1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 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.
51 @c man begin COPYRIGHT
52 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.3 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being ``Free Software'' and ``Free Software Needs
58 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
59 and with the Back-Cover Texts as in (a) below.
61 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
62 this GNU Manual. Buying copies from GNU Press supports the FSF in
63 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2013 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Man Pages:: Manual pages
187 * Copying:: GNU General Public License says
188 how you can copy and share GDB
189 * GNU Free Documentation License:: The license for this documentation
190 * Concept Index:: Index of @value{GDBN} concepts
191 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
192 functions, and Python data types
200 @unnumbered Summary of @value{GDBN}
202 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
203 going on ``inside'' another program while it executes---or what another
204 program was doing at the moment it crashed.
206 @value{GDBN} can do four main kinds of things (plus other things in support of
207 these) to help you catch bugs in the act:
211 Start your program, specifying anything that might affect its behavior.
214 Make your program stop on specified conditions.
217 Examine what has happened, when your program has stopped.
220 Change things in your program, so you can experiment with correcting the
221 effects of one bug and go on to learn about another.
224 You can use @value{GDBN} to debug programs written in C and C@t{++}.
225 For more information, see @ref{Supported Languages,,Supported Languages}.
226 For more information, see @ref{C,,C and C++}.
228 Support for D is partial. For information on D, see
232 Support for Modula-2 is partial. For information on Modula-2, see
233 @ref{Modula-2,,Modula-2}.
235 Support for OpenCL C is partial. For information on OpenCL C, see
236 @ref{OpenCL C,,OpenCL C}.
239 Debugging Pascal programs which use sets, subranges, file variables, or
240 nested functions does not currently work. @value{GDBN} does not support
241 entering expressions, printing values, or similar features using Pascal
245 @value{GDBN} can be used to debug programs written in Fortran, although
246 it may be necessary to refer to some variables with a trailing
249 @value{GDBN} can be used to debug programs written in Objective-C,
250 using either the Apple/NeXT or the GNU Objective-C runtime.
253 * Free Software:: Freely redistributable software
254 * Free Documentation:: Free Software Needs Free Documentation
255 * Contributors:: Contributors to GDB
259 @unnumberedsec Free Software
261 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
262 General Public License
263 (GPL). The GPL gives you the freedom to copy or adapt a licensed
264 program---but every person getting a copy also gets with it the
265 freedom to modify that copy (which means that they must get access to
266 the source code), and the freedom to distribute further copies.
267 Typical software companies use copyrights to limit your freedoms; the
268 Free Software Foundation uses the GPL to preserve these freedoms.
270 Fundamentally, the General Public License is a license which says that
271 you have these freedoms and that you cannot take these freedoms away
274 @node Free Documentation
275 @unnumberedsec Free Software Needs Free Documentation
277 The biggest deficiency in the free software community today is not in
278 the software---it is the lack of good free documentation that we can
279 include with the free software. Many of our most important
280 programs do not come with free reference manuals and free introductory
281 texts. Documentation is an essential part of any software package;
282 when an important free software package does not come with a free
283 manual and a free tutorial, that is a major gap. We have many such
286 Consider Perl, for instance. The tutorial manuals that people
287 normally use are non-free. How did this come about? Because the
288 authors of those manuals published them with restrictive terms---no
289 copying, no modification, source files not available---which exclude
290 them from the free software world.
292 That wasn't the first time this sort of thing happened, and it was far
293 from the last. Many times we have heard a GNU user eagerly describe a
294 manual that he is writing, his intended contribution to the community,
295 only to learn that he had ruined everything by signing a publication
296 contract to make it non-free.
298 Free documentation, like free software, is a matter of freedom, not
299 price. The problem with the non-free manual is not that publishers
300 charge a price for printed copies---that in itself is fine. (The Free
301 Software Foundation sells printed copies of manuals, too.) The
302 problem is the restrictions on the use of the manual. Free manuals
303 are available in source code form, and give you permission to copy and
304 modify. Non-free manuals do not allow this.
306 The criteria of freedom for a free manual are roughly the same as for
307 free software. Redistribution (including the normal kinds of
308 commercial redistribution) must be permitted, so that the manual can
309 accompany every copy of the program, both on-line and on paper.
311 Permission for modification of the technical content is crucial too.
312 When people modify the software, adding or changing features, if they
313 are conscientious they will change the manual too---so they can
314 provide accurate and clear documentation for the modified program. A
315 manual that leaves you no choice but to write a new manual to document
316 a changed version of the program is not really available to our
319 Some kinds of limits on the way modification is handled are
320 acceptable. For example, requirements to preserve the original
321 author's copyright notice, the distribution terms, or the list of
322 authors, are ok. It is also no problem to require modified versions
323 to include notice that they were modified. Even entire sections that
324 may not be deleted or changed are acceptable, as long as they deal
325 with nontechnical topics (like this one). These kinds of restrictions
326 are acceptable because they don't obstruct the community's normal use
329 However, it must be possible to modify all the @emph{technical}
330 content of the manual, and then distribute the result in all the usual
331 media, through all the usual channels. Otherwise, the restrictions
332 obstruct the use of the manual, it is not free, and we need another
333 manual to replace it.
335 Please spread the word about this issue. Our community continues to
336 lose manuals to proprietary publishing. If we spread the word that
337 free software needs free reference manuals and free tutorials, perhaps
338 the next person who wants to contribute by writing documentation will
339 realize, before it is too late, that only free manuals contribute to
340 the free software community.
342 If you are writing documentation, please insist on publishing it under
343 the GNU Free Documentation License or another free documentation
344 license. Remember that this decision requires your approval---you
345 don't have to let the publisher decide. Some commercial publishers
346 will use a free license if you insist, but they will not propose the
347 option; it is up to you to raise the issue and say firmly that this is
348 what you want. If the publisher you are dealing with refuses, please
349 try other publishers. If you're not sure whether a proposed license
350 is free, write to @email{licensing@@gnu.org}.
352 You can encourage commercial publishers to sell more free, copylefted
353 manuals and tutorials by buying them, and particularly by buying
354 copies from the publishers that paid for their writing or for major
355 improvements. Meanwhile, try to avoid buying non-free documentation
356 at all. Check the distribution terms of a manual before you buy it,
357 and insist that whoever seeks your business must respect your freedom.
358 Check the history of the book, and try to reward the publishers that
359 have paid or pay the authors to work on it.
361 The Free Software Foundation maintains a list of free documentation
362 published by other publishers, at
363 @url{http://www.fsf.org/doc/other-free-books.html}.
366 @unnumberedsec Contributors to @value{GDBN}
368 Richard Stallman was the original author of @value{GDBN}, and of many
369 other @sc{gnu} programs. Many others have contributed to its
370 development. This section attempts to credit major contributors. One
371 of the virtues of free software is that everyone is free to contribute
372 to it; with regret, we cannot actually acknowledge everyone here. The
373 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
374 blow-by-blow account.
376 Changes much prior to version 2.0 are lost in the mists of time.
379 @emph{Plea:} Additions to this section are particularly welcome. If you
380 or your friends (or enemies, to be evenhanded) have been unfairly
381 omitted from this list, we would like to add your names!
384 So that they may not regard their many labors as thankless, we
385 particularly thank those who shepherded @value{GDBN} through major
387 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
388 Jim Blandy (release 4.18);
389 Jason Molenda (release 4.17);
390 Stan Shebs (release 4.14);
391 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
392 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
393 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
394 Jim Kingdon (releases 3.5, 3.4, and 3.3);
395 and Randy Smith (releases 3.2, 3.1, and 3.0).
397 Richard Stallman, assisted at various times by Peter TerMaat, Chris
398 Hanson, and Richard Mlynarik, handled releases through 2.8.
400 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
401 in @value{GDBN}, with significant additional contributions from Per
402 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
403 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
404 much general update work leading to release 3.0).
406 @value{GDBN} uses the BFD subroutine library to examine multiple
407 object-file formats; BFD was a joint project of David V.
408 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
410 David Johnson wrote the original COFF support; Pace Willison did
411 the original support for encapsulated COFF.
413 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
415 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
416 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
418 Jean-Daniel Fekete contributed Sun 386i support.
419 Chris Hanson improved the HP9000 support.
420 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
421 David Johnson contributed Encore Umax support.
422 Jyrki Kuoppala contributed Altos 3068 support.
423 Jeff Law contributed HP PA and SOM support.
424 Keith Packard contributed NS32K support.
425 Doug Rabson contributed Acorn Risc Machine support.
426 Bob Rusk contributed Harris Nighthawk CX-UX support.
427 Chris Smith contributed Convex support (and Fortran debugging).
428 Jonathan Stone contributed Pyramid support.
429 Michael Tiemann contributed SPARC support.
430 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
431 Pace Willison contributed Intel 386 support.
432 Jay Vosburgh contributed Symmetry support.
433 Marko Mlinar contributed OpenRISC 1000 support.
435 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
437 Rich Schaefer and Peter Schauer helped with support of SunOS shared
440 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
441 about several machine instruction sets.
443 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
444 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
445 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
446 and RDI targets, respectively.
448 Brian Fox is the author of the readline libraries providing
449 command-line editing and command history.
451 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
452 Modula-2 support, and contributed the Languages chapter of this manual.
454 Fred Fish wrote most of the support for Unix System Vr4.
455 He also enhanced the command-completion support to cover C@t{++} overloaded
458 Hitachi America (now Renesas America), Ltd. sponsored the support for
459 H8/300, H8/500, and Super-H processors.
461 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
463 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
466 Toshiba sponsored the support for the TX39 Mips processor.
468 Matsushita sponsored the support for the MN10200 and MN10300 processors.
470 Fujitsu sponsored the support for SPARClite and FR30 processors.
472 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
475 Michael Snyder added support for tracepoints.
477 Stu Grossman wrote gdbserver.
479 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
480 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
482 The following people at the Hewlett-Packard Company contributed
483 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
484 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
485 compiler, and the Text User Interface (nee Terminal User Interface):
486 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
487 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
488 provided HP-specific information in this manual.
490 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
491 Robert Hoehne made significant contributions to the DJGPP port.
493 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
494 development since 1991. Cygnus engineers who have worked on @value{GDBN}
495 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
496 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
497 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
498 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
499 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
500 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
501 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
502 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
503 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
504 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
505 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
506 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
507 Zuhn have made contributions both large and small.
509 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
510 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
512 Jim Blandy added support for preprocessor macros, while working for Red
515 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
516 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
517 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
519 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
520 with the migration of old architectures to this new framework.
522 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
523 unwinder framework, this consisting of a fresh new design featuring
524 frame IDs, independent frame sniffers, and the sentinel frame. Mark
525 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
526 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
527 trad unwinders. The architecture-specific changes, each involving a
528 complete rewrite of the architecture's frame code, were carried out by
529 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
530 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
531 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
532 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
535 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
536 Tensilica, Inc.@: contributed support for Xtensa processors. Others
537 who have worked on the Xtensa port of @value{GDBN} in the past include
538 Steve Tjiang, John Newlin, and Scott Foehner.
540 Michael Eager and staff of Xilinx, Inc., contributed support for the
541 Xilinx MicroBlaze architecture.
544 @chapter A Sample @value{GDBN} Session
546 You can use this manual at your leisure to read all about @value{GDBN}.
547 However, a handful of commands are enough to get started using the
548 debugger. This chapter illustrates those commands.
551 In this sample session, we emphasize user input like this: @b{input},
552 to make it easier to pick out from the surrounding output.
555 @c FIXME: this example may not be appropriate for some configs, where
556 @c FIXME...primary interest is in remote use.
558 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
559 processor) exhibits the following bug: sometimes, when we change its
560 quote strings from the default, the commands used to capture one macro
561 definition within another stop working. In the following short @code{m4}
562 session, we define a macro @code{foo} which expands to @code{0000}; we
563 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
564 same thing. However, when we change the open quote string to
565 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
566 procedure fails to define a new synonym @code{baz}:
575 @b{define(bar,defn(`foo'))}
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
584 m4: End of input: 0: fatal error: EOF in string
588 Let us use @value{GDBN} to try to see what is going on.
591 $ @b{@value{GDBP} m4}
592 @c FIXME: this falsifies the exact text played out, to permit smallbook
593 @c FIXME... format to come out better.
594 @value{GDBN} is free software and you are welcome to distribute copies
595 of it under certain conditions; type "show copying" to see
597 There is absolutely no warranty for @value{GDBN}; type "show warranty"
600 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
605 @value{GDBN} reads only enough symbol data to know where to find the
606 rest when needed; as a result, the first prompt comes up very quickly.
607 We now tell @value{GDBN} to use a narrower display width than usual, so
608 that examples fit in this manual.
611 (@value{GDBP}) @b{set width 70}
615 We need to see how the @code{m4} built-in @code{changequote} works.
616 Having looked at the source, we know the relevant subroutine is
617 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
618 @code{break} command.
621 (@value{GDBP}) @b{break m4_changequote}
622 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
626 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
627 control; as long as control does not reach the @code{m4_changequote}
628 subroutine, the program runs as usual:
631 (@value{GDBP}) @b{run}
632 Starting program: /work/Editorial/gdb/gnu/m4/m4
640 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
641 suspends execution of @code{m4}, displaying information about the
642 context where it stops.
645 @b{changequote(<QUOTE>,<UNQUOTE>)}
647 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
649 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
653 Now we use the command @code{n} (@code{next}) to advance execution to
654 the next line of the current function.
658 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
663 @code{set_quotes} looks like a promising subroutine. We can go into it
664 by using the command @code{s} (@code{step}) instead of @code{next}.
665 @code{step} goes to the next line to be executed in @emph{any}
666 subroutine, so it steps into @code{set_quotes}.
670 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
672 530 if (lquote != def_lquote)
676 The display that shows the subroutine where @code{m4} is now
677 suspended (and its arguments) is called a stack frame display. It
678 shows a summary of the stack. We can use the @code{backtrace}
679 command (which can also be spelled @code{bt}), to see where we are
680 in the stack as a whole: the @code{backtrace} command displays a
681 stack frame for each active subroutine.
684 (@value{GDBP}) @b{bt}
685 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
687 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
689 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
690 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
692 #4 0x79dc in expand_input () at macro.c:40
693 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
697 We step through a few more lines to see what happens. The first two
698 times, we can use @samp{s}; the next two times we use @code{n} to avoid
699 falling into the @code{xstrdup} subroutine.
703 0x3b5c 532 if (rquote != def_rquote)
705 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
706 def_lquote : xstrdup(lq);
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
715 The last line displayed looks a little odd; we can examine the variables
716 @code{lquote} and @code{rquote} to see if they are in fact the new left
717 and right quotes we specified. We use the command @code{p}
718 (@code{print}) to see their values.
721 (@value{GDBP}) @b{p lquote}
722 $1 = 0x35d40 "<QUOTE>"
723 (@value{GDBP}) @b{p rquote}
724 $2 = 0x35d50 "<UNQUOTE>"
728 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
729 To look at some context, we can display ten lines of source
730 surrounding the current line with the @code{l} (@code{list}) command.
736 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
738 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
741 538 len_lquote = strlen(rquote);
742 539 len_rquote = strlen(lquote);
749 Let us step past the two lines that set @code{len_lquote} and
750 @code{len_rquote}, and then examine the values of those variables.
754 539 len_rquote = strlen(lquote);
757 (@value{GDBP}) @b{p len_lquote}
759 (@value{GDBP}) @b{p len_rquote}
764 That certainly looks wrong, assuming @code{len_lquote} and
765 @code{len_rquote} are meant to be the lengths of @code{lquote} and
766 @code{rquote} respectively. We can set them to better values using
767 the @code{p} command, since it can print the value of
768 any expression---and that expression can include subroutine calls and
772 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
774 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
779 Is that enough to fix the problem of using the new quotes with the
780 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
781 executing with the @code{c} (@code{continue}) command, and then try the
782 example that caused trouble initially:
788 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
795 Success! The new quotes now work just as well as the default ones. The
796 problem seems to have been just the two typos defining the wrong
797 lengths. We allow @code{m4} exit by giving it an EOF as input:
801 Program exited normally.
805 The message @samp{Program exited normally.} is from @value{GDBN}; it
806 indicates @code{m4} has finished executing. We can end our @value{GDBN}
807 session with the @value{GDBN} @code{quit} command.
810 (@value{GDBP}) @b{quit}
814 @chapter Getting In and Out of @value{GDBN}
816 This chapter discusses how to start @value{GDBN}, and how to get out of it.
820 type @samp{@value{GDBP}} to start @value{GDBN}.
822 type @kbd{quit} or @kbd{Ctrl-d} to exit.
826 * Invoking GDB:: How to start @value{GDBN}
827 * Quitting GDB:: How to quit @value{GDBN}
828 * Shell Commands:: How to use shell commands inside @value{GDBN}
829 * Logging Output:: How to log @value{GDBN}'s output to a file
833 @section Invoking @value{GDBN}
835 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
836 @value{GDBN} reads commands from the terminal until you tell it to exit.
838 You can also run @code{@value{GDBP}} with a variety of arguments and options,
839 to specify more of your debugging environment at the outset.
841 The command-line options described here are designed
842 to cover a variety of situations; in some environments, some of these
843 options may effectively be unavailable.
845 The most usual way to start @value{GDBN} is with one argument,
846 specifying an executable program:
849 @value{GDBP} @var{program}
853 You can also start with both an executable program and a core file
857 @value{GDBP} @var{program} @var{core}
860 You can, instead, specify a process ID as a second argument, if you want
861 to debug a running process:
864 @value{GDBP} @var{program} 1234
868 would attach @value{GDBN} to process @code{1234} (unless you also have a file
869 named @file{1234}; @value{GDBN} does check for a core file first).
871 Taking advantage of the second command-line argument requires a fairly
872 complete operating system; when you use @value{GDBN} as a remote
873 debugger attached to a bare board, there may not be any notion of
874 ``process'', and there is often no way to get a core dump. @value{GDBN}
875 will warn you if it is unable to attach or to read core dumps.
877 You can optionally have @code{@value{GDBP}} pass any arguments after the
878 executable file to the inferior using @code{--args}. This option stops
881 @value{GDBP} --args gcc -O2 -c foo.c
883 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
884 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
886 You can run @code{@value{GDBP}} without printing the front material, which describes
887 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
894 You can further control how @value{GDBN} starts up by using command-line
895 options. @value{GDBN} itself can remind you of the options available.
905 to display all available options and briefly describe their use
906 (@samp{@value{GDBP} -h} is a shorter equivalent).
908 All options and command line arguments you give are processed
909 in sequential order. The order makes a difference when the
910 @samp{-x} option is used.
914 * File Options:: Choosing files
915 * Mode Options:: Choosing modes
916 * Startup:: What @value{GDBN} does during startup
920 @subsection Choosing Files
922 When @value{GDBN} starts, it reads any arguments other than options as
923 specifying an executable file and core file (or process ID). This is
924 the same as if the arguments were specified by the @samp{-se} and
925 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
926 first argument that does not have an associated option flag as
927 equivalent to the @samp{-se} option followed by that argument; and the
928 second argument that does not have an associated option flag, if any, as
929 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
930 If the second argument begins with a decimal digit, @value{GDBN} will
931 first attempt to attach to it as a process, and if that fails, attempt
932 to open it as a corefile. If you have a corefile whose name begins with
933 a digit, you can prevent @value{GDBN} from treating it as a pid by
934 prefixing it with @file{./}, e.g.@: @file{./12345}.
936 If @value{GDBN} has not been configured to included core file support,
937 such as for most embedded targets, then it will complain about a second
938 argument and ignore it.
940 Many options have both long and short forms; both are shown in the
941 following list. @value{GDBN} also recognizes the long forms if you truncate
942 them, so long as enough of the option is present to be unambiguous.
943 (If you prefer, you can flag option arguments with @samp{--} rather
944 than @samp{-}, though we illustrate the more usual convention.)
946 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
947 @c way, both those who look for -foo and --foo in the index, will find
951 @item -symbols @var{file}
953 @cindex @code{--symbols}
955 Read symbol table from file @var{file}.
957 @item -exec @var{file}
959 @cindex @code{--exec}
961 Use file @var{file} as the executable file to execute when appropriate,
962 and for examining pure data in conjunction with a core dump.
966 Read symbol table from file @var{file} and use it as the executable
969 @item -core @var{file}
971 @cindex @code{--core}
973 Use file @var{file} as a core dump to examine.
975 @item -pid @var{number}
976 @itemx -p @var{number}
979 Connect to process ID @var{number}, as with the @code{attach} command.
981 @item -command @var{file}
983 @cindex @code{--command}
985 Execute commands from file @var{file}. The contents of this file is
986 evaluated exactly as the @code{source} command would.
987 @xref{Command Files,, Command files}.
989 @item -eval-command @var{command}
990 @itemx -ex @var{command}
991 @cindex @code{--eval-command}
993 Execute a single @value{GDBN} command.
995 This option may be used multiple times to call multiple commands. It may
996 also be interleaved with @samp{-command} as required.
999 @value{GDBP} -ex 'target sim' -ex 'load' \
1000 -x setbreakpoints -ex 'run' a.out
1003 @item -init-command @var{file}
1004 @itemx -ix @var{file}
1005 @cindex @code{--init-command}
1007 Execute commands from file @var{file} before loading the inferior (but
1008 after loading gdbinit files).
1011 @item -init-eval-command @var{command}
1012 @itemx -iex @var{command}
1013 @cindex @code{--init-eval-command}
1015 Execute a single @value{GDBN} command before loading the inferior (but
1016 after loading gdbinit files).
1019 @item -directory @var{directory}
1020 @itemx -d @var{directory}
1021 @cindex @code{--directory}
1023 Add @var{directory} to the path to search for source and script files.
1027 @cindex @code{--readnow}
1029 Read each symbol file's entire symbol table immediately, rather than
1030 the default, which is to read it incrementally as it is needed.
1031 This makes startup slower, but makes future operations faster.
1036 @subsection Choosing Modes
1038 You can run @value{GDBN} in various alternative modes---for example, in
1039 batch mode or quiet mode.
1047 Do not execute commands found in any initialization file.
1048 There are three init files, loaded in the following order:
1051 @item @file{system.gdbinit}
1052 This is the system-wide init file.
1053 Its location is specified with the @code{--with-system-gdbinit}
1054 configure option (@pxref{System-wide configuration}).
1055 It is loaded first when @value{GDBN} starts, before command line options
1056 have been processed.
1057 @item @file{~/.gdbinit}
1058 This is the init file in your home directory.
1059 It is loaded next, after @file{system.gdbinit}, and before
1060 command options have been processed.
1061 @item @file{./.gdbinit}
1062 This is the init file in the current directory.
1063 It is loaded last, after command line options other than @code{-x} and
1064 @code{-ex} have been processed. Command line options @code{-x} and
1065 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1068 For further documentation on startup processing, @xref{Startup}.
1069 For documentation on how to write command files,
1070 @xref{Command Files,,Command Files}.
1075 Do not execute commands found in @file{~/.gdbinit}, the init file
1076 in your home directory.
1082 @cindex @code{--quiet}
1083 @cindex @code{--silent}
1085 ``Quiet''. Do not print the introductory and copyright messages. These
1086 messages are also suppressed in batch mode.
1089 @cindex @code{--batch}
1090 Run in batch mode. Exit with status @code{0} after processing all the
1091 command files specified with @samp{-x} (and all commands from
1092 initialization files, if not inhibited with @samp{-n}). Exit with
1093 nonzero status if an error occurs in executing the @value{GDBN} commands
1094 in the command files. Batch mode also disables pagination, sets unlimited
1095 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1096 off} were in effect (@pxref{Messages/Warnings}).
1098 Batch mode may be useful for running @value{GDBN} as a filter, for
1099 example to download and run a program on another computer; in order to
1100 make this more useful, the message
1103 Program exited normally.
1107 (which is ordinarily issued whenever a program running under
1108 @value{GDBN} control terminates) is not issued when running in batch
1112 @cindex @code{--batch-silent}
1113 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1114 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1115 unaffected). This is much quieter than @samp{-silent} and would be useless
1116 for an interactive session.
1118 This is particularly useful when using targets that give @samp{Loading section}
1119 messages, for example.
1121 Note that targets that give their output via @value{GDBN}, as opposed to
1122 writing directly to @code{stdout}, will also be made silent.
1124 @item -return-child-result
1125 @cindex @code{--return-child-result}
1126 The return code from @value{GDBN} will be the return code from the child
1127 process (the process being debugged), with the following exceptions:
1131 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1132 internal error. In this case the exit code is the same as it would have been
1133 without @samp{-return-child-result}.
1135 The user quits with an explicit value. E.g., @samp{quit 1}.
1137 The child process never runs, or is not allowed to terminate, in which case
1138 the exit code will be -1.
1141 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1142 when @value{GDBN} is being used as a remote program loader or simulator
1147 @cindex @code{--nowindows}
1149 ``No windows''. If @value{GDBN} comes with a graphical user interface
1150 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1151 interface. If no GUI is available, this option has no effect.
1155 @cindex @code{--windows}
1157 If @value{GDBN} includes a GUI, then this option requires it to be
1160 @item -cd @var{directory}
1162 Run @value{GDBN} using @var{directory} as its working directory,
1163 instead of the current directory.
1165 @item -data-directory @var{directory}
1166 @cindex @code{--data-directory}
1167 Run @value{GDBN} using @var{directory} as its data directory.
1168 The data directory is where @value{GDBN} searches for its
1169 auxiliary files. @xref{Data Files}.
1173 @cindex @code{--fullname}
1175 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1176 subprocess. It tells @value{GDBN} to output the full file name and line
1177 number in a standard, recognizable fashion each time a stack frame is
1178 displayed (which includes each time your program stops). This
1179 recognizable format looks like two @samp{\032} characters, followed by
1180 the file name, line number and character position separated by colons,
1181 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1182 @samp{\032} characters as a signal to display the source code for the
1185 @item -annotate @var{level}
1186 @cindex @code{--annotate}
1187 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1188 effect is identical to using @samp{set annotate @var{level}}
1189 (@pxref{Annotations}). The annotation @var{level} controls how much
1190 information @value{GDBN} prints together with its prompt, values of
1191 expressions, source lines, and other types of output. Level 0 is the
1192 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1193 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1194 that control @value{GDBN}, and level 2 has been deprecated.
1196 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1200 @cindex @code{--args}
1201 Change interpretation of command line so that arguments following the
1202 executable file are passed as command line arguments to the inferior.
1203 This option stops option processing.
1205 @item -baud @var{bps}
1207 @cindex @code{--baud}
1209 Set the line speed (baud rate or bits per second) of any serial
1210 interface used by @value{GDBN} for remote debugging.
1212 @item -l @var{timeout}
1214 Set the timeout (in seconds) of any communication used by @value{GDBN}
1215 for remote debugging.
1217 @item -tty @var{device}
1218 @itemx -t @var{device}
1219 @cindex @code{--tty}
1221 Run using @var{device} for your program's standard input and output.
1222 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1224 @c resolve the situation of these eventually
1226 @cindex @code{--tui}
1227 Activate the @dfn{Text User Interface} when starting. The Text User
1228 Interface manages several text windows on the terminal, showing
1229 source, assembly, registers and @value{GDBN} command outputs
1230 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1231 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1232 Using @value{GDBN} under @sc{gnu} Emacs}).
1235 @c @cindex @code{--xdb}
1236 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1237 @c For information, see the file @file{xdb_trans.html}, which is usually
1238 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1241 @item -interpreter @var{interp}
1242 @cindex @code{--interpreter}
1243 Use the interpreter @var{interp} for interface with the controlling
1244 program or device. This option is meant to be set by programs which
1245 communicate with @value{GDBN} using it as a back end.
1246 @xref{Interpreters, , Command Interpreters}.
1248 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1249 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1250 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1251 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1252 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1253 @sc{gdb/mi} interfaces are no longer supported.
1256 @cindex @code{--write}
1257 Open the executable and core files for both reading and writing. This
1258 is equivalent to the @samp{set write on} command inside @value{GDBN}
1262 @cindex @code{--statistics}
1263 This option causes @value{GDBN} to print statistics about time and
1264 memory usage after it completes each command and returns to the prompt.
1267 @cindex @code{--version}
1268 This option causes @value{GDBN} to print its version number and
1269 no-warranty blurb, and exit.
1271 @item -configuration
1272 @cindex @code{--configuration}
1273 This option causes @value{GDBN} to print details about its build-time
1274 configuration parameters, and then exit. These details can be
1275 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are several miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1881 @kindex show configuration
1882 @item show configuration
1883 Display detailed information about the way @value{GDBN} was configured
1884 when it was built. This displays the optional arguments passed to the
1885 @file{configure} script and also configuration parameters detected
1886 automatically by @command{configure}. When reporting a @value{GDBN}
1887 bug (@pxref{GDB Bugs}), it is important to include this information in
1893 @chapter Running Programs Under @value{GDBN}
1895 When you run a program under @value{GDBN}, you must first generate
1896 debugging information when you compile it.
1898 You may start @value{GDBN} with its arguments, if any, in an environment
1899 of your choice. If you are doing native debugging, you may redirect
1900 your program's input and output, debug an already running process, or
1901 kill a child process.
1904 * Compilation:: Compiling for debugging
1905 * Starting:: Starting your program
1906 * Arguments:: Your program's arguments
1907 * Environment:: Your program's environment
1909 * Working Directory:: Your program's working directory
1910 * Input/Output:: Your program's input and output
1911 * Attach:: Debugging an already-running process
1912 * Kill Process:: Killing the child process
1914 * Inferiors and Programs:: Debugging multiple inferiors and programs
1915 * Threads:: Debugging programs with multiple threads
1916 * Forks:: Debugging forks
1917 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1921 @section Compiling for Debugging
1923 In order to debug a program effectively, you need to generate
1924 debugging information when you compile it. This debugging information
1925 is stored in the object file; it describes the data type of each
1926 variable or function and the correspondence between source line numbers
1927 and addresses in the executable code.
1929 To request debugging information, specify the @samp{-g} option when you run
1932 Programs that are to be shipped to your customers are compiled with
1933 optimizations, using the @samp{-O} compiler option. However, some
1934 compilers are unable to handle the @samp{-g} and @samp{-O} options
1935 together. Using those compilers, you cannot generate optimized
1936 executables containing debugging information.
1938 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1939 without @samp{-O}, making it possible to debug optimized code. We
1940 recommend that you @emph{always} use @samp{-g} whenever you compile a
1941 program. You may think your program is correct, but there is no sense
1942 in pushing your luck. For more information, see @ref{Optimized Code}.
1944 Older versions of the @sc{gnu} C compiler permitted a variant option
1945 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1946 format; if your @sc{gnu} C compiler has this option, do not use it.
1948 @value{GDBN} knows about preprocessor macros and can show you their
1949 expansion (@pxref{Macros}). Most compilers do not include information
1950 about preprocessor macros in the debugging information if you specify
1951 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1952 the @sc{gnu} C compiler, provides macro information if you are using
1953 the DWARF debugging format, and specify the option @option{-g3}.
1955 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1956 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1957 information on @value{NGCC} options affecting debug information.
1959 You will have the best debugging experience if you use the latest
1960 version of the DWARF debugging format that your compiler supports.
1961 DWARF is currently the most expressive and best supported debugging
1962 format in @value{GDBN}.
1966 @section Starting your Program
1972 @kindex r @r{(@code{run})}
1975 Use the @code{run} command to start your program under @value{GDBN}.
1976 You must first specify the program name (except on VxWorks) with an
1977 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1978 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1979 (@pxref{Files, ,Commands to Specify Files}).
1983 If you are running your program in an execution environment that
1984 supports processes, @code{run} creates an inferior process and makes
1985 that process run your program. In some environments without processes,
1986 @code{run} jumps to the start of your program. Other targets,
1987 like @samp{remote}, are always running. If you get an error
1988 message like this one:
1991 The "remote" target does not support "run".
1992 Try "help target" or "continue".
1996 then use @code{continue} to run your program. You may need @code{load}
1997 first (@pxref{load}).
1999 The execution of a program is affected by certain information it
2000 receives from its superior. @value{GDBN} provides ways to specify this
2001 information, which you must do @emph{before} starting your program. (You
2002 can change it after starting your program, but such changes only affect
2003 your program the next time you start it.) This information may be
2004 divided into four categories:
2007 @item The @emph{arguments.}
2008 Specify the arguments to give your program as the arguments of the
2009 @code{run} command. If a shell is available on your target, the shell
2010 is used to pass the arguments, so that you may use normal conventions
2011 (such as wildcard expansion or variable substitution) in describing
2013 In Unix systems, you can control which shell is used with the
2014 @code{SHELL} environment variable.
2015 @xref{Arguments, ,Your Program's Arguments}.
2017 @item The @emph{environment.}
2018 Your program normally inherits its environment from @value{GDBN}, but you can
2019 use the @value{GDBN} commands @code{set environment} and @code{unset
2020 environment} to change parts of the environment that affect
2021 your program. @xref{Environment, ,Your Program's Environment}.
2023 @item The @emph{working directory.}
2024 Your program inherits its working directory from @value{GDBN}. You can set
2025 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2026 @xref{Working Directory, ,Your Program's Working Directory}.
2028 @item The @emph{standard input and output.}
2029 Your program normally uses the same device for standard input and
2030 standard output as @value{GDBN} is using. You can redirect input and output
2031 in the @code{run} command line, or you can use the @code{tty} command to
2032 set a different device for your program.
2033 @xref{Input/Output, ,Your Program's Input and Output}.
2036 @emph{Warning:} While input and output redirection work, you cannot use
2037 pipes to pass the output of the program you are debugging to another
2038 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2042 When you issue the @code{run} command, your program begins to execute
2043 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2044 of how to arrange for your program to stop. Once your program has
2045 stopped, you may call functions in your program, using the @code{print}
2046 or @code{call} commands. @xref{Data, ,Examining Data}.
2048 If the modification time of your symbol file has changed since the last
2049 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2050 table, and reads it again. When it does this, @value{GDBN} tries to retain
2051 your current breakpoints.
2056 @cindex run to main procedure
2057 The name of the main procedure can vary from language to language.
2058 With C or C@t{++}, the main procedure name is always @code{main}, but
2059 other languages such as Ada do not require a specific name for their
2060 main procedure. The debugger provides a convenient way to start the
2061 execution of the program and to stop at the beginning of the main
2062 procedure, depending on the language used.
2064 The @samp{start} command does the equivalent of setting a temporary
2065 breakpoint at the beginning of the main procedure and then invoking
2066 the @samp{run} command.
2068 @cindex elaboration phase
2069 Some programs contain an @dfn{elaboration} phase where some startup code is
2070 executed before the main procedure is called. This depends on the
2071 languages used to write your program. In C@t{++}, for instance,
2072 constructors for static and global objects are executed before
2073 @code{main} is called. It is therefore possible that the debugger stops
2074 before reaching the main procedure. However, the temporary breakpoint
2075 will remain to halt execution.
2077 Specify the arguments to give to your program as arguments to the
2078 @samp{start} command. These arguments will be given verbatim to the
2079 underlying @samp{run} command. Note that the same arguments will be
2080 reused if no argument is provided during subsequent calls to
2081 @samp{start} or @samp{run}.
2083 It is sometimes necessary to debug the program during elaboration. In
2084 these cases, using the @code{start} command would stop the execution of
2085 your program too late, as the program would have already completed the
2086 elaboration phase. Under these circumstances, insert breakpoints in your
2087 elaboration code before running your program.
