be
3451 @item Source line, or label
3454 @kindex restart @var{checkpoint-id}
3455 @item restart @var{checkpoint-id}
3456 Restore the program state that was saved as checkpoint number
3457 @var{checkpoint-id}. All program variables, registers, stack frames
3458 etc.@: will be returned to the values that they had when the checkpoint
3459 was saved. In essence, gdb will ``wind back the clock'' to the point
3460 in time when the checkpoint was saved.
3462 Note that breakpoints, @value{GDBN} variables, command history etc.
3463 are not affected by restoring a checkpoint. In general, a checkpoint
3464 only restores things that reside in the program being debugged, not in
3467 @kindex delete checkpoint @var{checkpoint-id}
3468 @item delete checkpoint @var{checkpoint-id}
3469 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3473 Returning to a previously saved checkpoint will restore the user state
3474 of the program being debugged, plus a significant subset of the system
3475 (OS) state, including file pointers. It won't ``un-write'' data from
3476 a file, but it will rewind the file pointer to the previous location,
3477 so that the previously written data can be overwritten. For files
3478 opened in read mode, the pointer will also be restored so that the
3479 previously read data can be read again.
3481 Of course, characters that have been sent to a printer (or other
3482 external device) cannot be ``snatched back'', and characters received
3483 from eg.@: a serial device can be removed from internal program buffers,
3484 but they cannot be ``pushed back'' into the serial pipeline, ready to
3485 be received again. Similarly, the actual contents of files that have
3486 been changed cannot be restored (at this time).
3488 However, within those constraints, you actually can ``rewind'' your
3489 program to a previously saved point in time, and begin debugging it
3490 again --- and you can change the course of events so as to debug a
3491 different execution path this time.
3493 @cindex checkpoints and process id
3494 Finally, there is one bit of internal program state that will be
3495 different when you return to a checkpoint --- the program's process
3496 id. Each checkpoint will have a unique process id (or @var{pid}),
3497 and each will be different from the program's original @var{pid}.
3498 If your program has saved a local copy of its process id, this could
3499 potentially pose a problem.
3501 @subsection A Non-obvious Benefit of Using Checkpoints
3503 On some systems such as @sc{gnu}/Linux, address space randomization
3504 is performed on new processes for security reasons. This makes it
3505 difficult or impossible to set a breakpoint, or watchpoint, on an
3506 absolute address if you have to restart the program, since the
3507 absolute location of a symbol will change from one execution to the
3510 A checkpoint, however, is an @emph{identical} copy of a process.
3511 Therefore if you create a checkpoint at (eg.@:) the start of main,
3512 and simply return to that checkpoint instead of restarting the
3513 process, you can avoid the effects of address randomization and
3514 your symbols will all stay in the same place.
3517 @chapter Stopping and Continuing
3519 The principal purposes of using a debugger are so that you can stop your
3520 program before it terminates; or so that, if your program runs into
3521 trouble, you can investigate and find out why.
3523 Inside @value{GDBN}, your program may stop for any of several reasons,
3524 such as a signal, a breakpoint, or reaching a new line after a
3525 @value{GDBN} command such as @code{step}. You may then examine and
3526 change variables, set new breakpoints or remove old ones, and then
3527 continue execution. Usually, the messages shown by @value{GDBN} provide
3528 ample explanation of the status of your program---but you can also
3529 explicitly request this information at any time.
3532 @kindex info program
3534 Display information about the status of your program: whether it is
3535 running or not, what process it is, and why it stopped.
3539 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3540 * Continuing and Stepping:: Resuming execution
3541 * Skipping Over Functions and Files::
3542 Skipping over functions and files
3544 * Thread Stops:: Stopping and starting multi-thread programs
3548 @section Breakpoints, Watchpoints, and Catchpoints
3551 A @dfn{breakpoint} makes your program stop whenever a certain point in
3552 the program is reached. For each breakpoint, you can add conditions to
3553 control in finer detail whether your program stops. You can set
3554 breakpoints with the @code{break} command and its variants (@pxref{Set
3555 Breaks, ,Setting Breakpoints}), to specify the place where your program
3556 should stop by line number, function name or exact address in the
3559 On some systems, you can set breakpoints in shared libraries before
3560 the executable is run.
3563 @cindex data breakpoints
3564 @cindex memory tracing
3565 @cindex breakpoint on memory address
3566 @cindex breakpoint on variable modification
3567 A @dfn{watchpoint} is a special breakpoint that stops your program
3568 when the value of an expression changes. The expression may be a value
3569 of a variable, or it could involve values of one or more variables
3570 combined by operators, such as @samp{a + b}. This is sometimes called
3571 @dfn{data breakpoints}. You must use a different command to set
3572 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3573 from that, you can manage a watchpoint like any other breakpoint: you
3574 enable, disable, and delete both breakpoints and watchpoints using the
3577 You can arrange to have values from your program displayed automatically
3578 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3582 @cindex breakpoint on events
3583 A @dfn{catchpoint} is another special breakpoint that stops your program
3584 when a certain kind of event occurs, such as the throwing of a C@t{++}
3585 exception or the loading of a library. As with watchpoints, you use a
3586 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3587 Catchpoints}), but aside from that, you can manage a catchpoint like any
3588 other breakpoint. (To stop when your program receives a signal, use the
3589 @code{handle} command; see @ref{Signals, ,Signals}.)
3591 @cindex breakpoint numbers
3592 @cindex numbers for breakpoints
3593 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3594 catchpoint when you create it; these numbers are successive integers
3595 starting with one. In many of the commands for controlling various
3596 features of breakpoints you use the breakpoint number to say which
3597 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3598 @dfn{disabled}; if disabled, it has no effect on your program until you
3601 @cindex breakpoint ranges
3602 @cindex breakpoint lists
3603 @cindex ranges of breakpoints
3604 @cindex lists of breakpoints
3605 Some @value{GDBN} commands accept a space-separated list of breakpoints
3606 on which to operate. A list element can be either a single breakpoint number,
3607 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3608 When a breakpoint list is given to a command, all breakpoints in that list
3612 * Set Breaks:: Setting breakpoints
3613 * Set Watchpoints:: Setting watchpoints
3614 * Set Catchpoints:: Setting catchpoints
3615 * Delete Breaks:: Deleting breakpoints
3616 * Disabling:: Disabling breakpoints
3617 * Conditions:: Break conditions
3618 * Break Commands:: Breakpoint command lists
3619 * Dynamic Printf:: Dynamic printf
3620 * Save Breakpoints:: How to save breakpoints in a file
3621 * Static Probe Points:: Listing static probe points
3622 * Error in Breakpoints:: ``Cannot insert breakpoints''
3623 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3627 @subsection Setting Breakpoints
3629 @c FIXME LMB what does GDB do if no code on line of breakpt?
3630 @c consider in particular declaration with/without initialization.
3632 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3635 @kindex b @r{(@code{break})}
3636 @vindex $bpnum@r{, convenience variable}
3637 @cindex latest breakpoint
3638 Breakpoints are set with the @code{break} command (abbreviated
3639 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3640 number of the breakpoint you've set most recently; see @ref{Convenience
3641 Vars,, Convenience Variables}, for a discussion of what you can do with
3642 convenience variables.
3645 @item break @var{location}
3646 Set a breakpoint at the given @var{location}, which can specify a
3647 function name, a line number, or an address of an instruction.
3648 (@xref{Specify Location}, for a list of all the possible ways to
3649 specify a @var{location}.) The breakpoint will stop your program just
3650 before it executes any of the code in the specified @var{location}.
3652 When using source languages that permit overloading of symbols, such as
3653 C@t{++}, a function name may refer to more than one possible place to break.
3654 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3657 It is also possible to insert a breakpoint that will stop the program
3658 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3659 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3662 When called without any arguments, @code{break} sets a breakpoint at
3663 the next instruction to be executed in the selected stack frame
3664 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3665 innermost, this makes your program stop as soon as control
3666 returns to that frame. This is similar to the effect of a
3667 @code{finish} command in the frame inside the selected frame---except
3668 that @code{finish} does not leave an active breakpoint. If you use
3669 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3670 the next time it reaches the current location; this may be useful
3673 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3674 least one instruction has been executed. If it did not do this, you
3675 would be unable to proceed past a breakpoint without first disabling the
3676 breakpoint. This rule applies whether or not the breakpoint already
3677 existed when your program stopped.
3679 @item break @dots{} if @var{cond}
3680 Set a breakpoint with condition @var{cond}; evaluate the expression
3681 @var{cond} each time the breakpoint is reached, and stop only if the
3682 value is nonzero---that is, if @var{cond} evaluates as true.
3683 @samp{@dots{}} stands for one of the possible arguments described
3684 above (or no argument) specifying where to break. @xref{Conditions,
3685 ,Break Conditions}, for more information on breakpoint conditions.
3688 @item tbreak @var{args}
3689 Set a breakpoint enabled only for one stop. The @var{args} are the
3690 same as for the @code{break} command, and the breakpoint is set in the same
3691 way, but the breakpoint is automatically deleted after the first time your
3692 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3695 @cindex hardware breakpoints
3696 @item hbreak @var{args}
3697 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3698 @code{break} command and the breakpoint is set in the same way, but the
3699 breakpoint requires hardware support and some target hardware may not
3700 have this support. The main purpose of this is EPROM/ROM code
3701 debugging, so you can set a breakpoint at an instruction without
3702 changing the instruction. This can be used with the new trap-generation
3703 provided by SPARClite DSU and most x86-based targets. These targets
3704 will generate traps when a program accesses some data or instruction
3705 address that is assigned to the debug registers. However the hardware
3706 breakpoint registers can take a limited number of breakpoints. For
3707 example, on the DSU, only two data breakpoints can be set at a time, and
3708 @value{GDBN} will reject this command if more than two are used. Delete
3709 or disable unused hardware breakpoints before setting new ones
3710 (@pxref{Disabling, ,Disabling Breakpoints}).
3711 @xref{Conditions, ,Break Conditions}.
3712 For remote targets, you can restrict the number of hardware
3713 breakpoints @value{GDBN} will use, see @ref{set remote
3714 hardware-breakpoint-limit}.
3717 @item thbreak @var{args}
3718 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3719 are the same as for the @code{hbreak} command and the breakpoint is set in
3720 the same way. However, like the @code{tbreak} command,
3721 the breakpoint is automatically deleted after the
3722 first time your program stops there. Also, like the @code{hbreak}
3723 command, the breakpoint requires hardware support and some target hardware
3724 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3725 See also @ref{Conditions, ,Break Conditions}.
3728 @cindex regular expression
3729 @cindex breakpoints at functions matching a regexp
3730 @cindex set breakpoints in many functions
3731 @item rbreak @var{regex}
3732 Set breakpoints on all functions matching the regular expression
3733 @var{regex}. This command sets an unconditional breakpoint on all
3734 matches, printing a list of all breakpoints it set. Once these
3735 breakpoints are set, they are treated just like the breakpoints set with
3736 the @code{break} command. You can delete them, disable them, or make
3737 them conditional the same way as any other breakpoint.
3739 The syntax of the regular expression is the standard one used with tools
3740 like @file{grep}. Note that this is different from the syntax used by
3741 shells, so for instance @code{foo*} matches all functions that include
3742 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3743 @code{.*} leading and trailing the regular expression you supply, so to
3744 match only functions that begin with @code{foo}, use @code{^foo}.
3746 @cindex non-member C@t{++} functions, set breakpoint in
3747 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3748 breakpoints on overloaded functions that are not members of any special
3751 @cindex set breakpoints on all functions
3752 The @code{rbreak} command can be used to set breakpoints in
3753 @strong{all} the functions in a program, like this:
3756 (@value{GDBP}) rbreak .
3759 @item rbreak @var{file}:@var{regex}
3760 If @code{rbreak} is called with a filename qualification, it limits
3761 the search for functions matching the given regular expression to the
3762 specified @var{file}. This can be used, for example, to set breakpoints on
3763 every function in a given file:
3766 (@value{GDBP}) rbreak file.c:.
3769 The colon separating the filename qualifier from the regex may
3770 optionally be surrounded by spaces.
3772 @kindex info breakpoints
3773 @cindex @code{$_} and @code{info breakpoints}
3774 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3775 @itemx info break @r{[}@var{list}@dots{}@r{]}
3776 Print a table of all breakpoints, watchpoints, and catchpoints set and
3777 not deleted. Optional argument @var{n} means print information only
3778 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3779 For each breakpoint, following columns are printed:
3782 @item Breakpoint Numbers
3784 Breakpoint, watchpoint, or catchpoint.
3786 Whether the breakpoint is marked to be disabled or deleted when hit.
3787 @item Enabled or Disabled
3788 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3789 that are not enabled.
3791 Where the breakpoint is in your program, as a memory address. For a
3792 pending breakpoint whose address is not yet known, this field will
3793 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3794 library that has the symbol or line referred by breakpoint is loaded.
3795 See below for details. A breakpoint with several locations will
3796 have @samp{<MULTIPLE>} in this field---see below for details.
3798 Where the breakpoint is in the source for your program, as a file and
3799 line number. For a pending breakpoint, the original string passed to
3800 the breakpoint command will be listed as it cannot be resolved until
3801 the appropriate shared library is loaded in the future.
3805 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3806 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3807 @value{GDBN} on the host's side. If it is ``target'', then the condition
3808 is evaluated by the target. The @code{info break} command shows
3809 the condition on the line following the affected breakpoint, together with
3810 its condition evaluation mode in between parentheses.
3812 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3813 allowed to have a condition specified for it. The condition is not parsed for
3814 validity until a shared library is loaded that allows the pending
3815 breakpoint to resolve to a valid location.
3818 @code{info break} with a breakpoint
3819 number @var{n} as argument lists only that breakpoint. The
3820 convenience variable @code{$_} and the default examining-address for
3821 the @code{x} command are set to the address of the last breakpoint
3822 listed (@pxref{Memory, ,Examining Memory}).
3825 @code{info break} displays a count of the number of times the breakpoint
3826 has been hit. This is especially useful in conjunction with the
3827 @code{ignore} command. You can ignore a large number of breakpoint
3828 hits, look at the breakpoint info to see how many times the breakpoint
3829 was hit, and then run again, ignoring one less than that number. This
3830 will get you quickly to the last hit of that breakpoint.
3833 For a breakpoints with an enable count (xref) greater than 1,
3834 @code{info break} also displays that count.
3838 @value{GDBN} allows you to set any number of breakpoints at the same place in
3839 your program. There is nothing silly or meaningless about this. When
3840 the breakpoints are conditional, this is even useful
3841 (@pxref{Conditions, ,Break Conditions}).
3843 @cindex multiple locations, breakpoints
3844 @cindex breakpoints, multiple locations
3845 It is possible that a breakpoint corresponds to several locations
3846 in your program. Examples of this situation are:
3850 Multiple functions in the program may have the same name.
3853 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3854 instances of the function body, used in different cases.
3857 For a C@t{++} template function, a given line in the function can
3858 correspond to any number of instantiations.
3861 For an inlined function, a given source line can correspond to
3862 several places where that function is inlined.
3865 In all those cases, @value{GDBN} will insert a breakpoint at all
3866 the relevant locations.
3868 A breakpoint with multiple locations is displayed in the breakpoint
3869 table using several rows---one header row, followed by one row for
3870 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3871 address column. The rows for individual locations contain the actual
3872 addresses for locations, and show the functions to which those
3873 locations belong. The number column for a location is of the form
3874 @var{breakpoint-number}.@var{location-number}.
3879 Num Type Disp Enb Address What
3880 1 breakpoint keep y <MULTIPLE>
3882 breakpoint already hit 1 time
3883 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3884 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3887 Each location can be individually enabled or disabled by passing
3888 @var{breakpoint-number}.@var{location-number} as argument to the
3889 @code{enable} and @code{disable} commands. Note that you cannot
3890 delete the individual locations from the list, you can only delete the
3891 entire list of locations that belong to their parent breakpoint (with
3892 the @kbd{delete @var{num}} command, where @var{num} is the number of
3893 the parent breakpoint, 1 in the above example). Disabling or enabling
3894 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3895 that belong to that breakpoint.
3897 @cindex pending breakpoints
3898 It's quite common to have a breakpoint inside a shared library.
3899 Shared libraries can be loaded and unloaded explicitly,
3900 and possibly repeatedly, as the program is executed. To support
3901 this use case, @value{GDBN} updates breakpoint locations whenever
3902 any shared library is loaded or unloaded. Typically, you would
3903 set a breakpoint in a shared library at the beginning of your
3904 debugging session, when the library is not loaded, and when the
3905 symbols from the library are not available. When you try to set
3906 breakpoint, @value{GDBN} will ask you if you want to set
3907 a so called @dfn{pending breakpoint}---breakpoint whose address
3908 is not yet resolved.
3910 After the program is run, whenever a new shared library is loaded,
3911 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3912 shared library contains the symbol or line referred to by some
3913 pending breakpoint, that breakpoint is resolved and becomes an
3914 ordinary breakpoint. When a library is unloaded, all breakpoints
3915 that refer to its symbols or source lines become pending again.
3917 This logic works for breakpoints with multiple locations, too. For
3918 example, if you have a breakpoint in a C@t{++} template function, and
3919 a newly loaded shared library has an instantiation of that template,
3920 a new location is added to the list of locations for the breakpoint.
3922 Except for having unresolved address, pending breakpoints do not
3923 differ from regular breakpoints. You can set conditions or commands,
3924 enable and disable them and perform other breakpoint operations.
3926 @value{GDBN} provides some additional commands for controlling what
3927 happens when the @samp{break} command cannot resolve breakpoint
3928 address specification to an address:
3930 @kindex set breakpoint pending
3931 @kindex show breakpoint pending
3933 @item set breakpoint pending auto
3934 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3935 location, it queries you whether a pending breakpoint should be created.
3937 @item set breakpoint pending on
3938 This indicates that an unrecognized breakpoint location should automatically
3939 result in a pending breakpoint being created.
3941 @item set breakpoint pending off
3942 This indicates that pending breakpoints are not to be created. Any
3943 unrecognized breakpoint location results in an error. This setting does
3944 not affect any pending breakpoints previously created.
3946 @item show breakpoint pending
3947 Show the current behavior setting for creating pending breakpoints.
3950 The settings above only affect the @code{break} command and its
3951 variants. Once breakpoint is set, it will be automatically updated
3952 as shared libraries are loaded and unloaded.
3954 @cindex automatic hardware breakpoints
3955 For some targets, @value{GDBN} can automatically decide if hardware or
3956 software breakpoints should be used, depending on whether the
3957 breakpoint address is read-only or read-write. This applies to
3958 breakpoints set with the @code{break} command as well as to internal
3959 breakpoints set by commands like @code{next} and @code{finish}. For
3960 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3963 You can control this automatic behaviour with the following commands:
3965 @kindex set breakpoint auto-hw
3966 @kindex show breakpoint auto-hw
3968 @item set breakpoint auto-hw on
3969 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3970 will try to use the target memory map to decide if software or hardware
3971 breakpoint must be used.
3973 @item set breakpoint auto-hw off
3974 This indicates @value{GDBN} should not automatically select breakpoint
3975 type. If the target provides a memory map, @value{GDBN} will warn when
3976 trying to set software breakpoint at a read-only address.
3979 @value{GDBN} normally implements breakpoints by replacing the program code
3980 at the breakpoint address with a special instruction, which, when
3981 executed, given control to the debugger. By default, the program
3982 code is so modified only when the program is resumed. As soon as
3983 the program stops, @value{GDBN} restores the original instructions. This
3984 behaviour guards against leaving breakpoints inserted in the
3985 target should gdb abrubptly disconnect. However, with slow remote
3986 targets, inserting and removing breakpoint can reduce the performance.
3987 This behavior can be controlled with the following commands::
3989 @kindex set breakpoint always-inserted
3990 @kindex show breakpoint always-inserted
3992 @item set breakpoint always-inserted off
3993 All breakpoints, including newly added by the user, are inserted in
3994 the target only when the target is resumed. All breakpoints are
3995 removed from the target when it stops. This is the default mode.
3997 @item set breakpoint always-inserted on
3998 Causes all breakpoints to be inserted in the target at all times. If
3999 the user adds a new breakpoint, or changes an existing breakpoint, the
4000 breakpoints in the target are updated immediately. A breakpoint is
4001 removed from the target only when breakpoint itself is deleted.
4004 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4005 when a breakpoint breaks. If the condition is true, then the process being
4006 debugged stops, otherwise the process is resumed.
4008 If the target supports evaluating conditions on its end, @value{GDBN} may
4009 download the breakpoint, together with its conditions, to it.
4011 This feature can be controlled via the following commands:
4013 @kindex set breakpoint condition-evaluation
4014 @kindex show breakpoint condition-evaluation
4016 @item set breakpoint condition-evaluation host
4017 This option commands @value{GDBN} to evaluate the breakpoint
4018 conditions on the host's side. Unconditional breakpoints are sent to
4019 the target which in turn receives the triggers and reports them back to GDB
4020 for condition evaluation. This is the standard evaluation mode.
4022 @item set breakpoint condition-evaluation target
4023 This option commands @value{GDBN} to download breakpoint conditions
4024 to the target at the moment of their insertion. The target
4025 is responsible for evaluating the conditional expression and reporting
4026 breakpoint stop events back to @value{GDBN} whenever the condition
4027 is true. Due to limitations of target-side evaluation, some conditions
4028 cannot be evaluated there, e.g., conditions that depend on local data
4029 that is only known to the host. Examples include
4030 conditional expressions involving convenience variables, complex types
4031 that cannot be handled by the agent expression parser and expressions
4032 that are too long to be sent over to the target, specially when the
4033 target is a remote system. In these cases, the conditions will be
4034 evaluated by @value{GDBN}.
4036 @item set breakpoint condition-evaluation auto
4037 This is the default mode. If the target supports evaluating breakpoint
4038 conditions on its end, @value{GDBN} will download breakpoint conditions to
4039 the target (limitations mentioned previously apply). If the target does
4040 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4041 to evaluating all these conditions on the host's side.
4045 @cindex negative breakpoint numbers
4046 @cindex internal @value{GDBN} breakpoints
4047 @value{GDBN} itself sometimes sets breakpoints in your program for
4048 special purposes, such as proper handling of @code{longjmp} (in C
4049 programs). These internal breakpoints are assigned negative numbers,
4050 starting with @code{-1}; @samp{info breakpoints} does not display them.
4051 You can see these breakpoints with the @value{GDBN} maintenance command
4052 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4055 @node Set Watchpoints
4056 @subsection Setting Watchpoints
4058 @cindex setting watchpoints
4059 You can use a watchpoint to stop execution whenever the value of an
4060 expression changes, without having to predict a particular place where
4061 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4062 The expression may be as simple as the value of a single variable, or
4063 as complex as many variables combined by operators. Examples include:
4067 A reference to the value of a single variable.
4070 An address cast to an appropriate data type. For example,
4071 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4072 address (assuming an @code{int} occupies 4 bytes).
4075 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4076 expression can use any operators valid in the program's native
4077 language (@pxref{Languages}).
4080 You can set a watchpoint on an expression even if the expression can
4081 not be evaluated yet. For instance, you can set a watchpoint on
4082 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4083 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4084 the expression produces a valid value. If the expression becomes
4085 valid in some other way than changing a variable (e.g.@: if the memory
4086 pointed to by @samp{*global_ptr} becomes readable as the result of a
4087 @code{malloc} call), @value{GDBN} may not stop until the next time
4088 the expression changes.
4090 @cindex software watchpoints
4091 @cindex hardware watchpoints
4092 Depending on your system, watchpoints may be implemented in software or
4093 hardware. @value{GDBN} does software watchpointing by single-stepping your
4094 program and testing the variable's value each time, which is hundreds of
4095 times slower than normal execution. (But this may still be worth it, to
4096 catch errors where you have no clue what part of your program is the
4099 On some systems, such as most PowerPC or x86-based targets,
4100 @value{GDBN} includes support for hardware watchpoints, which do not
4101 slow down the running of your program.
4105 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4106 Set a watchpoint for an expression. @value{GDBN} will break when the
4107 expression @var{expr} is written into by the program and its value
4108 changes. The simplest (and the most popular) use of this command is
4109 to watch the value of a single variable:
4112 (@value{GDBP}) watch foo
4115 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4116 argument, @value{GDBN} breaks only when the thread identified by
4117 @var{thread-id} changes the value of @var{expr}. If any other threads
4118 change the value of @var{expr}, @value{GDBN} will not break. Note
4119 that watchpoints restricted to a single thread in this way only work
4120 with Hardware Watchpoints.
4122 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4123 (see below). The @code{-location} argument tells @value{GDBN} to
4124 instead watch the memory referred to by @var{expr}. In this case,
4125 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4126 and watch the memory at that address. The type of the result is used
4127 to determine the size of the watched memory. If the expression's
4128 result does not have an address, then @value{GDBN} will print an
4131 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4132 of masked watchpoints, if the current architecture supports this
4133 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4134 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4135 to an address to watch. The mask specifies that some bits of an address
4136 (the bits which are reset in the mask) should be ignored when matching
4137 the address accessed by the inferior against the watchpoint address.
4138 Thus, a masked watchpoint watches many addresses simultaneously---those
4139 addresses whose unmasked bits are identical to the unmasked bits in the
4140 watchpoint address. The @code{mask} argument implies @code{-location}.
4144 (@value{GDBP}) watch foo mask 0xffff00ff
4145 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4149 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4150 Set a watchpoint that will break when the value of @var{expr} is read
4154 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4155 Set a watchpoint that will break when @var{expr} is either read from
4156 or written into by the program.
4158 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4159 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4160 This command prints a list of watchpoints, using the same format as
4161 @code{info break} (@pxref{Set Breaks}).
4164 If you watch for a change in a numerically entered address you need to
4165 dereference it, as the address itself is just a constant number which will
4166 never change. @value{GDBN} refuses to create a watchpoint that watches
4167 a never-changing value:
4170 (@value{GDBP}) watch 0x600850
4171 Cannot watch constant value 0x600850.
4172 (@value{GDBP}) watch *(int *) 0x600850
4173 Watchpoint 1: *(int *) 6293584
4176 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4177 watchpoints execute very quickly, and the debugger reports a change in
4178 value at the exact instruction where the change occurs. If @value{GDBN}
4179 cannot set a hardware watchpoint, it sets a software watchpoint, which
4180 executes more slowly and reports the change in value at the next
4181 @emph{statement}, not the instruction, after the change occurs.
4183 @cindex use only software watchpoints
4184 You can force @value{GDBN} to use only software watchpoints with the
4185 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4186 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4187 the underlying system supports them. (Note that hardware-assisted
4188 watchpoints that were set @emph{before} setting
4189 @code{can-use-hw-watchpoints} to zero will still use the hardware
4190 mechanism of watching expression values.)
4193 @item set can-use-hw-watchpoints
4194 @kindex set can-use-hw-watchpoints
4195 Set whether or not to use hardware watchpoints.
4197 @item show can-use-hw-watchpoints
4198 @kindex show can-use-hw-watchpoints
4199 Show the current mode of using hardware watchpoints.
4202 For remote targets, you can restrict the number of hardware
4203 watchpoints @value{GDBN} will use, see @ref{set remote
4204 hardware-breakpoint-limit}.
4206 When you issue the @code{watch} command, @value{GDBN} reports
4209 Hardware watchpoint @var{num}: @var{expr}
4213 if it was able to set a hardware watchpoint.
4215 Currently, the @code{awatch} and @code{rwatch} commands can only set
4216 hardware watchpoints, because accesses to data that don't change the
4217 value of the watched expression cannot be detected without examining
4218 every instruction as it is being executed, and @value{GDBN} does not do
4219 that currently. If @value{GDBN} finds that it is unable to set a
4220 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4221 will print a message like this:
4224 Expression cannot be implemented with read/access watchpoint.
4227 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4228 data type of the watched expression is wider than what a hardware
4229 watchpoint on the target machine can handle. For example, some systems
4230 can only watch regions that are up to 4 bytes wide; on such systems you
4231 cannot set hardware watchpoints for an expression that yields a
4232 double-precision floating-point number (which is typically 8 bytes
4233 wide). As a work-around, it might be possible to break the large region
4234 into a series of smaller ones and watch them with separate watchpoints.
4236 If you set too many hardware watchpoints, @value{GDBN} might be unable
4237 to insert all of them when you resume the execution of your program.
4238 Since the precise number of active watchpoints is unknown until such
4239 time as the program is about to be resumed, @value{GDBN} might not be
4240 able to warn you about this when you set the watchpoints, and the
4241 warning will be printed only when the program is resumed:
4244 Hardware watchpoint @var{num}: Could not insert watchpoint
4248 If this happens, delete or disable some of the watchpoints.
4250 Watching complex expressions that reference many variables can also
4251 exhaust the resources available for hardware-assisted watchpoints.
4252 That's because @value{GDBN} needs to watch every variable in the
4253 expression with separately allocated resources.
4255 If you call a function interactively using @code{print} or @code{call},
4256 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4257 kind of breakpoint or the call completes.
4259 @value{GDBN} automatically deletes watchpoints that watch local
4260 (automatic) variables, or expressions that involve such variables, when
4261 they go out of scope, that is, when the execution leaves the block in
4262 which these variables were defined. In particular, when the program
4263 being debugged terminates, @emph{all} local variables go out of scope,
4264 and so only watchpoints that watch global variables remain set. If you
4265 rerun the program, you will need to set all such watchpoints again. One
4266 way of doing that would be to set a code breakpoint at the entry to the
4267 @code{main} function and when it breaks, set all the watchpoints.
4269 @cindex watchpoints and threads
4270 @cindex threads and watchpoints
4271 In multi-threaded programs, watchpoints will detect changes to the
4272 watched expression from every thread.
4275 @emph{Warning:} In multi-threaded programs, software watchpoints
4276 have only limited usefulness. If @value{GDBN} creates a software
4277 watchpoint, it can only watch the value of an expression @emph{in a
4278 single thread}. If you are confident that the expression can only
4279 change due to the current thread's activity (and if you are also
4280 confident that no other thread can become current), then you can use
4281 software watchpoints as usual. However, @value{GDBN} may not notice
4282 when a non-current thread's activity changes the expression. (Hardware
4283 watchpoints, in contrast, watch an expression in all threads.)
4286 @xref{set remote hardware-watchpoint-limit}.
4288 @node Set Catchpoints
4289 @subsection Setting Catchpoints
4290 @cindex catchpoints, setting
4291 @cindex exception handlers
4292 @cindex event handling
4294 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4295 kinds of program events, such as C@t{++} exceptions or the loading of a
4296 shared library. Use the @code{catch} command to set a catchpoint.
4300 @item catch @var{event}
4301 Stop when @var{event} occurs. The @var{event} can be any of the following:
4304 @item throw @r{[}@var{regexp}@r{]}
4305 @itemx rethrow @r{[}@var{regexp}@r{]}
4306 @itemx catch @r{[}@var{regexp}@r{]}
4308 @kindex catch rethrow
4310 @cindex stop on C@t{++} exceptions
4311 The throwing, re-throwing, or catching of a C@t{++} exception.
4313 If @var{regexp} is given, then only exceptions whose type matches the
4314 regular expression will be caught.
4316 @vindex $_exception@r{, convenience variable}
4317 The convenience variable @code{$_exception} is available at an
4318 exception-related catchpoint, on some systems. This holds the
4319 exception being thrown.
4321 There are currently some limitations to C@t{++} exception handling in
4326 The support for these commands is system-dependent. Currently, only
4327 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4331 The regular expression feature and the @code{$_exception} convenience
4332 variable rely on the presence of some SDT probes in @code{libstdc++}.
4333 If these probes are not present, then these features cannot be used.
4334 These probes were first available in the GCC 4.8 release, but whether
4335 or not they are available in your GCC also depends on how it was
4339 The @code{$_exception} convenience variable is only valid at the
4340 instruction at which an exception-related catchpoint is set.
4343 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4344 location in the system library which implements runtime exception
4345 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4346 (@pxref{Selection}) to get to your code.
4349 If you call a function interactively, @value{GDBN} normally returns
4350 control to you when the function has finished executing. If the call
4351 raises an exception, however, the call may bypass the mechanism that
4352 returns control to you and cause your program either to abort or to
4353 simply continue running until it hits a breakpoint, catches a signal
4354 that @value{GDBN} is listening for, or exits. This is the case even if
4355 you set a catchpoint for the exception; catchpoints on exceptions are
4356 disabled within interactive calls. @xref{Calling}, for information on
4357 controlling this with @code{set unwind-on-terminating-exception}.
4360 You cannot raise an exception interactively.
4363 You cannot install an exception handler interactively.
4367 @kindex catch exception
4368 @cindex Ada exception catching
4369 @cindex catch Ada exceptions
4370 An Ada exception being raised. If an exception name is specified
4371 at the end of the command (eg @code{catch exception Program_Error}),
4372 the debugger will stop only when this specific exception is raised.
4373 Otherwise, the debugger stops execution when any Ada exception is raised.
4375 When inserting an exception catchpoint on a user-defined exception whose
4376 name is identical to one of the exceptions defined by the language, the
4377 fully qualified name must be used as the exception name. Otherwise,
4378 @value{GDBN} will assume that it should stop on the pre-defined exception
4379 rather than the user-defined one. For instance, assuming an exception
4380 called @code{Constraint_Error} is defined in package @code{Pck}, then
4381 the command to use to catch such exceptions is @kbd{catch exception
4382 Pck.Constraint_Error}.
4384 @item exception unhandled
4385 @kindex catch exception unhandled
4386 An exception that was raised but is not handled by the program.
4389 @kindex catch assert
4390 A failed Ada assertion.
4394 @cindex break on fork/exec
4395 A call to @code{exec}.
4398 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4399 @kindex catch syscall
4400 @cindex break on a system call.
4401 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4402 syscall is a mechanism for application programs to request a service
4403 from the operating system (OS) or one of the OS system services.
4404 @value{GDBN} can catch some or all of the syscalls issued by the
4405 debuggee, and show the related information for each syscall. If no
4406 argument is specified, calls to and returns from all system calls
4409 @var{name} can be any system call name that is valid for the
4410 underlying OS. Just what syscalls are valid depends on the OS. On
4411 GNU and Unix systems, you can find the full list of valid syscall
4412 names on @file{/usr/include/asm/unistd.h}.
4414 @c For MS-Windows, the syscall names and the corresponding numbers
4415 @c can be found, e.g., on this URL:
4416 @c http://www.metasploit.com/users/opcode/syscalls.html
4417 @c but we don't support Windows syscalls yet.
4419 Normally, @value{GDBN} knows in advance which syscalls are valid for
4420 each OS, so you can use the @value{GDBN} command-line completion
4421 facilities (@pxref{Completion,, command completion}) to list the
4424 You may also specify the system call numerically. A syscall's
4425 number is the value passed to the OS's syscall dispatcher to
4426 identify the requested service. When you specify the syscall by its
4427 name, @value{GDBN} uses its database of syscalls to convert the name
4428 into the corresponding numeric code, but using the number directly
4429 may be useful if @value{GDBN}'s database does not have the complete
4430 list of syscalls on your system (e.g., because @value{GDBN} lags
4431 behind the OS upgrades).
4433 You may specify a group of related syscalls to be caught at once using
4434 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4435 instance, on some platforms @value{GDBN} allows you to catch all
4436 network related syscalls, by passing the argument @code{group:network}
4437 to @code{catch syscall}. Note that not all syscall groups are
4438 available in every system. You can use the command completion
4439 facilities (@pxref{Completion,, command completion}) to list the
4440 syscall groups available on your environment.
4442 The example below illustrates how this command works if you don't provide
4446 (@value{GDBP}) catch syscall
4447 Catchpoint 1 (syscall)
4449 Starting program: /tmp/catch-syscall
4451 Catchpoint 1 (call to syscall 'close'), \
4452 0xffffe424 in __kernel_vsyscall ()
4456 Catchpoint 1 (returned from syscall 'close'), \
4457 0xffffe424 in __kernel_vsyscall ()
4461 Here is an example of catching a system call by name:
4464 (@value{GDBP}) catch syscall chroot
4465 Catchpoint 1 (syscall 'chroot' [61])
4467 Starting program: /tmp/catch-syscall
4469 Catchpoint 1 (call to syscall 'chroot'), \
4470 0xffffe424 in __kernel_vsyscall ()
4474 Catchpoint 1 (returned from syscall 'chroot'), \
4475 0xffffe424 in __kernel_vsyscall ()
4479 An example of specifying a system call numerically. In the case
4480 below, the syscall number has a corresponding entry in the XML
4481 file, so @value{GDBN} finds its name and prints it:
4484 (@value{GDBP}) catch syscall 252
4485 Catchpoint 1 (syscall(s) 'exit_group')
4487 Starting program: /tmp/catch-syscall
4489 Catchpoint 1 (call to syscall 'exit_group'), \
4490 0xffffe424 in __kernel_vsyscall ()
4494 Program exited normally.
4498 Here is an example of catching a syscall group:
4501 (@value{GDBP}) catch syscall group:process
4502 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4503 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4504 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4506 Starting program: /tmp/catch-syscall
4508 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4509 from /lib64/ld-linux-x86-64.so.2
4515 However, there can be situations when there is no corresponding name
4516 in XML file for that syscall number. In this case, @value{GDBN} prints
4517 a warning message saying that it was not able to find the syscall name,
4518 but the catchpoint will be set anyway. See the example below:
4521 (@value{GDBP}) catch syscall 764
4522 warning: The number '764' does not represent a known syscall.
4523 Catchpoint 2 (syscall 764)
4527 If you configure @value{GDBN} using the @samp{--without-expat} option,
4528 it will not be able to display syscall names. Also, if your
4529 architecture does not have an XML file describing its system calls,
4530 you will not be able to see the syscall names. It is important to
4531 notice that these two features are used for accessing the syscall
4532 name database. In either case, you will see a warning like this:
4535 (@value{GDBP}) catch syscall
4536 warning: Could not open "syscalls/i386-linux.xml"
4537 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4538 GDB will not be able to display syscall names.
4539 Catchpoint 1 (syscall)
4543 Of course, the file name will change depending on your architecture and system.
4545 Still using the example above, you can also try to catch a syscall by its
4546 number. In this case, you would see something like:
4549 (@value{GDBP}) catch syscall 252
4550 Catchpoint 1 (syscall(s) 252)
4553 Again, in this case @value{GDBN} would not be able to display syscall's names.
4557 A call to @code{fork}.
4561 A call to @code{vfork}.
4563 @item load @r{[}regexp@r{]}
4564 @itemx unload @r{[}regexp@r{]}
4566 @kindex catch unload
4567 The loading or unloading of a shared library. If @var{regexp} is
4568 given, then the catchpoint will stop only if the regular expression
4569 matches one of the affected libraries.
4571 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4572 @kindex catch signal
4573 The delivery of a signal.
4575 With no arguments, this catchpoint will catch any signal that is not
4576 used internally by @value{GDBN}, specifically, all signals except
4577 @samp{SIGTRAP} and @samp{SIGINT}.
4579 With the argument @samp{all}, all signals, including those used by
4580 @value{GDBN}, will be caught. This argument cannot be used with other
4583 Otherwise, the arguments are a list of signal names as given to
4584 @code{handle} (@pxref{Signals}). Only signals specified in this list
4587 One reason that @code{catch signal} can be more useful than
4588 @code{handle} is that you can attach commands and conditions to the
4591 When a signal is caught by a catchpoint, the signal's @code{stop} and
4592 @code{print} settings, as specified by @code{handle}, are ignored.
4593 However, whether the signal is still delivered to the inferior depends
4594 on the @code{pass} setting; this can be changed in the catchpoint's
4599 @item tcatch @var{event}
4601 Set a catchpoint that is enabled only for one stop. The catchpoint is
4602 automatically deleted after the first time the event is caught.
4606 Use the @code{info break} command to list the current catchpoints.
4610 @subsection Deleting Breakpoints
4612 @cindex clearing breakpoints, watchpoints, catchpoints
4613 @cindex deleting breakpoints, watchpoints, catchpoints
4614 It is often necessary to eliminate a breakpoint, watchpoint, or
4615 catchpoint once it has done its job and you no longer want your program
4616 to stop there. This is called @dfn{deleting} the breakpoint. A
4617 breakpoint that has been deleted no longer exists; it is forgotten.
4619 With the @code{clear} command you can delete breakpoints according to
4620 where they are in your program. With the @code{delete} command you can
4621 delete individual breakpoints, watchpoints, or catchpoints by specifying
4622 their breakpoint numbers.
4624 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4625 automatically ignores breakpoints on the first instruction to be executed
4626 when you continue execution without changing the execution address.
4631 Delete any breakpoints at the next instruction to be executed in the
4632 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4633 the innermost frame is selected, this is a good way to delete a
4634 breakpoint where your program just stopped.
4636 @item clear @var{location}
4637 Delete any breakpoints set at the specified @var{location}.
4638 @xref{Specify Location}, for the various forms of @var{location}; the
4639 most useful ones are listed below:
4642 @item clear @var{function}
4643 @itemx clear @var{filename}:@var{function}
4644 Delete any breakpoints set at entry to the named @var{function}.
4646 @item clear @var{linenum}
4647 @itemx clear @var{filename}:@var{linenum}
4648 Delete any breakpoints set at or within the code of the specified
4649 @var{linenum} of the specified @var{filename}.
4652 @cindex delete breakpoints
4654 @kindex d @r{(@code{delete})}
4655 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4656 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4657 list specified as argument. If no argument is specified, delete all
4658 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4659 confirm off}). You can abbreviate this command as @code{d}.
4663 @subsection Disabling Breakpoints
4665 @cindex enable/disable a breakpoint
4666 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4667 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4668 it had been deleted, but remembers the information on the breakpoint so
4669 that you can @dfn{enable} it again later.
4671 You disable and enable breakpoints, watchpoints, and catchpoints with
4672 the @code{enable} and @code{disable} commands, optionally specifying
4673 one or more breakpoint numbers as arguments. Use @code{info break} to
4674 print a list of all breakpoints, watchpoints, and catchpoints if you
4675 do not know which numbers to use.
4677 Disabling and enabling a breakpoint that has multiple locations
4678 affects all of its locations.
4680 A breakpoint, watchpoint, or catchpoint can have any of several
4681 different states of enablement:
4685 Enabled. The breakpoint stops your program. A breakpoint set
4686 with the @code{break} command starts out in this state.
4688 Disabled. The breakpoint has no effect on your program.
4690 Enabled once. The breakpoint stops your program, but then becomes
4693 Enabled for a count. The breakpoint stops your program for the next
4694 N times, then becomes disabled.
4696 Enabled for deletion. The breakpoint stops your program, but
4697 immediately after it does so it is deleted permanently. A breakpoint
4698 set with the @code{tbreak} command starts out in this state.
4701 You can use the following commands to enable or disable breakpoints,
4702 watchpoints, and catchpoints:
4706 @kindex dis @r{(@code{disable})}
4707 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4708 Disable the specified breakpoints---or all breakpoints, if none are
4709 listed. A disabled breakpoint has no effect but is not forgotten. All
4710 options such as ignore-counts, conditions and commands are remembered in
4711 case the breakpoint is enabled again later. You may abbreviate
4712 @code{disable} as @code{dis}.
4715 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4716 Enable the specified breakpoints (or all defined breakpoints). They
4717 become effective once again in stopping your program.
4719 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4720 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4721 of these breakpoints immediately after stopping your program.
4723 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4724 Enable the specified breakpoints temporarily. @value{GDBN} records
4725 @var{count} with each of the specified breakpoints, and decrements a
4726 breakpoint's count when it is hit. When any count reaches 0,
4727 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4728 count (@pxref{Conditions, ,Break Conditions}), that will be
4729 decremented to 0 before @var{count} is affected.
4731 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4732 Enable the specified breakpoints to work once, then die. @value{GDBN}
4733 deletes any of these breakpoints as soon as your program stops there.
4734 Breakpoints set by the @code{tbreak} command start out in this state.
4737 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4738 @c confusing: tbreak is also initially enabled.
4739 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4740 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4741 subsequently, they become disabled or enabled only when you use one of
4742 the commands above. (The command @code{until} can set and delete a
4743 breakpoint of its own, but it does not change the state of your other
4744 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4748 @subsection Break Conditions
4749 @cindex conditional breakpoints
4750 @cindex breakpoint conditions
4752 @c FIXME what is scope of break condition expr? Context where wanted?
4753 @c in particular for a watchpoint?
4754 The simplest sort of breakpoint breaks every time your program reaches a
4755 specified place. You can also specify a @dfn{condition} for a
4756 breakpoint. A condition is just a Boolean expression in your
4757 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4758 a condition evaluates the expression each time your program reaches it,
4759 and your program stops only if the condition is @emph{true}.
4761 This is the converse of using assertions for program validation; in that
4762 situation, you want to stop when the assertion is violated---that is,
4763 when the condition is false. In C, if you want to test an assertion expressed
4764 by the condition @var{assert}, you should set the condition
4765 @samp{! @var{assert}} on the appropriate breakpoint.
4767 Conditions are also accepted for watchpoints; you may not need them,
4768 since a watchpoint is inspecting the value of an expression anyhow---but
4769 it might be simpler, say, to just set a watchpoint on a variable name,
4770 and specify a condition that tests whether the new value is an interesting
4773 Break conditions can have side effects, and may even call functions in
4774 your program. This can be useful, for example, to activate functions
4775 that log program progress, or to use your own print functions to
4776 format special data structures. The effects are completely predictable
4777 unless there is another enabled breakpoint at the same address. (In
4778 that case, @value{GDBN} might see the other breakpoint first and stop your
4779 program without checking the condition of this one.) Note that
4780 breakpoint commands are usually more convenient and flexible than break
4782 purpose of performing side effects when a breakpoint is reached
4783 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4785 Breakpoint conditions can also be evaluated on the target's side if
4786 the target supports it. Instead of evaluating the conditions locally,
4787 @value{GDBN} encodes the expression into an agent expression
4788 (@pxref{Agent Expressions}) suitable for execution on the target,
4789 independently of @value{GDBN}. Global variables become raw memory
4790 locations, locals become stack accesses, and so forth.
4792 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4793 when its condition evaluates to true. This mechanism may provide faster
4794 response times depending on the performance characteristics of the target
4795 since it does not need to keep @value{GDBN} informed about
4796 every breakpoint trigger, even those with false conditions.
4798 Break conditions can be specified when a breakpoint is set, by using
4799 @samp{if} in the arguments to the @code{break} command. @xref{Set
4800 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4801 with the @code{condition} command.
4803 You can also use the @code{if} keyword with the @code{watch} command.
4804 The @code{catch} command does not recognize the @code{if} keyword;
4805 @code{condition} is the only way to impose a further condition on a
4810 @item condition @var{bnum} @var{expression}
4811 Specify @var{expression} as the break condition for breakpoint,
4812 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4813 breakpoint @var{bnum} stops your program only if the value of
4814 @var{expression} is true (nonzero, in C). When you use
4815 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4816 syntactic correctness, and to determine whether symbols in it have
4817 referents in the context of your breakpoint. If @var{expression} uses
4818 symbols not referenced in the context of the breakpoint, @value{GDBN}
4819 prints an error message:
4822 No symbol "foo" in current context.
4827 not actually evaluate @var{expression} at the time the @code{condition}
4828 command (or a command that sets a breakpoint with a condition, like
4829 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4831 @item condition @var{bnum}
4832 Remove the condition from breakpoint number @var{bnum}. It becomes
4833 an ordinary unconditional breakpoint.
4836 @cindex ignore count (of breakpoint)
4837 A special case of a breakpoint condition is to stop only when the
4838 breakpoint has been reached a certain number of times. This is so
4839 useful that there is a special way to do it, using the @dfn{ignore
4840 count} of the breakpoint. Every breakpoint has an ignore count, which
4841 is an integer. Most of the time, the ignore count is zero, and
4842 therefore has no effect. But if your program reaches a breakpoint whose
4843 ignore count is positive, then instead of stopping, it just decrements
4844 the ignore count by one and continues. As a result, if the ignore count
4845 value is @var{n}, the breakpoint does not stop the next @var{n} times
4846 your program reaches it.
4850 @item ignore @var{bnum} @var{count}
4851 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4852 The next @var{count} times the breakpoint is reached, your program's
4853 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4856 To make the breakpoint stop the next time it is reached, specify
4859 When you use @code{continue} to resume execution of your program from a
4860 breakpoint, you can specify an ignore count directly as an argument to
4861 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4862 Stepping,,Continuing and Stepping}.
4864 If a breakpoint has a positive ignore count and a condition, the
4865 condition is not checked. Once the ignore count reaches zero,
4866 @value{GDBN} resumes checking the condition.
4868 You could achieve the effect of the ignore count with a condition such
4869 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4870 is decremented each time. @xref{Convenience Vars, ,Convenience
4874 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4877 @node Break Commands
4878 @subsection Breakpoint Command Lists
4880 @cindex breakpoint commands
4881 You can give any breakpoint (or watchpoint or catchpoint) a series of
4882 commands to execute when your program stops due to that breakpoint. For
4883 example, you might want to print the values of certain expressions, or
4884 enable other breakpoints.
4888 @kindex end@r{ (breakpoint commands)}
4889 @item commands @r{[}@var{list}@dots{}@r{]}
4890 @itemx @dots{} @var{command-list} @dots{}
4892 Specify a list of commands for the given breakpoints. The commands
4893 themselves appear on the following lines. Type a line containing just
4894 @code{end} to terminate the commands.
4896 To remove all commands from a breakpoint, type @code{commands} and
4897 follow it immediately with @code{end}; that is, give no commands.
4899 With no argument, @code{commands} refers to the last breakpoint,
4900 watchpoint, or catchpoint set (not to the breakpoint most recently
4901 encountered). If the most recent breakpoints were set with a single
4902 command, then the @code{commands} will apply to all the breakpoints
4903 set by that command. This applies to breakpoints set by
4904 @code{rbreak}, and also applies when a single @code{break} command
4905 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4909 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4910 disabled within a @var{command-list}.
4912 You can use breakpoint commands to start your program up again. Simply
4913 use the @code{continue} command, or @code{step}, or any other command
4914 that resumes execution.
4916 Any other commands in the command list, after a command that resumes
4917 execution, are ignored. This is because any time you resume execution
4918 (even with a simple @code{next} or @code{step}), you may encounter
4919 another breakpoint---which could have its own command list, leading to
4920 ambiguities about which list to execute.
4923 If the first command you specify in a command list is @code{silent}, the
4924 usual message about stopping at a breakpoint is not printed. This may
4925 be desirable for breakpoints that are to print a specific message and
4926 then continue. If none of the remaining commands print anything, you
4927 see no sign that the breakpoint was reached. @code{silent} is
4928 meaningful only at the beginning of a breakpoint command list.
4930 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4931 print precisely controlled output, and are often useful in silent
4932 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4934 For example, here is how you could use breakpoint commands to print the
4935 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4941 printf "x is %d\n",x
4946 One application for breakpoint commands is to compensate for one bug so
4947 you can test for another. Put a breakpoint just after the erroneous line
4948 of code, give it a condition to detect the case in which something
4949 erroneous has been done, and give it commands to assign correct values
4950 to any variables that need them. End with the @code{continue} command
4951 so that your program does not stop, and start with the @code{silent}
4952 command so that no output is produced. Here is an example:
4963 @node Dynamic Printf
4964 @subsection Dynamic Printf
4966 @cindex dynamic printf
4968 The dynamic printf command @code{dprintf} combines a breakpoint with
4969 formatted printing of your program's data to give you the effect of
4970 inserting @code{printf} calls into your program on-the-fly, without
4971 having to recompile it.
4973 In its most basic form, the output goes to the GDB console. However,
4974 you can set the variable @code{dprintf-style} for alternate handling.
4975 For instance, you can ask to format the output by calling your
4976 program's @code{printf} function. This has the advantage that the
4977 characters go to the program's output device, so they can recorded in
4978 redirects to files and so forth.
4980 If you are doing remote debugging with a stub or agent, you can also
4981 ask to have the printf handled by the remote agent. In addition to
4982 ensuring that the output goes to the remote program's device along
4983 with any other output the program might produce, you can also ask that
4984 the dprintf remain active even after disconnecting from the remote
4985 target. Using the stub/agent is also more efficient, as it can do
4986 everything without needing to communicate with @value{GDBN}.
4990 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4991 Whenever execution reaches @var{location}, print the values of one or
4992 more @var{expressions} under the control of the string @var{template}.
4993 To print several values, separate them with commas.
4995 @item set dprintf-style @var{style}
4996 Set the dprintf output to be handled in one of several different
4997 styles enumerated below. A change of style affects all existing
4998 dynamic printfs immediately. (If you need individual control over the
4999 print commands, simply define normal breakpoints with
5000 explicitly-supplied command lists.)
5004 @kindex dprintf-style gdb
5005 Handle the output using the @value{GDBN} @code{printf} command.
5008 @kindex dprintf-style call
5009 Handle the output by calling a function in your program (normally
5013 @kindex dprintf-style agent
5014 Have the remote debugging agent (such as @code{gdbserver}) handle
5015 the output itself. This style is only available for agents that
5016 support running commands on the target.
5019 @item set dprintf-function @var{function}
5020 Set the function to call if the dprintf style is @code{call}. By
5021 default its value is @code{printf}. You may set it to any expression.
5022 that @value{GDBN} can evaluate to a function, as per the @code{call}
5025 @item set dprintf-channel @var{channel}
5026 Set a ``channel'' for dprintf. If set to a non-empty value,
5027 @value{GDBN} will evaluate it as an expression and pass the result as
5028 a first argument to the @code{dprintf-function}, in the manner of
5029 @code{fprintf} and similar functions. Otherwise, the dprintf format
5030 string will be the first argument, in the manner of @code{printf}.
5032 As an example, if you wanted @code{dprintf} output to go to a logfile
5033 that is a standard I/O stream assigned to the variable @code{mylog},
5034 you could do the following:
5037 (gdb) set dprintf-style call
5038 (gdb) set dprintf-function fprintf
5039 (gdb) set dprintf-channel mylog
5040 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5041 Dprintf 1 at 0x123456: file main.c, line 25.
5043 1 dprintf keep y 0x00123456 in main at main.c:25
5044 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5049 Note that the @code{info break} displays the dynamic printf commands
5050 as normal breakpoint commands; you can thus easily see the effect of
5051 the variable settings.
5053 @item set disconnected-dprintf on
5054 @itemx set disconnected-dprintf off
5055 @kindex set disconnected-dprintf
5056 Choose whether @code{dprintf} commands should continue to run if
5057 @value{GDBN} has disconnected from the target. This only applies
5058 if the @code{dprintf-style} is @code{agent}.
5060 @item show disconnected-dprintf off
5061 @kindex show disconnected-dprintf
5062 Show the current choice for disconnected @code{dprintf}.
5066 @value{GDBN} does not check the validity of function and channel,
5067 relying on you to supply values that are meaningful for the contexts
5068 in which they are being used. For instance, the function and channel
5069 may be the values of local variables, but if that is the case, then
5070 all enabled dynamic prints must be at locations within the scope of
5071 those locals. If evaluation fails, @value{GDBN} will report an error.
5073 @node Save Breakpoints
5074 @subsection How to save breakpoints to a file
5076 To save breakpoint definitions to a file use the @w{@code{save
5077 breakpoints}} command.
5080 @kindex save breakpoints
5081 @cindex save breakpoints to a file for future sessions
5082 @item save breakpoints [@var{filename}]
5083 This command saves all current breakpoint definitions together with
5084 their commands and ignore counts, into a file @file{@var{filename}}
5085 suitable for use in a later debugging session. This includes all
5086 types of breakpoints (breakpoints, watchpoints, catchpoints,
5087 tracepoints). To read the saved breakpoint definitions, use the
5088 @code{source} command (@pxref{Command Files}). Note that watchpoints
5089 with expressions involving local variables may fail to be recreated
5090 because it may not be possible to access the context where the
5091 watchpoint is valid anymore. Because the saved breakpoint definitions
5092 are simply a sequence of @value{GDBN} commands that recreate the
5093 breakpoints, you can edit the file in your favorite editing program,
5094 and remove the breakpoint definitions you're not interested in, or
5095 that can no longer be recreated.
5098 @node Static Probe Points
5099 @subsection Static Probe Points
5101 @cindex static probe point, SystemTap
5102 @cindex static probe point, DTrace
5103 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5104 for Statically Defined Tracing, and the probes are designed to have a tiny
5105 runtime code and data footprint, and no dynamic relocations.
5107 Currently, the following types of probes are supported on
5108 ELF-compatible systems:
5112 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5113 @acronym{SDT} probes@footnote{See
5114 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5115 for more information on how to add @code{SystemTap} @acronym{SDT}
5116 probes in your applications.}. @code{SystemTap} probes are usable
5117 from assembly, C and C@t{++} languages@footnote{See
5118 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5119 for a good reference on how the @acronym{SDT} probes are implemented.}.
5121 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5122 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5126 @cindex semaphores on static probe points
5127 Some @code{SystemTap} probes have an associated semaphore variable;
5128 for instance, this happens automatically if you defined your probe
5129 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5130 @value{GDBN} will automatically enable it when you specify a
5131 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5132 breakpoint at a probe's location by some other method (e.g.,
5133 @code{break file:line}), then @value{GDBN} will not automatically set
5134 the semaphore. @code{DTrace} probes do not support semaphores.
5136 You can examine the available static static probes using @code{info
5137 probes}, with optional arguments:
5141 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5142 If given, @var{type} is either @code{stap} for listing
5143 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5144 probes. If omitted all probes are listed regardless of their types.
5146 If given, @var{provider} is a regular expression used to match against provider
5147 names when selecting which probes to list. If omitted, probes by all
5148 probes from all providers are listed.
5150 If given, @var{name} is a regular expression to match against probe names
5151 when selecting which probes to list. If omitted, probe names are not
5152 considered when deciding whether to display them.
5154 If given, @var{objfile} is a regular expression used to select which
5155 object files (executable or shared libraries) to examine. If not
5156 given, all object files are considered.
5158 @item info probes all
5159 List the available static probes, from all types.
5162 @cindex enabling and disabling probes
5163 Some probe points can be enabled and/or disabled. The effect of
5164 enabling or disabling a probe depends on the type of probe being
5165 handled. Some @code{DTrace} probes can be enabled or
5166 disabled, but @code{SystemTap} probes cannot be disabled.
5168 You can enable (or disable) one or more probes using the following
5169 commands, with optional arguments:
5172 @kindex enable probes
5173 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5174 If given, @var{provider} is a regular expression used to match against
5175 provider names when selecting which probes to enable. If omitted,
5176 all probes from all providers are enabled.
5178 If given, @var{name} is a regular expression to match against probe
5179 names when selecting which probes to enable. If omitted, probe names
5180 are not considered when deciding whether to enable them.
5182 If given, @var{objfile} is a regular expression used to select which
5183 object files (executable or shared libraries) to examine. If not
5184 given, all object files are considered.
5186 @kindex disable probes
5187 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5188 See the @code{enable probes} command above for a description of the
5189 optional arguments accepted by this command.
5192 @vindex $_probe_arg@r{, convenience variable}
5193 A probe may specify up to twelve arguments. These are available at the
5194 point at which the probe is defined---that is, when the current PC is
5195 at the probe's location. The arguments are available using the
5196 convenience variables (@pxref{Convenience Vars})
5197 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5198 probes each probe argument is an integer of the appropriate size;
5199 types are not preserved. In @code{DTrace} probes types are preserved
5200 provided that they are recognized as such by @value{GDBN}; otherwise
5201 the value of the probe argument will be a long integer. The
5202 convenience variable @code{$_probe_argc} holds the number of arguments
5203 at the current probe point.
5205 These variables are always available, but attempts to access them at
5206 any location other than a probe point will cause @value{GDBN} to give
5210 @c @ifclear BARETARGET
5211 @node Error in Breakpoints
5212 @subsection ``Cannot insert breakpoints''
5214 If you request too many active hardware-assisted breakpoints and
5215 watchpoints, you will see this error message:
5217 @c FIXME: the precise wording of this message may change; the relevant
5218 @c source change is not committed yet (Sep 3, 1999).
5220 Stopped; cannot insert breakpoints.
5221 You may have requested too many hardware breakpoints and watchpoints.
5225 This message is printed when you attempt to resume the program, since
5226 only then @value{GDBN} knows exactly how many hardware breakpoints and
5227 watchpoints it needs to insert.
5229 When this message is printed, you need to disable or remove some of the
5230 hardware-assisted breakpoints and watchpoints, and then continue.
5232 @node Breakpoint-related Warnings
5233 @subsection ``Breakpoint address adjusted...''
5234 @cindex breakpoint address adjusted
5236 Some processor architectures place constraints on the addresses at
5237 which breakpoints may be placed. For architectures thus constrained,
5238 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5239 with the constraints dictated by the architecture.
5241 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5242 a VLIW architecture in which a number of RISC-like instructions may be
5243 bundled together for parallel execution. The FR-V architecture
5244 constrains the location of a breakpoint instruction within such a
5245 bundle to the instruction with the lowest address. @value{GDBN}
5246 honors this constraint by adjusting a breakpoint's address to the
5247 first in the bundle.
5249 It is not uncommon for optimized code to have bundles which contain
5250 instructions from different source statements, thus it may happen that
5251 a breakpoint's address will be adjusted from one source statement to
5252 another. Since this adjustment may significantly alter @value{GDBN}'s
5253 breakpoint related behavior from what the user expects, a warning is
5254 printed when the breakpoint is first set and also when the breakpoint
5257 A warning like the one below is printed when setting a breakpoint
5258 that's been subject to address adjustment:
5261 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5264 Such warnings are printed both for user settable and @value{GDBN}'s
5265 internal breakpoints. If you see one of these warnings, you should
5266 verify that a breakpoint set at the adjusted address will have the
5267 desired affect. If not, the breakpoint in question may be removed and
5268 other breakpoints may be set which will have the desired behavior.
5269 E.g., it may be sufficient to place the breakpoint at a later
5270 instruction. A conditional breakpoint may also be useful in some
5271 cases to prevent the breakpoint from triggering too often.
5273 @value{GDBN} will also issue a warning when stopping at one of these
5274 adjusted breakpoints:
5277 warning: Breakpoint 1 address previously adjusted from 0x00010414
5281 When this warning is encountered, it may be too late to take remedial
5282 action except in cases where the breakpoint is hit earlier or more
5283 frequently than expected.
5285 @node Continuing and Stepping
5286 @section Continuing and Stepping
5290 @cindex resuming execution
5291 @dfn{Continuing} means resuming program execution until your program
5292 completes normally. In contrast, @dfn{stepping} means executing just
5293 one more ``step'' of your program, where ``step'' may mean either one
5294 line of source code, or one machine instruction (depending on what
5295 particular command you use). Either when continuing or when stepping,
5296 your program may stop even sooner, due to a breakpoint or a signal. (If
5297 it stops due to a signal, you may want to use @code{handle}, or use
5298 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5299 or you may step into the signal's handler (@pxref{stepping and signal
5304 @kindex c @r{(@code{continue})}
5305 @kindex fg @r{(resume foreground execution)}
5306 @item continue @r{[}@var{ignore-count}@r{]}
5307 @itemx c @r{[}@var{ignore-count}@r{]}
5308 @itemx fg @r{[}@var{ignore-count}@r{]}
5309 Resume program execution, at the address where your program last stopped;
5310 any breakpoints set at that address are bypassed. The optional argument
5311 @var{ignore-count} allows you to specify a further number of times to
5312 ignore a breakpoint at this location; its effect is like that of
5313 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5315 The argument @var{ignore-count} is meaningful only when your program
5316 stopped due to a breakpoint. At other times, the argument to
5317 @code{continue} is ignored.
5319 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5320 debugged program is deemed to be the foreground program) are provided
5321 purely for convenience, and have exactly the same behavior as
5325 To resume execution at a different place, you can use @code{return}
5326 (@pxref{Returning, ,Returning from a Function}) to go back to the
5327 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5328 Different Address}) to go to an arbitrary location in your program.
5330 A typical technique for using stepping is to set a breakpoint
5331 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5332 beginning of the function or the section of your program where a problem
5333 is believed to lie, run your program until it stops at that breakpoint,
5334 and then step through the suspect area, examining the variables that are
5335 interesting, until you see the problem happen.
5339 @kindex s @r{(@code{step})}
5341 Continue running your program until control reaches a different source
5342 line, then stop it and return control to @value{GDBN}. This command is
5343 abbreviated @code{s}.
5346 @c "without debugging information" is imprecise; actually "without line
5347 @c numbers in the debugging information". (gcc -g1 has debugging info but
5348 @c not line numbers). But it seems complex to try to make that
5349 @c distinction here.
5350 @emph{Warning:} If you use the @code{step} command while control is
5351 within a function that was compiled without debugging information,
5352 execution proceeds until control reaches a function that does have
5353 debugging information. Likewise, it will not step into a function which
5354 is compiled without debugging information. To step through functions
5355 without debugging information, use the @code{stepi} command, described
5359 The @code{step} command only stops at the first instruction of a source
5360 line. This prevents the multiple stops that could otherwise occur in
5361 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5362 to stop if a function that has debugging information is called within
5363 the line. In other words, @code{step} @emph{steps inside} any functions
5364 called within the line.
5366 Also, the @code{step} command only enters a function if there is line
5367 number information for the function. Otherwise it acts like the
5368 @code{next} command. This avoids problems when using @code{cc -gl}
5369 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5370 was any debugging information about the routine.
5372 @item step @var{count}
5373 Continue running as in @code{step}, but do so @var{count} times. If a
5374 breakpoint is reached, or a signal not related to stepping occurs before
5375 @var{count} steps, stepping stops right away.
5378 @kindex n @r{(@code{next})}
5379 @item next @r{[}@var{count}@r{]}
5380 Continue to the next source line in the current (innermost) stack frame.
5381 This is similar to @code{step}, but function calls that appear within
5382 the line of code are executed without stopping. Execution stops when
5383 control reaches a different line of code at the original stack level
5384 that was executing when you gave the @code{next} command. This command
5385 is abbreviated @code{n}.
5387 An argument @var{count} is a repeat count, as for @code{step}.
5390 @c FIX ME!! Do we delete this, or is there a way it fits in with
5391 @c the following paragraph? --- Vctoria
5393 @c @code{next} within a function that lacks debugging information acts like
5394 @c @code{step}, but any function calls appearing within the code of the
5395 @c function are executed without stopping.
5397 The @code{next} command only stops at the first instruction of a
5398 source line. This prevents multiple stops that could otherwise occur in
5399 @code{switch} statements, @code{for} loops, etc.
5401 @kindex set step-mode
5403 @cindex functions without line info, and stepping
5404 @cindex stepping into functions with no line info
5405 @itemx set step-mode on
5406 The @code{set step-mode on} command causes the @code{step} command to
5407 stop at the first instruction of a function which contains no debug line
5408 information rather than stepping over it.
5410 This is useful in cases where you may be interested in inspecting the
5411 machine instructions of a function which has no symbolic info and do not
5412 want @value{GDBN} to automatically skip over this function.
5414 @item set step-mode off
5415 Causes the @code{step} command to step over any functions which contains no
5416 debug information. This is the default.
5418 @item show step-mode
5419 Show whether @value{GDBN} will stop in or step over functions without
5420 source line debug information.
5423 @kindex fin @r{(@code{finish})}
5425 Continue running until just after function in the selected stack frame
5426 returns. Print the returned value (if any). This command can be
5427 abbreviated as @code{fin}.
5429 Contrast this with the @code{return} command (@pxref{Returning,
5430 ,Returning from a Function}).
5433 @kindex u @r{(@code{until})}
5434 @cindex run until specified location
5437 Continue running until a source line past the current line, in the
5438 current stack frame, is reached. This command is used to avoid single
5439 stepping through a loop more than once. It is like the @code{next}
5440 command, except that when @code{until} encounters a jump, it
5441 automatically continues execution until the program counter is greater
5442 than the address of the jump.
5444 This means that when you reach the end of a loop after single stepping
5445 though it, @code{until} makes your program continue execution until it
5446 exits the loop. In contrast, a @code{next} command at the end of a loop
5447 simply steps back to the beginning of the loop, which forces you to step
5448 through the next iteration.
5450 @code{until} always stops your program if it attempts to exit the current
5453 @code{until} may produce somewhat counterintuitive results if the order
5454 of machine code does not match the order of the source lines. For
5455 example, in the following excerpt from a debugging session, the @code{f}
5456 (@code{frame}) command shows that execution is stopped at line
5457 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5461 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5463 (@value{GDBP}) until
5464 195 for ( ; argc > 0; NEXTARG) @{
5467 This happened because, for execution efficiency, the compiler had
5468 generated code for the loop closure test at the end, rather than the
5469 start, of the loop---even though the test in a C @code{for}-loop is
5470 written before the body of the loop. The @code{until} command appeared
5471 to step back to the beginning of the loop when it advanced to this
5472 expression; however, it has not really gone to an earlier
5473 statement---not in terms of the actual machine code.
5475 @code{until} with no argument works by means of single
5476 instruction stepping, and hence is slower than @code{until} with an
5479 @item until @var{location}
5480 @itemx u @var{location}
5481 Continue running your program until either the specified @var{location} is
5482 reached, or the current stack frame returns. The location is any of
5483 the forms described in @ref{Specify Location}.
5484 This form of the command uses temporary breakpoints, and
5485 hence is quicker than @code{until} without an argument. The specified
5486 location is actually reached only if it is in the current frame. This
5487 implies that @code{until} can be used to skip over recursive function
5488 invocations. For instance in the code below, if the current location is
5489 line @code{96}, issuing @code{until 99} will execute the program up to
5490 line @code{99} in the same invocation of factorial, i.e., after the inner
5491 invocations have returned.
5494 94 int factorial (int value)
5496 96 if (value > 1) @{
5497 97 value *= factorial (value - 1);
5504 @kindex advance @var{location}
5505 @item advance @var{location}
5506 Continue running the program up to the given @var{location}. An argument is
5507 required, which should be of one of the forms described in
5508 @ref{Specify Location}.
5509 Execution will also stop upon exit from the current stack
5510 frame. This command is similar to @code{until}, but @code{advance} will
5511 not skip over recursive function calls, and the target location doesn't
5512 have to be in the same frame as the current one.
5516 @kindex si @r{(@code{stepi})}
5518 @itemx stepi @var{arg}
5520 Execute one machine instruction, then stop and return to the debugger.
5522 It is often useful to do @samp{display/i $pc} when stepping by machine
5523 instructions. This makes @value{GDBN} automatically display the next
5524 instruction to be executed, each time your program stops. @xref{Auto
5525 Display,, Automatic Display}.
5527 An argument is a repeat count, as in @code{step}.
5531 @kindex ni @r{(@code{nexti})}
5533 @itemx nexti @var{arg}
5535 Execute one machine instruction, but if it is a function call,
5536 proceed until the function returns.
5538 An argument is a repeat count, as in @code{next}.
5542 @anchor{range stepping}
5543 @cindex range stepping
5544 @cindex target-assisted range stepping
5545 By default, and if available, @value{GDBN} makes use of
5546 target-assisted @dfn{range stepping}. In other words, whenever you
5547 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5548 tells the target to step the corresponding range of instruction
5549 addresses instead of issuing multiple single-steps. This speeds up
5550 line stepping, particularly for remote targets. Ideally, there should
5551 be no reason you would want to turn range stepping off. However, it's
5552 possible that a bug in the debug info, a bug in the remote stub (for
5553 remote targets), or even a bug in @value{GDBN} could make line
5554 stepping behave incorrectly when target-assisted range stepping is
5555 enabled. You can use the following command to turn off range stepping
5559 @kindex set range-stepping
5560 @kindex show range-stepping
5561 @item set range-stepping
5562 @itemx show range-stepping
5563 Control whether range stepping is enabled.
5565 If @code{on}, and the target supports it, @value{GDBN} tells the
5566 target to step a range of addresses itself, instead of issuing
5567 multiple single-steps. If @code{off}, @value{GDBN} always issues
5568 single-steps, even if range stepping is supported by the target. The
5569 default is @code{on}.
5573 @node Skipping Over Functions and Files
5574 @section Skipping Over Functions and Files
5575 @cindex skipping over functions and files
5577 The program you are debugging may contain some functions which are
5578 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5579 skip a function, all functions in a file or a particular function in
5580 a particular file when stepping.
5582 For example, consider the following C function:
5593 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5594 are not interested in stepping through @code{boring}. If you run @code{step}
5595 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5596 step over both @code{foo} and @code{boring}!
5598 One solution is to @code{step} into @code{boring} and use the @code{finish}
5599 command to immediately exit it. But this can become tedious if @code{boring}
5600 is called from many places.
5602 A more flexible solution is to execute @kbd{skip boring}. This instructs
5603 @value{GDBN} never to step into @code{boring}. Now when you execute
5604 @code{step} at line 103, you'll step over @code{boring} and directly into
5607 Functions may be skipped by providing either a function name, linespec
5608 (@pxref{Specify Location}), regular expression that matches the function's
5609 name, file name or a @code{glob}-style pattern that matches the file name.
5611 On Posix systems the form of the regular expression is
5612 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5613 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5614 expression is whatever is provided by the @code{regcomp} function of
5615 the underlying system.
5616 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5617 description of @code{glob}-style patterns.
5621 @item skip @r{[}@var{options}@r{]}
5622 The basic form of the @code{skip} command takes zero or more options
5623 that specify what to skip.
5624 The @var{options} argument is any useful combination of the following:
5627 @item -file @var{file}
5628 @itemx -fi @var{file}
5629 Functions in @var{file} will be skipped over when stepping.
5631 @item -gfile @var{file-glob-pattern}
5632 @itemx -gfi @var{file-glob-pattern}
5633 @cindex skipping over files via glob-style patterns
5634 Functions in files matching @var{file-glob-pattern} will be skipped
5638 (gdb) skip -gfi utils/*.c
5641 @item -function @var{linespec}
5642 @itemx -fu @var{linespec}
5643 Functions named by @var{linespec} or the function containing the line
5644 named by @var{linespec} will be skipped over when stepping.
5645 @xref{Specify Location}.
5647 @item -rfunction @var{regexp}
5648 @itemx -rfu @var{regexp}
5649 @cindex skipping over functions via regular expressions
5650 Functions whose name matches @var{regexp} will be skipped over when stepping.
5652 This form is useful for complex function names.
5653 For example, there is generally no need to step into C@t{++} @code{std::string}
5654 constructors or destructors. Plus with C@t{++} templates it can be hard to
5655 write out the full name of the function, and often it doesn't matter what
5656 the template arguments are. Specifying the function to be skipped as a
5657 regular expression makes this easier.
5660 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5663 If you want to skip every templated C@t{++} constructor and destructor
5664 in the @code{std} namespace you can do:
5667 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5671 If no options are specified, the function you're currently debugging
5674 @kindex skip function
5675 @item skip function @r{[}@var{linespec}@r{]}
5676 After running this command, the function named by @var{linespec} or the
5677 function containing the line named by @var{linespec} will be skipped over when
5678 stepping. @xref{Specify Location}.
5680 If you do not specify @var{linespec}, the function you're currently debugging
5683 (If you have a function called @code{file} that you want to skip, use
5684 @kbd{skip function file}.)
5687 @item skip file @r{[}@var{filename}@r{]}
5688 After running this command, any function whose source lives in @var{filename}
5689 will be skipped over when stepping.
5692 (gdb) skip file boring.c
5693 File boring.c will be skipped when stepping.
5696 If you do not specify @var{filename}, functions whose source lives in the file
5697 you're currently debugging will be skipped.
5700 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5701 These are the commands for managing your list of skips:
5705 @item info skip @r{[}@var{range}@r{]}
5706 Print details about the specified skip(s). If @var{range} is not specified,
5707 print a table with details about all functions and files marked for skipping.
5708 @code{info skip} prints the following information about each skip:
5712 A number identifying this skip.
5713 @item Enabled or Disabled
5714 Enabled skips are marked with @samp{y}.
5715 Disabled skips are marked with @samp{n}.
5717 If the file name is a @samp{glob} pattern this is @samp{y}.
5718 Otherwise it is @samp{n}.
5720 The name or @samp{glob} pattern of the file to be skipped.
5721 If no file is specified this is @samp{<none>}.
5723 If the function name is a @samp{regular expression} this is @samp{y}.
5724 Otherwise it is @samp{n}.
5726 The name or regular expression of the function to skip.
5727 If no function is specified this is @samp{<none>}.
5731 @item skip delete @r{[}@var{range}@r{]}
5732 Delete the specified skip(s). If @var{range} is not specified, delete all
5736 @item skip enable @r{[}@var{range}@r{]}
5737 Enable the specified skip(s). If @var{range} is not specified, enable all
5740 @kindex skip disable
5741 @item skip disable @r{[}@var{range}@r{]}
5742 Disable the specified skip(s). If @var{range} is not specified, disable all
5751 A signal is an asynchronous event that can happen in a program. The
5752 operating system defines the possible kinds of signals, and gives each
5753 kind a name and a number. For example, in Unix @code{SIGINT} is the
5754 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5755 @code{SIGSEGV} is the signal a program gets from referencing a place in
5756 memory far away from all the areas in use; @code{SIGALRM} occurs when
5757 the alarm clock timer goes off (which happens only if your program has
5758 requested an alarm).
5760 @cindex fatal signals
5761 Some signals, including @code{SIGALRM}, are a normal part of the
5762 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5763 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5764 program has not specified in advance some other way to handle the signal.
5765 @code{SIGINT} does not indicate an error in your program, but it is normally
5766 fatal so it can carry out the purpose of the interrupt: to kill the program.
5768 @value{GDBN} has the ability to detect any occurrence of a signal in your
5769 program. You can tell @value{GDBN} in advance what to do for each kind of
5772 @cindex handling signals
5773 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5774 @code{SIGALRM} be silently passed to your program
5775 (so as not to interfere with their role in the program's functioning)
5776 but to stop your program immediately whenever an error signal happens.
5777 You can change these settings with the @code{handle} command.
5780 @kindex info signals
5784 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5785 handle each one. You can use this to see the signal numbers of all
5786 the defined types of signals.
5788 @item info signals @var{sig}
5789 Similar, but print information only about the specified signal number.
5791 @code{info handle} is an alias for @code{info signals}.
5793 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5794 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5795 for details about this command.
5798 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5799 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5800 can be the number of a signal or its name (with or without the
5801 @samp{SIG} at the beginning); a list of signal numbers of the form
5802 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5803 known signals. Optional arguments @var{keywords}, described below,
5804 say what change to make.
5808 The keywords allowed by the @code{handle} command can be abbreviated.
5809 Their full names are:
5813 @value{GDBN} should not stop your program when this signal happens. It may
5814 still print a message telling you that the signal has come in.
5817 @value{GDBN} should stop your program when this signal happens. This implies
5818 the @code{print} keyword as well.
5821 @value{GDBN} should print a message when this signal happens.
5824 @value{GDBN} should not mention the occurrence of the signal at all. This
5825 implies the @code{nostop} keyword as well.
5829 @value{GDBN} should allow your program to see this signal; your program
5830 can handle the signal, or else it may terminate if the signal is fatal
5831 and not handled. @code{pass} and @code{noignore} are synonyms.
5835 @value{GDBN} should not allow your program to see this signal.
5836 @code{nopass} and @code{ignore} are synonyms.
5840 When a signal stops your program, the signal is not visible to the
5842 continue. Your program sees the signal then, if @code{pass} is in
5843 effect for the signal in question @emph{at that time}. In other words,
5844 after @value{GDBN} reports a signal, you can use the @code{handle}
5845 command with @code{pass} or @code{nopass} to control whether your
5846 program sees that signal when you continue.
5848 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5849 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5850 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5853 You can also use the @code{signal} command to prevent your program from
5854 seeing a signal, or cause it to see a signal it normally would not see,
5855 or to give it any signal at any time. For example, if your program stopped
5856 due to some sort of memory reference error, you might store correct
5857 values into the erroneous variables and continue, hoping to see more
5858 execution; but your program would probably terminate immediately as
5859 a result of the fatal signal once it saw the signal. To prevent this,
5860 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5863 @cindex stepping and signal handlers
5864 @anchor{stepping and signal handlers}
5866 @value{GDBN} optimizes for stepping the mainline code. If a signal
5867 that has @code{handle nostop} and @code{handle pass} set arrives while
5868 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5869 in progress, @value{GDBN} lets the signal handler run and then resumes
5870 stepping the mainline code once the signal handler returns. In other
5871 words, @value{GDBN} steps over the signal handler. This prevents
5872 signals that you've specified as not interesting (with @code{handle
5873 nostop}) from changing the focus of debugging unexpectedly. Note that
5874 the signal handler itself may still hit a breakpoint, stop for another
5875 signal that has @code{handle stop} in effect, or for any other event
5876 that normally results in stopping the stepping command sooner. Also
5877 note that @value{GDBN} still informs you that the program received a
5878 signal if @code{handle print} is set.
5880 @anchor{stepping into signal handlers}
5882 If you set @code{handle pass} for a signal, and your program sets up a
5883 handler for it, then issuing a stepping command, such as @code{step}
5884 or @code{stepi}, when your program is stopped due to the signal will
5885 step @emph{into} the signal handler (if the target supports that).
5887 Likewise, if you use the @code{queue-signal} command to queue a signal
5888 to be delivered to the current thread when execution of the thread
5889 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5890 stepping command will step into the signal handler.
5892 Here's an example, using @code{stepi} to step to the first instruction
5893 of @code{SIGUSR1}'s handler:
5896 (@value{GDBP}) handle SIGUSR1
5897 Signal Stop Print Pass to program Description
5898 SIGUSR1 Yes Yes Yes User defined signal 1
5902 Program received signal SIGUSR1, User defined signal 1.
5903 main () sigusr1.c:28
5906 sigusr1_handler () at sigusr1.c:9
5910 The same, but using @code{queue-signal} instead of waiting for the
5911 program to receive the signal first:
5916 (@value{GDBP}) queue-signal SIGUSR1
5918 sigusr1_handler () at sigusr1.c:9
5923 @cindex extra signal information
5924 @anchor{extra signal information}
5926 On some targets, @value{GDBN} can inspect extra signal information
5927 associated with the intercepted signal, before it is actually
5928 delivered to the program being debugged. This information is exported
5929 by the convenience variable @code{$_siginfo}, and consists of data
5930 that is passed by the kernel to the signal handler at the time of the
5931 receipt of a signal. The data type of the information itself is
5932 target dependent. You can see the data type using the @code{ptype
5933 $_siginfo} command. On Unix systems, it typically corresponds to the
5934 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5937 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5938 referenced address that raised a segmentation fault.
5942 (@value{GDBP}) continue
5943 Program received signal SIGSEGV, Segmentation fault.
5944 0x0000000000400766 in main ()
5946 (@value{GDBP}) ptype $_siginfo
5953 struct @{...@} _kill;
5954 struct @{...@} _timer;
5956 struct @{...@} _sigchld;
5957 struct @{...@} _sigfault;
5958 struct @{...@} _sigpoll;
5961 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5965 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5966 $1 = (void *) 0x7ffff7ff7000
5970 Depending on target support, @code{$_siginfo} may also be writable.
5972 @cindex Intel MPX boundary violations
5973 @cindex boundary violations, Intel MPX
5974 On some targets, a @code{SIGSEGV} can be caused by a boundary
5975 violation, i.e., accessing an address outside of the allowed range.
5976 In those cases @value{GDBN} may displays additional information,
5977 depending on how @value{GDBN} has been told to handle the signal.
5978 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5979 kind: "Upper" or "Lower", the memory address accessed and the
5980 bounds, while with @code{handle nostop SIGSEGV} no additional
5981 information is displayed.
5983 The usual output of a segfault is:
5985 Program received signal SIGSEGV, Segmentation fault
5986 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5987 68 value = *(p + len);
5990 While a bound violation is presented as:
5992 Program received signal SIGSEGV, Segmentation fault
5993 Upper bound violation while accessing address 0x7fffffffc3b3
5994 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5995 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5996 68 value = *(p + len);
6000 @section Stopping and Starting Multi-thread Programs
6002 @cindex stopped threads
6003 @cindex threads, stopped
6005 @cindex continuing threads
6006 @cindex threads, continuing
6008 @value{GDBN} supports debugging programs with multiple threads
6009 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6010 are two modes of controlling execution of your program within the
6011 debugger. In the default mode, referred to as @dfn{all-stop mode},
6012 when any thread in your program stops (for example, at a breakpoint
6013 or while being stepped), all other threads in the program are also stopped by
6014 @value{GDBN}. On some targets, @value{GDBN} also supports
6015 @dfn{non-stop mode}, in which other threads can continue to run freely while
6016 you examine the stopped thread in the debugger.
6019 * All-Stop Mode:: All threads stop when GDB takes control
6020 * Non-Stop Mode:: Other threads continue to execute
6021 * Background Execution:: Running your program asynchronously
6022 * Thread-Specific Breakpoints:: Controlling breakpoints
6023 * Interrupted System Calls:: GDB may interfere with system calls
6024 * Observer Mode:: GDB does not alter program behavior
6028 @subsection All-Stop Mode
6030 @cindex all-stop mode
6032 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6033 @emph{all} threads of execution stop, not just the current thread. This
6034 allows you to examine the overall state of the program, including
6035 switching between threads, without worrying that things may change
6038 Conversely, whenever you restart the program, @emph{all} threads start
6039 executing. @emph{This is true even when single-stepping} with commands
6040 like @code{step} or @code{next}.
6042 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6043 Since thread scheduling is up to your debugging target's operating
6044 system (not controlled by @value{GDBN}), other threads may
6045 execute more than one statement while the current thread completes a
6046 single step. Moreover, in general other threads stop in the middle of a
6047 statement, rather than at a clean statement boundary, when the program
6050 You might even find your program stopped in another thread after
6051 continuing or even single-stepping. This happens whenever some other
6052 thread runs into a breakpoint, a signal, or an exception before the
6053 first thread completes whatever you requested.
6055 @cindex automatic thread selection
6056 @cindex switching threads automatically
6057 @cindex threads, automatic switching
6058 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6059 signal, it automatically selects the thread where that breakpoint or
6060 signal happened. @value{GDBN} alerts you to the context switch with a
6061 message such as @samp{[Switching to Thread @var{n}]} to identify the
6064 On some OSes, you can modify @value{GDBN}'s default behavior by
6065 locking the OS scheduler to allow only a single thread to run.
6068 @item set scheduler-locking @var{mode}
6069 @cindex scheduler locking mode
6070 @cindex lock scheduler
6071 Set the scheduler locking mode. It applies to normal execution,
6072 record mode, and replay mode. If it is @code{off}, then there is no
6073 locking and any thread may run at any time. If @code{on}, then only
6074 the current thread may run when the inferior is resumed. The
6075 @code{step} mode optimizes for single-stepping; it prevents other
6076 threads from preempting the current thread while you are stepping, so
6077 that the focus of debugging does not change unexpectedly. Other
6078 threads never get a chance to run when you step, and they are
6079 completely free to run when you use commands like @samp{continue},
6080 @samp{until}, or @samp{finish}. However, unless another thread hits a
6081 breakpoint during its timeslice, @value{GDBN} does not change the
6082 current thread away from the thread that you are debugging. The
6083 @code{replay} mode behaves like @code{off} in record mode and like
6084 @code{on} in replay mode.
6086 @item show scheduler-locking
6087 Display the current scheduler locking mode.
6090 @cindex resume threads of multiple processes simultaneously
6091 By default, when you issue one of the execution commands such as
6092 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6093 threads of the current inferior to run. For example, if @value{GDBN}
6094 is attached to two inferiors, each with two threads, the
6095 @code{continue} command resumes only the two threads of the current
6096 inferior. This is useful, for example, when you debug a program that
6097 forks and you want to hold the parent stopped (so that, for instance,
6098 it doesn't run to exit), while you debug the child. In other
6099 situations, you may not be interested in inspecting the current state
6100 of any of the processes @value{GDBN} is attached to, and you may want
6101 to resume them all until some breakpoint is hit. In the latter case,
6102 you can instruct @value{GDBN} to allow all threads of all the
6103 inferiors to run with the @w{@code{set schedule-multiple}} command.
6106 @kindex set schedule-multiple
6107 @item set schedule-multiple
6108 Set the mode for allowing threads of multiple processes to be resumed
6109 when an execution command is issued. When @code{on}, all threads of
6110 all processes are allowed to run. When @code{off}, only the threads
6111 of the current process are resumed. The default is @code{off}. The
6112 @code{scheduler-locking} mode takes precedence when set to @code{on},
6113 or while you are stepping and set to @code{step}.
6115 @item show schedule-multiple
6116 Display the current mode for resuming the execution of threads of
6121 @subsection Non-Stop Mode
6123 @cindex non-stop mode
6125 @c This section is really only a place-holder, and needs to be expanded
6126 @c with more details.
6128 For some multi-threaded targets, @value{GDBN} supports an optional
6129 mode of operation in which you can examine stopped program threads in
6130 the debugger while other threads continue to execute freely. This
6131 minimizes intrusion when debugging live systems, such as programs
6132 where some threads have real-time constraints or must continue to
6133 respond to external events. This is referred to as @dfn{non-stop} mode.
6135 In non-stop mode, when a thread stops to report a debugging event,
6136 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6137 threads as well, in contrast to the all-stop mode behavior. Additionally,
6138 execution commands such as @code{continue} and @code{step} apply by default
6139 only to the current thread in non-stop mode, rather than all threads as
6140 in all-stop mode. This allows you to control threads explicitly in
6141 ways that are not possible in all-stop mode --- for example, stepping
6142 one thread while allowing others to run freely, stepping
6143 one thread while holding all others stopped, or stepping several threads
6144 independently and simultaneously.
6146 To enter non-stop mode, use this sequence of commands before you run
6147 or attach to your program:
6150 # If using the CLI, pagination breaks non-stop.
6153 # Finally, turn it on!
6157 You can use these commands to manipulate the non-stop mode setting:
6160 @kindex set non-stop
6161 @item set non-stop on
6162 Enable selection of non-stop mode.
6163 @item set non-stop off
6164 Disable selection of non-stop mode.
6165 @kindex show non-stop
6167 Show the current non-stop enablement setting.
6170 Note these commands only reflect whether non-stop mode is enabled,
6171 not whether the currently-executing program is being run in non-stop mode.
6172 In particular, the @code{set non-stop} preference is only consulted when
6173 @value{GDBN} starts or connects to the target program, and it is generally
6174 not possible to switch modes once debugging has started. Furthermore,
6175 since not all targets support non-stop mode, even when you have enabled
6176 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6179 In non-stop mode, all execution commands apply only to the current thread
6180 by default. That is, @code{continue} only continues one thread.
6181 To continue all threads, issue @code{continue -a} or @code{c -a}.
6183 You can use @value{GDBN}'s background execution commands
6184 (@pxref{Background Execution}) to run some threads in the background
6185 while you continue to examine or step others from @value{GDBN}.
6186 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6187 always executed asynchronously in non-stop mode.
6189 Suspending execution is done with the @code{interrupt} command when
6190 running in the background, or @kbd{Ctrl-c} during foreground execution.
6191 In all-stop mode, this stops the whole process;
6192 but in non-stop mode the interrupt applies only to the current thread.
6193 To stop the whole program, use @code{interrupt -a}.
6195 Other execution commands do not currently support the @code{-a} option.
6197 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6198 that thread current, as it does in all-stop mode. This is because the
6199 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6200 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6201 changed to a different thread just as you entered a command to operate on the
6202 previously current thread.
6204 @node Background Execution
6205 @subsection Background Execution
6207 @cindex foreground execution
6208 @cindex background execution
6209 @cindex asynchronous execution
6210 @cindex execution, foreground, background and asynchronous
6212 @value{GDBN}'s execution commands have two variants: the normal
6213 foreground (synchronous) behavior, and a background
6214 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6215 the program to report that some thread has stopped before prompting for
6216 another command. In background execution, @value{GDBN} immediately gives
6217 a command prompt so that you can issue other commands while your program runs.
6219 If the target doesn't support async mode, @value{GDBN} issues an error
6220 message if you attempt to use the background execution commands.
6222 To specify background execution, add a @code{&} to the command. For example,
6223 the background form of the @code{continue} command is @code{continue&}, or
6224 just @code{c&}. The execution commands that accept background execution
6230 @xref{Starting, , Starting your Program}.
6234 @xref{Attach, , Debugging an Already-running Process}.
6238 @xref{Continuing and Stepping, step}.
6242 @xref{Continuing and Stepping, stepi}.
6246 @xref{Continuing and Stepping, next}.
6250 @xref{Continuing and Stepping, nexti}.
6254 @xref{Continuing and Stepping, continue}.
6258 @xref{Continuing and Stepping, finish}.
6262 @xref{Continuing and Stepping, until}.
6266 Background execution is especially useful in conjunction with non-stop
6267 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6268 However, you can also use these commands in the normal all-stop mode with
6269 the restriction that you cannot issue another execution command until the
6270 previous one finishes. Examples of commands that are valid in all-stop
6271 mode while the program is running include @code{help} and @code{info break}.
6273 You can interrupt your program while it is running in the background by
6274 using the @code{interrupt} command.
6281 Suspend execution of the running program. In all-stop mode,
6282 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6283 only the current thread. To stop the whole program in non-stop mode,
6284 use @code{interrupt -a}.
6287 @node Thread-Specific Breakpoints
6288 @subsection Thread-Specific Breakpoints
6290 When your program has multiple threads (@pxref{Threads,, Debugging
6291 Programs with Multiple Threads}), you can choose whether to set
6292 breakpoints on all threads, or on a particular thread.
6295 @cindex breakpoints and threads
6296 @cindex thread breakpoints
6297 @kindex break @dots{} thread @var{thread-id}
6298 @item break @var{location} thread @var{thread-id}
6299 @itemx break @var{location} thread @var{thread-id} if @dots{}
6300 @var{location} specifies source lines; there are several ways of
6301 writing them (@pxref{Specify Location}), but the effect is always to
6302 specify some source line.
6304 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6305 to specify that you only want @value{GDBN} to stop the program when a
6306 particular thread reaches this breakpoint. The @var{thread-id} specifier
6307 is one of the thread identifiers assigned by @value{GDBN}, shown
6308 in the first column of the @samp{info threads} display.
6310 If you do not specify @samp{thread @var{thread-id}} when you set a
6311 breakpoint, the breakpoint applies to @emph{all} threads of your
6314 You can use the @code{thread} qualifier on conditional breakpoints as
6315 well; in this case, place @samp{thread @var{thread-id}} before or
6316 after the breakpoint condition, like this:
6319 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6324 Thread-specific breakpoints are automatically deleted when
6325 @value{GDBN} detects the corresponding thread is no longer in the
6326 thread list. For example:
6330 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6333 There are several ways for a thread to disappear, such as a regular
6334 thread exit, but also when you detach from the process with the
6335 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6336 Process}), or if @value{GDBN} loses the remote connection
6337 (@pxref{Remote Debugging}), etc. Note that with some targets,
6338 @value{GDBN} is only able to detect a thread has exited when the user
6339 explictly asks for the thread list with the @code{info threads}
6342 @node Interrupted System Calls
6343 @subsection Interrupted System Calls
6345 @cindex thread breakpoints and system calls
6346 @cindex system calls and thread breakpoints
6347 @cindex premature return from system calls
6348 There is an unfortunate side effect when using @value{GDBN} to debug
6349 multi-threaded programs. If one thread stops for a
6350 breakpoint, or for some other reason, and another thread is blocked in a
6351 system call, then the system call may return prematurely. This is a
6352 consequence of the interaction between multiple threads and the signals
6353 that @value{GDBN} uses to implement breakpoints and other events that
6356 To handle this problem, your program should check the return value of
6357 each system call and react appropriately. This is good programming
6360 For example, do not write code like this:
6366 The call to @code{sleep} will return early if a different thread stops
6367 at a breakpoint or for some other reason.
6369 Instead, write this:
6374 unslept = sleep (unslept);
6377 A system call is allowed to return early, so the system is still
6378 conforming to its specification. But @value{GDBN} does cause your
6379 multi-threaded program to behave differently than it would without
6382 Also, @value{GDBN} uses internal breakpoints in the thread library to
6383 monitor certain events such as thread creation and thread destruction.
6384 When such an event happens, a system call in another thread may return
6385 prematurely, even though your program does not appear to stop.
6388 @subsection Observer Mode
6390 If you want to build on non-stop mode and observe program behavior
6391 without any chance of disruption by @value{GDBN}, you can set
6392 variables to disable all of the debugger's attempts to modify state,
6393 whether by writing memory, inserting breakpoints, etc. These operate
6394 at a low level, intercepting operations from all commands.
6396 When all of these are set to @code{off}, then @value{GDBN} is said to
6397 be @dfn{observer mode}. As a convenience, the variable
6398 @code{observer} can be set to disable these, plus enable non-stop
6401 Note that @value{GDBN} will not prevent you from making nonsensical
6402 combinations of these settings. For instance, if you have enabled
6403 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6404 then breakpoints that work by writing trap instructions into the code
6405 stream will still not be able to be placed.
6410 @item set observer on
6411 @itemx set observer off
6412 When set to @code{on}, this disables all the permission variables
6413 below (except for @code{insert-fast-tracepoints}), plus enables
6414 non-stop debugging. Setting this to @code{off} switches back to
6415 normal debugging, though remaining in non-stop mode.
6418 Show whether observer mode is on or off.
6420 @kindex may-write-registers
6421 @item set may-write-registers on
6422 @itemx set may-write-registers off
6423 This controls whether @value{GDBN} will attempt to alter the values of
6424 registers, such as with assignment expressions in @code{print}, or the
6425 @code{jump} command. It defaults to @code{on}.
6427 @item show may-write-registers
6428 Show the current permission to write registers.
6430 @kindex may-write-memory
6431 @item set may-write-memory on
6432 @itemx set may-write-memory off
6433 This controls whether @value{GDBN} will attempt to alter the contents
6434 of memory, such as with assignment expressions in @code{print}. It
6435 defaults to @code{on}.
6437 @item show may-write-memory
6438 Show the current permission to write memory.
6440 @kindex may-insert-breakpoints
6441 @item set may-insert-breakpoints on
6442 @itemx set may-insert-breakpoints off
6443 This controls whether @value{GDBN} will attempt to insert breakpoints.
6444 This affects all breakpoints, including internal breakpoints defined
6445 by @value{GDBN}. It defaults to @code{on}.
6447 @item show may-insert-breakpoints
6448 Show the current permission to insert breakpoints.
6450 @kindex may-insert-tracepoints
6451 @item set may-insert-tracepoints on
6452 @itemx set may-insert-tracepoints off
6453 This controls whether @value{GDBN} will attempt to insert (regular)
6454 tracepoints at the beginning of a tracing experiment. It affects only
6455 non-fast tracepoints, fast tracepoints being under the control of
6456 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6458 @item show may-insert-tracepoints
6459 Show the current permission to insert tracepoints.
6461 @kindex may-insert-fast-tracepoints
6462 @item set may-insert-fast-tracepoints on
6463 @itemx set may-insert-fast-tracepoints off
6464 This controls whether @value{GDBN} will attempt to insert fast
6465 tracepoints at the beginning of a tracing experiment. It affects only
6466 fast tracepoints, regular (non-fast) tracepoints being under the
6467 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6469 @item show may-insert-fast-tracepoints
6470 Show the current permission to insert fast tracepoints.
6472 @kindex may-interrupt
6473 @item set may-interrupt on
6474 @itemx set may-interrupt off
6475 This controls whether @value{GDBN} will attempt to interrupt or stop
6476 program execution. When this variable is @code{off}, the
6477 @code{interrupt} command will have no effect, nor will
6478 @kbd{Ctrl-c}. It defaults to @code{on}.
6480 @item show may-interrupt
6481 Show the current permission to interrupt or stop the program.
6485 @node Reverse Execution
6486 @chapter Running programs backward
6487 @cindex reverse execution
6488 @cindex running programs backward
6490 When you are debugging a program, it is not unusual to realize that
6491 you have gone too far, and some event of interest has already happened.
6492 If the target environment supports it, @value{GDBN} can allow you to
6493 ``rewind'' the program by running it backward.
6495 A target environment that supports reverse execution should be able
6496 to ``undo'' the changes in machine state that have taken place as the
6497 program was executing normally. Variables, registers etc.@: should
6498 revert to their previous values. Obviously this requires a great
6499 deal of sophistication on the part of the target environment; not
6500 all target environments can support reverse execution.
6502 When a program is executed in reverse, the instructions that
6503 have most recently been executed are ``un-executed'', in reverse
6504 order. The program counter runs backward, following the previous
6505 thread of execution in reverse. As each instruction is ``un-executed'',
6506 the values of memory and/or registers that were changed by that
6507 instruction are reverted to their previous states. After executing
6508 a piece of source code in reverse, all side effects of that code
6509 should be ``undone'', and all variables should be returned to their
6510 prior values@footnote{
6511 Note that some side effects are easier to undo than others. For instance,
6512 memory and registers are relatively easy, but device I/O is hard. Some
6513 targets may be able undo things like device I/O, and some may not.
6515 The contract between @value{GDBN} and the reverse executing target
6516 requires only that the target do something reasonable when
6517 @value{GDBN} tells it to execute backwards, and then report the
6518 results back to @value{GDBN}. Whatever the target reports back to
6519 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6520 assumes that the memory and registers that the target reports are in a
6521 consistant state, but @value{GDBN} accepts whatever it is given.
6524 If you are debugging in a target environment that supports
6525 reverse execution, @value{GDBN} provides the following commands.
6528 @kindex reverse-continue
6529 @kindex rc @r{(@code{reverse-continue})}
6530 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6531 @itemx rc @r{[}@var{ignore-count}@r{]}
6532 Beginning at the point where your program last stopped, start executing
6533 in reverse. Reverse execution will stop for breakpoints and synchronous
6534 exceptions (signals), just like normal execution. Behavior of
6535 asynchronous signals depends on the target environment.
6537 @kindex reverse-step
6538 @kindex rs @r{(@code{step})}
6539 @item reverse-step @r{[}@var{count}@r{]}
6540 Run the program backward until control reaches the start of a
6541 different source line; then stop it, and return control to @value{GDBN}.
6543 Like the @code{step} command, @code{reverse-step} will only stop
6544 at the beginning of a source line. It ``un-executes'' the previously
6545 executed source line. If the previous source line included calls to
6546 debuggable functions, @code{reverse-step} will step (backward) into
6547 the called function, stopping at the beginning of the @emph{last}
6548 statement in the called function (typically a return statement).
6550 Also, as with the @code{step} command, if non-debuggable functions are
6551 called, @code{reverse-step} will run thru them backward without stopping.
6553 @kindex reverse-stepi
6554 @kindex rsi @r{(@code{reverse-stepi})}
6555 @item reverse-stepi @r{[}@var{count}@r{]}
6556 Reverse-execute one machine instruction. Note that the instruction
6557 to be reverse-executed is @emph{not} the one pointed to by the program
6558 counter, but the instruction executed prior to that one. For instance,
6559 if the last instruction was a jump, @code{reverse-stepi} will take you
6560 back from the destination of the jump to the jump instruction itself.
6562 @kindex reverse-next
6563 @kindex rn @r{(@code{reverse-next})}
6564 @item reverse-next @r{[}@var{count}@r{]}
6565 Run backward to the beginning of the previous line executed in
6566 the current (innermost) stack frame. If the line contains function
6567 calls, they will be ``un-executed'' without stopping. Starting from
6568 the first line of a function, @code{reverse-next} will take you back
6569 to the caller of that function, @emph{before} the function was called,
6570 just as the normal @code{next} command would take you from the last
6571 line of a function back to its return to its caller
6572 @footnote{Unless the code is too heavily optimized.}.
6574 @kindex reverse-nexti
6575 @kindex rni @r{(@code{reverse-nexti})}
6576 @item reverse-nexti @r{[}@var{count}@r{]}
6577 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6578 in reverse, except that called functions are ``un-executed'' atomically.
6579 That is, if the previously executed instruction was a return from
6580 another function, @code{reverse-nexti} will continue to execute
6581 in reverse until the call to that function (from the current stack
6584 @kindex reverse-finish
6585 @item reverse-finish
6586 Just as the @code{finish} command takes you to the point where the
6587 current function returns, @code{reverse-finish} takes you to the point
6588 where it was called. Instead of ending up at the end of the current
6589 function invocation, you end up at the beginning.
6591 @kindex set exec-direction
6592 @item set exec-direction
6593 Set the direction of target execution.
6594 @item set exec-direction reverse
6595 @cindex execute forward or backward in time
6596 @value{GDBN} will perform all execution commands in reverse, until the
6597 exec-direction mode is changed to ``forward''. Affected commands include
6598 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6599 command cannot be used in reverse mode.
6600 @item set exec-direction forward
6601 @value{GDBN} will perform all execution commands in the normal fashion.
6602 This is the default.
6606 @node Process Record and Replay
6607 @chapter Recording Inferior's Execution and Replaying It
6608 @cindex process record and replay
6609 @cindex recording inferior's execution and replaying it
6611 On some platforms, @value{GDBN} provides a special @dfn{process record
6612 and replay} target that can record a log of the process execution, and
6613 replay it later with both forward and reverse execution commands.
6616 When this target is in use, if the execution log includes the record
6617 for the next instruction, @value{GDBN} will debug in @dfn{replay
6618 mode}. In the replay mode, the inferior does not really execute code
6619 instructions. Instead, all the events that normally happen during
6620 code execution are taken from the execution log. While code is not
6621 really executed in replay mode, the values of registers (including the
6622 program counter register) and the memory of the inferior are still
6623 changed as they normally would. Their contents are taken from the
6627 If the record for the next instruction is not in the execution log,
6628 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6629 inferior executes normally, and @value{GDBN} records the execution log
6632 The process record and replay target supports reverse execution
6633 (@pxref{Reverse Execution}), even if the platform on which the
6634 inferior runs does not. However, the reverse execution is limited in
6635 this case by the range of the instructions recorded in the execution
6636 log. In other words, reverse execution on platforms that don't
6637 support it directly can only be done in the replay mode.
6639 When debugging in the reverse direction, @value{GDBN} will work in
6640 replay mode as long as the execution log includes the record for the
6641 previous instruction; otherwise, it will work in record mode, if the
6642 platform supports reverse execution, or stop if not.
6644 For architecture environments that support process record and replay,
6645 @value{GDBN} provides the following commands:
6648 @kindex target record
6649 @kindex target record-full
6650 @kindex target record-btrace
6653 @kindex record btrace
6654 @kindex record btrace bts
6655 @kindex record btrace pt
6661 @kindex rec btrace bts
6662 @kindex rec btrace pt
6665 @item record @var{method}
6666 This command starts the process record and replay target. The
6667 recording method can be specified as parameter. Without a parameter
6668 the command uses the @code{full} recording method. The following
6669 recording methods are available:
6673 Full record/replay recording using @value{GDBN}'s software record and
6674 replay implementation. This method allows replaying and reverse
6677 @item btrace @var{format}
6678 Hardware-supported instruction recording. This method does not record
6679 data. Further, the data is collected in a ring buffer so old data will
6680 be overwritten when the buffer is full. It allows limited reverse
6681 execution. Variables and registers are not available during reverse
6682 execution. In remote debugging, recording continues on disconnect.
6683 Recorded data can be inspected after reconnecting. The recording may
6684 be stopped using @code{record stop}.
6686 The recording format can be specified as parameter. Without a parameter
6687 the command chooses the recording format. The following recording
6688 formats are available:
6692 @cindex branch trace store
6693 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6694 this format, the processor stores a from/to record for each executed
6695 branch in the btrace ring buffer.
6698 @cindex Intel Processor Trace
6699 Use the @dfn{Intel Processor Trace} recording format. In this
6700 format, the processor stores the execution trace in a compressed form
6701 that is afterwards decoded by @value{GDBN}.
6703 The trace can be recorded with very low overhead. The compressed
6704 trace format also allows small trace buffers to already contain a big
6705 number of instructions compared to @acronym{BTS}.
6707 Decoding the recorded execution trace, on the other hand, is more
6708 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6709 increased number of instructions to process. You should increase the
6710 buffer-size with care.
6713 Not all recording formats may be available on all processors.
6716 The process record and replay target can only debug a process that is
6717 already running. Therefore, you need first to start the process with
6718 the @kbd{run} or @kbd{start} commands, and then start the recording
6719 with the @kbd{record @var{method}} command.
6721 @cindex displaced stepping, and process record and replay
6722 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6723 will be automatically disabled when process record and replay target
6724 is started. That's because the process record and replay target
6725 doesn't support displaced stepping.
6727 @cindex non-stop mode, and process record and replay
6728 @cindex asynchronous execution, and process record and replay
6729 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6730 the asynchronous execution mode (@pxref{Background Execution}), not
6731 all recording methods are available. The @code{full} recording method
6732 does not support these two modes.
6737 Stop the process record and replay target. When process record and
6738 replay target stops, the entire execution log will be deleted and the
6739 inferior will either be terminated, or will remain in its final state.
6741 When you stop the process record and replay target in record mode (at
6742 the end of the execution log), the inferior will be stopped at the
6743 next instruction that would have been recorded. In other words, if
6744 you record for a while and then stop recording, the inferior process
6745 will be left in the same state as if the recording never happened.
6747 On the other hand, if the process record and replay target is stopped
6748 while in replay mode (that is, not at the end of the execution log,
6749 but at some earlier point), the inferior process will become ``live''
6750 at that earlier state, and it will then be possible to continue the
6751 usual ``live'' debugging of the process from that state.
6753 When the inferior process exits, or @value{GDBN} detaches from it,
6754 process record and replay target will automatically stop itself.
6758 Go to a specific location in the execution log. There are several
6759 ways to specify the location to go to:
6762 @item record goto begin
6763 @itemx record goto start
6764 Go to the beginning of the execution log.
6766 @item record goto end
6767 Go to the end of the execution log.
6769 @item record goto @var{n}
6770 Go to instruction number @var{n} in the execution log.
6774 @item record save @var{filename}
6775 Save the execution log to a file @file{@var{filename}}.
6776 Default filename is @file{gdb_record.@var{process_id}}, where
6777 @var{process_id} is the process ID of the inferior.
6779 This command may not be available for all recording methods.
6781 @kindex record restore
6782 @item record restore @var{filename}
6783 Restore the execution log from a file @file{@var{filename}}.
6784 File must have been created with @code{record save}.
6786 @kindex set record full
6787 @item set record full insn-number-max @var{limit}
6788 @itemx set record full insn-number-max unlimited
6789 Set the limit of instructions to be recorded for the @code{full}
6790 recording method. Default value is 200000.
6792 If @var{limit} is a positive number, then @value{GDBN} will start
6793 deleting instructions from the log once the number of the record
6794 instructions becomes greater than @var{limit}. For every new recorded
6795 instruction, @value{GDBN} will delete the earliest recorded
6796 instruction to keep the number of recorded instructions at the limit.
6797 (Since deleting recorded instructions loses information, @value{GDBN}
6798 lets you control what happens when the limit is reached, by means of
6799 the @code{stop-at-limit} option, described below.)
6801 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6802 delete recorded instructions from the execution log. The number of
6803 recorded instructions is limited only by the available memory.
6805 @kindex show record full
6806 @item show record full insn-number-max
6807 Show the limit of instructions to be recorded with the @code{full}
6810 @item set record full stop-at-limit
6811 Control the behavior of the @code{full} recording method when the
6812 number of recorded instructions reaches the limit. If ON (the
6813 default), @value{GDBN} will stop when the limit is reached for the
6814 first time and ask you whether you want to stop the inferior or
6815 continue running it and recording the execution log. If you decide
6816 to continue recording, each new recorded instruction will cause the
6817 oldest one to be deleted.
6819 If this option is OFF, @value{GDBN} will automatically delete the
6820 oldest record to make room for each new one, without asking.
6822 @item show record full stop-at-limit
6823 Show the current setting of @code{stop-at-limit}.
6825 @item set record full memory-query
6826 Control the behavior when @value{GDBN} is unable to record memory
6827 changes caused by an instruction for the @code{full} recording method.
6828 If ON, @value{GDBN} will query whether to stop the inferior in that
6831 If this option is OFF (the default), @value{GDBN} will automatically
6832 ignore the effect of such instructions on memory. Later, when
6833 @value{GDBN} replays this execution log, it will mark the log of this
6834 instruction as not accessible, and it will not affect the replay
6837 @item show record full memory-query
6838 Show the current setting of @code{memory-query}.
6840 @kindex set record btrace
6841 The @code{btrace} record target does not trace data. As a
6842 convenience, when replaying, @value{GDBN} reads read-only memory off
6843 the live program directly, assuming that the addresses of the
6844 read-only areas don't change. This for example makes it possible to
6845 disassemble code while replaying, but not to print variables.
6846 In some cases, being able to inspect variables might be useful.
6847 You can use the following command for that:
6849 @item set record btrace replay-memory-access
6850 Control the behavior of the @code{btrace} recording method when
6851 accessing memory during replay. If @code{read-only} (the default),
6852 @value{GDBN} will only allow accesses to read-only memory.
6853 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6854 and to read-write memory. Beware that the accessed memory corresponds
6855 to the live target and not necessarily to the current replay
6858 @kindex show record btrace
6859 @item show record btrace replay-memory-access
6860 Show the current setting of @code{replay-memory-access}.
6862 @kindex set record btrace bts
6863 @item set record btrace bts buffer-size @var{size}
6864 @itemx set record btrace bts buffer-size unlimited
6865 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6866 format. Default is 64KB.
6868 If @var{size} is a positive number, then @value{GDBN} will try to
6869 allocate a buffer of at least @var{size} bytes for each new thread
6870 that uses the btrace recording method and the @acronym{BTS} format.
6871 The actually obtained buffer size may differ from the requested
6872 @var{size}. Use the @code{info record} command to see the actual
6873 buffer size for each thread that uses the btrace recording method and
6874 the @acronym{BTS} format.
6876 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6877 allocate a buffer of 4MB.
6879 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6880 also need longer to process the branch trace data before it can be used.
6882 @item show record btrace bts buffer-size @var{size}
6883 Show the current setting of the requested ring buffer size for branch
6884 tracing in @acronym{BTS} format.
6886 @kindex set record btrace pt
6887 @item set record btrace pt buffer-size @var{size}
6888 @itemx set record btrace pt buffer-size unlimited
6889 Set the requested ring buffer size for branch tracing in Intel
6890 Processor Trace format. Default is 16KB.
6892 If @var{size} is a positive number, then @value{GDBN} will try to
6893 allocate a buffer of at least @var{size} bytes for each new thread
6894 that uses the btrace recording method and the Intel Processor Trace
6895 format. The actually obtained buffer size may differ from the
6896 requested @var{size}. Use the @code{info record} command to see the
6897 actual buffer size for each thread.
6899 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6900 allocate a buffer of 4MB.
6902 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6903 also need longer to process the branch trace data before it can be used.
6905 @item show record btrace pt buffer-size @var{size}
6906 Show the current setting of the requested ring buffer size for branch
6907 tracing in Intel Processor Trace format.
6911 Show various statistics about the recording depending on the recording
6916 For the @code{full} recording method, it shows the state of process
6917 record and its in-memory execution log buffer, including:
6921 Whether in record mode or replay mode.
6923 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6925 Highest recorded instruction number.
6927 Current instruction about to be replayed (if in replay mode).
6929 Number of instructions contained in the execution log.
6931 Maximum number of instructions that may be contained in the execution log.
6935 For the @code{btrace} recording method, it shows:
6941 Number of instructions that have been recorded.
6943 Number of blocks of sequential control-flow formed by the recorded
6946 Whether in record mode or replay mode.
6949 For the @code{bts} recording format, it also shows:
6952 Size of the perf ring buffer.
6955 For the @code{pt} recording format, it also shows:
6958 Size of the perf ring buffer.
6962 @kindex record delete
6965 When record target runs in replay mode (``in the past''), delete the
6966 subsequent execution log and begin to record a new execution log starting
6967 from the current address. This means you will abandon the previously
6968 recorded ``future'' and begin recording a new ``future''.
6970 @kindex record instruction-history
6971 @kindex rec instruction-history
6972 @item record instruction-history
6973 Disassembles instructions from the recorded execution log. By
6974 default, ten instructions are disassembled. This can be changed using
6975 the @code{set record instruction-history-size} command. Instructions
6976 are printed in execution order.
6978 It can also print mixed source+disassembly if you specify the the
6979 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6980 as well as in symbolic form by specifying the @code{/r} modifier.
6982 The current position marker is printed for the instruction at the
6983 current program counter value. This instruction can appear multiple
6984 times in the trace and the current position marker will be printed
6985 every time. To omit the current position marker, specify the
6988 To better align the printed instructions when the trace contains
6989 instructions from more than one function, the function name may be
6990 omitted by specifying the @code{/f} modifier.
6992 Speculatively executed instructions are prefixed with @samp{?}. This
6993 feature is not available for all recording formats.
6995 There are several ways to specify what part of the execution log to
6999 @item record instruction-history @var{insn}
7000 Disassembles ten instructions starting from instruction number
7003 @item record instruction-history @var{insn}, +/-@var{n}
7004 Disassembles @var{n} instructions around instruction number
7005 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7006 @var{n} instructions after instruction number @var{insn}. If
7007 @var{n} is preceded with @code{-}, disassembles @var{n}
7008 instructions before instruction number @var{insn}.
7010 @item record instruction-history
7011 Disassembles ten more instructions after the last disassembly.
7013 @item record instruction-history -
7014 Disassembles ten more instructions before the last disassembly.
7016 @item record instruction-history @var{begin}, @var{end}
7017 Disassembles instructions beginning with instruction number
7018 @var{begin} until instruction number @var{end}. The instruction
7019 number @var{end} is included.
7022 This command may not be available for all recording methods.
7025 @item set record instruction-history-size @var{size}
7026 @itemx set record instruction-history-size unlimited
7027 Define how many instructions to disassemble in the @code{record
7028 instruction-history} command. The default value is 10.
7029 A @var{size} of @code{unlimited} means unlimited instructions.
7032 @item show record instruction-history-size
7033 Show how many instructions to disassemble in the @code{record
7034 instruction-history} command.
7036 @kindex record function-call-history
7037 @kindex rec function-call-history
7038 @item record function-call-history
7039 Prints the execution history at function granularity. It prints one
7040 line for each sequence of instructions that belong to the same
7041 function giving the name of that function, the source lines
7042 for this instruction sequence (if the @code{/l} modifier is
7043 specified), and the instructions numbers that form the sequence (if
7044 the @code{/i} modifier is specified). The function names are indented
7045 to reflect the call stack depth if the @code{/c} modifier is
7046 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7050 (@value{GDBP}) @b{list 1, 10}
7061 (@value{GDBP}) @b{record function-call-history /ilc}
7062 1 bar inst 1,4 at foo.c:6,8
7063 2 foo inst 5,10 at foo.c:2,3
7064 3 bar inst 11,13 at foo.c:9,10
7067 By default, ten lines are printed. This can be changed using the
7068 @code{set record function-call-history-size} command. Functions are
7069 printed in execution order. There are several ways to specify what
7073 @item record function-call-history @var{func}
7074 Prints ten functions starting from function number @var{func}.
7076 @item record function-call-history @var{func}, +/-@var{n}
7077 Prints @var{n} functions around function number @var{func}. If
7078 @var{n} is preceded with @code{+}, prints @var{n} functions after
7079 function number @var{func}. If @var{n} is preceded with @code{-},
7080 prints @var{n} functions before function number @var{func}.
7082 @item record function-call-history
7083 Prints ten more functions after the last ten-line print.
7085 @item record function-call-history -
7086 Prints ten more functions before the last ten-line print.
7088 @item record function-call-history @var{begin}, @var{end}
7089 Prints functions beginning with function number @var{begin} until
7090 function number @var{end}. The function number @var{end} is included.
7093 This command may not be available for all recording methods.
7095 @item set record function-call-history-size @var{size}
7096 @itemx set record function-call-history-size unlimited
7097 Define how many lines to print in the
7098 @code{record function-call-history} command. The default value is 10.
7099 A size of @code{unlimited} means unlimited lines.
7101 @item show record function-call-history-size
7102 Show how many lines to print in the
7103 @code{record function-call-history} command.
7108 @chapter Examining the Stack
7110 When your program has stopped, the first thing you need to know is where it
7111 stopped and how it got there.
7114 Each time your program performs a function call, information about the call
7116 That information includes the location of the call in your program,
7117 the arguments of the call,
7118 and the local variables of the function being called.
7119 The information is saved in a block of data called a @dfn{stack frame}.
7120 The stack frames are allocated in a region of memory called the @dfn{call
7123 When your program stops, the @value{GDBN} commands for examining the
7124 stack allow you to see all of this information.
7126 @cindex selected frame
7127 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7128 @value{GDBN} commands refer implicitly to the selected frame. In
7129 particular, whenever you ask @value{GDBN} for the value of a variable in
7130 your program, the value is found in the selected frame. There are
7131 special @value{GDBN} commands to select whichever frame you are
7132 interested in. @xref{Selection, ,Selecting a Frame}.
7134 When your program stops, @value{GDBN} automatically selects the
7135 currently executing frame and describes it briefly, similar to the
7136 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7139 * Frames:: Stack frames
7140 * Backtrace:: Backtraces
7141 * Selection:: Selecting a frame
7142 * Frame Info:: Information on a frame
7143 * Frame Filter Management:: Managing frame filters
7148 @section Stack Frames
7150 @cindex frame, definition
7152 The call stack is divided up into contiguous pieces called @dfn{stack
7153 frames}, or @dfn{frames} for short; each frame is the data associated
7154 with one call to one function. The frame contains the arguments given
7155 to the function, the function's local variables, and the address at
7156 which the function is executing.
7158 @cindex initial frame
7159 @cindex outermost frame
7160 @cindex innermost frame
7161 When your program is started, the stack has only one frame, that of the
7162 function @code{main}. This is called the @dfn{initial} frame or the
7163 @dfn{outermost} frame. Each time a function is called, a new frame is
7164 made. Each time a function returns, the frame for that function invocation
7165 is eliminated. If a function is recursive, there can be many frames for
7166 the same function. The frame for the function in which execution is
7167 actually occurring is called the @dfn{innermost} frame. This is the most
7168 recently created of all the stack frames that still exist.
7170 @cindex frame pointer
7171 Inside your program, stack frames are identified by their addresses. A
7172 stack frame consists of many bytes, each of which has its own address; each
7173 kind of computer has a convention for choosing one byte whose
7174 address serves as the address of the frame. Usually this address is kept
7175 in a register called the @dfn{frame pointer register}
7176 (@pxref{Registers, $fp}) while execution is going on in that frame.
7178 @cindex frame number
7179 @value{GDBN} assigns numbers to all existing stack frames, starting with
7180 zero for the innermost frame, one for the frame that called it,
7181 and so on upward. These numbers do not really exist in your program;
7182 they are assigned by @value{GDBN} to give you a way of designating stack
7183 frames in @value{GDBN} commands.
7185 @c The -fomit-frame-pointer below perennially causes hbox overflow
7186 @c underflow problems.
7187 @cindex frameless execution
7188 Some compilers provide a way to compile functions so that they operate
7189 without stack frames. (For example, the @value{NGCC} option
7191 @samp{-fomit-frame-pointer}
7193 generates functions without a frame.)
7194 This is occasionally done with heavily used library functions to save
7195 the frame setup time. @value{GDBN} has limited facilities for dealing
7196 with these function invocations. If the innermost function invocation
7197 has no stack frame, @value{GDBN} nevertheless regards it as though
7198 it had a separate frame, which is numbered zero as usual, allowing
7199 correct tracing of the function call chain. However, @value{GDBN} has
7200 no provision for frameless functions elsewhere in the stack.
7206 @cindex call stack traces
7207 A backtrace is a summary of how your program got where it is. It shows one
7208 line per frame, for many frames, starting with the currently executing
7209 frame (frame zero), followed by its caller (frame one), and on up the
7212 @anchor{backtrace-command}
7215 @kindex bt @r{(@code{backtrace})}
7218 Print a backtrace of the entire stack: one line per frame for all
7219 frames in the stack.
7221 You can stop the backtrace at any time by typing the system interrupt
7222 character, normally @kbd{Ctrl-c}.
7224 @item backtrace @var{n}
7226 Similar, but print only the innermost @var{n} frames.
7228 @item backtrace -@var{n}
7230 Similar, but print only the outermost @var{n} frames.
7232 @item backtrace full
7234 @itemx bt full @var{n}
7235 @itemx bt full -@var{n}
7236 Print the values of the local variables also. As described above,
7237 @var{n} specifies the number of frames to print.
7239 @item backtrace no-filters
7240 @itemx bt no-filters
7241 @itemx bt no-filters @var{n}
7242 @itemx bt no-filters -@var{n}
7243 @itemx bt no-filters full
7244 @itemx bt no-filters full @var{n}
7245 @itemx bt no-filters full -@var{n}
7246 Do not run Python frame filters on this backtrace. @xref{Frame
7247 Filter API}, for more information. Additionally use @ref{disable
7248 frame-filter all} to turn off all frame filters. This is only
7249 relevant when @value{GDBN} has been configured with @code{Python}
7255 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7256 are additional aliases for @code{backtrace}.
7258 @cindex multiple threads, backtrace
7259 In a multi-threaded program, @value{GDBN} by default shows the
7260 backtrace only for the current thread. To display the backtrace for
7261 several or all of the threads, use the command @code{thread apply}
7262 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7263 apply all backtrace}, @value{GDBN} will display the backtrace for all
7264 the threads; this is handy when you debug a core dump of a
7265 multi-threaded program.
7267 Each line in the backtrace shows the frame number and the function name.
7268 The program counter value is also shown---unless you use @code{set
7269 print address off}. The backtrace also shows the source file name and
7270 line number, as well as the arguments to the function. The program
7271 counter value is omitted if it is at the beginning of the code for that
7274 Here is an example of a backtrace. It was made with the command
7275 @samp{bt 3}, so it shows the innermost three frames.
7279 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7281 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7282 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7284 (More stack frames follow...)
7289 The display for frame zero does not begin with a program counter
7290 value, indicating that your program has stopped at the beginning of the
7291 code for line @code{993} of @code{builtin.c}.
7294 The value of parameter @code{data} in frame 1 has been replaced by
7295 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7296 only if it is a scalar (integer, pointer, enumeration, etc). See command
7297 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7298 on how to configure the way function parameter values are printed.
7300 @cindex optimized out, in backtrace
7301 @cindex function call arguments, optimized out
7302 If your program was compiled with optimizations, some compilers will
7303 optimize away arguments passed to functions if those arguments are
7304 never used after the call. Such optimizations generate code that
7305 passes arguments through registers, but doesn't store those arguments
7306 in the stack frame. @value{GDBN} has no way of displaying such
7307 arguments in stack frames other than the innermost one. Here's what
7308 such a backtrace might look like:
7312 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7314 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7315 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7317 (More stack frames follow...)
7322 The values of arguments that were not saved in their stack frames are
7323 shown as @samp{<optimized out>}.
7325 If you need to display the values of such optimized-out arguments,
7326 either deduce that from other variables whose values depend on the one
7327 you are interested in, or recompile without optimizations.
7329 @cindex backtrace beyond @code{main} function
7330 @cindex program entry point
7331 @cindex startup code, and backtrace
7332 Most programs have a standard user entry point---a place where system
7333 libraries and startup code transition into user code. For C this is
7334 @code{main}@footnote{
7335 Note that embedded programs (the so-called ``free-standing''
7336 environment) are not required to have a @code{main} function as the
7337 entry point. They could even have multiple entry points.}.
7338 When @value{GDBN} finds the entry function in a backtrace
7339 it will terminate the backtrace, to avoid tracing into highly
7340 system-specific (and generally uninteresting) code.
7342 If you need to examine the startup code, or limit the number of levels
7343 in a backtrace, you can change this behavior:
7346 @item set backtrace past-main
7347 @itemx set backtrace past-main on
7348 @kindex set backtrace
7349 Backtraces will continue past the user entry point.
7351 @item set backtrace past-main off
7352 Backtraces will stop when they encounter the user entry point. This is the
7355 @item show backtrace past-main
7356 @kindex show backtrace
7357 Display the current user entry point backtrace policy.
7359 @item set backtrace past-entry
7360 @itemx set backtrace past-entry on
7361 Backtraces will continue past the internal entry point of an application.
7362 This entry point is encoded by the linker when the application is built,
7363 and is likely before the user entry point @code{main} (or equivalent) is called.
7365 @item set backtrace past-entry off
7366 Backtraces will stop when they encounter the internal entry point of an
7367 application. This is the default.
7369 @item show backtrace past-entry
7370 Display the current internal entry point backtrace policy.
7372 @item set backtrace limit @var{n}
7373 @itemx set backtrace limit 0
7374 @itemx set backtrace limit unlimited
7375 @cindex backtrace limit
7376 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7377 or zero means unlimited levels.
7379 @item show backtrace limit
7380 Display the current limit on backtrace levels.
7383 You can control how file names are displayed.
7386 @item set filename-display
7387 @itemx set filename-display relative
7388 @cindex filename-display
7389 Display file names relative to the compilation directory. This is the default.
7391 @item set filename-display basename
7392 Display only basename of a filename.
7394 @item set filename-display absolute
7395 Display an absolute filename.
7397 @item show filename-display
7398 Show the current way to display filenames.
7402 @section Selecting a Frame
7404 Most commands for examining the stack and other data in your program work on
7405 whichever stack frame is selected at the moment. Here are the commands for
7406 selecting a stack frame; all of them finish by printing a brief description
7407 of the stack frame just selected.
7410 @kindex frame@r{, selecting}
7411 @kindex f @r{(@code{frame})}
7414 Select frame number @var{n}. Recall that frame zero is the innermost
7415 (currently executing) frame, frame one is the frame that called the
7416 innermost one, and so on. The highest-numbered frame is the one for
7419 @item frame @var{stack-addr} [ @var{pc-addr} ]
7420 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7421 Select the frame at address @var{stack-addr}. This is useful mainly if the
7422 chaining of stack frames has been damaged by a bug, making it
7423 impossible for @value{GDBN} to assign numbers properly to all frames. In
7424 addition, this can be useful when your program has multiple stacks and
7425 switches between them. The optional @var{pc-addr} can also be given to
7426 specify the value of PC for the stack frame.
7430 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7431 numbers @var{n}, this advances toward the outermost frame, to higher
7432 frame numbers, to frames that have existed longer.
7435 @kindex do @r{(@code{down})}
7437 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7438 positive numbers @var{n}, this advances toward the innermost frame, to
7439 lower frame numbers, to frames that were created more recently.
7440 You may abbreviate @code{down} as @code{do}.
7443 All of these commands end by printing two lines of output describing the
7444 frame. The first line shows the frame number, the function name, the
7445 arguments, and the source file and line number of execution in that
7446 frame. The second line shows the text of that source line.
7454 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7456 10 read_input_file (argv[i]);
7460 After such a printout, the @code{list} command with no arguments
7461 prints ten lines centered on the point of execution in the frame.
7462 You can also edit the program at the point of execution with your favorite
7463 editing program by typing @code{edit}.
7464 @xref{List, ,Printing Source Lines},
7468 @kindex select-frame
7470 The @code{select-frame} command is a variant of @code{frame} that does
7471 not display the new frame after selecting it. This command is
7472 intended primarily for use in @value{GDBN} command scripts, where the
7473 output might be unnecessary and distracting.
7475 @kindex down-silently
7477 @item up-silently @var{n}
7478 @itemx down-silently @var{n}
7479 These two commands are variants of @code{up} and @code{down},
7480 respectively; they differ in that they do their work silently, without
7481 causing display of the new frame. They are intended primarily for use
7482 in @value{GDBN} command scripts, where the output might be unnecessary and
7487 @section Information About a Frame
7489 There are several other commands to print information about the selected
7495 When used without any argument, this command does not change which
7496 frame is selected, but prints a brief description of the currently
7497 selected stack frame. It can be abbreviated @code{f}. With an
7498 argument, this command is used to select a stack frame.
7499 @xref{Selection, ,Selecting a Frame}.
7502 @kindex info f @r{(@code{info frame})}
7505 This command prints a verbose description of the selected stack frame,
7510 the address of the frame
7512 the address of the next frame down (called by this frame)
7514 the address of the next frame up (caller of this frame)
7516 the language in which the source code corresponding to this frame is written
7518 the address of the frame's arguments
7520 the address of the frame's local variables
7522 the program counter saved in it (the address of execution in the caller frame)
7524 which registers were saved in the frame
7527 @noindent The verbose description is useful when
7528 something has gone wrong that has made the stack format fail to fit
7529 the usual conventions.
7531 @item info frame @var{addr}
7532 @itemx info f @var{addr}
7533 Print a verbose description of the frame at address @var{addr}, without
7534 selecting that frame. The selected frame remains unchanged by this
7535 command. This requires the same kind of address (more than one for some
7536 architectures) that you specify in the @code{frame} command.
7537 @xref{Selection, ,Selecting a Frame}.
7541 Print the arguments of the selected frame, each on a separate line.
7545 Print the local variables of the selected frame, each on a separate
7546 line. These are all variables (declared either static or automatic)
7547 accessible at the point of execution of the selected frame.
7551 @node Frame Filter Management
7552 @section Management of Frame Filters.
7553 @cindex managing frame filters
7555 Frame filters are Python based utilities to manage and decorate the
7556 output of frames. @xref{Frame Filter API}, for further information.
7558 Managing frame filters is performed by several commands available
7559 within @value{GDBN}, detailed here.
7562 @kindex info frame-filter
7563 @item info frame-filter
7564 Print a list of installed frame filters from all dictionaries, showing
7565 their name, priority and enabled status.
7567 @kindex disable frame-filter
7568 @anchor{disable frame-filter all}
7569 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7570 Disable a frame filter in the dictionary matching
7571 @var{filter-dictionary} and @var{filter-name}. The
7572 @var{filter-dictionary} may be @code{all}, @code{global},
7573 @code{progspace}, or the name of the object file where the frame filter
7574 dictionary resides. When @code{all} is specified, all frame filters
7575 across all dictionaries are disabled. The @var{filter-name} is the name
7576 of the frame filter and is used when @code{all} is not the option for
7577 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7578 may be enabled again later.
7580 @kindex enable frame-filter
7581 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7582 Enable a frame filter in the dictionary matching
7583 @var{filter-dictionary} and @var{filter-name}. The
7584 @var{filter-dictionary} may be @code{all}, @code{global},
7585 @code{progspace} or the name of the object file where the frame filter
7586 dictionary resides. When @code{all} is specified, all frame filters across
7587 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7588 filter and is used when @code{all} is not the option for
7589 @var{filter-dictionary}.
7594 (gdb) info frame-filter
7596 global frame-filters:
7597 Priority Enabled Name
7598 1000 No PrimaryFunctionFilter
7601 progspace /build/test frame-filters:
7602 Priority Enabled Name
7603 100 Yes ProgspaceFilter
7605 objfile /build/test frame-filters:
7606 Priority Enabled Name
7607 999 Yes BuildProgra Filter
7609 (gdb) disable frame-filter /build/test BuildProgramFilter
7610 (gdb) info frame-filter
7612 global frame-filters:
7613 Priority Enabled Name
7614 1000 No PrimaryFunctionFilter
7617 progspace /build/test frame-filters:
7618 Priority Enabled Name
7619 100 Yes ProgspaceFilter
7621 objfile /build/test frame-filters:
7622 Priority Enabled Name
7623 999 No BuildProgramFilter
7625 (gdb) enable frame-filter global PrimaryFunctionFilter
7626 (gdb) info frame-filter
7628 global frame-filters:
7629 Priority Enabled Name
7630 1000 Yes PrimaryFunctionFilter
7633 progspace /build/test frame-filters:
7634 Priority Enabled Name
7635 100 Yes ProgspaceFilter
7637 objfile /build/test frame-filters:
7638 Priority Enabled Name
7639 999 No BuildProgramFilter
7642 @kindex set frame-filter priority
7643 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7644 Set the @var{priority} of a frame filter in the dictionary matching
7645 @var{filter-dictionary}, and the frame filter name matching
7646 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7647 @code{progspace} or the name of the object file where the frame filter
7648 dictionary resides. The @var{priority} is an integer.
7650 @kindex show frame-filter priority
7651 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7652 Show the @var{priority} of a frame filter in the dictionary matching
7653 @var{filter-dictionary}, and the frame filter name matching
7654 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7655 @code{progspace} or the name of the object file where the frame filter
7661 (gdb) info frame-filter
7663 global frame-filters:
7664 Priority Enabled Name
7665 1000 Yes PrimaryFunctionFilter
7668 progspace /build/test frame-filters:
7669 Priority Enabled Name
7670 100 Yes ProgspaceFilter
7672 objfile /build/test frame-filters:
7673 Priority Enabled Name
7674 999 No BuildProgramFilter
7676 (gdb) set frame-filter priority global Reverse 50
7677 (gdb) info frame-filter
7679 global frame-filters:
7680 Priority Enabled Name
7681 1000 Yes PrimaryFunctionFilter
7684 progspace /build/test frame-filters:
7685 Priority Enabled Name
7686 100 Yes ProgspaceFilter
7688 objfile /build/test frame-filters:
7689 Priority Enabled Name
7690 999 No BuildProgramFilter
7695 @chapter Examining Source Files
7697 @value{GDBN} can print parts of your program's source, since the debugging
7698 information recorded in the program tells @value{GDBN} what source files were
7699 used to build it. When your program stops, @value{GDBN} spontaneously prints
7700 the line where it stopped. Likewise, when you select a stack frame
7701 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7702 execution in that frame has stopped. You can print other portions of
7703 source files by explicit command.