2089 @kindex set exec-wrapper
2090 @item set exec-wrapper @var{wrapper}
2091 @itemx show exec-wrapper
2092 @itemx unset exec-wrapper
2093 When @samp{exec-wrapper} is set, the specified wrapper is used to
2094 launch programs for debugging. @value{GDBN} starts your program
2095 with a shell command of the form @kbd{exec @var{wrapper}
2096 @var{program}}. Quoting is added to @var{program} and its
2097 arguments, but not to @var{wrapper}, so you should add quotes if
2098 appropriate for your shell. The wrapper runs until it executes
2099 your program, and then @value{GDBN} takes control.
2101 You can use any program that eventually calls @code{execve} with
2102 its arguments as a wrapper. Several standard Unix utilities do
2103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2104 with @code{exec "$@@"} will also work.
2106 For example, you can use @code{env} to pass an environment variable to
2107 the debugged program, without setting the variable in your shell's
2111 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2115 This command is available when debugging locally on most targets, excluding
2116 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2118 @kindex set disable-randomization
2119 @item set disable-randomization
2120 @itemx set disable-randomization on
2121 This option (enabled by default in @value{GDBN}) will turn off the native
2122 randomization of the virtual address space of the started program. This option
2123 is useful for multiple debugging sessions to make the execution better
2124 reproducible and memory addresses reusable across debugging sessions.
2126 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2127 On @sc{gnu}/Linux you can get the same behavior using
2130 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2133 @item set disable-randomization off
2134 Leave the behavior of the started executable unchanged. Some bugs rear their
2135 ugly heads only when the program is loaded at certain addresses. If your bug
2136 disappears when you run the program under @value{GDBN}, that might be because
2137 @value{GDBN} by default disables the address randomization on platforms, such
2138 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2139 disable-randomization off} to try to reproduce such elusive bugs.
2141 On targets where it is available, virtual address space randomization
2142 protects the programs against certain kinds of security attacks. In these
2143 cases the attacker needs to know the exact location of a concrete executable
2144 code. Randomizing its location makes it impossible to inject jumps misusing
2145 a code at its expected addresses.
2147 Prelinking shared libraries provides a startup performance advantage but it
2148 makes addresses in these libraries predictable for privileged processes by
2149 having just unprivileged access at the target system. Reading the shared
2150 library binary gives enough information for assembling the malicious code
2151 misusing it. Still even a prelinked shared library can get loaded at a new
2152 random address just requiring the regular relocation process during the
2153 startup. Shared libraries not already prelinked are always loaded at
2154 a randomly chosen address.
2156 Position independent executables (PIE) contain position independent code
2157 similar to the shared libraries and therefore such executables get loaded at
2158 a randomly chosen address upon startup. PIE executables always load even
2159 already prelinked shared libraries at a random address. You can build such
2160 executable using @command{gcc -fPIE -pie}.
2162 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2163 (as long as the randomization is enabled).
2165 @item show disable-randomization
2166 Show the current setting of the explicit disable of the native randomization of
2167 the virtual address space of the started program.
2172 @section Your Program's Arguments
2174 @cindex arguments (to your program)
2175 The arguments to your program can be specified by the arguments of the
2177 They are passed to a shell, which expands wildcard characters and
2178 performs redirection of I/O, and thence to your program. Your
2179 @code{SHELL} environment variable (if it exists) specifies what shell
2180 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2181 the default shell (@file{/bin/sh} on Unix).
2183 On non-Unix systems, the program is usually invoked directly by
2184 @value{GDBN}, which emulates I/O redirection via the appropriate system
2185 calls, and the wildcard characters are expanded by the startup code of
2186 the program, not by the shell.
2188 @code{run} with no arguments uses the same arguments used by the previous
2189 @code{run}, or those set by the @code{set args} command.
2194 Specify the arguments to be used the next time your program is run. If
2195 @code{set args} has no arguments, @code{run} executes your program
2196 with no arguments. Once you have run your program with arguments,
2197 using @code{set args} before the next @code{run} is the only way to run
2198 it again without arguments.
2202 Show the arguments to give your program when it is started.
2206 @section Your Program's Environment
2208 @cindex environment (of your program)
2209 The @dfn{environment} consists of a set of environment variables and
2210 their values. Environment variables conventionally record such things as
2211 your user name, your home directory, your terminal type, and your search
2212 path for programs to run. Usually you set up environment variables with
2213 the shell and they are inherited by all the other programs you run. When
2214 debugging, it can be useful to try running your program with a modified
2215 environment without having to start @value{GDBN} over again.
2219 @item path @var{directory}
2220 Add @var{directory} to the front of the @code{PATH} environment variable
2221 (the search path for executables) that will be passed to your program.
2222 The value of @code{PATH} used by @value{GDBN} does not change.
2223 You may specify several directory names, separated by whitespace or by a
2224 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2225 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2226 is moved to the front, so it is searched sooner.
2228 You can use the string @samp{$cwd} to refer to whatever is the current
2229 working directory at the time @value{GDBN} searches the path. If you
2230 use @samp{.} instead, it refers to the directory where you executed the
2231 @code{path} command. @value{GDBN} replaces @samp{.} in the
2232 @var{directory} argument (with the current path) before adding
2233 @var{directory} to the search path.
2234 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2235 @c document that, since repeating it would be a no-op.
2239 Display the list of search paths for executables (the @code{PATH}
2240 environment variable).
2242 @kindex show environment
2243 @item show environment @r{[}@var{varname}@r{]}
2244 Print the value of environment variable @var{varname} to be given to
2245 your program when it starts. If you do not supply @var{varname},
2246 print the names and values of all environment variables to be given to
2247 your program. You can abbreviate @code{environment} as @code{env}.
2249 @kindex set environment
2250 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2251 Set environment variable @var{varname} to @var{value}. The value
2252 changes for your program only, not for @value{GDBN} itself. @var{value} may
2253 be any string; the values of environment variables are just strings, and
2254 any interpretation is supplied by your program itself. The @var{value}
2255 parameter is optional; if it is eliminated, the variable is set to a
2257 @c "any string" here does not include leading, trailing
2258 @c blanks. Gnu asks: does anyone care?
2260 For example, this command:
2267 tells the debugged program, when subsequently run, that its user is named
2268 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2269 are not actually required.)
2271 @kindex unset environment
2272 @item unset environment @var{varname}
2273 Remove variable @var{varname} from the environment to be passed to your
2274 program. This is different from @samp{set env @var{varname} =};
2275 @code{unset environment} removes the variable from the environment,
2276 rather than assigning it an empty value.
2279 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2281 by your @code{SHELL} environment variable if it exists (or
2282 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2283 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2284 @file{.bashrc} for BASH---any variables you set in that file affect
2285 your program. You may wish to move setting of environment variables to
2286 files that are only run when you sign on, such as @file{.login} or
2289 @node Working Directory
2290 @section Your Program's Working Directory
2292 @cindex working directory (of your program)
2293 Each time you start your program with @code{run}, it inherits its
2294 working directory from the current working directory of @value{GDBN}.
2295 The @value{GDBN} working directory is initially whatever it inherited
2296 from its parent process (typically the shell), but you can specify a new
2297 working directory in @value{GDBN} with the @code{cd} command.
2299 The @value{GDBN} working directory also serves as a default for the commands
2300 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2305 @cindex change working directory
2306 @item cd @r{[}@var{directory}@r{]}
2307 Set the @value{GDBN} working directory to @var{directory}. If not
2308 given, @var{directory} uses @file{'~'}.
2312 Print the @value{GDBN} working directory.
2315 It is generally impossible to find the current working directory of
2316 the process being debugged (since a program can change its directory
2317 during its run). If you work on a system where @value{GDBN} is
2318 configured with the @file{/proc} support, you can use the @code{info
2319 proc} command (@pxref{SVR4 Process Information}) to find out the
2320 current working directory of the debuggee.
2323 @section Your Program's Input and Output
2328 By default, the program you run under @value{GDBN} does input and output to
2329 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2330 to its own terminal modes to interact with you, but it records the terminal
2331 modes your program was using and switches back to them when you continue
2332 running your program.
2335 @kindex info terminal
2337 Displays information recorded by @value{GDBN} about the terminal modes your
2341 You can redirect your program's input and/or output using shell
2342 redirection with the @code{run} command. For example,
2349 starts your program, diverting its output to the file @file{outfile}.
2352 @cindex controlling terminal
2353 Another way to specify where your program should do input and output is
2354 with the @code{tty} command. This command accepts a file name as
2355 argument, and causes this file to be the default for future @code{run}
2356 commands. It also resets the controlling terminal for the child
2357 process, for future @code{run} commands. For example,
2364 directs that processes started with subsequent @code{run} commands
2365 default to do input and output on the terminal @file{/dev/ttyb} and have
2366 that as their controlling terminal.
2368 An explicit redirection in @code{run} overrides the @code{tty} command's
2369 effect on the input/output device, but not its effect on the controlling
2372 When you use the @code{tty} command or redirect input in the @code{run}
2373 command, only the input @emph{for your program} is affected. The input
2374 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2375 for @code{set inferior-tty}.
2377 @cindex inferior tty
2378 @cindex set inferior controlling terminal
2379 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2380 display the name of the terminal that will be used for future runs of your
2384 @item set inferior-tty /dev/ttyb
2385 @kindex set inferior-tty
2386 Set the tty for the program being debugged to /dev/ttyb.
2388 @item show inferior-tty
2389 @kindex show inferior-tty
2390 Show the current tty for the program being debugged.
2394 @section Debugging an Already-running Process
2399 @item attach @var{process-id}
2400 This command attaches to a running process---one that was started
2401 outside @value{GDBN}. (@code{info files} shows your active
2402 targets.) The command takes as argument a process ID. The usual way to
2403 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2404 or with the @samp{jobs -l} shell command.
2406 @code{attach} does not repeat if you press @key{RET} a second time after
2407 executing the command.
2410 To use @code{attach}, your program must be running in an environment
2411 which supports processes; for example, @code{attach} does not work for
2412 programs on bare-board targets that lack an operating system. You must
2413 also have permission to send the process a signal.
2415 When you use @code{attach}, the debugger finds the program running in
2416 the process first by looking in the current working directory, then (if
2417 the program is not found) by using the source file search path
2418 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2419 the @code{file} command to load the program. @xref{Files, ,Commands to
2422 The first thing @value{GDBN} does after arranging to debug the specified
2423 process is to stop it. You can examine and modify an attached process
2424 with all the @value{GDBN} commands that are ordinarily available when
2425 you start processes with @code{run}. You can insert breakpoints; you
2426 can step and continue; you can modify storage. If you would rather the
2427 process continue running, you may use the @code{continue} command after
2428 attaching @value{GDBN} to the process.
2433 When you have finished debugging the attached process, you can use the
2434 @code{detach} command to release it from @value{GDBN} control. Detaching
2435 the process continues its execution. After the @code{detach} command,
2436 that process and @value{GDBN} become completely independent once more, and you
2437 are ready to @code{attach} another process or start one with @code{run}.
2438 @code{detach} does not repeat if you press @key{RET} again after
2439 executing the command.
2442 If you exit @value{GDBN} while you have an attached process, you detach
2443 that process. If you use the @code{run} command, you kill that process.
2444 By default, @value{GDBN} asks for confirmation if you try to do either of these
2445 things; you can control whether or not you need to confirm by using the
2446 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2450 @section Killing the Child Process
2455 Kill the child process in which your program is running under @value{GDBN}.
2458 This command is useful if you wish to debug a core dump instead of a
2459 running process. @value{GDBN} ignores any core dump file while your program
2462 On some operating systems, a program cannot be executed outside @value{GDBN}
2463 while you have breakpoints set on it inside @value{GDBN}. You can use the
2464 @code{kill} command in this situation to permit running your program
2465 outside the debugger.
2467 The @code{kill} command is also useful if you wish to recompile and
2468 relink your program, since on many systems it is impossible to modify an
2469 executable file while it is running in a process. In this case, when you
2470 next type @code{run}, @value{GDBN} notices that the file has changed, and
2471 reads the symbol table again (while trying to preserve your current
2472 breakpoint settings).
2474 @node Inferiors and Programs
2475 @section Debugging Multiple Inferiors and Programs
2477 @value{GDBN} lets you run and debug multiple programs in a single
2478 session. In addition, @value{GDBN} on some systems may let you run
2479 several programs simultaneously (otherwise you have to exit from one
2480 before starting another). In the most general case, you can have
2481 multiple threads of execution in each of multiple processes, launched
2482 from multiple executables.
2485 @value{GDBN} represents the state of each program execution with an
2486 object called an @dfn{inferior}. An inferior typically corresponds to
2487 a process, but is more general and applies also to targets that do not
2488 have processes. Inferiors may be created before a process runs, and
2489 may be retained after a process exits. Inferiors have unique
2490 identifiers that are different from process ids. Usually each
2491 inferior will also have its own distinct address space, although some
2492 embedded targets may have several inferiors running in different parts
2493 of a single address space. Each inferior may in turn have multiple
2494 threads running in it.
2496 To find out what inferiors exist at any moment, use @w{@code{info
2500 @kindex info inferiors
2501 @item info inferiors
2502 Print a list of all inferiors currently being managed by @value{GDBN}.
2504 @value{GDBN} displays for each inferior (in this order):
2508 the inferior number assigned by @value{GDBN}
2511 the target system's inferior identifier
2514 the name of the executable the inferior is running.
2519 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2520 indicates the current inferior.
2524 @c end table here to get a little more width for example
2527 (@value{GDBP}) info inferiors
2528 Num Description Executable
2529 2 process 2307 hello
2530 * 1 process 3401 goodbye
2533 To switch focus between inferiors, use the @code{inferior} command:
2536 @kindex inferior @var{infno}
2537 @item inferior @var{infno}
2538 Make inferior number @var{infno} the current inferior. The argument
2539 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2540 in the first field of the @samp{info inferiors} display.
2544 You can get multiple executables into a debugging session via the
2545 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2546 systems @value{GDBN} can add inferiors to the debug session
2547 automatically by following calls to @code{fork} and @code{exec}. To
2548 remove inferiors from the debugging session use the
2549 @w{@code{remove-inferiors}} command.
2552 @kindex add-inferior
2553 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2554 Adds @var{n} inferiors to be run using @var{executable} as the
2555 executable. @var{n} defaults to 1. If no executable is specified,
2556 the inferiors begins empty, with no program. You can still assign or
2557 change the program assigned to the inferior at any time by using the
2558 @code{file} command with the executable name as its argument.
2560 @kindex clone-inferior
2561 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2562 Adds @var{n} inferiors ready to execute the same program as inferior
2563 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2564 number of the current inferior. This is a convenient command when you
2565 want to run another instance of the inferior you are debugging.
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 * 1 process 29964 helloworld
2571 (@value{GDBP}) clone-inferior
2574 (@value{GDBP}) info inferiors
2575 Num Description Executable
2577 * 1 process 29964 helloworld
2580 You can now simply switch focus to inferior 2 and run it.
2582 @kindex remove-inferiors
2583 @item remove-inferiors @var{infno}@dots{}
2584 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2585 possible to remove an inferior that is running with this command. For
2586 those, use the @code{kill} or @code{detach} command first.
2590 To quit debugging one of the running inferiors that is not the current
2591 inferior, you can either detach from it by using the @w{@code{detach
2592 inferior}} command (allowing it to run independently), or kill it
2593 using the @w{@code{kill inferiors}} command:
2596 @kindex detach inferiors @var{infno}@dots{}
2597 @item detach inferior @var{infno}@dots{}
2598 Detach from the inferior or inferiors identified by @value{GDBN}
2599 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2600 still stays on the list of inferiors shown by @code{info inferiors},
2601 but its Description will show @samp{<null>}.
2603 @kindex kill inferiors @var{infno}@dots{}
2604 @item kill inferiors @var{infno}@dots{}
2605 Kill the inferior or inferiors identified by @value{GDBN} inferior
2606 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2607 stays on the list of inferiors shown by @code{info inferiors}, but its
2608 Description will show @samp{<null>}.
2611 After the successful completion of a command such as @code{detach},
2612 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2613 a normal process exit, the inferior is still valid and listed with
2614 @code{info inferiors}, ready to be restarted.
2617 To be notified when inferiors are started or exit under @value{GDBN}'s
2618 control use @w{@code{set print inferior-events}}:
2621 @kindex set print inferior-events
2622 @cindex print messages on inferior start and exit
2623 @item set print inferior-events
2624 @itemx set print inferior-events on
2625 @itemx set print inferior-events off
2626 The @code{set print inferior-events} command allows you to enable or
2627 disable printing of messages when @value{GDBN} notices that new
2628 inferiors have started or that inferiors have exited or have been
2629 detached. By default, these messages will not be printed.
2631 @kindex show print inferior-events
2632 @item show print inferior-events
2633 Show whether messages will be printed when @value{GDBN} detects that
2634 inferiors have started, exited or have been detached.
2637 Many commands will work the same with multiple programs as with a
2638 single program: e.g., @code{print myglobal} will simply display the
2639 value of @code{myglobal} in the current inferior.
2642 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2643 get more info about the relationship of inferiors, programs, address
2644 spaces in a debug session. You can do that with the @w{@code{maint
2645 info program-spaces}} command.
2648 @kindex maint info program-spaces
2649 @item maint info program-spaces
2650 Print a list of all program spaces currently being managed by
2653 @value{GDBN} displays for each program space (in this order):
2657 the program space number assigned by @value{GDBN}
2660 the name of the executable loaded into the program space, with e.g.,
2661 the @code{file} command.
2666 An asterisk @samp{*} preceding the @value{GDBN} program space number
2667 indicates the current program space.
2669 In addition, below each program space line, @value{GDBN} prints extra
2670 information that isn't suitable to display in tabular form. For
2671 example, the list of inferiors bound to the program space.
2674 (@value{GDBP}) maint info program-spaces
2677 Bound inferiors: ID 1 (process 21561)
2681 Here we can see that no inferior is running the program @code{hello},
2682 while @code{process 21561} is running the program @code{goodbye}. On
2683 some targets, it is possible that multiple inferiors are bound to the
2684 same program space. The most common example is that of debugging both
2685 the parent and child processes of a @code{vfork} call. For example,
2688 (@value{GDBP}) maint info program-spaces
2691 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2694 Here, both inferior 2 and inferior 1 are running in the same program
2695 space as a result of inferior 1 having executed a @code{vfork} call.
2699 @section Debugging Programs with Multiple Threads
2701 @cindex threads of execution
2702 @cindex multiple threads
2703 @cindex switching threads
2704 In some operating systems, such as HP-UX and Solaris, a single program
2705 may have more than one @dfn{thread} of execution. The precise semantics
2706 of threads differ from one operating system to another, but in general
2707 the threads of a single program are akin to multiple processes---except
2708 that they share one address space (that is, they can all examine and
2709 modify the same variables). On the other hand, each thread has its own
2710 registers and execution stack, and perhaps private memory.
2712 @value{GDBN} provides these facilities for debugging multi-thread
2716 @item automatic notification of new threads
2717 @item @samp{thread @var{threadno}}, a command to switch among threads
2718 @item @samp{info threads}, a command to inquire about existing threads
2719 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2720 a command to apply a command to a list of threads
2721 @item thread-specific breakpoints
2722 @item @samp{set print thread-events}, which controls printing of
2723 messages on thread start and exit.
2724 @item @samp{set libthread-db-search-path @var{path}}, which lets
2725 the user specify which @code{libthread_db} to use if the default choice
2726 isn't compatible with the program.
2730 @emph{Warning:} These facilities are not yet available on every
2731 @value{GDBN} configuration where the operating system supports threads.
2732 If your @value{GDBN} does not support threads, these commands have no
2733 effect. For example, a system without thread support shows no output
2734 from @samp{info threads}, and always rejects the @code{thread} command,
2738 (@value{GDBP}) info threads
2739 (@value{GDBP}) thread 1
2740 Thread ID 1 not known. Use the "info threads" command to
2741 see the IDs of currently known threads.
2743 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2744 @c doesn't support threads"?
2747 @cindex focus of debugging
2748 @cindex current thread
2749 The @value{GDBN} thread debugging facility allows you to observe all
2750 threads while your program runs---but whenever @value{GDBN} takes
2751 control, one thread in particular is always the focus of debugging.
2752 This thread is called the @dfn{current thread}. Debugging commands show
2753 program information from the perspective of the current thread.
2755 @cindex @code{New} @var{systag} message
2756 @cindex thread identifier (system)
2757 @c FIXME-implementors!! It would be more helpful if the [New...] message
2758 @c included GDB's numeric thread handle, so you could just go to that
2759 @c thread without first checking `info threads'.
2760 Whenever @value{GDBN} detects a new thread in your program, it displays
2761 the target system's identification for the thread with a message in the
2762 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2763 whose form varies depending on the particular system. For example, on
2764 @sc{gnu}/Linux, you might see
2767 [New Thread 0x41e02940 (LWP 25582)]
2771 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2772 the @var{systag} is simply something like @samp{process 368}, with no
2775 @c FIXME!! (1) Does the [New...] message appear even for the very first
2776 @c thread of a program, or does it only appear for the
2777 @c second---i.e.@: when it becomes obvious we have a multithread
2779 @c (2) *Is* there necessarily a first thread always? Or do some
2780 @c multithread systems permit starting a program with multiple
2781 @c threads ab initio?
2783 @cindex thread number
2784 @cindex thread identifier (GDB)
2785 For debugging purposes, @value{GDBN} associates its own thread
2786 number---always a single integer---with each thread in your program.
2789 @kindex info threads
2790 @item info threads @r{[}@var{id}@dots{}@r{]}
2791 Display a summary of all threads currently in your program. Optional
2792 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2793 means to print information only about the specified thread or threads.
2794 @value{GDBN} displays for each thread (in this order):
2798 the thread number assigned by @value{GDBN}
2801 the target system's thread identifier (@var{systag})
2804 the thread's name, if one is known. A thread can either be named by
2805 the user (see @code{thread name}, below), or, in some cases, by the
2809 the current stack frame summary for that thread
2813 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2814 indicates the current thread.
2818 @c end table here to get a little more width for example
2821 (@value{GDBP}) info threads
2823 3 process 35 thread 27 0x34e5 in sigpause ()
2824 2 process 35 thread 23 0x34e5 in sigpause ()
2825 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2829 On Solaris, you can display more information about user threads with a
2830 Solaris-specific command:
2833 @item maint info sol-threads
2834 @kindex maint info sol-threads
2835 @cindex thread info (Solaris)
2836 Display info on Solaris user threads.
2840 @kindex thread @var{threadno}
2841 @item thread @var{threadno}
2842 Make thread number @var{threadno} the current thread. The command
2843 argument @var{threadno} is the internal @value{GDBN} thread number, as
2844 shown in the first field of the @samp{info threads} display.
2845 @value{GDBN} responds by displaying the system identifier of the thread
2846 you selected, and its current stack frame summary:
2849 (@value{GDBP}) thread 2
2850 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2851 #0 some_function (ignore=0x0) at example.c:8
2852 8 printf ("hello\n");
2856 As with the @samp{[New @dots{}]} message, the form of the text after
2857 @samp{Switching to} depends on your system's conventions for identifying
2860 @vindex $_thread@r{, convenience variable}
2861 The debugger convenience variable @samp{$_thread} contains the number
2862 of the current thread. You may find this useful in writing breakpoint
2863 conditional expressions, command scripts, and so forth. See
2864 @xref{Convenience Vars,, Convenience Variables}, for general
2865 information on convenience variables.
2867 @kindex thread apply
2868 @cindex apply command to several threads
2869 @item thread apply [@var{threadno} | all] @var{command}
2870 The @code{thread apply} command allows you to apply the named
2871 @var{command} to one or more threads. Specify the numbers of the
2872 threads that you want affected with the command argument
2873 @var{threadno}. It can be a single thread number, one of the numbers
2874 shown in the first field of the @samp{info threads} display; or it
2875 could be a range of thread numbers, as in @code{2-4}. To apply a
2876 command to all threads, type @kbd{thread apply all @var{command}}.
2879 @cindex name a thread
2880 @item thread name [@var{name}]
2881 This command assigns a name to the current thread. If no argument is
2882 given, any existing user-specified name is removed. The thread name
2883 appears in the @samp{info threads} display.
2885 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2886 determine the name of the thread as given by the OS. On these
2887 systems, a name specified with @samp{thread name} will override the
2888 system-give name, and removing the user-specified name will cause
2889 @value{GDBN} to once again display the system-specified name.
2892 @cindex search for a thread
2893 @item thread find [@var{regexp}]
2894 Search for and display thread ids whose name or @var{systag}
2895 matches the supplied regular expression.
2897 As well as being the complement to the @samp{thread name} command,
2898 this command also allows you to identify a thread by its target
2899 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2903 (@value{GDBN}) thread find 26688
2904 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2905 (@value{GDBN}) info thread 4
2907 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2910 @kindex set print thread-events
2911 @cindex print messages on thread start and exit
2912 @item set print thread-events
2913 @itemx set print thread-events on
2914 @itemx set print thread-events off
2915 The @code{set print thread-events} command allows you to enable or
2916 disable printing of messages when @value{GDBN} notices that new threads have
2917 started or that threads have exited. By default, these messages will
2918 be printed if detection of these events is supported by the target.
2919 Note that these messages cannot be disabled on all targets.
2921 @kindex show print thread-events
2922 @item show print thread-events
2923 Show whether messages will be printed when @value{GDBN} detects that threads
2924 have started and exited.
2927 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2928 more information about how @value{GDBN} behaves when you stop and start
2929 programs with multiple threads.
2931 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2932 watchpoints in programs with multiple threads.
2934 @anchor{set libthread-db-search-path}
2936 @kindex set libthread-db-search-path
2937 @cindex search path for @code{libthread_db}
2938 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2939 If this variable is set, @var{path} is a colon-separated list of
2940 directories @value{GDBN} will use to search for @code{libthread_db}.
2941 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2942 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2943 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2946 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2947 @code{libthread_db} library to obtain information about threads in the
2948 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2949 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2950 specific thread debugging library loading is enabled
2951 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2953 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2954 refers to the default system directories that are
2955 normally searched for loading shared libraries. The @samp{$sdir} entry
2956 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2957 (@pxref{libthread_db.so.1 file}).
2959 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2960 refers to the directory from which @code{libpthread}
2961 was loaded in the inferior process.
2963 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2964 @value{GDBN} attempts to initialize it with the current inferior process.
2965 If this initialization fails (which could happen because of a version
2966 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2967 will unload @code{libthread_db}, and continue with the next directory.
2968 If none of @code{libthread_db} libraries initialize successfully,
2969 @value{GDBN} will issue a warning and thread debugging will be disabled.
2971 Setting @code{libthread-db-search-path} is currently implemented
2972 only on some platforms.
2974 @kindex show libthread-db-search-path
2975 @item show libthread-db-search-path
2976 Display current libthread_db search path.
2978 @kindex set debug libthread-db
2979 @kindex show debug libthread-db
2980 @cindex debugging @code{libthread_db}
2981 @item set debug libthread-db
2982 @itemx show debug libthread-db
2983 Turns on or off display of @code{libthread_db}-related events.
2984 Use @code{1} to enable, @code{0} to disable.
2988 @section Debugging Forks
2990 @cindex fork, debugging programs which call
2991 @cindex multiple processes
2992 @cindex processes, multiple
2993 On most systems, @value{GDBN} has no special support for debugging
2994 programs which create additional processes using the @code{fork}
2995 function. When a program forks, @value{GDBN} will continue to debug the
2996 parent process and the child process will run unimpeded. If you have
2997 set a breakpoint in any code which the child then executes, the child
2998 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2999 will cause it to terminate.
3001 However, if you want to debug the child process there is a workaround
3002 which isn't too painful. Put a call to @code{sleep} in the code which
3003 the child process executes after the fork. It may be useful to sleep
3004 only if a certain environment variable is set, or a certain file exists,
3005 so that the delay need not occur when you don't want to run @value{GDBN}
3006 on the child. While the child is sleeping, use the @code{ps} program to
3007 get its process ID. Then tell @value{GDBN} (a new invocation of
3008 @value{GDBN} if you are also debugging the parent process) to attach to
3009 the child process (@pxref{Attach}). From that point on you can debug
3010 the child process just like any other process which you attached to.
3012 On some systems, @value{GDBN} provides support for debugging programs that
3013 create additional processes using the @code{fork} or @code{vfork} functions.
3014 Currently, the only platforms with this feature are HP-UX (11.x and later
3015 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3017 By default, when a program forks, @value{GDBN} will continue to debug
3018 the parent process and the child process will run unimpeded.
3020 If you want to follow the child process instead of the parent process,
3021 use the command @w{@code{set follow-fork-mode}}.
3024 @kindex set follow-fork-mode
3025 @item set follow-fork-mode @var{mode}
3026 Set the debugger response to a program call of @code{fork} or
3027 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3028 process. The @var{mode} argument can be:
3032 The original process is debugged after a fork. The child process runs
3033 unimpeded. This is the default.
3036 The new process is debugged after a fork. The parent process runs
3041 @kindex show follow-fork-mode
3042 @item show follow-fork-mode
3043 Display the current debugger response to a @code{fork} or @code{vfork} call.
3046 @cindex debugging multiple processes
3047 On Linux, if you want to debug both the parent and child processes, use the
3048 command @w{@code{set detach-on-fork}}.
3051 @kindex set detach-on-fork
3052 @item set detach-on-fork @var{mode}
3053 Tells gdb whether to detach one of the processes after a fork, or
3054 retain debugger control over them both.
3058 The child process (or parent process, depending on the value of
3059 @code{follow-fork-mode}) will be detached and allowed to run
3060 independently. This is the default.
3063 Both processes will be held under the control of @value{GDBN}.
3064 One process (child or parent, depending on the value of
3065 @code{follow-fork-mode}) is debugged as usual, while the other
3070 @kindex show detach-on-fork
3071 @item show detach-on-fork
3072 Show whether detach-on-fork mode is on/off.
3075 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3076 will retain control of all forked processes (including nested forks).
3077 You can list the forked processes under the control of @value{GDBN} by
3078 using the @w{@code{info inferiors}} command, and switch from one fork
3079 to another by using the @code{inferior} command (@pxref{Inferiors and
3080 Programs, ,Debugging Multiple Inferiors and Programs}).
3082 To quit debugging one of the forked processes, you can either detach
3083 from it by using the @w{@code{detach inferiors}} command (allowing it
3084 to run independently), or kill it using the @w{@code{kill inferiors}}
3085 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3088 If you ask to debug a child process and a @code{vfork} is followed by an
3089 @code{exec}, @value{GDBN} executes the new target up to the first
3090 breakpoint in the new target. If you have a breakpoint set on
3091 @code{main} in your original program, the breakpoint will also be set on
3092 the child process's @code{main}.
3094 On some systems, when a child process is spawned by @code{vfork}, you
3095 cannot debug the child or parent until an @code{exec} call completes.
3097 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3098 call executes, the new target restarts. To restart the parent
3099 process, use the @code{file} command with the parent executable name
3100 as its argument. By default, after an @code{exec} call executes,
3101 @value{GDBN} discards the symbols of the previous executable image.
3102 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3106 @kindex set follow-exec-mode
3107 @item set follow-exec-mode @var{mode}
3109 Set debugger response to a program call of @code{exec}. An
3110 @code{exec} call replaces the program image of a process.
3112 @code{follow-exec-mode} can be:
3116 @value{GDBN} creates a new inferior and rebinds the process to this
3117 new inferior. The program the process was running before the
3118 @code{exec} call can be restarted afterwards by restarting the
3124 (@value{GDBP}) info inferiors
3126 Id Description Executable
3129 process 12020 is executing new program: prog2
3130 Program exited normally.
3131 (@value{GDBP}) info inferiors
3132 Id Description Executable
3138 @value{GDBN} keeps the process bound to the same inferior. The new
3139 executable image replaces the previous executable loaded in the
3140 inferior. Restarting the inferior after the @code{exec} call, with
3141 e.g., the @code{run} command, restarts the executable the process was
3142 running after the @code{exec} call. This is the default mode.
3147 (@value{GDBP}) info inferiors
3148 Id Description Executable
3151 process 12020 is executing new program: prog2
3152 Program exited normally.
3153 (@value{GDBP}) info inferiors
3154 Id Description Executable
3161 You can use the @code{catch} command to make @value{GDBN} stop whenever
3162 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3163 Catchpoints, ,Setting Catchpoints}.
3165 @node Checkpoint/Restart
3166 @section Setting a @emph{Bookmark} to Return to Later
3171 @cindex snapshot of a process
3172 @cindex rewind program state
3174 On certain operating systems@footnote{Currently, only
3175 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3176 program's state, called a @dfn{checkpoint}, and come back to it
3179 Returning to a checkpoint effectively undoes everything that has
3180 happened in the program since the @code{checkpoint} was saved. This
3181 includes changes in memory, registers, and even (within some limits)
3182 system state. Effectively, it is like going back in time to the
3183 moment when the checkpoint was saved.
3185 Thus, if you're stepping thru a program and you think you're
3186 getting close to the point where things go wrong, you can save
3187 a checkpoint. Then, if you accidentally go too far and miss
3188 the critical statement, instead of having to restart your program
3189 from the beginning, you can just go back to the checkpoint and
3190 start again from there.
3192 This can be especially useful if it takes a lot of time or
3193 steps to reach the point where you think the bug occurs.
3195 To use the @code{checkpoint}/@code{restart} method of debugging:
3200 Save a snapshot of the debugged program's current execution state.
3201 The @code{checkpoint} command takes no arguments, but each checkpoint
3202 is assigned a small integer id, similar to a breakpoint id.
3204 @kindex info checkpoints
3205 @item info checkpoints
3206 List the checkpoints that have been saved in the current debugging
3207 session. For each checkpoint, the following information will be
3214 @item Source line, or label
3217 @kindex restart @var{checkpoint-id}
3218 @item restart @var{checkpoint-id}
3219 Restore the program state that was saved as checkpoint number
3220 @var{checkpoint-id}. All program variables, registers, stack frames
3221 etc.@: will be returned to the values that they had when the checkpoint
3222 was saved. In essence, gdb will ``wind back the clock'' to the point
3223 in time when the checkpoint was saved.
3225 Note that breakpoints, @value{GDBN} variables, command history etc.
3226 are not affected by restoring a checkpoint. In general, a checkpoint
3227 only restores things that reside in the program being debugged, not in
3230 @kindex delete checkpoint @var{checkpoint-id}
3231 @item delete checkpoint @var{checkpoint-id}
3232 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3236 Returning to a previously saved checkpoint will restore the user state
3237 of the program being debugged, plus a significant subset of the system
3238 (OS) state, including file pointers. It won't ``un-write'' data from
3239 a file, but it will rewind the file pointer to the previous location,
3240 so that the previously written data can be overwritten. For files
3241 opened in read mode, the pointer will also be restored so that the
3242 previously read data can be read again.
3244 Of course, characters that have been sent to a printer (or other
3245 external device) cannot be ``snatched back'', and characters received
3246 from eg.@: a serial device can be removed from internal program buffers,
3247 but they cannot be ``pushed back'' into the serial pipeline, ready to
3248 be received again. Similarly, the actual contents of files that have
3249 been changed cannot be restored (at this time).
3251 However, within those constraints, you actually can ``rewind'' your
3252 program to a previously saved point in time, and begin debugging it
3253 again --- and you can change the course of events so as to debug a
3254 different execution path this time.
3256 @cindex checkpoints and process id
3257 Finally, there is one bit of internal program state that will be
3258 different when you return to a checkpoint --- the program's process
3259 id. Each checkpoint will have a unique process id (or @var{pid}),
3260 and each will be different from the program's original @var{pid}.
3261 If your program has saved a local copy of its process id, this could
3262 potentially pose a problem.
3264 @subsection A Non-obvious Benefit of Using Checkpoints
3266 On some systems such as @sc{gnu}/Linux, address space randomization
3267 is performed on new processes for security reasons. This makes it
3268 difficult or impossible to set a breakpoint, or watchpoint, on an
3269 absolute address if you have to restart the program, since the
3270 absolute location of a symbol will change from one execution to the
3273 A checkpoint, however, is an @emph{identical} copy of a process.
3274 Therefore if you create a checkpoint at (eg.@:) the start of main,
3275 and simply return to that checkpoint instead of restarting the
3276 process, you can avoid the effects of address randomization and
3277 your symbols will all stay in the same place.
3280 @chapter Stopping and Continuing
3282 The principal purposes of using a debugger are so that you can stop your
3283 program before it terminates; or so that, if your program runs into
3284 trouble, you can investigate and find out why.
3286 Inside @value{GDBN}, your program may stop for any of several reasons,
3287 such as a signal, a breakpoint, or reaching a new line after a
3288 @value{GDBN} command such as @code{step}. You may then examine and
3289 change variables, set new breakpoints or remove old ones, and then
3290 continue execution. Usually, the messages shown by @value{GDBN} provide
3291 ample explanation of the status of your program---but you can also
3292 explicitly request this information at any time.
3295 @kindex info program
3297 Display information about the status of your program: whether it is
3298 running or not, what process it is, and why it stopped.
3302 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3303 * Continuing and Stepping:: Resuming execution
3304 * Skipping Over Functions and Files::
3305 Skipping over functions and files
3307 * Thread Stops:: Stopping and starting multi-thread programs
3311 @section Breakpoints, Watchpoints, and Catchpoints
3314 A @dfn{breakpoint} makes your program stop whenever a certain point in
3315 the program is reached. For each breakpoint, you can add conditions to
3316 control in finer detail whether your program stops. You can set
3317 breakpoints with the @code{break} command and its variants (@pxref{Set
3318 Breaks, ,Setting Breakpoints}), to specify the place where your program
3319 should stop by line number, function name or exact address in the
3322 On some systems, you can set breakpoints in shared libraries before
3323 the executable is run. There is a minor limitation on HP-UX systems:
3324 you must wait until the executable is run in order to set breakpoints
3325 in shared library routines that are not called directly by the program
3326 (for example, routines that are arguments in a @code{pthread_create}
3330 @cindex data breakpoints
3331 @cindex memory tracing
3332 @cindex breakpoint on memory address
3333 @cindex breakpoint on variable modification
3334 A @dfn{watchpoint} is a special breakpoint that stops your program
3335 when the value of an expression changes. The expression may be a value
3336 of a variable, or it could involve values of one or more variables
3337 combined by operators, such as @samp{a + b}. This is sometimes called
3338 @dfn{data breakpoints}. You must use a different command to set
3339 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3340 from that, you can manage a watchpoint like any other breakpoint: you
3341 enable, disable, and delete both breakpoints and watchpoints using the
3344 You can arrange to have values from your program displayed automatically
3345 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3349 @cindex breakpoint on events
3350 A @dfn{catchpoint} is another special breakpoint that stops your program
3351 when a certain kind of event occurs, such as the throwing of a C@t{++}
3352 exception or the loading of a library. As with watchpoints, you use a
3353 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3354 Catchpoints}), but aside from that, you can manage a catchpoint like any
3355 other breakpoint. (To stop when your program receives a signal, use the
3356 @code{handle} command; see @ref{Signals, ,Signals}.)
3358 @cindex breakpoint numbers
3359 @cindex numbers for breakpoints
3360 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3361 catchpoint when you create it; these numbers are successive integers
3362 starting with one. In many of the commands for controlling various
3363 features of breakpoints you use the breakpoint number to say which
3364 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3365 @dfn{disabled}; if disabled, it has no effect on your program until you
3368 @cindex breakpoint ranges
3369 @cindex ranges of breakpoints
3370 Some @value{GDBN} commands accept a range of breakpoints on which to
3371 operate. A breakpoint range is either a single breakpoint number, like
3372 @samp{5}, or two such numbers, in increasing order, separated by a
3373 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3374 all breakpoints in that range are operated on.
3377 * Set Breaks:: Setting breakpoints
3378 * Set Watchpoints:: Setting watchpoints
3379 * Set Catchpoints:: Setting catchpoints
3380 * Delete Breaks:: Deleting breakpoints
3381 * Disabling:: Disabling breakpoints
3382 * Conditions:: Break conditions
3383 * Break Commands:: Breakpoint command lists
3384 * Dynamic Printf:: Dynamic printf
3385 * Save Breakpoints:: How to save breakpoints in a file
3386 * Static Probe Points:: Listing static probe points
3387 * Error in Breakpoints:: ``Cannot insert breakpoints''
3388 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3392 @subsection Setting Breakpoints
3394 @c FIXME LMB what does GDB do if no code on line of breakpt?
3395 @c consider in particular declaration with/without initialization.
3397 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3400 @kindex b @r{(@code{break})}
3401 @vindex $bpnum@r{, convenience variable}
3402 @cindex latest breakpoint
3403 Breakpoints are set with the @code{break} command (abbreviated
3404 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3405 number of the breakpoint you've set most recently; see @ref{Convenience
3406 Vars,, Convenience Variables}, for a discussion of what you can do with
3407 convenience variables.
3410 @item break @var{location}
3411 Set a breakpoint at the given @var{location}, which can specify a
3412 function name, a line number, or an address of an instruction.
3413 (@xref{Specify Location}, for a list of all the possible ways to
3414 specify a @var{location}.) The breakpoint will stop your program just
3415 before it executes any of the code in the specified @var{location}.
3417 When using source languages that permit overloading of symbols, such as
3418 C@t{++}, a function name may refer to more than one possible place to break.
3419 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3422 It is also possible to insert a breakpoint that will stop the program
3423 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3424 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3427 When called without any arguments, @code{break} sets a breakpoint at
3428 the next instruction to be executed in the selected stack frame
3429 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3430 innermost, this makes your program stop as soon as control
3431 returns to that frame. This is similar to the effect of a
3432 @code{finish} command in the frame inside the selected frame---except
3433 that @code{finish} does not leave an active breakpoint. If you use
3434 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3435 the next time it reaches the current location; this may be useful
3438 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3439 least one instruction has been executed. If it did not do this, you
3440 would be unable to proceed past a breakpoint without first disabling the
3441 breakpoint. This rule applies whether or not the breakpoint already
3442 existed when your program stopped.
3444 @item break @dots{} if @var{cond}
3445 Set a breakpoint with condition @var{cond}; evaluate the expression
3446 @var{cond} each time the breakpoint is reached, and stop only if the
3447 value is nonzero---that is, if @var{cond} evaluates as true.
3448 @samp{@dots{}} stands for one of the possible arguments described
3449 above (or no argument) specifying where to break. @xref{Conditions,
3450 ,Break Conditions}, for more information on breakpoint conditions.
3453 @item tbreak @var{args}
3454 Set a breakpoint enabled only for one stop. @var{args} are the
3455 same as for the @code{break} command, and the breakpoint is set in the same
3456 way, but the breakpoint is automatically deleted after the first time your
3457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3460 @cindex hardware breakpoints
3461 @item hbreak @var{args}
3462 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3463 @code{break} command and the breakpoint is set in the same way, but the
3464 breakpoint requires hardware support and some target hardware may not
3465 have this support. The main purpose of this is EPROM/ROM code
3466 debugging, so you can set a breakpoint at an instruction without
3467 changing the instruction. This can be used with the new trap-generation
3468 provided by SPARClite DSU and most x86-based targets. These targets
3469 will generate traps when a program accesses some data or instruction
3470 address that is assigned to the debug registers. However the hardware
3471 breakpoint registers can take a limited number of breakpoints. For
3472 example, on the DSU, only two data breakpoints can be set at a time, and
3473 @value{GDBN} will reject this command if more than two are used. Delete
3474 or disable unused hardware breakpoints before setting new ones
3475 (@pxref{Disabling, ,Disabling Breakpoints}).
3476 @xref{Conditions, ,Break Conditions}.
3477 For remote targets, you can restrict the number of hardware
3478 breakpoints @value{GDBN} will use, see @ref{set remote
3479 hardware-breakpoint-limit}.
3482 @item thbreak @var{args}
3483 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3484 are the same as for the @code{hbreak} command and the breakpoint is set in
3485 the same way. However, like the @code{tbreak} command,
3486 the breakpoint is automatically deleted after the
3487 first time your program stops there. Also, like the @code{hbreak}
3488 command, the breakpoint requires hardware support and some target hardware
3489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3490 See also @ref{Conditions, ,Break Conditions}.
3493 @cindex regular expression
3494 @cindex breakpoints at functions matching a regexp
3495 @cindex set breakpoints in many functions
3496 @item rbreak @var{regex}
3497 Set breakpoints on all functions matching the regular expression
3498 @var{regex}. This command sets an unconditional breakpoint on all
3499 matches, printing a list of all breakpoints it set. Once these
3500 breakpoints are set, they are treated just like the breakpoints set with
3501 the @code{break} command. You can delete them, disable them, or make
3502 them conditional the same way as any other breakpoint.
3504 The syntax of the regular expression is the standard one used with tools
3505 like @file{grep}. Note that this is different from the syntax used by
3506 shells, so for instance @code{foo*} matches all functions that include
3507 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3508 @code{.*} leading and trailing the regular expression you supply, so to
3509 match only functions that begin with @code{foo}, use @code{^foo}.
3511 @cindex non-member C@t{++} functions, set breakpoint in
3512 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3513 breakpoints on overloaded functions that are not members of any special
3516 @cindex set breakpoints on all functions
3517 The @code{rbreak} command can be used to set breakpoints in
3518 @strong{all} the functions in a program, like this:
3521 (@value{GDBP}) rbreak .
3524 @item rbreak @var{file}:@var{regex}
3525 If @code{rbreak} is called with a filename qualification, it limits
3526 the search for functions matching the given regular expression to the
3527 specified @var{file}. This can be used, for example, to set breakpoints on
3528 every function in a given file:
3531 (@value{GDBP}) rbreak file.c:.
3534 The colon separating the filename qualifier from the regex may
3535 optionally be surrounded by spaces.
3537 @kindex info breakpoints
3538 @cindex @code{$_} and @code{info breakpoints}
3539 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3540 @itemx info break @r{[}@var{n}@dots{}@r{]}
3541 Print a table of all breakpoints, watchpoints, and catchpoints set and
3542 not deleted. Optional argument @var{n} means print information only
3543 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3544 For each breakpoint, following columns are printed:
3547 @item Breakpoint Numbers
3549 Breakpoint, watchpoint, or catchpoint.
3551 Whether the breakpoint is marked to be disabled or deleted when hit.
3552 @item Enabled or Disabled
3553 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3554 that are not enabled.
3556 Where the breakpoint is in your program, as a memory address. For a
3557 pending breakpoint whose address is not yet known, this field will
3558 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3559 library that has the symbol or line referred by breakpoint is loaded.
3560 See below for details. A breakpoint with several locations will
3561 have @samp{<MULTIPLE>} in this field---see below for details.
3563 Where the breakpoint is in the source for your program, as a file and
3564 line number. For a pending breakpoint, the original string passed to
3565 the breakpoint command will be listed as it cannot be resolved until
3566 the appropriate shared library is loaded in the future.
3570 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3571 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3572 @value{GDBN} on the host's side. If it is ``target'', then the condition
3573 is evaluated by the target. The @code{info break} command shows
3574 the condition on the line following the affected breakpoint, together with
3575 its condition evaluation mode in between parentheses.
3577 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3578 allowed to have a condition specified for it. The condition is not parsed for
3579 validity until a shared library is loaded that allows the pending
3580 breakpoint to resolve to a valid location.
3583 @code{info break} with a breakpoint
3584 number @var{n} as argument lists only that breakpoint. The
3585 convenience variable @code{$_} and the default examining-address for
3586 the @code{x} command are set to the address of the last breakpoint
3587 listed (@pxref{Memory, ,Examining Memory}).
3590 @code{info break} displays a count of the number of times the breakpoint
3591 has been hit. This is especially useful in conjunction with the
3592 @code{ignore} command. You can ignore a large number of breakpoint
3593 hits, look at the breakpoint info to see how many times the breakpoint
3594 was hit, and then run again, ignoring one less than that number. This
3595 will get you quickly to the last hit of that breakpoint.
3598 For a breakpoints with an enable count (xref) greater than 1,
3599 @code{info break} also displays that count.
3603 @value{GDBN} allows you to set any number of breakpoints at the same place in
3604 your program. There is nothing silly or meaningless about this. When
3605 the breakpoints are conditional, this is even useful
3606 (@pxref{Conditions, ,Break Conditions}).
3608 @cindex multiple locations, breakpoints
3609 @cindex breakpoints, multiple locations
3610 It is possible that a breakpoint corresponds to several locations
3611 in your program. Examples of this situation are:
3615 Multiple functions in the program may have the same name.
3618 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3619 instances of the function body, used in different cases.
3622 For a C@t{++} template function, a given line in the function can
3623 correspond to any number of instantiations.
3626 For an inlined function, a given source line can correspond to
3627 several places where that function is inlined.
3630 In all those cases, @value{GDBN} will insert a breakpoint at all
3631 the relevant locations.
3633 A breakpoint with multiple locations is displayed in the breakpoint
3634 table using several rows---one header row, followed by one row for
3635 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3636 address column. The rows for individual locations contain the actual
3637 addresses for locations, and show the functions to which those
3638 locations belong. The number column for a location is of the form
3639 @var{breakpoint-number}.@var{location-number}.
3644 Num Type Disp Enb Address What
3645 1 breakpoint keep y <MULTIPLE>
3647 breakpoint already hit 1 time
3648 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3649 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3652 Each location can be individually enabled or disabled by passing
3653 @var{breakpoint-number}.@var{location-number} as argument to the
3654 @code{enable} and @code{disable} commands. Note that you cannot
3655 delete the individual locations from the list, you can only delete the
3656 entire list of locations that belong to their parent breakpoint (with
3657 the @kbd{delete @var{num}} command, where @var{num} is the number of
3658 the parent breakpoint, 1 in the above example). Disabling or enabling
3659 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3660 that belong to that breakpoint.
3662 @cindex pending breakpoints
3663 It's quite common to have a breakpoint inside a shared library.
3664 Shared libraries can be loaded and unloaded explicitly,
3665 and possibly repeatedly, as the program is executed. To support
3666 this use case, @value{GDBN} updates breakpoint locations whenever
3667 any shared library is loaded or unloaded. Typically, you would
3668 set a breakpoint in a shared library at the beginning of your
3669 debugging session, when the library is not loaded, and when the
3670 symbols from the library are not available. When you try to set
3671 breakpoint, @value{GDBN} will ask you if you want to set
3672 a so called @dfn{pending breakpoint}---breakpoint whose address
3673 is not yet resolved.
3675 After the program is run, whenever a new shared library is loaded,
3676 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3677 shared library contains the symbol or line referred to by some
3678 pending breakpoint, that breakpoint is resolved and becomes an
3679 ordinary breakpoint. When a library is unloaded, all breakpoints
3680 that refer to its symbols or source lines become pending again.
3682 This logic works for breakpoints with multiple locations, too. For
3683 example, if you have a breakpoint in a C@t{++} template function, and
3684 a newly loaded shared library has an instantiation of that template,
3685 a new location is added to the list of locations for the breakpoint.
3687 Except for having unresolved address, pending breakpoints do not
3688 differ from regular breakpoints. You can set conditions or commands,
3689 enable and disable them and perform other breakpoint operations.
3691 @value{GDBN} provides some additional commands for controlling what
3692 happens when the @samp{break} command cannot resolve breakpoint
3693 address specification to an address:
3695 @kindex set breakpoint pending
3696 @kindex show breakpoint pending
3698 @item set breakpoint pending auto
3699 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3700 location, it queries you whether a pending breakpoint should be created.
3702 @item set breakpoint pending on
3703 This indicates that an unrecognized breakpoint location should automatically
3704 result in a pending breakpoint being created.
3706 @item set breakpoint pending off
3707 This indicates that pending breakpoints are not to be created. Any
3708 unrecognized breakpoint location results in an error. This setting does
3709 not affect any pending breakpoints previously created.
3711 @item show breakpoint pending
3712 Show the current behavior setting for creating pending breakpoints.
3715 The settings above only affect the @code{break} command and its
3716 variants. Once breakpoint is set, it will be automatically updated
3717 as shared libraries are loaded and unloaded.
3719 @cindex automatic hardware breakpoints
3720 For some targets, @value{GDBN} can automatically decide if hardware or
3721 software breakpoints should be used, depending on whether the
3722 breakpoint address is read-only or read-write. This applies to
3723 breakpoints set with the @code{break} command as well as to internal
3724 breakpoints set by commands like @code{next} and @code{finish}. For
3725 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3728 You can control this automatic behaviour with the following commands::
3730 @kindex set breakpoint auto-hw
3731 @kindex show breakpoint auto-hw
3733 @item set breakpoint auto-hw on
3734 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3735 will try to use the target memory map to decide if software or hardware
3736 breakpoint must be used.
3738 @item set breakpoint auto-hw off
3739 This indicates @value{GDBN} should not automatically select breakpoint
3740 type. If the target provides a memory map, @value{GDBN} will warn when
3741 trying to set software breakpoint at a read-only address.
3744 @value{GDBN} normally implements breakpoints by replacing the program code
3745 at the breakpoint address with a special instruction, which, when
3746 executed, given control to the debugger. By default, the program
3747 code is so modified only when the program is resumed. As soon as
3748 the program stops, @value{GDBN} restores the original instructions. This
3749 behaviour guards against leaving breakpoints inserted in the
3750 target should gdb abrubptly disconnect. However, with slow remote
3751 targets, inserting and removing breakpoint can reduce the performance.
3752 This behavior can be controlled with the following commands::
3754 @kindex set breakpoint always-inserted
3755 @kindex show breakpoint always-inserted
3757 @item set breakpoint always-inserted off
3758 All breakpoints, including newly added by the user, are inserted in
3759 the target only when the target is resumed. All breakpoints are
3760 removed from the target when it stops.
3762 @item set breakpoint always-inserted on
3763 Causes all breakpoints to be inserted in the target at all times. If
3764 the user adds a new breakpoint, or changes an existing breakpoint, the
3765 breakpoints in the target are updated immediately. A breakpoint is
3766 removed from the target only when breakpoint itself is removed.
3768 @cindex non-stop mode, and @code{breakpoint always-inserted}
3769 @item set breakpoint always-inserted auto
3770 This is the default mode. If @value{GDBN} is controlling the inferior
3771 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3772 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3773 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3774 @code{breakpoint always-inserted} mode is off.
3777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3778 when a breakpoint breaks. If the condition is true, then the process being
3779 debugged stops, otherwise the process is resumed.
3781 If the target supports evaluating conditions on its end, @value{GDBN} may
3782 download the breakpoint, together with its conditions, to it.
3784 This feature can be controlled via the following commands:
3786 @kindex set breakpoint condition-evaluation
3787 @kindex show breakpoint condition-evaluation
3789 @item set breakpoint condition-evaluation host
3790 This option commands @value{GDBN} to evaluate the breakpoint
3791 conditions on the host's side. Unconditional breakpoints are sent to
3792 the target which in turn receives the triggers and reports them back to GDB
3793 for condition evaluation. This is the standard evaluation mode.
3795 @item set breakpoint condition-evaluation target
3796 This option commands @value{GDBN} to download breakpoint conditions
3797 to the target at the moment of their insertion. The target
3798 is responsible for evaluating the conditional expression and reporting
3799 breakpoint stop events back to @value{GDBN} whenever the condition
3800 is true. Due to limitations of target-side evaluation, some conditions
3801 cannot be evaluated there, e.g., conditions that depend on local data
3802 that is only known to the host. Examples include
3803 conditional expressions involving convenience variables, complex types
3804 that cannot be handled by the agent expression parser and expressions
3805 that are too long to be sent over to the target, specially when the
3806 target is a remote system. In these cases, the conditions will be
3807 evaluated by @value{GDBN}.
3809 @item set breakpoint condition-evaluation auto
3810 This is the default mode. If the target supports evaluating breakpoint
3811 conditions on its end, @value{GDBN} will download breakpoint conditions to
3812 the target (limitations mentioned previously apply). If the target does
3813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3814 to evaluating all these conditions on the host's side.
3818 @cindex negative breakpoint numbers
3819 @cindex internal @value{GDBN} breakpoints
3820 @value{GDBN} itself sometimes sets breakpoints in your program for
3821 special purposes, such as proper handling of @code{longjmp} (in C
3822 programs). These internal breakpoints are assigned negative numbers,
3823 starting with @code{-1}; @samp{info breakpoints} does not display them.
3824 You can see these breakpoints with the @value{GDBN} maintenance command
3825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3828 @node Set Watchpoints
3829 @subsection Setting Watchpoints
3831 @cindex setting watchpoints
3832 You can use a watchpoint to stop execution whenever the value of an
3833 expression changes, without having to predict a particular place where
3834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3835 The expression may be as simple as the value of a single variable, or
3836 as complex as many variables combined by operators. Examples include:
3840 A reference to the value of a single variable.
3843 An address cast to an appropriate data type. For example,
3844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3845 address (assuming an @code{int} occupies 4 bytes).
3848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3849 expression can use any operators valid in the program's native
3850 language (@pxref{Languages}).
3853 You can set a watchpoint on an expression even if the expression can
3854 not be evaluated yet. For instance, you can set a watchpoint on
3855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3857 the expression produces a valid value. If the expression becomes
3858 valid in some other way than changing a variable (e.g.@: if the memory
3859 pointed to by @samp{*global_ptr} becomes readable as the result of a
3860 @code{malloc} call), @value{GDBN} may not stop until the next time
3861 the expression changes.
3863 @cindex software watchpoints
3864 @cindex hardware watchpoints
3865 Depending on your system, watchpoints may be implemented in software or
3866 hardware. @value{GDBN} does software watchpointing by single-stepping your
3867 program and testing the variable's value each time, which is hundreds of
3868 times slower than normal execution. (But this may still be worth it, to
3869 catch errors where you have no clue what part of your program is the
3872 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3873 x86-based targets, @value{GDBN} includes support for hardware
3874 watchpoints, which do not slow down the running of your program.
3878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3879 Set a watchpoint for an expression. @value{GDBN} will break when the
3880 expression @var{expr} is written into by the program and its value
3881 changes. The simplest (and the most popular) use of this command is
3882 to watch the value of a single variable:
3885 (@value{GDBP}) watch foo
3888 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3889 argument, @value{GDBN} breaks only when the thread identified by
3890 @var{threadnum} changes the value of @var{expr}. If any other threads
3891 change the value of @var{expr}, @value{GDBN} will not break. Note
3892 that watchpoints restricted to a single thread in this way only work
3893 with Hardware Watchpoints.
3895 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3896 (see below). The @code{-location} argument tells @value{GDBN} to
3897 instead watch the memory referred to by @var{expr}. In this case,
3898 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3899 and watch the memory at that address. The type of the result is used
3900 to determine the size of the watched memory. If the expression's
3901 result does not have an address, then @value{GDBN} will print an
3904 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3905 of masked watchpoints, if the current architecture supports this
3906 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3907 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3908 to an address to watch. The mask specifies that some bits of an address
3909 (the bits which are reset in the mask) should be ignored when matching
3910 the address accessed by the inferior against the watchpoint address.
3911 Thus, a masked watchpoint watches many addresses simultaneously---those
3912 addresses whose unmasked bits are identical to the unmasked bits in the
3913 watchpoint address. The @code{mask} argument implies @code{-location}.
3917 (@value{GDBP}) watch foo mask 0xffff00ff
3918 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3922 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3923 Set a watchpoint that will break when the value of @var{expr} is read
3927 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3928 Set a watchpoint that will break when @var{expr} is either read from
3929 or written into by the program.
3931 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3932 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3933 This command prints a list of watchpoints, using the same format as
3934 @code{info break} (@pxref{Set Breaks}).
3937 If you watch for a change in a numerically entered address you need to
3938 dereference it, as the address itself is just a constant number which will
3939 never change. @value{GDBN} refuses to create a watchpoint that watches
3940 a never-changing value:
3943 (@value{GDBP}) watch 0x600850
3944 Cannot watch constant value 0x600850.
3945 (@value{GDBP}) watch *(int *) 0x600850
3946 Watchpoint 1: *(int *) 6293584
3949 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3950 watchpoints execute very quickly, and the debugger reports a change in
3951 value at the exact instruction where the change occurs. If @value{GDBN}
3952 cannot set a hardware watchpoint, it sets a software watchpoint, which
3953 executes more slowly and reports the change in value at the next
3954 @emph{statement}, not the instruction, after the change occurs.
3956 @cindex use only software watchpoints
3957 You can force @value{GDBN} to use only software watchpoints with the
3958 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3959 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3960 the underlying system supports them. (Note that hardware-assisted
3961 watchpoints that were set @emph{before} setting
3962 @code{can-use-hw-watchpoints} to zero will still use the hardware
3963 mechanism of watching expression values.)
3966 @item set can-use-hw-watchpoints
3967 @kindex set can-use-hw-watchpoints
3968 Set whether or not to use hardware watchpoints.
3970 @item show can-use-hw-watchpoints
3971 @kindex show can-use-hw-watchpoints
3972 Show the current mode of using hardware watchpoints.
3975 For remote targets, you can restrict the number of hardware
3976 watchpoints @value{GDBN} will use, see @ref{set remote
3977 hardware-breakpoint-limit}.
3979 When you issue the @code{watch} command, @value{GDBN} reports
3982 Hardware watchpoint @var{num}: @var{expr}
3986 if it was able to set a hardware watchpoint.
3988 Currently, the @code{awatch} and @code{rwatch} commands can only set
3989 hardware watchpoints, because accesses to data that don't change the
3990 value of the watched expression cannot be detected without examining
3991 every instruction as it is being executed, and @value{GDBN} does not do
3992 that currently. If @value{GDBN} finds that it is unable to set a
3993 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3994 will print a message like this:
3997 Expression cannot be implemented with read/access watchpoint.
4000 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4001 data type of the watched expression is wider than what a hardware
4002 watchpoint on the target machine can handle. For example, some systems
4003 can only watch regions that are up to 4 bytes wide; on such systems you
4004 cannot set hardware watchpoints for an expression that yields a
4005 double-precision floating-point number (which is typically 8 bytes
4006 wide). As a work-around, it might be possible to break the large region
4007 into a series of smaller ones and watch them with separate watchpoints.
4009 If you set too many hardware watchpoints, @value{GDBN} might be unable
4010 to insert all of them when you resume the execution of your program.
4011 Since the precise number of active watchpoints is unknown until such
4012 time as the program is about to be resumed, @value{GDBN} might not be
4013 able to warn you about this when you set the watchpoints, and the
4014 warning will be printed only when the program is resumed:
4017 Hardware watchpoint @var{num}: Could not insert watchpoint
4021 If this happens, delete or disable some of the watchpoints.
4023 Watching complex expressions that reference many variables can also
4024 exhaust the resources available for hardware-assisted watchpoints.
4025 That's because @value{GDBN} needs to watch every variable in the
4026 expression with separately allocated resources.
4028 If you call a function interactively using @code{print} or @code{call},
4029 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4030 kind of breakpoint or the call completes.
4032 @value{GDBN} automatically deletes watchpoints that watch local
4033 (automatic) variables, or expressions that involve such variables, when
4034 they go out of scope, that is, when the execution leaves the block in
4035 which these variables were defined. In particular, when the program
4036 being debugged terminates, @emph{all} local variables go out of scope,
4037 and so only watchpoints that watch global variables remain set. If you
4038 rerun the program, you will need to set all such watchpoints again. One
4039 way of doing that would be to set a code breakpoint at the entry to the
4040 @code{main} function and when it breaks, set all the watchpoints.
4042 @cindex watchpoints and threads
4043 @cindex threads and watchpoints
4044 In multi-threaded programs, watchpoints will detect changes to the
4045 watched expression from every thread.
4048 @emph{Warning:} In multi-threaded programs, software watchpoints
4049 have only limited usefulness. If @value{GDBN} creates a software
4050 watchpoint, it can only watch the value of an expression @emph{in a
4051 single thread}. If you are confident that the expression can only
4052 change due to the current thread's activity (and if you are also
4053 confident that no other thread can become current), then you can use
4054 software watchpoints as usual. However, @value{GDBN} may not notice
4055 when a non-current thread's activity changes the expression. (Hardware
4056 watchpoints, in contrast, watch an expression in all threads.)
4059 @xref{set remote hardware-watchpoint-limit}.
4061 @node Set Catchpoints
4062 @subsection Setting Catchpoints
4063 @cindex catchpoints, setting
4064 @cindex exception handlers
4065 @cindex event handling
4067 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4068 kinds of program events, such as C@t{++} exceptions or the loading of a
4069 shared library. Use the @code{catch} command to set a catchpoint.
4073 @item catch @var{event}
4074 Stop when @var{event} occurs. @var{event} can be any of the following:
4077 @item throw @r{[}@var{regexp}@r{]}
4078 @itemx rethrow @r{[}@var{regexp}@r{]}
4079 @itemx catch @r{[}@var{regexp}@r{]}
4080 @cindex stop on C@t{++} exceptions
4081 The throwing, re-throwing, or catching of a C@t{++} exception.
4083 If @var{regexp} is given, then only exceptions whose type matches the
4084 regular expression will be caught.
4086 @vindex $_exception@r{, convenience variable}
4087 The convenience variable @code{$_exception} is available at an
4088 exception-related catchpoint, on some systems. This holds the
4089 exception being thrown.
4091 There are currently some limitations to C@t{++} exception handling in
4096 The support for these commands is system-dependent. Currently, only
4097 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4101 The regular expression feature and the @code{$_exception} convenience
4102 variable rely on the presence of some SDT probes in @code{libstdc++}.
4103 If these probes are not present, then these features cannot be used.
4104 These probes were first available in the GCC 4.8 release, but whether
4105 or not they are available in your GCC also depends on how it was
4109 The @code{$_exception} convenience variable is only valid at the
4110 instruction at which an exception-related catchpoint is set.
4113 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4114 location in the system library which implements runtime exception
4115 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4116 (@pxref{Selection}) to get to your code.
4119 If you call a function interactively, @value{GDBN} normally returns
4120 control to you when the function has finished executing. If the call
4121 raises an exception, however, the call may bypass the mechanism that
4122 returns control to you and cause your program either to abort or to
4123 simply continue running until it hits a breakpoint, catches a signal
4124 that @value{GDBN} is listening for, or exits. This is the case even if
4125 you set a catchpoint for the exception; catchpoints on exceptions are
4126 disabled within interactive calls. @xref{Calling}, for information on
4127 controlling this with @code{set unwind-on-terminating-exception}.
4130 You cannot raise an exception interactively.
4133 You cannot install an exception handler interactively.
4137 @cindex Ada exception catching
4138 @cindex catch Ada exceptions
4139 An Ada exception being raised. If an exception name is specified
4140 at the end of the command (eg @code{catch exception Program_Error}),
4141 the debugger will stop only when this specific exception is raised.
4142 Otherwise, the debugger stops execution when any Ada exception is raised.
4144 When inserting an exception catchpoint on a user-defined exception whose
4145 name is identical to one of the exceptions defined by the language, the
4146 fully qualified name must be used as the exception name. Otherwise,
4147 @value{GDBN} will assume that it should stop on the pre-defined exception
4148 rather than the user-defined one. For instance, assuming an exception
4149 called @code{Constraint_Error} is defined in package @code{Pck}, then
4150 the command to use to catch such exceptions is @kbd{catch exception
4151 Pck.Constraint_Error}.
4153 @item exception unhandled
4154 An exception that was raised but is not handled by the program.
4157 A failed Ada assertion.
4160 @cindex break on fork/exec
4161 A call to @code{exec}. This is currently only available for HP-UX
4165 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4166 @cindex break on a system call.
4167 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4168 syscall is a mechanism for application programs to request a service
4169 from the operating system (OS) or one of the OS system services.
4170 @value{GDBN} can catch some or all of the syscalls issued by the
4171 debuggee, and show the related information for each syscall. If no
4172 argument is specified, calls to and returns from all system calls
4175 @var{name} can be any system call name that is valid for the
4176 underlying OS. Just what syscalls are valid depends on the OS. On
4177 GNU and Unix systems, you can find the full list of valid syscall
4178 names on @file{/usr/include/asm/unistd.h}.
4180 @c For MS-Windows, the syscall names and the corresponding numbers
4181 @c can be found, e.g., on this URL:
4182 @c http://www.metasploit.com/users/opcode/syscalls.html
4183 @c but we don't support Windows syscalls yet.
4185 Normally, @value{GDBN} knows in advance which syscalls are valid for
4186 each OS, so you can use the @value{GDBN} command-line completion
4187 facilities (@pxref{Completion,, command completion}) to list the
4190 You may also specify the system call numerically. A syscall's
4191 number is the value passed to the OS's syscall dispatcher to
4192 identify the requested service. When you specify the syscall by its
4193 name, @value{GDBN} uses its database of syscalls to convert the name
4194 into the corresponding numeric code, but using the number directly
4195 may be useful if @value{GDBN}'s database does not have the complete
4196 list of syscalls on your system (e.g., because @value{GDBN} lags
4197 behind the OS upgrades).
4199 The example below illustrates how this command works if you don't provide
4203 (@value{GDBP}) catch syscall
4204 Catchpoint 1 (syscall)
4206 Starting program: /tmp/catch-syscall
4208 Catchpoint 1 (call to syscall 'close'), \
4209 0xffffe424 in __kernel_vsyscall ()
4213 Catchpoint 1 (returned from syscall 'close'), \
4214 0xffffe424 in __kernel_vsyscall ()
4218 Here is an example of catching a system call by name:
4221 (@value{GDBP}) catch syscall chroot
4222 Catchpoint 1 (syscall 'chroot' [61])
4224 Starting program: /tmp/catch-syscall
4226 Catchpoint 1 (call to syscall 'chroot'), \
4227 0xffffe424 in __kernel_vsyscall ()
4231 Catchpoint 1 (returned from syscall 'chroot'), \
4232 0xffffe424 in __kernel_vsyscall ()
4236 An example of specifying a system call numerically. In the case
4237 below, the syscall number has a corresponding entry in the XML
4238 file, so @value{GDBN} finds its name and prints it:
4241 (@value{GDBP}) catch syscall 252
4242 Catchpoint 1 (syscall(s) 'exit_group')
4244 Starting program: /tmp/catch-syscall
4246 Catchpoint 1 (call to syscall 'exit_group'), \
4247 0xffffe424 in __kernel_vsyscall ()
4251 Program exited normally.
4255 However, there can be situations when there is no corresponding name
4256 in XML file for that syscall number. In this case, @value{GDBN} prints
4257 a warning message saying that it was not able to find the syscall name,
4258 but the catchpoint will be set anyway. See the example below:
4261 (@value{GDBP}) catch syscall 764
4262 warning: The number '764' does not represent a known syscall.
4263 Catchpoint 2 (syscall 764)
4267 If you configure @value{GDBN} using the @samp{--without-expat} option,
4268 it will not be able to display syscall names. Also, if your
4269 architecture does not have an XML file describing its system calls,
4270 you will not be able to see the syscall names. It is important to
4271 notice that these two features are used for accessing the syscall
4272 name database. In either case, you will see a warning like this:
4275 (@value{GDBP}) catch syscall
4276 warning: Could not open "syscalls/i386-linux.xml"
4277 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4278 GDB will not be able to display syscall names.