7705 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7706 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7707 @value{GDBN} under @sc{gnu} Emacs}.
7710 * List:: Printing source lines
7711 * Specify Location:: How to specify code locations
7712 * Edit:: Editing source files
7713 * Search:: Searching source files
7714 * Source Path:: Specifying source directories
7715 * Machine Code:: Source and machine code
7719 @section Printing Source Lines
7722 @kindex l @r{(@code{list})}
7723 To print lines from a source file, use the @code{list} command
7724 (abbreviated @code{l}). By default, ten lines are printed.
7725 There are several ways to specify what part of the file you want to
7726 print; see @ref{Specify Location}, for the full list.
7728 Here are the forms of the @code{list} command most commonly used:
7731 @item list @var{linenum}
7732 Print lines centered around line number @var{linenum} in the
7733 current source file.
7735 @item list @var{function}
7736 Print lines centered around the beginning of function
7740 Print more lines. If the last lines printed were printed with a
7741 @code{list} command, this prints lines following the last lines
7742 printed; however, if the last line printed was a solitary line printed
7743 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7744 Stack}), this prints lines centered around that line.
7747 Print lines just before the lines last printed.
7750 @cindex @code{list}, how many lines to display
7751 By default, @value{GDBN} prints ten source lines with any of these forms of
7752 the @code{list} command. You can change this using @code{set listsize}:
7755 @kindex set listsize
7756 @item set listsize @var{count}
7757 @itemx set listsize unlimited
7758 Make the @code{list} command display @var{count} source lines (unless
7759 the @code{list} argument explicitly specifies some other number).
7760 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7762 @kindex show listsize
7764 Display the number of lines that @code{list} prints.
7767 Repeating a @code{list} command with @key{RET} discards the argument,
7768 so it is equivalent to typing just @code{list}. This is more useful
7769 than listing the same lines again. An exception is made for an
7770 argument of @samp{-}; that argument is preserved in repetition so that
7771 each repetition moves up in the source file.
7773 In general, the @code{list} command expects you to supply zero, one or two
7774 @dfn{locations}. Locations specify source lines; there are several ways
7775 of writing them (@pxref{Specify Location}), but the effect is always
7776 to specify some source line.
7778 Here is a complete description of the possible arguments for @code{list}:
7781 @item list @var{location}
7782 Print lines centered around the line specified by @var{location}.
7784 @item list @var{first},@var{last}
7785 Print lines from @var{first} to @var{last}. Both arguments are
7786 locations. When a @code{list} command has two locations, and the
7787 source file of the second location is omitted, this refers to
7788 the same source file as the first location.
7790 @item list ,@var{last}
7791 Print lines ending with @var{last}.
7793 @item list @var{first},
7794 Print lines starting with @var{first}.
7797 Print lines just after the lines last printed.
7800 Print lines just before the lines last printed.
7803 As described in the preceding table.
7806 @node Specify Location
7807 @section Specifying a Location
7808 @cindex specifying location
7810 @cindex source location
7813 * Linespec Locations:: Linespec locations
7814 * Explicit Locations:: Explicit locations
7815 * Address Locations:: Address locations
7818 Several @value{GDBN} commands accept arguments that specify a location
7819 of your program's code. Since @value{GDBN} is a source-level
7820 debugger, a location usually specifies some line in the source code.
7821 Locations may be specified using three different formats:
7822 linespec locations, explicit locations, or address locations.
7824 @node Linespec Locations
7825 @subsection Linespec Locations
7826 @cindex linespec locations
7828 A @dfn{linespec} is a colon-separated list of source location parameters such
7829 as file name, function name, etc. Here are all the different ways of
7830 specifying a linespec:
7834 Specifies the line number @var{linenum} of the current source file.
7837 @itemx +@var{offset}
7838 Specifies the line @var{offset} lines before or after the @dfn{current
7839 line}. For the @code{list} command, the current line is the last one
7840 printed; for the breakpoint commands, this is the line at which
7841 execution stopped in the currently selected @dfn{stack frame}
7842 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7843 used as the second of the two linespecs in a @code{list} command,
7844 this specifies the line @var{offset} lines up or down from the first
7847 @item @var{filename}:@var{linenum}
7848 Specifies the line @var{linenum} in the source file @var{filename}.
7849 If @var{filename} is a relative file name, then it will match any
7850 source file name with the same trailing components. For example, if
7851 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7852 name of @file{/build/trunk/gcc/expr.c}, but not
7853 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7855 @item @var{function}
7856 Specifies the line that begins the body of the function @var{function}.
7857 For example, in C, this is the line with the open brace.
7859 @item @var{function}:@var{label}
7860 Specifies the line where @var{label} appears in @var{function}.
7862 @item @var{filename}:@var{function}
7863 Specifies the line that begins the body of the function @var{function}
7864 in the file @var{filename}. You only need the file name with a
7865 function name to avoid ambiguity when there are identically named
7866 functions in different source files.
7869 Specifies the line at which the label named @var{label} appears
7870 in the function corresponding to the currently selected stack frame.
7871 If there is no current selected stack frame (for instance, if the inferior
7872 is not running), then @value{GDBN} will not search for a label.
7874 @cindex breakpoint at static probe point
7875 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7876 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7877 applications to embed static probes. @xref{Static Probe Points}, for more
7878 information on finding and using static probes. This form of linespec
7879 specifies the location of such a static probe.
7881 If @var{objfile} is given, only probes coming from that shared library
7882 or executable matching @var{objfile} as a regular expression are considered.
7883 If @var{provider} is given, then only probes from that provider are considered.
7884 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7885 each one of those probes.
7888 @node Explicit Locations
7889 @subsection Explicit Locations
7890 @cindex explicit locations
7892 @dfn{Explicit locations} allow the user to directly specify the source
7893 location's parameters using option-value pairs.
7895 Explicit locations are useful when several functions, labels, or
7896 file names have the same name (base name for files) in the program's
7897 sources. In these cases, explicit locations point to the source
7898 line you meant more accurately and unambiguously. Also, using
7899 explicit locations might be faster in large programs.
7901 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7902 defined in the file named @file{foo} or the label @code{bar} in a function
7903 named @code{foo}. @value{GDBN} must search either the file system or
7904 the symbol table to know.
7906 The list of valid explicit location options is summarized in the
7910 @item -source @var{filename}
7911 The value specifies the source file name. To differentiate between
7912 files with the same base name, prepend as many directories as is necessary
7913 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7914 @value{GDBN} will use the first file it finds with the given base
7915 name. This option requires the use of either @code{-function} or @code{-line}.
7917 @item -function @var{function}
7918 The value specifies the name of a function. Operations
7919 on function locations unmodified by other options (such as @code{-label}
7920 or @code{-line}) refer to the line that begins the body of the function.
7921 In C, for example, this is the line with the open brace.
7923 @item -label @var{label}
7924 The value specifies the name of a label. When the function
7925 name is not specified, the label is searched in the function of the currently
7926 selected stack frame.
7928 @item -line @var{number}
7929 The value specifies a line offset for the location. The offset may either
7930 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7931 the command. When specified without any other options, the line offset is
7932 relative to the current line.
7935 Explicit location options may be abbreviated by omitting any non-unique
7936 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7938 @node Address Locations
7939 @subsection Address Locations
7940 @cindex address locations
7942 @dfn{Address locations} indicate a specific program address. They have
7943 the generalized form *@var{address}.
7945 For line-oriented commands, such as @code{list} and @code{edit}, this
7946 specifies a source line that contains @var{address}. For @code{break} and
7947 other breakpoint-oriented commands, this can be used to set breakpoints in
7948 parts of your program which do not have debugging information or
7951 Here @var{address} may be any expression valid in the current working
7952 language (@pxref{Languages, working language}) that specifies a code
7953 address. In addition, as a convenience, @value{GDBN} extends the
7954 semantics of expressions used in locations to cover several situations
7955 that frequently occur during debugging. Here are the various forms
7959 @item @var{expression}
7960 Any expression valid in the current working language.
7962 @item @var{funcaddr}
7963 An address of a function or procedure derived from its name. In C,
7964 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
7965 simply the function's name @var{function} (and actually a special case
7966 of a valid expression). In Pascal and Modula-2, this is
7967 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7968 (although the Pascal form also works).
7970 This form specifies the address of the function's first instruction,
7971 before the stack frame and arguments have been set up.
7973 @item '@var{filename}':@var{funcaddr}
7974 Like @var{funcaddr} above, but also specifies the name of the source
7975 file explicitly. This is useful if the name of the function does not
7976 specify the function unambiguously, e.g., if there are several
7977 functions with identical names in different source files.
7981 @section Editing Source Files
7982 @cindex editing source files
7985 @kindex e @r{(@code{edit})}
7986 To edit the lines in a source file, use the @code{edit} command.
7987 The editing program of your choice
7988 is invoked with the current line set to
7989 the active line in the program.
7990 Alternatively, there are several ways to specify what part of the file you
7991 want to print if you want to see other parts of the program:
7994 @item edit @var{location}
7995 Edit the source file specified by @code{location}. Editing starts at
7996 that @var{location}, e.g., at the specified source line of the
7997 specified file. @xref{Specify Location}, for all the possible forms
7998 of the @var{location} argument; here are the forms of the @code{edit}
7999 command most commonly used:
8002 @item edit @var{number}
8003 Edit the current source file with @var{number} as the active line number.
8005 @item edit @var{function}
8006 Edit the file containing @var{function} at the beginning of its definition.
8011 @subsection Choosing your Editor
8012 You can customize @value{GDBN} to use any editor you want
8014 The only restriction is that your editor (say @code{ex}), recognizes the
8015 following command-line syntax:
8017 ex +@var{number} file
8019 The optional numeric value +@var{number} specifies the number of the line in
8020 the file where to start editing.}.
8021 By default, it is @file{@value{EDITOR}}, but you can change this
8022 by setting the environment variable @code{EDITOR} before using
8023 @value{GDBN}. For example, to configure @value{GDBN} to use the
8024 @code{vi} editor, you could use these commands with the @code{sh} shell:
8030 or in the @code{csh} shell,
8032 setenv EDITOR /usr/bin/vi
8037 @section Searching Source Files
8038 @cindex searching source files
8040 There are two commands for searching through the current source file for a
8045 @kindex forward-search
8046 @kindex fo @r{(@code{forward-search})}
8047 @item forward-search @var{regexp}
8048 @itemx search @var{regexp}
8049 The command @samp{forward-search @var{regexp}} checks each line,
8050 starting with the one following the last line listed, for a match for
8051 @var{regexp}. It lists the line that is found. You can use the
8052 synonym @samp{search @var{regexp}} or abbreviate the command name as
8055 @kindex reverse-search
8056 @item reverse-search @var{regexp}
8057 The command @samp{reverse-search @var{regexp}} checks each line, starting
8058 with the one before the last line listed and going backward, for a match
8059 for @var{regexp}. It lists the line that is found. You can abbreviate
8060 this command as @code{rev}.
8064 @section Specifying Source Directories
8067 @cindex directories for source files
8068 Executable programs sometimes do not record the directories of the source
8069 files from which they were compiled, just the names. Even when they do,
8070 the directories could be moved between the compilation and your debugging
8071 session. @value{GDBN} has a list of directories to search for source files;
8072 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8073 it tries all the directories in the list, in the order they are present
8074 in the list, until it finds a file with the desired name.
8076 For example, suppose an executable references the file
8077 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8078 @file{/mnt/cross}. The file is first looked up literally; if this
8079 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8080 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8081 message is printed. @value{GDBN} does not look up the parts of the
8082 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8083 Likewise, the subdirectories of the source path are not searched: if
8084 the source path is @file{/mnt/cross}, and the binary refers to
8085 @file{foo.c}, @value{GDBN} would not find it under
8086 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8088 Plain file names, relative file names with leading directories, file
8089 names containing dots, etc.@: are all treated as described above; for
8090 instance, if the source path is @file{/mnt/cross}, and the source file
8091 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8092 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8093 that---@file{/mnt/cross/foo.c}.
8095 Note that the executable search path is @emph{not} used to locate the
8098 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8099 any information it has cached about where source files are found and where
8100 each line is in the file.
8104 When you start @value{GDBN}, its source path includes only @samp{cdir}
8105 and @samp{cwd}, in that order.
8106 To add other directories, use the @code{directory} command.
8108 The search path is used to find both program source files and @value{GDBN}
8109 script files (read using the @samp{-command} option and @samp{source} command).
8111 In addition to the source path, @value{GDBN} provides a set of commands
8112 that manage a list of source path substitution rules. A @dfn{substitution
8113 rule} specifies how to rewrite source directories stored in the program's
8114 debug information in case the sources were moved to a different
8115 directory between compilation and debugging. A rule is made of
8116 two strings, the first specifying what needs to be rewritten in
8117 the path, and the second specifying how it should be rewritten.
8118 In @ref{set substitute-path}, we name these two parts @var{from} and
8119 @var{to} respectively. @value{GDBN} does a simple string replacement
8120 of @var{from} with @var{to} at the start of the directory part of the
8121 source file name, and uses that result instead of the original file
8122 name to look up the sources.
8124 Using the previous example, suppose the @file{foo-1.0} tree has been
8125 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8126 @value{GDBN} to replace @file{/usr/src} in all source path names with
8127 @file{/mnt/cross}. The first lookup will then be
8128 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8129 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8130 substitution rule, use the @code{set substitute-path} command
8131 (@pxref{set substitute-path}).
8133 To avoid unexpected substitution results, a rule is applied only if the
8134 @var{from} part of the directory name ends at a directory separator.
8135 For instance, a rule substituting @file{/usr/source} into
8136 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8137 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8138 is applied only at the beginning of the directory name, this rule will
8139 not be applied to @file{/root/usr/source/baz.c} either.
8141 In many cases, you can achieve the same result using the @code{directory}
8142 command. However, @code{set substitute-path} can be more efficient in
8143 the case where the sources are organized in a complex tree with multiple
8144 subdirectories. With the @code{directory} command, you need to add each
8145 subdirectory of your project. If you moved the entire tree while
8146 preserving its internal organization, then @code{set substitute-path}
8147 allows you to direct the debugger to all the sources with one single
8150 @code{set substitute-path} is also more than just a shortcut command.
8151 The source path is only used if the file at the original location no
8152 longer exists. On the other hand, @code{set substitute-path} modifies
8153 the debugger behavior to look at the rewritten location instead. So, if
8154 for any reason a source file that is not relevant to your executable is
8155 located at the original location, a substitution rule is the only
8156 method available to point @value{GDBN} at the new location.
8158 @cindex @samp{--with-relocated-sources}
8159 @cindex default source path substitution
8160 You can configure a default source path substitution rule by
8161 configuring @value{GDBN} with the
8162 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8163 should be the name of a directory under @value{GDBN}'s configured
8164 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8165 directory names in debug information under @var{dir} will be adjusted
8166 automatically if the installed @value{GDBN} is moved to a new
8167 location. This is useful if @value{GDBN}, libraries or executables
8168 with debug information and corresponding source code are being moved
8172 @item directory @var{dirname} @dots{}
8173 @item dir @var{dirname} @dots{}
8174 Add directory @var{dirname} to the front of the source path. Several
8175 directory names may be given to this command, separated by @samp{:}
8176 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8177 part of absolute file names) or
8178 whitespace. You may specify a directory that is already in the source
8179 path; this moves it forward, so @value{GDBN} searches it sooner.
8183 @vindex $cdir@r{, convenience variable}
8184 @vindex $cwd@r{, convenience variable}
8185 @cindex compilation directory
8186 @cindex current directory
8187 @cindex working directory
8188 @cindex directory, current
8189 @cindex directory, compilation
8190 You can use the string @samp{$cdir} to refer to the compilation
8191 directory (if one is recorded), and @samp{$cwd} to refer to the current
8192 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8193 tracks the current working directory as it changes during your @value{GDBN}
8194 session, while the latter is immediately expanded to the current
8195 directory at the time you add an entry to the source path.
8198 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8200 @c RET-repeat for @code{directory} is explicitly disabled, but since
8201 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8203 @item set directories @var{path-list}
8204 @kindex set directories
8205 Set the source path to @var{path-list}.
8206 @samp{$cdir:$cwd} are added if missing.
8208 @item show directories
8209 @kindex show directories
8210 Print the source path: show which directories it contains.
8212 @anchor{set substitute-path}
8213 @item set substitute-path @var{from} @var{to}
8214 @kindex set substitute-path
8215 Define a source path substitution rule, and add it at the end of the
8216 current list of existing substitution rules. If a rule with the same
8217 @var{from} was already defined, then the old rule is also deleted.
8219 For example, if the file @file{/foo/bar/baz.c} was moved to
8220 @file{/mnt/cross/baz.c}, then the command
8223 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8227 will tell @value{GDBN} to replace @samp{/foo/bar} with
8228 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8229 @file{baz.c} even though it was moved.
8231 In the case when more than one substitution rule have been defined,
8232 the rules are evaluated one by one in the order where they have been
8233 defined. The first one matching, if any, is selected to perform
8236 For instance, if we had entered the following commands:
8239 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8240 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8244 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8245 @file{/mnt/include/defs.h} by using the first rule. However, it would
8246 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8247 @file{/mnt/src/lib/foo.c}.
8250 @item unset substitute-path [path]
8251 @kindex unset substitute-path
8252 If a path is specified, search the current list of substitution rules
8253 for a rule that would rewrite that path. Delete that rule if found.
8254 A warning is emitted by the debugger if no rule could be found.
8256 If no path is specified, then all substitution rules are deleted.
8258 @item show substitute-path [path]
8259 @kindex show substitute-path
8260 If a path is specified, then print the source path substitution rule
8261 which would rewrite that path, if any.
8263 If no path is specified, then print all existing source path substitution
8268 If your source path is cluttered with directories that are no longer of
8269 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8270 versions of source. You can correct the situation as follows:
8274 Use @code{directory} with no argument to reset the source path to its default value.
8277 Use @code{directory} with suitable arguments to reinstall the
8278 directories you want in the source path. You can add all the
8279 directories in one command.
8283 @section Source and Machine Code
8284 @cindex source line and its code address
8286 You can use the command @code{info line} to map source lines to program
8287 addresses (and vice versa), and the command @code{disassemble} to display
8288 a range of addresses as machine instructions. You can use the command
8289 @code{set disassemble-next-line} to set whether to disassemble next
8290 source line when execution stops. When run under @sc{gnu} Emacs
8291 mode, the @code{info line} command causes the arrow to point to the
8292 line specified. Also, @code{info line} prints addresses in symbolic form as
8297 @item info line @var{location}
8298 Print the starting and ending addresses of the compiled code for
8299 source line @var{location}. You can specify source lines in any of
8300 the ways documented in @ref{Specify Location}.
8303 For example, we can use @code{info line} to discover the location of
8304 the object code for the first line of function
8305 @code{m4_changequote}:
8307 @c FIXME: I think this example should also show the addresses in
8308 @c symbolic form, as they usually would be displayed.
8310 (@value{GDBP}) info line m4_changequote
8311 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8315 @cindex code address and its source line
8316 We can also inquire (using @code{*@var{addr}} as the form for
8317 @var{location}) what source line covers a particular address:
8319 (@value{GDBP}) info line *0x63ff
8320 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8323 @cindex @code{$_} and @code{info line}
8324 @cindex @code{x} command, default address
8325 @kindex x@r{(examine), and} info line
8326 After @code{info line}, the default address for the @code{x} command
8327 is changed to the starting address of the line, so that @samp{x/i} is
8328 sufficient to begin examining the machine code (@pxref{Memory,
8329 ,Examining Memory}). Also, this address is saved as the value of the
8330 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8335 @cindex assembly instructions
8336 @cindex instructions, assembly
8337 @cindex machine instructions
8338 @cindex listing machine instructions
8340 @itemx disassemble /m
8341 @itemx disassemble /s
8342 @itemx disassemble /r
8343 This specialized command dumps a range of memory as machine
8344 instructions. It can also print mixed source+disassembly by specifying
8345 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8346 as well as in symbolic form by specifying the @code{/r} modifier.
8347 The default memory range is the function surrounding the
8348 program counter of the selected frame. A single argument to this
8349 command is a program counter value; @value{GDBN} dumps the function
8350 surrounding this value. When two arguments are given, they should
8351 be separated by a comma, possibly surrounded by whitespace. The
8352 arguments specify a range of addresses to dump, in one of two forms:
8355 @item @var{start},@var{end}
8356 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8357 @item @var{start},+@var{length}
8358 the addresses from @var{start} (inclusive) to
8359 @code{@var{start}+@var{length}} (exclusive).
8363 When 2 arguments are specified, the name of the function is also
8364 printed (since there could be several functions in the given range).
8366 The argument(s) can be any expression yielding a numeric value, such as
8367 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8369 If the range of memory being disassembled contains current program counter,
8370 the instruction at that location is shown with a @code{=>} marker.
8373 The following example shows the disassembly of a range of addresses of
8374 HP PA-RISC 2.0 code:
8377 (@value{GDBP}) disas 0x32c4, 0x32e4
8378 Dump of assembler code from 0x32c4 to 0x32e4:
8379 0x32c4 <main+204>: addil 0,dp
8380 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8381 0x32cc <main+212>: ldil 0x3000,r31
8382 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8383 0x32d4 <main+220>: ldo 0(r31),rp
8384 0x32d8 <main+224>: addil -0x800,dp
8385 0x32dc <main+228>: ldo 0x588(r1),r26
8386 0x32e0 <main+232>: ldil 0x3000,r31
8387 End of assembler dump.
8390 Here is an example showing mixed source+assembly for Intel x86
8391 with @code{/m} or @code{/s}, when the program is stopped just after
8392 function prologue in a non-optimized function with no inline code.
8395 (@value{GDBP}) disas /m main
8396 Dump of assembler code for function main:
8398 0x08048330 <+0>: push %ebp
8399 0x08048331 <+1>: mov %esp,%ebp
8400 0x08048333 <+3>: sub $0x8,%esp
8401 0x08048336 <+6>: and $0xfffffff0,%esp
8402 0x08048339 <+9>: sub $0x10,%esp
8404 6 printf ("Hello.\n");
8405 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8406 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8410 0x08048348 <+24>: mov $0x0,%eax
8411 0x0804834d <+29>: leave
8412 0x0804834e <+30>: ret
8414 End of assembler dump.
8417 The @code{/m} option is deprecated as its output is not useful when
8418 there is either inlined code or re-ordered code.
8419 The @code{/s} option is the preferred choice.
8420 Here is an example for AMD x86-64 showing the difference between
8421 @code{/m} output and @code{/s} output.
8422 This example has one inline function defined in a header file,
8423 and the code is compiled with @samp{-O2} optimization.
8424 Note how the @code{/m} output is missing the disassembly of
8425 several instructions that are present in the @code{/s} output.
8455 (@value{GDBP}) disas /m main
8456 Dump of assembler code for function main:
8460 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8461 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8465 0x000000000040041d <+29>: xor %eax,%eax
8466 0x000000000040041f <+31>: retq
8467 0x0000000000400420 <+32>: add %eax,%eax
8468 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8470 End of assembler dump.
8471 (@value{GDBP}) disas /s main
8472 Dump of assembler code for function main:
8476 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8480 0x0000000000400406 <+6>: test %eax,%eax
8481 0x0000000000400408 <+8>: js 0x400420 <main+32>
8486 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8487 0x000000000040040d <+13>: test %eax,%eax
8488 0x000000000040040f <+15>: mov $0x1,%eax
8489 0x0000000000400414 <+20>: cmovne %edx,%eax
8493 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8497 0x000000000040041d <+29>: xor %eax,%eax
8498 0x000000000040041f <+31>: retq
8502 0x0000000000400420 <+32>: add %eax,%eax
8503 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8504 End of assembler dump.
8507 Here is another example showing raw instructions in hex for AMD x86-64,
8510 (gdb) disas /r 0x400281,+10
8511 Dump of assembler code from 0x400281 to 0x40028b:
8512 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8513 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8514 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8515 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8516 End of assembler dump.
8519 Addresses cannot be specified as a location (@pxref{Specify Location}).
8520 So, for example, if you want to disassemble function @code{bar}
8521 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8522 and not @samp{disassemble foo.c:bar}.
8524 Some architectures have more than one commonly-used set of instruction
8525 mnemonics or other syntax.
8527 For programs that were dynamically linked and use shared libraries,
8528 instructions that call functions or branch to locations in the shared
8529 libraries might show a seemingly bogus location---it's actually a
8530 location of the relocation table. On some architectures, @value{GDBN}
8531 might be able to resolve these to actual function names.
8534 @kindex set disassembler-options
8535 @cindex disassembler options
8536 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8537 This command controls the passing of target specific information to
8538 the disassembler. For a list of valid options, please refer to the
8539 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8540 manual and/or the output of @kbd{objdump --help}
8541 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8542 The default value is the empty string.
8544 If it is necessary to specify more than one disassembler option, then
8545 multiple options can be placed together into a comma separated list.
8546 Currently this command is only supported on targets ARM, PowerPC
8549 @kindex show disassembler-options
8550 @item show disassembler-options
8551 Show the current setting of the disassembler options.
8555 @kindex set disassembly-flavor
8556 @cindex Intel disassembly flavor
8557 @cindex AT&T disassembly flavor
8558 @item set disassembly-flavor @var{instruction-set}
8559 Select the instruction set to use when disassembling the
8560 program via the @code{disassemble} or @code{x/i} commands.
8562 Currently this command is only defined for the Intel x86 family. You
8563 can set @var{instruction-set} to either @code{intel} or @code{att}.
8564 The default is @code{att}, the AT&T flavor used by default by Unix
8565 assemblers for x86-based targets.
8567 @kindex show disassembly-flavor
8568 @item show disassembly-flavor
8569 Show the current setting of the disassembly flavor.
8573 @kindex set disassemble-next-line
8574 @kindex show disassemble-next-line
8575 @item set disassemble-next-line
8576 @itemx show disassemble-next-line
8577 Control whether or not @value{GDBN} will disassemble the next source
8578 line or instruction when execution stops. If ON, @value{GDBN} will
8579 display disassembly of the next source line when execution of the
8580 program being debugged stops. This is @emph{in addition} to
8581 displaying the source line itself, which @value{GDBN} always does if
8582 possible. If the next source line cannot be displayed for some reason
8583 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8584 info in the debug info), @value{GDBN} will display disassembly of the
8585 next @emph{instruction} instead of showing the next source line. If
8586 AUTO, @value{GDBN} will display disassembly of next instruction only
8587 if the source line cannot be displayed. This setting causes
8588 @value{GDBN} to display some feedback when you step through a function
8589 with no line info or whose source file is unavailable. The default is
8590 OFF, which means never display the disassembly of the next line or
8596 @chapter Examining Data
8598 @cindex printing data
8599 @cindex examining data
8602 The usual way to examine data in your program is with the @code{print}
8603 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8604 evaluates and prints the value of an expression of the language your
8605 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8606 Different Languages}). It may also print the expression using a
8607 Python-based pretty-printer (@pxref{Pretty Printing}).
8610 @item print @var{expr}
8611 @itemx print /@var{f} @var{expr}
8612 @var{expr} is an expression (in the source language). By default the
8613 value of @var{expr} is printed in a format appropriate to its data type;
8614 you can choose a different format by specifying @samp{/@var{f}}, where
8615 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8619 @itemx print /@var{f}
8620 @cindex reprint the last value
8621 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8622 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8623 conveniently inspect the same value in an alternative format.
8626 A more low-level way of examining data is with the @code{x} command.
8627 It examines data in memory at a specified address and prints it in a
8628 specified format. @xref{Memory, ,Examining Memory}.
8630 If you are interested in information about types, or about how the
8631 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8632 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8635 @cindex exploring hierarchical data structures
8637 Another way of examining values of expressions and type information is
8638 through the Python extension command @code{explore} (available only if
8639 the @value{GDBN} build is configured with @code{--with-python}). It
8640 offers an interactive way to start at the highest level (or, the most
8641 abstract level) of the data type of an expression (or, the data type
8642 itself) and explore all the way down to leaf scalar values/fields
8643 embedded in the higher level data types.
8646 @item explore @var{arg}
8647 @var{arg} is either an expression (in the source language), or a type
8648 visible in the current context of the program being debugged.
8651 The working of the @code{explore} command can be illustrated with an
8652 example. If a data type @code{struct ComplexStruct} is defined in your
8662 struct ComplexStruct
8664 struct SimpleStruct *ss_p;
8670 followed by variable declarations as
8673 struct SimpleStruct ss = @{ 10, 1.11 @};
8674 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8678 then, the value of the variable @code{cs} can be explored using the
8679 @code{explore} command as follows.
8683 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8684 the following fields:
8686 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8687 arr = <Enter 1 to explore this field of type `int [10]'>
8689 Enter the field number of choice:
8693 Since the fields of @code{cs} are not scalar values, you are being
8694 prompted to chose the field you want to explore. Let's say you choose
8695 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8696 pointer, you will be asked if it is pointing to a single value. From
8697 the declaration of @code{cs} above, it is indeed pointing to a single
8698 value, hence you enter @code{y}. If you enter @code{n}, then you will
8699 be asked if it were pointing to an array of values, in which case this
8700 field will be explored as if it were an array.
8703 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8704 Continue exploring it as a pointer to a single value [y/n]: y
8705 The value of `*(cs.ss_p)' is a struct/class of type `struct
8706 SimpleStruct' with the following fields:
8708 i = 10 .. (Value of type `int')
8709 d = 1.1100000000000001 .. (Value of type `double')
8711 Press enter to return to parent value:
8715 If the field @code{arr} of @code{cs} was chosen for exploration by
8716 entering @code{1} earlier, then since it is as array, you will be
8717 prompted to enter the index of the element in the array that you want
8721 `cs.arr' is an array of `int'.
8722 Enter the index of the element you want to explore in `cs.arr': 5
8724 `(cs.arr)[5]' is a scalar value of type `int'.
8728 Press enter to return to parent value:
8731 In general, at any stage of exploration, you can go deeper towards the
8732 leaf values by responding to the prompts appropriately, or hit the
8733 return key to return to the enclosing data structure (the @i{higher}
8734 level data structure).
8736 Similar to exploring values, you can use the @code{explore} command to
8737 explore types. Instead of specifying a value (which is typically a
8738 variable name or an expression valid in the current context of the
8739 program being debugged), you specify a type name. If you consider the
8740 same example as above, your can explore the type
8741 @code{struct ComplexStruct} by passing the argument
8742 @code{struct ComplexStruct} to the @code{explore} command.
8745 (gdb) explore struct ComplexStruct
8749 By responding to the prompts appropriately in the subsequent interactive
8750 session, you can explore the type @code{struct ComplexStruct} in a
8751 manner similar to how the value @code{cs} was explored in the above
8754 The @code{explore} command also has two sub-commands,
8755 @code{explore value} and @code{explore type}. The former sub-command is
8756 a way to explicitly specify that value exploration of the argument is
8757 being invoked, while the latter is a way to explicitly specify that type
8758 exploration of the argument is being invoked.
8761 @item explore value @var{expr}
8762 @cindex explore value
8763 This sub-command of @code{explore} explores the value of the
8764 expression @var{expr} (if @var{expr} is an expression valid in the
8765 current context of the program being debugged). The behavior of this
8766 command is identical to that of the behavior of the @code{explore}
8767 command being passed the argument @var{expr}.
8769 @item explore type @var{arg}
8770 @cindex explore type
8771 This sub-command of @code{explore} explores the type of @var{arg} (if
8772 @var{arg} is a type visible in the current context of program being
8773 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8774 is an expression valid in the current context of the program being
8775 debugged). If @var{arg} is a type, then the behavior of this command is
8776 identical to that of the @code{explore} command being passed the
8777 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8778 this command will be identical to that of the @code{explore} command
8779 being passed the type of @var{arg} as the argument.
8783 * Expressions:: Expressions
8784 * Ambiguous Expressions:: Ambiguous Expressions
8785 * Variables:: Program variables
8786 * Arrays:: Artificial arrays
8787 * Output Formats:: Output formats
8788 * Memory:: Examining memory
8789 * Auto Display:: Automatic display
8790 * Print Settings:: Print settings
8791 * Pretty Printing:: Python pretty printing
8792 * Value History:: Value history
8793 * Convenience Vars:: Convenience variables
8794 * Convenience Funs:: Convenience functions
8795 * Registers:: Registers
8796 * Floating Point Hardware:: Floating point hardware
8797 * Vector Unit:: Vector Unit
8798 * OS Information:: Auxiliary data provided by operating system
8799 * Memory Region Attributes:: Memory region attributes
8800 * Dump/Restore Files:: Copy between memory and a file
8801 * Core File Generation:: Cause a program dump its core
8802 * Character Sets:: Debugging programs that use a different
8803 character set than GDB does
8804 * Caching Target Data:: Data caching for targets
8805 * Searching Memory:: Searching memory for a sequence of bytes
8806 * Value Sizes:: Managing memory allocated for values
8810 @section Expressions
8813 @code{print} and many other @value{GDBN} commands accept an expression and
8814 compute its value. Any kind of constant, variable or operator defined
8815 by the programming language you are using is valid in an expression in
8816 @value{GDBN}. This includes conditional expressions, function calls,
8817 casts, and string constants. It also includes preprocessor macros, if
8818 you compiled your program to include this information; see
8821 @cindex arrays in expressions
8822 @value{GDBN} supports array constants in expressions input by
8823 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8824 you can use the command @code{print @{1, 2, 3@}} to create an array
8825 of three integers. If you pass an array to a function or assign it
8826 to a program variable, @value{GDBN} copies the array to memory that
8827 is @code{malloc}ed in the target program.
8829 Because C is so widespread, most of the expressions shown in examples in
8830 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8831 Languages}, for information on how to use expressions in other
8834 In this section, we discuss operators that you can use in @value{GDBN}
8835 expressions regardless of your programming language.
8837 @cindex casts, in expressions
8838 Casts are supported in all languages, not just in C, because it is so
8839 useful to cast a number into a pointer in order to examine a structure
8840 at that address in memory.
8841 @c FIXME: casts supported---Mod2 true?
8843 @value{GDBN} supports these operators, in addition to those common
8844 to programming languages:
8848 @samp{@@} is a binary operator for treating parts of memory as arrays.
8849 @xref{Arrays, ,Artificial Arrays}, for more information.
8852 @samp{::} allows you to specify a variable in terms of the file or
8853 function where it is defined. @xref{Variables, ,Program Variables}.
8855 @cindex @{@var{type}@}
8856 @cindex type casting memory
8857 @cindex memory, viewing as typed object
8858 @cindex casts, to view memory
8859 @item @{@var{type}@} @var{addr}
8860 Refers to an object of type @var{type} stored at address @var{addr} in
8861 memory. The address @var{addr} may be any expression whose value is
8862 an integer or pointer (but parentheses are required around binary
8863 operators, just as in a cast). This construct is allowed regardless
8864 of what kind of data is normally supposed to reside at @var{addr}.
8867 @node Ambiguous Expressions
8868 @section Ambiguous Expressions
8869 @cindex ambiguous expressions
8871 Expressions can sometimes contain some ambiguous elements. For instance,
8872 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8873 a single function name to be defined several times, for application in
8874 different contexts. This is called @dfn{overloading}. Another example
8875 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8876 templates and is typically instantiated several times, resulting in
8877 the same function name being defined in different contexts.
8879 In some cases and depending on the language, it is possible to adjust
8880 the expression to remove the ambiguity. For instance in C@t{++}, you
8881 can specify the signature of the function you want to break on, as in
8882 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8883 qualified name of your function often makes the expression unambiguous
8886 When an ambiguity that needs to be resolved is detected, the debugger
8887 has the capability to display a menu of numbered choices for each
8888 possibility, and then waits for the selection with the prompt @samp{>}.
8889 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8890 aborts the current command. If the command in which the expression was
8891 used allows more than one choice to be selected, the next option in the
8892 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8895 For example, the following session excerpt shows an attempt to set a
8896 breakpoint at the overloaded symbol @code{String::after}.
8897 We choose three particular definitions of that function name:
8899 @c FIXME! This is likely to change to show arg type lists, at least
8902 (@value{GDBP}) b String::after
8905 [2] file:String.cc; line number:867
8906 [3] file:String.cc; line number:860
8907 [4] file:String.cc; line number:875
8908 [5] file:String.cc; line number:853
8909 [6] file:String.cc; line number:846
8910 [7] file:String.cc; line number:735
8912 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8913 Breakpoint 2 at 0xb344: file String.cc, line 875.
8914 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8915 Multiple breakpoints were set.
8916 Use the "delete" command to delete unwanted
8923 @kindex set multiple-symbols
8924 @item set multiple-symbols @var{mode}
8925 @cindex multiple-symbols menu
8927 This option allows you to adjust the debugger behavior when an expression
8930 By default, @var{mode} is set to @code{all}. If the command with which
8931 the expression is used allows more than one choice, then @value{GDBN}
8932 automatically selects all possible choices. For instance, inserting
8933 a breakpoint on a function using an ambiguous name results in a breakpoint
8934 inserted on each possible match. However, if a unique choice must be made,
8935 then @value{GDBN} uses the menu to help you disambiguate the expression.
8936 For instance, printing the address of an overloaded function will result
8937 in the use of the menu.
8939 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8940 when an ambiguity is detected.
8942 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8943 an error due to the ambiguity and the command is aborted.
8945 @kindex show multiple-symbols
8946 @item show multiple-symbols
8947 Show the current value of the @code{multiple-symbols} setting.
8951 @section Program Variables
8953 The most common kind of expression to use is the name of a variable
8956 Variables in expressions are understood in the selected stack frame
8957 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8961 global (or file-static)
8968 visible according to the scope rules of the
8969 programming language from the point of execution in that frame
8972 @noindent This means that in the function
8987 you can examine and use the variable @code{a} whenever your program is
8988 executing within the function @code{foo}, but you can only use or
8989 examine the variable @code{b} while your program is executing inside
8990 the block where @code{b} is declared.
8992 @cindex variable name conflict
8993 There is an exception: you can refer to a variable or function whose
8994 scope is a single source file even if the current execution point is not
8995 in this file. But it is possible to have more than one such variable or
8996 function with the same name (in different source files). If that
8997 happens, referring to that name has unpredictable effects. If you wish,
8998 you can specify a static variable in a particular function or file by
8999 using the colon-colon (@code{::}) notation:
9001 @cindex colon-colon, context for variables/functions
9003 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9004 @cindex @code{::}, context for variables/functions
9007 @var{file}::@var{variable}
9008 @var{function}::@var{variable}
9012 Here @var{file} or @var{function} is the name of the context for the
9013 static @var{variable}. In the case of file names, you can use quotes to
9014 make sure @value{GDBN} parses the file name as a single word---for example,
9015 to print a global value of @code{x} defined in @file{f2.c}:
9018 (@value{GDBP}) p 'f2.c'::x
9021 The @code{::} notation is normally used for referring to
9022 static variables, since you typically disambiguate uses of local variables
9023 in functions by selecting the appropriate frame and using the
9024 simple name of the variable. However, you may also use this notation
9025 to refer to local variables in frames enclosing the selected frame:
9034 process (a); /* Stop here */
9045 For example, if there is a breakpoint at the commented line,
9046 here is what you might see
9047 when the program stops after executing the call @code{bar(0)}:
9052 (@value{GDBP}) p bar::a
9055 #2 0x080483d0 in foo (a=5) at foobar.c:12
9058 (@value{GDBP}) p bar::a
9062 @cindex C@t{++} scope resolution
9063 These uses of @samp{::} are very rarely in conflict with the very
9064 similar use of the same notation in C@t{++}. When they are in
9065 conflict, the C@t{++} meaning takes precedence; however, this can be
9066 overridden by quoting the file or function name with single quotes.
9068 For example, suppose the program is stopped in a method of a class
9069 that has a field named @code{includefile}, and there is also an
9070 include file named @file{includefile} that defines a variable,
9074 (@value{GDBP}) p includefile
9076 (@value{GDBP}) p includefile::some_global
9077 A syntax error in expression, near `'.
9078 (@value{GDBP}) p 'includefile'::some_global
9082 @cindex wrong values
9083 @cindex variable values, wrong
9084 @cindex function entry/exit, wrong values of variables
9085 @cindex optimized code, wrong values of variables
9087 @emph{Warning:} Occasionally, a local variable may appear to have the
9088 wrong value at certain points in a function---just after entry to a new
9089 scope, and just before exit.
9091 You may see this problem when you are stepping by machine instructions.
9092 This is because, on most machines, it takes more than one instruction to
9093 set up a stack frame (including local variable definitions); if you are
9094 stepping by machine instructions, variables may appear to have the wrong
9095 values until the stack frame is completely built. On exit, it usually
9096 also takes more than one machine instruction to destroy a stack frame;
9097 after you begin stepping through that group of instructions, local
9098 variable definitions may be gone.
9100 This may also happen when the compiler does significant optimizations.
9101 To be sure of always seeing accurate values, turn off all optimization
9104 @cindex ``No symbol "foo" in current context''
9105 Another possible effect of compiler optimizations is to optimize
9106 unused variables out of existence, or assign variables to registers (as
9107 opposed to memory addresses). Depending on the support for such cases
9108 offered by the debug info format used by the compiler, @value{GDBN}
9109 might not be able to display values for such local variables. If that
9110 happens, @value{GDBN} will print a message like this:
9113 No symbol "foo" in current context.
9116 To solve such problems, either recompile without optimizations, or use a
9117 different debug info format, if the compiler supports several such
9118 formats. @xref{Compilation}, for more information on choosing compiler
9119 options. @xref{C, ,C and C@t{++}}, for more information about debug
9120 info formats that are best suited to C@t{++} programs.
9122 If you ask to print an object whose contents are unknown to
9123 @value{GDBN}, e.g., because its data type is not completely specified
9124 by the debug information, @value{GDBN} will say @samp{<incomplete
9125 type>}. @xref{Symbols, incomplete type}, for more about this.
9127 If you append @kbd{@@entry} string to a function parameter name you get its
9128 value at the time the function got called. If the value is not available an
9129 error message is printed. Entry values are available only with some compilers.
9130 Entry values are normally also printed at the function parameter list according
9131 to @ref{set print entry-values}.
9134 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9140 (gdb) print i@@entry
9144 Strings are identified as arrays of @code{char} values without specified
9145 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9146 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9147 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9148 defines literal string type @code{"char"} as @code{char} without a sign.
9153 signed char var1[] = "A";
9156 You get during debugging
9161 $2 = @{65 'A', 0 '\0'@}
9165 @section Artificial Arrays
9167 @cindex artificial array
9169 @kindex @@@r{, referencing memory as an array}
9170 It is often useful to print out several successive objects of the
9171 same type in memory; a section of an array, or an array of
9172 dynamically determined size for which only a pointer exists in the
9175 You can do this by referring to a contiguous span of memory as an
9176 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9177 operand of @samp{@@} should be the first element of the desired array
9178 and be an individual object. The right operand should be the desired length
9179 of the array. The result is an array value whose elements are all of
9180 the type of the left argument. The first element is actually the left
9181 argument; the second element comes from bytes of memory immediately
9182 following those that hold the first element, and so on. Here is an
9183 example. If a program says
9186 int *array = (int *) malloc (len * sizeof (int));
9190 you can print the contents of @code{array} with
9196 The left operand of @samp{@@} must reside in memory. Array values made
9197 with @samp{@@} in this way behave just like other arrays in terms of
9198 subscripting, and are coerced to pointers when used in expressions.
9199 Artificial arrays most often appear in expressions via the value history
9200 (@pxref{Value History, ,Value History}), after printing one out.
9202 Another way to create an artificial array is to use a cast.
9203 This re-interprets a value as if it were an array.
9204 The value need not be in memory:
9206 (@value{GDBP}) p/x (short[2])0x12345678
9207 $1 = @{0x1234, 0x5678@}
9210 As a convenience, if you leave the array length out (as in
9211 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9212 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9214 (@value{GDBP}) p/x (short[])0x12345678
9215 $2 = @{0x1234, 0x5678@}
9218 Sometimes the artificial array mechanism is not quite enough; in
9219 moderately complex data structures, the elements of interest may not
9220 actually be adjacent---for example, if you are interested in the values
9221 of pointers in an array. One useful work-around in this situation is
9222 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9223 Variables}) as a counter in an expression that prints the first
9224 interesting value, and then repeat that expression via @key{RET}. For
9225 instance, suppose you have an array @code{dtab} of pointers to
9226 structures, and you are interested in the values of a field @code{fv}
9227 in each structure. Here is an example of what you might type:
9237 @node Output Formats
9238 @section Output Formats
9240 @cindex formatted output
9241 @cindex output formats
9242 By default, @value{GDBN} prints a value according to its data type. Sometimes
9243 this is not what you want. For example, you might want to print a number
9244 in hex, or a pointer in decimal. Or you might want to view data in memory
9245 at a certain address as a character string or as an instruction. To do
9246 these things, specify an @dfn{output format} when you print a value.
9248 The simplest use of output formats is to say how to print a value
9249 already computed. This is done by starting the arguments of the
9250 @code{print} command with a slash and a format letter. The format
9251 letters supported are:
9255 Regard the bits of the value as an integer, and print the integer in
9259 Print as integer in signed decimal.
9262 Print as integer in unsigned decimal.
9265 Print as integer in octal.
9268 Print as integer in binary. The letter @samp{t} stands for ``two''.
9269 @footnote{@samp{b} cannot be used because these format letters are also
9270 used with the @code{x} command, where @samp{b} stands for ``byte'';
9271 see @ref{Memory,,Examining Memory}.}
9274 @cindex unknown address, locating
9275 @cindex locate address
9276 Print as an address, both absolute in hexadecimal and as an offset from
9277 the nearest preceding symbol. You can use this format used to discover
9278 where (in what function) an unknown address is located:
9281 (@value{GDBP}) p/a 0x54320
9282 $3 = 0x54320 <_initialize_vx+396>
9286 The command @code{info symbol 0x54320} yields similar results.
9287 @xref{Symbols, info symbol}.
9290 Regard as an integer and print it as a character constant. This
9291 prints both the numerical value and its character representation. The
9292 character representation is replaced with the octal escape @samp{\nnn}
9293 for characters outside the 7-bit @sc{ascii} range.
9295 Without this format, @value{GDBN} displays @code{char},
9296 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9297 constants. Single-byte members of vectors are displayed as integer
9301 Regard the bits of the value as a floating point number and print
9302 using typical floating point syntax.
9305 @cindex printing strings
9306 @cindex printing byte arrays
9307 Regard as a string, if possible. With this format, pointers to single-byte
9308 data are displayed as null-terminated strings and arrays of single-byte data
9309 are displayed as fixed-length strings. Other values are displayed in their
9312 Without this format, @value{GDBN} displays pointers to and arrays of
9313 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9314 strings. Single-byte members of a vector are displayed as an integer
9318 Like @samp{x} formatting, the value is treated as an integer and
9319 printed as hexadecimal, but leading zeros are printed to pad the value
9320 to the size of the integer type.
9323 @cindex raw printing
9324 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9325 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9326 Printing}). This typically results in a higher-level display of the
9327 value's contents. The @samp{r} format bypasses any Python
9328 pretty-printer which might exist.
9331 For example, to print the program counter in hex (@pxref{Registers}), type
9338 Note that no space is required before the slash; this is because command
9339 names in @value{GDBN} cannot contain a slash.
9341 To reprint the last value in the value history with a different format,
9342 you can use the @code{print} command with just a format and no
9343 expression. For example, @samp{p/x} reprints the last value in hex.
9346 @section Examining Memory
9348 You can use the command @code{x} (for ``examine'') to examine memory in
9349 any of several formats, independently of your program's data types.
9351 @cindex examining memory
9353 @kindex x @r{(examine memory)}
9354 @item x/@var{nfu} @var{addr}
9357 Use the @code{x} command to examine memory.
9360 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9361 much memory to display and how to format it; @var{addr} is an
9362 expression giving the address where you want to start displaying memory.
9363 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9364 Several commands set convenient defaults for @var{addr}.
9367 @item @var{n}, the repeat count
9368 The repeat count is a decimal integer; the default is 1. It specifies
9369 how much memory (counting by units @var{u}) to display. If a negative
9370 number is specified, memory is examined backward from @var{addr}.
9371 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9374 @item @var{f}, the display format
9375 The display format is one of the formats used by @code{print}
9376 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9377 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9378 The default is @samp{x} (hexadecimal) initially. The default changes
9379 each time you use either @code{x} or @code{print}.
9381 @item @var{u}, the unit size
9382 The unit size is any of
9388 Halfwords (two bytes).
9390 Words (four bytes). This is the initial default.
9392 Giant words (eight bytes).
9395 Each time you specify a unit size with @code{x}, that size becomes the
9396 default unit the next time you use @code{x}. For the @samp{i} format,
9397 the unit size is ignored and is normally not written. For the @samp{s} format,
9398 the unit size defaults to @samp{b}, unless it is explicitly given.
9399 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9400 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9401 Note that the results depend on the programming language of the
9402 current compilation unit. If the language is C, the @samp{s}
9403 modifier will use the UTF-16 encoding while @samp{w} will use
9404 UTF-32. The encoding is set by the programming language and cannot
9407 @item @var{addr}, starting display address
9408 @var{addr} is the address where you want @value{GDBN} to begin displaying
9409 memory. The expression need not have a pointer value (though it may);
9410 it is always interpreted as an integer address of a byte of memory.
9411 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9412 @var{addr} is usually just after the last address examined---but several
9413 other commands also set the default address: @code{info breakpoints} (to
9414 the address of the last breakpoint listed), @code{info line} (to the
9415 starting address of a line), and @code{print} (if you use it to display
9416 a value from memory).
9419 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9420 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9421 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9422 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9423 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9425 You can also specify a negative repeat count to examine memory backward
9426 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9427 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9429 Since the letters indicating unit sizes are all distinct from the
9430 letters specifying output formats, you do not have to remember whether
9431 unit size or format comes first; either order works. The output
9432 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9433 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9435 Even though the unit size @var{u} is ignored for the formats @samp{s}
9436 and @samp{i}, you might still want to use a count @var{n}; for example,
9437 @samp{3i} specifies that you want to see three machine instructions,
9438 including any operands. For convenience, especially when used with
9439 the @code{display} command, the @samp{i} format also prints branch delay
9440 slot instructions, if any, beyond the count specified, which immediately
9441 follow the last instruction that is within the count. The command
9442 @code{disassemble} gives an alternative way of inspecting machine
9443 instructions; see @ref{Machine Code,,Source and Machine Code}.
9445 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9446 the command displays null-terminated strings or instructions before the given
9447 address as many as the absolute value of the given number. For the @samp{i}
9448 format, we use line number information in the debug info to accurately locate
9449 instruction boundaries while disassembling backward. If line info is not
9450 available, the command stops examining memory with an error message.
9452 All the defaults for the arguments to @code{x} are designed to make it
9453 easy to continue scanning memory with minimal specifications each time
9454 you use @code{x}. For example, after you have inspected three machine
9455 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9456 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9457 the repeat count @var{n} is used again; the other arguments default as
9458 for successive uses of @code{x}.
9460 When examining machine instructions, the instruction at current program
9461 counter is shown with a @code{=>} marker. For example:
9464 (@value{GDBP}) x/5i $pc-6
9465 0x804837f <main+11>: mov %esp,%ebp
9466 0x8048381 <main+13>: push %ecx
9467 0x8048382 <main+14>: sub $0x4,%esp
9468 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9469 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9472 @cindex @code{$_}, @code{$__}, and value history
9473 The addresses and contents printed by the @code{x} command are not saved
9474 in the value history because there is often too much of them and they
9475 would get in the way. Instead, @value{GDBN} makes these values available for
9476 subsequent use in expressions as values of the convenience variables
9477 @code{$_} and @code{$__}. After an @code{x} command, the last address
9478 examined is available for use in expressions in the convenience variable
9479 @code{$_}. The contents of that address, as examined, are available in
9480 the convenience variable @code{$__}.
9482 If the @code{x} command has a repeat count, the address and contents saved
9483 are from the last memory unit printed; this is not the same as the last
9484 address printed if several units were printed on the last line of output.
9486 @anchor{addressable memory unit}
9487 @cindex addressable memory unit
9488 Most targets have an addressable memory unit size of 8 bits. This means
9489 that to each memory address are associated 8 bits of data. Some
9490 targets, however, have other addressable memory unit sizes.
9491 Within @value{GDBN} and this document, the term
9492 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9493 when explicitly referring to a chunk of data of that size. The word
9494 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9495 the addressable memory unit size of the target. For most systems,
9496 addressable memory unit is a synonym of byte.
9498 @cindex remote memory comparison
9499 @cindex target memory comparison
9500 @cindex verify remote memory image
9501 @cindex verify target memory image
9502 When you are debugging a program running on a remote target machine
9503 (@pxref{Remote Debugging}), you may wish to verify the program's image
9504 in the remote machine's memory against the executable file you
9505 downloaded to the target. Or, on any target, you may want to check
9506 whether the program has corrupted its own read-only sections. The
9507 @code{compare-sections} command is provided for such situations.
9510 @kindex compare-sections
9511 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9512 Compare the data of a loadable section @var{section-name} in the
9513 executable file of the program being debugged with the same section in
9514 the target machine's memory, and report any mismatches. With no
9515 arguments, compares all loadable sections. With an argument of
9516 @code{-r}, compares all loadable read-only sections.
9518 Note: for remote targets, this command can be accelerated if the
9519 target supports computing the CRC checksum of a block of memory
9520 (@pxref{qCRC packet}).
9524 @section Automatic Display
9525 @cindex automatic display
9526 @cindex display of expressions
9528 If you find that you want to print the value of an expression frequently
9529 (to see how it changes), you might want to add it to the @dfn{automatic
9530 display list} so that @value{GDBN} prints its value each time your program stops.
9531 Each expression added to the list is given a number to identify it;
9532 to remove an expression from the list, you specify that number.
9533 The automatic display looks like this:
9537 3: bar[5] = (struct hack *) 0x3804
9541 This display shows item numbers, expressions and their current values. As with
9542 displays you request manually using @code{x} or @code{print}, you can
9543 specify the output format you prefer; in fact, @code{display} decides
9544 whether to use @code{print} or @code{x} depending your format
9545 specification---it uses @code{x} if you specify either the @samp{i}
9546 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9550 @item display @var{expr}
9551 Add the expression @var{expr} to the list of expressions to display
9552 each time your program stops. @xref{Expressions, ,Expressions}.
9554 @code{display} does not repeat if you press @key{RET} again after using it.
9556 @item display/@var{fmt} @var{expr}
9557 For @var{fmt} specifying only a display format and not a size or
9558 count, add the expression @var{expr} to the auto-display list but
9559 arrange to display it each time in the specified format @var{fmt}.
9560 @xref{Output Formats,,Output Formats}.
9562 @item display/@var{fmt} @var{addr}
9563 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9564 number of units, add the expression @var{addr} as a memory address to
9565 be examined each time your program stops. Examining means in effect
9566 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9569 For example, @samp{display/i $pc} can be helpful, to see the machine
9570 instruction about to be executed each time execution stops (@samp{$pc}
9571 is a common name for the program counter; @pxref{Registers, ,Registers}).
9574 @kindex delete display
9576 @item undisplay @var{dnums}@dots{}
9577 @itemx delete display @var{dnums}@dots{}
9578 Remove items from the list of expressions to display. Specify the
9579 numbers of the displays that you want affected with the command
9580 argument @var{dnums}. It can be a single display number, one of the
9581 numbers shown in the first field of the @samp{info display} display;
9582 or it could be a range of display numbers, as in @code{2-4}.
9584 @code{undisplay} does not repeat if you press @key{RET} after using it.
9585 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9587 @kindex disable display
9588 @item disable display @var{dnums}@dots{}
9589 Disable the display of item numbers @var{dnums}. A disabled display
9590 item is not printed automatically, but is not forgotten. It may be
9591 enabled again later. Specify the numbers of the displays that you
9592 want affected with the command argument @var{dnums}. It can be a
9593 single display number, one of the numbers shown in the first field of
9594 the @samp{info display} display; or it could be a range of display
9595 numbers, as in @code{2-4}.
9597 @kindex enable display
9598 @item enable display @var{dnums}@dots{}
9599 Enable display of item numbers @var{dnums}. It becomes effective once
9600 again in auto display of its expression, until you specify otherwise.
9601 Specify the numbers of the displays that you want affected with the
9602 command argument @var{dnums}. It can be a single display number, one
9603 of the numbers shown in the first field of the @samp{info display}
9604 display; or it could be a range of display numbers, as in @code{2-4}.
9607 Display the current values of the expressions on the list, just as is
9608 done when your program stops.
9610 @kindex info display
9612 Print the list of expressions previously set up to display
9613 automatically, each one with its item number, but without showing the
9614 values. This includes disabled expressions, which are marked as such.
9615 It also includes expressions which would not be displayed right now
9616 because they refer to automatic variables not currently available.
9619 @cindex display disabled out of scope
9620 If a display expression refers to local variables, then it does not make
9621 sense outside the lexical context for which it was set up. Such an
9622 expression is disabled when execution enters a context where one of its
9623 variables is not defined. For example, if you give the command
9624 @code{display last_char} while inside a function with an argument
9625 @code{last_char}, @value{GDBN} displays this argument while your program
9626 continues to stop inside that function. When it stops elsewhere---where
9627 there is no variable @code{last_char}---the display is disabled
9628 automatically. The next time your program stops where @code{last_char}
9629 is meaningful, you can enable the display expression once again.
9631 @node Print Settings
9632 @section Print Settings
9634 @cindex format options
9635 @cindex print settings
9636 @value{GDBN} provides the following ways to control how arrays, structures,
9637 and symbols are printed.
9640 These settings are useful for debugging programs in any language:
9644 @item set print address
9645 @itemx set print address on
9646 @cindex print/don't print memory addresses
9647 @value{GDBN} prints memory addresses showing the location of stack
9648 traces, structure values, pointer values, breakpoints, and so forth,
9649 even when it also displays the contents of those addresses. The default
9650 is @code{on}. For example, this is what a stack frame display looks like with
9651 @code{set print address on}:
9656 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9658 530 if (lquote != def_lquote)
9662 @item set print address off
9663 Do not print addresses when displaying their contents. For example,
9664 this is the same stack frame displayed with @code{set print address off}:
9668 (@value{GDBP}) set print addr off
9670 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9671 530 if (lquote != def_lquote)
9675 You can use @samp{set print address off} to eliminate all machine
9676 dependent displays from the @value{GDBN} interface. For example, with
9677 @code{print address off}, you should get the same text for backtraces on
9678 all machines---whether or not they involve pointer arguments.
9681 @item show print address
9682 Show whether or not addresses are to be printed.
9685 When @value{GDBN} prints a symbolic address, it normally prints the
9686 closest earlier symbol plus an offset. If that symbol does not uniquely
9687 identify the address (for example, it is a name whose scope is a single
9688 source file), you may need to clarify. One way to do this is with
9689 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9690 you can set @value{GDBN} to print the source file and line number when
9691 it prints a symbolic address:
9694 @item set print symbol-filename on
9695 @cindex source file and line of a symbol
9696 @cindex symbol, source file and line
9697 Tell @value{GDBN} to print the source file name and line number of a
9698 symbol in the symbolic form of an address.
9700 @item set print symbol-filename off
9701 Do not print source file name and line number of a symbol. This is the
9704 @item show print symbol-filename
9705 Show whether or not @value{GDBN} will print the source file name and
9706 line number of a symbol in the symbolic form of an address.
9709 Another situation where it is helpful to show symbol filenames and line
9710 numbers is when disassembling code; @value{GDBN} shows you the line
9711 number and source file that corresponds to each instruction.
9713 Also, you may wish to see the symbolic form only if the address being
9714 printed is reasonably close to the closest earlier symbol:
9717 @item set print max-symbolic-offset @var{max-offset}
9718 @itemx set print max-symbolic-offset unlimited
9719 @cindex maximum value for offset of closest symbol
9720 Tell @value{GDBN} to only display the symbolic form of an address if the
9721 offset between the closest earlier symbol and the address is less than
9722 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9723 to always print the symbolic form of an address if any symbol precedes
9724 it. Zero is equivalent to @code{unlimited}.
9726 @item show print max-symbolic-offset
9727 Ask how large the maximum offset is that @value{GDBN} prints in a
9731 @cindex wild pointer, interpreting
9732 @cindex pointer, finding referent
9733 If you have a pointer and you are not sure where it points, try
9734 @samp{set print symbol-filename on}. Then you can determine the name
9735 and source file location of the variable where it points, using
9736 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9737 For example, here @value{GDBN} shows that a variable @code{ptt} points
9738 at another variable @code{t}, defined in @file{hi2.c}:
9741 (@value{GDBP}) set print symbol-filename on
9742 (@value{GDBP}) p/a ptt
9743 $4 = 0xe008 <t in hi2.c>
9747 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9748 does not show the symbol name and filename of the referent, even with
9749 the appropriate @code{set print} options turned on.
9752 You can also enable @samp{/a}-like formatting all the time using
9753 @samp{set print symbol on}:
9756 @item set print symbol on
9757 Tell @value{GDBN} to print the symbol corresponding to an address, if
9760 @item set print symbol off
9761 Tell @value{GDBN} not to print the symbol corresponding to an
9762 address. In this mode, @value{GDBN} will still print the symbol
9763 corresponding to pointers to functions. This is the default.
9765 @item show print symbol
9766 Show whether @value{GDBN} will display the symbol corresponding to an
9770 Other settings control how different kinds of objects are printed:
9773 @item set print array
9774 @itemx set print array on
9775 @cindex pretty print arrays
9776 Pretty print arrays. This format is more convenient to read,
9777 but uses more space. The default is off.
9779 @item set print array off
9780 Return to compressed format for arrays.
9782 @item show print array
9783 Show whether compressed or pretty format is selected for displaying
9786 @cindex print array indexes
9787 @item set print array-indexes
9788 @itemx set print array-indexes on
9789 Print the index of each element when displaying arrays. May be more
9790 convenient to locate a given element in the array or quickly find the
9791 index of a given element in that printed array. The default is off.
9793 @item set print array-indexes off
9794 Stop printing element indexes when displaying arrays.
9796 @item show print array-indexes
9797 Show whether the index of each element is printed when displaying
9800 @item set print elements @var{number-of-elements}
9801 @itemx set print elements unlimited
9802 @cindex number of array elements to print
9803 @cindex limit on number of printed array elements
9804 Set a limit on how many elements of an array @value{GDBN} will print.
9805 If @value{GDBN} is printing a large array, it stops printing after it has
9806 printed the number of elements set by the @code{set print elements} command.
9807 This limit also applies to the display of strings.
9808 When @value{GDBN} starts, this limit is set to 200.
9809 Setting @var{number-of-elements} to @code{unlimited} or zero means
9810 that the number of elements to print is unlimited.
9812 @item show print elements
9813 Display the number of elements of a large array that @value{GDBN} will print.
9814 If the number is 0, then the printing is unlimited.
9816 @item set print frame-arguments @var{value}
9817 @kindex set print frame-arguments
9818 @cindex printing frame argument values
9819 @cindex print all frame argument values
9820 @cindex print frame argument values for scalars only
9821 @cindex do not print frame argument values
9822 This command allows to control how the values of arguments are printed
9823 when the debugger prints a frame (@pxref{Frames}). The possible
9828 The values of all arguments are printed.
9831 Print the value of an argument only if it is a scalar. The value of more
9832 complex arguments such as arrays, structures, unions, etc, is replaced
9833 by @code{@dots{}}. This is the default. Here is an example where
9834 only scalar arguments are shown:
9837 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9842 None of the argument values are printed. Instead, the value of each argument
9843 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9846 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9851 By default, only scalar arguments are printed. This command can be used
9852 to configure the debugger to print the value of all arguments, regardless
9853 of their type. However, it is often advantageous to not print the value
9854 of more complex parameters. For instance, it reduces the amount of
9855 information printed in each frame, making the backtrace more readable.
9856 Also, it improves performance when displaying Ada frames, because
9857 the computation of large arguments can sometimes be CPU-intensive,
9858 especially in large applications. Setting @code{print frame-arguments}
9859 to @code{scalars} (the default) or @code{none} avoids this computation,
9860 thus speeding up the display of each Ada frame.
9862 @item show print frame-arguments
9863 Show how the value of arguments should be displayed when printing a frame.
9865 @item set print raw frame-arguments on
9866 Print frame arguments in raw, non pretty-printed, form.
9868 @item set print raw frame-arguments off
9869 Print frame arguments in pretty-printed form, if there is a pretty-printer
9870 for the value (@pxref{Pretty Printing}),
9871 otherwise print the value in raw form.
9872 This is the default.
9874 @item show print raw frame-arguments
9875 Show whether to print frame arguments in raw form.
9877 @anchor{set print entry-values}
9878 @item set print entry-values @var{value}
9879 @kindex set print entry-values
9880 Set printing of frame argument values at function entry. In some cases
9881 @value{GDBN} can determine the value of function argument which was passed by
9882 the function caller, even if the value was modified inside the called function
9883 and therefore is different. With optimized code, the current value could be
9884 unavailable, but the entry value may still be known.
9886 The default value is @code{default} (see below for its description). Older
9887 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9888 this feature will behave in the @code{default} setting the same way as with the
9891 This functionality is currently supported only by DWARF 2 debugging format and
9892 the compiler has to produce @samp{DW_TAG_call_site} tags. With
9893 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9896 The @var{value} parameter can be one of the following:
9900 Print only actual parameter values, never print values from function entry
9904 #0 different (val=6)
9905 #0 lost (val=<optimized out>)
9907 #0 invalid (val=<optimized out>)
9911 Print only parameter values from function entry point. The actual parameter
9912 values are never printed.
9914 #0 equal (val@@entry=5)
9915 #0 different (val@@entry=5)
9916 #0 lost (val@@entry=5)
9917 #0 born (val@@entry=<optimized out>)
9918 #0 invalid (val@@entry=<optimized out>)
9922 Print only parameter values from function entry point. If value from function
9923 entry point is not known while the actual value is known, print the actual
9924 value for such parameter.
9926 #0 equal (val@@entry=5)
9927 #0 different (val@@entry=5)
9928 #0 lost (val@@entry=5)
9930 #0 invalid (val@@entry=<optimized out>)
9934 Print actual parameter values. If actual parameter value is not known while
9935 value from function entry point is known, print the entry point value for such
9939 #0 different (val=6)
9940 #0 lost (val@@entry=5)
9942 #0 invalid (val=<optimized out>)
9946 Always print both the actual parameter value and its value from function entry
9947 point, even if values of one or both are not available due to compiler
9950 #0 equal (val=5, val@@entry=5)
9951 #0 different (val=6, val@@entry=5)
9952 #0 lost (val=<optimized out>, val@@entry=5)
9953 #0 born (val=10, val@@entry=<optimized out>)
9954 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9958 Print the actual parameter value if it is known and also its value from
9959 function entry point if it is known. If neither is known, print for the actual
9960 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9961 values are known and identical, print the shortened
9962 @code{param=param@@entry=VALUE} notation.
9964 #0 equal (val=val@@entry=5)
9965 #0 different (val=6, val@@entry=5)
9966 #0 lost (val@@entry=5)
9968 #0 invalid (val=<optimized out>)
9972 Always print the actual parameter value. Print also its value from function
9973 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9974 if both values are known and identical, print the shortened
9975 @code{param=param@@entry=VALUE} notation.
9977 #0 equal (val=val@@entry=5)
9978 #0 different (val=6, val@@entry=5)
9979 #0 lost (val=<optimized out>, val@@entry=5)
9981 #0 invalid (val=<optimized out>)
9985 For analysis messages on possible failures of frame argument values at function
9986 entry resolution see @ref{set debug entry-values}.
9988 @item show print entry-values
9989 Show the method being used for printing of frame argument values at function
9992 @item set print repeats @var{number-of-repeats}
9993 @itemx set print repeats unlimited
9994 @cindex repeated array elements
9995 Set the threshold for suppressing display of repeated array
9996 elements. When the number of consecutive identical elements of an
9997 array exceeds the threshold, @value{GDBN} prints the string
9998 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9999 identical repetitions, instead of displaying the identical elements
10000 themselves. Setting the threshold to @code{unlimited} or zero will
10001 cause all elements to be individually printed. The default threshold
10004 @item show print repeats
10005 Display the current threshold for printing repeated identical
10008 @item set print null-stop
10009 @cindex @sc{null} elements in arrays
10010 Cause @value{GDBN} to stop printing the characters of an array when the first
10011 @sc{null} is encountered. This is useful when large arrays actually
10012 contain only short strings.
10013 The default is off.
10015 @item show print null-stop
10016 Show whether @value{GDBN} stops printing an array on the first
10017 @sc{null} character.
10019 @item set print pretty on
10020 @cindex print structures in indented form
10021 @cindex indentation in structure display
10022 Cause @value{GDBN} to print structures in an indented format with one member
10023 per line, like this:
10038 @item set print pretty off
10039 Cause @value{GDBN} to print structures in a compact format, like this:
10043 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10044 meat = 0x54 "Pork"@}
10049 This is the default format.
10051 @item show print pretty
10052 Show which format @value{GDBN} is using to print structures.
10054 @item set print sevenbit-strings on
10055 @cindex eight-bit characters in strings
10056 @cindex octal escapes in strings
10057 Print using only seven-bit characters; if this option is set,
10058 @value{GDBN} displays any eight-bit characters (in strings or
10059 character values) using the notation @code{\}@var{nnn}. This setting is
10060 best if you are working in English (@sc{ascii}) and you use the
10061 high-order bit of characters as a marker or ``meta'' bit.
10063 @item set print sevenbit-strings off
10064 Print full eight-bit characters. This allows the use of more
10065 international character sets, and is the default.
10067 @item show print sevenbit-strings
10068 Show whether or not @value{GDBN} is printing only seven-bit characters.
10070 @item set print union on
10071 @cindex unions in structures, printing
10072 Tell @value{GDBN} to print unions which are contained in structures
10073 and other unions. This is the default setting.
10075 @item set print union off
10076 Tell @value{GDBN} not to print unions which are contained in
10077 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10080 @item show print union
10081 Ask @value{GDBN} whether or not it will print unions which are contained in
10082 structures and other unions.
10084 For example, given the declarations
10087 typedef enum @{Tree, Bug@} Species;
10088 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10089 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10100 struct thing foo = @{Tree, @{Acorn@}@};
10104 with @code{set print union on} in effect @samp{p foo} would print
10107 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10111 and with @code{set print union off} in effect it would print
10114 $1 = @{it = Tree, form = @{...@}@}
10118 @code{set print union} affects programs written in C-like languages
10124 These settings are of interest when debugging C@t{++} programs:
10127 @cindex demangling C@t{++} names
10128 @item set print demangle
10129 @itemx set print demangle on
10130 Print C@t{++} names in their source form rather than in the encoded
10131 (``mangled'') form passed to the assembler and linker for type-safe
10132 linkage. The default is on.
10134 @item show print demangle
10135 Show whether C@t{++} names are printed in mangled or demangled form.
10137 @item set print asm-demangle
10138 @itemx set print asm-demangle on
10139 Print C@t{++} names in their source form rather than their mangled form, even
10140 in assembler code printouts such as instruction disassemblies.
10141 The default is off.
10143 @item show print asm-demangle
10144 Show whether C@t{++} names in assembly listings are printed in mangled
10147 @cindex C@t{++} symbol decoding style
10148 @cindex symbol decoding style, C@t{++}
10149 @kindex set demangle-style
10150 @item set demangle-style @var{style}
10151 Choose among several encoding schemes used by different compilers to
10152 represent C@t{++} names. The choices for @var{style} are currently:
10156 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10157 This is the default.
10160 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10163 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10166 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10169 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10170 @strong{Warning:} this setting alone is not sufficient to allow
10171 debugging @code{cfront}-generated executables. @value{GDBN} would
10172 require further enhancement to permit that.
10175 If you omit @var{style}, you will see a list of possible formats.
10177 @item show demangle-style
10178 Display the encoding style currently in use for decoding C@t{++} symbols.
10180 @item set print object
10181 @itemx set print object on
10182 @cindex derived type of an object, printing
10183 @cindex display derived types
10184 When displaying a pointer to an object, identify the @emph{actual}
10185 (derived) type of the object rather than the @emph{declared} type, using
10186 the virtual function table. Note that the virtual function table is
10187 required---this feature can only work for objects that have run-time
10188 type identification; a single virtual method in the object's declared
10189 type is sufficient. Note that this setting is also taken into account when
10190 working with variable objects via MI (@pxref{GDB/MI}).
10192 @item set print object off
10193 Display only the declared type of objects, without reference to the
10194 virtual function table. This is the default setting.
10196 @item show print object
10197 Show whether actual, or declared, object types are displayed.
10199 @item set print static-members
10200 @itemx set print static-members on
10201 @cindex static members of C@t{++} objects
10202 Print static members when displaying a C@t{++} object. The default is on.
10204 @item set print static-members off
10205 Do not print static members when displaying a C@t{++} object.
10207 @item show print static-members
10208 Show whether C@t{++} static members are printed or not.
10210 @item set print pascal_static-members
10211 @itemx set print pascal_static-members on
10212 @cindex static members of Pascal objects
10213 @cindex Pascal objects, static members display
10214 Print static members when displaying a Pascal object. The default is on.
10216 @item set print pascal_static-members off
10217 Do not print static members when displaying a Pascal object.
10219 @item show print pascal_static-members
10220 Show whether Pascal static members are printed or not.
10222 @c These don't work with HP ANSI C++ yet.
10223 @item set print vtbl
10224 @itemx set print vtbl on
10225 @cindex pretty print C@t{++} virtual function tables
10226 @cindex virtual functions (C@t{++}) display
10227 @cindex VTBL display
10228 Pretty print C@t{++} virtual function tables. The default is off.
10229 (The @code{vtbl} commands do not work on programs compiled with the HP
10230 ANSI C@t{++} compiler (@code{aCC}).)
10232 @item set print vtbl off
10233 Do not pretty print C@t{++} virtual function tables.
10235 @item show print vtbl
10236 Show whether C@t{++} virtual function tables are pretty printed, or not.
10239 @node Pretty Printing
10240 @section Pretty Printing
10242 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10243 Python code. It greatly simplifies the display of complex objects. This
10244 mechanism works for both MI and the CLI.
10247 * Pretty-Printer Introduction:: Introduction to pretty-printers
10248 * Pretty-Printer Example:: An example pretty-printer
10249 * Pretty-Printer Commands:: Pretty-printer commands
10252 @node Pretty-Printer Introduction
10253 @subsection Pretty-Printer Introduction
10255 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10256 registered for the value. If there is then @value{GDBN} invokes the
10257 pretty-printer to print the value. Otherwise the value is printed normally.
10259 Pretty-printers are normally named. This makes them easy to manage.
10260 The @samp{info pretty-printer} command will list all the installed
10261 pretty-printers with their names.
10262 If a pretty-printer can handle multiple data types, then its
10263 @dfn{subprinters} are the printers for the individual data types.
10264 Each such subprinter has its own name.
10265 The format of the name is @var{printer-name};@var{subprinter-name}.
10267 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10268 Typically they are automatically loaded and registered when the corresponding
10269 debug information is loaded, thus making them available without having to
10270 do anything special.
10272 There are three places where a pretty-printer can be registered.
10276 Pretty-printers registered globally are available when debugging
10280 Pretty-printers registered with a program space are available only
10281 when debugging that program.
10282 @xref{Progspaces In Python}, for more details on program spaces in Python.
10285 Pretty-printers registered with an objfile are loaded and unloaded
10286 with the corresponding objfile (e.g., shared library).
10287 @xref{Objfiles In Python}, for more details on objfiles in Python.
10290 @xref{Selecting Pretty-Printers}, for further information on how
10291 pretty-printers are selected,
10293 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10296 @node Pretty-Printer Example
10297 @subsection Pretty-Printer Example
10299 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10302 (@value{GDBP}) print s
10304 static npos = 4294967295,
10306 <std::allocator<char>> = @{
10307 <__gnu_cxx::new_allocator<char>> = @{
10308 <No data fields>@}, <No data fields>
10310 members of std::basic_string<char, std::char_traits<char>,
10311 std::allocator<char> >::_Alloc_hider:
10312 _M_p = 0x804a014 "abcd"
10317 With a pretty-printer for @code{std::string} only the contents are printed:
10320 (@value{GDBP}) print s
10324 @node Pretty-Printer Commands
10325 @subsection Pretty-Printer Commands
10326 @cindex pretty-printer commands
10329 @kindex info pretty-printer
10330 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10331 Print the list of installed pretty-printers.
10332 This includes disabled pretty-printers, which are marked as such.
10334 @var{object-regexp} is a regular expression matching the objects
10335 whose pretty-printers to list.
10336 Objects can be @code{global}, the program space's file
10337 (@pxref{Progspaces In Python}),
10338 and the object files within that program space (@pxref{Objfiles In Python}).
10339 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10340 looks up a printer from these three objects.
10342 @var{name-regexp} is a regular expression matching the name of the printers
10345 @kindex disable pretty-printer
10346 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10347 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10348 A disabled pretty-printer is not forgotten, it may be enabled again later.
10350 @kindex enable pretty-printer
10351 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10352 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10357 Suppose we have three pretty-printers installed: one from library1.so
10358 named @code{foo} that prints objects of type @code{foo}, and
10359 another from library2.so named @code{bar} that prints two types of objects,
10360 @code{bar1} and @code{bar2}.
10363 (gdb) info pretty-printer
10370 (gdb) info pretty-printer library2
10375 (gdb) disable pretty-printer library1
10377 2 of 3 printers enabled
10378 (gdb) info pretty-printer
10385 (gdb) disable pretty-printer library2 bar:bar1
10387 1 of 3 printers enabled
10388 (gdb) info pretty-printer library2
10395 (gdb) disable pretty-printer library2 bar
10397 0 of 3 printers enabled
10398 (gdb) info pretty-printer library2
10407 Note that for @code{bar} the entire printer can be disabled,
10408 as can each individual subprinter.
10410 @node Value History
10411 @section Value History
10413 @cindex value history
10414 @cindex history of values printed by @value{GDBN}
10415 Values printed by the @code{print} command are saved in the @value{GDBN}
10416 @dfn{value history}. This allows you to refer to them in other expressions.
10417 Values are kept until the symbol table is re-read or discarded
10418 (for example with the @code{file} or @code{symbol-file} commands).
10419 When the symbol table changes, the value history is discarded,
10420 since the values may contain pointers back to the types defined in the
10425 @cindex history number
10426 The values printed are given @dfn{history numbers} by which you can
10427 refer to them. These are successive integers starting with one.
10428 @code{print} shows you the history number assigned to a value by
10429 printing @samp{$@var{num} = } before the value; here @var{num} is the
10432 To refer to any previous value, use @samp{$} followed by the value's
10433 history number. The way @code{print} labels its output is designed to
10434 remind you of this. Just @code{$} refers to the most recent value in
10435 the history, and @code{$$} refers to the value before that.
10436 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10437 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10438 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10440 For example, suppose you have just printed a pointer to a structure and
10441 want to see the contents of the structure. It suffices to type
10447 If you have a chain of structures where the component @code{next} points
10448 to the next one, you can print the contents of the next one with this:
10455 You can print successive links in the chain by repeating this
10456 command---which you can do by just typing @key{RET}.
10458 Note that the history records values, not expressions. If the value of
10459 @code{x} is 4 and you type these commands:
10467 then the value recorded in the value history by the @code{print} command
10468 remains 4 even though the value of @code{x} has changed.
10471 @kindex show values
10473 Print the last ten values in the value history, with their item numbers.
10474 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10475 values} does not change the history.
10477 @item show values @var{n}
10478 Print ten history values centered on history item number @var{n}.
10480 @item show values +
10481 Print ten history values just after the values last printed. If no more
10482 values are available, @code{show values +} produces no display.
10485 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10486 same effect as @samp{show values +}.
10488 @node Convenience Vars
10489 @section Convenience Variables
10491 @cindex convenience variables
10492 @cindex user-defined variables
10493 @value{GDBN} provides @dfn{convenience variables} that you can use within
10494 @value{GDBN} to hold on to a value and refer to it later. These variables
10495 exist entirely within @value{GDBN}; they are not part of your program, and
10496 setting a convenience variable has no direct effect on further execution
10497 of your program. That is why you can use them freely.
10499 Convenience variables are prefixed with @samp{$}. Any name preceded by
10500 @samp{$} can be used for a convenience variable, unless it is one of
10501 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10502 (Value history references, in contrast, are @emph{numbers} preceded
10503 by @samp{$}. @xref{Value History, ,Value History}.)
10505 You can save a value in a convenience variable with an assignment
10506 expression, just as you would set a variable in your program.
10510 set $foo = *object_ptr
10514 would save in @code{$foo} the value contained in the object pointed to by
10517 Using a convenience variable for the first time creates it, but its
10518 value is @code{void} until you assign a new value. You can alter the
10519 value with another assignment at any time.
10521 Convenience variables have no fixed types. You can assign a convenience
10522 variable any type of value, including structures and arrays, even if
10523 that variable already has a value of a different type. The convenience
10524 variable, when used as an expression, has the type of its current value.
10527 @kindex show convenience
10528 @cindex show all user variables and functions
10529 @item show convenience
10530 Print a list of convenience variables used so far, and their values,
10531 as well as a list of the convenience functions.
10532 Abbreviated @code{show conv}.
10534 @kindex init-if-undefined
10535 @cindex convenience variables, initializing
10536 @item init-if-undefined $@var{variable} = @var{expression}
10537 Set a convenience variable if it has not already been set. This is useful
10538 for user-defined commands that keep some state. It is similar, in concept,
10539 to using local static variables with initializers in C (except that
10540 convenience variables are global). It can also be used to allow users to
10541 override default values used in a command script.
10543 If the variable is already defined then the expression is not evaluated so
10544 any side-effects do not occur.
10547 One of the ways to use a convenience variable is as a counter to be
10548 incremented or a pointer to be advanced. For example, to print
10549 a field from successive elements of an array of structures:
10553 print bar[$i++]->contents
10557 Repeat that command by typing @key{RET}.
10559 Some convenience variables are created automatically by @value{GDBN} and given
10560 values likely to be useful.
10563 @vindex $_@r{, convenience variable}
10565 The variable @code{$_} is automatically set by the @code{x} command to
10566 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10567 commands which provide a default address for @code{x} to examine also
10568 set @code{$_} to that address; these commands include @code{info line}
10569 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10570 except when set by the @code{x} command, in which case it is a pointer
10571 to the type of @code{$__}.
10573 @vindex $__@r{, convenience variable}
10575 The variable @code{$__} is automatically set by the @code{x} command
10576 to the value found in the last address examined. Its type is chosen
10577 to match the format in which the data was printed.
10580 @vindex $_exitcode@r{, convenience variable}
10581 When the program being debugged terminates normally, @value{GDBN}
10582 automatically sets this variable to the exit code of the program, and
10583 resets @code{$_exitsignal} to @code{void}.
10586 @vindex $_exitsignal@r{, convenience variable}
10587 When the program being debugged dies due to an uncaught signal,
10588 @value{GDBN} automatically sets this variable to that signal's number,
10589 and resets @code{$_exitcode} to @code{void}.
10591 To distinguish between whether the program being debugged has exited
10592 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10593 @code{$_exitsignal} is not @code{void}), the convenience function
10594 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10595 Functions}). For example, considering the following source code:
10598 #include <signal.h>
10601 main (int argc, char *argv[])
10608 A valid way of telling whether the program being debugged has exited
10609 or signalled would be:
10612 (@value{GDBP}) define has_exited_or_signalled
10613 Type commands for definition of ``has_exited_or_signalled''.
10614 End with a line saying just ``end''.
10615 >if $_isvoid ($_exitsignal)
10616 >echo The program has exited\n
10618 >echo The program has signalled\n
10624 Program terminated with signal SIGALRM, Alarm clock.
10625 The program no longer exists.
10626 (@value{GDBP}) has_exited_or_signalled
10627 The program has signalled
10630 As can be seen, @value{GDBN} correctly informs that the program being
10631 debugged has signalled, since it calls @code{raise} and raises a
10632 @code{SIGALRM} signal. If the program being debugged had not called
10633 @code{raise}, then @value{GDBN} would report a normal exit:
10636 (@value{GDBP}) has_exited_or_signalled
10637 The program has exited
10641 The variable @code{$_exception} is set to the exception object being
10642 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10645 @itemx $_probe_arg0@dots{}$_probe_arg11
10646 Arguments to a static probe. @xref{Static Probe Points}.
10649 @vindex $_sdata@r{, inspect, convenience variable}
10650 The variable @code{$_sdata} contains extra collected static tracepoint
10651 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10652 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10653 if extra static tracepoint data has not been collected.
10656 @vindex $_siginfo@r{, convenience variable}
10657 The variable @code{$_siginfo} contains extra signal information
10658 (@pxref{extra signal information}). Note that @code{$_siginfo}
10659 could be empty, if the application has not yet received any signals.
10660 For example, it will be empty before you execute the @code{run} command.
10663 @vindex $_tlb@r{, convenience variable}
10664 The variable @code{$_tlb} is automatically set when debugging
10665 applications running on MS-Windows in native mode or connected to
10666 gdbserver that supports the @code{qGetTIBAddr} request.
10667 @xref{General Query Packets}.
10668 This variable contains the address of the thread information block.
10671 The number of the current inferior. @xref{Inferiors and
10672 Programs, ,Debugging Multiple Inferiors and Programs}.
10675 The thread number of the current thread. @xref{thread numbers}.
10678 The global number of the current thread. @xref{global thread numbers}.
10682 @node Convenience Funs
10683 @section Convenience Functions
10685 @cindex convenience functions
10686 @value{GDBN} also supplies some @dfn{convenience functions}. These
10687 have a syntax similar to convenience variables. A convenience
10688 function can be used in an expression just like an ordinary function;
10689 however, a convenience function is implemented internally to
10692 These functions do not require @value{GDBN} to be configured with
10693 @code{Python} support, which means that they are always available.
10697 @item $_isvoid (@var{expr})
10698 @findex $_isvoid@r{, convenience function}
10699 Return one if the expression @var{expr} is @code{void}. Otherwise it
10702 A @code{void} expression is an expression where the type of the result
10703 is @code{void}. For example, you can examine a convenience variable
10704 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10708 (@value{GDBP}) print $_exitcode
10710 (@value{GDBP}) print $_isvoid ($_exitcode)
10713 Starting program: ./a.out
10714 [Inferior 1 (process 29572) exited normally]
10715 (@value{GDBP}) print $_exitcode
10717 (@value{GDBP}) print $_isvoid ($_exitcode)
10721 In the example above, we used @code{$_isvoid} to check whether
10722 @code{$_exitcode} is @code{void} before and after the execution of the
10723 program being debugged. Before the execution there is no exit code to
10724 be examined, therefore @code{$_exitcode} is @code{void}. After the
10725 execution the program being debugged returned zero, therefore
10726 @code{$_exitcode} is zero, which means that it is not @code{void}
10729 The @code{void} expression can also be a call of a function from the
10730 program being debugged. For example, given the following function:
10739 The result of calling it inside @value{GDBN} is @code{void}:
10742 (@value{GDBP}) print foo ()
10744 (@value{GDBP}) print $_isvoid (foo ())
10746 (@value{GDBP}) set $v = foo ()
10747 (@value{GDBP}) print $v
10749 (@value{GDBP}) print $_isvoid ($v)
10755 These functions require @value{GDBN} to be configured with
10756 @code{Python} support.
10760 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10761 @findex $_memeq@r{, convenience function}
10762 Returns one if the @var{length} bytes at the addresses given by
10763 @var{buf1} and @var{buf2} are equal.
10764 Otherwise it returns zero.
10766 @item $_regex(@var{str}, @var{regex})
10767 @findex $_regex@r{, convenience function}
10768 Returns one if the string @var{str} matches the regular expression
10769 @var{regex}. Otherwise it returns zero.
10770 The syntax of the regular expression is that specified by @code{Python}'s
10771 regular expression support.
10773 @item $_streq(@var{str1}, @var{str2})
10774 @findex $_streq@r{, convenience function}
10775 Returns one if the strings @var{str1} and @var{str2} are equal.
10776 Otherwise it returns zero.
10778 @item $_strlen(@var{str})
10779 @findex $_strlen@r{, convenience function}
10780 Returns the length of string @var{str}.
10782 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10783 @findex $_caller_is@r{, convenience function}
10784 Returns one if the calling function's name is equal to @var{name}.
10785 Otherwise it returns zero.
10787 If the optional argument @var{number_of_frames} is provided,
10788 it is the number of frames up in the stack to look.
10796 at testsuite/gdb.python/py-caller-is.c:21
10797 #1 0x00000000004005a0 in middle_func ()
10798 at testsuite/gdb.python/py-caller-is.c:27
10799 #2 0x00000000004005ab in top_func ()
10800 at testsuite/gdb.python/py-caller-is.c:33
10801 #3 0x00000000004005b6 in main ()
10802 at testsuite/gdb.python/py-caller-is.c:39
10803 (gdb) print $_caller_is ("middle_func")
10805 (gdb) print $_caller_is ("top_func", 2)
10809 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10810 @findex $_caller_matches@r{, convenience function}
10811 Returns one if the calling function's name matches the regular expression
10812 @var{regexp}. Otherwise it returns zero.
10814 If the optional argument @var{number_of_frames} is provided,
10815 it is the number of frames up in the stack to look.
10818 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10819 @findex $_any_caller_is@r{, convenience function}
10820 Returns one if any calling function's name is equal to @var{name}.
10821 Otherwise it returns zero.
10823 If the optional argument @var{number_of_frames} is provided,
10824 it is the number of frames up in the stack to look.
10827 This function differs from @code{$_caller_is} in that this function
10828 checks all stack frames from the immediate caller to the frame specified
10829 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10830 frame specified by @var{number_of_frames}.
10832 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10833 @findex $_any_caller_matches@r{, convenience function}
10834 Returns one if any calling function's name matches the regular expression
10835 @var{regexp}. Otherwise it returns zero.
10837 If the optional argument @var{number_of_frames} is provided,
10838 it is the number of frames up in the stack to look.
10841 This function differs from @code{$_caller_matches} in that this function
10842 checks all stack frames from the immediate caller to the frame specified
10843 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10844 frame specified by @var{number_of_frames}.
10846 @item $_as_string(@var{value})
10847 @findex $_as_string@r{, convenience function}
10848 Return the string representation of @var{value}.
10850 This function is useful to obtain the textual label (enumerator) of an
10851 enumeration value. For example, assuming the variable @var{node} is of
10852 an enumerated type:
10855 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10856 Visiting node of type NODE_INTEGER
10861 @value{GDBN} provides the ability to list and get help on
10862 convenience functions.
10865 @item help function
10866 @kindex help function
10867 @cindex show all convenience functions
10868 Print a list of all convenience functions.
10875 You can refer to machine register contents, in expressions, as variables
10876 with names starting with @samp{$}. The names of registers are different
10877 for each machine; use @code{info registers} to see the names used on
10881 @kindex info registers
10882 @item info registers
10883 Print the names and values of all registers except floating-point
10884 and vector registers (in the selected stack frame).
10886 @kindex info all-registers
10887 @cindex floating point registers
10888 @item info all-registers
10889 Print the names and values of all registers, including floating-point
10890 and vector registers (in the selected stack frame).
10892 @item info registers @var{regname} @dots{}
10893 Print the @dfn{relativized} value of each specified register @var{regname}.
10894 As discussed in detail below, register values are normally relative to
10895 the selected stack frame. The @var{regname} may be any register name valid on
10896 the machine you are using, with or without the initial @samp{$}.
10899 @anchor{standard registers}
10900 @cindex stack pointer register
10901 @cindex program counter register
10902 @cindex process status register
10903 @cindex frame pointer register
10904 @cindex standard registers
10905 @value{GDBN} has four ``standard'' register names that are available (in
10906 expressions) on most machines---whenever they do not conflict with an
10907 architecture's canonical mnemonics for registers. The register names
10908 @code{$pc} and @code{$sp} are used for the program counter register and
10909 the stack pointer. @code{$fp} is used for a register that contains a
10910 pointer to the current stack frame, and @code{$ps} is used for a
10911 register that contains the processor status. For example,
10912 you could print the program counter in hex with
10919 or print the instruction to be executed next with
10926 or add four to the stack pointer@footnote{This is a way of removing
10927 one word from the stack, on machines where stacks grow downward in
10928 memory (most machines, nowadays). This assumes that the innermost
10929 stack frame is selected; setting @code{$sp} is not allowed when other
10930 stack frames are selected. To pop entire frames off the stack,
10931 regardless of machine architecture, use @code{return};
10932 see @ref{Returning, ,Returning from a Function}.} with
10938 Whenever possible, these four standard register names are available on
10939 your machine even though the machine has different canonical mnemonics,
10940 so long as there is no conflict. The @code{info registers} command
10941 shows the canonical names. For example, on the SPARC, @code{info
10942 registers} displays the processor status register as @code{$psr} but you
10943 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10944 is an alias for the @sc{eflags} register.
10946 @value{GDBN} always considers the contents of an ordinary register as an
10947 integer when the register is examined in this way. Some machines have
10948 special registers which can hold nothing but floating point; these
10949 registers are considered to have floating point values. There is no way
10950 to refer to the contents of an ordinary register as floating point value
10951 (although you can @emph{print} it as a floating point value with
10952 @samp{print/f $@var{regname}}).
10954 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10955 means that the data format in which the register contents are saved by
10956 the operating system is not the same one that your program normally
10957 sees. For example, the registers of the 68881 floating point
10958 coprocessor are always saved in ``extended'' (raw) format, but all C
10959 programs expect to work with ``double'' (virtual) format. In such
10960 cases, @value{GDBN} normally works with the virtual format only (the format
10961 that makes sense for your program), but the @code{info registers} command
10962 prints the data in both formats.
10964 @cindex SSE registers (x86)
10965 @cindex MMX registers (x86)
10966 Some machines have special registers whose contents can be interpreted
10967 in several different ways. For example, modern x86-based machines
10968 have SSE and MMX registers that can hold several values packed
10969 together in several different formats. @value{GDBN} refers to such
10970 registers in @code{struct} notation:
10973 (@value{GDBP}) print $xmm1
10975 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10976 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10977 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10978 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10979 v4_int32 = @{0, 20657912, 11, 13@},
10980 v2_int64 = @{88725056443645952, 55834574859@},
10981 uint128 = 0x0000000d0000000b013b36f800000000
10986 To set values of such registers, you need to tell @value{GDBN} which
10987 view of the register you wish to change, as if you were assigning
10988 value to a @code{struct} member:
10991 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10994 Normally, register values are relative to the selected stack frame
10995 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10996 value that the register would contain if all stack frames farther in
10997 were exited and their saved registers restored. In order to see the
10998 true contents of hardware registers, you must select the innermost
10999 frame (with @samp{frame 0}).
11001 @cindex caller-saved registers
11002 @cindex call-clobbered registers
11003 @cindex volatile registers
11004 @cindex <not saved> values
11005 Usually ABIs reserve some registers as not needed to be saved by the
11006 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11007 registers). It may therefore not be possible for @value{GDBN} to know
11008 the value a register had before the call (in other words, in the outer
11009 frame), if the register value has since been changed by the callee.
11010 @value{GDBN} tries to deduce where the inner frame saved
11011 (``callee-saved'') registers, from the debug info, unwind info, or the
11012 machine code generated by your compiler. If some register is not
11013 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11014 its own knowledge of the ABI, or because the debug/unwind info
11015 explicitly says the register's value is undefined), @value{GDBN}
11016 displays @w{@samp{<not saved>}} as the register's value. With targets
11017 that @value{GDBN} has no knowledge of the register saving convention,
11018 if a register was not saved by the callee, then its value and location
11019 in the outer frame are assumed to be the same of the inner frame.
11020 This is usually harmless, because if the register is call-clobbered,
11021 the caller either does not care what is in the register after the
11022 call, or has code to restore the value that it does care about. Note,
11023 however, that if you change such a register in the outer frame, you
11024 may also be affecting the inner frame. Also, the more ``outer'' the
11025 frame is you're looking at, the more likely a call-clobbered
11026 register's value is to be wrong, in the sense that it doesn't actually
11027 represent the value the register had just before the call.
11029 @node Floating Point Hardware
11030 @section Floating Point Hardware
11031 @cindex floating point
11033 Depending on the configuration, @value{GDBN} may be able to give
11034 you more information about the status of the floating point hardware.
11039 Display hardware-dependent information about the floating
11040 point unit. The exact contents and layout vary depending on the
11041 floating point chip. Currently, @samp{info float} is supported on
11042 the ARM and x86 machines.
11046 @section Vector Unit
11047 @cindex vector unit
11049 Depending on the configuration, @value{GDBN} may be able to give you
11050 more information about the status of the vector unit.
11053 @kindex info vector
11055 Display information about the vector unit. The exact contents and
11056 layout vary depending on the hardware.
11059 @node OS Information
11060 @section Operating System Auxiliary Information
11061 @cindex OS information
11063 @value{GDBN} provides interfaces to useful OS facilities that can help
11064 you debug your program.
11066 @cindex auxiliary vector
11067 @cindex vector, auxiliary
11068 Some operating systems supply an @dfn{auxiliary vector} to programs at
11069 startup. This is akin to the arguments and environment that you
11070 specify for a program, but contains a system-dependent variety of
11071 binary values that tell system libraries important details about the
11072 hardware, operating system, and process. Each value's purpose is
11073 identified by an integer tag; the meanings are well-known but system-specific.
11074 Depending on the configuration and operating system facilities,
11075 @value{GDBN} may be able to show you this information. For remote
11076 targets, this functionality may further depend on the remote stub's
11077 support of the @samp{qXfer:auxv:read} packet, see
11078 @ref{qXfer auxiliary vector read}.
11083 Display the auxiliary vector of the inferior, which can be either a
11084 live process or a core dump file. @value{GDBN} prints each tag value
11085 numerically, and also shows names and text descriptions for recognized
11086 tags. Some values in the vector are numbers, some bit masks, and some
11087 pointers to strings or other data. @value{GDBN} displays each value in the
11088 most appropriate form for a recognized tag, and in hexadecimal for
11089 an unrecognized tag.
11092 On some targets, @value{GDBN} can access operating system-specific
11093 information and show it to you. The types of information available
11094 will differ depending on the type of operating system running on the
11095 target. The mechanism used to fetch the data is described in
11096 @ref{Operating System Information}. For remote targets, this
11097 functionality depends on the remote stub's support of the
11098 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11102 @item info os @var{infotype}
11104 Display OS information of the requested type.
11106 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11108 @anchor{linux info os infotypes}
11110 @kindex info os cpus
11112 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11113 the available fields from /proc/cpuinfo. For each supported architecture
11114 different fields are available. Two common entries are processor which gives
11115 CPU number and bogomips; a system constant that is calculated during
11116 kernel initialization.
11118 @kindex info os files
11120 Display the list of open file descriptors on the target. For each
11121 file descriptor, @value{GDBN} prints the identifier of the process
11122 owning the descriptor, the command of the owning process, the value
11123 of the descriptor, and the target of the descriptor.
11125 @kindex info os modules
11127 Display the list of all loaded kernel modules on the target. For each
11128 module, @value{GDBN} prints the module name, the size of the module in
11129 bytes, the number of times the module is used, the dependencies of the
11130 module, the status of the module, and the address of the loaded module
11133 @kindex info os msg
11135 Display the list of all System V message queues on the target. For each
11136 message queue, @value{GDBN} prints the message queue key, the message
11137 queue identifier, the access permissions, the current number of bytes
11138 on the queue, the current number of messages on the queue, the processes
11139 that last sent and received a message on the queue, the user and group
11140 of the owner and creator of the message queue, the times at which a
11141 message was last sent and received on the queue, and the time at which
11142 the message queue was last changed.
11144 @kindex info os processes
11146 Display the list of processes on the target. For each process,
11147 @value{GDBN} prints the process identifier, the name of the user, the
11148 command corresponding to the process, and the list of processor cores
11149 that the process is currently running on. (To understand what these
11150 properties mean, for this and the following info types, please consult
11151 the general @sc{gnu}/Linux documentation.)
11153 @kindex info os procgroups
11155 Display the list of process groups on the target. For each process,
11156 @value{GDBN} prints the identifier of the process group that it belongs
11157 to, the command corresponding to the process group leader, the process
11158 identifier, and the command line of the process. The list is sorted
11159 first by the process group identifier, then by the process identifier,
11160 so that processes belonging to the same process group are grouped together
11161 and the process group leader is listed first.
11163 @kindex info os semaphores
11165 Display the list of all System V semaphore sets on the target. For each
11166 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11167 set identifier, the access permissions, the number of semaphores in the
11168 set, the user and group of the owner and creator of the semaphore set,
11169 and the times at which the semaphore set was operated upon and changed.
11171 @kindex info os shm
11173 Display the list of all System V shared-memory regions on the target.
11174 For each shared-memory region, @value{GDBN} prints the region key,
11175 the shared-memory identifier, the access permissions, the size of the
11176 region, the process that created the region, the process that last
11177 attached to or detached from the region, the current number of live
11178 attaches to the region, and the times at which the region was last
11179 attached to, detach from, and changed.
11181 @kindex info os sockets
11183 Display the list of Internet-domain sockets on the target. For each
11184 socket, @value{GDBN} prints the address and port of the local and
11185 remote endpoints, the current state of the connection, the creator of
11186 the socket, the IP address family of the socket, and the type of the
11189 @kindex info os threads
11191 Display the list of threads running on the target. For each thread,
11192 @value{GDBN} prints the identifier of the process that the thread
11193 belongs to, the command of the process, the thread identifier, and the
11194 processor core that it is currently running on. The main thread of a
11195 process is not listed.
11199 If @var{infotype} is omitted, then list the possible values for
11200 @var{infotype} and the kind of OS information available for each
11201 @var{infotype}. If the target does not return a list of possible
11202 types, this command will report an error.
11205 @node Memory Region Attributes
11206 @section Memory Region Attributes
11207 @cindex memory region attributes
11209 @dfn{Memory region attributes} allow you to describe special handling
11210 required by regions of your target's memory. @value{GDBN} uses
11211 attributes to determine whether to allow certain types of memory
11212 accesses; whether to use specific width accesses; and whether to cache
11213 target memory. By default the description of memory regions is
11214 fetched from the target (if the current target supports this), but the
11215 user can override the fetched regions.
11217 Defined memory regions can be individually enabled and disabled. When a
11218 memory region is disabled, @value{GDBN} uses the default attributes when
11219 accessing memory in that region. Similarly, if no memory regions have
11220 been defined, @value{GDBN} uses the default attributes when accessing
11223 When a memory region is defined, it is given a number to identify it;
11224 to enable, disable, or remove a memory region, you specify that number.
11228 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11229 Define a memory region bounded by @var{lower} and @var{upper} with
11230 attributes @var{attributes}@dots{}, and add it to the list of regions
11231 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11232 case: it is treated as the target's maximum memory address.
11233 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11236 Discard any user changes to the memory regions and use target-supplied
11237 regions, if available, or no regions if the target does not support.
11240 @item delete mem @var{nums}@dots{}
11241 Remove memory regions @var{nums}@dots{} from the list of regions
11242 monitored by @value{GDBN}.
11244 @kindex disable mem
11245 @item disable mem @var{nums}@dots{}
11246 Disable monitoring of memory regions @var{nums}@dots{}.
11247 A disabled memory region is not forgotten.
11248 It may be enabled again later.
11251 @item enable mem @var{nums}@dots{}
11252 Enable monitoring of memory regions @var{nums}@dots{}.
11256 Print a table of all defined memory regions, with the following columns
11260 @item Memory Region Number
11261 @item Enabled or Disabled.
11262 Enabled memory regions are marked with @samp{y}.
11263 Disabled memory regions are marked with @samp{n}.
11266 The address defining the inclusive lower bound of the memory region.
11269 The address defining the exclusive upper bound of the memory region.
11272 The list of attributes set for this memory region.
11277 @subsection Attributes
11279 @subsubsection Memory Access Mode
11280 The access mode attributes set whether @value{GDBN} may make read or
11281 write accesses to a memory region.
11283 While these attributes prevent @value{GDBN} from performing invalid
11284 memory accesses, they do nothing to prevent the target system, I/O DMA,
11285 etc.@: from accessing memory.
11289 Memory is read only.
11291 Memory is write only.
11293 Memory is read/write. This is the default.
11296 @subsubsection Memory Access Size
11297 The access size attribute tells @value{GDBN} to use specific sized
11298 accesses in the memory region. Often memory mapped device registers
11299 require specific sized accesses. If no access size attribute is
11300 specified, @value{GDBN} may use accesses of any size.
11304 Use 8 bit memory accesses.
11306 Use 16 bit memory accesses.
11308 Use 32 bit memory accesses.
11310 Use 64 bit memory accesses.
11313 @c @subsubsection Hardware/Software Breakpoints
11314 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11315 @c will use hardware or software breakpoints for the internal breakpoints
11316 @c used by the step, next, finish, until, etc. commands.
11320 @c Always use hardware breakpoints
11321 @c @item swbreak (default)
11324 @subsubsection Data Cache
11325 The data cache attributes set whether @value{GDBN} will cache target
11326 memory. While this generally improves performance by reducing debug
11327 protocol overhead, it can lead to incorrect results because @value{GDBN}
11328 does not know about volatile variables or memory mapped device
11333 Enable @value{GDBN} to cache target memory.
11335 Disable @value{GDBN} from caching target memory. This is the default.
11338 @subsection Memory Access Checking
11339 @value{GDBN} can be instructed to refuse accesses to memory that is
11340 not explicitly described. This can be useful if accessing such
11341 regions has undesired effects for a specific target, or to provide
11342 better error checking. The following commands control this behaviour.
11345 @kindex set mem inaccessible-by-default
11346 @item set mem inaccessible-by-default [on|off]
11347 If @code{on} is specified, make @value{GDBN} treat memory not
11348 explicitly described by the memory ranges as non-existent and refuse accesses
11349 to such memory. The checks are only performed if there's at least one
11350 memory range defined. If @code{off} is specified, make @value{GDBN}
11351 treat the memory not explicitly described by the memory ranges as RAM.
11352 The default value is @code{on}.
11353 @kindex show mem inaccessible-by-default
11354 @item show mem inaccessible-by-default
11355 Show the current handling of accesses to unknown memory.
11359 @c @subsubsection Memory Write Verification
11360 @c The memory write verification attributes set whether @value{GDBN}
11361 @c will re-reads data after each write to verify the write was successful.
11365 @c @item noverify (default)
11368 @node Dump/Restore Files
11369 @section Copy Between Memory and a File
11370 @cindex dump/restore files
11371 @cindex append data to a file
11372 @cindex dump data to a file
11373 @cindex restore data from a file
11375 You can use the commands @code{dump}, @code{append}, and
11376 @code{restore} to copy data between target memory and a file. The
11377 @code{dump} and @code{append} commands write data to a file, and the
11378 @code{restore} command reads data from a file back into the inferior's
11379 memory. Files may be in binary, Motorola S-record, Intel hex,
11380 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11381 append to binary files, and cannot read from Verilog Hex files.
11386 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11387 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11388 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11389 or the value of @var{expr}, to @var{filename} in the given format.
11391 The @var{format} parameter may be any one of:
11398 Motorola S-record format.
11400 Tektronix Hex format.
11402 Verilog Hex format.
11405 @value{GDBN} uses the same definitions of these formats as the
11406 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11407 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11411 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11412 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11413 Append the contents of memory from @var{start_addr} to @var{end_addr},
11414 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11415 (@value{GDBN} can only append data to files in raw binary form.)
11418 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11419 Restore the contents of file @var{filename} into memory. The
11420 @code{restore} command can automatically recognize any known @sc{bfd}
11421 file format, except for raw binary. To restore a raw binary file you
11422 must specify the optional keyword @code{binary} after the filename.
11424 If @var{bias} is non-zero, its value will be added to the addresses
11425 contained in the file. Binary files always start at address zero, so
11426 they will be restored at address @var{bias}. Other bfd files have
11427 a built-in location; they will be restored at offset @var{bias}
11428 from that location.
11430 If @var{start} and/or @var{end} are non-zero, then only data between
11431 file offset @var{start} and file offset @var{end} will be restored.
11432 These offsets are relative to the addresses in the file, before
11433 the @var{bias} argument is applied.
11437 @node Core File Generation
11438 @section How to Produce a Core File from Your Program
11439 @cindex dump core from inferior
11441 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11442 image of a running process and its process status (register values
11443 etc.). Its primary use is post-mortem debugging of a program that
11444 crashed while it ran outside a debugger. A program that crashes
11445 automatically produces a core file, unless this feature is disabled by
11446 the user. @xref{Files}, for information on invoking @value{GDBN} in
11447 the post-mortem debugging mode.
11449 Occasionally, you may wish to produce a core file of the program you
11450 are debugging in order to preserve a snapshot of its state.
11451 @value{GDBN} has a special command for that.
11455 @kindex generate-core-file
11456 @item generate-core-file [@var{file}]
11457 @itemx gcore [@var{file}]
11458 Produce a core dump of the inferior process. The optional argument
11459 @var{file} specifies the file name where to put the core dump. If not
11460 specified, the file name defaults to @file{core.@var{pid}}, where
11461 @var{pid} is the inferior process ID.
11463 Note that this command is implemented only for some systems (as of
11464 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11466 On @sc{gnu}/Linux, this command can take into account the value of the
11467 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11468 dump (@pxref{set use-coredump-filter}).
11470 @kindex set use-coredump-filter
11471 @anchor{set use-coredump-filter}
11472 @item set use-coredump-filter on
11473 @itemx set use-coredump-filter off
11474 Enable or disable the use of the file
11475 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11476 files. This file is used by the Linux kernel to decide what types of
11477 memory mappings will be dumped or ignored when generating a core dump
11478 file. @var{pid} is the process ID of a currently running process.
11480 To make use of this feature, you have to write in the
11481 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11482 which is a bit mask representing the memory mapping types. If a bit
11483 is set in the bit mask, then the memory mappings of the corresponding
11484 types will be dumped; otherwise, they will be ignored. This
11485 configuration is inherited by child processes. For more information
11486 about the bits that can be set in the
11487 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11488 manpage of @code{core(5)}.
11490 By default, this option is @code{on}. If this option is turned
11491 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11492 and instead uses the same default value as the Linux kernel in order
11493 to decide which pages will be dumped in the core dump file. This
11494 value is currently @code{0x33}, which means that bits @code{0}
11495 (anonymous private mappings), @code{1} (anonymous shared mappings),
11496 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11497 This will cause these memory mappings to be dumped automatically.
11500 @node Character Sets
11501 @section Character Sets
11502 @cindex character sets
11504 @cindex translating between character sets
11505 @cindex host character set
11506 @cindex target character set
11508 If the program you are debugging uses a different character set to
11509 represent characters and strings than the one @value{GDBN} uses itself,
11510 @value{GDBN} can automatically translate between the character sets for
11511 you. The character set @value{GDBN} uses we call the @dfn{host
11512 character set}; the one the inferior program uses we call the
11513 @dfn{target character set}.
11515 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11516 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11517 remote protocol (@pxref{Remote Debugging}) to debug a program
11518 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11519 then the host character set is Latin-1, and the target character set is
11520 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11521 target-charset EBCDIC-US}, then @value{GDBN} translates between
11522 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11523 character and string literals in expressions.
11525 @value{GDBN} has no way to automatically recognize which character set
11526 the inferior program uses; you must tell it, using the @code{set
11527 target-charset} command, described below.
11529 Here are the commands for controlling @value{GDBN}'s character set
11533 @item set target-charset @var{charset}
11534 @kindex set target-charset
11535 Set the current target character set to @var{charset}. To display the
11536 list of supported target character sets, type
11537 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11539 @item set host-charset @var{charset}
11540 @kindex set host-charset
11541 Set the current host character set to @var{charset}.
11543 By default, @value{GDBN} uses a host character set appropriate to the
11544 system it is running on; you can override that default using the
11545 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11546 automatically determine the appropriate host character set. In this
11547 case, @value{GDBN} uses @samp{UTF-8}.
11549 @value{GDBN} can only use certain character sets as its host character
11550 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11551 @value{GDBN} will list the host character sets it supports.
11553 @item set charset @var{charset}
11554 @kindex set charset
11555 Set the current host and target character sets to @var{charset}. As
11556 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11557 @value{GDBN} will list the names of the character sets that can be used
11558 for both host and target.
11561 @kindex show charset
11562 Show the names of the current host and target character sets.
11564 @item show host-charset
11565 @kindex show host-charset
11566 Show the name of the current host character set.
11568 @item show target-charset
11569 @kindex show target-charset
11570 Show the name of the current target character set.
11572 @item set target-wide-charset @var{charset}
11573 @kindex set target-wide-charset
11574 Set the current target's wide character set to @var{charset}. This is
11575 the character set used by the target's @code{wchar_t} type. To
11576 display the list of supported wide character sets, type
11577 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11579 @item show target-wide-charset
11580 @kindex show target-wide-charset
11581 Show the name of the current target's wide character set.
11584 Here is an example of @value{GDBN}'s character set support in action.
11585 Assume that the following source code has been placed in the file
11586 @file{charset-test.c}:
11592 = @{72, 101, 108, 108, 111, 44, 32, 119,
11593 111, 114, 108, 100, 33, 10, 0@};
11594 char ibm1047_hello[]
11595 = @{200, 133, 147, 147, 150, 107, 64, 166,
11596 150, 153, 147, 132, 90, 37, 0@};
11600 printf ("Hello, world!\n");
11604 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11605 containing the string @samp{Hello, world!} followed by a newline,
11606 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11608 We compile the program, and invoke the debugger on it:
11611 $ gcc -g charset-test.c -o charset-test
11612 $ gdb -nw charset-test
11613 GNU gdb 2001-12-19-cvs
11614 Copyright 2001 Free Software Foundation, Inc.
11619 We can use the @code{show charset} command to see what character sets
11620 @value{GDBN} is currently using to interpret and display characters and
11624 (@value{GDBP}) show charset
11625 The current host and target character set is `ISO-8859-1'.
11629 For the sake of printing this manual, let's use @sc{ascii} as our
11630 initial character set:
11632 (@value{GDBP}) set charset ASCII
11633 (@value{GDBP}) show charset
11634 The current host and target character set is `ASCII'.
11638 Let's assume that @sc{ascii} is indeed the correct character set for our
11639 host system --- in other words, let's assume that if @value{GDBN} prints
11640 characters using the @sc{ascii} character set, our terminal will display
11641 them properly. Since our current target character set is also
11642 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11645 (@value{GDBP}) print ascii_hello
11646 $1 = 0x401698 "Hello, world!\n"
11647 (@value{GDBP}) print ascii_hello[0]
11652 @value{GDBN} uses the target character set for character and string
11653 literals you use in expressions:
11656 (@value{GDBP}) print '+'
11661 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11664 @value{GDBN} relies on the user to tell it which character set the
11665 target program uses. If we print @code{ibm1047_hello} while our target
11666 character set is still @sc{ascii}, we get jibberish:
11669 (@value{GDBP}) print ibm1047_hello
11670 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11671 (@value{GDBP}) print ibm1047_hello[0]
11676 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11677 @value{GDBN} tells us the character sets it supports:
11680 (@value{GDBP}) set target-charset
11681 ASCII EBCDIC-US IBM1047 ISO-8859-1
11682 (@value{GDBP}) set target-charset
11685 We can select @sc{ibm1047} as our target character set, and examine the
11686 program's strings again. Now the @sc{ascii} string is wrong, but
11687 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11688 target character set, @sc{ibm1047}, to the host character set,
11689 @sc{ascii}, and they display correctly:
11692 (@value{GDBP}) set target-charset IBM1047
11693 (@value{GDBP}) show charset
11694 The current host character set is `ASCII'.
11695 The current target character set is `IBM1047'.
11696 (@value{GDBP}) print ascii_hello
11697 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11698 (@value{GDBP}) print ascii_hello[0]
11700 (@value{GDBP}) print ibm1047_hello
11701 $8 = 0x4016a8 "Hello, world!\n"
11702 (@value{GDBP}) print ibm1047_hello[0]
11707 As above, @value{GDBN} uses the target character set for character and
11708 string literals you use in expressions:
11711 (@value{GDBP}) print '+'
11716 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11719 @node Caching Target Data
11720 @section Caching Data of Targets
11721 @cindex caching data of targets
11723 @value{GDBN} caches data exchanged between the debugger and a target.
11724 Each cache is associated with the address space of the inferior.
11725 @xref{Inferiors and Programs}, about inferior and address space.
11726 Such caching generally improves performance in remote debugging
11727 (@pxref{Remote Debugging}), because it reduces the overhead of the
11728 remote protocol by bundling memory reads and writes into large chunks.
11729 Unfortunately, simply caching everything would lead to incorrect results,
11730 since @value{GDBN} does not necessarily know anything about volatile
11731 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11732 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11734 Therefore, by default, @value{GDBN} only caches data
11735 known to be on the stack@footnote{In non-stop mode, it is moderately
11736 rare for a running thread to modify the stack of a stopped thread
11737 in a way that would interfere with a backtrace, and caching of
11738 stack reads provides a significant speed up of remote backtraces.} or
11739 in the code segment.
11740 Other regions of memory can be explicitly marked as
11741 cacheable; @pxref{Memory Region Attributes}.
11744 @kindex set remotecache
11745 @item set remotecache on
11746 @itemx set remotecache off
11747 This option no longer does anything; it exists for compatibility
11750 @kindex show remotecache
11751 @item show remotecache
11752 Show the current state of the obsolete remotecache flag.
11754 @kindex set stack-cache
11755 @item set stack-cache on
11756 @itemx set stack-cache off
11757 Enable or disable caching of stack accesses. When @code{on}, use
11758 caching. By default, this option is @code{on}.
11760 @kindex show stack-cache
11761 @item show stack-cache
11762 Show the current state of data caching for memory accesses.
11764 @kindex set code-cache
11765 @item set code-cache on
11766 @itemx set code-cache off
11767 Enable or disable caching of code segment accesses. When @code{on},
11768 use caching. By default, this option is @code{on}. This improves
11769 performance of disassembly in remote debugging.
11771 @kindex show code-cache
11772 @item show code-cache
11773 Show the current state of target memory cache for code segment
11776 @kindex info dcache
11777 @item info dcache @r{[}line@r{]}
11778 Print the information about the performance of data cache of the
11779 current inferior's address space. The information displayed
11780 includes the dcache width and depth, and for each cache line, its
11781 number, address, and how many times it was referenced. This
11782 command is useful for debugging the data cache operation.
11784 If a line number is specified, the contents of that line will be
11787 @item set dcache size @var{size}
11788 @cindex dcache size
11789 @kindex set dcache size
11790 Set maximum number of entries in dcache (dcache depth above).
11792 @item set dcache line-size @var{line-size}
11793 @cindex dcache line-size
11794 @kindex set dcache line-size
11795 Set number of bytes each dcache entry caches (dcache width above).
11796 Must be a power of 2.
11798 @item show dcache size
11799 @kindex show dcache size
11800 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11802 @item show dcache line-size
11803 @kindex show dcache line-size
11804 Show default size of dcache lines.
11808 @node Searching Memory
11809 @section Search Memory
11810 @cindex searching memory
11812 Memory can be searched for a particular sequence of bytes with the
11813 @code{find} command.
11817 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11818 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11819 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11820 etc. The search begins at address @var{start_addr} and continues for either
11821 @var{len} bytes or through to @var{end_addr} inclusive.
11824 @var{s} and @var{n} are optional parameters.
11825 They may be specified in either order, apart or together.
11828 @item @var{s}, search query size
11829 The size of each search query value.
11835 halfwords (two bytes)
11839 giant words (eight bytes)
11842 All values are interpreted in the current language.
11843 This means, for example, that if the current source language is C/C@t{++}
11844 then searching for the string ``hello'' includes the trailing '\0'.
11846 If the value size is not specified, it is taken from the
11847 value's type in the current language.
11848 This is useful when one wants to specify the search
11849 pattern as a mixture of types.
11850 Note that this means, for example, that in the case of C-like languages
11851 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11852 which is typically four bytes.
11854 @item @var{n}, maximum number of finds
11855 The maximum number of matches to print. The default is to print all finds.
11858 You can use strings as search values. Quote them with double-quotes
11860 The string value is copied into the search pattern byte by byte,
11861 regardless of the endianness of the target and the size specification.
11863 The address of each match found is printed as well as a count of the
11864 number of matches found.
11866 The address of the last value found is stored in convenience variable
11868 A count of the number of matches is stored in @samp{$numfound}.
11870 For example, if stopped at the @code{printf} in this function:
11876 static char hello[] = "hello-hello";
11877 static struct @{ char c; short s; int i; @}
11878 __attribute__ ((packed)) mixed
11879 = @{ 'c', 0x1234, 0x87654321 @};
11880 printf ("%s\n", hello);
11885 you get during debugging:
11888 (gdb) find &hello[0], +sizeof(hello), "hello"
11889 0x804956d <hello.1620+6>
11891 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11892 0x8049567 <hello.1620>
11893 0x804956d <hello.1620+6>
11895 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11896 0x8049567 <hello.1620>
11898 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11899 0x8049560 <mixed.1625>
11901 (gdb) print $numfound
11904 $2 = (void *) 0x8049560
11908 @section Value Sizes
11910 Whenever @value{GDBN} prints a value memory will be allocated within
11911 @value{GDBN} to hold the contents of the value. It is possible in
11912 some languages with dynamic typing systems, that an invalid program
11913 may indicate a value that is incorrectly large, this in turn may cause
11914 @value{GDBN} to try and allocate an overly large ammount of memory.
11917 @kindex set max-value-size
11918 @item set max-value-size @var{bytes}
11919 @itemx set max-value-size unlimited
11920 Set the maximum size of memory that @value{GDBN} will allocate for the
11921 contents of a value to @var{bytes}, trying to display a value that
11922 requires more memory than that will result in an error.
11924 Setting this variable does not effect values that have already been
11925 allocated within @value{GDBN}, only future allocations.
11927 There's a minimum size that @code{max-value-size} can be set to in
11928 order that @value{GDBN} can still operate correctly, this minimum is
11929 currently 16 bytes.
11931 The limit applies to the results of some subexpressions as well as to
11932 complete expressions. For example, an expression denoting a simple
11933 integer component, such as @code{x.y.z}, may fail if the size of
11934 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11935 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11936 @var{A} is an array variable with non-constant size, will generally
11937 succeed regardless of the bounds on @var{A}, as long as the component
11938 size is less than @var{bytes}.
11940 The default value of @code{max-value-size} is currently 64k.
11942 @kindex show max-value-size
11943 @item show max-value-size
11944 Show the maximum size of memory, in bytes, that @value{GDBN} will
11945 allocate for the contents of a value.
11948 @node Optimized Code
11949 @chapter Debugging Optimized Code
11950 @cindex optimized code, debugging
11951 @cindex debugging optimized code
11953 Almost all compilers support optimization. With optimization
11954 disabled, the compiler generates assembly code that corresponds
11955 directly to your source code, in a simplistic way. As the compiler
11956 applies more powerful optimizations, the generated assembly code
11957 diverges from your original source code. With help from debugging
11958 information generated by the compiler, @value{GDBN} can map from
11959 the running program back to constructs from your original source.
11961 @value{GDBN} is more accurate with optimization disabled. If you
11962 can recompile without optimization, it is easier to follow the
11963 progress of your program during debugging. But, there are many cases
11964 where you may need to debug an optimized version.
11966 When you debug a program compiled with @samp{-g -O}, remember that the
11967 optimizer has rearranged your code; the debugger shows you what is
11968 really there. Do not be too surprised when the execution path does not
11969 exactly match your source file! An extreme example: if you define a
11970 variable, but never use it, @value{GDBN} never sees that
11971 variable---because the compiler optimizes it out of existence.
11973 Some things do not work as well with @samp{-g -O} as with just
11974 @samp{-g}, particularly on machines with instruction scheduling. If in
11975 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11976 please report it to us as a bug (including a test case!).
11977 @xref{Variables}, for more information about debugging optimized code.
11980 * Inline Functions:: How @value{GDBN} presents inlining
11981 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11984 @node Inline Functions
11985 @section Inline Functions
11986 @cindex inline functions, debugging
11988 @dfn{Inlining} is an optimization that inserts a copy of the function
11989 body directly at each call site, instead of jumping to a shared
11990 routine. @value{GDBN} displays inlined functions just like
11991 non-inlined functions. They appear in backtraces. You can view their
11992 arguments and local variables, step into them with @code{step}, skip
11993 them with @code{next}, and escape from them with @code{finish}.
11994 You can check whether a function was inlined by using the
11995 @code{info frame} command.
11997 For @value{GDBN} to support inlined functions, the compiler must
11998 record information about inlining in the debug information ---
11999 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12000 other compilers do also. @value{GDBN} only supports inlined functions
12001 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12002 do not emit two required attributes (@samp{DW_AT_call_file} and
12003 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12004 function calls with earlier versions of @value{NGCC}. It instead
12005 displays the arguments and local variables of inlined functions as
12006 local variables in the caller.
12008 The body of an inlined function is directly included at its call site;
12009 unlike a non-inlined function, there are no instructions devoted to
12010 the call. @value{GDBN} still pretends that the call site and the
12011 start of the inlined function are different instructions. Stepping to
12012 the call site shows the call site, and then stepping again shows
12013 the first line of the inlined function, even though no additional
12014 instructions are executed.
12016 This makes source-level debugging much clearer; you can see both the
12017 context of the call and then the effect of the call. Only stepping by
12018 a single instruction using @code{stepi} or @code{nexti} does not do
12019 this; single instruction steps always show the inlined body.
12021 There are some ways that @value{GDBN} does not pretend that inlined
12022 function calls are the same as normal calls:
12026 Setting breakpoints at the call site of an inlined function may not
12027 work, because the call site does not contain any code. @value{GDBN}
12028 may incorrectly move the breakpoint to the next line of the enclosing
12029 function, after the call. This limitation will be removed in a future
12030 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12031 or inside the inlined function instead.
12034 @value{GDBN} cannot locate the return value of inlined calls after
12035 using the @code{finish} command. This is a limitation of compiler-generated
12036 debugging information; after @code{finish}, you can step to the next line
12037 and print a variable where your program stored the return value.
12041 @node Tail Call Frames
12042 @section Tail Call Frames
12043 @cindex tail call frames, debugging
12045 Function @code{B} can call function @code{C} in its very last statement. In
12046 unoptimized compilation the call of @code{C} is immediately followed by return
12047 instruction at the end of @code{B} code. Optimizing compiler may replace the
12048 call and return in function @code{B} into one jump to function @code{C}
12049 instead. Such use of a jump instruction is called @dfn{tail call}.
12051 During execution of function @code{C}, there will be no indication in the
12052 function call stack frames that it was tail-called from @code{B}. If function
12053 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12054 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12055 some cases @value{GDBN} can determine that @code{C} was tail-called from
12056 @code{B}, and it will then create fictitious call frame for that, with the
12057 return address set up as if @code{B} called @code{C} normally.
12059 This functionality is currently supported only by DWARF 2 debugging format and
12060 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12061 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12064 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12065 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12069 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12071 Stack level 1, frame at 0x7fffffffda30:
12072 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12073 tail call frame, caller of frame at 0x7fffffffda30
12074 source language c++.
12075 Arglist at unknown address.
12076 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12079 The detection of all the possible code path executions can find them ambiguous.
12080 There is no execution history stored (possible @ref{Reverse Execution} is never
12081 used for this purpose) and the last known caller could have reached the known
12082 callee by multiple different jump sequences. In such case @value{GDBN} still
12083 tries to show at least all the unambiguous top tail callers and all the
12084 unambiguous bottom tail calees, if any.
12087 @anchor{set debug entry-values}
12088 @item set debug entry-values
12089 @kindex set debug entry-values
12090 When set to on, enables printing of analysis messages for both frame argument
12091 values at function entry and tail calls. It will show all the possible valid
12092 tail calls code paths it has considered. It will also print the intersection
12093 of them with the final unambiguous (possibly partial or even empty) code path
12096 @item show debug entry-values
12097 @kindex show debug entry-values
12098 Show the current state of analysis messages printing for both frame argument
12099 values at function entry and tail calls.
12102 The analysis messages for tail calls can for example show why the virtual tail
12103 call frame for function @code{c} has not been recognized (due to the indirect
12104 reference by variable @code{x}):
12107 static void __attribute__((noinline, noclone)) c (void);
12108 void (*x) (void) = c;
12109 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12110 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12111 int main (void) @{ x (); return 0; @}
12113 Breakpoint 1, DW_OP_entry_value resolving cannot find
12114 DW_TAG_call_site 0x40039a in main
12116 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12119 #1 0x000000000040039a in main () at t.c:5
12122 Another possibility is an ambiguous virtual tail call frames resolution:
12126 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12127 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12128 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12129 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12130 static void __attribute__((noinline, noclone)) b (void)
12131 @{ if (i) c (); else e (); @}
12132 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12133 int main (void) @{ a (); return 0; @}
12135 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12136 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12137 tailcall: reduced: 0x4004d2(a) |
12140 #1 0x00000000004004d2 in a () at t.c:8
12141 #2 0x0000000000400395 in main () at t.c:9
12144 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12145 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12147 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12148 @ifset HAVE_MAKEINFO_CLICK
12149 @set ARROW @click{}
12150 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12151 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12153 @ifclear HAVE_MAKEINFO_CLICK
12155 @set CALLSEQ1B @value{CALLSEQ1A}
12156 @set CALLSEQ2B @value{CALLSEQ2A}
12159 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12160 The code can have possible execution paths @value{CALLSEQ1B} or
12161 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12163 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12164 has found. It then finds another possible calling sequcen - that one is
12165 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12166 printed as the @code{reduced:} calling sequence. That one could have many
12167 futher @code{compare:} and @code{reduced:} statements as long as there remain
12168 any non-ambiguous sequence entries.
12170 For the frame of function @code{b} in both cases there are different possible
12171 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12172 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12173 therefore this one is displayed to the user while the ambiguous frames are
12176 There can be also reasons why printing of frame argument values at function
12181 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12182 static void __attribute__((noinline, noclone)) a (int i);
12183 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12184 static void __attribute__((noinline, noclone)) a (int i)
12185 @{ if (i) b (i - 1); else c (0); @}
12186 int main (void) @{ a (5); return 0; @}
12189 #0 c (i=i@@entry=0) at t.c:2
12190 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12191 function "a" at 0x400420 can call itself via tail calls
12192 i=<optimized out>) at t.c:6
12193 #2 0x000000000040036e in main () at t.c:7
12196 @value{GDBN} cannot find out from the inferior state if and how many times did
12197 function @code{a} call itself (via function @code{b}) as these calls would be
12198 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12199 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12200 prints @code{<optimized out>} instead.
12203 @chapter C Preprocessor Macros
12205 Some languages, such as C and C@t{++}, provide a way to define and invoke
12206 ``preprocessor macros'' which expand into strings of tokens.
12207 @value{GDBN} can evaluate expressions containing macro invocations, show
12208 the result of macro expansion, and show a macro's definition, including
12209 where it was defined.
12211 You may need to compile your program specially to provide @value{GDBN}
12212 with information about preprocessor macros. Most compilers do not
12213 include macros in their debugging information, even when you compile
12214 with the @option{-g} flag. @xref{Compilation}.
12216 A program may define a macro at one point, remove that definition later,
12217 and then provide a different definition after that. Thus, at different
12218 points in the program, a macro may have different definitions, or have
12219 no definition at all. If there is a current stack frame, @value{GDBN}
12220 uses the macros in scope at that frame's source code line. Otherwise,
12221 @value{GDBN} uses the macros in scope at the current listing location;
12224 Whenever @value{GDBN} evaluates an expression, it always expands any
12225 macro invocations present in the expression. @value{GDBN} also provides
12226 the following commands for working with macros explicitly.
12230 @kindex macro expand
12231 @cindex macro expansion, showing the results of preprocessor
12232 @cindex preprocessor macro expansion, showing the results of
12233 @cindex expanding preprocessor macros
12234 @item macro expand @var{expression}
12235 @itemx macro exp @var{expression}
12236 Show the results of expanding all preprocessor macro invocations in
12237 @var{expression}. Since @value{GDBN} simply expands macros, but does
12238 not parse the result, @var{expression} need not be a valid expression;
12239 it can be any string of tokens.
12242 @item macro expand-once @var{expression}
12243 @itemx macro exp1 @var{expression}
12244 @cindex expand macro once
12245 @i{(This command is not yet implemented.)} Show the results of
12246 expanding those preprocessor macro invocations that appear explicitly in
12247 @var{expression}. Macro invocations appearing in that expansion are
12248 left unchanged. This command allows you to see the effect of a
12249 particular macro more clearly, without being confused by further
12250 expansions. Since @value{GDBN} simply expands macros, but does not
12251 parse the result, @var{expression} need not be a valid expression; it
12252 can be any string of tokens.
12255 @cindex macro definition, showing
12256 @cindex definition of a macro, showing
12257 @cindex macros, from debug info
12258 @item info macro [-a|-all] [--] @var{macro}
12259 Show the current definition or all definitions of the named @var{macro},
12260 and describe the source location or compiler command-line where that
12261 definition was established. The optional double dash is to signify the end of
12262 argument processing and the beginning of @var{macro} for non C-like macros where
12263 the macro may begin with a hyphen.
12265 @kindex info macros
12266 @item info macros @var{location}
12267 Show all macro definitions that are in effect at the location specified
12268 by @var{location}, and describe the source location or compiler
12269 command-line where those definitions were established.
12271 @kindex macro define
12272 @cindex user-defined macros
12273 @cindex defining macros interactively
12274 @cindex macros, user-defined
12275 @item macro define @var{macro} @var{replacement-list}
12276 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12277 Introduce a definition for a preprocessor macro named @var{macro},
12278 invocations of which are replaced by the tokens given in
12279 @var{replacement-list}. The first form of this command defines an
12280 ``object-like'' macro, which takes no arguments; the second form
12281 defines a ``function-like'' macro, which takes the arguments given in
12284 A definition introduced by this command is in scope in every
12285 expression evaluated in @value{GDBN}, until it is removed with the
12286 @code{macro undef} command, described below. The definition overrides
12287 all definitions for @var{macro} present in the program being debugged,
12288 as well as any previous user-supplied definition.
12290 @kindex macro undef
12291 @item macro undef @var{macro}
12292 Remove any user-supplied definition for the macro named @var{macro}.
12293 This command only affects definitions provided with the @code{macro
12294 define} command, described above; it cannot remove definitions present
12295 in the program being debugged.
12299 List all the macros defined using the @code{macro define} command.
12302 @cindex macros, example of debugging with
12303 Here is a transcript showing the above commands in action. First, we
12304 show our source files:
12309 #include "sample.h"
12312 #define ADD(x) (M + x)
12317 printf ("Hello, world!\n");
12319 printf ("We're so creative.\n");
12321 printf ("Goodbye, world!\n");
12328 Now, we compile the program using the @sc{gnu} C compiler,
12329 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12330 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12331 and @option{-gdwarf-4}; we recommend always choosing the most recent
12332 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12333 includes information about preprocessor macros in the debugging
12337 $ gcc -gdwarf-2 -g3 sample.c -o sample
12341 Now, we start @value{GDBN} on our sample program:
12345 GNU gdb 2002-05-06-cvs
12346 Copyright 2002 Free Software Foundation, Inc.
12347 GDB is free software, @dots{}
12351 We can expand macros and examine their definitions, even when the
12352 program is not running. @value{GDBN} uses the current listing position
12353 to decide which macro definitions are in scope:
12356 (@value{GDBP}) list main
12359 5 #define ADD(x) (M + x)
12364 10 printf ("Hello, world!\n");
12366 12 printf ("We're so creative.\n");
12367 (@value{GDBP}) info macro ADD
12368 Defined at /home/jimb/gdb/macros/play/sample.c:5
12369 #define ADD(x) (M + x)
12370 (@value{GDBP}) info macro Q
12371 Defined at /home/jimb/gdb/macros/play/sample.h:1
12372 included at /home/jimb/gdb/macros/play/sample.c:2
12374 (@value{GDBP}) macro expand ADD(1)
12375 expands to: (42 + 1)
12376 (@value{GDBP}) macro expand-once ADD(1)
12377 expands to: once (M + 1)
12381 In the example above, note that @code{macro expand-once} expands only
12382 the macro invocation explicit in the original text --- the invocation of
12383 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12384 which was introduced by @code{ADD}.
12386 Once the program is running, @value{GDBN} uses the macro definitions in
12387 force at the source line of the current stack frame:
12390 (@value{GDBP}) break main
12391 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12393 Starting program: /home/jimb/gdb/macros/play/sample
12395 Breakpoint 1, main () at sample.c:10
12396 10 printf ("Hello, world!\n");
12400 At line 10, the definition of the macro @code{N} at line 9 is in force:
12403 (@value{GDBP}) info macro N
12404 Defined at /home/jimb/gdb/macros/play/sample.c:9
12406 (@value{GDBP}) macro expand N Q M
12407 expands to: 28 < 42
12408 (@value{GDBP}) print N Q M
12413 As we step over directives that remove @code{N}'s definition, and then
12414 give it a new definition, @value{GDBN} finds the definition (or lack
12415 thereof) in force at each point:
12418 (@value{GDBP}) next
12420 12 printf ("We're so creative.\n");
12421 (@value{GDBP}) info macro N
12422 The symbol `N' has no definition as a C/C++ preprocessor macro
12423 at /home/jimb/gdb/macros/play/sample.c:12
12424 (@value{GDBP}) next
12426 14 printf ("Goodbye, world!\n");
12427 (@value{GDBP}) info macro N
12428 Defined at /home/jimb/gdb/macros/play/sample.c:13
12430 (@value{GDBP}) macro expand N Q M
12431 expands to: 1729 < 42
12432 (@value{GDBP}) print N Q M
12437 In addition to source files, macros can be defined on the compilation command
12438 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12439 such a way, @value{GDBN} displays the location of their definition as line zero
12440 of the source file submitted to the compiler.