4279 Catchpoint 1 (syscall)
4283 Of course, the file name will change depending on your architecture and system.
4285 Still using the example above, you can also try to catch a syscall by its
4286 number. In this case, you would see something like:
4289 (@value{GDBP}) catch syscall 252
4290 Catchpoint 1 (syscall(s) 252)
4293 Again, in this case @value{GDBN} would not be able to display syscall's names.
4296 A call to @code{fork}. This is currently only available for HP-UX
4300 A call to @code{vfork}. This is currently only available for HP-UX
4303 @item load @r{[}regexp@r{]}
4304 @itemx unload @r{[}regexp@r{]}
4305 The loading or unloading of a shared library. If @var{regexp} is
4306 given, then the catchpoint will stop only if the regular expression
4307 matches one of the affected libraries.
4309 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4310 The delivery of a signal.
4312 With no arguments, this catchpoint will catch any signal that is not
4313 used internally by @value{GDBN}, specifically, all signals except
4314 @samp{SIGTRAP} and @samp{SIGINT}.
4316 With the argument @samp{all}, all signals, including those used by
4317 @value{GDBN}, will be caught. This argument cannot be used with other
4320 Otherwise, the arguments are a list of signal names as given to
4321 @code{handle} (@pxref{Signals}). Only signals specified in this list
4324 One reason that @code{catch signal} can be more useful than
4325 @code{handle} is that you can attach commands and conditions to the
4328 When a signal is caught by a catchpoint, the signal's @code{stop} and
4329 @code{print} settings, as specified by @code{handle}, are ignored.
4330 However, whether the signal is still delivered to the inferior depends
4331 on the @code{pass} setting; this can be changed in the catchpoint's
4336 @item tcatch @var{event}
4337 Set a catchpoint that is enabled only for one stop. The catchpoint is
4338 automatically deleted after the first time the event is caught.
4342 Use the @code{info break} command to list the current catchpoints.
4346 @subsection Deleting Breakpoints
4348 @cindex clearing breakpoints, watchpoints, catchpoints
4349 @cindex deleting breakpoints, watchpoints, catchpoints
4350 It is often necessary to eliminate a breakpoint, watchpoint, or
4351 catchpoint once it has done its job and you no longer want your program
4352 to stop there. This is called @dfn{deleting} the breakpoint. A
4353 breakpoint that has been deleted no longer exists; it is forgotten.
4355 With the @code{clear} command you can delete breakpoints according to
4356 where they are in your program. With the @code{delete} command you can
4357 delete individual breakpoints, watchpoints, or catchpoints by specifying
4358 their breakpoint numbers.
4360 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4361 automatically ignores breakpoints on the first instruction to be executed
4362 when you continue execution without changing the execution address.
4367 Delete any breakpoints at the next instruction to be executed in the
4368 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4369 the innermost frame is selected, this is a good way to delete a
4370 breakpoint where your program just stopped.
4372 @item clear @var{location}
4373 Delete any breakpoints set at the specified @var{location}.
4374 @xref{Specify Location}, for the various forms of @var{location}; the
4375 most useful ones are listed below:
4378 @item clear @var{function}
4379 @itemx clear @var{filename}:@var{function}
4380 Delete any breakpoints set at entry to the named @var{function}.
4382 @item clear @var{linenum}
4383 @itemx clear @var{filename}:@var{linenum}
4384 Delete any breakpoints set at or within the code of the specified
4385 @var{linenum} of the specified @var{filename}.
4388 @cindex delete breakpoints
4390 @kindex d @r{(@code{delete})}
4391 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4392 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4393 ranges specified as arguments. If no argument is specified, delete all
4394 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4395 confirm off}). You can abbreviate this command as @code{d}.
4399 @subsection Disabling Breakpoints
4401 @cindex enable/disable a breakpoint
4402 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4403 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4404 it had been deleted, but remembers the information on the breakpoint so
4405 that you can @dfn{enable} it again later.
4407 You disable and enable breakpoints, watchpoints, and catchpoints with
4408 the @code{enable} and @code{disable} commands, optionally specifying
4409 one or more breakpoint numbers as arguments. Use @code{info break} to
4410 print a list of all breakpoints, watchpoints, and catchpoints if you
4411 do not know which numbers to use.
4413 Disabling and enabling a breakpoint that has multiple locations
4414 affects all of its locations.
4416 A breakpoint, watchpoint, or catchpoint can have any of several
4417 different states of enablement:
4421 Enabled. The breakpoint stops your program. A breakpoint set
4422 with the @code{break} command starts out in this state.
4424 Disabled. The breakpoint has no effect on your program.
4426 Enabled once. The breakpoint stops your program, but then becomes
4429 Enabled for a count. The breakpoint stops your program for the next
4430 N times, then becomes disabled.
4432 Enabled for deletion. The breakpoint stops your program, but
4433 immediately after it does so it is deleted permanently. A breakpoint
4434 set with the @code{tbreak} command starts out in this state.
4437 You can use the following commands to enable or disable breakpoints,
4438 watchpoints, and catchpoints:
4442 @kindex dis @r{(@code{disable})}
4443 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4444 Disable the specified breakpoints---or all breakpoints, if none are
4445 listed. A disabled breakpoint has no effect but is not forgotten. All
4446 options such as ignore-counts, conditions and commands are remembered in
4447 case the breakpoint is enabled again later. You may abbreviate
4448 @code{disable} as @code{dis}.
4451 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4452 Enable the specified breakpoints (or all defined breakpoints). They
4453 become effective once again in stopping your program.
4455 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4456 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4457 of these breakpoints immediately after stopping your program.
4459 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4460 Enable the specified breakpoints temporarily. @value{GDBN} records
4461 @var{count} with each of the specified breakpoints, and decrements a
4462 breakpoint's count when it is hit. When any count reaches 0,
4463 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4464 count (@pxref{Conditions, ,Break Conditions}), that will be
4465 decremented to 0 before @var{count} is affected.
4467 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4468 Enable the specified breakpoints to work once, then die. @value{GDBN}
4469 deletes any of these breakpoints as soon as your program stops there.
4470 Breakpoints set by the @code{tbreak} command start out in this state.
4473 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4474 @c confusing: tbreak is also initially enabled.
4475 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4476 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4477 subsequently, they become disabled or enabled only when you use one of
4478 the commands above. (The command @code{until} can set and delete a
4479 breakpoint of its own, but it does not change the state of your other
4480 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4484 @subsection Break Conditions
4485 @cindex conditional breakpoints
4486 @cindex breakpoint conditions
4488 @c FIXME what is scope of break condition expr? Context where wanted?
4489 @c in particular for a watchpoint?
4490 The simplest sort of breakpoint breaks every time your program reaches a
4491 specified place. You can also specify a @dfn{condition} for a
4492 breakpoint. A condition is just a Boolean expression in your
4493 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4494 a condition evaluates the expression each time your program reaches it,
4495 and your program stops only if the condition is @emph{true}.
4497 This is the converse of using assertions for program validation; in that
4498 situation, you want to stop when the assertion is violated---that is,
4499 when the condition is false. In C, if you want to test an assertion expressed
4500 by the condition @var{assert}, you should set the condition
4501 @samp{! @var{assert}} on the appropriate breakpoint.
4503 Conditions are also accepted for watchpoints; you may not need them,
4504 since a watchpoint is inspecting the value of an expression anyhow---but
4505 it might be simpler, say, to just set a watchpoint on a variable name,
4506 and specify a condition that tests whether the new value is an interesting
4509 Break conditions can have side effects, and may even call functions in
4510 your program. This can be useful, for example, to activate functions
4511 that log program progress, or to use your own print functions to
4512 format special data structures. The effects are completely predictable
4513 unless there is another enabled breakpoint at the same address. (In
4514 that case, @value{GDBN} might see the other breakpoint first and stop your
4515 program without checking the condition of this one.) Note that
4516 breakpoint commands are usually more convenient and flexible than break
4518 purpose of performing side effects when a breakpoint is reached
4519 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4521 Breakpoint conditions can also be evaluated on the target's side if
4522 the target supports it. Instead of evaluating the conditions locally,
4523 @value{GDBN} encodes the expression into an agent expression
4524 (@pxref{Agent Expressions}) suitable for execution on the target,
4525 independently of @value{GDBN}. Global variables become raw memory
4526 locations, locals become stack accesses, and so forth.
4528 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4529 when its condition evaluates to true. This mechanism may provide faster
4530 response times depending on the performance characteristics of the target
4531 since it does not need to keep @value{GDBN} informed about
4532 every breakpoint trigger, even those with false conditions.
4534 Break conditions can be specified when a breakpoint is set, by using
4535 @samp{if} in the arguments to the @code{break} command. @xref{Set
4536 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4537 with the @code{condition} command.
4539 You can also use the @code{if} keyword with the @code{watch} command.
4540 The @code{catch} command does not recognize the @code{if} keyword;
4541 @code{condition} is the only way to impose a further condition on a
4546 @item condition @var{bnum} @var{expression}
4547 Specify @var{expression} as the break condition for breakpoint,
4548 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4549 breakpoint @var{bnum} stops your program only if the value of
4550 @var{expression} is true (nonzero, in C). When you use
4551 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4552 syntactic correctness, and to determine whether symbols in it have
4553 referents in the context of your breakpoint. If @var{expression} uses
4554 symbols not referenced in the context of the breakpoint, @value{GDBN}
4555 prints an error message:
4558 No symbol "foo" in current context.
4563 not actually evaluate @var{expression} at the time the @code{condition}
4564 command (or a command that sets a breakpoint with a condition, like
4565 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4567 @item condition @var{bnum}
4568 Remove the condition from breakpoint number @var{bnum}. It becomes
4569 an ordinary unconditional breakpoint.
4572 @cindex ignore count (of breakpoint)
4573 A special case of a breakpoint condition is to stop only when the
4574 breakpoint has been reached a certain number of times. This is so
4575 useful that there is a special way to do it, using the @dfn{ignore
4576 count} of the breakpoint. Every breakpoint has an ignore count, which
4577 is an integer. Most of the time, the ignore count is zero, and
4578 therefore has no effect. But if your program reaches a breakpoint whose
4579 ignore count is positive, then instead of stopping, it just decrements
4580 the ignore count by one and continues. As a result, if the ignore count
4581 value is @var{n}, the breakpoint does not stop the next @var{n} times
4582 your program reaches it.
4586 @item ignore @var{bnum} @var{count}
4587 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4588 The next @var{count} times the breakpoint is reached, your program's
4589 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4592 To make the breakpoint stop the next time it is reached, specify
4595 When you use @code{continue} to resume execution of your program from a
4596 breakpoint, you can specify an ignore count directly as an argument to
4597 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4598 Stepping,,Continuing and Stepping}.
4600 If a breakpoint has a positive ignore count and a condition, the
4601 condition is not checked. Once the ignore count reaches zero,
4602 @value{GDBN} resumes checking the condition.
4604 You could achieve the effect of the ignore count with a condition such
4605 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4606 is decremented each time. @xref{Convenience Vars, ,Convenience
4610 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4613 @node Break Commands
4614 @subsection Breakpoint Command Lists
4616 @cindex breakpoint commands
4617 You can give any breakpoint (or watchpoint or catchpoint) a series of
4618 commands to execute when your program stops due to that breakpoint. For
4619 example, you might want to print the values of certain expressions, or
4620 enable other breakpoints.
4624 @kindex end@r{ (breakpoint commands)}
4625 @item commands @r{[}@var{range}@dots{}@r{]}
4626 @itemx @dots{} @var{command-list} @dots{}
4628 Specify a list of commands for the given breakpoints. The commands
4629 themselves appear on the following lines. Type a line containing just
4630 @code{end} to terminate the commands.
4632 To remove all commands from a breakpoint, type @code{commands} and
4633 follow it immediately with @code{end}; that is, give no commands.
4635 With no argument, @code{commands} refers to the last breakpoint,
4636 watchpoint, or catchpoint set (not to the breakpoint most recently
4637 encountered). If the most recent breakpoints were set with a single
4638 command, then the @code{commands} will apply to all the breakpoints
4639 set by that command. This applies to breakpoints set by
4640 @code{rbreak}, and also applies when a single @code{break} command
4641 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4645 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4646 disabled within a @var{command-list}.
4648 You can use breakpoint commands to start your program up again. Simply
4649 use the @code{continue} command, or @code{step}, or any other command
4650 that resumes execution.
4652 Any other commands in the command list, after a command that resumes
4653 execution, are ignored. This is because any time you resume execution
4654 (even with a simple @code{next} or @code{step}), you may encounter
4655 another breakpoint---which could have its own command list, leading to
4656 ambiguities about which list to execute.
4659 If the first command you specify in a command list is @code{silent}, the
4660 usual message about stopping at a breakpoint is not printed. This may
4661 be desirable for breakpoints that are to print a specific message and
4662 then continue. If none of the remaining commands print anything, you
4663 see no sign that the breakpoint was reached. @code{silent} is
4664 meaningful only at the beginning of a breakpoint command list.
4666 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4667 print precisely controlled output, and are often useful in silent
4668 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4670 For example, here is how you could use breakpoint commands to print the
4671 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4677 printf "x is %d\n",x
4682 One application for breakpoint commands is to compensate for one bug so
4683 you can test for another. Put a breakpoint just after the erroneous line
4684 of code, give it a condition to detect the case in which something
4685 erroneous has been done, and give it commands to assign correct values
4686 to any variables that need them. End with the @code{continue} command
4687 so that your program does not stop, and start with the @code{silent}
4688 command so that no output is produced. Here is an example:
4699 @node Dynamic Printf
4700 @subsection Dynamic Printf
4702 @cindex dynamic printf
4704 The dynamic printf command @code{dprintf} combines a breakpoint with
4705 formatted printing of your program's data to give you the effect of
4706 inserting @code{printf} calls into your program on-the-fly, without
4707 having to recompile it.
4709 In its most basic form, the output goes to the GDB console. However,
4710 you can set the variable @code{dprintf-style} for alternate handling.
4711 For instance, you can ask to format the output by calling your
4712 program's @code{printf} function. This has the advantage that the
4713 characters go to the program's output device, so they can recorded in
4714 redirects to files and so forth.
4716 If you are doing remote debugging with a stub or agent, you can also
4717 ask to have the printf handled by the remote agent. In addition to
4718 ensuring that the output goes to the remote program's device along
4719 with any other output the program might produce, you can also ask that
4720 the dprintf remain active even after disconnecting from the remote
4721 target. Using the stub/agent is also more efficient, as it can do
4722 everything without needing to communicate with @value{GDBN}.
4726 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4727 Whenever execution reaches @var{location}, print the values of one or
4728 more @var{expressions} under the control of the string @var{template}.
4729 To print several values, separate them with commas.
4731 @item set dprintf-style @var{style}
4732 Set the dprintf output to be handled in one of several different
4733 styles enumerated below. A change of style affects all existing
4734 dynamic printfs immediately. (If you need individual control over the
4735 print commands, simply define normal breakpoints with
4736 explicitly-supplied command lists.)
4739 @kindex dprintf-style gdb
4740 Handle the output using the @value{GDBN} @code{printf} command.
4743 @kindex dprintf-style call
4744 Handle the output by calling a function in your program (normally
4748 @kindex dprintf-style agent
4749 Have the remote debugging agent (such as @code{gdbserver}) handle
4750 the output itself. This style is only available for agents that
4751 support running commands on the target.
4753 @item set dprintf-function @var{function}
4754 Set the function to call if the dprintf style is @code{call}. By
4755 default its value is @code{printf}. You may set it to any expression.
4756 that @value{GDBN} can evaluate to a function, as per the @code{call}
4759 @item set dprintf-channel @var{channel}
4760 Set a ``channel'' for dprintf. If set to a non-empty value,
4761 @value{GDBN} will evaluate it as an expression and pass the result as
4762 a first argument to the @code{dprintf-function}, in the manner of
4763 @code{fprintf} and similar functions. Otherwise, the dprintf format
4764 string will be the first argument, in the manner of @code{printf}.
4766 As an example, if you wanted @code{dprintf} output to go to a logfile
4767 that is a standard I/O stream assigned to the variable @code{mylog},
4768 you could do the following:
4771 (gdb) set dprintf-style call
4772 (gdb) set dprintf-function fprintf
4773 (gdb) set dprintf-channel mylog
4774 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4775 Dprintf 1 at 0x123456: file main.c, line 25.
4777 1 dprintf keep y 0x00123456 in main at main.c:25
4778 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4783 Note that the @code{info break} displays the dynamic printf commands
4784 as normal breakpoint commands; you can thus easily see the effect of
4785 the variable settings.
4787 @item set disconnected-dprintf on
4788 @itemx set disconnected-dprintf off
4789 @kindex set disconnected-dprintf
4790 Choose whether @code{dprintf} commands should continue to run if
4791 @value{GDBN} has disconnected from the target. This only applies
4792 if the @code{dprintf-style} is @code{agent}.
4794 @item show disconnected-dprintf off
4795 @kindex show disconnected-dprintf
4796 Show the current choice for disconnected @code{dprintf}.
4800 @value{GDBN} does not check the validity of function and channel,
4801 relying on you to supply values that are meaningful for the contexts
4802 in which they are being used. For instance, the function and channel
4803 may be the values of local variables, but if that is the case, then
4804 all enabled dynamic prints must be at locations within the scope of
4805 those locals. If evaluation fails, @value{GDBN} will report an error.
4807 @node Save Breakpoints
4808 @subsection How to save breakpoints to a file
4810 To save breakpoint definitions to a file use the @w{@code{save
4811 breakpoints}} command.
4814 @kindex save breakpoints
4815 @cindex save breakpoints to a file for future sessions
4816 @item save breakpoints [@var{filename}]
4817 This command saves all current breakpoint definitions together with
4818 their commands and ignore counts, into a file @file{@var{filename}}
4819 suitable for use in a later debugging session. This includes all
4820 types of breakpoints (breakpoints, watchpoints, catchpoints,
4821 tracepoints). To read the saved breakpoint definitions, use the
4822 @code{source} command (@pxref{Command Files}). Note that watchpoints
4823 with expressions involving local variables may fail to be recreated
4824 because it may not be possible to access the context where the
4825 watchpoint is valid anymore. Because the saved breakpoint definitions
4826 are simply a sequence of @value{GDBN} commands that recreate the
4827 breakpoints, you can edit the file in your favorite editing program,
4828 and remove the breakpoint definitions you're not interested in, or
4829 that can no longer be recreated.
4832 @node Static Probe Points
4833 @subsection Static Probe Points
4835 @cindex static probe point, SystemTap
4836 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4837 for Statically Defined Tracing, and the probes are designed to have a tiny
4838 runtime code and data footprint, and no dynamic relocations. They are
4839 usable from assembly, C and C@t{++} languages. See
4840 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4841 for a good reference on how the @acronym{SDT} probes are implemented.
4843 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4844 @acronym{SDT} probes are supported on ELF-compatible systems. See
4845 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4846 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4847 in your applications.
4849 @cindex semaphores on static probe points
4850 Some probes have an associated semaphore variable; for instance, this
4851 happens automatically if you defined your probe using a DTrace-style
4852 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4853 automatically enable it when you specify a breakpoint using the
4854 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4855 location by some other method (e.g., @code{break file:line}), then
4856 @value{GDBN} will not automatically set the semaphore.
4858 You can examine the available static static probes using @code{info
4859 probes}, with optional arguments:
4863 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4864 If given, @var{provider} is a regular expression used to match against provider
4865 names when selecting which probes to list. If omitted, probes by all
4866 probes from all providers are listed.
4868 If given, @var{name} is a regular expression to match against probe names
4869 when selecting which probes to list. If omitted, probe names are not
4870 considered when deciding whether to display them.
4872 If given, @var{objfile} is a regular expression used to select which
4873 object files (executable or shared libraries) to examine. If not
4874 given, all object files are considered.
4876 @item info probes all
4877 List the available static probes, from all types.
4880 @vindex $_probe_arg@r{, convenience variable}
4881 A probe may specify up to twelve arguments. These are available at the
4882 point at which the probe is defined---that is, when the current PC is
4883 at the probe's location. The arguments are available using the
4884 convenience variables (@pxref{Convenience Vars})
4885 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4886 an integer of the appropriate size; types are not preserved. The
4887 convenience variable @code{$_probe_argc} holds the number of arguments
4888 at the current probe point.
4890 These variables are always available, but attempts to access them at
4891 any location other than a probe point will cause @value{GDBN} to give
4895 @c @ifclear BARETARGET
4896 @node Error in Breakpoints
4897 @subsection ``Cannot insert breakpoints''
4899 If you request too many active hardware-assisted breakpoints and
4900 watchpoints, you will see this error message:
4902 @c FIXME: the precise wording of this message may change; the relevant
4903 @c source change is not committed yet (Sep 3, 1999).
4905 Stopped; cannot insert breakpoints.
4906 You may have requested too many hardware breakpoints and watchpoints.
4910 This message is printed when you attempt to resume the program, since
4911 only then @value{GDBN} knows exactly how many hardware breakpoints and
4912 watchpoints it needs to insert.
4914 When this message is printed, you need to disable or remove some of the
4915 hardware-assisted breakpoints and watchpoints, and then continue.
4917 @node Breakpoint-related Warnings
4918 @subsection ``Breakpoint address adjusted...''
4919 @cindex breakpoint address adjusted
4921 Some processor architectures place constraints on the addresses at
4922 which breakpoints may be placed. For architectures thus constrained,
4923 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4924 with the constraints dictated by the architecture.
4926 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4927 a VLIW architecture in which a number of RISC-like instructions may be
4928 bundled together for parallel execution. The FR-V architecture
4929 constrains the location of a breakpoint instruction within such a
4930 bundle to the instruction with the lowest address. @value{GDBN}
4931 honors this constraint by adjusting a breakpoint's address to the
4932 first in the bundle.
4934 It is not uncommon for optimized code to have bundles which contain
4935 instructions from different source statements, thus it may happen that
4936 a breakpoint's address will be adjusted from one source statement to
4937 another. Since this adjustment may significantly alter @value{GDBN}'s
4938 breakpoint related behavior from what the user expects, a warning is
4939 printed when the breakpoint is first set and also when the breakpoint
4942 A warning like the one below is printed when setting a breakpoint
4943 that's been subject to address adjustment:
4946 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4949 Such warnings are printed both for user settable and @value{GDBN}'s
4950 internal breakpoints. If you see one of these warnings, you should
4951 verify that a breakpoint set at the adjusted address will have the
4952 desired affect. If not, the breakpoint in question may be removed and
4953 other breakpoints may be set which will have the desired behavior.
4954 E.g., it may be sufficient to place the breakpoint at a later
4955 instruction. A conditional breakpoint may also be useful in some
4956 cases to prevent the breakpoint from triggering too often.
4958 @value{GDBN} will also issue a warning when stopping at one of these
4959 adjusted breakpoints:
4962 warning: Breakpoint 1 address previously adjusted from 0x00010414
4966 When this warning is encountered, it may be too late to take remedial
4967 action except in cases where the breakpoint is hit earlier or more
4968 frequently than expected.
4970 @node Continuing and Stepping
4971 @section Continuing and Stepping
4975 @cindex resuming execution
4976 @dfn{Continuing} means resuming program execution until your program
4977 completes normally. In contrast, @dfn{stepping} means executing just
4978 one more ``step'' of your program, where ``step'' may mean either one
4979 line of source code, or one machine instruction (depending on what
4980 particular command you use). Either when continuing or when stepping,
4981 your program may stop even sooner, due to a breakpoint or a signal. (If
4982 it stops due to a signal, you may want to use @code{handle}, or use
4983 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4987 @kindex c @r{(@code{continue})}
4988 @kindex fg @r{(resume foreground execution)}
4989 @item continue @r{[}@var{ignore-count}@r{]}
4990 @itemx c @r{[}@var{ignore-count}@r{]}
4991 @itemx fg @r{[}@var{ignore-count}@r{]}
4992 Resume program execution, at the address where your program last stopped;
4993 any breakpoints set at that address are bypassed. The optional argument
4994 @var{ignore-count} allows you to specify a further number of times to
4995 ignore a breakpoint at this location; its effect is like that of
4996 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4998 The argument @var{ignore-count} is meaningful only when your program
4999 stopped due to a breakpoint. At other times, the argument to
5000 @code{continue} is ignored.
5002 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5003 debugged program is deemed to be the foreground program) are provided
5004 purely for convenience, and have exactly the same behavior as
5008 To resume execution at a different place, you can use @code{return}
5009 (@pxref{Returning, ,Returning from a Function}) to go back to the
5010 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5011 Different Address}) to go to an arbitrary location in your program.
5013 A typical technique for using stepping is to set a breakpoint
5014 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5015 beginning of the function or the section of your program where a problem
5016 is believed to lie, run your program until it stops at that breakpoint,
5017 and then step through the suspect area, examining the variables that are
5018 interesting, until you see the problem happen.
5022 @kindex s @r{(@code{step})}
5024 Continue running your program until control reaches a different source
5025 line, then stop it and return control to @value{GDBN}. This command is
5026 abbreviated @code{s}.
5029 @c "without debugging information" is imprecise; actually "without line
5030 @c numbers in the debugging information". (gcc -g1 has debugging info but
5031 @c not line numbers). But it seems complex to try to make that
5032 @c distinction here.
5033 @emph{Warning:} If you use the @code{step} command while control is
5034 within a function that was compiled without debugging information,
5035 execution proceeds until control reaches a function that does have
5036 debugging information. Likewise, it will not step into a function which
5037 is compiled without debugging information. To step through functions
5038 without debugging information, use the @code{stepi} command, described
5042 The @code{step} command only stops at the first instruction of a source
5043 line. This prevents the multiple stops that could otherwise occur in
5044 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5045 to stop if a function that has debugging information is called within
5046 the line. In other words, @code{step} @emph{steps inside} any functions
5047 called within the line.
5049 Also, the @code{step} command only enters a function if there is line
5050 number information for the function. Otherwise it acts like the
5051 @code{next} command. This avoids problems when using @code{cc -gl}
5052 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5053 was any debugging information about the routine.
5055 @item step @var{count}
5056 Continue running as in @code{step}, but do so @var{count} times. If a
5057 breakpoint is reached, or a signal not related to stepping occurs before
5058 @var{count} steps, stepping stops right away.
5061 @kindex n @r{(@code{next})}
5062 @item next @r{[}@var{count}@r{]}
5063 Continue to the next source line in the current (innermost) stack frame.
5064 This is similar to @code{step}, but function calls that appear within
5065 the line of code are executed without stopping. Execution stops when
5066 control reaches a different line of code at the original stack level
5067 that was executing when you gave the @code{next} command. This command
5068 is abbreviated @code{n}.
5070 An argument @var{count} is a repeat count, as for @code{step}.
5073 @c FIX ME!! Do we delete this, or is there a way it fits in with
5074 @c the following paragraph? --- Vctoria
5076 @c @code{next} within a function that lacks debugging information acts like
5077 @c @code{step}, but any function calls appearing within the code of the
5078 @c function are executed without stopping.
5080 The @code{next} command only stops at the first instruction of a
5081 source line. This prevents multiple stops that could otherwise occur in
5082 @code{switch} statements, @code{for} loops, etc.
5084 @kindex set step-mode
5086 @cindex functions without line info, and stepping
5087 @cindex stepping into functions with no line info
5088 @itemx set step-mode on
5089 The @code{set step-mode on} command causes the @code{step} command to
5090 stop at the first instruction of a function which contains no debug line
5091 information rather than stepping over it.
5093 This is useful in cases where you may be interested in inspecting the
5094 machine instructions of a function which has no symbolic info and do not
5095 want @value{GDBN} to automatically skip over this function.
5097 @item set step-mode off
5098 Causes the @code{step} command to step over any functions which contains no
5099 debug information. This is the default.
5101 @item show step-mode
5102 Show whether @value{GDBN} will stop in or step over functions without
5103 source line debug information.
5106 @kindex fin @r{(@code{finish})}
5108 Continue running until just after function in the selected stack frame
5109 returns. Print the returned value (if any). This command can be
5110 abbreviated as @code{fin}.
5112 Contrast this with the @code{return} command (@pxref{Returning,
5113 ,Returning from a Function}).
5116 @kindex u @r{(@code{until})}
5117 @cindex run until specified location
5120 Continue running until a source line past the current line, in the
5121 current stack frame, is reached. This command is used to avoid single
5122 stepping through a loop more than once. It is like the @code{next}
5123 command, except that when @code{until} encounters a jump, it
5124 automatically continues execution until the program counter is greater
5125 than the address of the jump.
5127 This means that when you reach the end of a loop after single stepping
5128 though it, @code{until} makes your program continue execution until it
5129 exits the loop. In contrast, a @code{next} command at the end of a loop
5130 simply steps back to the beginning of the loop, which forces you to step
5131 through the next iteration.
5133 @code{until} always stops your program if it attempts to exit the current
5136 @code{until} may produce somewhat counterintuitive results if the order
5137 of machine code does not match the order of the source lines. For
5138 example, in the following excerpt from a debugging session, the @code{f}
5139 (@code{frame}) command shows that execution is stopped at line
5140 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5144 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5146 (@value{GDBP}) until
5147 195 for ( ; argc > 0; NEXTARG) @{
5150 This happened because, for execution efficiency, the compiler had
5151 generated code for the loop closure test at the end, rather than the
5152 start, of the loop---even though the test in a C @code{for}-loop is
5153 written before the body of the loop. The @code{until} command appeared
5154 to step back to the beginning of the loop when it advanced to this
5155 expression; however, it has not really gone to an earlier
5156 statement---not in terms of the actual machine code.
5158 @code{until} with no argument works by means of single
5159 instruction stepping, and hence is slower than @code{until} with an
5162 @item until @var{location}
5163 @itemx u @var{location}
5164 Continue running your program until either the specified location is
5165 reached, or the current stack frame returns. @var{location} is any of
5166 the forms described in @ref{Specify Location}.
5167 This form of the command uses temporary breakpoints, and
5168 hence is quicker than @code{until} without an argument. The specified
5169 location is actually reached only if it is in the current frame. This
5170 implies that @code{until} can be used to skip over recursive function
5171 invocations. For instance in the code below, if the current location is
5172 line @code{96}, issuing @code{until 99} will execute the program up to
5173 line @code{99} in the same invocation of factorial, i.e., after the inner
5174 invocations have returned.
5177 94 int factorial (int value)
5179 96 if (value > 1) @{
5180 97 value *= factorial (value - 1);
5187 @kindex advance @var{location}
5188 @item advance @var{location}
5189 Continue running the program up to the given @var{location}. An argument is
5190 required, which should be of one of the forms described in
5191 @ref{Specify Location}.
5192 Execution will also stop upon exit from the current stack
5193 frame. This command is similar to @code{until}, but @code{advance} will
5194 not skip over recursive function calls, and the target location doesn't
5195 have to be in the same frame as the current one.
5199 @kindex si @r{(@code{stepi})}
5201 @itemx stepi @var{arg}
5203 Execute one machine instruction, then stop and return to the debugger.
5205 It is often useful to do @samp{display/i $pc} when stepping by machine
5206 instructions. This makes @value{GDBN} automatically display the next
5207 instruction to be executed, each time your program stops. @xref{Auto
5208 Display,, Automatic Display}.
5210 An argument is a repeat count, as in @code{step}.
5214 @kindex ni @r{(@code{nexti})}
5216 @itemx nexti @var{arg}
5218 Execute one machine instruction, but if it is a function call,
5219 proceed until the function returns.
5221 An argument is a repeat count, as in @code{next}.
5224 @node Skipping Over Functions and Files
5225 @section Skipping Over Functions and Files
5226 @cindex skipping over functions and files
5228 The program you are debugging may contain some functions which are
5229 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5230 skip a function or all functions in a file when stepping.
5232 For example, consider the following C function:
5243 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5244 are not interested in stepping through @code{boring}. If you run @code{step}
5245 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5246 step over both @code{foo} and @code{boring}!
5248 One solution is to @code{step} into @code{boring} and use the @code{finish}
5249 command to immediately exit it. But this can become tedious if @code{boring}
5250 is called from many places.
5252 A more flexible solution is to execute @kbd{skip boring}. This instructs
5253 @value{GDBN} never to step into @code{boring}. Now when you execute
5254 @code{step} at line 103, you'll step over @code{boring} and directly into
5257 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5258 example, @code{skip file boring.c}.
5261 @kindex skip function
5262 @item skip @r{[}@var{linespec}@r{]}
5263 @itemx skip function @r{[}@var{linespec}@r{]}
5264 After running this command, the function named by @var{linespec} or the
5265 function containing the line named by @var{linespec} will be skipped over when
5266 stepping. @xref{Specify Location}.
5268 If you do not specify @var{linespec}, the function you're currently debugging
5271 (If you have a function called @code{file} that you want to skip, use
5272 @kbd{skip function file}.)
5275 @item skip file @r{[}@var{filename}@r{]}
5276 After running this command, any function whose source lives in @var{filename}
5277 will be skipped over when stepping.
5279 If you do not specify @var{filename}, functions whose source lives in the file
5280 you're currently debugging will be skipped.
5283 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5284 These are the commands for managing your list of skips:
5288 @item info skip @r{[}@var{range}@r{]}
5289 Print details about the specified skip(s). If @var{range} is not specified,
5290 print a table with details about all functions and files marked for skipping.
5291 @code{info skip} prints the following information about each skip:
5295 A number identifying this skip.
5297 The type of this skip, either @samp{function} or @samp{file}.
5298 @item Enabled or Disabled
5299 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5301 For function skips, this column indicates the address in memory of the function
5302 being skipped. If you've set a function skip on a function which has not yet
5303 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5304 which has the function is loaded, @code{info skip} will show the function's
5307 For file skips, this field contains the filename being skipped. For functions
5308 skips, this field contains the function name and its line number in the file
5309 where it is defined.
5313 @item skip delete @r{[}@var{range}@r{]}
5314 Delete the specified skip(s). If @var{range} is not specified, delete all
5318 @item skip enable @r{[}@var{range}@r{]}
5319 Enable the specified skip(s). If @var{range} is not specified, enable all
5322 @kindex skip disable
5323 @item skip disable @r{[}@var{range}@r{]}
5324 Disable the specified skip(s). If @var{range} is not specified, disable all
5333 A signal is an asynchronous event that can happen in a program. The
5334 operating system defines the possible kinds of signals, and gives each
5335 kind a name and a number. For example, in Unix @code{SIGINT} is the
5336 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5337 @code{SIGSEGV} is the signal a program gets from referencing a place in
5338 memory far away from all the areas in use; @code{SIGALRM} occurs when
5339 the alarm clock timer goes off (which happens only if your program has
5340 requested an alarm).
5342 @cindex fatal signals
5343 Some signals, including @code{SIGALRM}, are a normal part of the
5344 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5345 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5346 program has not specified in advance some other way to handle the signal.
5347 @code{SIGINT} does not indicate an error in your program, but it is normally
5348 fatal so it can carry out the purpose of the interrupt: to kill the program.
5350 @value{GDBN} has the ability to detect any occurrence of a signal in your
5351 program. You can tell @value{GDBN} in advance what to do for each kind of
5354 @cindex handling signals
5355 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5356 @code{SIGALRM} be silently passed to your program
5357 (so as not to interfere with their role in the program's functioning)
5358 but to stop your program immediately whenever an error signal happens.
5359 You can change these settings with the @code{handle} command.
5362 @kindex info signals
5366 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5367 handle each one. You can use this to see the signal numbers of all
5368 the defined types of signals.
5370 @item info signals @var{sig}
5371 Similar, but print information only about the specified signal number.
5373 @code{info handle} is an alias for @code{info signals}.
5375 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5376 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5377 for details about this command.
5380 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5381 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5382 can be the number of a signal or its name (with or without the
5383 @samp{SIG} at the beginning); a list of signal numbers of the form
5384 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5385 known signals. Optional arguments @var{keywords}, described below,
5386 say what change to make.