12443 (@value{GDBP}) info macro __STDC__
12444 Defined at /home/jimb/gdb/macros/play/sample.c:0
12451 @chapter Tracepoints
12452 @c This chapter is based on the documentation written by Michael
12453 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12455 @cindex tracepoints
12456 In some applications, it is not feasible for the debugger to interrupt
12457 the program's execution long enough for the developer to learn
12458 anything helpful about its behavior. If the program's correctness
12459 depends on its real-time behavior, delays introduced by a debugger
12460 might cause the program to change its behavior drastically, or perhaps
12461 fail, even when the code itself is correct. It is useful to be able
12462 to observe the program's behavior without interrupting it.
12464 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12465 specify locations in the program, called @dfn{tracepoints}, and
12466 arbitrary expressions to evaluate when those tracepoints are reached.
12467 Later, using the @code{tfind} command, you can examine the values
12468 those expressions had when the program hit the tracepoints. The
12469 expressions may also denote objects in memory---structures or arrays,
12470 for example---whose values @value{GDBN} should record; while visiting
12471 a particular tracepoint, you may inspect those objects as if they were
12472 in memory at that moment. However, because @value{GDBN} records these
12473 values without interacting with you, it can do so quickly and
12474 unobtrusively, hopefully not disturbing the program's behavior.
12476 The tracepoint facility is currently available only for remote
12477 targets. @xref{Targets}. In addition, your remote target must know
12478 how to collect trace data. This functionality is implemented in the
12479 remote stub; however, none of the stubs distributed with @value{GDBN}
12480 support tracepoints as of this writing. The format of the remote
12481 packets used to implement tracepoints are described in @ref{Tracepoint
12484 It is also possible to get trace data from a file, in a manner reminiscent
12485 of corefiles; you specify the filename, and use @code{tfind} to search
12486 through the file. @xref{Trace Files}, for more details.
12488 This chapter describes the tracepoint commands and features.
12491 * Set Tracepoints::
12492 * Analyze Collected Data::
12493 * Tracepoint Variables::
12497 @node Set Tracepoints
12498 @section Commands to Set Tracepoints
12500 Before running such a @dfn{trace experiment}, an arbitrary number of
12501 tracepoints can be set. A tracepoint is actually a special type of
12502 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12503 standard breakpoint commands. For instance, as with breakpoints,
12504 tracepoint numbers are successive integers starting from one, and many
12505 of the commands associated with tracepoints take the tracepoint number
12506 as their argument, to identify which tracepoint to work on.
12508 For each tracepoint, you can specify, in advance, some arbitrary set
12509 of data that you want the target to collect in the trace buffer when
12510 it hits that tracepoint. The collected data can include registers,
12511 local variables, or global data. Later, you can use @value{GDBN}
12512 commands to examine the values these data had at the time the
12513 tracepoint was hit.
12515 Tracepoints do not support every breakpoint feature. Ignore counts on
12516 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12517 commands when they are hit. Tracepoints may not be thread-specific
12520 @cindex fast tracepoints
12521 Some targets may support @dfn{fast tracepoints}, which are inserted in
12522 a different way (such as with a jump instead of a trap), that is
12523 faster but possibly restricted in where they may be installed.
12525 @cindex static tracepoints
12526 @cindex markers, static tracepoints
12527 @cindex probing markers, static tracepoints
12528 Regular and fast tracepoints are dynamic tracing facilities, meaning
12529 that they can be used to insert tracepoints at (almost) any location
12530 in the target. Some targets may also support controlling @dfn{static
12531 tracepoints} from @value{GDBN}. With static tracing, a set of
12532 instrumentation points, also known as @dfn{markers}, are embedded in
12533 the target program, and can be activated or deactivated by name or
12534 address. These are usually placed at locations which facilitate
12535 investigating what the target is actually doing. @value{GDBN}'s
12536 support for static tracing includes being able to list instrumentation
12537 points, and attach them with @value{GDBN} defined high level
12538 tracepoints that expose the whole range of convenience of
12539 @value{GDBN}'s tracepoints support. Namely, support for collecting
12540 registers values and values of global or local (to the instrumentation
12541 point) variables; tracepoint conditions and trace state variables.
12542 The act of installing a @value{GDBN} static tracepoint on an
12543 instrumentation point, or marker, is referred to as @dfn{probing} a
12544 static tracepoint marker.
12546 @code{gdbserver} supports tracepoints on some target systems.
12547 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12549 This section describes commands to set tracepoints and associated
12550 conditions and actions.
12553 * Create and Delete Tracepoints::
12554 * Enable and Disable Tracepoints::
12555 * Tracepoint Passcounts::
12556 * Tracepoint Conditions::
12557 * Trace State Variables::
12558 * Tracepoint Actions::
12559 * Listing Tracepoints::
12560 * Listing Static Tracepoint Markers::
12561 * Starting and Stopping Trace Experiments::
12562 * Tracepoint Restrictions::
12565 @node Create and Delete Tracepoints
12566 @subsection Create and Delete Tracepoints
12569 @cindex set tracepoint
12571 @item trace @var{location}
12572 The @code{trace} command is very similar to the @code{break} command.
12573 Its argument @var{location} can be any valid location.
12574 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12575 which is a point in the target program where the debugger will briefly stop,
12576 collect some data, and then allow the program to continue. Setting a tracepoint
12577 or changing its actions takes effect immediately if the remote stub
12578 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12580 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12581 these changes don't take effect until the next @code{tstart}
12582 command, and once a trace experiment is running, further changes will
12583 not have any effect until the next trace experiment starts. In addition,
12584 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12585 address is not yet resolved. (This is similar to pending breakpoints.)
12586 Pending tracepoints are not downloaded to the target and not installed
12587 until they are resolved. The resolution of pending tracepoints requires
12588 @value{GDBN} support---when debugging with the remote target, and
12589 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12590 tracing}), pending tracepoints can not be resolved (and downloaded to
12591 the remote stub) while @value{GDBN} is disconnected.
12593 Here are some examples of using the @code{trace} command:
12596 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12598 (@value{GDBP}) @b{trace +2} // 2 lines forward
12600 (@value{GDBP}) @b{trace my_function} // first source line of function
12602 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12604 (@value{GDBP}) @b{trace *0x2117c4} // an address
12608 You can abbreviate @code{trace} as @code{tr}.
12610 @item trace @var{location} if @var{cond}
12611 Set a tracepoint with condition @var{cond}; evaluate the expression
12612 @var{cond} each time the tracepoint is reached, and collect data only
12613 if the value is nonzero---that is, if @var{cond} evaluates as true.
12614 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12615 information on tracepoint conditions.
12617 @item ftrace @var{location} [ if @var{cond} ]
12618 @cindex set fast tracepoint
12619 @cindex fast tracepoints, setting
12621 The @code{ftrace} command sets a fast tracepoint. For targets that
12622 support them, fast tracepoints will use a more efficient but possibly
12623 less general technique to trigger data collection, such as a jump
12624 instruction instead of a trap, or some sort of hardware support. It
12625 may not be possible to create a fast tracepoint at the desired
12626 location, in which case the command will exit with an explanatory
12629 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12632 On 32-bit x86-architecture systems, fast tracepoints normally need to
12633 be placed at an instruction that is 5 bytes or longer, but can be
12634 placed at 4-byte instructions if the low 64K of memory of the target
12635 program is available to install trampolines. Some Unix-type systems,
12636 such as @sc{gnu}/Linux, exclude low addresses from the program's
12637 address space; but for instance with the Linux kernel it is possible
12638 to let @value{GDBN} use this area by doing a @command{sysctl} command
12639 to set the @code{mmap_min_addr} kernel parameter, as in
12642 sudo sysctl -w vm.mmap_min_addr=32768
12646 which sets the low address to 32K, which leaves plenty of room for
12647 trampolines. The minimum address should be set to a page boundary.
12649 @item strace @var{location} [ if @var{cond} ]
12650 @cindex set static tracepoint
12651 @cindex static tracepoints, setting
12652 @cindex probe static tracepoint marker
12654 The @code{strace} command sets a static tracepoint. For targets that
12655 support it, setting a static tracepoint probes a static
12656 instrumentation point, or marker, found at @var{location}. It may not
12657 be possible to set a static tracepoint at the desired location, in
12658 which case the command will exit with an explanatory message.
12660 @value{GDBN} handles arguments to @code{strace} exactly as for
12661 @code{trace}, with the addition that the user can also specify
12662 @code{-m @var{marker}} as @var{location}. This probes the marker
12663 identified by the @var{marker} string identifier. This identifier
12664 depends on the static tracepoint backend library your program is
12665 using. You can find all the marker identifiers in the @samp{ID} field
12666 of the @code{info static-tracepoint-markers} command output.
12667 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12668 Markers}. For example, in the following small program using the UST
12674 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12679 the marker id is composed of joining the first two arguments to the
12680 @code{trace_mark} call with a slash, which translates to:
12683 (@value{GDBP}) info static-tracepoint-markers
12684 Cnt Enb ID Address What
12685 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12691 so you may probe the marker above with:
12694 (@value{GDBP}) strace -m ust/bar33
12697 Static tracepoints accept an extra collect action --- @code{collect
12698 $_sdata}. This collects arbitrary user data passed in the probe point
12699 call to the tracing library. In the UST example above, you'll see
12700 that the third argument to @code{trace_mark} is a printf-like format
12701 string. The user data is then the result of running that formating
12702 string against the following arguments. Note that @code{info
12703 static-tracepoint-markers} command output lists that format string in
12704 the @samp{Data:} field.
12706 You can inspect this data when analyzing the trace buffer, by printing
12707 the $_sdata variable like any other variable available to
12708 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12711 @cindex last tracepoint number
12712 @cindex recent tracepoint number
12713 @cindex tracepoint number
12714 The convenience variable @code{$tpnum} records the tracepoint number
12715 of the most recently set tracepoint.
12717 @kindex delete tracepoint
12718 @cindex tracepoint deletion
12719 @item delete tracepoint @r{[}@var{num}@r{]}
12720 Permanently delete one or more tracepoints. With no argument, the
12721 default is to delete all tracepoints. Note that the regular
12722 @code{delete} command can remove tracepoints also.
12727 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12729 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12733 You can abbreviate this command as @code{del tr}.
12736 @node Enable and Disable Tracepoints
12737 @subsection Enable and Disable Tracepoints
12739 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12742 @kindex disable tracepoint
12743 @item disable tracepoint @r{[}@var{num}@r{]}
12744 Disable tracepoint @var{num}, or all tracepoints if no argument
12745 @var{num} is given. A disabled tracepoint will have no effect during
12746 a trace experiment, but it is not forgotten. You can re-enable
12747 a disabled tracepoint using the @code{enable tracepoint} command.
12748 If the command is issued during a trace experiment and the debug target
12749 has support for disabling tracepoints during a trace experiment, then the
12750 change will be effective immediately. Otherwise, it will be applied to the
12751 next trace experiment.
12753 @kindex enable tracepoint
12754 @item enable tracepoint @r{[}@var{num}@r{]}
12755 Enable tracepoint @var{num}, or all tracepoints. If this command is
12756 issued during a trace experiment and the debug target supports enabling
12757 tracepoints during a trace experiment, then the enabled tracepoints will
12758 become effective immediately. Otherwise, they will become effective the
12759 next time a trace experiment is run.
12762 @node Tracepoint Passcounts
12763 @subsection Tracepoint Passcounts
12767 @cindex tracepoint pass count
12768 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12769 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12770 automatically stop a trace experiment. If a tracepoint's passcount is
12771 @var{n}, then the trace experiment will be automatically stopped on
12772 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12773 @var{num} is not specified, the @code{passcount} command sets the
12774 passcount of the most recently defined tracepoint. If no passcount is
12775 given, the trace experiment will run until stopped explicitly by the
12781 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12782 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12784 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12785 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12786 (@value{GDBP}) @b{trace foo}
12787 (@value{GDBP}) @b{pass 3}
12788 (@value{GDBP}) @b{trace bar}
12789 (@value{GDBP}) @b{pass 2}
12790 (@value{GDBP}) @b{trace baz}
12791 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12792 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12793 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12794 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12798 @node Tracepoint Conditions
12799 @subsection Tracepoint Conditions
12800 @cindex conditional tracepoints
12801 @cindex tracepoint conditions
12803 The simplest sort of tracepoint collects data every time your program
12804 reaches a specified place. You can also specify a @dfn{condition} for
12805 a tracepoint. A condition is just a Boolean expression in your
12806 programming language (@pxref{Expressions, ,Expressions}). A
12807 tracepoint with a condition evaluates the expression each time your
12808 program reaches it, and data collection happens only if the condition
12811 Tracepoint conditions can be specified when a tracepoint is set, by
12812 using @samp{if} in the arguments to the @code{trace} command.
12813 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12814 also be set or changed at any time with the @code{condition} command,
12815 just as with breakpoints.
12817 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12818 the conditional expression itself. Instead, @value{GDBN} encodes the
12819 expression into an agent expression (@pxref{Agent Expressions})
12820 suitable for execution on the target, independently of @value{GDBN}.
12821 Global variables become raw memory locations, locals become stack
12822 accesses, and so forth.
12824 For instance, suppose you have a function that is usually called
12825 frequently, but should not be called after an error has occurred. You
12826 could use the following tracepoint command to collect data about calls
12827 of that function that happen while the error code is propagating
12828 through the program; an unconditional tracepoint could end up
12829 collecting thousands of useless trace frames that you would have to
12833 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12836 @node Trace State Variables
12837 @subsection Trace State Variables
12838 @cindex trace state variables
12840 A @dfn{trace state variable} is a special type of variable that is
12841 created and managed by target-side code. The syntax is the same as
12842 that for GDB's convenience variables (a string prefixed with ``$''),
12843 but they are stored on the target. They must be created explicitly,
12844 using a @code{tvariable} command. They are always 64-bit signed
12847 Trace state variables are remembered by @value{GDBN}, and downloaded
12848 to the target along with tracepoint information when the trace
12849 experiment starts. There are no intrinsic limits on the number of
12850 trace state variables, beyond memory limitations of the target.
12852 @cindex convenience variables, and trace state variables
12853 Although trace state variables are managed by the target, you can use
12854 them in print commands and expressions as if they were convenience
12855 variables; @value{GDBN} will get the current value from the target
12856 while the trace experiment is running. Trace state variables share
12857 the same namespace as other ``$'' variables, which means that you
12858 cannot have trace state variables with names like @code{$23} or
12859 @code{$pc}, nor can you have a trace state variable and a convenience
12860 variable with the same name.
12864 @item tvariable $@var{name} [ = @var{expression} ]
12866 The @code{tvariable} command creates a new trace state variable named
12867 @code{$@var{name}}, and optionally gives it an initial value of
12868 @var{expression}. The @var{expression} is evaluated when this command is
12869 entered; the result will be converted to an integer if possible,
12870 otherwise @value{GDBN} will report an error. A subsequent
12871 @code{tvariable} command specifying the same name does not create a
12872 variable, but instead assigns the supplied initial value to the
12873 existing variable of that name, overwriting any previous initial
12874 value. The default initial value is 0.
12876 @item info tvariables
12877 @kindex info tvariables
12878 List all the trace state variables along with their initial values.
12879 Their current values may also be displayed, if the trace experiment is
12882 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12883 @kindex delete tvariable
12884 Delete the given trace state variables, or all of them if no arguments
12889 @node Tracepoint Actions
12890 @subsection Tracepoint Action Lists
12894 @cindex tracepoint actions
12895 @item actions @r{[}@var{num}@r{]}
12896 This command will prompt for a list of actions to be taken when the
12897 tracepoint is hit. If the tracepoint number @var{num} is not
12898 specified, this command sets the actions for the one that was most
12899 recently defined (so that you can define a tracepoint and then say
12900 @code{actions} without bothering about its number). You specify the
12901 actions themselves on the following lines, one action at a time, and
12902 terminate the actions list with a line containing just @code{end}. So
12903 far, the only defined actions are @code{collect}, @code{teval}, and
12904 @code{while-stepping}.
12906 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12907 Commands, ,Breakpoint Command Lists}), except that only the defined
12908 actions are allowed; any other @value{GDBN} command is rejected.
12910 @cindex remove actions from a tracepoint
12911 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12912 and follow it immediately with @samp{end}.
12915 (@value{GDBP}) @b{collect @var{data}} // collect some data
12917 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12919 (@value{GDBP}) @b{end} // signals the end of actions.
12922 In the following example, the action list begins with @code{collect}
12923 commands indicating the things to be collected when the tracepoint is
12924 hit. Then, in order to single-step and collect additional data
12925 following the tracepoint, a @code{while-stepping} command is used,
12926 followed by the list of things to be collected after each step in a
12927 sequence of single steps. The @code{while-stepping} command is
12928 terminated by its own separate @code{end} command. Lastly, the action
12929 list is terminated by an @code{end} command.
12932 (@value{GDBP}) @b{trace foo}
12933 (@value{GDBP}) @b{actions}
12934 Enter actions for tracepoint 1, one per line:
12937 > while-stepping 12
12938 > collect $pc, arr[i]
12943 @kindex collect @r{(tracepoints)}
12944 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12945 Collect values of the given expressions when the tracepoint is hit.
12946 This command accepts a comma-separated list of any valid expressions.
12947 In addition to global, static, or local variables, the following
12948 special arguments are supported:
12952 Collect all registers.
12955 Collect all function arguments.
12958 Collect all local variables.
12961 Collect the return address. This is helpful if you want to see more
12964 @emph{Note:} The return address location can not always be reliably
12965 determined up front, and the wrong address / registers may end up
12966 collected instead. On some architectures the reliability is higher
12967 for tracepoints at function entry, while on others it's the opposite.
12968 When this happens, backtracing will stop because the return address is
12969 found unavailable (unless another collect rule happened to match it).
12972 Collects the number of arguments from the static probe at which the
12973 tracepoint is located.
12974 @xref{Static Probe Points}.
12976 @item $_probe_arg@var{n}
12977 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12978 from the static probe at which the tracepoint is located.
12979 @xref{Static Probe Points}.
12982 @vindex $_sdata@r{, collect}
12983 Collect static tracepoint marker specific data. Only available for
12984 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12985 Lists}. On the UST static tracepoints library backend, an
12986 instrumentation point resembles a @code{printf} function call. The
12987 tracing library is able to collect user specified data formatted to a
12988 character string using the format provided by the programmer that
12989 instrumented the program. Other backends have similar mechanisms.
12990 Here's an example of a UST marker call:
12993 const char master_name[] = "$your_name";
12994 trace_mark(channel1, marker1, "hello %s", master_name)
12997 In this case, collecting @code{$_sdata} collects the string
12998 @samp{hello $yourname}. When analyzing the trace buffer, you can
12999 inspect @samp{$_sdata} like any other variable available to
13003 You can give several consecutive @code{collect} commands, each one
13004 with a single argument, or one @code{collect} command with several
13005 arguments separated by commas; the effect is the same.
13007 The optional @var{mods} changes the usual handling of the arguments.
13008 @code{s} requests that pointers to chars be handled as strings, in
13009 particular collecting the contents of the memory being pointed at, up
13010 to the first zero. The upper bound is by default the value of the
13011 @code{print elements} variable; if @code{s} is followed by a decimal
13012 number, that is the upper bound instead. So for instance
13013 @samp{collect/s25 mystr} collects as many as 25 characters at
13016 The command @code{info scope} (@pxref{Symbols, info scope}) is
13017 particularly useful for figuring out what data to collect.
13019 @kindex teval @r{(tracepoints)}
13020 @item teval @var{expr1}, @var{expr2}, @dots{}
13021 Evaluate the given expressions when the tracepoint is hit. This
13022 command accepts a comma-separated list of expressions. The results
13023 are discarded, so this is mainly useful for assigning values to trace
13024 state variables (@pxref{Trace State Variables}) without adding those
13025 values to the trace buffer, as would be the case if the @code{collect}
13028 @kindex while-stepping @r{(tracepoints)}
13029 @item while-stepping @var{n}
13030 Perform @var{n} single-step instruction traces after the tracepoint,
13031 collecting new data after each step. The @code{while-stepping}
13032 command is followed by the list of what to collect while stepping
13033 (followed by its own @code{end} command):
13036 > while-stepping 12
13037 > collect $regs, myglobal
13043 Note that @code{$pc} is not automatically collected by
13044 @code{while-stepping}; you need to explicitly collect that register if
13045 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13048 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13049 @kindex set default-collect
13050 @cindex default collection action
13051 This variable is a list of expressions to collect at each tracepoint
13052 hit. It is effectively an additional @code{collect} action prepended
13053 to every tracepoint action list. The expressions are parsed
13054 individually for each tracepoint, so for instance a variable named
13055 @code{xyz} may be interpreted as a global for one tracepoint, and a
13056 local for another, as appropriate to the tracepoint's location.
13058 @item show default-collect
13059 @kindex show default-collect
13060 Show the list of expressions that are collected by default at each
13065 @node Listing Tracepoints
13066 @subsection Listing Tracepoints
13069 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13070 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13071 @cindex information about tracepoints
13072 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13073 Display information about the tracepoint @var{num}. If you don't
13074 specify a tracepoint number, displays information about all the
13075 tracepoints defined so far. The format is similar to that used for
13076 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13077 command, simply restricting itself to tracepoints.
13079 A tracepoint's listing may include additional information specific to
13084 its passcount as given by the @code{passcount @var{n}} command
13087 the state about installed on target of each location
13091 (@value{GDBP}) @b{info trace}
13092 Num Type Disp Enb Address What
13093 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13095 collect globfoo, $regs
13100 2 tracepoint keep y <MULTIPLE>
13102 2.1 y 0x0804859c in func4 at change-loc.h:35
13103 installed on target
13104 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13105 installed on target
13106 2.3 y <PENDING> set_tracepoint
13107 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13108 not installed on target
13113 This command can be abbreviated @code{info tp}.
13116 @node Listing Static Tracepoint Markers
13117 @subsection Listing Static Tracepoint Markers
13120 @kindex info static-tracepoint-markers
13121 @cindex information about static tracepoint markers
13122 @item info static-tracepoint-markers
13123 Display information about all static tracepoint markers defined in the
13126 For each marker, the following columns are printed:
13130 An incrementing counter, output to help readability. This is not a
13133 The marker ID, as reported by the target.
13134 @item Enabled or Disabled
13135 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13136 that are not enabled.
13138 Where the marker is in your program, as a memory address.
13140 Where the marker is in the source for your program, as a file and line
13141 number. If the debug information included in the program does not
13142 allow @value{GDBN} to locate the source of the marker, this column
13143 will be left blank.
13147 In addition, the following information may be printed for each marker:
13151 User data passed to the tracing library by the marker call. In the
13152 UST backend, this is the format string passed as argument to the
13154 @item Static tracepoints probing the marker
13155 The list of static tracepoints attached to the marker.
13159 (@value{GDBP}) info static-tracepoint-markers
13160 Cnt ID Enb Address What
13161 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13162 Data: number1 %d number2 %d
13163 Probed by static tracepoints: #2
13164 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13170 @node Starting and Stopping Trace Experiments
13171 @subsection Starting and Stopping Trace Experiments
13174 @kindex tstart [ @var{notes} ]
13175 @cindex start a new trace experiment
13176 @cindex collected data discarded
13178 This command starts the trace experiment, and begins collecting data.
13179 It has the side effect of discarding all the data collected in the
13180 trace buffer during the previous trace experiment. If any arguments
13181 are supplied, they are taken as a note and stored with the trace
13182 experiment's state. The notes may be arbitrary text, and are
13183 especially useful with disconnected tracing in a multi-user context;
13184 the notes can explain what the trace is doing, supply user contact
13185 information, and so forth.
13187 @kindex tstop [ @var{notes} ]
13188 @cindex stop a running trace experiment
13190 This command stops the trace experiment. If any arguments are
13191 supplied, they are recorded with the experiment as a note. This is
13192 useful if you are stopping a trace started by someone else, for
13193 instance if the trace is interfering with the system's behavior and
13194 needs to be stopped quickly.
13196 @strong{Note}: a trace experiment and data collection may stop
13197 automatically if any tracepoint's passcount is reached
13198 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13201 @cindex status of trace data collection
13202 @cindex trace experiment, status of
13204 This command displays the status of the current trace data
13208 Here is an example of the commands we described so far:
13211 (@value{GDBP}) @b{trace gdb_c_test}
13212 (@value{GDBP}) @b{actions}
13213 Enter actions for tracepoint #1, one per line.
13214 > collect $regs,$locals,$args
13215 > while-stepping 11
13219 (@value{GDBP}) @b{tstart}
13220 [time passes @dots{}]
13221 (@value{GDBP}) @b{tstop}
13224 @anchor{disconnected tracing}
13225 @cindex disconnected tracing
13226 You can choose to continue running the trace experiment even if
13227 @value{GDBN} disconnects from the target, voluntarily or
13228 involuntarily. For commands such as @code{detach}, the debugger will
13229 ask what you want to do with the trace. But for unexpected
13230 terminations (@value{GDBN} crash, network outage), it would be
13231 unfortunate to lose hard-won trace data, so the variable
13232 @code{disconnected-tracing} lets you decide whether the trace should
13233 continue running without @value{GDBN}.
13236 @item set disconnected-tracing on
13237 @itemx set disconnected-tracing off
13238 @kindex set disconnected-tracing
13239 Choose whether a tracing run should continue to run if @value{GDBN}
13240 has disconnected from the target. Note that @code{detach} or
13241 @code{quit} will ask you directly what to do about a running trace no
13242 matter what this variable's setting, so the variable is mainly useful
13243 for handling unexpected situations, such as loss of the network.
13245 @item show disconnected-tracing
13246 @kindex show disconnected-tracing
13247 Show the current choice for disconnected tracing.
13251 When you reconnect to the target, the trace experiment may or may not
13252 still be running; it might have filled the trace buffer in the
13253 meantime, or stopped for one of the other reasons. If it is running,
13254 it will continue after reconnection.
13256 Upon reconnection, the target will upload information about the
13257 tracepoints in effect. @value{GDBN} will then compare that
13258 information to the set of tracepoints currently defined, and attempt
13259 to match them up, allowing for the possibility that the numbers may
13260 have changed due to creation and deletion in the meantime. If one of
13261 the target's tracepoints does not match any in @value{GDBN}, the
13262 debugger will create a new tracepoint, so that you have a number with
13263 which to specify that tracepoint. This matching-up process is
13264 necessarily heuristic, and it may result in useless tracepoints being
13265 created; you may simply delete them if they are of no use.
13267 @cindex circular trace buffer
13268 If your target agent supports a @dfn{circular trace buffer}, then you
13269 can run a trace experiment indefinitely without filling the trace
13270 buffer; when space runs out, the agent deletes already-collected trace
13271 frames, oldest first, until there is enough room to continue
13272 collecting. This is especially useful if your tracepoints are being
13273 hit too often, and your trace gets terminated prematurely because the
13274 buffer is full. To ask for a circular trace buffer, simply set
13275 @samp{circular-trace-buffer} to on. You can set this at any time,
13276 including during tracing; if the agent can do it, it will change
13277 buffer handling on the fly, otherwise it will not take effect until
13281 @item set circular-trace-buffer on
13282 @itemx set circular-trace-buffer off
13283 @kindex set circular-trace-buffer
13284 Choose whether a tracing run should use a linear or circular buffer
13285 for trace data. A linear buffer will not lose any trace data, but may
13286 fill up prematurely, while a circular buffer will discard old trace
13287 data, but it will have always room for the latest tracepoint hits.
13289 @item show circular-trace-buffer
13290 @kindex show circular-trace-buffer
13291 Show the current choice for the trace buffer. Note that this may not
13292 match the agent's current buffer handling, nor is it guaranteed to
13293 match the setting that might have been in effect during a past run,
13294 for instance if you are looking at frames from a trace file.
13299 @item set trace-buffer-size @var{n}
13300 @itemx set trace-buffer-size unlimited
13301 @kindex set trace-buffer-size
13302 Request that the target use a trace buffer of @var{n} bytes. Not all
13303 targets will honor the request; they may have a compiled-in size for
13304 the trace buffer, or some other limitation. Set to a value of
13305 @code{unlimited} or @code{-1} to let the target use whatever size it
13306 likes. This is also the default.
13308 @item show trace-buffer-size
13309 @kindex show trace-buffer-size
13310 Show the current requested size for the trace buffer. Note that this
13311 will only match the actual size if the target supports size-setting,
13312 and was able to handle the requested size. For instance, if the
13313 target can only change buffer size between runs, this variable will
13314 not reflect the change until the next run starts. Use @code{tstatus}
13315 to get a report of the actual buffer size.
13319 @item set trace-user @var{text}
13320 @kindex set trace-user
13322 @item show trace-user
13323 @kindex show trace-user
13325 @item set trace-notes @var{text}
13326 @kindex set trace-notes
13327 Set the trace run's notes.
13329 @item show trace-notes
13330 @kindex show trace-notes
13331 Show the trace run's notes.
13333 @item set trace-stop-notes @var{text}
13334 @kindex set trace-stop-notes
13335 Set the trace run's stop notes. The handling of the note is as for
13336 @code{tstop} arguments; the set command is convenient way to fix a
13337 stop note that is mistaken or incomplete.
13339 @item show trace-stop-notes
13340 @kindex show trace-stop-notes
13341 Show the trace run's stop notes.
13345 @node Tracepoint Restrictions
13346 @subsection Tracepoint Restrictions
13348 @cindex tracepoint restrictions
13349 There are a number of restrictions on the use of tracepoints. As
13350 described above, tracepoint data gathering occurs on the target
13351 without interaction from @value{GDBN}. Thus the full capabilities of
13352 the debugger are not available during data gathering, and then at data
13353 examination time, you will be limited by only having what was
13354 collected. The following items describe some common problems, but it
13355 is not exhaustive, and you may run into additional difficulties not
13361 Tracepoint expressions are intended to gather objects (lvalues). Thus
13362 the full flexibility of GDB's expression evaluator is not available.
13363 You cannot call functions, cast objects to aggregate types, access
13364 convenience variables or modify values (except by assignment to trace
13365 state variables). Some language features may implicitly call
13366 functions (for instance Objective-C fields with accessors), and therefore
13367 cannot be collected either.
13370 Collection of local variables, either individually or in bulk with
13371 @code{$locals} or @code{$args}, during @code{while-stepping} may
13372 behave erratically. The stepping action may enter a new scope (for
13373 instance by stepping into a function), or the location of the variable
13374 may change (for instance it is loaded into a register). The
13375 tracepoint data recorded uses the location information for the
13376 variables that is correct for the tracepoint location. When the
13377 tracepoint is created, it is not possible, in general, to determine
13378 where the steps of a @code{while-stepping} sequence will advance the
13379 program---particularly if a conditional branch is stepped.
13382 Collection of an incompletely-initialized or partially-destroyed object
13383 may result in something that @value{GDBN} cannot display, or displays
13384 in a misleading way.
13387 When @value{GDBN} displays a pointer to character it automatically
13388 dereferences the pointer to also display characters of the string
13389 being pointed to. However, collecting the pointer during tracing does
13390 not automatically collect the string. You need to explicitly
13391 dereference the pointer and provide size information if you want to
13392 collect not only the pointer, but the memory pointed to. For example,
13393 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13397 It is not possible to collect a complete stack backtrace at a
13398 tracepoint. Instead, you may collect the registers and a few hundred
13399 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13400 (adjust to use the name of the actual stack pointer register on your
13401 target architecture, and the amount of stack you wish to capture).
13402 Then the @code{backtrace} command will show a partial backtrace when
13403 using a trace frame. The number of stack frames that can be examined
13404 depends on the sizes of the frames in the collected stack. Note that
13405 if you ask for a block so large that it goes past the bottom of the
13406 stack, the target agent may report an error trying to read from an
13410 If you do not collect registers at a tracepoint, @value{GDBN} can
13411 infer that the value of @code{$pc} must be the same as the address of
13412 the tracepoint and use that when you are looking at a trace frame
13413 for that tracepoint. However, this cannot work if the tracepoint has
13414 multiple locations (for instance if it was set in a function that was
13415 inlined), or if it has a @code{while-stepping} loop. In those cases
13416 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13421 @node Analyze Collected Data
13422 @section Using the Collected Data
13424 After the tracepoint experiment ends, you use @value{GDBN} commands
13425 for examining the trace data. The basic idea is that each tracepoint
13426 collects a trace @dfn{snapshot} every time it is hit and another
13427 snapshot every time it single-steps. All these snapshots are
13428 consecutively numbered from zero and go into a buffer, and you can
13429 examine them later. The way you examine them is to @dfn{focus} on a
13430 specific trace snapshot. When the remote stub is focused on a trace
13431 snapshot, it will respond to all @value{GDBN} requests for memory and
13432 registers by reading from the buffer which belongs to that snapshot,
13433 rather than from @emph{real} memory or registers of the program being
13434 debugged. This means that @strong{all} @value{GDBN} commands
13435 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13436 behave as if we were currently debugging the program state as it was
13437 when the tracepoint occurred. Any requests for data that are not in
13438 the buffer will fail.
13441 * tfind:: How to select a trace snapshot
13442 * tdump:: How to display all data for a snapshot
13443 * save tracepoints:: How to save tracepoints for a future run
13447 @subsection @code{tfind @var{n}}
13450 @cindex select trace snapshot
13451 @cindex find trace snapshot
13452 The basic command for selecting a trace snapshot from the buffer is
13453 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13454 counting from zero. If no argument @var{n} is given, the next
13455 snapshot is selected.
13457 Here are the various forms of using the @code{tfind} command.
13461 Find the first snapshot in the buffer. This is a synonym for
13462 @code{tfind 0} (since 0 is the number of the first snapshot).
13465 Stop debugging trace snapshots, resume @emph{live} debugging.
13468 Same as @samp{tfind none}.
13471 No argument means find the next trace snapshot or find the first
13472 one if no trace snapshot is selected.
13475 Find the previous trace snapshot before the current one. This permits
13476 retracing earlier steps.
13478 @item tfind tracepoint @var{num}
13479 Find the next snapshot associated with tracepoint @var{num}. Search
13480 proceeds forward from the last examined trace snapshot. If no
13481 argument @var{num} is given, it means find the next snapshot collected
13482 for the same tracepoint as the current snapshot.
13484 @item tfind pc @var{addr}
13485 Find the next snapshot associated with the value @var{addr} of the
13486 program counter. Search proceeds forward from the last examined trace
13487 snapshot. If no argument @var{addr} is given, it means find the next
13488 snapshot with the same value of PC as the current snapshot.
13490 @item tfind outside @var{addr1}, @var{addr2}
13491 Find the next snapshot whose PC is outside the given range of
13492 addresses (exclusive).
13494 @item tfind range @var{addr1}, @var{addr2}
13495 Find the next snapshot whose PC is between @var{addr1} and
13496 @var{addr2} (inclusive).
13498 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13499 Find the next snapshot associated with the source line @var{n}. If
13500 the optional argument @var{file} is given, refer to line @var{n} in
13501 that source file. Search proceeds forward from the last examined
13502 trace snapshot. If no argument @var{n} is given, it means find the
13503 next line other than the one currently being examined; thus saying
13504 @code{tfind line} repeatedly can appear to have the same effect as
13505 stepping from line to line in a @emph{live} debugging session.
13508 The default arguments for the @code{tfind} commands are specifically
13509 designed to make it easy to scan through the trace buffer. For
13510 instance, @code{tfind} with no argument selects the next trace
13511 snapshot, and @code{tfind -} with no argument selects the previous
13512 trace snapshot. So, by giving one @code{tfind} command, and then
13513 simply hitting @key{RET} repeatedly you can examine all the trace
13514 snapshots in order. Or, by saying @code{tfind -} and then hitting
13515 @key{RET} repeatedly you can examine the snapshots in reverse order.
13516 The @code{tfind line} command with no argument selects the snapshot
13517 for the next source line executed. The @code{tfind pc} command with
13518 no argument selects the next snapshot with the same program counter
13519 (PC) as the current frame. The @code{tfind tracepoint} command with
13520 no argument selects the next trace snapshot collected by the same
13521 tracepoint as the current one.
13523 In addition to letting you scan through the trace buffer manually,
13524 these commands make it easy to construct @value{GDBN} scripts that
13525 scan through the trace buffer and print out whatever collected data
13526 you are interested in. Thus, if we want to examine the PC, FP, and SP
13527 registers from each trace frame in the buffer, we can say this:
13530 (@value{GDBP}) @b{tfind start}
13531 (@value{GDBP}) @b{while ($trace_frame != -1)}
13532 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13533 $trace_frame, $pc, $sp, $fp
13537 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13538 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13539 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13540 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13541 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13542 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13543 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13544 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13545 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13546 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13547 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13550 Or, if we want to examine the variable @code{X} at each source line in
13554 (@value{GDBP}) @b{tfind start}
13555 (@value{GDBP}) @b{while ($trace_frame != -1)}
13556 > printf "Frame %d, X == %d\n", $trace_frame, X
13566 @subsection @code{tdump}
13568 @cindex dump all data collected at tracepoint
13569 @cindex tracepoint data, display
13571 This command takes no arguments. It prints all the data collected at
13572 the current trace snapshot.
13575 (@value{GDBP}) @b{trace 444}
13576 (@value{GDBP}) @b{actions}
13577 Enter actions for tracepoint #2, one per line:
13578 > collect $regs, $locals, $args, gdb_long_test
13581 (@value{GDBP}) @b{tstart}
13583 (@value{GDBP}) @b{tfind line 444}
13584 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13586 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13588 (@value{GDBP}) @b{tdump}
13589 Data collected at tracepoint 2, trace frame 1:
13590 d0 0xc4aa0085 -995491707
13594 d4 0x71aea3d 119204413
13597 d7 0x380035 3670069
13598 a0 0x19e24a 1696330
13599 a1 0x3000668 50333288
13601 a3 0x322000 3284992
13602 a4 0x3000698 50333336
13603 a5 0x1ad3cc 1758156
13604 fp 0x30bf3c 0x30bf3c
13605 sp 0x30bf34 0x30bf34
13607 pc 0x20b2c8 0x20b2c8
13611 p = 0x20e5b4 "gdb-test"
13618 gdb_long_test = 17 '\021'
13623 @code{tdump} works by scanning the tracepoint's current collection
13624 actions and printing the value of each expression listed. So
13625 @code{tdump} can fail, if after a run, you change the tracepoint's
13626 actions to mention variables that were not collected during the run.
13628 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13629 uses the collected value of @code{$pc} to distinguish between trace
13630 frames that were collected at the tracepoint hit, and frames that were
13631 collected while stepping. This allows it to correctly choose whether
13632 to display the basic list of collections, or the collections from the
13633 body of the while-stepping loop. However, if @code{$pc} was not collected,
13634 then @code{tdump} will always attempt to dump using the basic collection
13635 list, and may fail if a while-stepping frame does not include all the
13636 same data that is collected at the tracepoint hit.
13637 @c This is getting pretty arcane, example would be good.
13639 @node save tracepoints
13640 @subsection @code{save tracepoints @var{filename}}
13641 @kindex save tracepoints
13642 @kindex save-tracepoints
13643 @cindex save tracepoints for future sessions
13645 This command saves all current tracepoint definitions together with
13646 their actions and passcounts, into a file @file{@var{filename}}
13647 suitable for use in a later debugging session. To read the saved
13648 tracepoint definitions, use the @code{source} command (@pxref{Command
13649 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13650 alias for @w{@code{save tracepoints}}
13652 @node Tracepoint Variables
13653 @section Convenience Variables for Tracepoints
13654 @cindex tracepoint variables
13655 @cindex convenience variables for tracepoints
13658 @vindex $trace_frame
13659 @item (int) $trace_frame
13660 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13661 snapshot is selected.
13663 @vindex $tracepoint
13664 @item (int) $tracepoint
13665 The tracepoint for the current trace snapshot.
13667 @vindex $trace_line
13668 @item (int) $trace_line
13669 The line number for the current trace snapshot.
13671 @vindex $trace_file
13672 @item (char []) $trace_file
13673 The source file for the current trace snapshot.
13675 @vindex $trace_func
13676 @item (char []) $trace_func
13677 The name of the function containing @code{$tracepoint}.
13680 Note: @code{$trace_file} is not suitable for use in @code{printf},
13681 use @code{output} instead.
13683 Here's a simple example of using these convenience variables for
13684 stepping through all the trace snapshots and printing some of their
13685 data. Note that these are not the same as trace state variables,
13686 which are managed by the target.
13689 (@value{GDBP}) @b{tfind start}
13691 (@value{GDBP}) @b{while $trace_frame != -1}
13692 > output $trace_file
13693 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13699 @section Using Trace Files
13700 @cindex trace files
13702 In some situations, the target running a trace experiment may no
13703 longer be available; perhaps it crashed, or the hardware was needed
13704 for a different activity. To handle these cases, you can arrange to
13705 dump the trace data into a file, and later use that file as a source
13706 of trace data, via the @code{target tfile} command.
13711 @item tsave [ -r ] @var{filename}
13712 @itemx tsave [-ctf] @var{dirname}
13713 Save the trace data to @var{filename}. By default, this command
13714 assumes that @var{filename} refers to the host filesystem, so if
13715 necessary @value{GDBN} will copy raw trace data up from the target and
13716 then save it. If the target supports it, you can also supply the
13717 optional argument @code{-r} (``remote'') to direct the target to save
13718 the data directly into @var{filename} in its own filesystem, which may be
13719 more efficient if the trace buffer is very large. (Note, however, that
13720 @code{target tfile} can only read from files accessible to the host.)
13721 By default, this command will save trace frame in tfile format.
13722 You can supply the optional argument @code{-ctf} to save data in CTF
13723 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13724 that can be shared by multiple debugging and tracing tools. Please go to
13725 @indicateurl{http://www.efficios.com/ctf} to get more information.
13727 @kindex target tfile
13731 @item target tfile @var{filename}
13732 @itemx target ctf @var{dirname}
13733 Use the file named @var{filename} or directory named @var{dirname} as
13734 a source of trace data. Commands that examine data work as they do with
13735 a live target, but it is not possible to run any new trace experiments.
13736 @code{tstatus} will report the state of the trace run at the moment
13737 the data was saved, as well as the current trace frame you are examining.
13738 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13742 (@value{GDBP}) target ctf ctf.ctf
13743 (@value{GDBP}) tfind
13744 Found trace frame 0, tracepoint 2
13745 39 ++a; /* set tracepoint 1 here */
13746 (@value{GDBP}) tdump
13747 Data collected at tracepoint 2, trace frame 0:
13751 c = @{"123", "456", "789", "123", "456", "789"@}
13752 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13760 @chapter Debugging Programs That Use Overlays
13763 If your program is too large to fit completely in your target system's
13764 memory, you can sometimes use @dfn{overlays} to work around this
13765 problem. @value{GDBN} provides some support for debugging programs that
13769 * How Overlays Work:: A general explanation of overlays.
13770 * Overlay Commands:: Managing overlays in @value{GDBN}.
13771 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13772 mapped by asking the inferior.
13773 * Overlay Sample Program:: A sample program using overlays.
13776 @node How Overlays Work
13777 @section How Overlays Work
13778 @cindex mapped overlays
13779 @cindex unmapped overlays
13780 @cindex load address, overlay's
13781 @cindex mapped address
13782 @cindex overlay area
13784 Suppose you have a computer whose instruction address space is only 64
13785 kilobytes long, but which has much more memory which can be accessed by
13786 other means: special instructions, segment registers, or memory
13787 management hardware, for example. Suppose further that you want to
13788 adapt a program which is larger than 64 kilobytes to run on this system.
13790 One solution is to identify modules of your program which are relatively
13791 independent, and need not call each other directly; call these modules
13792 @dfn{overlays}. Separate the overlays from the main program, and place
13793 their machine code in the larger memory. Place your main program in
13794 instruction memory, but leave at least enough space there to hold the
13795 largest overlay as well.
13797 Now, to call a function located in an overlay, you must first copy that
13798 overlay's machine code from the large memory into the space set aside
13799 for it in the instruction memory, and then jump to its entry point
13802 @c NB: In the below the mapped area's size is greater or equal to the
13803 @c size of all overlays. This is intentional to remind the developer
13804 @c that overlays don't necessarily need to be the same size.
13808 Data Instruction Larger
13809 Address Space Address Space Address Space
13810 +-----------+ +-----------+ +-----------+
13812 +-----------+ +-----------+ +-----------+<-- overlay 1
13813 | program | | main | .----| overlay 1 | load address
13814 | variables | | program | | +-----------+
13815 | and heap | | | | | |
13816 +-----------+ | | | +-----------+<-- overlay 2
13817 | | +-----------+ | | | load address
13818 +-----------+ | | | .-| overlay 2 |
13820 mapped --->+-----------+ | | +-----------+
13821 address | | | | | |
13822 | overlay | <-' | | |
13823 | area | <---' +-----------+<-- overlay 3
13824 | | <---. | | load address
13825 +-----------+ `--| overlay 3 |
13832 @anchor{A code overlay}A code overlay
13836 The diagram (@pxref{A code overlay}) shows a system with separate data
13837 and instruction address spaces. To map an overlay, the program copies
13838 its code from the larger address space to the instruction address space.
13839 Since the overlays shown here all use the same mapped address, only one
13840 may be mapped at a time. For a system with a single address space for
13841 data and instructions, the diagram would be similar, except that the
13842 program variables and heap would share an address space with the main
13843 program and the overlay area.
13845 An overlay loaded into instruction memory and ready for use is called a
13846 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13847 instruction memory. An overlay not present (or only partially present)
13848 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13849 is its address in the larger memory. The mapped address is also called
13850 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13851 called the @dfn{load memory address}, or @dfn{LMA}.
13853 Unfortunately, overlays are not a completely transparent way to adapt a
13854 program to limited instruction memory. They introduce a new set of
13855 global constraints you must keep in mind as you design your program:
13860 Before calling or returning to a function in an overlay, your program
13861 must make sure that overlay is actually mapped. Otherwise, the call or
13862 return will transfer control to the right address, but in the wrong
13863 overlay, and your program will probably crash.
13866 If the process of mapping an overlay is expensive on your system, you
13867 will need to choose your overlays carefully to minimize their effect on
13868 your program's performance.
13871 The executable file you load onto your system must contain each
13872 overlay's instructions, appearing at the overlay's load address, not its
13873 mapped address. However, each overlay's instructions must be relocated
13874 and its symbols defined as if the overlay were at its mapped address.
13875 You can use GNU linker scripts to specify different load and relocation
13876 addresses for pieces of your program; see @ref{Overlay Description,,,
13877 ld.info, Using ld: the GNU linker}.
13880 The procedure for loading executable files onto your system must be able
13881 to load their contents into the larger address space as well as the
13882 instruction and data spaces.
13886 The overlay system described above is rather simple, and could be
13887 improved in many ways:
13892 If your system has suitable bank switch registers or memory management
13893 hardware, you could use those facilities to make an overlay's load area
13894 contents simply appear at their mapped address in instruction space.
13895 This would probably be faster than copying the overlay to its mapped
13896 area in the usual way.
13899 If your overlays are small enough, you could set aside more than one
13900 overlay area, and have more than one overlay mapped at a time.
13903 You can use overlays to manage data, as well as instructions. In
13904 general, data overlays are even less transparent to your design than
13905 code overlays: whereas code overlays only require care when you call or
13906 return to functions, data overlays require care every time you access
13907 the data. Also, if you change the contents of a data overlay, you
13908 must copy its contents back out to its load address before you can copy a
13909 different data overlay into the same mapped area.
13914 @node Overlay Commands
13915 @section Overlay Commands
13917 To use @value{GDBN}'s overlay support, each overlay in your program must
13918 correspond to a separate section of the executable file. The section's
13919 virtual memory address and load memory address must be the overlay's
13920 mapped and load addresses. Identifying overlays with sections allows
13921 @value{GDBN} to determine the appropriate address of a function or
13922 variable, depending on whether the overlay is mapped or not.
13924 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13925 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13930 Disable @value{GDBN}'s overlay support. When overlay support is
13931 disabled, @value{GDBN} assumes that all functions and variables are
13932 always present at their mapped addresses. By default, @value{GDBN}'s
13933 overlay support is disabled.
13935 @item overlay manual
13936 @cindex manual overlay debugging
13937 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13938 relies on you to tell it which overlays are mapped, and which are not,
13939 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13940 commands described below.
13942 @item overlay map-overlay @var{overlay}
13943 @itemx overlay map @var{overlay}
13944 @cindex map an overlay
13945 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13946 be the name of the object file section containing the overlay. When an
13947 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13948 functions and variables at their mapped addresses. @value{GDBN} assumes
13949 that any other overlays whose mapped ranges overlap that of
13950 @var{overlay} are now unmapped.
13952 @item overlay unmap-overlay @var{overlay}
13953 @itemx overlay unmap @var{overlay}
13954 @cindex unmap an overlay
13955 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13956 must be the name of the object file section containing the overlay.
13957 When an overlay is unmapped, @value{GDBN} assumes it can find the
13958 overlay's functions and variables at their load addresses.
13961 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13962 consults a data structure the overlay manager maintains in the inferior
13963 to see which overlays are mapped. For details, see @ref{Automatic
13964 Overlay Debugging}.
13966 @item overlay load-target
13967 @itemx overlay load
13968 @cindex reloading the overlay table
13969 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13970 re-reads the table @value{GDBN} automatically each time the inferior
13971 stops, so this command should only be necessary if you have changed the
13972 overlay mapping yourself using @value{GDBN}. This command is only
13973 useful when using automatic overlay debugging.
13975 @item overlay list-overlays
13976 @itemx overlay list
13977 @cindex listing mapped overlays
13978 Display a list of the overlays currently mapped, along with their mapped
13979 addresses, load addresses, and sizes.
13983 Normally, when @value{GDBN} prints a code address, it includes the name
13984 of the function the address falls in:
13987 (@value{GDBP}) print main
13988 $3 = @{int ()@} 0x11a0 <main>
13991 When overlay debugging is enabled, @value{GDBN} recognizes code in
13992 unmapped overlays, and prints the names of unmapped functions with
13993 asterisks around them. For example, if @code{foo} is a function in an
13994 unmapped overlay, @value{GDBN} prints it this way:
13997 (@value{GDBP}) overlay list
13998 No sections are mapped.
13999 (@value{GDBP}) print foo
14000 $5 = @{int (int)@} 0x100000 <*foo*>
14003 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14007 (@value{GDBP}) overlay list
14008 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14009 mapped at 0x1016 - 0x104a
14010 (@value{GDBP}) print foo
14011 $6 = @{int (int)@} 0x1016 <foo>
14014 When overlay debugging is enabled, @value{GDBN} can find the correct
14015 address for functions and variables in an overlay, whether or not the
14016 overlay is mapped. This allows most @value{GDBN} commands, like
14017 @code{break} and @code{disassemble}, to work normally, even on unmapped
14018 code. However, @value{GDBN}'s breakpoint support has some limitations:
14022 @cindex breakpoints in overlays
14023 @cindex overlays, setting breakpoints in
14024 You can set breakpoints in functions in unmapped overlays, as long as
14025 @value{GDBN} can write to the overlay at its load address.
14027 @value{GDBN} can not set hardware or simulator-based breakpoints in
14028 unmapped overlays. However, if you set a breakpoint at the end of your
14029 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14030 you are using manual overlay management), @value{GDBN} will re-set its
14031 breakpoints properly.
14035 @node Automatic Overlay Debugging
14036 @section Automatic Overlay Debugging
14037 @cindex automatic overlay debugging
14039 @value{GDBN} can automatically track which overlays are mapped and which
14040 are not, given some simple co-operation from the overlay manager in the
14041 inferior. If you enable automatic overlay debugging with the
14042 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14043 looks in the inferior's memory for certain variables describing the
14044 current state of the overlays.
14046 Here are the variables your overlay manager must define to support
14047 @value{GDBN}'s automatic overlay debugging:
14051 @item @code{_ovly_table}:
14052 This variable must be an array of the following structures:
14057 /* The overlay's mapped address. */
14060 /* The size of the overlay, in bytes. */
14061 unsigned long size;
14063 /* The overlay's load address. */
14066 /* Non-zero if the overlay is currently mapped;
14068 unsigned long mapped;
14072 @item @code{_novlys}:
14073 This variable must be a four-byte signed integer, holding the total
14074 number of elements in @code{_ovly_table}.
14078 To decide whether a particular overlay is mapped or not, @value{GDBN}
14079 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14080 @code{lma} members equal the VMA and LMA of the overlay's section in the
14081 executable file. When @value{GDBN} finds a matching entry, it consults
14082 the entry's @code{mapped} member to determine whether the overlay is
14085 In addition, your overlay manager may define a function called
14086 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14087 will silently set a breakpoint there. If the overlay manager then
14088 calls this function whenever it has changed the overlay table, this
14089 will enable @value{GDBN} to accurately keep track of which overlays
14090 are in program memory, and update any breakpoints that may be set
14091 in overlays. This will allow breakpoints to work even if the
14092 overlays are kept in ROM or other non-writable memory while they
14093 are not being executed.
14095 @node Overlay Sample Program
14096 @section Overlay Sample Program
14097 @cindex overlay example program
14099 When linking a program which uses overlays, you must place the overlays
14100 at their load addresses, while relocating them to run at their mapped
14101 addresses. To do this, you must write a linker script (@pxref{Overlay
14102 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14103 since linker scripts are specific to a particular host system, target
14104 architecture, and target memory layout, this manual cannot provide
14105 portable sample code demonstrating @value{GDBN}'s overlay support.
14107 However, the @value{GDBN} source distribution does contain an overlaid
14108 program, with linker scripts for a few systems, as part of its test
14109 suite. The program consists of the following files from
14110 @file{gdb/testsuite/gdb.base}:
14114 The main program file.
14116 A simple overlay manager, used by @file{overlays.c}.
14121 Overlay modules, loaded and used by @file{overlays.c}.
14124 Linker scripts for linking the test program on the @code{d10v-elf}
14125 and @code{m32r-elf} targets.
14128 You can build the test program using the @code{d10v-elf} GCC
14129 cross-compiler like this:
14132 $ d10v-elf-gcc -g -c overlays.c
14133 $ d10v-elf-gcc -g -c ovlymgr.c
14134 $ d10v-elf-gcc -g -c foo.c
14135 $ d10v-elf-gcc -g -c bar.c
14136 $ d10v-elf-gcc -g -c baz.c
14137 $ d10v-elf-gcc -g -c grbx.c
14138 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14139 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14142 The build process is identical for any other architecture, except that
14143 you must substitute the appropriate compiler and linker script for the
14144 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14148 @chapter Using @value{GDBN} with Different Languages
14151 Although programming languages generally have common aspects, they are
14152 rarely expressed in the same manner. For instance, in ANSI C,
14153 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14154 Modula-2, it is accomplished by @code{p^}. Values can also be
14155 represented (and displayed) differently. Hex numbers in C appear as
14156 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14158 @cindex working language
14159 Language-specific information is built into @value{GDBN} for some languages,
14160 allowing you to express operations like the above in your program's
14161 native language, and allowing @value{GDBN} to output values in a manner
14162 consistent with the syntax of your program's native language. The
14163 language you use to build expressions is called the @dfn{working
14167 * Setting:: Switching between source languages
14168 * Show:: Displaying the language
14169 * Checks:: Type and range checks
14170 * Supported Languages:: Supported languages
14171 * Unsupported Languages:: Unsupported languages
14175 @section Switching Between Source Languages
14177 There are two ways to control the working language---either have @value{GDBN}
14178 set it automatically, or select it manually yourself. You can use the
14179 @code{set language} command for either purpose. On startup, @value{GDBN}
14180 defaults to setting the language automatically. The working language is
14181 used to determine how expressions you type are interpreted, how values
14184 In addition to the working language, every source file that
14185 @value{GDBN} knows about has its own working language. For some object
14186 file formats, the compiler might indicate which language a particular
14187 source file is in. However, most of the time @value{GDBN} infers the
14188 language from the name of the file. The language of a source file
14189 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14190 show each frame appropriately for its own language. There is no way to
14191 set the language of a source file from within @value{GDBN}, but you can
14192 set the language associated with a filename extension. @xref{Show, ,
14193 Displaying the Language}.
14195 This is most commonly a problem when you use a program, such
14196 as @code{cfront} or @code{f2c}, that generates C but is written in
14197 another language. In that case, make the
14198 program use @code{#line} directives in its C output; that way
14199 @value{GDBN} will know the correct language of the source code of the original
14200 program, and will display that source code, not the generated C code.
14203 * Filenames:: Filename extensions and languages.
14204 * Manually:: Setting the working language manually
14205 * Automatically:: Having @value{GDBN} infer the source language
14209 @subsection List of Filename Extensions and Languages
14211 If a source file name ends in one of the following extensions, then
14212 @value{GDBN} infers that its language is the one indicated.
14230 C@t{++} source file
14236 Objective-C source file
14240 Fortran source file
14243 Modula-2 source file
14247 Assembler source file. This actually behaves almost like C, but
14248 @value{GDBN} does not skip over function prologues when stepping.
14251 In addition, you may set the language associated with a filename
14252 extension. @xref{Show, , Displaying the Language}.
14255 @subsection Setting the Working Language
14257 If you allow @value{GDBN} to set the language automatically,
14258 expressions are interpreted the same way in your debugging session and
14261 @kindex set language
14262 If you wish, you may set the language manually. To do this, issue the
14263 command @samp{set language @var{lang}}, where @var{lang} is the name of
14264 a language, such as
14265 @code{c} or @code{modula-2}.
14266 For a list of the supported languages, type @samp{set language}.
14268 Setting the language manually prevents @value{GDBN} from updating the working
14269 language automatically. This can lead to confusion if you try
14270 to debug a program when the working language is not the same as the
14271 source language, when an expression is acceptable to both
14272 languages---but means different things. For instance, if the current
14273 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14281 might not have the effect you intended. In C, this means to add
14282 @code{b} and @code{c} and place the result in @code{a}. The result
14283 printed would be the value of @code{a}. In Modula-2, this means to compare
14284 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14286 @node Automatically
14287 @subsection Having @value{GDBN} Infer the Source Language
14289 To have @value{GDBN} set the working language automatically, use
14290 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14291 then infers the working language. That is, when your program stops in a
14292 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14293 working language to the language recorded for the function in that
14294 frame. If the language for a frame is unknown (that is, if the function
14295 or block corresponding to the frame was defined in a source file that
14296 does not have a recognized extension), the current working language is
14297 not changed, and @value{GDBN} issues a warning.
14299 This may not seem necessary for most programs, which are written
14300 entirely in one source language. However, program modules and libraries
14301 written in one source language can be used by a main program written in
14302 a different source language. Using @samp{set language auto} in this
14303 case frees you from having to set the working language manually.
14306 @section Displaying the Language
14308 The following commands help you find out which language is the
14309 working language, and also what language source files were written in.
14312 @item show language
14313 @anchor{show language}
14314 @kindex show language
14315 Display the current working language. This is the
14316 language you can use with commands such as @code{print} to
14317 build and compute expressions that may involve variables in your program.
14320 @kindex info frame@r{, show the source language}
14321 Display the source language for this frame. This language becomes the
14322 working language if you use an identifier from this frame.
14323 @xref{Frame Info, ,Information about a Frame}, to identify the other
14324 information listed here.
14327 @kindex info source@r{, show the source language}
14328 Display the source language of this source file.
14329 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14330 information listed here.
14333 In unusual circumstances, you may have source files with extensions
14334 not in the standard list. You can then set the extension associated
14335 with a language explicitly:
14338 @item set extension-language @var{ext} @var{language}
14339 @kindex set extension-language
14340 Tell @value{GDBN} that source files with extension @var{ext} are to be
14341 assumed as written in the source language @var{language}.
14343 @item info extensions
14344 @kindex info extensions
14345 List all the filename extensions and the associated languages.
14349 @section Type and Range Checking
14351 Some languages are designed to guard you against making seemingly common
14352 errors through a series of compile- and run-time checks. These include
14353 checking the type of arguments to functions and operators and making
14354 sure mathematical overflows are caught at run time. Checks such as
14355 these help to ensure a program's correctness once it has been compiled
14356 by eliminating type mismatches and providing active checks for range
14357 errors when your program is running.
14359 By default @value{GDBN} checks for these errors according to the
14360 rules of the current source language. Although @value{GDBN} does not check
14361 the statements in your program, it can check expressions entered directly
14362 into @value{GDBN} for evaluation via the @code{print} command, for example.
14365 * Type Checking:: An overview of type checking
14366 * Range Checking:: An overview of range checking
14369 @cindex type checking
14370 @cindex checks, type
14371 @node Type Checking
14372 @subsection An Overview of Type Checking
14374 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14375 arguments to operators and functions have to be of the correct type,
14376 otherwise an error occurs. These checks prevent type mismatch
14377 errors from ever causing any run-time problems. For example,
14380 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14382 (@value{GDBP}) print obj.my_method (0)
14385 (@value{GDBP}) print obj.my_method (0x1234)
14386 Cannot resolve method klass::my_method to any overloaded instance
14389 The second example fails because in C@t{++} the integer constant
14390 @samp{0x1234} is not type-compatible with the pointer parameter type.
14392 For the expressions you use in @value{GDBN} commands, you can tell
14393 @value{GDBN} to not enforce strict type checking or
14394 to treat any mismatches as errors and abandon the expression;
14395 When type checking is disabled, @value{GDBN} successfully evaluates
14396 expressions like the second example above.
14398 Even if type checking is off, there may be other reasons
14399 related to type that prevent @value{GDBN} from evaluating an expression.
14400 For instance, @value{GDBN} does not know how to add an @code{int} and
14401 a @code{struct foo}. These particular type errors have nothing to do
14402 with the language in use and usually arise from expressions which make
14403 little sense to evaluate anyway.
14405 @value{GDBN} provides some additional commands for controlling type checking:
14407 @kindex set check type
14408 @kindex show check type
14410 @item set check type on
14411 @itemx set check type off
14412 Set strict type checking on or off. If any type mismatches occur in
14413 evaluating an expression while type checking is on, @value{GDBN} prints a
14414 message and aborts evaluation of the expression.
14416 @item show check type
14417 Show the current setting of type checking and whether @value{GDBN}
14418 is enforcing strict type checking rules.
14421 @cindex range checking
14422 @cindex checks, range
14423 @node Range Checking
14424 @subsection An Overview of Range Checking
14426 In some languages (such as Modula-2), it is an error to exceed the
14427 bounds of a type; this is enforced with run-time checks. Such range
14428 checking is meant to ensure program correctness by making sure
14429 computations do not overflow, or indices on an array element access do
14430 not exceed the bounds of the array.
14432 For expressions you use in @value{GDBN} commands, you can tell
14433 @value{GDBN} to treat range errors in one of three ways: ignore them,
14434 always treat them as errors and abandon the expression, or issue
14435 warnings but evaluate the expression anyway.
14437 A range error can result from numerical overflow, from exceeding an
14438 array index bound, or when you type a constant that is not a member
14439 of any type. Some languages, however, do not treat overflows as an
14440 error. In many implementations of C, mathematical overflow causes the
14441 result to ``wrap around'' to lower values---for example, if @var{m} is
14442 the largest integer value, and @var{s} is the smallest, then
14445 @var{m} + 1 @result{} @var{s}
14448 This, too, is specific to individual languages, and in some cases
14449 specific to individual compilers or machines. @xref{Supported Languages, ,
14450 Supported Languages}, for further details on specific languages.
14452 @value{GDBN} provides some additional commands for controlling the range checker:
14454 @kindex set check range
14455 @kindex show check range
14457 @item set check range auto
14458 Set range checking on or off based on the current working language.
14459 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14462 @item set check range on
14463 @itemx set check range off
14464 Set range checking on or off, overriding the default setting for the
14465 current working language. A warning is issued if the setting does not
14466 match the language default. If a range error occurs and range checking is on,
14467 then a message is printed and evaluation of the expression is aborted.
14469 @item set check range warn
14470 Output messages when the @value{GDBN} range checker detects a range error,
14471 but attempt to evaluate the expression anyway. Evaluating the
14472 expression may still be impossible for other reasons, such as accessing
14473 memory that the process does not own (a typical example from many Unix
14477 Show the current setting of the range checker, and whether or not it is
14478 being set automatically by @value{GDBN}.
14481 @node Supported Languages
14482 @section Supported Languages
14484 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14485 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14486 @c This is false ...
14487 Some @value{GDBN} features may be used in expressions regardless of the
14488 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14489 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14490 ,Expressions}) can be used with the constructs of any supported
14493 The following sections detail to what degree each source language is
14494 supported by @value{GDBN}. These sections are not meant to be language
14495 tutorials or references, but serve only as a reference guide to what the
14496 @value{GDBN} expression parser accepts, and what input and output
14497 formats should look like for different languages. There are many good
14498 books written on each of these languages; please look to these for a
14499 language reference or tutorial.
14502 * C:: C and C@t{++}
14505 * Objective-C:: Objective-C
14506 * OpenCL C:: OpenCL C
14507 * Fortran:: Fortran
14510 * Modula-2:: Modula-2
14515 @subsection C and C@t{++}
14517 @cindex C and C@t{++}
14518 @cindex expressions in C or C@t{++}
14520 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14521 to both languages. Whenever this is the case, we discuss those languages
14525 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14526 @cindex @sc{gnu} C@t{++}
14527 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14528 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14529 effectively, you must compile your C@t{++} programs with a supported
14530 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14531 compiler (@code{aCC}).
14534 * C Operators:: C and C@t{++} operators
14535 * C Constants:: C and C@t{++} constants
14536 * C Plus Plus Expressions:: C@t{++} expressions
14537 * C Defaults:: Default settings for C and C@t{++}
14538 * C Checks:: C and C@t{++} type and range checks
14539 * Debugging C:: @value{GDBN} and C
14540 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14541 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14545 @subsubsection C and C@t{++} Operators
14547 @cindex C and C@t{++} operators
14549 Operators must be defined on values of specific types. For instance,
14550 @code{+} is defined on numbers, but not on structures. Operators are
14551 often defined on groups of types.
14553 For the purposes of C and C@t{++}, the following definitions hold:
14558 @emph{Integral types} include @code{int} with any of its storage-class
14559 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14562 @emph{Floating-point types} include @code{float}, @code{double}, and
14563 @code{long double} (if supported by the target platform).
14566 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14569 @emph{Scalar types} include all of the above.
14574 The following operators are supported. They are listed here
14575 in order of increasing precedence:
14579 The comma or sequencing operator. Expressions in a comma-separated list
14580 are evaluated from left to right, with the result of the entire
14581 expression being the last expression evaluated.
14584 Assignment. The value of an assignment expression is the value
14585 assigned. Defined on scalar types.
14588 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14589 and translated to @w{@code{@var{a} = @var{a op b}}}.
14590 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14591 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14592 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14595 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14596 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14597 should be of an integral type.
14600 Logical @sc{or}. Defined on integral types.
14603 Logical @sc{and}. Defined on integral types.
14606 Bitwise @sc{or}. Defined on integral types.
14609 Bitwise exclusive-@sc{or}. Defined on integral types.
14612 Bitwise @sc{and}. Defined on integral types.
14615 Equality and inequality. Defined on scalar types. The value of these
14616 expressions is 0 for false and non-zero for true.
14618 @item <@r{, }>@r{, }<=@r{, }>=
14619 Less than, greater than, less than or equal, greater than or equal.
14620 Defined on scalar types. The value of these expressions is 0 for false
14621 and non-zero for true.
14624 left shift, and right shift. Defined on integral types.
14627 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14630 Addition and subtraction. Defined on integral types, floating-point types and
14633 @item *@r{, }/@r{, }%
14634 Multiplication, division, and modulus. Multiplication and division are
14635 defined on integral and floating-point types. Modulus is defined on
14639 Increment and decrement. When appearing before a variable, the
14640 operation is performed before the variable is used in an expression;
14641 when appearing after it, the variable's value is used before the
14642 operation takes place.
14645 Pointer dereferencing. Defined on pointer types. Same precedence as
14649 Address operator. Defined on variables. Same precedence as @code{++}.
14651 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14652 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14653 to examine the address
14654 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14658 Negative. Defined on integral and floating-point types. Same
14659 precedence as @code{++}.
14662 Logical negation. Defined on integral types. Same precedence as
14666 Bitwise complement operator. Defined on integral types. Same precedence as
14671 Structure member, and pointer-to-structure member. For convenience,
14672 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14673 pointer based on the stored type information.
14674 Defined on @code{struct} and @code{union} data.
14677 Dereferences of pointers to members.
14680 Array indexing. @code{@var{a}[@var{i}]} is defined as
14681 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14684 Function parameter list. Same precedence as @code{->}.
14687 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14688 and @code{class} types.
14691 Doubled colons also represent the @value{GDBN} scope operator
14692 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14696 If an operator is redefined in the user code, @value{GDBN} usually
14697 attempts to invoke the redefined version instead of using the operator's
14698 predefined meaning.
14701 @subsubsection C and C@t{++} Constants
14703 @cindex C and C@t{++} constants
14705 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14710 Integer constants are a sequence of digits. Octal constants are
14711 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14712 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14713 @samp{l}, specifying that the constant should be treated as a
14717 Floating point constants are a sequence of digits, followed by a decimal
14718 point, followed by a sequence of digits, and optionally followed by an
14719 exponent. An exponent is of the form:
14720 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14721 sequence of digits. The @samp{+} is optional for positive exponents.
14722 A floating-point constant may also end with a letter @samp{f} or
14723 @samp{F}, specifying that the constant should be treated as being of
14724 the @code{float} (as opposed to the default @code{double}) type; or with
14725 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14729 Enumerated constants consist of enumerated identifiers, or their
14730 integral equivalents.
14733 Character constants are a single character surrounded by single quotes
14734 (@code{'}), or a number---the ordinal value of the corresponding character
14735 (usually its @sc{ascii} value). Within quotes, the single character may
14736 be represented by a letter or by @dfn{escape sequences}, which are of
14737 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14738 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14739 @samp{@var{x}} is a predefined special character---for example,
14740 @samp{\n} for newline.
14742 Wide character constants can be written by prefixing a character
14743 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14744 form of @samp{x}. The target wide character set is used when
14745 computing the value of this constant (@pxref{Character Sets}).
14748 String constants are a sequence of character constants surrounded by
14749 double quotes (@code{"}). Any valid character constant (as described
14750 above) may appear. Double quotes within the string must be preceded by
14751 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14754 Wide string constants can be written by prefixing a string constant
14755 with @samp{L}, as in C. The target wide character set is used when
14756 computing the value of this constant (@pxref{Character Sets}).
14759 Pointer constants are an integral value. You can also write pointers
14760 to constants using the C operator @samp{&}.
14763 Array constants are comma-separated lists surrounded by braces @samp{@{}
14764 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14765 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14766 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14769 @node C Plus Plus Expressions
14770 @subsubsection C@t{++} Expressions
14772 @cindex expressions in C@t{++}
14773 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14775 @cindex debugging C@t{++} programs
14776 @cindex C@t{++} compilers
14777 @cindex debug formats and C@t{++}
14778 @cindex @value{NGCC} and C@t{++}
14780 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14781 the proper compiler and the proper debug format. Currently,
14782 @value{GDBN} works best when debugging C@t{++} code that is compiled
14783 with the most recent version of @value{NGCC} possible. The DWARF
14784 debugging format is preferred; @value{NGCC} defaults to this on most
14785 popular platforms. Other compilers and/or debug formats are likely to
14786 work badly or not at all when using @value{GDBN} to debug C@t{++}
14787 code. @xref{Compilation}.
14792 @cindex member functions
14794 Member function calls are allowed; you can use expressions like
14797 count = aml->GetOriginal(x, y)
14800 @vindex this@r{, inside C@t{++} member functions}
14801 @cindex namespace in C@t{++}
14803 While a member function is active (in the selected stack frame), your
14804 expressions have the same namespace available as the member function;
14805 that is, @value{GDBN} allows implicit references to the class instance
14806 pointer @code{this} following the same rules as C@t{++}. @code{using}
14807 declarations in the current scope are also respected by @value{GDBN}.
14809 @cindex call overloaded functions
14810 @cindex overloaded functions, calling
14811 @cindex type conversions in C@t{++}
14813 You can call overloaded functions; @value{GDBN} resolves the function
14814 call to the right definition, with some restrictions. @value{GDBN} does not
14815 perform overload resolution involving user-defined type conversions,
14816 calls to constructors, or instantiations of templates that do not exist
14817 in the program. It also cannot handle ellipsis argument lists or
14820 It does perform integral conversions and promotions, floating-point
14821 promotions, arithmetic conversions, pointer conversions, conversions of
14822 class objects to base classes, and standard conversions such as those of
14823 functions or arrays to pointers; it requires an exact match on the
14824 number of function arguments.
14826 Overload resolution is always performed, unless you have specified
14827 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14828 ,@value{GDBN} Features for C@t{++}}.
14830 You must specify @code{set overload-resolution off} in order to use an
14831 explicit function signature to call an overloaded function, as in
14833 p 'foo(char,int)'('x', 13)
14836 The @value{GDBN} command-completion facility can simplify this;
14837 see @ref{Completion, ,Command Completion}.
14839 @cindex reference declarations
14841 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14842 references; you can use them in expressions just as you do in C@t{++}
14843 source---they are automatically dereferenced.
14845 In the parameter list shown when @value{GDBN} displays a frame, the values of
14846 reference variables are not displayed (unlike other variables); this
14847 avoids clutter, since references are often used for large structures.
14848 The @emph{address} of a reference variable is always shown, unless
14849 you have specified @samp{set print address off}.
14852 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14853 expressions can use it just as expressions in your program do. Since
14854 one scope may be defined in another, you can use @code{::} repeatedly if
14855 necessary, for example in an expression like
14856 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14857 resolving name scope by reference to source files, in both C and C@t{++}
14858 debugging (@pxref{Variables, ,Program Variables}).
14861 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14866 @subsubsection C and C@t{++} Defaults
14868 @cindex C and C@t{++} defaults
14870 If you allow @value{GDBN} to set range checking automatically, it
14871 defaults to @code{off} whenever the working language changes to
14872 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14873 selects the working language.
14875 If you allow @value{GDBN} to set the language automatically, it
14876 recognizes source files whose names end with @file{.c}, @file{.C}, or
14877 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14878 these files, it sets the working language to C or C@t{++}.
14879 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14880 for further details.
14883 @subsubsection C and C@t{++} Type and Range Checks
14885 @cindex C and C@t{++} checks
14887 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14888 checking is used. However, if you turn type checking off, @value{GDBN}
14889 will allow certain non-standard conversions, such as promoting integer
14890 constants to pointers.
14892 Range checking, if turned on, is done on mathematical operations. Array
14893 indices are not checked, since they are often used to index a pointer
14894 that is not itself an array.
14897 @subsubsection @value{GDBN} and C
14899 The @code{set print union} and @code{show print union} commands apply to
14900 the @code{union} type. When set to @samp{on}, any @code{union} that is
14901 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14902 appears as @samp{@{...@}}.
14904 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14905 with pointers and a memory allocation function. @xref{Expressions,
14908 @node Debugging C Plus Plus
14909 @subsubsection @value{GDBN} Features for C@t{++}
14911 @cindex commands for C@t{++}
14913 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14914 designed specifically for use with C@t{++}. Here is a summary:
14917 @cindex break in overloaded functions
14918 @item @r{breakpoint menus}
14919 When you want a breakpoint in a function whose name is overloaded,
14920 @value{GDBN} has the capability to display a menu of possible breakpoint
14921 locations to help you specify which function definition you want.
14922 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14924 @cindex overloading in C@t{++}
14925 @item rbreak @var{regex}
14926 Setting breakpoints using regular expressions is helpful for setting
14927 breakpoints on overloaded functions that are not members of any special
14929 @xref{Set Breaks, ,Setting Breakpoints}.
14931 @cindex C@t{++} exception handling
14933 @itemx catch rethrow
14935 Debug C@t{++} exception handling using these commands. @xref{Set
14936 Catchpoints, , Setting Catchpoints}.
14938 @cindex inheritance
14939 @item ptype @var{typename}
14940 Print inheritance relationships as well as other information for type
14942 @xref{Symbols, ,Examining the Symbol Table}.
14944 @item info vtbl @var{expression}.
14945 The @code{info vtbl} command can be used to display the virtual
14946 method tables of the object computed by @var{expression}. This shows
14947 one entry per virtual table; there may be multiple virtual tables when
14948 multiple inheritance is in use.
14950 @cindex C@t{++} demangling
14951 @item demangle @var{name}
14952 Demangle @var{name}.
14953 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14955 @cindex C@t{++} symbol display
14956 @item set print demangle
14957 @itemx show print demangle
14958 @itemx set print asm-demangle
14959 @itemx show print asm-demangle
14960 Control whether C@t{++} symbols display in their source form, both when
14961 displaying code as C@t{++} source and when displaying disassemblies.
14962 @xref{Print Settings, ,Print Settings}.
14964 @item set print object
14965 @itemx show print object
14966 Choose whether to print derived (actual) or declared types of objects.
14967 @xref{Print Settings, ,Print Settings}.
14969 @item set print vtbl
14970 @itemx show print vtbl
14971 Control the format for printing virtual function tables.
14972 @xref{Print Settings, ,Print Settings}.
14973 (The @code{vtbl} commands do not work on programs compiled with the HP
14974 ANSI C@t{++} compiler (@code{aCC}).)
14976 @kindex set overload-resolution
14977 @cindex overloaded functions, overload resolution
14978 @item set overload-resolution on
14979 Enable overload resolution for C@t{++} expression evaluation. The default
14980 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14981 and searches for a function whose signature matches the argument types,
14982 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14983 Expressions, ,C@t{++} Expressions}, for details).
14984 If it cannot find a match, it emits a message.
14986 @item set overload-resolution off
14987 Disable overload resolution for C@t{++} expression evaluation. For
14988 overloaded functions that are not class member functions, @value{GDBN}
14989 chooses the first function of the specified name that it finds in the
14990 symbol table, whether or not its arguments are of the correct type. For
14991 overloaded functions that are class member functions, @value{GDBN}
14992 searches for a function whose signature @emph{exactly} matches the
14995 @kindex show overload-resolution
14996 @item show overload-resolution
14997 Show the current setting of overload resolution.
14999 @item @r{Overloaded symbol names}
15000 You can specify a particular definition of an overloaded symbol, using
15001 the same notation that is used to declare such symbols in C@t{++}: type
15002 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15003 also use the @value{GDBN} command-line word completion facilities to list the
15004 available choices, or to finish the type list for you.
15005 @xref{Completion,, Command Completion}, for details on how to do this.
15008 @node Decimal Floating Point
15009 @subsubsection Decimal Floating Point format
15010 @cindex decimal floating point format
15012 @value{GDBN} can examine, set and perform computations with numbers in
15013 decimal floating point format, which in the C language correspond to the
15014 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15015 specified by the extension to support decimal floating-point arithmetic.
15017 There are two encodings in use, depending on the architecture: BID (Binary
15018 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15019 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15022 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15023 to manipulate decimal floating point numbers, it is not possible to convert
15024 (using a cast, for example) integers wider than 32-bit to decimal float.
15026 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15027 point computations, error checking in decimal float operations ignores
15028 underflow, overflow and divide by zero exceptions.
15030 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15031 to inspect @code{_Decimal128} values stored in floating point registers.
15032 See @ref{PowerPC,,PowerPC} for more details.
15038 @value{GDBN} can be used to debug programs written in D and compiled with
15039 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15040 specific feature --- dynamic arrays.
15045 @cindex Go (programming language)
15046 @value{GDBN} can be used to debug programs written in Go and compiled with
15047 @file{gccgo} or @file{6g} compilers.
15049 Here is a summary of the Go-specific features and restrictions:
15052 @cindex current Go package
15053 @item The current Go package
15054 The name of the current package does not need to be specified when
15055 specifying global variables and functions.
15057 For example, given the program:
15061 var myglob = "Shall we?"
15067 When stopped inside @code{main} either of these work:
15071 (gdb) p main.myglob
15074 @cindex builtin Go types
15075 @item Builtin Go types
15076 The @code{string} type is recognized by @value{GDBN} and is printed
15079 @cindex builtin Go functions
15080 @item Builtin Go functions
15081 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15082 function and handles it internally.
15084 @cindex restrictions on Go expressions
15085 @item Restrictions on Go expressions
15086 All Go operators are supported except @code{&^}.
15087 The Go @code{_} ``blank identifier'' is not supported.
15088 Automatic dereferencing of pointers is not supported.
15092 @subsection Objective-C
15094 @cindex Objective-C
15095 This section provides information about some commands and command
15096 options that are useful for debugging Objective-C code. See also
15097 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15098 few more commands specific to Objective-C support.
15101 * Method Names in Commands::
15102 * The Print Command with Objective-C::
15105 @node Method Names in Commands
15106 @subsubsection Method Names in Commands
15108 The following commands have been extended to accept Objective-C method
15109 names as line specifications:
15111 @kindex clear@r{, and Objective-C}
15112 @kindex break@r{, and Objective-C}
15113 @kindex info line@r{, and Objective-C}
15114 @kindex jump@r{, and Objective-C}
15115 @kindex list@r{, and Objective-C}
15119 @item @code{info line}
15124 A fully qualified Objective-C method name is specified as
15127 -[@var{Class} @var{methodName}]
15130 where the minus sign is used to indicate an instance method and a
15131 plus sign (not shown) is used to indicate a class method. The class
15132 name @var{Class} and method name @var{methodName} are enclosed in
15133 brackets, similar to the way messages are specified in Objective-C
15134 source code. For example, to set a breakpoint at the @code{create}
15135 instance method of class @code{Fruit} in the program currently being
15139 break -[Fruit create]
15142 To list ten program lines around the @code{initialize} class method,
15146 list +[NSText initialize]
15149 In the current version of @value{GDBN}, the plus or minus sign is
15150 required. In future versions of @value{GDBN}, the plus or minus
15151 sign will be optional, but you can use it to narrow the search. It
15152 is also possible to specify just a method name:
15158 You must specify the complete method name, including any colons. If
15159 your program's source files contain more than one @code{create} method,
15160 you'll be presented with a numbered list of classes that implement that
15161 method. Indicate your choice by number, or type @samp{0} to exit if
15164 As another example, to clear a breakpoint established at the
15165 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15168 clear -[NSWindow makeKeyAndOrderFront:]
15171 @node The Print Command with Objective-C
15172 @subsubsection The Print Command With Objective-C
15173 @cindex Objective-C, print objects
15174 @kindex print-object
15175 @kindex po @r{(@code{print-object})}
15177 The print command has also been extended to accept methods. For example:
15180 print -[@var{object} hash]
15183 @cindex print an Objective-C object description
15184 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15186 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15187 and print the result. Also, an additional command has been added,
15188 @code{print-object} or @code{po} for short, which is meant to print
15189 the description of an object. However, this command may only work
15190 with certain Objective-C libraries that have a particular hook
15191 function, @code{_NSPrintForDebugger}, defined.
15194 @subsection OpenCL C
15197 This section provides information about @value{GDBN}s OpenCL C support.
15200 * OpenCL C Datatypes::
15201 * OpenCL C Expressions::
15202 * OpenCL C Operators::
15205 @node OpenCL C Datatypes
15206 @subsubsection OpenCL C Datatypes
15208 @cindex OpenCL C Datatypes
15209 @value{GDBN} supports the builtin scalar and vector datatypes specified
15210 by OpenCL 1.1. In addition the half- and double-precision floating point
15211 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15212 extensions are also known to @value{GDBN}.
15214 @node OpenCL C Expressions
15215 @subsubsection OpenCL C Expressions
15217 @cindex OpenCL C Expressions
15218 @value{GDBN} supports accesses to vector components including the access as
15219 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15220 supported by @value{GDBN} can be used as well.
15222 @node OpenCL C Operators
15223 @subsubsection OpenCL C Operators
15225 @cindex OpenCL C Operators
15226 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15230 @subsection Fortran
15231 @cindex Fortran-specific support in @value{GDBN}
15233 @value{GDBN} can be used to debug programs written in Fortran, but it
15234 currently supports only the features of Fortran 77 language.
15236 @cindex trailing underscore, in Fortran symbols
15237 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15238 among them) append an underscore to the names of variables and
15239 functions. When you debug programs compiled by those compilers, you
15240 will need to refer to variables and functions with a trailing
15244 * Fortran Operators:: Fortran operators and expressions
15245 * Fortran Defaults:: Default settings for Fortran
15246 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15249 @node Fortran Operators
15250 @subsubsection Fortran Operators and Expressions
15252 @cindex Fortran operators and expressions
15254 Operators must be defined on values of specific types. For instance,
15255 @code{+} is defined on numbers, but not on characters or other non-
15256 arithmetic types. Operators are often defined on groups of types.
15260 The exponentiation operator. It raises the first operand to the power
15264 The range operator. Normally used in the form of array(low:high) to
15265 represent a section of array.
15268 The access component operator. Normally used to access elements in derived
15269 types. Also suitable for unions. As unions aren't part of regular Fortran,
15270 this can only happen when accessing a register that uses a gdbarch-defined
15274 @node Fortran Defaults
15275 @subsubsection Fortran Defaults
15277 @cindex Fortran Defaults
15279 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15280 default uses case-insensitive matches for Fortran symbols. You can
15281 change that with the @samp{set case-insensitive} command, see
15282 @ref{Symbols}, for the details.
15284 @node Special Fortran Commands
15285 @subsubsection Special Fortran Commands
15287 @cindex Special Fortran commands
15289 @value{GDBN} has some commands to support Fortran-specific features,
15290 such as displaying common blocks.
15293 @cindex @code{COMMON} blocks, Fortran
15294 @kindex info common
15295 @item info common @r{[}@var{common-name}@r{]}
15296 This command prints the values contained in the Fortran @code{COMMON}
15297 block whose name is @var{common-name}. With no argument, the names of
15298 all @code{COMMON} blocks visible at the current program location are
15305 @cindex Pascal support in @value{GDBN}, limitations
15306 Debugging Pascal programs which use sets, subranges, file variables, or
15307 nested functions does not currently work. @value{GDBN} does not support
15308 entering expressions, printing values, or similar features using Pascal
15311 The Pascal-specific command @code{set print pascal_static-members}
15312 controls whether static members of Pascal objects are displayed.
15313 @xref{Print Settings, pascal_static-members}.
15318 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15319 Programming Language}. Type- and value-printing, and expression
15320 parsing, are reasonably complete. However, there are a few
15321 peculiarities and holes to be aware of.
15325 Linespecs (@pxref{Specify Location}) are never relative to the current
15326 crate. Instead, they act as if there were a global namespace of
15327 crates, somewhat similar to the way @code{extern crate} behaves.
15329 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15330 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15331 to set a breakpoint in a function named @samp{f} in a crate named
15334 As a consequence of this approach, linespecs also cannot refer to
15335 items using @samp{self::} or @samp{super::}.
15338 Because @value{GDBN} implements Rust name-lookup semantics in
15339 expressions, it will sometimes prepend the current crate to a name.
15340 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15341 @samp{K}, then @code{print ::x::y} will try to find the symbol
15344 However, since it is useful to be able to refer to other crates when
15345 debugging, @value{GDBN} provides the @code{extern} extension to
15346 circumvent this. To use the extension, just put @code{extern} before
15347 a path expression to refer to the otherwise unavailable ``global''
15350 In the above example, if you wanted to refer to the symbol @samp{y} in
15351 the crate @samp{x}, you would use @code{print extern x::y}.
15354 The Rust expression evaluator does not support ``statement-like''
15355 expressions such as @code{if} or @code{match}, or lambda expressions.
15358 Tuple expressions are not implemented.
15361 The Rust expression evaluator does not currently implement the
15362 @code{Drop} trait. Objects that may be created by the evaluator will
15363 never be destroyed.
15366 @value{GDBN} does not implement type inference for generics. In order
15367 to call generic functions or otherwise refer to generic items, you
15368 will have to specify the type parameters manually.
15371 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15372 cases this does not cause any problems. However, in an expression
15373 context, completing a generic function name will give syntactically
15374 invalid results. This happens because Rust requires the @samp{::}
15375 operator between the function name and its generic arguments. For
15376 example, @value{GDBN} might provide a completion like
15377 @code{crate::f<u32>}, where the parser would require
15378 @code{crate::f::<u32>}.
15381 As of this writing, the Rust compiler (version 1.8) has a few holes in
15382 the debugging information it generates. These holes prevent certain
15383 features from being implemented by @value{GDBN}:
15387 Method calls cannot be made via traits.
15390 Trait objects cannot be created or inspected.
15393 Operator overloading is not implemented.
15396 When debugging in a monomorphized function, you cannot use the generic
15400 The type @code{Self} is not available.
15403 @code{use} statements are not available, so some names may not be
15404 available in the crate.
15409 @subsection Modula-2
15411 @cindex Modula-2, @value{GDBN} support
15413 The extensions made to @value{GDBN} to support Modula-2 only support
15414 output from the @sc{gnu} Modula-2 compiler (which is currently being
15415 developed). Other Modula-2 compilers are not currently supported, and
15416 attempting to debug executables produced by them is most likely
15417 to give an error as @value{GDBN} reads in the executable's symbol
15420 @cindex expressions in Modula-2
15422 * M2 Operators:: Built-in operators
15423 * Built-In Func/Proc:: Built-in functions and procedures
15424 * M2 Constants:: Modula-2 constants
15425 * M2 Types:: Modula-2 types
15426 * M2 Defaults:: Default settings for Modula-2
15427 * Deviations:: Deviations from standard Modula-2
15428 * M2 Checks:: Modula-2 type and range checks
15429 * M2 Scope:: The scope operators @code{::} and @code{.}
15430 * GDB/M2:: @value{GDBN} and Modula-2
15434 @subsubsection Operators
15435 @cindex Modula-2 operators
15437 Operators must be defined on values of specific types. For instance,
15438 @code{+} is defined on numbers, but not on structures. Operators are
15439 often defined on groups of types. For the purposes of Modula-2, the
15440 following definitions hold:
15445 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15449 @emph{Character types} consist of @code{CHAR} and its subranges.
15452 @emph{Floating-point types} consist of @code{REAL}.
15455 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15459 @emph{Scalar types} consist of all of the above.
15462 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15465 @emph{Boolean types} consist of @code{BOOLEAN}.
15469 The following operators are supported, and appear in order of
15470 increasing precedence:
15474 Function argument or array index separator.
15477 Assignment. The value of @var{var} @code{:=} @var{value} is
15481 Less than, greater than on integral, floating-point, or enumerated
15485 Less than or equal to, greater than or equal to
15486 on integral, floating-point and enumerated types, or set inclusion on
15487 set types. Same precedence as @code{<}.
15489 @item =@r{, }<>@r{, }#
15490 Equality and two ways of expressing inequality, valid on scalar types.
15491 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15492 available for inequality, since @code{#} conflicts with the script
15496 Set membership. Defined on set types and the types of their members.
15497 Same precedence as @code{<}.
15500 Boolean disjunction. Defined on boolean types.
15503 Boolean conjunction. Defined on boolean types.
15506 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15509 Addition and subtraction on integral and floating-point types, or union
15510 and difference on set types.
15513 Multiplication on integral and floating-point types, or set intersection
15517 Division on floating-point types, or symmetric set difference on set
15518 types. Same precedence as @code{*}.
15521 Integer division and remainder. Defined on integral types. Same
15522 precedence as @code{*}.
15525 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15528 Pointer dereferencing. Defined on pointer types.
15531 Boolean negation. Defined on boolean types. Same precedence as
15535 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15536 precedence as @code{^}.
15539 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15542 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15546 @value{GDBN} and Modula-2 scope operators.
15550 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15551 treats the use of the operator @code{IN}, or the use of operators
15552 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15553 @code{<=}, and @code{>=} on sets as an error.
15557 @node Built-In Func/Proc
15558 @subsubsection Built-in Functions and Procedures
15559 @cindex Modula-2 built-ins
15561 Modula-2 also makes available several built-in procedures and functions.
15562 In describing these, the following metavariables are used:
15567 represents an @code{ARRAY} variable.
15570 represents a @code{CHAR} constant or variable.
15573 represents a variable or constant of integral type.
15576 represents an identifier that belongs to a set. Generally used in the
15577 same function with the metavariable @var{s}. The type of @var{s} should
15578 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15581 represents a variable or constant of integral or floating-point type.
15584 represents a variable or constant of floating-point type.
15590 represents a variable.
15593 represents a variable or constant of one of many types. See the
15594 explanation of the function for details.
15597 All Modula-2 built-in procedures also return a result, described below.
15601 Returns the absolute value of @var{n}.
15604 If @var{c} is a lower case letter, it returns its upper case
15605 equivalent, otherwise it returns its argument.
15608 Returns the character whose ordinal value is @var{i}.
15611 Decrements the value in the variable @var{v} by one. Returns the new value.
15613 @item DEC(@var{v},@var{i})
15614 Decrements the value in the variable @var{v} by @var{i}. Returns the
15617 @item EXCL(@var{m},@var{s})
15618 Removes the element @var{m} from the set @var{s}. Returns the new
15621 @item FLOAT(@var{i})
15622 Returns the floating point equivalent of the integer @var{i}.
15624 @item HIGH(@var{a})
15625 Returns the index of the last member of @var{a}.
15628 Increments the value in the variable @var{v} by one. Returns the new value.
15630 @item INC(@var{v},@var{i})
15631 Increments the value in the variable @var{v} by @var{i}. Returns the
15634 @item INCL(@var{m},@var{s})
15635 Adds the element @var{m} to the set @var{s} if it is not already
15636 there. Returns the new set.
15639 Returns the maximum value of the type @var{t}.
15642 Returns the minimum value of the type @var{t}.
15645 Returns boolean TRUE if @var{i} is an odd number.
15648 Returns the ordinal value of its argument. For example, the ordinal
15649 value of a character is its @sc{ascii} value (on machines supporting
15650 the @sc{ascii} character set). The argument @var{x} must be of an
15651 ordered type, which include integral, character and enumerated types.
15653 @item SIZE(@var{x})
15654 Returns the size of its argument. The argument @var{x} can be a
15655 variable or a type.
15657 @item TRUNC(@var{r})
15658 Returns the integral part of @var{r}.
15660 @item TSIZE(@var{x})
15661 Returns the size of its argument. The argument @var{x} can be a
15662 variable or a type.
15664 @item VAL(@var{t},@var{i})
15665 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15669 @emph{Warning:} Sets and their operations are not yet supported, so
15670 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15674 @cindex Modula-2 constants
15676 @subsubsection Constants
15678 @value{GDBN} allows you to express the constants of Modula-2 in the following
15684 Integer constants are simply a sequence of digits. When used in an
15685 expression, a constant is interpreted to be type-compatible with the
15686 rest of the expression. Hexadecimal integers are specified by a
15687 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15690 Floating point constants appear as a sequence of digits, followed by a
15691 decimal point and another sequence of digits. An optional exponent can
15692 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15693 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15694 digits of the floating point constant must be valid decimal (base 10)
15698 Character constants consist of a single character enclosed by a pair of
15699 like quotes, either single (@code{'}) or double (@code{"}). They may
15700 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15701 followed by a @samp{C}.
15704 String constants consist of a sequence of characters enclosed by a
15705 pair of like quotes, either single (@code{'}) or double (@code{"}).
15706 Escape sequences in the style of C are also allowed. @xref{C
15707 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15711 Enumerated constants consist of an enumerated identifier.
15714 Boolean constants consist of the identifiers @code{TRUE} and
15718 Pointer constants consist of integral values only.
15721 Set constants are not yet supported.
15725 @subsubsection Modula-2 Types
15726 @cindex Modula-2 types
15728 Currently @value{GDBN} can print the following data types in Modula-2
15729 syntax: array types, record types, set types, pointer types, procedure
15730 types, enumerated types, subrange types and base types. You can also
15731 print the contents of variables declared using these type.
15732 This section gives a number of simple source code examples together with
15733 sample @value{GDBN} sessions.
15735 The first example contains the following section of code:
15744 and you can request @value{GDBN} to interrogate the type and value of
15745 @code{r} and @code{s}.
15748 (@value{GDBP}) print s
15750 (@value{GDBP}) ptype s
15752 (@value{GDBP}) print r
15754 (@value{GDBP}) ptype r
15759 Likewise if your source code declares @code{s} as:
15763 s: SET ['A'..'Z'] ;
15767 then you may query the type of @code{s} by:
15770 (@value{GDBP}) ptype s
15771 type = SET ['A'..'Z']
15775 Note that at present you cannot interactively manipulate set
15776 expressions using the debugger.
15778 The following example shows how you might declare an array in Modula-2
15779 and how you can interact with @value{GDBN} to print its type and contents:
15783 s: ARRAY [-10..10] OF CHAR ;
15787 (@value{GDBP}) ptype s
15788 ARRAY [-10..10] OF CHAR
15791 Note that the array handling is not yet complete and although the type
15792 is printed correctly, expression handling still assumes that all
15793 arrays have a lower bound of zero and not @code{-10} as in the example
15796 Here are some more type related Modula-2 examples:
15800 colour = (blue, red, yellow, green) ;
15801 t = [blue..yellow] ;
15809 The @value{GDBN} interaction shows how you can query the data type
15810 and value of a variable.
15813 (@value{GDBP}) print s
15815 (@value{GDBP}) ptype t
15816 type = [blue..yellow]
15820 In this example a Modula-2 array is declared and its contents
15821 displayed. Observe that the contents are written in the same way as
15822 their @code{C} counterparts.
15826 s: ARRAY [1..5] OF CARDINAL ;
15832 (@value{GDBP}) print s
15833 $1 = @{1, 0, 0, 0, 0@}
15834 (@value{GDBP}) ptype s
15835 type = ARRAY [1..5] OF CARDINAL
15838 The Modula-2 language interface to @value{GDBN} also understands
15839 pointer types as shown in this example:
15843 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15850 and you can request that @value{GDBN} describes the type of @code{s}.
15853 (@value{GDBP}) ptype s
15854 type = POINTER TO ARRAY [1..5] OF CARDINAL
15857 @value{GDBN} handles compound types as we can see in this example.
15858 Here we combine array types, record types, pointer types and subrange
15869 myarray = ARRAY myrange OF CARDINAL ;
15870 myrange = [-2..2] ;
15872 s: POINTER TO ARRAY myrange OF foo ;
15876 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15880 (@value{GDBP}) ptype s
15881 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15884 f3 : ARRAY [-2..2] OF CARDINAL;
15889 @subsubsection Modula-2 Defaults
15890 @cindex Modula-2 defaults
15892 If type and range checking are set automatically by @value{GDBN}, they
15893 both default to @code{on} whenever the working language changes to
15894 Modula-2. This happens regardless of whether you or @value{GDBN}
15895 selected the working language.
15897 If you allow @value{GDBN} to set the language automatically, then entering
15898 code compiled from a file whose name ends with @file{.mod} sets the
15899 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15900 Infer the Source Language}, for further details.
15903 @subsubsection Deviations from Standard Modula-2
15904 @cindex Modula-2, deviations from
15906 A few changes have been made to make Modula-2 programs easier to debug.
15907 This is done primarily via loosening its type strictness:
15911 Unlike in standard Modula-2, pointer constants can be formed by
15912 integers. This allows you to modify pointer variables during
15913 debugging. (In standard Modula-2, the actual address contained in a
15914 pointer variable is hidden from you; it can only be modified
15915 through direct assignment to another pointer variable or expression that
15916 returned a pointer.)
15919 C escape sequences can be used in strings and characters to represent
15920 non-printable characters. @value{GDBN} prints out strings with these
15921 escape sequences embedded. Single non-printable characters are
15922 printed using the @samp{CHR(@var{nnn})} format.
15925 The assignment operator (@code{:=}) returns the value of its right-hand
15929 All built-in procedures both modify @emph{and} return their argument.
15933 @subsubsection Modula-2 Type and Range Checks
15934 @cindex Modula-2 checks
15937 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15940 @c FIXME remove warning when type/range checks added
15942 @value{GDBN} considers two Modula-2 variables type equivalent if:
15946 They are of types that have been declared equivalent via a @code{TYPE
15947 @var{t1} = @var{t2}} statement
15950 They have been declared on the same line. (Note: This is true of the
15951 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15954 As long as type checking is enabled, any attempt to combine variables
15955 whose types are not equivalent is an error.
15957 Range checking is done on all mathematical operations, assignment, array
15958 index bounds, and all built-in functions and procedures.
15961 @subsubsection The Scope Operators @code{::} and @code{.}
15963 @cindex @code{.}, Modula-2 scope operator
15964 @cindex colon, doubled as scope operator
15966 @vindex colon-colon@r{, in Modula-2}
15967 @c Info cannot handle :: but TeX can.
15970 @vindex ::@r{, in Modula-2}
15973 There are a few subtle differences between the Modula-2 scope operator
15974 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15979 @var{module} . @var{id}
15980 @var{scope} :: @var{id}
15984 where @var{scope} is the name of a module or a procedure,
15985 @var{module} the name of a module, and @var{id} is any declared
15986 identifier within your program, except another module.
15988 Using the @code{::} operator makes @value{GDBN} search the scope
15989 specified by @var{scope} for the identifier @var{id}. If it is not
15990 found in the specified scope, then @value{GDBN} searches all scopes
15991 enclosing the one specified by @var{scope}.
15993 Using the @code{.} operator makes @value{GDBN} search the current scope for
15994 the identifier specified by @var{id} that was imported from the
15995 definition module specified by @var{module}. With this operator, it is
15996 an error if the identifier @var{id} was not imported from definition
15997 module @var{module}, or if @var{id} is not an identifier in
16001 @subsubsection @value{GDBN} and Modula-2
16003 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16004 Five subcommands of @code{set print} and @code{show print} apply
16005 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16006 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16007 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16008 analogue in Modula-2.
16010 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16011 with any language, is not useful with Modula-2. Its
16012 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16013 created in Modula-2 as they can in C or C@t{++}. However, because an
16014 address can be specified by an integral constant, the construct
16015 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16017 @cindex @code{#} in Modula-2
16018 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16019 interpreted as the beginning of a comment. Use @code{<>} instead.
16025 The extensions made to @value{GDBN} for Ada only support
16026 output from the @sc{gnu} Ada (GNAT) compiler.
16027 Other Ada compilers are not currently supported, and
16028 attempting to debug executables produced by them is most likely
16032 @cindex expressions in Ada
16034 * Ada Mode Intro:: General remarks on the Ada syntax
16035 and semantics supported by Ada mode
16037 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16038 * Additions to Ada:: Extensions of the Ada expression syntax.
16039 * Overloading support for Ada:: Support for expressions involving overloaded
16041 * Stopping Before Main Program:: Debugging the program during elaboration.
16042 * Ada Exceptions:: Ada Exceptions
16043 * Ada Tasks:: Listing and setting breakpoints in tasks.
16044 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16045 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16047 * Ada Glitches:: Known peculiarities of Ada mode.
16050 @node Ada Mode Intro
16051 @subsubsection Introduction
16052 @cindex Ada mode, general
16054 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16055 syntax, with some extensions.
16056 The philosophy behind the design of this subset is
16060 That @value{GDBN} should provide basic literals and access to operations for
16061 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16062 leaving more sophisticated computations to subprograms written into the
16063 program (which therefore may be called from @value{GDBN}).
16066 That type safety and strict adherence to Ada language restrictions
16067 are not particularly important to the @value{GDBN} user.
16070 That brevity is important to the @value{GDBN} user.
16073 Thus, for brevity, the debugger acts as if all names declared in
16074 user-written packages are directly visible, even if they are not visible
16075 according to Ada rules, thus making it unnecessary to fully qualify most
16076 names with their packages, regardless of context. Where this causes
16077 ambiguity, @value{GDBN} asks the user's intent.
16079 The debugger will start in Ada mode if it detects an Ada main program.
16080 As for other languages, it will enter Ada mode when stopped in a program that
16081 was translated from an Ada source file.
16083 While in Ada mode, you may use `@t{--}' for comments. This is useful
16084 mostly for documenting command files. The standard @value{GDBN} comment
16085 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16086 middle (to allow based literals).
16088 @node Omissions from Ada
16089 @subsubsection Omissions from Ada
16090 @cindex Ada, omissions from
16092 Here are the notable omissions from the subset:
16096 Only a subset of the attributes are supported:
16100 @t{'First}, @t{'Last}, and @t{'Length}
16101 on array objects (not on types and subtypes).
16104 @t{'Min} and @t{'Max}.
16107 @t{'Pos} and @t{'Val}.
16113 @t{'Range} on array objects (not subtypes), but only as the right
16114 operand of the membership (@code{in}) operator.
16117 @t{'Access}, @t{'Unchecked_Access}, and
16118 @t{'Unrestricted_Access} (a GNAT extension).
16126 @code{Characters.Latin_1} are not available and
16127 concatenation is not implemented. Thus, escape characters in strings are
16128 not currently available.
16131 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16132 equality of representations. They will generally work correctly
16133 for strings and arrays whose elements have integer or enumeration types.
16134 They may not work correctly for arrays whose element
16135 types have user-defined equality, for arrays of real values
16136 (in particular, IEEE-conformant floating point, because of negative
16137 zeroes and NaNs), and for arrays whose elements contain unused bits with
16138 indeterminate values.
16141 The other component-by-component array operations (@code{and}, @code{or},
16142 @code{xor}, @code{not}, and relational tests other than equality)
16143 are not implemented.
16146 @cindex array aggregates (Ada)
16147 @cindex record aggregates (Ada)
16148 @cindex aggregates (Ada)
16149 There is limited support for array and record aggregates. They are
16150 permitted only on the right sides of assignments, as in these examples:
16153 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16154 (@value{GDBP}) set An_Array := (1, others => 0)
16155 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16156 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16157 (@value{GDBP}) set A_Record := (1, "Peter", True);
16158 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16162 discriminant's value by assigning an aggregate has an
16163 undefined effect if that discriminant is used within the record.
16164 However, you can first modify discriminants by directly assigning to
16165 them (which normally would not be allowed in Ada), and then performing an
16166 aggregate assignment. For example, given a variable @code{A_Rec}
16167 declared to have a type such as:
16170 type Rec (Len : Small_Integer := 0) is record
16172 Vals : IntArray (1 .. Len);
16176 you can assign a value with a different size of @code{Vals} with two
16180 (@value{GDBP}) set A_Rec.Len := 4
16181 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16184 As this example also illustrates, @value{GDBN} is very loose about the usual
16185 rules concerning aggregates. You may leave out some of the
16186 components of an array or record aggregate (such as the @code{Len}
16187 component in the assignment to @code{A_Rec} above); they will retain their
16188 original values upon assignment. You may freely use dynamic values as
16189 indices in component associations. You may even use overlapping or
16190 redundant component associations, although which component values are
16191 assigned in such cases is not defined.
16194 Calls to dispatching subprograms are not implemented.
16197 The overloading algorithm is much more limited (i.e., less selective)
16198 than that of real Ada. It makes only limited use of the context in
16199 which a subexpression appears to resolve its meaning, and it is much
16200 looser in its rules for allowing type matches. As a result, some
16201 function calls will be ambiguous, and the user will be asked to choose
16202 the proper resolution.
16205 The @code{new} operator is not implemented.
16208 Entry calls are not implemented.
16211 Aside from printing, arithmetic operations on the native VAX floating-point
16212 formats are not supported.
16215 It is not possible to slice a packed array.
16218 The names @code{True} and @code{False}, when not part of a qualified name,
16219 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16221 Should your program
16222 redefine these names in a package or procedure (at best a dubious practice),
16223 you will have to use fully qualified names to access their new definitions.
16226 @node Additions to Ada
16227 @subsubsection Additions to Ada
16228 @cindex Ada, deviations from
16230 As it does for other languages, @value{GDBN} makes certain generic
16231 extensions to Ada (@pxref{Expressions}):
16235 If the expression @var{E} is a variable residing in memory (typically
16236 a local variable or array element) and @var{N} is a positive integer,
16237 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16238 @var{N}-1 adjacent variables following it in memory as an array. In
16239 Ada, this operator is generally not necessary, since its prime use is
16240 in displaying parts of an array, and slicing will usually do this in
16241 Ada. However, there are occasional uses when debugging programs in
16242 which certain debugging information has been optimized away.
16245 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16246 appears in function or file @var{B}.'' When @var{B} is a file name,
16247 you must typically surround it in single quotes.
16250 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16251 @var{type} that appears at address @var{addr}.''
16254 A name starting with @samp{$} is a convenience variable
16255 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16258 In addition, @value{GDBN} provides a few other shortcuts and outright
16259 additions specific to Ada:
16263 The assignment statement is allowed as an expression, returning
16264 its right-hand operand as its value. Thus, you may enter
16267 (@value{GDBP}) set x := y + 3
16268 (@value{GDBP}) print A(tmp := y + 1)
16272 The semicolon is allowed as an ``operator,'' returning as its value
16273 the value of its right-hand operand.
16274 This allows, for example,
16275 complex conditional breaks:
16278 (@value{GDBP}) break f
16279 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16283 Rather than use catenation and symbolic character names to introduce special
16284 characters into strings, one may instead use a special bracket notation,
16285 which is also used to print strings. A sequence of characters of the form
16286 @samp{["@var{XX}"]} within a string or character literal denotes the
16287 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16288 sequence of characters @samp{["""]} also denotes a single quotation mark
16289 in strings. For example,
16291 "One line.["0a"]Next line.["0a"]"
16294 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16298 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16299 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16303 (@value{GDBP}) print 'max(x, y)
16307 When printing arrays, @value{GDBN} uses positional notation when the
16308 array has a lower bound of 1, and uses a modified named notation otherwise.
16309 For example, a one-dimensional array of three integers with a lower bound
16310 of 3 might print as
16317 That is, in contrast to valid Ada, only the first component has a @code{=>}
16321 You may abbreviate attributes in expressions with any unique,
16322 multi-character subsequence of
16323 their names (an exact match gets preference).
16324 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16325 in place of @t{a'length}.
16328 @cindex quoting Ada internal identifiers
16329 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16330 to lower case. The GNAT compiler uses upper-case characters for
16331 some of its internal identifiers, which are normally of no interest to users.
16332 For the rare occasions when you actually have to look at them,
16333 enclose them in angle brackets to avoid the lower-case mapping.
16336 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16340 Printing an object of class-wide type or dereferencing an
16341 access-to-class-wide value will display all the components of the object's
16342 specific type (as indicated by its run-time tag). Likewise, component
16343 selection on such a value will operate on the specific type of the
16348 @node Overloading support for Ada
16349 @subsubsection Overloading support for Ada
16350 @cindex overloading, Ada
16352 The debugger supports limited overloading. Given a subprogram call in which
16353 the function symbol has multiple definitions, it will use the number of
16354 actual parameters and some information about their types to attempt to narrow
16355 the set of definitions. It also makes very limited use of context, preferring
16356 procedures to functions in the context of the @code{call} command, and
16357 functions to procedures elsewhere.
16359 If, after narrowing, the set of matching definitions still contains more than
16360 one definition, @value{GDBN} will display a menu to query which one it should
16364 (@value{GDBP}) print f(1)
16365 Multiple matches for f
16367 [1] foo.f (integer) return boolean at foo.adb:23
16368 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16372 In this case, just select one menu entry either to cancel expression evaluation
16373 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16374 instance (type the corresponding number and press @key{RET}).
16376 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16381 @kindex set ada print-signatures
16382 @item set ada print-signatures
16383 Control whether parameter types and return types are displayed in overloads
16384 selection menus. It is @code{on} by default.
16385 @xref{Overloading support for Ada}.
16387 @kindex show ada print-signatures
16388 @item show ada print-signatures
16389 Show the current setting for displaying parameter types and return types in
16390 overloads selection menu.
16391 @xref{Overloading support for Ada}.
16395 @node Stopping Before Main Program
16396 @subsubsection Stopping at the Very Beginning
16398 @cindex breakpointing Ada elaboration code
16399 It is sometimes necessary to debug the program during elaboration, and
16400 before reaching the main procedure.
16401 As defined in the Ada Reference
16402 Manual, the elaboration code is invoked from a procedure called
16403 @code{adainit}. To run your program up to the beginning of
16404 elaboration, simply use the following two commands:
16405 @code{tbreak adainit} and @code{run}.
16407 @node Ada Exceptions
16408 @subsubsection Ada Exceptions
16410 A command is provided to list all Ada exceptions:
16413 @kindex info exceptions
16414 @item info exceptions
16415 @itemx info exceptions @var{regexp}
16416 The @code{info exceptions} command allows you to list all Ada exceptions
16417 defined within the program being debugged, as well as their addresses.
16418 With a regular expression, @var{regexp}, as argument, only those exceptions
16419 whose names match @var{regexp} are listed.
16422 Below is a small example, showing how the command can be used, first
16423 without argument, and next with a regular expression passed as an
16427 (@value{GDBP}) info exceptions
16428 All defined Ada exceptions:
16429 constraint_error: 0x613da0
16430 program_error: 0x613d20
16431 storage_error: 0x613ce0
16432 tasking_error: 0x613ca0
16433 const.aint_global_e: 0x613b00
16434 (@value{GDBP}) info exceptions const.aint
16435 All Ada exceptions matching regular expression "const.aint":
16436 constraint_error: 0x613da0
16437 const.aint_global_e: 0x613b00
16440 It is also possible to ask @value{GDBN} to stop your program's execution
16441 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16444 @subsubsection Extensions for Ada Tasks
16445 @cindex Ada, tasking
16447 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16448 @value{GDBN} provides the following task-related commands:
16453 This command shows a list of current Ada tasks, as in the following example:
16460 (@value{GDBP}) info tasks
16461 ID TID P-ID Pri State Name
16462 1 8088000 0 15 Child Activation Wait main_task
16463 2 80a4000 1 15 Accept Statement b
16464 3 809a800 1 15 Child Activation Wait a
16465 * 4 80ae800 3 15 Runnable c
16470 In this listing, the asterisk before the last task indicates it to be the
16471 task currently being inspected.
16475 Represents @value{GDBN}'s internal task number.
16481 The parent's task ID (@value{GDBN}'s internal task number).
16484 The base priority of the task.
16487 Current state of the task.
16491 The task has been created but has not been activated. It cannot be
16495 The task is not blocked for any reason known to Ada. (It may be waiting
16496 for a mutex, though.) It is conceptually "executing" in normal mode.
16499 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16500 that were waiting on terminate alternatives have been awakened and have
16501 terminated themselves.
16503 @item Child Activation Wait
16504 The task is waiting for created tasks to complete activation.
16506 @item Accept Statement
16507 The task is waiting on an accept or selective wait statement.
16509 @item Waiting on entry call
16510 The task is waiting on an entry call.
16512 @item Async Select Wait
16513 The task is waiting to start the abortable part of an asynchronous
16517 The task is waiting on a select statement with only a delay
16520 @item Child Termination Wait
16521 The task is sleeping having completed a master within itself, and is
16522 waiting for the tasks dependent on that master to become terminated or
16523 waiting on a terminate Phase.
16525 @item Wait Child in Term Alt
16526 The task is sleeping waiting for tasks on terminate alternatives to
16527 finish terminating.
16529 @item Accepting RV with @var{taskno}
16530 The task is accepting a rendez-vous with the task @var{taskno}.
16534 Name of the task in the program.
16538 @kindex info task @var{taskno}
16539 @item info task @var{taskno}
16540 This command shows detailled informations on the specified task, as in
16541 the following example:
16546 (@value{GDBP}) info tasks
16547 ID TID P-ID Pri State Name
16548 1 8077880 0 15 Child Activation Wait main_task
16549 * 2 807c468 1 15 Runnable task_1
16550 (@value{GDBP}) info task 2
16551 Ada Task: 0x807c468
16554 Parent: 1 (main_task)
16560 @kindex task@r{ (Ada)}
16561 @cindex current Ada task ID
16562 This command prints the ID of the current task.
16568 (@value{GDBP}) info tasks
16569 ID TID P-ID Pri State Name
16570 1 8077870 0 15 Child Activation Wait main_task
16571 * 2 807c458 1 15 Runnable t
16572 (@value{GDBP}) task
16573 [Current task is 2]
16576 @item task @var{taskno}
16577 @cindex Ada task switching
16578 This command is like the @code{thread @var{thread-id}}
16579 command (@pxref{Threads}). It switches the context of debugging
16580 from the current task to the given task.
16586 (@value{GDBP}) info tasks
16587 ID TID P-ID Pri State Name
16588 1 8077870 0 15 Child Activation Wait main_task
16589 * 2 807c458 1 15 Runnable t
16590 (@value{GDBP}) task 1
16591 [Switching to task 1]
16592 #0 0x8067726 in pthread_cond_wait ()
16594 #0 0x8067726 in pthread_cond_wait ()
16595 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16596 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16597 #3 0x806153e in system.tasking.stages.activate_tasks ()
16598 #4 0x804aacc in un () at un.adb:5
16601 @item break @var{location} task @var{taskno}
16602 @itemx break @var{location} task @var{taskno} if @dots{}
16603 @cindex breakpoints and tasks, in Ada
16604 @cindex task breakpoints, in Ada
16605 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16606 These commands are like the @code{break @dots{} thread @dots{}}
16607 command (@pxref{Thread Stops}). The
16608 @var{location} argument specifies source lines, as described
16609 in @ref{Specify Location}.
16611 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16612 to specify that you only want @value{GDBN} to stop the program when a
16613 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16614 numeric task identifiers assigned by @value{GDBN}, shown in the first
16615 column of the @samp{info tasks} display.
16617 If you do not specify @samp{task @var{taskno}} when you set a
16618 breakpoint, the breakpoint applies to @emph{all} tasks of your
16621 You can use the @code{task} qualifier on conditional breakpoints as
16622 well; in this case, place @samp{task @var{taskno}} before the
16623 breakpoint condition (before the @code{if}).
16631 (@value{GDBP}) info tasks
16632 ID TID P-ID Pri State Name
16633 1 140022020 0 15 Child Activation Wait main_task
16634 2 140045060 1 15 Accept/Select Wait t2
16635 3 140044840 1 15 Runnable t1
16636 * 4 140056040 1 15 Runnable t3
16637 (@value{GDBP}) b 15 task 2
16638 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16639 (@value{GDBP}) cont
16644 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16646 (@value{GDBP}) info tasks
16647 ID TID P-ID Pri State Name
16648 1 140022020 0 15 Child Activation Wait main_task
16649 * 2 140045060 1 15 Runnable t2
16650 3 140044840 1 15 Runnable t1
16651 4 140056040 1 15 Delay Sleep t3
16655 @node Ada Tasks and Core Files
16656 @subsubsection Tasking Support when Debugging Core Files
16657 @cindex Ada tasking and core file debugging
16659 When inspecting a core file, as opposed to debugging a live program,
16660 tasking support may be limited or even unavailable, depending on
16661 the platform being used.
16662 For instance, on x86-linux, the list of tasks is available, but task
16663 switching is not supported.
16665 On certain platforms, the debugger needs to perform some
16666 memory writes in order to provide Ada tasking support. When inspecting
16667 a core file, this means that the core file must be opened with read-write
16668 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16669 Under these circumstances, you should make a backup copy of the core
16670 file before inspecting it with @value{GDBN}.
16672 @node Ravenscar Profile
16673 @subsubsection Tasking Support when using the Ravenscar Profile
16674 @cindex Ravenscar Profile
16676 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16677 specifically designed for systems with safety-critical real-time
16681 @kindex set ravenscar task-switching on
16682 @cindex task switching with program using Ravenscar Profile
16683 @item set ravenscar task-switching on
16684 Allows task switching when debugging a program that uses the Ravenscar
16685 Profile. This is the default.
16687 @kindex set ravenscar task-switching off
16688 @item set ravenscar task-switching off
16689 Turn off task switching when debugging a program that uses the Ravenscar
16690 Profile. This is mostly intended to disable the code that adds support
16691 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16692 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16693 To be effective, this command should be run before the program is started.
16695 @kindex show ravenscar task-switching
16696 @item show ravenscar task-switching
16697 Show whether it is possible to switch from task to task in a program
16698 using the Ravenscar Profile.
16703 @subsubsection Known Peculiarities of Ada Mode
16704 @cindex Ada, problems
16706 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16707 we know of several problems with and limitations of Ada mode in
16709 some of which will be fixed with planned future releases of the debugger
16710 and the GNU Ada compiler.
16714 Static constants that the compiler chooses not to materialize as objects in
16715 storage are invisible to the debugger.
16718 Named parameter associations in function argument lists are ignored (the
16719 argument lists are treated as positional).
16722 Many useful library packages are currently invisible to the debugger.
16725 Fixed-point arithmetic, conversions, input, and output is carried out using
16726 floating-point arithmetic, and may give results that only approximate those on
16730 The GNAT compiler never generates the prefix @code{Standard} for any of
16731 the standard symbols defined by the Ada language. @value{GDBN} knows about
16732 this: it will strip the prefix from names when you use it, and will never
16733 look for a name you have so qualified among local symbols, nor match against
16734 symbols in other packages or subprograms. If you have
16735 defined entities anywhere in your program other than parameters and
16736 local variables whose simple names match names in @code{Standard},
16737 GNAT's lack of qualification here can cause confusion. When this happens,
16738 you can usually resolve the confusion
16739 by qualifying the problematic names with package
16740 @code{Standard} explicitly.
16743 Older versions of the compiler sometimes generate erroneous debugging
16744 information, resulting in the debugger incorrectly printing the value
16745 of affected entities. In some cases, the debugger is able to work
16746 around an issue automatically. In other cases, the debugger is able
16747 to work around the issue, but the work-around has to be specifically
16750 @kindex set ada trust-PAD-over-XVS
16751 @kindex show ada trust-PAD-over-XVS
16754 @item set ada trust-PAD-over-XVS on
16755 Configure GDB to strictly follow the GNAT encoding when computing the
16756 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16757 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16758 a complete description of the encoding used by the GNAT compiler).
16759 This is the default.
16761 @item set ada trust-PAD-over-XVS off
16762 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16763 sometimes prints the wrong value for certain entities, changing @code{ada
16764 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16765 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16766 @code{off}, but this incurs a slight performance penalty, so it is
16767 recommended to leave this setting to @code{on} unless necessary.
16771 @cindex GNAT descriptive types
16772 @cindex GNAT encoding
16773 Internally, the debugger also relies on the compiler following a number
16774 of conventions known as the @samp{GNAT Encoding}, all documented in
16775 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16776 how the debugging information should be generated for certain types.
16777 In particular, this convention makes use of @dfn{descriptive types},
16778 which are artificial types generated purely to help the debugger.
16780 These encodings were defined at a time when the debugging information
16781 format used was not powerful enough to describe some of the more complex
16782 types available in Ada. Since DWARF allows us to express nearly all
16783 Ada features, the long-term goal is to slowly replace these descriptive
16784 types by their pure DWARF equivalent. To facilitate that transition,
16785 a new maintenance option is available to force the debugger to ignore
16786 those descriptive types. It allows the user to quickly evaluate how
16787 well @value{GDBN} works without them.
16791 @kindex maint ada set ignore-descriptive-types
16792 @item maintenance ada set ignore-descriptive-types [on|off]
16793 Control whether the debugger should ignore descriptive types.
16794 The default is not to ignore descriptives types (@code{off}).
16796 @kindex maint ada show ignore-descriptive-types
16797 @item maintenance ada show ignore-descriptive-types
16798 Show if descriptive types are ignored by @value{GDBN}.
16802 @node Unsupported Languages
16803 @section Unsupported Languages
16805 @cindex unsupported languages
16806 @cindex minimal language
16807 In addition to the other fully-supported programming languages,
16808 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16809 It does not represent a real programming language, but provides a set
16810 of capabilities close to what the C or assembly languages provide.
16811 This should allow most simple operations to be performed while debugging
16812 an application that uses a language currently not supported by @value{GDBN}.
16814 If the language is set to @code{auto}, @value{GDBN} will automatically
16815 select this language if the current frame corresponds to an unsupported
16819 @chapter Examining the Symbol Table
16821 The commands described in this chapter allow you to inquire about the
16822 symbols (names of variables, functions and types) defined in your
16823 program. This information is inherent in the text of your program and
16824 does not change as your program executes. @value{GDBN} finds it in your
16825 program's symbol table, in the file indicated when you started @value{GDBN}
16826 (@pxref{File Options, ,Choosing Files}), or by one of the
16827 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16829 @cindex symbol names
16830 @cindex names of symbols
16831 @cindex quoting names
16832 Occasionally, you may need to refer to symbols that contain unusual
16833 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16834 most frequent case is in referring to static variables in other
16835 source files (@pxref{Variables,,Program Variables}). File names
16836 are recorded in object files as debugging symbols, but @value{GDBN} would
16837 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16838 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16839 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16846 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16849 @cindex case-insensitive symbol names
16850 @cindex case sensitivity in symbol names
16851 @kindex set case-sensitive
16852 @item set case-sensitive on
16853 @itemx set case-sensitive off
16854 @itemx set case-sensitive auto
16855 Normally, when @value{GDBN} looks up symbols, it matches their names
16856 with case sensitivity determined by the current source language.
16857 Occasionally, you may wish to control that. The command @code{set
16858 case-sensitive} lets you do that by specifying @code{on} for
16859 case-sensitive matches or @code{off} for case-insensitive ones. If
16860 you specify @code{auto}, case sensitivity is reset to the default
16861 suitable for the source language. The default is case-sensitive
16862 matches for all languages except for Fortran, for which the default is
16863 case-insensitive matches.
16865 @kindex show case-sensitive
16866 @item show case-sensitive
16867 This command shows the current setting of case sensitivity for symbols
16870 @kindex set print type methods
16871 @item set print type methods
16872 @itemx set print type methods on
16873 @itemx set print type methods off
16874 Normally, when @value{GDBN} prints a class, it displays any methods
16875 declared in that class. You can control this behavior either by
16876 passing the appropriate flag to @code{ptype}, or using @command{set
16877 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16878 display the methods; this is the default. Specifying @code{off} will
16879 cause @value{GDBN} to omit the methods.
16881 @kindex show print type methods
16882 @item show print type methods
16883 This command shows the current setting of method display when printing
16886 @kindex set print type typedefs
16887 @item set print type typedefs
16888 @itemx set print type typedefs on
16889 @itemx set print type typedefs off
16891 Normally, when @value{GDBN} prints a class, it displays any typedefs
16892 defined in that class. You can control this behavior either by
16893 passing the appropriate flag to @code{ptype}, or using @command{set
16894 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16895 display the typedef definitions; this is the default. Specifying
16896 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16897 Note that this controls whether the typedef definition itself is
16898 printed, not whether typedef names are substituted when printing other
16901 @kindex show print type typedefs
16902 @item show print type typedefs
16903 This command shows the current setting of typedef display when
16906 @kindex info address
16907 @cindex address of a symbol
16908 @item info address @var{symbol}
16909 Describe where the data for @var{symbol} is stored. For a register
16910 variable, this says which register it is kept in. For a non-register
16911 local variable, this prints the stack-frame offset at which the variable
16914 Note the contrast with @samp{print &@var{symbol}}, which does not work
16915 at all for a register variable, and for a stack local variable prints
16916 the exact address of the current instantiation of the variable.
16918 @kindex info symbol
16919 @cindex symbol from address
16920 @cindex closest symbol and offset for an address
16921 @item info symbol @var{addr}
16922 Print the name of a symbol which is stored at the address @var{addr}.
16923 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16924 nearest symbol and an offset from it:
16927 (@value{GDBP}) info symbol 0x54320
16928 _initialize_vx + 396 in section .text
16932 This is the opposite of the @code{info address} command. You can use
16933 it to find out the name of a variable or a function given its address.
16935 For dynamically linked executables, the name of executable or shared
16936 library containing the symbol is also printed:
16939 (@value{GDBP}) info symbol 0x400225
16940 _start + 5 in section .text of /tmp/a.out
16941 (@value{GDBP}) info symbol 0x2aaaac2811cf
16942 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16947 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16948 Demangle @var{name}.
16949 If @var{language} is provided it is the name of the language to demangle
16950 @var{name} in. Otherwise @var{name} is demangled in the current language.
16952 The @samp{--} option specifies the end of options,
16953 and is useful when @var{name} begins with a dash.
16955 The parameter @code{demangle-style} specifies how to interpret the kind
16956 of mangling used. @xref{Print Settings}.
16959 @item whatis[/@var{flags}] [@var{arg}]
16960 Print the data type of @var{arg}, which can be either an expression
16961 or a name of a data type. With no argument, print the data type of
16962 @code{$}, the last value in the value history.
16964 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16965 is not actually evaluated, and any side-effecting operations (such as
16966 assignments or function calls) inside it do not take place.
16968 If @var{arg} is a variable or an expression, @code{whatis} prints its
16969 literal type as it is used in the source code. If the type was
16970 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16971 the data type underlying the @code{typedef}. If the type of the
16972 variable or the expression is a compound data type, such as
16973 @code{struct} or @code{class}, @code{whatis} never prints their
16974 fields or methods. It just prints the @code{struct}/@code{class}
16975 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16976 such a compound data type, use @code{ptype}.
16978 If @var{arg} is a type name that was defined using @code{typedef},
16979 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16980 Unrolling means that @code{whatis} will show the underlying type used
16981 in the @code{typedef} declaration of @var{arg}. However, if that
16982 underlying type is also a @code{typedef}, @code{whatis} will not
16985 For C code, the type names may also have the form @samp{class
16986 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16987 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16989 @var{flags} can be used to modify how the type is displayed.
16990 Available flags are:
16994 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16995 parameters and typedefs defined in a class when printing the class'
16996 members. The @code{/r} flag disables this.
16999 Do not print methods defined in the class.
17002 Print methods defined in the class. This is the default, but the flag
17003 exists in case you change the default with @command{set print type methods}.
17006 Do not print typedefs defined in the class. Note that this controls
17007 whether the typedef definition itself is printed, not whether typedef
17008 names are substituted when printing other types.
17011 Print typedefs defined in the class. This is the default, but the flag
17012 exists in case you change the default with @command{set print type typedefs}.
17016 @item ptype[/@var{flags}] [@var{arg}]
17017 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17018 detailed description of the type, instead of just the name of the type.
17019 @xref{Expressions, ,Expressions}.
17021 Contrary to @code{whatis}, @code{ptype} always unrolls any
17022 @code{typedef}s in its argument declaration, whether the argument is
17023 a variable, expression, or a data type. This means that @code{ptype}
17024 of a variable or an expression will not print literally its type as
17025 present in the source code---use @code{whatis} for that. @code{typedef}s at
17026 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17027 fields, methods and inner @code{class typedef}s of @code{struct}s,
17028 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17030 For example, for this variable declaration:
17033 typedef double real_t;
17034 struct complex @{ real_t real; double imag; @};
17035 typedef struct complex complex_t;
17037 real_t *real_pointer_var;
17041 the two commands give this output:
17045 (@value{GDBP}) whatis var
17047 (@value{GDBP}) ptype var
17048 type = struct complex @{
17052 (@value{GDBP}) whatis complex_t
17053 type = struct complex
17054 (@value{GDBP}) whatis struct complex
17055 type = struct complex
17056 (@value{GDBP}) ptype struct complex
17057 type = struct complex @{
17061 (@value{GDBP}) whatis real_pointer_var
17063 (@value{GDBP}) ptype real_pointer_var
17069 As with @code{whatis}, using @code{ptype} without an argument refers to
17070 the type of @code{$}, the last value in the value history.
17072 @cindex incomplete type
17073 Sometimes, programs use opaque data types or incomplete specifications
17074 of complex data structure. If the debug information included in the
17075 program does not allow @value{GDBN} to display a full declaration of
17076 the data type, it will say @samp{<incomplete type>}. For example,
17077 given these declarations:
17081 struct foo *fooptr;
17085 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17088 (@value{GDBP}) ptype foo
17089 $1 = <incomplete type>
17093 ``Incomplete type'' is C terminology for data types that are not
17094 completely specified.
17097 @item info types @var{regexp}
17099 Print a brief description of all types whose names match the regular
17100 expression @var{regexp} (or all types in your program, if you supply
17101 no argument). Each complete typename is matched as though it were a
17102 complete line; thus, @samp{i type value} gives information on all
17103 types in your program whose names include the string @code{value}, but
17104 @samp{i type ^value$} gives information only on types whose complete
17105 name is @code{value}.
17107 This command differs from @code{ptype} in two ways: first, like
17108 @code{whatis}, it does not print a detailed description; second, it
17109 lists all source files where a type is defined.
17111 @kindex info type-printers
17112 @item info type-printers
17113 Versions of @value{GDBN} that ship with Python scripting enabled may
17114 have ``type printers'' available. When using @command{ptype} or
17115 @command{whatis}, these printers are consulted when the name of a type
17116 is needed. @xref{Type Printing API}, for more information on writing
17119 @code{info type-printers} displays all the available type printers.
17121 @kindex enable type-printer
17122 @kindex disable type-printer
17123 @item enable type-printer @var{name}@dots{}
17124 @item disable type-printer @var{name}@dots{}
17125 These commands can be used to enable or disable type printers.
17128 @cindex local variables
17129 @item info scope @var{location}
17130 List all the variables local to a particular scope. This command
17131 accepts a @var{location} argument---a function name, a source line, or
17132 an address preceded by a @samp{*}, and prints all the variables local
17133 to the scope defined by that location. (@xref{Specify Location}, for
17134 details about supported forms of @var{location}.) For example:
17137 (@value{GDBP}) @b{info scope command_line_handler}
17138 Scope for command_line_handler:
17139 Symbol rl is an argument at stack/frame offset 8, length 4.
17140 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17141 Symbol linelength is in static storage at address 0x150a1c, length 4.
17142 Symbol p is a local variable in register $esi, length 4.
17143 Symbol p1 is a local variable in register $ebx, length 4.
17144 Symbol nline is a local variable in register $edx, length 4.
17145 Symbol repeat is a local variable at frame offset -8, length 4.
17149 This command is especially useful for determining what data to collect
17150 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17153 @kindex info source
17155 Show information about the current source file---that is, the source file for
17156 the function containing the current point of execution:
17159 the name of the source file, and the directory containing it,
17161 the directory it was compiled in,
17163 its length, in lines,
17165 which programming language it is written in,
17167 if the debug information provides it, the program that compiled the file
17168 (which may include, e.g., the compiler version and command line arguments),
17170 whether the executable includes debugging information for that file, and
17171 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17173 whether the debugging information includes information about
17174 preprocessor macros.
17178 @kindex info sources
17180 Print the names of all source files in your program for which there is
17181 debugging information, organized into two lists: files whose symbols
17182 have already been read, and files whose symbols will be read when needed.
17184 @kindex info functions
17185 @item info functions
17186 Print the names and data types of all defined functions.
17188 @item info functions @var{regexp}
17189 Print the names and data types of all defined functions
17190 whose names contain a match for regular expression @var{regexp}.
17191 Thus, @samp{info fun step} finds all functions whose names
17192 include @code{step}; @samp{info fun ^step} finds those whose names
17193 start with @code{step}. If a function name contains characters
17194 that conflict with the regular expression language (e.g.@:
17195 @samp{operator*()}), they may be quoted with a backslash.
17197 @kindex info variables
17198 @item info variables
17199 Print the names and data types of all variables that are defined
17200 outside of functions (i.e.@: excluding local variables).
17202 @item info variables @var{regexp}
17203 Print the names and data types of all variables (except for local
17204 variables) whose names contain a match for regular expression
17207 @kindex info classes
17208 @cindex Objective-C, classes and selectors
17210 @itemx info classes @var{regexp}
17211 Display all Objective-C classes in your program, or
17212 (with the @var{regexp} argument) all those matching a particular regular
17215 @kindex info selectors
17216 @item info selectors
17217 @itemx info selectors @var{regexp}
17218 Display all Objective-C selectors in your program, or
17219 (with the @var{regexp} argument) all those matching a particular regular
17223 This was never implemented.
17224 @kindex info methods
17226 @itemx info methods @var{regexp}
17227 The @code{info methods} command permits the user to examine all defined
17228 methods within C@t{++} program, or (with the @var{regexp} argument) a
17229 specific set of methods found in the various C@t{++} classes. Many
17230 C@t{++} classes provide a large number of methods. Thus, the output
17231 from the @code{ptype} command can be overwhelming and hard to use. The
17232 @code{info-methods} command filters the methods, printing only those
17233 which match the regular-expression @var{regexp}.
17236 @cindex opaque data types
17237 @kindex set opaque-type-resolution
17238 @item set opaque-type-resolution on
17239 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17240 declared as a pointer to a @code{struct}, @code{class}, or
17241 @code{union}---for example, @code{struct MyType *}---that is used in one
17242 source file although the full declaration of @code{struct MyType} is in
17243 another source file. The default is on.
17245 A change in the setting of this subcommand will not take effect until
17246 the next time symbols for a file are loaded.
17248 @item set opaque-type-resolution off
17249 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17250 is printed as follows:
17252 @{<no data fields>@}
17255 @kindex show opaque-type-resolution
17256 @item show opaque-type-resolution
17257 Show whether opaque types are resolved or not.
17259 @kindex set print symbol-loading
17260 @cindex print messages when symbols are loaded
17261 @item set print symbol-loading
17262 @itemx set print symbol-loading full
17263 @itemx set print symbol-loading brief
17264 @itemx set print symbol-loading off
17265 The @code{set print symbol-loading} command allows you to control the
17266 printing of messages when @value{GDBN} loads symbol information.
17267 By default a message is printed for the executable and one for each
17268 shared library, and normally this is what you want. However, when
17269 debugging apps with large numbers of shared libraries these messages
17271 When set to @code{brief} a message is printed for each executable,
17272 and when @value{GDBN} loads a collection of shared libraries at once
17273 it will only print one message regardless of the number of shared
17274 libraries. When set to @code{off} no messages are printed.
17276 @kindex show print symbol-loading
17277 @item show print symbol-loading
17278 Show whether messages will be printed when a @value{GDBN} command
17279 entered from the keyboard causes symbol information to be loaded.
17281 @kindex maint print symbols
17282 @cindex symbol dump
17283 @kindex maint print psymbols
17284 @cindex partial symbol dump
17285 @kindex maint print msymbols
17286 @cindex minimal symbol dump
17287 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17288 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17289 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17290 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17291 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17292 Write a dump of debugging symbol data into the file @var{filename} or
17293 the terminal if @var{filename} is unspecified.
17294 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17296 If @code{-pc @var{address}} is specified, only dump symbols for the file
17297 with code at that address. Note that @var{address} may be a symbol like
17299 If @code{-source @var{source}} is specified, only dump symbols for that
17302 These commands are used to debug the @value{GDBN} symbol-reading code.
17303 These commands do not modify internal @value{GDBN} state, therefore
17304 @samp{maint print symbols} will only print symbols for already expanded symbol
17306 You can use the command @code{info sources} to find out which files these are.
17307 If you use @samp{maint print psymbols} instead, the dump shows information
17308 about symbols that @value{GDBN} only knows partially---that is, symbols
17309 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17310 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17313 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17314 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17316 @kindex maint info symtabs
17317 @kindex maint info psymtabs
17318 @cindex listing @value{GDBN}'s internal symbol tables
17319 @cindex symbol tables, listing @value{GDBN}'s internal
17320 @cindex full symbol tables, listing @value{GDBN}'s internal
17321 @cindex partial symbol tables, listing @value{GDBN}'s internal
17322 @item maint info symtabs @r{[} @var{regexp} @r{]}
17323 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17325 List the @code{struct symtab} or @code{struct partial_symtab}
17326 structures whose names match @var{regexp}. If @var{regexp} is not
17327 given, list them all. The output includes expressions which you can
17328 copy into a @value{GDBN} debugging this one to examine a particular
17329 structure in more detail. For example:
17332 (@value{GDBP}) maint info psymtabs dwarf2read
17333 @{ objfile /home/gnu/build/gdb/gdb
17334 ((struct objfile *) 0x82e69d0)
17335 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17336 ((struct partial_symtab *) 0x8474b10)
17339 text addresses 0x814d3c8 -- 0x8158074
17340 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17341 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17342 dependencies (none)
17345 (@value{GDBP}) maint info symtabs
17349 We see that there is one partial symbol table whose filename contains
17350 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17351 and we see that @value{GDBN} has not read in any symtabs yet at all.
17352 If we set a breakpoint on a function, that will cause @value{GDBN} to
17353 read the symtab for the compilation unit containing that function:
17356 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17357 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17359 (@value{GDBP}) maint info symtabs
17360 @{ objfile /home/gnu/build/gdb/gdb
17361 ((struct objfile *) 0x82e69d0)
17362 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17363 ((struct symtab *) 0x86c1f38)
17366 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17367 linetable ((struct linetable *) 0x8370fa0)
17368 debugformat DWARF 2
17374 @kindex maint info line-table
17375 @cindex listing @value{GDBN}'s internal line tables
17376 @cindex line tables, listing @value{GDBN}'s internal
17377 @item maint info line-table @r{[} @var{regexp} @r{]}
17379 List the @code{struct linetable} from all @code{struct symtab}
17380 instances whose name matches @var{regexp}. If @var{regexp} is not
17381 given, list the @code{struct linetable} from all @code{struct symtab}.
17383 @kindex maint set symbol-cache-size
17384 @cindex symbol cache size
17385 @item maint set symbol-cache-size @var{size}
17386 Set the size of the symbol cache to @var{size}.
17387 The default size is intended to be good enough for debugging
17388 most applications. This option exists to allow for experimenting
17389 with different sizes.
17391 @kindex maint show symbol-cache-size
17392 @item maint show symbol-cache-size
17393 Show the size of the symbol cache.
17395 @kindex maint print symbol-cache
17396 @cindex symbol cache, printing its contents
17397 @item maint print symbol-cache
17398 Print the contents of the symbol cache.
17399 This is useful when debugging symbol cache issues.
17401 @kindex maint print symbol-cache-statistics
17402 @cindex symbol cache, printing usage statistics
17403 @item maint print symbol-cache-statistics
17404 Print symbol cache usage statistics.
17405 This helps determine how well the cache is being utilized.
17407 @kindex maint flush-symbol-cache
17408 @cindex symbol cache, flushing
17409 @item maint flush-symbol-cache
17410 Flush the contents of the symbol cache, all entries are removed.
17411 This command is useful when debugging the symbol cache.
17412 It is also useful when collecting performance data.
17417 @chapter Altering Execution
17419 Once you think you have found an error in your program, you might want to
17420 find out for certain whether correcting the apparent error would lead to
17421 correct results in the rest of the run. You can find the answer by
17422 experiment, using the @value{GDBN} features for altering execution of the
17425 For example, you can store new values into variables or memory
17426 locations, give your program a signal, restart it at a different
17427 address, or even return prematurely from a function.
17430 * Assignment:: Assignment to variables
17431 * Jumping:: Continuing at a different address
17432 * Signaling:: Giving your program a signal
17433 * Returning:: Returning from a function
17434 * Calling:: Calling your program's functions
17435 * Patching:: Patching your program
17436 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17440 @section Assignment to Variables
17443 @cindex setting variables
17444 To alter the value of a variable, evaluate an assignment expression.
17445 @xref{Expressions, ,Expressions}. For example,
17452 stores the value 4 into the variable @code{x}, and then prints the
17453 value of the assignment expression (which is 4).
17454 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17455 information on operators in supported languages.
17457 @kindex set variable
17458 @cindex variables, setting
17459 If you are not interested in seeing the value of the assignment, use the
17460 @code{set} command instead of the @code{print} command. @code{set} is
17461 really the same as @code{print} except that the expression's value is
17462 not printed and is not put in the value history (@pxref{Value History,
17463 ,Value History}). The expression is evaluated only for its effects.
17465 If the beginning of the argument string of the @code{set} command
17466 appears identical to a @code{set} subcommand, use the @code{set
17467 variable} command instead of just @code{set}. This command is identical
17468 to @code{set} except for its lack of subcommands. For example, if your
17469 program has a variable @code{width}, you get an error if you try to set
17470 a new value with just @samp{set width=13}, because @value{GDBN} has the
17471 command @code{set width}:
17474 (@value{GDBP}) whatis width
17476 (@value{GDBP}) p width
17478 (@value{GDBP}) set width=47
17479 Invalid syntax in expression.
17483 The invalid expression, of course, is @samp{=47}. In
17484 order to actually set the program's variable @code{width}, use
17487 (@value{GDBP}) set var width=47
17490 Because the @code{set} command has many subcommands that can conflict
17491 with the names of program variables, it is a good idea to use the
17492 @code{set variable} command instead of just @code{set}. For example, if
17493 your program has a variable @code{g}, you run into problems if you try
17494 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17495 the command @code{set gnutarget}, abbreviated @code{set g}:
17499 (@value{GDBP}) whatis g
17503 (@value{GDBP}) set g=4
17507 The program being debugged has been started already.
17508 Start it from the beginning? (y or n) y
17509 Starting program: /home/smith/cc_progs/a.out
17510 "/home/smith/cc_progs/a.out": can't open to read symbols:
17511 Invalid bfd target.
17512 (@value{GDBP}) show g
17513 The current BFD target is "=4".
17518 The program variable @code{g} did not change, and you silently set the
17519 @code{gnutarget} to an invalid value. In order to set the variable
17523 (@value{GDBP}) set var g=4
17526 @value{GDBN} allows more implicit conversions in assignments than C; you can
17527 freely store an integer value into a pointer variable or vice versa,
17528 and you can convert any structure to any other structure that is the
17529 same length or shorter.
17530 @comment FIXME: how do structs align/pad in these conversions?
17531 @comment /doc@cygnus.com 18dec1990
17533 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17534 construct to generate a value of specified type at a specified address
17535 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17536 to memory location @code{0x83040} as an integer (which implies a certain size
17537 and representation in memory), and
17540 set @{int@}0x83040 = 4
17544 stores the value 4 into that memory location.
17547 @section Continuing at a Different Address
17549 Ordinarily, when you continue your program, you do so at the place where
17550 it stopped, with the @code{continue} command. You can instead continue at
17551 an address of your own choosing, with the following commands:
17555 @kindex j @r{(@code{jump})}
17556 @item jump @var{location}
17557 @itemx j @var{location}
17558 Resume execution at @var{location}. Execution stops again immediately
17559 if there is a breakpoint there. @xref{Specify Location}, for a description
17560 of the different forms of @var{location}. It is common
17561 practice to use the @code{tbreak} command in conjunction with
17562 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17564 The @code{jump} command does not change the current stack frame, or
17565 the stack pointer, or the contents of any memory location or any
17566 register other than the program counter. If @var{location} is in
17567 a different function from the one currently executing, the results may
17568 be bizarre if the two functions expect different patterns of arguments or
17569 of local variables. For this reason, the @code{jump} command requests
17570 confirmation if the specified line is not in the function currently
17571 executing. However, even bizarre results are predictable if you are
17572 well acquainted with the machine-language code of your program.
17575 On many systems, you can get much the same effect as the @code{jump}
17576 command by storing a new value into the register @code{$pc}. The
17577 difference is that this does not start your program running; it only
17578 changes the address of where it @emph{will} run when you continue. For
17586 makes the next @code{continue} command or stepping command execute at
17587 address @code{0x485}, rather than at the address where your program stopped.
17588 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17590 The most common occasion to use the @code{jump} command is to back
17591 up---perhaps with more breakpoints set---over a portion of a program
17592 that has already executed, in order to examine its execution in more
17597 @section Giving your Program a Signal
17598 @cindex deliver a signal to a program
17602 @item signal @var{signal}
17603 Resume execution where your program is stopped, but immediately give it the
17604 signal @var{signal}. The @var{signal} can be the name or the number of a
17605 signal. For example, on many systems @code{signal 2} and @code{signal
17606 SIGINT} are both ways of sending an interrupt signal.
17608 Alternatively, if @var{signal} is zero, continue execution without
17609 giving a signal. This is useful when your program stopped on account of
17610 a signal and would ordinarily see the signal when resumed with the
17611 @code{continue} command; @samp{signal 0} causes it to resume without a
17614 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17615 delivered to the currently selected thread, not the thread that last
17616 reported a stop. This includes the situation where a thread was
17617 stopped due to a signal. So if you want to continue execution
17618 suppressing the signal that stopped a thread, you should select that
17619 same thread before issuing the @samp{signal 0} command. If you issue
17620 the @samp{signal 0} command with another thread as the selected one,
17621 @value{GDBN} detects that and asks for confirmation.
17623 Invoking the @code{signal} command is not the same as invoking the
17624 @code{kill} utility from the shell. Sending a signal with @code{kill}
17625 causes @value{GDBN} to decide what to do with the signal depending on
17626 the signal handling tables (@pxref{Signals}). The @code{signal} command
17627 passes the signal directly to your program.
17629 @code{signal} does not repeat when you press @key{RET} a second time
17630 after executing the command.
17632 @kindex queue-signal
17633 @item queue-signal @var{signal}
17634 Queue @var{signal} to be delivered immediately to the current thread
17635 when execution of the thread resumes. The @var{signal} can be the name or
17636 the number of a signal. For example, on many systems @code{signal 2} and
17637 @code{signal SIGINT} are both ways of sending an interrupt signal.
17638 The handling of the signal must be set to pass the signal to the program,
17639 otherwise @value{GDBN} will report an error.
17640 You can control the handling of signals from @value{GDBN} with the
17641 @code{handle} command (@pxref{Signals}).
17643 Alternatively, if @var{signal} is zero, any currently queued signal
17644 for the current thread is discarded and when execution resumes no signal
17645 will be delivered. This is useful when your program stopped on account
17646 of a signal and would ordinarily see the signal when resumed with the
17647 @code{continue} command.
17649 This command differs from the @code{signal} command in that the signal
17650 is just queued, execution is not resumed. And @code{queue-signal} cannot
17651 be used to pass a signal whose handling state has been set to @code{nopass}
17656 @xref{stepping into signal handlers}, for information on how stepping
17657 commands behave when the thread has a signal queued.
17660 @section Returning from a Function
17663 @cindex returning from a function
17666 @itemx return @var{expression}
17667 You can cancel execution of a function call with the @code{return}
17668 command. If you give an
17669 @var{expression} argument, its value is used as the function's return
17673 When you use @code{return}, @value{GDBN} discards the selected stack frame
17674 (and all frames within it). You can think of this as making the
17675 discarded frame return prematurely. If you wish to specify a value to
17676 be returned, give that value as the argument to @code{return}.
17678 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17679 Frame}), and any other frames inside of it, leaving its caller as the
17680 innermost remaining frame. That frame becomes selected. The
17681 specified value is stored in the registers used for returning values
17684 The @code{return} command does not resume execution; it leaves the
17685 program stopped in the state that would exist if the function had just
17686 returned. In contrast, the @code{finish} command (@pxref{Continuing
17687 and Stepping, ,Continuing and Stepping}) resumes execution until the
17688 selected stack frame returns naturally.
17690 @value{GDBN} needs to know how the @var{expression} argument should be set for
17691 the inferior. The concrete registers assignment depends on the OS ABI and the
17692 type being returned by the selected stack frame. For example it is common for
17693 OS ABI to return floating point values in FPU registers while integer values in
17694 CPU registers. Still some ABIs return even floating point values in CPU
17695 registers. Larger integer widths (such as @code{long long int}) also have
17696 specific placement rules. @value{GDBN} already knows the OS ABI from its
17697 current target so it needs to find out also the type being returned to make the
17698 assignment into the right register(s).
17700 Normally, the selected stack frame has debug info. @value{GDBN} will always
17701 use the debug info instead of the implicit type of @var{expression} when the
17702 debug info is available. For example, if you type @kbd{return -1}, and the
17703 function in the current stack frame is declared to return a @code{long long
17704 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17705 into a @code{long long int}:
17708 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17710 (@value{GDBP}) return -1
17711 Make func return now? (y or n) y
17712 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17713 43 printf ("result=%lld\n", func ());
17717 However, if the selected stack frame does not have a debug info, e.g., if the
17718 function was compiled without debug info, @value{GDBN} has to find out the type
17719 to return from user. Specifying a different type by mistake may set the value
17720 in different inferior registers than the caller code expects. For example,
17721 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17722 of a @code{long long int} result for a debug info less function (on 32-bit
17723 architectures). Therefore the user is required to specify the return type by
17724 an appropriate cast explicitly:
17727 Breakpoint 2, 0x0040050b in func ()
17728 (@value{GDBP}) return -1
17729 Return value type not available for selected stack frame.
17730 Please use an explicit cast of the value to return.
17731 (@value{GDBP}) return (long long int) -1
17732 Make selected stack frame return now? (y or n) y
17733 #0 0x00400526 in main ()
17738 @section Calling Program Functions
17741 @cindex calling functions
17742 @cindex inferior functions, calling
17743 @item print @var{expr}
17744 Evaluate the expression @var{expr} and display the resulting value.
17745 The expression may include calls to functions in the program being
17749 @item call @var{expr}
17750 Evaluate the expression @var{expr} without displaying @code{void}
17753 You can use this variant of the @code{print} command if you want to
17754 execute a function from your program that does not return anything
17755 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17756 with @code{void} returned values that @value{GDBN} will otherwise
17757 print. If the result is not void, it is printed and saved in the
17761 It is possible for the function you call via the @code{print} or
17762 @code{call} command to generate a signal (e.g., if there's a bug in
17763 the function, or if you passed it incorrect arguments). What happens
17764 in that case is controlled by the @code{set unwindonsignal} command.
17766 Similarly, with a C@t{++} program it is possible for the function you
17767 call via the @code{print} or @code{call} command to generate an
17768 exception that is not handled due to the constraints of the dummy
17769 frame. In this case, any exception that is raised in the frame, but has
17770 an out-of-frame exception handler will not be found. GDB builds a
17771 dummy-frame for the inferior function call, and the unwinder cannot
17772 seek for exception handlers outside of this dummy-frame. What happens
17773 in that case is controlled by the
17774 @code{set unwind-on-terminating-exception} command.
17777 @item set unwindonsignal
17778 @kindex set unwindonsignal
17779 @cindex unwind stack in called functions
17780 @cindex call dummy stack unwinding
17781 Set unwinding of the stack if a signal is received while in a function
17782 that @value{GDBN} called in the program being debugged. If set to on,
17783 @value{GDBN} unwinds the stack it created for the call and restores
17784 the context to what it was before the call. If set to off (the
17785 default), @value{GDBN} stops in the frame where the signal was
17788 @item show unwindonsignal
17789 @kindex show unwindonsignal
17790 Show the current setting of stack unwinding in the functions called by
17793 @item set unwind-on-terminating-exception
17794 @kindex set unwind-on-terminating-exception
17795 @cindex unwind stack in called functions with unhandled exceptions
17796 @cindex call dummy stack unwinding on unhandled exception.
17797 Set unwinding of the stack if a C@t{++} exception is raised, but left
17798 unhandled while in a function that @value{GDBN} called in the program being
17799 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17800 it created for the call and restores the context to what it was before
17801 the call. If set to off, @value{GDBN} the exception is delivered to
17802 the default C@t{++} exception handler and the inferior terminated.
17804 @item show unwind-on-terminating-exception
17805 @kindex show unwind-on-terminating-exception
17806 Show the current setting of stack unwinding in the functions called by
17811 @cindex weak alias functions
17812 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17813 for another function. In such case, @value{GDBN} might not pick up
17814 the type information, including the types of the function arguments,
17815 which causes @value{GDBN} to call the inferior function incorrectly.
17816 As a result, the called function will function erroneously and may
17817 even crash. A solution to that is to use the name of the aliased
17821 @section Patching Programs
17823 @cindex patching binaries
17824 @cindex writing into executables
17825 @cindex writing into corefiles
17827 By default, @value{GDBN} opens the file containing your program's
17828 executable code (or the corefile) read-only. This prevents accidental
17829 alterations to machine code; but it also prevents you from intentionally
17830 patching your program's binary.
17832 If you'd like to be able to patch the binary, you can specify that
17833 explicitly with the @code{set write} command. For example, you might
17834 want to turn on internal debugging flags, or even to make emergency
17840 @itemx set write off
17841 If you specify @samp{set write on}, @value{GDBN} opens executable and
17842 core files for both reading and writing; if you specify @kbd{set write
17843 off} (the default), @value{GDBN} opens them read-only.
17845 If you have already loaded a file, you must load it again (using the
17846 @code{exec-file} or @code{core-file} command) after changing @code{set
17847 write}, for your new setting to take effect.
17851 Display whether executable files and core files are opened for writing
17852 as well as reading.
17855 @node Compiling and Injecting Code
17856 @section Compiling and injecting code in @value{GDBN}
17857 @cindex injecting code
17858 @cindex writing into executables
17859 @cindex compiling code
17861 @value{GDBN} supports on-demand compilation and code injection into
17862 programs running under @value{GDBN}. GCC 5.0 or higher built with
17863 @file{libcc1.so} must be installed for this functionality to be enabled.
17864 This functionality is implemented with the following commands.
17867 @kindex compile code
17868 @item compile code @var{source-code}
17869 @itemx compile code -raw @var{--} @var{source-code}
17870 Compile @var{source-code} with the compiler language found as the current
17871 language in @value{GDBN} (@pxref{Languages}). If compilation and
17872 injection is not supported with the current language specified in
17873 @value{GDBN}, or the compiler does not support this feature, an error
17874 message will be printed. If @var{source-code} compiles and links
17875 successfully, @value{GDBN} will load the object-code emitted,
17876 and execute it within the context of the currently selected inferior.
17877 It is important to note that the compiled code is executed immediately.
17878 After execution, the compiled code is removed from @value{GDBN} and any
17879 new types or variables you have defined will be deleted.
17881 The command allows you to specify @var{source-code} in two ways.
17882 The simplest method is to provide a single line of code to the command.
17886 compile code printf ("hello world\n");
17889 If you specify options on the command line as well as source code, they
17890 may conflict. The @samp{--} delimiter can be used to separate options
17891 from actual source code. E.g.:
17894 compile code -r -- printf ("hello world\n");
17897 Alternatively you can enter source code as multiple lines of text. To
17898 enter this mode, invoke the @samp{compile code} command without any text
17899 following the command. This will start the multiple-line editor and
17900 allow you to type as many lines of source code as required. When you
17901 have completed typing, enter @samp{end} on its own line to exit the
17906 >printf ("hello\n");
17907 >printf ("world\n");
17911 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17912 provided @var{source-code} in a callable scope. In this case, you must
17913 specify the entry point of the code by defining a function named
17914 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17915 inferior. Using @samp{-raw} option may be needed for example when
17916 @var{source-code} requires @samp{#include} lines which may conflict with
17917 inferior symbols otherwise.
17919 @kindex compile file
17920 @item compile file @var{filename}
17921 @itemx compile file -raw @var{filename}
17922 Like @code{compile code}, but take the source code from @var{filename}.
17925 compile file /home/user/example.c
17930 @item compile print @var{expr}
17931 @itemx compile print /@var{f} @var{expr}
17932 Compile and execute @var{expr} with the compiler language found as the
17933 current language in @value{GDBN} (@pxref{Languages}). By default the
17934 value of @var{expr} is printed in a format appropriate to its data type;
17935 you can choose a different format by specifying @samp{/@var{f}}, where
17936 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17939 @item compile print
17940 @itemx compile print /@var{f}
17941 @cindex reprint the last value
17942 Alternatively you can enter the expression (source code producing it) as
17943 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17944 command without any text following the command. This will start the
17945 multiple-line editor.
17949 The process of compiling and injecting the code can be inspected using:
17952 @anchor{set debug compile}
17953 @item set debug compile
17954 @cindex compile command debugging info
17955 Turns on or off display of @value{GDBN} process of compiling and
17956 injecting the code. The default is off.
17958 @item show debug compile
17959 Displays the current state of displaying @value{GDBN} process of
17960 compiling and injecting the code.
17963 @subsection Compilation options for the @code{compile} command
17965 @value{GDBN} needs to specify the right compilation options for the code
17966 to be injected, in part to make its ABI compatible with the inferior
17967 and in part to make the injected code compatible with @value{GDBN}'s
17971 The options used, in increasing precedence:
17974 @item target architecture and OS options (@code{gdbarch})
17975 These options depend on target processor type and target operating
17976 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17977 (@code{-m64}) compilation option.
17979 @item compilation options recorded in the target
17980 @value{NGCC} (since version 4.7) stores the options used for compilation
17981 into @code{DW_AT_producer} part of DWARF debugging information according
17982 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17983 explicitly specify @code{-g} during inferior compilation otherwise
17984 @value{NGCC} produces no DWARF. This feature is only relevant for
17985 platforms where @code{-g} produces DWARF by default, otherwise one may
17986 try to enforce DWARF by using @code{-gdwarf-4}.
17988 @item compilation options set by @code{set compile-args}
17992 You can override compilation options using the following command:
17995 @item set compile-args
17996 @cindex compile command options override
17997 Set compilation options used for compiling and injecting code with the
17998 @code{compile} commands. These options override any conflicting ones
17999 from the target architecture and/or options stored during inferior
18002 @item show compile-args
18003 Displays the current state of compilation options override.
18004 This does not show all the options actually used during compilation,
18005 use @ref{set debug compile} for that.
18008 @subsection Caveats when using the @code{compile} command
18010 There are a few caveats to keep in mind when using the @code{compile}
18011 command. As the caveats are different per language, the table below
18012 highlights specific issues on a per language basis.
18015 @item C code examples and caveats
18016 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18017 attempt to compile the source code with a @samp{C} compiler. The source
18018 code provided to the @code{compile} command will have much the same
18019 access to variables and types as it normally would if it were part of
18020 the program currently being debugged in @value{GDBN}.
18022 Below is a sample program that forms the basis of the examples that
18023 follow. This program has been compiled and loaded into @value{GDBN},
18024 much like any other normal debugging session.
18027 void function1 (void)
18030 printf ("function 1\n");
18033 void function2 (void)
18048 For the purposes of the examples in this section, the program above has
18049 been compiled, loaded into @value{GDBN}, stopped at the function
18050 @code{main}, and @value{GDBN} is awaiting input from the user.
18052 To access variables and types for any program in @value{GDBN}, the
18053 program must be compiled and packaged with debug information. The
18054 @code{compile} command is not an exception to this rule. Without debug
18055 information, you can still use the @code{compile} command, but you will
18056 be very limited in what variables and types you can access.
18058 So with that in mind, the example above has been compiled with debug
18059 information enabled. The @code{compile} command will have access to
18060 all variables and types (except those that may have been optimized
18061 out). Currently, as @value{GDBN} has stopped the program in the
18062 @code{main} function, the @code{compile} command would have access to
18063 the variable @code{k}. You could invoke the @code{compile} command
18064 and type some source code to set the value of @code{k}. You can also
18065 read it, or do anything with that variable you would normally do in
18066 @code{C}. Be aware that changes to inferior variables in the
18067 @code{compile} command are persistent. In the following example:
18070 compile code k = 3;
18074 the variable @code{k} is now 3. It will retain that value until
18075 something else in the example program changes it, or another
18076 @code{compile} command changes it.
18078 Normal scope and access rules apply to source code compiled and
18079 injected by the @code{compile} command. In the example, the variables
18080 @code{j} and @code{k} are not accessible yet, because the program is
18081 currently stopped in the @code{main} function, where these variables
18082 are not in scope. Therefore, the following command
18085 compile code j = 3;
18089 will result in a compilation error message.
18091 Once the program is continued, execution will bring these variables in
18092 scope, and they will become accessible; then the code you specify via
18093 the @code{compile} command will be able to access them.
18095 You can create variables and types with the @code{compile} command as
18096 part of your source code. Variables and types that are created as part
18097 of the @code{compile} command are not visible to the rest of the program for
18098 the duration of its run. This example is valid:
18101 compile code int ff = 5; printf ("ff is %d\n", ff);
18104 However, if you were to type the following into @value{GDBN} after that
18105 command has completed:
18108 compile code printf ("ff is %d\n'', ff);
18112 a compiler error would be raised as the variable @code{ff} no longer
18113 exists. Object code generated and injected by the @code{compile}
18114 command is removed when its execution ends. Caution is advised
18115 when assigning to program variables values of variables created by the
18116 code submitted to the @code{compile} command. This example is valid:
18119 compile code int ff = 5; k = ff;
18122 The value of the variable @code{ff} is assigned to @code{k}. The variable
18123 @code{k} does not require the existence of @code{ff} to maintain the value
18124 it has been assigned. However, pointers require particular care in
18125 assignment. If the source code compiled with the @code{compile} command
18126 changed the address of a pointer in the example program, perhaps to a
18127 variable created in the @code{compile} command, that pointer would point
18128 to an invalid location when the command exits. The following example
18129 would likely cause issues with your debugged program:
18132 compile code int ff = 5; p = &ff;
18135 In this example, @code{p} would point to @code{ff} when the
18136 @code{compile} command is executing the source code provided to it.
18137 However, as variables in the (example) program persist with their
18138 assigned values, the variable @code{p} would point to an invalid
18139 location when the command exists. A general rule should be followed
18140 in that you should either assign @code{NULL} to any assigned pointers,
18141 or restore a valid location to the pointer before the command exits.
18143 Similar caution must be exercised with any structs, unions, and typedefs
18144 defined in @code{compile} command. Types defined in the @code{compile}
18145 command will no longer be available in the next @code{compile} command.
18146 Therefore, if you cast a variable to a type defined in the
18147 @code{compile} command, care must be taken to ensure that any future
18148 need to resolve the type can be achieved.
18151 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18152 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18153 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18154 Compilation failed.
18155 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18159 Variables that have been optimized away by the compiler are not
18160 accessible to the code submitted to the @code{compile} command.
18161 Access to those variables will generate a compiler error which @value{GDBN}
18162 will print to the console.
18165 @subsection Compiler search for the @code{compile} command
18167 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18168 which may not be obvious for remote targets of different architecture
18169 than where @value{GDBN} is running. Environment variable @code{PATH} on
18170 @value{GDBN} host is searched for @value{NGCC} binary matching the
18171 target architecture and operating system. This search can be overriden
18172 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18173 taken from shell that executed @value{GDBN}, it is not the value set by
18174 @value{GDBN} command @code{set environment}). @xref{Environment}.
18177 Specifically @code{PATH} is searched for binaries matching regular expression
18178 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18179 debugged. @var{arch} is processor name --- multiarch is supported, so for
18180 example both @code{i386} and @code{x86_64} targets look for pattern
18181 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18182 for pattern @code{s390x?}. @var{os} is currently supported only for
18183 pattern @code{linux(-gnu)?}.
18185 On Posix hosts the compiler driver @value{GDBN} needs to find also
18186 shared library @file{libcc1.so} from the compiler. It is searched in
18187 default shared library search path (overridable with usual environment
18188 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18189 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18190 according to the installation of the found compiler --- as possibly
18191 specified by the @code{set compile-gcc} command.
18194 @item set compile-gcc
18195 @cindex compile command driver filename override
18196 Set compilation command used for compiling and injecting code with the
18197 @code{compile} commands. If this option is not set (it is set to
18198 an empty string), the search described above will occur --- that is the
18201 @item show compile-gcc
18202 Displays the current compile command @value{NGCC} driver filename.
18203 If set, it is the main command @command{gcc}, found usually for example
18204 under name @file{x86_64-linux-gnu-gcc}.
18208 @chapter @value{GDBN} Files
18210 @value{GDBN} needs to know the file name of the program to be debugged,
18211 both in order to read its symbol table and in order to start your
18212 program. To debug a core dump of a previous run, you must also tell
18213 @value{GDBN} the name of the core dump file.
18216 * Files:: Commands to specify files
18217 * File Caching:: Information about @value{GDBN}'s file caching
18218 * Separate Debug Files:: Debugging information in separate files
18219 * MiniDebugInfo:: Debugging information in a special section
18220 * Index Files:: Index files speed up GDB
18221 * Symbol Errors:: Errors reading symbol files
18222 * Data Files:: GDB data files
18226 @section Commands to Specify Files
18228 @cindex symbol table
18229 @cindex core dump file
18231 You may want to specify executable and core dump file names. The usual
18232 way to do this is at start-up time, using the arguments to
18233 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18234 Out of @value{GDBN}}).
18236 Occasionally it is necessary to change to a different file during a
18237 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18238 specify a file you want to use. Or you are debugging a remote target
18239 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18240 Program}). In these situations the @value{GDBN} commands to specify
18241 new files are useful.
18244 @cindex executable file
18246 @item file @var{filename}
18247 Use @var{filename} as the program to be debugged. It is read for its
18248 symbols and for the contents of pure memory. It is also the program
18249 executed when you use the @code{run} command. If you do not specify a
18250 directory and the file is not found in the @value{GDBN} working directory,
18251 @value{GDBN} uses the environment variable @code{PATH} as a list of
18252 directories to search, just as the shell does when looking for a program
18253 to run. You can change the value of this variable, for both @value{GDBN}
18254 and your program, using the @code{path} command.
18256 @cindex unlinked object files
18257 @cindex patching object files
18258 You can load unlinked object @file{.o} files into @value{GDBN} using
18259 the @code{file} command. You will not be able to ``run'' an object
18260 file, but you can disassemble functions and inspect variables. Also,
18261 if the underlying BFD functionality supports it, you could use
18262 @kbd{gdb -write} to patch object files using this technique. Note
18263 that @value{GDBN} can neither interpret nor modify relocations in this
18264 case, so branches and some initialized variables will appear to go to
18265 the wrong place. But this feature is still handy from time to time.
18268 @code{file} with no argument makes @value{GDBN} discard any information it
18269 has on both executable file and the symbol table.
18272 @item exec-file @r{[} @var{filename} @r{]}
18273 Specify that the program to be run (but not the symbol table) is found
18274 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18275 if necessary to locate your program. Omitting @var{filename} means to
18276 discard information on the executable file.
18278 @kindex symbol-file
18279 @item symbol-file @r{[} @var{filename} @r{]}
18280 Read symbol table information from file @var{filename}. @code{PATH} is
18281 searched when necessary. Use the @code{file} command to get both symbol
18282 table and program to run from the same file.
18284 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18285 program's symbol table.
18287 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18288 some breakpoints and auto-display expressions. This is because they may
18289 contain pointers to the internal data recording symbols and data types,
18290 which are part of the old symbol table data being discarded inside
18293 @code{symbol-file} does not repeat if you press @key{RET} again after
18296 When @value{GDBN} is configured for a particular environment, it
18297 understands debugging information in whatever format is the standard
18298 generated for that environment; you may use either a @sc{gnu} compiler, or
18299 other compilers that adhere to the local conventions.
18300 Best results are usually obtained from @sc{gnu} compilers; for example,
18301 using @code{@value{NGCC}} you can generate debugging information for
18304 For most kinds of object files, with the exception of old SVR3 systems
18305 using COFF, the @code{symbol-file} command does not normally read the
18306 symbol table in full right away. Instead, it scans the symbol table
18307 quickly to find which source files and which symbols are present. The
18308 details are read later, one source file at a time, as they are needed.
18310 The purpose of this two-stage reading strategy is to make @value{GDBN}
18311 start up faster. For the most part, it is invisible except for
18312 occasional pauses while the symbol table details for a particular source
18313 file are being read. (The @code{set verbose} command can turn these
18314 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18315 Warnings and Messages}.)
18317 We have not implemented the two-stage strategy for COFF yet. When the
18318 symbol table is stored in COFF format, @code{symbol-file} reads the
18319 symbol table data in full right away. Note that ``stabs-in-COFF''
18320 still does the two-stage strategy, since the debug info is actually
18324 @cindex reading symbols immediately
18325 @cindex symbols, reading immediately
18326 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18327 @itemx file @r{[} -readnow @r{]} @var{filename}
18328 You can override the @value{GDBN} two-stage strategy for reading symbol
18329 tables by using the @samp{-readnow} option with any of the commands that
18330 load symbol table information, if you want to be sure @value{GDBN} has the
18331 entire symbol table available.
18333 @c FIXME: for now no mention of directories, since this seems to be in
18334 @c flux. 13mar1992 status is that in theory GDB would look either in
18335 @c current dir or in same dir as myprog; but issues like competing
18336 @c GDB's, or clutter in system dirs, mean that in practice right now
18337 @c only current dir is used. FFish says maybe a special GDB hierarchy
18338 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18342 @item core-file @r{[}@var{filename}@r{]}
18344 Specify the whereabouts of a core dump file to be used as the ``contents
18345 of memory''. Traditionally, core files contain only some parts of the
18346 address space of the process that generated them; @value{GDBN} can access the
18347 executable file itself for other parts.
18349 @code{core-file} with no argument specifies that no core file is
18352 Note that the core file is ignored when your program is actually running
18353 under @value{GDBN}. So, if you have been running your program and you
18354 wish to debug a core file instead, you must kill the subprocess in which
18355 the program is running. To do this, use the @code{kill} command
18356 (@pxref{Kill Process, ,Killing the Child Process}).
18358 @kindex add-symbol-file
18359 @cindex dynamic linking
18360 @item add-symbol-file @var{filename} @var{address}
18361 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18362 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18363 The @code{add-symbol-file} command reads additional symbol table
18364 information from the file @var{filename}. You would use this command
18365 when @var{filename} has been dynamically loaded (by some other means)
18366 into the program that is running. The @var{address} should give the memory
18367 address at which the file has been loaded; @value{GDBN} cannot figure
18368 this out for itself. You can additionally specify an arbitrary number
18369 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18370 section name and base address for that section. You can specify any
18371 @var{address} as an expression.
18373 The symbol table of the file @var{filename} is added to the symbol table
18374 originally read with the @code{symbol-file} command. You can use the
18375 @code{add-symbol-file} command any number of times; the new symbol data
18376 thus read is kept in addition to the old.
18378 Changes can be reverted using the command @code{remove-symbol-file}.
18380 @cindex relocatable object files, reading symbols from
18381 @cindex object files, relocatable, reading symbols from
18382 @cindex reading symbols from relocatable object files
18383 @cindex symbols, reading from relocatable object files
18384 @cindex @file{.o} files, reading symbols from
18385 Although @var{filename} is typically a shared library file, an
18386 executable file, or some other object file which has been fully
18387 relocated for loading into a process, you can also load symbolic
18388 information from relocatable @file{.o} files, as long as:
18392 the file's symbolic information refers only to linker symbols defined in
18393 that file, not to symbols defined by other object files,
18395 every section the file's symbolic information refers to has actually
18396 been loaded into the inferior, as it appears in the file, and
18398 you can determine the address at which every section was loaded, and
18399 provide these to the @code{add-symbol-file} command.
18403 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18404 relocatable files into an already running program; such systems
18405 typically make the requirements above easy to meet. However, it's
18406 important to recognize that many native systems use complex link
18407 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18408 assembly, for example) that make the requirements difficult to meet. In
18409 general, one cannot assume that using @code{add-symbol-file} to read a
18410 relocatable object file's symbolic information will have the same effect
18411 as linking the relocatable object file into the program in the normal
18414 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18416 @kindex remove-symbol-file
18417 @item remove-symbol-file @var{filename}
18418 @item remove-symbol-file -a @var{address}
18419 Remove a symbol file added via the @code{add-symbol-file} command. The
18420 file to remove can be identified by its @var{filename} or by an @var{address}
18421 that lies within the boundaries of this symbol file in memory. Example:
18424 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18425 add symbol table from file "/home/user/gdb/mylib.so" at
18426 .text_addr = 0x7ffff7ff9480
18428 Reading symbols from /home/user/gdb/mylib.so...done.
18429 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18430 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18435 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18437 @kindex add-symbol-file-from-memory
18438 @cindex @code{syscall DSO}
18439 @cindex load symbols from memory
18440 @item add-symbol-file-from-memory @var{address}
18441 Load symbols from the given @var{address} in a dynamically loaded
18442 object file whose image is mapped directly into the inferior's memory.
18443 For example, the Linux kernel maps a @code{syscall DSO} into each
18444 process's address space; this DSO provides kernel-specific code for
18445 some system calls. The argument can be any expression whose
18446 evaluation yields the address of the file's shared object file header.
18447 For this command to work, you must have used @code{symbol-file} or
18448 @code{exec-file} commands in advance.
18451 @item section @var{section} @var{addr}
18452 The @code{section} command changes the base address of the named
18453 @var{section} of the exec file to @var{addr}. This can be used if the
18454 exec file does not contain section addresses, (such as in the
18455 @code{a.out} format), or when the addresses specified in the file
18456 itself are wrong. Each section must be changed separately. The
18457 @code{info files} command, described below, lists all the sections and
18461 @kindex info target
18464 @code{info files} and @code{info target} are synonymous; both print the
18465 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18466 including the names of the executable and core dump files currently in
18467 use by @value{GDBN}, and the files from which symbols were loaded. The
18468 command @code{help target} lists all possible targets rather than
18471 @kindex maint info sections
18472 @item maint info sections
18473 Another command that can give you extra information about program sections
18474 is @code{maint info sections}. In addition to the section information
18475 displayed by @code{info files}, this command displays the flags and file
18476 offset of each section in the executable and core dump files. In addition,
18477 @code{maint info sections} provides the following command options (which
18478 may be arbitrarily combined):
18482 Display sections for all loaded object files, including shared libraries.
18483 @item @var{sections}
18484 Display info only for named @var{sections}.
18485 @item @var{section-flags}
18486 Display info only for sections for which @var{section-flags} are true.
18487 The section flags that @value{GDBN} currently knows about are:
18490 Section will have space allocated in the process when loaded.
18491 Set for all sections except those containing debug information.
18493 Section will be loaded from the file into the child process memory.
18494 Set for pre-initialized code and data, clear for @code{.bss} sections.
18496 Section needs to be relocated before loading.
18498 Section cannot be modified by the child process.
18500 Section contains executable code only.
18502 Section contains data only (no executable code).
18504 Section will reside in ROM.
18506 Section contains data for constructor/destructor lists.
18508 Section is not empty.
18510 An instruction to the linker to not output the section.
18511 @item COFF_SHARED_LIBRARY
18512 A notification to the linker that the section contains
18513 COFF shared library information.
18515 Section contains common symbols.
18518 @kindex set trust-readonly-sections
18519 @cindex read-only sections
18520 @item set trust-readonly-sections on
18521 Tell @value{GDBN} that readonly sections in your object file
18522 really are read-only (i.e.@: that their contents will not change).
18523 In that case, @value{GDBN} can fetch values from these sections
18524 out of the object file, rather than from the target program.
18525 For some targets (notably embedded ones), this can be a significant
18526 enhancement to debugging performance.
18528 The default is off.
18530 @item set trust-readonly-sections off
18531 Tell @value{GDBN} not to trust readonly sections. This means that
18532 the contents of the section might change while the program is running,
18533 and must therefore be fetched from the target when needed.
18535 @item show trust-readonly-sections
18536 Show the current setting of trusting readonly sections.
18539 All file-specifying commands allow both absolute and relative file names
18540 as arguments. @value{GDBN} always converts the file name to an absolute file
18541 name and remembers it that way.
18543 @cindex shared libraries
18544 @anchor{Shared Libraries}
18545 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18546 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18547 DSBT (TIC6X) shared libraries.
18549 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18550 shared libraries. @xref{Expat}.
18552 @value{GDBN} automatically loads symbol definitions from shared libraries
18553 when you use the @code{run} command, or when you examine a core file.
18554 (Before you issue the @code{run} command, @value{GDBN} does not understand
18555 references to a function in a shared library, however---unless you are
18556 debugging a core file).
18558 @c FIXME: some @value{GDBN} release may permit some refs to undef
18559 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18560 @c FIXME...lib; check this from time to time when updating manual
18562 There are times, however, when you may wish to not automatically load
18563 symbol definitions from shared libraries, such as when they are
18564 particularly large or there are many of them.
18566 To control the automatic loading of shared library symbols, use the
18570 @kindex set auto-solib-add
18571 @item set auto-solib-add @var{mode}
18572 If @var{mode} is @code{on}, symbols from all shared object libraries
18573 will be loaded automatically when the inferior begins execution, you
18574 attach to an independently started inferior, or when the dynamic linker
18575 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18576 is @code{off}, symbols must be loaded manually, using the
18577 @code{sharedlibrary} command. The default value is @code{on}.
18579 @cindex memory used for symbol tables
18580 If your program uses lots of shared libraries with debug info that
18581 takes large amounts of memory, you can decrease the @value{GDBN}
18582 memory footprint by preventing it from automatically loading the
18583 symbols from shared libraries. To that end, type @kbd{set
18584 auto-solib-add off} before running the inferior, then load each
18585 library whose debug symbols you do need with @kbd{sharedlibrary
18586 @var{regexp}}, where @var{regexp} is a regular expression that matches
18587 the libraries whose symbols you want to be loaded.
18589 @kindex show auto-solib-add
18590 @item show auto-solib-add
18591 Display the current autoloading mode.
18594 @cindex load shared library
18595 To explicitly load shared library symbols, use the @code{sharedlibrary}
18599 @kindex info sharedlibrary
18601 @item info share @var{regex}
18602 @itemx info sharedlibrary @var{regex}
18603 Print the names of the shared libraries which are currently loaded
18604 that match @var{regex}. If @var{regex} is omitted then print
18605 all shared libraries that are loaded.
18608 @item info dll @var{regex}
18609 This is an alias of @code{info sharedlibrary}.
18611 @kindex sharedlibrary
18613 @item sharedlibrary @var{regex}
18614 @itemx share @var{regex}
18615 Load shared object library symbols for files matching a
18616 Unix regular expression.
18617 As with files loaded automatically, it only loads shared libraries
18618 required by your program for a core file or after typing @code{run}. If
18619 @var{regex} is omitted all shared libraries required by your program are
18622 @item nosharedlibrary
18623 @kindex nosharedlibrary
18624 @cindex unload symbols from shared libraries
18625 Unload all shared object library symbols. This discards all symbols
18626 that have been loaded from all shared libraries. Symbols from shared
18627 libraries that were loaded by explicit user requests are not
18631 Sometimes you may wish that @value{GDBN} stops and gives you control
18632 when any of shared library events happen. The best way to do this is
18633 to use @code{catch load} and @code{catch unload} (@pxref{Set
18636 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18637 command for this. This command exists for historical reasons. It is
18638 less useful than setting a catchpoint, because it does not allow for
18639 conditions or commands as a catchpoint does.
18642 @item set stop-on-solib-events
18643 @kindex set stop-on-solib-events
18644 This command controls whether @value{GDBN} should give you control
18645 when the dynamic linker notifies it about some shared library event.
18646 The most common event of interest is loading or unloading of a new
18649 @item show stop-on-solib-events
18650 @kindex show stop-on-solib-events
18651 Show whether @value{GDBN} stops and gives you control when shared
18652 library events happen.
18655 Shared libraries are also supported in many cross or remote debugging
18656 configurations. @value{GDBN} needs to have access to the target's libraries;
18657 this can be accomplished either by providing copies of the libraries
18658 on the host system, or by asking @value{GDBN} to automatically retrieve the
18659 libraries from the target. If copies of the target libraries are
18660 provided, they need to be the same as the target libraries, although the
18661 copies on the target can be stripped as long as the copies on the host are
18664 @cindex where to look for shared libraries
18665 For remote debugging, you need to tell @value{GDBN} where the target
18666 libraries are, so that it can load the correct copies---otherwise, it
18667 may try to load the host's libraries. @value{GDBN} has two variables
18668 to specify the search directories for target libraries.
18671 @cindex prefix for executable and shared library file names
18672 @cindex system root, alternate
18673 @kindex set solib-absolute-prefix
18674 @kindex set sysroot
18675 @item set sysroot @var{path}
18676 Use @var{path} as the system root for the program being debugged. Any
18677 absolute shared library paths will be prefixed with @var{path}; many
18678 runtime loaders store the absolute paths to the shared library in the
18679 target program's memory. When starting processes remotely, and when
18680 attaching to already-running processes (local or remote), their
18681 executable filenames will be prefixed with @var{path} if reported to
18682 @value{GDBN} as absolute by the operating system. If you use
18683 @code{set sysroot} to find executables and shared libraries, they need
18684 to be laid out in the same way that they are on the target, with
18685 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18688 If @var{path} starts with the sequence @file{target:} and the target
18689 system is remote then @value{GDBN} will retrieve the target binaries
18690 from the remote system. This is only supported when using a remote
18691 target that supports the @code{remote get} command (@pxref{File
18692 Transfer,,Sending files to a remote system}). The part of @var{path}
18693 following the initial @file{target:} (if present) is used as system
18694 root prefix on the remote file system. If @var{path} starts with the
18695 sequence @file{remote:} this is converted to the sequence
18696 @file{target:} by @code{set sysroot}@footnote{Historically the
18697 functionality to retrieve binaries from the remote system was
18698 provided by prefixing @var{path} with @file{remote:}}. If you want
18699 to specify a local system root using a directory that happens to be
18700 named @file{target:} or @file{remote:}, you need to use some
18701 equivalent variant of the name like @file{./target:}.
18703 For targets with an MS-DOS based filesystem, such as MS-Windows and
18704 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18705 absolute file name with @var{path}. But first, on Unix hosts,
18706 @value{GDBN} converts all backslash directory separators into forward
18707 slashes, because the backslash is not a directory separator on Unix:
18710 c:\foo\bar.dll @result{} c:/foo/bar.dll
18713 Then, @value{GDBN} attempts prefixing the target file name with
18714 @var{path}, and looks for the resulting file name in the host file
18718 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18721 If that does not find the binary, @value{GDBN} tries removing
18722 the @samp{:} character from the drive spec, both for convenience, and,
18723 for the case of the host file system not supporting file names with
18727 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18730 This makes it possible to have a system root that mirrors a target
18731 with more than one drive. E.g., you may want to setup your local
18732 copies of the target system shared libraries like so (note @samp{c} vs
18736 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18737 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18738 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18742 and point the system root at @file{/path/to/sysroot}, so that
18743 @value{GDBN} can find the correct copies of both
18744 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18746 If that still does not find the binary, @value{GDBN} tries
18747 removing the whole drive spec from the target file name:
18750 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18753 This last lookup makes it possible to not care about the drive name,
18754 if you don't want or need to.
18756 The @code{set solib-absolute-prefix} command is an alias for @code{set
18759 @cindex default system root
18760 @cindex @samp{--with-sysroot}
18761 You can set the default system root by using the configure-time
18762 @samp{--with-sysroot} option. If the system root is inside
18763 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18764 @samp{--exec-prefix}), then the default system root will be updated
18765 automatically if the installed @value{GDBN} is moved to a new
18768 @kindex show sysroot
18770 Display the current executable and shared library prefix.
18772 @kindex set solib-search-path
18773 @item set solib-search-path @var{path}
18774 If this variable is set, @var{path} is a colon-separated list of
18775 directories to search for shared libraries. @samp{solib-search-path}
18776 is used after @samp{sysroot} fails to locate the library, or if the
18777 path to the library is relative instead of absolute. If you want to
18778 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18779 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18780 finding your host's libraries. @samp{sysroot} is preferred; setting
18781 it to a nonexistent directory may interfere with automatic loading
18782 of shared library symbols.
18784 @kindex show solib-search-path
18785 @item show solib-search-path
18786 Display the current shared library search path.
18788 @cindex DOS file-name semantics of file names.
18789 @kindex set target-file-system-kind (unix|dos-based|auto)
18790 @kindex show target-file-system-kind
18791 @item set target-file-system-kind @var{kind}
18792 Set assumed file system kind for target reported file names.
18794 Shared library file names as reported by the target system may not
18795 make sense as is on the system @value{GDBN} is running on. For
18796 example, when remote debugging a target that has MS-DOS based file
18797 system semantics, from a Unix host, the target may be reporting to
18798 @value{GDBN} a list of loaded shared libraries with file names such as
18799 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18800 drive letters, so the @samp{c:\} prefix is not normally understood as
18801 indicating an absolute file name, and neither is the backslash
18802 normally considered a directory separator character. In that case,
18803 the native file system would interpret this whole absolute file name
18804 as a relative file name with no directory components. This would make
18805 it impossible to point @value{GDBN} at a copy of the remote target's
18806 shared libraries on the host using @code{set sysroot}, and impractical
18807 with @code{set solib-search-path}. Setting
18808 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18809 to interpret such file names similarly to how the target would, and to
18810 map them to file names valid on @value{GDBN}'s native file system
18811 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18812 to one of the supported file system kinds. In that case, @value{GDBN}
18813 tries to determine the appropriate file system variant based on the
18814 current target's operating system (@pxref{ABI, ,Configuring the
18815 Current ABI}). The supported file system settings are:
18819 Instruct @value{GDBN} to assume the target file system is of Unix
18820 kind. Only file names starting the forward slash (@samp{/}) character
18821 are considered absolute, and the directory separator character is also
18825 Instruct @value{GDBN} to assume the target file system is DOS based.
18826 File names starting with either a forward slash, or a drive letter
18827 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18828 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18829 considered directory separators.
18832 Instruct @value{GDBN} to use the file system kind associated with the
18833 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18834 This is the default.
18838 @cindex file name canonicalization
18839 @cindex base name differences
18840 When processing file names provided by the user, @value{GDBN}
18841 frequently needs to compare them to the file names recorded in the
18842 program's debug info. Normally, @value{GDBN} compares just the
18843 @dfn{base names} of the files as strings, which is reasonably fast
18844 even for very large programs. (The base name of a file is the last
18845 portion of its name, after stripping all the leading directories.)
18846 This shortcut in comparison is based upon the assumption that files
18847 cannot have more than one base name. This is usually true, but
18848 references to files that use symlinks or similar filesystem
18849 facilities violate that assumption. If your program records files
18850 using such facilities, or if you provide file names to @value{GDBN}
18851 using symlinks etc., you can set @code{basenames-may-differ} to
18852 @code{true} to instruct @value{GDBN} to completely canonicalize each
18853 pair of file names it needs to compare. This will make file-name
18854 comparisons accurate, but at a price of a significant slowdown.
18857 @item set basenames-may-differ
18858 @kindex set basenames-may-differ
18859 Set whether a source file may have multiple base names.
18861 @item show basenames-may-differ
18862 @kindex show basenames-may-differ
18863 Show whether a source file may have multiple base names.
18867 @section File Caching
18868 @cindex caching of opened files
18869 @cindex caching of bfd objects
18871 To speed up file loading, and reduce memory usage, @value{GDBN} will
18872 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18873 BFD, bfd, The Binary File Descriptor Library}. The following commands
18874 allow visibility and control of the caching behavior.
18877 @kindex maint info bfds
18878 @item maint info bfds
18879 This prints information about each @code{bfd} object that is known to
18882 @kindex maint set bfd-sharing
18883 @kindex maint show bfd-sharing
18884 @kindex bfd caching
18885 @item maint set bfd-sharing
18886 @item maint show bfd-sharing
18887 Control whether @code{bfd} objects can be shared. When sharing is
18888 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18889 than reopening the same file. Turning sharing off does not cause
18890 already shared @code{bfd} objects to be unshared, but all future files
18891 that are opened will create a new @code{bfd} object. Similarly,
18892 re-enabling sharing does not cause multiple existing @code{bfd}
18893 objects to be collapsed into a single shared @code{bfd} object.
18895 @kindex set debug bfd-cache @var{level}
18896 @kindex bfd caching
18897 @item set debug bfd-cache @var{level}
18898 Turns on debugging of the bfd cache, setting the level to @var{level}.
18900 @kindex show debug bfd-cache
18901 @kindex bfd caching
18902 @item show debug bfd-cache
18903 Show the current debugging level of the bfd cache.
18906 @node Separate Debug Files
18907 @section Debugging Information in Separate Files
18908 @cindex separate debugging information files
18909 @cindex debugging information in separate files
18910 @cindex @file{.debug} subdirectories
18911 @cindex debugging information directory, global
18912 @cindex global debugging information directories
18913 @cindex build ID, and separate debugging files
18914 @cindex @file{.build-id} directory
18916 @value{GDBN} allows you to put a program's debugging information in a
18917 file separate from the executable itself, in a way that allows
18918 @value{GDBN} to find and load the debugging information automatically.
18919 Since debugging information can be very large---sometimes larger
18920 than the executable code itself---some systems distribute debugging
18921 information for their executables in separate files, which users can
18922 install only when they need to debug a problem.
18924 @value{GDBN} supports two ways of specifying the separate debug info
18929 The executable contains a @dfn{debug link} that specifies the name of
18930 the separate debug info file. The separate debug file's name is
18931 usually @file{@var{executable}.debug}, where @var{executable} is the
18932 name of the corresponding executable file without leading directories
18933 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18934 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18935 checksum for the debug file, which @value{GDBN} uses to validate that
18936 the executable and the debug file came from the same build.
18939 The executable contains a @dfn{build ID}, a unique bit string that is
18940 also present in the corresponding debug info file. (This is supported
18941 only on some operating systems, when using the ELF or PE file formats
18942 for binary files and the @sc{gnu} Binutils.) For more details about
18943 this feature, see the description of the @option{--build-id}
18944 command-line option in @ref{Options, , Command Line Options, ld.info,
18945 The GNU Linker}. The debug info file's name is not specified
18946 explicitly by the build ID, but can be computed from the build ID, see
18950 Depending on the way the debug info file is specified, @value{GDBN}
18951 uses two different methods of looking for the debug file:
18955 For the ``debug link'' method, @value{GDBN} looks up the named file in
18956 the directory of the executable file, then in a subdirectory of that
18957 directory named @file{.debug}, and finally under each one of the global debug
18958 directories, in a subdirectory whose name is identical to the leading
18959 directories of the executable's absolute file name.
18962 For the ``build ID'' method, @value{GDBN} looks in the
18963 @file{.build-id} subdirectory of each one of the global debug directories for
18964 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18965 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18966 are the rest of the bit string. (Real build ID strings are 32 or more
18967 hex characters, not 10.)
18970 So, for example, suppose you ask @value{GDBN} to debug
18971 @file{/usr/bin/ls}, which has a debug link that specifies the
18972 file @file{ls.debug}, and a build ID whose value in hex is
18973 @code{abcdef1234}. If the list of the global debug directories includes
18974 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18975 debug information files, in the indicated order:
18979 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18981 @file{/usr/bin/ls.debug}
18983 @file{/usr/bin/.debug/ls.debug}
18985 @file{/usr/lib/debug/usr/bin/ls.debug}.
18988 @anchor{debug-file-directory}
18989 Global debugging info directories default to what is set by @value{GDBN}
18990 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18991 you can also set the global debugging info directories, and view the list
18992 @value{GDBN} is currently using.
18996 @kindex set debug-file-directory
18997 @item set debug-file-directory @var{directories}
18998 Set the directories which @value{GDBN} searches for separate debugging
18999 information files to @var{directory}. Multiple path components can be set
19000 concatenating them by a path separator.
19002 @kindex show debug-file-directory
19003 @item show debug-file-directory
19004 Show the directories @value{GDBN} searches for separate debugging
19009 @cindex @code{.gnu_debuglink} sections
19010 @cindex debug link sections
19011 A debug link is a special section of the executable file named
19012 @code{.gnu_debuglink}. The section must contain:
19016 A filename, with any leading directory components removed, followed by
19019 zero to three bytes of padding, as needed to reach the next four-byte
19020 boundary within the section, and
19022 a four-byte CRC checksum, stored in the same endianness used for the
19023 executable file itself. The checksum is computed on the debugging
19024 information file's full contents by the function given below, passing
19025 zero as the @var{crc} argument.
19028 Any executable file format can carry a debug link, as long as it can
19029 contain a section named @code{.gnu_debuglink} with the contents
19032 @cindex @code{.note.gnu.build-id} sections
19033 @cindex build ID sections
19034 The build ID is a special section in the executable file (and in other
19035 ELF binary files that @value{GDBN} may consider). This section is
19036 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19037 It contains unique identification for the built files---the ID remains
19038 the same across multiple builds of the same build tree. The default
19039 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19040 content for the build ID string. The same section with an identical
19041 value is present in the original built binary with symbols, in its
19042 stripped variant, and in the separate debugging information file.
19044 The debugging information file itself should be an ordinary
19045 executable, containing a full set of linker symbols, sections, and
19046 debugging information. The sections of the debugging information file
19047 should have the same names, addresses, and sizes as the original file,
19048 but they need not contain any data---much like a @code{.bss} section
19049 in an ordinary executable.
19051 The @sc{gnu} binary utilities (Binutils) package includes the
19052 @samp{objcopy} utility that can produce
19053 the separated executable / debugging information file pairs using the
19054 following commands:
19057 @kbd{objcopy --only-keep-debug foo foo.debug}
19062 These commands remove the debugging
19063 information from the executable file @file{foo} and place it in the file
19064 @file{foo.debug}. You can use the first, second or both methods to link the
19069 The debug link method needs the following additional command to also leave
19070 behind a debug link in @file{foo}:
19073 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19076 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19077 a version of the @code{strip} command such that the command @kbd{strip foo -f
19078 foo.debug} has the same functionality as the two @code{objcopy} commands and
19079 the @code{ln -s} command above, together.
19082 Build ID gets embedded into the main executable using @code{ld --build-id} or
19083 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19084 compatibility fixes for debug files separation are present in @sc{gnu} binary
19085 utilities (Binutils) package since version 2.18.
19090 @cindex CRC algorithm definition
19091 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19092 IEEE 802.3 using the polynomial:
19094 @c TexInfo requires naked braces for multi-digit exponents for Tex
19095 @c output, but this causes HTML output to barf. HTML has to be set using
19096 @c raw commands. So we end up having to specify this equation in 2
19101 <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>
19102 + <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
19108 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19109 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19113 The function is computed byte at a time, taking the least
19114 significant bit of each byte first. The initial pattern
19115 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19116 the final result is inverted to ensure trailing zeros also affect the
19119 @emph{Note:} This is the same CRC polynomial as used in handling the
19120 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19121 However in the case of the Remote Serial Protocol, the CRC is computed
19122 @emph{most} significant bit first, and the result is not inverted, so
19123 trailing zeros have no effect on the CRC value.
19125 To complete the description, we show below the code of the function
19126 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19127 initially supplied @code{crc} argument means that an initial call to
19128 this function passing in zero will start computing the CRC using
19131 @kindex gnu_debuglink_crc32
19134 gnu_debuglink_crc32 (unsigned long crc,
19135 unsigned char *buf, size_t len)
19137 static const unsigned long crc32_table[256] =
19139 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19140 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19141 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19142 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19143 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19144 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19145 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19146 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19147 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19148 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19149 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19150 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19151 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19152 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19153 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19154 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19155 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19156 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19157 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19158 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19159 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19160 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19161 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19162 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19163 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19164 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19165 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19166 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19167 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19168 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19169 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19170 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19171 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19172 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19173 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19174 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19175 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19176 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19177 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19178 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19179 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19180 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19181 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19182 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19183 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19184 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19185 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19186 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19187 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19188 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19189 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19192 unsigned char *end;
19194 crc = ~crc & 0xffffffff;
19195 for (end = buf + len; buf < end; ++buf)
19196 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19197 return ~crc & 0xffffffff;
19202 This computation does not apply to the ``build ID'' method.
19204 @node MiniDebugInfo
19205 @section Debugging information in a special section
19206 @cindex separate debug sections
19207 @cindex @samp{.gnu_debugdata} section
19209 Some systems ship pre-built executables and libraries that have a
19210 special @samp{.gnu_debugdata} section. This feature is called
19211 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19212 is used to supply extra symbols for backtraces.
19214 The intent of this section is to provide extra minimal debugging
19215 information for use in simple backtraces. It is not intended to be a
19216 replacement for full separate debugging information (@pxref{Separate
19217 Debug Files}). The example below shows the intended use; however,
19218 @value{GDBN} does not currently put restrictions on what sort of
19219 debugging information might be included in the section.
19221 @value{GDBN} has support for this extension. If the section exists,
19222 then it is used provided that no other source of debugging information
19223 can be found, and that @value{GDBN} was configured with LZMA support.
19225 This section can be easily created using @command{objcopy} and other
19226 standard utilities:
19229 # Extract the dynamic symbols from the main binary, there is no need
19230 # to also have these in the normal symbol table.
19231 nm -D @var{binary} --format=posix --defined-only \
19232 | awk '@{ print $1 @}' | sort > dynsyms
19234 # Extract all the text (i.e. function) symbols from the debuginfo.
19235 # (Note that we actually also accept "D" symbols, for the benefit
19236 # of platforms like PowerPC64 that use function descriptors.)
19237 nm @var{binary} --format=posix --defined-only \
19238 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19241 # Keep all the function symbols not already in the dynamic symbol
19243 comm -13 dynsyms funcsyms > keep_symbols
19245 # Separate full debug info into debug binary.
19246 objcopy --only-keep-debug @var{binary} debug
19248 # Copy the full debuginfo, keeping only a minimal set of symbols and
19249 # removing some unnecessary sections.
19250 objcopy -S --remove-section .gdb_index --remove-section .comment \
19251 --keep-symbols=keep_symbols debug mini_debuginfo
19253 # Drop the full debug info from the original binary.
19254 strip --strip-all -R .comment @var{binary}
19256 # Inject the compressed data into the .gnu_debugdata section of the
19259 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19263 @section Index Files Speed Up @value{GDBN}
19264 @cindex index files
19265 @cindex @samp{.gdb_index} section
19267 When @value{GDBN} finds a symbol file, it scans the symbols in the
19268 file in order to construct an internal symbol table. This lets most
19269 @value{GDBN} operations work quickly---at the cost of a delay early
19270 on. For large programs, this delay can be quite lengthy, so
19271 @value{GDBN} provides a way to build an index, which speeds up
19274 The index is stored as a section in the symbol file. @value{GDBN} can
19275 write the index to a file, then you can put it into the symbol file
19276 using @command{objcopy}.
19278 To create an index file, use the @code{save gdb-index} command:
19281 @item save gdb-index @var{directory}
19282 @kindex save gdb-index
19283 Create an index file for each symbol file currently known by
19284 @value{GDBN}. Each file is named after its corresponding symbol file,
19285 with @samp{.gdb-index} appended, and is written into the given
19289 Once you have created an index file you can merge it into your symbol
19290 file, here named @file{symfile}, using @command{objcopy}:
19293 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19294 --set-section-flags .gdb_index=readonly symfile symfile
19297 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19298 sections that have been deprecated. Usually they are deprecated because
19299 they are missing a new feature or have performance issues.
19300 To tell @value{GDBN} to use a deprecated index section anyway
19301 specify @code{set use-deprecated-index-sections on}.
19302 The default is @code{off}.
19303 This can speed up startup, but may result in some functionality being lost.
19304 @xref{Index Section Format}.
19306 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19307 must be done before gdb reads the file. The following will not work:
19310 $ gdb -ex "set use-deprecated-index-sections on" <program>
19313 Instead you must do, for example,
19316 $ gdb -iex "set use-deprecated-index-sections on" <program>
19319 There are currently some limitation on indices. They only work when
19320 for DWARF debugging information, not stabs. And, they do not
19321 currently work for programs using Ada.
19323 @node Symbol Errors
19324 @section Errors Reading Symbol Files
19326 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19327 such as symbol types it does not recognize, or known bugs in compiler
19328 output. By default, @value{GDBN} does not notify you of such problems, since
19329 they are relatively common and primarily of interest to people
19330 debugging compilers. If you are interested in seeing information
19331 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19332 only one message about each such type of problem, no matter how many
19333 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19334 to see how many times the problems occur, with the @code{set
19335 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19338 The messages currently printed, and their meanings, include:
19341 @item inner block not inside outer block in @var{symbol}
19343 The symbol information shows where symbol scopes begin and end
19344 (such as at the start of a function or a block of statements). This
19345 error indicates that an inner scope block is not fully contained
19346 in its outer scope blocks.
19348 @value{GDBN} circumvents the problem by treating the inner block as if it had
19349 the same scope as the outer block. In the error message, @var{symbol}
19350 may be shown as ``@code{(don't know)}'' if the outer block is not a
19353 @item block at @var{address} out of order
19355 The symbol information for symbol scope blocks should occur in
19356 order of increasing addresses. This error indicates that it does not
19359 @value{GDBN} does not circumvent this problem, and has trouble
19360 locating symbols in the source file whose symbols it is reading. (You
19361 can often determine what source file is affected by specifying
19362 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19365 @item bad block start address patched
19367 The symbol information for a symbol scope block has a start address
19368 smaller than the address of the preceding source line. This is known
19369 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19371 @value{GDBN} circumvents the problem by treating the symbol scope block as
19372 starting on the previous source line.
19374 @item bad string table offset in symbol @var{n}
19377 Symbol number @var{n} contains a pointer into the string table which is
19378 larger than the size of the string table.
19380 @value{GDBN} circumvents the problem by considering the symbol to have the
19381 name @code{foo}, which may cause other problems if many symbols end up
19384 @item unknown symbol type @code{0x@var{nn}}
19386 The symbol information contains new data types that @value{GDBN} does
19387 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19388 uncomprehended information, in hexadecimal.
19390 @value{GDBN} circumvents the error by ignoring this symbol information.
19391 This usually allows you to debug your program, though certain symbols
19392 are not accessible. If you encounter such a problem and feel like
19393 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19394 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19395 and examine @code{*bufp} to see the symbol.
19397 @item stub type has NULL name
19399 @value{GDBN} could not find the full definition for a struct or class.
19401 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19402 The symbol information for a C@t{++} member function is missing some
19403 information that recent versions of the compiler should have output for
19406 @item info mismatch between compiler and debugger
19408 @value{GDBN} could not parse a type specification output by the compiler.
19413 @section GDB Data Files
19415 @cindex prefix for data files
19416 @value{GDBN} will sometimes read an auxiliary data file. These files
19417 are kept in a directory known as the @dfn{data directory}.
19419 You can set the data directory's name, and view the name @value{GDBN}
19420 is currently using.
19423 @kindex set data-directory
19424 @item set data-directory @var{directory}
19425 Set the directory which @value{GDBN} searches for auxiliary data files
19426 to @var{directory}.
19428 @kindex show data-directory
19429 @item show data-directory
19430 Show the directory @value{GDBN} searches for auxiliary data files.
19433 @cindex default data directory
19434 @cindex @samp{--with-gdb-datadir}
19435 You can set the default data directory by using the configure-time
19436 @samp{--with-gdb-datadir} option. If the data directory is inside
19437 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19438 @samp{--exec-prefix}), then the default data directory will be updated
19439 automatically if the installed @value{GDBN} is moved to a new
19442 The data directory may also be specified with the
19443 @code{--data-directory} command line option.
19444 @xref{Mode Options}.
19447 @chapter Specifying a Debugging Target
19449 @cindex debugging target
19450 A @dfn{target} is the execution environment occupied by your program.
19452 Often, @value{GDBN} runs in the same host environment as your program;
19453 in that case, the debugging target is specified as a side effect when
19454 you use the @code{file} or @code{core} commands. When you need more
19455 flexibility---for example, running @value{GDBN} on a physically separate
19456 host, or controlling a standalone system over a serial port or a
19457 realtime system over a TCP/IP connection---you can use the @code{target}
19458 command to specify one of the target types configured for @value{GDBN}
19459 (@pxref{Target Commands, ,Commands for Managing Targets}).
19461 @cindex target architecture
19462 It is possible to build @value{GDBN} for several different @dfn{target
19463 architectures}. When @value{GDBN} is built like that, you can choose
19464 one of the available architectures with the @kbd{set architecture}
19468 @kindex set architecture
19469 @kindex show architecture
19470 @item set architecture @var{arch}
19471 This command sets the current target architecture to @var{arch}. The
19472 value of @var{arch} can be @code{"auto"}, in addition to one of the
19473 supported architectures.
19475 @item show architecture
19476 Show the current target architecture.
19478 @item set processor
19480 @kindex set processor
19481 @kindex show processor
19482 These are alias commands for, respectively, @code{set architecture}
19483 and @code{show architecture}.
19487 * Active Targets:: Active targets
19488 * Target Commands:: Commands for managing targets
19489 * Byte Order:: Choosing target byte order
19492 @node Active Targets
19493 @section Active Targets
19495 @cindex stacking targets
19496 @cindex active targets
19497 @cindex multiple targets
19499 There are multiple classes of targets such as: processes, executable files or
19500 recording sessions. Core files belong to the process class, making core file
19501 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19502 on multiple active targets, one in each class. This allows you to (for
19503 example) start a process and inspect its activity, while still having access to
19504 the executable file after the process finishes. Or if you start process
19505 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19506 presented a virtual layer of the recording target, while the process target
19507 remains stopped at the chronologically last point of the process execution.
19509 Use the @code{core-file} and @code{exec-file} commands to select a new core
19510 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19511 specify as a target a process that is already running, use the @code{attach}
19512 command (@pxref{Attach, ,Debugging an Already-running Process}).
19514 @node Target Commands
19515 @section Commands for Managing Targets
19518 @item target @var{type} @var{parameters}
19519 Connects the @value{GDBN} host environment to a target machine or
19520 process. A target is typically a protocol for talking to debugging
19521 facilities. You use the argument @var{type} to specify the type or
19522 protocol of the target machine.
19524 Further @var{parameters} are interpreted by the target protocol, but
19525 typically include things like device names or host names to connect
19526 with, process numbers, and baud rates.
19528 The @code{target} command does not repeat if you press @key{RET} again
19529 after executing the command.
19531 @kindex help target
19533 Displays the names of all targets available. To display targets
19534 currently selected, use either @code{info target} or @code{info files}
19535 (@pxref{Files, ,Commands to Specify Files}).
19537 @item help target @var{name}
19538 Describe a particular target, including any parameters necessary to
19541 @kindex set gnutarget
19542 @item set gnutarget @var{args}
19543 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19544 knows whether it is reading an @dfn{executable},
19545 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19546 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19547 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19550 @emph{Warning:} To specify a file format with @code{set gnutarget},
19551 you must know the actual BFD name.
19555 @xref{Files, , Commands to Specify Files}.
19557 @kindex show gnutarget
19558 @item show gnutarget
19559 Use the @code{show gnutarget} command to display what file format
19560 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19561 @value{GDBN} will determine the file format for each file automatically,
19562 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19565 @cindex common targets
19566 Here are some common targets (available, or not, depending on the GDB
19571 @item target exec @var{program}
19572 @cindex executable file target
19573 An executable file. @samp{target exec @var{program}} is the same as
19574 @samp{exec-file @var{program}}.
19576 @item target core @var{filename}
19577 @cindex core dump file target
19578 A core dump file. @samp{target core @var{filename}} is the same as
19579 @samp{core-file @var{filename}}.
19581 @item target remote @var{medium}
19582 @cindex remote target
19583 A remote system connected to @value{GDBN} via a serial line or network
19584 connection. This command tells @value{GDBN} to use its own remote
19585 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19587 For example, if you have a board connected to @file{/dev/ttya} on the
19588 machine running @value{GDBN}, you could say:
19591 target remote /dev/ttya
19594 @code{target remote} supports the @code{load} command. This is only
19595 useful if you have some other way of getting the stub to the target
19596 system, and you can put it somewhere in memory where it won't get
19597 clobbered by the download.
19599 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19600 @cindex built-in simulator target
19601 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19609 works; however, you cannot assume that a specific memory map, device
19610 drivers, or even basic I/O is available, although some simulators do
19611 provide these. For info about any processor-specific simulator details,
19612 see the appropriate section in @ref{Embedded Processors, ,Embedded
19615 @item target native
19616 @cindex native target
19617 Setup for local/native process debugging. Useful to make the
19618 @code{run} command spawn native processes (likewise @code{attach},
19619 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19620 (@pxref{set auto-connect-native-target}).
19624 Different targets are available on different configurations of @value{GDBN};
19625 your configuration may have more or fewer targets.
19627 Many remote targets require you to download the executable's code once
19628 you've successfully established a connection. You may wish to control
19629 various aspects of this process.
19634 @kindex set hash@r{, for remote monitors}
19635 @cindex hash mark while downloading
19636 This command controls whether a hash mark @samp{#} is displayed while
19637 downloading a file to the remote monitor. If on, a hash mark is
19638 displayed after each S-record is successfully downloaded to the
19642 @kindex show hash@r{, for remote monitors}
19643 Show the current status of displaying the hash mark.
19645 @item set debug monitor
19646 @kindex set debug monitor
19647 @cindex display remote monitor communications
19648 Enable or disable display of communications messages between
19649 @value{GDBN} and the remote monitor.
19651 @item show debug monitor
19652 @kindex show debug monitor
19653 Show the current status of displaying communications between
19654 @value{GDBN} and the remote monitor.
19659 @kindex load @var{filename} @var{offset}
19660 @item load @var{filename} @var{offset}
19662 Depending on what remote debugging facilities are configured into
19663 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19664 is meant to make @var{filename} (an executable) available for debugging
19665 on the remote system---by downloading, or dynamic linking, for example.
19666 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19667 the @code{add-symbol-file} command.
19669 If your @value{GDBN} does not have a @code{load} command, attempting to
19670 execute it gets the error message ``@code{You can't do that when your
19671 target is @dots{}}''
19673 The file is loaded at whatever address is specified in the executable.
19674 For some object file formats, you can specify the load address when you
19675 link the program; for other formats, like a.out, the object file format
19676 specifies a fixed address.
19677 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19679 It is also possible to tell @value{GDBN} to load the executable file at a
19680 specific offset described by the optional argument @var{offset}. When
19681 @var{offset} is provided, @var{filename} must also be provided.
19683 Depending on the remote side capabilities, @value{GDBN} may be able to
19684 load programs into flash memory.
19686 @code{load} does not repeat if you press @key{RET} again after using it.
19691 @kindex flash-erase
19693 @anchor{flash-erase}
19695 Erases all known flash memory regions on the target.
19700 @section Choosing Target Byte Order
19702 @cindex choosing target byte order
19703 @cindex target byte order
19705 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19706 offer the ability to run either big-endian or little-endian byte
19707 orders. Usually the executable or symbol will include a bit to
19708 designate the endian-ness, and you will not need to worry about
19709 which to use. However, you may still find it useful to adjust
19710 @value{GDBN}'s idea of processor endian-ness manually.
19714 @item set endian big
19715 Instruct @value{GDBN} to assume the target is big-endian.
19717 @item set endian little
19718 Instruct @value{GDBN} to assume the target is little-endian.
19720 @item set endian auto
19721 Instruct @value{GDBN} to use the byte order associated with the
19725 Display @value{GDBN}'s current idea of the target byte order.
19729 Note that these commands merely adjust interpretation of symbolic
19730 data on the host, and that they have absolutely no effect on the
19734 @node Remote Debugging
19735 @chapter Debugging Remote Programs
19736 @cindex remote debugging
19738 If you are trying to debug a program running on a machine that cannot run
19739 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19740 For example, you might use remote debugging on an operating system kernel,
19741 or on a small system which does not have a general purpose operating system
19742 powerful enough to run a full-featured debugger.
19744 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19745 to make this work with particular debugging targets. In addition,
19746 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19747 but not specific to any particular target system) which you can use if you
19748 write the remote stubs---the code that runs on the remote system to
19749 communicate with @value{GDBN}.
19751 Other remote targets may be available in your
19752 configuration of @value{GDBN}; use @code{help target} to list them.
19755 * Connecting:: Connecting to a remote target
19756 * File Transfer:: Sending files to a remote system
19757 * Server:: Using the gdbserver program
19758 * Remote Configuration:: Remote configuration
19759 * Remote Stub:: Implementing a remote stub
19763 @section Connecting to a Remote Target
19764 @cindex remote debugging, connecting
19765 @cindex @code{gdbserver}, connecting
19766 @cindex remote debugging, types of connections
19767 @cindex @code{gdbserver}, types of connections
19768 @cindex @code{gdbserver}, @code{target remote} mode
19769 @cindex @code{gdbserver}, @code{target extended-remote} mode
19771 This section describes how to connect to a remote target, including the
19772 types of connections and their differences, how to set up executable and
19773 symbol files on the host and target, and the commands used for
19774 connecting to and disconnecting from the remote target.
19776 @subsection Types of Remote Connections
19778 @value{GDBN} supports two types of remote connections, @code{target remote}
19779 mode and @code{target extended-remote} mode. Note that many remote targets
19780 support only @code{target remote} mode. There are several major
19781 differences between the two types of connections, enumerated here:
19785 @cindex remote debugging, detach and program exit
19786 @item Result of detach or program exit
19787 @strong{With target remote mode:} When the debugged program exits or you
19788 detach from it, @value{GDBN} disconnects from the target. When using
19789 @code{gdbserver}, @code{gdbserver} will exit.
19791 @strong{With target extended-remote mode:} When the debugged program exits or
19792 you detach from it, @value{GDBN} remains connected to the target, even
19793 though no program is running. You can rerun the program, attach to a
19794 running program, or use @code{monitor} commands specific to the target.
19796 When using @code{gdbserver} in this case, it does not exit unless it was
19797 invoked using the @option{--once} option. If the @option{--once} option
19798 was not used, you can ask @code{gdbserver} to exit using the
19799 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19801 @item Specifying the program to debug
19802 For both connection types you use the @code{file} command to specify the
19803 program on the host system. If you are using @code{gdbserver} there are
19804 some differences in how to specify the location of the program on the
19807 @strong{With target remote mode:} You must either specify the program to debug
19808 on the @code{gdbserver} command line or use the @option{--attach} option
19809 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19811 @cindex @option{--multi}, @code{gdbserver} option
19812 @strong{With target extended-remote mode:} You may specify the program to debug
19813 on the @code{gdbserver} command line, or you can load the program or attach
19814 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19816 @anchor{--multi Option in Types of Remote Connnections}
19817 You can start @code{gdbserver} without supplying an initial command to run
19818 or process ID to attach. To do this, use the @option{--multi} command line
19819 option. Then you can connect using @code{target extended-remote} and start
19820 the program you want to debug (see below for details on using the
19821 @code{run} command in this scenario). Note that the conditions under which
19822 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19823 (@code{target remote} or @code{target extended-remote}). The
19824 @option{--multi} option to @code{gdbserver} has no influence on that.
19826 @item The @code{run} command
19827 @strong{With target remote mode:} The @code{run} command is not
19828 supported. Once a connection has been established, you can use all
19829 the usual @value{GDBN} commands to examine and change data. The
19830 remote program is already running, so you can use commands like
19831 @kbd{step} and @kbd{continue}.
19833 @strong{With target extended-remote mode:} The @code{run} command is
19834 supported. The @code{run} command uses the value set by
19835 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19836 the program to run. Command line arguments are supported, except for
19837 wildcard expansion and I/O redirection (@pxref{Arguments}).
19839 If you specify the program to debug on the command line, then the
19840 @code{run} command is not required to start execution, and you can
19841 resume using commands like @kbd{step} and @kbd{continue} as with
19842 @code{target remote} mode.
19844 @anchor{Attaching in Types of Remote Connections}
19846 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19847 not supported. To attach to a running program using @code{gdbserver}, you
19848 must use the @option{--attach} option (@pxref{Running gdbserver}).
19850 @strong{With target extended-remote mode:} To attach to a running program,
19851 you may use the @code{attach} command after the connection has been
19852 established. If you are using @code{gdbserver}, you may also invoke
19853 @code{gdbserver} using the @option{--attach} option
19854 (@pxref{Running gdbserver}).
19858 @anchor{Host and target files}
19859 @subsection Host and Target Files
19860 @cindex remote debugging, symbol files
19861 @cindex symbol files, remote debugging
19863 @value{GDBN}, running on the host, needs access to symbol and debugging
19864 information for your program running on the target. This requires
19865 access to an unstripped copy of your program, and possibly any associated
19866 symbol files. Note that this section applies equally to both @code{target
19867 remote} mode and @code{target extended-remote} mode.
19869 Some remote targets (@pxref{qXfer executable filename read}, and
19870 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19871 the same connection used to communicate with @value{GDBN}. With such a
19872 target, if the remote program is unstripped, the only command you need is
19873 @code{target remote} (or @code{target extended-remote}).
19875 If the remote program is stripped, or the target does not support remote
19876 program file access, start up @value{GDBN} using the name of the local
19877 unstripped copy of your program as the first argument, or use the
19878 @code{file} command. Use @code{set sysroot} to specify the location (on
19879 the host) of target libraries (unless your @value{GDBN} was compiled with
19880 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19881 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19884 The symbol file and target libraries must exactly match the executable
19885 and libraries on the target, with one exception: the files on the host
19886 system should not be stripped, even if the files on the target system
19887 are. Mismatched or missing files will lead to confusing results
19888 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19889 files may also prevent @code{gdbserver} from debugging multi-threaded
19892 @subsection Remote Connection Commands
19893 @cindex remote connection commands
19894 @value{GDBN} can communicate with the target over a serial line, or
19895 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19896 each case, @value{GDBN} uses the same protocol for debugging your
19897 program; only the medium carrying the debugging packets varies. The
19898 @code{target remote} and @code{target extended-remote} commands
19899 establish a connection to the target. Both commands accept the same
19900 arguments, which indicate the medium to use:
19904 @item target remote @var{serial-device}
19905 @itemx target extended-remote @var{serial-device}
19906 @cindex serial line, @code{target remote}
19907 Use @var{serial-device} to communicate with the target. For example,
19908 to use a serial line connected to the device named @file{/dev/ttyb}:
19911 target remote /dev/ttyb
19914 If you're using a serial line, you may want to give @value{GDBN} the
19915 @samp{--baud} option, or use the @code{set serial baud} command
19916 (@pxref{Remote Configuration, set serial baud}) before the
19917 @code{target} command.
19919 @item target remote @code{@var{host}:@var{port}}
19920 @itemx target remote @code{tcp:@var{host}:@var{port}}
19921 @itemx target extended-remote @code{@var{host}:@var{port}}
19922 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19923 @cindex @acronym{TCP} port, @code{target remote}
19924 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19925 The @var{host} may be either a host name or a numeric @acronym{IP}
19926 address; @var{port} must be a decimal number. The @var{host} could be
19927 the target machine itself, if it is directly connected to the net, or
19928 it might be a terminal server which in turn has a serial line to the
19931 For example, to connect to port 2828 on a terminal server named
19935 target remote manyfarms:2828
19938 If your remote target is actually running on the same machine as your
19939 debugger session (e.g.@: a simulator for your target running on the
19940 same host), you can omit the hostname. For example, to connect to
19941 port 1234 on your local machine:
19944 target remote :1234
19948 Note that the colon is still required here.
19950 @item target remote @code{udp:@var{host}:@var{port}}
19951 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19952 @cindex @acronym{UDP} port, @code{target remote}
19953 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19954 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19957 target remote udp:manyfarms:2828
19960 When using a @acronym{UDP} connection for remote debugging, you should
19961 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19962 can silently drop packets on busy or unreliable networks, which will
19963 cause havoc with your debugging session.
19965 @item target remote | @var{command}
19966 @itemx target extended-remote | @var{command}
19967 @cindex pipe, @code{target remote} to
19968 Run @var{command} in the background and communicate with it using a
19969 pipe. The @var{command} is a shell command, to be parsed and expanded
19970 by the system's command shell, @code{/bin/sh}; it should expect remote
19971 protocol packets on its standard input, and send replies on its
19972 standard output. You could use this to run a stand-alone simulator
19973 that speaks the remote debugging protocol, to make net connections
19974 using programs like @code{ssh}, or for other similar tricks.
19976 If @var{command} closes its standard output (perhaps by exiting),
19977 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19978 program has already exited, this will have no effect.)
19982 @cindex interrupting remote programs
19983 @cindex remote programs, interrupting
19984 Whenever @value{GDBN} is waiting for the remote program, if you type the
19985 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19986 program. This may or may not succeed, depending in part on the hardware
19987 and the serial drivers the remote system uses. If you type the
19988 interrupt character once again, @value{GDBN} displays this prompt:
19991 Interrupted while waiting for the program.
19992 Give up (and stop debugging it)? (y or n)
19995 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19996 the remote debugging session. (If you decide you want to try again later,
19997 you can use @kbd{target remote} again to connect once more.) If you type
19998 @kbd{n}, @value{GDBN} goes back to waiting.
20000 In @code{target extended-remote} mode, typing @kbd{n} will leave
20001 @value{GDBN} connected to the target.
20004 @kindex detach (remote)
20006 When you have finished debugging the remote program, you can use the
20007 @code{detach} command to release it from @value{GDBN} control.
20008 Detaching from the target normally resumes its execution, but the results
20009 will depend on your particular remote stub. After the @code{detach}
20010 command in @code{target remote} mode, @value{GDBN} is free to connect to
20011 another target. In @code{target extended-remote} mode, @value{GDBN} is
20012 still connected to the target.
20016 The @code{disconnect} command closes the connection to the target, and
20017 the target is generally not resumed. It will wait for @value{GDBN}
20018 (this instance or another one) to connect and continue debugging. After
20019 the @code{disconnect} command, @value{GDBN} is again free to connect to
20022 @cindex send command to remote monitor
20023 @cindex extend @value{GDBN} for remote targets
20024 @cindex add new commands for external monitor
20026 @item monitor @var{cmd}
20027 This command allows you to send arbitrary commands directly to the
20028 remote monitor. Since @value{GDBN} doesn't care about the commands it
20029 sends like this, this command is the way to extend @value{GDBN}---you
20030 can add new commands that only the external monitor will understand
20034 @node File Transfer
20035 @section Sending files to a remote system
20036 @cindex remote target, file transfer
20037 @cindex file transfer
20038 @cindex sending files to remote systems
20040 Some remote targets offer the ability to transfer files over the same
20041 connection used to communicate with @value{GDBN}. This is convenient
20042 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20043 running @code{gdbserver} over a network interface. For other targets,
20044 e.g.@: embedded devices with only a single serial port, this may be
20045 the only way to upload or download files.
20047 Not all remote targets support these commands.
20051 @item remote put @var{hostfile} @var{targetfile}
20052 Copy file @var{hostfile} from the host system (the machine running
20053 @value{GDBN}) to @var{targetfile} on the target system.
20056 @item remote get @var{targetfile} @var{hostfile}
20057 Copy file @var{targetfile} from the target system to @var{hostfile}
20058 on the host system.
20060 @kindex remote delete
20061 @item remote delete @var{targetfile}
20062 Delete @var{targetfile} from the target system.
20067 @section Using the @code{gdbserver} Program
20070 @cindex remote connection without stubs
20071 @code{gdbserver} is a control program for Unix-like systems, which
20072 allows you to connect your program with a remote @value{GDBN} via
20073 @code{target remote} or @code{target extended-remote}---but without
20074 linking in the usual debugging stub.
20076 @code{gdbserver} is not a complete replacement for the debugging stubs,
20077 because it requires essentially the same operating-system facilities
20078 that @value{GDBN} itself does. In fact, a system that can run
20079 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20080 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20081 because it is a much smaller program than @value{GDBN} itself. It is
20082 also easier to port than all of @value{GDBN}, so you may be able to get
20083 started more quickly on a new system by using @code{gdbserver}.
20084 Finally, if you develop code for real-time systems, you may find that
20085 the tradeoffs involved in real-time operation make it more convenient to
20086 do as much development work as possible on another system, for example
20087 by cross-compiling. You can use @code{gdbserver} to make a similar
20088 choice for debugging.
20090 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20091 or a TCP connection, using the standard @value{GDBN} remote serial
20095 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20096 Do not run @code{gdbserver} connected to any public network; a
20097 @value{GDBN} connection to @code{gdbserver} provides access to the
20098 target system with the same privileges as the user running
20102 @anchor{Running gdbserver}
20103 @subsection Running @code{gdbserver}
20104 @cindex arguments, to @code{gdbserver}
20105 @cindex @code{gdbserver}, command-line arguments
20107 Run @code{gdbserver} on the target system. You need a copy of the
20108 program you want to debug, including any libraries it requires.
20109 @code{gdbserver} does not need your program's symbol table, so you can
20110 strip the program if necessary to save space. @value{GDBN} on the host
20111 system does all the symbol handling.
20113 To use the server, you must tell it how to communicate with @value{GDBN};
20114 the name of your program; and the arguments for your program. The usual
20118 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20121 @var{comm} is either a device name (to use a serial line), or a TCP
20122 hostname and portnumber, or @code{-} or @code{stdio} to use
20123 stdin/stdout of @code{gdbserver}.
20124 For example, to debug Emacs with the argument
20125 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20129 target> gdbserver /dev/com1 emacs foo.txt
20132 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20135 To use a TCP connection instead of a serial line:
20138 target> gdbserver host:2345 emacs foo.txt
20141 The only difference from the previous example is the first argument,
20142 specifying that you are communicating with the host @value{GDBN} via
20143 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20144 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20145 (Currently, the @samp{host} part is ignored.) You can choose any number
20146 you want for the port number as long as it does not conflict with any
20147 TCP ports already in use on the target system (for example, @code{23} is
20148 reserved for @code{telnet}).@footnote{If you choose a port number that
20149 conflicts with another service, @code{gdbserver} prints an error message
20150 and exits.} You must use the same port number with the host @value{GDBN}
20151 @code{target remote} command.
20153 The @code{stdio} connection is useful when starting @code{gdbserver}
20157 (gdb) target remote | ssh -T hostname gdbserver - hello
20160 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20161 and we don't want escape-character handling. Ssh does this by default when
20162 a command is provided, the flag is provided to make it explicit.
20163 You could elide it if you want to.
20165 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20166 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20167 display through a pipe connected to gdbserver.
20168 Both @code{stdout} and @code{stderr} use the same pipe.
20170 @anchor{Attaching to a program}
20171 @subsubsection Attaching to a Running Program
20172 @cindex attach to a program, @code{gdbserver}
20173 @cindex @option{--attach}, @code{gdbserver} option
20175 On some targets, @code{gdbserver} can also attach to running programs.
20176 This is accomplished via the @code{--attach} argument. The syntax is:
20179 target> gdbserver --attach @var{comm} @var{pid}
20182 @var{pid} is the process ID of a currently running process. It isn't
20183 necessary to point @code{gdbserver} at a binary for the running process.
20185 In @code{target extended-remote} mode, you can also attach using the
20186 @value{GDBN} attach command
20187 (@pxref{Attaching in Types of Remote Connections}).
20190 You can debug processes by name instead of process ID if your target has the
20191 @code{pidof} utility:
20194 target> gdbserver --attach @var{comm} `pidof @var{program}`
20197 In case more than one copy of @var{program} is running, or @var{program}
20198 has multiple threads, most versions of @code{pidof} support the
20199 @code{-s} option to only return the first process ID.
20201 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20203 This section applies only when @code{gdbserver} is run to listen on a TCP
20206 @code{gdbserver} normally terminates after all of its debugged processes have
20207 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20208 extended-remote}, @code{gdbserver} stays running even with no processes left.
20209 @value{GDBN} normally terminates the spawned debugged process on its exit,
20210 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20211 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20212 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20213 stays running even in the @kbd{target remote} mode.
20215 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20216 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20217 completeness, at most one @value{GDBN} can be connected at a time.
20219 @cindex @option{--once}, @code{gdbserver} option
20220 By default, @code{gdbserver} keeps the listening TCP port open, so that
20221 subsequent connections are possible. However, if you start @code{gdbserver}
20222 with the @option{--once} option, it will stop listening for any further
20223 connection attempts after connecting to the first @value{GDBN} session. This
20224 means no further connections to @code{gdbserver} will be possible after the
20225 first one. It also means @code{gdbserver} will terminate after the first
20226 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20227 connections and even in the @kbd{target extended-remote} mode. The
20228 @option{--once} option allows reusing the same port number for connecting to
20229 multiple instances of @code{gdbserver} running on the same host, since each
20230 instance closes its port after the first connection.
20232 @anchor{Other Command-Line Arguments for gdbserver}
20233 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20235 You can use the @option{--multi} option to start @code{gdbserver} without
20236 specifying a program to debug or a process to attach to. Then you can
20237 attach in @code{target extended-remote} mode and run or attach to a
20238 program. For more information,
20239 @pxref{--multi Option in Types of Remote Connnections}.
20241 @cindex @option{--debug}, @code{gdbserver} option
20242 The @option{--debug} option tells @code{gdbserver} to display extra
20243 status information about the debugging process.
20244 @cindex @option{--remote-debug}, @code{gdbserver} option
20245 The @option{--remote-debug} option tells @code{gdbserver} to display
20246 remote protocol debug output. These options are intended for
20247 @code{gdbserver} development and for bug reports to the developers.
20249 @cindex @option{--debug-format}, @code{gdbserver} option
20250 The @option{--debug-format=option1[,option2,...]} option tells
20251 @code{gdbserver} to include additional information in each output.
20252 Possible options are:
20256 Turn off all extra information in debugging output.
20258 Turn on all extra information in debugging output.
20260 Include a timestamp in each line of debugging output.
20263 Options are processed in order. Thus, for example, if @option{none}
20264 appears last then no additional information is added to debugging output.
20266 @cindex @option{--wrapper}, @code{gdbserver} option
20267 The @option{--wrapper} option specifies a wrapper to launch programs
20268 for debugging. The option should be followed by the name of the
20269 wrapper, then any command-line arguments to pass to the wrapper, then
20270 @kbd{--} indicating the end of the wrapper arguments.
20272 @code{gdbserver} runs the specified wrapper program with a combined
20273 command line including the wrapper arguments, then the name of the
20274 program to debug, then any arguments to the program. The wrapper
20275 runs until it executes your program, and then @value{GDBN} gains control.
20277 You can use any program that eventually calls @code{execve} with
20278 its arguments as a wrapper. Several standard Unix utilities do
20279 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20280 with @code{exec "$@@"} will also work.
20282 For example, you can use @code{env} to pass an environment variable to
20283 the debugged program, without setting the variable in @code{gdbserver}'s
20287 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20290 @cindex @option{--selftest}
20291 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20294 $ gdbserver --selftest
20295 Ran 2 unit tests, 0 failed
20298 These tests are disabled in release.
20299 @subsection Connecting to @code{gdbserver}
20301 The basic procedure for connecting to the remote target is:
20305 Run @value{GDBN} on the host system.
20308 Make sure you have the necessary symbol files
20309 (@pxref{Host and target files}).
20310 Load symbols for your application using the @code{file} command before you
20311 connect. Use @code{set sysroot} to locate target libraries (unless your
20312 @value{GDBN} was compiled with the correct sysroot using
20313 @code{--with-sysroot}).
20316 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20317 For TCP connections, you must start up @code{gdbserver} prior to using
20318 the @code{target} command. Otherwise you may get an error whose
20319 text depends on the host system, but which usually looks something like
20320 @samp{Connection refused}. Don't use the @code{load}
20321 command in @value{GDBN} when using @code{target remote} mode, since the
20322 program is already on the target.
20326 @anchor{Monitor Commands for gdbserver}
20327 @subsection Monitor Commands for @code{gdbserver}
20328 @cindex monitor commands, for @code{gdbserver}
20330 During a @value{GDBN} session using @code{gdbserver}, you can use the
20331 @code{monitor} command to send special requests to @code{gdbserver}.
20332 Here are the available commands.
20336 List the available monitor commands.
20338 @item monitor set debug 0
20339 @itemx monitor set debug 1
20340 Disable or enable general debugging messages.
20342 @item monitor set remote-debug 0
20343 @itemx monitor set remote-debug 1
20344 Disable or enable specific debugging messages associated with the remote
20345 protocol (@pxref{Remote Protocol}).
20347 @item monitor set debug-format option1@r{[},option2,...@r{]}
20348 Specify additional text to add to debugging messages.
20349 Possible options are:
20353 Turn off all extra information in debugging output.
20355 Turn on all extra information in debugging output.
20357 Include a timestamp in each line of debugging output.
20360 Options are processed in order. Thus, for example, if @option{none}
20361 appears last then no additional information is added to debugging output.
20363 @item monitor set libthread-db-search-path [PATH]
20364 @cindex gdbserver, search path for @code{libthread_db}
20365 When this command is issued, @var{path} is a colon-separated list of
20366 directories to search for @code{libthread_db} (@pxref{Threads,,set
20367 libthread-db-search-path}). If you omit @var{path},
20368 @samp{libthread-db-search-path} will be reset to its default value.
20370 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20371 not supported in @code{gdbserver}.
20374 Tell gdbserver to exit immediately. This command should be followed by
20375 @code{disconnect} to close the debugging session. @code{gdbserver} will
20376 detach from any attached processes and kill any processes it created.
20377 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20378 of a multi-process mode debug session.
20382 @subsection Tracepoints support in @code{gdbserver}
20383 @cindex tracepoints support in @code{gdbserver}
20385 On some targets, @code{gdbserver} supports tracepoints, fast
20386 tracepoints and static tracepoints.
20388 For fast or static tracepoints to work, a special library called the
20389 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20390 This library is built and distributed as an integral part of
20391 @code{gdbserver}. In addition, support for static tracepoints
20392 requires building the in-process agent library with static tracepoints
20393 support. At present, the UST (LTTng Userspace Tracer,
20394 @url{http://lttng.org/ust}) tracing engine is supported. This support
20395 is automatically available if UST development headers are found in the
20396 standard include path when @code{gdbserver} is built, or if
20397 @code{gdbserver} was explicitly configured using @option{--with-ust}
20398 to point at such headers. You can explicitly disable the support
20399 using @option{--with-ust=no}.
20401 There are several ways to load the in-process agent in your program:
20404 @item Specifying it as dependency at link time
20406 You can link your program dynamically with the in-process agent
20407 library. On most systems, this is accomplished by adding
20408 @code{-linproctrace} to the link command.
20410 @item Using the system's preloading mechanisms
20412 You can force loading the in-process agent at startup time by using
20413 your system's support for preloading shared libraries. Many Unixes
20414 support the concept of preloading user defined libraries. In most
20415 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20416 in the environment. See also the description of @code{gdbserver}'s
20417 @option{--wrapper} command line option.
20419 @item Using @value{GDBN} to force loading the agent at run time
20421 On some systems, you can force the inferior to load a shared library,
20422 by calling a dynamic loader function in the inferior that takes care
20423 of dynamically looking up and loading a shared library. On most Unix
20424 systems, the function is @code{dlopen}. You'll use the @code{call}
20425 command for that. For example:
20428 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20431 Note that on most Unix systems, for the @code{dlopen} function to be
20432 available, the program needs to be linked with @code{-ldl}.
20435 On systems that have a userspace dynamic loader, like most Unix
20436 systems, when you connect to @code{gdbserver} using @code{target
20437 remote}, you'll find that the program is stopped at the dynamic
20438 loader's entry point, and no shared library has been loaded in the
20439 program's address space yet, including the in-process agent. In that
20440 case, before being able to use any of the fast or static tracepoints
20441 features, you need to let the loader run and load the shared
20442 libraries. The simplest way to do that is to run the program to the
20443 main procedure. E.g., if debugging a C or C@t{++} program, start
20444 @code{gdbserver} like so:
20447 $ gdbserver :9999 myprogram
20450 Start GDB and connect to @code{gdbserver} like so, and run to main:
20454 (@value{GDBP}) target remote myhost:9999
20455 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20456 (@value{GDBP}) b main
20457 (@value{GDBP}) continue
20460 The in-process tracing agent library should now be loaded into the
20461 process; you can confirm it with the @code{info sharedlibrary}
20462 command, which will list @file{libinproctrace.so} as loaded in the
20463 process. You are now ready to install fast tracepoints, list static
20464 tracepoint markers, probe static tracepoints markers, and start
20467 @node Remote Configuration
20468 @section Remote Configuration
20471 @kindex show remote
20472 This section documents the configuration options available when
20473 debugging remote programs. For the options related to the File I/O
20474 extensions of the remote protocol, see @ref{system,
20475 system-call-allowed}.
20478 @item set remoteaddresssize @var{bits}
20479 @cindex address size for remote targets
20480 @cindex bits in remote address
20481 Set the maximum size of address in a memory packet to the specified
20482 number of bits. @value{GDBN} will mask off the address bits above
20483 that number, when it passes addresses to the remote target. The
20484 default value is the number of bits in the target's address.
20486 @item show remoteaddresssize
20487 Show the current value of remote address size in bits.
20489 @item set serial baud @var{n}
20490 @cindex baud rate for remote targets
20491 Set the baud rate for the remote serial I/O to @var{n} baud. The
20492 value is used to set the speed of the serial port used for debugging
20495 @item show serial baud
20496 Show the current speed of the remote connection.
20498 @item set serial parity @var{parity}
20499 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20500 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20502 @item show serial parity
20503 Show the current parity of the serial port.
20505 @item set remotebreak
20506 @cindex interrupt remote programs
20507 @cindex BREAK signal instead of Ctrl-C
20508 @anchor{set remotebreak}
20509 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20510 when you type @kbd{Ctrl-c} to interrupt the program running
20511 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20512 character instead. The default is off, since most remote systems
20513 expect to see @samp{Ctrl-C} as the interrupt signal.
20515 @item show remotebreak
20516 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20517 interrupt the remote program.
20519 @item set remoteflow on
20520 @itemx set remoteflow off
20521 @kindex set remoteflow
20522 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20523 on the serial port used to communicate to the remote target.
20525 @item show remoteflow
20526 @kindex show remoteflow
20527 Show the current setting of hardware flow control.
20529 @item set remotelogbase @var{base}
20530 Set the base (a.k.a.@: radix) of logging serial protocol
20531 communications to @var{base}. Supported values of @var{base} are:
20532 @code{ascii}, @code{octal}, and @code{hex}. The default is
20535 @item show remotelogbase
20536 Show the current setting of the radix for logging remote serial
20539 @item set remotelogfile @var{file}
20540 @cindex record serial communications on file
20541 Record remote serial communications on the named @var{file}. The
20542 default is not to record at all.
20544 @item show remotelogfile.
20545 Show the current setting of the file name on which to record the
20546 serial communications.
20548 @item set remotetimeout @var{num}
20549 @cindex timeout for serial communications
20550 @cindex remote timeout
20551 Set the timeout limit to wait for the remote target to respond to
20552 @var{num} seconds. The default is 2 seconds.
20554 @item show remotetimeout
20555 Show the current number of seconds to wait for the remote target
20558 @cindex limit hardware breakpoints and watchpoints
20559 @cindex remote target, limit break- and watchpoints
20560 @anchor{set remote hardware-watchpoint-limit}
20561 @anchor{set remote hardware-breakpoint-limit}
20562 @item set remote hardware-watchpoint-limit @var{limit}
20563 @itemx set remote hardware-breakpoint-limit @var{limit}
20564 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20565 watchpoints. A limit of -1, the default, is treated as unlimited.
20567 @cindex limit hardware watchpoints length
20568 @cindex remote target, limit watchpoints length
20569 @anchor{set remote hardware-watchpoint-length-limit}
20570 @item set remote hardware-watchpoint-length-limit @var{limit}
20571 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20572 a remote hardware watchpoint. A limit of -1, the default, is treated
20575 @item show remote hardware-watchpoint-length-limit
20576 Show the current limit (in bytes) of the maximum length of
20577 a remote hardware watchpoint.
20579 @item set remote exec-file @var{filename}
20580 @itemx show remote exec-file
20581 @anchor{set remote exec-file}
20582 @cindex executable file, for remote target
20583 Select the file used for @code{run} with @code{target
20584 extended-remote}. This should be set to a filename valid on the
20585 target system. If it is not set, the target will use a default
20586 filename (e.g.@: the last program run).
20588 @item set remote interrupt-sequence
20589 @cindex interrupt remote programs
20590 @cindex select Ctrl-C, BREAK or BREAK-g
20591 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20592 @samp{BREAK-g} as the
20593 sequence to the remote target in order to interrupt the execution.
20594 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20595 is high level of serial line for some certain time.
20596 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20597 It is @code{BREAK} signal followed by character @code{g}.
20599 @item show interrupt-sequence
20600 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20601 is sent by @value{GDBN} to interrupt the remote program.
20602 @code{BREAK-g} is BREAK signal followed by @code{g} and
20603 also known as Magic SysRq g.
20605 @item set remote interrupt-on-connect
20606 @cindex send interrupt-sequence on start
20607 Specify whether interrupt-sequence is sent to remote target when
20608 @value{GDBN} connects to it. This is mostly needed when you debug
20609 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20610 which is known as Magic SysRq g in order to connect @value{GDBN}.
20612 @item show interrupt-on-connect
20613 Show whether interrupt-sequence is sent
20614 to remote target when @value{GDBN} connects to it.
20618 @item set tcp auto-retry on
20619 @cindex auto-retry, for remote TCP target
20620 Enable auto-retry for remote TCP connections. This is useful if the remote
20621 debugging agent is launched in parallel with @value{GDBN}; there is a race
20622 condition because the agent may not become ready to accept the connection
20623 before @value{GDBN} attempts to connect. When auto-retry is
20624 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20625 to establish the connection using the timeout specified by
20626 @code{set tcp connect-timeout}.
20628 @item set tcp auto-retry off
20629 Do not auto-retry failed TCP connections.
20631 @item show tcp auto-retry
20632 Show the current auto-retry setting.
20634 @item set tcp connect-timeout @var{seconds}
20635 @itemx set tcp connect-timeout unlimited
20636 @cindex connection timeout, for remote TCP target
20637 @cindex timeout, for remote target connection
20638 Set the timeout for establishing a TCP connection to the remote target to
20639 @var{seconds}. The timeout affects both polling to retry failed connections
20640 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20641 that are merely slow to complete, and represents an approximate cumulative
20642 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20643 @value{GDBN} will keep attempting to establish a connection forever,
20644 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20646 @item show tcp connect-timeout
20647 Show the current connection timeout setting.
20650 @cindex remote packets, enabling and disabling
20651 The @value{GDBN} remote protocol autodetects the packets supported by
20652 your debugging stub. If you need to override the autodetection, you
20653 can use these commands to enable or disable individual packets. Each
20654 packet can be set to @samp{on} (the remote target supports this
20655 packet), @samp{off} (the remote target does not support this packet),
20656 or @samp{auto} (detect remote target support for this packet). They
20657 all default to @samp{auto}. For more information about each packet,
20658 see @ref{Remote Protocol}.
20660 During normal use, you should not have to use any of these commands.
20661 If you do, that may be a bug in your remote debugging stub, or a bug
20662 in @value{GDBN}. You may want to report the problem to the
20663 @value{GDBN} developers.
20665 For each packet @var{name}, the command to enable or disable the
20666 packet is @code{set remote @var{name}-packet}. The available settings
20669 @multitable @columnfractions 0.28 0.32 0.25
20672 @tab Related Features
20674 @item @code{fetch-register}
20676 @tab @code{info registers}
20678 @item @code{set-register}
20682 @item @code{binary-download}
20684 @tab @code{load}, @code{set}
20686 @item @code{read-aux-vector}
20687 @tab @code{qXfer:auxv:read}
20688 @tab @code{info auxv}
20690 @item @code{symbol-lookup}
20691 @tab @code{qSymbol}
20692 @tab Detecting multiple threads
20694 @item @code{attach}
20695 @tab @code{vAttach}
20698 @item @code{verbose-resume}
20700 @tab Stepping or resuming multiple threads
20706 @item @code{software-breakpoint}
20710 @item @code{hardware-breakpoint}
20714 @item @code{write-watchpoint}
20718 @item @code{read-watchpoint}
20722 @item @code{access-watchpoint}
20726 @item @code{pid-to-exec-file}
20727 @tab @code{qXfer:exec-file:read}
20728 @tab @code{attach}, @code{run}
20730 @item @code{target-features}
20731 @tab @code{qXfer:features:read}
20732 @tab @code{set architecture}
20734 @item @code{library-info}
20735 @tab @code{qXfer:libraries:read}
20736 @tab @code{info sharedlibrary}
20738 @item @code{memory-map}
20739 @tab @code{qXfer:memory-map:read}
20740 @tab @code{info mem}
20742 @item @code{read-sdata-object}
20743 @tab @code{qXfer:sdata:read}
20744 @tab @code{print $_sdata}
20746 @item @code{read-spu-object}
20747 @tab @code{qXfer:spu:read}
20748 @tab @code{info spu}
20750 @item @code{write-spu-object}
20751 @tab @code{qXfer:spu:write}
20752 @tab @code{info spu}
20754 @item @code{read-siginfo-object}
20755 @tab @code{qXfer:siginfo:read}
20756 @tab @code{print $_siginfo}
20758 @item @code{write-siginfo-object}
20759 @tab @code{qXfer:siginfo:write}
20760 @tab @code{set $_siginfo}
20762 @item @code{threads}
20763 @tab @code{qXfer:threads:read}
20764 @tab @code{info threads}
20766 @item @code{get-thread-local-@*storage-address}
20767 @tab @code{qGetTLSAddr}
20768 @tab Displaying @code{__thread} variables
20770 @item @code{get-thread-information-block-address}
20771 @tab @code{qGetTIBAddr}
20772 @tab Display MS-Windows Thread Information Block.
20774 @item @code{search-memory}
20775 @tab @code{qSearch:memory}
20778 @item @code{supported-packets}
20779 @tab @code{qSupported}
20780 @tab Remote communications parameters
20782 @item @code{catch-syscalls}
20783 @tab @code{QCatchSyscalls}
20784 @tab @code{catch syscall}
20786 @item @code{pass-signals}
20787 @tab @code{QPassSignals}
20788 @tab @code{handle @var{signal}}
20790 @item @code{program-signals}
20791 @tab @code{QProgramSignals}
20792 @tab @code{handle @var{signal}}
20794 @item @code{hostio-close-packet}
20795 @tab @code{vFile:close}
20796 @tab @code{remote get}, @code{remote put}
20798 @item @code{hostio-open-packet}
20799 @tab @code{vFile:open}
20800 @tab @code{remote get}, @code{remote put}
20802 @item @code{hostio-pread-packet}
20803 @tab @code{vFile:pread}
20804 @tab @code{remote get}, @code{remote put}
20806 @item @code{hostio-pwrite-packet}
20807 @tab @code{vFile:pwrite}
20808 @tab @code{remote get}, @code{remote put}
20810 @item @code{hostio-unlink-packet}
20811 @tab @code{vFile:unlink}
20812 @tab @code{remote delete}
20814 @item @code{hostio-readlink-packet}
20815 @tab @code{vFile:readlink}
20818 @item @code{hostio-fstat-packet}
20819 @tab @code{vFile:fstat}
20822 @item @code{hostio-setfs-packet}
20823 @tab @code{vFile:setfs}
20826 @item @code{noack-packet}
20827 @tab @code{QStartNoAckMode}
20828 @tab Packet acknowledgment
20830 @item @code{osdata}
20831 @tab @code{qXfer:osdata:read}
20832 @tab @code{info os}
20834 @item @code{query-attached}
20835 @tab @code{qAttached}
20836 @tab Querying remote process attach state.
20838 @item @code{trace-buffer-size}
20839 @tab @code{QTBuffer:size}
20840 @tab @code{set trace-buffer-size}
20842 @item @code{trace-status}
20843 @tab @code{qTStatus}
20844 @tab @code{tstatus}
20846 @item @code{traceframe-info}
20847 @tab @code{qXfer:traceframe-info:read}
20848 @tab Traceframe info
20850 @item @code{install-in-trace}
20851 @tab @code{InstallInTrace}
20852 @tab Install tracepoint in tracing
20854 @item @code{disable-randomization}
20855 @tab @code{QDisableRandomization}
20856 @tab @code{set disable-randomization}
20858 @item @code{startup-with-shell}
20859 @tab @code{QStartupWithShell}
20860 @tab @code{set startup-with-shell}
20862 @item @code{environment-hex-encoded}
20863 @tab @code{QEnvironmentHexEncoded}
20864 @tab @code{set environment}
20866 @item @code{environment-unset}
20867 @tab @code{QEnvironmentUnset}
20868 @tab @code{unset environment}
20870 @item @code{environment-reset}
20871 @tab @code{QEnvironmentReset}
20872 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
20874 @item @code{conditional-breakpoints-packet}
20875 @tab @code{Z0 and Z1}
20876 @tab @code{Support for target-side breakpoint condition evaluation}
20878 @item @code{multiprocess-extensions}
20879 @tab @code{multiprocess extensions}
20880 @tab Debug multiple processes and remote process PID awareness
20882 @item @code{swbreak-feature}
20883 @tab @code{swbreak stop reason}
20886 @item @code{hwbreak-feature}
20887 @tab @code{hwbreak stop reason}
20890 @item @code{fork-event-feature}
20891 @tab @code{fork stop reason}
20894 @item @code{vfork-event-feature}
20895 @tab @code{vfork stop reason}
20898 @item @code{exec-event-feature}
20899 @tab @code{exec stop reason}
20902 @item @code{thread-events}
20903 @tab @code{QThreadEvents}
20904 @tab Tracking thread lifetime.
20906 @item @code{no-resumed-stop-reply}
20907 @tab @code{no resumed thread left stop reply}
20908 @tab Tracking thread lifetime.
20913 @section Implementing a Remote Stub
20915 @cindex debugging stub, example
20916 @cindex remote stub, example
20917 @cindex stub example, remote debugging
20918 The stub files provided with @value{GDBN} implement the target side of the
20919 communication protocol, and the @value{GDBN} side is implemented in the
20920 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20921 these subroutines to communicate, and ignore the details. (If you're
20922 implementing your own stub file, you can still ignore the details: start
20923 with one of the existing stub files. @file{sparc-stub.c} is the best
20924 organized, and therefore the easiest to read.)
20926 @cindex remote serial debugging, overview
20927 To debug a program running on another machine (the debugging
20928 @dfn{target} machine), you must first arrange for all the usual
20929 prerequisites for the program to run by itself. For example, for a C
20934 A startup routine to set up the C runtime environment; these usually
20935 have a name like @file{crt0}. The startup routine may be supplied by
20936 your hardware supplier, or you may have to write your own.
20939 A C subroutine library to support your program's
20940 subroutine calls, notably managing input and output.
20943 A way of getting your program to the other machine---for example, a
20944 download program. These are often supplied by the hardware
20945 manufacturer, but you may have to write your own from hardware
20949 The next step is to arrange for your program to use a serial port to
20950 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20951 machine). In general terms, the scheme looks like this:
20955 @value{GDBN} already understands how to use this protocol; when everything
20956 else is set up, you can simply use the @samp{target remote} command
20957 (@pxref{Targets,,Specifying a Debugging Target}).
20959 @item On the target,
20960 you must link with your program a few special-purpose subroutines that
20961 implement the @value{GDBN} remote serial protocol. The file containing these
20962 subroutines is called a @dfn{debugging stub}.
20964 On certain remote targets, you can use an auxiliary program
20965 @code{gdbserver} instead of linking a stub into your program.
20966 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20969 The debugging stub is specific to the architecture of the remote
20970 machine; for example, use @file{sparc-stub.c} to debug programs on
20973 @cindex remote serial stub list
20974 These working remote stubs are distributed with @value{GDBN}:
20979 @cindex @file{i386-stub.c}
20982 For Intel 386 and compatible architectures.
20985 @cindex @file{m68k-stub.c}
20986 @cindex Motorola 680x0
20988 For Motorola 680x0 architectures.
20991 @cindex @file{sh-stub.c}
20994 For Renesas SH architectures.
20997 @cindex @file{sparc-stub.c}
20999 For @sc{sparc} architectures.
21001 @item sparcl-stub.c
21002 @cindex @file{sparcl-stub.c}
21005 For Fujitsu @sc{sparclite} architectures.
21009 The @file{README} file in the @value{GDBN} distribution may list other
21010 recently added stubs.
21013 * Stub Contents:: What the stub can do for you
21014 * Bootstrapping:: What you must do for the stub
21015 * Debug Session:: Putting it all together
21018 @node Stub Contents
21019 @subsection What the Stub Can Do for You
21021 @cindex remote serial stub
21022 The debugging stub for your architecture supplies these three
21026 @item set_debug_traps
21027 @findex set_debug_traps
21028 @cindex remote serial stub, initialization
21029 This routine arranges for @code{handle_exception} to run when your
21030 program stops. You must call this subroutine explicitly in your
21031 program's startup code.
21033 @item handle_exception
21034 @findex handle_exception
21035 @cindex remote serial stub, main routine
21036 This is the central workhorse, but your program never calls it
21037 explicitly---the setup code arranges for @code{handle_exception} to
21038 run when a trap is triggered.
21040 @code{handle_exception} takes control when your program stops during
21041 execution (for example, on a breakpoint), and mediates communications
21042 with @value{GDBN} on the host machine. This is where the communications
21043 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21044 representative on the target machine. It begins by sending summary
21045 information on the state of your program, then continues to execute,
21046 retrieving and transmitting any information @value{GDBN} needs, until you
21047 execute a @value{GDBN} command that makes your program resume; at that point,
21048 @code{handle_exception} returns control to your own code on the target
21052 @cindex @code{breakpoint} subroutine, remote
21053 Use this auxiliary subroutine to make your program contain a
21054 breakpoint. Depending on the particular situation, this may be the only
21055 way for @value{GDBN} to get control. For instance, if your target
21056 machine has some sort of interrupt button, you won't need to call this;
21057 pressing the interrupt button transfers control to
21058 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21059 simply receiving characters on the serial port may also trigger a trap;
21060 again, in that situation, you don't need to call @code{breakpoint} from
21061 your own program---simply running @samp{target remote} from the host
21062 @value{GDBN} session gets control.
21064 Call @code{breakpoint} if none of these is true, or if you simply want
21065 to make certain your program stops at a predetermined point for the
21066 start of your debugging session.
21069 @node Bootstrapping
21070 @subsection What You Must Do for the Stub
21072 @cindex remote stub, support routines
21073 The debugging stubs that come with @value{GDBN} are set up for a particular
21074 chip architecture, but they have no information about the rest of your
21075 debugging target machine.
21077 First of all you need to tell the stub how to communicate with the
21081 @item int getDebugChar()
21082 @findex getDebugChar
21083 Write this subroutine to read a single character from the serial port.
21084 It may be identical to @code{getchar} for your target system; a
21085 different name is used to allow you to distinguish the two if you wish.
21087 @item void putDebugChar(int)
21088 @findex putDebugChar
21089 Write this subroutine to write a single character to the serial port.
21090 It may be identical to @code{putchar} for your target system; a
21091 different name is used to allow you to distinguish the two if you wish.
21094 @cindex control C, and remote debugging
21095 @cindex interrupting remote targets
21096 If you want @value{GDBN} to be able to stop your program while it is
21097 running, you need to use an interrupt-driven serial driver, and arrange
21098 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21099 character). That is the character which @value{GDBN} uses to tell the
21100 remote system to stop.
21102 Getting the debugging target to return the proper status to @value{GDBN}
21103 probably requires changes to the standard stub; one quick and dirty way
21104 is to just execute a breakpoint instruction (the ``dirty'' part is that
21105 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21107 Other routines you need to supply are:
21110 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21111 @findex exceptionHandler
21112 Write this function to install @var{exception_address} in the exception
21113 handling tables. You need to do this because the stub does not have any
21114 way of knowing what the exception handling tables on your target system
21115 are like (for example, the processor's table might be in @sc{rom},
21116 containing entries which point to a table in @sc{ram}).
21117 The @var{exception_number} specifies the exception which should be changed;
21118 its meaning is architecture-dependent (for example, different numbers
21119 might represent divide by zero, misaligned access, etc). When this
21120 exception occurs, control should be transferred directly to
21121 @var{exception_address}, and the processor state (stack, registers,
21122 and so on) should be just as it is when a processor exception occurs. So if
21123 you want to use a jump instruction to reach @var{exception_address}, it
21124 should be a simple jump, not a jump to subroutine.
21126 For the 386, @var{exception_address} should be installed as an interrupt
21127 gate so that interrupts are masked while the handler runs. The gate
21128 should be at privilege level 0 (the most privileged level). The
21129 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21130 help from @code{exceptionHandler}.
21132 @item void flush_i_cache()
21133 @findex flush_i_cache
21134 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21135 instruction cache, if any, on your target machine. If there is no
21136 instruction cache, this subroutine may be a no-op.
21138 On target machines that have instruction caches, @value{GDBN} requires this
21139 function to make certain that the state of your program is stable.
21143 You must also make sure this library routine is available:
21146 @item void *memset(void *, int, int)
21148 This is the standard library function @code{memset} that sets an area of
21149 memory to a known value. If you have one of the free versions of
21150 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21151 either obtain it from your hardware manufacturer, or write your own.
21154 If you do not use the GNU C compiler, you may need other standard
21155 library subroutines as well; this varies from one stub to another,
21156 but in general the stubs are likely to use any of the common library
21157 subroutines which @code{@value{NGCC}} generates as inline code.
21160 @node Debug Session
21161 @subsection Putting it All Together
21163 @cindex remote serial debugging summary
21164 In summary, when your program is ready to debug, you must follow these
21169 Make sure you have defined the supporting low-level routines
21170 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21172 @code{getDebugChar}, @code{putDebugChar},
21173 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21177 Insert these lines in your program's startup code, before the main
21178 procedure is called:
21185 On some machines, when a breakpoint trap is raised, the hardware
21186 automatically makes the PC point to the instruction after the
21187 breakpoint. If your machine doesn't do that, you may need to adjust
21188 @code{handle_exception} to arrange for it to return to the instruction
21189 after the breakpoint on this first invocation, so that your program
21190 doesn't keep hitting the initial breakpoint instead of making
21194 For the 680x0 stub only, you need to provide a variable called
21195 @code{exceptionHook}. Normally you just use:
21198 void (*exceptionHook)() = 0;
21202 but if before calling @code{set_debug_traps}, you set it to point to a
21203 function in your program, that function is called when
21204 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21205 error). The function indicated by @code{exceptionHook} is called with
21206 one parameter: an @code{int} which is the exception number.
21209 Compile and link together: your program, the @value{GDBN} debugging stub for
21210 your target architecture, and the supporting subroutines.
21213 Make sure you have a serial connection between your target machine and
21214 the @value{GDBN} host, and identify the serial port on the host.
21217 @c The "remote" target now provides a `load' command, so we should
21218 @c document that. FIXME.
21219 Download your program to your target machine (or get it there by
21220 whatever means the manufacturer provides), and start it.
21223 Start @value{GDBN} on the host, and connect to the target
21224 (@pxref{Connecting,,Connecting to a Remote Target}).
21228 @node Configurations
21229 @chapter Configuration-Specific Information
21231 While nearly all @value{GDBN} commands are available for all native and
21232 cross versions of the debugger, there are some exceptions. This chapter
21233 describes things that are only available in certain configurations.
21235 There are three major categories of configurations: native
21236 configurations, where the host and target are the same, embedded
21237 operating system configurations, which are usually the same for several
21238 different processor architectures, and bare embedded processors, which
21239 are quite different from each other.
21244 * Embedded Processors::
21251 This section describes details specific to particular native
21255 * BSD libkvm Interface:: Debugging BSD kernel memory images
21256 * SVR4 Process Information:: SVR4 process information
21257 * DJGPP Native:: Features specific to the DJGPP port
21258 * Cygwin Native:: Features specific to the Cygwin port
21259 * Hurd Native:: Features specific to @sc{gnu} Hurd
21260 * Darwin:: Features specific to Darwin
21263 @node BSD libkvm Interface
21264 @subsection BSD libkvm Interface
21267 @cindex kernel memory image
21268 @cindex kernel crash dump
21270 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21271 interface that provides a uniform interface for accessing kernel virtual
21272 memory images, including live systems and crash dumps. @value{GDBN}
21273 uses this interface to allow you to debug live kernels and kernel crash
21274 dumps on many native BSD configurations. This is implemented as a
21275 special @code{kvm} debugging target. For debugging a live system, load
21276 the currently running kernel into @value{GDBN} and connect to the
21280 (@value{GDBP}) @b{target kvm}
21283 For debugging crash dumps, provide the file name of the crash dump as an
21287 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21290 Once connected to the @code{kvm} target, the following commands are
21296 Set current context from the @dfn{Process Control Block} (PCB) address.
21299 Set current context from proc address. This command isn't available on
21300 modern FreeBSD systems.
21303 @node SVR4 Process Information
21304 @subsection SVR4 Process Information
21306 @cindex examine process image
21307 @cindex process info via @file{/proc}
21309 Many versions of SVR4 and compatible systems provide a facility called
21310 @samp{/proc} that can be used to examine the image of a running
21311 process using file-system subroutines.
21313 If @value{GDBN} is configured for an operating system with this
21314 facility, the command @code{info proc} is available to report
21315 information about the process running your program, or about any
21316 process running on your system. This includes, as of this writing,
21317 @sc{gnu}/Linux and Solaris, for example.
21319 This command may also work on core files that were created on a system
21320 that has the @samp{/proc} facility.
21326 @itemx info proc @var{process-id}
21327 Summarize available information about any running process. If a
21328 process ID is specified by @var{process-id}, display information about
21329 that process; otherwise display information about the program being
21330 debugged. The summary includes the debugged process ID, the command
21331 line used to invoke it, its current working directory, and its
21332 executable file's absolute file name.
21334 On some systems, @var{process-id} can be of the form
21335 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21336 within a process. If the optional @var{pid} part is missing, it means
21337 a thread from the process being debugged (the leading @samp{/} still
21338 needs to be present, or else @value{GDBN} will interpret the number as
21339 a process ID rather than a thread ID).
21341 @item info proc cmdline
21342 @cindex info proc cmdline
21343 Show the original command line of the process. This command is
21344 specific to @sc{gnu}/Linux.
21346 @item info proc cwd
21347 @cindex info proc cwd
21348 Show the current working directory of the process. This command is
21349 specific to @sc{gnu}/Linux.
21351 @item info proc exe
21352 @cindex info proc exe
21353 Show the name of executable of the process. This command is specific
21356 @item info proc mappings
21357 @cindex memory address space mappings
21358 Report the memory address space ranges accessible in the program, with
21359 information on whether the process has read, write, or execute access
21360 rights to each range. On @sc{gnu}/Linux systems, each memory range
21361 includes the object file which is mapped to that range, instead of the
21362 memory access rights to that range.
21364 @item info proc stat
21365 @itemx info proc status
21366 @cindex process detailed status information
21367 These subcommands are specific to @sc{gnu}/Linux systems. They show
21368 the process-related information, including the user ID and group ID;
21369 how many threads are there in the process; its virtual memory usage;
21370 the signals that are pending, blocked, and ignored; its TTY; its
21371 consumption of system and user time; its stack size; its @samp{nice}
21372 value; etc. For more information, see the @samp{proc} man page
21373 (type @kbd{man 5 proc} from your shell prompt).
21375 @item info proc all
21376 Show all the information about the process described under all of the
21377 above @code{info proc} subcommands.
21380 @comment These sub-options of 'info proc' were not included when
21381 @comment procfs.c was re-written. Keep their descriptions around
21382 @comment against the day when someone finds the time to put them back in.
21383 @kindex info proc times
21384 @item info proc times
21385 Starting time, user CPU time, and system CPU time for your program and
21388 @kindex info proc id
21390 Report on the process IDs related to your program: its own process ID,
21391 the ID of its parent, the process group ID, and the session ID.
21394 @item set procfs-trace
21395 @kindex set procfs-trace
21396 @cindex @code{procfs} API calls
21397 This command enables and disables tracing of @code{procfs} API calls.
21399 @item show procfs-trace
21400 @kindex show procfs-trace
21401 Show the current state of @code{procfs} API call tracing.
21403 @item set procfs-file @var{file}
21404 @kindex set procfs-file
21405 Tell @value{GDBN} to write @code{procfs} API trace to the named
21406 @var{file}. @value{GDBN} appends the trace info to the previous
21407 contents of the file. The default is to display the trace on the
21410 @item show procfs-file
21411 @kindex show procfs-file
21412 Show the file to which @code{procfs} API trace is written.
21414 @item proc-trace-entry
21415 @itemx proc-trace-exit
21416 @itemx proc-untrace-entry
21417 @itemx proc-untrace-exit
21418 @kindex proc-trace-entry
21419 @kindex proc-trace-exit
21420 @kindex proc-untrace-entry
21421 @kindex proc-untrace-exit
21422 These commands enable and disable tracing of entries into and exits
21423 from the @code{syscall} interface.
21426 @kindex info pidlist
21427 @cindex process list, QNX Neutrino
21428 For QNX Neutrino only, this command displays the list of all the
21429 processes and all the threads within each process.
21432 @kindex info meminfo
21433 @cindex mapinfo list, QNX Neutrino
21434 For QNX Neutrino only, this command displays the list of all mapinfos.
21438 @subsection Features for Debugging @sc{djgpp} Programs
21439 @cindex @sc{djgpp} debugging
21440 @cindex native @sc{djgpp} debugging
21441 @cindex MS-DOS-specific commands
21444 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21445 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21446 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21447 top of real-mode DOS systems and their emulations.
21449 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21450 defines a few commands specific to the @sc{djgpp} port. This
21451 subsection describes those commands.
21456 This is a prefix of @sc{djgpp}-specific commands which print
21457 information about the target system and important OS structures.
21460 @cindex MS-DOS system info
21461 @cindex free memory information (MS-DOS)
21462 @item info dos sysinfo
21463 This command displays assorted information about the underlying
21464 platform: the CPU type and features, the OS version and flavor, the
21465 DPMI version, and the available conventional and DPMI memory.
21470 @cindex segment descriptor tables
21471 @cindex descriptor tables display
21473 @itemx info dos ldt
21474 @itemx info dos idt
21475 These 3 commands display entries from, respectively, Global, Local,
21476 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21477 tables are data structures which store a descriptor for each segment
21478 that is currently in use. The segment's selector is an index into a
21479 descriptor table; the table entry for that index holds the
21480 descriptor's base address and limit, and its attributes and access
21483 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21484 segment (used for both data and the stack), and a DOS segment (which
21485 allows access to DOS/BIOS data structures and absolute addresses in
21486 conventional memory). However, the DPMI host will usually define
21487 additional segments in order to support the DPMI environment.
21489 @cindex garbled pointers
21490 These commands allow to display entries from the descriptor tables.
21491 Without an argument, all entries from the specified table are
21492 displayed. An argument, which should be an integer expression, means
21493 display a single entry whose index is given by the argument. For
21494 example, here's a convenient way to display information about the
21495 debugged program's data segment:
21498 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21499 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21503 This comes in handy when you want to see whether a pointer is outside
21504 the data segment's limit (i.e.@: @dfn{garbled}).
21506 @cindex page tables display (MS-DOS)
21508 @itemx info dos pte
21509 These two commands display entries from, respectively, the Page
21510 Directory and the Page Tables. Page Directories and Page Tables are
21511 data structures which control how virtual memory addresses are mapped
21512 into physical addresses. A Page Table includes an entry for every
21513 page of memory that is mapped into the program's address space; there
21514 may be several Page Tables, each one holding up to 4096 entries. A
21515 Page Directory has up to 4096 entries, one each for every Page Table
21516 that is currently in use.
21518 Without an argument, @kbd{info dos pde} displays the entire Page
21519 Directory, and @kbd{info dos pte} displays all the entries in all of
21520 the Page Tables. An argument, an integer expression, given to the
21521 @kbd{info dos pde} command means display only that entry from the Page
21522 Directory table. An argument given to the @kbd{info dos pte} command
21523 means display entries from a single Page Table, the one pointed to by
21524 the specified entry in the Page Directory.
21526 @cindex direct memory access (DMA) on MS-DOS
21527 These commands are useful when your program uses @dfn{DMA} (Direct
21528 Memory Access), which needs physical addresses to program the DMA
21531 These commands are supported only with some DPMI servers.
21533 @cindex physical address from linear address
21534 @item info dos address-pte @var{addr}
21535 This command displays the Page Table entry for a specified linear
21536 address. The argument @var{addr} is a linear address which should
21537 already have the appropriate segment's base address added to it,
21538 because this command accepts addresses which may belong to @emph{any}
21539 segment. For example, here's how to display the Page Table entry for
21540 the page where a variable @code{i} is stored:
21543 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21544 @exdent @code{Page Table entry for address 0x11a00d30:}
21545 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21549 This says that @code{i} is stored at offset @code{0xd30} from the page
21550 whose physical base address is @code{0x02698000}, and shows all the
21551 attributes of that page.
21553 Note that you must cast the addresses of variables to a @code{char *},
21554 since otherwise the value of @code{__djgpp_base_address}, the base
21555 address of all variables and functions in a @sc{djgpp} program, will
21556 be added using the rules of C pointer arithmetics: if @code{i} is
21557 declared an @code{int}, @value{GDBN} will add 4 times the value of
21558 @code{__djgpp_base_address} to the address of @code{i}.
21560 Here's another example, it displays the Page Table entry for the
21564 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21565 @exdent @code{Page Table entry for address 0x29110:}
21566 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21570 (The @code{+ 3} offset is because the transfer buffer's address is the
21571 3rd member of the @code{_go32_info_block} structure.) The output
21572 clearly shows that this DPMI server maps the addresses in conventional
21573 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21574 linear (@code{0x29110}) addresses are identical.
21576 This command is supported only with some DPMI servers.
21579 @cindex DOS serial data link, remote debugging
21580 In addition to native debugging, the DJGPP port supports remote
21581 debugging via a serial data link. The following commands are specific
21582 to remote serial debugging in the DJGPP port of @value{GDBN}.
21585 @kindex set com1base
21586 @kindex set com1irq
21587 @kindex set com2base
21588 @kindex set com2irq
21589 @kindex set com3base
21590 @kindex set com3irq
21591 @kindex set com4base
21592 @kindex set com4irq
21593 @item set com1base @var{addr}
21594 This command sets the base I/O port address of the @file{COM1} serial
21597 @item set com1irq @var{irq}
21598 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21599 for the @file{COM1} serial port.
21601 There are similar commands @samp{set com2base}, @samp{set com3irq},
21602 etc.@: for setting the port address and the @code{IRQ} lines for the
21605 @kindex show com1base
21606 @kindex show com1irq
21607 @kindex show com2base
21608 @kindex show com2irq
21609 @kindex show com3base
21610 @kindex show com3irq
21611 @kindex show com4base
21612 @kindex show com4irq
21613 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21614 display the current settings of the base address and the @code{IRQ}
21615 lines used by the COM ports.
21618 @kindex info serial
21619 @cindex DOS serial port status
21620 This command prints the status of the 4 DOS serial ports. For each
21621 port, it prints whether it's active or not, its I/O base address and
21622 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21623 counts of various errors encountered so far.
21627 @node Cygwin Native
21628 @subsection Features for Debugging MS Windows PE Executables
21629 @cindex MS Windows debugging
21630 @cindex native Cygwin debugging
21631 @cindex Cygwin-specific commands
21633 @value{GDBN} supports native debugging of MS Windows programs, including
21634 DLLs with and without symbolic debugging information.
21636 @cindex Ctrl-BREAK, MS-Windows
21637 @cindex interrupt debuggee on MS-Windows
21638 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21639 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21640 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21641 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21642 sequence, which can be used to interrupt the debuggee even if it
21645 There are various additional Cygwin-specific commands, described in
21646 this section. Working with DLLs that have no debugging symbols is
21647 described in @ref{Non-debug DLL Symbols}.
21652 This is a prefix of MS Windows-specific commands which print
21653 information about the target system and important OS structures.
21655 @item info w32 selector
21656 This command displays information returned by
21657 the Win32 API @code{GetThreadSelectorEntry} function.
21658 It takes an optional argument that is evaluated to
21659 a long value to give the information about this given selector.