5390 The keywords allowed by the @code{handle} command can be abbreviated.
5391 Their full names are:
5395 @value{GDBN} should not stop your program when this signal happens. It may
5396 still print a message telling you that the signal has come in.
5399 @value{GDBN} should stop your program when this signal happens. This implies
5400 the @code{print} keyword as well.
5403 @value{GDBN} should print a message when this signal happens.
5406 @value{GDBN} should not mention the occurrence of the signal at all. This
5407 implies the @code{nostop} keyword as well.
5411 @value{GDBN} should allow your program to see this signal; your program
5412 can handle the signal, or else it may terminate if the signal is fatal
5413 and not handled. @code{pass} and @code{noignore} are synonyms.
5417 @value{GDBN} should not allow your program to see this signal.
5418 @code{nopass} and @code{ignore} are synonyms.
5422 When a signal stops your program, the signal is not visible to the
5424 continue. Your program sees the signal then, if @code{pass} is in
5425 effect for the signal in question @emph{at that time}. In other words,
5426 after @value{GDBN} reports a signal, you can use the @code{handle}
5427 command with @code{pass} or @code{nopass} to control whether your
5428 program sees that signal when you continue.
5430 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5431 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5432 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5435 You can also use the @code{signal} command to prevent your program from
5436 seeing a signal, or cause it to see a signal it normally would not see,
5437 or to give it any signal at any time. For example, if your program stopped
5438 due to some sort of memory reference error, you might store correct
5439 values into the erroneous variables and continue, hoping to see more
5440 execution; but your program would probably terminate immediately as
5441 a result of the fatal signal once it saw the signal. To prevent this,
5442 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5445 @cindex extra signal information
5446 @anchor{extra signal information}
5448 On some targets, @value{GDBN} can inspect extra signal information
5449 associated with the intercepted signal, before it is actually
5450 delivered to the program being debugged. This information is exported
5451 by the convenience variable @code{$_siginfo}, and consists of data
5452 that is passed by the kernel to the signal handler at the time of the
5453 receipt of a signal. The data type of the information itself is
5454 target dependent. You can see the data type using the @code{ptype
5455 $_siginfo} command. On Unix systems, it typically corresponds to the
5456 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5459 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5460 referenced address that raised a segmentation fault.
5464 (@value{GDBP}) continue
5465 Program received signal SIGSEGV, Segmentation fault.
5466 0x0000000000400766 in main ()
5468 (@value{GDBP}) ptype $_siginfo
5475 struct @{...@} _kill;
5476 struct @{...@} _timer;
5478 struct @{...@} _sigchld;
5479 struct @{...@} _sigfault;
5480 struct @{...@} _sigpoll;
5483 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5487 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5488 $1 = (void *) 0x7ffff7ff7000
5492 Depending on target support, @code{$_siginfo} may also be writable.
5495 @section Stopping and Starting Multi-thread Programs
5497 @cindex stopped threads
5498 @cindex threads, stopped
5500 @cindex continuing threads
5501 @cindex threads, continuing
5503 @value{GDBN} supports debugging programs with multiple threads
5504 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5505 are two modes of controlling execution of your program within the
5506 debugger. In the default mode, referred to as @dfn{all-stop mode},
5507 when any thread in your program stops (for example, at a breakpoint
5508 or while being stepped), all other threads in the program are also stopped by
5509 @value{GDBN}. On some targets, @value{GDBN} also supports
5510 @dfn{non-stop mode}, in which other threads can continue to run freely while
5511 you examine the stopped thread in the debugger.
5514 * All-Stop Mode:: All threads stop when GDB takes control
5515 * Non-Stop Mode:: Other threads continue to execute
5516 * Background Execution:: Running your program asynchronously
5517 * Thread-Specific Breakpoints:: Controlling breakpoints
5518 * Interrupted System Calls:: GDB may interfere with system calls
5519 * Observer Mode:: GDB does not alter program behavior
5523 @subsection All-Stop Mode
5525 @cindex all-stop mode
5527 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5528 @emph{all} threads of execution stop, not just the current thread. This
5529 allows you to examine the overall state of the program, including
5530 switching between threads, without worrying that things may change
5533 Conversely, whenever you restart the program, @emph{all} threads start
5534 executing. @emph{This is true even when single-stepping} with commands
5535 like @code{step} or @code{next}.
5537 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5538 Since thread scheduling is up to your debugging target's operating
5539 system (not controlled by @value{GDBN}), other threads may
5540 execute more than one statement while the current thread completes a
5541 single step. Moreover, in general other threads stop in the middle of a
5542 statement, rather than at a clean statement boundary, when the program
5545 You might even find your program stopped in another thread after
5546 continuing or even single-stepping. This happens whenever some other
5547 thread runs into a breakpoint, a signal, or an exception before the
5548 first thread completes whatever you requested.
5550 @cindex automatic thread selection
5551 @cindex switching threads automatically
5552 @cindex threads, automatic switching
5553 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5554 signal, it automatically selects the thread where that breakpoint or
5555 signal happened. @value{GDBN} alerts you to the context switch with a
5556 message such as @samp{[Switching to Thread @var{n}]} to identify the
5559 On some OSes, you can modify @value{GDBN}'s default behavior by
5560 locking the OS scheduler to allow only a single thread to run.
5563 @item set scheduler-locking @var{mode}
5564 @cindex scheduler locking mode
5565 @cindex lock scheduler
5566 Set the scheduler locking mode. If it is @code{off}, then there is no
5567 locking and any thread may run at any time. If @code{on}, then only the
5568 current thread may run when the inferior is resumed. The @code{step}
5569 mode optimizes for single-stepping; it prevents other threads
5570 from preempting the current thread while you are stepping, so that
5571 the focus of debugging does not change unexpectedly.
5572 Other threads only rarely (or never) get a chance to run
5573 when you step. They are more likely to run when you @samp{next} over a
5574 function call, and they are completely free to run when you use commands
5575 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5576 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5577 the current thread away from the thread that you are debugging.
5579 @item show scheduler-locking
5580 Display the current scheduler locking mode.
5583 @cindex resume threads of multiple processes simultaneously
5584 By default, when you issue one of the execution commands such as
5585 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5586 threads of the current inferior to run. For example, if @value{GDBN}
5587 is attached to two inferiors, each with two threads, the
5588 @code{continue} command resumes only the two threads of the current
5589 inferior. This is useful, for example, when you debug a program that
5590 forks and you want to hold the parent stopped (so that, for instance,
5591 it doesn't run to exit), while you debug the child. In other
5592 situations, you may not be interested in inspecting the current state
5593 of any of the processes @value{GDBN} is attached to, and you may want
5594 to resume them all until some breakpoint is hit. In the latter case,
5595 you can instruct @value{GDBN} to allow all threads of all the
5596 inferiors to run with the @w{@code{set schedule-multiple}} command.
5599 @kindex set schedule-multiple
5600 @item set schedule-multiple
5601 Set the mode for allowing threads of multiple processes to be resumed
5602 when an execution command is issued. When @code{on}, all threads of
5603 all processes are allowed to run. When @code{off}, only the threads
5604 of the current process are resumed. The default is @code{off}. The
5605 @code{scheduler-locking} mode takes precedence when set to @code{on},
5606 or while you are stepping and set to @code{step}.
5608 @item show schedule-multiple
5609 Display the current mode for resuming the execution of threads of
5614 @subsection Non-Stop Mode
5616 @cindex non-stop mode
5618 @c This section is really only a place-holder, and needs to be expanded
5619 @c with more details.
5621 For some multi-threaded targets, @value{GDBN} supports an optional
5622 mode of operation in which you can examine stopped program threads in
5623 the debugger while other threads continue to execute freely. This
5624 minimizes intrusion when debugging live systems, such as programs
5625 where some threads have real-time constraints or must continue to
5626 respond to external events. This is referred to as @dfn{non-stop} mode.
5628 In non-stop mode, when a thread stops to report a debugging event,
5629 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5630 threads as well, in contrast to the all-stop mode behavior. Additionally,
5631 execution commands such as @code{continue} and @code{step} apply by default
5632 only to the current thread in non-stop mode, rather than all threads as
5633 in all-stop mode. This allows you to control threads explicitly in
5634 ways that are not possible in all-stop mode --- for example, stepping
5635 one thread while allowing others to run freely, stepping
5636 one thread while holding all others stopped, or stepping several threads
5637 independently and simultaneously.
5639 To enter non-stop mode, use this sequence of commands before you run
5640 or attach to your program:
5643 # Enable the async interface.
5646 # If using the CLI, pagination breaks non-stop.
5649 # Finally, turn it on!
5653 You can use these commands to manipulate the non-stop mode setting:
5656 @kindex set non-stop
5657 @item set non-stop on
5658 Enable selection of non-stop mode.
5659 @item set non-stop off
5660 Disable selection of non-stop mode.
5661 @kindex show non-stop
5663 Show the current non-stop enablement setting.
5666 Note these commands only reflect whether non-stop mode is enabled,
5667 not whether the currently-executing program is being run in non-stop mode.
5668 In particular, the @code{set non-stop} preference is only consulted when
5669 @value{GDBN} starts or connects to the target program, and it is generally
5670 not possible to switch modes once debugging has started. Furthermore,
5671 since not all targets support non-stop mode, even when you have enabled
5672 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5675 In non-stop mode, all execution commands apply only to the current thread
5676 by default. That is, @code{continue} only continues one thread.
5677 To continue all threads, issue @code{continue -a} or @code{c -a}.
5679 You can use @value{GDBN}'s background execution commands
5680 (@pxref{Background Execution}) to run some threads in the background
5681 while you continue to examine or step others from @value{GDBN}.
5682 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5683 always executed asynchronously in non-stop mode.
5685 Suspending execution is done with the @code{interrupt} command when
5686 running in the background, or @kbd{Ctrl-c} during foreground execution.
5687 In all-stop mode, this stops the whole process;
5688 but in non-stop mode the interrupt applies only to the current thread.
5689 To stop the whole program, use @code{interrupt -a}.
5691 Other execution commands do not currently support the @code{-a} option.
5693 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5694 that thread current, as it does in all-stop mode. This is because the
5695 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5696 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5697 changed to a different thread just as you entered a command to operate on the
5698 previously current thread.
5700 @node Background Execution
5701 @subsection Background Execution
5703 @cindex foreground execution
5704 @cindex background execution
5705 @cindex asynchronous execution
5706 @cindex execution, foreground, background and asynchronous
5708 @value{GDBN}'s execution commands have two variants: the normal
5709 foreground (synchronous) behavior, and a background
5710 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5711 the program to report that some thread has stopped before prompting for
5712 another command. In background execution, @value{GDBN} immediately gives
5713 a command prompt so that you can issue other commands while your program runs.
5715 You need to explicitly enable asynchronous mode before you can use
5716 background execution commands. You can use these commands to
5717 manipulate the asynchronous mode setting:
5720 @kindex set target-async
5721 @item set target-async on
5722 Enable asynchronous mode.
5723 @item set target-async off
5724 Disable asynchronous mode.
5725 @kindex show target-async
5726 @item show target-async
5727 Show the current target-async setting.
5730 If the target doesn't support async mode, @value{GDBN} issues an error
5731 message if you attempt to use the background execution commands.
5733 To specify background execution, add a @code{&} to the command. For example,
5734 the background form of the @code{continue} command is @code{continue&}, or
5735 just @code{c&}. The execution commands that accept background execution
5741 @xref{Starting, , Starting your Program}.
5745 @xref{Attach, , Debugging an Already-running Process}.
5749 @xref{Continuing and Stepping, step}.
5753 @xref{Continuing and Stepping, stepi}.
5757 @xref{Continuing and Stepping, next}.
5761 @xref{Continuing and Stepping, nexti}.
5765 @xref{Continuing and Stepping, continue}.
5769 @xref{Continuing and Stepping, finish}.
5773 @xref{Continuing and Stepping, until}.
5777 Background execution is especially useful in conjunction with non-stop
5778 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5779 However, you can also use these commands in the normal all-stop mode with
5780 the restriction that you cannot issue another execution command until the
5781 previous one finishes. Examples of commands that are valid in all-stop
5782 mode while the program is running include @code{help} and @code{info break}.
5784 You can interrupt your program while it is running in the background by
5785 using the @code{interrupt} command.
5792 Suspend execution of the running program. In all-stop mode,
5793 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5794 only the current thread. To stop the whole program in non-stop mode,
5795 use @code{interrupt -a}.
5798 @node Thread-Specific Breakpoints
5799 @subsection Thread-Specific Breakpoints
5801 When your program has multiple threads (@pxref{Threads,, Debugging
5802 Programs with Multiple Threads}), you can choose whether to set
5803 breakpoints on all threads, or on a particular thread.
5806 @cindex breakpoints and threads
5807 @cindex thread breakpoints
5808 @kindex break @dots{} thread @var{threadno}
5809 @item break @var{linespec} thread @var{threadno}
5810 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5811 @var{linespec} specifies source lines; there are several ways of
5812 writing them (@pxref{Specify Location}), but the effect is always to
5813 specify some source line.
5815 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5816 to specify that you only want @value{GDBN} to stop the program when a
5817 particular thread reaches this breakpoint. @var{threadno} is one of the
5818 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5819 column of the @samp{info threads} display.
5821 If you do not specify @samp{thread @var{threadno}} when you set a
5822 breakpoint, the breakpoint applies to @emph{all} threads of your
5825 You can use the @code{thread} qualifier on conditional breakpoints as
5826 well; in this case, place @samp{thread @var{threadno}} before or
5827 after the breakpoint condition, like this:
5830 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5835 @node Interrupted System Calls
5836 @subsection Interrupted System Calls
5838 @cindex thread breakpoints and system calls
5839 @cindex system calls and thread breakpoints
5840 @cindex premature return from system calls
5841 There is an unfortunate side effect when using @value{GDBN} to debug
5842 multi-threaded programs. If one thread stops for a
5843 breakpoint, or for some other reason, and another thread is blocked in a
5844 system call, then the system call may return prematurely. This is a
5845 consequence of the interaction between multiple threads and the signals
5846 that @value{GDBN} uses to implement breakpoints and other events that
5849 To handle this problem, your program should check the return value of
5850 each system call and react appropriately. This is good programming
5853 For example, do not write code like this:
5859 The call to @code{sleep} will return early if a different thread stops
5860 at a breakpoint or for some other reason.
5862 Instead, write this:
5867 unslept = sleep (unslept);
5870 A system call is allowed to return early, so the system is still
5871 conforming to its specification. But @value{GDBN} does cause your
5872 multi-threaded program to behave differently than it would without
5875 Also, @value{GDBN} uses internal breakpoints in the thread library to
5876 monitor certain events such as thread creation and thread destruction.
5877 When such an event happens, a system call in another thread may return
5878 prematurely, even though your program does not appear to stop.
5881 @subsection Observer Mode
5883 If you want to build on non-stop mode and observe program behavior
5884 without any chance of disruption by @value{GDBN}, you can set
5885 variables to disable all of the debugger's attempts to modify state,
5886 whether by writing memory, inserting breakpoints, etc. These operate
5887 at a low level, intercepting operations from all commands.
5889 When all of these are set to @code{off}, then @value{GDBN} is said to
5890 be @dfn{observer mode}. As a convenience, the variable
5891 @code{observer} can be set to disable these, plus enable non-stop
5894 Note that @value{GDBN} will not prevent you from making nonsensical
5895 combinations of these settings. For instance, if you have enabled
5896 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5897 then breakpoints that work by writing trap instructions into the code
5898 stream will still not be able to be placed.
5903 @item set observer on
5904 @itemx set observer off
5905 When set to @code{on}, this disables all the permission variables
5906 below (except for @code{insert-fast-tracepoints}), plus enables
5907 non-stop debugging. Setting this to @code{off} switches back to
5908 normal debugging, though remaining in non-stop mode.
5911 Show whether observer mode is on or off.
5913 @kindex may-write-registers
5914 @item set may-write-registers on
5915 @itemx set may-write-registers off
5916 This controls whether @value{GDBN} will attempt to alter the values of
5917 registers, such as with assignment expressions in @code{print}, or the
5918 @code{jump} command. It defaults to @code{on}.
5920 @item show may-write-registers
5921 Show the current permission to write registers.
5923 @kindex may-write-memory
5924 @item set may-write-memory on
5925 @itemx set may-write-memory off
5926 This controls whether @value{GDBN} will attempt to alter the contents
5927 of memory, such as with assignment expressions in @code{print}. It
5928 defaults to @code{on}.
5930 @item show may-write-memory
5931 Show the current permission to write memory.
5933 @kindex may-insert-breakpoints
5934 @item set may-insert-breakpoints on
5935 @itemx set may-insert-breakpoints off
5936 This controls whether @value{GDBN} will attempt to insert breakpoints.
5937 This affects all breakpoints, including internal breakpoints defined
5938 by @value{GDBN}. It defaults to @code{on}.
5940 @item show may-insert-breakpoints
5941 Show the current permission to insert breakpoints.
5943 @kindex may-insert-tracepoints
5944 @item set may-insert-tracepoints on
5945 @itemx set may-insert-tracepoints off
5946 This controls whether @value{GDBN} will attempt to insert (regular)
5947 tracepoints at the beginning of a tracing experiment. It affects only
5948 non-fast tracepoints, fast tracepoints being under the control of
5949 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5951 @item show may-insert-tracepoints
5952 Show the current permission to insert tracepoints.
5954 @kindex may-insert-fast-tracepoints
5955 @item set may-insert-fast-tracepoints on
5956 @itemx set may-insert-fast-tracepoints off
5957 This controls whether @value{GDBN} will attempt to insert fast
5958 tracepoints at the beginning of a tracing experiment. It affects only
5959 fast tracepoints, regular (non-fast) tracepoints being under the
5960 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5962 @item show may-insert-fast-tracepoints
5963 Show the current permission to insert fast tracepoints.
5965 @kindex may-interrupt
5966 @item set may-interrupt on
5967 @itemx set may-interrupt off
5968 This controls whether @value{GDBN} will attempt to interrupt or stop
5969 program execution. When this variable is @code{off}, the
5970 @code{interrupt} command will have no effect, nor will
5971 @kbd{Ctrl-c}. It defaults to @code{on}.
5973 @item show may-interrupt
5974 Show the current permission to interrupt or stop the program.
5978 @node Reverse Execution
5979 @chapter Running programs backward
5980 @cindex reverse execution
5981 @cindex running programs backward
5983 When you are debugging a program, it is not unusual to realize that
5984 you have gone too far, and some event of interest has already happened.
5985 If the target environment supports it, @value{GDBN} can allow you to
5986 ``rewind'' the program by running it backward.
5988 A target environment that supports reverse execution should be able
5989 to ``undo'' the changes in machine state that have taken place as the
5990 program was executing normally. Variables, registers etc.@: should
5991 revert to their previous values. Obviously this requires a great
5992 deal of sophistication on the part of the target environment; not
5993 all target environments can support reverse execution.
5995 When a program is executed in reverse, the instructions that
5996 have most recently been executed are ``un-executed'', in reverse
5997 order. The program counter runs backward, following the previous
5998 thread of execution in reverse. As each instruction is ``un-executed'',
5999 the values of memory and/or registers that were changed by that
6000 instruction are reverted to their previous states. After executing
6001 a piece of source code in reverse, all side effects of that code
6002 should be ``undone'', and all variables should be returned to their
6003 prior values@footnote{
6004 Note that some side effects are easier to undo than others. For instance,
6005 memory and registers are relatively easy, but device I/O is hard. Some
6006 targets may be able undo things like device I/O, and some may not.
6008 The contract between @value{GDBN} and the reverse executing target
6009 requires only that the target do something reasonable when
6010 @value{GDBN} tells it to execute backwards, and then report the
6011 results back to @value{GDBN}. Whatever the target reports back to
6012 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6013 assumes that the memory and registers that the target reports are in a
6014 consistant state, but @value{GDBN} accepts whatever it is given.
6017 If you are debugging in a target environment that supports
6018 reverse execution, @value{GDBN} provides the following commands.
6021 @kindex reverse-continue
6022 @kindex rc @r{(@code{reverse-continue})}
6023 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6024 @itemx rc @r{[}@var{ignore-count}@r{]}
6025 Beginning at the point where your program last stopped, start executing
6026 in reverse. Reverse execution will stop for breakpoints and synchronous
6027 exceptions (signals), just like normal execution. Behavior of
6028 asynchronous signals depends on the target environment.
6030 @kindex reverse-step
6031 @kindex rs @r{(@code{step})}
6032 @item reverse-step @r{[}@var{count}@r{]}
6033 Run the program backward until control reaches the start of a
6034 different source line; then stop it, and return control to @value{GDBN}.
6036 Like the @code{step} command, @code{reverse-step} will only stop
6037 at the beginning of a source line. It ``un-executes'' the previously
6038 executed source line. If the previous source line included calls to
6039 debuggable functions, @code{reverse-step} will step (backward) into
6040 the called function, stopping at the beginning of the @emph{last}
6041 statement in the called function (typically a return statement).
6043 Also, as with the @code{step} command, if non-debuggable functions are
6044 called, @code{reverse-step} will run thru them backward without stopping.
6046 @kindex reverse-stepi
6047 @kindex rsi @r{(@code{reverse-stepi})}
6048 @item reverse-stepi @r{[}@var{count}@r{]}
6049 Reverse-execute one machine instruction. Note that the instruction
6050 to be reverse-executed is @emph{not} the one pointed to by the program
6051 counter, but the instruction executed prior to that one. For instance,
6052 if the last instruction was a jump, @code{reverse-stepi} will take you
6053 back from the destination of the jump to the jump instruction itself.
6055 @kindex reverse-next
6056 @kindex rn @r{(@code{reverse-next})}
6057 @item reverse-next @r{[}@var{count}@r{]}
6058 Run backward to the beginning of the previous line executed in
6059 the current (innermost) stack frame. If the line contains function
6060 calls, they will be ``un-executed'' without stopping. Starting from
6061 the first line of a function, @code{reverse-next} will take you back
6062 to the caller of that function, @emph{before} the function was called,
6063 just as the normal @code{next} command would take you from the last
6064 line of a function back to its return to its caller
6065 @footnote{Unless the code is too heavily optimized.}.
6067 @kindex reverse-nexti
6068 @kindex rni @r{(@code{reverse-nexti})}
6069 @item reverse-nexti @r{[}@var{count}@r{]}
6070 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6071 in reverse, except that called functions are ``un-executed'' atomically.
6072 That is, if the previously executed instruction was a return from
6073 another function, @code{reverse-nexti} will continue to execute
6074 in reverse until the call to that function (from the current stack
6077 @kindex reverse-finish
6078 @item reverse-finish
6079 Just as the @code{finish} command takes you to the point where the
6080 current function returns, @code{reverse-finish} takes you to the point
6081 where it was called. Instead of ending up at the end of the current
6082 function invocation, you end up at the beginning.
6084 @kindex set exec-direction
6085 @item set exec-direction
6086 Set the direction of target execution.
6087 @item set exec-direction reverse
6088 @cindex execute forward or backward in time
6089 @value{GDBN} will perform all execution commands in reverse, until the
6090 exec-direction mode is changed to ``forward''. Affected commands include
6091 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6092 command cannot be used in reverse mode.
6093 @item set exec-direction forward
6094 @value{GDBN} will perform all execution commands in the normal fashion.
6095 This is the default.
6099 @node Process Record and Replay
6100 @chapter Recording Inferior's Execution and Replaying It
6101 @cindex process record and replay
6102 @cindex recording inferior's execution and replaying it
6104 On some platforms, @value{GDBN} provides a special @dfn{process record
6105 and replay} target that can record a log of the process execution, and
6106 replay it later with both forward and reverse execution commands.
6109 When this target is in use, if the execution log includes the record
6110 for the next instruction, @value{GDBN} will debug in @dfn{replay
6111 mode}. In the replay mode, the inferior does not really execute code
6112 instructions. Instead, all the events that normally happen during
6113 code execution are taken from the execution log. While code is not
6114 really executed in replay mode, the values of registers (including the
6115 program counter register) and the memory of the inferior are still
6116 changed as they normally would. Their contents are taken from the
6120 If the record for the next instruction is not in the execution log,
6121 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6122 inferior executes normally, and @value{GDBN} records the execution log
6125 The process record and replay target supports reverse execution
6126 (@pxref{Reverse Execution}), even if the platform on which the
6127 inferior runs does not. However, the reverse execution is limited in
6128 this case by the range of the instructions recorded in the execution
6129 log. In other words, reverse execution on platforms that don't
6130 support it directly can only be done in the replay mode.
6132 When debugging in the reverse direction, @value{GDBN} will work in
6133 replay mode as long as the execution log includes the record for the
6134 previous instruction; otherwise, it will work in record mode, if the
6135 platform supports reverse execution, or stop if not.
6137 For architecture environments that support process record and replay,
6138 @value{GDBN} provides the following commands:
6141 @kindex target record
6142 @kindex target record-full
6143 @kindex target record-btrace
6146 @kindex record btrace
6150 @item record @var{method}
6151 This command starts the process record and replay target. The
6152 recording method can be specified as parameter. Without a parameter
6153 the command uses the @code{full} recording method. The following
6154 recording methods are available:
6158 Full record/replay recording using @value{GDBN}'s software record and
6159 replay implementation. This method allows replaying and reverse
6163 Hardware-supported instruction recording. This method does not allow
6164 replaying and reverse execution.
6166 This recording method may not be available on all processors.
6169 The process record and replay target can only debug a process that is
6170 already running. Therefore, you need first to start the process with
6171 the @kbd{run} or @kbd{start} commands, and then start the recording
6172 with the @kbd{record @var{method}} command.
6174 Both @code{record @var{method}} and @code{rec @var{method}} are
6175 aliases of @code{target record-@var{method}}.
6177 @cindex displaced stepping, and process record and replay
6178 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6179 will be automatically disabled when process record and replay target
6180 is started. That's because the process record and replay target
6181 doesn't support displaced stepping.
6183 @cindex non-stop mode, and process record and replay
6184 @cindex asynchronous execution, and process record and replay
6185 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6186 the asynchronous execution mode (@pxref{Background Execution}), not
6187 all recording methods are available. The @code{full} recording method
6188 does not support these two modes.
6193 Stop the process record and replay target. When process record and
6194 replay target stops, the entire execution log will be deleted and the
6195 inferior will either be terminated, or will remain in its final state.
6197 When you stop the process record and replay target in record mode (at
6198 the end of the execution log), the inferior will be stopped at the
6199 next instruction that would have been recorded. In other words, if
6200 you record for a while and then stop recording, the inferior process
6201 will be left in the same state as if the recording never happened.
6203 On the other hand, if the process record and replay target is stopped
6204 while in replay mode (that is, not at the end of the execution log,
6205 but at some earlier point), the inferior process will become ``live''
6206 at that earlier state, and it will then be possible to continue the
6207 usual ``live'' debugging of the process from that state.
6209 When the inferior process exits, or @value{GDBN} detaches from it,
6210 process record and replay target will automatically stop itself.
6213 @item record save @var{filename}
6214 Save the execution log to a file @file{@var{filename}}.
6215 Default filename is @file{gdb_record.@var{process_id}}, where
6216 @var{process_id} is the process ID of the inferior.
6218 This command may not be available for all recording methods.
6220 @kindex record restore
6221 @item record restore @var{filename}
6222 Restore the execution log from a file @file{@var{filename}}.
6223 File must have been created with @code{record save}.
6225 @kindex set record full
6226 @item set record full insn-number-max @var{limit}
6227 @itemx set record full insn-number-max unlimited
6228 Set the limit of instructions to be recorded for the @code{full}
6229 recording method. Default value is 200000.
6231 If @var{limit} is a positive number, then @value{GDBN} will start
6232 deleting instructions from the log once the number of the record
6233 instructions becomes greater than @var{limit}. For every new recorded
6234 instruction, @value{GDBN} will delete the earliest recorded
6235 instruction to keep the number of recorded instructions at the limit.
6236 (Since deleting recorded instructions loses information, @value{GDBN}
6237 lets you control what happens when the limit is reached, by means of
6238 the @code{stop-at-limit} option, described below.)
6240 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6241 delete recorded instructions from the execution log. The number of
6242 recorded instructions is limited only by the available memory.
6244 @kindex show record full
6245 @item show record full insn-number-max
6246 Show the limit of instructions to be recorded with the @code{full}
6249 @item set record full stop-at-limit
6250 Control the behavior of the @code{full} recording method when the
6251 number of recorded instructions reaches the limit. If ON (the
6252 default), @value{GDBN} will stop when the limit is reached for the
6253 first time and ask you whether you want to stop the inferior or
6254 continue running it and recording the execution log. If you decide
6255 to continue recording, each new recorded instruction will cause the
6256 oldest one to be deleted.
6258 If this option is OFF, @value{GDBN} will automatically delete the
6259 oldest record to make room for each new one, without asking.
6261 @item show record full stop-at-limit
6262 Show the current setting of @code{stop-at-limit}.
6264 @item set record full memory-query
6265 Control the behavior when @value{GDBN} is unable to record memory
6266 changes caused by an instruction for the @code{full} recording method.
6267 If ON, @value{GDBN} will query whether to stop the inferior in that
6270 If this option is OFF (the default), @value{GDBN} will automatically
6271 ignore the effect of such instructions on memory. Later, when
6272 @value{GDBN} replays this execution log, it will mark the log of this
6273 instruction as not accessible, and it will not affect the replay
6276 @item show record full memory-query
6277 Show the current setting of @code{memory-query}.
6281 Show various statistics about the recording depending on the recording
6286 For the @code{full} recording method, it shows the state of process
6287 record and its in-memory execution log buffer, including:
6291 Whether in record mode or replay mode.
6293 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6295 Highest recorded instruction number.
6297 Current instruction about to be replayed (if in replay mode).
6299 Number of instructions contained in the execution log.
6301 Maximum number of instructions that may be contained in the execution log.
6305 For the @code{btrace} recording method, it shows the number of
6306 instructions that have been recorded and the number of blocks of
6307 sequential control-flow that is formed by the recorded instructions.
6310 @kindex record delete
6313 When record target runs in replay mode (``in the past''), delete the
6314 subsequent execution log and begin to record a new execution log starting
6315 from the current address. This means you will abandon the previously
6316 recorded ``future'' and begin recording a new ``future''.
6318 @kindex record instruction-history
6319 @kindex rec instruction-history
6320 @item record instruction-history
6321 Disassembles instructions from the recorded execution log. By
6322 default, ten instructions are disassembled. This can be changed using
6323 the @code{set record instruction-history-size} command. Instructions
6324 are printed in execution order. There are several ways to specify
6325 what part of the execution log to disassemble:
6328 @item record instruction-history @var{insn}
6329 Disassembles ten instructions starting from instruction number
6332 @item record instruction-history @var{insn}, +/-@var{n}
6333 Disassembles @var{n} instructions around instruction number
6334 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6335 @var{n} instructions after instruction number @var{insn}. If
6336 @var{n} is preceded with @code{-}, disassembles @var{n}
6337 instructions before instruction number @var{insn}.
6339 @item record instruction-history
6340 Disassembles ten more instructions after the last disassembly.
6342 @item record instruction-history -
6343 Disassembles ten more instructions before the last disassembly.
6345 @item record instruction-history @var{begin} @var{end}
6346 Disassembles instructions beginning with instruction number
6347 @var{begin} until instruction number @var{end}. The instruction
6348 number @var{end} is not included.
6351 This command may not be available for all recording methods.
6354 @item set record instruction-history-size @var{size}
6355 @itemx set record instruction-history-size unlimited
6356 Define how many instructions to disassemble in the @code{record
6357 instruction-history} command. The default value is 10.
6358 A @var{size} of @code{unlimited} means unlimited instructions.
6361 @item show record instruction-history-size
6362 Show how many instructions to disassemble in the @code{record
6363 instruction-history} command.
6365 @kindex record function-call-history
6366 @kindex rec function-call-history
6367 @item record function-call-history
6368 Prints the execution history at function granularity. It prints one
6369 line for each sequence of instructions that belong to the same
6370 function giving the name of that function, the source lines
6371 for this instruction sequence (if the @code{/l} modifier is
6372 specified), and the instructions numbers that form the sequence (if
6373 the @code{/i} modifier is specified).
6376 (@value{GDBP}) @b{list 1, 10}
6387 (@value{GDBP}) @b{record function-call-history /l}
6393 By default, ten lines are printed. This can be changed using the
6394 @code{set record function-call-history-size} command. Functions are
6395 printed in execution order. There are several ways to specify what
6399 @item record function-call-history @var{func}
6400 Prints ten functions starting from function number @var{func}.
6402 @item record function-call-history @var{func}, +/-@var{n}
6403 Prints @var{n} functions around function number @var{func}. If
6404 @var{n} is preceded with @code{+}, prints @var{n} functions after
6405 function number @var{func}. If @var{n} is preceded with @code{-},
6406 prints @var{n} functions before function number @var{func}.
6408 @item record function-call-history
6409 Prints ten more functions after the last ten-line print.
6411 @item record function-call-history -
6412 Prints ten more functions before the last ten-line print.
6414 @item record function-call-history @var{begin} @var{end}
6415 Prints functions beginning with function number @var{begin} until
6416 function number @var{end}. The function number @var{end} is not
6420 This command may not be available for all recording methods.
6422 @item set record function-call-history-size @var{size}
6423 @itemx set record function-call-history-size unlimited
6424 Define how many lines to print in the
6425 @code{record function-call-history} command. The default value is 10.
6426 A size of @code{unlimited} means unlimited lines.
6428 @item show record function-call-history-size
6429 Show how many lines to print in the
6430 @code{record function-call-history} command.
6435 @chapter Examining the Stack
6437 When your program has stopped, the first thing you need to know is where it
6438 stopped and how it got there.
6441 Each time your program performs a function call, information about the call
6443 That information includes the location of the call in your program,
6444 the arguments of the call,
6445 and the local variables of the function being called.
6446 The information is saved in a block of data called a @dfn{stack frame}.
6447 The stack frames are allocated in a region of memory called the @dfn{call
6450 When your program stops, the @value{GDBN} commands for examining the
6451 stack allow you to see all of this information.
6453 @cindex selected frame
6454 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6455 @value{GDBN} commands refer implicitly to the selected frame. In
6456 particular, whenever you ask @value{GDBN} for the value of a variable in
6457 your program, the value is found in the selected frame. There are
6458 special @value{GDBN} commands to select whichever frame you are
6459 interested in. @xref{Selection, ,Selecting a Frame}.
6461 When your program stops, @value{GDBN} automatically selects the
6462 currently executing frame and describes it briefly, similar to the
6463 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6466 * Frames:: Stack frames
6467 * Backtrace:: Backtraces
6468 * Selection:: Selecting a frame
6469 * Frame Info:: Information on a frame
6474 @section Stack Frames
6476 @cindex frame, definition
6478 The call stack is divided up into contiguous pieces called @dfn{stack
6479 frames}, or @dfn{frames} for short; each frame is the data associated
6480 with one call to one function. The frame contains the arguments given
6481 to the function, the function's local variables, and the address at
6482 which the function is executing.
6484 @cindex initial frame
6485 @cindex outermost frame
6486 @cindex innermost frame
6487 When your program is started, the stack has only one frame, that of the
6488 function @code{main}. This is called the @dfn{initial} frame or the
6489 @dfn{outermost} frame. Each time a function is called, a new frame is
6490 made. Each time a function returns, the frame for that function invocation
6491 is eliminated. If a function is recursive, there can be many frames for
6492 the same function. The frame for the function in which execution is
6493 actually occurring is called the @dfn{innermost} frame. This is the most
6494 recently created of all the stack frames that still exist.