21660 Without argument, this command displays information
21661 about the six segment registers.
21663 @item info w32 thread-information-block
21664 This command displays thread specific information stored in the
21665 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21666 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21668 @kindex signal-event
21669 @item signal-event @var{id}
21670 This command signals an event with user-provided @var{id}. Used to resume
21671 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21673 To use it, create or edit the following keys in
21674 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21675 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21676 (for x86_64 versions):
21680 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21681 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21682 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21684 The first @code{%ld} will be replaced by the process ID of the
21685 crashing process, the second @code{%ld} will be replaced by the ID of
21686 the event that blocks the crashing process, waiting for @value{GDBN}
21690 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21691 make the system run debugger specified by the Debugger key
21692 automatically, @code{0} will cause a dialog box with ``OK'' and
21693 ``Cancel'' buttons to appear, which allows the user to either
21694 terminate the crashing process (OK) or debug it (Cancel).
21697 @kindex set cygwin-exceptions
21698 @cindex debugging the Cygwin DLL
21699 @cindex Cygwin DLL, debugging
21700 @item set cygwin-exceptions @var{mode}
21701 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21702 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21703 @value{GDBN} will delay recognition of exceptions, and may ignore some
21704 exceptions which seem to be caused by internal Cygwin DLL
21705 ``bookkeeping''. This option is meant primarily for debugging the
21706 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21707 @value{GDBN} users with false @code{SIGSEGV} signals.
21709 @kindex show cygwin-exceptions
21710 @item show cygwin-exceptions
21711 Displays whether @value{GDBN} will break on exceptions that happen
21712 inside the Cygwin DLL itself.
21714 @kindex set new-console
21715 @item set new-console @var{mode}
21716 If @var{mode} is @code{on} the debuggee will
21717 be started in a new console on next start.
21718 If @var{mode} is @code{off}, the debuggee will
21719 be started in the same console as the debugger.
21721 @kindex show new-console
21722 @item show new-console
21723 Displays whether a new console is used
21724 when the debuggee is started.
21726 @kindex set new-group
21727 @item set new-group @var{mode}
21728 This boolean value controls whether the debuggee should
21729 start a new group or stay in the same group as the debugger.
21730 This affects the way the Windows OS handles
21733 @kindex show new-group
21734 @item show new-group
21735 Displays current value of new-group boolean.
21737 @kindex set debugevents
21738 @item set debugevents
21739 This boolean value adds debug output concerning kernel events related
21740 to the debuggee seen by the debugger. This includes events that
21741 signal thread and process creation and exit, DLL loading and
21742 unloading, console interrupts, and debugging messages produced by the
21743 Windows @code{OutputDebugString} API call.
21745 @kindex set debugexec
21746 @item set debugexec
21747 This boolean value adds debug output concerning execute events
21748 (such as resume thread) seen by the debugger.
21750 @kindex set debugexceptions
21751 @item set debugexceptions
21752 This boolean value adds debug output concerning exceptions in the
21753 debuggee seen by the debugger.
21755 @kindex set debugmemory
21756 @item set debugmemory
21757 This boolean value adds debug output concerning debuggee memory reads
21758 and writes by the debugger.
21762 This boolean values specifies whether the debuggee is called
21763 via a shell or directly (default value is on).
21767 Displays if the debuggee will be started with a shell.
21772 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21775 @node Non-debug DLL Symbols
21776 @subsubsection Support for DLLs without Debugging Symbols
21777 @cindex DLLs with no debugging symbols
21778 @cindex Minimal symbols and DLLs
21780 Very often on windows, some of the DLLs that your program relies on do
21781 not include symbolic debugging information (for example,
21782 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21783 symbols in a DLL, it relies on the minimal amount of symbolic
21784 information contained in the DLL's export table. This section
21785 describes working with such symbols, known internally to @value{GDBN} as
21786 ``minimal symbols''.
21788 Note that before the debugged program has started execution, no DLLs
21789 will have been loaded. The easiest way around this problem is simply to
21790 start the program --- either by setting a breakpoint or letting the
21791 program run once to completion.
21793 @subsubsection DLL Name Prefixes
21795 In keeping with the naming conventions used by the Microsoft debugging
21796 tools, DLL export symbols are made available with a prefix based on the
21797 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21798 also entered into the symbol table, so @code{CreateFileA} is often
21799 sufficient. In some cases there will be name clashes within a program
21800 (particularly if the executable itself includes full debugging symbols)
21801 necessitating the use of the fully qualified name when referring to the
21802 contents of the DLL. Use single-quotes around the name to avoid the
21803 exclamation mark (``!'') being interpreted as a language operator.
21805 Note that the internal name of the DLL may be all upper-case, even
21806 though the file name of the DLL is lower-case, or vice-versa. Since
21807 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21808 some confusion. If in doubt, try the @code{info functions} and
21809 @code{info variables} commands or even @code{maint print msymbols}
21810 (@pxref{Symbols}). Here's an example:
21813 (@value{GDBP}) info function CreateFileA
21814 All functions matching regular expression "CreateFileA":
21816 Non-debugging symbols:
21817 0x77e885f4 CreateFileA
21818 0x77e885f4 KERNEL32!CreateFileA
21822 (@value{GDBP}) info function !
21823 All functions matching regular expression "!":
21825 Non-debugging symbols:
21826 0x6100114c cygwin1!__assert
21827 0x61004034 cygwin1!_dll_crt0@@0
21828 0x61004240 cygwin1!dll_crt0(per_process *)
21832 @subsubsection Working with Minimal Symbols
21834 Symbols extracted from a DLL's export table do not contain very much
21835 type information. All that @value{GDBN} can do is guess whether a symbol
21836 refers to a function or variable depending on the linker section that
21837 contains the symbol. Also note that the actual contents of the memory
21838 contained in a DLL are not available unless the program is running. This
21839 means that you cannot examine the contents of a variable or disassemble
21840 a function within a DLL without a running program.
21842 Variables are generally treated as pointers and dereferenced
21843 automatically. For this reason, it is often necessary to prefix a
21844 variable name with the address-of operator (``&'') and provide explicit
21845 type information in the command. Here's an example of the type of
21849 (@value{GDBP}) print 'cygwin1!__argv'
21854 (@value{GDBP}) x 'cygwin1!__argv'
21855 0x10021610: "\230y\""
21858 And two possible solutions:
21861 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21862 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21866 (@value{GDBP}) x/2x &'cygwin1!__argv'
21867 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21868 (@value{GDBP}) x/x 0x10021608
21869 0x10021608: 0x0022fd98
21870 (@value{GDBP}) x/s 0x0022fd98
21871 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21874 Setting a break point within a DLL is possible even before the program
21875 starts execution. However, under these circumstances, @value{GDBN} can't
21876 examine the initial instructions of the function in order to skip the
21877 function's frame set-up code. You can work around this by using ``*&''
21878 to set the breakpoint at a raw memory address:
21881 (@value{GDBP}) break *&'python22!PyOS_Readline'
21882 Breakpoint 1 at 0x1e04eff0
21885 The author of these extensions is not entirely convinced that setting a
21886 break point within a shared DLL like @file{kernel32.dll} is completely
21890 @subsection Commands Specific to @sc{gnu} Hurd Systems
21891 @cindex @sc{gnu} Hurd debugging
21893 This subsection describes @value{GDBN} commands specific to the
21894 @sc{gnu} Hurd native debugging.
21899 @kindex set signals@r{, Hurd command}
21900 @kindex set sigs@r{, Hurd command}
21901 This command toggles the state of inferior signal interception by
21902 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21903 affected by this command. @code{sigs} is a shorthand alias for
21908 @kindex show signals@r{, Hurd command}
21909 @kindex show sigs@r{, Hurd command}
21910 Show the current state of intercepting inferior's signals.
21912 @item set signal-thread
21913 @itemx set sigthread
21914 @kindex set signal-thread
21915 @kindex set sigthread
21916 This command tells @value{GDBN} which thread is the @code{libc} signal
21917 thread. That thread is run when a signal is delivered to a running
21918 process. @code{set sigthread} is the shorthand alias of @code{set
21921 @item show signal-thread
21922 @itemx show sigthread
21923 @kindex show signal-thread
21924 @kindex show sigthread
21925 These two commands show which thread will run when the inferior is
21926 delivered a signal.
21929 @kindex set stopped@r{, Hurd command}
21930 This commands tells @value{GDBN} that the inferior process is stopped,
21931 as with the @code{SIGSTOP} signal. The stopped process can be
21932 continued by delivering a signal to it.
21935 @kindex show stopped@r{, Hurd command}
21936 This command shows whether @value{GDBN} thinks the debuggee is
21939 @item set exceptions
21940 @kindex set exceptions@r{, Hurd command}
21941 Use this command to turn off trapping of exceptions in the inferior.
21942 When exception trapping is off, neither breakpoints nor
21943 single-stepping will work. To restore the default, set exception
21946 @item show exceptions
21947 @kindex show exceptions@r{, Hurd command}
21948 Show the current state of trapping exceptions in the inferior.
21950 @item set task pause
21951 @kindex set task@r{, Hurd commands}
21952 @cindex task attributes (@sc{gnu} Hurd)
21953 @cindex pause current task (@sc{gnu} Hurd)
21954 This command toggles task suspension when @value{GDBN} has control.
21955 Setting it to on takes effect immediately, and the task is suspended
21956 whenever @value{GDBN} gets control. Setting it to off will take
21957 effect the next time the inferior is continued. If this option is set
21958 to off, you can use @code{set thread default pause on} or @code{set
21959 thread pause on} (see below) to pause individual threads.
21961 @item show task pause
21962 @kindex show task@r{, Hurd commands}
21963 Show the current state of task suspension.
21965 @item set task detach-suspend-count
21966 @cindex task suspend count
21967 @cindex detach from task, @sc{gnu} Hurd
21968 This command sets the suspend count the task will be left with when
21969 @value{GDBN} detaches from it.
21971 @item show task detach-suspend-count
21972 Show the suspend count the task will be left with when detaching.
21974 @item set task exception-port
21975 @itemx set task excp
21976 @cindex task exception port, @sc{gnu} Hurd
21977 This command sets the task exception port to which @value{GDBN} will
21978 forward exceptions. The argument should be the value of the @dfn{send
21979 rights} of the task. @code{set task excp} is a shorthand alias.
21981 @item set noninvasive
21982 @cindex noninvasive task options
21983 This command switches @value{GDBN} to a mode that is the least
21984 invasive as far as interfering with the inferior is concerned. This
21985 is the same as using @code{set task pause}, @code{set exceptions}, and
21986 @code{set signals} to values opposite to the defaults.
21988 @item info send-rights
21989 @itemx info receive-rights
21990 @itemx info port-rights
21991 @itemx info port-sets
21992 @itemx info dead-names
21995 @cindex send rights, @sc{gnu} Hurd
21996 @cindex receive rights, @sc{gnu} Hurd
21997 @cindex port rights, @sc{gnu} Hurd
21998 @cindex port sets, @sc{gnu} Hurd
21999 @cindex dead names, @sc{gnu} Hurd
22000 These commands display information about, respectively, send rights,
22001 receive rights, port rights, port sets, and dead names of a task.
22002 There are also shorthand aliases: @code{info ports} for @code{info
22003 port-rights} and @code{info psets} for @code{info port-sets}.
22005 @item set thread pause
22006 @kindex set thread@r{, Hurd command}
22007 @cindex thread properties, @sc{gnu} Hurd
22008 @cindex pause current thread (@sc{gnu} Hurd)
22009 This command toggles current thread suspension when @value{GDBN} has
22010 control. Setting it to on takes effect immediately, and the current
22011 thread is suspended whenever @value{GDBN} gets control. Setting it to
22012 off will take effect the next time the inferior is continued.
22013 Normally, this command has no effect, since when @value{GDBN} has
22014 control, the whole task is suspended. However, if you used @code{set
22015 task pause off} (see above), this command comes in handy to suspend
22016 only the current thread.
22018 @item show thread pause
22019 @kindex show thread@r{, Hurd command}
22020 This command shows the state of current thread suspension.
22022 @item set thread run
22023 This command sets whether the current thread is allowed to run.
22025 @item show thread run
22026 Show whether the current thread is allowed to run.
22028 @item set thread detach-suspend-count
22029 @cindex thread suspend count, @sc{gnu} Hurd
22030 @cindex detach from thread, @sc{gnu} Hurd
22031 This command sets the suspend count @value{GDBN} will leave on a
22032 thread when detaching. This number is relative to the suspend count
22033 found by @value{GDBN} when it notices the thread; use @code{set thread
22034 takeover-suspend-count} to force it to an absolute value.
22036 @item show thread detach-suspend-count
22037 Show the suspend count @value{GDBN} will leave on the thread when
22040 @item set thread exception-port
22041 @itemx set thread excp
22042 Set the thread exception port to which to forward exceptions. This
22043 overrides the port set by @code{set task exception-port} (see above).
22044 @code{set thread excp} is the shorthand alias.
22046 @item set thread takeover-suspend-count
22047 Normally, @value{GDBN}'s thread suspend counts are relative to the
22048 value @value{GDBN} finds when it notices each thread. This command
22049 changes the suspend counts to be absolute instead.
22051 @item set thread default
22052 @itemx show thread default
22053 @cindex thread default settings, @sc{gnu} Hurd
22054 Each of the above @code{set thread} commands has a @code{set thread
22055 default} counterpart (e.g., @code{set thread default pause}, @code{set
22056 thread default exception-port}, etc.). The @code{thread default}
22057 variety of commands sets the default thread properties for all
22058 threads; you can then change the properties of individual threads with
22059 the non-default commands.
22066 @value{GDBN} provides the following commands specific to the Darwin target:
22069 @item set debug darwin @var{num}
22070 @kindex set debug darwin
22071 When set to a non zero value, enables debugging messages specific to
22072 the Darwin support. Higher values produce more verbose output.
22074 @item show debug darwin
22075 @kindex show debug darwin
22076 Show the current state of Darwin messages.
22078 @item set debug mach-o @var{num}
22079 @kindex set debug mach-o
22080 When set to a non zero value, enables debugging messages while
22081 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22082 file format used on Darwin for object and executable files.) Higher
22083 values produce more verbose output. This is a command to diagnose
22084 problems internal to @value{GDBN} and should not be needed in normal
22087 @item show debug mach-o
22088 @kindex show debug mach-o
22089 Show the current state of Mach-O file messages.
22091 @item set mach-exceptions on
22092 @itemx set mach-exceptions off
22093 @kindex set mach-exceptions
22094 On Darwin, faults are first reported as a Mach exception and are then
22095 mapped to a Posix signal. Use this command to turn on trapping of
22096 Mach exceptions in the inferior. This might be sometimes useful to
22097 better understand the cause of a fault. The default is off.
22099 @item show mach-exceptions
22100 @kindex show mach-exceptions
22101 Show the current state of exceptions trapping.
22106 @section Embedded Operating Systems
22108 This section describes configurations involving the debugging of
22109 embedded operating systems that are available for several different
22112 @value{GDBN} includes the ability to debug programs running on
22113 various real-time operating systems.
22115 @node Embedded Processors
22116 @section Embedded Processors
22118 This section goes into details specific to particular embedded
22121 @cindex send command to simulator
22122 Whenever a specific embedded processor has a simulator, @value{GDBN}
22123 allows to send an arbitrary command to the simulator.
22126 @item sim @var{command}
22127 @kindex sim@r{, a command}
22128 Send an arbitrary @var{command} string to the simulator. Consult the
22129 documentation for the specific simulator in use for information about
22130 acceptable commands.
22135 * ARC:: Synopsys ARC
22137 * M68K:: Motorola M68K
22138 * MicroBlaze:: Xilinx MicroBlaze
22139 * MIPS Embedded:: MIPS Embedded
22140 * PowerPC Embedded:: PowerPC Embedded
22143 * Super-H:: Renesas Super-H
22147 @subsection Synopsys ARC
22148 @cindex Synopsys ARC
22149 @cindex ARC specific commands
22155 @value{GDBN} provides the following ARC-specific commands:
22158 @item set debug arc
22159 @kindex set debug arc
22160 Control the level of ARC specific debug messages. Use 0 for no messages (the
22161 default), 1 for debug messages, and 2 for even more debug messages.
22163 @item show debug arc
22164 @kindex show debug arc
22165 Show the level of ARC specific debugging in operation.
22167 @item maint print arc arc-instruction @var{address}
22168 @kindex maint print arc arc-instruction
22169 Print internal disassembler information about instruction at a given address.
22176 @value{GDBN} provides the following ARM-specific commands:
22179 @item set arm disassembler
22181 This commands selects from a list of disassembly styles. The
22182 @code{"std"} style is the standard style.
22184 @item show arm disassembler
22186 Show the current disassembly style.
22188 @item set arm apcs32
22189 @cindex ARM 32-bit mode
22190 This command toggles ARM operation mode between 32-bit and 26-bit.
22192 @item show arm apcs32
22193 Display the current usage of the ARM 32-bit mode.
22195 @item set arm fpu @var{fputype}
22196 This command sets the ARM floating-point unit (FPU) type. The
22197 argument @var{fputype} can be one of these:
22201 Determine the FPU type by querying the OS ABI.
22203 Software FPU, with mixed-endian doubles on little-endian ARM
22206 GCC-compiled FPA co-processor.
22208 Software FPU with pure-endian doubles.
22214 Show the current type of the FPU.
22217 This command forces @value{GDBN} to use the specified ABI.
22220 Show the currently used ABI.
22222 @item set arm fallback-mode (arm|thumb|auto)
22223 @value{GDBN} uses the symbol table, when available, to determine
22224 whether instructions are ARM or Thumb. This command controls
22225 @value{GDBN}'s default behavior when the symbol table is not
22226 available. The default is @samp{auto}, which causes @value{GDBN} to
22227 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22230 @item show arm fallback-mode
22231 Show the current fallback instruction mode.
22233 @item set arm force-mode (arm|thumb|auto)
22234 This command overrides use of the symbol table to determine whether
22235 instructions are ARM or Thumb. The default is @samp{auto}, which
22236 causes @value{GDBN} to use the symbol table and then the setting
22237 of @samp{set arm fallback-mode}.
22239 @item show arm force-mode
22240 Show the current forced instruction mode.
22242 @item set debug arm
22243 Toggle whether to display ARM-specific debugging messages from the ARM
22244 target support subsystem.
22246 @item show debug arm
22247 Show whether ARM-specific debugging messages are enabled.
22251 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22252 The @value{GDBN} ARM simulator accepts the following optional arguments.
22255 @item --swi-support=@var{type}
22256 Tell the simulator which SWI interfaces to support. The argument
22257 @var{type} may be a comma separated list of the following values.
22258 The default value is @code{all}.
22273 The Motorola m68k configuration includes ColdFire support.
22276 @subsection MicroBlaze
22277 @cindex Xilinx MicroBlaze
22278 @cindex XMD, Xilinx Microprocessor Debugger
22280 The MicroBlaze is a soft-core processor supported on various Xilinx
22281 FPGAs, such as Spartan or Virtex series. Boards with these processors
22282 usually have JTAG ports which connect to a host system running the Xilinx
22283 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22284 This host system is used to download the configuration bitstream to
22285 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22286 communicates with the target board using the JTAG interface and
22287 presents a @code{gdbserver} interface to the board. By default
22288 @code{xmd} uses port @code{1234}. (While it is possible to change
22289 this default port, it requires the use of undocumented @code{xmd}
22290 commands. Contact Xilinx support if you need to do this.)
22292 Use these GDB commands to connect to the MicroBlaze target processor.
22295 @item target remote :1234
22296 Use this command to connect to the target if you are running @value{GDBN}
22297 on the same system as @code{xmd}.
22299 @item target remote @var{xmd-host}:1234
22300 Use this command to connect to the target if it is connected to @code{xmd}
22301 running on a different system named @var{xmd-host}.
22304 Use this command to download a program to the MicroBlaze target.
22306 @item set debug microblaze @var{n}
22307 Enable MicroBlaze-specific debugging messages if non-zero.
22309 @item show debug microblaze @var{n}
22310 Show MicroBlaze-specific debugging level.
22313 @node MIPS Embedded
22314 @subsection @acronym{MIPS} Embedded
22317 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22320 @item set mipsfpu double
22321 @itemx set mipsfpu single
22322 @itemx set mipsfpu none
22323 @itemx set mipsfpu auto
22324 @itemx show mipsfpu
22325 @kindex set mipsfpu
22326 @kindex show mipsfpu
22327 @cindex @acronym{MIPS} remote floating point
22328 @cindex floating point, @acronym{MIPS} remote
22329 If your target board does not support the @acronym{MIPS} floating point
22330 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22331 need this, you may wish to put the command in your @value{GDBN} init
22332 file). This tells @value{GDBN} how to find the return value of
22333 functions which return floating point values. It also allows
22334 @value{GDBN} to avoid saving the floating point registers when calling
22335 functions on the board. If you are using a floating point coprocessor
22336 with only single precision floating point support, as on the @sc{r4650}
22337 processor, use the command @samp{set mipsfpu single}. The default
22338 double precision floating point coprocessor may be selected using
22339 @samp{set mipsfpu double}.
22341 In previous versions the only choices were double precision or no
22342 floating point, so @samp{set mipsfpu on} will select double precision
22343 and @samp{set mipsfpu off} will select no floating point.
22345 As usual, you can inquire about the @code{mipsfpu} variable with
22346 @samp{show mipsfpu}.
22349 @node PowerPC Embedded
22350 @subsection PowerPC Embedded
22352 @cindex DVC register
22353 @value{GDBN} supports using the DVC (Data Value Compare) register to
22354 implement in hardware simple hardware watchpoint conditions of the form:
22357 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22358 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22361 The DVC register will be automatically used when @value{GDBN} detects
22362 such pattern in a condition expression, and the created watchpoint uses one
22363 debug register (either the @code{exact-watchpoints} option is on and the
22364 variable is scalar, or the variable has a length of one byte). This feature
22365 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22368 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22369 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22370 in which case watchpoints using only one debug register are created when
22371 watching variables of scalar types.
22373 You can create an artificial array to watch an arbitrary memory
22374 region using one of the following commands (@pxref{Expressions}):
22377 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22378 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22381 PowerPC embedded processors support masked watchpoints. See the discussion
22382 about the @code{mask} argument in @ref{Set Watchpoints}.
22384 @cindex ranged breakpoint
22385 PowerPC embedded processors support hardware accelerated
22386 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22387 the inferior whenever it executes an instruction at any address within
22388 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22389 use the @code{break-range} command.
22391 @value{GDBN} provides the following PowerPC-specific commands:
22394 @kindex break-range
22395 @item break-range @var{start-location}, @var{end-location}
22396 Set a breakpoint for an address range given by
22397 @var{start-location} and @var{end-location}, which can specify a function name,
22398 a line number, an offset of lines from the current line or from the start
22399 location, or an address of an instruction (see @ref{Specify Location},
22400 for a list of all the possible ways to specify a @var{location}.)
22401 The breakpoint will stop execution of the inferior whenever it
22402 executes an instruction at any address within the specified range,
22403 (including @var{start-location} and @var{end-location}.)
22405 @kindex set powerpc
22406 @item set powerpc soft-float
22407 @itemx show powerpc soft-float
22408 Force @value{GDBN} to use (or not use) a software floating point calling
22409 convention. By default, @value{GDBN} selects the calling convention based
22410 on the selected architecture and the provided executable file.
22412 @item set powerpc vector-abi
22413 @itemx show powerpc vector-abi
22414 Force @value{GDBN} to use the specified calling convention for vector
22415 arguments and return values. The valid options are @samp{auto};
22416 @samp{generic}, to avoid vector registers even if they are present;
22417 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22418 registers. By default, @value{GDBN} selects the calling convention
22419 based on the selected architecture and the provided executable file.
22421 @item set powerpc exact-watchpoints
22422 @itemx show powerpc exact-watchpoints
22423 Allow @value{GDBN} to use only one debug register when watching a variable
22424 of scalar type, thus assuming that the variable is accessed through the
22425 address of its first byte.
22430 @subsection Atmel AVR
22433 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22434 following AVR-specific commands:
22437 @item info io_registers
22438 @kindex info io_registers@r{, AVR}
22439 @cindex I/O registers (Atmel AVR)
22440 This command displays information about the AVR I/O registers. For
22441 each register, @value{GDBN} prints its number and value.
22448 When configured for debugging CRIS, @value{GDBN} provides the
22449 following CRIS-specific commands:
22452 @item set cris-version @var{ver}
22453 @cindex CRIS version
22454 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22455 The CRIS version affects register names and sizes. This command is useful in
22456 case autodetection of the CRIS version fails.
22458 @item show cris-version
22459 Show the current CRIS version.
22461 @item set cris-dwarf2-cfi
22462 @cindex DWARF-2 CFI and CRIS
22463 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22464 Change to @samp{off} when using @code{gcc-cris} whose version is below
22467 @item show cris-dwarf2-cfi
22468 Show the current state of using DWARF-2 CFI.
22470 @item set cris-mode @var{mode}
22472 Set the current CRIS mode to @var{mode}. It should only be changed when
22473 debugging in guru mode, in which case it should be set to
22474 @samp{guru} (the default is @samp{normal}).
22476 @item show cris-mode
22477 Show the current CRIS mode.
22481 @subsection Renesas Super-H
22484 For the Renesas Super-H processor, @value{GDBN} provides these
22488 @item set sh calling-convention @var{convention}
22489 @kindex set sh calling-convention
22490 Set the calling-convention used when calling functions from @value{GDBN}.
22491 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22492 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22493 convention. If the DWARF-2 information of the called function specifies
22494 that the function follows the Renesas calling convention, the function
22495 is called using the Renesas calling convention. If the calling convention
22496 is set to @samp{renesas}, the Renesas calling convention is always used,
22497 regardless of the DWARF-2 information. This can be used to override the
22498 default of @samp{gcc} if debug information is missing, or the compiler
22499 does not emit the DWARF-2 calling convention entry for a function.
22501 @item show sh calling-convention
22502 @kindex show sh calling-convention
22503 Show the current calling convention setting.
22508 @node Architectures
22509 @section Architectures
22511 This section describes characteristics of architectures that affect
22512 all uses of @value{GDBN} with the architecture, both native and cross.
22519 * HPPA:: HP PA architecture
22520 * SPU:: Cell Broadband Engine SPU architecture
22527 @subsection AArch64
22528 @cindex AArch64 support
22530 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22531 following special commands:
22534 @item set debug aarch64
22535 @kindex set debug aarch64
22536 This command determines whether AArch64 architecture-specific debugging
22537 messages are to be displayed.
22539 @item show debug aarch64
22540 Show whether AArch64 debugging messages are displayed.
22545 @subsection x86 Architecture-specific Issues
22548 @item set struct-convention @var{mode}
22549 @kindex set struct-convention
22550 @cindex struct return convention
22551 @cindex struct/union returned in registers
22552 Set the convention used by the inferior to return @code{struct}s and
22553 @code{union}s from functions to @var{mode}. Possible values of
22554 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22555 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22556 are returned on the stack, while @code{"reg"} means that a
22557 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22558 be returned in a register.
22560 @item show struct-convention
22561 @kindex show struct-convention
22562 Show the current setting of the convention to return @code{struct}s
22567 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22568 @cindex Intel Memory Protection Extensions (MPX).
22570 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22571 @footnote{The register named with capital letters represent the architecture
22572 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22573 which are the lower bound and upper bound. Bounds are effective addresses or
22574 memory locations. The upper bounds are architecturally represented in 1's
22575 complement form. A bound having lower bound = 0, and upper bound = 0
22576 (1's complement of all bits set) will allow access to the entire address space.
22578 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22579 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22580 display the upper bound performing the complement of one operation on the
22581 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22582 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22583 can also be noted that the upper bounds are inclusive.
22585 As an example, assume that the register BND0 holds bounds for a pointer having
22586 access allowed for the range between 0x32 and 0x71. The values present on
22587 bnd0raw and bnd registers are presented as follows:
22590 bnd0raw = @{0x32, 0xffffffff8e@}
22591 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22594 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22595 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22596 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22597 Python, the display includes the memory size, in bits, accessible to
22600 Bounds can also be stored in bounds tables, which are stored in
22601 application memory. These tables store bounds for pointers by specifying
22602 the bounds pointer's value along with its bounds. Evaluating and changing
22603 bounds located in bound tables is therefore interesting while investigating
22604 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22607 @item show mpx bound @var{pointer}
22608 @kindex show mpx bound
22609 Display bounds of the given @var{pointer}.
22611 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22612 @kindex set mpx bound
22613 Set the bounds of a pointer in the bound table.
22614 This command takes three parameters: @var{pointer} is the pointers
22615 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22616 for lower and upper bounds respectively.
22619 When you call an inferior function on an Intel MPX enabled program,
22620 GDB sets the inferior's bound registers to the init (disabled) state
22621 before calling the function. As a consequence, bounds checks for the
22622 pointer arguments passed to the function will always pass.
22624 This is necessary because when you call an inferior function, the
22625 program is usually in the middle of the execution of other function.
22626 Since at that point bound registers are in an arbitrary state, not
22627 clearing them would lead to random bound violations in the called
22630 You can still examine the influence of the bound registers on the
22631 execution of the called function by stopping the execution of the
22632 called function at its prologue, setting bound registers, and
22633 continuing the execution. For example:
22637 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22638 $ print upper (a, b, c, d, 1)
22639 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22641 @{lbound = 0x0, ubound = ffffffff@} : size -1
22644 At this last step the value of bnd0 can be changed for investigation of bound
22645 violations caused along the execution of the call. In order to know how to
22646 set the bound registers or bound table for the call consult the ABI.
22651 See the following section.
22654 @subsection @acronym{MIPS}
22656 @cindex stack on Alpha
22657 @cindex stack on @acronym{MIPS}
22658 @cindex Alpha stack
22659 @cindex @acronym{MIPS} stack
22660 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22661 sometimes requires @value{GDBN} to search backward in the object code to
22662 find the beginning of a function.
22664 @cindex response time, @acronym{MIPS} debugging
22665 To improve response time (especially for embedded applications, where
22666 @value{GDBN} may be restricted to a slow serial line for this search)
22667 you may want to limit the size of this search, using one of these
22671 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22672 @item set heuristic-fence-post @var{limit}
22673 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22674 search for the beginning of a function. A value of @var{0} (the
22675 default) means there is no limit. However, except for @var{0}, the
22676 larger the limit the more bytes @code{heuristic-fence-post} must search
22677 and therefore the longer it takes to run. You should only need to use
22678 this command when debugging a stripped executable.
22680 @item show heuristic-fence-post
22681 Display the current limit.
22685 These commands are available @emph{only} when @value{GDBN} is configured
22686 for debugging programs on Alpha or @acronym{MIPS} processors.
22688 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22692 @item set mips abi @var{arg}
22693 @kindex set mips abi
22694 @cindex set ABI for @acronym{MIPS}
22695 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22696 values of @var{arg} are:
22700 The default ABI associated with the current binary (this is the
22710 @item show mips abi
22711 @kindex show mips abi
22712 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22714 @item set mips compression @var{arg}
22715 @kindex set mips compression
22716 @cindex code compression, @acronym{MIPS}
22717 Tell @value{GDBN} which @acronym{MIPS} compressed
22718 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22719 inferior. @value{GDBN} uses this for code disassembly and other
22720 internal interpretation purposes. This setting is only referred to
22721 when no executable has been associated with the debugging session or
22722 the executable does not provide information about the encoding it uses.
22723 Otherwise this setting is automatically updated from information
22724 provided by the executable.
22726 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22727 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22728 executables containing @acronym{MIPS16} code frequently are not
22729 identified as such.
22731 This setting is ``sticky''; that is, it retains its value across
22732 debugging sessions until reset either explicitly with this command or
22733 implicitly from an executable.
22735 The compiler and/or assembler typically add symbol table annotations to
22736 identify functions compiled for the @acronym{MIPS16} or
22737 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22738 are present, @value{GDBN} uses them in preference to the global
22739 compressed @acronym{ISA} encoding setting.
22741 @item show mips compression
22742 @kindex show mips compression
22743 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22744 @value{GDBN} to debug the inferior.
22747 @itemx show mipsfpu
22748 @xref{MIPS Embedded, set mipsfpu}.
22750 @item set mips mask-address @var{arg}
22751 @kindex set mips mask-address
22752 @cindex @acronym{MIPS} addresses, masking
22753 This command determines whether the most-significant 32 bits of 64-bit
22754 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22755 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22756 setting, which lets @value{GDBN} determine the correct value.
22758 @item show mips mask-address
22759 @kindex show mips mask-address
22760 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22763 @item set remote-mips64-transfers-32bit-regs
22764 @kindex set remote-mips64-transfers-32bit-regs
22765 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22766 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22767 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22768 and 64 bits for other registers, set this option to @samp{on}.
22770 @item show remote-mips64-transfers-32bit-regs
22771 @kindex show remote-mips64-transfers-32bit-regs
22772 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22774 @item set debug mips
22775 @kindex set debug mips
22776 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22777 target code in @value{GDBN}.
22779 @item show debug mips
22780 @kindex show debug mips
22781 Show the current setting of @acronym{MIPS} debugging messages.
22787 @cindex HPPA support
22789 When @value{GDBN} is debugging the HP PA architecture, it provides the
22790 following special commands:
22793 @item set debug hppa
22794 @kindex set debug hppa
22795 This command determines whether HPPA architecture-specific debugging
22796 messages are to be displayed.
22798 @item show debug hppa
22799 Show whether HPPA debugging messages are displayed.
22801 @item maint print unwind @var{address}
22802 @kindex maint print unwind@r{, HPPA}
22803 This command displays the contents of the unwind table entry at the
22804 given @var{address}.
22810 @subsection Cell Broadband Engine SPU architecture
22811 @cindex Cell Broadband Engine
22814 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22815 it provides the following special commands:
22818 @item info spu event
22820 Display SPU event facility status. Shows current event mask
22821 and pending event status.
22823 @item info spu signal
22824 Display SPU signal notification facility status. Shows pending
22825 signal-control word and signal notification mode of both signal
22826 notification channels.
22828 @item info spu mailbox
22829 Display SPU mailbox facility status. Shows all pending entries,
22830 in order of processing, in each of the SPU Write Outbound,
22831 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22834 Display MFC DMA status. Shows all pending commands in the MFC
22835 DMA queue. For each entry, opcode, tag, class IDs, effective
22836 and local store addresses and transfer size are shown.
22838 @item info spu proxydma
22839 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22840 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22841 and local store addresses and transfer size are shown.
22845 When @value{GDBN} is debugging a combined PowerPC/SPU application
22846 on the Cell Broadband Engine, it provides in addition the following
22850 @item set spu stop-on-load @var{arg}
22852 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22853 will give control to the user when a new SPE thread enters its @code{main}
22854 function. The default is @code{off}.
22856 @item show spu stop-on-load
22858 Show whether to stop for new SPE threads.
22860 @item set spu auto-flush-cache @var{arg}
22861 Set whether to automatically flush the software-managed cache. When set to
22862 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22863 cache to be flushed whenever SPE execution stops. This provides a consistent
22864 view of PowerPC memory that is accessed via the cache. If an application
22865 does not use the software-managed cache, this option has no effect.
22867 @item show spu auto-flush-cache
22868 Show whether to automatically flush the software-managed cache.
22873 @subsection PowerPC
22874 @cindex PowerPC architecture
22876 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22877 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22878 numbers stored in the floating point registers. These values must be stored
22879 in two consecutive registers, always starting at an even register like
22880 @code{f0} or @code{f2}.
22882 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22883 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22884 @code{f2} and @code{f3} for @code{$dl1} and so on.
22886 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22887 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22890 @subsection Nios II
22891 @cindex Nios II architecture
22893 When @value{GDBN} is debugging the Nios II architecture,
22894 it provides the following special commands:
22898 @item set debug nios2
22899 @kindex set debug nios2
22900 This command turns on and off debugging messages for the Nios II
22901 target code in @value{GDBN}.
22903 @item show debug nios2
22904 @kindex show debug nios2
22905 Show the current setting of Nios II debugging messages.
22909 @subsection Sparc64
22910 @cindex Sparc64 support
22911 @cindex Application Data Integrity
22912 @subsubsection ADI Support
22914 The M7 processor supports an Application Data Integrity (ADI) feature that
22915 detects invalid data accesses. When software allocates memory and enables
22916 ADI on the allocated memory, it chooses a 4-bit version number, sets the
22917 version in the upper 4 bits of the 64-bit pointer to that data, and stores
22918 the 4-bit version in every cacheline of that data. Hardware saves the latter
22919 in spare bits in the cache and memory hierarchy. On each load and store,
22920 the processor compares the upper 4 VA (virtual address) bits to the
22921 cacheline's version. If there is a mismatch, the processor generates a
22922 version mismatch trap which can be either precise or disrupting. The trap
22923 is an error condition which the kernel delivers to the process as a SIGSEGV
22926 Note that only 64-bit applications can use ADI and need to be built with
22929 Values of the ADI version tags, which are in granularity of a
22930 cacheline (64 bytes), can be viewed or modified.
22934 @kindex adi examine
22935 @item adi (examine | x) [ / @var{n} ] @var{addr}
22937 The @code{adi examine} command displays the value of one ADI version tag per
22940 @var{n} is a decimal integer specifying the number in bytes; the default
22941 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
22942 block size, to display.
22944 @var{addr} is the address in user address space where you want @value{GDBN}
22945 to begin displaying the ADI version tags.
22947 Below is an example of displaying ADI versions of variable "shmaddr".
22950 (@value{GDBP}) adi x/100 shmaddr
22951 0xfff800010002c000: 0 0
22955 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
22957 The @code{adi assign} command is used to assign new ADI version tag
22960 @var{n} is a decimal integer specifying the number in bytes;
22961 the default is 1. It specifies how much ADI version information, at the
22962 ratio of 1:ADI block size, to modify.
22964 @var{addr} is the address in user address space where you want @value{GDBN}
22965 to begin modifying the ADI version tags.
22967 @var{tag} is the new ADI version tag.
22969 For example, do the following to modify then verify ADI versions of
22970 variable "shmaddr":
22973 (@value{GDBP}) adi a/100 shmaddr = 7
22974 (@value{GDBP}) adi x/100 shmaddr
22975 0xfff800010002c000: 7 7
22980 @node Controlling GDB
22981 @chapter Controlling @value{GDBN}
22983 You can alter the way @value{GDBN} interacts with you by using the
22984 @code{set} command. For commands controlling how @value{GDBN} displays
22985 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22990 * Editing:: Command editing
22991 * Command History:: Command history
22992 * Screen Size:: Screen size
22993 * Numbers:: Numbers
22994 * ABI:: Configuring the current ABI
22995 * Auto-loading:: Automatically loading associated files
22996 * Messages/Warnings:: Optional warnings and messages
22997 * Debugging Output:: Optional messages about internal happenings
22998 * Other Misc Settings:: Other Miscellaneous Settings
23006 @value{GDBN} indicates its readiness to read a command by printing a string
23007 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23008 can change the prompt string with the @code{set prompt} command. For
23009 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23010 the prompt in one of the @value{GDBN} sessions so that you can always tell
23011 which one you are talking to.
23013 @emph{Note:} @code{set prompt} does not add a space for you after the
23014 prompt you set. This allows you to set a prompt which ends in a space
23015 or a prompt that does not.
23019 @item set prompt @var{newprompt}
23020 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23022 @kindex show prompt
23024 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23027 Versions of @value{GDBN} that ship with Python scripting enabled have
23028 prompt extensions. The commands for interacting with these extensions
23032 @kindex set extended-prompt
23033 @item set extended-prompt @var{prompt}
23034 Set an extended prompt that allows for substitutions.
23035 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23036 substitution. Any escape sequences specified as part of the prompt
23037 string are replaced with the corresponding strings each time the prompt
23043 set extended-prompt Current working directory: \w (gdb)
23046 Note that when an extended-prompt is set, it takes control of the
23047 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23049 @kindex show extended-prompt
23050 @item show extended-prompt
23051 Prints the extended prompt. Any escape sequences specified as part of
23052 the prompt string with @code{set extended-prompt}, are replaced with the
23053 corresponding strings each time the prompt is displayed.
23057 @section Command Editing
23059 @cindex command line editing
23061 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23062 @sc{gnu} library provides consistent behavior for programs which provide a
23063 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23064 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23065 substitution, and a storage and recall of command history across
23066 debugging sessions.
23068 You may control the behavior of command line editing in @value{GDBN} with the
23069 command @code{set}.
23072 @kindex set editing
23075 @itemx set editing on
23076 Enable command line editing (enabled by default).
23078 @item set editing off
23079 Disable command line editing.
23081 @kindex show editing
23083 Show whether command line editing is enabled.
23086 @ifset SYSTEM_READLINE
23087 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23089 @ifclear SYSTEM_READLINE
23090 @xref{Command Line Editing},
23092 for more details about the Readline
23093 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23094 encouraged to read that chapter.
23096 @node Command History
23097 @section Command History
23098 @cindex command history
23100 @value{GDBN} can keep track of the commands you type during your
23101 debugging sessions, so that you can be certain of precisely what
23102 happened. Use these commands to manage the @value{GDBN} command
23105 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23106 package, to provide the history facility.
23107 @ifset SYSTEM_READLINE
23108 @xref{Using History Interactively, , , history, GNU History Library},
23110 @ifclear SYSTEM_READLINE
23111 @xref{Using History Interactively},
23113 for the detailed description of the History library.
23115 To issue a command to @value{GDBN} without affecting certain aspects of
23116 the state which is seen by users, prefix it with @samp{server }
23117 (@pxref{Server Prefix}). This
23118 means that this command will not affect the command history, nor will it
23119 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23120 pressed on a line by itself.
23122 @cindex @code{server}, command prefix
23123 The server prefix does not affect the recording of values into the value
23124 history; to print a value without recording it into the value history,
23125 use the @code{output} command instead of the @code{print} command.
23127 Here is the description of @value{GDBN} commands related to command
23131 @cindex history substitution
23132 @cindex history file
23133 @kindex set history filename
23134 @cindex @env{GDBHISTFILE}, environment variable
23135 @item set history filename @var{fname}
23136 Set the name of the @value{GDBN} command history file to @var{fname}.
23137 This is the file where @value{GDBN} reads an initial command history
23138 list, and where it writes the command history from this session when it
23139 exits. You can access this list through history expansion or through
23140 the history command editing characters listed below. This file defaults
23141 to the value of the environment variable @code{GDBHISTFILE}, or to
23142 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23145 @cindex save command history
23146 @kindex set history save
23147 @item set history save
23148 @itemx set history save on
23149 Record command history in a file, whose name may be specified with the
23150 @code{set history filename} command. By default, this option is disabled.
23152 @item set history save off
23153 Stop recording command history in a file.
23155 @cindex history size
23156 @kindex set history size
23157 @cindex @env{GDBHISTSIZE}, environment variable
23158 @item set history size @var{size}
23159 @itemx set history size unlimited
23160 Set the number of commands which @value{GDBN} keeps in its history list.
23161 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23162 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23163 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23164 either a negative number or the empty string, then the number of commands
23165 @value{GDBN} keeps in the history list is unlimited.
23167 @cindex remove duplicate history
23168 @kindex set history remove-duplicates
23169 @item set history remove-duplicates @var{count}
23170 @itemx set history remove-duplicates unlimited
23171 Control the removal of duplicate history entries in the command history list.
23172 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23173 history entries and remove the first entry that is a duplicate of the current
23174 entry being added to the command history list. If @var{count} is
23175 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23176 removal of duplicate history entries is disabled.
23178 Only history entries added during the current session are considered for
23179 removal. This option is set to 0 by default.
23183 History expansion assigns special meaning to the character @kbd{!}.
23184 @ifset SYSTEM_READLINE
23185 @xref{Event Designators, , , history, GNU History Library},
23187 @ifclear SYSTEM_READLINE
23188 @xref{Event Designators},
23192 @cindex history expansion, turn on/off
23193 Since @kbd{!} is also the logical not operator in C, history expansion
23194 is off by default. If you decide to enable history expansion with the
23195 @code{set history expansion on} command, you may sometimes need to
23196 follow @kbd{!} (when it is used as logical not, in an expression) with
23197 a space or a tab to prevent it from being expanded. The readline
23198 history facilities do not attempt substitution on the strings
23199 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23201 The commands to control history expansion are:
23204 @item set history expansion on
23205 @itemx set history expansion
23206 @kindex set history expansion
23207 Enable history expansion. History expansion is off by default.
23209 @item set history expansion off
23210 Disable history expansion.
23213 @kindex show history
23215 @itemx show history filename
23216 @itemx show history save
23217 @itemx show history size
23218 @itemx show history expansion
23219 These commands display the state of the @value{GDBN} history parameters.
23220 @code{show history} by itself displays all four states.
23225 @kindex show commands
23226 @cindex show last commands
23227 @cindex display command history
23228 @item show commands
23229 Display the last ten commands in the command history.
23231 @item show commands @var{n}
23232 Print ten commands centered on command number @var{n}.
23234 @item show commands +
23235 Print ten commands just after the commands last printed.
23239 @section Screen Size
23240 @cindex size of screen
23241 @cindex screen size
23244 @cindex pauses in output
23246 Certain commands to @value{GDBN} may produce large amounts of
23247 information output to the screen. To help you read all of it,
23248 @value{GDBN} pauses and asks you for input at the end of each page of
23249 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23250 to discard the remaining output. Also, the screen width setting
23251 determines when to wrap lines of output. Depending on what is being
23252 printed, @value{GDBN} tries to break the line at a readable place,
23253 rather than simply letting it overflow onto the following line.
23255 Normally @value{GDBN} knows the size of the screen from the terminal
23256 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23257 together with the value of the @code{TERM} environment variable and the
23258 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23259 you can override it with the @code{set height} and @code{set
23266 @kindex show height
23267 @item set height @var{lpp}
23268 @itemx set height unlimited
23270 @itemx set width @var{cpl}
23271 @itemx set width unlimited
23273 These @code{set} commands specify a screen height of @var{lpp} lines and
23274 a screen width of @var{cpl} characters. The associated @code{show}
23275 commands display the current settings.
23277 If you specify a height of either @code{unlimited} or zero lines,
23278 @value{GDBN} does not pause during output no matter how long the
23279 output is. This is useful if output is to a file or to an editor
23282 Likewise, you can specify @samp{set width unlimited} or @samp{set
23283 width 0} to prevent @value{GDBN} from wrapping its output.
23285 @item set pagination on
23286 @itemx set pagination off
23287 @kindex set pagination
23288 Turn the output pagination on or off; the default is on. Turning
23289 pagination off is the alternative to @code{set height unlimited}. Note that
23290 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23291 Options, -batch}) also automatically disables pagination.
23293 @item show pagination
23294 @kindex show pagination
23295 Show the current pagination mode.
23300 @cindex number representation
23301 @cindex entering numbers
23303 You can always enter numbers in octal, decimal, or hexadecimal in
23304 @value{GDBN} by the usual conventions: octal numbers begin with
23305 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23306 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23307 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23308 10; likewise, the default display for numbers---when no particular
23309 format is specified---is base 10. You can change the default base for
23310 both input and output with the commands described below.
23313 @kindex set input-radix
23314 @item set input-radix @var{base}
23315 Set the default base for numeric input. Supported choices
23316 for @var{base} are decimal 8, 10, or 16. The base must itself be
23317 specified either unambiguously or using the current input radix; for
23321 set input-radix 012
23322 set input-radix 10.
23323 set input-radix 0xa
23327 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23328 leaves the input radix unchanged, no matter what it was, since
23329 @samp{10}, being without any leading or trailing signs of its base, is
23330 interpreted in the current radix. Thus, if the current radix is 16,
23331 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23334 @kindex set output-radix
23335 @item set output-radix @var{base}
23336 Set the default base for numeric display. Supported choices
23337 for @var{base} are decimal 8, 10, or 16. The base must itself be
23338 specified either unambiguously or using the current input radix.
23340 @kindex show input-radix
23341 @item show input-radix
23342 Display the current default base for numeric input.
23344 @kindex show output-radix
23345 @item show output-radix
23346 Display the current default base for numeric display.
23348 @item set radix @r{[}@var{base}@r{]}
23352 These commands set and show the default base for both input and output
23353 of numbers. @code{set radix} sets the radix of input and output to
23354 the same base; without an argument, it resets the radix back to its
23355 default value of 10.
23360 @section Configuring the Current ABI
23362 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23363 application automatically. However, sometimes you need to override its
23364 conclusions. Use these commands to manage @value{GDBN}'s view of the
23370 @cindex Newlib OS ABI and its influence on the longjmp handling
23372 One @value{GDBN} configuration can debug binaries for multiple operating
23373 system targets, either via remote debugging or native emulation.
23374 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23375 but you can override its conclusion using the @code{set osabi} command.
23376 One example where this is useful is in debugging of binaries which use
23377 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23378 not have the same identifying marks that the standard C library for your
23381 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23382 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23383 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23384 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23388 Show the OS ABI currently in use.
23391 With no argument, show the list of registered available OS ABI's.
23393 @item set osabi @var{abi}
23394 Set the current OS ABI to @var{abi}.
23397 @cindex float promotion
23399 Generally, the way that an argument of type @code{float} is passed to a
23400 function depends on whether the function is prototyped. For a prototyped
23401 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23402 according to the architecture's convention for @code{float}. For unprototyped
23403 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23404 @code{double} and then passed.
23406 Unfortunately, some forms of debug information do not reliably indicate whether
23407 a function is prototyped. If @value{GDBN} calls a function that is not marked
23408 as prototyped, it consults @kbd{set coerce-float-to-double}.
23411 @kindex set coerce-float-to-double
23412 @item set coerce-float-to-double
23413 @itemx set coerce-float-to-double on
23414 Arguments of type @code{float} will be promoted to @code{double} when passed
23415 to an unprototyped function. This is the default setting.
23417 @item set coerce-float-to-double off
23418 Arguments of type @code{float} will be passed directly to unprototyped
23421 @kindex show coerce-float-to-double
23422 @item show coerce-float-to-double
23423 Show the current setting of promoting @code{float} to @code{double}.
23427 @kindex show cp-abi
23428 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23429 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23430 used to build your application. @value{GDBN} only fully supports
23431 programs with a single C@t{++} ABI; if your program contains code using
23432 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23433 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23434 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23435 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23436 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23437 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23442 Show the C@t{++} ABI currently in use.
23445 With no argument, show the list of supported C@t{++} ABI's.
23447 @item set cp-abi @var{abi}
23448 @itemx set cp-abi auto
23449 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23453 @section Automatically loading associated files
23454 @cindex auto-loading
23456 @value{GDBN} sometimes reads files with commands and settings automatically,
23457 without being explicitly told so by the user. We call this feature
23458 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23459 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23460 results or introduce security risks (e.g., if the file comes from untrusted
23464 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23465 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23467 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23468 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23471 There are various kinds of files @value{GDBN} can automatically load.
23472 In addition to these files, @value{GDBN} supports auto-loading code written
23473 in various extension languages. @xref{Auto-loading extensions}.
23475 Note that loading of these associated files (including the local @file{.gdbinit}
23476 file) requires accordingly configured @code{auto-load safe-path}
23477 (@pxref{Auto-loading safe path}).
23479 For these reasons, @value{GDBN} includes commands and options to let you
23480 control when to auto-load files and which files should be auto-loaded.
23483 @anchor{set auto-load off}
23484 @kindex set auto-load off
23485 @item set auto-load off
23486 Globally disable loading of all auto-loaded files.
23487 You may want to use this command with the @samp{-iex} option
23488 (@pxref{Option -init-eval-command}) such as:
23490 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23493 Be aware that system init file (@pxref{System-wide configuration})
23494 and init files from your home directory (@pxref{Home Directory Init File})
23495 still get read (as they come from generally trusted directories).
23496 To prevent @value{GDBN} from auto-loading even those init files, use the
23497 @option{-nx} option (@pxref{Mode Options}), in addition to
23498 @code{set auto-load no}.
23500 @anchor{show auto-load}
23501 @kindex show auto-load
23502 @item show auto-load
23503 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23507 (gdb) show auto-load
23508 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23509 libthread-db: Auto-loading of inferior specific libthread_db is on.
23510 local-gdbinit: Auto-loading of .gdbinit script from current directory
23512 python-scripts: Auto-loading of Python scripts is on.
23513 safe-path: List of directories from which it is safe to auto-load files
23514 is $debugdir:$datadir/auto-load.
23515 scripts-directory: List of directories from which to load auto-loaded scripts
23516 is $debugdir:$datadir/auto-load.
23519 @anchor{info auto-load}
23520 @kindex info auto-load
23521 @item info auto-load
23522 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23526 (gdb) info auto-load
23529 Yes /home/user/gdb/gdb-gdb.gdb
23530 libthread-db: No auto-loaded libthread-db.
23531 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23535 Yes /home/user/gdb/gdb-gdb.py
23539 These are @value{GDBN} control commands for the auto-loading:
23541 @multitable @columnfractions .5 .5
23542 @item @xref{set auto-load off}.
23543 @tab Disable auto-loading globally.
23544 @item @xref{show auto-load}.
23545 @tab Show setting of all kinds of files.
23546 @item @xref{info auto-load}.
23547 @tab Show state of all kinds of files.
23548 @item @xref{set auto-load gdb-scripts}.
23549 @tab Control for @value{GDBN} command scripts.
23550 @item @xref{show auto-load gdb-scripts}.
23551 @tab Show setting of @value{GDBN} command scripts.
23552 @item @xref{info auto-load gdb-scripts}.
23553 @tab Show state of @value{GDBN} command scripts.
23554 @item @xref{set auto-load python-scripts}.
23555 @tab Control for @value{GDBN} Python scripts.
23556 @item @xref{show auto-load python-scripts}.
23557 @tab Show setting of @value{GDBN} Python scripts.
23558 @item @xref{info auto-load python-scripts}.
23559 @tab Show state of @value{GDBN} Python scripts.
23560 @item @xref{set auto-load guile-scripts}.
23561 @tab Control for @value{GDBN} Guile scripts.
23562 @item @xref{show auto-load guile-scripts}.
23563 @tab Show setting of @value{GDBN} Guile scripts.
23564 @item @xref{info auto-load guile-scripts}.
23565 @tab Show state of @value{GDBN} Guile scripts.
23566 @item @xref{set auto-load scripts-directory}.
23567 @tab Control for @value{GDBN} auto-loaded scripts location.
23568 @item @xref{show auto-load scripts-directory}.
23569 @tab Show @value{GDBN} auto-loaded scripts location.
23570 @item @xref{add-auto-load-scripts-directory}.
23571 @tab Add directory for auto-loaded scripts location list.
23572 @item @xref{set auto-load local-gdbinit}.
23573 @tab Control for init file in the current directory.
23574 @item @xref{show auto-load local-gdbinit}.
23575 @tab Show setting of init file in the current directory.
23576 @item @xref{info auto-load local-gdbinit}.
23577 @tab Show state of init file in the current directory.
23578 @item @xref{set auto-load libthread-db}.
23579 @tab Control for thread debugging library.
23580 @item @xref{show auto-load libthread-db}.
23581 @tab Show setting of thread debugging library.
23582 @item @xref{info auto-load libthread-db}.
23583 @tab Show state of thread debugging library.
23584 @item @xref{set auto-load safe-path}.
23585 @tab Control directories trusted for automatic loading.
23586 @item @xref{show auto-load safe-path}.
23587 @tab Show directories trusted for automatic loading.
23588 @item @xref{add-auto-load-safe-path}.
23589 @tab Add directory trusted for automatic loading.
23592 @node Init File in the Current Directory
23593 @subsection Automatically loading init file in the current directory
23594 @cindex auto-loading init file in the current directory
23596 By default, @value{GDBN} reads and executes the canned sequences of commands
23597 from init file (if any) in the current working directory,
23598 see @ref{Init File in the Current Directory during Startup}.
23600 Note that loading of this local @file{.gdbinit} file also requires accordingly
23601 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23604 @anchor{set auto-load local-gdbinit}
23605 @kindex set auto-load local-gdbinit
23606 @item set auto-load local-gdbinit [on|off]
23607 Enable or disable the auto-loading of canned sequences of commands
23608 (@pxref{Sequences}) found in init file in the current directory.
23610 @anchor{show auto-load local-gdbinit}
23611 @kindex show auto-load local-gdbinit
23612 @item show auto-load local-gdbinit
23613 Show whether auto-loading of canned sequences of commands from init file in the
23614 current directory is enabled or disabled.
23616 @anchor{info auto-load local-gdbinit}
23617 @kindex info auto-load local-gdbinit
23618 @item info auto-load local-gdbinit
23619 Print whether canned sequences of commands from init file in the
23620 current directory have been auto-loaded.
23623 @node libthread_db.so.1 file
23624 @subsection Automatically loading thread debugging library
23625 @cindex auto-loading libthread_db.so.1
23627 This feature is currently present only on @sc{gnu}/Linux native hosts.
23629 @value{GDBN} reads in some cases thread debugging library from places specific
23630 to the inferior (@pxref{set libthread-db-search-path}).
23632 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23633 without checking this @samp{set auto-load libthread-db} switch as system
23634 libraries have to be trusted in general. In all other cases of
23635 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23636 auto-load libthread-db} is enabled before trying to open such thread debugging
23639 Note that loading of this debugging library also requires accordingly configured
23640 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23643 @anchor{set auto-load libthread-db}
23644 @kindex set auto-load libthread-db
23645 @item set auto-load libthread-db [on|off]
23646 Enable or disable the auto-loading of inferior specific thread debugging library.
23648 @anchor{show auto-load libthread-db}
23649 @kindex show auto-load libthread-db
23650 @item show auto-load libthread-db
23651 Show whether auto-loading of inferior specific thread debugging library is
23652 enabled or disabled.
23654 @anchor{info auto-load libthread-db}
23655 @kindex info auto-load libthread-db
23656 @item info auto-load libthread-db
23657 Print the list of all loaded inferior specific thread debugging libraries and
23658 for each such library print list of inferior @var{pid}s using it.
23661 @node Auto-loading safe path
23662 @subsection Security restriction for auto-loading
23663 @cindex auto-loading safe-path
23665 As the files of inferior can come from untrusted source (such as submitted by
23666 an application user) @value{GDBN} does not always load any files automatically.
23667 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23668 directories trusted for loading files not explicitly requested by user.
23669 Each directory can also be a shell wildcard pattern.
23671 If the path is not set properly you will see a warning and the file will not
23676 Reading symbols from /home/user/gdb/gdb...done.
23677 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23678 declined by your `auto-load safe-path' set
23679 to "$debugdir:$datadir/auto-load".
23680 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23681 declined by your `auto-load safe-path' set
23682 to "$debugdir:$datadir/auto-load".
23686 To instruct @value{GDBN} to go ahead and use the init files anyway,
23687 invoke @value{GDBN} like this:
23690 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23693 The list of trusted directories is controlled by the following commands:
23696 @anchor{set auto-load safe-path}
23697 @kindex set auto-load safe-path
23698 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23699 Set the list of directories (and their subdirectories) trusted for automatic
23700 loading and execution of scripts. You can also enter a specific trusted file.
23701 Each directory can also be a shell wildcard pattern; wildcards do not match
23702 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23703 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23704 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23705 its default value as specified during @value{GDBN} compilation.
23707 The list of directories uses path separator (@samp{:} on GNU and Unix
23708 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23709 to the @env{PATH} environment variable.
23711 @anchor{show auto-load safe-path}
23712 @kindex show auto-load safe-path
23713 @item show auto-load safe-path
23714 Show the list of directories trusted for automatic loading and execution of
23717 @anchor{add-auto-load-safe-path}
23718 @kindex add-auto-load-safe-path
23719 @item add-auto-load-safe-path
23720 Add an entry (or list of entries) to the list of directories trusted for
23721 automatic loading and execution of scripts. Multiple entries may be delimited
23722 by the host platform path separator in use.
23725 This variable defaults to what @code{--with-auto-load-dir} has been configured
23726 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23727 substitution applies the same as for @ref{set auto-load scripts-directory}.
23728 The default @code{set auto-load safe-path} value can be also overriden by
23729 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23731 Setting this variable to @file{/} disables this security protection,
23732 corresponding @value{GDBN} configuration option is
23733 @option{--without-auto-load-safe-path}.
23734 This variable is supposed to be set to the system directories writable by the
23735 system superuser only. Users can add their source directories in init files in
23736 their home directories (@pxref{Home Directory Init File}). See also deprecated
23737 init file in the current directory
23738 (@pxref{Init File in the Current Directory during Startup}).
23740 To force @value{GDBN} to load the files it declined to load in the previous
23741 example, you could use one of the following ways:
23744 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23745 Specify this trusted directory (or a file) as additional component of the list.
23746 You have to specify also any existing directories displayed by
23747 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23749 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23750 Specify this directory as in the previous case but just for a single
23751 @value{GDBN} session.
23753 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23754 Disable auto-loading safety for a single @value{GDBN} session.
23755 This assumes all the files you debug during this @value{GDBN} session will come
23756 from trusted sources.
23758 @item @kbd{./configure --without-auto-load-safe-path}
23759 During compilation of @value{GDBN} you may disable any auto-loading safety.
23760 This assumes all the files you will ever debug with this @value{GDBN} come from
23764 On the other hand you can also explicitly forbid automatic files loading which
23765 also suppresses any such warning messages:
23768 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23769 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23771 @item @file{~/.gdbinit}: @samp{set auto-load no}
23772 Disable auto-loading globally for the user
23773 (@pxref{Home Directory Init File}). While it is improbable, you could also
23774 use system init file instead (@pxref{System-wide configuration}).
23777 This setting applies to the file names as entered by user. If no entry matches
23778 @value{GDBN} tries as a last resort to also resolve all the file names into
23779 their canonical form (typically resolving symbolic links) and compare the
23780 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23781 own before starting the comparison so a canonical form of directories is
23782 recommended to be entered.
23784 @node Auto-loading verbose mode
23785 @subsection Displaying files tried for auto-load
23786 @cindex auto-loading verbose mode
23788 For better visibility of all the file locations where you can place scripts to
23789 be auto-loaded with inferior --- or to protect yourself against accidental
23790 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23791 all the files attempted to be loaded. Both existing and non-existing files may
23794 For example the list of directories from which it is safe to auto-load files
23795 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23796 may not be too obvious while setting it up.
23799 (gdb) set debug auto-load on
23800 (gdb) file ~/src/t/true
23801 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23802 for objfile "/tmp/true".
23803 auto-load: Updating directories of "/usr:/opt".
23804 auto-load: Using directory "/usr".
23805 auto-load: Using directory "/opt".
23806 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23807 by your `auto-load safe-path' set to "/usr:/opt".
23811 @anchor{set debug auto-load}
23812 @kindex set debug auto-load
23813 @item set debug auto-load [on|off]
23814 Set whether to print the filenames attempted to be auto-loaded.
23816 @anchor{show debug auto-load}
23817 @kindex show debug auto-load
23818 @item show debug auto-load
23819 Show whether printing of the filenames attempted to be auto-loaded is turned
23823 @node Messages/Warnings
23824 @section Optional Warnings and Messages
23826 @cindex verbose operation
23827 @cindex optional warnings
23828 By default, @value{GDBN} is silent about its inner workings. If you are
23829 running on a slow machine, you may want to use the @code{set verbose}
23830 command. This makes @value{GDBN} tell you when it does a lengthy
23831 internal operation, so you will not think it has crashed.
23833 Currently, the messages controlled by @code{set verbose} are those
23834 which announce that the symbol table for a source file is being read;
23835 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23838 @kindex set verbose
23839 @item set verbose on
23840 Enables @value{GDBN} output of certain informational messages.
23842 @item set verbose off
23843 Disables @value{GDBN} output of certain informational messages.
23845 @kindex show verbose
23847 Displays whether @code{set verbose} is on or off.
23850 By default, if @value{GDBN} encounters bugs in the symbol table of an
23851 object file, it is silent; but if you are debugging a compiler, you may
23852 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23857 @kindex set complaints
23858 @item set complaints @var{limit}
23859 Permits @value{GDBN} to output @var{limit} complaints about each type of
23860 unusual symbols before becoming silent about the problem. Set
23861 @var{limit} to zero to suppress all complaints; set it to a large number
23862 to prevent complaints from being suppressed.
23864 @kindex show complaints
23865 @item show complaints
23866 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23870 @anchor{confirmation requests}
23871 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23872 lot of stupid questions to confirm certain commands. For example, if
23873 you try to run a program which is already running:
23877 The program being debugged has been started already.
23878 Start it from the beginning? (y or n)
23881 If you are willing to unflinchingly face the consequences of your own
23882 commands, you can disable this ``feature'':
23886 @kindex set confirm
23888 @cindex confirmation
23889 @cindex stupid questions
23890 @item set confirm off
23891 Disables confirmation requests. Note that running @value{GDBN} with
23892 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23893 automatically disables confirmation requests.
23895 @item set confirm on
23896 Enables confirmation requests (the default).
23898 @kindex show confirm
23900 Displays state of confirmation requests.
23904 @cindex command tracing
23905 If you need to debug user-defined commands or sourced files you may find it
23906 useful to enable @dfn{command tracing}. In this mode each command will be
23907 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23908 quantity denoting the call depth of each command.
23911 @kindex set trace-commands
23912 @cindex command scripts, debugging
23913 @item set trace-commands on
23914 Enable command tracing.
23915 @item set trace-commands off
23916 Disable command tracing.
23917 @item show trace-commands
23918 Display the current state of command tracing.
23921 @node Debugging Output
23922 @section Optional Messages about Internal Happenings
23923 @cindex optional debugging messages
23925 @value{GDBN} has commands that enable optional debugging messages from
23926 various @value{GDBN} subsystems; normally these commands are of
23927 interest to @value{GDBN} maintainers, or when reporting a bug. This
23928 section documents those commands.
23931 @kindex set exec-done-display
23932 @item set exec-done-display
23933 Turns on or off the notification of asynchronous commands'
23934 completion. When on, @value{GDBN} will print a message when an
23935 asynchronous command finishes its execution. The default is off.
23936 @kindex show exec-done-display
23937 @item show exec-done-display
23938 Displays the current setting of asynchronous command completion
23941 @cindex ARM AArch64
23942 @item set debug aarch64
23943 Turns on or off display of debugging messages related to ARM AArch64.
23944 The default is off.
23946 @item show debug aarch64
23947 Displays the current state of displaying debugging messages related to
23949 @cindex gdbarch debugging info
23950 @cindex architecture debugging info
23951 @item set debug arch
23952 Turns on or off display of gdbarch debugging info. The default is off
23953 @item show debug arch
23954 Displays the current state of displaying gdbarch debugging info.
23955 @item set debug aix-solib
23956 @cindex AIX shared library debugging
23957 Control display of debugging messages from the AIX shared library
23958 support module. The default is off.
23959 @item show debug aix-thread
23960 Show the current state of displaying AIX shared library debugging messages.
23961 @item set debug aix-thread
23962 @cindex AIX threads
23963 Display debugging messages about inner workings of the AIX thread
23965 @item show debug aix-thread
23966 Show the current state of AIX thread debugging info display.
23967 @item set debug check-physname
23969 Check the results of the ``physname'' computation. When reading DWARF
23970 debugging information for C@t{++}, @value{GDBN} attempts to compute
23971 each entity's name. @value{GDBN} can do this computation in two
23972 different ways, depending on exactly what information is present.
23973 When enabled, this setting causes @value{GDBN} to compute the names
23974 both ways and display any discrepancies.
23975 @item show debug check-physname
23976 Show the current state of ``physname'' checking.
23977 @item set debug coff-pe-read
23978 @cindex COFF/PE exported symbols
23979 Control display of debugging messages related to reading of COFF/PE
23980 exported symbols. The default is off.
23981 @item show debug coff-pe-read
23982 Displays the current state of displaying debugging messages related to
23983 reading of COFF/PE exported symbols.
23984 @item set debug dwarf-die
23986 Dump DWARF DIEs after they are read in.
23987 The value is the number of nesting levels to print.
23988 A value of zero turns off the display.
23989 @item show debug dwarf-die
23990 Show the current state of DWARF DIE debugging.
23991 @item set debug dwarf-line
23992 @cindex DWARF Line Tables
23993 Turns on or off display of debugging messages related to reading
23994 DWARF line tables. The default is 0 (off).
23995 A value of 1 provides basic information.
23996 A value greater than 1 provides more verbose information.
23997 @item show debug dwarf-line
23998 Show the current state of DWARF line table debugging.
23999 @item set debug dwarf-read
24000 @cindex DWARF Reading
24001 Turns on or off display of debugging messages related to reading
24002 DWARF debug info. The default is 0 (off).
24003 A value of 1 provides basic information.
24004 A value greater than 1 provides more verbose information.
24005 @item show debug dwarf-read
24006 Show the current state of DWARF reader debugging.
24007 @item set debug displaced
24008 @cindex displaced stepping debugging info
24009 Turns on or off display of @value{GDBN} debugging info for the
24010 displaced stepping support. The default is off.
24011 @item show debug displaced
24012 Displays the current state of displaying @value{GDBN} debugging info
24013 related to displaced stepping.
24014 @item set debug event
24015 @cindex event debugging info
24016 Turns on or off display of @value{GDBN} event debugging info. The
24018 @item show debug event
24019 Displays the current state of displaying @value{GDBN} event debugging
24021 @item set debug expression
24022 @cindex expression debugging info
24023 Turns on or off display of debugging info about @value{GDBN}
24024 expression parsing. The default is off.
24025 @item show debug expression
24026 Displays the current state of displaying debugging info about
24027 @value{GDBN} expression parsing.
24028 @item set debug fbsd-lwp
24029 @cindex FreeBSD LWP debug messages
24030 Turns on or off debugging messages from the FreeBSD LWP debug support.
24031 @item show debug fbsd-lwp
24032 Show the current state of FreeBSD LWP debugging messages.
24033 @item set debug frame
24034 @cindex frame debugging info
24035 Turns on or off display of @value{GDBN} frame debugging info. The
24037 @item show debug frame
24038 Displays the current state of displaying @value{GDBN} frame debugging
24040 @item set debug gnu-nat
24041 @cindex @sc{gnu}/Hurd debug messages
24042 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24043 @item show debug gnu-nat
24044 Show the current state of @sc{gnu}/Hurd debugging messages.
24045 @item set debug infrun
24046 @cindex inferior debugging info
24047 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24048 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24049 for implementing operations such as single-stepping the inferior.
24050 @item show debug infrun
24051 Displays the current state of @value{GDBN} inferior debugging.
24052 @item set debug jit
24053 @cindex just-in-time compilation, debugging messages
24054 Turn on or off debugging messages from JIT debug support.
24055 @item show debug jit
24056 Displays the current state of @value{GDBN} JIT debugging.
24057 @item set debug lin-lwp
24058 @cindex @sc{gnu}/Linux LWP debug messages
24059 @cindex Linux lightweight processes
24060 Turn on or off debugging messages from the Linux LWP debug support.
24061 @item show debug lin-lwp
24062 Show the current state of Linux LWP debugging messages.
24063 @item set debug linux-namespaces
24064 @cindex @sc{gnu}/Linux namespaces debug messages
24065 Turn on or off debugging messages from the Linux namespaces debug support.
24066 @item show debug linux-namespaces
24067 Show the current state of Linux namespaces debugging messages.
24068 @item set debug mach-o
24069 @cindex Mach-O symbols processing
24070 Control display of debugging messages related to Mach-O symbols
24071 processing. The default is off.
24072 @item show debug mach-o
24073 Displays the current state of displaying debugging messages related to
24074 reading of COFF/PE exported symbols.
24075 @item set debug notification
24076 @cindex remote async notification debugging info
24077 Turn on or off debugging messages about remote async notification.
24078 The default is off.
24079 @item show debug notification
24080 Displays the current state of remote async notification debugging messages.
24081 @item set debug observer
24082 @cindex observer debugging info
24083 Turns on or off display of @value{GDBN} observer debugging. This
24084 includes info such as the notification of observable events.
24085 @item show debug observer
24086 Displays the current state of observer debugging.
24087 @item set debug overload
24088 @cindex C@t{++} overload debugging info
24089 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24090 info. This includes info such as ranking of functions, etc. The default
24092 @item show debug overload
24093 Displays the current state of displaying @value{GDBN} C@t{++} overload
24095 @cindex expression parser, debugging info
24096 @cindex debug expression parser
24097 @item set debug parser
24098 Turns on or off the display of expression parser debugging output.
24099 Internally, this sets the @code{yydebug} variable in the expression
24100 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24101 details. The default is off.
24102 @item show debug parser
24103 Show the current state of expression parser debugging.
24104 @cindex packets, reporting on stdout
24105 @cindex serial connections, debugging
24106 @cindex debug remote protocol
24107 @cindex remote protocol debugging
24108 @cindex display remote packets
24109 @item set debug remote
24110 Turns on or off display of reports on all packets sent back and forth across
24111 the serial line to the remote machine. The info is printed on the
24112 @value{GDBN} standard output stream. The default is off.
24113 @item show debug remote
24114 Displays the state of display of remote packets.
24116 @item set debug separate-debug-file
24117 Turns on or off display of debug output about separate debug file search.
24118 @item show debug separate-debug-file
24119 Displays the state of separate debug file search debug output.
24121 @item set debug serial
24122 Turns on or off display of @value{GDBN} serial debugging info. The
24124 @item show debug serial
24125 Displays the current state of displaying @value{GDBN} serial debugging
24127 @item set debug solib-frv
24128 @cindex FR-V shared-library debugging
24129 Turn on or off debugging messages for FR-V shared-library code.
24130 @item show debug solib-frv
24131 Display the current state of FR-V shared-library code debugging
24133 @item set debug symbol-lookup
24134 @cindex symbol lookup
24135 Turns on or off display of debugging messages related to symbol lookup.
24136 The default is 0 (off).
24137 A value of 1 provides basic information.
24138 A value greater than 1 provides more verbose information.
24139 @item show debug symbol-lookup
24140 Show the current state of symbol lookup debugging messages.
24141 @item set debug symfile
24142 @cindex symbol file functions
24143 Turns on or off display of debugging messages related to symbol file functions.
24144 The default is off. @xref{Files}.
24145 @item show debug symfile
24146 Show the current state of symbol file debugging messages.
24147 @item set debug symtab-create
24148 @cindex symbol table creation
24149 Turns on or off display of debugging messages related to symbol table creation.
24150 The default is 0 (off).
24151 A value of 1 provides basic information.
24152 A value greater than 1 provides more verbose information.
24153 @item show debug symtab-create
24154 Show the current state of symbol table creation debugging.
24155 @item set debug target
24156 @cindex target debugging info
24157 Turns on or off display of @value{GDBN} target debugging info. This info
24158 includes what is going on at the target level of GDB, as it happens. The
24159 default is 0. Set it to 1 to track events, and to 2 to also track the
24160 value of large memory transfers.
24161 @item show debug target
24162 Displays the current state of displaying @value{GDBN} target debugging
24164 @item set debug timestamp
24165 @cindex timestampping debugging info
24166 Turns on or off display of timestamps with @value{GDBN} debugging info.
24167 When enabled, seconds and microseconds are displayed before each debugging
24169 @item show debug timestamp
24170 Displays the current state of displaying timestamps with @value{GDBN}
24172 @item set debug varobj
24173 @cindex variable object debugging info
24174 Turns on or off display of @value{GDBN} variable object debugging
24175 info. The default is off.
24176 @item show debug varobj
24177 Displays the current state of displaying @value{GDBN} variable object
24179 @item set debug xml
24180 @cindex XML parser debugging
24181 Turn on or off debugging messages for built-in XML parsers.
24182 @item show debug xml
24183 Displays the current state of XML debugging messages.
24186 @node Other Misc Settings
24187 @section Other Miscellaneous Settings
24188 @cindex miscellaneous settings
24191 @kindex set interactive-mode
24192 @item set interactive-mode
24193 If @code{on}, forces @value{GDBN} to assume that GDB was started
24194 in a terminal. In practice, this means that @value{GDBN} should wait
24195 for the user to answer queries generated by commands entered at
24196 the command prompt. If @code{off}, forces @value{GDBN} to operate
24197 in the opposite mode, and it uses the default answers to all queries.
24198 If @code{auto} (the default), @value{GDBN} tries to determine whether
24199 its standard input is a terminal, and works in interactive-mode if it
24200 is, non-interactively otherwise.
24202 In the vast majority of cases, the debugger should be able to guess
24203 correctly which mode should be used. But this setting can be useful
24204 in certain specific cases, such as running a MinGW @value{GDBN}
24205 inside a cygwin window.
24207 @kindex show interactive-mode
24208 @item show interactive-mode
24209 Displays whether the debugger is operating in interactive mode or not.
24212 @node Extending GDB
24213 @chapter Extending @value{GDBN}
24214 @cindex extending GDB
24216 @value{GDBN} provides several mechanisms for extension.
24217 @value{GDBN} also provides the ability to automatically load
24218 extensions when it reads a file for debugging. This allows the
24219 user to automatically customize @value{GDBN} for the program
24223 * Sequences:: Canned Sequences of @value{GDBN} Commands
24224 * Python:: Extending @value{GDBN} using Python
24225 * Guile:: Extending @value{GDBN} using Guile
24226 * Auto-loading extensions:: Automatically loading extensions
24227 * Multiple Extension Languages:: Working with multiple extension languages
24228 * Aliases:: Creating new spellings of existing commands
24231 To facilitate the use of extension languages, @value{GDBN} is capable
24232 of evaluating the contents of a file. When doing so, @value{GDBN}
24233 can recognize which extension language is being used by looking at
24234 the filename extension. Files with an unrecognized filename extension
24235 are always treated as a @value{GDBN} Command Files.
24236 @xref{Command Files,, Command files}.
24238 You can control how @value{GDBN} evaluates these files with the following
24242 @kindex set script-extension
24243 @kindex show script-extension
24244 @item set script-extension off
24245 All scripts are always evaluated as @value{GDBN} Command Files.
24247 @item set script-extension soft
24248 The debugger determines the scripting language based on filename
24249 extension. If this scripting language is supported, @value{GDBN}
24250 evaluates the script using that language. Otherwise, it evaluates
24251 the file as a @value{GDBN} Command File.
24253 @item set script-extension strict
24254 The debugger determines the scripting language based on filename
24255 extension, and evaluates the script using that language. If the
24256 language is not supported, then the evaluation fails.
24258 @item show script-extension
24259 Display the current value of the @code{script-extension} option.
24264 @section Canned Sequences of Commands
24266 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24267 Command Lists}), @value{GDBN} provides two ways to store sequences of
24268 commands for execution as a unit: user-defined commands and command
24272 * Define:: How to define your own commands
24273 * Hooks:: Hooks for user-defined commands
24274 * Command Files:: How to write scripts of commands to be stored in a file
24275 * Output:: Commands for controlled output
24276 * Auto-loading sequences:: Controlling auto-loaded command files
24280 @subsection User-defined Commands
24282 @cindex user-defined command
24283 @cindex arguments, to user-defined commands
24284 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24285 which you assign a new name as a command. This is done with the
24286 @code{define} command. User commands may accept an unlimited number of arguments
24287 separated by whitespace. Arguments are accessed within the user command
24288 via @code{$arg0@dots{}$argN}. A trivial example:
24292 print $arg0 + $arg1 + $arg2
24297 To execute the command use:
24304 This defines the command @code{adder}, which prints the sum of
24305 its three arguments. Note the arguments are text substitutions, so they may
24306 reference variables, use complex expressions, or even perform inferior
24309 @cindex argument count in user-defined commands
24310 @cindex how many arguments (user-defined commands)
24311 In addition, @code{$argc} may be used to find out how many arguments have
24317 print $arg0 + $arg1
24320 print $arg0 + $arg1 + $arg2
24325 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24326 to process a variable number of arguments:
24333 eval "set $sum = $sum + $arg%d", $i
24343 @item define @var{commandname}
24344 Define a command named @var{commandname}. If there is already a command
24345 by that name, you are asked to confirm that you want to redefine it.
24346 The argument @var{commandname} may be a bare command name consisting of letters,
24347 numbers, dashes, and underscores. It may also start with any predefined
24348 prefix command. For example, @samp{define target my-target} creates
24349 a user-defined @samp{target my-target} command.
24351 The definition of the command is made up of other @value{GDBN} command lines,
24352 which are given following the @code{define} command. The end of these
24353 commands is marked by a line containing @code{end}.
24356 @kindex end@r{ (user-defined commands)}
24357 @item document @var{commandname}
24358 Document the user-defined command @var{commandname}, so that it can be
24359 accessed by @code{help}. The command @var{commandname} must already be
24360 defined. This command reads lines of documentation just as @code{define}
24361 reads the lines of the command definition, ending with @code{end}.
24362 After the @code{document} command is finished, @code{help} on command
24363 @var{commandname} displays the documentation you have written.
24365 You may use the @code{document} command again to change the
24366 documentation of a command. Redefining the command with @code{define}
24367 does not change the documentation.
24369 @kindex dont-repeat
24370 @cindex don't repeat command
24372 Used inside a user-defined command, this tells @value{GDBN} that this
24373 command should not be repeated when the user hits @key{RET}
24374 (@pxref{Command Syntax, repeat last command}).
24376 @kindex help user-defined
24377 @item help user-defined
24378 List all user-defined commands and all python commands defined in class
24379 COMAND_USER. The first line of the documentation or docstring is
24384 @itemx show user @var{commandname}
24385 Display the @value{GDBN} commands used to define @var{commandname} (but
24386 not its documentation). If no @var{commandname} is given, display the
24387 definitions for all user-defined commands.
24388 This does not work for user-defined python commands.
24390 @cindex infinite recursion in user-defined commands
24391 @kindex show max-user-call-depth
24392 @kindex set max-user-call-depth
24393 @item show max-user-call-depth
24394 @itemx set max-user-call-depth
24395 The value of @code{max-user-call-depth} controls how many recursion
24396 levels are allowed in user-defined commands before @value{GDBN} suspects an
24397 infinite recursion and aborts the command.
24398 This does not apply to user-defined python commands.
24401 In addition to the above commands, user-defined commands frequently
24402 use control flow commands, described in @ref{Command Files}.
24404 When user-defined commands are executed, the
24405 commands of the definition are not printed. An error in any command
24406 stops execution of the user-defined command.
24408 If used interactively, commands that would ask for confirmation proceed
24409 without asking when used inside a user-defined command. Many @value{GDBN}
24410 commands that normally print messages to say what they are doing omit the
24411 messages when used in a user-defined command.
24414 @subsection User-defined Command Hooks
24415 @cindex command hooks
24416 @cindex hooks, for commands
24417 @cindex hooks, pre-command
24420 You may define @dfn{hooks}, which are a special kind of user-defined
24421 command. Whenever you run the command @samp{foo}, if the user-defined
24422 command @samp{hook-foo} exists, it is executed (with no arguments)
24423 before that command.
24425 @cindex hooks, post-command
24427 A hook may also be defined which is run after the command you executed.
24428 Whenever you run the command @samp{foo}, if the user-defined command
24429 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24430 that command. Post-execution hooks may exist simultaneously with
24431 pre-execution hooks, for the same command.
24433 It is valid for a hook to call the command which it hooks. If this
24434 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24436 @c It would be nice if hookpost could be passed a parameter indicating
24437 @c if the command it hooks executed properly or not. FIXME!
24439 @kindex stop@r{, a pseudo-command}
24440 In addition, a pseudo-command, @samp{stop} exists. Defining
24441 (@samp{hook-stop}) makes the associated commands execute every time
24442 execution stops in your program: before breakpoint commands are run,
24443 displays are printed, or the stack frame is printed.
24445 For example, to ignore @code{SIGALRM} signals while
24446 single-stepping, but treat them normally during normal execution,
24451 handle SIGALRM nopass
24455 handle SIGALRM pass
24458 define hook-continue
24459 handle SIGALRM pass
24463 As a further example, to hook at the beginning and end of the @code{echo}
24464 command, and to add extra text to the beginning and end of the message,
24472 define hookpost-echo
24476 (@value{GDBP}) echo Hello World
24477 <<<---Hello World--->>>
24482 You can define a hook for any single-word command in @value{GDBN}, but
24483 not for command aliases; you should define a hook for the basic command
24484 name, e.g.@: @code{backtrace} rather than @code{bt}.
24485 @c FIXME! So how does Joe User discover whether a command is an alias
24487 You can hook a multi-word command by adding @code{hook-} or
24488 @code{hookpost-} to the last word of the command, e.g.@:
24489 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24491 If an error occurs during the execution of your hook, execution of
24492 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24493 (before the command that you actually typed had a chance to run).
24495 If you try to define a hook which does not match any known command, you
24496 get a warning from the @code{define} command.
24498 @node Command Files
24499 @subsection Command Files
24501 @cindex command files
24502 @cindex scripting commands
24503 A command file for @value{GDBN} is a text file made of lines that are
24504 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24505 also be included. An empty line in a command file does nothing; it
24506 does not mean to repeat the last command, as it would from the
24509 You can request the execution of a command file with the @code{source}
24510 command. Note that the @code{source} command is also used to evaluate
24511 scripts that are not Command Files. The exact behavior can be configured
24512 using the @code{script-extension} setting.
24513 @xref{Extending GDB,, Extending GDB}.
24517 @cindex execute commands from a file
24518 @item source [-s] [-v] @var{filename}
24519 Execute the command file @var{filename}.
24522 The lines in a command file are generally executed sequentially,
24523 unless the order of execution is changed by one of the
24524 @emph{flow-control commands} described below. The commands are not
24525 printed as they are executed. An error in any command terminates
24526 execution of the command file and control is returned to the console.
24528 @value{GDBN} first searches for @var{filename} in the current directory.
24529 If the file is not found there, and @var{filename} does not specify a
24530 directory, then @value{GDBN} also looks for the file on the source search path
24531 (specified with the @samp{directory} command);
24532 except that @file{$cdir} is not searched because the compilation directory
24533 is not relevant to scripts.
24535 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24536 on the search path even if @var{filename} specifies a directory.
24537 The search is done by appending @var{filename} to each element of the
24538 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24539 and the search path contains @file{/home/user} then @value{GDBN} will
24540 look for the script @file{/home/user/mylib/myscript}.
24541 The search is also done if @var{filename} is an absolute path.
24542 For example, if @var{filename} is @file{/tmp/myscript} and
24543 the search path contains @file{/home/user} then @value{GDBN} will
24544 look for the script @file{/home/user/tmp/myscript}.
24545 For DOS-like systems, if @var{filename} contains a drive specification,
24546 it is stripped before concatenation. For example, if @var{filename} is
24547 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24548 will look for the script @file{c:/tmp/myscript}.
24550 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24551 each command as it is executed. The option must be given before
24552 @var{filename}, and is interpreted as part of the filename anywhere else.
24554 Commands that would ask for confirmation if used interactively proceed
24555 without asking when used in a command file. Many @value{GDBN} commands that
24556 normally print messages to say what they are doing omit the messages
24557 when called from command files.
24559 @value{GDBN} also accepts command input from standard input. In this
24560 mode, normal output goes to standard output and error output goes to
24561 standard error. Errors in a command file supplied on standard input do
24562 not terminate execution of the command file---execution continues with
24566 gdb < cmds > log 2>&1
24569 (The syntax above will vary depending on the shell used.) This example
24570 will execute commands from the file @file{cmds}. All output and errors
24571 would be directed to @file{log}.
24573 Since commands stored on command files tend to be more general than
24574 commands typed interactively, they frequently need to deal with
24575 complicated situations, such as different or unexpected values of
24576 variables and symbols, changes in how the program being debugged is
24577 built, etc. @value{GDBN} provides a set of flow-control commands to
24578 deal with these complexities. Using these commands, you can write
24579 complex scripts that loop over data structures, execute commands
24580 conditionally, etc.
24587 This command allows to include in your script conditionally executed
24588 commands. The @code{if} command takes a single argument, which is an
24589 expression to evaluate. It is followed by a series of commands that
24590 are executed only if the expression is true (its value is nonzero).
24591 There can then optionally be an @code{else} line, followed by a series
24592 of commands that are only executed if the expression was false. The
24593 end of the list is marked by a line containing @code{end}.
24597 This command allows to write loops. Its syntax is similar to
24598 @code{if}: the command takes a single argument, which is an expression
24599 to evaluate, and must be followed by the commands to execute, one per
24600 line, terminated by an @code{end}. These commands are called the
24601 @dfn{body} of the loop. The commands in the body of @code{while} are
24602 executed repeatedly as long as the expression evaluates to true.
24606 This command exits the @code{while} loop in whose body it is included.
24607 Execution of the script continues after that @code{while}s @code{end}
24610 @kindex loop_continue
24611 @item loop_continue
24612 This command skips the execution of the rest of the body of commands
24613 in the @code{while} loop in whose body it is included. Execution
24614 branches to the beginning of the @code{while} loop, where it evaluates
24615 the controlling expression.
24617 @kindex end@r{ (if/else/while commands)}
24619 Terminate the block of commands that are the body of @code{if},
24620 @code{else}, or @code{while} flow-control commands.
24625 @subsection Commands for Controlled Output
24627 During the execution of a command file or a user-defined command, normal
24628 @value{GDBN} output is suppressed; the only output that appears is what is
24629 explicitly printed by the commands in the definition. This section
24630 describes three commands useful for generating exactly the output you
24635 @item echo @var{text}
24636 @c I do not consider backslash-space a standard C escape sequence
24637 @c because it is not in ANSI.
24638 Print @var{text}. Nonprinting characters can be included in
24639 @var{text} using C escape sequences, such as @samp{\n} to print a
24640 newline. @strong{No newline is printed unless you specify one.}
24641 In addition to the standard C escape sequences, a backslash followed
24642 by a space stands for a space. This is useful for displaying a
24643 string with spaces at the beginning or the end, since leading and
24644 trailing spaces are otherwise trimmed from all arguments.
24645 To print @samp{@w{ }and foo =@w{ }}, use the command
24646 @samp{echo \@w{ }and foo = \@w{ }}.
24648 A backslash at the end of @var{text} can be used, as in C, to continue
24649 the command onto subsequent lines. For example,
24652 echo This is some text\n\
24653 which is continued\n\
24654 onto several lines.\n
24657 produces the same output as
24660 echo This is some text\n
24661 echo which is continued\n
24662 echo onto several lines.\n
24666 @item output @var{expression}
24667 Print the value of @var{expression} and nothing but that value: no
24668 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24669 value history either. @xref{Expressions, ,Expressions}, for more information
24672 @item output/@var{fmt} @var{expression}
24673 Print the value of @var{expression} in format @var{fmt}. You can use
24674 the same formats as for @code{print}. @xref{Output Formats,,Output
24675 Formats}, for more information.
24678 @item printf @var{template}, @var{expressions}@dots{}
24679 Print the values of one or more @var{expressions} under the control of
24680 the string @var{template}. To print several values, make
24681 @var{expressions} be a comma-separated list of individual expressions,
24682 which may be either numbers or pointers. Their values are printed as
24683 specified by @var{template}, exactly as a C program would do by
24684 executing the code below:
24687 printf (@var{template}, @var{expressions}@dots{});
24690 As in @code{C} @code{printf}, ordinary characters in @var{template}
24691 are printed verbatim, while @dfn{conversion specification} introduced
24692 by the @samp{%} character cause subsequent @var{expressions} to be
24693 evaluated, their values converted and formatted according to type and
24694 style information encoded in the conversion specifications, and then
24697 For example, you can print two values in hex like this:
24700 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24703 @code{printf} supports all the standard @code{C} conversion
24704 specifications, including the flags and modifiers between the @samp{%}
24705 character and the conversion letter, with the following exceptions:
24709 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24712 The modifier @samp{*} is not supported for specifying precision or
24716 The @samp{'} flag (for separation of digits into groups according to
24717 @code{LC_NUMERIC'}) is not supported.
24720 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24724 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24727 The conversion letters @samp{a} and @samp{A} are not supported.
24731 Note that the @samp{ll} type modifier is supported only if the
24732 underlying @code{C} implementation used to build @value{GDBN} supports
24733 the @code{long long int} type, and the @samp{L} type modifier is
24734 supported only if @code{long double} type is available.
24736 As in @code{C}, @code{printf} supports simple backslash-escape
24737 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24738 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24739 single character. Octal and hexadecimal escape sequences are not
24742 Additionally, @code{printf} supports conversion specifications for DFP
24743 (@dfn{Decimal Floating Point}) types using the following length modifiers
24744 together with a floating point specifier.
24749 @samp{H} for printing @code{Decimal32} types.
24752 @samp{D} for printing @code{Decimal64} types.
24755 @samp{DD} for printing @code{Decimal128} types.
24758 If the underlying @code{C} implementation used to build @value{GDBN} has
24759 support for the three length modifiers for DFP types, other modifiers
24760 such as width and precision will also be available for @value{GDBN} to use.
24762 In case there is no such @code{C} support, no additional modifiers will be
24763 available and the value will be printed in the standard way.
24765 Here's an example of printing DFP types using the above conversion letters:
24767 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24772 @item eval @var{template}, @var{expressions}@dots{}
24773 Convert the values of one or more @var{expressions} under the control of
24774 the string @var{template} to a command line, and call it.
24778 @node Auto-loading sequences
24779 @subsection Controlling auto-loading native @value{GDBN} scripts
24780 @cindex native script auto-loading
24782 When a new object file is read (for example, due to the @code{file}
24783 command, or because the inferior has loaded a shared library),
24784 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24785 @xref{Auto-loading extensions}.
24787 Auto-loading can be enabled or disabled,
24788 and the list of auto-loaded scripts can be printed.
24791 @anchor{set auto-load gdb-scripts}
24792 @kindex set auto-load gdb-scripts
24793 @item set auto-load gdb-scripts [on|off]
24794 Enable or disable the auto-loading of canned sequences of commands scripts.
24796 @anchor{show auto-load gdb-scripts}
24797 @kindex show auto-load gdb-scripts
24798 @item show auto-load gdb-scripts
24799 Show whether auto-loading of canned sequences of commands scripts is enabled or
24802 @anchor{info auto-load gdb-scripts}
24803 @kindex info auto-load gdb-scripts
24804 @cindex print list of auto-loaded canned sequences of commands scripts
24805 @item info auto-load gdb-scripts [@var{regexp}]
24806 Print the list of all canned sequences of commands scripts that @value{GDBN}
24810 If @var{regexp} is supplied only canned sequences of commands scripts with
24811 matching names are printed.
24813 @c Python docs live in a separate file.
24814 @include python.texi
24816 @c Guile docs live in a separate file.
24817 @include guile.texi
24819 @node Auto-loading extensions
24820 @section Auto-loading extensions
24821 @cindex auto-loading extensions
24823 @value{GDBN} provides two mechanisms for automatically loading extensions
24824 when a new object file is read (for example, due to the @code{file}
24825 command, or because the inferior has loaded a shared library):
24826 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24827 section of modern file formats like ELF.
24830 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24831 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24832 * Which flavor to choose?::
24835 The auto-loading feature is useful for supplying application-specific
24836 debugging commands and features.
24838 Auto-loading can be enabled or disabled,
24839 and the list of auto-loaded scripts can be printed.
24840 See the @samp{auto-loading} section of each extension language
24841 for more information.
24842 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24843 For Python files see @ref{Python Auto-loading}.
24845 Note that loading of this script file also requires accordingly configured
24846 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24848 @node objfile-gdbdotext file
24849 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24850 @cindex @file{@var{objfile}-gdb.gdb}
24851 @cindex @file{@var{objfile}-gdb.py}
24852 @cindex @file{@var{objfile}-gdb.scm}
24854 When a new object file is read, @value{GDBN} looks for a file named
24855 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24856 where @var{objfile} is the object file's name and
24857 where @var{ext} is the file extension for the extension language:
24860 @item @file{@var{objfile}-gdb.gdb}
24861 GDB's own command language
24862 @item @file{@var{objfile}-gdb.py}
24864 @item @file{@var{objfile}-gdb.scm}
24868 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24869 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24870 components, and appending the @file{-gdb.@var{ext}} suffix.
24871 If this file exists and is readable, @value{GDBN} will evaluate it as a
24872 script in the specified extension language.
24874 If this file does not exist, then @value{GDBN} will look for
24875 @var{script-name} file in all of the directories as specified below.
24877 Note that loading of these files requires an accordingly configured
24878 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24880 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24881 scripts normally according to its @file{.exe} filename. But if no scripts are
24882 found @value{GDBN} also tries script filenames matching the object file without
24883 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24884 is attempted on any platform. This makes the script filenames compatible
24885 between Unix and MS-Windows hosts.
24888 @anchor{set auto-load scripts-directory}
24889 @kindex set auto-load scripts-directory
24890 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24891 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24892 may be delimited by the host platform path separator in use
24893 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24895 Each entry here needs to be covered also by the security setting
24896 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24898 @anchor{with-auto-load-dir}
24899 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24900 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24901 configuration option @option{--with-auto-load-dir}.
24903 Any reference to @file{$debugdir} will get replaced by
24904 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24905 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24906 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24907 @file{$datadir} must be placed as a directory component --- either alone or
24908 delimited by @file{/} or @file{\} directory separators, depending on the host
24911 The list of directories uses path separator (@samp{:} on GNU and Unix
24912 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24913 to the @env{PATH} environment variable.
24915 @anchor{show auto-load scripts-directory}
24916 @kindex show auto-load scripts-directory
24917 @item show auto-load scripts-directory
24918 Show @value{GDBN} auto-loaded scripts location.
24920 @anchor{add-auto-load-scripts-directory}
24921 @kindex add-auto-load-scripts-directory
24922 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24923 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24924 Multiple entries may be delimited by the host platform path separator in use.
24927 @value{GDBN} does not track which files it has already auto-loaded this way.
24928 @value{GDBN} will load the associated script every time the corresponding
24929 @var{objfile} is opened.
24930 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24931 is evaluated more than once.
24933 @node dotdebug_gdb_scripts section
24934 @subsection The @code{.debug_gdb_scripts} section
24935 @cindex @code{.debug_gdb_scripts} section
24937 For systems using file formats like ELF and COFF,
24938 when @value{GDBN} loads a new object file
24939 it will look for a special section named @code{.debug_gdb_scripts}.
24940 If this section exists, its contents is a list of null-terminated entries
24941 specifying scripts to load. Each entry begins with a non-null prefix byte that
24942 specifies the kind of entry, typically the extension language and whether the
24943 script is in a file or inlined in @code{.debug_gdb_scripts}.
24945 The following entries are supported:
24948 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24949 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24950 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24951 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24954 @subsubsection Script File Entries
24956 If the entry specifies a file, @value{GDBN} will look for the file first
24957 in the current directory and then along the source search path
24958 (@pxref{Source Path, ,Specifying Source Directories}),
24959 except that @file{$cdir} is not searched, since the compilation
24960 directory is not relevant to scripts.
24962 File entries can be placed in section @code{.debug_gdb_scripts} with,
24963 for example, this GCC macro for Python scripts.
24966 /* Note: The "MS" section flags are to remove duplicates. */
24967 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24969 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24970 .byte 1 /* Python */\n\
24971 .asciz \"" script_name "\"\n\
24977 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24978 Then one can reference the macro in a header or source file like this:
24981 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24984 The script name may include directories if desired.
24986 Note that loading of this script file also requires accordingly configured
24987 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24989 If the macro invocation is put in a header, any application or library
24990 using this header will get a reference to the specified script,
24991 and with the use of @code{"MS"} attributes on the section, the linker
24992 will remove duplicates.
24994 @subsubsection Script Text Entries
24996 Script text entries allow to put the executable script in the entry
24997 itself instead of loading it from a file.
24998 The first line of the entry, everything after the prefix byte and up to
24999 the first newline (@code{0xa}) character, is the script name, and must not
25000 contain any kind of space character, e.g., spaces or tabs.
25001 The rest of the entry, up to the trailing null byte, is the script to
25002 execute in the specified language. The name needs to be unique among
25003 all script names, as @value{GDBN} executes each script only once based
25006 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25010 #include "symcat.h"
25011 #include "gdb/section-scripts.h"
25013 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25014 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25015 ".ascii \"gdb.inlined-script\\n\"\n"
25016 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25017 ".ascii \" def __init__ (self):\\n\"\n"
25018 ".ascii \" super (test_cmd, self).__init__ ("
25019 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25020 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25021 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25022 ".ascii \"test_cmd ()\\n\"\n"
25028 Loading of inlined scripts requires a properly configured
25029 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25030 The path to specify in @code{auto-load safe-path} is the path of the file
25031 containing the @code{.debug_gdb_scripts} section.
25033 @node Which flavor to choose?
25034 @subsection Which flavor to choose?
25036 Given the multiple ways of auto-loading extensions, it might not always
25037 be clear which one to choose. This section provides some guidance.
25040 Benefits of the @file{-gdb.@var{ext}} way:
25044 Can be used with file formats that don't support multiple sections.
25047 Ease of finding scripts for public libraries.
25049 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25050 in the source search path.
25051 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25052 isn't a source directory in which to find the script.
25055 Doesn't require source code additions.
25059 Benefits of the @code{.debug_gdb_scripts} way:
25063 Works with static linking.
25065 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25066 trigger their loading. When an application is statically linked the only
25067 objfile available is the executable, and it is cumbersome to attach all the
25068 scripts from all the input libraries to the executable's
25069 @file{-gdb.@var{ext}} script.
25072 Works with classes that are entirely inlined.
25074 Some classes can be entirely inlined, and thus there may not be an associated
25075 shared library to attach a @file{-gdb.@var{ext}} script to.
25078 Scripts needn't be copied out of the source tree.
25080 In some circumstances, apps can be built out of large collections of internal
25081 libraries, and the build infrastructure necessary to install the
25082 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25083 cumbersome. It may be easier to specify the scripts in the
25084 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25085 top of the source tree to the source search path.
25088 @node Multiple Extension Languages
25089 @section Multiple Extension Languages
25091 The Guile and Python extension languages do not share any state,
25092 and generally do not interfere with each other.
25093 There are some things to be aware of, however.
25095 @subsection Python comes first
25097 Python was @value{GDBN}'s first extension language, and to avoid breaking
25098 existing behaviour Python comes first. This is generally solved by the
25099 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25100 extension languages, and when it makes a call to an extension language,
25101 (say to pretty-print a value), it tries each in turn until an extension
25102 language indicates it has performed the request (e.g., has returned the
25103 pretty-printed form of a value).
25104 This extends to errors while performing such requests: If an error happens
25105 while, for example, trying to pretty-print an object then the error is
25106 reported and any following extension languages are not tried.
25109 @section Creating new spellings of existing commands
25110 @cindex aliases for commands
25112 It is often useful to define alternate spellings of existing commands.
25113 For example, if a new @value{GDBN} command defined in Python has
25114 a long name to type, it is handy to have an abbreviated version of it
25115 that involves less typing.
25117 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25118 of the @samp{step} command even though it is otherwise an ambiguous
25119 abbreviation of other commands like @samp{set} and @samp{show}.
25121 Aliases are also used to provide shortened or more common versions
25122 of multi-word commands. For example, @value{GDBN} provides the
25123 @samp{tty} alias of the @samp{set inferior-tty} command.
25125 You can define a new alias with the @samp{alias} command.
25130 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25134 @var{ALIAS} specifies the name of the new alias.
25135 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25138 @var{COMMAND} specifies the name of an existing command
25139 that is being aliased.
25141 The @samp{-a} option specifies that the new alias is an abbreviation
25142 of the command. Abbreviations are not shown in command
25143 lists displayed by the @samp{help} command.
25145 The @samp{--} option specifies the end of options,
25146 and is useful when @var{ALIAS} begins with a dash.
25148 Here is a simple example showing how to make an abbreviation
25149 of a command so that there is less to type.
25150 Suppose you were tired of typing @samp{disas}, the current
25151 shortest unambiguous abbreviation of the @samp{disassemble} command
25152 and you wanted an even shorter version named @samp{di}.
25153 The following will accomplish this.
25156 (gdb) alias -a di = disas
25159 Note that aliases are different from user-defined commands.
25160 With a user-defined command, you also need to write documentation
25161 for it with the @samp{document} command.
25162 An alias automatically picks up the documentation of the existing command.
25164 Here is an example where we make @samp{elms} an abbreviation of
25165 @samp{elements} in the @samp{set print elements} command.
25166 This is to show that you can make an abbreviation of any part
25170 (gdb) alias -a set print elms = set print elements
25171 (gdb) alias -a show print elms = show print elements
25172 (gdb) set p elms 20
25174 Limit on string chars or array elements to print is 200.
25177 Note that if you are defining an alias of a @samp{set} command,
25178 and you want to have an alias for the corresponding @samp{show}
25179 command, then you need to define the latter separately.
25181 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25182 @var{ALIAS}, just as they are normally.
25185 (gdb) alias -a set pr elms = set p ele
25188 Finally, here is an example showing the creation of a one word
25189 alias for a more complex command.
25190 This creates alias @samp{spe} of the command @samp{set print elements}.
25193 (gdb) alias spe = set print elements
25198 @chapter Command Interpreters
25199 @cindex command interpreters
25201 @value{GDBN} supports multiple command interpreters, and some command
25202 infrastructure to allow users or user interface writers to switch
25203 between interpreters or run commands in other interpreters.
25205 @value{GDBN} currently supports two command interpreters, the console
25206 interpreter (sometimes called the command-line interpreter or @sc{cli})
25207 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25208 describes both of these interfaces in great detail.
25210 By default, @value{GDBN} will start with the console interpreter.
25211 However, the user may choose to start @value{GDBN} with another
25212 interpreter by specifying the @option{-i} or @option{--interpreter}
25213 startup options. Defined interpreters include:
25217 @cindex console interpreter
25218 The traditional console or command-line interpreter. This is the most often
25219 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25220 @value{GDBN} will use this interpreter.
25223 @cindex mi interpreter
25224 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25225 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25226 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25230 @cindex mi2 interpreter
25231 The current @sc{gdb/mi} interface.
25234 @cindex mi1 interpreter
25235 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25239 @cindex invoke another interpreter
25241 @kindex interpreter-exec
25242 You may execute commands in any interpreter from the current
25243 interpreter using the appropriate command. If you are running the
25244 console interpreter, simply use the @code{interpreter-exec} command:
25247 interpreter-exec mi "-data-list-register-names"
25250 @sc{gdb/mi} has a similar command, although it is only available in versions of
25251 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25253 Note that @code{interpreter-exec} only changes the interpreter for the
25254 duration of the specified command. It does not change the interpreter
25257 @cindex start a new independent interpreter
25259 Although you may only choose a single interpreter at startup, it is
25260 possible to run an independent interpreter on a specified input/output
25261 device (usually a tty).
25263 For example, consider a debugger GUI or IDE that wants to provide a
25264 @value{GDBN} console view. It may do so by embedding a terminal
25265 emulator widget in its GUI, starting @value{GDBN} in the traditional
25266 command-line mode with stdin/stdout/stderr redirected to that
25267 terminal, and then creating an MI interpreter running on a specified
25268 input/output device. The console interpreter created by @value{GDBN}
25269 at startup handles commands the user types in the terminal widget,
25270 while the GUI controls and synchronizes state with @value{GDBN} using
25271 the separate MI interpreter.
25273 To start a new secondary @dfn{user interface} running MI, use the
25274 @code{new-ui} command:
25277 @cindex new user interface
25279 new-ui @var{interpreter} @var{tty}
25282 The @var{interpreter} parameter specifies the interpreter to run.
25283 This accepts the same values as the @code{interpreter-exec} command.
25284 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25285 @var{tty} parameter specifies the name of the bidirectional file the
25286 interpreter uses for input/output, usually the name of a
25287 pseudoterminal slave on Unix systems. For example:
25290 (@value{GDBP}) new-ui mi /dev/pts/9
25294 runs an MI interpreter on @file{/dev/pts/9}.
25297 @chapter @value{GDBN} Text User Interface
25299 @cindex Text User Interface
25302 * TUI Overview:: TUI overview
25303 * TUI Keys:: TUI key bindings
25304 * TUI Single Key Mode:: TUI single key mode
25305 * TUI Commands:: TUI-specific commands
25306 * TUI Configuration:: TUI configuration variables
25309 The @value{GDBN} Text User Interface (TUI) is a terminal
25310 interface which uses the @code{curses} library to show the source
25311 file, the assembly output, the program registers and @value{GDBN}
25312 commands in separate text windows. The TUI mode is supported only
25313 on platforms where a suitable version of the @code{curses} library
25316 The TUI mode is enabled by default when you invoke @value{GDBN} as
25317 @samp{@value{GDBP} -tui}.
25318 You can also switch in and out of TUI mode while @value{GDBN} runs by
25319 using various TUI commands and key bindings, such as @command{tui
25320 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25321 @ref{TUI Keys, ,TUI Key Bindings}.
25324 @section TUI Overview
25326 In TUI mode, @value{GDBN} can display several text windows:
25330 This window is the @value{GDBN} command window with the @value{GDBN}
25331 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25332 managed using readline.
25335 The source window shows the source file of the program. The current
25336 line and active breakpoints are displayed in this window.
25339 The assembly window shows the disassembly output of the program.
25342 This window shows the processor registers. Registers are highlighted
25343 when their values change.
25346 The source and assembly windows show the current program position
25347 by highlighting the current line and marking it with a @samp{>} marker.
25348 Breakpoints are indicated with two markers. The first marker
25349 indicates the breakpoint type:
25353 Breakpoint which was hit at least once.
25356 Breakpoint which was never hit.
25359 Hardware breakpoint which was hit at least once.
25362 Hardware breakpoint which was never hit.
25365 The second marker indicates whether the breakpoint is enabled or not:
25369 Breakpoint is enabled.
25372 Breakpoint is disabled.
25375 The source, assembly and register windows are updated when the current
25376 thread changes, when the frame changes, or when the program counter
25379 These windows are not all visible at the same time. The command
25380 window is always visible. The others can be arranged in several
25391 source and assembly,
25394 source and registers, or
25397 assembly and registers.
25400 A status line above the command window shows the following information:
25404 Indicates the current @value{GDBN} target.
25405 (@pxref{Targets, ,Specifying a Debugging Target}).
25408 Gives the current process or thread number.
25409 When no process is being debugged, this field is set to @code{No process}.
25412 Gives the current function name for the selected frame.
25413 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25414 When there is no symbol corresponding to the current program counter,
25415 the string @code{??} is displayed.
25418 Indicates the current line number for the selected frame.
25419 When the current line number is not known, the string @code{??} is displayed.
25422 Indicates the current program counter address.
25426 @section TUI Key Bindings
25427 @cindex TUI key bindings
25429 The TUI installs several key bindings in the readline keymaps
25430 @ifset SYSTEM_READLINE
25431 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25433 @ifclear SYSTEM_READLINE
25434 (@pxref{Command Line Editing}).
25436 The following key bindings are installed for both TUI mode and the
25437 @value{GDBN} standard mode.
25446 Enter or leave the TUI mode. When leaving the TUI mode,
25447 the curses window management stops and @value{GDBN} operates using
25448 its standard mode, writing on the terminal directly. When reentering
25449 the TUI mode, control is given back to the curses windows.
25450 The screen is then refreshed.
25454 Use a TUI layout with only one window. The layout will
25455 either be @samp{source} or @samp{assembly}. When the TUI mode
25456 is not active, it will switch to the TUI mode.
25458 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25462 Use a TUI layout with at least two windows. When the current
25463 layout already has two windows, the next layout with two windows is used.
25464 When a new layout is chosen, one window will always be common to the
25465 previous layout and the new one.
25467 Think of it as the Emacs @kbd{C-x 2} binding.
25471 Change the active window. The TUI associates several key bindings
25472 (like scrolling and arrow keys) with the active window. This command
25473 gives the focus to the next TUI window.
25475 Think of it as the Emacs @kbd{C-x o} binding.
25479 Switch in and out of the TUI SingleKey mode that binds single
25480 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25483 The following key bindings only work in the TUI mode:
25488 Scroll the active window one page up.
25492 Scroll the active window one page down.
25496 Scroll the active window one line up.
25500 Scroll the active window one line down.
25504 Scroll the active window one column left.
25508 Scroll the active window one column right.
25512 Refresh the screen.
25515 Because the arrow keys scroll the active window in the TUI mode, they
25516 are not available for their normal use by readline unless the command
25517 window has the focus. When another window is active, you must use
25518 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25519 and @kbd{C-f} to control the command window.
25521 @node TUI Single Key Mode
25522 @section TUI Single Key Mode
25523 @cindex TUI single key mode
25525 The TUI also provides a @dfn{SingleKey} mode, which binds several
25526 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25527 switch into this mode, where the following key bindings are used:
25530 @kindex c @r{(SingleKey TUI key)}
25534 @kindex d @r{(SingleKey TUI key)}
25538 @kindex f @r{(SingleKey TUI key)}
25542 @kindex n @r{(SingleKey TUI key)}
25546 @kindex o @r{(SingleKey TUI key)}
25548 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25550 @kindex q @r{(SingleKey TUI key)}
25552 exit the SingleKey mode.
25554 @kindex r @r{(SingleKey TUI key)}
25558 @kindex s @r{(SingleKey TUI key)}
25562 @kindex i @r{(SingleKey TUI key)}
25564 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25566 @kindex u @r{(SingleKey TUI key)}
25570 @kindex v @r{(SingleKey TUI key)}
25574 @kindex w @r{(SingleKey TUI key)}
25579 Other keys temporarily switch to the @value{GDBN} command prompt.
25580 The key that was pressed is inserted in the editing buffer so that
25581 it is possible to type most @value{GDBN} commands without interaction
25582 with the TUI SingleKey mode. Once the command is entered the TUI
25583 SingleKey mode is restored. The only way to permanently leave
25584 this mode is by typing @kbd{q} or @kbd{C-x s}.
25588 @section TUI-specific Commands
25589 @cindex TUI commands
25591 The TUI has specific commands to control the text windows.
25592 These commands are always available, even when @value{GDBN} is not in
25593 the TUI mode. When @value{GDBN} is in the standard mode, most
25594 of these commands will automatically switch to the TUI mode.
25596 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25597 terminal, or @value{GDBN} has been started with the machine interface
25598 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25599 these commands will fail with an error, because it would not be
25600 possible or desirable to enable curses window management.
25605 Activate TUI mode. The last active TUI window layout will be used if
25606 TUI mode has prevsiouly been used in the current debugging session,
25607 otherwise a default layout is used.
25610 @kindex tui disable
25611 Disable TUI mode, returning to the console interpreter.
25615 List and give the size of all displayed windows.
25617 @item layout @var{name}
25619 Changes which TUI windows are displayed. In each layout the command
25620 window is always displayed, the @var{name} parameter controls which
25621 additional windows are displayed, and can be any of the following:
25625 Display the next layout.
25628 Display the previous layout.
25631 Display the source and command windows.
25634 Display the assembly and command windows.
25637 Display the source, assembly, and command windows.
25640 When in @code{src} layout display the register, source, and command
25641 windows. When in @code{asm} or @code{split} layout display the
25642 register, assembler, and command windows.
25645 @item focus @var{name}
25647 Changes which TUI window is currently active for scrolling. The
25648 @var{name} parameter can be any of the following:
25652 Make the next window active for scrolling.
25655 Make the previous window active for scrolling.
25658 Make the source window active for scrolling.
25661 Make the assembly window active for scrolling.
25664 Make the register window active for scrolling.
25667 Make the command window active for scrolling.
25672 Refresh the screen. This is similar to typing @kbd{C-L}.
25674 @item tui reg @var{group}
25676 Changes the register group displayed in the tui register window to
25677 @var{group}. If the register window is not currently displayed this
25678 command will cause the register window to be displayed. The list of
25679 register groups, as well as their order is target specific. The
25680 following groups are available on most targets:
25683 Repeatedly selecting this group will cause the display to cycle
25684 through all of the available register groups.
25687 Repeatedly selecting this group will cause the display to cycle
25688 through all of the available register groups in the reverse order to
25692 Display the general registers.
25694 Display the floating point registers.
25696 Display the system registers.
25698 Display the vector registers.
25700 Display all registers.
25705 Update the source window and the current execution point.
25707 @item winheight @var{name} +@var{count}
25708 @itemx winheight @var{name} -@var{count}
25710 Change the height of the window @var{name} by @var{count}
25711 lines. Positive counts increase the height, while negative counts
25712 decrease it. The @var{name} parameter can be one of @code{src} (the
25713 source window), @code{cmd} (the command window), @code{asm} (the
25714 disassembly window), or @code{regs} (the register display window).
25716 @item tabset @var{nchars}
25718 Set the width of tab stops to be @var{nchars} characters. This
25719 setting affects the display of TAB characters in the source and
25723 @node TUI Configuration
25724 @section TUI Configuration Variables
25725 @cindex TUI configuration variables
25727 Several configuration variables control the appearance of TUI windows.
25730 @item set tui border-kind @var{kind}
25731 @kindex set tui border-kind
25732 Select the border appearance for the source, assembly and register windows.
25733 The possible values are the following:
25736 Use a space character to draw the border.
25739 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25742 Use the Alternate Character Set to draw the border. The border is
25743 drawn using character line graphics if the terminal supports them.
25746 @item set tui border-mode @var{mode}
25747 @kindex set tui border-mode
25748 @itemx set tui active-border-mode @var{mode}
25749 @kindex set tui active-border-mode
25750 Select the display attributes for the borders of the inactive windows
25751 or the active window. The @var{mode} can be one of the following:
25754 Use normal attributes to display the border.
25760 Use reverse video mode.
25763 Use half bright mode.
25765 @item half-standout
25766 Use half bright and standout mode.
25769 Use extra bright or bold mode.
25771 @item bold-standout
25772 Use extra bright or bold and standout mode.
25777 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25780 @cindex @sc{gnu} Emacs
25781 A special interface allows you to use @sc{gnu} Emacs to view (and
25782 edit) the source files for the program you are debugging with
25785 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25786 executable file you want to debug as an argument. This command starts
25787 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25788 created Emacs buffer.
25789 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25791 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25796 All ``terminal'' input and output goes through an Emacs buffer, called
25799 This applies both to @value{GDBN} commands and their output, and to the input
25800 and output done by the program you are debugging.
25802 This is useful because it means that you can copy the text of previous
25803 commands and input them again; you can even use parts of the output
25806 All the facilities of Emacs' Shell mode are available for interacting
25807 with your program. In particular, you can send signals the usual
25808 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25812 @value{GDBN} displays source code through Emacs.
25814 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25815 source file for that frame and puts an arrow (@samp{=>}) at the
25816 left margin of the current line. Emacs uses a separate buffer for
25817 source display, and splits the screen to show both your @value{GDBN} session
25820 Explicit @value{GDBN} @code{list} or search commands still produce output as
25821 usual, but you probably have no reason to use them from Emacs.
25824 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25825 a graphical mode, enabled by default, which provides further buffers
25826 that can control the execution and describe the state of your program.
25827 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25829 If you specify an absolute file name when prompted for the @kbd{M-x
25830 gdb} argument, then Emacs sets your current working directory to where
25831 your program resides. If you only specify the file name, then Emacs
25832 sets your current working directory to the directory associated
25833 with the previous buffer. In this case, @value{GDBN} may find your
25834 program by searching your environment's @code{PATH} variable, but on
25835 some operating systems it might not find the source. So, although the
25836 @value{GDBN} input and output session proceeds normally, the auxiliary
25837 buffer does not display the current source and line of execution.
25839 The initial working directory of @value{GDBN} is printed on the top
25840 line of the GUD buffer and this serves as a default for the commands
25841 that specify files for @value{GDBN} to operate on. @xref{Files,
25842 ,Commands to Specify Files}.
25844 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25845 need to call @value{GDBN} by a different name (for example, if you
25846 keep several configurations around, with different names) you can
25847 customize the Emacs variable @code{gud-gdb-command-name} to run the
25850 In the GUD buffer, you can use these special Emacs commands in
25851 addition to the standard Shell mode commands:
25855 Describe the features of Emacs' GUD Mode.
25858 Execute to another source line, like the @value{GDBN} @code{step} command; also
25859 update the display window to show the current file and location.
25862 Execute to next source line in this function, skipping all function
25863 calls, like the @value{GDBN} @code{next} command. Then update the display window
25864 to show the current file and location.
25867 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25868 display window accordingly.
25871 Execute until exit from the selected stack frame, like the @value{GDBN}
25872 @code{finish} command.
25875 Continue execution of your program, like the @value{GDBN} @code{continue}
25879 Go up the number of frames indicated by the numeric argument
25880 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25881 like the @value{GDBN} @code{up} command.
25884 Go down the number of frames indicated by the numeric argument, like the
25885 @value{GDBN} @code{down} command.
25888 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25889 tells @value{GDBN} to set a breakpoint on the source line point is on.
25891 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25892 separate frame which shows a backtrace when the GUD buffer is current.
25893 Move point to any frame in the stack and type @key{RET} to make it
25894 become the current frame and display the associated source in the
25895 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25896 selected frame become the current one. In graphical mode, the
25897 speedbar displays watch expressions.
25899 If you accidentally delete the source-display buffer, an easy way to get
25900 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25901 request a frame display; when you run under Emacs, this recreates
25902 the source buffer if necessary to show you the context of the current
25905 The source files displayed in Emacs are in ordinary Emacs buffers
25906 which are visiting the source files in the usual way. You can edit
25907 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25908 communicates with Emacs in terms of line numbers. If you add or
25909 delete lines from the text, the line numbers that @value{GDBN} knows cease
25910 to correspond properly with the code.
25912 A more detailed description of Emacs' interaction with @value{GDBN} is
25913 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25917 @chapter The @sc{gdb/mi} Interface
25919 @unnumberedsec Function and Purpose
25921 @cindex @sc{gdb/mi}, its purpose
25922 @sc{gdb/mi} is a line based machine oriented text interface to
25923 @value{GDBN} and is activated by specifying using the
25924 @option{--interpreter} command line option (@pxref{Mode Options}). It
25925 is specifically intended to support the development of systems which
25926 use the debugger as just one small component of a larger system.
25928 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25929 in the form of a reference manual.
25931 Note that @sc{gdb/mi} is still under construction, so some of the
25932 features described below are incomplete and subject to change
25933 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25935 @unnumberedsec Notation and Terminology
25937 @cindex notational conventions, for @sc{gdb/mi}
25938 This chapter uses the following notation:
25942 @code{|} separates two alternatives.
25945 @code{[ @var{something} ]} indicates that @var{something} is optional:
25946 it may or may not be given.
25949 @code{( @var{group} )*} means that @var{group} inside the parentheses
25950 may repeat zero or more times.
25953 @code{( @var{group} )+} means that @var{group} inside the parentheses
25954 may repeat one or more times.
25957 @code{"@var{string}"} means a literal @var{string}.
25961 @heading Dependencies
25965 * GDB/MI General Design::
25966 * GDB/MI Command Syntax::
25967 * GDB/MI Compatibility with CLI::
25968 * GDB/MI Development and Front Ends::
25969 * GDB/MI Output Records::
25970 * GDB/MI Simple Examples::
25971 * GDB/MI Command Description Format::
25972 * GDB/MI Breakpoint Commands::
25973 * GDB/MI Catchpoint Commands::
25974 * GDB/MI Program Context::
25975 * GDB/MI Thread Commands::
25976 * GDB/MI Ada Tasking Commands::
25977 * GDB/MI Program Execution::
25978 * GDB/MI Stack Manipulation::
25979 * GDB/MI Variable Objects::
25980 * GDB/MI Data Manipulation::
25981 * GDB/MI Tracepoint Commands::
25982 * GDB/MI Symbol Query::
25983 * GDB/MI File Commands::
25985 * GDB/MI Kod Commands::
25986 * GDB/MI Memory Overlay Commands::
25987 * GDB/MI Signal Handling Commands::
25989 * GDB/MI Target Manipulation::
25990 * GDB/MI File Transfer Commands::
25991 * GDB/MI Ada Exceptions Commands::
25992 * GDB/MI Support Commands::
25993 * GDB/MI Miscellaneous Commands::
25996 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25997 @node GDB/MI General Design
25998 @section @sc{gdb/mi} General Design
25999 @cindex GDB/MI General Design
26001 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26002 parts---commands sent to @value{GDBN}, responses to those commands
26003 and notifications. Each command results in exactly one response,
26004 indicating either successful completion of the command, or an error.
26005 For the commands that do not resume the target, the response contains the
26006 requested information. For the commands that resume the target, the
26007 response only indicates whether the target was successfully resumed.
26008 Notifications is the mechanism for reporting changes in the state of the
26009 target, or in @value{GDBN} state, that cannot conveniently be associated with
26010 a command and reported as part of that command response.
26012 The important examples of notifications are:
26016 Exec notifications. These are used to report changes in
26017 target state---when a target is resumed, or stopped. It would not
26018 be feasible to include this information in response of resuming
26019 commands, because one resume commands can result in multiple events in
26020 different threads. Also, quite some time may pass before any event
26021 happens in the target, while a frontend needs to know whether the resuming
26022 command itself was successfully executed.
26025 Console output, and status notifications. Console output
26026 notifications are used to report output of CLI commands, as well as
26027 diagnostics for other commands. Status notifications are used to
26028 report the progress of a long-running operation. Naturally, including
26029 this information in command response would mean no output is produced
26030 until the command is finished, which is undesirable.
26033 General notifications. Commands may have various side effects on
26034 the @value{GDBN} or target state beyond their official purpose. For example,
26035 a command may change the selected thread. Although such changes can
26036 be included in command response, using notification allows for more
26037 orthogonal frontend design.
26041 There's no guarantee that whenever an MI command reports an error,
26042 @value{GDBN} or the target are in any specific state, and especially,
26043 the state is not reverted to the state before the MI command was
26044 processed. Therefore, whenever an MI command results in an error,
26045 we recommend that the frontend refreshes all the information shown in
26046 the user interface.
26050 * Context management::
26051 * Asynchronous and non-stop modes::
26055 @node Context management
26056 @subsection Context management
26058 @subsubsection Threads and Frames
26060 In most cases when @value{GDBN} accesses the target, this access is
26061 done in context of a specific thread and frame (@pxref{Frames}).
26062 Often, even when accessing global data, the target requires that a thread
26063 be specified. The CLI interface maintains the selected thread and frame,
26064 and supplies them to target on each command. This is convenient,
26065 because a command line user would not want to specify that information
26066 explicitly on each command, and because user interacts with
26067 @value{GDBN} via a single terminal, so no confusion is possible as
26068 to what thread and frame are the current ones.
26070 In the case of MI, the concept of selected thread and frame is less
26071 useful. First, a frontend can easily remember this information
26072 itself. Second, a graphical frontend can have more than one window,
26073 each one used for debugging a different thread, and the frontend might
26074 want to access additional threads for internal purposes. This
26075 increases the risk that by relying on implicitly selected thread, the
26076 frontend may be operating on a wrong one. Therefore, each MI command
26077 should explicitly specify which thread and frame to operate on. To
26078 make it possible, each MI command accepts the @samp{--thread} and
26079 @samp{--frame} options, the value to each is @value{GDBN} global
26080 identifier for thread and frame to operate on.
26082 Usually, each top-level window in a frontend allows the user to select
26083 a thread and a frame, and remembers the user selection for further
26084 operations. However, in some cases @value{GDBN} may suggest that the
26085 current thread or frame be changed. For example, when stopping on a
26086 breakpoint it is reasonable to switch to the thread where breakpoint is
26087 hit. For another example, if the user issues the CLI @samp{thread} or
26088 @samp{frame} commands via the frontend, it is desirable to change the
26089 frontend's selection to the one specified by user. @value{GDBN}
26090 communicates the suggestion to change current thread and frame using the
26091 @samp{=thread-selected} notification.
26093 Note that historically, MI shares the selected thread with CLI, so
26094 frontends used the @code{-thread-select} to execute commands in the
26095 right context. However, getting this to work right is cumbersome. The
26096 simplest way is for frontend to emit @code{-thread-select} command
26097 before every command. This doubles the number of commands that need
26098 to be sent. The alternative approach is to suppress @code{-thread-select}
26099 if the selected thread in @value{GDBN} is supposed to be identical to the
26100 thread the frontend wants to operate on. However, getting this
26101 optimization right can be tricky. In particular, if the frontend
26102 sends several commands to @value{GDBN}, and one of the commands changes the
26103 selected thread, then the behaviour of subsequent commands will
26104 change. So, a frontend should either wait for response from such
26105 problematic commands, or explicitly add @code{-thread-select} for
26106 all subsequent commands. No frontend is known to do this exactly
26107 right, so it is suggested to just always pass the @samp{--thread} and
26108 @samp{--frame} options.
26110 @subsubsection Language
26112 The execution of several commands depends on which language is selected.
26113 By default, the current language (@pxref{show language}) is used.
26114 But for commands known to be language-sensitive, it is recommended
26115 to use the @samp{--language} option. This option takes one argument,
26116 which is the name of the language to use while executing the command.
26120 -data-evaluate-expression --language c "sizeof (void*)"
26125 The valid language names are the same names accepted by the
26126 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26127 @samp{local} or @samp{unknown}.
26129 @node Asynchronous and non-stop modes
26130 @subsection Asynchronous command execution and non-stop mode
26132 On some targets, @value{GDBN} is capable of processing MI commands
26133 even while the target is running. This is called @dfn{asynchronous
26134 command execution} (@pxref{Background Execution}). The frontend may
26135 specify a preferrence for asynchronous execution using the
26136 @code{-gdb-set mi-async 1} command, which should be emitted before
26137 either running the executable or attaching to the target. After the
26138 frontend has started the executable or attached to the target, it can
26139 find if asynchronous execution is enabled using the
26140 @code{-list-target-features} command.
26143 @item -gdb-set mi-async on
26144 @item -gdb-set mi-async off
26145 Set whether MI is in asynchronous mode.
26147 When @code{off}, which is the default, MI execution commands (e.g.,
26148 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26149 for the program to stop before processing further commands.
26151 When @code{on}, MI execution commands are background execution
26152 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26153 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26154 MI commands even while the target is running.
26156 @item -gdb-show mi-async
26157 Show whether MI asynchronous mode is enabled.
26160 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26161 @code{target-async} instead of @code{mi-async}, and it had the effect
26162 of both putting MI in asynchronous mode and making CLI background
26163 commands possible. CLI background commands are now always possible
26164 ``out of the box'' if the target supports them. The old spelling is
26165 kept as a deprecated alias for backwards compatibility.
26167 Even if @value{GDBN} can accept a command while target is running,
26168 many commands that access the target do not work when the target is
26169 running. Therefore, asynchronous command execution is most useful
26170 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26171 it is possible to examine the state of one thread, while other threads
26174 When a given thread is running, MI commands that try to access the
26175 target in the context of that thread may not work, or may work only on
26176 some targets. In particular, commands that try to operate on thread's
26177 stack will not work, on any target. Commands that read memory, or
26178 modify breakpoints, may work or not work, depending on the target. Note
26179 that even commands that operate on global state, such as @code{print},
26180 @code{set}, and breakpoint commands, still access the target in the
26181 context of a specific thread, so frontend should try to find a
26182 stopped thread and perform the operation on that thread (using the
26183 @samp{--thread} option).
26185 Which commands will work in the context of a running thread is
26186 highly target dependent. However, the two commands
26187 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26188 to find the state of a thread, will always work.
26190 @node Thread groups
26191 @subsection Thread groups
26192 @value{GDBN} may be used to debug several processes at the same time.
26193 On some platfroms, @value{GDBN} may support debugging of several
26194 hardware systems, each one having several cores with several different
26195 processes running on each core. This section describes the MI
26196 mechanism to support such debugging scenarios.
26198 The key observation is that regardless of the structure of the
26199 target, MI can have a global list of threads, because most commands that
26200 accept the @samp{--thread} option do not need to know what process that
26201 thread belongs to. Therefore, it is not necessary to introduce
26202 neither additional @samp{--process} option, nor an notion of the
26203 current process in the MI interface. The only strictly new feature
26204 that is required is the ability to find how the threads are grouped
26207 To allow the user to discover such grouping, and to support arbitrary
26208 hierarchy of machines/cores/processes, MI introduces the concept of a
26209 @dfn{thread group}. Thread group is a collection of threads and other
26210 thread groups. A thread group always has a string identifier, a type,
26211 and may have additional attributes specific to the type. A new
26212 command, @code{-list-thread-groups}, returns the list of top-level
26213 thread groups, which correspond to processes that @value{GDBN} is
26214 debugging at the moment. By passing an identifier of a thread group
26215 to the @code{-list-thread-groups} command, it is possible to obtain
26216 the members of specific thread group.
26218 To allow the user to easily discover processes, and other objects, he
26219 wishes to debug, a concept of @dfn{available thread group} is
26220 introduced. Available thread group is an thread group that
26221 @value{GDBN} is not debugging, but that can be attached to, using the
26222 @code{-target-attach} command. The list of available top-level thread
26223 groups can be obtained using @samp{-list-thread-groups --available}.
26224 In general, the content of a thread group may be only retrieved only
26225 after attaching to that thread group.
26227 Thread groups are related to inferiors (@pxref{Inferiors and
26228 Programs}). Each inferior corresponds to a thread group of a special
26229 type @samp{process}, and some additional operations are permitted on
26230 such thread groups.
26232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26233 @node GDB/MI Command Syntax
26234 @section @sc{gdb/mi} Command Syntax
26237 * GDB/MI Input Syntax::
26238 * GDB/MI Output Syntax::
26241 @node GDB/MI Input Syntax
26242 @subsection @sc{gdb/mi} Input Syntax
26244 @cindex input syntax for @sc{gdb/mi}
26245 @cindex @sc{gdb/mi}, input syntax
26247 @item @var{command} @expansion{}
26248 @code{@var{cli-command} | @var{mi-command}}
26250 @item @var{cli-command} @expansion{}
26251 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26252 @var{cli-command} is any existing @value{GDBN} CLI command.
26254 @item @var{mi-command} @expansion{}
26255 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26256 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26258 @item @var{token} @expansion{}
26259 "any sequence of digits"
26261 @item @var{option} @expansion{}
26262 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26264 @item @var{parameter} @expansion{}
26265 @code{@var{non-blank-sequence} | @var{c-string}}
26267 @item @var{operation} @expansion{}
26268 @emph{any of the operations described in this chapter}
26270 @item @var{non-blank-sequence} @expansion{}
26271 @emph{anything, provided it doesn't contain special characters such as
26272 "-", @var{nl}, """ and of course " "}
26274 @item @var{c-string} @expansion{}
26275 @code{""" @var{seven-bit-iso-c-string-content} """}
26277 @item @var{nl} @expansion{}
26286 The CLI commands are still handled by the @sc{mi} interpreter; their
26287 output is described below.
26290 The @code{@var{token}}, when present, is passed back when the command
26294 Some @sc{mi} commands accept optional arguments as part of the parameter
26295 list. Each option is identified by a leading @samp{-} (dash) and may be
26296 followed by an optional argument parameter. Options occur first in the
26297 parameter list and can be delimited from normal parameters using
26298 @samp{--} (this is useful when some parameters begin with a dash).
26305 We want easy access to the existing CLI syntax (for debugging).
26308 We want it to be easy to spot a @sc{mi} operation.
26311 @node GDB/MI Output Syntax
26312 @subsection @sc{gdb/mi} Output Syntax
26314 @cindex output syntax of @sc{gdb/mi}
26315 @cindex @sc{gdb/mi}, output syntax
26316 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26317 followed, optionally, by a single result record. This result record
26318 is for the most recent command. The sequence of output records is
26319 terminated by @samp{(gdb)}.
26321 If an input command was prefixed with a @code{@var{token}} then the
26322 corresponding output for that command will also be prefixed by that same
26326 @item @var{output} @expansion{}
26327 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26329 @item @var{result-record} @expansion{}
26330 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26332 @item @var{out-of-band-record} @expansion{}
26333 @code{@var{async-record} | @var{stream-record}}
26335 @item @var{async-record} @expansion{}
26336 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26338 @item @var{exec-async-output} @expansion{}
26339 @code{[ @var{token} ] "*" @var{async-output nl}}
26341 @item @var{status-async-output} @expansion{}
26342 @code{[ @var{token} ] "+" @var{async-output nl}}
26344 @item @var{notify-async-output} @expansion{}
26345 @code{[ @var{token} ] "=" @var{async-output nl}}
26347 @item @var{async-output} @expansion{}
26348 @code{@var{async-class} ( "," @var{result} )*}
26350 @item @var{result-class} @expansion{}
26351 @code{"done" | "running" | "connected" | "error" | "exit"}
26353 @item @var{async-class} @expansion{}
26354 @code{"stopped" | @var{others}} (where @var{others} will be added
26355 depending on the needs---this is still in development).
26357 @item @var{result} @expansion{}
26358 @code{ @var{variable} "=" @var{value}}
26360 @item @var{variable} @expansion{}
26361 @code{ @var{string} }
26363 @item @var{value} @expansion{}
26364 @code{ @var{const} | @var{tuple} | @var{list} }
26366 @item @var{const} @expansion{}
26367 @code{@var{c-string}}
26369 @item @var{tuple} @expansion{}
26370 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26372 @item @var{list} @expansion{}
26373 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26374 @var{result} ( "," @var{result} )* "]" }
26376 @item @var{stream-record} @expansion{}
26377 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26379 @item @var{console-stream-output} @expansion{}
26380 @code{"~" @var{c-string nl}}
26382 @item @var{target-stream-output} @expansion{}
26383 @code{"@@" @var{c-string nl}}
26385 @item @var{log-stream-output} @expansion{}
26386 @code{"&" @var{c-string nl}}
26388 @item @var{nl} @expansion{}
26391 @item @var{token} @expansion{}
26392 @emph{any sequence of digits}.
26400 All output sequences end in a single line containing a period.
26403 The @code{@var{token}} is from the corresponding request. Note that
26404 for all async output, while the token is allowed by the grammar and
26405 may be output by future versions of @value{GDBN} for select async
26406 output messages, it is generally omitted. Frontends should treat
26407 all async output as reporting general changes in the state of the
26408 target and there should be no need to associate async output to any
26412 @cindex status output in @sc{gdb/mi}
26413 @var{status-async-output} contains on-going status information about the
26414 progress of a slow operation. It can be discarded. All status output is
26415 prefixed by @samp{+}.
26418 @cindex async output in @sc{gdb/mi}
26419 @var{exec-async-output} contains asynchronous state change on the target
26420 (stopped, started, disappeared). All async output is prefixed by
26424 @cindex notify output in @sc{gdb/mi}
26425 @var{notify-async-output} contains supplementary information that the
26426 client should handle (e.g., a new breakpoint information). All notify
26427 output is prefixed by @samp{=}.
26430 @cindex console output in @sc{gdb/mi}
26431 @var{console-stream-output} is output that should be displayed as is in the
26432 console. It is the textual response to a CLI command. All the console
26433 output is prefixed by @samp{~}.
26436 @cindex target output in @sc{gdb/mi}
26437 @var{target-stream-output} is the output produced by the target program.
26438 All the target output is prefixed by @samp{@@}.
26441 @cindex log output in @sc{gdb/mi}
26442 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26443 instance messages that should be displayed as part of an error log. All
26444 the log output is prefixed by @samp{&}.
26447 @cindex list output in @sc{gdb/mi}
26448 New @sc{gdb/mi} commands should only output @var{lists} containing
26454 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26455 details about the various output records.
26457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26458 @node GDB/MI Compatibility with CLI
26459 @section @sc{gdb/mi} Compatibility with CLI
26461 @cindex compatibility, @sc{gdb/mi} and CLI
26462 @cindex @sc{gdb/mi}, compatibility with CLI
26464 For the developers convenience CLI commands can be entered directly,
26465 but there may be some unexpected behaviour. For example, commands
26466 that query the user will behave as if the user replied yes, breakpoint
26467 command lists are not executed and some CLI commands, such as
26468 @code{if}, @code{when} and @code{define}, prompt for further input with
26469 @samp{>}, which is not valid MI output.
26471 This feature may be removed at some stage in the future and it is
26472 recommended that front ends use the @code{-interpreter-exec} command
26473 (@pxref{-interpreter-exec}).
26475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26476 @node GDB/MI Development and Front Ends
26477 @section @sc{gdb/mi} Development and Front Ends
26478 @cindex @sc{gdb/mi} development
26480 The application which takes the MI output and presents the state of the
26481 program being debugged to the user is called a @dfn{front end}.
26483 Although @sc{gdb/mi} is still incomplete, it is currently being used
26484 by a variety of front ends to @value{GDBN}. This makes it difficult
26485 to introduce new functionality without breaking existing usage. This
26486 section tries to minimize the problems by describing how the protocol
26489 Some changes in MI need not break a carefully designed front end, and
26490 for these the MI version will remain unchanged. The following is a
26491 list of changes that may occur within one level, so front ends should
26492 parse MI output in a way that can handle them:
26496 New MI commands may be added.
26499 New fields may be added to the output of any MI command.
26502 The range of values for fields with specified values, e.g.,
26503 @code{in_scope} (@pxref{-var-update}) may be extended.
26505 @c The format of field's content e.g type prefix, may change so parse it
26506 @c at your own risk. Yes, in general?
26508 @c The order of fields may change? Shouldn't really matter but it might
26509 @c resolve inconsistencies.
26512 If the changes are likely to break front ends, the MI version level
26513 will be increased by one. This will allow the front end to parse the
26514 output according to the MI version. Apart from mi0, new versions of
26515 @value{GDBN} will not support old versions of MI and it will be the
26516 responsibility of the front end to work with the new one.
26518 @c Starting with mi3, add a new command -mi-version that prints the MI
26521 The best way to avoid unexpected changes in MI that might break your front
26522 end is to make your project known to @value{GDBN} developers and
26523 follow development on @email{gdb@@sourceware.org} and
26524 @email{gdb-patches@@sourceware.org}.
26525 @cindex mailing lists
26527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26528 @node GDB/MI Output Records
26529 @section @sc{gdb/mi} Output Records
26532 * GDB/MI Result Records::
26533 * GDB/MI Stream Records::
26534 * GDB/MI Async Records::
26535 * GDB/MI Breakpoint Information::
26536 * GDB/MI Frame Information::
26537 * GDB/MI Thread Information::
26538 * GDB/MI Ada Exception Information::
26541 @node GDB/MI Result Records
26542 @subsection @sc{gdb/mi} Result Records
26544 @cindex result records in @sc{gdb/mi}
26545 @cindex @sc{gdb/mi}, result records
26546 In addition to a number of out-of-band notifications, the response to a
26547 @sc{gdb/mi} command includes one of the following result indications:
26551 @item "^done" [ "," @var{results} ]
26552 The synchronous operation was successful, @code{@var{results}} are the return
26557 This result record is equivalent to @samp{^done}. Historically, it
26558 was output instead of @samp{^done} if the command has resumed the
26559 target. This behaviour is maintained for backward compatibility, but
26560 all frontends should treat @samp{^done} and @samp{^running}
26561 identically and rely on the @samp{*running} output record to determine
26562 which threads are resumed.
26566 @value{GDBN} has connected to a remote target.
26568 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26570 The operation failed. The @code{msg=@var{c-string}} variable contains
26571 the corresponding error message.
26573 If present, the @code{code=@var{c-string}} variable provides an error
26574 code on which consumers can rely on to detect the corresponding
26575 error condition. At present, only one error code is defined:
26578 @item "undefined-command"
26579 Indicates that the command causing the error does not exist.
26584 @value{GDBN} has terminated.
26588 @node GDB/MI Stream Records
26589 @subsection @sc{gdb/mi} Stream Records
26591 @cindex @sc{gdb/mi}, stream records
26592 @cindex stream records in @sc{gdb/mi}
26593 @value{GDBN} internally maintains a number of output streams: the console, the
26594 target, and the log. The output intended for each of these streams is
26595 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26597 Each stream record begins with a unique @dfn{prefix character} which
26598 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26599 Syntax}). In addition to the prefix, each stream record contains a
26600 @code{@var{string-output}}. This is either raw text (with an implicit new
26601 line) or a quoted C string (which does not contain an implicit newline).
26604 @item "~" @var{string-output}
26605 The console output stream contains text that should be displayed in the
26606 CLI console window. It contains the textual responses to CLI commands.
26608 @item "@@" @var{string-output}
26609 The target output stream contains any textual output from the running
26610 target. This is only present when GDB's event loop is truly
26611 asynchronous, which is currently only the case for remote targets.
26613 @item "&" @var{string-output}
26614 The log stream contains debugging messages being produced by @value{GDBN}'s
26618 @node GDB/MI Async Records
26619 @subsection @sc{gdb/mi} Async Records
26621 @cindex async records in @sc{gdb/mi}
26622 @cindex @sc{gdb/mi}, async records
26623 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26624 additional changes that have occurred. Those changes can either be a
26625 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26626 target activity (e.g., target stopped).
26628 The following is the list of possible async records:
26632 @item *running,thread-id="@var{thread}"
26633 The target is now running. The @var{thread} field can be the global
26634 thread ID of the the thread that is now running, and it can be
26635 @samp{all} if all threads are running. The frontend should assume
26636 that no interaction with a running thread is possible after this
26637 notification is produced. The frontend should not assume that this
26638 notification is output only once for any command. @value{GDBN} may
26639 emit this notification several times, either for different threads,
26640 because it cannot resume all threads together, or even for a single
26641 thread, if the thread must be stepped though some code before letting
26644 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26645 The target has stopped. The @var{reason} field can have one of the
26649 @item breakpoint-hit
26650 A breakpoint was reached.
26651 @item watchpoint-trigger
26652 A watchpoint was triggered.
26653 @item read-watchpoint-trigger
26654 A read watchpoint was triggered.
26655 @item access-watchpoint-trigger
26656 An access watchpoint was triggered.
26657 @item function-finished
26658 An -exec-finish or similar CLI command was accomplished.
26659 @item location-reached
26660 An -exec-until or similar CLI command was accomplished.
26661 @item watchpoint-scope
26662 A watchpoint has gone out of scope.
26663 @item end-stepping-range
26664 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26665 similar CLI command was accomplished.
26666 @item exited-signalled
26667 The inferior exited because of a signal.
26669 The inferior exited.
26670 @item exited-normally
26671 The inferior exited normally.
26672 @item signal-received
26673 A signal was received by the inferior.
26675 The inferior has stopped due to a library being loaded or unloaded.
26676 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26677 set or when a @code{catch load} or @code{catch unload} catchpoint is
26678 in use (@pxref{Set Catchpoints}).
26680 The inferior has forked. This is reported when @code{catch fork}
26681 (@pxref{Set Catchpoints}) has been used.
26683 The inferior has vforked. This is reported in when @code{catch vfork}
26684 (@pxref{Set Catchpoints}) has been used.
26685 @item syscall-entry
26686 The inferior entered a system call. This is reported when @code{catch
26687 syscall} (@pxref{Set Catchpoints}) has been used.
26688 @item syscall-return
26689 The inferior returned from a system call. This is reported when
26690 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26692 The inferior called @code{exec}. This is reported when @code{catch exec}
26693 (@pxref{Set Catchpoints}) has been used.
26696 The @var{id} field identifies the global thread ID of the thread
26697 that directly caused the stop -- for example by hitting a breakpoint.
26698 Depending on whether all-stop
26699 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26700 stop all threads, or only the thread that directly triggered the stop.
26701 If all threads are stopped, the @var{stopped} field will have the
26702 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26703 field will be a list of thread identifiers. Presently, this list will
26704 always include a single thread, but frontend should be prepared to see
26705 several threads in the list. The @var{core} field reports the
26706 processor core on which the stop event has happened. This field may be absent
26707 if such information is not available.
26709 @item =thread-group-added,id="@var{id}"
26710 @itemx =thread-group-removed,id="@var{id}"
26711 A thread group was either added or removed. The @var{id} field
26712 contains the @value{GDBN} identifier of the thread group. When a thread
26713 group is added, it generally might not be associated with a running
26714 process. When a thread group is removed, its id becomes invalid and
26715 cannot be used in any way.
26717 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26718 A thread group became associated with a running program,
26719 either because the program was just started or the thread group
26720 was attached to a program. The @var{id} field contains the
26721 @value{GDBN} identifier of the thread group. The @var{pid} field
26722 contains process identifier, specific to the operating system.
26724 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26725 A thread group is no longer associated with a running program,
26726 either because the program has exited, or because it was detached
26727 from. The @var{id} field contains the @value{GDBN} identifier of the
26728 thread group. The @var{code} field is the exit code of the inferior; it exists
26729 only when the inferior exited with some code.
26731 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26732 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26733 A thread either was created, or has exited. The @var{id} field
26734 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26735 field identifies the thread group this thread belongs to.
26737 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26738 Informs that the selected thread or frame were changed. This notification
26739 is not emitted as result of the @code{-thread-select} or
26740 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26741 that is not documented to change the selected thread and frame actually
26742 changes them. In particular, invoking, directly or indirectly
26743 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26744 will generate this notification. Changing the thread or frame from another
26745 user interface (see @ref{Interpreters}) will also generate this notification.
26747 The @var{frame} field is only present if the newly selected thread is
26748 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26750 We suggest that in response to this notification, front ends
26751 highlight the selected thread and cause subsequent commands to apply to
26754 @item =library-loaded,...
26755 Reports that a new library file was loaded by the program. This
26756 notification has 5 fields---@var{id}, @var{target-name},
26757 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
26758 opaque identifier of the library. For remote debugging case,
26759 @var{target-name} and @var{host-name} fields give the name of the
26760 library file on the target, and on the host respectively. For native
26761 debugging, both those fields have the same value. The
26762 @var{symbols-loaded} field is emitted only for backward compatibility
26763 and should not be relied on to convey any useful information. The
26764 @var{thread-group} field, if present, specifies the id of the thread
26765 group in whose context the library was loaded. If the field is
26766 absent, it means the library was loaded in the context of all present
26767 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
26770 @item =library-unloaded,...
26771 Reports that a library was unloaded by the program. This notification
26772 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26773 the same meaning as for the @code{=library-loaded} notification.
26774 The @var{thread-group} field, if present, specifies the id of the
26775 thread group in whose context the library was unloaded. If the field is
26776 absent, it means the library was unloaded in the context of all present
26779 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26780 @itemx =traceframe-changed,end
26781 Reports that the trace frame was changed and its new number is
26782 @var{tfnum}. The number of the tracepoint associated with this trace
26783 frame is @var{tpnum}.
26785 @item =tsv-created,name=@var{name},initial=@var{initial}
26786 Reports that the new trace state variable @var{name} is created with
26787 initial value @var{initial}.
26789 @item =tsv-deleted,name=@var{name}
26790 @itemx =tsv-deleted
26791 Reports that the trace state variable @var{name} is deleted or all
26792 trace state variables are deleted.
26794 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26795 Reports that the trace state variable @var{name} is modified with
26796 the initial value @var{initial}. The current value @var{current} of
26797 trace state variable is optional and is reported if the current
26798 value of trace state variable is known.
26800 @item =breakpoint-created,bkpt=@{...@}
26801 @itemx =breakpoint-modified,bkpt=@{...@}
26802 @itemx =breakpoint-deleted,id=@var{number}
26803 Reports that a breakpoint was created, modified, or deleted,
26804 respectively. Only user-visible breakpoints are reported to the MI
26807 The @var{bkpt} argument is of the same form as returned by the various
26808 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26809 @var{number} is the ordinal number of the breakpoint.
26811 Note that if a breakpoint is emitted in the result record of a
26812 command, then it will not also be emitted in an async record.
26814 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26815 @itemx =record-stopped,thread-group="@var{id}"
26816 Execution log recording was either started or stopped on an
26817 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26818 group corresponding to the affected inferior.
26820 The @var{method} field indicates the method used to record execution. If the
26821 method in use supports multiple recording formats, @var{format} will be present
26822 and contain the currently used format. @xref{Process Record and Replay},
26823 for existing method and format values.
26825 @item =cmd-param-changed,param=@var{param},value=@var{value}
26826 Reports that a parameter of the command @code{set @var{param}} is
26827 changed to @var{value}. In the multi-word @code{set} command,
26828 the @var{param} is the whole parameter list to @code{set} command.
26829 For example, In command @code{set check type on}, @var{param}
26830 is @code{check type} and @var{value} is @code{on}.
26832 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26833 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26834 written in an inferior. The @var{id} is the identifier of the
26835 thread group corresponding to the affected inferior. The optional
26836 @code{type="code"} part is reported if the memory written to holds
26840 @node GDB/MI Breakpoint Information
26841 @subsection @sc{gdb/mi} Breakpoint Information
26843 When @value{GDBN} reports information about a breakpoint, a
26844 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26849 The breakpoint number. For a breakpoint that represents one location
26850 of a multi-location breakpoint, this will be a dotted pair, like
26854 The type of the breakpoint. For ordinary breakpoints this will be
26855 @samp{breakpoint}, but many values are possible.
26858 If the type of the breakpoint is @samp{catchpoint}, then this
26859 indicates the exact type of catchpoint.
26862 This is the breakpoint disposition---either @samp{del}, meaning that
26863 the breakpoint will be deleted at the next stop, or @samp{keep},
26864 meaning that the breakpoint will not be deleted.
26867 This indicates whether the breakpoint is enabled, in which case the
26868 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26869 Note that this is not the same as the field @code{enable}.
26872 The address of the breakpoint. This may be a hexidecimal number,
26873 giving the address; or the string @samp{<PENDING>}, for a pending
26874 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26875 multiple locations. This field will not be present if no address can
26876 be determined. For example, a watchpoint does not have an address.
26879 If known, the function in which the breakpoint appears.
26880 If not known, this field is not present.
26883 The name of the source file which contains this function, if known.
26884 If not known, this field is not present.
26887 The full file name of the source file which contains this function, if
26888 known. If not known, this field is not present.
26891 The line number at which this breakpoint appears, if known.
26892 If not known, this field is not present.
26895 If the source file is not known, this field may be provided. If
26896 provided, this holds the address of the breakpoint, possibly followed
26900 If this breakpoint is pending, this field is present and holds the
26901 text used to set the breakpoint, as entered by the user.
26904 Where this breakpoint's condition is evaluated, either @samp{host} or
26908 If this is a thread-specific breakpoint, then this identifies the
26909 thread in which the breakpoint can trigger.
26912 If this breakpoint is restricted to a particular Ada task, then this
26913 field will hold the task identifier.
26916 If the breakpoint is conditional, this is the condition expression.
26919 The ignore count of the breakpoint.
26922 The enable count of the breakpoint.
26924 @item traceframe-usage
26927 @item static-tracepoint-marker-string-id
26928 For a static tracepoint, the name of the static tracepoint marker.
26931 For a masked watchpoint, this is the mask.
26934 A tracepoint's pass count.
26936 @item original-location
26937 The location of the breakpoint as originally specified by the user.
26938 This field is optional.
26941 The number of times the breakpoint has been hit.
26944 This field is only given for tracepoints. This is either @samp{y},
26945 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26949 Some extra data, the exact contents of which are type-dependent.
26953 For example, here is what the output of @code{-break-insert}
26954 (@pxref{GDB/MI Breakpoint Commands}) might be:
26957 -> -break-insert main
26958 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26959 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26960 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26965 @node GDB/MI Frame Information
26966 @subsection @sc{gdb/mi} Frame Information
26968 Response from many MI commands includes an information about stack
26969 frame. This information is a tuple that may have the following
26974 The level of the stack frame. The innermost frame has the level of
26975 zero. This field is always present.
26978 The name of the function corresponding to the frame. This field may
26979 be absent if @value{GDBN} is unable to determine the function name.
26982 The code address for the frame. This field is always present.
26985 The name of the source files that correspond to the frame's code
26986 address. This field may be absent.
26989 The source line corresponding to the frames' code address. This field
26993 The name of the binary file (either executable or shared library) the
26994 corresponds to the frame's code address. This field may be absent.
26998 @node GDB/MI Thread Information
26999 @subsection @sc{gdb/mi} Thread Information
27001 Whenever @value{GDBN} has to report an information about a thread, it
27002 uses a tuple with the following fields. The fields are always present unless
27007 The global numeric id assigned to the thread by @value{GDBN}.
27010 The target-specific string identifying the thread.
27013 Additional information about the thread provided by the target.
27014 It is supposed to be human-readable and not interpreted by the
27015 frontend. This field is optional.
27018 The name of the thread. If the user specified a name using the
27019 @code{thread name} command, then this name is given. Otherwise, if
27020 @value{GDBN} can extract the thread name from the target, then that
27021 name is given. If @value{GDBN} cannot find the thread name, then this
27025 The execution state of the thread, either @samp{stopped} or @samp{running},
27026 depending on whether the thread is presently running.
27029 The stack frame currently executing in the thread. This field is only present
27030 if the thread is stopped. Its format is documented in
27031 @ref{GDB/MI Frame Information}.
27034 The value of this field is an integer number of the processor core the
27035 thread was last seen on. This field is optional.
27038 @node GDB/MI Ada Exception Information
27039 @subsection @sc{gdb/mi} Ada Exception Information
27041 Whenever a @code{*stopped} record is emitted because the program
27042 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27043 @value{GDBN} provides the name of the exception that was raised via
27044 the @code{exception-name} field.
27046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27047 @node GDB/MI Simple Examples
27048 @section Simple Examples of @sc{gdb/mi} Interaction
27049 @cindex @sc{gdb/mi}, simple examples
27051 This subsection presents several simple examples of interaction using
27052 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27053 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27054 the output received from @sc{gdb/mi}.
27056 Note the line breaks shown in the examples are here only for
27057 readability, they don't appear in the real output.
27059 @subheading Setting a Breakpoint
27061 Setting a breakpoint generates synchronous output which contains detailed
27062 information of the breakpoint.
27065 -> -break-insert main
27066 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27067 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27068 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27073 @subheading Program Execution
27075 Program execution generates asynchronous records and MI gives the
27076 reason that execution stopped.
27082 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27083 frame=@{addr="0x08048564",func="main",
27084 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27085 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27090 <- *stopped,reason="exited-normally"
27094 @subheading Quitting @value{GDBN}
27096 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27104 Please note that @samp{^exit} is printed immediately, but it might
27105 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27106 performs necessary cleanups, including killing programs being debugged
27107 or disconnecting from debug hardware, so the frontend should wait till
27108 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27109 fails to exit in reasonable time.
27111 @subheading A Bad Command
27113 Here's what happens if you pass a non-existent command:
27117 <- ^error,msg="Undefined MI command: rubbish"
27122 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27123 @node GDB/MI Command Description Format
27124 @section @sc{gdb/mi} Command Description Format
27126 The remaining sections describe blocks of commands. Each block of
27127 commands is laid out in a fashion similar to this section.
27129 @subheading Motivation
27131 The motivation for this collection of commands.
27133 @subheading Introduction
27135 A brief introduction to this collection of commands as a whole.
27137 @subheading Commands
27139 For each command in the block, the following is described:
27141 @subsubheading Synopsis
27144 -command @var{args}@dots{}
27147 @subsubheading Result
27149 @subsubheading @value{GDBN} Command
27151 The corresponding @value{GDBN} CLI command(s), if any.
27153 @subsubheading Example
27155 Example(s) formatted for readability. Some of the described commands have
27156 not been implemented yet and these are labeled N.A.@: (not available).
27159 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27160 @node GDB/MI Breakpoint Commands
27161 @section @sc{gdb/mi} Breakpoint Commands
27163 @cindex breakpoint commands for @sc{gdb/mi}
27164 @cindex @sc{gdb/mi}, breakpoint commands
27165 This section documents @sc{gdb/mi} commands for manipulating
27168 @subheading The @code{-break-after} Command
27169 @findex -break-after
27171 @subsubheading Synopsis
27174 -break-after @var{number} @var{count}
27177 The breakpoint number @var{number} is not in effect until it has been
27178 hit @var{count} times. To see how this is reflected in the output of
27179 the @samp{-break-list} command, see the description of the
27180 @samp{-break-list} command below.
27182 @subsubheading @value{GDBN} Command
27184 The corresponding @value{GDBN} command is @samp{ignore}.
27186 @subsubheading Example
27191 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27192 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27193 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27201 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27202 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27203 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27204 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27205 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27206 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27207 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27208 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27209 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27210 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27215 @subheading The @code{-break-catch} Command
27216 @findex -break-catch
27219 @subheading The @code{-break-commands} Command
27220 @findex -break-commands
27222 @subsubheading Synopsis
27225 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27228 Specifies the CLI commands that should be executed when breakpoint
27229 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27230 are the commands. If no command is specified, any previously-set
27231 commands are cleared. @xref{Break Commands}. Typical use of this
27232 functionality is tracing a program, that is, printing of values of
27233 some variables whenever breakpoint is hit and then continuing.
27235 @subsubheading @value{GDBN} Command
27237 The corresponding @value{GDBN} command is @samp{commands}.
27239 @subsubheading Example
27244 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27245 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27246 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27249 -break-commands 1 "print v" "continue"
27254 @subheading The @code{-break-condition} Command
27255 @findex -break-condition
27257 @subsubheading Synopsis
27260 -break-condition @var{number} @var{expr}
27263 Breakpoint @var{number} will stop the program only if the condition in
27264 @var{expr} is true. The condition becomes part of the
27265 @samp{-break-list} output (see the description of the @samp{-break-list}
27268 @subsubheading @value{GDBN} Command
27270 The corresponding @value{GDBN} command is @samp{condition}.
27272 @subsubheading Example
27276 -break-condition 1 1
27280 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27281 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27282 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27283 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27284 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27285 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27286 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27287 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27288 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27289 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27293 @subheading The @code{-break-delete} Command
27294 @findex -break-delete
27296 @subsubheading Synopsis
27299 -break-delete ( @var{breakpoint} )+
27302 Delete the breakpoint(s) whose number(s) are specified in the argument
27303 list. This is obviously reflected in the breakpoint list.
27305 @subsubheading @value{GDBN} Command
27307 The corresponding @value{GDBN} command is @samp{delete}.
27309 @subsubheading Example
27317 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27318 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27319 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27320 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27321 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27322 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27323 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27328 @subheading The @code{-break-disable} Command
27329 @findex -break-disable
27331 @subsubheading Synopsis
27334 -break-disable ( @var{breakpoint} )+
27337 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27338 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27340 @subsubheading @value{GDBN} Command
27342 The corresponding @value{GDBN} command is @samp{disable}.
27344 @subsubheading Example
27352 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27353 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27354 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27355 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27356 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27357 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27358 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27359 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27360 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27361 line="5",thread-groups=["i1"],times="0"@}]@}
27365 @subheading The @code{-break-enable} Command
27366 @findex -break-enable
27368 @subsubheading Synopsis
27371 -break-enable ( @var{breakpoint} )+
27374 Enable (previously disabled) @var{breakpoint}(s).
27376 @subsubheading @value{GDBN} Command
27378 The corresponding @value{GDBN} command is @samp{enable}.
27380 @subsubheading Example
27388 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27389 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27390 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27391 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27392 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27393 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27394 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27395 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27396 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27397 line="5",thread-groups=["i1"],times="0"@}]@}
27401 @subheading The @code{-break-info} Command
27402 @findex -break-info
27404 @subsubheading Synopsis
27407 -break-info @var{breakpoint}
27411 Get information about a single breakpoint.
27413 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27414 Information}, for details on the format of each breakpoint in the
27417 @subsubheading @value{GDBN} Command
27419 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27421 @subsubheading Example
27424 @subheading The @code{-break-insert} Command
27425 @findex -break-insert
27426 @anchor{-break-insert}
27428 @subsubheading Synopsis
27431 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27432 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27433 [ -p @var{thread-id} ] [ @var{location} ]
27437 If specified, @var{location}, can be one of:
27440 @item linespec location
27441 A linespec location. @xref{Linespec Locations}.
27443 @item explicit location
27444 An explicit location. @sc{gdb/mi} explicit locations are
27445 analogous to the CLI's explicit locations using the option names
27446 listed below. @xref{Explicit Locations}.
27449 @item --source @var{filename}
27450 The source file name of the location. This option requires the use
27451 of either @samp{--function} or @samp{--line}.
27453 @item --function @var{function}
27454 The name of a function or method.
27456 @item --label @var{label}
27457 The name of a label.
27459 @item --line @var{lineoffset}
27460 An absolute or relative line offset from the start of the location.
27463 @item address location
27464 An address location, *@var{address}. @xref{Address Locations}.
27468 The possible optional parameters of this command are:
27472 Insert a temporary breakpoint.
27474 Insert a hardware breakpoint.
27476 If @var{location} cannot be parsed (for example if it
27477 refers to unknown files or functions), create a pending
27478 breakpoint. Without this flag, @value{GDBN} will report
27479 an error, and won't create a breakpoint, if @var{location}
27482 Create a disabled breakpoint.
27484 Create a tracepoint. @xref{Tracepoints}. When this parameter
27485 is used together with @samp{-h}, a fast tracepoint is created.
27486 @item -c @var{condition}
27487 Make the breakpoint conditional on @var{condition}.
27488 @item -i @var{ignore-count}
27489 Initialize the @var{ignore-count}.
27490 @item -p @var{thread-id}
27491 Restrict the breakpoint to the thread with the specified global
27495 @subsubheading Result
27497 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27498 resulting breakpoint.
27500 Note: this format is open to change.
27501 @c An out-of-band breakpoint instead of part of the result?
27503 @subsubheading @value{GDBN} Command
27505 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27506 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27508 @subsubheading Example
27513 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27514 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27517 -break-insert -t foo
27518 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27519 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27523 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27524 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27525 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27526 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27527 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27528 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27529 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27530 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27531 addr="0x0001072c", func="main",file="recursive2.c",
27532 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27534 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27535 addr="0x00010774",func="foo",file="recursive2.c",
27536 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27539 @c -break-insert -r foo.*
27540 @c ~int foo(int, int);
27541 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27542 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27547 @subheading The @code{-dprintf-insert} Command
27548 @findex -dprintf-insert
27550 @subsubheading Synopsis
27553 -dprintf-insert [ -t ] [ -f ] [ -d ]
27554 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27555 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27560 If supplied, @var{location} may be specified the same way as for
27561 the @code{-break-insert} command. @xref{-break-insert}.
27563 The possible optional parameters of this command are:
27567 Insert a temporary breakpoint.
27569 If @var{location} cannot be parsed (for example, if it
27570 refers to unknown files or functions), create a pending
27571 breakpoint. Without this flag, @value{GDBN} will report
27572 an error, and won't create a breakpoint, if @var{location}
27575 Create a disabled breakpoint.
27576 @item -c @var{condition}
27577 Make the breakpoint conditional on @var{condition}.
27578 @item -i @var{ignore-count}
27579 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27580 to @var{ignore-count}.
27581 @item -p @var{thread-id}
27582 Restrict the breakpoint to the thread with the specified global
27586 @subsubheading Result
27588 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27589 resulting breakpoint.
27591 @c An out-of-band breakpoint instead of part of the result?
27593 @subsubheading @value{GDBN} Command
27595 The corresponding @value{GDBN} command is @samp{dprintf}.
27597 @subsubheading Example
27601 4-dprintf-insert foo "At foo entry\n"
27602 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27603 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27604 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27605 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27606 original-location="foo"@}
27608 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27609 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27610 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27611 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27612 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27613 original-location="mi-dprintf.c:26"@}
27617 @subheading The @code{-break-list} Command
27618 @findex -break-list
27620 @subsubheading Synopsis
27626 Displays the list of inserted breakpoints, showing the following fields:
27630 number of the breakpoint
27632 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27634 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27637 is the breakpoint enabled or no: @samp{y} or @samp{n}
27639 memory location at which the breakpoint is set
27641 logical location of the breakpoint, expressed by function name, file
27643 @item Thread-groups
27644 list of thread groups to which this breakpoint applies
27646 number of times the breakpoint has been hit
27649 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27650 @code{body} field is an empty list.
27652 @subsubheading @value{GDBN} Command
27654 The corresponding @value{GDBN} command is @samp{info break}.
27656 @subsubheading Example
27661 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27668 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27669 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27671 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27672 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27673 line="13",thread-groups=["i1"],times="0"@}]@}
27677 Here's an example of the result when there are no breakpoints:
27682 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27683 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27684 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27685 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27686 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27687 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27688 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27693 @subheading The @code{-break-passcount} Command
27694 @findex -break-passcount
27696 @subsubheading Synopsis
27699 -break-passcount @var{tracepoint-number} @var{passcount}
27702 Set the passcount for tracepoint @var{tracepoint-number} to
27703 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27704 is not a tracepoint, error is emitted. This corresponds to CLI
27705 command @samp{passcount}.
27707 @subheading The @code{-break-watch} Command
27708 @findex -break-watch
27710 @subsubheading Synopsis
27713 -break-watch [ -a | -r ]
27716 Create a watchpoint. With the @samp{-a} option it will create an
27717 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27718 read from or on a write to the memory location. With the @samp{-r}
27719 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27720 trigger only when the memory location is accessed for reading. Without
27721 either of the options, the watchpoint created is a regular watchpoint,
27722 i.e., it will trigger when the memory location is accessed for writing.
27723 @xref{Set Watchpoints, , Setting Watchpoints}.
27725 Note that @samp{-break-list} will report a single list of watchpoints and
27726 breakpoints inserted.
27728 @subsubheading @value{GDBN} Command
27730 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27733 @subsubheading Example
27735 Setting a watchpoint on a variable in the @code{main} function:
27740 ^done,wpt=@{number="2",exp="x"@}
27745 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27746 value=@{old="-268439212",new="55"@},
27747 frame=@{func="main",args=[],file="recursive2.c",
27748 fullname="/home/foo/bar/recursive2.c",line="5"@}
27752 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27753 the program execution twice: first for the variable changing value, then
27754 for the watchpoint going out of scope.
27759 ^done,wpt=@{number="5",exp="C"@}
27764 *stopped,reason="watchpoint-trigger",
27765 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27766 frame=@{func="callee4",args=[],
27767 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27768 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27773 *stopped,reason="watchpoint-scope",wpnum="5",
27774 frame=@{func="callee3",args=[@{name="strarg",
27775 value="0x11940 \"A string argument.\""@}],
27776 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27777 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27781 Listing breakpoints and watchpoints, at different points in the program
27782 execution. Note that once the watchpoint goes out of scope, it is
27788 ^done,wpt=@{number="2",exp="C"@}
27791 ^done,BreakpointTable=@{nr_rows="2",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"@}],
27798 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27799 addr="0x00010734",func="callee4",
27800 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27801 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27803 bkpt=@{number="2",type="watchpoint",disp="keep",
27804 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27809 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27810 value=@{old="-276895068",new="3"@},
27811 frame=@{func="callee4",args=[],
27812 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27813 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27816 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27817 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27818 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27819 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27820 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27821 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27822 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27823 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27824 addr="0x00010734",func="callee4",
27825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27826 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27828 bkpt=@{number="2",type="watchpoint",disp="keep",
27829 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27833 ^done,reason="watchpoint-scope",wpnum="2",
27834 frame=@{func="callee3",args=[@{name="strarg",
27835 value="0x11940 \"A string argument.\""@}],
27836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27837 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27840 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27841 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27842 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27843 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27844 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27845 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27846 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27847 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27848 addr="0x00010734",func="callee4",
27849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27850 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27851 thread-groups=["i1"],times="1"@}]@}
27856 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27857 @node GDB/MI Catchpoint Commands
27858 @section @sc{gdb/mi} Catchpoint Commands
27860 This section documents @sc{gdb/mi} commands for manipulating
27864 * Shared Library GDB/MI Catchpoint Commands::
27865 * Ada Exception GDB/MI Catchpoint Commands::
27868 @node Shared Library GDB/MI Catchpoint Commands
27869 @subsection Shared Library @sc{gdb/mi} Catchpoints
27871 @subheading The @code{-catch-load} Command
27872 @findex -catch-load
27874 @subsubheading Synopsis
27877 -catch-load [ -t ] [ -d ] @var{regexp}
27880 Add a catchpoint for library load events. If the @samp{-t} option is used,
27881 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27882 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27883 in a disabled state. The @samp{regexp} argument is a regular
27884 expression used to match the name of the loaded library.
27887 @subsubheading @value{GDBN} Command
27889 The corresponding @value{GDBN} command is @samp{catch load}.
27891 @subsubheading Example
27894 -catch-load -t foo.so
27895 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27896 what="load of library matching foo.so",catch-type="load",times="0"@}
27901 @subheading The @code{-catch-unload} Command
27902 @findex -catch-unload
27904 @subsubheading Synopsis
27907 -catch-unload [ -t ] [ -d ] @var{regexp}
27910 Add a catchpoint for library unload events. If the @samp{-t} option is
27911 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27912 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27913 created in a disabled state. The @samp{regexp} argument is a regular
27914 expression used to match the name of the unloaded library.
27916 @subsubheading @value{GDBN} Command
27918 The corresponding @value{GDBN} command is @samp{catch unload}.
27920 @subsubheading Example
27923 -catch-unload -d bar.so
27924 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27925 what="load of library matching bar.so",catch-type="unload",times="0"@}
27929 @node Ada Exception GDB/MI Catchpoint Commands
27930 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27932 The following @sc{gdb/mi} commands can be used to create catchpoints
27933 that stop the execution when Ada exceptions are being raised.
27935 @subheading The @code{-catch-assert} Command
27936 @findex -catch-assert
27938 @subsubheading Synopsis
27941 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27944 Add a catchpoint for failed Ada assertions.
27946 The possible optional parameters for this command are:
27949 @item -c @var{condition}
27950 Make the catchpoint conditional on @var{condition}.
27952 Create a disabled catchpoint.
27954 Create a temporary catchpoint.
27957 @subsubheading @value{GDBN} Command
27959 The corresponding @value{GDBN} command is @samp{catch assert}.
27961 @subsubheading Example
27965 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27966 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27967 thread-groups=["i1"],times="0",
27968 original-location="__gnat_debug_raise_assert_failure"@}
27972 @subheading The @code{-catch-exception} Command
27973 @findex -catch-exception
27975 @subsubheading Synopsis
27978 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27982 Add a catchpoint stopping when Ada exceptions are raised.
27983 By default, the command stops the program when any Ada exception
27984 gets raised. But it is also possible, by using some of the
27985 optional parameters described below, to create more selective
27988 The possible optional parameters for this command are:
27991 @item -c @var{condition}
27992 Make the catchpoint conditional on @var{condition}.
27994 Create a disabled catchpoint.
27995 @item -e @var{exception-name}
27996 Only stop when @var{exception-name} is raised. This option cannot
27997 be used combined with @samp{-u}.
27999 Create a temporary catchpoint.
28001 Stop only when an unhandled exception gets raised. This option
28002 cannot be used combined with @samp{-e}.
28005 @subsubheading @value{GDBN} Command
28007 The corresponding @value{GDBN} commands are @samp{catch exception}
28008 and @samp{catch exception unhandled}.
28010 @subsubheading Example
28013 -catch-exception -e Program_Error
28014 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28015 enabled="y",addr="0x0000000000404874",
28016 what="`Program_Error' Ada exception", thread-groups=["i1"],
28017 times="0",original-location="__gnat_debug_raise_exception"@}
28021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28022 @node GDB/MI Program Context
28023 @section @sc{gdb/mi} Program Context
28025 @subheading The @code{-exec-arguments} Command
28026 @findex -exec-arguments
28029 @subsubheading Synopsis
28032 -exec-arguments @var{args}
28035 Set the inferior program arguments, to be used in the next
28038 @subsubheading @value{GDBN} Command
28040 The corresponding @value{GDBN} command is @samp{set args}.
28042 @subsubheading Example
28046 -exec-arguments -v word
28053 @subheading The @code{-exec-show-arguments} Command
28054 @findex -exec-show-arguments
28056 @subsubheading Synopsis
28059 -exec-show-arguments
28062 Print the arguments of the program.
28064 @subsubheading @value{GDBN} Command
28066 The corresponding @value{GDBN} command is @samp{show args}.
28068 @subsubheading Example
28073 @subheading The @code{-environment-cd} Command
28074 @findex -environment-cd
28076 @subsubheading Synopsis
28079 -environment-cd @var{pathdir}
28082 Set @value{GDBN}'s working directory.
28084 @subsubheading @value{GDBN} Command
28086 The corresponding @value{GDBN} command is @samp{cd}.
28088 @subsubheading Example
28092 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28098 @subheading The @code{-environment-directory} Command
28099 @findex -environment-directory
28101 @subsubheading Synopsis
28104 -environment-directory [ -r ] [ @var{pathdir} ]+
28107 Add directories @var{pathdir} to beginning of search path for source files.
28108 If the @samp{-r} option is used, the search path is reset to the default
28109 search path. If directories @var{pathdir} are supplied in addition to the
28110 @samp{-r} option, the search path is first reset and then addition
28112 Multiple directories may be specified, separated by blanks. Specifying
28113 multiple directories in a single command
28114 results in the directories added to the beginning of the
28115 search path in the same order they were presented in the command.
28116 If blanks are needed as
28117 part of a directory name, double-quotes should be used around
28118 the name. In the command output, the path will show up separated
28119 by the system directory-separator character. The directory-separator
28120 character must not be used
28121 in any directory name.
28122 If no directories are specified, the current search path is displayed.
28124 @subsubheading @value{GDBN} Command
28126 The corresponding @value{GDBN} command is @samp{dir}.
28128 @subsubheading Example
28132 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28133 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28135 -environment-directory ""
28136 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28138 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28139 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28141 -environment-directory -r
28142 ^done,source-path="$cdir:$cwd"
28147 @subheading The @code{-environment-path} Command
28148 @findex -environment-path
28150 @subsubheading Synopsis
28153 -environment-path [ -r ] [ @var{pathdir} ]+
28156 Add directories @var{pathdir} to beginning of search path for object files.
28157 If the @samp{-r} option is used, the search path is reset to the original
28158 search path that existed at gdb start-up. If directories @var{pathdir} are
28159 supplied in addition to the
28160 @samp{-r} option, the search path is first reset and then addition
28162 Multiple directories may be specified, separated by blanks. Specifying
28163 multiple directories in a single command
28164 results in the directories added to the beginning of the
28165 search path in the same order they were presented in the command.
28166 If blanks are needed as
28167 part of a directory name, double-quotes should be used around
28168 the name. In the command output, the path will show up separated
28169 by the system directory-separator character. The directory-separator
28170 character must not be used
28171 in any directory name.
28172 If no directories are specified, the current path is displayed.
28175 @subsubheading @value{GDBN} Command
28177 The corresponding @value{GDBN} command is @samp{path}.
28179 @subsubheading Example
28184 ^done,path="/usr/bin"
28186 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28187 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28189 -environment-path -r /usr/local/bin
28190 ^done,path="/usr/local/bin:/usr/bin"
28195 @subheading The @code{-environment-pwd} Command
28196 @findex -environment-pwd
28198 @subsubheading Synopsis
28204 Show the current working directory.
28206 @subsubheading @value{GDBN} Command
28208 The corresponding @value{GDBN} command is @samp{pwd}.
28210 @subsubheading Example
28215 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28219 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28220 @node GDB/MI Thread Commands
28221 @section @sc{gdb/mi} Thread Commands
28224 @subheading The @code{-thread-info} Command
28225 @findex -thread-info
28227 @subsubheading Synopsis
28230 -thread-info [ @var{thread-id} ]
28233 Reports information about either a specific thread, if the
28234 @var{thread-id} parameter is present, or about all threads.
28235 @var{thread-id} is the thread's global thread ID. When printing
28236 information about all threads, also reports the global ID of the
28239 @subsubheading @value{GDBN} Command
28241 The @samp{info thread} command prints the same information
28244 @subsubheading Result
28246 The result contains the following attributes:
28250 A list of threads. The format of the elements of the list is described in
28251 @ref{GDB/MI Thread Information}.
28253 @item current-thread-id
28254 The global id of the currently selected thread. This field is omitted if there
28255 is no selected thread (for example, when the selected inferior is not running,
28256 and therefore has no threads) or if a @var{thread-id} argument was passed to
28261 @subsubheading Example
28266 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28267 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28268 args=[]@},state="running"@},
28269 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28270 frame=@{level="0",addr="0x0804891f",func="foo",
28271 args=[@{name="i",value="10"@}],
28272 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28273 state="running"@}],
28274 current-thread-id="1"
28278 @subheading The @code{-thread-list-ids} Command
28279 @findex -thread-list-ids
28281 @subsubheading Synopsis
28287 Produces a list of the currently known global @value{GDBN} thread ids.
28288 At the end of the list it also prints the total number of such
28291 This command is retained for historical reasons, the
28292 @code{-thread-info} command should be used instead.
28294 @subsubheading @value{GDBN} Command
28296 Part of @samp{info threads} supplies the same information.
28298 @subsubheading Example
28303 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28304 current-thread-id="1",number-of-threads="3"
28309 @subheading The @code{-thread-select} Command
28310 @findex -thread-select
28312 @subsubheading Synopsis
28315 -thread-select @var{thread-id}
28318 Make thread with global thread number @var{thread-id} the current
28319 thread. It prints the number of the new current thread, and the
28320 topmost frame for that thread.
28322 This command is deprecated in favor of explicitly using the
28323 @samp{--thread} option to each command.
28325 @subsubheading @value{GDBN} Command
28327 The corresponding @value{GDBN} command is @samp{thread}.
28329 @subsubheading Example
28336 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28337 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28341 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28342 number-of-threads="3"
28345 ^done,new-thread-id="3",
28346 frame=@{level="0",func="vprintf",
28347 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28348 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28353 @node GDB/MI Ada Tasking Commands
28354 @section @sc{gdb/mi} Ada Tasking Commands
28356 @subheading The @code{-ada-task-info} Command
28357 @findex -ada-task-info
28359 @subsubheading Synopsis
28362 -ada-task-info [ @var{task-id} ]
28365 Reports information about either a specific Ada task, if the
28366 @var{task-id} parameter is present, or about all Ada tasks.
28368 @subsubheading @value{GDBN} Command
28370 The @samp{info tasks} command prints the same information
28371 about all Ada tasks (@pxref{Ada Tasks}).
28373 @subsubheading Result
28375 The result is a table of Ada tasks. The following columns are
28376 defined for each Ada task:
28380 This field exists only for the current thread. It has the value @samp{*}.
28383 The identifier that @value{GDBN} uses to refer to the Ada task.
28386 The identifier that the target uses to refer to the Ada task.
28389 The global thread identifier of the thread corresponding to the Ada
28392 This field should always exist, as Ada tasks are always implemented
28393 on top of a thread. But if @value{GDBN} cannot find this corresponding
28394 thread for any reason, the field is omitted.
28397 This field exists only when the task was created by another task.
28398 In this case, it provides the ID of the parent task.
28401 The base priority of the task.
28404 The current state of the task. For a detailed description of the
28405 possible states, see @ref{Ada Tasks}.
28408 The name of the task.
28412 @subsubheading Example
28416 ^done,tasks=@{nr_rows="3",nr_cols="8",
28417 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28418 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28419 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28420 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28421 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28422 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28423 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28424 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28425 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28426 state="Child Termination Wait",name="main_task"@}]@}
28430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28431 @node GDB/MI Program Execution
28432 @section @sc{gdb/mi} Program Execution
28434 These are the asynchronous commands which generate the out-of-band
28435 record @samp{*stopped}. Currently @value{GDBN} only really executes
28436 asynchronously with remote targets and this interaction is mimicked in
28439 @subheading The @code{-exec-continue} Command
28440 @findex -exec-continue
28442 @subsubheading Synopsis
28445 -exec-continue [--reverse] [--all|--thread-group N]
28448 Resumes the execution of the inferior program, which will continue
28449 to execute until it reaches a debugger stop event. If the
28450 @samp{--reverse} option is specified, execution resumes in reverse until
28451 it reaches a stop event. Stop events may include
28454 breakpoints or watchpoints
28456 signals or exceptions
28458 the end of the process (or its beginning under @samp{--reverse})
28460 the end or beginning of a replay log if one is being used.
28462 In all-stop mode (@pxref{All-Stop
28463 Mode}), may resume only one thread, or all threads, depending on the
28464 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28465 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28466 ignored in all-stop mode. If the @samp{--thread-group} options is
28467 specified, then all threads in that thread group are resumed.
28469 @subsubheading @value{GDBN} Command
28471 The corresponding @value{GDBN} corresponding is @samp{continue}.
28473 @subsubheading Example
28480 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28481 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28487 @subheading The @code{-exec-finish} Command
28488 @findex -exec-finish
28490 @subsubheading Synopsis
28493 -exec-finish [--reverse]
28496 Resumes the execution of the inferior program until the current
28497 function is exited. Displays the results returned by the function.
28498 If the @samp{--reverse} option is specified, resumes the reverse
28499 execution of the inferior program until the point where current
28500 function was called.
28502 @subsubheading @value{GDBN} Command
28504 The corresponding @value{GDBN} command is @samp{finish}.
28506 @subsubheading Example
28508 Function returning @code{void}.
28515 *stopped,reason="function-finished",frame=@{func="main",args=[],
28516 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28520 Function returning other than @code{void}. The name of the internal
28521 @value{GDBN} variable storing the result is printed, together with the
28528 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28529 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28531 gdb-result-var="$1",return-value="0"
28536 @subheading The @code{-exec-interrupt} Command
28537 @findex -exec-interrupt
28539 @subsubheading Synopsis
28542 -exec-interrupt [--all|--thread-group N]
28545 Interrupts the background execution of the target. Note how the token
28546 associated with the stop message is the one for the execution command
28547 that has been interrupted. The token for the interrupt itself only
28548 appears in the @samp{^done} output. If the user is trying to
28549 interrupt a non-running program, an error message will be printed.
28551 Note that when asynchronous execution is enabled, this command is
28552 asynchronous just like other execution commands. That is, first the
28553 @samp{^done} response will be printed, and the target stop will be
28554 reported after that using the @samp{*stopped} notification.
28556 In non-stop mode, only the context thread is interrupted by default.
28557 All threads (in all inferiors) will be interrupted if the
28558 @samp{--all} option is specified. If the @samp{--thread-group}
28559 option is specified, all threads in that group will be interrupted.
28561 @subsubheading @value{GDBN} Command
28563 The corresponding @value{GDBN} command is @samp{interrupt}.
28565 @subsubheading Example
28576 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28577 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28578 fullname="/home/foo/bar/try.c",line="13"@}
28583 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28587 @subheading The @code{-exec-jump} Command
28590 @subsubheading Synopsis
28593 -exec-jump @var{location}
28596 Resumes execution of the inferior program at the location specified by
28597 parameter. @xref{Specify Location}, for a description of the
28598 different forms of @var{location}.
28600 @subsubheading @value{GDBN} Command
28602 The corresponding @value{GDBN} command is @samp{jump}.
28604 @subsubheading Example
28607 -exec-jump foo.c:10
28608 *running,thread-id="all"
28613 @subheading The @code{-exec-next} Command
28616 @subsubheading Synopsis
28619 -exec-next [--reverse]
28622 Resumes execution of the inferior program, stopping when the beginning
28623 of the next source line is reached.
28625 If the @samp{--reverse} option is specified, resumes reverse execution
28626 of the inferior program, stopping at the beginning of the previous
28627 source line. If you issue this command on the first line of a
28628 function, it will take you back to the caller of that function, to the
28629 source line where the function was called.
28632 @subsubheading @value{GDBN} Command
28634 The corresponding @value{GDBN} command is @samp{next}.
28636 @subsubheading Example
28642 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28647 @subheading The @code{-exec-next-instruction} Command
28648 @findex -exec-next-instruction
28650 @subsubheading Synopsis
28653 -exec-next-instruction [--reverse]
28656 Executes one machine instruction. If the instruction is a function
28657 call, continues until the function returns. If the program stops at an
28658 instruction in the middle of a source line, the address will be
28661 If the @samp{--reverse} option is specified, resumes reverse execution
28662 of the inferior program, stopping at the previous instruction. If the
28663 previously executed instruction was a return from another function,
28664 it will continue to execute in reverse until the call to that function
28665 (from the current stack frame) is reached.
28667 @subsubheading @value{GDBN} Command
28669 The corresponding @value{GDBN} command is @samp{nexti}.
28671 @subsubheading Example
28675 -exec-next-instruction
28679 *stopped,reason="end-stepping-range",
28680 addr="0x000100d4",line="5",file="hello.c"
28685 @subheading The @code{-exec-return} Command
28686 @findex -exec-return
28688 @subsubheading Synopsis
28694 Makes current function return immediately. Doesn't execute the inferior.
28695 Displays the new current frame.
28697 @subsubheading @value{GDBN} Command
28699 The corresponding @value{GDBN} command is @samp{return}.
28701 @subsubheading Example
28705 200-break-insert callee4
28706 200^done,bkpt=@{number="1",addr="0x00010734",
28707 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28712 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28713 frame=@{func="callee4",args=[],
28714 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28715 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28721 111^done,frame=@{level="0",func="callee3",
28722 args=[@{name="strarg",
28723 value="0x11940 \"A string argument.\""@}],
28724 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28725 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28730 @subheading The @code{-exec-run} Command
28733 @subsubheading Synopsis
28736 -exec-run [ --all | --thread-group N ] [ --start ]
28739 Starts execution of the inferior from the beginning. The inferior
28740 executes until either a breakpoint is encountered or the program
28741 exits. In the latter case the output will include an exit code, if
28742 the program has exited exceptionally.
28744 When neither the @samp{--all} nor the @samp{--thread-group} option
28745 is specified, the current inferior is started. If the
28746 @samp{--thread-group} option is specified, it should refer to a thread
28747 group of type @samp{process}, and that thread group will be started.
28748 If the @samp{--all} option is specified, then all inferiors will be started.
28750 Using the @samp{--start} option instructs the debugger to stop
28751 the execution at the start of the inferior's main subprogram,
28752 following the same behavior as the @code{start} command
28753 (@pxref{Starting}).
28755 @subsubheading @value{GDBN} Command
28757 The corresponding @value{GDBN} command is @samp{run}.
28759 @subsubheading Examples
28764 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28769 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28770 frame=@{func="main",args=[],file="recursive2.c",
28771 fullname="/home/foo/bar/recursive2.c",line="4"@}
28776 Program exited normally:
28784 *stopped,reason="exited-normally"
28789 Program exited exceptionally:
28797 *stopped,reason="exited",exit-code="01"
28801 Another way the program can terminate is if it receives a signal such as
28802 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28806 *stopped,reason="exited-signalled",signal-name="SIGINT",
28807 signal-meaning="Interrupt"
28811 @c @subheading -exec-signal
28814 @subheading The @code{-exec-step} Command
28817 @subsubheading Synopsis
28820 -exec-step [--reverse]
28823 Resumes execution of the inferior program, stopping when the beginning
28824 of the next source line is reached, if the next source line is not a
28825 function call. If it is, stop at the first instruction of the called
28826 function. If the @samp{--reverse} option is specified, resumes reverse
28827 execution of the inferior program, stopping at the beginning of the
28828 previously executed source line.
28830 @subsubheading @value{GDBN} Command
28832 The corresponding @value{GDBN} command is @samp{step}.
28834 @subsubheading Example
28836 Stepping into a function:
28842 *stopped,reason="end-stepping-range",
28843 frame=@{func="foo",args=[@{name="a",value="10"@},
28844 @{name="b",value="0"@}],file="recursive2.c",
28845 fullname="/home/foo/bar/recursive2.c",line="11"@}
28855 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28860 @subheading The @code{-exec-step-instruction} Command
28861 @findex -exec-step-instruction
28863 @subsubheading Synopsis
28866 -exec-step-instruction [--reverse]
28869 Resumes the inferior which executes one machine instruction. If the
28870 @samp{--reverse} option is specified, resumes reverse execution of the
28871 inferior program, stopping at the previously executed instruction.
28872 The output, once @value{GDBN} has stopped, will vary depending on
28873 whether we have stopped in the middle of a source line or not. In the
28874 former case, the address at which the program stopped will be printed
28877 @subsubheading @value{GDBN} Command
28879 The corresponding @value{GDBN} command is @samp{stepi}.
28881 @subsubheading Example
28885 -exec-step-instruction
28889 *stopped,reason="end-stepping-range",
28890 frame=@{func="foo",args=[],file="try.c",
28891 fullname="/home/foo/bar/try.c",line="10"@}
28893 -exec-step-instruction
28897 *stopped,reason="end-stepping-range",
28898 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28899 fullname="/home/foo/bar/try.c",line="10"@}
28904 @subheading The @code{-exec-until} Command
28905 @findex -exec-until
28907 @subsubheading Synopsis
28910 -exec-until [ @var{location} ]
28913 Executes the inferior until the @var{location} specified in the
28914 argument is reached. If there is no argument, the inferior executes
28915 until a source line greater than the current one is reached. The
28916 reason for stopping in this case will be @samp{location-reached}.
28918 @subsubheading @value{GDBN} Command
28920 The corresponding @value{GDBN} command is @samp{until}.
28922 @subsubheading Example
28926 -exec-until recursive2.c:6
28930 *stopped,reason="location-reached",frame=@{func="main",args=[],
28931 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28936 @subheading -file-clear
28937 Is this going away????
28940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28941 @node GDB/MI Stack Manipulation
28942 @section @sc{gdb/mi} Stack Manipulation Commands
28944 @subheading The @code{-enable-frame-filters} Command
28945 @findex -enable-frame-filters
28948 -enable-frame-filters
28951 @value{GDBN} allows Python-based frame filters to affect the output of
28952 the MI commands relating to stack traces. As there is no way to
28953 implement this in a fully backward-compatible way, a front end must
28954 request that this functionality be enabled.
28956 Once enabled, this feature cannot be disabled.
28958 Note that if Python support has not been compiled into @value{GDBN},
28959 this command will still succeed (and do nothing).
28961 @subheading The @code{-stack-info-frame} Command
28962 @findex -stack-info-frame
28964 @subsubheading Synopsis
28970 Get info on the selected frame.
28972 @subsubheading @value{GDBN} Command
28974 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28975 (without arguments).
28977 @subsubheading Example
28982 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28984 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28988 @subheading The @code{-stack-info-depth} Command
28989 @findex -stack-info-depth
28991 @subsubheading Synopsis
28994 -stack-info-depth [ @var{max-depth} ]
28997 Return the depth of the stack. If the integer argument @var{max-depth}
28998 is specified, do not count beyond @var{max-depth} frames.
29000 @subsubheading @value{GDBN} Command
29002 There's no equivalent @value{GDBN} command.
29004 @subsubheading Example
29006 For a stack with frame levels 0 through 11:
29013 -stack-info-depth 4
29016 -stack-info-depth 12
29019 -stack-info-depth 11
29022 -stack-info-depth 13
29027 @anchor{-stack-list-arguments}
29028 @subheading The @code{-stack-list-arguments} Command
29029 @findex -stack-list-arguments
29031 @subsubheading Synopsis
29034 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29035 [ @var{low-frame} @var{high-frame} ]
29038 Display a list of the arguments for the frames between @var{low-frame}
29039 and @var{high-frame} (inclusive). If @var{low-frame} and
29040 @var{high-frame} are not provided, list the arguments for the whole
29041 call stack. If the two arguments are equal, show the single frame
29042 at the corresponding level. It is an error if @var{low-frame} is
29043 larger than the actual number of frames. On the other hand,
29044 @var{high-frame} may be larger than the actual number of frames, in
29045 which case only existing frames will be returned.
29047 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29048 the variables; if it is 1 or @code{--all-values}, print also their
29049 values; and if it is 2 or @code{--simple-values}, print the name,
29050 type and value for simple data types, and the name and type for arrays,
29051 structures and unions. If the option @code{--no-frame-filters} is
29052 supplied, then Python frame filters will not be executed.
29054 If the @code{--skip-unavailable} option is specified, arguments that
29055 are not available are not listed. Partially available arguments
29056 are still displayed, however.
29058 Use of this command to obtain arguments in a single frame is
29059 deprecated in favor of the @samp{-stack-list-variables} command.
29061 @subsubheading @value{GDBN} Command
29063 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29064 @samp{gdb_get_args} command which partially overlaps with the
29065 functionality of @samp{-stack-list-arguments}.
29067 @subsubheading Example
29074 frame=@{level="0",addr="0x00010734",func="callee4",
29075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29076 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29077 frame=@{level="1",addr="0x0001076c",func="callee3",
29078 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29079 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29080 frame=@{level="2",addr="0x0001078c",func="callee2",
29081 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29082 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29083 frame=@{level="3",addr="0x000107b4",func="callee1",
29084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29085 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29086 frame=@{level="4",addr="0x000107e0",func="main",
29087 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29088 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29090 -stack-list-arguments 0
29093 frame=@{level="0",args=[]@},
29094 frame=@{level="1",args=[name="strarg"]@},
29095 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29096 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29097 frame=@{level="4",args=[]@}]
29099 -stack-list-arguments 1
29102 frame=@{level="0",args=[]@},
29104 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29105 frame=@{level="2",args=[
29106 @{name="intarg",value="2"@},
29107 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29108 @{frame=@{level="3",args=[
29109 @{name="intarg",value="2"@},
29110 @{name="strarg",value="0x11940 \"A string argument.\""@},
29111 @{name="fltarg",value="3.5"@}]@},
29112 frame=@{level="4",args=[]@}]
29114 -stack-list-arguments 0 2 2
29115 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29117 -stack-list-arguments 1 2 2
29118 ^done,stack-args=[frame=@{level="2",
29119 args=[@{name="intarg",value="2"@},
29120 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29124 @c @subheading -stack-list-exception-handlers
29127 @anchor{-stack-list-frames}
29128 @subheading The @code{-stack-list-frames} Command
29129 @findex -stack-list-frames
29131 @subsubheading Synopsis
29134 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29137 List the frames currently on the stack. For each frame it displays the
29142 The frame number, 0 being the topmost frame, i.e., the innermost function.
29144 The @code{$pc} value for that frame.
29148 File name of the source file where the function lives.
29149 @item @var{fullname}
29150 The full file name of the source file where the function lives.
29152 Line number corresponding to the @code{$pc}.
29154 The shared library where this function is defined. This is only given
29155 if the frame's function is not known.
29158 If invoked without arguments, this command prints a backtrace for the
29159 whole stack. If given two integer arguments, it shows the frames whose
29160 levels are between the two arguments (inclusive). If the two arguments
29161 are equal, it shows the single frame at the corresponding level. It is
29162 an error if @var{low-frame} is larger than the actual number of
29163 frames. On the other hand, @var{high-frame} may be larger than the
29164 actual number of frames, in which case only existing frames will be
29165 returned. If the option @code{--no-frame-filters} is supplied, then
29166 Python frame filters will not be executed.
29168 @subsubheading @value{GDBN} Command
29170 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29172 @subsubheading Example
29174 Full stack backtrace:
29180 [frame=@{level="0",addr="0x0001076c",func="foo",
29181 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29182 frame=@{level="1",addr="0x000107a4",func="foo",
29183 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29184 frame=@{level="2",addr="0x000107a4",func="foo",
29185 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29186 frame=@{level="3",addr="0x000107a4",func="foo",
29187 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29188 frame=@{level="4",addr="0x000107a4",func="foo",
29189 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29190 frame=@{level="5",addr="0x000107a4",func="foo",
29191 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29192 frame=@{level="6",addr="0x000107a4",func="foo",
29193 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29194 frame=@{level="7",addr="0x000107a4",func="foo",
29195 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29196 frame=@{level="8",addr="0x000107a4",func="foo",
29197 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29198 frame=@{level="9",addr="0x000107a4",func="foo",
29199 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29200 frame=@{level="10",addr="0x000107a4",func="foo",
29201 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29202 frame=@{level="11",addr="0x00010738",func="main",
29203 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29207 Show frames between @var{low_frame} and @var{high_frame}:
29211 -stack-list-frames 3 5
29213 [frame=@{level="3",addr="0x000107a4",func="foo",
29214 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29215 frame=@{level="4",addr="0x000107a4",func="foo",
29216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29217 frame=@{level="5",addr="0x000107a4",func="foo",
29218 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29222 Show a single frame:
29226 -stack-list-frames 3 3
29228 [frame=@{level="3",addr="0x000107a4",func="foo",
29229 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29234 @subheading The @code{-stack-list-locals} Command
29235 @findex -stack-list-locals
29236 @anchor{-stack-list-locals}
29238 @subsubheading Synopsis
29241 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29244 Display the local variable names for the selected frame. If
29245 @var{print-values} is 0 or @code{--no-values}, print only the names of
29246 the variables; if it is 1 or @code{--all-values}, print also their
29247 values; and if it is 2 or @code{--simple-values}, print the name,
29248 type and value for simple data types, and the name and type for arrays,
29249 structures and unions. In this last case, a frontend can immediately
29250 display the value of simple data types and create variable objects for
29251 other data types when the user wishes to explore their values in
29252 more detail. If the option @code{--no-frame-filters} is supplied, then
29253 Python frame filters will not be executed.
29255 If the @code{--skip-unavailable} option is specified, local variables
29256 that are not available are not listed. Partially available local
29257 variables are still displayed, however.
29259 This command is deprecated in favor of the
29260 @samp{-stack-list-variables} command.
29262 @subsubheading @value{GDBN} Command
29264 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29266 @subsubheading Example
29270 -stack-list-locals 0
29271 ^done,locals=[name="A",name="B",name="C"]
29273 -stack-list-locals --all-values
29274 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29275 @{name="C",value="@{1, 2, 3@}"@}]
29276 -stack-list-locals --simple-values
29277 ^done,locals=[@{name="A",type="int",value="1"@},
29278 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29282 @anchor{-stack-list-variables}
29283 @subheading The @code{-stack-list-variables} Command
29284 @findex -stack-list-variables
29286 @subsubheading Synopsis
29289 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29292 Display the names of local variables and function arguments for the selected frame. If
29293 @var{print-values} is 0 or @code{--no-values}, print only the names of
29294 the variables; if it is 1 or @code{--all-values}, print also their
29295 values; and if it is 2 or @code{--simple-values}, print the name,
29296 type and value for simple data types, and the name and type for arrays,
29297 structures and unions. If the option @code{--no-frame-filters} is
29298 supplied, then Python frame filters will not be executed.
29300 If the @code{--skip-unavailable} option is specified, local variables
29301 and arguments that are not available are not listed. Partially
29302 available arguments and local variables are still displayed, however.
29304 @subsubheading Example
29308 -stack-list-variables --thread 1 --frame 0 --all-values
29309 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29314 @subheading The @code{-stack-select-frame} Command
29315 @findex -stack-select-frame
29317 @subsubheading Synopsis
29320 -stack-select-frame @var{framenum}
29323 Change the selected frame. Select a different frame @var{framenum} on
29326 This command in deprecated in favor of passing the @samp{--frame}
29327 option to every command.
29329 @subsubheading @value{GDBN} Command
29331 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29332 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29334 @subsubheading Example
29338 -stack-select-frame 2
29343 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29344 @node GDB/MI Variable Objects
29345 @section @sc{gdb/mi} Variable Objects
29349 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29351 For the implementation of a variable debugger window (locals, watched
29352 expressions, etc.), we are proposing the adaptation of the existing code
29353 used by @code{Insight}.
29355 The two main reasons for that are:
29359 It has been proven in practice (it is already on its second generation).
29362 It will shorten development time (needless to say how important it is
29366 The original interface was designed to be used by Tcl code, so it was
29367 slightly changed so it could be used through @sc{gdb/mi}. This section
29368 describes the @sc{gdb/mi} operations that will be available and gives some
29369 hints about their use.
29371 @emph{Note}: In addition to the set of operations described here, we
29372 expect the @sc{gui} implementation of a variable window to require, at
29373 least, the following operations:
29376 @item @code{-gdb-show} @code{output-radix}
29377 @item @code{-stack-list-arguments}
29378 @item @code{-stack-list-locals}
29379 @item @code{-stack-select-frame}
29384 @subheading Introduction to Variable Objects
29386 @cindex variable objects in @sc{gdb/mi}
29388 Variable objects are "object-oriented" MI interface for examining and
29389 changing values of expressions. Unlike some other MI interfaces that
29390 work with expressions, variable objects are specifically designed for
29391 simple and efficient presentation in the frontend. A variable object
29392 is identified by string name. When a variable object is created, the
29393 frontend specifies the expression for that variable object. The
29394 expression can be a simple variable, or it can be an arbitrary complex
29395 expression, and can even involve CPU registers. After creating a
29396 variable object, the frontend can invoke other variable object
29397 operations---for example to obtain or change the value of a variable
29398 object, or to change display format.
29400 Variable objects have hierarchical tree structure. Any variable object
29401 that corresponds to a composite type, such as structure in C, has
29402 a number of child variable objects, for example corresponding to each
29403 element of a structure. A child variable object can itself have
29404 children, recursively. Recursion ends when we reach
29405 leaf variable objects, which always have built-in types. Child variable
29406 objects are created only by explicit request, so if a frontend
29407 is not interested in the children of a particular variable object, no
29408 child will be created.
29410 For a leaf variable object it is possible to obtain its value as a
29411 string, or set the value from a string. String value can be also
29412 obtained for a non-leaf variable object, but it's generally a string
29413 that only indicates the type of the object, and does not list its
29414 contents. Assignment to a non-leaf variable object is not allowed.
29416 A frontend does not need to read the values of all variable objects each time
29417 the program stops. Instead, MI provides an update command that lists all
29418 variable objects whose values has changed since the last update
29419 operation. This considerably reduces the amount of data that must
29420 be transferred to the frontend. As noted above, children variable
29421 objects are created on demand, and only leaf variable objects have a
29422 real value. As result, gdb will read target memory only for leaf
29423 variables that frontend has created.
29425 The automatic update is not always desirable. For example, a frontend
29426 might want to keep a value of some expression for future reference,
29427 and never update it. For another example, fetching memory is
29428 relatively slow for embedded targets, so a frontend might want
29429 to disable automatic update for the variables that are either not
29430 visible on the screen, or ``closed''. This is possible using so
29431 called ``frozen variable objects''. Such variable objects are never
29432 implicitly updated.
29434 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29435 fixed variable object, the expression is parsed when the variable
29436 object is created, including associating identifiers to specific
29437 variables. The meaning of expression never changes. For a floating
29438 variable object the values of variables whose names appear in the
29439 expressions are re-evaluated every time in the context of the current
29440 frame. Consider this example:
29445 struct work_state state;
29452 If a fixed variable object for the @code{state} variable is created in
29453 this function, and we enter the recursive call, the variable
29454 object will report the value of @code{state} in the top-level
29455 @code{do_work} invocation. On the other hand, a floating variable
29456 object will report the value of @code{state} in the current frame.
29458 If an expression specified when creating a fixed variable object
29459 refers to a local variable, the variable object becomes bound to the
29460 thread and frame in which the variable object is created. When such
29461 variable object is updated, @value{GDBN} makes sure that the
29462 thread/frame combination the variable object is bound to still exists,
29463 and re-evaluates the variable object in context of that thread/frame.
29465 The following is the complete set of @sc{gdb/mi} operations defined to
29466 access this functionality:
29468 @multitable @columnfractions .4 .6
29469 @item @strong{Operation}
29470 @tab @strong{Description}
29472 @item @code{-enable-pretty-printing}
29473 @tab enable Python-based pretty-printing
29474 @item @code{-var-create}
29475 @tab create a variable object
29476 @item @code{-var-delete}
29477 @tab delete the variable object and/or its children
29478 @item @code{-var-set-format}
29479 @tab set the display format of this variable
29480 @item @code{-var-show-format}
29481 @tab show the display format of this variable
29482 @item @code{-var-info-num-children}
29483 @tab tells how many children this object has
29484 @item @code{-var-list-children}
29485 @tab return a list of the object's children
29486 @item @code{-var-info-type}
29487 @tab show the type of this variable object
29488 @item @code{-var-info-expression}
29489 @tab print parent-relative expression that this variable object represents
29490 @item @code{-var-info-path-expression}
29491 @tab print full expression that this variable object represents
29492 @item @code{-var-show-attributes}
29493 @tab is this variable editable? does it exist here?
29494 @item @code{-var-evaluate-expression}
29495 @tab get the value of this variable
29496 @item @code{-var-assign}
29497 @tab set the value of this variable
29498 @item @code{-var-update}
29499 @tab update the variable and its children
29500 @item @code{-var-set-frozen}
29501 @tab set frozeness attribute
29502 @item @code{-var-set-update-range}
29503 @tab set range of children to display on update
29506 In the next subsection we describe each operation in detail and suggest
29507 how it can be used.
29509 @subheading Description And Use of Operations on Variable Objects
29511 @subheading The @code{-enable-pretty-printing} Command
29512 @findex -enable-pretty-printing
29515 -enable-pretty-printing
29518 @value{GDBN} allows Python-based visualizers to affect the output of the
29519 MI variable object commands. However, because there was no way to
29520 implement this in a fully backward-compatible way, a front end must
29521 request that this functionality be enabled.
29523 Once enabled, this feature cannot be disabled.
29525 Note that if Python support has not been compiled into @value{GDBN},
29526 this command will still succeed (and do nothing).
29528 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29529 may work differently in future versions of @value{GDBN}.
29531 @subheading The @code{-var-create} Command
29532 @findex -var-create
29534 @subsubheading Synopsis
29537 -var-create @{@var{name} | "-"@}
29538 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29541 This operation creates a variable object, which allows the monitoring of
29542 a variable, the result of an expression, a memory cell or a CPU
29545 The @var{name} parameter is the string by which the object can be
29546 referenced. It must be unique. If @samp{-} is specified, the varobj
29547 system will generate a string ``varNNNNNN'' automatically. It will be
29548 unique provided that one does not specify @var{name} of that format.
29549 The command fails if a duplicate name is found.
29551 The frame under which the expression should be evaluated can be
29552 specified by @var{frame-addr}. A @samp{*} indicates that the current
29553 frame should be used. A @samp{@@} indicates that a floating variable
29554 object must be created.
29556 @var{expression} is any expression valid on the current language set (must not
29557 begin with a @samp{*}), or one of the following:
29561 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29564 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29567 @samp{$@var{regname}} --- a CPU register name
29570 @cindex dynamic varobj
29571 A varobj's contents may be provided by a Python-based pretty-printer. In this
29572 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29573 have slightly different semantics in some cases. If the
29574 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29575 will never create a dynamic varobj. This ensures backward
29576 compatibility for existing clients.
29578 @subsubheading Result
29580 This operation returns attributes of the newly-created varobj. These
29585 The name of the varobj.
29588 The number of children of the varobj. This number is not necessarily
29589 reliable for a dynamic varobj. Instead, you must examine the
29590 @samp{has_more} attribute.
29593 The varobj's scalar value. For a varobj whose type is some sort of
29594 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29595 will not be interesting.
29598 The varobj's type. This is a string representation of the type, as
29599 would be printed by the @value{GDBN} CLI. If @samp{print object}
29600 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29601 @emph{actual} (derived) type of the object is shown rather than the
29602 @emph{declared} one.
29605 If a variable object is bound to a specific thread, then this is the
29606 thread's global identifier.
29609 For a dynamic varobj, this indicates whether there appear to be any
29610 children available. For a non-dynamic varobj, this will be 0.
29613 This attribute will be present and have the value @samp{1} if the
29614 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29615 then this attribute will not be present.
29618 A dynamic varobj can supply a display hint to the front end. The
29619 value comes directly from the Python pretty-printer object's
29620 @code{display_hint} method. @xref{Pretty Printing API}.
29623 Typical output will look like this:
29626 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29627 has_more="@var{has_more}"
29631 @subheading The @code{-var-delete} Command
29632 @findex -var-delete
29634 @subsubheading Synopsis
29637 -var-delete [ -c ] @var{name}
29640 Deletes a previously created variable object and all of its children.
29641 With the @samp{-c} option, just deletes the children.
29643 Returns an error if the object @var{name} is not found.
29646 @subheading The @code{-var-set-format} Command
29647 @findex -var-set-format
29649 @subsubheading Synopsis
29652 -var-set-format @var{name} @var{format-spec}
29655 Sets the output format for the value of the object @var{name} to be
29658 @anchor{-var-set-format}
29659 The syntax for the @var{format-spec} is as follows:
29662 @var{format-spec} @expansion{}
29663 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29666 The natural format is the default format choosen automatically
29667 based on the variable type (like decimal for an @code{int}, hex
29668 for pointers, etc.).
29670 The zero-hexadecimal format has a representation similar to hexadecimal
29671 but with padding zeroes to the left of the value. For example, a 32-bit
29672 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29673 zero-hexadecimal format.
29675 For a variable with children, the format is set only on the
29676 variable itself, and the children are not affected.
29678 @subheading The @code{-var-show-format} Command
29679 @findex -var-show-format
29681 @subsubheading Synopsis
29684 -var-show-format @var{name}
29687 Returns the format used to display the value of the object @var{name}.
29690 @var{format} @expansion{}
29695 @subheading The @code{-var-info-num-children} Command
29696 @findex -var-info-num-children
29698 @subsubheading Synopsis
29701 -var-info-num-children @var{name}
29704 Returns the number of children of a variable object @var{name}:
29710 Note that this number is not completely reliable for a dynamic varobj.
29711 It will return the current number of children, but more children may
29715 @subheading The @code{-var-list-children} Command
29716 @findex -var-list-children
29718 @subsubheading Synopsis
29721 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29723 @anchor{-var-list-children}
29725 Return a list of the children of the specified variable object and
29726 create variable objects for them, if they do not already exist. With
29727 a single argument or if @var{print-values} has a value of 0 or
29728 @code{--no-values}, print only the names of the variables; if
29729 @var{print-values} is 1 or @code{--all-values}, also print their
29730 values; and if it is 2 or @code{--simple-values} print the name and
29731 value for simple data types and just the name for arrays, structures
29734 @var{from} and @var{to}, if specified, indicate the range of children
29735 to report. If @var{from} or @var{to} is less than zero, the range is
29736 reset and all children will be reported. Otherwise, children starting
29737 at @var{from} (zero-based) and up to and excluding @var{to} will be
29740 If a child range is requested, it will only affect the current call to
29741 @code{-var-list-children}, but not future calls to @code{-var-update}.
29742 For this, you must instead use @code{-var-set-update-range}. The
29743 intent of this approach is to enable a front end to implement any
29744 update approach it likes; for example, scrolling a view may cause the
29745 front end to request more children with @code{-var-list-children}, and
29746 then the front end could call @code{-var-set-update-range} with a
29747 different range to ensure that future updates are restricted to just
29750 For each child the following results are returned:
29755 Name of the variable object created for this child.
29758 The expression to be shown to the user by the front end to designate this child.
29759 For example this may be the name of a structure member.
29761 For a dynamic varobj, this value cannot be used to form an
29762 expression. There is no way to do this at all with a dynamic varobj.
29764 For C/C@t{++} structures there are several pseudo children returned to
29765 designate access qualifiers. For these pseudo children @var{exp} is
29766 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29767 type and value are not present.
29769 A dynamic varobj will not report the access qualifying
29770 pseudo-children, regardless of the language. This information is not
29771 available at all with a dynamic varobj.
29774 Number of children this child has. For a dynamic varobj, this will be
29778 The type of the child. If @samp{print object}
29779 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29780 @emph{actual} (derived) type of the object is shown rather than the
29781 @emph{declared} one.
29784 If values were requested, this is the value.
29787 If this variable object is associated with a thread, this is the
29788 thread's global thread id. Otherwise this result is not present.
29791 If the variable object is frozen, this variable will be present with a value of 1.
29794 A dynamic varobj can supply a display hint to the front end. The
29795 value comes directly from the Python pretty-printer object's
29796 @code{display_hint} method. @xref{Pretty Printing API}.
29799 This attribute will be present and have the value @samp{1} if the
29800 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29801 then this attribute will not be present.
29805 The result may have its own attributes:
29809 A dynamic varobj can supply a display hint to the front end. The
29810 value comes directly from the Python pretty-printer object's
29811 @code{display_hint} method. @xref{Pretty Printing API}.
29814 This is an integer attribute which is nonzero if there are children
29815 remaining after the end of the selected range.
29818 @subsubheading Example
29822 -var-list-children n
29823 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29824 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29826 -var-list-children --all-values n
29827 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29828 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29832 @subheading The @code{-var-info-type} Command
29833 @findex -var-info-type
29835 @subsubheading Synopsis
29838 -var-info-type @var{name}
29841 Returns the type of the specified variable @var{name}. The type is
29842 returned as a string in the same format as it is output by the
29846 type=@var{typename}
29850 @subheading The @code{-var-info-expression} Command
29851 @findex -var-info-expression
29853 @subsubheading Synopsis
29856 -var-info-expression @var{name}
29859 Returns a string that is suitable for presenting this
29860 variable object in user interface. The string is generally
29861 not valid expression in the current language, and cannot be evaluated.
29863 For example, if @code{a} is an array, and variable object
29864 @code{A} was created for @code{a}, then we'll get this output:
29867 (gdb) -var-info-expression A.1
29868 ^done,lang="C",exp="1"
29872 Here, the value of @code{lang} is the language name, which can be
29873 found in @ref{Supported Languages}.
29875 Note that the output of the @code{-var-list-children} command also
29876 includes those expressions, so the @code{-var-info-expression} command
29879 @subheading The @code{-var-info-path-expression} Command
29880 @findex -var-info-path-expression
29882 @subsubheading Synopsis
29885 -var-info-path-expression @var{name}
29888 Returns an expression that can be evaluated in the current
29889 context and will yield the same value that a variable object has.
29890 Compare this with the @code{-var-info-expression} command, which
29891 result can be used only for UI presentation. Typical use of
29892 the @code{-var-info-path-expression} command is creating a
29893 watchpoint from a variable object.
29895 This command is currently not valid for children of a dynamic varobj,
29896 and will give an error when invoked on one.
29898 For example, suppose @code{C} is a C@t{++} class, derived from class
29899 @code{Base}, and that the @code{Base} class has a member called
29900 @code{m_size}. Assume a variable @code{c} is has the type of
29901 @code{C} and a variable object @code{C} was created for variable
29902 @code{c}. Then, we'll get this output:
29904 (gdb) -var-info-path-expression C.Base.public.m_size
29905 ^done,path_expr=((Base)c).m_size)
29908 @subheading The @code{-var-show-attributes} Command
29909 @findex -var-show-attributes
29911 @subsubheading Synopsis
29914 -var-show-attributes @var{name}
29917 List attributes of the specified variable object @var{name}:
29920 status=@var{attr} [ ( ,@var{attr} )* ]
29924 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29926 @subheading The @code{-var-evaluate-expression} Command
29927 @findex -var-evaluate-expression
29929 @subsubheading Synopsis
29932 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29935 Evaluates the expression that is represented by the specified variable
29936 object and returns its value as a string. The format of the string
29937 can be specified with the @samp{-f} option. The possible values of
29938 this option are the same as for @code{-var-set-format}
29939 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29940 the current display format will be used. The current display format
29941 can be changed using the @code{-var-set-format} command.
29947 Note that one must invoke @code{-var-list-children} for a variable
29948 before the value of a child variable can be evaluated.
29950 @subheading The @code{-var-assign} Command
29951 @findex -var-assign
29953 @subsubheading Synopsis
29956 -var-assign @var{name} @var{expression}
29959 Assigns the value of @var{expression} to the variable object specified
29960 by @var{name}. The object must be @samp{editable}. If the variable's
29961 value is altered by the assign, the variable will show up in any
29962 subsequent @code{-var-update} list.
29964 @subsubheading Example
29972 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29976 @subheading The @code{-var-update} Command
29977 @findex -var-update
29979 @subsubheading Synopsis
29982 -var-update [@var{print-values}] @{@var{name} | "*"@}
29985 Reevaluate the expressions corresponding to the variable object
29986 @var{name} and all its direct and indirect children, and return the
29987 list of variable objects whose values have changed; @var{name} must
29988 be a root variable object. Here, ``changed'' means that the result of
29989 @code{-var-evaluate-expression} before and after the
29990 @code{-var-update} is different. If @samp{*} is used as the variable
29991 object names, all existing variable objects are updated, except
29992 for frozen ones (@pxref{-var-set-frozen}). The option
29993 @var{print-values} determines whether both names and values, or just
29994 names are printed. The possible values of this option are the same
29995 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29996 recommended to use the @samp{--all-values} option, to reduce the
29997 number of MI commands needed on each program stop.
29999 With the @samp{*} parameter, if a variable object is bound to a
30000 currently running thread, it will not be updated, without any
30003 If @code{-var-set-update-range} was previously used on a varobj, then
30004 only the selected range of children will be reported.
30006 @code{-var-update} reports all the changed varobjs in a tuple named
30009 Each item in the change list is itself a tuple holding:
30013 The name of the varobj.
30016 If values were requested for this update, then this field will be
30017 present and will hold the value of the varobj.
30020 @anchor{-var-update}
30021 This field is a string which may take one of three values:
30025 The variable object's current value is valid.
30028 The variable object does not currently hold a valid value but it may
30029 hold one in the future if its associated expression comes back into
30033 The variable object no longer holds a valid value.
30034 This can occur when the executable file being debugged has changed,
30035 either through recompilation or by using the @value{GDBN} @code{file}
30036 command. The front end should normally choose to delete these variable
30040 In the future new values may be added to this list so the front should
30041 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30044 This is only present if the varobj is still valid. If the type
30045 changed, then this will be the string @samp{true}; otherwise it will
30048 When a varobj's type changes, its children are also likely to have
30049 become incorrect. Therefore, the varobj's children are automatically
30050 deleted when this attribute is @samp{true}. Also, the varobj's update
30051 range, when set using the @code{-var-set-update-range} command, is
30055 If the varobj's type changed, then this field will be present and will
30058 @item new_num_children
30059 For a dynamic varobj, if the number of children changed, or if the
30060 type changed, this will be the new number of children.
30062 The @samp{numchild} field in other varobj responses is generally not
30063 valid for a dynamic varobj -- it will show the number of children that
30064 @value{GDBN} knows about, but because dynamic varobjs lazily
30065 instantiate their children, this will not reflect the number of
30066 children which may be available.
30068 The @samp{new_num_children} attribute only reports changes to the
30069 number of children known by @value{GDBN}. This is the only way to
30070 detect whether an update has removed children (which necessarily can
30071 only happen at the end of the update range).
30074 The display hint, if any.
30077 This is an integer value, which will be 1 if there are more children
30078 available outside the varobj's update range.
30081 This attribute will be present and have the value @samp{1} if the
30082 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30083 then this attribute will not be present.
30086 If new children were added to a dynamic varobj within the selected
30087 update range (as set by @code{-var-set-update-range}), then they will
30088 be listed in this attribute.
30091 @subsubheading Example
30098 -var-update --all-values var1
30099 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30100 type_changed="false"@}]
30104 @subheading The @code{-var-set-frozen} Command
30105 @findex -var-set-frozen
30106 @anchor{-var-set-frozen}
30108 @subsubheading Synopsis
30111 -var-set-frozen @var{name} @var{flag}
30114 Set the frozenness flag on the variable object @var{name}. The
30115 @var{flag} parameter should be either @samp{1} to make the variable
30116 frozen or @samp{0} to make it unfrozen. If a variable object is
30117 frozen, then neither itself, nor any of its children, are
30118 implicitly updated by @code{-var-update} of
30119 a parent variable or by @code{-var-update *}. Only
30120 @code{-var-update} of the variable itself will update its value and
30121 values of its children. After a variable object is unfrozen, it is
30122 implicitly updated by all subsequent @code{-var-update} operations.
30123 Unfreezing a variable does not update it, only subsequent
30124 @code{-var-update} does.
30126 @subsubheading Example
30130 -var-set-frozen V 1
30135 @subheading The @code{-var-set-update-range} command
30136 @findex -var-set-update-range
30137 @anchor{-var-set-update-range}
30139 @subsubheading Synopsis
30142 -var-set-update-range @var{name} @var{from} @var{to}
30145 Set the range of children to be returned by future invocations of
30146 @code{-var-update}.
30148 @var{from} and @var{to} indicate the range of children to report. If
30149 @var{from} or @var{to} is less than zero, the range is reset and all
30150 children will be reported. Otherwise, children starting at @var{from}
30151 (zero-based) and up to and excluding @var{to} will be reported.
30153 @subsubheading Example
30157 -var-set-update-range V 1 2
30161 @subheading The @code{-var-set-visualizer} command
30162 @findex -var-set-visualizer
30163 @anchor{-var-set-visualizer}
30165 @subsubheading Synopsis
30168 -var-set-visualizer @var{name} @var{visualizer}
30171 Set a visualizer for the variable object @var{name}.
30173 @var{visualizer} is the visualizer to use. The special value
30174 @samp{None} means to disable any visualizer in use.
30176 If not @samp{None}, @var{visualizer} must be a Python expression.
30177 This expression must evaluate to a callable object which accepts a
30178 single argument. @value{GDBN} will call this object with the value of
30179 the varobj @var{name} as an argument (this is done so that the same
30180 Python pretty-printing code can be used for both the CLI and MI).
30181 When called, this object must return an object which conforms to the
30182 pretty-printing interface (@pxref{Pretty Printing API}).
30184 The pre-defined function @code{gdb.default_visualizer} may be used to
30185 select a visualizer by following the built-in process
30186 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30187 a varobj is created, and so ordinarily is not needed.
30189 This feature is only available if Python support is enabled. The MI
30190 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30191 can be used to check this.
30193 @subsubheading Example
30195 Resetting the visualizer:
30199 -var-set-visualizer V None
30203 Reselecting the default (type-based) visualizer:
30207 -var-set-visualizer V gdb.default_visualizer
30211 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30212 can be used to instantiate this class for a varobj:
30216 -var-set-visualizer V "lambda val: SomeClass()"
30220 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30221 @node GDB/MI Data Manipulation
30222 @section @sc{gdb/mi} Data Manipulation
30224 @cindex data manipulation, in @sc{gdb/mi}
30225 @cindex @sc{gdb/mi}, data manipulation
30226 This section describes the @sc{gdb/mi} commands that manipulate data:
30227 examine memory and registers, evaluate expressions, etc.
30229 For details about what an addressable memory unit is,
30230 @pxref{addressable memory unit}.
30232 @c REMOVED FROM THE INTERFACE.
30233 @c @subheading -data-assign
30234 @c Change the value of a program variable. Plenty of side effects.
30235 @c @subsubheading GDB Command
30237 @c @subsubheading Example
30240 @subheading The @code{-data-disassemble} Command
30241 @findex -data-disassemble
30243 @subsubheading Synopsis
30247 [ -s @var{start-addr} -e @var{end-addr} ]
30248 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30256 @item @var{start-addr}
30257 is the beginning address (or @code{$pc})
30258 @item @var{end-addr}
30260 @item @var{filename}
30261 is the name of the file to disassemble
30262 @item @var{linenum}
30263 is the line number to disassemble around
30265 is the number of disassembly lines to be produced. If it is -1,
30266 the whole function will be disassembled, in case no @var{end-addr} is
30267 specified. If @var{end-addr} is specified as a non-zero value, and
30268 @var{lines} is lower than the number of disassembly lines between
30269 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30270 displayed; if @var{lines} is higher than the number of lines between
30271 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30276 @item 0 disassembly only
30277 @item 1 mixed source and disassembly (deprecated)
30278 @item 2 disassembly with raw opcodes
30279 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30280 @item 4 mixed source and disassembly
30281 @item 5 mixed source and disassembly with raw opcodes
30284 Modes 1 and 3 are deprecated. The output is ``source centric''
30285 which hasn't proved useful in practice.
30286 @xref{Machine Code}, for a discussion of the difference between
30287 @code{/m} and @code{/s} output of the @code{disassemble} command.
30290 @subsubheading Result
30292 The result of the @code{-data-disassemble} command will be a list named
30293 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30294 used with the @code{-data-disassemble} command.
30296 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30301 The address at which this instruction was disassembled.
30304 The name of the function this instruction is within.
30307 The decimal offset in bytes from the start of @samp{func-name}.
30310 The text disassembly for this @samp{address}.
30313 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30314 bytes for the @samp{inst} field.
30318 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30319 @samp{src_and_asm_line}, each of which has the following fields:
30323 The line number within @samp{file}.
30326 The file name from the compilation unit. This might be an absolute
30327 file name or a relative file name depending on the compile command
30331 Absolute file name of @samp{file}. It is converted to a canonical form
30332 using the source file search path
30333 (@pxref{Source Path, ,Specifying Source Directories})
30334 and after resolving all the symbolic links.
30336 If the source file is not found this field will contain the path as
30337 present in the debug information.
30339 @item line_asm_insn
30340 This is a list of tuples containing the disassembly for @samp{line} in
30341 @samp{file}. The fields of each tuple are the same as for
30342 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30343 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30348 Note that whatever included in the @samp{inst} field, is not
30349 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30352 @subsubheading @value{GDBN} Command
30354 The corresponding @value{GDBN} command is @samp{disassemble}.
30356 @subsubheading Example
30358 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30362 -data-disassemble -s $pc -e "$pc + 20" -- 0
30365 @{address="0x000107c0",func-name="main",offset="4",
30366 inst="mov 2, %o0"@},
30367 @{address="0x000107c4",func-name="main",offset="8",
30368 inst="sethi %hi(0x11800), %o2"@},
30369 @{address="0x000107c8",func-name="main",offset="12",
30370 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30371 @{address="0x000107cc",func-name="main",offset="16",
30372 inst="sethi %hi(0x11800), %o2"@},
30373 @{address="0x000107d0",func-name="main",offset="20",
30374 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30378 Disassemble the whole @code{main} function. Line 32 is part of
30382 -data-disassemble -f basics.c -l 32 -- 0
30384 @{address="0x000107bc",func-name="main",offset="0",
30385 inst="save %sp, -112, %sp"@},
30386 @{address="0x000107c0",func-name="main",offset="4",
30387 inst="mov 2, %o0"@},
30388 @{address="0x000107c4",func-name="main",offset="8",
30389 inst="sethi %hi(0x11800), %o2"@},
30391 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30392 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30396 Disassemble 3 instructions from the start of @code{main}:
30400 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30402 @{address="0x000107bc",func-name="main",offset="0",
30403 inst="save %sp, -112, %sp"@},
30404 @{address="0x000107c0",func-name="main",offset="4",
30405 inst="mov 2, %o0"@},
30406 @{address="0x000107c4",func-name="main",offset="8",
30407 inst="sethi %hi(0x11800), %o2"@}]
30411 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30415 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30417 src_and_asm_line=@{line="31",
30418 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30419 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30420 line_asm_insn=[@{address="0x000107bc",
30421 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30422 src_and_asm_line=@{line="32",
30423 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30424 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30425 line_asm_insn=[@{address="0x000107c0",
30426 func-name="main",offset="4",inst="mov 2, %o0"@},
30427 @{address="0x000107c4",func-name="main",offset="8",
30428 inst="sethi %hi(0x11800), %o2"@}]@}]
30433 @subheading The @code{-data-evaluate-expression} Command
30434 @findex -data-evaluate-expression
30436 @subsubheading Synopsis
30439 -data-evaluate-expression @var{expr}
30442 Evaluate @var{expr} as an expression. The expression could contain an
30443 inferior function call. The function call will execute synchronously.
30444 If the expression contains spaces, it must be enclosed in double quotes.
30446 @subsubheading @value{GDBN} Command
30448 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30449 @samp{call}. In @code{gdbtk} only, there's a corresponding
30450 @samp{gdb_eval} command.
30452 @subsubheading Example
30454 In the following example, the numbers that precede the commands are the
30455 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30456 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30460 211-data-evaluate-expression A
30463 311-data-evaluate-expression &A
30464 311^done,value="0xefffeb7c"
30466 411-data-evaluate-expression A+3
30469 511-data-evaluate-expression "A + 3"
30475 @subheading The @code{-data-list-changed-registers} Command
30476 @findex -data-list-changed-registers
30478 @subsubheading Synopsis
30481 -data-list-changed-registers
30484 Display a list of the registers that have changed.
30486 @subsubheading @value{GDBN} Command
30488 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30489 has the corresponding command @samp{gdb_changed_register_list}.
30491 @subsubheading Example
30493 On a PPC MBX board:
30501 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30502 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30505 -data-list-changed-registers
30506 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30507 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30508 "24","25","26","27","28","30","31","64","65","66","67","69"]
30513 @subheading The @code{-data-list-register-names} Command
30514 @findex -data-list-register-names
30516 @subsubheading Synopsis
30519 -data-list-register-names [ ( @var{regno} )+ ]
30522 Show a list of register names for the current target. If no arguments
30523 are given, it shows a list of the names of all the registers. If
30524 integer numbers are given as arguments, it will print a list of the
30525 names of the registers corresponding to the arguments. To ensure
30526 consistency between a register name and its number, the output list may
30527 include empty register names.
30529 @subsubheading @value{GDBN} Command
30531 @value{GDBN} does not have a command which corresponds to
30532 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30533 corresponding command @samp{gdb_regnames}.
30535 @subsubheading Example
30537 For the PPC MBX board:
30540 -data-list-register-names
30541 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30542 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30543 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30544 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30545 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30546 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30547 "", "pc","ps","cr","lr","ctr","xer"]
30549 -data-list-register-names 1 2 3
30550 ^done,register-names=["r1","r2","r3"]
30554 @subheading The @code{-data-list-register-values} Command
30555 @findex -data-list-register-values
30557 @subsubheading Synopsis
30560 -data-list-register-values
30561 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30564 Display the registers' contents. The format according to which the
30565 registers' contents are to be returned is given by @var{fmt}, followed
30566 by an optional list of numbers specifying the registers to display. A
30567 missing list of numbers indicates that the contents of all the
30568 registers must be returned. The @code{--skip-unavailable} option
30569 indicates that only the available registers are to be returned.
30571 Allowed formats for @var{fmt} are:
30588 @subsubheading @value{GDBN} Command
30590 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30591 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30593 @subsubheading Example
30595 For a PPC MBX board (note: line breaks are for readability only, they
30596 don't appear in the actual output):
30600 -data-list-register-values r 64 65
30601 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30602 @{number="65",value="0x00029002"@}]
30604 -data-list-register-values x
30605 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30606 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30607 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30608 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30609 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30610 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30611 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30612 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30613 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30614 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30615 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30616 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30617 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30618 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30619 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30620 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30621 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30622 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30623 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30624 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30625 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30626 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30627 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30628 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30629 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30630 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30631 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30632 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30633 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30634 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30635 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30636 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30637 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30638 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30639 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30640 @{number="69",value="0x20002b03"@}]
30645 @subheading The @code{-data-read-memory} Command
30646 @findex -data-read-memory
30648 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30650 @subsubheading Synopsis
30653 -data-read-memory [ -o @var{byte-offset} ]
30654 @var{address} @var{word-format} @var{word-size}
30655 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30662 @item @var{address}
30663 An expression specifying the address of the first memory word to be
30664 read. Complex expressions containing embedded white space should be
30665 quoted using the C convention.
30667 @item @var{word-format}
30668 The format to be used to print the memory words. The notation is the
30669 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30672 @item @var{word-size}
30673 The size of each memory word in bytes.
30675 @item @var{nr-rows}
30676 The number of rows in the output table.
30678 @item @var{nr-cols}
30679 The number of columns in the output table.
30682 If present, indicates that each row should include an @sc{ascii} dump. The
30683 value of @var{aschar} is used as a padding character when a byte is not a
30684 member of the printable @sc{ascii} character set (printable @sc{ascii}
30685 characters are those whose code is between 32 and 126, inclusively).
30687 @item @var{byte-offset}
30688 An offset to add to the @var{address} before fetching memory.
30691 This command displays memory contents as a table of @var{nr-rows} by
30692 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30693 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30694 (returned as @samp{total-bytes}). Should less than the requested number
30695 of bytes be returned by the target, the missing words are identified
30696 using @samp{N/A}. The number of bytes read from the target is returned
30697 in @samp{nr-bytes} and the starting address used to read memory in
30700 The address of the next/previous row or page is available in
30701 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30704 @subsubheading @value{GDBN} Command
30706 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30707 @samp{gdb_get_mem} memory read command.
30709 @subsubheading Example
30711 Read six bytes of memory starting at @code{bytes+6} but then offset by
30712 @code{-6} bytes. Format as three rows of two columns. One byte per
30713 word. Display each word in hex.
30717 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30718 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30719 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30720 prev-page="0x0000138a",memory=[
30721 @{addr="0x00001390",data=["0x00","0x01"]@},
30722 @{addr="0x00001392",data=["0x02","0x03"]@},
30723 @{addr="0x00001394",data=["0x04","0x05"]@}]
30727 Read two bytes of memory starting at address @code{shorts + 64} and
30728 display as a single word formatted in decimal.
30732 5-data-read-memory shorts+64 d 2 1 1
30733 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30734 next-row="0x00001512",prev-row="0x0000150e",
30735 next-page="0x00001512",prev-page="0x0000150e",memory=[
30736 @{addr="0x00001510",data=["128"]@}]
30740 Read thirty two bytes of memory starting at @code{bytes+16} and format
30741 as eight rows of four columns. Include a string encoding with @samp{x}
30742 used as the non-printable character.
30746 4-data-read-memory bytes+16 x 1 8 4 x
30747 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30748 next-row="0x000013c0",prev-row="0x0000139c",
30749 next-page="0x000013c0",prev-page="0x00001380",memory=[
30750 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30751 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30752 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30753 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30754 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30755 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30756 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30757 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30761 @subheading The @code{-data-read-memory-bytes} Command
30762 @findex -data-read-memory-bytes
30764 @subsubheading Synopsis
30767 -data-read-memory-bytes [ -o @var{offset} ]
30768 @var{address} @var{count}
30775 @item @var{address}
30776 An expression specifying the address of the first addressable memory unit
30777 to be read. Complex expressions containing embedded white space should be
30778 quoted using the C convention.
30781 The number of addressable memory units to read. This should be an integer
30785 The offset relative to @var{address} at which to start reading. This
30786 should be an integer literal. This option is provided so that a frontend
30787 is not required to first evaluate address and then perform address
30788 arithmetics itself.
30792 This command attempts to read all accessible memory regions in the
30793 specified range. First, all regions marked as unreadable in the memory
30794 map (if one is defined) will be skipped. @xref{Memory Region
30795 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30796 regions. For each one, if reading full region results in an errors,
30797 @value{GDBN} will try to read a subset of the region.
30799 In general, every single memory unit in the region may be readable or not,
30800 and the only way to read every readable unit is to try a read at
30801 every address, which is not practical. Therefore, @value{GDBN} will
30802 attempt to read all accessible memory units at either beginning or the end
30803 of the region, using a binary division scheme. This heuristic works
30804 well for reading accross a memory map boundary. Note that if a region
30805 has a readable range that is neither at the beginning or the end,
30806 @value{GDBN} will not read it.
30808 The result record (@pxref{GDB/MI Result Records}) that is output of
30809 the command includes a field named @samp{memory} whose content is a
30810 list of tuples. Each tuple represent a successfully read memory block
30811 and has the following fields:
30815 The start address of the memory block, as hexadecimal literal.
30818 The end address of the memory block, as hexadecimal literal.
30821 The offset of the memory block, as hexadecimal literal, relative to
30822 the start address passed to @code{-data-read-memory-bytes}.
30825 The contents of the memory block, in hex.
30831 @subsubheading @value{GDBN} Command
30833 The corresponding @value{GDBN} command is @samp{x}.
30835 @subsubheading Example
30839 -data-read-memory-bytes &a 10
30840 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30842 contents="01000000020000000300"@}]
30847 @subheading The @code{-data-write-memory-bytes} Command
30848 @findex -data-write-memory-bytes
30850 @subsubheading Synopsis
30853 -data-write-memory-bytes @var{address} @var{contents}
30854 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30861 @item @var{address}
30862 An expression specifying the address of the first addressable memory unit
30863 to be written. Complex expressions containing embedded white space should
30864 be quoted using the C convention.
30866 @item @var{contents}
30867 The hex-encoded data to write. It is an error if @var{contents} does
30868 not represent an integral number of addressable memory units.
30871 Optional argument indicating the number of addressable memory units to be
30872 written. If @var{count} is greater than @var{contents}' length,
30873 @value{GDBN} will repeatedly write @var{contents} until it fills
30874 @var{count} memory units.
30878 @subsubheading @value{GDBN} Command
30880 There's no corresponding @value{GDBN} command.
30882 @subsubheading Example
30886 -data-write-memory-bytes &a "aabbccdd"
30893 -data-write-memory-bytes &a "aabbccdd" 16e
30898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30899 @node GDB/MI Tracepoint Commands
30900 @section @sc{gdb/mi} Tracepoint Commands
30902 The commands defined in this section implement MI support for
30903 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30905 @subheading The @code{-trace-find} Command
30906 @findex -trace-find
30908 @subsubheading Synopsis
30911 -trace-find @var{mode} [@var{parameters}@dots{}]
30914 Find a trace frame using criteria defined by @var{mode} and
30915 @var{parameters}. The following table lists permissible
30916 modes and their parameters. For details of operation, see @ref{tfind}.
30921 No parameters are required. Stops examining trace frames.
30924 An integer is required as parameter. Selects tracepoint frame with
30927 @item tracepoint-number
30928 An integer is required as parameter. Finds next
30929 trace frame that corresponds to tracepoint with the specified number.
30932 An address is required as parameter. Finds
30933 next trace frame that corresponds to any tracepoint at the specified
30936 @item pc-inside-range
30937 Two addresses are required as parameters. Finds next trace
30938 frame that corresponds to a tracepoint at an address inside the
30939 specified range. Both bounds are considered to be inside the range.
30941 @item pc-outside-range
30942 Two addresses are required as parameters. Finds
30943 next trace frame that corresponds to a tracepoint at an address outside
30944 the specified range. Both bounds are considered to be inside the range.
30947 Line specification is required as parameter. @xref{Specify Location}.
30948 Finds next trace frame that corresponds to a tracepoint at
30949 the specified location.
30953 If @samp{none} was passed as @var{mode}, the response does not
30954 have fields. Otherwise, the response may have the following fields:
30958 This field has either @samp{0} or @samp{1} as the value, depending
30959 on whether a matching tracepoint was found.
30962 The index of the found traceframe. This field is present iff
30963 the @samp{found} field has value of @samp{1}.
30966 The index of the found tracepoint. This field is present iff
30967 the @samp{found} field has value of @samp{1}.
30970 The information about the frame corresponding to the found trace
30971 frame. This field is present only if a trace frame was found.
30972 @xref{GDB/MI Frame Information}, for description of this field.
30976 @subsubheading @value{GDBN} Command
30978 The corresponding @value{GDBN} command is @samp{tfind}.
30980 @subheading -trace-define-variable
30981 @findex -trace-define-variable
30983 @subsubheading Synopsis
30986 -trace-define-variable @var{name} [ @var{value} ]
30989 Create trace variable @var{name} if it does not exist. If
30990 @var{value} is specified, sets the initial value of the specified
30991 trace variable to that value. Note that the @var{name} should start
30992 with the @samp{$} character.
30994 @subsubheading @value{GDBN} Command
30996 The corresponding @value{GDBN} command is @samp{tvariable}.
30998 @subheading The @code{-trace-frame-collected} Command
30999 @findex -trace-frame-collected
31001 @subsubheading Synopsis
31004 -trace-frame-collected
31005 [--var-print-values @var{var_pval}]
31006 [--comp-print-values @var{comp_pval}]
31007 [--registers-format @var{regformat}]
31008 [--memory-contents]
31011 This command returns the set of collected objects, register names,
31012 trace state variable names, memory ranges and computed expressions
31013 that have been collected at a particular trace frame. The optional
31014 parameters to the command affect the output format in different ways.
31015 See the output description table below for more details.
31017 The reported names can be used in the normal manner to create
31018 varobjs and inspect the objects themselves. The items returned by
31019 this command are categorized so that it is clear which is a variable,
31020 which is a register, which is a trace state variable, which is a
31021 memory range and which is a computed expression.
31023 For instance, if the actions were
31025 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31026 collect *(int*)0xaf02bef0@@40
31030 the object collected in its entirety would be @code{myVar}. The
31031 object @code{myArray} would be partially collected, because only the
31032 element at index @code{myIndex} would be collected. The remaining
31033 objects would be computed expressions.
31035 An example output would be:
31039 -trace-frame-collected
31041 explicit-variables=[@{name="myVar",value="1"@}],
31042 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31043 @{name="myObj.field",value="0"@},
31044 @{name="myPtr->field",value="1"@},
31045 @{name="myCount + 2",value="3"@},
31046 @{name="$tvar1 + 1",value="43970027"@}],
31047 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31048 @{number="1",value="0x0"@},
31049 @{number="2",value="0x4"@},
31051 @{number="125",value="0x0"@}],
31052 tvars=[@{name="$tvar1",current="43970026"@}],
31053 memory=[@{address="0x0000000000602264",length="4"@},
31054 @{address="0x0000000000615bc0",length="4"@}]
31061 @item explicit-variables
31062 The set of objects that have been collected in their entirety (as
31063 opposed to collecting just a few elements of an array or a few struct
31064 members). For each object, its name and value are printed.
31065 The @code{--var-print-values} option affects how or whether the value
31066 field is output. If @var{var_pval} is 0, then print only the names;
31067 if it is 1, print also their values; and if it is 2, print the name,
31068 type and value for simple data types, and the name and type for
31069 arrays, structures and unions.
31071 @item computed-expressions
31072 The set of computed expressions that have been collected at the
31073 current trace frame. The @code{--comp-print-values} option affects
31074 this set like the @code{--var-print-values} option affects the
31075 @code{explicit-variables} set. See above.
31078 The registers that have been collected at the current trace frame.
31079 For each register collected, the name and current value are returned.
31080 The value is formatted according to the @code{--registers-format}
31081 option. See the @command{-data-list-register-values} command for a
31082 list of the allowed formats. The default is @samp{x}.
31085 The trace state variables that have been collected at the current
31086 trace frame. For each trace state variable collected, the name and
31087 current value are returned.
31090 The set of memory ranges that have been collected at the current trace
31091 frame. Its content is a list of tuples. Each tuple represents a
31092 collected memory range and has the following fields:
31096 The start address of the memory range, as hexadecimal literal.
31099 The length of the memory range, as decimal literal.
31102 The contents of the memory block, in hex. This field is only present
31103 if the @code{--memory-contents} option is specified.
31109 @subsubheading @value{GDBN} Command
31111 There is no corresponding @value{GDBN} command.
31113 @subsubheading Example
31115 @subheading -trace-list-variables
31116 @findex -trace-list-variables
31118 @subsubheading Synopsis
31121 -trace-list-variables
31124 Return a table of all defined trace variables. Each element of the
31125 table has the following fields:
31129 The name of the trace variable. This field is always present.
31132 The initial value. This is a 64-bit signed integer. This
31133 field is always present.
31136 The value the trace variable has at the moment. This is a 64-bit
31137 signed integer. This field is absent iff current value is
31138 not defined, for example if the trace was never run, or is
31143 @subsubheading @value{GDBN} Command
31145 The corresponding @value{GDBN} command is @samp{tvariables}.
31147 @subsubheading Example
31151 -trace-list-variables
31152 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31153 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31154 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31155 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31156 body=[variable=@{name="$trace_timestamp",initial="0"@}
31157 variable=@{name="$foo",initial="10",current="15"@}]@}
31161 @subheading -trace-save
31162 @findex -trace-save
31164 @subsubheading Synopsis
31167 -trace-save [ -r ] [ -ctf ] @var{filename}
31170 Saves the collected trace data to @var{filename}. Without the
31171 @samp{-r} option, the data is downloaded from the target and saved
31172 in a local file. With the @samp{-r} option the target is asked
31173 to perform the save.
31175 By default, this command will save the trace in the tfile format. You can
31176 supply the optional @samp{-ctf} argument to save it the CTF format. See
31177 @ref{Trace Files} for more information about CTF.
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{tsave}.
31184 @subheading -trace-start
31185 @findex -trace-start
31187 @subsubheading Synopsis
31193 Starts a tracing experiment. The result of this command does not
31196 @subsubheading @value{GDBN} Command
31198 The corresponding @value{GDBN} command is @samp{tstart}.
31200 @subheading -trace-status
31201 @findex -trace-status
31203 @subsubheading Synopsis
31209 Obtains the status of a tracing experiment. The result may include
31210 the following fields:
31215 May have a value of either @samp{0}, when no tracing operations are
31216 supported, @samp{1}, when all tracing operations are supported, or
31217 @samp{file} when examining trace file. In the latter case, examining
31218 of trace frame is possible but new tracing experiement cannot be
31219 started. This field is always present.
31222 May have a value of either @samp{0} or @samp{1} depending on whether
31223 tracing experiement is in progress on target. This field is present
31224 if @samp{supported} field is not @samp{0}.
31227 Report the reason why the tracing was stopped last time. This field
31228 may be absent iff tracing was never stopped on target yet. The
31229 value of @samp{request} means the tracing was stopped as result of
31230 the @code{-trace-stop} command. The value of @samp{overflow} means
31231 the tracing buffer is full. The value of @samp{disconnection} means
31232 tracing was automatically stopped when @value{GDBN} has disconnected.
31233 The value of @samp{passcount} means tracing was stopped when a
31234 tracepoint was passed a maximal number of times for that tracepoint.
31235 This field is present if @samp{supported} field is not @samp{0}.
31237 @item stopping-tracepoint
31238 The number of tracepoint whose passcount as exceeded. This field is
31239 present iff the @samp{stop-reason} field has the value of
31243 @itemx frames-created
31244 The @samp{frames} field is a count of the total number of trace frames
31245 in the trace buffer, while @samp{frames-created} is the total created
31246 during the run, including ones that were discarded, such as when a
31247 circular trace buffer filled up. Both fields are optional.
31251 These fields tell the current size of the tracing buffer and the
31252 remaining space. These fields are optional.
31255 The value of the circular trace buffer flag. @code{1} means that the
31256 trace buffer is circular and old trace frames will be discarded if
31257 necessary to make room, @code{0} means that the trace buffer is linear
31261 The value of the disconnected tracing flag. @code{1} means that
31262 tracing will continue after @value{GDBN} disconnects, @code{0} means
31263 that the trace run will stop.
31266 The filename of the trace file being examined. This field is
31267 optional, and only present when examining a trace file.
31271 @subsubheading @value{GDBN} Command
31273 The corresponding @value{GDBN} command is @samp{tstatus}.
31275 @subheading -trace-stop
31276 @findex -trace-stop
31278 @subsubheading Synopsis
31284 Stops a tracing experiment. The result of this command has the same
31285 fields as @code{-trace-status}, except that the @samp{supported} and
31286 @samp{running} fields are not output.
31288 @subsubheading @value{GDBN} Command
31290 The corresponding @value{GDBN} command is @samp{tstop}.
31293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31294 @node GDB/MI Symbol Query
31295 @section @sc{gdb/mi} Symbol Query Commands
31299 @subheading The @code{-symbol-info-address} Command
31300 @findex -symbol-info-address
31302 @subsubheading Synopsis
31305 -symbol-info-address @var{symbol}
31308 Describe where @var{symbol} is stored.
31310 @subsubheading @value{GDBN} Command
31312 The corresponding @value{GDBN} command is @samp{info address}.
31314 @subsubheading Example
31318 @subheading The @code{-symbol-info-file} Command
31319 @findex -symbol-info-file
31321 @subsubheading Synopsis
31327 Show the file for the symbol.
31329 @subsubheading @value{GDBN} Command
31331 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31332 @samp{gdb_find_file}.
31334 @subsubheading Example
31338 @subheading The @code{-symbol-info-function} Command
31339 @findex -symbol-info-function
31341 @subsubheading Synopsis
31344 -symbol-info-function
31347 Show which function the symbol lives in.
31349 @subsubheading @value{GDBN} Command
31351 @samp{gdb_get_function} in @code{gdbtk}.
31353 @subsubheading Example
31357 @subheading The @code{-symbol-info-line} Command
31358 @findex -symbol-info-line
31360 @subsubheading Synopsis
31366 Show the core addresses of the code for a source line.
31368 @subsubheading @value{GDBN} Command
31370 The corresponding @value{GDBN} command is @samp{info line}.
31371 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31373 @subsubheading Example
31377 @subheading The @code{-symbol-info-symbol} Command
31378 @findex -symbol-info-symbol
31380 @subsubheading Synopsis
31383 -symbol-info-symbol @var{addr}
31386 Describe what symbol is at location @var{addr}.
31388 @subsubheading @value{GDBN} Command
31390 The corresponding @value{GDBN} command is @samp{info symbol}.
31392 @subsubheading Example
31396 @subheading The @code{-symbol-list-functions} Command
31397 @findex -symbol-list-functions
31399 @subsubheading Synopsis
31402 -symbol-list-functions
31405 List the functions in the executable.
31407 @subsubheading @value{GDBN} Command
31409 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31410 @samp{gdb_search} in @code{gdbtk}.
31412 @subsubheading Example
31417 @subheading The @code{-symbol-list-lines} Command
31418 @findex -symbol-list-lines
31420 @subsubheading Synopsis
31423 -symbol-list-lines @var{filename}
31426 Print the list of lines that contain code and their associated program
31427 addresses for the given source filename. The entries are sorted in
31428 ascending PC order.
31430 @subsubheading @value{GDBN} Command
31432 There is no corresponding @value{GDBN} command.
31434 @subsubheading Example
31437 -symbol-list-lines basics.c
31438 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31444 @subheading The @code{-symbol-list-types} Command
31445 @findex -symbol-list-types
31447 @subsubheading Synopsis
31453 List all the type names.
31455 @subsubheading @value{GDBN} Command
31457 The corresponding commands are @samp{info types} in @value{GDBN},
31458 @samp{gdb_search} in @code{gdbtk}.
31460 @subsubheading Example
31464 @subheading The @code{-symbol-list-variables} Command
31465 @findex -symbol-list-variables
31467 @subsubheading Synopsis
31470 -symbol-list-variables
31473 List all the global and static variable names.
31475 @subsubheading @value{GDBN} Command
31477 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31479 @subsubheading Example
31483 @subheading The @code{-symbol-locate} Command
31484 @findex -symbol-locate
31486 @subsubheading Synopsis
31492 @subsubheading @value{GDBN} Command
31494 @samp{gdb_loc} in @code{gdbtk}.
31496 @subsubheading Example
31500 @subheading The @code{-symbol-type} Command
31501 @findex -symbol-type
31503 @subsubheading Synopsis
31506 -symbol-type @var{variable}
31509 Show type of @var{variable}.
31511 @subsubheading @value{GDBN} Command
31513 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31514 @samp{gdb_obj_variable}.
31516 @subsubheading Example
31521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31522 @node GDB/MI File Commands
31523 @section @sc{gdb/mi} File Commands
31525 This section describes the GDB/MI commands to specify executable file names
31526 and to read in and obtain symbol table information.
31528 @subheading The @code{-file-exec-and-symbols} Command
31529 @findex -file-exec-and-symbols
31531 @subsubheading Synopsis
31534 -file-exec-and-symbols @var{file}
31537 Specify the executable file to be debugged. This file is the one from
31538 which the symbol table is also read. If no file is specified, the
31539 command clears the executable and symbol information. If breakpoints
31540 are set when using this command with no arguments, @value{GDBN} will produce
31541 error messages. Otherwise, no output is produced, except a completion
31544 @subsubheading @value{GDBN} Command
31546 The corresponding @value{GDBN} command is @samp{file}.
31548 @subsubheading Example
31552 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31558 @subheading The @code{-file-exec-file} Command
31559 @findex -file-exec-file
31561 @subsubheading Synopsis
31564 -file-exec-file @var{file}
31567 Specify the executable file to be debugged. Unlike
31568 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31569 from this file. If used without argument, @value{GDBN} clears the information
31570 about the executable file. No output is produced, except a completion
31573 @subsubheading @value{GDBN} Command
31575 The corresponding @value{GDBN} command is @samp{exec-file}.
31577 @subsubheading Example
31581 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31588 @subheading The @code{-file-list-exec-sections} Command
31589 @findex -file-list-exec-sections
31591 @subsubheading Synopsis
31594 -file-list-exec-sections
31597 List the sections of the current executable file.
31599 @subsubheading @value{GDBN} Command
31601 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31602 information as this command. @code{gdbtk} has a corresponding command
31603 @samp{gdb_load_info}.
31605 @subsubheading Example
31610 @subheading The @code{-file-list-exec-source-file} Command
31611 @findex -file-list-exec-source-file
31613 @subsubheading Synopsis
31616 -file-list-exec-source-file
31619 List the line number, the current source file, and the absolute path
31620 to the current source file for the current executable. The macro
31621 information field has a value of @samp{1} or @samp{0} depending on
31622 whether or not the file includes preprocessor macro information.
31624 @subsubheading @value{GDBN} Command
31626 The @value{GDBN} equivalent is @samp{info source}
31628 @subsubheading Example
31632 123-file-list-exec-source-file
31633 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31638 @subheading The @code{-file-list-exec-source-files} Command
31639 @findex -file-list-exec-source-files
31641 @subsubheading Synopsis
31644 -file-list-exec-source-files
31647 List the source files for the current executable.
31649 It will always output both the filename and fullname (absolute file
31650 name) of a source file.
31652 @subsubheading @value{GDBN} Command
31654 The @value{GDBN} equivalent is @samp{info sources}.
31655 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31657 @subsubheading Example
31660 -file-list-exec-source-files
31662 @{file=foo.c,fullname=/home/foo.c@},
31663 @{file=/home/bar.c,fullname=/home/bar.c@},
31664 @{file=gdb_could_not_find_fullpath.c@}]
31668 @subheading The @code{-file-list-shared-libraries} Command
31669 @findex -file-list-shared-libraries
31671 @subsubheading Synopsis
31674 -file-list-shared-libraries [ @var{regexp} ]
31677 List the shared libraries in the program.
31678 With a regular expression @var{regexp}, only those libraries whose
31679 names match @var{regexp} are listed.
31681 @subsubheading @value{GDBN} Command
31683 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31684 have a similar meaning to the @code{=library-loaded} notification.
31685 The @code{ranges} field specifies the multiple segments belonging to this
31686 library. Each range has the following fields:
31690 The address defining the inclusive lower bound of the segment.
31692 The address defining the exclusive upper bound of the segment.
31695 @subsubheading Example
31698 -file-list-exec-source-files
31699 ^done,shared-libraries=[
31700 @{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"@}]@},
31701 @{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"@}]@}]
31707 @subheading The @code{-file-list-symbol-files} Command
31708 @findex -file-list-symbol-files
31710 @subsubheading Synopsis
31713 -file-list-symbol-files
31718 @subsubheading @value{GDBN} Command
31720 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31722 @subsubheading Example
31727 @subheading The @code{-file-symbol-file} Command
31728 @findex -file-symbol-file
31730 @subsubheading Synopsis
31733 -file-symbol-file @var{file}
31736 Read symbol table info from the specified @var{file} argument. When
31737 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31738 produced, except for a completion notification.
31740 @subsubheading @value{GDBN} Command
31742 The corresponding @value{GDBN} command is @samp{symbol-file}.
31744 @subsubheading Example
31748 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31755 @node GDB/MI Memory Overlay Commands
31756 @section @sc{gdb/mi} Memory Overlay Commands
31758 The memory overlay commands are not implemented.
31760 @c @subheading -overlay-auto
31762 @c @subheading -overlay-list-mapping-state
31764 @c @subheading -overlay-list-overlays
31766 @c @subheading -overlay-map
31768 @c @subheading -overlay-off
31770 @c @subheading -overlay-on
31772 @c @subheading -overlay-unmap
31774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31775 @node GDB/MI Signal Handling Commands
31776 @section @sc{gdb/mi} Signal Handling Commands
31778 Signal handling commands are not implemented.
31780 @c @subheading -signal-handle
31782 @c @subheading -signal-list-handle-actions
31784 @c @subheading -signal-list-signal-types
31788 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31789 @node GDB/MI Target Manipulation
31790 @section @sc{gdb/mi} Target Manipulation Commands
31793 @subheading The @code{-target-attach} Command
31794 @findex -target-attach
31796 @subsubheading Synopsis
31799 -target-attach @var{pid} | @var{gid} | @var{file}
31802 Attach to a process @var{pid} or a file @var{file} outside of
31803 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31804 group, the id previously returned by
31805 @samp{-list-thread-groups --available} must be used.
31807 @subsubheading @value{GDBN} Command
31809 The corresponding @value{GDBN} command is @samp{attach}.
31811 @subsubheading Example
31815 =thread-created,id="1"
31816 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31822 @subheading The @code{-target-compare-sections} Command
31823 @findex -target-compare-sections
31825 @subsubheading Synopsis
31828 -target-compare-sections [ @var{section} ]
31831 Compare data of section @var{section} on target to the exec file.
31832 Without the argument, all sections are compared.
31834 @subsubheading @value{GDBN} Command
31836 The @value{GDBN} equivalent is @samp{compare-sections}.
31838 @subsubheading Example
31843 @subheading The @code{-target-detach} Command
31844 @findex -target-detach
31846 @subsubheading Synopsis
31849 -target-detach [ @var{pid} | @var{gid} ]
31852 Detach from the remote target which normally resumes its execution.
31853 If either @var{pid} or @var{gid} is specified, detaches from either
31854 the specified process, or specified thread group. There's no output.
31856 @subsubheading @value{GDBN} Command
31858 The corresponding @value{GDBN} command is @samp{detach}.
31860 @subsubheading Example
31870 @subheading The @code{-target-disconnect} Command
31871 @findex -target-disconnect
31873 @subsubheading Synopsis
31879 Disconnect from the remote target. There's no output and the target is
31880 generally not resumed.
31882 @subsubheading @value{GDBN} Command
31884 The corresponding @value{GDBN} command is @samp{disconnect}.
31886 @subsubheading Example
31896 @subheading The @code{-target-download} Command
31897 @findex -target-download
31899 @subsubheading Synopsis
31905 Loads the executable onto the remote target.
31906 It prints out an update message every half second, which includes the fields:
31910 The name of the section.
31912 The size of what has been sent so far for that section.
31914 The size of the section.
31916 The total size of what was sent so far (the current and the previous sections).
31918 The size of the overall executable to download.
31922 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31923 @sc{gdb/mi} Output Syntax}).
31925 In addition, it prints the name and size of the sections, as they are
31926 downloaded. These messages include the following fields:
31930 The name of the section.
31932 The size of the section.
31934 The size of the overall executable to download.
31938 At the end, a summary is printed.
31940 @subsubheading @value{GDBN} Command
31942 The corresponding @value{GDBN} command is @samp{load}.
31944 @subsubheading Example
31946 Note: each status message appears on a single line. Here the messages
31947 have been broken down so that they can fit onto a page.
31952 +download,@{section=".text",section-size="6668",total-size="9880"@}
31953 +download,@{section=".text",section-sent="512",section-size="6668",
31954 total-sent="512",total-size="9880"@}
31955 +download,@{section=".text",section-sent="1024",section-size="6668",
31956 total-sent="1024",total-size="9880"@}
31957 +download,@{section=".text",section-sent="1536",section-size="6668",
31958 total-sent="1536",total-size="9880"@}
31959 +download,@{section=".text",section-sent="2048",section-size="6668",
31960 total-sent="2048",total-size="9880"@}
31961 +download,@{section=".text",section-sent="2560",section-size="6668",
31962 total-sent="2560",total-size="9880"@}
31963 +download,@{section=".text",section-sent="3072",section-size="6668",
31964 total-sent="3072",total-size="9880"@}
31965 +download,@{section=".text",section-sent="3584",section-size="6668",
31966 total-sent="3584",total-size="9880"@}
31967 +download,@{section=".text",section-sent="4096",section-size="6668",
31968 total-sent="4096",total-size="9880"@}
31969 +download,@{section=".text",section-sent="4608",section-size="6668",
31970 total-sent="4608",total-size="9880"@}
31971 +download,@{section=".text",section-sent="5120",section-size="6668",
31972 total-sent="5120",total-size="9880"@}
31973 +download,@{section=".text",section-sent="5632",section-size="6668",
31974 total-sent="5632",total-size="9880"@}
31975 +download,@{section=".text",section-sent="6144",section-size="6668",
31976 total-sent="6144",total-size="9880"@}
31977 +download,@{section=".text",section-sent="6656",section-size="6668",
31978 total-sent="6656",total-size="9880"@}
31979 +download,@{section=".init",section-size="28",total-size="9880"@}
31980 +download,@{section=".fini",section-size="28",total-size="9880"@}
31981 +download,@{section=".data",section-size="3156",total-size="9880"@}
31982 +download,@{section=".data",section-sent="512",section-size="3156",
31983 total-sent="7236",total-size="9880"@}
31984 +download,@{section=".data",section-sent="1024",section-size="3156",
31985 total-sent="7748",total-size="9880"@}
31986 +download,@{section=".data",section-sent="1536",section-size="3156",
31987 total-sent="8260",total-size="9880"@}
31988 +download,@{section=".data",section-sent="2048",section-size="3156",
31989 total-sent="8772",total-size="9880"@}
31990 +download,@{section=".data",section-sent="2560",section-size="3156",
31991 total-sent="9284",total-size="9880"@}
31992 +download,@{section=".data",section-sent="3072",section-size="3156",
31993 total-sent="9796",total-size="9880"@}
31994 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32001 @subheading The @code{-target-exec-status} Command
32002 @findex -target-exec-status
32004 @subsubheading Synopsis
32007 -target-exec-status
32010 Provide information on the state of the target (whether it is running or
32011 not, for instance).
32013 @subsubheading @value{GDBN} Command
32015 There's no equivalent @value{GDBN} command.
32017 @subsubheading Example
32021 @subheading The @code{-target-list-available-targets} Command
32022 @findex -target-list-available-targets
32024 @subsubheading Synopsis
32027 -target-list-available-targets
32030 List the possible targets to connect to.
32032 @subsubheading @value{GDBN} Command
32034 The corresponding @value{GDBN} command is @samp{help target}.
32036 @subsubheading Example
32040 @subheading The @code{-target-list-current-targets} Command
32041 @findex -target-list-current-targets
32043 @subsubheading Synopsis
32046 -target-list-current-targets
32049 Describe the current target.
32051 @subsubheading @value{GDBN} Command
32053 The corresponding information is printed by @samp{info file} (among
32056 @subsubheading Example
32060 @subheading The @code{-target-list-parameters} Command
32061 @findex -target-list-parameters
32063 @subsubheading Synopsis
32066 -target-list-parameters
32072 @subsubheading @value{GDBN} Command
32076 @subsubheading Example
32079 @subheading The @code{-target-flash-erase} Command
32080 @findex -target-flash-erase
32082 @subsubheading Synopsis
32085 -target-flash-erase
32088 Erases all known flash memory regions on the target.
32090 The corresponding @value{GDBN} command is @samp{flash-erase}.
32092 The output is a list of flash regions that have been erased, with starting
32093 addresses and memory region sizes.
32097 -target-flash-erase
32098 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32102 @subheading The @code{-target-select} Command
32103 @findex -target-select
32105 @subsubheading Synopsis
32108 -target-select @var{type} @var{parameters @dots{}}
32111 Connect @value{GDBN} to the remote target. This command takes two args:
32115 The type of target, for instance @samp{remote}, etc.
32116 @item @var{parameters}
32117 Device names, host names and the like. @xref{Target Commands, ,
32118 Commands for Managing Targets}, for more details.
32121 The output is a connection notification, followed by the address at
32122 which the target program is, in the following form:
32125 ^connected,addr="@var{address}",func="@var{function name}",
32126 args=[@var{arg list}]
32129 @subsubheading @value{GDBN} Command
32131 The corresponding @value{GDBN} command is @samp{target}.
32133 @subsubheading Example
32137 -target-select remote /dev/ttya
32138 ^connected,addr="0xfe00a300",func="??",args=[]
32142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32143 @node GDB/MI File Transfer Commands
32144 @section @sc{gdb/mi} File Transfer Commands
32147 @subheading The @code{-target-file-put} Command
32148 @findex -target-file-put
32150 @subsubheading Synopsis
32153 -target-file-put @var{hostfile} @var{targetfile}
32156 Copy file @var{hostfile} from the host system (the machine running
32157 @value{GDBN}) to @var{targetfile} on the target system.
32159 @subsubheading @value{GDBN} Command
32161 The corresponding @value{GDBN} command is @samp{remote put}.
32163 @subsubheading Example
32167 -target-file-put localfile remotefile
32173 @subheading The @code{-target-file-get} Command
32174 @findex -target-file-get
32176 @subsubheading Synopsis
32179 -target-file-get @var{targetfile} @var{hostfile}
32182 Copy file @var{targetfile} from the target system to @var{hostfile}
32183 on the host system.
32185 @subsubheading @value{GDBN} Command
32187 The corresponding @value{GDBN} command is @samp{remote get}.
32189 @subsubheading Example
32193 -target-file-get remotefile localfile
32199 @subheading The @code{-target-file-delete} Command
32200 @findex -target-file-delete
32202 @subsubheading Synopsis
32205 -target-file-delete @var{targetfile}
32208 Delete @var{targetfile} from the target system.
32210 @subsubheading @value{GDBN} Command
32212 The corresponding @value{GDBN} command is @samp{remote delete}.
32214 @subsubheading Example
32218 -target-file-delete remotefile
32224 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32225 @node GDB/MI Ada Exceptions Commands
32226 @section Ada Exceptions @sc{gdb/mi} Commands
32228 @subheading The @code{-info-ada-exceptions} Command
32229 @findex -info-ada-exceptions
32231 @subsubheading Synopsis
32234 -info-ada-exceptions [ @var{regexp}]
32237 List all Ada exceptions defined within the program being debugged.
32238 With a regular expression @var{regexp}, only those exceptions whose
32239 names match @var{regexp} are listed.
32241 @subsubheading @value{GDBN} Command
32243 The corresponding @value{GDBN} command is @samp{info exceptions}.
32245 @subsubheading Result
32247 The result is a table of Ada exceptions. The following columns are
32248 defined for each exception:
32252 The name of the exception.
32255 The address of the exception.
32259 @subsubheading Example
32262 -info-ada-exceptions aint
32263 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32264 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32265 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32266 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32267 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32270 @subheading Catching Ada Exceptions
32272 The commands describing how to ask @value{GDBN} to stop when a program
32273 raises an exception are described at @ref{Ada Exception GDB/MI
32274 Catchpoint Commands}.
32277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32278 @node GDB/MI Support Commands
32279 @section @sc{gdb/mi} Support Commands
32281 Since new commands and features get regularly added to @sc{gdb/mi},
32282 some commands are available to help front-ends query the debugger
32283 about support for these capabilities. Similarly, it is also possible
32284 to query @value{GDBN} about target support of certain features.
32286 @subheading The @code{-info-gdb-mi-command} Command
32287 @cindex @code{-info-gdb-mi-command}
32288 @findex -info-gdb-mi-command
32290 @subsubheading Synopsis
32293 -info-gdb-mi-command @var{cmd_name}
32296 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32298 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32299 is technically not part of the command name (@pxref{GDB/MI Input
32300 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32301 for ease of use, this command also accepts the form with the leading
32304 @subsubheading @value{GDBN} Command
32306 There is no corresponding @value{GDBN} command.
32308 @subsubheading Result
32310 The result is a tuple. There is currently only one field:
32314 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32315 @code{"false"} otherwise.
32319 @subsubheading Example
32321 Here is an example where the @sc{gdb/mi} command does not exist:
32324 -info-gdb-mi-command unsupported-command
32325 ^done,command=@{exists="false"@}
32329 And here is an example where the @sc{gdb/mi} command is known
32333 -info-gdb-mi-command symbol-list-lines
32334 ^done,command=@{exists="true"@}
32337 @subheading The @code{-list-features} Command
32338 @findex -list-features
32339 @cindex supported @sc{gdb/mi} features, list
32341 Returns a list of particular features of the MI protocol that
32342 this version of gdb implements. A feature can be a command,
32343 or a new field in an output of some command, or even an
32344 important bugfix. While a frontend can sometimes detect presence
32345 of a feature at runtime, it is easier to perform detection at debugger
32348 The command returns a list of strings, with each string naming an
32349 available feature. Each returned string is just a name, it does not
32350 have any internal structure. The list of possible feature names
32356 (gdb) -list-features
32357 ^done,result=["feature1","feature2"]
32360 The current list of features is:
32363 @item frozen-varobjs
32364 Indicates support for the @code{-var-set-frozen} command, as well
32365 as possible presense of the @code{frozen} field in the output
32366 of @code{-varobj-create}.
32367 @item pending-breakpoints
32368 Indicates support for the @option{-f} option to the @code{-break-insert}
32371 Indicates Python scripting support, Python-based
32372 pretty-printing commands, and possible presence of the
32373 @samp{display_hint} field in the output of @code{-var-list-children}
32375 Indicates support for the @code{-thread-info} command.
32376 @item data-read-memory-bytes
32377 Indicates support for the @code{-data-read-memory-bytes} and the
32378 @code{-data-write-memory-bytes} commands.
32379 @item breakpoint-notifications
32380 Indicates that changes to breakpoints and breakpoints created via the
32381 CLI will be announced via async records.
32382 @item ada-task-info
32383 Indicates support for the @code{-ada-task-info} command.
32384 @item language-option
32385 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32386 option (@pxref{Context management}).
32387 @item info-gdb-mi-command
32388 Indicates support for the @code{-info-gdb-mi-command} command.
32389 @item undefined-command-error-code
32390 Indicates support for the "undefined-command" error code in error result
32391 records, produced when trying to execute an undefined @sc{gdb/mi} command
32392 (@pxref{GDB/MI Result Records}).
32393 @item exec-run-start-option
32394 Indicates that the @code{-exec-run} command supports the @option{--start}
32395 option (@pxref{GDB/MI Program Execution}).
32398 @subheading The @code{-list-target-features} Command
32399 @findex -list-target-features
32401 Returns a list of particular features that are supported by the
32402 target. Those features affect the permitted MI commands, but
32403 unlike the features reported by the @code{-list-features} command, the
32404 features depend on which target GDB is using at the moment. Whenever
32405 a target can change, due to commands such as @code{-target-select},
32406 @code{-target-attach} or @code{-exec-run}, the list of target features
32407 may change, and the frontend should obtain it again.
32411 (gdb) -list-target-features
32412 ^done,result=["async"]
32415 The current list of features is:
32419 Indicates that the target is capable of asynchronous command
32420 execution, which means that @value{GDBN} will accept further commands
32421 while the target is running.
32424 Indicates that the target is capable of reverse execution.
32425 @xref{Reverse Execution}, for more information.
32429 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32430 @node GDB/MI Miscellaneous Commands
32431 @section Miscellaneous @sc{gdb/mi} Commands
32433 @c @subheading -gdb-complete
32435 @subheading The @code{-gdb-exit} Command
32438 @subsubheading Synopsis
32444 Exit @value{GDBN} immediately.
32446 @subsubheading @value{GDBN} Command
32448 Approximately corresponds to @samp{quit}.
32450 @subsubheading Example
32460 @subheading The @code{-exec-abort} Command
32461 @findex -exec-abort
32463 @subsubheading Synopsis
32469 Kill the inferior running program.
32471 @subsubheading @value{GDBN} Command
32473 The corresponding @value{GDBN} command is @samp{kill}.
32475 @subsubheading Example
32480 @subheading The @code{-gdb-set} Command
32483 @subsubheading Synopsis
32489 Set an internal @value{GDBN} variable.
32490 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32492 @subsubheading @value{GDBN} Command
32494 The corresponding @value{GDBN} command is @samp{set}.
32496 @subsubheading Example
32506 @subheading The @code{-gdb-show} Command
32509 @subsubheading Synopsis
32515 Show the current value of a @value{GDBN} variable.
32517 @subsubheading @value{GDBN} Command
32519 The corresponding @value{GDBN} command is @samp{show}.
32521 @subsubheading Example
32530 @c @subheading -gdb-source
32533 @subheading The @code{-gdb-version} Command
32534 @findex -gdb-version
32536 @subsubheading Synopsis
32542 Show version information for @value{GDBN}. Used mostly in testing.
32544 @subsubheading @value{GDBN} Command
32546 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32547 default shows this information when you start an interactive session.