6496 @cindex frame pointer
6497 Inside your program, stack frames are identified by their addresses. A
6498 stack frame consists of many bytes, each of which has its own address; each
6499 kind of computer has a convention for choosing one byte whose
6500 address serves as the address of the frame. Usually this address is kept
6501 in a register called the @dfn{frame pointer register}
6502 (@pxref{Registers, $fp}) while execution is going on in that frame.
6504 @cindex frame number
6505 @value{GDBN} assigns numbers to all existing stack frames, starting with
6506 zero for the innermost frame, one for the frame that called it,
6507 and so on upward. These numbers do not really exist in your program;
6508 they are assigned by @value{GDBN} to give you a way of designating stack
6509 frames in @value{GDBN} commands.
6511 @c The -fomit-frame-pointer below perennially causes hbox overflow
6512 @c underflow problems.
6513 @cindex frameless execution
6514 Some compilers provide a way to compile functions so that they operate
6515 without stack frames. (For example, the @value{NGCC} option
6517 @samp{-fomit-frame-pointer}
6519 generates functions without a frame.)
6520 This is occasionally done with heavily used library functions to save
6521 the frame setup time. @value{GDBN} has limited facilities for dealing
6522 with these function invocations. If the innermost function invocation
6523 has no stack frame, @value{GDBN} nevertheless regards it as though
6524 it had a separate frame, which is numbered zero as usual, allowing
6525 correct tracing of the function call chain. However, @value{GDBN} has
6526 no provision for frameless functions elsewhere in the stack.
6529 @kindex frame@r{, command}
6530 @cindex current stack frame
6531 @item frame @var{args}
6532 The @code{frame} command allows you to move from one stack frame to another,
6533 and to print the stack frame you select. @var{args} may be either the
6534 address of the frame or the stack frame number. Without an argument,
6535 @code{frame} prints the current stack frame.
6537 @kindex select-frame
6538 @cindex selecting frame silently
6540 The @code{select-frame} command allows you to move from one stack frame
6541 to another without printing the frame. This is the silent version of
6549 @cindex call stack traces
6550 A backtrace is a summary of how your program got where it is. It shows one
6551 line per frame, for many frames, starting with the currently executing
6552 frame (frame zero), followed by its caller (frame one), and on up the
6557 @kindex bt @r{(@code{backtrace})}
6560 Print a backtrace of the entire stack: one line per frame for all
6561 frames in the stack.
6563 You can stop the backtrace at any time by typing the system interrupt
6564 character, normally @kbd{Ctrl-c}.
6566 @item backtrace @var{n}
6568 Similar, but print only the innermost @var{n} frames.
6570 @item backtrace -@var{n}
6572 Similar, but print only the outermost @var{n} frames.
6574 @item backtrace full
6576 @itemx bt full @var{n}
6577 @itemx bt full -@var{n}
6578 Print the values of the local variables also. @var{n} specifies the
6579 number of frames to print, as described above.
6584 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6585 are additional aliases for @code{backtrace}.
6587 @cindex multiple threads, backtrace
6588 In a multi-threaded program, @value{GDBN} by default shows the
6589 backtrace only for the current thread. To display the backtrace for
6590 several or all of the threads, use the command @code{thread apply}
6591 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6592 apply all backtrace}, @value{GDBN} will display the backtrace for all
6593 the threads; this is handy when you debug a core dump of a
6594 multi-threaded program.
6596 Each line in the backtrace shows the frame number and the function name.
6597 The program counter value is also shown---unless you use @code{set
6598 print address off}. The backtrace also shows the source file name and
6599 line number, as well as the arguments to the function. The program
6600 counter value is omitted if it is at the beginning of the code for that
6603 Here is an example of a backtrace. It was made with the command
6604 @samp{bt 3}, so it shows the innermost three frames.
6608 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6610 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6611 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6613 (More stack frames follow...)
6618 The display for frame zero does not begin with a program counter
6619 value, indicating that your program has stopped at the beginning of the
6620 code for line @code{993} of @code{builtin.c}.
6623 The value of parameter @code{data} in frame 1 has been replaced by
6624 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6625 only if it is a scalar (integer, pointer, enumeration, etc). See command
6626 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6627 on how to configure the way function parameter values are printed.
6629 @cindex optimized out, in backtrace
6630 @cindex function call arguments, optimized out
6631 If your program was compiled with optimizations, some compilers will
6632 optimize away arguments passed to functions if those arguments are
6633 never used after the call. Such optimizations generate code that
6634 passes arguments through registers, but doesn't store those arguments
6635 in the stack frame. @value{GDBN} has no way of displaying such
6636 arguments in stack frames other than the innermost one. Here's what
6637 such a backtrace might look like:
6641 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6643 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6644 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6646 (More stack frames follow...)
6651 The values of arguments that were not saved in their stack frames are
6652 shown as @samp{<optimized out>}.
6654 If you need to display the values of such optimized-out arguments,
6655 either deduce that from other variables whose values depend on the one
6656 you are interested in, or recompile without optimizations.
6658 @cindex backtrace beyond @code{main} function
6659 @cindex program entry point
6660 @cindex startup code, and backtrace
6661 Most programs have a standard user entry point---a place where system
6662 libraries and startup code transition into user code. For C this is
6663 @code{main}@footnote{
6664 Note that embedded programs (the so-called ``free-standing''
6665 environment) are not required to have a @code{main} function as the
6666 entry point. They could even have multiple entry points.}.
6667 When @value{GDBN} finds the entry function in a backtrace
6668 it will terminate the backtrace, to avoid tracing into highly
6669 system-specific (and generally uninteresting) code.
6671 If you need to examine the startup code, or limit the number of levels
6672 in a backtrace, you can change this behavior:
6675 @item set backtrace past-main
6676 @itemx set backtrace past-main on
6677 @kindex set backtrace
6678 Backtraces will continue past the user entry point.
6680 @item set backtrace past-main off
6681 Backtraces will stop when they encounter the user entry point. This is the
6684 @item show backtrace past-main
6685 @kindex show backtrace
6686 Display the current user entry point backtrace policy.
6688 @item set backtrace past-entry
6689 @itemx set backtrace past-entry on
6690 Backtraces will continue past the internal entry point of an application.
6691 This entry point is encoded by the linker when the application is built,
6692 and is likely before the user entry point @code{main} (or equivalent) is called.
6694 @item set backtrace past-entry off
6695 Backtraces will stop when they encounter the internal entry point of an
6696 application. This is the default.
6698 @item show backtrace past-entry
6699 Display the current internal entry point backtrace policy.
6701 @item set backtrace limit @var{n}
6702 @itemx set backtrace limit 0
6703 @itemx set backtrace limit unlimited
6704 @cindex backtrace limit
6705 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6706 or zero means unlimited levels.
6708 @item show backtrace limit
6709 Display the current limit on backtrace levels.
6712 You can control how file names are displayed.
6715 @item set filename-display
6716 @itemx set filename-display relative
6717 @cindex filename-display
6718 Display file names relative to the compilation directory. This is the default.
6720 @item set filename-display basename
6721 Display only basename of a filename.
6723 @item set filename-display absolute
6724 Display an absolute filename.
6726 @item show filename-display
6727 Show the current way to display filenames.
6731 @section Selecting a Frame
6733 Most commands for examining the stack and other data in your program work on
6734 whichever stack frame is selected at the moment. Here are the commands for
6735 selecting a stack frame; all of them finish by printing a brief description
6736 of the stack frame just selected.
6739 @kindex frame@r{, selecting}
6740 @kindex f @r{(@code{frame})}
6743 Select frame number @var{n}. Recall that frame zero is the innermost
6744 (currently executing) frame, frame one is the frame that called the
6745 innermost one, and so on. The highest-numbered frame is the one for
6748 @item frame @var{addr}
6750 Select the frame at address @var{addr}. This is useful mainly if the
6751 chaining of stack frames has been damaged by a bug, making it
6752 impossible for @value{GDBN} to assign numbers properly to all frames. In
6753 addition, this can be useful when your program has multiple stacks and
6754 switches between them.
6756 On the SPARC architecture, @code{frame} needs two addresses to
6757 select an arbitrary frame: a frame pointer and a stack pointer.
6759 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6760 pointer and a program counter.
6762 On the 29k architecture, it needs three addresses: a register stack
6763 pointer, a program counter, and a memory stack pointer.
6767 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6768 advances toward the outermost frame, to higher frame numbers, to frames
6769 that have existed longer. @var{n} defaults to one.
6772 @kindex do @r{(@code{down})}
6774 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6775 advances toward the innermost frame, to lower frame numbers, to frames
6776 that were created more recently. @var{n} defaults to one. You may
6777 abbreviate @code{down} as @code{do}.
6780 All of these commands end by printing two lines of output describing the
6781 frame. The first line shows the frame number, the function name, the
6782 arguments, and the source file and line number of execution in that
6783 frame. The second line shows the text of that source line.
6791 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6793 10 read_input_file (argv[i]);
6797 After such a printout, the @code{list} command with no arguments
6798 prints ten lines centered on the point of execution in the frame.
6799 You can also edit the program at the point of execution with your favorite
6800 editing program by typing @code{edit}.
6801 @xref{List, ,Printing Source Lines},
6805 @kindex down-silently
6807 @item up-silently @var{n}
6808 @itemx down-silently @var{n}
6809 These two commands are variants of @code{up} and @code{down},
6810 respectively; they differ in that they do their work silently, without
6811 causing display of the new frame. They are intended primarily for use
6812 in @value{GDBN} command scripts, where the output might be unnecessary and
6817 @section Information About a Frame
6819 There are several other commands to print information about the selected
6825 When used without any argument, this command does not change which
6826 frame is selected, but prints a brief description of the currently
6827 selected stack frame. It can be abbreviated @code{f}. With an
6828 argument, this command is used to select a stack frame.
6829 @xref{Selection, ,Selecting a Frame}.
6832 @kindex info f @r{(@code{info frame})}
6835 This command prints a verbose description of the selected stack frame,
6840 the address of the frame
6842 the address of the next frame down (called by this frame)
6844 the address of the next frame up (caller of this frame)
6846 the language in which the source code corresponding to this frame is written
6848 the address of the frame's arguments
6850 the address of the frame's local variables
6852 the program counter saved in it (the address of execution in the caller frame)
6854 which registers were saved in the frame
6857 @noindent The verbose description is useful when
6858 something has gone wrong that has made the stack format fail to fit
6859 the usual conventions.
6861 @item info frame @var{addr}
6862 @itemx info f @var{addr}
6863 Print a verbose description of the frame at address @var{addr}, without
6864 selecting that frame. The selected frame remains unchanged by this
6865 command. This requires the same kind of address (more than one for some
6866 architectures) that you specify in the @code{frame} command.
6867 @xref{Selection, ,Selecting a Frame}.
6871 Print the arguments of the selected frame, each on a separate line.
6875 Print the local variables of the selected frame, each on a separate
6876 line. These are all variables (declared either static or automatic)
6877 accessible at the point of execution of the selected frame.
6883 @chapter Examining Source Files
6885 @value{GDBN} can print parts of your program's source, since the debugging
6886 information recorded in the program tells @value{GDBN} what source files were
6887 used to build it. When your program stops, @value{GDBN} spontaneously prints
6888 the line where it stopped. Likewise, when you select a stack frame
6889 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6890 execution in that frame has stopped. You can print other portions of
6891 source files by explicit command.
6893 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6894 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6895 @value{GDBN} under @sc{gnu} Emacs}.
6898 * List:: Printing source lines
6899 * Specify Location:: How to specify code locations
6900 * Edit:: Editing source files
6901 * Search:: Searching source files
6902 * Source Path:: Specifying source directories
6903 * Machine Code:: Source and machine code
6907 @section Printing Source Lines
6910 @kindex l @r{(@code{list})}
6911 To print lines from a source file, use the @code{list} command
6912 (abbreviated @code{l}). By default, ten lines are printed.
6913 There are several ways to specify what part of the file you want to
6914 print; see @ref{Specify Location}, for the full list.
6916 Here are the forms of the @code{list} command most commonly used:
6919 @item list @var{linenum}
6920 Print lines centered around line number @var{linenum} in the
6921 current source file.
6923 @item list @var{function}
6924 Print lines centered around the beginning of function
6928 Print more lines. If the last lines printed were printed with a
6929 @code{list} command, this prints lines following the last lines
6930 printed; however, if the last line printed was a solitary line printed
6931 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6932 Stack}), this prints lines centered around that line.
6935 Print lines just before the lines last printed.
6938 @cindex @code{list}, how many lines to display
6939 By default, @value{GDBN} prints ten source lines with any of these forms of
6940 the @code{list} command. You can change this using @code{set listsize}:
6943 @kindex set listsize
6944 @item set listsize @var{count}
6945 @itemx set listsize unlimited
6946 Make the @code{list} command display @var{count} source lines (unless
6947 the @code{list} argument explicitly specifies some other number).
6948 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6950 @kindex show listsize
6952 Display the number of lines that @code{list} prints.
6955 Repeating a @code{list} command with @key{RET} discards the argument,
6956 so it is equivalent to typing just @code{list}. This is more useful
6957 than listing the same lines again. An exception is made for an
6958 argument of @samp{-}; that argument is preserved in repetition so that
6959 each repetition moves up in the source file.
6961 In general, the @code{list} command expects you to supply zero, one or two
6962 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6963 of writing them (@pxref{Specify Location}), but the effect is always
6964 to specify some source line.
6966 Here is a complete description of the possible arguments for @code{list}:
6969 @item list @var{linespec}
6970 Print lines centered around the line specified by @var{linespec}.
6972 @item list @var{first},@var{last}
6973 Print lines from @var{first} to @var{last}. Both arguments are
6974 linespecs. When a @code{list} command has two linespecs, and the
6975 source file of the second linespec is omitted, this refers to
6976 the same source file as the first linespec.
6978 @item list ,@var{last}
6979 Print lines ending with @var{last}.
6981 @item list @var{first},
6982 Print lines starting with @var{first}.
6985 Print lines just after the lines last printed.
6988 Print lines just before the lines last printed.
6991 As described in the preceding table.
6994 @node Specify Location
6995 @section Specifying a Location
6996 @cindex specifying location
6999 Several @value{GDBN} commands accept arguments that specify a location
7000 of your program's code. Since @value{GDBN} is a source-level
7001 debugger, a location usually specifies some line in the source code;
7002 for that reason, locations are also known as @dfn{linespecs}.
7004 Here are all the different ways of specifying a code location that
7005 @value{GDBN} understands:
7009 Specifies the line number @var{linenum} of the current source file.
7012 @itemx +@var{offset}
7013 Specifies the line @var{offset} lines before or after the @dfn{current
7014 line}. For the @code{list} command, the current line is the last one
7015 printed; for the breakpoint commands, this is the line at which
7016 execution stopped in the currently selected @dfn{stack frame}
7017 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7018 used as the second of the two linespecs in a @code{list} command,
7019 this specifies the line @var{offset} lines up or down from the first
7022 @item @var{filename}:@var{linenum}
7023 Specifies the line @var{linenum} in the source file @var{filename}.
7024 If @var{filename} is a relative file name, then it will match any
7025 source file name with the same trailing components. For example, if
7026 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7027 name of @file{/build/trunk/gcc/expr.c}, but not
7028 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7030 @item @var{function}
7031 Specifies the line that begins the body of the function @var{function}.
7032 For example, in C, this is the line with the open brace.
7034 @item @var{function}:@var{label}
7035 Specifies the line where @var{label} appears in @var{function}.
7037 @item @var{filename}:@var{function}
7038 Specifies the line that begins the body of the function @var{function}
7039 in the file @var{filename}. You only need the file name with a
7040 function name to avoid ambiguity when there are identically named
7041 functions in different source files.
7044 Specifies the line at which the label named @var{label} appears.
7045 @value{GDBN} searches for the label in the function corresponding to
7046 the currently selected stack frame. If there is no current selected
7047 stack frame (for instance, if the inferior is not running), then
7048 @value{GDBN} will not search for a label.
7050 @item *@var{address}
7051 Specifies the program address @var{address}. For line-oriented
7052 commands, such as @code{list} and @code{edit}, this specifies a source
7053 line that contains @var{address}. For @code{break} and other
7054 breakpoint oriented commands, this can be used to set breakpoints in
7055 parts of your program which do not have debugging information or
7058 Here @var{address} may be any expression valid in the current working
7059 language (@pxref{Languages, working language}) that specifies a code
7060 address. In addition, as a convenience, @value{GDBN} extends the
7061 semantics of expressions used in locations to cover the situations
7062 that frequently happen during debugging. Here are the various forms
7066 @item @var{expression}
7067 Any expression valid in the current working language.
7069 @item @var{funcaddr}
7070 An address of a function or procedure derived from its name. In C,
7071 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7072 simply the function's name @var{function} (and actually a special case
7073 of a valid expression). In Pascal and Modula-2, this is
7074 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7075 (although the Pascal form also works).
7077 This form specifies the address of the function's first instruction,
7078 before the stack frame and arguments have been set up.
7080 @item '@var{filename}'::@var{funcaddr}
7081 Like @var{funcaddr} above, but also specifies the name of the source
7082 file explicitly. This is useful if the name of the function does not
7083 specify the function unambiguously, e.g., if there are several
7084 functions with identical names in different source files.
7087 @cindex breakpoint at static probe point
7088 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7089 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7090 applications to embed static probes. @xref{Static Probe Points}, for more
7091 information on finding and using static probes. This form of linespec
7092 specifies the location of such a static probe.
7094 If @var{objfile} is given, only probes coming from that shared library
7095 or executable matching @var{objfile} as a regular expression are considered.
7096 If @var{provider} is given, then only probes from that provider are considered.
7097 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7098 each one of those probes.
7104 @section Editing Source Files
7105 @cindex editing source files
7108 @kindex e @r{(@code{edit})}
7109 To edit the lines in a source file, use the @code{edit} command.
7110 The editing program of your choice
7111 is invoked with the current line set to
7112 the active line in the program.
7113 Alternatively, there are several ways to specify what part of the file you
7114 want to print if you want to see other parts of the program:
7117 @item edit @var{location}
7118 Edit the source file specified by @code{location}. Editing starts at
7119 that @var{location}, e.g., at the specified source line of the
7120 specified file. @xref{Specify Location}, for all the possible forms
7121 of the @var{location} argument; here are the forms of the @code{edit}
7122 command most commonly used:
7125 @item edit @var{number}
7126 Edit the current source file with @var{number} as the active line number.
7128 @item edit @var{function}
7129 Edit the file containing @var{function} at the beginning of its definition.
7134 @subsection Choosing your Editor
7135 You can customize @value{GDBN} to use any editor you want
7137 The only restriction is that your editor (say @code{ex}), recognizes the
7138 following command-line syntax:
7140 ex +@var{number} file
7142 The optional numeric value +@var{number} specifies the number of the line in
7143 the file where to start editing.}.
7144 By default, it is @file{@value{EDITOR}}, but you can change this
7145 by setting the environment variable @code{EDITOR} before using
7146 @value{GDBN}. For example, to configure @value{GDBN} to use the
7147 @code{vi} editor, you could use these commands with the @code{sh} shell:
7153 or in the @code{csh} shell,
7155 setenv EDITOR /usr/bin/vi
7160 @section Searching Source Files
7161 @cindex searching source files
7163 There are two commands for searching through the current source file for a
7168 @kindex forward-search
7169 @kindex fo @r{(@code{forward-search})}
7170 @item forward-search @var{regexp}
7171 @itemx search @var{regexp}
7172 The command @samp{forward-search @var{regexp}} checks each line,
7173 starting with the one following the last line listed, for a match for
7174 @var{regexp}. It lists the line that is found. You can use the
7175 synonym @samp{search @var{regexp}} or abbreviate the command name as
7178 @kindex reverse-search
7179 @item reverse-search @var{regexp}
7180 The command @samp{reverse-search @var{regexp}} checks each line, starting
7181 with the one before the last line listed and going backward, for a match
7182 for @var{regexp}. It lists the line that is found. You can abbreviate
7183 this command as @code{rev}.
7187 @section Specifying Source Directories
7190 @cindex directories for source files
7191 Executable programs sometimes do not record the directories of the source
7192 files from which they were compiled, just the names. Even when they do,
7193 the directories could be moved between the compilation and your debugging
7194 session. @value{GDBN} has a list of directories to search for source files;
7195 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7196 it tries all the directories in the list, in the order they are present
7197 in the list, until it finds a file with the desired name.
7199 For example, suppose an executable references the file
7200 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7201 @file{/mnt/cross}. The file is first looked up literally; if this
7202 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7203 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7204 message is printed. @value{GDBN} does not look up the parts of the
7205 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7206 Likewise, the subdirectories of the source path are not searched: if
7207 the source path is @file{/mnt/cross}, and the binary refers to
7208 @file{foo.c}, @value{GDBN} would not find it under
7209 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7211 Plain file names, relative file names with leading directories, file
7212 names containing dots, etc.@: are all treated as described above; for
7213 instance, if the source path is @file{/mnt/cross}, and the source file
7214 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7215 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7216 that---@file{/mnt/cross/foo.c}.
7218 Note that the executable search path is @emph{not} used to locate the
7221 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7222 any information it has cached about where source files are found and where
7223 each line is in the file.
7227 When you start @value{GDBN}, its source path includes only @samp{cdir}
7228 and @samp{cwd}, in that order.
7229 To add other directories, use the @code{directory} command.
7231 The search path is used to find both program source files and @value{GDBN}
7232 script files (read using the @samp{-command} option and @samp{source} command).
7234 In addition to the source path, @value{GDBN} provides a set of commands
7235 that manage a list of source path substitution rules. A @dfn{substitution
7236 rule} specifies how to rewrite source directories stored in the program's
7237 debug information in case the sources were moved to a different
7238 directory between compilation and debugging. A rule is made of
7239 two strings, the first specifying what needs to be rewritten in
7240 the path, and the second specifying how it should be rewritten.
7241 In @ref{set substitute-path}, we name these two parts @var{from} and
7242 @var{to} respectively. @value{GDBN} does a simple string replacement
7243 of @var{from} with @var{to} at the start of the directory part of the
7244 source file name, and uses that result instead of the original file
7245 name to look up the sources.
7247 Using the previous example, suppose the @file{foo-1.0} tree has been
7248 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7249 @value{GDBN} to replace @file{/usr/src} in all source path names with
7250 @file{/mnt/cross}. The first lookup will then be
7251 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7252 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7253 substitution rule, use the @code{set substitute-path} command
7254 (@pxref{set substitute-path}).
7256 To avoid unexpected substitution results, a rule is applied only if the
7257 @var{from} part of the directory name ends at a directory separator.
7258 For instance, a rule substituting @file{/usr/source} into
7259 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7260 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7261 is applied only at the beginning of the directory name, this rule will
7262 not be applied to @file{/root/usr/source/baz.c} either.
7264 In many cases, you can achieve the same result using the @code{directory}
7265 command. However, @code{set substitute-path} can be more efficient in
7266 the case where the sources are organized in a complex tree with multiple
7267 subdirectories. With the @code{directory} command, you need to add each
7268 subdirectory of your project. If you moved the entire tree while
7269 preserving its internal organization, then @code{set substitute-path}
7270 allows you to direct the debugger to all the sources with one single
7273 @code{set substitute-path} is also more than just a shortcut command.
7274 The source path is only used if the file at the original location no
7275 longer exists. On the other hand, @code{set substitute-path} modifies
7276 the debugger behavior to look at the rewritten location instead. So, if
7277 for any reason a source file that is not relevant to your executable is
7278 located at the original location, a substitution rule is the only
7279 method available to point @value{GDBN} at the new location.
7281 @cindex @samp{--with-relocated-sources}
7282 @cindex default source path substitution
7283 You can configure a default source path substitution rule by
7284 configuring @value{GDBN} with the
7285 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7286 should be the name of a directory under @value{GDBN}'s configured
7287 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7288 directory names in debug information under @var{dir} will be adjusted
7289 automatically if the installed @value{GDBN} is moved to a new
7290 location. This is useful if @value{GDBN}, libraries or executables
7291 with debug information and corresponding source code are being moved
7295 @item directory @var{dirname} @dots{}
7296 @item dir @var{dirname} @dots{}
7297 Add directory @var{dirname} to the front of the source path. Several
7298 directory names may be given to this command, separated by @samp{:}
7299 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7300 part of absolute file names) or
7301 whitespace. You may specify a directory that is already in the source
7302 path; this moves it forward, so @value{GDBN} searches it sooner.
7306 @vindex $cdir@r{, convenience variable}
7307 @vindex $cwd@r{, convenience variable}
7308 @cindex compilation directory
7309 @cindex current directory
7310 @cindex working directory
7311 @cindex directory, current
7312 @cindex directory, compilation
7313 You can use the string @samp{$cdir} to refer to the compilation
7314 directory (if one is recorded), and @samp{$cwd} to refer to the current
7315 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7316 tracks the current working directory as it changes during your @value{GDBN}
7317 session, while the latter is immediately expanded to the current
7318 directory at the time you add an entry to the source path.
7321 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7323 @c RET-repeat for @code{directory} is explicitly disabled, but since
7324 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7326 @item set directories @var{path-list}
7327 @kindex set directories
7328 Set the source path to @var{path-list}.
7329 @samp{$cdir:$cwd} are added if missing.
7331 @item show directories
7332 @kindex show directories
7333 Print the source path: show which directories it contains.
7335 @anchor{set substitute-path}
7336 @item set substitute-path @var{from} @var{to}
7337 @kindex set substitute-path
7338 Define a source path substitution rule, and add it at the end of the
7339 current list of existing substitution rules. If a rule with the same
7340 @var{from} was already defined, then the old rule is also deleted.
7342 For example, if the file @file{/foo/bar/baz.c} was moved to
7343 @file{/mnt/cross/baz.c}, then the command
7346 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7350 will tell @value{GDBN} to replace @samp{/usr/src} with
7351 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7352 @file{baz.c} even though it was moved.
7354 In the case when more than one substitution rule have been defined,
7355 the rules are evaluated one by one in the order where they have been
7356 defined. The first one matching, if any, is selected to perform
7359 For instance, if we had entered the following commands:
7362 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7363 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7367 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7368 @file{/mnt/include/defs.h} by using the first rule. However, it would
7369 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7370 @file{/mnt/src/lib/foo.c}.
7373 @item unset substitute-path [path]
7374 @kindex unset substitute-path
7375 If a path is specified, search the current list of substitution rules
7376 for a rule that would rewrite that path. Delete that rule if found.
7377 A warning is emitted by the debugger if no rule could be found.
7379 If no path is specified, then all substitution rules are deleted.
7381 @item show substitute-path [path]
7382 @kindex show substitute-path
7383 If a path is specified, then print the source path substitution rule
7384 which would rewrite that path, if any.
7386 If no path is specified, then print all existing source path substitution
7391 If your source path is cluttered with directories that are no longer of
7392 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7393 versions of source. You can correct the situation as follows:
7397 Use @code{directory} with no argument to reset the source path to its default value.
7400 Use @code{directory} with suitable arguments to reinstall the
7401 directories you want in the source path. You can add all the
7402 directories in one command.
7406 @section Source and Machine Code
7407 @cindex source line and its code address
7409 You can use the command @code{info line} to map source lines to program
7410 addresses (and vice versa), and the command @code{disassemble} to display
7411 a range of addresses as machine instructions. You can use the command
7412 @code{set disassemble-next-line} to set whether to disassemble next
7413 source line when execution stops. When run under @sc{gnu} Emacs
7414 mode, the @code{info line} command causes the arrow to point to the
7415 line specified. Also, @code{info line} prints addresses in symbolic form as
7420 @item info line @var{linespec}
7421 Print the starting and ending addresses of the compiled code for
7422 source line @var{linespec}. You can specify source lines in any of
7423 the ways documented in @ref{Specify Location}.
7426 For example, we can use @code{info line} to discover the location of
7427 the object code for the first line of function
7428 @code{m4_changequote}:
7430 @c FIXME: I think this example should also show the addresses in
7431 @c symbolic form, as they usually would be displayed.
7433 (@value{GDBP}) info line m4_changequote
7434 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7438 @cindex code address and its source line
7439 We can also inquire (using @code{*@var{addr}} as the form for
7440 @var{linespec}) what source line covers a particular address:
7442 (@value{GDBP}) info line *0x63ff
7443 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7446 @cindex @code{$_} and @code{info line}
7447 @cindex @code{x} command, default address
7448 @kindex x@r{(examine), and} info line
7449 After @code{info line}, the default address for the @code{x} command
7450 is changed to the starting address of the line, so that @samp{x/i} is
7451 sufficient to begin examining the machine code (@pxref{Memory,
7452 ,Examining Memory}). Also, this address is saved as the value of the
7453 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7458 @cindex assembly instructions
7459 @cindex instructions, assembly
7460 @cindex machine instructions
7461 @cindex listing machine instructions
7463 @itemx disassemble /m
7464 @itemx disassemble /r
7465 This specialized command dumps a range of memory as machine
7466 instructions. It can also print mixed source+disassembly by specifying
7467 the @code{/m} modifier and print the raw instructions in hex as well as
7468 in symbolic form by specifying the @code{/r}.
7469 The default memory range is the function surrounding the
7470 program counter of the selected frame. A single argument to this
7471 command is a program counter value; @value{GDBN} dumps the function
7472 surrounding this value. When two arguments are given, they should
7473 be separated by a comma, possibly surrounded by whitespace. The
7474 arguments specify a range of addresses to dump, in one of two forms:
7477 @item @var{start},@var{end}
7478 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7479 @item @var{start},+@var{length}
7480 the addresses from @var{start} (inclusive) to
7481 @code{@var{start}+@var{length}} (exclusive).
7485 When 2 arguments are specified, the name of the function is also
7486 printed (since there could be several functions in the given range).
7488 The argument(s) can be any expression yielding a numeric value, such as
7489 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7491 If the range of memory being disassembled contains current program counter,
7492 the instruction at that location is shown with a @code{=>} marker.
7495 The following example shows the disassembly of a range of addresses of
7496 HP PA-RISC 2.0 code:
7499 (@value{GDBP}) disas 0x32c4, 0x32e4
7500 Dump of assembler code from 0x32c4 to 0x32e4:
7501 0x32c4 <main+204>: addil 0,dp
7502 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7503 0x32cc <main+212>: ldil 0x3000,r31
7504 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7505 0x32d4 <main+220>: ldo 0(r31),rp
7506 0x32d8 <main+224>: addil -0x800,dp
7507 0x32dc <main+228>: ldo 0x588(r1),r26
7508 0x32e0 <main+232>: ldil 0x3000,r31
7509 End of assembler dump.
7512 Here is an example showing mixed source+assembly for Intel x86, when the
7513 program is stopped just after function prologue:
7516 (@value{GDBP}) disas /m main
7517 Dump of assembler code for function main:
7519 0x08048330 <+0>: push %ebp
7520 0x08048331 <+1>: mov %esp,%ebp
7521 0x08048333 <+3>: sub $0x8,%esp
7522 0x08048336 <+6>: and $0xfffffff0,%esp
7523 0x08048339 <+9>: sub $0x10,%esp
7525 6 printf ("Hello.\n");
7526 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7527 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7531 0x08048348 <+24>: mov $0x0,%eax
7532 0x0804834d <+29>: leave
7533 0x0804834e <+30>: ret
7535 End of assembler dump.
7538 Here is another example showing raw instructions in hex for AMD x86-64,
7541 (gdb) disas /r 0x400281,+10
7542 Dump of assembler code from 0x400281 to 0x40028b:
7543 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7544 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7545 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7546 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7547 End of assembler dump.
7550 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7551 So, for example, if you want to disassemble function @code{bar}
7552 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7553 and not @samp{disassemble foo.c:bar}.
7555 Some architectures have more than one commonly-used set of instruction
7556 mnemonics or other syntax.
7558 For programs that were dynamically linked and use shared libraries,
7559 instructions that call functions or branch to locations in the shared
7560 libraries might show a seemingly bogus location---it's actually a
7561 location of the relocation table. On some architectures, @value{GDBN}
7562 might be able to resolve these to actual function names.
7565 @kindex set disassembly-flavor
7566 @cindex Intel disassembly flavor
7567 @cindex AT&T disassembly flavor
7568 @item set disassembly-flavor @var{instruction-set}
7569 Select the instruction set to use when disassembling the
7570 program via the @code{disassemble} or @code{x/i} commands.
7572 Currently this command is only defined for the Intel x86 family. You
7573 can set @var{instruction-set} to either @code{intel} or @code{att}.
7574 The default is @code{att}, the AT&T flavor used by default by Unix
7575 assemblers for x86-based targets.
7577 @kindex show disassembly-flavor
7578 @item show disassembly-flavor
7579 Show the current setting of the disassembly flavor.
7583 @kindex set disassemble-next-line
7584 @kindex show disassemble-next-line
7585 @item set disassemble-next-line
7586 @itemx show disassemble-next-line
7587 Control whether or not @value{GDBN} will disassemble the next source
7588 line or instruction when execution stops. If ON, @value{GDBN} will
7589 display disassembly of the next source line when execution of the
7590 program being debugged stops. This is @emph{in addition} to
7591 displaying the source line itself, which @value{GDBN} always does if
7592 possible. If the next source line cannot be displayed for some reason
7593 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7594 info in the debug info), @value{GDBN} will display disassembly of the
7595 next @emph{instruction} instead of showing the next source line. If
7596 AUTO, @value{GDBN} will display disassembly of next instruction only
7597 if the source line cannot be displayed. This setting causes
7598 @value{GDBN} to display some feedback when you step through a function
7599 with no line info or whose source file is unavailable. The default is
7600 OFF, which means never display the disassembly of the next line or
7606 @chapter Examining Data
7608 @cindex printing data
7609 @cindex examining data
7612 The usual way to examine data in your program is with the @code{print}
7613 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7614 evaluates and prints the value of an expression of the language your
7615 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7616 Different Languages}). It may also print the expression using a
7617 Python-based pretty-printer (@pxref{Pretty Printing}).
7620 @item print @var{expr}
7621 @itemx print /@var{f} @var{expr}
7622 @var{expr} is an expression (in the source language). By default the
7623 value of @var{expr} is printed in a format appropriate to its data type;
7624 you can choose a different format by specifying @samp{/@var{f}}, where
7625 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7629 @itemx print /@var{f}
7630 @cindex reprint the last value
7631 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7632 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7633 conveniently inspect the same value in an alternative format.
7636 A more low-level way of examining data is with the @code{x} command.
7637 It examines data in memory at a specified address and prints it in a
7638 specified format. @xref{Memory, ,Examining Memory}.
7640 If you are interested in information about types, or about how the
7641 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7642 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7645 @cindex exploring hierarchical data structures
7647 Another way of examining values of expressions and type information is
7648 through the Python extension command @code{explore} (available only if
7649 the @value{GDBN} build is configured with @code{--with-python}). It
7650 offers an interactive way to start at the highest level (or, the most
7651 abstract level) of the data type of an expression (or, the data type
7652 itself) and explore all the way down to leaf scalar values/fields
7653 embedded in the higher level data types.
7656 @item explore @var{arg}
7657 @var{arg} is either an expression (in the source language), or a type
7658 visible in the current context of the program being debugged.
7661 The working of the @code{explore} command can be illustrated with an
7662 example. If a data type @code{struct ComplexStruct} is defined in your
7672 struct ComplexStruct
7674 struct SimpleStruct *ss_p;
7680 followed by variable declarations as
7683 struct SimpleStruct ss = @{ 10, 1.11 @};
7684 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7688 then, the value of the variable @code{cs} can be explored using the
7689 @code{explore} command as follows.