32549 @subsubheading Example
32551 @c This example modifies the actual output from GDB to avoid overfull
32557 ~Copyright 2000 Free Software Foundation, Inc.
32558 ~GDB is free software, covered by the GNU General Public License, and
32559 ~you are welcome to change it and/or distribute copies of it under
32560 ~ certain conditions.
32561 ~Type "show copying" to see the conditions.
32562 ~There is absolutely no warranty for GDB. Type "show warranty" for
32564 ~This GDB was configured as
32565 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32570 @subheading The @code{-list-thread-groups} Command
32571 @findex -list-thread-groups
32573 @subheading Synopsis
32576 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32579 Lists thread groups (@pxref{Thread groups}). When a single thread
32580 group is passed as the argument, lists the children of that group.
32581 When several thread group are passed, lists information about those
32582 thread groups. Without any parameters, lists information about all
32583 top-level thread groups.
32585 Normally, thread groups that are being debugged are reported.
32586 With the @samp{--available} option, @value{GDBN} reports thread groups
32587 available on the target.
32589 The output of this command may have either a @samp{threads} result or
32590 a @samp{groups} result. The @samp{thread} result has a list of tuples
32591 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32592 Information}). The @samp{groups} result has a list of tuples as value,
32593 each tuple describing a thread group. If top-level groups are
32594 requested (that is, no parameter is passed), or when several groups
32595 are passed, the output always has a @samp{groups} result. The format
32596 of the @samp{group} result is described below.
32598 To reduce the number of roundtrips it's possible to list thread groups
32599 together with their children, by passing the @samp{--recurse} option
32600 and the recursion depth. Presently, only recursion depth of 1 is
32601 permitted. If this option is present, then every reported thread group
32602 will also include its children, either as @samp{group} or
32603 @samp{threads} field.
32605 In general, any combination of option and parameters is permitted, with
32606 the following caveats:
32610 When a single thread group is passed, the output will typically
32611 be the @samp{threads} result. Because threads may not contain
32612 anything, the @samp{recurse} option will be ignored.
32615 When the @samp{--available} option is passed, limited information may
32616 be available. In particular, the list of threads of a process might
32617 be inaccessible. Further, specifying specific thread groups might
32618 not give any performance advantage over listing all thread groups.
32619 The frontend should assume that @samp{-list-thread-groups --available}
32620 is always an expensive operation and cache the results.
32624 The @samp{groups} result is a list of tuples, where each tuple may
32625 have the following fields:
32629 Identifier of the thread group. This field is always present.
32630 The identifier is an opaque string; frontends should not try to
32631 convert it to an integer, even though it might look like one.
32634 The type of the thread group. At present, only @samp{process} is a
32638 The target-specific process identifier. This field is only present
32639 for thread groups of type @samp{process} and only if the process exists.
32642 The exit code of this group's last exited thread, formatted in octal.
32643 This field is only present for thread groups of type @samp{process} and
32644 only if the process is not running.
32647 The number of children this thread group has. This field may be
32648 absent for an available thread group.
32651 This field has a list of tuples as value, each tuple describing a
32652 thread. It may be present if the @samp{--recurse} option is
32653 specified, and it's actually possible to obtain the threads.
32656 This field is a list of integers, each identifying a core that one
32657 thread of the group is running on. This field may be absent if
32658 such information is not available.
32661 The name of the executable file that corresponds to this thread group.
32662 The field is only present for thread groups of type @samp{process},
32663 and only if there is a corresponding executable file.
32667 @subheading Example
32671 -list-thread-groups
32672 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32673 -list-thread-groups 17
32674 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32675 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32676 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32677 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32678 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32679 -list-thread-groups --available
32680 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32681 -list-thread-groups --available --recurse 1
32682 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32683 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32684 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32685 -list-thread-groups --available --recurse 1 17 18
32686 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32687 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32688 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32691 @subheading The @code{-info-os} Command
32694 @subsubheading Synopsis
32697 -info-os [ @var{type} ]
32700 If no argument is supplied, the command returns a table of available
32701 operating-system-specific information types. If one of these types is
32702 supplied as an argument @var{type}, then the command returns a table
32703 of data of that type.
32705 The types of information available depend on the target operating
32708 @subsubheading @value{GDBN} Command
32710 The corresponding @value{GDBN} command is @samp{info os}.
32712 @subsubheading Example
32714 When run on a @sc{gnu}/Linux system, the output will look something
32720 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32721 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32722 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32723 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32724 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32726 item=@{col0="files",col1="Listing of all file descriptors",
32727 col2="File descriptors"@},
32728 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32729 col2="Kernel modules"@},
32730 item=@{col0="msg",col1="Listing of all message queues",
32731 col2="Message queues"@},
32732 item=@{col0="processes",col1="Listing of all processes",
32733 col2="Processes"@},
32734 item=@{col0="procgroups",col1="Listing of all process groups",
32735 col2="Process groups"@},
32736 item=@{col0="semaphores",col1="Listing of all semaphores",
32737 col2="Semaphores"@},
32738 item=@{col0="shm",col1="Listing of all shared-memory regions",
32739 col2="Shared-memory regions"@},
32740 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32742 item=@{col0="threads",col1="Listing of all threads",
32746 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32747 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32748 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32749 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32750 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32751 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32752 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32753 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32755 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32756 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32760 (Note that the MI output here includes a @code{"Title"} column that
32761 does not appear in command-line @code{info os}; this column is useful
32762 for MI clients that want to enumerate the types of data, such as in a
32763 popup menu, but is needless clutter on the command line, and
32764 @code{info os} omits it.)
32766 @subheading The @code{-add-inferior} Command
32767 @findex -add-inferior
32769 @subheading Synopsis
32775 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32776 inferior is not associated with any executable. Such association may
32777 be established with the @samp{-file-exec-and-symbols} command
32778 (@pxref{GDB/MI File Commands}). The command response has a single
32779 field, @samp{inferior}, whose value is the identifier of the
32780 thread group corresponding to the new inferior.
32782 @subheading Example
32787 ^done,inferior="i3"
32790 @subheading The @code{-interpreter-exec} Command
32791 @findex -interpreter-exec
32793 @subheading Synopsis
32796 -interpreter-exec @var{interpreter} @var{command}
32798 @anchor{-interpreter-exec}
32800 Execute the specified @var{command} in the given @var{interpreter}.
32802 @subheading @value{GDBN} Command
32804 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32806 @subheading Example
32810 -interpreter-exec console "break main"
32811 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32812 &"During symbol reading, bad structure-type format.\n"
32813 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32818 @subheading The @code{-inferior-tty-set} Command
32819 @findex -inferior-tty-set
32821 @subheading Synopsis
32824 -inferior-tty-set /dev/pts/1
32827 Set terminal for future runs of the program being debugged.
32829 @subheading @value{GDBN} Command
32831 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32833 @subheading Example
32837 -inferior-tty-set /dev/pts/1
32842 @subheading The @code{-inferior-tty-show} Command
32843 @findex -inferior-tty-show
32845 @subheading Synopsis
32851 Show terminal for future runs of program being debugged.
32853 @subheading @value{GDBN} Command
32855 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32857 @subheading Example
32861 -inferior-tty-set /dev/pts/1
32865 ^done,inferior_tty_terminal="/dev/pts/1"
32869 @subheading The @code{-enable-timings} Command
32870 @findex -enable-timings
32872 @subheading Synopsis
32875 -enable-timings [yes | no]
32878 Toggle the printing of the wallclock, user and system times for an MI
32879 command as a field in its output. This command is to help frontend
32880 developers optimize the performance of their code. No argument is
32881 equivalent to @samp{yes}.
32883 @subheading @value{GDBN} Command
32887 @subheading Example
32895 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32896 addr="0x080484ed",func="main",file="myprog.c",
32897 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32899 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32907 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32908 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32909 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32910 fullname="/home/nickrob/myprog.c",line="73"@}
32915 @chapter @value{GDBN} Annotations
32917 This chapter describes annotations in @value{GDBN}. Annotations were
32918 designed to interface @value{GDBN} to graphical user interfaces or other
32919 similar programs which want to interact with @value{GDBN} at a
32920 relatively high level.
32922 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32926 This is Edition @value{EDITION}, @value{DATE}.
32930 * Annotations Overview:: What annotations are; the general syntax.
32931 * Server Prefix:: Issuing a command without affecting user state.
32932 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32933 * Errors:: Annotations for error messages.
32934 * Invalidation:: Some annotations describe things now invalid.
32935 * Annotations for Running::
32936 Whether the program is running, how it stopped, etc.
32937 * Source Annotations:: Annotations describing source code.
32940 @node Annotations Overview
32941 @section What is an Annotation?
32942 @cindex annotations
32944 Annotations start with a newline character, two @samp{control-z}
32945 characters, and the name of the annotation. If there is no additional
32946 information associated with this annotation, the name of the annotation
32947 is followed immediately by a newline. If there is additional
32948 information, the name of the annotation is followed by a space, the
32949 additional information, and a newline. The additional information
32950 cannot contain newline characters.
32952 Any output not beginning with a newline and two @samp{control-z}
32953 characters denotes literal output from @value{GDBN}. Currently there is
32954 no need for @value{GDBN} to output a newline followed by two
32955 @samp{control-z} characters, but if there was such a need, the
32956 annotations could be extended with an @samp{escape} annotation which
32957 means those three characters as output.
32959 The annotation @var{level}, which is specified using the
32960 @option{--annotate} command line option (@pxref{Mode Options}), controls
32961 how much information @value{GDBN} prints together with its prompt,
32962 values of expressions, source lines, and other types of output. Level 0
32963 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32964 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32965 for programs that control @value{GDBN}, and level 2 annotations have
32966 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32967 Interface, annotate, GDB's Obsolete Annotations}).
32970 @kindex set annotate
32971 @item set annotate @var{level}
32972 The @value{GDBN} command @code{set annotate} sets the level of
32973 annotations to the specified @var{level}.
32975 @item show annotate
32976 @kindex show annotate
32977 Show the current annotation level.
32980 This chapter describes level 3 annotations.
32982 A simple example of starting up @value{GDBN} with annotations is:
32985 $ @kbd{gdb --annotate=3}
32987 Copyright 2003 Free Software Foundation, Inc.
32988 GDB is free software, covered by the GNU General Public License,
32989 and you are welcome to change it and/or distribute copies of it
32990 under certain conditions.
32991 Type "show copying" to see the conditions.
32992 There is absolutely no warranty for GDB. Type "show warranty"
32994 This GDB was configured as "i386-pc-linux-gnu"
33005 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33006 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33007 denotes a @samp{control-z} character) are annotations; the rest is
33008 output from @value{GDBN}.
33010 @node Server Prefix
33011 @section The Server Prefix
33012 @cindex server prefix
33014 If you prefix a command with @samp{server } then it will not affect
33015 the command history, nor will it affect @value{GDBN}'s notion of which
33016 command to repeat if @key{RET} is pressed on a line by itself. This
33017 means that commands can be run behind a user's back by a front-end in
33018 a transparent manner.
33020 The @code{server } prefix does not affect the recording of values into
33021 the value history; to print a value without recording it into the
33022 value history, use the @code{output} command instead of the
33023 @code{print} command.
33025 Using this prefix also disables confirmation requests
33026 (@pxref{confirmation requests}).
33029 @section Annotation for @value{GDBN} Input
33031 @cindex annotations for prompts
33032 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33033 to know when to send output, when the output from a given command is
33036 Different kinds of input each have a different @dfn{input type}. Each
33037 input type has three annotations: a @code{pre-} annotation, which
33038 denotes the beginning of any prompt which is being output, a plain
33039 annotation, which denotes the end of the prompt, and then a @code{post-}
33040 annotation which denotes the end of any echo which may (or may not) be
33041 associated with the input. For example, the @code{prompt} input type
33042 features the following annotations:
33050 The input types are
33053 @findex pre-prompt annotation
33054 @findex prompt annotation
33055 @findex post-prompt annotation
33057 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33059 @findex pre-commands annotation
33060 @findex commands annotation
33061 @findex post-commands annotation
33063 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33064 command. The annotations are repeated for each command which is input.
33066 @findex pre-overload-choice annotation
33067 @findex overload-choice annotation
33068 @findex post-overload-choice annotation
33069 @item overload-choice
33070 When @value{GDBN} wants the user to select between various overloaded functions.
33072 @findex pre-query annotation
33073 @findex query annotation
33074 @findex post-query annotation
33076 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33078 @findex pre-prompt-for-continue annotation
33079 @findex prompt-for-continue annotation
33080 @findex post-prompt-for-continue annotation
33081 @item prompt-for-continue
33082 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33083 expect this to work well; instead use @code{set height 0} to disable
33084 prompting. This is because the counting of lines is buggy in the
33085 presence of annotations.
33090 @cindex annotations for errors, warnings and interrupts
33092 @findex quit annotation
33097 This annotation occurs right before @value{GDBN} responds to an interrupt.
33099 @findex error annotation
33104 This annotation occurs right before @value{GDBN} responds to an error.
33106 Quit and error annotations indicate that any annotations which @value{GDBN} was
33107 in the middle of may end abruptly. For example, if a
33108 @code{value-history-begin} annotation is followed by a @code{error}, one
33109 cannot expect to receive the matching @code{value-history-end}. One
33110 cannot expect not to receive it either, however; an error annotation
33111 does not necessarily mean that @value{GDBN} is immediately returning all the way
33114 @findex error-begin annotation
33115 A quit or error annotation may be preceded by
33121 Any output between that and the quit or error annotation is the error
33124 Warning messages are not yet annotated.
33125 @c If we want to change that, need to fix warning(), type_error(),
33126 @c range_error(), and possibly other places.
33129 @section Invalidation Notices
33131 @cindex annotations for invalidation messages
33132 The following annotations say that certain pieces of state may have
33136 @findex frames-invalid annotation
33137 @item ^Z^Zframes-invalid
33139 The frames (for example, output from the @code{backtrace} command) may
33142 @findex breakpoints-invalid annotation
33143 @item ^Z^Zbreakpoints-invalid
33145 The breakpoints may have changed. For example, the user just added or
33146 deleted a breakpoint.
33149 @node Annotations for Running
33150 @section Running the Program
33151 @cindex annotations for running programs
33153 @findex starting annotation
33154 @findex stopping annotation
33155 When the program starts executing due to a @value{GDBN} command such as
33156 @code{step} or @code{continue},
33162 is output. When the program stops,
33168 is output. Before the @code{stopped} annotation, a variety of
33169 annotations describe how the program stopped.
33172 @findex exited annotation
33173 @item ^Z^Zexited @var{exit-status}
33174 The program exited, and @var{exit-status} is the exit status (zero for
33175 successful exit, otherwise nonzero).
33177 @findex signalled annotation
33178 @findex signal-name annotation
33179 @findex signal-name-end annotation
33180 @findex signal-string annotation
33181 @findex signal-string-end annotation
33182 @item ^Z^Zsignalled
33183 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33184 annotation continues:
33190 ^Z^Zsignal-name-end
33194 ^Z^Zsignal-string-end
33199 where @var{name} is the name of the signal, such as @code{SIGILL} or
33200 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33201 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33202 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33203 user's benefit and have no particular format.
33205 @findex signal annotation
33207 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33208 just saying that the program received the signal, not that it was
33209 terminated with it.
33211 @findex breakpoint annotation
33212 @item ^Z^Zbreakpoint @var{number}
33213 The program hit breakpoint number @var{number}.
33215 @findex watchpoint annotation
33216 @item ^Z^Zwatchpoint @var{number}
33217 The program hit watchpoint number @var{number}.
33220 @node Source Annotations
33221 @section Displaying Source
33222 @cindex annotations for source display
33224 @findex source annotation
33225 The following annotation is used instead of displaying source code:
33228 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33231 where @var{filename} is an absolute file name indicating which source
33232 file, @var{line} is the line number within that file (where 1 is the
33233 first line in the file), @var{character} is the character position
33234 within the file (where 0 is the first character in the file) (for most
33235 debug formats this will necessarily point to the beginning of a line),
33236 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33237 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33238 @var{addr} is the address in the target program associated with the
33239 source which is being displayed. The @var{addr} is in the form @samp{0x}
33240 followed by one or more lowercase hex digits (note that this does not
33241 depend on the language).
33243 @node JIT Interface
33244 @chapter JIT Compilation Interface
33245 @cindex just-in-time compilation
33246 @cindex JIT compilation interface
33248 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33249 interface. A JIT compiler is a program or library that generates native
33250 executable code at runtime and executes it, usually in order to achieve good
33251 performance while maintaining platform independence.
33253 Programs that use JIT compilation are normally difficult to debug because
33254 portions of their code are generated at runtime, instead of being loaded from
33255 object files, which is where @value{GDBN} normally finds the program's symbols
33256 and debug information. In order to debug programs that use JIT compilation,
33257 @value{GDBN} has an interface that allows the program to register in-memory
33258 symbol files with @value{GDBN} at runtime.
33260 If you are using @value{GDBN} to debug a program that uses this interface, then
33261 it should work transparently so long as you have not stripped the binary. If
33262 you are developing a JIT compiler, then the interface is documented in the rest
33263 of this chapter. At this time, the only known client of this interface is the
33266 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33267 JIT compiler communicates with @value{GDBN} by writing data into a global
33268 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33269 attaches, it reads a linked list of symbol files from the global variable to
33270 find existing code, and puts a breakpoint in the function so that it can find
33271 out about additional code.
33274 * Declarations:: Relevant C struct declarations
33275 * Registering Code:: Steps to register code
33276 * Unregistering Code:: Steps to unregister code
33277 * Custom Debug Info:: Emit debug information in a custom format
33281 @section JIT Declarations
33283 These are the relevant struct declarations that a C program should include to
33284 implement the interface:
33294 struct jit_code_entry
33296 struct jit_code_entry *next_entry;
33297 struct jit_code_entry *prev_entry;
33298 const char *symfile_addr;
33299 uint64_t symfile_size;
33302 struct jit_descriptor
33305 /* This type should be jit_actions_t, but we use uint32_t
33306 to be explicit about the bitwidth. */
33307 uint32_t action_flag;
33308 struct jit_code_entry *relevant_entry;
33309 struct jit_code_entry *first_entry;
33312 /* GDB puts a breakpoint in this function. */
33313 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33315 /* Make sure to specify the version statically, because the
33316 debugger may check the version before we can set it. */
33317 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33320 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33321 modifications to this global data properly, which can easily be done by putting
33322 a global mutex around modifications to these structures.
33324 @node Registering Code
33325 @section Registering Code
33327 To register code with @value{GDBN}, the JIT should follow this protocol:
33331 Generate an object file in memory with symbols and other desired debug
33332 information. The file must include the virtual addresses of the sections.
33335 Create a code entry for the file, which gives the start and size of the symbol
33339 Add it to the linked list in the JIT descriptor.
33342 Point the relevant_entry field of the descriptor at the entry.
33345 Set @code{action_flag} to @code{JIT_REGISTER} and call
33346 @code{__jit_debug_register_code}.
33349 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33350 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33351 new code. However, the linked list must still be maintained in order to allow
33352 @value{GDBN} to attach to a running process and still find the symbol files.
33354 @node Unregistering Code
33355 @section Unregistering Code
33357 If code is freed, then the JIT should use the following protocol:
33361 Remove the code entry corresponding to the code from the linked list.
33364 Point the @code{relevant_entry} field of the descriptor at the code entry.
33367 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33368 @code{__jit_debug_register_code}.
33371 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33372 and the JIT will leak the memory used for the associated symbol files.
33374 @node Custom Debug Info
33375 @section Custom Debug Info
33376 @cindex custom JIT debug info
33377 @cindex JIT debug info reader
33379 Generating debug information in platform-native file formats (like ELF
33380 or COFF) may be an overkill for JIT compilers; especially if all the
33381 debug info is used for is displaying a meaningful backtrace. The
33382 issue can be resolved by having the JIT writers decide on a debug info
33383 format and also provide a reader that parses the debug info generated
33384 by the JIT compiler. This section gives a brief overview on writing
33385 such a parser. More specific details can be found in the source file
33386 @file{gdb/jit-reader.in}, which is also installed as a header at
33387 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33389 The reader is implemented as a shared object (so this functionality is
33390 not available on platforms which don't allow loading shared objects at
33391 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33392 @code{jit-reader-unload} are provided, to be used to load and unload
33393 the readers from a preconfigured directory. Once loaded, the shared
33394 object is used the parse the debug information emitted by the JIT
33398 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33399 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33402 @node Using JIT Debug Info Readers
33403 @subsection Using JIT Debug Info Readers
33404 @kindex jit-reader-load
33405 @kindex jit-reader-unload
33407 Readers can be loaded and unloaded using the @code{jit-reader-load}
33408 and @code{jit-reader-unload} commands.
33411 @item jit-reader-load @var{reader}
33412 Load the JIT reader named @var{reader}, which is a shared
33413 object specified as either an absolute or a relative file name. In
33414 the latter case, @value{GDBN} will try to load the reader from a
33415 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33416 system (here @var{libdir} is the system library directory, often
33417 @file{/usr/local/lib}).
33419 Only one reader can be active at a time; trying to load a second
33420 reader when one is already loaded will result in @value{GDBN}
33421 reporting an error. A new JIT reader can be loaded by first unloading
33422 the current one using @code{jit-reader-unload} and then invoking
33423 @code{jit-reader-load}.
33425 @item jit-reader-unload
33426 Unload the currently loaded JIT reader.
33430 @node Writing JIT Debug Info Readers
33431 @subsection Writing JIT Debug Info Readers
33432 @cindex writing JIT debug info readers
33434 As mentioned, a reader is essentially a shared object conforming to a
33435 certain ABI. This ABI is described in @file{jit-reader.h}.
33437 @file{jit-reader.h} defines the structures, macros and functions
33438 required to write a reader. It is installed (along with
33439 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33440 the system include directory.
33442 Readers need to be released under a GPL compatible license. A reader
33443 can be declared as released under such a license by placing the macro
33444 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33446 The entry point for readers is the symbol @code{gdb_init_reader},
33447 which is expected to be a function with the prototype
33449 @findex gdb_init_reader
33451 extern struct gdb_reader_funcs *gdb_init_reader (void);
33454 @cindex @code{struct gdb_reader_funcs}
33456 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33457 functions. These functions are executed to read the debug info
33458 generated by the JIT compiler (@code{read}), to unwind stack frames
33459 (@code{unwind}) and to create canonical frame IDs
33460 (@code{get_Frame_id}). It also has a callback that is called when the
33461 reader is being unloaded (@code{destroy}). The struct looks like this
33464 struct gdb_reader_funcs
33466 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33467 int reader_version;
33469 /* For use by the reader. */
33472 gdb_read_debug_info *read;
33473 gdb_unwind_frame *unwind;
33474 gdb_get_frame_id *get_frame_id;
33475 gdb_destroy_reader *destroy;
33479 @cindex @code{struct gdb_symbol_callbacks}
33480 @cindex @code{struct gdb_unwind_callbacks}
33482 The callbacks are provided with another set of callbacks by
33483 @value{GDBN} to do their job. For @code{read}, these callbacks are
33484 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33485 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33486 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33487 files and new symbol tables inside those object files. @code{struct
33488 gdb_unwind_callbacks} has callbacks to read registers off the current
33489 frame and to write out the values of the registers in the previous
33490 frame. Both have a callback (@code{target_read}) to read bytes off the
33491 target's address space.
33493 @node In-Process Agent
33494 @chapter In-Process Agent
33495 @cindex debugging agent
33496 The traditional debugging model is conceptually low-speed, but works fine,
33497 because most bugs can be reproduced in debugging-mode execution. However,
33498 as multi-core or many-core processors are becoming mainstream, and
33499 multi-threaded programs become more and more popular, there should be more
33500 and more bugs that only manifest themselves at normal-mode execution, for
33501 example, thread races, because debugger's interference with the program's
33502 timing may conceal the bugs. On the other hand, in some applications,
33503 it is not feasible for the debugger to interrupt the program's execution
33504 long enough for the developer to learn anything helpful about its behavior.
33505 If the program's correctness depends on its real-time behavior, delays
33506 introduced by a debugger might cause the program to fail, even when the
33507 code itself is correct. It is useful to be able to observe the program's
33508 behavior without interrupting it.
33510 Therefore, traditional debugging model is too intrusive to reproduce
33511 some bugs. In order to reduce the interference with the program, we can
33512 reduce the number of operations performed by debugger. The
33513 @dfn{In-Process Agent}, a shared library, is running within the same
33514 process with inferior, and is able to perform some debugging operations
33515 itself. As a result, debugger is only involved when necessary, and
33516 performance of debugging can be improved accordingly. Note that
33517 interference with program can be reduced but can't be removed completely,
33518 because the in-process agent will still stop or slow down the program.
33520 The in-process agent can interpret and execute Agent Expressions
33521 (@pxref{Agent Expressions}) during performing debugging operations. The
33522 agent expressions can be used for different purposes, such as collecting
33523 data in tracepoints, and condition evaluation in breakpoints.
33525 @anchor{Control Agent}
33526 You can control whether the in-process agent is used as an aid for
33527 debugging with the following commands:
33530 @kindex set agent on
33532 Causes the in-process agent to perform some operations on behalf of the
33533 debugger. Just which operations requested by the user will be done
33534 by the in-process agent depends on the its capabilities. For example,
33535 if you request to evaluate breakpoint conditions in the in-process agent,
33536 and the in-process agent has such capability as well, then breakpoint
33537 conditions will be evaluated in the in-process agent.
33539 @kindex set agent off
33540 @item set agent off
33541 Disables execution of debugging operations by the in-process agent. All
33542 of the operations will be performed by @value{GDBN}.
33546 Display the current setting of execution of debugging operations by
33547 the in-process agent.
33551 * In-Process Agent Protocol::
33554 @node In-Process Agent Protocol
33555 @section In-Process Agent Protocol
33556 @cindex in-process agent protocol
33558 The in-process agent is able to communicate with both @value{GDBN} and
33559 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33560 used for communications between @value{GDBN} or GDBserver and the IPA.
33561 In general, @value{GDBN} or GDBserver sends commands
33562 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33563 in-process agent replies back with the return result of the command, or
33564 some other information. The data sent to in-process agent is composed
33565 of primitive data types, such as 4-byte or 8-byte type, and composite
33566 types, which are called objects (@pxref{IPA Protocol Objects}).
33569 * IPA Protocol Objects::
33570 * IPA Protocol Commands::
33573 @node IPA Protocol Objects
33574 @subsection IPA Protocol Objects
33575 @cindex ipa protocol objects
33577 The commands sent to and results received from agent may contain some
33578 complex data types called @dfn{objects}.
33580 The in-process agent is running on the same machine with @value{GDBN}
33581 or GDBserver, so it doesn't have to handle as much differences between
33582 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33583 However, there are still some differences of two ends in two processes:
33587 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33588 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33590 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33591 GDBserver is compiled with one, and in-process agent is compiled with
33595 Here are the IPA Protocol Objects:
33599 agent expression object. It represents an agent expression
33600 (@pxref{Agent Expressions}).
33601 @anchor{agent expression object}
33603 tracepoint action object. It represents a tracepoint action
33604 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33605 memory, static trace data and to evaluate expression.
33606 @anchor{tracepoint action object}
33608 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33609 @anchor{tracepoint object}
33613 The following table describes important attributes of each IPA protocol
33616 @multitable @columnfractions .30 .20 .50
33617 @headitem Name @tab Size @tab Description
33618 @item @emph{agent expression object} @tab @tab
33619 @item length @tab 4 @tab length of bytes code
33620 @item byte code @tab @var{length} @tab contents of byte code
33621 @item @emph{tracepoint action for collecting memory} @tab @tab
33622 @item 'M' @tab 1 @tab type of tracepoint action
33623 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33624 address of the lowest byte to collect, otherwise @var{addr} is the offset
33625 of @var{basereg} for memory collecting.
33626 @item len @tab 8 @tab length of memory for collecting
33627 @item basereg @tab 4 @tab the register number containing the starting
33628 memory address for collecting.
33629 @item @emph{tracepoint action for collecting registers} @tab @tab
33630 @item 'R' @tab 1 @tab type of tracepoint action
33631 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33632 @item 'L' @tab 1 @tab type of tracepoint action
33633 @item @emph{tracepoint action for expression evaluation} @tab @tab
33634 @item 'X' @tab 1 @tab type of tracepoint action
33635 @item agent expression @tab length of @tab @ref{agent expression object}
33636 @item @emph{tracepoint object} @tab @tab
33637 @item number @tab 4 @tab number of tracepoint
33638 @item address @tab 8 @tab address of tracepoint inserted on
33639 @item type @tab 4 @tab type of tracepoint
33640 @item enabled @tab 1 @tab enable or disable of tracepoint
33641 @item step_count @tab 8 @tab step
33642 @item pass_count @tab 8 @tab pass
33643 @item numactions @tab 4 @tab number of tracepoint actions
33644 @item hit count @tab 8 @tab hit count
33645 @item trace frame usage @tab 8 @tab trace frame usage
33646 @item compiled_cond @tab 8 @tab compiled condition
33647 @item orig_size @tab 8 @tab orig size
33648 @item condition @tab 4 if condition is NULL otherwise length of
33649 @ref{agent expression object}
33650 @tab zero if condition is NULL, otherwise is
33651 @ref{agent expression object}
33652 @item actions @tab variable
33653 @tab numactions number of @ref{tracepoint action object}
33656 @node IPA Protocol Commands
33657 @subsection IPA Protocol Commands
33658 @cindex ipa protocol commands
33660 The spaces in each command are delimiters to ease reading this commands
33661 specification. They don't exist in real commands.
33665 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33666 Installs a new fast tracepoint described by @var{tracepoint_object}
33667 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33668 head of @dfn{jumppad}, which is used to jump to data collection routine
33673 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33674 @var{target_address} is address of tracepoint in the inferior.
33675 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33676 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33677 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33678 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33685 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33686 is about to kill inferiors.
33694 @item probe_marker_at:@var{address}
33695 Asks in-process agent to probe the marker at @var{address}.
33702 @item unprobe_marker_at:@var{address}
33703 Asks in-process agent to unprobe the marker at @var{address}.
33707 @chapter Reporting Bugs in @value{GDBN}
33708 @cindex bugs in @value{GDBN}
33709 @cindex reporting bugs in @value{GDBN}
33711 Your bug reports play an essential role in making @value{GDBN} reliable.
33713 Reporting a bug may help you by bringing a solution to your problem, or it
33714 may not. But in any case the principal function of a bug report is to help
33715 the entire community by making the next version of @value{GDBN} work better. Bug
33716 reports are your contribution to the maintenance of @value{GDBN}.
33718 In order for a bug report to serve its purpose, you must include the
33719 information that enables us to fix the bug.
33722 * Bug Criteria:: Have you found a bug?
33723 * Bug Reporting:: How to report bugs
33727 @section Have You Found a Bug?
33728 @cindex bug criteria
33730 If you are not sure whether you have found a bug, here are some guidelines:
33733 @cindex fatal signal
33734 @cindex debugger crash
33735 @cindex crash of debugger
33737 If the debugger gets a fatal signal, for any input whatever, that is a
33738 @value{GDBN} bug. Reliable debuggers never crash.
33740 @cindex error on valid input
33742 If @value{GDBN} produces an error message for valid input, that is a
33743 bug. (Note that if you're cross debugging, the problem may also be
33744 somewhere in the connection to the target.)
33746 @cindex invalid input
33748 If @value{GDBN} does not produce an error message for invalid input,
33749 that is a bug. However, you should note that your idea of
33750 ``invalid input'' might be our idea of ``an extension'' or ``support
33751 for traditional practice''.
33754 If you are an experienced user of debugging tools, your suggestions
33755 for improvement of @value{GDBN} are welcome in any case.
33758 @node Bug Reporting
33759 @section How to Report Bugs
33760 @cindex bug reports
33761 @cindex @value{GDBN} bugs, reporting
33763 A number of companies and individuals offer support for @sc{gnu} products.
33764 If you obtained @value{GDBN} from a support organization, we recommend you
33765 contact that organization first.
33767 You can find contact information for many support companies and
33768 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33770 @c should add a web page ref...
33773 @ifset BUGURL_DEFAULT
33774 In any event, we also recommend that you submit bug reports for
33775 @value{GDBN}. The preferred method is to submit them directly using
33776 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33777 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33780 @strong{Do not send bug reports to @samp{info-gdb}, or to
33781 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33782 not want to receive bug reports. Those that do have arranged to receive
33785 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33786 serves as a repeater. The mailing list and the newsgroup carry exactly
33787 the same messages. Often people think of posting bug reports to the
33788 newsgroup instead of mailing them. This appears to work, but it has one
33789 problem which can be crucial: a newsgroup posting often lacks a mail
33790 path back to the sender. Thus, if we need to ask for more information,
33791 we may be unable to reach you. For this reason, it is better to send
33792 bug reports to the mailing list.
33794 @ifclear BUGURL_DEFAULT
33795 In any event, we also recommend that you submit bug reports for
33796 @value{GDBN} to @value{BUGURL}.
33800 The fundamental principle of reporting bugs usefully is this:
33801 @strong{report all the facts}. If you are not sure whether to state a
33802 fact or leave it out, state it!
33804 Often people omit facts because they think they know what causes the
33805 problem and assume that some details do not matter. Thus, you might
33806 assume that the name of the variable you use in an example does not matter.
33807 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33808 stray memory reference which happens to fetch from the location where that
33809 name is stored in memory; perhaps, if the name were different, the contents
33810 of that location would fool the debugger into doing the right thing despite
33811 the bug. Play it safe and give a specific, complete example. That is the
33812 easiest thing for you to do, and the most helpful.
33814 Keep in mind that the purpose of a bug report is to enable us to fix the
33815 bug. It may be that the bug has been reported previously, but neither
33816 you nor we can know that unless your bug report is complete and
33819 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33820 bell?'' Those bug reports are useless, and we urge everyone to
33821 @emph{refuse to respond to them} except to chide the sender to report
33824 To enable us to fix the bug, you should include all these things:
33828 The version of @value{GDBN}. @value{GDBN} announces it if you start
33829 with no arguments; you can also print it at any time using @code{show
33832 Without this, we will not know whether there is any point in looking for
33833 the bug in the current version of @value{GDBN}.
33836 The type of machine you are using, and the operating system name and
33840 The details of the @value{GDBN} build-time configuration.
33841 @value{GDBN} shows these details if you invoke it with the
33842 @option{--configuration} command-line option, or if you type
33843 @code{show configuration} at @value{GDBN}'s prompt.
33846 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33847 ``@value{GCC}--2.8.1''.
33850 What compiler (and its version) was used to compile the program you are
33851 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33852 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33853 to get this information; for other compilers, see the documentation for
33857 The command arguments you gave the compiler to compile your example and
33858 observe the bug. For example, did you use @samp{-O}? To guarantee
33859 you will not omit something important, list them all. A copy of the
33860 Makefile (or the output from make) is sufficient.
33862 If we were to try to guess the arguments, we would probably guess wrong
33863 and then we might not encounter the bug.
33866 A complete input script, and all necessary source files, that will
33870 A description of what behavior you observe that you believe is
33871 incorrect. For example, ``It gets a fatal signal.''
33873 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33874 will certainly notice it. But if the bug is incorrect output, we might
33875 not notice unless it is glaringly wrong. You might as well not give us
33876 a chance to make a mistake.
33878 Even if the problem you experience is a fatal signal, you should still
33879 say so explicitly. Suppose something strange is going on, such as, your
33880 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33881 the C library on your system. (This has happened!) Your copy might
33882 crash and ours would not. If you told us to expect a crash, then when
33883 ours fails to crash, we would know that the bug was not happening for
33884 us. If you had not told us to expect a crash, then we would not be able
33885 to draw any conclusion from our observations.
33888 @cindex recording a session script
33889 To collect all this information, you can use a session recording program
33890 such as @command{script}, which is available on many Unix systems.
33891 Just run your @value{GDBN} session inside @command{script} and then
33892 include the @file{typescript} file with your bug report.
33894 Another way to record a @value{GDBN} session is to run @value{GDBN}
33895 inside Emacs and then save the entire buffer to a file.
33898 If you wish to suggest changes to the @value{GDBN} source, send us context
33899 diffs. If you even discuss something in the @value{GDBN} source, refer to
33900 it by context, not by line number.
33902 The line numbers in our development sources will not match those in your
33903 sources. Your line numbers would convey no useful information to us.
33907 Here are some things that are not necessary:
33911 A description of the envelope of the bug.
33913 Often people who encounter a bug spend a lot of time investigating
33914 which changes to the input file will make the bug go away and which
33915 changes will not affect it.
33917 This is often time consuming and not very useful, because the way we
33918 will find the bug is by running a single example under the debugger
33919 with breakpoints, not by pure deduction from a series of examples.
33920 We recommend that you save your time for something else.
33922 Of course, if you can find a simpler example to report @emph{instead}
33923 of the original one, that is a convenience for us. Errors in the
33924 output will be easier to spot, running under the debugger will take
33925 less time, and so on.
33927 However, simplification is not vital; if you do not want to do this,
33928 report the bug anyway and send us the entire test case you used.
33931 A patch for the bug.
33933 A patch for the bug does help us if it is a good one. But do not omit
33934 the necessary information, such as the test case, on the assumption that
33935 a patch is all we need. We might see problems with your patch and decide
33936 to fix the problem another way, or we might not understand it at all.
33938 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33939 construct an example that will make the program follow a certain path
33940 through the code. If you do not send us the example, we will not be able
33941 to construct one, so we will not be able to verify that the bug is fixed.
33943 And if we cannot understand what bug you are trying to fix, or why your
33944 patch should be an improvement, we will not install it. A test case will
33945 help us to understand.
33948 A guess about what the bug is or what it depends on.
33950 Such guesses are usually wrong. Even we cannot guess right about such
33951 things without first using the debugger to find the facts.
33954 @c The readline documentation is distributed with the readline code
33955 @c and consists of the two following files:
33958 @c Use -I with makeinfo to point to the appropriate directory,
33959 @c environment var TEXINPUTS with TeX.
33960 @ifclear SYSTEM_READLINE
33961 @include rluser.texi
33962 @include hsuser.texi
33966 @appendix In Memoriam
33968 The @value{GDBN} project mourns the loss of the following long-time
33973 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33974 to Free Software in general. Outside of @value{GDBN}, he was known in
33975 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33977 @item Michael Snyder
33978 Michael was one of the Global Maintainers of the @value{GDBN} project,
33979 with contributions recorded as early as 1996, until 2011. In addition
33980 to his day to day participation, he was a large driving force behind
33981 adding Reverse Debugging to @value{GDBN}.
33984 Beyond their technical contributions to the project, they were also
33985 enjoyable members of the Free Software Community. We will miss them.
33987 @node Formatting Documentation
33988 @appendix Formatting Documentation
33990 @cindex @value{GDBN} reference card
33991 @cindex reference card
33992 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33993 for printing with PostScript or Ghostscript, in the @file{gdb}
33994 subdirectory of the main source directory@footnote{In
33995 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33996 release.}. If you can use PostScript or Ghostscript with your printer,
33997 you can print the reference card immediately with @file{refcard.ps}.
33999 The release also includes the source for the reference card. You
34000 can format it, using @TeX{}, by typing:
34006 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34007 mode on US ``letter'' size paper;
34008 that is, on a sheet 11 inches wide by 8.5 inches
34009 high. You will need to specify this form of printing as an option to
34010 your @sc{dvi} output program.
34012 @cindex documentation
34014 All the documentation for @value{GDBN} comes as part of the machine-readable
34015 distribution. The documentation is written in Texinfo format, which is
34016 a documentation system that uses a single source file to produce both
34017 on-line information and a printed manual. You can use one of the Info
34018 formatting commands to create the on-line version of the documentation
34019 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34021 @value{GDBN} includes an already formatted copy of the on-line Info
34022 version of this manual in the @file{gdb} subdirectory. The main Info
34023 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34024 subordinate files matching @samp{gdb.info*} in the same directory. If
34025 necessary, you can print out these files, or read them with any editor;
34026 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34027 Emacs or the standalone @code{info} program, available as part of the
34028 @sc{gnu} Texinfo distribution.
34030 If you want to format these Info files yourself, you need one of the
34031 Info formatting programs, such as @code{texinfo-format-buffer} or
34034 If you have @code{makeinfo} installed, and are in the top level
34035 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34036 version @value{GDBVN}), you can make the Info file by typing:
34043 If you want to typeset and print copies of this manual, you need @TeX{},
34044 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34045 Texinfo definitions file.
34047 @TeX{} is a typesetting program; it does not print files directly, but
34048 produces output files called @sc{dvi} files. To print a typeset
34049 document, you need a program to print @sc{dvi} files. If your system
34050 has @TeX{} installed, chances are it has such a program. The precise
34051 command to use depends on your system; @kbd{lpr -d} is common; another
34052 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34053 require a file name without any extension or a @samp{.dvi} extension.
34055 @TeX{} also requires a macro definitions file called
34056 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34057 written in Texinfo format. On its own, @TeX{} cannot either read or
34058 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34059 and is located in the @file{gdb-@var{version-number}/texinfo}
34062 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34063 typeset and print this manual. First switch to the @file{gdb}
34064 subdirectory of the main source directory (for example, to
34065 @file{gdb-@value{GDBVN}/gdb}) and type:
34071 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34073 @node Installing GDB
34074 @appendix Installing @value{GDBN}
34075 @cindex installation
34078 * Requirements:: Requirements for building @value{GDBN}
34079 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34080 * Separate Objdir:: Compiling @value{GDBN} in another directory
34081 * Config Names:: Specifying names for hosts and targets
34082 * Configure Options:: Summary of options for configure
34083 * System-wide configuration:: Having a system-wide init file
34087 @section Requirements for Building @value{GDBN}
34088 @cindex building @value{GDBN}, requirements for
34090 Building @value{GDBN} requires various tools and packages to be available.
34091 Other packages will be used only if they are found.
34093 @heading Tools/Packages Necessary for Building @value{GDBN}
34095 @item ISO C90 compiler
34096 @value{GDBN} is written in ISO C90. It should be buildable with any
34097 working C90 compiler, e.g.@: GCC.
34101 @heading Tools/Packages Optional for Building @value{GDBN}
34105 @value{GDBN} can use the Expat XML parsing library. This library may be
34106 included with your operating system distribution; if it is not, you
34107 can get the latest version from @url{http://expat.sourceforge.net}.
34108 The @file{configure} script will search for this library in several
34109 standard locations; if it is installed in an unusual path, you can
34110 use the @option{--with-libexpat-prefix} option to specify its location.
34116 Remote protocol memory maps (@pxref{Memory Map Format})
34118 Target descriptions (@pxref{Target Descriptions})
34120 Remote shared library lists (@xref{Library List Format},
34121 or alternatively @pxref{Library List Format for SVR4 Targets})
34123 MS-Windows shared libraries (@pxref{Shared Libraries})
34125 Traceframe info (@pxref{Traceframe Info Format})
34127 Branch trace (@pxref{Branch Trace Format},
34128 @pxref{Branch Trace Configuration Format})
34132 @cindex compressed debug sections
34133 @value{GDBN} will use the @samp{zlib} library, if available, to read
34134 compressed debug sections. Some linkers, such as GNU gold, are capable
34135 of producing binaries with compressed debug sections. If @value{GDBN}
34136 is compiled with @samp{zlib}, it will be able to read the debug
34137 information in such binaries.
34139 The @samp{zlib} library is likely included with your operating system
34140 distribution; if it is not, you can get the latest version from
34141 @url{http://zlib.net}.
34144 @value{GDBN}'s features related to character sets (@pxref{Character
34145 Sets}) require a functioning @code{iconv} implementation. If you are
34146 on a GNU system, then this is provided by the GNU C Library. Some
34147 other systems also provide a working @code{iconv}.
34149 If @value{GDBN} is using the @code{iconv} program which is installed
34150 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34151 This is done with @option{--with-iconv-bin} which specifies the
34152 directory that contains the @code{iconv} program.
34154 On systems without @code{iconv}, you can install GNU Libiconv. If you
34155 have previously installed Libiconv, you can use the
34156 @option{--with-libiconv-prefix} option to configure.
34158 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34159 arrange to build Libiconv if a directory named @file{libiconv} appears
34160 in the top-most source directory. If Libiconv is built this way, and
34161 if the operating system does not provide a suitable @code{iconv}
34162 implementation, then the just-built library will automatically be used
34163 by @value{GDBN}. One easy way to set this up is to download GNU
34164 Libiconv, unpack it, and then rename the directory holding the
34165 Libiconv source code to @samp{libiconv}.
34168 @node Running Configure
34169 @section Invoking the @value{GDBN} @file{configure} Script
34170 @cindex configuring @value{GDBN}
34171 @value{GDBN} comes with a @file{configure} script that automates the process
34172 of preparing @value{GDBN} for installation; you can then use @code{make} to
34173 build the @code{gdb} program.
34175 @c irrelevant in info file; it's as current as the code it lives with.
34176 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34177 look at the @file{README} file in the sources; we may have improved the
34178 installation procedures since publishing this manual.}
34181 The @value{GDBN} distribution includes all the source code you need for
34182 @value{GDBN} in a single directory, whose name is usually composed by
34183 appending the version number to @samp{gdb}.
34185 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34186 @file{gdb-@value{GDBVN}} directory. That directory contains:
34189 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34190 script for configuring @value{GDBN} and all its supporting libraries
34192 @item gdb-@value{GDBVN}/gdb
34193 the source specific to @value{GDBN} itself
34195 @item gdb-@value{GDBVN}/bfd
34196 source for the Binary File Descriptor library
34198 @item gdb-@value{GDBVN}/include
34199 @sc{gnu} include files
34201 @item gdb-@value{GDBVN}/libiberty
34202 source for the @samp{-liberty} free software library
34204 @item gdb-@value{GDBVN}/opcodes
34205 source for the library of opcode tables and disassemblers
34207 @item gdb-@value{GDBVN}/readline
34208 source for the @sc{gnu} command-line interface
34210 @item gdb-@value{GDBVN}/glob
34211 source for the @sc{gnu} filename pattern-matching subroutine
34213 @item gdb-@value{GDBVN}/mmalloc
34214 source for the @sc{gnu} memory-mapped malloc package
34217 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34218 from the @file{gdb-@var{version-number}} source directory, which in
34219 this example is the @file{gdb-@value{GDBVN}} directory.
34221 First switch to the @file{gdb-@var{version-number}} source directory
34222 if you are not already in it; then run @file{configure}. Pass the
34223 identifier for the platform on which @value{GDBN} will run as an
34229 cd gdb-@value{GDBVN}
34230 ./configure @var{host}
34235 where @var{host} is an identifier such as @samp{sun4} or
34236 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34237 (You can often leave off @var{host}; @file{configure} tries to guess the
34238 correct value by examining your system.)
34240 Running @samp{configure @var{host}} and then running @code{make} builds the
34241 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34242 libraries, then @code{gdb} itself. The configured source files, and the
34243 binaries, are left in the corresponding source directories.
34246 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34247 system does not recognize this automatically when you run a different
34248 shell, you may need to run @code{sh} on it explicitly:
34251 sh configure @var{host}
34254 If you run @file{configure} from a directory that contains source
34255 directories for multiple libraries or programs, such as the
34256 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34258 creates configuration files for every directory level underneath (unless
34259 you tell it not to, with the @samp{--norecursion} option).
34261 You should run the @file{configure} script from the top directory in the
34262 source tree, the @file{gdb-@var{version-number}} directory. If you run
34263 @file{configure} from one of the subdirectories, you will configure only
34264 that subdirectory. That is usually not what you want. In particular,
34265 if you run the first @file{configure} from the @file{gdb} subdirectory
34266 of the @file{gdb-@var{version-number}} directory, you will omit the
34267 configuration of @file{bfd}, @file{readline}, and other sibling
34268 directories of the @file{gdb} subdirectory. This leads to build errors
34269 about missing include files such as @file{bfd/bfd.h}.
34271 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34272 However, you should make sure that the shell on your path (named by
34273 the @samp{SHELL} environment variable) is publicly readable. Remember
34274 that @value{GDBN} uses the shell to start your program---some systems refuse to
34275 let @value{GDBN} debug child processes whose programs are not readable.
34277 @node Separate Objdir
34278 @section Compiling @value{GDBN} in Another Directory
34280 If you want to run @value{GDBN} versions for several host or target machines,
34281 you need a different @code{gdb} compiled for each combination of
34282 host and target. @file{configure} is designed to make this easy by
34283 allowing you to generate each configuration in a separate subdirectory,
34284 rather than in the source directory. If your @code{make} program
34285 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34286 @code{make} in each of these directories builds the @code{gdb}
34287 program specified there.
34289 To build @code{gdb} in a separate directory, run @file{configure}
34290 with the @samp{--srcdir} option to specify where to find the source.
34291 (You also need to specify a path to find @file{configure}
34292 itself from your working directory. If the path to @file{configure}
34293 would be the same as the argument to @samp{--srcdir}, you can leave out
34294 the @samp{--srcdir} option; it is assumed.)
34296 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34297 separate directory for a Sun 4 like this:
34301 cd gdb-@value{GDBVN}
34304 ../gdb-@value{GDBVN}/configure sun4
34309 When @file{configure} builds a configuration using a remote source
34310 directory, it creates a tree for the binaries with the same structure
34311 (and using the same names) as the tree under the source directory. In
34312 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34313 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34314 @file{gdb-sun4/gdb}.
34316 Make sure that your path to the @file{configure} script has just one
34317 instance of @file{gdb} in it. If your path to @file{configure} looks
34318 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34319 one subdirectory of @value{GDBN}, not the whole package. This leads to
34320 build errors about missing include files such as @file{bfd/bfd.h}.
34322 One popular reason to build several @value{GDBN} configurations in separate
34323 directories is to configure @value{GDBN} for cross-compiling (where
34324 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34325 programs that run on another machine---the @dfn{target}).
34326 You specify a cross-debugging target by
34327 giving the @samp{--target=@var{target}} option to @file{configure}.
34329 When you run @code{make} to build a program or library, you must run
34330 it in a configured directory---whatever directory you were in when you
34331 called @file{configure} (or one of its subdirectories).
34333 The @code{Makefile} that @file{configure} generates in each source
34334 directory also runs recursively. If you type @code{make} in a source
34335 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34336 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34337 will build all the required libraries, and then build GDB.
34339 When you have multiple hosts or targets configured in separate
34340 directories, you can run @code{make} on them in parallel (for example,
34341 if they are NFS-mounted on each of the hosts); they will not interfere
34345 @section Specifying Names for Hosts and Targets
34347 The specifications used for hosts and targets in the @file{configure}
34348 script are based on a three-part naming scheme, but some short predefined
34349 aliases are also supported. The full naming scheme encodes three pieces
34350 of information in the following pattern:
34353 @var{architecture}-@var{vendor}-@var{os}
34356 For example, you can use the alias @code{sun4} as a @var{host} argument,
34357 or as the value for @var{target} in a @code{--target=@var{target}}
34358 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34360 The @file{configure} script accompanying @value{GDBN} does not provide
34361 any query facility to list all supported host and target names or
34362 aliases. @file{configure} calls the Bourne shell script
34363 @code{config.sub} to map abbreviations to full names; you can read the
34364 script, if you wish, or you can use it to test your guesses on
34365 abbreviations---for example:
34368 % sh config.sub i386-linux
34370 % sh config.sub alpha-linux
34371 alpha-unknown-linux-gnu
34372 % sh config.sub hp9k700
34374 % sh config.sub sun4
34375 sparc-sun-sunos4.1.1
34376 % sh config.sub sun3
34377 m68k-sun-sunos4.1.1
34378 % sh config.sub i986v
34379 Invalid configuration `i986v': machine `i986v' not recognized
34383 @code{config.sub} is also distributed in the @value{GDBN} source
34384 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34386 @node Configure Options
34387 @section @file{configure} Options
34389 Here is a summary of the @file{configure} options and arguments that
34390 are most often useful for building @value{GDBN}. @file{configure} also has
34391 several other options not listed here. @inforef{What Configure
34392 Does,,configure.info}, for a full explanation of @file{configure}.
34395 configure @r{[}--help@r{]}
34396 @r{[}--prefix=@var{dir}@r{]}
34397 @r{[}--exec-prefix=@var{dir}@r{]}
34398 @r{[}--srcdir=@var{dirname}@r{]}
34399 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34400 @r{[}--target=@var{target}@r{]}
34405 You may introduce options with a single @samp{-} rather than
34406 @samp{--} if you prefer; but you may abbreviate option names if you use
34411 Display a quick summary of how to invoke @file{configure}.
34413 @item --prefix=@var{dir}
34414 Configure the source to install programs and files under directory
34417 @item --exec-prefix=@var{dir}
34418 Configure the source to install programs under directory
34421 @c avoid splitting the warning from the explanation:
34423 @item --srcdir=@var{dirname}
34424 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34425 @code{make} that implements the @code{VPATH} feature.}@*
34426 Use this option to make configurations in directories separate from the
34427 @value{GDBN} source directories. Among other things, you can use this to
34428 build (or maintain) several configurations simultaneously, in separate
34429 directories. @file{configure} writes configuration-specific files in
34430 the current directory, but arranges for them to use the source in the
34431 directory @var{dirname}. @file{configure} creates directories under
34432 the working directory in parallel to the source directories below
34435 @item --norecursion
34436 Configure only the directory level where @file{configure} is executed; do not
34437 propagate configuration to subdirectories.
34439 @item --target=@var{target}
34440 Configure @value{GDBN} for cross-debugging programs running on the specified
34441 @var{target}. Without this option, @value{GDBN} is configured to debug
34442 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34444 There is no convenient way to generate a list of all available targets.
34446 @item @var{host} @dots{}
34447 Configure @value{GDBN} to run on the specified @var{host}.
34449 There is no convenient way to generate a list of all available hosts.
34452 There are many other options available as well, but they are generally
34453 needed for special purposes only.
34455 @node System-wide configuration
34456 @section System-wide configuration and settings
34457 @cindex system-wide init file
34459 @value{GDBN} can be configured to have a system-wide init file;
34460 this file will be read and executed at startup (@pxref{Startup, , What
34461 @value{GDBN} does during startup}).
34463 Here is the corresponding configure option:
34466 @item --with-system-gdbinit=@var{file}
34467 Specify that the default location of the system-wide init file is
34471 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34472 it may be subject to relocation. Two possible cases:
34476 If the default location of this init file contains @file{$prefix},
34477 it will be subject to relocation. Suppose that the configure options
34478 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34479 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34480 init file is looked for as @file{$install/etc/gdbinit} instead of
34481 @file{$prefix/etc/gdbinit}.
34484 By contrast, if the default location does not contain the prefix,
34485 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34486 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34487 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34488 wherever @value{GDBN} is installed.
34491 If the configured location of the system-wide init file (as given by the
34492 @option{--with-system-gdbinit} option at configure time) is in the
34493 data-directory (as specified by @option{--with-gdb-datadir} at configure
34494 time) or in one of its subdirectories, then @value{GDBN} will look for the
34495 system-wide init file in the directory specified by the
34496 @option{--data-directory} command-line option.
34497 Note that the system-wide init file is only read once, during @value{GDBN}
34498 initialization. If the data-directory is changed after @value{GDBN} has
34499 started with the @code{set data-directory} command, the file will not be
34503 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34506 @node System-wide Configuration Scripts
34507 @subsection Installed System-wide Configuration Scripts
34508 @cindex system-wide configuration scripts
34510 The @file{system-gdbinit} directory, located inside the data-directory
34511 (as specified by @option{--with-gdb-datadir} at configure time) contains
34512 a number of scripts which can be used as system-wide init files. To
34513 automatically source those scripts at startup, @value{GDBN} should be
34514 configured with @option{--with-system-gdbinit}. Otherwise, any user
34515 should be able to source them by hand as needed.
34517 The following scripts are currently available:
34520 @item @file{elinos.py}
34522 @cindex ELinOS system-wide configuration script
34523 This script is useful when debugging a program on an ELinOS target.
34524 It takes advantage of the environment variables defined in a standard
34525 ELinOS environment in order to determine the location of the system
34526 shared libraries, and then sets the @samp{solib-absolute-prefix}
34527 and @samp{solib-search-path} variables appropriately.
34529 @item @file{wrs-linux.py}
34530 @pindex wrs-linux.py
34531 @cindex Wind River Linux system-wide configuration script
34532 This script is useful when debugging a program on a target running
34533 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34534 the host-side sysroot used by the target system.
34538 @node Maintenance Commands
34539 @appendix Maintenance Commands
34540 @cindex maintenance commands
34541 @cindex internal commands
34543 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34544 includes a number of commands intended for @value{GDBN} developers,
34545 that are not documented elsewhere in this manual. These commands are
34546 provided here for reference. (For commands that turn on debugging
34547 messages, see @ref{Debugging Output}.)
34550 @kindex maint agent
34551 @kindex maint agent-eval
34552 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34553 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34554 Translate the given @var{expression} into remote agent bytecodes.
34555 This command is useful for debugging the Agent Expression mechanism
34556 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34557 expression useful for data collection, such as by tracepoints, while
34558 @samp{maint agent-eval} produces an expression that evaluates directly
34559 to a result. For instance, a collection expression for @code{globa +
34560 globb} will include bytecodes to record four bytes of memory at each
34561 of the addresses of @code{globa} and @code{globb}, while discarding
34562 the result of the addition, while an evaluation expression will do the
34563 addition and return the sum.
34564 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34565 If not, generate remote agent bytecode for current frame PC address.
34567 @kindex maint agent-printf
34568 @item maint agent-printf @var{format},@var{expr},...
34569 Translate the given format string and list of argument expressions
34570 into remote agent bytecodes and display them as a disassembled list.
34571 This command is useful for debugging the agent version of dynamic
34572 printf (@pxref{Dynamic Printf}).
34574 @kindex maint info breakpoints
34575 @item @anchor{maint info breakpoints}maint info breakpoints
34576 Using the same format as @samp{info breakpoints}, display both the
34577 breakpoints you've set explicitly, and those @value{GDBN} is using for
34578 internal purposes. Internal breakpoints are shown with negative
34579 breakpoint numbers. The type column identifies what kind of breakpoint
34584 Normal, explicitly set breakpoint.
34587 Normal, explicitly set watchpoint.
34590 Internal breakpoint, used to handle correctly stepping through
34591 @code{longjmp} calls.
34593 @item longjmp resume
34594 Internal breakpoint at the target of a @code{longjmp}.
34597 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34600 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34603 Shared library events.
34607 @kindex maint info btrace
34608 @item maint info btrace
34609 Pint information about raw branch tracing data.
34611 @kindex maint btrace packet-history
34612 @item maint btrace packet-history
34613 Print the raw branch trace packets that are used to compute the
34614 execution history for the @samp{record btrace} command. Both the
34615 information and the format in which it is printed depend on the btrace
34620 For the BTS recording format, print a list of blocks of sequential
34621 code. For each block, the following information is printed:
34625 Newer blocks have higher numbers. The oldest block has number zero.
34626 @item Lowest @samp{PC}
34627 @item Highest @samp{PC}
34631 For the Intel Processor Trace recording format, print a list of
34632 Intel Processor Trace packets. For each packet, the following
34633 information is printed:
34636 @item Packet number
34637 Newer packets have higher numbers. The oldest packet has number zero.
34639 The packet's offset in the trace stream.
34640 @item Packet opcode and payload
34644 @kindex maint btrace clear-packet-history
34645 @item maint btrace clear-packet-history
34646 Discards the cached packet history printed by the @samp{maint btrace
34647 packet-history} command. The history will be computed again when
34650 @kindex maint btrace clear
34651 @item maint btrace clear
34652 Discard the branch trace data. The data will be fetched anew and the
34653 branch trace will be recomputed when needed.
34655 This implicitly truncates the branch trace to a single branch trace
34656 buffer. When updating branch trace incrementally, the branch trace
34657 available to @value{GDBN} may be bigger than a single branch trace
34660 @kindex maint set btrace pt skip-pad
34661 @item maint set btrace pt skip-pad
34662 @kindex maint show btrace pt skip-pad
34663 @item maint show btrace pt skip-pad
34664 Control whether @value{GDBN} will skip PAD packets when computing the
34667 @kindex set displaced-stepping
34668 @kindex show displaced-stepping
34669 @cindex displaced stepping support
34670 @cindex out-of-line single-stepping
34671 @item set displaced-stepping
34672 @itemx show displaced-stepping
34673 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34674 if the target supports it. Displaced stepping is a way to single-step
34675 over breakpoints without removing them from the inferior, by executing
34676 an out-of-line copy of the instruction that was originally at the
34677 breakpoint location. It is also known as out-of-line single-stepping.
34680 @item set displaced-stepping on
34681 If the target architecture supports it, @value{GDBN} will use
34682 displaced stepping to step over breakpoints.
34684 @item set displaced-stepping off
34685 @value{GDBN} will not use displaced stepping to step over breakpoints,
34686 even if such is supported by the target architecture.
34688 @cindex non-stop mode, and @samp{set displaced-stepping}
34689 @item set displaced-stepping auto
34690 This is the default mode. @value{GDBN} will use displaced stepping
34691 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34692 architecture supports displaced stepping.
34695 @kindex maint check-psymtabs
34696 @item maint check-psymtabs
34697 Check the consistency of currently expanded psymtabs versus symtabs.
34698 Use this to check, for example, whether a symbol is in one but not the other.
34700 @kindex maint check-symtabs
34701 @item maint check-symtabs
34702 Check the consistency of currently expanded symtabs.
34704 @kindex maint expand-symtabs
34705 @item maint expand-symtabs [@var{regexp}]
34706 Expand symbol tables.
34707 If @var{regexp} is specified, only expand symbol tables for file
34708 names matching @var{regexp}.
34710 @kindex maint set catch-demangler-crashes
34711 @kindex maint show catch-demangler-crashes
34712 @cindex demangler crashes
34713 @item maint set catch-demangler-crashes [on|off]
34714 @itemx maint show catch-demangler-crashes
34715 Control whether @value{GDBN} should attempt to catch crashes in the
34716 symbol name demangler. The default is to attempt to catch crashes.
34717 If enabled, the first time a crash is caught, a core file is created,
34718 the offending symbol is displayed and the user is presented with the
34719 option to terminate the current session.
34721 @kindex maint cplus first_component
34722 @item maint cplus first_component @var{name}
34723 Print the first C@t{++} class/namespace component of @var{name}.
34725 @kindex maint cplus namespace
34726 @item maint cplus namespace
34727 Print the list of possible C@t{++} namespaces.
34729 @kindex maint deprecate
34730 @kindex maint undeprecate
34731 @cindex deprecated commands
34732 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34733 @itemx maint undeprecate @var{command}
34734 Deprecate or undeprecate the named @var{command}. Deprecated commands
34735 cause @value{GDBN} to issue a warning when you use them. The optional
34736 argument @var{replacement} says which newer command should be used in
34737 favor of the deprecated one; if it is given, @value{GDBN} will mention
34738 the replacement as part of the warning.
34740 @kindex maint dump-me
34741 @item maint dump-me
34742 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34743 Cause a fatal signal in the debugger and force it to dump its core.
34744 This is supported only on systems which support aborting a program
34745 with the @code{SIGQUIT} signal.
34747 @kindex maint internal-error
34748 @kindex maint internal-warning
34749 @kindex maint demangler-warning
34750 @cindex demangler crashes
34751 @item maint internal-error @r{[}@var{message-text}@r{]}
34752 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34753 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34755 Cause @value{GDBN} to call the internal function @code{internal_error},
34756 @code{internal_warning} or @code{demangler_warning} and hence behave
34757 as though an internal problem has been detected. In addition to
34758 reporting the internal problem, these functions give the user the
34759 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34760 and @code{internal_warning}) create a core file of the current
34761 @value{GDBN} session.
34763 These commands take an optional parameter @var{message-text} that is
34764 used as the text of the error or warning message.
34766 Here's an example of using @code{internal-error}:
34769 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34770 @dots{}/maint.c:121: internal-error: testing, 1, 2
34771 A problem internal to GDB has been detected. Further
34772 debugging may prove unreliable.
34773 Quit this debugging session? (y or n) @kbd{n}
34774 Create a core file? (y or n) @kbd{n}
34778 @cindex @value{GDBN} internal error
34779 @cindex internal errors, control of @value{GDBN} behavior
34780 @cindex demangler crashes
34782 @kindex maint set internal-error
34783 @kindex maint show internal-error
34784 @kindex maint set internal-warning
34785 @kindex maint show internal-warning
34786 @kindex maint set demangler-warning
34787 @kindex maint show demangler-warning
34788 @item maint set internal-error @var{action} [ask|yes|no]
34789 @itemx maint show internal-error @var{action}
34790 @itemx maint set internal-warning @var{action} [ask|yes|no]
34791 @itemx maint show internal-warning @var{action}
34792 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34793 @itemx maint show demangler-warning @var{action}
34794 When @value{GDBN} reports an internal problem (error or warning) it
34795 gives the user the opportunity to both quit @value{GDBN} and create a
34796 core file of the current @value{GDBN} session. These commands let you
34797 override the default behaviour for each particular @var{action},
34798 described in the table below.
34802 You can specify that @value{GDBN} should always (yes) or never (no)
34803 quit. The default is to ask the user what to do.
34806 You can specify that @value{GDBN} should always (yes) or never (no)
34807 create a core file. The default is to ask the user what to do. Note
34808 that there is no @code{corefile} option for @code{demangler-warning}:
34809 demangler warnings always create a core file and this cannot be
34813 @kindex maint packet
34814 @item maint packet @var{text}
34815 If @value{GDBN} is talking to an inferior via the serial protocol,
34816 then this command sends the string @var{text} to the inferior, and
34817 displays the response packet. @value{GDBN} supplies the initial
34818 @samp{$} character, the terminating @samp{#} character, and the
34821 @kindex maint print architecture
34822 @item maint print architecture @r{[}@var{file}@r{]}
34823 Print the entire architecture configuration. The optional argument
34824 @var{file} names the file where the output goes.
34826 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
34827 @item maint print c-tdesc
34828 Print the target description (@pxref{Target Descriptions}) as
34829 a C source file. By default, the target description is for the current
34830 target, but if the optional argument @var{file} is provided, that file
34831 is used to produce the description. The @var{file} should be an XML
34832 document, of the form described in @ref{Target Description Format}.
34833 The created source file is built into @value{GDBN} when @value{GDBN} is
34834 built again. This command is used by developers after they add or
34835 modify XML target descriptions.
34837 @kindex maint check xml-descriptions
34838 @item maint check xml-descriptions @var{dir}
34839 Check that the target descriptions dynamically created by @value{GDBN}
34840 equal the descriptions created from XML files found in @var{dir}.
34842 @kindex maint print dummy-frames
34843 @item maint print dummy-frames
34844 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34847 (@value{GDBP}) @kbd{b add}
34849 (@value{GDBP}) @kbd{print add(2,3)}
34850 Breakpoint 2, add (a=2, b=3) at @dots{}
34852 The program being debugged stopped while in a function called from GDB.
34854 (@value{GDBP}) @kbd{maint print dummy-frames}
34855 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34859 Takes an optional file parameter.
34861 @kindex maint print registers
34862 @kindex maint print raw-registers
34863 @kindex maint print cooked-registers
34864 @kindex maint print register-groups
34865 @kindex maint print remote-registers
34866 @item maint print registers @r{[}@var{file}@r{]}
34867 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34868 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34869 @itemx maint print register-groups @r{[}@var{file}@r{]}
34870 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34871 Print @value{GDBN}'s internal register data structures.
34873 The command @code{maint print raw-registers} includes the contents of
34874 the raw register cache; the command @code{maint print
34875 cooked-registers} includes the (cooked) value of all registers,
34876 including registers which aren't available on the target nor visible
34877 to user; the command @code{maint print register-groups} includes the
34878 groups that each register is a member of; and the command @code{maint
34879 print remote-registers} includes the remote target's register numbers
34880 and offsets in the `G' packets.
34882 These commands take an optional parameter, a file name to which to
34883 write the information.
34885 @kindex maint print reggroups
34886 @item maint print reggroups @r{[}@var{file}@r{]}
34887 Print @value{GDBN}'s internal register group data structures. The
34888 optional argument @var{file} tells to what file to write the
34891 The register groups info looks like this:
34894 (@value{GDBP}) @kbd{maint print reggroups}
34907 This command forces @value{GDBN} to flush its internal register cache.
34909 @kindex maint print objfiles
34910 @cindex info for known object files
34911 @item maint print objfiles @r{[}@var{regexp}@r{]}
34912 Print a dump of all known object files.
34913 If @var{regexp} is specified, only print object files whose names
34914 match @var{regexp}. For each object file, this command prints its name,
34915 address in memory, and all of its psymtabs and symtabs.
34917 @kindex maint print user-registers
34918 @cindex user registers
34919 @item maint print user-registers
34920 List all currently available @dfn{user registers}. User registers
34921 typically provide alternate names for actual hardware registers. They
34922 include the four ``standard'' registers @code{$fp}, @code{$pc},
34923 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34924 registers can be used in expressions in the same way as the canonical
34925 register names, but only the latter are listed by the @code{info
34926 registers} and @code{maint print registers} commands.
34928 @kindex maint print section-scripts
34929 @cindex info for known .debug_gdb_scripts-loaded scripts
34930 @item maint print section-scripts [@var{regexp}]
34931 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34932 If @var{regexp} is specified, only print scripts loaded by object files
34933 matching @var{regexp}.
34934 For each script, this command prints its name as specified in the objfile,
34935 and the full path if known.
34936 @xref{dotdebug_gdb_scripts section}.
34938 @kindex maint print statistics
34939 @cindex bcache statistics
34940 @item maint print statistics
34941 This command prints, for each object file in the program, various data
34942 about that object file followed by the byte cache (@dfn{bcache})
34943 statistics for the object file. The objfile data includes the number
34944 of minimal, partial, full, and stabs symbols, the number of types
34945 defined by the objfile, the number of as yet unexpanded psym tables,
34946 the number of line tables and string tables, and the amount of memory
34947 used by the various tables. The bcache statistics include the counts,
34948 sizes, and counts of duplicates of all and unique objects, max,
34949 average, and median entry size, total memory used and its overhead and
34950 savings, and various measures of the hash table size and chain
34953 @kindex maint print target-stack
34954 @cindex target stack description
34955 @item maint print target-stack
34956 A @dfn{target} is an interface between the debugger and a particular
34957 kind of file or process. Targets can be stacked in @dfn{strata},
34958 so that more than one target can potentially respond to a request.
34959 In particular, memory accesses will walk down the stack of targets
34960 until they find a target that is interested in handling that particular
34963 This command prints a short description of each layer that was pushed on
34964 the @dfn{target stack}, starting from the top layer down to the bottom one.
34966 @kindex maint print type
34967 @cindex type chain of a data type
34968 @item maint print type @var{expr}
34969 Print the type chain for a type specified by @var{expr}. The argument
34970 can be either a type name or a symbol. If it is a symbol, the type of
34971 that symbol is described. The type chain produced by this command is
34972 a recursive definition of the data type as stored in @value{GDBN}'s
34973 data structures, including its flags and contained types.
34975 @kindex maint selftest
34977 Run any self tests that were compiled in to @value{GDBN}. This will
34978 print a message showing how many tests were run, and how many failed.
34980 @kindex maint set dwarf always-disassemble
34981 @kindex maint show dwarf always-disassemble
34982 @item maint set dwarf always-disassemble
34983 @item maint show dwarf always-disassemble
34984 Control the behavior of @code{info address} when using DWARF debugging
34987 The default is @code{off}, which means that @value{GDBN} should try to
34988 describe a variable's location in an easily readable format. When
34989 @code{on}, @value{GDBN} will instead display the DWARF location
34990 expression in an assembly-like format. Note that some locations are
34991 too complex for @value{GDBN} to describe simply; in this case you will
34992 always see the disassembly form.
34994 Here is an example of the resulting disassembly:
34997 (gdb) info addr argc
34998 Symbol "argc" is a complex DWARF expression:
35002 For more information on these expressions, see
35003 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35005 @kindex maint set dwarf max-cache-age
35006 @kindex maint show dwarf max-cache-age
35007 @item maint set dwarf max-cache-age
35008 @itemx maint show dwarf max-cache-age
35009 Control the DWARF compilation unit cache.
35011 @cindex DWARF compilation units cache
35012 In object files with inter-compilation-unit references, such as those
35013 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35014 reader needs to frequently refer to previously read compilation units.
35015 This setting controls how long a compilation unit will remain in the
35016 cache if it is not referenced. A higher limit means that cached
35017 compilation units will be stored in memory longer, and more total
35018 memory will be used. Setting it to zero disables caching, which will
35019 slow down @value{GDBN} startup, but reduce memory consumption.
35021 @kindex maint set profile
35022 @kindex maint show profile
35023 @cindex profiling GDB
35024 @item maint set profile
35025 @itemx maint show profile
35026 Control profiling of @value{GDBN}.
35028 Profiling will be disabled until you use the @samp{maint set profile}
35029 command to enable it. When you enable profiling, the system will begin
35030 collecting timing and execution count data; when you disable profiling or
35031 exit @value{GDBN}, the results will be written to a log file. Remember that
35032 if you use profiling, @value{GDBN} will overwrite the profiling log file
35033 (often called @file{gmon.out}). If you have a record of important profiling
35034 data in a @file{gmon.out} file, be sure to move it to a safe location.
35036 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35037 compiled with the @samp{-pg} compiler option.
35039 @kindex maint set show-debug-regs
35040 @kindex maint show show-debug-regs
35041 @cindex hardware debug registers
35042 @item maint set show-debug-regs
35043 @itemx maint show show-debug-regs
35044 Control whether to show variables that mirror the hardware debug
35045 registers. Use @code{on} to enable, @code{off} to disable. If
35046 enabled, the debug registers values are shown when @value{GDBN} inserts or
35047 removes a hardware breakpoint or watchpoint, and when the inferior
35048 triggers a hardware-assisted breakpoint or watchpoint.
35050 @kindex maint set show-all-tib
35051 @kindex maint show show-all-tib
35052 @item maint set show-all-tib
35053 @itemx maint show show-all-tib
35054 Control whether to show all non zero areas within a 1k block starting
35055 at thread local base, when using the @samp{info w32 thread-information-block}
35058 @kindex maint set target-async
35059 @kindex maint show target-async
35060 @item maint set target-async
35061 @itemx maint show target-async
35062 This controls whether @value{GDBN} targets operate in synchronous or
35063 asynchronous mode (@pxref{Background Execution}). Normally the
35064 default is asynchronous, if it is available; but this can be changed
35065 to more easily debug problems occurring only in synchronous mode.
35067 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35068 @kindex maint show target-non-stop
35069 @item maint set target-non-stop
35070 @itemx maint show target-non-stop
35072 This controls whether @value{GDBN} targets always operate in non-stop
35073 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35074 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35075 if supported by the target.
35078 @item maint set target-non-stop auto
35079 This is the default mode. @value{GDBN} controls the target in
35080 non-stop mode if the target supports it.
35082 @item maint set target-non-stop on
35083 @value{GDBN} controls the target in non-stop mode even if the target
35084 does not indicate support.
35086 @item maint set target-non-stop off
35087 @value{GDBN} does not control the target in non-stop mode even if the
35088 target supports it.
35091 @kindex maint set per-command
35092 @kindex maint show per-command
35093 @item maint set per-command
35094 @itemx maint show per-command
35095 @cindex resources used by commands
35097 @value{GDBN} can display the resources used by each command.
35098 This is useful in debugging performance problems.
35101 @item maint set per-command space [on|off]
35102 @itemx maint show per-command space
35103 Enable or disable the printing of the memory used by GDB for each command.
35104 If enabled, @value{GDBN} will display how much memory each command
35105 took, following the command's own output.
35106 This can also be requested by invoking @value{GDBN} with the
35107 @option{--statistics} command-line switch (@pxref{Mode Options}).
35109 @item maint set per-command time [on|off]
35110 @itemx maint show per-command time
35111 Enable or disable the printing of the execution time of @value{GDBN}
35113 If enabled, @value{GDBN} will display how much time it
35114 took to execute each command, following the command's own output.
35115 Both CPU time and wallclock time are printed.
35116 Printing both is useful when trying to determine whether the cost is
35117 CPU or, e.g., disk/network latency.
35118 Note that the CPU time printed is for @value{GDBN} only, it does not include
35119 the execution time of the inferior because there's no mechanism currently
35120 to compute how much time was spent by @value{GDBN} and how much time was
35121 spent by the program been debugged.
35122 This can also be requested by invoking @value{GDBN} with the
35123 @option{--statistics} command-line switch (@pxref{Mode Options}).
35125 @item maint set per-command symtab [on|off]
35126 @itemx maint show per-command symtab
35127 Enable or disable the printing of basic symbol table statistics
35129 If enabled, @value{GDBN} will display the following information:
35133 number of symbol tables
35135 number of primary symbol tables
35137 number of blocks in the blockvector
35141 @kindex maint space
35142 @cindex memory used by commands
35143 @item maint space @var{value}
35144 An alias for @code{maint set per-command space}.
35145 A non-zero value enables it, zero disables it.
35148 @cindex time of command execution
35149 @item maint time @var{value}
35150 An alias for @code{maint set per-command time}.
35151 A non-zero value enables it, zero disables it.
35153 @kindex maint translate-address
35154 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35155 Find the symbol stored at the location specified by the address
35156 @var{addr} and an optional section name @var{section}. If found,
35157 @value{GDBN} prints the name of the closest symbol and an offset from
35158 the symbol's location to the specified address. This is similar to
35159 the @code{info address} command (@pxref{Symbols}), except that this
35160 command also allows to find symbols in other sections.
35162 If section was not specified, the section in which the symbol was found
35163 is also printed. For dynamically linked executables, the name of
35164 executable or shared library containing the symbol is printed as well.
35168 The following command is useful for non-interactive invocations of
35169 @value{GDBN}, such as in the test suite.
35172 @item set watchdog @var{nsec}
35173 @kindex set watchdog
35174 @cindex watchdog timer
35175 @cindex timeout for commands
35176 Set the maximum number of seconds @value{GDBN} will wait for the
35177 target operation to finish. If this time expires, @value{GDBN}
35178 reports and error and the command is aborted.
35180 @item show watchdog
35181 Show the current setting of the target wait timeout.
35184 @node Remote Protocol
35185 @appendix @value{GDBN} Remote Serial Protocol
35190 * Stop Reply Packets::
35191 * General Query Packets::
35192 * Architecture-Specific Protocol Details::
35193 * Tracepoint Packets::
35194 * Host I/O Packets::
35196 * Notification Packets::
35197 * Remote Non-Stop::
35198 * Packet Acknowledgment::
35200 * File-I/O Remote Protocol Extension::
35201 * Library List Format::
35202 * Library List Format for SVR4 Targets::
35203 * Memory Map Format::
35204 * Thread List Format::
35205 * Traceframe Info Format::
35206 * Branch Trace Format::
35207 * Branch Trace Configuration Format::
35213 There may be occasions when you need to know something about the
35214 protocol---for example, if there is only one serial port to your target
35215 machine, you might want your program to do something special if it
35216 recognizes a packet meant for @value{GDBN}.
35218 In the examples below, @samp{->} and @samp{<-} are used to indicate
35219 transmitted and received data, respectively.
35221 @cindex protocol, @value{GDBN} remote serial
35222 @cindex serial protocol, @value{GDBN} remote
35223 @cindex remote serial protocol
35224 All @value{GDBN} commands and responses (other than acknowledgments
35225 and notifications, see @ref{Notification Packets}) are sent as a
35226 @var{packet}. A @var{packet} is introduced with the character
35227 @samp{$}, the actual @var{packet-data}, and the terminating character
35228 @samp{#} followed by a two-digit @var{checksum}:
35231 @code{$}@var{packet-data}@code{#}@var{checksum}
35235 @cindex checksum, for @value{GDBN} remote
35237 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35238 characters between the leading @samp{$} and the trailing @samp{#} (an
35239 eight bit unsigned checksum).
35241 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35242 specification also included an optional two-digit @var{sequence-id}:
35245 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35248 @cindex sequence-id, for @value{GDBN} remote
35250 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35251 has never output @var{sequence-id}s. Stubs that handle packets added
35252 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35254 When either the host or the target machine receives a packet, the first
35255 response expected is an acknowledgment: either @samp{+} (to indicate
35256 the package was received correctly) or @samp{-} (to request
35260 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35265 The @samp{+}/@samp{-} acknowledgments can be disabled
35266 once a connection is established.
35267 @xref{Packet Acknowledgment}, for details.
35269 The host (@value{GDBN}) sends @var{command}s, and the target (the
35270 debugging stub incorporated in your program) sends a @var{response}. In
35271 the case of step and continue @var{command}s, the response is only sent
35272 when the operation has completed, and the target has again stopped all
35273 threads in all attached processes. This is the default all-stop mode
35274 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35275 execution mode; see @ref{Remote Non-Stop}, for details.
35277 @var{packet-data} consists of a sequence of characters with the
35278 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35281 @cindex remote protocol, field separator
35282 Fields within the packet should be separated using @samp{,} @samp{;} or
35283 @samp{:}. Except where otherwise noted all numbers are represented in
35284 @sc{hex} with leading zeros suppressed.
35286 Implementors should note that prior to @value{GDBN} 5.0, the character
35287 @samp{:} could not appear as the third character in a packet (as it
35288 would potentially conflict with the @var{sequence-id}).
35290 @cindex remote protocol, binary data
35291 @anchor{Binary Data}
35292 Binary data in most packets is encoded either as two hexadecimal
35293 digits per byte of binary data. This allowed the traditional remote
35294 protocol to work over connections which were only seven-bit clean.
35295 Some packets designed more recently assume an eight-bit clean
35296 connection, and use a more efficient encoding to send and receive
35299 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35300 as an escape character. Any escaped byte is transmitted as the escape
35301 character followed by the original character XORed with @code{0x20}.
35302 For example, the byte @code{0x7d} would be transmitted as the two
35303 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35304 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35305 @samp{@}}) must always be escaped. Responses sent by the stub
35306 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35307 is not interpreted as the start of a run-length encoded sequence
35310 Response @var{data} can be run-length encoded to save space.
35311 Run-length encoding replaces runs of identical characters with one
35312 instance of the repeated character, followed by a @samp{*} and a
35313 repeat count. The repeat count is itself sent encoded, to avoid
35314 binary characters in @var{data}: a value of @var{n} is sent as
35315 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35316 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35317 code 32) for a repeat count of 3. (This is because run-length
35318 encoding starts to win for counts 3 or more.) Thus, for example,
35319 @samp{0* } is a run-length encoding of ``0000'': the space character
35320 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35323 The printable characters @samp{#} and @samp{$} or with a numeric value
35324 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35325 seven repeats (@samp{$}) can be expanded using a repeat count of only
35326 five (@samp{"}). For example, @samp{00000000} can be encoded as
35329 The error response returned for some packets includes a two character
35330 error number. That number is not well defined.
35332 @cindex empty response, for unsupported packets
35333 For any @var{command} not supported by the stub, an empty response
35334 (@samp{$#00}) should be returned. That way it is possible to extend the
35335 protocol. A newer @value{GDBN} can tell if a packet is supported based
35338 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35339 commands for register access, and the @samp{m} and @samp{M} commands
35340 for memory access. Stubs that only control single-threaded targets
35341 can implement run control with the @samp{c} (continue), and @samp{s}
35342 (step) commands. Stubs that support multi-threading targets should
35343 support the @samp{vCont} command. All other commands are optional.
35348 The following table provides a complete list of all currently defined
35349 @var{command}s and their corresponding response @var{data}.
35350 @xref{File-I/O Remote Protocol Extension}, for details about the File
35351 I/O extension of the remote protocol.
35353 Each packet's description has a template showing the packet's overall
35354 syntax, followed by an explanation of the packet's meaning. We
35355 include spaces in some of the templates for clarity; these are not
35356 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35357 separate its components. For example, a template like @samp{foo
35358 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35359 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35360 @var{baz}. @value{GDBN} does not transmit a space character between the
35361 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35364 @cindex @var{thread-id}, in remote protocol
35365 @anchor{thread-id syntax}
35366 Several packets and replies include a @var{thread-id} field to identify
35367 a thread. Normally these are positive numbers with a target-specific
35368 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35369 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35372 In addition, the remote protocol supports a multiprocess feature in
35373 which the @var{thread-id} syntax is extended to optionally include both
35374 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35375 The @var{pid} (process) and @var{tid} (thread) components each have the
35376 format described above: a positive number with target-specific
35377 interpretation formatted as a big-endian hex string, literal @samp{-1}
35378 to indicate all processes or threads (respectively), or @samp{0} to
35379 indicate an arbitrary process or thread. Specifying just a process, as
35380 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35381 error to specify all processes but a specific thread, such as
35382 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35383 for those packets and replies explicitly documented to include a process
35384 ID, rather than a @var{thread-id}.
35386 The multiprocess @var{thread-id} syntax extensions are only used if both
35387 @value{GDBN} and the stub report support for the @samp{multiprocess}
35388 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35391 Note that all packet forms beginning with an upper- or lower-case
35392 letter, other than those described here, are reserved for future use.
35394 Here are the packet descriptions.
35399 @cindex @samp{!} packet
35400 @anchor{extended mode}
35401 Enable extended mode. In extended mode, the remote server is made
35402 persistent. The @samp{R} packet is used to restart the program being
35408 The remote target both supports and has enabled extended mode.
35412 @cindex @samp{?} packet
35414 Indicate the reason the target halted. The reply is the same as for
35415 step and continue. This packet has a special interpretation when the
35416 target is in non-stop mode; see @ref{Remote Non-Stop}.
35419 @xref{Stop Reply Packets}, for the reply specifications.
35421 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35422 @cindex @samp{A} packet
35423 Initialized @code{argv[]} array passed into program. @var{arglen}
35424 specifies the number of bytes in the hex encoded byte stream
35425 @var{arg}. See @code{gdbserver} for more details.
35430 The arguments were set.
35436 @cindex @samp{b} packet
35437 (Don't use this packet; its behavior is not well-defined.)
35438 Change the serial line speed to @var{baud}.
35440 JTC: @emph{When does the transport layer state change? When it's
35441 received, or after the ACK is transmitted. In either case, there are
35442 problems if the command or the acknowledgment packet is dropped.}
35444 Stan: @emph{If people really wanted to add something like this, and get
35445 it working for the first time, they ought to modify ser-unix.c to send
35446 some kind of out-of-band message to a specially-setup stub and have the
35447 switch happen "in between" packets, so that from remote protocol's point
35448 of view, nothing actually happened.}
35450 @item B @var{addr},@var{mode}
35451 @cindex @samp{B} packet
35452 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35453 breakpoint at @var{addr}.
35455 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35456 (@pxref{insert breakpoint or watchpoint packet}).
35458 @cindex @samp{bc} packet
35461 Backward continue. Execute the target system in reverse. No parameter.
35462 @xref{Reverse Execution}, for more information.
35465 @xref{Stop Reply Packets}, for the reply specifications.
35467 @cindex @samp{bs} packet
35470 Backward single step. Execute one instruction in reverse. No parameter.
35471 @xref{Reverse Execution}, for more information.
35474 @xref{Stop Reply Packets}, for the reply specifications.
35476 @item c @r{[}@var{addr}@r{]}
35477 @cindex @samp{c} packet
35478 Continue at @var{addr}, which is the address to resume. If @var{addr}
35479 is omitted, resume at current address.
35481 This packet is deprecated for multi-threading support. @xref{vCont
35485 @xref{Stop Reply Packets}, for the reply specifications.
35487 @item C @var{sig}@r{[};@var{addr}@r{]}
35488 @cindex @samp{C} packet
35489 Continue with signal @var{sig} (hex signal number). If
35490 @samp{;@var{addr}} is omitted, resume at same address.
35492 This packet is deprecated for multi-threading support. @xref{vCont
35496 @xref{Stop Reply Packets}, for the reply specifications.
35499 @cindex @samp{d} packet
35502 Don't use this packet; instead, define a general set packet
35503 (@pxref{General Query Packets}).
35507 @cindex @samp{D} packet
35508 The first form of the packet is used to detach @value{GDBN} from the
35509 remote system. It is sent to the remote target
35510 before @value{GDBN} disconnects via the @code{detach} command.
35512 The second form, including a process ID, is used when multiprocess
35513 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35514 detach only a specific process. The @var{pid} is specified as a
35515 big-endian hex string.
35525 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35526 @cindex @samp{F} packet
35527 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35528 This is part of the File-I/O protocol extension. @xref{File-I/O
35529 Remote Protocol Extension}, for the specification.
35532 @anchor{read registers packet}
35533 @cindex @samp{g} packet
35534 Read general registers.
35538 @item @var{XX@dots{}}
35539 Each byte of register data is described by two hex digits. The bytes
35540 with the register are transmitted in target byte order. The size of
35541 each register and their position within the @samp{g} packet are
35542 determined by the @value{GDBN} internal gdbarch functions
35543 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35545 When reading registers from a trace frame (@pxref{Analyze Collected
35546 Data,,Using the Collected Data}), the stub may also return a string of
35547 literal @samp{x}'s in place of the register data digits, to indicate
35548 that the corresponding register has not been collected, thus its value
35549 is unavailable. For example, for an architecture with 4 registers of
35550 4 bytes each, the following reply indicates to @value{GDBN} that
35551 registers 0 and 2 have not been collected, while registers 1 and 3
35552 have been collected, and both have zero value:
35556 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35563 @item G @var{XX@dots{}}
35564 @cindex @samp{G} packet
35565 Write general registers. @xref{read registers packet}, for a
35566 description of the @var{XX@dots{}} data.
35576 @item H @var{op} @var{thread-id}
35577 @cindex @samp{H} packet
35578 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35579 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35580 should be @samp{c} for step and continue operations (note that this
35581 is deprecated, supporting the @samp{vCont} command is a better
35582 option), and @samp{g} for other operations. The thread designator
35583 @var{thread-id} has the format and interpretation described in
35584 @ref{thread-id syntax}.
35595 @c 'H': How restrictive (or permissive) is the thread model. If a
35596 @c thread is selected and stopped, are other threads allowed
35597 @c to continue to execute? As I mentioned above, I think the
35598 @c semantics of each command when a thread is selected must be
35599 @c described. For example:
35601 @c 'g': If the stub supports threads and a specific thread is
35602 @c selected, returns the register block from that thread;
35603 @c otherwise returns current registers.
35605 @c 'G' If the stub supports threads and a specific thread is
35606 @c selected, sets the registers of the register block of
35607 @c that thread; otherwise sets current registers.
35609 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35610 @anchor{cycle step packet}
35611 @cindex @samp{i} packet
35612 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35613 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35614 step starting at that address.
35617 @cindex @samp{I} packet
35618 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35622 @cindex @samp{k} packet
35625 The exact effect of this packet is not specified.
35627 For a bare-metal target, it may power cycle or reset the target
35628 system. For that reason, the @samp{k} packet has no reply.
35630 For a single-process target, it may kill that process if possible.
35632 A multiple-process target may choose to kill just one process, or all
35633 that are under @value{GDBN}'s control. For more precise control, use
35634 the vKill packet (@pxref{vKill packet}).
35636 If the target system immediately closes the connection in response to
35637 @samp{k}, @value{GDBN} does not consider the lack of packet
35638 acknowledgment to be an error, and assumes the kill was successful.
35640 If connected using @kbd{target extended-remote}, and the target does
35641 not close the connection in response to a kill request, @value{GDBN}
35642 probes the target state as if a new connection was opened
35643 (@pxref{? packet}).
35645 @item m @var{addr},@var{length}
35646 @cindex @samp{m} packet
35647 Read @var{length} addressable memory units starting at address @var{addr}
35648 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35649 any particular boundary.
35651 The stub need not use any particular size or alignment when gathering
35652 data from memory for the response; even if @var{addr} is word-aligned
35653 and @var{length} is a multiple of the word size, the stub is free to
35654 use byte accesses, or not. For this reason, this packet may not be
35655 suitable for accessing memory-mapped I/O devices.
35656 @cindex alignment of remote memory accesses
35657 @cindex size of remote memory accesses
35658 @cindex memory, alignment and size of remote accesses
35662 @item @var{XX@dots{}}
35663 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35664 The reply may contain fewer addressable memory units than requested if the
35665 server was able to read only part of the region of memory.
35670 @item M @var{addr},@var{length}:@var{XX@dots{}}
35671 @cindex @samp{M} packet
35672 Write @var{length} addressable memory units starting at address @var{addr}
35673 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35674 byte is transmitted as a two-digit hexadecimal number.
35681 for an error (this includes the case where only part of the data was
35686 @cindex @samp{p} packet
35687 Read the value of register @var{n}; @var{n} is in hex.
35688 @xref{read registers packet}, for a description of how the returned
35689 register value is encoded.
35693 @item @var{XX@dots{}}
35694 the register's value
35698 Indicating an unrecognized @var{query}.
35701 @item P @var{n@dots{}}=@var{r@dots{}}
35702 @anchor{write register packet}
35703 @cindex @samp{P} packet
35704 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35705 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35706 digits for each byte in the register (target byte order).
35716 @item q @var{name} @var{params}@dots{}
35717 @itemx Q @var{name} @var{params}@dots{}
35718 @cindex @samp{q} packet
35719 @cindex @samp{Q} packet
35720 General query (@samp{q}) and set (@samp{Q}). These packets are
35721 described fully in @ref{General Query Packets}.
35724 @cindex @samp{r} packet
35725 Reset the entire system.
35727 Don't use this packet; use the @samp{R} packet instead.
35730 @cindex @samp{R} packet
35731 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35732 This packet is only available in extended mode (@pxref{extended mode}).
35734 The @samp{R} packet has no reply.
35736 @item s @r{[}@var{addr}@r{]}
35737 @cindex @samp{s} packet
35738 Single step, resuming at @var{addr}. If
35739 @var{addr} is omitted, resume at same address.
35741 This packet is deprecated for multi-threading support. @xref{vCont
35745 @xref{Stop Reply Packets}, for the reply specifications.
35747 @item S @var{sig}@r{[};@var{addr}@r{]}
35748 @anchor{step with signal packet}
35749 @cindex @samp{S} packet
35750 Step with signal. This is analogous to the @samp{C} packet, but
35751 requests a single-step, rather than a normal resumption of execution.
35753 This packet is deprecated for multi-threading support. @xref{vCont
35757 @xref{Stop Reply Packets}, for the reply specifications.
35759 @item t @var{addr}:@var{PP},@var{MM}
35760 @cindex @samp{t} packet
35761 Search backwards starting at address @var{addr} for a match with pattern
35762 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35763 There must be at least 3 digits in @var{addr}.
35765 @item T @var{thread-id}
35766 @cindex @samp{T} packet
35767 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35772 thread is still alive
35778 Packets starting with @samp{v} are identified by a multi-letter name,
35779 up to the first @samp{;} or @samp{?} (or the end of the packet).
35781 @item vAttach;@var{pid}
35782 @cindex @samp{vAttach} packet
35783 Attach to a new process with the specified process ID @var{pid}.
35784 The process ID is a
35785 hexadecimal integer identifying the process. In all-stop mode, all
35786 threads in the attached process are stopped; in non-stop mode, it may be
35787 attached without being stopped if that is supported by the target.
35789 @c In non-stop mode, on a successful vAttach, the stub should set the
35790 @c current thread to a thread of the newly-attached process. After
35791 @c attaching, GDB queries for the attached process's thread ID with qC.
35792 @c Also note that, from a user perspective, whether or not the
35793 @c target is stopped on attach in non-stop mode depends on whether you
35794 @c use the foreground or background version of the attach command, not
35795 @c on what vAttach does; GDB does the right thing with respect to either
35796 @c stopping or restarting threads.
35798 This packet is only available in extended mode (@pxref{extended mode}).
35804 @item @r{Any stop packet}
35805 for success in all-stop mode (@pxref{Stop Reply Packets})
35807 for success in non-stop mode (@pxref{Remote Non-Stop})
35810 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35811 @cindex @samp{vCont} packet
35812 @anchor{vCont packet}
35813 Resume the inferior, specifying different actions for each thread.
35815 For each inferior thread, the leftmost action with a matching
35816 @var{thread-id} is applied. Threads that don't match any action
35817 remain in their current state. Thread IDs are specified using the
35818 syntax described in @ref{thread-id syntax}. If multiprocess
35819 extensions (@pxref{multiprocess extensions}) are supported, actions
35820 can be specified to match all threads in a process by using the
35821 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35822 @var{thread-id} matches all threads. Specifying no actions is an
35825 Currently supported actions are:
35831 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35835 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35838 @item r @var{start},@var{end}
35839 Step once, and then keep stepping as long as the thread stops at
35840 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35841 The remote stub reports a stop reply when either the thread goes out
35842 of the range or is stopped due to an unrelated reason, such as hitting
35843 a breakpoint. @xref{range stepping}.
35845 If the range is empty (@var{start} == @var{end}), then the action
35846 becomes equivalent to the @samp{s} action. In other words,
35847 single-step once, and report the stop (even if the stepped instruction
35848 jumps to @var{start}).
35850 (A stop reply may be sent at any point even if the PC is still within
35851 the stepping range; for example, it is valid to implement this packet
35852 in a degenerate way as a single instruction step operation.)
35856 The optional argument @var{addr} normally associated with the
35857 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35858 not supported in @samp{vCont}.
35860 The @samp{t} action is only relevant in non-stop mode
35861 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35862 A stop reply should be generated for any affected thread not already stopped.
35863 When a thread is stopped by means of a @samp{t} action,
35864 the corresponding stop reply should indicate that the thread has stopped with
35865 signal @samp{0}, regardless of whether the target uses some other signal
35866 as an implementation detail.
35868 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35869 @samp{r} actions for threads that are already running. Conversely,
35870 the server must ignore @samp{t} actions for threads that are already
35873 @emph{Note:} In non-stop mode, a thread is considered running until
35874 @value{GDBN} acknowleges an asynchronous stop notification for it with
35875 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35877 The stub must support @samp{vCont} if it reports support for
35878 multiprocess extensions (@pxref{multiprocess extensions}).
35881 @xref{Stop Reply Packets}, for the reply specifications.
35884 @cindex @samp{vCont?} packet
35885 Request a list of actions supported by the @samp{vCont} packet.
35889 @item vCont@r{[};@var{action}@dots{}@r{]}
35890 The @samp{vCont} packet is supported. Each @var{action} is a supported
35891 command in the @samp{vCont} packet.
35893 The @samp{vCont} packet is not supported.
35896 @anchor{vCtrlC packet}
35898 @cindex @samp{vCtrlC} packet
35899 Interrupt remote target as if a control-C was pressed on the remote
35900 terminal. This is the equivalent to reacting to the @code{^C}
35901 (@samp{\003}, the control-C character) character in all-stop mode
35902 while the target is running, except this works in non-stop mode.
35903 @xref{interrupting remote targets}, for more info on the all-stop
35914 @item vFile:@var{operation}:@var{parameter}@dots{}
35915 @cindex @samp{vFile} packet
35916 Perform a file operation on the target system. For details,
35917 see @ref{Host I/O Packets}.
35919 @item vFlashErase:@var{addr},@var{length}
35920 @cindex @samp{vFlashErase} packet
35921 Direct the stub to erase @var{length} bytes of flash starting at
35922 @var{addr}. The region may enclose any number of flash blocks, but
35923 its start and end must fall on block boundaries, as indicated by the
35924 flash block size appearing in the memory map (@pxref{Memory Map
35925 Format}). @value{GDBN} groups flash memory programming operations
35926 together, and sends a @samp{vFlashDone} request after each group; the
35927 stub is allowed to delay erase operation until the @samp{vFlashDone}
35928 packet is received.
35938 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35939 @cindex @samp{vFlashWrite} packet
35940 Direct the stub to write data to flash address @var{addr}. The data
35941 is passed in binary form using the same encoding as for the @samp{X}
35942 packet (@pxref{Binary Data}). The memory ranges specified by
35943 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35944 not overlap, and must appear in order of increasing addresses
35945 (although @samp{vFlashErase} packets for higher addresses may already
35946 have been received; the ordering is guaranteed only between
35947 @samp{vFlashWrite} packets). If a packet writes to an address that was
35948 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35949 target-specific method, the results are unpredictable.
35957 for vFlashWrite addressing non-flash memory
35963 @cindex @samp{vFlashDone} packet
35964 Indicate to the stub that flash programming operation is finished.
35965 The stub is permitted to delay or batch the effects of a group of
35966 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35967 @samp{vFlashDone} packet is received. The contents of the affected
35968 regions of flash memory are unpredictable until the @samp{vFlashDone}
35969 request is completed.
35971 @item vKill;@var{pid}
35972 @cindex @samp{vKill} packet
35973 @anchor{vKill packet}
35974 Kill the process with the specified process ID @var{pid}, which is a
35975 hexadecimal integer identifying the process. This packet is used in
35976 preference to @samp{k} when multiprocess protocol extensions are
35977 supported; see @ref{multiprocess extensions}.
35987 @item vMustReplyEmpty
35988 @cindex @samp{vMustReplyEmpty} packet
35989 The correct reply to an unknown @samp{v} packet is to return the empty
35990 string, however, some older versions of @command{gdbserver} would
35991 incorrectly return @samp{OK} for unknown @samp{v} packets.
35993 The @samp{vMustReplyEmpty} is used as a feature test to check how
35994 @command{gdbserver} handles unknown packets, it is important that this
35995 packet be handled in the same way as other unknown @samp{v} packets.
35996 If this packet is handled differently to other unknown @samp{v}
35997 packets then it is possile that @value{GDBN} may run into problems in
35998 other areas, specifically around use of @samp{vFile:setfs:}.
36000 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36001 @cindex @samp{vRun} packet
36002 Run the program @var{filename}, passing it each @var{argument} on its
36003 command line. The file and arguments are hex-encoded strings. If
36004 @var{filename} is an empty string, the stub may use a default program
36005 (e.g.@: the last program run). The program is created in the stopped
36008 @c FIXME: What about non-stop mode?
36010 This packet is only available in extended mode (@pxref{extended mode}).
36016 @item @r{Any stop packet}
36017 for success (@pxref{Stop Reply Packets})
36021 @cindex @samp{vStopped} packet
36022 @xref{Notification Packets}.
36024 @item X @var{addr},@var{length}:@var{XX@dots{}}
36026 @cindex @samp{X} packet
36027 Write data to memory, where the data is transmitted in binary.
36028 Memory is specified by its address @var{addr} and number of addressable memory
36029 units @var{length} (@pxref{addressable memory unit});
36030 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36040 @item z @var{type},@var{addr},@var{kind}
36041 @itemx Z @var{type},@var{addr},@var{kind}
36042 @anchor{insert breakpoint or watchpoint packet}
36043 @cindex @samp{z} packet
36044 @cindex @samp{Z} packets
36045 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36046 watchpoint starting at address @var{address} of kind @var{kind}.
36048 Each breakpoint and watchpoint packet @var{type} is documented
36051 @emph{Implementation notes: A remote target shall return an empty string
36052 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36053 remote target shall support either both or neither of a given
36054 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36055 avoid potential problems with duplicate packets, the operations should
36056 be implemented in an idempotent way.}
36058 @item z0,@var{addr},@var{kind}
36059 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36060 @cindex @samp{z0} packet
36061 @cindex @samp{Z0} packet
36062 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36063 @var{addr} of type @var{kind}.
36065 A software breakpoint is implemented by replacing the instruction at
36066 @var{addr} with a software breakpoint or trap instruction. The
36067 @var{kind} is target-specific and typically indicates the size of the
36068 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36069 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36070 architectures have additional meanings for @var{kind}
36071 (@pxref{Architecture-Specific Protocol Details}); if no
36072 architecture-specific value is being used, it should be @samp{0}.
36073 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36074 conditional expressions in bytecode form that should be evaluated on
36075 the target's side. These are the conditions that should be taken into
36076 consideration when deciding if the breakpoint trigger should be
36077 reported back to @value{GDBN}.
36079 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36080 for how to best report a software breakpoint event to @value{GDBN}.
36082 The @var{cond_list} parameter is comprised of a series of expressions,
36083 concatenated without separators. Each expression has the following form:
36087 @item X @var{len},@var{expr}
36088 @var{len} is the length of the bytecode expression and @var{expr} is the
36089 actual conditional expression in bytecode form.
36093 The optional @var{cmd_list} parameter introduces commands that may be
36094 run on the target, rather than being reported back to @value{GDBN}.
36095 The parameter starts with a numeric flag @var{persist}; if the flag is
36096 nonzero, then the breakpoint may remain active and the commands
36097 continue to be run even when @value{GDBN} disconnects from the target.
36098 Following this flag is a series of expressions concatenated with no
36099 separators. Each expression has the following form:
36103 @item X @var{len},@var{expr}
36104 @var{len} is the length of the bytecode expression and @var{expr} is the
36105 actual commands expression in bytecode form.
36109 @emph{Implementation note: It is possible for a target to copy or move
36110 code that contains software breakpoints (e.g., when implementing
36111 overlays). The behavior of this packet, in the presence of such a
36112 target, is not defined.}
36124 @item z1,@var{addr},@var{kind}
36125 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36126 @cindex @samp{z1} packet
36127 @cindex @samp{Z1} packet
36128 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36129 address @var{addr}.
36131 A hardware breakpoint is implemented using a mechanism that is not
36132 dependent on being able to modify the target's memory. The
36133 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36134 same meaning as in @samp{Z0} packets.
36136 @emph{Implementation note: A hardware breakpoint is not affected by code
36149 @item z2,@var{addr},@var{kind}
36150 @itemx Z2,@var{addr},@var{kind}
36151 @cindex @samp{z2} packet
36152 @cindex @samp{Z2} packet
36153 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36154 The number of bytes to watch is specified by @var{kind}.
36166 @item z3,@var{addr},@var{kind}
36167 @itemx Z3,@var{addr},@var{kind}
36168 @cindex @samp{z3} packet
36169 @cindex @samp{Z3} packet
36170 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36171 The number of bytes to watch is specified by @var{kind}.
36183 @item z4,@var{addr},@var{kind}
36184 @itemx Z4,@var{addr},@var{kind}
36185 @cindex @samp{z4} packet
36186 @cindex @samp{Z4} packet
36187 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36188 The number of bytes to watch is specified by @var{kind}.
36202 @node Stop Reply Packets
36203 @section Stop Reply Packets
36204 @cindex stop reply packets
36206 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36207 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36208 receive any of the below as a reply. Except for @samp{?}
36209 and @samp{vStopped}, that reply is only returned
36210 when the target halts. In the below the exact meaning of @dfn{signal
36211 number} is defined by the header @file{include/gdb/signals.h} in the
36212 @value{GDBN} source code.
36214 In non-stop mode, the server will simply reply @samp{OK} to commands
36215 such as @samp{vCont}; any stop will be the subject of a future
36216 notification. @xref{Remote Non-Stop}.
36218 As in the description of request packets, we include spaces in the
36219 reply templates for clarity; these are not part of the reply packet's
36220 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36226 The program received signal number @var{AA} (a two-digit hexadecimal
36227 number). This is equivalent to a @samp{T} response with no
36228 @var{n}:@var{r} pairs.
36230 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36231 @cindex @samp{T} packet reply
36232 The program received signal number @var{AA} (a two-digit hexadecimal
36233 number). This is equivalent to an @samp{S} response, except that the
36234 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36235 and other information directly in the stop reply packet, reducing
36236 round-trip latency. Single-step and breakpoint traps are reported
36237 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36241 If @var{n} is a hexadecimal number, it is a register number, and the
36242 corresponding @var{r} gives that register's value. The data @var{r} is a
36243 series of bytes in target byte order, with each byte given by a
36244 two-digit hex number.
36247 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36248 the stopped thread, as specified in @ref{thread-id syntax}.
36251 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36252 the core on which the stop event was detected.
36255 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36256 specific event that stopped the target. The currently defined stop
36257 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36258 signal. At most one stop reason should be present.
36261 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36262 and go on to the next; this allows us to extend the protocol in the
36266 The currently defined stop reasons are:
36272 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36275 @item syscall_entry
36276 @itemx syscall_return
36277 The packet indicates a syscall entry or return, and @var{r} is the
36278 syscall number, in hex.
36280 @cindex shared library events, remote reply
36282 The packet indicates that the loaded libraries have changed.
36283 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36284 list of loaded libraries. The @var{r} part is ignored.
36286 @cindex replay log events, remote reply
36288 The packet indicates that the target cannot continue replaying
36289 logged execution events, because it has reached the end (or the
36290 beginning when executing backward) of the log. The value of @var{r}
36291 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36292 for more information.
36295 @anchor{swbreak stop reason}
36296 The packet indicates a software breakpoint instruction was executed,
36297 irrespective of whether it was @value{GDBN} that planted the
36298 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36299 part must be left empty.
36301 On some architectures, such as x86, at the architecture level, when a
36302 breakpoint instruction executes the program counter points at the
36303 breakpoint address plus an offset. On such targets, the stub is
36304 responsible for adjusting the PC to point back at the breakpoint
36307 This packet should not be sent by default; older @value{GDBN} versions
36308 did not support it. @value{GDBN} requests it, by supplying an
36309 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36310 remote stub must also supply the appropriate @samp{qSupported} feature
36311 indicating support.
36313 This packet is required for correct non-stop mode operation.
36316 The packet indicates the target stopped for a hardware breakpoint.
36317 The @var{r} part must be left empty.
36319 The same remarks about @samp{qSupported} and non-stop mode above
36322 @cindex fork events, remote reply
36324 The packet indicates that @code{fork} was called, and @var{r}
36325 is the thread ID of the new child process. Refer to
36326 @ref{thread-id syntax} for the format of the @var{thread-id}
36327 field. This packet is only applicable to targets that support
36330 This packet should not be sent by default; older @value{GDBN} versions
36331 did not support it. @value{GDBN} requests it, by supplying an
36332 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36333 remote stub must also supply the appropriate @samp{qSupported} feature
36334 indicating support.
36336 @cindex vfork events, remote reply
36338 The packet indicates that @code{vfork} was called, and @var{r}
36339 is the thread ID of the new child process. Refer to
36340 @ref{thread-id syntax} for the format of the @var{thread-id}
36341 field. This packet is only applicable to targets that support
36344 This packet should not be sent by default; older @value{GDBN} versions
36345 did not support it. @value{GDBN} requests it, by supplying an
36346 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36347 remote stub must also supply the appropriate @samp{qSupported} feature
36348 indicating support.
36350 @cindex vforkdone events, remote reply
36352 The packet indicates that a child process created by a vfork
36353 has either called @code{exec} or terminated, so that the
36354 address spaces of the parent and child process are no longer
36355 shared. The @var{r} part is ignored. This packet is only
36356 applicable to targets that support vforkdone events.
36358 This packet should not be sent by default; older @value{GDBN} versions
36359 did not support it. @value{GDBN} requests it, by supplying an
36360 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36361 remote stub must also supply the appropriate @samp{qSupported} feature
36362 indicating support.
36364 @cindex exec events, remote reply
36366 The packet indicates that @code{execve} was called, and @var{r}
36367 is the absolute pathname of the file that was executed, in hex.
36368 This packet is only applicable to targets that support exec events.
36370 This packet should not be sent by default; older @value{GDBN} versions
36371 did not support it. @value{GDBN} requests it, by supplying an
36372 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36373 remote stub must also supply the appropriate @samp{qSupported} feature
36374 indicating support.
36376 @cindex thread create event, remote reply
36377 @anchor{thread create event}
36379 The packet indicates that the thread was just created. The new thread
36380 is stopped until @value{GDBN} sets it running with a resumption packet
36381 (@pxref{vCont packet}). This packet should not be sent by default;
36382 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36383 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36384 @var{r} part is ignored.
36389 @itemx W @var{AA} ; process:@var{pid}
36390 The process exited, and @var{AA} is the exit status. This is only
36391 applicable to certain targets.
36393 The second form of the response, including the process ID of the
36394 exited process, can be used only when @value{GDBN} has reported
36395 support for multiprocess protocol extensions; see @ref{multiprocess
36396 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36400 @itemx X @var{AA} ; process:@var{pid}
36401 The process terminated with signal @var{AA}.
36403 The second form of the response, including the process ID of the
36404 terminated process, can be used only when @value{GDBN} has reported
36405 support for multiprocess protocol extensions; see @ref{multiprocess
36406 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36409 @anchor{thread exit event}
36410 @cindex thread exit event, remote reply
36411 @item w @var{AA} ; @var{tid}
36413 The thread exited, and @var{AA} is the exit status. This response
36414 should not be sent by default; @value{GDBN} requests it with the
36415 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36416 @var{AA} is formatted as a big-endian hex string.
36419 There are no resumed threads left in the target. In other words, even
36420 though the process is alive, the last resumed thread has exited. For
36421 example, say the target process has two threads: thread 1 and thread
36422 2. The client leaves thread 1 stopped, and resumes thread 2, which
36423 subsequently exits. At this point, even though the process is still
36424 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36425 executing either. The @samp{N} stop reply thus informs the client
36426 that it can stop waiting for stop replies. This packet should not be
36427 sent by default; older @value{GDBN} versions did not support it.
36428 @value{GDBN} requests it, by supplying an appropriate
36429 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36430 also supply the appropriate @samp{qSupported} feature indicating
36433 @item O @var{XX}@dots{}
36434 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36435 written as the program's console output. This can happen at any time
36436 while the program is running and the debugger should continue to wait
36437 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36439 @item F @var{call-id},@var{parameter}@dots{}
36440 @var{call-id} is the identifier which says which host system call should
36441 be called. This is just the name of the function. Translation into the
36442 correct system call is only applicable as it's defined in @value{GDBN}.
36443 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36446 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36447 this very system call.
36449 The target replies with this packet when it expects @value{GDBN} to
36450 call a host system call on behalf of the target. @value{GDBN} replies
36451 with an appropriate @samp{F} packet and keeps up waiting for the next
36452 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36453 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36454 Protocol Extension}, for more details.
36458 @node General Query Packets
36459 @section General Query Packets
36460 @cindex remote query requests
36462 Packets starting with @samp{q} are @dfn{general query packets};
36463 packets starting with @samp{Q} are @dfn{general set packets}. General
36464 query and set packets are a semi-unified form for retrieving and
36465 sending information to and from the stub.
36467 The initial letter of a query or set packet is followed by a name
36468 indicating what sort of thing the packet applies to. For example,
36469 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36470 definitions with the stub. These packet names follow some
36475 The name must not contain commas, colons or semicolons.
36477 Most @value{GDBN} query and set packets have a leading upper case
36480 The names of custom vendor packets should use a company prefix, in
36481 lower case, followed by a period. For example, packets designed at
36482 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36483 foos) or @samp{Qacme.bar} (for setting bars).
36486 The name of a query or set packet should be separated from any
36487 parameters by a @samp{:}; the parameters themselves should be
36488 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36489 full packet name, and check for a separator or the end of the packet,
36490 in case two packet names share a common prefix. New packets should not begin
36491 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36492 packets predate these conventions, and have arguments without any terminator
36493 for the packet name; we suspect they are in widespread use in places that
36494 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36495 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36498 Like the descriptions of the other packets, each description here
36499 has a template showing the packet's overall syntax, followed by an
36500 explanation of the packet's meaning. We include spaces in some of the
36501 templates for clarity; these are not part of the packet's syntax. No
36502 @value{GDBN} packet uses spaces to separate its components.
36504 Here are the currently defined query and set packets:
36510 Turn on or off the agent as a helper to perform some debugging operations
36511 delegated from @value{GDBN} (@pxref{Control Agent}).
36513 @item QAllow:@var{op}:@var{val}@dots{}
36514 @cindex @samp{QAllow} packet
36515 Specify which operations @value{GDBN} expects to request of the
36516 target, as a semicolon-separated list of operation name and value
36517 pairs. Possible values for @var{op} include @samp{WriteReg},
36518 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36519 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36520 indicating that @value{GDBN} will not request the operation, or 1,
36521 indicating that it may. (The target can then use this to set up its
36522 own internals optimally, for instance if the debugger never expects to
36523 insert breakpoints, it may not need to install its own trap handler.)
36526 @cindex current thread, remote request
36527 @cindex @samp{qC} packet
36528 Return the current thread ID.
36532 @item QC @var{thread-id}
36533 Where @var{thread-id} is a thread ID as documented in
36534 @ref{thread-id syntax}.
36535 @item @r{(anything else)}
36536 Any other reply implies the old thread ID.
36539 @item qCRC:@var{addr},@var{length}
36540 @cindex CRC of memory block, remote request
36541 @cindex @samp{qCRC} packet
36542 @anchor{qCRC packet}
36543 Compute the CRC checksum of a block of memory using CRC-32 defined in
36544 IEEE 802.3. The CRC is computed byte at a time, taking the most
36545 significant bit of each byte first. The initial pattern code
36546 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36548 @emph{Note:} This is the same CRC used in validating separate debug
36549 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36550 Files}). However the algorithm is slightly different. When validating
36551 separate debug files, the CRC is computed taking the @emph{least}
36552 significant bit of each byte first, and the final result is inverted to
36553 detect trailing zeros.
36558 An error (such as memory fault)
36559 @item C @var{crc32}
36560 The specified memory region's checksum is @var{crc32}.
36563 @item QDisableRandomization:@var{value}
36564 @cindex disable address space randomization, remote request
36565 @cindex @samp{QDisableRandomization} packet
36566 Some target operating systems will randomize the virtual address space
36567 of the inferior process as a security feature, but provide a feature
36568 to disable such randomization, e.g.@: to allow for a more deterministic
36569 debugging experience. On such systems, this packet with a @var{value}
36570 of 1 directs the target to disable address space randomization for
36571 processes subsequently started via @samp{vRun} packets, while a packet
36572 with a @var{value} of 0 tells the target to enable address space
36575 This packet is only available in extended mode (@pxref{extended mode}).
36580 The request succeeded.
36583 An error occurred. The error number @var{nn} is given as hex digits.
36586 An empty reply indicates that @samp{QDisableRandomization} is not supported
36590 This packet is not probed by default; the remote stub must request it,
36591 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36592 This should only be done on targets that actually support disabling
36593 address space randomization.
36595 @item QStartupWithShell:@var{value}
36596 @cindex startup with shell, remote request
36597 @cindex @samp{QStartupWithShell} packet
36598 On UNIX-like targets, it is possible to start the inferior using a
36599 shell program. This is the default behavior on both @value{GDBN} and
36600 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36601 used to inform @command{gdbserver} whether it should start the
36602 inferior using a shell or not.
36604 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36605 to start the inferior. If @var{value} is @samp{1},
36606 @command{gdbserver} will use a shell to start the inferior. All other
36607 values are considered an error.
36609 This packet is only available in extended mode (@pxref{extended
36615 The request succeeded.
36618 An error occurred. The error number @var{nn} is given as hex digits.
36621 This packet is not probed by default; the remote stub must request it,
36622 by supplying an appropriate @samp{qSupported} response
36623 (@pxref{qSupported}). This should only be done on targets that
36624 actually support starting the inferior using a shell.
36626 Use of this packet is controlled by the @code{set startup-with-shell}
36627 command; @pxref{set startup-with-shell}.
36629 @item QEnvironmentHexEncoded:@var{hex-value}
36630 @anchor{QEnvironmentHexEncoded}
36631 @cindex set environment variable, remote request
36632 @cindex @samp{QEnvironmentHexEncoded} packet
36633 On UNIX-like targets, it is possible to set environment variables that
36634 will be passed to the inferior during the startup process. This
36635 packet is used to inform @command{gdbserver} of an environment
36636 variable that has been defined by the user on @value{GDBN} (@pxref{set
36639 The packet is composed by @var{hex-value}, an hex encoded
36640 representation of the @var{name=value} format representing an
36641 environment variable. The name of the environment variable is
36642 represented by @var{name}, and the value to be assigned to the
36643 environment variable is represented by @var{value}. If the variable
36644 has no value (i.e., the value is @code{null}), then @var{value} will
36647 This packet is only available in extended mode (@pxref{extended
36653 The request succeeded.
36656 This packet is not probed by default; the remote stub must request it,
36657 by supplying an appropriate @samp{qSupported} response
36658 (@pxref{qSupported}). This should only be done on targets that
36659 actually support passing environment variables to the starting
36662 This packet is related to the @code{set environment} command;
36663 @pxref{set environment}.
36665 @item QEnvironmentUnset:@var{hex-value}
36666 @anchor{QEnvironmentUnset}
36667 @cindex unset environment variable, remote request
36668 @cindex @samp{QEnvironmentUnset} packet
36669 On UNIX-like targets, it is possible to unset environment variables
36670 before starting the inferior in the remote target. This packet is
36671 used to inform @command{gdbserver} of an environment variable that has
36672 been unset by the user on @value{GDBN} (@pxref{unset environment}).
36674 The packet is composed by @var{hex-value}, an hex encoded
36675 representation of the name of the environment variable to be unset.
36677 This packet is only available in extended mode (@pxref{extended
36683 The request succeeded.
36686 This packet is not probed by default; the remote stub must request it,
36687 by supplying an appropriate @samp{qSupported} response
36688 (@pxref{qSupported}). This should only be done on targets that
36689 actually support passing environment variables to the starting
36692 This packet is related to the @code{unset environment} command;
36693 @pxref{unset environment}.
36695 @item QEnvironmentReset
36696 @anchor{QEnvironmentReset}
36697 @cindex reset environment, remote request
36698 @cindex @samp{QEnvironmentReset} packet
36699 On UNIX-like targets, this packet is used to reset the state of
36700 environment variables in the remote target before starting the
36701 inferior. In this context, reset means unsetting all environment
36702 variables that were previously set by the user (i.e., were not
36703 initially present in the environment). It is sent to
36704 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
36705 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
36706 (@pxref{QEnvironmentUnset}) packets.
36708 This packet is only available in extended mode (@pxref{extended
36714 The request succeeded.
36717 This packet is not probed by default; the remote stub must request it,
36718 by supplying an appropriate @samp{qSupported} response
36719 (@pxref{qSupported}). This should only be done on targets that
36720 actually support passing environment variables to the starting
36724 @itemx qsThreadInfo
36725 @cindex list active threads, remote request
36726 @cindex @samp{qfThreadInfo} packet
36727 @cindex @samp{qsThreadInfo} packet
36728 Obtain a list of all active thread IDs from the target (OS). Since there
36729 may be too many active threads to fit into one reply packet, this query
36730 works iteratively: it may require more than one query/reply sequence to
36731 obtain the entire list of threads. The first query of the sequence will
36732 be the @samp{qfThreadInfo} query; subsequent queries in the
36733 sequence will be the @samp{qsThreadInfo} query.
36735 NOTE: This packet replaces the @samp{qL} query (see below).
36739 @item m @var{thread-id}
36741 @item m @var{thread-id},@var{thread-id}@dots{}
36742 a comma-separated list of thread IDs
36744 (lower case letter @samp{L}) denotes end of list.
36747 In response to each query, the target will reply with a list of one or
36748 more thread IDs, separated by commas.
36749 @value{GDBN} will respond to each reply with a request for more thread
36750 ids (using the @samp{qs} form of the query), until the target responds
36751 with @samp{l} (lower-case ell, for @dfn{last}).
36752 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36755 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36756 initial connection with the remote target, and the very first thread ID
36757 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36758 message. Therefore, the stub should ensure that the first thread ID in
36759 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36761 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36762 @cindex get thread-local storage address, remote request
36763 @cindex @samp{qGetTLSAddr} packet
36764 Fetch the address associated with thread local storage specified
36765 by @var{thread-id}, @var{offset}, and @var{lm}.
36767 @var{thread-id} is the thread ID associated with the
36768 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36770 @var{offset} is the (big endian, hex encoded) offset associated with the
36771 thread local variable. (This offset is obtained from the debug
36772 information associated with the variable.)
36774 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36775 load module associated with the thread local storage. For example,
36776 a @sc{gnu}/Linux system will pass the link map address of the shared
36777 object associated with the thread local storage under consideration.
36778 Other operating environments may choose to represent the load module
36779 differently, so the precise meaning of this parameter will vary.
36783 @item @var{XX}@dots{}
36784 Hex encoded (big endian) bytes representing the address of the thread
36785 local storage requested.
36788 An error occurred. The error number @var{nn} is given as hex digits.
36791 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36794 @item qGetTIBAddr:@var{thread-id}
36795 @cindex get thread information block address
36796 @cindex @samp{qGetTIBAddr} packet
36797 Fetch address of the Windows OS specific Thread Information Block.
36799 @var{thread-id} is the thread ID associated with the thread.
36803 @item @var{XX}@dots{}
36804 Hex encoded (big endian) bytes representing the linear address of the
36805 thread information block.
36808 An error occured. This means that either the thread was not found, or the
36809 address could not be retrieved.
36812 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36815 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36816 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36817 digit) is one to indicate the first query and zero to indicate a
36818 subsequent query; @var{threadcount} (two hex digits) is the maximum
36819 number of threads the response packet can contain; and @var{nextthread}
36820 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36821 returned in the response as @var{argthread}.
36823 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36827 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36828 Where: @var{count} (two hex digits) is the number of threads being
36829 returned; @var{done} (one hex digit) is zero to indicate more threads
36830 and one indicates no further threads; @var{argthreadid} (eight hex
36831 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36832 is a sequence of thread IDs, @var{threadid} (eight hex
36833 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36837 @cindex section offsets, remote request
36838 @cindex @samp{qOffsets} packet
36839 Get section offsets that the target used when relocating the downloaded
36844 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36845 Relocate the @code{Text} section by @var{xxx} from its original address.
36846 Relocate the @code{Data} section by @var{yyy} from its original address.
36847 If the object file format provides segment information (e.g.@: @sc{elf}
36848 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36849 segments by the supplied offsets.
36851 @emph{Note: while a @code{Bss} offset may be included in the response,
36852 @value{GDBN} ignores this and instead applies the @code{Data} offset
36853 to the @code{Bss} section.}
36855 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36856 Relocate the first segment of the object file, which conventionally
36857 contains program code, to a starting address of @var{xxx}. If
36858 @samp{DataSeg} is specified, relocate the second segment, which
36859 conventionally contains modifiable data, to a starting address of
36860 @var{yyy}. @value{GDBN} will report an error if the object file
36861 does not contain segment information, or does not contain at least
36862 as many segments as mentioned in the reply. Extra segments are
36863 kept at fixed offsets relative to the last relocated segment.
36866 @item qP @var{mode} @var{thread-id}
36867 @cindex thread information, remote request
36868 @cindex @samp{qP} packet
36869 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36870 encoded 32 bit mode; @var{thread-id} is a thread ID
36871 (@pxref{thread-id syntax}).
36873 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36876 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36880 @cindex non-stop mode, remote request
36881 @cindex @samp{QNonStop} packet
36883 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36884 @xref{Remote Non-Stop}, for more information.
36889 The request succeeded.
36892 An error occurred. The error number @var{nn} is given as hex digits.
36895 An empty reply indicates that @samp{QNonStop} is not supported by
36899 This packet is not probed by default; the remote stub must request it,
36900 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36901 Use of this packet is controlled by the @code{set non-stop} command;
36902 @pxref{Non-Stop Mode}.
36904 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36905 @itemx QCatchSyscalls:0
36906 @cindex catch syscalls from inferior, remote request
36907 @cindex @samp{QCatchSyscalls} packet
36908 @anchor{QCatchSyscalls}
36909 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36910 catching syscalls from the inferior process.
36912 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36913 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36914 is listed, every system call should be reported.
36916 Note that if a syscall not in the list is reported, @value{GDBN} will
36917 still filter the event according to its own list from all corresponding
36918 @code{catch syscall} commands. However, it is more efficient to only
36919 report the requested syscalls.
36921 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36922 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36924 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36925 kept for the new process too. On targets where exec may affect syscall
36926 numbers, for example with exec between 32 and 64-bit processes, the
36927 client should send a new packet with the new syscall list.
36932 The request succeeded.
36935 An error occurred. @var{nn} are hex digits.
36938 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36942 Use of this packet is controlled by the @code{set remote catch-syscalls}
36943 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36944 This packet is not probed by default; the remote stub must request it,
36945 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36947 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36948 @cindex pass signals to inferior, remote request
36949 @cindex @samp{QPassSignals} packet
36950 @anchor{QPassSignals}
36951 Each listed @var{signal} should be passed directly to the inferior process.
36952 Signals are numbered identically to continue packets and stop replies
36953 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36954 strictly greater than the previous item. These signals do not need to stop
36955 the inferior, or be reported to @value{GDBN}. All other signals should be
36956 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36957 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36958 new list. This packet improves performance when using @samp{handle
36959 @var{signal} nostop noprint pass}.
36964 The request succeeded.
36967 An error occurred. The error number @var{nn} is given as hex digits.
36970 An empty reply indicates that @samp{QPassSignals} is not supported by
36974 Use of this packet is controlled by the @code{set remote pass-signals}
36975 command (@pxref{Remote Configuration, set remote pass-signals}).
36976 This packet is not probed by default; the remote stub must request it,
36977 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36979 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36980 @cindex signals the inferior may see, remote request
36981 @cindex @samp{QProgramSignals} packet
36982 @anchor{QProgramSignals}
36983 Each listed @var{signal} may be delivered to the inferior process.
36984 Others should be silently discarded.
36986 In some cases, the remote stub may need to decide whether to deliver a
36987 signal to the program or not without @value{GDBN} involvement. One
36988 example of that is while detaching --- the program's threads may have
36989 stopped for signals that haven't yet had a chance of being reported to
36990 @value{GDBN}, and so the remote stub can use the signal list specified
36991 by this packet to know whether to deliver or ignore those pending
36994 This does not influence whether to deliver a signal as requested by a
36995 resumption packet (@pxref{vCont packet}).
36997 Signals are numbered identically to continue packets and stop replies
36998 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36999 strictly greater than the previous item. Multiple
37000 @samp{QProgramSignals} packets do not combine; any earlier
37001 @samp{QProgramSignals} list is completely replaced by the new list.
37006 The request succeeded.
37009 An error occurred. The error number @var{nn} is given as hex digits.
37012 An empty reply indicates that @samp{QProgramSignals} is not supported
37016 Use of this packet is controlled by the @code{set remote program-signals}
37017 command (@pxref{Remote Configuration, set remote program-signals}).
37018 This packet is not probed by default; the remote stub must request it,
37019 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37021 @anchor{QThreadEvents}
37022 @item QThreadEvents:1
37023 @itemx QThreadEvents:0
37024 @cindex thread create/exit events, remote request
37025 @cindex @samp{QThreadEvents} packet
37027 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37028 reporting of thread create and exit events. @xref{thread create
37029 event}, for the reply specifications. For example, this is used in
37030 non-stop mode when @value{GDBN} stops a set of threads and
37031 synchronously waits for the their corresponding stop replies. Without
37032 exit events, if one of the threads exits, @value{GDBN} would hang
37033 forever not knowing that it should no longer expect a stop for that
37034 same thread. @value{GDBN} does not enable this feature unless the
37035 stub reports that it supports it by including @samp{QThreadEvents+} in
37036 its @samp{qSupported} reply.
37041 The request succeeded.
37044 An error occurred. The error number @var{nn} is given as hex digits.
37047 An empty reply indicates that @samp{QThreadEvents} is not supported by
37051 Use of this packet is controlled by the @code{set remote thread-events}
37052 command (@pxref{Remote Configuration, set remote thread-events}).
37054 @item qRcmd,@var{command}
37055 @cindex execute remote command, remote request
37056 @cindex @samp{qRcmd} packet
37057 @var{command} (hex encoded) is passed to the local interpreter for
37058 execution. Invalid commands should be reported using the output
37059 string. Before the final result packet, the target may also respond
37060 with a number of intermediate @samp{O@var{output}} console output
37061 packets. @emph{Implementors should note that providing access to a
37062 stubs's interpreter may have security implications}.
37067 A command response with no output.
37069 A command response with the hex encoded output string @var{OUTPUT}.
37071 Indicate a badly formed request.
37073 An empty reply indicates that @samp{qRcmd} is not recognized.
37076 (Note that the @code{qRcmd} packet's name is separated from the
37077 command by a @samp{,}, not a @samp{:}, contrary to the naming
37078 conventions above. Please don't use this packet as a model for new
37081 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37082 @cindex searching memory, in remote debugging
37084 @cindex @samp{qSearch:memory} packet
37086 @cindex @samp{qSearch memory} packet
37087 @anchor{qSearch memory}
37088 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37089 Both @var{address} and @var{length} are encoded in hex;
37090 @var{search-pattern} is a sequence of bytes, also hex encoded.
37095 The pattern was not found.
37097 The pattern was found at @var{address}.
37099 A badly formed request or an error was encountered while searching memory.
37101 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37104 @item QStartNoAckMode
37105 @cindex @samp{QStartNoAckMode} packet
37106 @anchor{QStartNoAckMode}
37107 Request that the remote stub disable the normal @samp{+}/@samp{-}
37108 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37113 The stub has switched to no-acknowledgment mode.
37114 @value{GDBN} acknowledges this reponse,
37115 but neither the stub nor @value{GDBN} shall send or expect further
37116 @samp{+}/@samp{-} acknowledgments in the current connection.
37118 An empty reply indicates that the stub does not support no-acknowledgment mode.
37121 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37122 @cindex supported packets, remote query
37123 @cindex features of the remote protocol
37124 @cindex @samp{qSupported} packet
37125 @anchor{qSupported}
37126 Tell the remote stub about features supported by @value{GDBN}, and
37127 query the stub for features it supports. This packet allows
37128 @value{GDBN} and the remote stub to take advantage of each others'
37129 features. @samp{qSupported} also consolidates multiple feature probes
37130 at startup, to improve @value{GDBN} performance---a single larger
37131 packet performs better than multiple smaller probe packets on
37132 high-latency links. Some features may enable behavior which must not
37133 be on by default, e.g.@: because it would confuse older clients or
37134 stubs. Other features may describe packets which could be
37135 automatically probed for, but are not. These features must be
37136 reported before @value{GDBN} will use them. This ``default
37137 unsupported'' behavior is not appropriate for all packets, but it
37138 helps to keep the initial connection time under control with new
37139 versions of @value{GDBN} which support increasing numbers of packets.
37143 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37144 The stub supports or does not support each returned @var{stubfeature},
37145 depending on the form of each @var{stubfeature} (see below for the
37148 An empty reply indicates that @samp{qSupported} is not recognized,
37149 or that no features needed to be reported to @value{GDBN}.
37152 The allowed forms for each feature (either a @var{gdbfeature} in the
37153 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37157 @item @var{name}=@var{value}
37158 The remote protocol feature @var{name} is supported, and associated
37159 with the specified @var{value}. The format of @var{value} depends
37160 on the feature, but it must not include a semicolon.
37162 The remote protocol feature @var{name} is supported, and does not
37163 need an associated value.
37165 The remote protocol feature @var{name} is not supported.
37167 The remote protocol feature @var{name} may be supported, and
37168 @value{GDBN} should auto-detect support in some other way when it is
37169 needed. This form will not be used for @var{gdbfeature} notifications,
37170 but may be used for @var{stubfeature} responses.
37173 Whenever the stub receives a @samp{qSupported} request, the
37174 supplied set of @value{GDBN} features should override any previous
37175 request. This allows @value{GDBN} to put the stub in a known
37176 state, even if the stub had previously been communicating with
37177 a different version of @value{GDBN}.
37179 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37184 This feature indicates whether @value{GDBN} supports multiprocess
37185 extensions to the remote protocol. @value{GDBN} does not use such
37186 extensions unless the stub also reports that it supports them by
37187 including @samp{multiprocess+} in its @samp{qSupported} reply.
37188 @xref{multiprocess extensions}, for details.
37191 This feature indicates that @value{GDBN} supports the XML target
37192 description. If the stub sees @samp{xmlRegisters=} with target
37193 specific strings separated by a comma, it will report register
37197 This feature indicates whether @value{GDBN} supports the
37198 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37199 instruction reply packet}).
37202 This feature indicates whether @value{GDBN} supports the swbreak stop
37203 reason in stop replies. @xref{swbreak stop reason}, for details.
37206 This feature indicates whether @value{GDBN} supports the hwbreak stop
37207 reason in stop replies. @xref{swbreak stop reason}, for details.
37210 This feature indicates whether @value{GDBN} supports fork event
37211 extensions to the remote protocol. @value{GDBN} does not use such
37212 extensions unless the stub also reports that it supports them by
37213 including @samp{fork-events+} in its @samp{qSupported} reply.
37216 This feature indicates whether @value{GDBN} supports vfork event
37217 extensions to the remote protocol. @value{GDBN} does not use such
37218 extensions unless the stub also reports that it supports them by
37219 including @samp{vfork-events+} in its @samp{qSupported} reply.
37222 This feature indicates whether @value{GDBN} supports exec event
37223 extensions to the remote protocol. @value{GDBN} does not use such
37224 extensions unless the stub also reports that it supports them by
37225 including @samp{exec-events+} in its @samp{qSupported} reply.
37227 @item vContSupported
37228 This feature indicates whether @value{GDBN} wants to know the
37229 supported actions in the reply to @samp{vCont?} packet.
37232 Stubs should ignore any unknown values for
37233 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37234 packet supports receiving packets of unlimited length (earlier
37235 versions of @value{GDBN} may reject overly long responses). Additional values
37236 for @var{gdbfeature} may be defined in the future to let the stub take
37237 advantage of new features in @value{GDBN}, e.g.@: incompatible
37238 improvements in the remote protocol---the @samp{multiprocess} feature is
37239 an example of such a feature. The stub's reply should be independent
37240 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37241 describes all the features it supports, and then the stub replies with
37242 all the features it supports.
37244 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37245 responses, as long as each response uses one of the standard forms.
37247 Some features are flags. A stub which supports a flag feature
37248 should respond with a @samp{+} form response. Other features
37249 require values, and the stub should respond with an @samp{=}
37252 Each feature has a default value, which @value{GDBN} will use if
37253 @samp{qSupported} is not available or if the feature is not mentioned
37254 in the @samp{qSupported} response. The default values are fixed; a
37255 stub is free to omit any feature responses that match the defaults.
37257 Not all features can be probed, but for those which can, the probing
37258 mechanism is useful: in some cases, a stub's internal
37259 architecture may not allow the protocol layer to know some information
37260 about the underlying target in advance. This is especially common in
37261 stubs which may be configured for multiple targets.
37263 These are the currently defined stub features and their properties:
37265 @multitable @columnfractions 0.35 0.2 0.12 0.2
37266 @c NOTE: The first row should be @headitem, but we do not yet require
37267 @c a new enough version of Texinfo (4.7) to use @headitem.
37269 @tab Value Required
37273 @item @samp{PacketSize}
37278 @item @samp{qXfer:auxv:read}
37283 @item @samp{qXfer:btrace:read}
37288 @item @samp{qXfer:btrace-conf:read}
37293 @item @samp{qXfer:exec-file:read}
37298 @item @samp{qXfer:features:read}
37303 @item @samp{qXfer:libraries:read}
37308 @item @samp{qXfer:libraries-svr4:read}
37313 @item @samp{augmented-libraries-svr4-read}
37318 @item @samp{qXfer:memory-map:read}
37323 @item @samp{qXfer:sdata:read}
37328 @item @samp{qXfer:spu:read}
37333 @item @samp{qXfer:spu:write}
37338 @item @samp{qXfer:siginfo:read}
37343 @item @samp{qXfer:siginfo:write}
37348 @item @samp{qXfer:threads:read}
37353 @item @samp{qXfer:traceframe-info:read}
37358 @item @samp{qXfer:uib:read}
37363 @item @samp{qXfer:fdpic:read}
37368 @item @samp{Qbtrace:off}
37373 @item @samp{Qbtrace:bts}
37378 @item @samp{Qbtrace:pt}
37383 @item @samp{Qbtrace-conf:bts:size}
37388 @item @samp{Qbtrace-conf:pt:size}
37393 @item @samp{QNonStop}
37398 @item @samp{QCatchSyscalls}
37403 @item @samp{QPassSignals}
37408 @item @samp{QStartNoAckMode}
37413 @item @samp{multiprocess}
37418 @item @samp{ConditionalBreakpoints}
37423 @item @samp{ConditionalTracepoints}
37428 @item @samp{ReverseContinue}
37433 @item @samp{ReverseStep}
37438 @item @samp{TracepointSource}
37443 @item @samp{QAgent}
37448 @item @samp{QAllow}
37453 @item @samp{QDisableRandomization}
37458 @item @samp{EnableDisableTracepoints}
37463 @item @samp{QTBuffer:size}
37468 @item @samp{tracenz}
37473 @item @samp{BreakpointCommands}
37478 @item @samp{swbreak}
37483 @item @samp{hwbreak}
37488 @item @samp{fork-events}
37493 @item @samp{vfork-events}
37498 @item @samp{exec-events}
37503 @item @samp{QThreadEvents}
37508 @item @samp{no-resumed}
37515 These are the currently defined stub features, in more detail:
37518 @cindex packet size, remote protocol
37519 @item PacketSize=@var{bytes}
37520 The remote stub can accept packets up to at least @var{bytes} in
37521 length. @value{GDBN} will send packets up to this size for bulk
37522 transfers, and will never send larger packets. This is a limit on the
37523 data characters in the packet, including the frame and checksum.
37524 There is no trailing NUL byte in a remote protocol packet; if the stub
37525 stores packets in a NUL-terminated format, it should allow an extra
37526 byte in its buffer for the NUL. If this stub feature is not supported,
37527 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37529 @item qXfer:auxv:read
37530 The remote stub understands the @samp{qXfer:auxv:read} packet
37531 (@pxref{qXfer auxiliary vector read}).
37533 @item qXfer:btrace:read
37534 The remote stub understands the @samp{qXfer:btrace:read}
37535 packet (@pxref{qXfer btrace read}).
37537 @item qXfer:btrace-conf:read
37538 The remote stub understands the @samp{qXfer:btrace-conf:read}
37539 packet (@pxref{qXfer btrace-conf read}).
37541 @item qXfer:exec-file:read
37542 The remote stub understands the @samp{qXfer:exec-file:read} packet
37543 (@pxref{qXfer executable filename read}).
37545 @item qXfer:features:read
37546 The remote stub understands the @samp{qXfer:features:read} packet
37547 (@pxref{qXfer target description read}).
37549 @item qXfer:libraries:read
37550 The remote stub understands the @samp{qXfer:libraries:read} packet
37551 (@pxref{qXfer library list read}).
37553 @item qXfer:libraries-svr4:read
37554 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37555 (@pxref{qXfer svr4 library list read}).
37557 @item augmented-libraries-svr4-read
37558 The remote stub understands the augmented form of the
37559 @samp{qXfer:libraries-svr4:read} packet
37560 (@pxref{qXfer svr4 library list read}).
37562 @item qXfer:memory-map:read
37563 The remote stub understands the @samp{qXfer:memory-map:read} packet
37564 (@pxref{qXfer memory map read}).
37566 @item qXfer:sdata:read
37567 The remote stub understands the @samp{qXfer:sdata:read} packet
37568 (@pxref{qXfer sdata read}).
37570 @item qXfer:spu:read
37571 The remote stub understands the @samp{qXfer:spu:read} packet
37572 (@pxref{qXfer spu read}).
37574 @item qXfer:spu:write
37575 The remote stub understands the @samp{qXfer:spu:write} packet
37576 (@pxref{qXfer spu write}).
37578 @item qXfer:siginfo:read
37579 The remote stub understands the @samp{qXfer:siginfo:read} packet
37580 (@pxref{qXfer siginfo read}).
37582 @item qXfer:siginfo:write
37583 The remote stub understands the @samp{qXfer:siginfo:write} packet
37584 (@pxref{qXfer siginfo write}).
37586 @item qXfer:threads:read
37587 The remote stub understands the @samp{qXfer:threads:read} packet
37588 (@pxref{qXfer threads read}).
37590 @item qXfer:traceframe-info:read
37591 The remote stub understands the @samp{qXfer:traceframe-info:read}
37592 packet (@pxref{qXfer traceframe info read}).
37594 @item qXfer:uib:read
37595 The remote stub understands the @samp{qXfer:uib:read}
37596 packet (@pxref{qXfer unwind info block}).
37598 @item qXfer:fdpic:read
37599 The remote stub understands the @samp{qXfer:fdpic:read}
37600 packet (@pxref{qXfer fdpic loadmap read}).
37603 The remote stub understands the @samp{QNonStop} packet
37604 (@pxref{QNonStop}).
37606 @item QCatchSyscalls
37607 The remote stub understands the @samp{QCatchSyscalls} packet
37608 (@pxref{QCatchSyscalls}).
37611 The remote stub understands the @samp{QPassSignals} packet
37612 (@pxref{QPassSignals}).
37614 @item QStartNoAckMode
37615 The remote stub understands the @samp{QStartNoAckMode} packet and
37616 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37619 @anchor{multiprocess extensions}
37620 @cindex multiprocess extensions, in remote protocol
37621 The remote stub understands the multiprocess extensions to the remote
37622 protocol syntax. The multiprocess extensions affect the syntax of
37623 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37624 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37625 replies. Note that reporting this feature indicates support for the
37626 syntactic extensions only, not that the stub necessarily supports
37627 debugging of more than one process at a time. The stub must not use
37628 multiprocess extensions in packet replies unless @value{GDBN} has also
37629 indicated it supports them in its @samp{qSupported} request.
37631 @item qXfer:osdata:read
37632 The remote stub understands the @samp{qXfer:osdata:read} packet
37633 ((@pxref{qXfer osdata read}).
37635 @item ConditionalBreakpoints
37636 The target accepts and implements evaluation of conditional expressions
37637 defined for breakpoints. The target will only report breakpoint triggers
37638 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37640 @item ConditionalTracepoints
37641 The remote stub accepts and implements conditional expressions defined
37642 for tracepoints (@pxref{Tracepoint Conditions}).
37644 @item ReverseContinue
37645 The remote stub accepts and implements the reverse continue packet
37649 The remote stub accepts and implements the reverse step packet
37652 @item TracepointSource
37653 The remote stub understands the @samp{QTDPsrc} packet that supplies
37654 the source form of tracepoint definitions.
37657 The remote stub understands the @samp{QAgent} packet.
37660 The remote stub understands the @samp{QAllow} packet.
37662 @item QDisableRandomization
37663 The remote stub understands the @samp{QDisableRandomization} packet.
37665 @item StaticTracepoint
37666 @cindex static tracepoints, in remote protocol
37667 The remote stub supports static tracepoints.
37669 @item InstallInTrace
37670 @anchor{install tracepoint in tracing}
37671 The remote stub supports installing tracepoint in tracing.
37673 @item EnableDisableTracepoints
37674 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37675 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37676 to be enabled and disabled while a trace experiment is running.
37678 @item QTBuffer:size
37679 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37680 packet that allows to change the size of the trace buffer.
37683 @cindex string tracing, in remote protocol
37684 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37685 See @ref{Bytecode Descriptions} for details about the bytecode.
37687 @item BreakpointCommands
37688 @cindex breakpoint commands, in remote protocol
37689 The remote stub supports running a breakpoint's command list itself,
37690 rather than reporting the hit to @value{GDBN}.
37693 The remote stub understands the @samp{Qbtrace:off} packet.
37696 The remote stub understands the @samp{Qbtrace:bts} packet.
37699 The remote stub understands the @samp{Qbtrace:pt} packet.
37701 @item Qbtrace-conf:bts:size
37702 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37704 @item Qbtrace-conf:pt:size
37705 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37708 The remote stub reports the @samp{swbreak} stop reason for memory
37712 The remote stub reports the @samp{hwbreak} stop reason for hardware
37716 The remote stub reports the @samp{fork} stop reason for fork events.
37719 The remote stub reports the @samp{vfork} stop reason for vfork events
37720 and vforkdone events.
37723 The remote stub reports the @samp{exec} stop reason for exec events.
37725 @item vContSupported
37726 The remote stub reports the supported actions in the reply to
37727 @samp{vCont?} packet.
37729 @item QThreadEvents
37730 The remote stub understands the @samp{QThreadEvents} packet.
37733 The remote stub reports the @samp{N} stop reply.
37738 @cindex symbol lookup, remote request
37739 @cindex @samp{qSymbol} packet
37740 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37741 requests. Accept requests from the target for the values of symbols.
37746 The target does not need to look up any (more) symbols.
37747 @item qSymbol:@var{sym_name}
37748 The target requests the value of symbol @var{sym_name} (hex encoded).
37749 @value{GDBN} may provide the value by using the
37750 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37754 @item qSymbol:@var{sym_value}:@var{sym_name}
37755 Set the value of @var{sym_name} to @var{sym_value}.
37757 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37758 target has previously requested.
37760 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37761 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37767 The target does not need to look up any (more) symbols.
37768 @item qSymbol:@var{sym_name}
37769 The target requests the value of a new symbol @var{sym_name} (hex
37770 encoded). @value{GDBN} will continue to supply the values of symbols
37771 (if available), until the target ceases to request them.
37776 @itemx QTDisconnected
37783 @itemx qTMinFTPILen
37785 @xref{Tracepoint Packets}.
37787 @item qThreadExtraInfo,@var{thread-id}
37788 @cindex thread attributes info, remote request
37789 @cindex @samp{qThreadExtraInfo} packet
37790 Obtain from the target OS a printable string description of thread
37791 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37792 for the forms of @var{thread-id}. This
37793 string may contain anything that the target OS thinks is interesting
37794 for @value{GDBN} to tell the user about the thread. The string is
37795 displayed in @value{GDBN}'s @code{info threads} display. Some
37796 examples of possible thread extra info strings are @samp{Runnable}, or
37797 @samp{Blocked on Mutex}.
37801 @item @var{XX}@dots{}
37802 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37803 comprising the printable string containing the extra information about
37804 the thread's attributes.
37807 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37808 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37809 conventions above. Please don't use this packet as a model for new
37828 @xref{Tracepoint Packets}.
37830 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37831 @cindex read special object, remote request
37832 @cindex @samp{qXfer} packet
37833 @anchor{qXfer read}
37834 Read uninterpreted bytes from the target's special data area
37835 identified by the keyword @var{object}. Request @var{length} bytes
37836 starting at @var{offset} bytes into the data. The content and
37837 encoding of @var{annex} is specific to @var{object}; it can supply
37838 additional details about what data to access.
37843 Data @var{data} (@pxref{Binary Data}) has been read from the
37844 target. There may be more data at a higher address (although
37845 it is permitted to return @samp{m} even for the last valid
37846 block of data, as long as at least one byte of data was read).
37847 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37851 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37852 There is no more data to be read. It is possible for @var{data} to
37853 have fewer bytes than the @var{length} in the request.
37856 The @var{offset} in the request is at the end of the data.
37857 There is no more data to be read.
37860 The request was malformed, or @var{annex} was invalid.
37863 The offset was invalid, or there was an error encountered reading the data.
37864 The @var{nn} part is a hex-encoded @code{errno} value.
37867 An empty reply indicates the @var{object} string was not recognized by
37868 the stub, or that the object does not support reading.
37871 Here are the specific requests of this form defined so far. All the
37872 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37873 formats, listed above.
37876 @item qXfer:auxv:read::@var{offset},@var{length}
37877 @anchor{qXfer auxiliary vector read}
37878 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37879 auxiliary vector}. Note @var{annex} must be empty.
37881 This packet is not probed by default; the remote stub must request it,
37882 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37884 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37885 @anchor{qXfer btrace read}
37887 Return a description of the current branch trace.
37888 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37889 packet may have one of the following values:
37893 Returns all available branch trace.
37896 Returns all available branch trace if the branch trace changed since
37897 the last read request.
37900 Returns the new branch trace since the last read request. Adds a new
37901 block to the end of the trace that begins at zero and ends at the source
37902 location of the first branch in the trace buffer. This extra block is
37903 used to stitch traces together.
37905 If the trace buffer overflowed, returns an error indicating the overflow.
37908 This packet is not probed by default; the remote stub must request it
37909 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37911 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37912 @anchor{qXfer btrace-conf read}
37914 Return a description of the current branch trace configuration.
37915 @xref{Branch Trace Configuration Format}.
37917 This packet is not probed by default; the remote stub must request it
37918 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37920 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37921 @anchor{qXfer executable filename read}
37922 Return the full absolute name of the file that was executed to create
37923 a process running on the remote system. The annex specifies the
37924 numeric process ID of the process to query, encoded as a hexadecimal
37925 number. If the annex part is empty the remote stub should return the
37926 filename corresponding to the currently executing process.
37928 This packet is not probed by default; the remote stub must request it,
37929 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37931 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37932 @anchor{qXfer target description read}
37933 Access the @dfn{target description}. @xref{Target Descriptions}. The
37934 annex specifies which XML document to access. The main description is
37935 always loaded from the @samp{target.xml} annex.
37937 This packet is not probed by default; the remote stub must request it,
37938 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37940 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37941 @anchor{qXfer library list read}
37942 Access the target's list of loaded libraries. @xref{Library List Format}.
37943 The annex part of the generic @samp{qXfer} packet must be empty
37944 (@pxref{qXfer read}).
37946 Targets which maintain a list of libraries in the program's memory do
37947 not need to implement this packet; it is designed for platforms where
37948 the operating system manages the list of loaded libraries.
37950 This packet is not probed by default; the remote stub must request it,
37951 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37953 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37954 @anchor{qXfer svr4 library list read}
37955 Access the target's list of loaded libraries when the target is an SVR4
37956 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37957 of the generic @samp{qXfer} packet must be empty unless the remote
37958 stub indicated it supports the augmented form of this packet
37959 by supplying an appropriate @samp{qSupported} response
37960 (@pxref{qXfer read}, @ref{qSupported}).
37962 This packet is optional for better performance on SVR4 targets.
37963 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37965 This packet is not probed by default; the remote stub must request it,
37966 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37968 If the remote stub indicates it supports the augmented form of this
37969 packet then the annex part of the generic @samp{qXfer} packet may
37970 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37971 arguments. The currently supported arguments are:
37974 @item start=@var{address}
37975 A hexadecimal number specifying the address of the @samp{struct
37976 link_map} to start reading the library list from. If unset or zero
37977 then the first @samp{struct link_map} in the library list will be
37978 chosen as the starting point.
37980 @item prev=@var{address}
37981 A hexadecimal number specifying the address of the @samp{struct
37982 link_map} immediately preceding the @samp{struct link_map}
37983 specified by the @samp{start} argument. If unset or zero then
37984 the remote stub will expect that no @samp{struct link_map}
37985 exists prior to the starting point.
37989 Arguments that are not understood by the remote stub will be silently
37992 @item qXfer:memory-map:read::@var{offset},@var{length}
37993 @anchor{qXfer memory map read}
37994 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37995 annex part of the generic @samp{qXfer} packet must be empty
37996 (@pxref{qXfer read}).
37998 This packet is not probed by default; the remote stub must request it,
37999 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38001 @item qXfer:sdata:read::@var{offset},@var{length}
38002 @anchor{qXfer sdata read}
38004 Read contents of the extra collected static tracepoint marker
38005 information. The annex part of the generic @samp{qXfer} packet must
38006 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38009 This packet is not probed by default; the remote stub must request it,
38010 by supplying an appropriate @samp{qSupported} response
38011 (@pxref{qSupported}).
38013 @item qXfer:siginfo:read::@var{offset},@var{length}
38014 @anchor{qXfer siginfo read}
38015 Read contents of the extra signal information on the target
38016 system. The annex part of the generic @samp{qXfer} packet must be
38017 empty (@pxref{qXfer read}).
38019 This packet is not probed by default; the remote stub must request it,
38020 by supplying an appropriate @samp{qSupported} response
38021 (@pxref{qSupported}).
38023 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38024 @anchor{qXfer spu read}
38025 Read contents of an @code{spufs} file on the target system. The
38026 annex specifies which file to read; it must be of the form
38027 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38028 in the target process, and @var{name} identifes the @code{spufs} file
38029 in that context to be accessed.
38031 This packet is not probed by default; the remote stub must request it,
38032 by supplying an appropriate @samp{qSupported} response
38033 (@pxref{qSupported}).
38035 @item qXfer:threads:read::@var{offset},@var{length}
38036 @anchor{qXfer threads read}
38037 Access the list of threads on target. @xref{Thread List Format}. The
38038 annex part of the generic @samp{qXfer} packet must be empty
38039 (@pxref{qXfer read}).
38041 This packet is not probed by default; the remote stub must request it,
38042 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38044 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38045 @anchor{qXfer traceframe info read}
38047 Return a description of the current traceframe's contents.
38048 @xref{Traceframe Info Format}. The annex part of the generic
38049 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38051 This packet is not probed by default; the remote stub must request it,
38052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38054 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38055 @anchor{qXfer unwind info block}
38057 Return the unwind information block for @var{pc}. This packet is used
38058 on OpenVMS/ia64 to ask the kernel unwind information.
38060 This packet is not probed by default.
38062 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38063 @anchor{qXfer fdpic loadmap read}
38064 Read contents of @code{loadmap}s on the target system. The
38065 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38066 executable @code{loadmap} or interpreter @code{loadmap} to read.
38068 This packet is not probed by default; the remote stub must request it,
38069 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38071 @item qXfer:osdata:read::@var{offset},@var{length}
38072 @anchor{qXfer osdata read}
38073 Access the target's @dfn{operating system information}.
38074 @xref{Operating System Information}.
38078 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38079 @cindex write data into object, remote request
38080 @anchor{qXfer write}
38081 Write uninterpreted bytes into the target's special data area
38082 identified by the keyword @var{object}, starting at @var{offset} bytes
38083 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38084 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38085 is specific to @var{object}; it can supply additional details about what data
38091 @var{nn} (hex encoded) is the number of bytes written.
38092 This may be fewer bytes than supplied in the request.
38095 The request was malformed, or @var{annex} was invalid.
38098 The offset was invalid, or there was an error encountered writing the data.
38099 The @var{nn} part is a hex-encoded @code{errno} value.
38102 An empty reply indicates the @var{object} string was not
38103 recognized by the stub, or that the object does not support writing.
38106 Here are the specific requests of this form defined so far. All the
38107 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38108 formats, listed above.
38111 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38112 @anchor{qXfer siginfo write}
38113 Write @var{data} to the extra signal information on the target system.
38114 The annex part of the generic @samp{qXfer} packet must be
38115 empty (@pxref{qXfer write}).
38117 This packet is not probed by default; the remote stub must request it,
38118 by supplying an appropriate @samp{qSupported} response
38119 (@pxref{qSupported}).
38121 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38122 @anchor{qXfer spu write}
38123 Write @var{data} to an @code{spufs} file on the target system. The
38124 annex specifies which file to write; it must be of the form
38125 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38126 in the target process, and @var{name} identifes the @code{spufs} file
38127 in that context to be accessed.
38129 This packet is not probed by default; the remote stub must request it,
38130 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38133 @item qXfer:@var{object}:@var{operation}:@dots{}
38134 Requests of this form may be added in the future. When a stub does
38135 not recognize the @var{object} keyword, or its support for
38136 @var{object} does not recognize the @var{operation} keyword, the stub
38137 must respond with an empty packet.
38139 @item qAttached:@var{pid}
38140 @cindex query attached, remote request
38141 @cindex @samp{qAttached} packet
38142 Return an indication of whether the remote server attached to an
38143 existing process or created a new process. When the multiprocess
38144 protocol extensions are supported (@pxref{multiprocess extensions}),
38145 @var{pid} is an integer in hexadecimal format identifying the target
38146 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38147 the query packet will be simplified as @samp{qAttached}.
38149 This query is used, for example, to know whether the remote process
38150 should be detached or killed when a @value{GDBN} session is ended with
38151 the @code{quit} command.
38156 The remote server attached to an existing process.
38158 The remote server created a new process.
38160 A badly formed request or an error was encountered.
38164 Enable branch tracing for the current thread using Branch Trace Store.
38169 Branch tracing has been enabled.
38171 A badly formed request or an error was encountered.
38175 Enable branch tracing for the current thread using Intel Processor Trace.
38180 Branch tracing has been enabled.
38182 A badly formed request or an error was encountered.
38186 Disable branch tracing for the current thread.
38191 Branch tracing has been disabled.
38193 A badly formed request or an error was encountered.
38196 @item Qbtrace-conf:bts:size=@var{value}
38197 Set the requested ring buffer size for new threads that use the
38198 btrace recording method in bts format.
38203 The ring buffer size has been set.
38205 A badly formed request or an error was encountered.
38208 @item Qbtrace-conf:pt:size=@var{value}
38209 Set the requested ring buffer size for new threads that use the
38210 btrace recording method in pt format.
38215 The ring buffer size has been set.
38217 A badly formed request or an error was encountered.
38222 @node Architecture-Specific Protocol Details
38223 @section Architecture-Specific Protocol Details
38225 This section describes how the remote protocol is applied to specific
38226 target architectures. Also see @ref{Standard Target Features}, for
38227 details of XML target descriptions for each architecture.
38230 * ARM-Specific Protocol Details::
38231 * MIPS-Specific Protocol Details::
38234 @node ARM-Specific Protocol Details
38235 @subsection @acronym{ARM}-specific Protocol Details
38238 * ARM Breakpoint Kinds::
38241 @node ARM Breakpoint Kinds
38242 @subsubsection @acronym{ARM} Breakpoint Kinds
38243 @cindex breakpoint kinds, @acronym{ARM}
38245 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38250 16-bit Thumb mode breakpoint.
38253 32-bit Thumb mode (Thumb-2) breakpoint.
38256 32-bit @acronym{ARM} mode breakpoint.
38260 @node MIPS-Specific Protocol Details
38261 @subsection @acronym{MIPS}-specific Protocol Details
38264 * MIPS Register packet Format::
38265 * MIPS Breakpoint Kinds::
38268 @node MIPS Register packet Format
38269 @subsubsection @acronym{MIPS} Register Packet Format
38270 @cindex register packet format, @acronym{MIPS}
38272 The following @code{g}/@code{G} packets have previously been defined.
38273 In the below, some thirty-two bit registers are transferred as
38274 sixty-four bits. Those registers should be zero/sign extended (which?)
38275 to fill the space allocated. Register bytes are transferred in target
38276 byte order. The two nibbles within a register byte are transferred
38277 most-significant -- least-significant.
38282 All registers are transferred as thirty-two bit quantities in the order:
38283 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38284 registers; fsr; fir; fp.
38287 All registers are transferred as sixty-four bit quantities (including
38288 thirty-two bit registers such as @code{sr}). The ordering is the same
38293 @node MIPS Breakpoint Kinds
38294 @subsubsection @acronym{MIPS} Breakpoint Kinds
38295 @cindex breakpoint kinds, @acronym{MIPS}
38297 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38302 16-bit @acronym{MIPS16} mode breakpoint.
38305 16-bit @acronym{microMIPS} mode breakpoint.
38308 32-bit standard @acronym{MIPS} mode breakpoint.
38311 32-bit @acronym{microMIPS} mode breakpoint.
38315 @node Tracepoint Packets
38316 @section Tracepoint Packets
38317 @cindex tracepoint packets
38318 @cindex packets, tracepoint
38320 Here we describe the packets @value{GDBN} uses to implement
38321 tracepoints (@pxref{Tracepoints}).
38325 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38326 @cindex @samp{QTDP} packet
38327 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38328 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38329 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38330 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38331 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38332 the number of bytes that the target should copy elsewhere to make room
38333 for the tracepoint. If an @samp{X} is present, it introduces a
38334 tracepoint condition, which consists of a hexadecimal length, followed
38335 by a comma and hex-encoded bytes, in a manner similar to action
38336 encodings as described below. If the trailing @samp{-} is present,
38337 further @samp{QTDP} packets will follow to specify this tracepoint's
38343 The packet was understood and carried out.
38345 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38347 The packet was not recognized.
38350 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38351 Define actions to be taken when a tracepoint is hit. The @var{n} and
38352 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38353 this tracepoint. This packet may only be sent immediately after
38354 another @samp{QTDP} packet that ended with a @samp{-}. If the
38355 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38356 specifying more actions for this tracepoint.
38358 In the series of action packets for a given tracepoint, at most one
38359 can have an @samp{S} before its first @var{action}. If such a packet
38360 is sent, it and the following packets define ``while-stepping''
38361 actions. Any prior packets define ordinary actions --- that is, those
38362 taken when the tracepoint is first hit. If no action packet has an
38363 @samp{S}, then all the packets in the series specify ordinary
38364 tracepoint actions.
38366 The @samp{@var{action}@dots{}} portion of the packet is a series of
38367 actions, concatenated without separators. Each action has one of the
38373 Collect the registers whose bits are set in @var{mask},
38374 a hexadecimal number whose @var{i}'th bit is set if register number
38375 @var{i} should be collected. (The least significant bit is numbered
38376 zero.) Note that @var{mask} may be any number of digits long; it may
38377 not fit in a 32-bit word.
38379 @item M @var{basereg},@var{offset},@var{len}
38380 Collect @var{len} bytes of memory starting at the address in register
38381 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38382 @samp{-1}, then the range has a fixed address: @var{offset} is the
38383 address of the lowest byte to collect. The @var{basereg},
38384 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38385 values (the @samp{-1} value for @var{basereg} is a special case).
38387 @item X @var{len},@var{expr}
38388 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38389 it directs. The agent expression @var{expr} is as described in
38390 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38391 two-digit hex number in the packet; @var{len} is the number of bytes
38392 in the expression (and thus one-half the number of hex digits in the
38397 Any number of actions may be packed together in a single @samp{QTDP}
38398 packet, as long as the packet does not exceed the maximum packet
38399 length (400 bytes, for many stubs). There may be only one @samp{R}
38400 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38401 actions. Any registers referred to by @samp{M} and @samp{X} actions
38402 must be collected by a preceding @samp{R} action. (The
38403 ``while-stepping'' actions are treated as if they were attached to a
38404 separate tracepoint, as far as these restrictions are concerned.)
38409 The packet was understood and carried out.
38411 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38413 The packet was not recognized.
38416 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38417 @cindex @samp{QTDPsrc} packet
38418 Specify a source string of tracepoint @var{n} at address @var{addr}.
38419 This is useful to get accurate reproduction of the tracepoints
38420 originally downloaded at the beginning of the trace run. The @var{type}
38421 is the name of the tracepoint part, such as @samp{cond} for the
38422 tracepoint's conditional expression (see below for a list of types), while
38423 @var{bytes} is the string, encoded in hexadecimal.
38425 @var{start} is the offset of the @var{bytes} within the overall source
38426 string, while @var{slen} is the total length of the source string.
38427 This is intended for handling source strings that are longer than will
38428 fit in a single packet.
38429 @c Add detailed example when this info is moved into a dedicated
38430 @c tracepoint descriptions section.
38432 The available string types are @samp{at} for the location,
38433 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38434 @value{GDBN} sends a separate packet for each command in the action
38435 list, in the same order in which the commands are stored in the list.
38437 The target does not need to do anything with source strings except
38438 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38441 Although this packet is optional, and @value{GDBN} will only send it
38442 if the target replies with @samp{TracepointSource} @xref{General
38443 Query Packets}, it makes both disconnected tracing and trace files
38444 much easier to use. Otherwise the user must be careful that the
38445 tracepoints in effect while looking at trace frames are identical to
38446 the ones in effect during the trace run; even a small discrepancy
38447 could cause @samp{tdump} not to work, or a particular trace frame not
38450 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38451 @cindex define trace state variable, remote request
38452 @cindex @samp{QTDV} packet
38453 Create a new trace state variable, number @var{n}, with an initial
38454 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38455 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38456 the option of not using this packet for initial values of zero; the
38457 target should simply create the trace state variables as they are
38458 mentioned in expressions. The value @var{builtin} should be 1 (one)
38459 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38460 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38461 @samp{qTsV} packet had it set. The contents of @var{name} is the
38462 hex-encoded name (without the leading @samp{$}) of the trace state
38465 @item QTFrame:@var{n}
38466 @cindex @samp{QTFrame} packet
38467 Select the @var{n}'th tracepoint frame from the buffer, and use the
38468 register and memory contents recorded there to answer subsequent
38469 request packets from @value{GDBN}.
38471 A successful reply from the stub indicates that the stub has found the
38472 requested frame. The response is a series of parts, concatenated
38473 without separators, describing the frame we selected. Each part has
38474 one of the following forms:
38478 The selected frame is number @var{n} in the trace frame buffer;
38479 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38480 was no frame matching the criteria in the request packet.
38483 The selected trace frame records a hit of tracepoint number @var{t};
38484 @var{t} is a hexadecimal number.
38488 @item QTFrame:pc:@var{addr}
38489 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38490 currently selected frame whose PC is @var{addr};
38491 @var{addr} is a hexadecimal number.
38493 @item QTFrame:tdp:@var{t}
38494 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38495 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38496 is a hexadecimal number.
38498 @item QTFrame:range:@var{start}:@var{end}
38499 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38500 currently selected frame whose PC is between @var{start} (inclusive)
38501 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38504 @item QTFrame:outside:@var{start}:@var{end}
38505 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38506 frame @emph{outside} the given range of addresses (exclusive).
38509 @cindex @samp{qTMinFTPILen} packet
38510 This packet requests the minimum length of instruction at which a fast
38511 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38512 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38513 it depends on the target system being able to create trampolines in
38514 the first 64K of memory, which might or might not be possible for that
38515 system. So the reply to this packet will be 4 if it is able to
38522 The minimum instruction length is currently unknown.
38524 The minimum instruction length is @var{length}, where @var{length}
38525 is a hexadecimal number greater or equal to 1. A reply
38526 of 1 means that a fast tracepoint may be placed on any instruction
38527 regardless of size.
38529 An error has occurred.
38531 An empty reply indicates that the request is not supported by the stub.
38535 @cindex @samp{QTStart} packet
38536 Begin the tracepoint experiment. Begin collecting data from
38537 tracepoint hits in the trace frame buffer. This packet supports the
38538 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38539 instruction reply packet}).
38542 @cindex @samp{QTStop} packet
38543 End the tracepoint experiment. Stop collecting trace frames.
38545 @item QTEnable:@var{n}:@var{addr}
38547 @cindex @samp{QTEnable} packet
38548 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38549 experiment. If the tracepoint was previously disabled, then collection
38550 of data from it will resume.
38552 @item QTDisable:@var{n}:@var{addr}
38554 @cindex @samp{QTDisable} packet
38555 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38556 experiment. No more data will be collected from the tracepoint unless
38557 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38560 @cindex @samp{QTinit} packet
38561 Clear the table of tracepoints, and empty the trace frame buffer.
38563 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38564 @cindex @samp{QTro} packet
38565 Establish the given ranges of memory as ``transparent''. The stub
38566 will answer requests for these ranges from memory's current contents,
38567 if they were not collected as part of the tracepoint hit.
38569 @value{GDBN} uses this to mark read-only regions of memory, like those
38570 containing program code. Since these areas never change, they should
38571 still have the same contents they did when the tracepoint was hit, so
38572 there's no reason for the stub to refuse to provide their contents.
38574 @item QTDisconnected:@var{value}
38575 @cindex @samp{QTDisconnected} packet
38576 Set the choice to what to do with the tracing run when @value{GDBN}
38577 disconnects from the target. A @var{value} of 1 directs the target to
38578 continue the tracing run, while 0 tells the target to stop tracing if
38579 @value{GDBN} is no longer in the picture.
38582 @cindex @samp{qTStatus} packet
38583 Ask the stub if there is a trace experiment running right now.
38585 The reply has the form:
38589 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38590 @var{running} is a single digit @code{1} if the trace is presently
38591 running, or @code{0} if not. It is followed by semicolon-separated
38592 optional fields that an agent may use to report additional status.
38596 If the trace is not running, the agent may report any of several
38597 explanations as one of the optional fields:
38602 No trace has been run yet.
38604 @item tstop[:@var{text}]:0
38605 The trace was stopped by a user-originated stop command. The optional
38606 @var{text} field is a user-supplied string supplied as part of the
38607 stop command (for instance, an explanation of why the trace was
38608 stopped manually). It is hex-encoded.
38611 The trace stopped because the trace buffer filled up.
38613 @item tdisconnected:0
38614 The trace stopped because @value{GDBN} disconnected from the target.
38616 @item tpasscount:@var{tpnum}
38617 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38619 @item terror:@var{text}:@var{tpnum}
38620 The trace stopped because tracepoint @var{tpnum} had an error. The
38621 string @var{text} is available to describe the nature of the error
38622 (for instance, a divide by zero in the condition expression); it
38626 The trace stopped for some other reason.
38630 Additional optional fields supply statistical and other information.
38631 Although not required, they are extremely useful for users monitoring
38632 the progress of a trace run. If a trace has stopped, and these
38633 numbers are reported, they must reflect the state of the just-stopped
38638 @item tframes:@var{n}
38639 The number of trace frames in the buffer.
38641 @item tcreated:@var{n}
38642 The total number of trace frames created during the run. This may
38643 be larger than the trace frame count, if the buffer is circular.
38645 @item tsize:@var{n}
38646 The total size of the trace buffer, in bytes.
38648 @item tfree:@var{n}
38649 The number of bytes still unused in the buffer.
38651 @item circular:@var{n}
38652 The value of the circular trace buffer flag. @code{1} means that the
38653 trace buffer is circular and old trace frames will be discarded if
38654 necessary to make room, @code{0} means that the trace buffer is linear
38657 @item disconn:@var{n}
38658 The value of the disconnected tracing flag. @code{1} means that
38659 tracing will continue after @value{GDBN} disconnects, @code{0} means
38660 that the trace run will stop.
38664 @item qTP:@var{tp}:@var{addr}
38665 @cindex tracepoint status, remote request
38666 @cindex @samp{qTP} packet
38667 Ask the stub for the current state of tracepoint number @var{tp} at
38668 address @var{addr}.
38672 @item V@var{hits}:@var{usage}
38673 The tracepoint has been hit @var{hits} times so far during the trace
38674 run, and accounts for @var{usage} in the trace buffer. Note that
38675 @code{while-stepping} steps are not counted as separate hits, but the
38676 steps' space consumption is added into the usage number.
38680 @item qTV:@var{var}
38681 @cindex trace state variable value, remote request
38682 @cindex @samp{qTV} packet
38683 Ask the stub for the value of the trace state variable number @var{var}.
38688 The value of the variable is @var{value}. This will be the current
38689 value of the variable if the user is examining a running target, or a
38690 saved value if the variable was collected in the trace frame that the
38691 user is looking at. Note that multiple requests may result in
38692 different reply values, such as when requesting values while the
38693 program is running.
38696 The value of the variable is unknown. This would occur, for example,
38697 if the user is examining a trace frame in which the requested variable
38702 @cindex @samp{qTfP} packet
38704 @cindex @samp{qTsP} packet
38705 These packets request data about tracepoints that are being used by
38706 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38707 of data, and multiple @code{qTsP} to get additional pieces. Replies
38708 to these packets generally take the form of the @code{QTDP} packets
38709 that define tracepoints. (FIXME add detailed syntax)
38712 @cindex @samp{qTfV} packet
38714 @cindex @samp{qTsV} packet
38715 These packets request data about trace state variables that are on the
38716 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38717 and multiple @code{qTsV} to get additional variables. Replies to
38718 these packets follow the syntax of the @code{QTDV} packets that define
38719 trace state variables.
38725 @cindex @samp{qTfSTM} packet
38726 @cindex @samp{qTsSTM} packet
38727 These packets request data about static tracepoint markers that exist
38728 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38729 first piece of data, and multiple @code{qTsSTM} to get additional
38730 pieces. Replies to these packets take the following form:
38734 @item m @var{address}:@var{id}:@var{extra}
38736 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38737 a comma-separated list of markers
38739 (lower case letter @samp{L}) denotes end of list.
38741 An error occurred. The error number @var{nn} is given as hex digits.
38743 An empty reply indicates that the request is not supported by the
38747 The @var{address} is encoded in hex;
38748 @var{id} and @var{extra} are strings encoded in hex.
38750 In response to each query, the target will reply with a list of one or
38751 more markers, separated by commas. @value{GDBN} will respond to each
38752 reply with a request for more markers (using the @samp{qs} form of the
38753 query), until the target responds with @samp{l} (lower-case ell, for
38756 @item qTSTMat:@var{address}
38758 @cindex @samp{qTSTMat} packet
38759 This packets requests data about static tracepoint markers in the
38760 target program at @var{address}. Replies to this packet follow the
38761 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38762 tracepoint markers.
38764 @item QTSave:@var{filename}
38765 @cindex @samp{QTSave} packet
38766 This packet directs the target to save trace data to the file name
38767 @var{filename} in the target's filesystem. The @var{filename} is encoded
38768 as a hex string; the interpretation of the file name (relative vs
38769 absolute, wild cards, etc) is up to the target.
38771 @item qTBuffer:@var{offset},@var{len}
38772 @cindex @samp{qTBuffer} packet
38773 Return up to @var{len} bytes of the current contents of trace buffer,
38774 starting at @var{offset}. The trace buffer is treated as if it were
38775 a contiguous collection of traceframes, as per the trace file format.
38776 The reply consists as many hex-encoded bytes as the target can deliver
38777 in a packet; it is not an error to return fewer than were asked for.
38778 A reply consisting of just @code{l} indicates that no bytes are
38781 @item QTBuffer:circular:@var{value}
38782 This packet directs the target to use a circular trace buffer if
38783 @var{value} is 1, or a linear buffer if the value is 0.
38785 @item QTBuffer:size:@var{size}
38786 @anchor{QTBuffer-size}
38787 @cindex @samp{QTBuffer size} packet
38788 This packet directs the target to make the trace buffer be of size
38789 @var{size} if possible. A value of @code{-1} tells the target to
38790 use whatever size it prefers.
38792 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38793 @cindex @samp{QTNotes} packet
38794 This packet adds optional textual notes to the trace run. Allowable
38795 types include @code{user}, @code{notes}, and @code{tstop}, the
38796 @var{text} fields are arbitrary strings, hex-encoded.
38800 @subsection Relocate instruction reply packet
38801 When installing fast tracepoints in memory, the target may need to
38802 relocate the instruction currently at the tracepoint address to a
38803 different address in memory. For most instructions, a simple copy is
38804 enough, but, for example, call instructions that implicitly push the
38805 return address on the stack, and relative branches or other
38806 PC-relative instructions require offset adjustment, so that the effect
38807 of executing the instruction at a different address is the same as if
38808 it had executed in the original location.
38810 In response to several of the tracepoint packets, the target may also
38811 respond with a number of intermediate @samp{qRelocInsn} request
38812 packets before the final result packet, to have @value{GDBN} handle
38813 this relocation operation. If a packet supports this mechanism, its
38814 documentation will explicitly say so. See for example the above
38815 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38816 format of the request is:
38819 @item qRelocInsn:@var{from};@var{to}
38821 This requests @value{GDBN} to copy instruction at address @var{from}
38822 to address @var{to}, possibly adjusted so that executing the
38823 instruction at @var{to} has the same effect as executing it at
38824 @var{from}. @value{GDBN} writes the adjusted instruction to target
38825 memory starting at @var{to}.
38830 @item qRelocInsn:@var{adjusted_size}
38831 Informs the stub the relocation is complete. The @var{adjusted_size} is
38832 the length in bytes of resulting relocated instruction sequence.
38834 A badly formed request was detected, or an error was encountered while
38835 relocating the instruction.
38838 @node Host I/O Packets
38839 @section Host I/O Packets
38840 @cindex Host I/O, remote protocol
38841 @cindex file transfer, remote protocol
38843 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38844 operations on the far side of a remote link. For example, Host I/O is
38845 used to upload and download files to a remote target with its own
38846 filesystem. Host I/O uses the same constant values and data structure
38847 layout as the target-initiated File-I/O protocol. However, the
38848 Host I/O packets are structured differently. The target-initiated
38849 protocol relies on target memory to store parameters and buffers.
38850 Host I/O requests are initiated by @value{GDBN}, and the
38851 target's memory is not involved. @xref{File-I/O Remote Protocol
38852 Extension}, for more details on the target-initiated protocol.
38854 The Host I/O request packets all encode a single operation along with
38855 its arguments. They have this format:
38859 @item vFile:@var{operation}: @var{parameter}@dots{}
38860 @var{operation} is the name of the particular request; the target
38861 should compare the entire packet name up to the second colon when checking
38862 for a supported operation. The format of @var{parameter} depends on
38863 the operation. Numbers are always passed in hexadecimal. Negative
38864 numbers have an explicit minus sign (i.e.@: two's complement is not
38865 used). Strings (e.g.@: filenames) are encoded as a series of
38866 hexadecimal bytes. The last argument to a system call may be a
38867 buffer of escaped binary data (@pxref{Binary Data}).
38871 The valid responses to Host I/O packets are:
38875 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38876 @var{result} is the integer value returned by this operation, usually
38877 non-negative for success and -1 for errors. If an error has occured,
38878 @var{errno} will be included in the result specifying a
38879 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38880 operations which return data, @var{attachment} supplies the data as a
38881 binary buffer. Binary buffers in response packets are escaped in the
38882 normal way (@pxref{Binary Data}). See the individual packet
38883 documentation for the interpretation of @var{result} and
38887 An empty response indicates that this operation is not recognized.
38891 These are the supported Host I/O operations:
38894 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38895 Open a file at @var{filename} and return a file descriptor for it, or
38896 return -1 if an error occurs. The @var{filename} is a string,
38897 @var{flags} is an integer indicating a mask of open flags
38898 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38899 of mode bits to use if the file is created (@pxref{mode_t Values}).
38900 @xref{open}, for details of the open flags and mode values.
38902 @item vFile:close: @var{fd}
38903 Close the open file corresponding to @var{fd} and return 0, or
38904 -1 if an error occurs.
38906 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38907 Read data from the open file corresponding to @var{fd}. Up to
38908 @var{count} bytes will be read from the file, starting at @var{offset}
38909 relative to the start of the file. The target may read fewer bytes;
38910 common reasons include packet size limits and an end-of-file
38911 condition. The number of bytes read is returned. Zero should only be
38912 returned for a successful read at the end of the file, or if
38913 @var{count} was zero.
38915 The data read should be returned as a binary attachment on success.
38916 If zero bytes were read, the response should include an empty binary
38917 attachment (i.e.@: a trailing semicolon). The return value is the
38918 number of target bytes read; the binary attachment may be longer if
38919 some characters were escaped.
38921 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38922 Write @var{data} (a binary buffer) to the open file corresponding
38923 to @var{fd}. Start the write at @var{offset} from the start of the
38924 file. Unlike many @code{write} system calls, there is no
38925 separate @var{count} argument; the length of @var{data} in the
38926 packet is used. @samp{vFile:write} returns the number of bytes written,
38927 which may be shorter than the length of @var{data}, or -1 if an
38930 @item vFile:fstat: @var{fd}
38931 Get information about the open file corresponding to @var{fd}.
38932 On success the information is returned as a binary attachment
38933 and the return value is the size of this attachment in bytes.
38934 If an error occurs the return value is -1. The format of the
38935 returned binary attachment is as described in @ref{struct stat}.
38937 @item vFile:unlink: @var{filename}
38938 Delete the file at @var{filename} on the target. Return 0,
38939 or -1 if an error occurs. The @var{filename} is a string.
38941 @item vFile:readlink: @var{filename}
38942 Read value of symbolic link @var{filename} on the target. Return
38943 the number of bytes read, or -1 if an error occurs.
38945 The data read should be returned as a binary attachment on success.
38946 If zero bytes were read, the response should include an empty binary
38947 attachment (i.e.@: a trailing semicolon). The return value is the
38948 number of target bytes read; the binary attachment may be longer if
38949 some characters were escaped.
38951 @item vFile:setfs: @var{pid}
38952 Select the filesystem on which @code{vFile} operations with
38953 @var{filename} arguments will operate. This is required for
38954 @value{GDBN} to be able to access files on remote targets where
38955 the remote stub does not share a common filesystem with the
38958 If @var{pid} is nonzero, select the filesystem as seen by process
38959 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38960 the remote stub. Return 0 on success, or -1 if an error occurs.
38961 If @code{vFile:setfs:} indicates success, the selected filesystem
38962 remains selected until the next successful @code{vFile:setfs:}
38968 @section Interrupts
38969 @cindex interrupts (remote protocol)
38970 @anchor{interrupting remote targets}
38972 In all-stop mode, when a program on the remote target is running,
38973 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38974 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38975 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38977 The precise meaning of @code{BREAK} is defined by the transport
38978 mechanism and may, in fact, be undefined. @value{GDBN} does not
38979 currently define a @code{BREAK} mechanism for any of the network
38980 interfaces except for TCP, in which case @value{GDBN} sends the
38981 @code{telnet} BREAK sequence.
38983 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38984 transport mechanisms. It is represented by sending the single byte
38985 @code{0x03} without any of the usual packet overhead described in
38986 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38987 transmitted as part of a packet, it is considered to be packet data
38988 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38989 (@pxref{X packet}), used for binary downloads, may include an unescaped
38990 @code{0x03} as part of its packet.
38992 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38993 When Linux kernel receives this sequence from serial port,
38994 it stops execution and connects to gdb.
38996 In non-stop mode, because packet resumptions are asynchronous
38997 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38998 command to the remote stub, even when the target is running. For that
38999 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39000 packet}) with the usual packet framing instead of the single byte
39003 Stubs are not required to recognize these interrupt mechanisms and the
39004 precise meaning associated with receipt of the interrupt is
39005 implementation defined. If the target supports debugging of multiple
39006 threads and/or processes, it should attempt to interrupt all
39007 currently-executing threads and processes.
39008 If the stub is successful at interrupting the
39009 running program, it should send one of the stop
39010 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39011 of successfully stopping the program in all-stop mode, and a stop reply
39012 for each stopped thread in non-stop mode.
39013 Interrupts received while the
39014 program is stopped are queued and the program will be interrupted when
39015 it is resumed next time.
39017 @node Notification Packets
39018 @section Notification Packets
39019 @cindex notification packets
39020 @cindex packets, notification
39022 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39023 packets that require no acknowledgment. Both the GDB and the stub
39024 may send notifications (although the only notifications defined at
39025 present are sent by the stub). Notifications carry information
39026 without incurring the round-trip latency of an acknowledgment, and so
39027 are useful for low-impact communications where occasional packet loss
39030 A notification packet has the form @samp{% @var{data} #
39031 @var{checksum}}, where @var{data} is the content of the notification,
39032 and @var{checksum} is a checksum of @var{data}, computed and formatted
39033 as for ordinary @value{GDBN} packets. A notification's @var{data}
39034 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39035 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39036 to acknowledge the notification's receipt or to report its corruption.
39038 Every notification's @var{data} begins with a name, which contains no
39039 colon characters, followed by a colon character.
39041 Recipients should silently ignore corrupted notifications and
39042 notifications they do not understand. Recipients should restart
39043 timeout periods on receipt of a well-formed notification, whether or
39044 not they understand it.
39046 Senders should only send the notifications described here when this
39047 protocol description specifies that they are permitted. In the
39048 future, we may extend the protocol to permit existing notifications in
39049 new contexts; this rule helps older senders avoid confusing newer
39052 (Older versions of @value{GDBN} ignore bytes received until they see
39053 the @samp{$} byte that begins an ordinary packet, so new stubs may
39054 transmit notifications without fear of confusing older clients. There
39055 are no notifications defined for @value{GDBN} to send at the moment, but we
39056 assume that most older stubs would ignore them, as well.)
39058 Each notification is comprised of three parts:
39060 @item @var{name}:@var{event}
39061 The notification packet is sent by the side that initiates the
39062 exchange (currently, only the stub does that), with @var{event}
39063 carrying the specific information about the notification, and
39064 @var{name} specifying the name of the notification.
39066 The acknowledge sent by the other side, usually @value{GDBN}, to
39067 acknowledge the exchange and request the event.
39070 The purpose of an asynchronous notification mechanism is to report to
39071 @value{GDBN} that something interesting happened in the remote stub.
39073 The remote stub may send notification @var{name}:@var{event}
39074 at any time, but @value{GDBN} acknowledges the notification when
39075 appropriate. The notification event is pending before @value{GDBN}
39076 acknowledges. Only one notification at a time may be pending; if
39077 additional events occur before @value{GDBN} has acknowledged the
39078 previous notification, they must be queued by the stub for later
39079 synchronous transmission in response to @var{ack} packets from
39080 @value{GDBN}. Because the notification mechanism is unreliable,
39081 the stub is permitted to resend a notification if it believes
39082 @value{GDBN} may not have received it.
39084 Specifically, notifications may appear when @value{GDBN} is not
39085 otherwise reading input from the stub, or when @value{GDBN} is
39086 expecting to read a normal synchronous response or a
39087 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39088 Notification packets are distinct from any other communication from
39089 the stub so there is no ambiguity.
39091 After receiving a notification, @value{GDBN} shall acknowledge it by
39092 sending a @var{ack} packet as a regular, synchronous request to the
39093 stub. Such acknowledgment is not required to happen immediately, as
39094 @value{GDBN} is permitted to send other, unrelated packets to the
39095 stub first, which the stub should process normally.
39097 Upon receiving a @var{ack} packet, if the stub has other queued
39098 events to report to @value{GDBN}, it shall respond by sending a
39099 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39100 packet to solicit further responses; again, it is permitted to send
39101 other, unrelated packets as well which the stub should process
39104 If the stub receives a @var{ack} packet and there are no additional
39105 @var{event} to report, the stub shall return an @samp{OK} response.
39106 At this point, @value{GDBN} has finished processing a notification
39107 and the stub has completed sending any queued events. @value{GDBN}
39108 won't accept any new notifications until the final @samp{OK} is
39109 received . If further notification events occur, the stub shall send
39110 a new notification, @value{GDBN} shall accept the notification, and
39111 the process shall be repeated.
39113 The process of asynchronous notification can be illustrated by the
39116 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39119 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39121 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39126 The following notifications are defined:
39127 @multitable @columnfractions 0.12 0.12 0.38 0.38
39136 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39137 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39138 for information on how these notifications are acknowledged by
39140 @tab Report an asynchronous stop event in non-stop mode.
39144 @node Remote Non-Stop
39145 @section Remote Protocol Support for Non-Stop Mode
39147 @value{GDBN}'s remote protocol supports non-stop debugging of
39148 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39149 supports non-stop mode, it should report that to @value{GDBN} by including
39150 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39152 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39153 establishing a new connection with the stub. Entering non-stop mode
39154 does not alter the state of any currently-running threads, but targets
39155 must stop all threads in any already-attached processes when entering
39156 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39157 probe the target state after a mode change.
39159 In non-stop mode, when an attached process encounters an event that
39160 would otherwise be reported with a stop reply, it uses the
39161 asynchronous notification mechanism (@pxref{Notification Packets}) to
39162 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39163 in all processes are stopped when a stop reply is sent, in non-stop
39164 mode only the thread reporting the stop event is stopped. That is,
39165 when reporting a @samp{S} or @samp{T} response to indicate completion
39166 of a step operation, hitting a breakpoint, or a fault, only the
39167 affected thread is stopped; any other still-running threads continue
39168 to run. When reporting a @samp{W} or @samp{X} response, all running
39169 threads belonging to other attached processes continue to run.
39171 In non-stop mode, the target shall respond to the @samp{?} packet as
39172 follows. First, any incomplete stop reply notification/@samp{vStopped}
39173 sequence in progress is abandoned. The target must begin a new
39174 sequence reporting stop events for all stopped threads, whether or not
39175 it has previously reported those events to @value{GDBN}. The first
39176 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39177 subsequent stop replies are sent as responses to @samp{vStopped} packets
39178 using the mechanism described above. The target must not send
39179 asynchronous stop reply notifications until the sequence is complete.
39180 If all threads are running when the target receives the @samp{?} packet,
39181 or if the target is not attached to any process, it shall respond
39184 If the stub supports non-stop mode, it should also support the
39185 @samp{swbreak} stop reason if software breakpoints are supported, and
39186 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39187 (@pxref{swbreak stop reason}). This is because given the asynchronous
39188 nature of non-stop mode, between the time a thread hits a breakpoint
39189 and the time the event is finally processed by @value{GDBN}, the
39190 breakpoint may have already been removed from the target. Due to
39191 this, @value{GDBN} needs to be able to tell whether a trap stop was
39192 caused by a delayed breakpoint event, which should be ignored, as
39193 opposed to a random trap signal, which should be reported to the user.
39194 Note the @samp{swbreak} feature implies that the target is responsible
39195 for adjusting the PC when a software breakpoint triggers, if
39196 necessary, such as on the x86 architecture.
39198 @node Packet Acknowledgment
39199 @section Packet Acknowledgment
39201 @cindex acknowledgment, for @value{GDBN} remote
39202 @cindex packet acknowledgment, for @value{GDBN} remote
39203 By default, when either the host or the target machine receives a packet,
39204 the first response expected is an acknowledgment: either @samp{+} (to indicate
39205 the package was received correctly) or @samp{-} (to request retransmission).
39206 This mechanism allows the @value{GDBN} remote protocol to operate over
39207 unreliable transport mechanisms, such as a serial line.
39209 In cases where the transport mechanism is itself reliable (such as a pipe or
39210 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39211 It may be desirable to disable them in that case to reduce communication
39212 overhead, or for other reasons. This can be accomplished by means of the
39213 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39215 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39216 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39217 and response format still includes the normal checksum, as described in
39218 @ref{Overview}, but the checksum may be ignored by the receiver.
39220 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39221 no-acknowledgment mode, it should report that to @value{GDBN}
39222 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39223 @pxref{qSupported}.
39224 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39225 disabled via the @code{set remote noack-packet off} command
39226 (@pxref{Remote Configuration}),
39227 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39228 Only then may the stub actually turn off packet acknowledgments.
39229 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39230 response, which can be safely ignored by the stub.
39232 Note that @code{set remote noack-packet} command only affects negotiation
39233 between @value{GDBN} and the stub when subsequent connections are made;
39234 it does not affect the protocol acknowledgment state for any current
39236 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39237 new connection is established,
39238 there is also no protocol request to re-enable the acknowledgments
39239 for the current connection, once disabled.
39244 Example sequence of a target being re-started. Notice how the restart
39245 does not get any direct output:
39250 @emph{target restarts}
39253 <- @code{T001:1234123412341234}
39257 Example sequence of a target being stepped by a single instruction:
39260 -> @code{G1445@dots{}}
39265 <- @code{T001:1234123412341234}
39269 <- @code{1455@dots{}}
39273 @node File-I/O Remote Protocol Extension
39274 @section File-I/O Remote Protocol Extension
39275 @cindex File-I/O remote protocol extension
39278 * File-I/O Overview::
39279 * Protocol Basics::
39280 * The F Request Packet::
39281 * The F Reply Packet::
39282 * The Ctrl-C Message::
39284 * List of Supported Calls::
39285 * Protocol-specific Representation of Datatypes::
39287 * File-I/O Examples::
39290 @node File-I/O Overview
39291 @subsection File-I/O Overview
39292 @cindex file-i/o overview
39294 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39295 target to use the host's file system and console I/O to perform various
39296 system calls. System calls on the target system are translated into a
39297 remote protocol packet to the host system, which then performs the needed
39298 actions and returns a response packet to the target system.
39299 This simulates file system operations even on targets that lack file systems.
39301 The protocol is defined to be independent of both the host and target systems.
39302 It uses its own internal representation of datatypes and values. Both
39303 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39304 translating the system-dependent value representations into the internal
39305 protocol representations when data is transmitted.
39307 The communication is synchronous. A system call is possible only when
39308 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39309 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39310 the target is stopped to allow deterministic access to the target's
39311 memory. Therefore File-I/O is not interruptible by target signals. On
39312 the other hand, it is possible to interrupt File-I/O by a user interrupt
39313 (@samp{Ctrl-C}) within @value{GDBN}.
39315 The target's request to perform a host system call does not finish
39316 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39317 after finishing the system call, the target returns to continuing the
39318 previous activity (continue, step). No additional continue or step
39319 request from @value{GDBN} is required.
39322 (@value{GDBP}) continue
39323 <- target requests 'system call X'
39324 target is stopped, @value{GDBN} executes system call
39325 -> @value{GDBN} returns result
39326 ... target continues, @value{GDBN} returns to wait for the target
39327 <- target hits breakpoint and sends a Txx packet
39330 The protocol only supports I/O on the console and to regular files on
39331 the host file system. Character or block special devices, pipes,
39332 named pipes, sockets or any other communication method on the host
39333 system are not supported by this protocol.
39335 File I/O is not supported in non-stop mode.
39337 @node Protocol Basics
39338 @subsection Protocol Basics
39339 @cindex protocol basics, file-i/o
39341 The File-I/O protocol uses the @code{F} packet as the request as well
39342 as reply packet. Since a File-I/O system call can only occur when
39343 @value{GDBN} is waiting for a response from the continuing or stepping target,
39344 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39345 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39346 This @code{F} packet contains all information needed to allow @value{GDBN}
39347 to call the appropriate host system call:
39351 A unique identifier for the requested system call.
39354 All parameters to the system call. Pointers are given as addresses
39355 in the target memory address space. Pointers to strings are given as
39356 pointer/length pair. Numerical values are given as they are.
39357 Numerical control flags are given in a protocol-specific representation.
39361 At this point, @value{GDBN} has to perform the following actions.
39365 If the parameters include pointer values to data needed as input to a
39366 system call, @value{GDBN} requests this data from the target with a
39367 standard @code{m} packet request. This additional communication has to be
39368 expected by the target implementation and is handled as any other @code{m}
39372 @value{GDBN} translates all value from protocol representation to host
39373 representation as needed. Datatypes are coerced into the host types.
39376 @value{GDBN} calls the system call.
39379 It then coerces datatypes back to protocol representation.
39382 If the system call is expected to return data in buffer space specified
39383 by pointer parameters to the call, the data is transmitted to the
39384 target using a @code{M} or @code{X} packet. This packet has to be expected
39385 by the target implementation and is handled as any other @code{M} or @code{X}
39390 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39391 necessary information for the target to continue. This at least contains
39398 @code{errno}, if has been changed by the system call.
39405 After having done the needed type and value coercion, the target continues
39406 the latest continue or step action.
39408 @node The F Request Packet
39409 @subsection The @code{F} Request Packet
39410 @cindex file-i/o request packet
39411 @cindex @code{F} request packet
39413 The @code{F} request packet has the following format:
39416 @item F@var{call-id},@var{parameter@dots{}}
39418 @var{call-id} is the identifier to indicate the host system call to be called.
39419 This is just the name of the function.
39421 @var{parameter@dots{}} are the parameters to the system call.
39422 Parameters are hexadecimal integer values, either the actual values in case
39423 of scalar datatypes, pointers to target buffer space in case of compound
39424 datatypes and unspecified memory areas, or pointer/length pairs in case
39425 of string parameters. These are appended to the @var{call-id} as a
39426 comma-delimited list. All values are transmitted in ASCII
39427 string representation, pointer/length pairs separated by a slash.
39433 @node The F Reply Packet
39434 @subsection The @code{F} Reply Packet
39435 @cindex file-i/o reply packet
39436 @cindex @code{F} reply packet
39438 The @code{F} reply packet has the following format:
39442 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39444 @var{retcode} is the return code of the system call as hexadecimal value.
39446 @var{errno} is the @code{errno} set by the call, in protocol-specific
39448 This parameter can be omitted if the call was successful.
39450 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39451 case, @var{errno} must be sent as well, even if the call was successful.
39452 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39459 or, if the call was interrupted before the host call has been performed:
39466 assuming 4 is the protocol-specific representation of @code{EINTR}.
39471 @node The Ctrl-C Message
39472 @subsection The @samp{Ctrl-C} Message
39473 @cindex ctrl-c message, in file-i/o protocol
39475 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39476 reply packet (@pxref{The F Reply Packet}),
39477 the target should behave as if it had
39478 gotten a break message. The meaning for the target is ``system call
39479 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39480 (as with a break message) and return to @value{GDBN} with a @code{T02}
39483 It's important for the target to know in which
39484 state the system call was interrupted. There are two possible cases:
39488 The system call hasn't been performed on the host yet.
39491 The system call on the host has been finished.
39495 These two states can be distinguished by the target by the value of the
39496 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39497 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39498 on POSIX systems. In any other case, the target may presume that the
39499 system call has been finished --- successfully or not --- and should behave
39500 as if the break message arrived right after the system call.
39502 @value{GDBN} must behave reliably. If the system call has not been called
39503 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39504 @code{errno} in the packet. If the system call on the host has been finished
39505 before the user requests a break, the full action must be finished by
39506 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39507 The @code{F} packet may only be sent when either nothing has happened
39508 or the full action has been completed.
39511 @subsection Console I/O
39512 @cindex console i/o as part of file-i/o
39514 By default and if not explicitly closed by the target system, the file
39515 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39516 on the @value{GDBN} console is handled as any other file output operation
39517 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39518 by @value{GDBN} so that after the target read request from file descriptor
39519 0 all following typing is buffered until either one of the following
39524 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39526 system call is treated as finished.
39529 The user presses @key{RET}. This is treated as end of input with a trailing
39533 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39534 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39538 If the user has typed more characters than fit in the buffer given to
39539 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39540 either another @code{read(0, @dots{})} is requested by the target, or debugging
39541 is stopped at the user's request.
39544 @node List of Supported Calls
39545 @subsection List of Supported Calls
39546 @cindex list of supported file-i/o calls
39563 @unnumberedsubsubsec open
39564 @cindex open, file-i/o system call
39569 int open(const char *pathname, int flags);
39570 int open(const char *pathname, int flags, mode_t mode);
39574 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39577 @var{flags} is the bitwise @code{OR} of the following values:
39581 If the file does not exist it will be created. The host
39582 rules apply as far as file ownership and time stamps
39586 When used with @code{O_CREAT}, if the file already exists it is
39587 an error and open() fails.
39590 If the file already exists and the open mode allows
39591 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39592 truncated to zero length.
39595 The file is opened in append mode.
39598 The file is opened for reading only.
39601 The file is opened for writing only.
39604 The file is opened for reading and writing.
39608 Other bits are silently ignored.
39612 @var{mode} is the bitwise @code{OR} of the following values:
39616 User has read permission.
39619 User has write permission.
39622 Group has read permission.
39625 Group has write permission.
39628 Others have read permission.
39631 Others have write permission.
39635 Other bits are silently ignored.
39638 @item Return value:
39639 @code{open} returns the new file descriptor or -1 if an error
39646 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39649 @var{pathname} refers to a directory.
39652 The requested access is not allowed.
39655 @var{pathname} was too long.
39658 A directory component in @var{pathname} does not exist.
39661 @var{pathname} refers to a device, pipe, named pipe or socket.
39664 @var{pathname} refers to a file on a read-only filesystem and
39665 write access was requested.
39668 @var{pathname} is an invalid pointer value.
39671 No space on device to create the file.
39674 The process already has the maximum number of files open.
39677 The limit on the total number of files open on the system
39681 The call was interrupted by the user.
39687 @unnumberedsubsubsec close
39688 @cindex close, file-i/o system call
39697 @samp{Fclose,@var{fd}}
39699 @item Return value:
39700 @code{close} returns zero on success, or -1 if an error occurred.
39706 @var{fd} isn't a valid open file descriptor.
39709 The call was interrupted by the user.
39715 @unnumberedsubsubsec read
39716 @cindex read, file-i/o system call
39721 int read(int fd, void *buf, unsigned int count);
39725 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39727 @item Return value:
39728 On success, the number of bytes read is returned.
39729 Zero indicates end of file. If count is zero, read
39730 returns zero as well. On error, -1 is returned.
39736 @var{fd} is not a valid file descriptor or is not open for
39740 @var{bufptr} is an invalid pointer value.
39743 The call was interrupted by the user.
39749 @unnumberedsubsubsec write
39750 @cindex write, file-i/o system call
39755 int write(int fd, const void *buf, unsigned int count);
39759 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39761 @item Return value:
39762 On success, the number of bytes written are returned.
39763 Zero indicates nothing was written. On error, -1
39770 @var{fd} is not a valid file descriptor or is not open for
39774 @var{bufptr} is an invalid pointer value.
39777 An attempt was made to write a file that exceeds the
39778 host-specific maximum file size allowed.
39781 No space on device to write the data.
39784 The call was interrupted by the user.
39790 @unnumberedsubsubsec lseek
39791 @cindex lseek, file-i/o system call
39796 long lseek (int fd, long offset, int flag);
39800 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39802 @var{flag} is one of:
39806 The offset is set to @var{offset} bytes.
39809 The offset is set to its current location plus @var{offset}
39813 The offset is set to the size of the file plus @var{offset}
39817 @item Return value:
39818 On success, the resulting unsigned offset in bytes from
39819 the beginning of the file is returned. Otherwise, a
39820 value of -1 is returned.
39826 @var{fd} is not a valid open file descriptor.
39829 @var{fd} is associated with the @value{GDBN} console.
39832 @var{flag} is not a proper value.
39835 The call was interrupted by the user.
39841 @unnumberedsubsubsec rename
39842 @cindex rename, file-i/o system call
39847 int rename(const char *oldpath, const char *newpath);
39851 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39853 @item Return value:
39854 On success, zero is returned. On error, -1 is returned.
39860 @var{newpath} is an existing directory, but @var{oldpath} is not a
39864 @var{newpath} is a non-empty directory.
39867 @var{oldpath} or @var{newpath} is a directory that is in use by some
39871 An attempt was made to make a directory a subdirectory
39875 A component used as a directory in @var{oldpath} or new
39876 path is not a directory. Or @var{oldpath} is a directory
39877 and @var{newpath} exists but is not a directory.
39880 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39883 No access to the file or the path of the file.
39887 @var{oldpath} or @var{newpath} was too long.
39890 A directory component in @var{oldpath} or @var{newpath} does not exist.
39893 The file is on a read-only filesystem.
39896 The device containing the file has no room for the new
39900 The call was interrupted by the user.
39906 @unnumberedsubsubsec unlink
39907 @cindex unlink, file-i/o system call
39912 int unlink(const char *pathname);
39916 @samp{Funlink,@var{pathnameptr}/@var{len}}
39918 @item Return value:
39919 On success, zero is returned. On error, -1 is returned.
39925 No access to the file or the path of the file.
39928 The system does not allow unlinking of directories.
39931 The file @var{pathname} cannot be unlinked because it's
39932 being used by another process.
39935 @var{pathnameptr} is an invalid pointer value.
39938 @var{pathname} was too long.
39941 A directory component in @var{pathname} does not exist.
39944 A component of the path is not a directory.
39947 The file is on a read-only filesystem.
39950 The call was interrupted by the user.
39956 @unnumberedsubsubsec stat/fstat
39957 @cindex fstat, file-i/o system call
39958 @cindex stat, file-i/o system call
39963 int stat(const char *pathname, struct stat *buf);
39964 int fstat(int fd, struct stat *buf);
39968 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39969 @samp{Ffstat,@var{fd},@var{bufptr}}
39971 @item Return value:
39972 On success, zero is returned. On error, -1 is returned.
39978 @var{fd} is not a valid open file.
39981 A directory component in @var{pathname} does not exist or the
39982 path is an empty string.
39985 A component of the path is not a directory.
39988 @var{pathnameptr} is an invalid pointer value.
39991 No access to the file or the path of the file.
39994 @var{pathname} was too long.
39997 The call was interrupted by the user.
40003 @unnumberedsubsubsec gettimeofday
40004 @cindex gettimeofday, file-i/o system call
40009 int gettimeofday(struct timeval *tv, void *tz);
40013 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40015 @item Return value:
40016 On success, 0 is returned, -1 otherwise.
40022 @var{tz} is a non-NULL pointer.
40025 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40031 @unnumberedsubsubsec isatty
40032 @cindex isatty, file-i/o system call
40037 int isatty(int fd);
40041 @samp{Fisatty,@var{fd}}
40043 @item Return value:
40044 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40050 The call was interrupted by the user.
40055 Note that the @code{isatty} call is treated as a special case: it returns
40056 1 to the target if the file descriptor is attached
40057 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40058 would require implementing @code{ioctl} and would be more complex than
40063 @unnumberedsubsubsec system
40064 @cindex system, file-i/o system call
40069 int system(const char *command);
40073 @samp{Fsystem,@var{commandptr}/@var{len}}
40075 @item Return value:
40076 If @var{len} is zero, the return value indicates whether a shell is
40077 available. A zero return value indicates a shell is not available.
40078 For non-zero @var{len}, the value returned is -1 on error and the
40079 return status of the command otherwise. Only the exit status of the
40080 command is returned, which is extracted from the host's @code{system}
40081 return value by calling @code{WEXITSTATUS(retval)}. In case
40082 @file{/bin/sh} could not be executed, 127 is returned.
40088 The call was interrupted by the user.
40093 @value{GDBN} takes over the full task of calling the necessary host calls
40094 to perform the @code{system} call. The return value of @code{system} on
40095 the host is simplified before it's returned
40096 to the target. Any termination signal information from the child process
40097 is discarded, and the return value consists
40098 entirely of the exit status of the called command.
40100 Due to security concerns, the @code{system} call is by default refused
40101 by @value{GDBN}. The user has to allow this call explicitly with the
40102 @code{set remote system-call-allowed 1} command.
40105 @item set remote system-call-allowed
40106 @kindex set remote system-call-allowed
40107 Control whether to allow the @code{system} calls in the File I/O
40108 protocol for the remote target. The default is zero (disabled).
40110 @item show remote system-call-allowed
40111 @kindex show remote system-call-allowed
40112 Show whether the @code{system} calls are allowed in the File I/O
40116 @node Protocol-specific Representation of Datatypes
40117 @subsection Protocol-specific Representation of Datatypes
40118 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40121 * Integral Datatypes::
40123 * Memory Transfer::
40128 @node Integral Datatypes
40129 @unnumberedsubsubsec Integral Datatypes
40130 @cindex integral datatypes, in file-i/o protocol
40132 The integral datatypes used in the system calls are @code{int},
40133 @code{unsigned int}, @code{long}, @code{unsigned long},
40134 @code{mode_t}, and @code{time_t}.
40136 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40137 implemented as 32 bit values in this protocol.
40139 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40141 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40142 in @file{limits.h}) to allow range checking on host and target.
40144 @code{time_t} datatypes are defined as seconds since the Epoch.
40146 All integral datatypes transferred as part of a memory read or write of a
40147 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40150 @node Pointer Values
40151 @unnumberedsubsubsec Pointer Values
40152 @cindex pointer values, in file-i/o protocol
40154 Pointers to target data are transmitted as they are. An exception
40155 is made for pointers to buffers for which the length isn't
40156 transmitted as part of the function call, namely strings. Strings
40157 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40164 which is a pointer to data of length 18 bytes at position 0x1aaf.
40165 The length is defined as the full string length in bytes, including
40166 the trailing null byte. For example, the string @code{"hello world"}
40167 at address 0x123456 is transmitted as
40173 @node Memory Transfer
40174 @unnumberedsubsubsec Memory Transfer
40175 @cindex memory transfer, in file-i/o protocol
40177 Structured data which is transferred using a memory read or write (for
40178 example, a @code{struct stat}) is expected to be in a protocol-specific format
40179 with all scalar multibyte datatypes being big endian. Translation to
40180 this representation needs to be done both by the target before the @code{F}
40181 packet is sent, and by @value{GDBN} before
40182 it transfers memory to the target. Transferred pointers to structured
40183 data should point to the already-coerced data at any time.
40187 @unnumberedsubsubsec struct stat
40188 @cindex struct stat, in file-i/o protocol
40190 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40191 is defined as follows:
40195 unsigned int st_dev; /* device */
40196 unsigned int st_ino; /* inode */
40197 mode_t st_mode; /* protection */
40198 unsigned int st_nlink; /* number of hard links */
40199 unsigned int st_uid; /* user ID of owner */
40200 unsigned int st_gid; /* group ID of owner */
40201 unsigned int st_rdev; /* device type (if inode device) */
40202 unsigned long st_size; /* total size, in bytes */
40203 unsigned long st_blksize; /* blocksize for filesystem I/O */
40204 unsigned long st_blocks; /* number of blocks allocated */
40205 time_t st_atime; /* time of last access */
40206 time_t st_mtime; /* time of last modification */
40207 time_t st_ctime; /* time of last change */
40211 The integral datatypes conform to the definitions given in the
40212 appropriate section (see @ref{Integral Datatypes}, for details) so this
40213 structure is of size 64 bytes.
40215 The values of several fields have a restricted meaning and/or
40221 A value of 0 represents a file, 1 the console.
40224 No valid meaning for the target. Transmitted unchanged.
40227 Valid mode bits are described in @ref{Constants}. Any other
40228 bits have currently no meaning for the target.
40233 No valid meaning for the target. Transmitted unchanged.
40238 These values have a host and file system dependent
40239 accuracy. Especially on Windows hosts, the file system may not
40240 support exact timing values.
40243 The target gets a @code{struct stat} of the above representation and is
40244 responsible for coercing it to the target representation before
40247 Note that due to size differences between the host, target, and protocol
40248 representations of @code{struct stat} members, these members could eventually
40249 get truncated on the target.
40251 @node struct timeval
40252 @unnumberedsubsubsec struct timeval
40253 @cindex struct timeval, in file-i/o protocol
40255 The buffer of type @code{struct timeval} used by the File-I/O protocol
40256 is defined as follows:
40260 time_t tv_sec; /* second */
40261 long tv_usec; /* microsecond */
40265 The integral datatypes conform to the definitions given in the
40266 appropriate section (see @ref{Integral Datatypes}, for details) so this
40267 structure is of size 8 bytes.
40270 @subsection Constants
40271 @cindex constants, in file-i/o protocol
40273 The following values are used for the constants inside of the
40274 protocol. @value{GDBN} and target are responsible for translating these
40275 values before and after the call as needed.
40286 @unnumberedsubsubsec Open Flags
40287 @cindex open flags, in file-i/o protocol
40289 All values are given in hexadecimal representation.
40301 @node mode_t Values
40302 @unnumberedsubsubsec mode_t Values
40303 @cindex mode_t values, in file-i/o protocol
40305 All values are given in octal representation.
40322 @unnumberedsubsubsec Errno Values
40323 @cindex errno values, in file-i/o protocol
40325 All values are given in decimal representation.
40350 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40351 any error value not in the list of supported error numbers.
40354 @unnumberedsubsubsec Lseek Flags
40355 @cindex lseek flags, in file-i/o protocol
40364 @unnumberedsubsubsec Limits
40365 @cindex limits, in file-i/o protocol
40367 All values are given in decimal representation.
40370 INT_MIN -2147483648
40372 UINT_MAX 4294967295
40373 LONG_MIN -9223372036854775808
40374 LONG_MAX 9223372036854775807
40375 ULONG_MAX 18446744073709551615
40378 @node File-I/O Examples
40379 @subsection File-I/O Examples
40380 @cindex file-i/o examples
40382 Example sequence of a write call, file descriptor 3, buffer is at target
40383 address 0x1234, 6 bytes should be written:
40386 <- @code{Fwrite,3,1234,6}
40387 @emph{request memory read from target}
40390 @emph{return "6 bytes written"}
40394 Example sequence of a read call, file descriptor 3, buffer is at target
40395 address 0x1234, 6 bytes should be read:
40398 <- @code{Fread,3,1234,6}
40399 @emph{request memory write to target}
40400 -> @code{X1234,6:XXXXXX}
40401 @emph{return "6 bytes read"}
40405 Example sequence of a read call, call fails on the host due to invalid
40406 file descriptor (@code{EBADF}):
40409 <- @code{Fread,3,1234,6}
40413 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40417 <- @code{Fread,3,1234,6}
40422 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40426 <- @code{Fread,3,1234,6}
40427 -> @code{X1234,6:XXXXXX}
40431 @node Library List Format
40432 @section Library List Format
40433 @cindex library list format, remote protocol
40435 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40436 same process as your application to manage libraries. In this case,
40437 @value{GDBN} can use the loader's symbol table and normal memory
40438 operations to maintain a list of shared libraries. On other
40439 platforms, the operating system manages loaded libraries.
40440 @value{GDBN} can not retrieve the list of currently loaded libraries
40441 through memory operations, so it uses the @samp{qXfer:libraries:read}
40442 packet (@pxref{qXfer library list read}) instead. The remote stub
40443 queries the target's operating system and reports which libraries
40446 The @samp{qXfer:libraries:read} packet returns an XML document which
40447 lists loaded libraries and their offsets. Each library has an
40448 associated name and one or more segment or section base addresses,
40449 which report where the library was loaded in memory.
40451 For the common case of libraries that are fully linked binaries, the
40452 library should have a list of segments. If the target supports
40453 dynamic linking of a relocatable object file, its library XML element
40454 should instead include a list of allocated sections. The segment or
40455 section bases are start addresses, not relocation offsets; they do not
40456 depend on the library's link-time base addresses.
40458 @value{GDBN} must be linked with the Expat library to support XML
40459 library lists. @xref{Expat}.
40461 A simple memory map, with one loaded library relocated by a single
40462 offset, looks like this:
40466 <library name="/lib/libc.so.6">
40467 <segment address="0x10000000"/>
40472 Another simple memory map, with one loaded library with three
40473 allocated sections (.text, .data, .bss), looks like this:
40477 <library name="sharedlib.o">
40478 <section address="0x10000000"/>
40479 <section address="0x20000000"/>
40480 <section address="0x30000000"/>
40485 The format of a library list is described by this DTD:
40488 <!-- library-list: Root element with versioning -->
40489 <!ELEMENT library-list (library)*>
40490 <!ATTLIST library-list version CDATA #FIXED "1.0">
40491 <!ELEMENT library (segment*, section*)>
40492 <!ATTLIST library name CDATA #REQUIRED>
40493 <!ELEMENT segment EMPTY>
40494 <!ATTLIST segment address CDATA #REQUIRED>
40495 <!ELEMENT section EMPTY>
40496 <!ATTLIST section address CDATA #REQUIRED>
40499 In addition, segments and section descriptors cannot be mixed within a
40500 single library element, and you must supply at least one segment or
40501 section for each library.
40503 @node Library List Format for SVR4 Targets
40504 @section Library List Format for SVR4 Targets
40505 @cindex library list format, remote protocol
40507 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40508 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40509 shared libraries. Still a special library list provided by this packet is
40510 more efficient for the @value{GDBN} remote protocol.
40512 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40513 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40514 target, the following parameters are reported:
40518 @code{name}, the absolute file name from the @code{l_name} field of
40519 @code{struct link_map}.
40521 @code{lm} with address of @code{struct link_map} used for TLS
40522 (Thread Local Storage) access.
40524 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40525 @code{struct link_map}. For prelinked libraries this is not an absolute
40526 memory address. It is a displacement of absolute memory address against
40527 address the file was prelinked to during the library load.
40529 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40532 Additionally the single @code{main-lm} attribute specifies address of
40533 @code{struct link_map} used for the main executable. This parameter is used
40534 for TLS access and its presence is optional.
40536 @value{GDBN} must be linked with the Expat library to support XML
40537 SVR4 library lists. @xref{Expat}.
40539 A simple memory map, with two loaded libraries (which do not use prelink),
40543 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40544 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40546 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40548 </library-list-svr>
40551 The format of an SVR4 library list is described by this DTD:
40554 <!-- library-list-svr4: Root element with versioning -->
40555 <!ELEMENT library-list-svr4 (library)*>
40556 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40557 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40558 <!ELEMENT library EMPTY>
40559 <!ATTLIST library name CDATA #REQUIRED>
40560 <!ATTLIST library lm CDATA #REQUIRED>
40561 <!ATTLIST library l_addr CDATA #REQUIRED>
40562 <!ATTLIST library l_ld CDATA #REQUIRED>
40565 @node Memory Map Format
40566 @section Memory Map Format
40567 @cindex memory map format
40569 To be able to write into flash memory, @value{GDBN} needs to obtain a
40570 memory map from the target. This section describes the format of the
40573 The memory map is obtained using the @samp{qXfer:memory-map:read}
40574 (@pxref{qXfer memory map read}) packet and is an XML document that
40575 lists memory regions.
40577 @value{GDBN} must be linked with the Expat library to support XML
40578 memory maps. @xref{Expat}.
40580 The top-level structure of the document is shown below:
40583 <?xml version="1.0"?>
40584 <!DOCTYPE memory-map
40585 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40586 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40592 Each region can be either:
40597 A region of RAM starting at @var{addr} and extending for @var{length}
40601 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40606 A region of read-only memory:
40609 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40614 A region of flash memory, with erasure blocks @var{blocksize}
40618 <memory type="flash" start="@var{addr}" length="@var{length}">
40619 <property name="blocksize">@var{blocksize}</property>
40625 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40626 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40627 packets to write to addresses in such ranges.
40629 The formal DTD for memory map format is given below:
40632 <!-- ................................................... -->
40633 <!-- Memory Map XML DTD ................................ -->
40634 <!-- File: memory-map.dtd .............................. -->
40635 <!-- .................................... .............. -->
40636 <!-- memory-map.dtd -->
40637 <!-- memory-map: Root element with versioning -->
40638 <!ELEMENT memory-map (memory | property)>
40639 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40640 <!ELEMENT memory (property)>
40641 <!-- memory: Specifies a memory region,
40642 and its type, or device. -->
40643 <!ATTLIST memory type CDATA #REQUIRED
40644 start CDATA #REQUIRED
40645 length CDATA #REQUIRED
40646 device CDATA #IMPLIED>
40647 <!-- property: Generic attribute tag -->
40648 <!ELEMENT property (#PCDATA | property)*>
40649 <!ATTLIST property name CDATA #REQUIRED>
40652 @node Thread List Format
40653 @section Thread List Format
40654 @cindex thread list format
40656 To efficiently update the list of threads and their attributes,
40657 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40658 (@pxref{qXfer threads read}) and obtains the XML document with
40659 the following structure:
40662 <?xml version="1.0"?>
40664 <thread id="id" core="0" name="name">
40665 ... description ...
40670 Each @samp{thread} element must have the @samp{id} attribute that
40671 identifies the thread (@pxref{thread-id syntax}). The
40672 @samp{core} attribute, if present, specifies which processor core
40673 the thread was last executing on. The @samp{name} attribute, if
40674 present, specifies the human-readable name of the thread. The content
40675 of the of @samp{thread} element is interpreted as human-readable
40676 auxiliary information.
40678 @node Traceframe Info Format
40679 @section Traceframe Info Format
40680 @cindex traceframe info format
40682 To be able to know which objects in the inferior can be examined when
40683 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40684 memory ranges, registers and trace state variables that have been
40685 collected in a traceframe.
40687 This list is obtained using the @samp{qXfer:traceframe-info:read}
40688 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40690 @value{GDBN} must be linked with the Expat library to support XML
40691 traceframe info discovery. @xref{Expat}.
40693 The top-level structure of the document is shown below:
40696 <?xml version="1.0"?>
40697 <!DOCTYPE traceframe-info
40698 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40699 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40705 Each traceframe block can be either:
40710 A region of collected memory starting at @var{addr} and extending for
40711 @var{length} bytes from there:
40714 <memory start="@var{addr}" length="@var{length}"/>
40718 A block indicating trace state variable numbered @var{number} has been
40722 <tvar id="@var{number}"/>
40727 The formal DTD for the traceframe info format is given below:
40730 <!ELEMENT traceframe-info (memory | tvar)* >
40731 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40733 <!ELEMENT memory EMPTY>
40734 <!ATTLIST memory start CDATA #REQUIRED
40735 length CDATA #REQUIRED>
40737 <!ATTLIST tvar id CDATA #REQUIRED>
40740 @node Branch Trace Format
40741 @section Branch Trace Format
40742 @cindex branch trace format
40744 In order to display the branch trace of an inferior thread,
40745 @value{GDBN} needs to obtain the list of branches. This list is
40746 represented as list of sequential code blocks that are connected via
40747 branches. The code in each block has been executed sequentially.
40749 This list is obtained using the @samp{qXfer:btrace:read}
40750 (@pxref{qXfer btrace read}) packet and is an XML document.
40752 @value{GDBN} must be linked with the Expat library to support XML
40753 traceframe info discovery. @xref{Expat}.
40755 The top-level structure of the document is shown below:
40758 <?xml version="1.0"?>
40760 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40761 "http://sourceware.org/gdb/gdb-btrace.dtd">
40770 A block of sequentially executed instructions starting at @var{begin}
40771 and ending at @var{end}:
40774 <block begin="@var{begin}" end="@var{end}"/>
40779 The formal DTD for the branch trace format is given below:
40782 <!ELEMENT btrace (block* | pt) >
40783 <!ATTLIST btrace version CDATA #FIXED "1.0">
40785 <!ELEMENT block EMPTY>
40786 <!ATTLIST block begin CDATA #REQUIRED
40787 end CDATA #REQUIRED>
40789 <!ELEMENT pt (pt-config?, raw?)>
40791 <!ELEMENT pt-config (cpu?)>
40793 <!ELEMENT cpu EMPTY>
40794 <!ATTLIST cpu vendor CDATA #REQUIRED
40795 family CDATA #REQUIRED
40796 model CDATA #REQUIRED
40797 stepping CDATA #REQUIRED>
40799 <!ELEMENT raw (#PCDATA)>
40802 @node Branch Trace Configuration Format
40803 @section Branch Trace Configuration Format
40804 @cindex branch trace configuration format
40806 For each inferior thread, @value{GDBN} can obtain the branch trace
40807 configuration using the @samp{qXfer:btrace-conf:read}
40808 (@pxref{qXfer btrace-conf read}) packet.
40810 The configuration describes the branch trace format and configuration
40811 settings for that format. The following information is described:
40815 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40818 The size of the @acronym{BTS} ring buffer in bytes.
40821 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40825 The size of the @acronym{Intel PT} ring buffer in bytes.
40829 @value{GDBN} must be linked with the Expat library to support XML
40830 branch trace configuration discovery. @xref{Expat}.
40832 The formal DTD for the branch trace configuration format is given below:
40835 <!ELEMENT btrace-conf (bts?, pt?)>
40836 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40838 <!ELEMENT bts EMPTY>
40839 <!ATTLIST bts size CDATA #IMPLIED>
40841 <!ELEMENT pt EMPTY>
40842 <!ATTLIST pt size CDATA #IMPLIED>
40845 @include agentexpr.texi
40847 @node Target Descriptions
40848 @appendix Target Descriptions
40849 @cindex target descriptions
40851 One of the challenges of using @value{GDBN} to debug embedded systems
40852 is that there are so many minor variants of each processor
40853 architecture in use. It is common practice for vendors to start with
40854 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40855 and then make changes to adapt it to a particular market niche. Some
40856 architectures have hundreds of variants, available from dozens of
40857 vendors. This leads to a number of problems:
40861 With so many different customized processors, it is difficult for
40862 the @value{GDBN} maintainers to keep up with the changes.
40864 Since individual variants may have short lifetimes or limited
40865 audiences, it may not be worthwhile to carry information about every
40866 variant in the @value{GDBN} source tree.
40868 When @value{GDBN} does support the architecture of the embedded system
40869 at hand, the task of finding the correct architecture name to give the
40870 @command{set architecture} command can be error-prone.
40873 To address these problems, the @value{GDBN} remote protocol allows a
40874 target system to not only identify itself to @value{GDBN}, but to
40875 actually describe its own features. This lets @value{GDBN} support
40876 processor variants it has never seen before --- to the extent that the
40877 descriptions are accurate, and that @value{GDBN} understands them.
40879 @value{GDBN} must be linked with the Expat library to support XML
40880 target descriptions. @xref{Expat}.
40883 * Retrieving Descriptions:: How descriptions are fetched from a target.
40884 * Target Description Format:: The contents of a target description.
40885 * Predefined Target Types:: Standard types available for target
40887 * Enum Target Types:: How to define enum target types.
40888 * Standard Target Features:: Features @value{GDBN} knows about.
40891 @node Retrieving Descriptions
40892 @section Retrieving Descriptions
40894 Target descriptions can be read from the target automatically, or
40895 specified by the user manually. The default behavior is to read the
40896 description from the target. @value{GDBN} retrieves it via the remote
40897 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40898 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40899 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40900 XML document, of the form described in @ref{Target Description
40903 Alternatively, you can specify a file to read for the target description.
40904 If a file is set, the target will not be queried. The commands to
40905 specify a file are:
40908 @cindex set tdesc filename
40909 @item set tdesc filename @var{path}
40910 Read the target description from @var{path}.
40912 @cindex unset tdesc filename
40913 @item unset tdesc filename
40914 Do not read the XML target description from a file. @value{GDBN}
40915 will use the description supplied by the current target.
40917 @cindex show tdesc filename
40918 @item show tdesc filename
40919 Show the filename to read for a target description, if any.
40923 @node Target Description Format
40924 @section Target Description Format
40925 @cindex target descriptions, XML format
40927 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40928 document which complies with the Document Type Definition provided in
40929 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40930 means you can use generally available tools like @command{xmllint} to
40931 check that your feature descriptions are well-formed and valid.
40932 However, to help people unfamiliar with XML write descriptions for
40933 their targets, we also describe the grammar here.
40935 Target descriptions can identify the architecture of the remote target
40936 and (for some architectures) provide information about custom register
40937 sets. They can also identify the OS ABI of the remote target.
40938 @value{GDBN} can use this information to autoconfigure for your
40939 target, or to warn you if you connect to an unsupported target.
40941 Here is a simple target description:
40944 <target version="1.0">
40945 <architecture>i386:x86-64</architecture>
40950 This minimal description only says that the target uses
40951 the x86-64 architecture.
40953 A target description has the following overall form, with [ ] marking
40954 optional elements and @dots{} marking repeatable elements. The elements
40955 are explained further below.
40958 <?xml version="1.0"?>
40959 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40960 <target version="1.0">
40961 @r{[}@var{architecture}@r{]}
40962 @r{[}@var{osabi}@r{]}
40963 @r{[}@var{compatible}@r{]}
40964 @r{[}@var{feature}@dots{}@r{]}
40969 The description is generally insensitive to whitespace and line
40970 breaks, under the usual common-sense rules. The XML version
40971 declaration and document type declaration can generally be omitted
40972 (@value{GDBN} does not require them), but specifying them may be
40973 useful for XML validation tools. The @samp{version} attribute for
40974 @samp{<target>} may also be omitted, but we recommend
40975 including it; if future versions of @value{GDBN} use an incompatible
40976 revision of @file{gdb-target.dtd}, they will detect and report
40977 the version mismatch.
40979 @subsection Inclusion
40980 @cindex target descriptions, inclusion
40983 @cindex <xi:include>
40986 It can sometimes be valuable to split a target description up into
40987 several different annexes, either for organizational purposes, or to
40988 share files between different possible target descriptions. You can
40989 divide a description into multiple files by replacing any element of
40990 the target description with an inclusion directive of the form:
40993 <xi:include href="@var{document}"/>
40997 When @value{GDBN} encounters an element of this form, it will retrieve
40998 the named XML @var{document}, and replace the inclusion directive with
40999 the contents of that document. If the current description was read
41000 using @samp{qXfer}, then so will be the included document;
41001 @var{document} will be interpreted as the name of an annex. If the
41002 current description was read from a file, @value{GDBN} will look for
41003 @var{document} as a file in the same directory where it found the
41004 original description.
41006 @subsection Architecture
41007 @cindex <architecture>
41009 An @samp{<architecture>} element has this form:
41012 <architecture>@var{arch}</architecture>
41015 @var{arch} is one of the architectures from the set accepted by
41016 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41019 @cindex @code{<osabi>}
41021 This optional field was introduced in @value{GDBN} version 7.0.
41022 Previous versions of @value{GDBN} ignore it.
41024 An @samp{<osabi>} element has this form:
41027 <osabi>@var{abi-name}</osabi>
41030 @var{abi-name} is an OS ABI name from the same selection accepted by
41031 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41033 @subsection Compatible Architecture
41034 @cindex @code{<compatible>}
41036 This optional field was introduced in @value{GDBN} version 7.0.
41037 Previous versions of @value{GDBN} ignore it.
41039 A @samp{<compatible>} element has this form:
41042 <compatible>@var{arch}</compatible>
41045 @var{arch} is one of the architectures from the set accepted by
41046 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41048 A @samp{<compatible>} element is used to specify that the target
41049 is able to run binaries in some other than the main target architecture
41050 given by the @samp{<architecture>} element. For example, on the
41051 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41052 or @code{powerpc:common64}, but the system is able to run binaries
41053 in the @code{spu} architecture as well. The way to describe this
41054 capability with @samp{<compatible>} is as follows:
41057 <architecture>powerpc:common</architecture>
41058 <compatible>spu</compatible>
41061 @subsection Features
41064 Each @samp{<feature>} describes some logical portion of the target
41065 system. Features are currently used to describe available CPU
41066 registers and the types of their contents. A @samp{<feature>} element
41070 <feature name="@var{name}">
41071 @r{[}@var{type}@dots{}@r{]}
41077 Each feature's name should be unique within the description. The name
41078 of a feature does not matter unless @value{GDBN} has some special
41079 knowledge of the contents of that feature; if it does, the feature
41080 should have its standard name. @xref{Standard Target Features}.
41084 Any register's value is a collection of bits which @value{GDBN} must
41085 interpret. The default interpretation is a two's complement integer,
41086 but other types can be requested by name in the register description.
41087 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41088 Target Types}), and the description can define additional composite
41091 Each type element must have an @samp{id} attribute, which gives
41092 a unique (within the containing @samp{<feature>}) name to the type.
41093 Types must be defined before they are used.
41096 Some targets offer vector registers, which can be treated as arrays
41097 of scalar elements. These types are written as @samp{<vector>} elements,
41098 specifying the array element type, @var{type}, and the number of elements,
41102 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41106 If a register's value is usefully viewed in multiple ways, define it
41107 with a union type containing the useful representations. The
41108 @samp{<union>} element contains one or more @samp{<field>} elements,
41109 each of which has a @var{name} and a @var{type}:
41112 <union id="@var{id}">
41113 <field name="@var{name}" type="@var{type}"/>
41120 If a register's value is composed from several separate values, define
41121 it with either a structure type or a flags type.
41122 A flags type may only contain bitfields.
41123 A structure type may either contain only bitfields or contain no bitfields.
41124 If the value contains only bitfields, its total size in bytes must be
41127 Non-bitfield values have a @var{name} and @var{type}.
41130 <struct id="@var{id}">
41131 <field name="@var{name}" type="@var{type}"/>
41136 Both @var{name} and @var{type} values are required.
41137 No implicit padding is added.
41139 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41142 <struct id="@var{id}" size="@var{size}">
41143 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41149 <flags id="@var{id}" size="@var{size}">
41150 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41155 The @var{name} value is required.
41156 Bitfield values may be named with the empty string, @samp{""},
41157 in which case the field is ``filler'' and its value is not printed.
41158 Not all bits need to be specified, so ``filler'' fields are optional.
41160 The @var{start} and @var{end} values are required, and @var{type}
41162 The field's @var{start} must be less than or equal to its @var{end},
41163 and zero represents the least significant bit.
41165 The default value of @var{type} is @code{bool} for single bit fields,
41166 and an unsigned integer otherwise.
41168 Which to choose? Structures or flags?
41170 Registers defined with @samp{flags} have these advantages over
41171 defining them with @samp{struct}:
41175 Arithmetic may be performed on them as if they were integers.
41177 They are printed in a more readable fashion.
41180 Registers defined with @samp{struct} have one advantage over
41181 defining them with @samp{flags}:
41185 One can fetch individual fields like in @samp{C}.
41188 (gdb) print $my_struct_reg.field3
41194 @subsection Registers
41197 Each register is represented as an element with this form:
41200 <reg name="@var{name}"
41201 bitsize="@var{size}"
41202 @r{[}regnum="@var{num}"@r{]}
41203 @r{[}save-restore="@var{save-restore}"@r{]}
41204 @r{[}type="@var{type}"@r{]}
41205 @r{[}group="@var{group}"@r{]}/>
41209 The components are as follows:
41214 The register's name; it must be unique within the target description.
41217 The register's size, in bits.
41220 The register's number. If omitted, a register's number is one greater
41221 than that of the previous register (either in the current feature or in
41222 a preceding feature); the first register in the target description
41223 defaults to zero. This register number is used to read or write
41224 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41225 packets, and registers appear in the @code{g} and @code{G} packets
41226 in order of increasing register number.
41229 Whether the register should be preserved across inferior function
41230 calls; this must be either @code{yes} or @code{no}. The default is
41231 @code{yes}, which is appropriate for most registers except for
41232 some system control registers; this is not related to the target's
41236 The type of the register. It may be a predefined type, a type
41237 defined in the current feature, or one of the special types @code{int}
41238 and @code{float}. @code{int} is an integer type of the correct size
41239 for @var{bitsize}, and @code{float} is a floating point type (in the
41240 architecture's normal floating point format) of the correct size for
41241 @var{bitsize}. The default is @code{int}.
41244 The register group to which this register belongs. It must
41245 be either @code{general}, @code{float}, or @code{vector}. If no
41246 @var{group} is specified, @value{GDBN} will not display the register
41247 in @code{info registers}.
41251 @node Predefined Target Types
41252 @section Predefined Target Types
41253 @cindex target descriptions, predefined types
41255 Type definitions in the self-description can build up composite types
41256 from basic building blocks, but can not define fundamental types. Instead,
41257 standard identifiers are provided by @value{GDBN} for the fundamental
41258 types. The currently supported types are:
41263 Boolean type, occupying a single bit.
41270 Signed integer types holding the specified number of bits.
41277 Unsigned integer types holding the specified number of bits.
41281 Pointers to unspecified code and data. The program counter and
41282 any dedicated return address register may be marked as code
41283 pointers; printing a code pointer converts it into a symbolic
41284 address. The stack pointer and any dedicated address registers
41285 may be marked as data pointers.
41288 Single precision IEEE floating point.
41291 Double precision IEEE floating point.
41294 The 12-byte extended precision format used by ARM FPA registers.
41297 The 10-byte extended precision format used by x87 registers.
41300 32bit @sc{eflags} register used by x86.
41303 32bit @sc{mxcsr} register used by x86.
41307 @node Enum Target Types
41308 @section Enum Target Types
41309 @cindex target descriptions, enum types
41311 Enum target types are useful in @samp{struct} and @samp{flags}
41312 register descriptions. @xref{Target Description Format}.
41314 Enum types have a name, size and a list of name/value pairs.
41317 <enum id="@var{id}" size="@var{size}">
41318 <evalue name="@var{name}" value="@var{value}"/>
41323 Enums must be defined before they are used.
41326 <enum id="levels_type" size="4">
41327 <evalue name="low" value="0"/>
41328 <evalue name="high" value="1"/>
41330 <flags id="flags_type" size="4">
41331 <field name="X" start="0"/>
41332 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41334 <reg name="flags" bitsize="32" type="flags_type"/>
41337 Given that description, a value of 3 for the @samp{flags} register
41338 would be printed as:
41341 (gdb) info register flags
41342 flags 0x3 [ X LEVEL=high ]
41345 @node Standard Target Features
41346 @section Standard Target Features
41347 @cindex target descriptions, standard features
41349 A target description must contain either no registers or all the
41350 target's registers. If the description contains no registers, then
41351 @value{GDBN} will assume a default register layout, selected based on
41352 the architecture. If the description contains any registers, the
41353 default layout will not be used; the standard registers must be
41354 described in the target description, in such a way that @value{GDBN}
41355 can recognize them.
41357 This is accomplished by giving specific names to feature elements
41358 which contain standard registers. @value{GDBN} will look for features
41359 with those names and verify that they contain the expected registers;
41360 if any known feature is missing required registers, or if any required
41361 feature is missing, @value{GDBN} will reject the target
41362 description. You can add additional registers to any of the
41363 standard features --- @value{GDBN} will display them just as if
41364 they were added to an unrecognized feature.
41366 This section lists the known features and their expected contents.
41367 Sample XML documents for these features are included in the
41368 @value{GDBN} source tree, in the directory @file{gdb/features}.
41370 Names recognized by @value{GDBN} should include the name of the
41371 company or organization which selected the name, and the overall
41372 architecture to which the feature applies; so e.g.@: the feature
41373 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41375 The names of registers are not case sensitive for the purpose
41376 of recognizing standard features, but @value{GDBN} will only display
41377 registers using the capitalization used in the description.
41380 * AArch64 Features::
41384 * MicroBlaze Features::
41388 * Nios II Features::
41389 * PowerPC Features::
41390 * S/390 and System z Features::
41396 @node AArch64 Features
41397 @subsection AArch64 Features
41398 @cindex target descriptions, AArch64 features
41400 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41401 targets. It should contain registers @samp{x0} through @samp{x30},
41402 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41404 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41405 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41409 @subsection ARC Features
41410 @cindex target descriptions, ARC Features
41412 ARC processors are highly configurable, so even core registers and their number
41413 are not completely predetermined. In addition flags and PC registers which are
41414 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41415 that one of the core registers features is present.
41416 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41418 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41419 targets with a normal register file. It should contain registers @samp{r0}
41420 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41421 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41422 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41423 @samp{ilink} and extension core registers are not available to read/write, when
41424 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41426 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41427 ARC HS targets with a reduced register file. It should contain registers
41428 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41429 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41430 This feature may contain register @samp{ilink} and any of extension core
41431 registers @samp{r32} through @samp{r59/acch}.
41433 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41434 targets with a normal register file. It should contain registers @samp{r0}
41435 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41436 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41437 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41438 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41439 registers are not available when debugging GNU/Linux applications. The only
41440 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41441 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41442 ARC v2, but @samp{ilink2} is optional on ARCompact.
41444 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41445 targets. It should contain registers @samp{pc} and @samp{status32}.
41448 @subsection ARM Features
41449 @cindex target descriptions, ARM features
41451 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41453 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41454 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41456 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41457 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41458 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41461 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41462 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41464 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41465 it should contain at least registers @samp{wR0} through @samp{wR15} and
41466 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41467 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41469 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41470 should contain at least registers @samp{d0} through @samp{d15}. If
41471 they are present, @samp{d16} through @samp{d31} should also be included.
41472 @value{GDBN} will synthesize the single-precision registers from
41473 halves of the double-precision registers.
41475 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41476 need to contain registers; it instructs @value{GDBN} to display the
41477 VFP double-precision registers as vectors and to synthesize the
41478 quad-precision registers from pairs of double-precision registers.
41479 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41480 be present and include 32 double-precision registers.
41482 @node i386 Features
41483 @subsection i386 Features
41484 @cindex target descriptions, i386 features
41486 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41487 targets. It should describe the following registers:
41491 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41493 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41495 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41496 @samp{fs}, @samp{gs}
41498 @samp{st0} through @samp{st7}
41500 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41501 @samp{foseg}, @samp{fooff} and @samp{fop}
41504 The register sets may be different, depending on the target.
41506 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41507 describe registers:
41511 @samp{xmm0} through @samp{xmm7} for i386
41513 @samp{xmm0} through @samp{xmm15} for amd64
41518 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41519 @samp{org.gnu.gdb.i386.sse} feature. It should
41520 describe the upper 128 bits of @sc{ymm} registers:
41524 @samp{ymm0h} through @samp{ymm7h} for i386
41526 @samp{ymm0h} through @samp{ymm15h} for amd64
41529 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41530 Memory Protection Extension (MPX). It should describe the following registers:
41534 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41536 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41539 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41540 describe a single register, @samp{orig_eax}.
41542 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41543 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41545 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41546 @samp{org.gnu.gdb.i386.avx} feature. It should
41547 describe additional @sc{xmm} registers:
41551 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41554 It should describe the upper 128 bits of additional @sc{ymm} registers:
41558 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41562 describe the upper 256 bits of @sc{zmm} registers:
41566 @samp{zmm0h} through @samp{zmm7h} for i386.
41568 @samp{zmm0h} through @samp{zmm15h} for amd64.
41572 describe the additional @sc{zmm} registers:
41576 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41579 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41580 describe a single register, @samp{pkru}. It is a 32-bit register
41581 valid for i386 and amd64.
41583 @node MicroBlaze Features
41584 @subsection MicroBlaze Features
41585 @cindex target descriptions, MicroBlaze features
41587 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41588 targets. It should contain registers @samp{r0} through @samp{r31},
41589 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41590 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41591 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41593 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41594 If present, it should contain registers @samp{rshr} and @samp{rslr}
41596 @node MIPS Features
41597 @subsection @acronym{MIPS} Features
41598 @cindex target descriptions, @acronym{MIPS} features
41600 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41601 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41602 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41605 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41606 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41607 registers. They may be 32-bit or 64-bit depending on the target.
41609 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41610 it may be optional in a future version of @value{GDBN}. It should
41611 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41612 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41614 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41615 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41616 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41617 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41619 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41620 contain a single register, @samp{restart}, which is used by the
41621 Linux kernel to control restartable syscalls.
41623 @node M68K Features
41624 @subsection M68K Features
41625 @cindex target descriptions, M68K features
41628 @item @samp{org.gnu.gdb.m68k.core}
41629 @itemx @samp{org.gnu.gdb.coldfire.core}
41630 @itemx @samp{org.gnu.gdb.fido.core}
41631 One of those features must be always present.
41632 The feature that is present determines which flavor of m68k is
41633 used. The feature that is present should contain registers
41634 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41635 @samp{sp}, @samp{ps} and @samp{pc}.
41637 @item @samp{org.gnu.gdb.coldfire.fp}
41638 This feature is optional. If present, it should contain registers
41639 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41643 @node NDS32 Features
41644 @subsection NDS32 Features
41645 @cindex target descriptions, NDS32 features
41647 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41648 targets. It should contain at least registers @samp{r0} through
41649 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41652 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41653 it should contain 64-bit double-precision floating-point registers
41654 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41655 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41657 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41658 registers are overlapped with the thirty-two 32-bit single-precision
41659 floating-point registers. The 32-bit single-precision registers, if
41660 not being listed explicitly, will be synthesized from halves of the
41661 overlapping 64-bit double-precision registers. Listing 32-bit
41662 single-precision registers explicitly is deprecated, and the
41663 support to it could be totally removed some day.
41665 @node Nios II Features
41666 @subsection Nios II Features
41667 @cindex target descriptions, Nios II features
41669 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41670 targets. It should contain the 32 core registers (@samp{zero},
41671 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41672 @samp{pc}, and the 16 control registers (@samp{status} through
41675 @node PowerPC Features
41676 @subsection PowerPC Features
41677 @cindex target descriptions, PowerPC features
41679 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41680 targets. It should contain registers @samp{r0} through @samp{r31},
41681 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41682 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41684 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41685 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41687 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41688 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41691 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41692 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41693 will combine these registers with the floating point registers
41694 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41695 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41696 through @samp{vs63}, the set of vector registers for POWER7.
41698 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41699 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41700 @samp{spefscr}. SPE targets should provide 32-bit registers in
41701 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41702 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41703 these to present registers @samp{ev0} through @samp{ev31} to the
41706 @node S/390 and System z Features
41707 @subsection S/390 and System z Features
41708 @cindex target descriptions, S/390 features
41709 @cindex target descriptions, System z features
41711 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41712 System z targets. It should contain the PSW and the 16 general
41713 registers. In particular, System z targets should provide the 64-bit
41714 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41715 S/390 targets should provide the 32-bit versions of these registers.
41716 A System z target that runs in 31-bit addressing mode should provide
41717 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41718 register's upper halves @samp{r0h} through @samp{r15h}, and their
41719 lower halves @samp{r0l} through @samp{r15l}.
41721 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41722 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41725 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41726 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41728 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41729 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41730 targets and 32-bit otherwise. In addition, the feature may contain
41731 the @samp{last_break} register, whose width depends on the addressing
41732 mode, as well as the @samp{system_call} register, which is always
41735 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41736 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41737 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41739 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41740 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41741 combined by @value{GDBN} with the floating point registers @samp{f0}
41742 through @samp{f15} to present the 128-bit wide vector registers
41743 @samp{v0} through @samp{v15}. In addition, this feature should
41744 contain the 128-bit wide vector registers @samp{v16} through
41747 @node Sparc Features
41748 @subsection Sparc Features
41749 @cindex target descriptions, sparc32 features
41750 @cindex target descriptions, sparc64 features
41751 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
41752 targets. It should describe the following registers:
41756 @samp{g0} through @samp{g7}
41758 @samp{o0} through @samp{o7}
41760 @samp{l0} through @samp{l7}
41762 @samp{i0} through @samp{i7}
41765 They may be 32-bit or 64-bit depending on the target.
41767 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
41768 targets. It should describe the following registers:
41772 @samp{f0} through @samp{f31}
41774 @samp{f32} through @samp{f62} for sparc64
41777 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
41778 targets. It should describe the following registers:
41782 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
41783 @samp{fsr}, and @samp{csr} for sparc32
41785 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
41789 @node TIC6x Features
41790 @subsection TMS320C6x Features
41791 @cindex target descriptions, TIC6x features
41792 @cindex target descriptions, TMS320C6x features
41793 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41794 targets. It should contain registers @samp{A0} through @samp{A15},
41795 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41797 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41798 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41799 through @samp{B31}.
41801 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41802 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41804 @node Operating System Information
41805 @appendix Operating System Information
41806 @cindex operating system information
41812 Users of @value{GDBN} often wish to obtain information about the state of
41813 the operating system running on the target---for example the list of
41814 processes, or the list of open files. This section describes the
41815 mechanism that makes it possible. This mechanism is similar to the
41816 target features mechanism (@pxref{Target Descriptions}), but focuses
41817 on a different aspect of target.
41819 Operating system information is retrived from the target via the
41820 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41821 read}). The object name in the request should be @samp{osdata}, and
41822 the @var{annex} identifies the data to be fetched.
41825 @appendixsection Process list
41826 @cindex operating system information, process list
41828 When requesting the process list, the @var{annex} field in the
41829 @samp{qXfer} request should be @samp{processes}. The returned data is
41830 an XML document. The formal syntax of this document is defined in
41831 @file{gdb/features/osdata.dtd}.
41833 An example document is:
41836 <?xml version="1.0"?>
41837 <!DOCTYPE target SYSTEM "osdata.dtd">
41838 <osdata type="processes">
41840 <column name="pid">1</column>
41841 <column name="user">root</column>
41842 <column name="command">/sbin/init</column>
41843 <column name="cores">1,2,3</column>
41848 Each item should include a column whose name is @samp{pid}. The value
41849 of that column should identify the process on the target. The
41850 @samp{user} and @samp{command} columns are optional, and will be
41851 displayed by @value{GDBN}. The @samp{cores} column, if present,
41852 should contain a comma-separated list of cores that this process
41853 is running on. Target may provide additional columns,
41854 which @value{GDBN} currently ignores.
41856 @node Trace File Format
41857 @appendix Trace File Format
41858 @cindex trace file format
41860 The trace file comes in three parts: a header, a textual description
41861 section, and a trace frame section with binary data.
41863 The header has the form @code{\x7fTRACE0\n}. The first byte is
41864 @code{0x7f} so as to indicate that the file contains binary data,
41865 while the @code{0} is a version number that may have different values
41868 The description section consists of multiple lines of @sc{ascii} text
41869 separated by newline characters (@code{0xa}). The lines may include a
41870 variety of optional descriptive or context-setting information, such
41871 as tracepoint definitions or register set size. @value{GDBN} will
41872 ignore any line that it does not recognize. An empty line marks the end
41877 Specifies the size of a register block in bytes. This is equal to the
41878 size of a @code{g} packet payload in the remote protocol. @var{size}
41879 is an ascii decimal number. There should be only one such line in
41880 a single trace file.
41882 @item status @var{status}
41883 Trace status. @var{status} has the same format as a @code{qTStatus}
41884 remote packet reply. There should be only one such line in a single trace
41887 @item tp @var{payload}
41888 Tracepoint definition. The @var{payload} has the same format as
41889 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41890 may take multiple lines of definition, corresponding to the multiple
41893 @item tsv @var{payload}
41894 Trace state variable definition. The @var{payload} has the same format as
41895 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41896 may take multiple lines of definition, corresponding to the multiple
41899 @item tdesc @var{payload}
41900 Target description in XML format. The @var{payload} is a single line of
41901 the XML file. All such lines should be concatenated together to get
41902 the original XML file. This file is in the same format as @code{qXfer}
41903 @code{features} payload, and corresponds to the main @code{target.xml}
41904 file. Includes are not allowed.
41908 The trace frame section consists of a number of consecutive frames.
41909 Each frame begins with a two-byte tracepoint number, followed by a
41910 four-byte size giving the amount of data in the frame. The data in
41911 the frame consists of a number of blocks, each introduced by a
41912 character indicating its type (at least register, memory, and trace
41913 state variable). The data in this section is raw binary, not a
41914 hexadecimal or other encoding; its endianness matches the target's
41917 @c FIXME bi-arch may require endianness/arch info in description section
41920 @item R @var{bytes}
41921 Register block. The number and ordering of bytes matches that of a
41922 @code{g} packet in the remote protocol. Note that these are the
41923 actual bytes, in target order, not a hexadecimal encoding.
41925 @item M @var{address} @var{length} @var{bytes}...
41926 Memory block. This is a contiguous block of memory, at the 8-byte
41927 address @var{address}, with a 2-byte length @var{length}, followed by
41928 @var{length} bytes.
41930 @item V @var{number} @var{value}
41931 Trace state variable block. This records the 8-byte signed value
41932 @var{value} of trace state variable numbered @var{number}.
41936 Future enhancements of the trace file format may include additional types
41939 @node Index Section Format
41940 @appendix @code{.gdb_index} section format
41941 @cindex .gdb_index section format
41942 @cindex index section format
41944 This section documents the index section that is created by @code{save
41945 gdb-index} (@pxref{Index Files}). The index section is
41946 DWARF-specific; some knowledge of DWARF is assumed in this
41949 The mapped index file format is designed to be directly
41950 @code{mmap}able on any architecture. In most cases, a datum is
41951 represented using a little-endian 32-bit integer value, called an
41952 @code{offset_type}. Big endian machines must byte-swap the values
41953 before using them. Exceptions to this rule are noted. The data is
41954 laid out such that alignment is always respected.
41956 A mapped index consists of several areas, laid out in order.
41960 The file header. This is a sequence of values, of @code{offset_type}
41961 unless otherwise noted:
41965 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41966 Version 4 uses a different hashing function from versions 5 and 6.
41967 Version 6 includes symbols for inlined functions, whereas versions 4
41968 and 5 do not. Version 7 adds attributes to the CU indices in the
41969 symbol table. Version 8 specifies that symbols from DWARF type units
41970 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41971 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41973 @value{GDBN} will only read version 4, 5, or 6 indices
41974 by specifying @code{set use-deprecated-index-sections on}.
41975 GDB has a workaround for potentially broken version 7 indices so it is
41976 currently not flagged as deprecated.
41979 The offset, from the start of the file, of the CU list.
41982 The offset, from the start of the file, of the types CU list. Note
41983 that this area can be empty, in which case this offset will be equal
41984 to the next offset.
41987 The offset, from the start of the file, of the address area.
41990 The offset, from the start of the file, of the symbol table.
41993 The offset, from the start of the file, of the constant pool.
41997 The CU list. This is a sequence of pairs of 64-bit little-endian
41998 values, sorted by the CU offset. The first element in each pair is
41999 the offset of a CU in the @code{.debug_info} section. The second
42000 element in each pair is the length of that CU. References to a CU
42001 elsewhere in the map are done using a CU index, which is just the
42002 0-based index into this table. Note that if there are type CUs, then
42003 conceptually CUs and type CUs form a single list for the purposes of
42007 The types CU list. This is a sequence of triplets of 64-bit
42008 little-endian values. In a triplet, the first value is the CU offset,
42009 the second value is the type offset in the CU, and the third value is
42010 the type signature. The types CU list is not sorted.
42013 The address area. The address area consists of a sequence of address
42014 entries. Each address entry has three elements:
42018 The low address. This is a 64-bit little-endian value.
42021 The high address. This is a 64-bit little-endian value. Like
42022 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42025 The CU index. This is an @code{offset_type} value.
42029 The symbol table. This is an open-addressed hash table. The size of
42030 the hash table is always a power of 2.
42032 Each slot in the hash table consists of a pair of @code{offset_type}
42033 values. The first value is the offset of the symbol's name in the
42034 constant pool. The second value is the offset of the CU vector in the
42037 If both values are 0, then this slot in the hash table is empty. This
42038 is ok because while 0 is a valid constant pool index, it cannot be a
42039 valid index for both a string and a CU vector.
42041 The hash value for a table entry is computed by applying an
42042 iterative hash function to the symbol's name. Starting with an
42043 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42044 the string is incorporated into the hash using the formula depending on the
42049 The formula is @code{r = r * 67 + c - 113}.
42051 @item Versions 5 to 7
42052 The formula is @code{r = r * 67 + tolower (c) - 113}.
42055 The terminating @samp{\0} is not incorporated into the hash.
42057 The step size used in the hash table is computed via
42058 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42059 value, and @samp{size} is the size of the hash table. The step size
42060 is used to find the next candidate slot when handling a hash
42063 The names of C@t{++} symbols in the hash table are canonicalized. We
42064 don't currently have a simple description of the canonicalization
42065 algorithm; if you intend to create new index sections, you must read
42069 The constant pool. This is simply a bunch of bytes. It is organized
42070 so that alignment is correct: CU vectors are stored first, followed by
42073 A CU vector in the constant pool is a sequence of @code{offset_type}
42074 values. The first value is the number of CU indices in the vector.
42075 Each subsequent value is the index and symbol attributes of a CU in
42076 the CU list. This element in the hash table is used to indicate which
42077 CUs define the symbol and how the symbol is used.
42078 See below for the format of each CU index+attributes entry.
42080 A string in the constant pool is zero-terminated.
42083 Attributes were added to CU index values in @code{.gdb_index} version 7.
42084 If a symbol has multiple uses within a CU then there is one
42085 CU index+attributes value for each use.
42087 The format of each CU index+attributes entry is as follows
42093 This is the index of the CU in the CU list.
42095 These bits are reserved for future purposes and must be zero.
42097 The kind of the symbol in the CU.
42101 This value is reserved and should not be used.
42102 By reserving zero the full @code{offset_type} value is backwards compatible
42103 with previous versions of the index.
42105 The symbol is a type.
42107 The symbol is a variable or an enum value.
42109 The symbol is a function.
42111 Any other kind of symbol.
42113 These values are reserved.
42117 This bit is zero if the value is global and one if it is static.
42119 The determination of whether a symbol is global or static is complicated.
42120 The authorative reference is the file @file{dwarf2read.c} in
42121 @value{GDBN} sources.
42125 This pseudo-code describes the computation of a symbol's kind and
42126 global/static attributes in the index.
42129 is_external = get_attribute (die, DW_AT_external);
42130 language = get_attribute (cu_die, DW_AT_language);
42133 case DW_TAG_typedef:
42134 case DW_TAG_base_type:
42135 case DW_TAG_subrange_type:
42139 case DW_TAG_enumerator:
42141 is_static = language != CPLUS;
42143 case DW_TAG_subprogram:
42145 is_static = ! (is_external || language == ADA);
42147 case DW_TAG_constant:
42149 is_static = ! is_external;
42151 case DW_TAG_variable:
42153 is_static = ! is_external;
42155 case DW_TAG_namespace:
42159 case DW_TAG_class_type:
42160 case DW_TAG_interface_type:
42161 case DW_TAG_structure_type:
42162 case DW_TAG_union_type:
42163 case DW_TAG_enumeration_type:
42165 is_static = language != CPLUS;
42173 @appendix Manual pages
42177 * gdb man:: The GNU Debugger man page
42178 * gdbserver man:: Remote Server for the GNU Debugger man page
42179 * gcore man:: Generate a core file of a running program
42180 * gdbinit man:: gdbinit scripts
42186 @c man title gdb The GNU Debugger
42188 @c man begin SYNOPSIS gdb
42189 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42190 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42191 [@option{-b}@w{ }@var{bps}]
42192 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42193 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42194 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42195 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42196 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42199 @c man begin DESCRIPTION gdb
42200 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42201 going on ``inside'' another program while it executes -- or what another
42202 program was doing at the moment it crashed.
42204 @value{GDBN} can do four main kinds of things (plus other things in support of
42205 these) to help you catch bugs in the act:
42209 Start your program, specifying anything that might affect its behavior.
42212 Make your program stop on specified conditions.
42215 Examine what has happened, when your program has stopped.
42218 Change things in your program, so you can experiment with correcting the
42219 effects of one bug and go on to learn about another.
42222 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42225 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42226 commands from the terminal until you tell it to exit with the @value{GDBN}
42227 command @code{quit}. You can get online help from @value{GDBN} itself
42228 by using the command @code{help}.
42230 You can run @code{gdb} with no arguments or options; but the most
42231 usual way to start @value{GDBN} is with one argument or two, specifying an
42232 executable program as the argument:
42238 You can also start with both an executable program and a core file specified:
42244 You can, instead, specify a process ID as a second argument, if you want
42245 to debug a running process:
42253 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42254 named @file{1234}; @value{GDBN} does check for a core file first).
42255 With option @option{-p} you can omit the @var{program} filename.
42257 Here are some of the most frequently needed @value{GDBN} commands:
42259 @c pod2man highlights the right hand side of the @item lines.
42261 @item break [@var{file}:]@var{function}
42262 Set a breakpoint at @var{function} (in @var{file}).
42264 @item run [@var{arglist}]
42265 Start your program (with @var{arglist}, if specified).
42268 Backtrace: display the program stack.
42270 @item print @var{expr}
42271 Display the value of an expression.
42274 Continue running your program (after stopping, e.g. at a breakpoint).
42277 Execute next program line (after stopping); step @emph{over} any
42278 function calls in the line.
42280 @item edit [@var{file}:]@var{function}
42281 look at the program line where it is presently stopped.
42283 @item list [@var{file}:]@var{function}
42284 type the text of the program in the vicinity of where it is presently stopped.
42287 Execute next program line (after stopping); step @emph{into} any
42288 function calls in the line.
42290 @item help [@var{name}]
42291 Show information about @value{GDBN} command @var{name}, or general information
42292 about using @value{GDBN}.
42295 Exit from @value{GDBN}.
42299 For full details on @value{GDBN},
42300 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42301 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42302 as the @code{gdb} entry in the @code{info} program.
42306 @c man begin OPTIONS gdb
42307 Any arguments other than options specify an executable
42308 file and core file (or process ID); that is, the first argument
42309 encountered with no
42310 associated option flag is equivalent to a @option{-se} option, and the second,
42311 if any, is equivalent to a @option{-c} option if it's the name of a file.
42313 both long and short forms; both are shown here. The long forms are also
42314 recognized if you truncate them, so long as enough of the option is
42315 present to be unambiguous. (If you prefer, you can flag option
42316 arguments with @option{+} rather than @option{-}, though we illustrate the
42317 more usual convention.)
42319 All the options and command line arguments you give are processed
42320 in sequential order. The order makes a difference when the @option{-x}
42326 List all options, with brief explanations.
42328 @item -symbols=@var{file}
42329 @itemx -s @var{file}
42330 Read symbol table from file @var{file}.
42333 Enable writing into executable and core files.
42335 @item -exec=@var{file}
42336 @itemx -e @var{file}
42337 Use file @var{file} as the executable file to execute when
42338 appropriate, and for examining pure data in conjunction with a core
42341 @item -se=@var{file}
42342 Read symbol table from file @var{file} and use it as the executable
42345 @item -core=@var{file}
42346 @itemx -c @var{file}
42347 Use file @var{file} as a core dump to examine.
42349 @item -command=@var{file}
42350 @itemx -x @var{file}
42351 Execute @value{GDBN} commands from file @var{file}.
42353 @item -ex @var{command}
42354 Execute given @value{GDBN} @var{command}.
42356 @item -directory=@var{directory}
42357 @itemx -d @var{directory}
42358 Add @var{directory} to the path to search for source files.
42361 Do not execute commands from @file{~/.gdbinit}.
42365 Do not execute commands from any @file{.gdbinit} initialization files.
42369 ``Quiet''. Do not print the introductory and copyright messages. These
42370 messages are also suppressed in batch mode.
42373 Run in batch mode. Exit with status @code{0} after processing all the command
42374 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42375 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42376 commands in the command files.
42378 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42379 download and run a program on another computer; in order to make this
42380 more useful, the message
42383 Program exited normally.
42387 (which is ordinarily issued whenever a program running under @value{GDBN} control
42388 terminates) is not issued when running in batch mode.
42390 @item -cd=@var{directory}
42391 Run @value{GDBN} using @var{directory} as its working directory,
42392 instead of the current directory.
42396 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42397 @value{GDBN} to output the full file name and line number in a standard,
42398 recognizable fashion each time a stack frame is displayed (which
42399 includes each time the program stops). This recognizable format looks
42400 like two @samp{\032} characters, followed by the file name, line number
42401 and character position separated by colons, and a newline. The
42402 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42403 characters as a signal to display the source code for the frame.
42406 Set the line speed (baud rate or bits per second) of any serial
42407 interface used by @value{GDBN} for remote debugging.
42409 @item -tty=@var{device}
42410 Run using @var{device} for your program's standard input and output.
42414 @c man begin SEEALSO gdb
42416 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42417 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42418 documentation are properly installed at your site, the command
42425 should give you access to the complete manual.
42427 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42428 Richard M. Stallman and Roland H. Pesch, July 1991.
42432 @node gdbserver man
42433 @heading gdbserver man
42435 @c man title gdbserver Remote Server for the GNU Debugger
42437 @c man begin SYNOPSIS gdbserver
42438 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42440 gdbserver --attach @var{comm} @var{pid}
42442 gdbserver --multi @var{comm}
42446 @c man begin DESCRIPTION gdbserver
42447 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42448 than the one which is running the program being debugged.
42451 @subheading Usage (server (target) side)
42454 Usage (server (target) side):
42457 First, you need to have a copy of the program you want to debug put onto
42458 the target system. The program can be stripped to save space if needed, as
42459 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42460 the @value{GDBN} running on the host system.
42462 To use the server, you log on to the target system, and run the @command{gdbserver}
42463 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42464 your program, and (c) its arguments. The general syntax is:
42467 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42470 For example, using a serial port, you might say:
42474 @c @file would wrap it as F</dev/com1>.
42475 target> gdbserver /dev/com1 emacs foo.txt
42478 target> gdbserver @file{/dev/com1} emacs foo.txt
42482 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42483 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42484 waits patiently for the host @value{GDBN} to communicate with it.
42486 To use a TCP connection, you could say:
42489 target> gdbserver host:2345 emacs foo.txt
42492 This says pretty much the same thing as the last example, except that we are
42493 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42494 that we are expecting to see a TCP connection from @code{host} to local TCP port
42495 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42496 want for the port number as long as it does not conflict with any existing TCP
42497 ports on the target system. This same port number must be used in the host
42498 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42499 you chose a port number that conflicts with another service, @command{gdbserver} will
42500 print an error message and exit.
42502 @command{gdbserver} can also attach to running programs.
42503 This is accomplished via the @option{--attach} argument. The syntax is:
42506 target> gdbserver --attach @var{comm} @var{pid}
42509 @var{pid} is the process ID of a currently running process. It isn't
42510 necessary to point @command{gdbserver} at a binary for the running process.
42512 To start @code{gdbserver} without supplying an initial command to run
42513 or process ID to attach, use the @option{--multi} command line option.
42514 In such case you should connect using @kbd{target extended-remote} to start
42515 the program you want to debug.
42518 target> gdbserver --multi @var{comm}
42522 @subheading Usage (host side)
42528 You need an unstripped copy of the target program on your host system, since
42529 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42530 would, with the target program as the first argument. (You may need to use the
42531 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42532 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42533 new command you need to know about is @code{target remote}
42534 (or @code{target extended-remote}). Its argument is either
42535 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42536 descriptor. For example:
42540 @c @file would wrap it as F</dev/ttyb>.
42541 (gdb) target remote /dev/ttyb
42544 (gdb) target remote @file{/dev/ttyb}
42549 communicates with the server via serial line @file{/dev/ttyb}, and:
42552 (gdb) target remote the-target:2345
42556 communicates via a TCP connection to port 2345 on host `the-target', where
42557 you previously started up @command{gdbserver} with the same port number. Note that for
42558 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42559 command, otherwise you may get an error that looks something like
42560 `Connection refused'.
42562 @command{gdbserver} can also debug multiple inferiors at once,
42565 the @value{GDBN} manual in node @code{Inferiors and Programs}
42566 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42569 @ref{Inferiors and Programs}.
42571 In such case use the @code{extended-remote} @value{GDBN} command variant:
42574 (gdb) target extended-remote the-target:2345
42577 The @command{gdbserver} option @option{--multi} may or may not be used in such
42581 @c man begin OPTIONS gdbserver
42582 There are three different modes for invoking @command{gdbserver}:
42587 Debug a specific program specified by its program name:
42590 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42593 The @var{comm} parameter specifies how should the server communicate
42594 with @value{GDBN}; it is either a device name (to use a serial line),
42595 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42596 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42597 debug in @var{prog}. Any remaining arguments will be passed to the
42598 program verbatim. When the program exits, @value{GDBN} will close the
42599 connection, and @code{gdbserver} will exit.
42602 Debug a specific program by specifying the process ID of a running
42606 gdbserver --attach @var{comm} @var{pid}
42609 The @var{comm} parameter is as described above. Supply the process ID
42610 of a running program in @var{pid}; @value{GDBN} will do everything
42611 else. Like with the previous mode, when the process @var{pid} exits,
42612 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42615 Multi-process mode -- debug more than one program/process:
42618 gdbserver --multi @var{comm}
42621 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42622 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42623 close the connection when a process being debugged exits, so you can
42624 debug several processes in the same session.
42627 In each of the modes you may specify these options:
42632 List all options, with brief explanations.
42635 This option causes @command{gdbserver} to print its version number and exit.
42638 @command{gdbserver} will attach to a running program. The syntax is:
42641 target> gdbserver --attach @var{comm} @var{pid}
42644 @var{pid} is the process ID of a currently running process. It isn't
42645 necessary to point @command{gdbserver} at a binary for the running process.
42648 To start @code{gdbserver} without supplying an initial command to run
42649 or process ID to attach, use this command line option.
42650 Then you can connect using @kbd{target extended-remote} and start
42651 the program you want to debug. The syntax is:
42654 target> gdbserver --multi @var{comm}
42658 Instruct @code{gdbserver} to display extra status information about the debugging
42660 This option is intended for @code{gdbserver} development and for bug reports to
42663 @item --remote-debug
42664 Instruct @code{gdbserver} to display remote protocol debug output.
42665 This option is intended for @code{gdbserver} development and for bug reports to
42668 @item --debug-format=option1@r{[},option2,...@r{]}
42669 Instruct @code{gdbserver} to include extra information in each line
42670 of debugging output.
42671 @xref{Other Command-Line Arguments for gdbserver}.
42674 Specify a wrapper to launch programs
42675 for debugging. The option should be followed by the name of the
42676 wrapper, then any command-line arguments to pass to the wrapper, then
42677 @kbd{--} indicating the end of the wrapper arguments.
42680 By default, @command{gdbserver} keeps the listening TCP port open, so that
42681 additional connections are possible. However, if you start @code{gdbserver}
42682 with the @option{--once} option, it will stop listening for any further
42683 connection attempts after connecting to the first @value{GDBN} session.
42685 @c --disable-packet is not documented for users.
42687 @c --disable-randomization and --no-disable-randomization are superseded by
42688 @c QDisableRandomization.
42693 @c man begin SEEALSO gdbserver
42695 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42696 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42697 documentation are properly installed at your site, the command
42703 should give you access to the complete manual.
42705 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42706 Richard M. Stallman and Roland H. Pesch, July 1991.
42713 @c man title gcore Generate a core file of a running program
42716 @c man begin SYNOPSIS gcore
42717 gcore [-o @var{filename}] @var{pid}
42721 @c man begin DESCRIPTION gcore
42722 Generate a core dump of a running program with process ID @var{pid}.
42723 Produced file is equivalent to a kernel produced core file as if the process
42724 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42725 limit). Unlike after a crash, after @command{gcore} the program remains
42726 running without any change.
42729 @c man begin OPTIONS gcore
42731 @item -o @var{filename}
42732 The optional argument
42733 @var{filename} specifies the file name where to put the core dump.
42734 If not specified, the file name defaults to @file{core.@var{pid}},
42735 where @var{pid} is the running program process ID.
42739 @c man begin SEEALSO gcore
42741 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42742 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42743 documentation are properly installed at your site, the command
42750 should give you access to the complete manual.
42752 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42753 Richard M. Stallman and Roland H. Pesch, July 1991.
42760 @c man title gdbinit GDB initialization scripts
42763 @c man begin SYNOPSIS gdbinit
42764 @ifset SYSTEM_GDBINIT
42765 @value{SYSTEM_GDBINIT}
42774 @c man begin DESCRIPTION gdbinit
42775 These files contain @value{GDBN} commands to automatically execute during
42776 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42779 the @value{GDBN} manual in node @code{Sequences}
42780 -- shell command @code{info -f gdb -n Sequences}.
42786 Please read more in
42788 the @value{GDBN} manual in node @code{Startup}
42789 -- shell command @code{info -f gdb -n Startup}.
42796 @ifset SYSTEM_GDBINIT
42797 @item @value{SYSTEM_GDBINIT}
42799 @ifclear SYSTEM_GDBINIT
42800 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42802 System-wide initialization file. It is executed unless user specified
42803 @value{GDBN} option @code{-nx} or @code{-n}.
42806 the @value{GDBN} manual in node @code{System-wide configuration}
42807 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42810 @ref{System-wide configuration}.
42814 User initialization file. It is executed unless user specified
42815 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42818 Initialization file for current directory. It may need to be enabled with
42819 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42822 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42823 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42826 @ref{Init File in the Current Directory}.
42831 @c man begin SEEALSO gdbinit
42833 gdb(1), @code{info -f gdb -n Startup}
42835 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42836 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42837 documentation are properly installed at your site, the command
42843 should give you access to the complete manual.
42845 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42846 Richard M. Stallman and Roland H. Pesch, July 1991.
42852 @node GNU Free Documentation License
42853 @appendix GNU Free Documentation License
42856 @node Concept Index
42857 @unnumbered Concept Index
42861 @node Command and Variable Index
42862 @unnumbered Command, Variable, and Function Index
42867 % I think something like @@colophon should be in texinfo. In the
42869 \long\def\colophon{\hbox to0pt{}\vfill
42870 \centerline{The body of this manual is set in}
42871 \centerline{\fontname\tenrm,}
42872 \centerline{with headings in {\bf\fontname\tenbf}}
42873 \centerline{and examples in {\tt\fontname\tentt}.}
42874 \centerline{{\it\fontname\tenit\/},}
42875 \centerline{{\bf\fontname\tenbf}, and}
42876 \centerline{{\sl\fontname\tensl\/}}
42877 \centerline{are used for emphasis.}\vfill}
42879 % Blame: doc@@cygnus.com, 1991.