7693 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7694 the following fields:
7696 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7697 arr = <Enter 1 to explore this field of type `int [10]'>
7699 Enter the field number of choice:
7703 Since the fields of @code{cs} are not scalar values, you are being
7704 prompted to chose the field you want to explore. Let's say you choose
7705 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7706 pointer, you will be asked if it is pointing to a single value. From
7707 the declaration of @code{cs} above, it is indeed pointing to a single
7708 value, hence you enter @code{y}. If you enter @code{n}, then you will
7709 be asked if it were pointing to an array of values, in which case this
7710 field will be explored as if it were an array.
7713 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7714 Continue exploring it as a pointer to a single value [y/n]: y
7715 The value of `*(cs.ss_p)' is a struct/class of type `struct
7716 SimpleStruct' with the following fields:
7718 i = 10 .. (Value of type `int')
7719 d = 1.1100000000000001 .. (Value of type `double')
7721 Press enter to return to parent value:
7725 If the field @code{arr} of @code{cs} was chosen for exploration by
7726 entering @code{1} earlier, then since it is as array, you will be
7727 prompted to enter the index of the element in the array that you want
7731 `cs.arr' is an array of `int'.
7732 Enter the index of the element you want to explore in `cs.arr': 5
7734 `(cs.arr)[5]' is a scalar value of type `int'.
7738 Press enter to return to parent value:
7741 In general, at any stage of exploration, you can go deeper towards the
7742 leaf values by responding to the prompts appropriately, or hit the
7743 return key to return to the enclosing data structure (the @i{higher}
7744 level data structure).
7746 Similar to exploring values, you can use the @code{explore} command to
7747 explore types. Instead of specifying a value (which is typically a
7748 variable name or an expression valid in the current context of the
7749 program being debugged), you specify a type name. If you consider the
7750 same example as above, your can explore the type
7751 @code{struct ComplexStruct} by passing the argument
7752 @code{struct ComplexStruct} to the @code{explore} command.
7755 (gdb) explore struct ComplexStruct
7759 By responding to the prompts appropriately in the subsequent interactive
7760 session, you can explore the type @code{struct ComplexStruct} in a
7761 manner similar to how the value @code{cs} was explored in the above
7764 The @code{explore} command also has two sub-commands,
7765 @code{explore value} and @code{explore type}. The former sub-command is
7766 a way to explicitly specify that value exploration of the argument is
7767 being invoked, while the latter is a way to explicitly specify that type
7768 exploration of the argument is being invoked.
7771 @item explore value @var{expr}
7772 @cindex explore value
7773 This sub-command of @code{explore} explores the value of the
7774 expression @var{expr} (if @var{expr} is an expression valid in the
7775 current context of the program being debugged). The behavior of this
7776 command is identical to that of the behavior of the @code{explore}
7777 command being passed the argument @var{expr}.
7779 @item explore type @var{arg}
7780 @cindex explore type
7781 This sub-command of @code{explore} explores the type of @var{arg} (if
7782 @var{arg} is a type visible in the current context of program being
7783 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7784 is an expression valid in the current context of the program being
7785 debugged). If @var{arg} is a type, then the behavior of this command is
7786 identical to that of the @code{explore} command being passed the
7787 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7788 this command will be identical to that of the @code{explore} command
7789 being passed the type of @var{arg} as the argument.
7793 * Expressions:: Expressions
7794 * Ambiguous Expressions:: Ambiguous Expressions
7795 * Variables:: Program variables
7796 * Arrays:: Artificial arrays
7797 * Output Formats:: Output formats
7798 * Memory:: Examining memory
7799 * Auto Display:: Automatic display
7800 * Print Settings:: Print settings
7801 * Pretty Printing:: Python pretty printing
7802 * Value History:: Value history
7803 * Convenience Vars:: Convenience variables
7804 * Convenience Funs:: Convenience functions
7805 * Registers:: Registers
7806 * Floating Point Hardware:: Floating point hardware
7807 * Vector Unit:: Vector Unit
7808 * OS Information:: Auxiliary data provided by operating system
7809 * Memory Region Attributes:: Memory region attributes
7810 * Dump/Restore Files:: Copy between memory and a file
7811 * Core File Generation:: Cause a program dump its core
7812 * Character Sets:: Debugging programs that use a different
7813 character set than GDB does
7814 * Caching Remote Data:: Data caching for remote targets
7815 * Searching Memory:: Searching memory for a sequence of bytes
7819 @section Expressions
7822 @code{print} and many other @value{GDBN} commands accept an expression and
7823 compute its value. Any kind of constant, variable or operator defined
7824 by the programming language you are using is valid in an expression in
7825 @value{GDBN}. This includes conditional expressions, function calls,
7826 casts, and string constants. It also includes preprocessor macros, if
7827 you compiled your program to include this information; see
7830 @cindex arrays in expressions
7831 @value{GDBN} supports array constants in expressions input by
7832 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7833 you can use the command @code{print @{1, 2, 3@}} to create an array
7834 of three integers. If you pass an array to a function or assign it
7835 to a program variable, @value{GDBN} copies the array to memory that
7836 is @code{malloc}ed in the target program.
7838 Because C is so widespread, most of the expressions shown in examples in
7839 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7840 Languages}, for information on how to use expressions in other
7843 In this section, we discuss operators that you can use in @value{GDBN}
7844 expressions regardless of your programming language.
7846 @cindex casts, in expressions
7847 Casts are supported in all languages, not just in C, because it is so
7848 useful to cast a number into a pointer in order to examine a structure
7849 at that address in memory.
7850 @c FIXME: casts supported---Mod2 true?
7852 @value{GDBN} supports these operators, in addition to those common
7853 to programming languages:
7857 @samp{@@} is a binary operator for treating parts of memory as arrays.
7858 @xref{Arrays, ,Artificial Arrays}, for more information.
7861 @samp{::} allows you to specify a variable in terms of the file or
7862 function where it is defined. @xref{Variables, ,Program Variables}.
7864 @cindex @{@var{type}@}
7865 @cindex type casting memory
7866 @cindex memory, viewing as typed object
7867 @cindex casts, to view memory
7868 @item @{@var{type}@} @var{addr}
7869 Refers to an object of type @var{type} stored at address @var{addr} in
7870 memory. @var{addr} may be any expression whose value is an integer or
7871 pointer (but parentheses are required around binary operators, just as in
7872 a cast). This construct is allowed regardless of what kind of data is
7873 normally supposed to reside at @var{addr}.
7876 @node Ambiguous Expressions
7877 @section Ambiguous Expressions
7878 @cindex ambiguous expressions
7880 Expressions can sometimes contain some ambiguous elements. For instance,
7881 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7882 a single function name to be defined several times, for application in
7883 different contexts. This is called @dfn{overloading}. Another example
7884 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7885 templates and is typically instantiated several times, resulting in
7886 the same function name being defined in different contexts.
7888 In some cases and depending on the language, it is possible to adjust
7889 the expression to remove the ambiguity. For instance in C@t{++}, you
7890 can specify the signature of the function you want to break on, as in
7891 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7892 qualified name of your function often makes the expression unambiguous
7895 When an ambiguity that needs to be resolved is detected, the debugger
7896 has the capability to display a menu of numbered choices for each
7897 possibility, and then waits for the selection with the prompt @samp{>}.
7898 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7899 aborts the current command. If the command in which the expression was
7900 used allows more than one choice to be selected, the next option in the
7901 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7904 For example, the following session excerpt shows an attempt to set a
7905 breakpoint at the overloaded symbol @code{String::after}.
7906 We choose three particular definitions of that function name:
7908 @c FIXME! This is likely to change to show arg type lists, at least
7911 (@value{GDBP}) b String::after
7914 [2] file:String.cc; line number:867
7915 [3] file:String.cc; line number:860
7916 [4] file:String.cc; line number:875
7917 [5] file:String.cc; line number:853
7918 [6] file:String.cc; line number:846
7919 [7] file:String.cc; line number:735
7921 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7922 Breakpoint 2 at 0xb344: file String.cc, line 875.
7923 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7924 Multiple breakpoints were set.
7925 Use the "delete" command to delete unwanted
7932 @kindex set multiple-symbols
7933 @item set multiple-symbols @var{mode}
7934 @cindex multiple-symbols menu
7936 This option allows you to adjust the debugger behavior when an expression
7939 By default, @var{mode} is set to @code{all}. If the command with which
7940 the expression is used allows more than one choice, then @value{GDBN}
7941 automatically selects all possible choices. For instance, inserting
7942 a breakpoint on a function using an ambiguous name results in a breakpoint
7943 inserted on each possible match. However, if a unique choice must be made,
7944 then @value{GDBN} uses the menu to help you disambiguate the expression.
7945 For instance, printing the address of an overloaded function will result
7946 in the use of the menu.
7948 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7949 when an ambiguity is detected.
7951 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7952 an error due to the ambiguity and the command is aborted.
7954 @kindex show multiple-symbols
7955 @item show multiple-symbols
7956 Show the current value of the @code{multiple-symbols} setting.
7960 @section Program Variables
7962 The most common kind of expression to use is the name of a variable
7965 Variables in expressions are understood in the selected stack frame
7966 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7970 global (or file-static)
7977 visible according to the scope rules of the
7978 programming language from the point of execution in that frame
7981 @noindent This means that in the function
7996 you can examine and use the variable @code{a} whenever your program is
7997 executing within the function @code{foo}, but you can only use or
7998 examine the variable @code{b} while your program is executing inside
7999 the block where @code{b} is declared.
8001 @cindex variable name conflict
8002 There is an exception: you can refer to a variable or function whose
8003 scope is a single source file even if the current execution point is not
8004 in this file. But it is possible to have more than one such variable or
8005 function with the same name (in different source files). If that
8006 happens, referring to that name has unpredictable effects. If you wish,
8007 you can specify a static variable in a particular function or file by
8008 using the colon-colon (@code{::}) notation:
8010 @cindex colon-colon, context for variables/functions
8012 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8013 @cindex @code{::}, context for variables/functions
8016 @var{file}::@var{variable}
8017 @var{function}::@var{variable}
8021 Here @var{file} or @var{function} is the name of the context for the
8022 static @var{variable}. In the case of file names, you can use quotes to
8023 make sure @value{GDBN} parses the file name as a single word---for example,
8024 to print a global value of @code{x} defined in @file{f2.c}:
8027 (@value{GDBP}) p 'f2.c'::x
8030 The @code{::} notation is normally used for referring to
8031 static variables, since you typically disambiguate uses of local variables
8032 in functions by selecting the appropriate frame and using the
8033 simple name of the variable. However, you may also use this notation
8034 to refer to local variables in frames enclosing the selected frame:
8043 process (a); /* Stop here */
8054 For example, if there is a breakpoint at the commented line,
8055 here is what you might see
8056 when the program stops after executing the call @code{bar(0)}:
8061 (@value{GDBP}) p bar::a
8064 #2 0x080483d0 in foo (a=5) at foobar.c:12
8067 (@value{GDBP}) p bar::a
8071 @cindex C@t{++} scope resolution
8072 These uses of @samp{::} are very rarely in conflict with the very similar
8073 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8074 scope resolution operator in @value{GDBN} expressions.
8075 @c FIXME: Um, so what happens in one of those rare cases where it's in
8078 @cindex wrong values
8079 @cindex variable values, wrong
8080 @cindex function entry/exit, wrong values of variables
8081 @cindex optimized code, wrong values of variables
8083 @emph{Warning:} Occasionally, a local variable may appear to have the
8084 wrong value at certain points in a function---just after entry to a new
8085 scope, and just before exit.
8087 You may see this problem when you are stepping by machine instructions.
8088 This is because, on most machines, it takes more than one instruction to
8089 set up a stack frame (including local variable definitions); if you are
8090 stepping by machine instructions, variables may appear to have the wrong
8091 values until the stack frame is completely built. On exit, it usually
8092 also takes more than one machine instruction to destroy a stack frame;
8093 after you begin stepping through that group of instructions, local
8094 variable definitions may be gone.
8096 This may also happen when the compiler does significant optimizations.
8097 To be sure of always seeing accurate values, turn off all optimization
8100 @cindex ``No symbol "foo" in current context''
8101 Another possible effect of compiler optimizations is to optimize
8102 unused variables out of existence, or assign variables to registers (as
8103 opposed to memory addresses). Depending on the support for such cases
8104 offered by the debug info format used by the compiler, @value{GDBN}
8105 might not be able to display values for such local variables. If that
8106 happens, @value{GDBN} will print a message like this:
8109 No symbol "foo" in current context.
8112 To solve such problems, either recompile without optimizations, or use a
8113 different debug info format, if the compiler supports several such
8114 formats. @xref{Compilation}, for more information on choosing compiler
8115 options. @xref{C, ,C and C@t{++}}, for more information about debug
8116 info formats that are best suited to C@t{++} programs.
8118 If you ask to print an object whose contents are unknown to
8119 @value{GDBN}, e.g., because its data type is not completely specified
8120 by the debug information, @value{GDBN} will say @samp{<incomplete
8121 type>}. @xref{Symbols, incomplete type}, for more about this.
8123 If you append @kbd{@@entry} string to a function parameter name you get its
8124 value at the time the function got called. If the value is not available an
8125 error message is printed. Entry values are available only with some compilers.
8126 Entry values are normally also printed at the function parameter list according
8127 to @ref{set print entry-values}.
8130 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8136 (gdb) print i@@entry
8140 Strings are identified as arrays of @code{char} values without specified
8141 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8142 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8143 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8144 defines literal string type @code{"char"} as @code{char} without a sign.
8149 signed char var1[] = "A";
8152 You get during debugging
8157 $2 = @{65 'A', 0 '\0'@}
8161 @section Artificial Arrays
8163 @cindex artificial array
8165 @kindex @@@r{, referencing memory as an array}
8166 It is often useful to print out several successive objects of the
8167 same type in memory; a section of an array, or an array of
8168 dynamically determined size for which only a pointer exists in the
8171 You can do this by referring to a contiguous span of memory as an
8172 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8173 operand of @samp{@@} should be the first element of the desired array
8174 and be an individual object. The right operand should be the desired length
8175 of the array. The result is an array value whose elements are all of
8176 the type of the left argument. The first element is actually the left
8177 argument; the second element comes from bytes of memory immediately
8178 following those that hold the first element, and so on. Here is an
8179 example. If a program says
8182 int *array = (int *) malloc (len * sizeof (int));
8186 you can print the contents of @code{array} with
8192 The left operand of @samp{@@} must reside in memory. Array values made
8193 with @samp{@@} in this way behave just like other arrays in terms of
8194 subscripting, and are coerced to pointers when used in expressions.
8195 Artificial arrays most often appear in expressions via the value history
8196 (@pxref{Value History, ,Value History}), after printing one out.
8198 Another way to create an artificial array is to use a cast.
8199 This re-interprets a value as if it were an array.
8200 The value need not be in memory:
8202 (@value{GDBP}) p/x (short[2])0x12345678
8203 $1 = @{0x1234, 0x5678@}
8206 As a convenience, if you leave the array length out (as in
8207 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8208 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8210 (@value{GDBP}) p/x (short[])0x12345678
8211 $2 = @{0x1234, 0x5678@}
8214 Sometimes the artificial array mechanism is not quite enough; in
8215 moderately complex data structures, the elements of interest may not
8216 actually be adjacent---for example, if you are interested in the values
8217 of pointers in an array. One useful work-around in this situation is
8218 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8219 Variables}) as a counter in an expression that prints the first
8220 interesting value, and then repeat that expression via @key{RET}. For
8221 instance, suppose you have an array @code{dtab} of pointers to
8222 structures, and you are interested in the values of a field @code{fv}
8223 in each structure. Here is an example of what you might type:
8233 @node Output Formats
8234 @section Output Formats
8236 @cindex formatted output
8237 @cindex output formats
8238 By default, @value{GDBN} prints a value according to its data type. Sometimes
8239 this is not what you want. For example, you might want to print a number
8240 in hex, or a pointer in decimal. Or you might want to view data in memory
8241 at a certain address as a character string or as an instruction. To do
8242 these things, specify an @dfn{output format} when you print a value.
8244 The simplest use of output formats is to say how to print a value
8245 already computed. This is done by starting the arguments of the
8246 @code{print} command with a slash and a format letter. The format
8247 letters supported are:
8251 Regard the bits of the value as an integer, and print the integer in
8255 Print as integer in signed decimal.
8258 Print as integer in unsigned decimal.
8261 Print as integer in octal.
8264 Print as integer in binary. The letter @samp{t} stands for ``two''.
8265 @footnote{@samp{b} cannot be used because these format letters are also
8266 used with the @code{x} command, where @samp{b} stands for ``byte'';
8267 see @ref{Memory,,Examining Memory}.}
8270 @cindex unknown address, locating
8271 @cindex locate address
8272 Print as an address, both absolute in hexadecimal and as an offset from
8273 the nearest preceding symbol. You can use this format used to discover
8274 where (in what function) an unknown address is located:
8277 (@value{GDBP}) p/a 0x54320
8278 $3 = 0x54320 <_initialize_vx+396>
8282 The command @code{info symbol 0x54320} yields similar results.
8283 @xref{Symbols, info symbol}.
8286 Regard as an integer and print it as a character constant. This
8287 prints both the numerical value and its character representation. The
8288 character representation is replaced with the octal escape @samp{\nnn}
8289 for characters outside the 7-bit @sc{ascii} range.
8291 Without this format, @value{GDBN} displays @code{char},
8292 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8293 constants. Single-byte members of vectors are displayed as integer
8297 Regard the bits of the value as a floating point number and print
8298 using typical floating point syntax.
8301 @cindex printing strings
8302 @cindex printing byte arrays
8303 Regard as a string, if possible. With this format, pointers to single-byte
8304 data are displayed as null-terminated strings and arrays of single-byte data
8305 are displayed as fixed-length strings. Other values are displayed in their
8308 Without this format, @value{GDBN} displays pointers to and arrays of
8309 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8310 strings. Single-byte members of a vector are displayed as an integer
8314 @cindex raw printing
8315 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8316 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8317 Printing}). This typically results in a higher-level display of the
8318 value's contents. The @samp{r} format bypasses any Python
8319 pretty-printer which might exist.
8322 For example, to print the program counter in hex (@pxref{Registers}), type
8329 Note that no space is required before the slash; this is because command
8330 names in @value{GDBN} cannot contain a slash.
8332 To reprint the last value in the value history with a different format,
8333 you can use the @code{print} command with just a format and no
8334 expression. For example, @samp{p/x} reprints the last value in hex.
8337 @section Examining Memory
8339 You can use the command @code{x} (for ``examine'') to examine memory in
8340 any of several formats, independently of your program's data types.
8342 @cindex examining memory
8344 @kindex x @r{(examine memory)}
8345 @item x/@var{nfu} @var{addr}
8348 Use the @code{x} command to examine memory.
8351 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8352 much memory to display and how to format it; @var{addr} is an
8353 expression giving the address where you want to start displaying memory.
8354 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8355 Several commands set convenient defaults for @var{addr}.
8358 @item @var{n}, the repeat count
8359 The repeat count is a decimal integer; the default is 1. It specifies
8360 how much memory (counting by units @var{u}) to display.
8361 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8364 @item @var{f}, the display format
8365 The display format is one of the formats used by @code{print}
8366 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8367 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8368 The default is @samp{x} (hexadecimal) initially. The default changes
8369 each time you use either @code{x} or @code{print}.
8371 @item @var{u}, the unit size
8372 The unit size is any of
8378 Halfwords (two bytes).
8380 Words (four bytes). This is the initial default.
8382 Giant words (eight bytes).
8385 Each time you specify a unit size with @code{x}, that size becomes the
8386 default unit the next time you use @code{x}. For the @samp{i} format,
8387 the unit size is ignored and is normally not written. For the @samp{s} format,
8388 the unit size defaults to @samp{b}, unless it is explicitly given.
8389 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8390 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8391 Note that the results depend on the programming language of the
8392 current compilation unit. If the language is C, the @samp{s}
8393 modifier will use the UTF-16 encoding while @samp{w} will use
8394 UTF-32. The encoding is set by the programming language and cannot
8397 @item @var{addr}, starting display address
8398 @var{addr} is the address where you want @value{GDBN} to begin displaying
8399 memory. The expression need not have a pointer value (though it may);
8400 it is always interpreted as an integer address of a byte of memory.
8401 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8402 @var{addr} is usually just after the last address examined---but several
8403 other commands also set the default address: @code{info breakpoints} (to
8404 the address of the last breakpoint listed), @code{info line} (to the
8405 starting address of a line), and @code{print} (if you use it to display
8406 a value from memory).
8409 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8410 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8411 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8412 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8413 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8415 Since the letters indicating unit sizes are all distinct from the
8416 letters specifying output formats, you do not have to remember whether
8417 unit size or format comes first; either order works. The output
8418 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8419 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8421 Even though the unit size @var{u} is ignored for the formats @samp{s}
8422 and @samp{i}, you might still want to use a count @var{n}; for example,
8423 @samp{3i} specifies that you want to see three machine instructions,
8424 including any operands. For convenience, especially when used with
8425 the @code{display} command, the @samp{i} format also prints branch delay
8426 slot instructions, if any, beyond the count specified, which immediately
8427 follow the last instruction that is within the count. The command
8428 @code{disassemble} gives an alternative way of inspecting machine
8429 instructions; see @ref{Machine Code,,Source and Machine Code}.
8431 All the defaults for the arguments to @code{x} are designed to make it
8432 easy to continue scanning memory with minimal specifications each time
8433 you use @code{x}. For example, after you have inspected three machine
8434 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8435 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8436 the repeat count @var{n} is used again; the other arguments default as
8437 for successive uses of @code{x}.
8439 When examining machine instructions, the instruction at current program
8440 counter is shown with a @code{=>} marker. For example:
8443 (@value{GDBP}) x/5i $pc-6
8444 0x804837f <main+11>: mov %esp,%ebp
8445 0x8048381 <main+13>: push %ecx
8446 0x8048382 <main+14>: sub $0x4,%esp
8447 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8448 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8451 @cindex @code{$_}, @code{$__}, and value history
8452 The addresses and contents printed by the @code{x} command are not saved
8453 in the value history because there is often too much of them and they
8454 would get in the way. Instead, @value{GDBN} makes these values available for
8455 subsequent use in expressions as values of the convenience variables
8456 @code{$_} and @code{$__}. After an @code{x} command, the last address
8457 examined is available for use in expressions in the convenience variable
8458 @code{$_}. The contents of that address, as examined, are available in
8459 the convenience variable @code{$__}.
8461 If the @code{x} command has a repeat count, the address and contents saved
8462 are from the last memory unit printed; this is not the same as the last
8463 address printed if several units were printed on the last line of output.
8465 @cindex remote memory comparison
8466 @cindex verify remote memory image
8467 When you are debugging a program running on a remote target machine
8468 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8469 remote machine's memory against the executable file you downloaded to
8470 the target. The @code{compare-sections} command is provided for such
8474 @kindex compare-sections
8475 @item compare-sections @r{[}@var{section-name}@r{]}
8476 Compare the data of a loadable section @var{section-name} in the
8477 executable file of the program being debugged with the same section in
8478 the remote machine's memory, and report any mismatches. With no
8479 arguments, compares all loadable sections. This command's
8480 availability depends on the target's support for the @code{"qCRC"}
8485 @section Automatic Display
8486 @cindex automatic display
8487 @cindex display of expressions
8489 If you find that you want to print the value of an expression frequently
8490 (to see how it changes), you might want to add it to the @dfn{automatic
8491 display list} so that @value{GDBN} prints its value each time your program stops.
8492 Each expression added to the list is given a number to identify it;
8493 to remove an expression from the list, you specify that number.
8494 The automatic display looks like this:
8498 3: bar[5] = (struct hack *) 0x3804
8502 This display shows item numbers, expressions and their current values. As with
8503 displays you request manually using @code{x} or @code{print}, you can
8504 specify the output format you prefer; in fact, @code{display} decides
8505 whether to use @code{print} or @code{x} depending your format
8506 specification---it uses @code{x} if you specify either the @samp{i}
8507 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8511 @item display @var{expr}
8512 Add the expression @var{expr} to the list of expressions to display
8513 each time your program stops. @xref{Expressions, ,Expressions}.
8515 @code{display} does not repeat if you press @key{RET} again after using it.
8517 @item display/@var{fmt} @var{expr}
8518 For @var{fmt} specifying only a display format and not a size or
8519 count, add the expression @var{expr} to the auto-display list but
8520 arrange to display it each time in the specified format @var{fmt}.
8521 @xref{Output Formats,,Output Formats}.
8523 @item display/@var{fmt} @var{addr}
8524 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8525 number of units, add the expression @var{addr} as a memory address to
8526 be examined each time your program stops. Examining means in effect
8527 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8530 For example, @samp{display/i $pc} can be helpful, to see the machine
8531 instruction about to be executed each time execution stops (@samp{$pc}
8532 is a common name for the program counter; @pxref{Registers, ,Registers}).
8535 @kindex delete display
8537 @item undisplay @var{dnums}@dots{}
8538 @itemx delete display @var{dnums}@dots{}
8539 Remove items from the list of expressions to display. Specify the
8540 numbers of the displays that you want affected with the command
8541 argument @var{dnums}. It can be a single display number, one of the
8542 numbers shown in the first field of the @samp{info display} display;
8543 or it could be a range of display numbers, as in @code{2-4}.
8545 @code{undisplay} does not repeat if you press @key{RET} after using it.
8546 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8548 @kindex disable display
8549 @item disable display @var{dnums}@dots{}
8550 Disable the display of item numbers @var{dnums}. A disabled display
8551 item is not printed automatically, but is not forgotten. It may be
8552 enabled again later. Specify the numbers of the displays that you
8553 want affected with the command argument @var{dnums}. It can be a
8554 single display number, one of the numbers shown in the first field of
8555 the @samp{info display} display; or it could be a range of display
8556 numbers, as in @code{2-4}.
8558 @kindex enable display
8559 @item enable display @var{dnums}@dots{}
8560 Enable display of item numbers @var{dnums}. It becomes effective once
8561 again in auto display of its expression, until you specify otherwise.
8562 Specify the numbers of the displays that you want affected with the
8563 command argument @var{dnums}. It can be a single display number, one
8564 of the numbers shown in the first field of the @samp{info display}
8565 display; or it could be a range of display numbers, as in @code{2-4}.
8568 Display the current values of the expressions on the list, just as is
8569 done when your program stops.
8571 @kindex info display
8573 Print the list of expressions previously set up to display
8574 automatically, each one with its item number, but without showing the
8575 values. This includes disabled expressions, which are marked as such.
8576 It also includes expressions which would not be displayed right now
8577 because they refer to automatic variables not currently available.
8580 @cindex display disabled out of scope
8581 If a display expression refers to local variables, then it does not make
8582 sense outside the lexical context for which it was set up. Such an
8583 expression is disabled when execution enters a context where one of its
8584 variables is not defined. For example, if you give the command
8585 @code{display last_char} while inside a function with an argument
8586 @code{last_char}, @value{GDBN} displays this argument while your program
8587 continues to stop inside that function. When it stops elsewhere---where
8588 there is no variable @code{last_char}---the display is disabled
8589 automatically. The next time your program stops where @code{last_char}
8590 is meaningful, you can enable the display expression once again.
8592 @node Print Settings
8593 @section Print Settings
8595 @cindex format options
8596 @cindex print settings
8597 @value{GDBN} provides the following ways to control how arrays, structures,
8598 and symbols are printed.
8601 These settings are useful for debugging programs in any language:
8605 @item set print address
8606 @itemx set print address on
8607 @cindex print/don't print memory addresses
8608 @value{GDBN} prints memory addresses showing the location of stack
8609 traces, structure values, pointer values, breakpoints, and so forth,
8610 even when it also displays the contents of those addresses. The default
8611 is @code{on}. For example, this is what a stack frame display looks like with
8612 @code{set print address on}:
8617 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8619 530 if (lquote != def_lquote)
8623 @item set print address off
8624 Do not print addresses when displaying their contents. For example,
8625 this is the same stack frame displayed with @code{set print address off}:
8629 (@value{GDBP}) set print addr off
8631 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8632 530 if (lquote != def_lquote)
8636 You can use @samp{set print address off} to eliminate all machine
8637 dependent displays from the @value{GDBN} interface. For example, with
8638 @code{print address off}, you should get the same text for backtraces on
8639 all machines---whether or not they involve pointer arguments.
8642 @item show print address
8643 Show whether or not addresses are to be printed.
8646 When @value{GDBN} prints a symbolic address, it normally prints the
8647 closest earlier symbol plus an offset. If that symbol does not uniquely
8648 identify the address (for example, it is a name whose scope is a single
8649 source file), you may need to clarify. One way to do this is with
8650 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8651 you can set @value{GDBN} to print the source file and line number when
8652 it prints a symbolic address:
8655 @item set print symbol-filename on
8656 @cindex source file and line of a symbol
8657 @cindex symbol, source file and line
8658 Tell @value{GDBN} to print the source file name and line number of a
8659 symbol in the symbolic form of an address.
8661 @item set print symbol-filename off
8662 Do not print source file name and line number of a symbol. This is the
8665 @item show print symbol-filename
8666 Show whether or not @value{GDBN} will print the source file name and
8667 line number of a symbol in the symbolic form of an address.
8670 Another situation where it is helpful to show symbol filenames and line
8671 numbers is when disassembling code; @value{GDBN} shows you the line
8672 number and source file that corresponds to each instruction.
8674 Also, you may wish to see the symbolic form only if the address being
8675 printed is reasonably close to the closest earlier symbol:
8678 @item set print max-symbolic-offset @var{max-offset}
8679 @itemx set print max-symbolic-offset unlimited
8680 @cindex maximum value for offset of closest symbol
8681 Tell @value{GDBN} to only display the symbolic form of an address if the
8682 offset between the closest earlier symbol and the address is less than
8683 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8684 to always print the symbolic form of an address if any symbol precedes
8685 it. Zero is equivalent to @code{unlimited}.
8687 @item show print max-symbolic-offset
8688 Ask how large the maximum offset is that @value{GDBN} prints in a
8692 @cindex wild pointer, interpreting
8693 @cindex pointer, finding referent
8694 If you have a pointer and you are not sure where it points, try
8695 @samp{set print symbol-filename on}. Then you can determine the name
8696 and source file location of the variable where it points, using
8697 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8698 For example, here @value{GDBN} shows that a variable @code{ptt} points
8699 at another variable @code{t}, defined in @file{hi2.c}:
8702 (@value{GDBP}) set print symbol-filename on
8703 (@value{GDBP}) p/a ptt
8704 $4 = 0xe008 <t in hi2.c>
8708 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8709 does not show the symbol name and filename of the referent, even with
8710 the appropriate @code{set print} options turned on.
8713 You can also enable @samp{/a}-like formatting all the time using
8714 @samp{set print symbol on}:
8717 @item set print symbol on
8718 Tell @value{GDBN} to print the symbol corresponding to an address, if
8721 @item set print symbol off
8722 Tell @value{GDBN} not to print the symbol corresponding to an
8723 address. In this mode, @value{GDBN} will still print the symbol
8724 corresponding to pointers to functions. This is the default.
8726 @item show print symbol
8727 Show whether @value{GDBN} will display the symbol corresponding to an
8731 Other settings control how different kinds of objects are printed:
8734 @item set print array
8735 @itemx set print array on
8736 @cindex pretty print arrays
8737 Pretty print arrays. This format is more convenient to read,
8738 but uses more space. The default is off.
8740 @item set print array off
8741 Return to compressed format for arrays.
8743 @item show print array
8744 Show whether compressed or pretty format is selected for displaying
8747 @cindex print array indexes
8748 @item set print array-indexes
8749 @itemx set print array-indexes on
8750 Print the index of each element when displaying arrays. May be more
8751 convenient to locate a given element in the array or quickly find the
8752 index of a given element in that printed array. The default is off.
8754 @item set print array-indexes off
8755 Stop printing element indexes when displaying arrays.
8757 @item show print array-indexes
8758 Show whether the index of each element is printed when displaying
8761 @item set print elements @var{number-of-elements}
8762 @itemx set print elements unlimited
8763 @cindex number of array elements to print
8764 @cindex limit on number of printed array elements
8765 Set a limit on how many elements of an array @value{GDBN} will print.
8766 If @value{GDBN} is printing a large array, it stops printing after it has
8767 printed the number of elements set by the @code{set print elements} command.
8768 This limit also applies to the display of strings.
8769 When @value{GDBN} starts, this limit is set to 200.
8770 Setting @var{number-of-elements} to @code{unlimited} or zero means
8771 that the number of elements to print is unlimited.
8773 @item show print elements
8774 Display the number of elements of a large array that @value{GDBN} will print.
8775 If the number is 0, then the printing is unlimited.
8777 @item set print frame-arguments @var{value}
8778 @kindex set print frame-arguments
8779 @cindex printing frame argument values
8780 @cindex print all frame argument values
8781 @cindex print frame argument values for scalars only
8782 @cindex do not print frame argument values
8783 This command allows to control how the values of arguments are printed
8784 when the debugger prints a frame (@pxref{Frames}). The possible
8789 The values of all arguments are printed.
8792 Print the value of an argument only if it is a scalar. The value of more
8793 complex arguments such as arrays, structures, unions, etc, is replaced
8794 by @code{@dots{}}. This is the default. Here is an example where
8795 only scalar arguments are shown:
8798 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8803 None of the argument values are printed. Instead, the value of each argument
8804 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8807 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8812 By default, only scalar arguments are printed. This command can be used
8813 to configure the debugger to print the value of all arguments, regardless
8814 of their type. However, it is often advantageous to not print the value
8815 of more complex parameters. For instance, it reduces the amount of
8816 information printed in each frame, making the backtrace more readable.
8817 Also, it improves performance when displaying Ada frames, because
8818 the computation of large arguments can sometimes be CPU-intensive,
8819 especially in large applications. Setting @code{print frame-arguments}
8820 to @code{scalars} (the default) or @code{none} avoids this computation,
8821 thus speeding up the display of each Ada frame.
8823 @item show print frame-arguments
8824 Show how the value of arguments should be displayed when printing a frame.
8826 @anchor{set print entry-values}
8827 @item set print entry-values @var{value}
8828 @kindex set print entry-values
8829 Set printing of frame argument values at function entry. In some cases
8830 @value{GDBN} can determine the value of function argument which was passed by
8831 the function caller, even if the value was modified inside the called function
8832 and therefore is different. With optimized code, the current value could be
8833 unavailable, but the entry value may still be known.
8835 The default value is @code{default} (see below for its description). Older
8836 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8837 this feature will behave in the @code{default} setting the same way as with the
8840 This functionality is currently supported only by DWARF 2 debugging format and
8841 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8842 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8845 The @var{value} parameter can be one of the following:
8849 Print only actual parameter values, never print values from function entry
8853 #0 different (val=6)
8854 #0 lost (val=<optimized out>)
8856 #0 invalid (val=<optimized out>)
8860 Print only parameter values from function entry point. The actual parameter
8861 values are never printed.
8863 #0 equal (val@@entry=5)
8864 #0 different (val@@entry=5)
8865 #0 lost (val@@entry=5)
8866 #0 born (val@@entry=<optimized out>)
8867 #0 invalid (val@@entry=<optimized out>)
8871 Print only parameter values from function entry point. If value from function
8872 entry point is not known while the actual value is known, print the actual
8873 value for such parameter.
8875 #0 equal (val@@entry=5)
8876 #0 different (val@@entry=5)
8877 #0 lost (val@@entry=5)
8879 #0 invalid (val@@entry=<optimized out>)
8883 Print actual parameter values. If actual parameter value is not known while
8884 value from function entry point is known, print the entry point value for such
8888 #0 different (val=6)
8889 #0 lost (val@@entry=5)
8891 #0 invalid (val=<optimized out>)
8895 Always print both the actual parameter value and its value from function entry
8896 point, even if values of one or both are not available due to compiler
8899 #0 equal (val=5, val@@entry=5)
8900 #0 different (val=6, val@@entry=5)
8901 #0 lost (val=<optimized out>, val@@entry=5)
8902 #0 born (val=10, val@@entry=<optimized out>)
8903 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8907 Print the actual parameter value if it is known and also its value from
8908 function entry point if it is known. If neither is known, print for the actual
8909 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8910 values are known and identical, print the shortened
8911 @code{param=param@@entry=VALUE} notation.
8913 #0 equal (val=val@@entry=5)
8914 #0 different (val=6, val@@entry=5)
8915 #0 lost (val@@entry=5)
8917 #0 invalid (val=<optimized out>)
8921 Always print the actual parameter value. Print also its value from function
8922 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8923 if both values are known and identical, print the shortened
8924 @code{param=param@@entry=VALUE} notation.
8926 #0 equal (val=val@@entry=5)
8927 #0 different (val=6, val@@entry=5)
8928 #0 lost (val=<optimized out>, val@@entry=5)
8930 #0 invalid (val=<optimized out>)
8934 For analysis messages on possible failures of frame argument values at function
8935 entry resolution see @ref{set debug entry-values}.
8937 @item show print entry-values
8938 Show the method being used for printing of frame argument values at function
8941 @item set print repeats @var{number-of-repeats}
8942 @itemx set print repeats unlimited
8943 @cindex repeated array elements
8944 Set the threshold for suppressing display of repeated array
8945 elements. When the number of consecutive identical elements of an
8946 array exceeds the threshold, @value{GDBN} prints the string
8947 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8948 identical repetitions, instead of displaying the identical elements
8949 themselves. Setting the threshold to @code{unlimited} or zero will
8950 cause all elements to be individually printed. The default threshold
8953 @item show print repeats
8954 Display the current threshold for printing repeated identical
8957 @item set print null-stop
8958 @cindex @sc{null} elements in arrays
8959 Cause @value{GDBN} to stop printing the characters of an array when the first
8960 @sc{null} is encountered. This is useful when large arrays actually
8961 contain only short strings.
8964 @item show print null-stop
8965 Show whether @value{GDBN} stops printing an array on the first
8966 @sc{null} character.
8968 @item set print pretty on
8969 @cindex print structures in indented form
8970 @cindex indentation in structure display
8971 Cause @value{GDBN} to print structures in an indented format with one member
8972 per line, like this:
8987 @item set print pretty off
8988 Cause @value{GDBN} to print structures in a compact format, like this:
8992 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8993 meat = 0x54 "Pork"@}
8998 This is the default format.
9000 @item show print pretty
9001 Show which format @value{GDBN} is using to print structures.
9003 @item set print sevenbit-strings on
9004 @cindex eight-bit characters in strings
9005 @cindex octal escapes in strings
9006 Print using only seven-bit characters; if this option is set,
9007 @value{GDBN} displays any eight-bit characters (in strings or
9008 character values) using the notation @code{\}@var{nnn}. This setting is
9009 best if you are working in English (@sc{ascii}) and you use the
9010 high-order bit of characters as a marker or ``meta'' bit.
9012 @item set print sevenbit-strings off
9013 Print full eight-bit characters. This allows the use of more
9014 international character sets, and is the default.
9016 @item show print sevenbit-strings
9017 Show whether or not @value{GDBN} is printing only seven-bit characters.
9019 @item set print union on
9020 @cindex unions in structures, printing
9021 Tell @value{GDBN} to print unions which are contained in structures
9022 and other unions. This is the default setting.
9024 @item set print union off
9025 Tell @value{GDBN} not to print unions which are contained in
9026 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9029 @item show print union
9030 Ask @value{GDBN} whether or not it will print unions which are contained in
9031 structures and other unions.
9033 For example, given the declarations
9036 typedef enum @{Tree, Bug@} Species;
9037 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9038 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9049 struct thing foo = @{Tree, @{Acorn@}@};
9053 with @code{set print union on} in effect @samp{p foo} would print
9056 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9060 and with @code{set print union off} in effect it would print
9063 $1 = @{it = Tree, form = @{...@}@}
9067 @code{set print union} affects programs written in C-like languages
9073 These settings are of interest when debugging C@t{++} programs:
9076 @cindex demangling C@t{++} names
9077 @item set print demangle
9078 @itemx set print demangle on
9079 Print C@t{++} names in their source form rather than in the encoded
9080 (``mangled'') form passed to the assembler and linker for type-safe
9081 linkage. The default is on.
9083 @item show print demangle
9084 Show whether C@t{++} names are printed in mangled or demangled form.
9086 @item set print asm-demangle
9087 @itemx set print asm-demangle on
9088 Print C@t{++} names in their source form rather than their mangled form, even
9089 in assembler code printouts such as instruction disassemblies.
9092 @item show print asm-demangle
9093 Show whether C@t{++} names in assembly listings are printed in mangled
9096 @cindex C@t{++} symbol decoding style
9097 @cindex symbol decoding style, C@t{++}
9098 @kindex set demangle-style
9099 @item set demangle-style @var{style}
9100 Choose among several encoding schemes used by different compilers to
9101 represent C@t{++} names. The choices for @var{style} are currently:
9105 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9106 This is the default.
9109 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9112 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9115 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9118 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9119 @strong{Warning:} this setting alone is not sufficient to allow
9120 debugging @code{cfront}-generated executables. @value{GDBN} would
9121 require further enhancement to permit that.
9124 If you omit @var{style}, you will see a list of possible formats.
9126 @item show demangle-style
9127 Display the encoding style currently in use for decoding C@t{++} symbols.
9129 @item set print object
9130 @itemx set print object on
9131 @cindex derived type of an object, printing
9132 @cindex display derived types
9133 When displaying a pointer to an object, identify the @emph{actual}
9134 (derived) type of the object rather than the @emph{declared} type, using
9135 the virtual function table. Note that the virtual function table is
9136 required---this feature can only work for objects that have run-time
9137 type identification; a single virtual method in the object's declared
9138 type is sufficient. Note that this setting is also taken into account when
9139 working with variable objects via MI (@pxref{GDB/MI}).
9141 @item set print object off
9142 Display only the declared type of objects, without reference to the
9143 virtual function table. This is the default setting.
9145 @item show print object
9146 Show whether actual, or declared, object types are displayed.
9148 @item set print static-members
9149 @itemx set print static-members on
9150 @cindex static members of C@t{++} objects
9151 Print static members when displaying a C@t{++} object. The default is on.
9153 @item set print static-members off
9154 Do not print static members when displaying a C@t{++} object.
9156 @item show print static-members
9157 Show whether C@t{++} static members are printed or not.
9159 @item set print pascal_static-members
9160 @itemx set print pascal_static-members on
9161 @cindex static members of Pascal objects
9162 @cindex Pascal objects, static members display
9163 Print static members when displaying a Pascal object. The default is on.
9165 @item set print pascal_static-members off
9166 Do not print static members when displaying a Pascal object.
9168 @item show print pascal_static-members
9169 Show whether Pascal static members are printed or not.
9171 @c These don't work with HP ANSI C++ yet.
9172 @item set print vtbl
9173 @itemx set print vtbl on
9174 @cindex pretty print C@t{++} virtual function tables
9175 @cindex virtual functions (C@t{++}) display
9176 @cindex VTBL display
9177 Pretty print C@t{++} virtual function tables. The default is off.
9178 (The @code{vtbl} commands do not work on programs compiled with the HP
9179 ANSI C@t{++} compiler (@code{aCC}).)
9181 @item set print vtbl off
9182 Do not pretty print C@t{++} virtual function tables.
9184 @item show print vtbl
9185 Show whether C@t{++} virtual function tables are pretty printed, or not.
9188 @node Pretty Printing
9189 @section Pretty Printing
9191 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9192 Python code. It greatly simplifies the display of complex objects. This
9193 mechanism works for both MI and the CLI.
9196 * Pretty-Printer Introduction:: Introduction to pretty-printers
9197 * Pretty-Printer Example:: An example pretty-printer
9198 * Pretty-Printer Commands:: Pretty-printer commands
9201 @node Pretty-Printer Introduction
9202 @subsection Pretty-Printer Introduction
9204 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9205 registered for the value. If there is then @value{GDBN} invokes the
9206 pretty-printer to print the value. Otherwise the value is printed normally.
9208 Pretty-printers are normally named. This makes them easy to manage.
9209 The @samp{info pretty-printer} command will list all the installed
9210 pretty-printers with their names.
9211 If a pretty-printer can handle multiple data types, then its
9212 @dfn{subprinters} are the printers for the individual data types.
9213 Each such subprinter has its own name.
9214 The format of the name is @var{printer-name};@var{subprinter-name}.
9216 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9217 Typically they are automatically loaded and registered when the corresponding
9218 debug information is loaded, thus making them available without having to
9219 do anything special.
9221 There are three places where a pretty-printer can be registered.
9225 Pretty-printers registered globally are available when debugging
9229 Pretty-printers registered with a program space are available only
9230 when debugging that program.
9231 @xref{Progspaces In Python}, for more details on program spaces in Python.
9234 Pretty-printers registered with an objfile are loaded and unloaded
9235 with the corresponding objfile (e.g., shared library).
9236 @xref{Objfiles In Python}, for more details on objfiles in Python.
9239 @xref{Selecting Pretty-Printers}, for further information on how
9240 pretty-printers are selected,
9242 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9245 @node Pretty-Printer Example
9246 @subsection Pretty-Printer Example
9248 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9251 (@value{GDBP}) print s
9253 static npos = 4294967295,
9255 <std::allocator<char>> = @{
9256 <__gnu_cxx::new_allocator<char>> = @{
9257 <No data fields>@}, <No data fields>
9259 members of std::basic_string<char, std::char_traits<char>,
9260 std::allocator<char> >::_Alloc_hider:
9261 _M_p = 0x804a014 "abcd"
9266 With a pretty-printer for @code{std::string} only the contents are printed:
9269 (@value{GDBP}) print s
9273 @node Pretty-Printer Commands
9274 @subsection Pretty-Printer Commands
9275 @cindex pretty-printer commands
9278 @kindex info pretty-printer
9279 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9280 Print the list of installed pretty-printers.
9281 This includes disabled pretty-printers, which are marked as such.
9283 @var{object-regexp} is a regular expression matching the objects
9284 whose pretty-printers to list.
9285 Objects can be @code{global}, the program space's file
9286 (@pxref{Progspaces In Python}),
9287 and the object files within that program space (@pxref{Objfiles In Python}).
9288 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9289 looks up a printer from these three objects.
9291 @var{name-regexp} is a regular expression matching the name of the printers
9294 @kindex disable pretty-printer
9295 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9296 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9297 A disabled pretty-printer is not forgotten, it may be enabled again later.
9299 @kindex enable pretty-printer
9300 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9301 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9306 Suppose we have three pretty-printers installed: one from library1.so
9307 named @code{foo} that prints objects of type @code{foo}, and
9308 another from library2.so named @code{bar} that prints two types of objects,
9309 @code{bar1} and @code{bar2}.
9312 (gdb) info pretty-printer
9319 (gdb) info pretty-printer library2
9324 (gdb) disable pretty-printer library1
9326 2 of 3 printers enabled
9327 (gdb) info pretty-printer
9334 (gdb) disable pretty-printer library2 bar:bar1
9336 1 of 3 printers enabled
9337 (gdb) info pretty-printer library2
9344 (gdb) disable pretty-printer library2 bar
9346 0 of 3 printers enabled
9347 (gdb) info pretty-printer library2
9356 Note that for @code{bar} the entire printer can be disabled,
9357 as can each individual subprinter.
9360 @section Value History
9362 @cindex value history
9363 @cindex history of values printed by @value{GDBN}
9364 Values printed by the @code{print} command are saved in the @value{GDBN}
9365 @dfn{value history}. This allows you to refer to them in other expressions.
9366 Values are kept until the symbol table is re-read or discarded
9367 (for example with the @code{file} or @code{symbol-file} commands).
9368 When the symbol table changes, the value history is discarded,
9369 since the values may contain pointers back to the types defined in the
9374 @cindex history number
9375 The values printed are given @dfn{history numbers} by which you can
9376 refer to them. These are successive integers starting with one.
9377 @code{print} shows you the history number assigned to a value by
9378 printing @samp{$@var{num} = } before the value; here @var{num} is the
9381 To refer to any previous value, use @samp{$} followed by the value's
9382 history number. The way @code{print} labels its output is designed to
9383 remind you of this. Just @code{$} refers to the most recent value in
9384 the history, and @code{$$} refers to the value before that.
9385 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9386 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9387 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9389 For example, suppose you have just printed a pointer to a structure and
9390 want to see the contents of the structure. It suffices to type
9396 If you have a chain of structures where the component @code{next} points
9397 to the next one, you can print the contents of the next one with this:
9404 You can print successive links in the chain by repeating this
9405 command---which you can do by just typing @key{RET}.
9407 Note that the history records values, not expressions. If the value of
9408 @code{x} is 4 and you type these commands:
9416 then the value recorded in the value history by the @code{print} command
9417 remains 4 even though the value of @code{x} has changed.
9422 Print the last ten values in the value history, with their item numbers.
9423 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9424 values} does not change the history.
9426 @item show values @var{n}
9427 Print ten history values centered on history item number @var{n}.
9430 Print ten history values just after the values last printed. If no more
9431 values are available, @code{show values +} produces no display.
9434 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9435 same effect as @samp{show values +}.
9437 @node Convenience Vars
9438 @section Convenience Variables
9440 @cindex convenience variables
9441 @cindex user-defined variables
9442 @value{GDBN} provides @dfn{convenience variables} that you can use within
9443 @value{GDBN} to hold on to a value and refer to it later. These variables
9444 exist entirely within @value{GDBN}; they are not part of your program, and
9445 setting a convenience variable has no direct effect on further execution
9446 of your program. That is why you can use them freely.
9448 Convenience variables are prefixed with @samp{$}. Any name preceded by
9449 @samp{$} can be used for a convenience variable, unless it is one of
9450 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9451 (Value history references, in contrast, are @emph{numbers} preceded
9452 by @samp{$}. @xref{Value History, ,Value History}.)
9454 You can save a value in a convenience variable with an assignment
9455 expression, just as you would set a variable in your program.
9459 set $foo = *object_ptr
9463 would save in @code{$foo} the value contained in the object pointed to by
9466 Using a convenience variable for the first time creates it, but its
9467 value is @code{void} until you assign a new value. You can alter the
9468 value with another assignment at any time.
9470 Convenience variables have no fixed types. You can assign a convenience
9471 variable any type of value, including structures and arrays, even if
9472 that variable already has a value of a different type. The convenience
9473 variable, when used as an expression, has the type of its current value.
9476 @kindex show convenience
9477 @cindex show all user variables and functions
9478 @item show convenience
9479 Print a list of convenience variables used so far, and their values,
9480 as well as a list of the convenience functions.
9481 Abbreviated @code{show conv}.
9483 @kindex init-if-undefined
9484 @cindex convenience variables, initializing
9485 @item init-if-undefined $@var{variable} = @var{expression}
9486 Set a convenience variable if it has not already been set. This is useful
9487 for user-defined commands that keep some state. It is similar, in concept,
9488 to using local static variables with initializers in C (except that
9489 convenience variables are global). It can also be used to allow users to
9490 override default values used in a command script.
9492 If the variable is already defined then the expression is not evaluated so
9493 any side-effects do not occur.
9496 One of the ways to use a convenience variable is as a counter to be
9497 incremented or a pointer to be advanced. For example, to print
9498 a field from successive elements of an array of structures:
9502 print bar[$i++]->contents
9506 Repeat that command by typing @key{RET}.
9508 Some convenience variables are created automatically by @value{GDBN} and given
9509 values likely to be useful.
9512 @vindex $_@r{, convenience variable}
9514 The variable @code{$_} is automatically set by the @code{x} command to
9515 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9516 commands which provide a default address for @code{x} to examine also
9517 set @code{$_} to that address; these commands include @code{info line}
9518 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9519 except when set by the @code{x} command, in which case it is a pointer
9520 to the type of @code{$__}.
9522 @vindex $__@r{, convenience variable}
9524 The variable @code{$__} is automatically set by the @code{x} command
9525 to the value found in the last address examined. Its type is chosen
9526 to match the format in which the data was printed.
9529 @vindex $_exitcode@r{, convenience variable}
9530 The variable @code{$_exitcode} is automatically set to the exit code when
9531 the program being debugged terminates.
9534 The variable @code{$_exception} is set to the exception object being
9535 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9538 @itemx $_probe_arg0@dots{}$_probe_arg11
9539 Arguments to a static probe. @xref{Static Probe Points}.
9542 @vindex $_sdata@r{, inspect, convenience variable}
9543 The variable @code{$_sdata} contains extra collected static tracepoint
9544 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9545 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9546 if extra static tracepoint data has not been collected.
9549 @vindex $_siginfo@r{, convenience variable}
9550 The variable @code{$_siginfo} contains extra signal information
9551 (@pxref{extra signal information}). Note that @code{$_siginfo}
9552 could be empty, if the application has not yet received any signals.
9553 For example, it will be empty before you execute the @code{run} command.
9556 @vindex $_tlb@r{, convenience variable}
9557 The variable @code{$_tlb} is automatically set when debugging
9558 applications running on MS-Windows in native mode or connected to
9559 gdbserver that supports the @code{qGetTIBAddr} request.
9560 @xref{General Query Packets}.
9561 This variable contains the address of the thread information block.
9565 On HP-UX systems, if you refer to a function or variable name that
9566 begins with a dollar sign, @value{GDBN} searches for a user or system
9567 name first, before it searches for a convenience variable.
9569 @node Convenience Funs
9570 @section Convenience Functions
9572 @cindex convenience functions
9573 @value{GDBN} also supplies some @dfn{convenience functions}. These
9574 have a syntax similar to convenience variables. A convenience
9575 function can be used in an expression just like an ordinary function;
9576 however, a convenience function is implemented internally to
9579 These functions require @value{GDBN} to be configured with
9580 @code{Python} support.
9584 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9585 @findex $_memeq@r{, convenience function}
9586 Returns one if the @var{length} bytes at the addresses given by
9587 @var{buf1} and @var{buf2} are equal.
9588 Otherwise it returns zero.
9590 @item $_regex(@var{str}, @var{regex})
9591 @findex $_regex@r{, convenience function}
9592 Returns one if the string @var{str} matches the regular expression
9593 @var{regex}. Otherwise it returns zero.
9594 The syntax of the regular expression is that specified by @code{Python}'s
9595 regular expression support.
9597 @item $_streq(@var{str1}, @var{str2})
9598 @findex $_streq@r{, convenience function}
9599 Returns one if the strings @var{str1} and @var{str2} are equal.
9600 Otherwise it returns zero.
9602 @item $_strlen(@var{str})
9603 @findex $_strlen@r{, convenience function}
9604 Returns the length of string @var{str}.
9608 @value{GDBN} provides the ability to list and get help on
9609 convenience functions.
9613 @kindex help function
9614 @cindex show all convenience functions
9615 Print a list of all convenience functions.
9622 You can refer to machine register contents, in expressions, as variables
9623 with names starting with @samp{$}. The names of registers are different
9624 for each machine; use @code{info registers} to see the names used on
9628 @kindex info registers
9629 @item info registers
9630 Print the names and values of all registers except floating-point
9631 and vector registers (in the selected stack frame).
9633 @kindex info all-registers
9634 @cindex floating point registers
9635 @item info all-registers
9636 Print the names and values of all registers, including floating-point
9637 and vector registers (in the selected stack frame).
9639 @item info registers @var{regname} @dots{}
9640 Print the @dfn{relativized} value of each specified register @var{regname}.
9641 As discussed in detail below, register values are normally relative to
9642 the selected stack frame. @var{regname} may be any register name valid on
9643 the machine you are using, with or without the initial @samp{$}.
9646 @cindex stack pointer register
9647 @cindex program counter register
9648 @cindex process status register
9649 @cindex frame pointer register
9650 @cindex standard registers
9651 @value{GDBN} has four ``standard'' register names that are available (in
9652 expressions) on most machines---whenever they do not conflict with an
9653 architecture's canonical mnemonics for registers. The register names
9654 @code{$pc} and @code{$sp} are used for the program counter register and
9655 the stack pointer. @code{$fp} is used for a register that contains a
9656 pointer to the current stack frame, and @code{$ps} is used for a
9657 register that contains the processor status. For example,
9658 you could print the program counter in hex with
9665 or print the instruction to be executed next with
9672 or add four to the stack pointer@footnote{This is a way of removing
9673 one word from the stack, on machines where stacks grow downward in
9674 memory (most machines, nowadays). This assumes that the innermost
9675 stack frame is selected; setting @code{$sp} is not allowed when other
9676 stack frames are selected. To pop entire frames off the stack,
9677 regardless of machine architecture, use @code{return};
9678 see @ref{Returning, ,Returning from a Function}.} with
9684 Whenever possible, these four standard register names are available on
9685 your machine even though the machine has different canonical mnemonics,
9686 so long as there is no conflict. The @code{info registers} command
9687 shows the canonical names. For example, on the SPARC, @code{info
9688 registers} displays the processor status register as @code{$psr} but you
9689 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9690 is an alias for the @sc{eflags} register.
9692 @value{GDBN} always considers the contents of an ordinary register as an
9693 integer when the register is examined in this way. Some machines have
9694 special registers which can hold nothing but floating point; these
9695 registers are considered to have floating point values. There is no way
9696 to refer to the contents of an ordinary register as floating point value
9697 (although you can @emph{print} it as a floating point value with
9698 @samp{print/f $@var{regname}}).
9700 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9701 means that the data format in which the register contents are saved by
9702 the operating system is not the same one that your program normally
9703 sees. For example, the registers of the 68881 floating point
9704 coprocessor are always saved in ``extended'' (raw) format, but all C
9705 programs expect to work with ``double'' (virtual) format. In such
9706 cases, @value{GDBN} normally works with the virtual format only (the format
9707 that makes sense for your program), but the @code{info registers} command
9708 prints the data in both formats.
9710 @cindex SSE registers (x86)
9711 @cindex MMX registers (x86)
9712 Some machines have special registers whose contents can be interpreted
9713 in several different ways. For example, modern x86-based machines
9714 have SSE and MMX registers that can hold several values packed
9715 together in several different formats. @value{GDBN} refers to such
9716 registers in @code{struct} notation:
9719 (@value{GDBP}) print $xmm1
9721 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9722 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9723 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9724 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9725 v4_int32 = @{0, 20657912, 11, 13@},
9726 v2_int64 = @{88725056443645952, 55834574859@},
9727 uint128 = 0x0000000d0000000b013b36f800000000
9732 To set values of such registers, you need to tell @value{GDBN} which
9733 view of the register you wish to change, as if you were assigning
9734 value to a @code{struct} member:
9737 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9740 Normally, register values are relative to the selected stack frame
9741 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9742 value that the register would contain if all stack frames farther in
9743 were exited and their saved registers restored. In order to see the
9744 true contents of hardware registers, you must select the innermost
9745 frame (with @samp{frame 0}).
9747 However, @value{GDBN} must deduce where registers are saved, from the machine
9748 code generated by your compiler. If some registers are not saved, or if
9749 @value{GDBN} is unable to locate the saved registers, the selected stack
9750 frame makes no difference.
9752 @node Floating Point Hardware
9753 @section Floating Point Hardware
9754 @cindex floating point
9756 Depending on the configuration, @value{GDBN} may be able to give
9757 you more information about the status of the floating point hardware.
9762 Display hardware-dependent information about the floating
9763 point unit. The exact contents and layout vary depending on the
9764 floating point chip. Currently, @samp{info float} is supported on
9765 the ARM and x86 machines.
9769 @section Vector Unit
9772 Depending on the configuration, @value{GDBN} may be able to give you
9773 more information about the status of the vector unit.
9778 Display information about the vector unit. The exact contents and
9779 layout vary depending on the hardware.
9782 @node OS Information
9783 @section Operating System Auxiliary Information
9784 @cindex OS information
9786 @value{GDBN} provides interfaces to useful OS facilities that can help
9787 you debug your program.
9789 @cindex auxiliary vector
9790 @cindex vector, auxiliary
9791 Some operating systems supply an @dfn{auxiliary vector} to programs at
9792 startup. This is akin to the arguments and environment that you
9793 specify for a program, but contains a system-dependent variety of
9794 binary values that tell system libraries important details about the
9795 hardware, operating system, and process. Each value's purpose is
9796 identified by an integer tag; the meanings are well-known but system-specific.
9797 Depending on the configuration and operating system facilities,
9798 @value{GDBN} may be able to show you this information. For remote
9799 targets, this functionality may further depend on the remote stub's
9800 support of the @samp{qXfer:auxv:read} packet, see
9801 @ref{qXfer auxiliary vector read}.
9806 Display the auxiliary vector of the inferior, which can be either a
9807 live process or a core dump file. @value{GDBN} prints each tag value
9808 numerically, and also shows names and text descriptions for recognized
9809 tags. Some values in the vector are numbers, some bit masks, and some
9810 pointers to strings or other data. @value{GDBN} displays each value in the
9811 most appropriate form for a recognized tag, and in hexadecimal for
9812 an unrecognized tag.
9815 On some targets, @value{GDBN} can access operating system-specific
9816 information and show it to you. The types of information available
9817 will differ depending on the type of operating system running on the
9818 target. The mechanism used to fetch the data is described in
9819 @ref{Operating System Information}. For remote targets, this
9820 functionality depends on the remote stub's support of the
9821 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9825 @item info os @var{infotype}
9827 Display OS information of the requested type.
9829 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9831 @anchor{linux info os infotypes}
9833 @kindex info os processes
9835 Display the list of processes on the target. For each process,
9836 @value{GDBN} prints the process identifier, the name of the user, the
9837 command corresponding to the process, and the list of processor cores
9838 that the process is currently running on. (To understand what these
9839 properties mean, for this and the following info types, please consult
9840 the general @sc{gnu}/Linux documentation.)
9842 @kindex info os procgroups
9844 Display the list of process groups on the target. For each process,
9845 @value{GDBN} prints the identifier of the process group that it belongs
9846 to, the command corresponding to the process group leader, the process
9847 identifier, and the command line of the process. The list is sorted
9848 first by the process group identifier, then by the process identifier,
9849 so that processes belonging to the same process group are grouped together
9850 and the process group leader is listed first.
9852 @kindex info os threads
9854 Display the list of threads running on the target. For each thread,
9855 @value{GDBN} prints the identifier of the process that the thread
9856 belongs to, the command of the process, the thread identifier, and the
9857 processor core that it is currently running on. The main thread of a
9858 process is not listed.
9860 @kindex info os files
9862 Display the list of open file descriptors on the target. For each
9863 file descriptor, @value{GDBN} prints the identifier of the process
9864 owning the descriptor, the command of the owning process, the value
9865 of the descriptor, and the target of the descriptor.
9867 @kindex info os sockets
9869 Display the list of Internet-domain sockets on the target. For each
9870 socket, @value{GDBN} prints the address and port of the local and
9871 remote endpoints, the current state of the connection, the creator of
9872 the socket, the IP address family of the socket, and the type of the
9877 Display the list of all System V shared-memory regions on the target.
9878 For each shared-memory region, @value{GDBN} prints the region key,
9879 the shared-memory identifier, the access permissions, the size of the
9880 region, the process that created the region, the process that last
9881 attached to or detached from the region, the current number of live
9882 attaches to the region, and the times at which the region was last
9883 attached to, detach from, and changed.
9885 @kindex info os semaphores
9887 Display the list of all System V semaphore sets on the target. For each
9888 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9889 set identifier, the access permissions, the number of semaphores in the
9890 set, the user and group of the owner and creator of the semaphore set,
9891 and the times at which the semaphore set was operated upon and changed.
9895 Display the list of all System V message queues on the target. For each
9896 message queue, @value{GDBN} prints the message queue key, the message
9897 queue identifier, the access permissions, the current number of bytes
9898 on the queue, the current number of messages on the queue, the processes
9899 that last sent and received a message on the queue, the user and group
9900 of the owner and creator of the message queue, the times at which a
9901 message was last sent and received on the queue, and the time at which
9902 the message queue was last changed.
9904 @kindex info os modules
9906 Display the list of all loaded kernel modules on the target. For each
9907 module, @value{GDBN} prints the module name, the size of the module in
9908 bytes, the number of times the module is used, the dependencies of the
9909 module, the status of the module, and the address of the loaded module
9914 If @var{infotype} is omitted, then list the possible values for
9915 @var{infotype} and the kind of OS information available for each
9916 @var{infotype}. If the target does not return a list of possible
9917 types, this command will report an error.
9920 @node Memory Region Attributes
9921 @section Memory Region Attributes
9922 @cindex memory region attributes
9924 @dfn{Memory region attributes} allow you to describe special handling
9925 required by regions of your target's memory. @value{GDBN} uses
9926 attributes to determine whether to allow certain types of memory
9927 accesses; whether to use specific width accesses; and whether to cache
9928 target memory. By default the description of memory regions is
9929 fetched from the target (if the current target supports this), but the
9930 user can override the fetched regions.
9932 Defined memory regions can be individually enabled and disabled. When a
9933 memory region is disabled, @value{GDBN} uses the default attributes when
9934 accessing memory in that region. Similarly, if no memory regions have
9935 been defined, @value{GDBN} uses the default attributes when accessing
9938 When a memory region is defined, it is given a number to identify it;
9939 to enable, disable, or remove a memory region, you specify that number.
9943 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9944 Define a memory region bounded by @var{lower} and @var{upper} with
9945 attributes @var{attributes}@dots{}, and add it to the list of regions
9946 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9947 case: it is treated as the target's maximum memory address.
9948 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9951 Discard any user changes to the memory regions and use target-supplied
9952 regions, if available, or no regions if the target does not support.
9955 @item delete mem @var{nums}@dots{}
9956 Remove memory regions @var{nums}@dots{} from the list of regions
9957 monitored by @value{GDBN}.
9960 @item disable mem @var{nums}@dots{}
9961 Disable monitoring of memory regions @var{nums}@dots{}.
9962 A disabled memory region is not forgotten.
9963 It may be enabled again later.
9966 @item enable mem @var{nums}@dots{}
9967 Enable monitoring of memory regions @var{nums}@dots{}.
9971 Print a table of all defined memory regions, with the following columns
9975 @item Memory Region Number
9976 @item Enabled or Disabled.
9977 Enabled memory regions are marked with @samp{y}.
9978 Disabled memory regions are marked with @samp{n}.
9981 The address defining the inclusive lower bound of the memory region.
9984 The address defining the exclusive upper bound of the memory region.
9987 The list of attributes set for this memory region.
9992 @subsection Attributes
9994 @subsubsection Memory Access Mode
9995 The access mode attributes set whether @value{GDBN} may make read or
9996 write accesses to a memory region.
9998 While these attributes prevent @value{GDBN} from performing invalid
9999 memory accesses, they do nothing to prevent the target system, I/O DMA,
10000 etc.@: from accessing memory.
10004 Memory is read only.
10006 Memory is write only.
10008 Memory is read/write. This is the default.
10011 @subsubsection Memory Access Size
10012 The access size attribute tells @value{GDBN} to use specific sized
10013 accesses in the memory region. Often memory mapped device registers
10014 require specific sized accesses. If no access size attribute is
10015 specified, @value{GDBN} may use accesses of any size.
10019 Use 8 bit memory accesses.
10021 Use 16 bit memory accesses.
10023 Use 32 bit memory accesses.
10025 Use 64 bit memory accesses.
10028 @c @subsubsection Hardware/Software Breakpoints
10029 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10030 @c will use hardware or software breakpoints for the internal breakpoints
10031 @c used by the step, next, finish, until, etc. commands.
10035 @c Always use hardware breakpoints
10036 @c @item swbreak (default)
10039 @subsubsection Data Cache
10040 The data cache attributes set whether @value{GDBN} will cache target
10041 memory. While this generally improves performance by reducing debug
10042 protocol overhead, it can lead to incorrect results because @value{GDBN}
10043 does not know about volatile variables or memory mapped device
10048 Enable @value{GDBN} to cache target memory.
10050 Disable @value{GDBN} from caching target memory. This is the default.
10053 @subsection Memory Access Checking
10054 @value{GDBN} can be instructed to refuse accesses to memory that is
10055 not explicitly described. This can be useful if accessing such
10056 regions has undesired effects for a specific target, or to provide
10057 better error checking. The following commands control this behaviour.
10060 @kindex set mem inaccessible-by-default
10061 @item set mem inaccessible-by-default [on|off]
10062 If @code{on} is specified, make @value{GDBN} treat memory not
10063 explicitly described by the memory ranges as non-existent and refuse accesses
10064 to such memory. The checks are only performed if there's at least one
10065 memory range defined. If @code{off} is specified, make @value{GDBN}
10066 treat the memory not explicitly described by the memory ranges as RAM.
10067 The default value is @code{on}.
10068 @kindex show mem inaccessible-by-default
10069 @item show mem inaccessible-by-default
10070 Show the current handling of accesses to unknown memory.
10074 @c @subsubsection Memory Write Verification
10075 @c The memory write verification attributes set whether @value{GDBN}
10076 @c will re-reads data after each write to verify the write was successful.
10080 @c @item noverify (default)
10083 @node Dump/Restore Files
10084 @section Copy Between Memory and a File
10085 @cindex dump/restore files
10086 @cindex append data to a file
10087 @cindex dump data to a file
10088 @cindex restore data from a file
10090 You can use the commands @code{dump}, @code{append}, and
10091 @code{restore} to copy data between target memory and a file. The
10092 @code{dump} and @code{append} commands write data to a file, and the
10093 @code{restore} command reads data from a file back into the inferior's
10094 memory. Files may be in binary, Motorola S-record, Intel hex, or
10095 Tektronix Hex format; however, @value{GDBN} can only append to binary
10101 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10102 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10103 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10104 or the value of @var{expr}, to @var{filename} in the given format.
10106 The @var{format} parameter may be any one of:
10113 Motorola S-record format.
10115 Tektronix Hex format.
10118 @value{GDBN} uses the same definitions of these formats as the
10119 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10120 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10124 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10125 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10126 Append the contents of memory from @var{start_addr} to @var{end_addr},
10127 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10128 (@value{GDBN} can only append data to files in raw binary form.)
10131 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10132 Restore the contents of file @var{filename} into memory. The
10133 @code{restore} command can automatically recognize any known @sc{bfd}
10134 file format, except for raw binary. To restore a raw binary file you
10135 must specify the optional keyword @code{binary} after the filename.
10137 If @var{bias} is non-zero, its value will be added to the addresses
10138 contained in the file. Binary files always start at address zero, so
10139 they will be restored at address @var{bias}. Other bfd files have
10140 a built-in location; they will be restored at offset @var{bias}
10141 from that location.
10143 If @var{start} and/or @var{end} are non-zero, then only data between
10144 file offset @var{start} and file offset @var{end} will be restored.
10145 These offsets are relative to the addresses in the file, before
10146 the @var{bias} argument is applied.
10150 @node Core File Generation
10151 @section How to Produce a Core File from Your Program
10152 @cindex dump core from inferior
10154 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10155 image of a running process and its process status (register values
10156 etc.). Its primary use is post-mortem debugging of a program that
10157 crashed while it ran outside a debugger. A program that crashes
10158 automatically produces a core file, unless this feature is disabled by
10159 the user. @xref{Files}, for information on invoking @value{GDBN} in
10160 the post-mortem debugging mode.
10162 Occasionally, you may wish to produce a core file of the program you
10163 are debugging in order to preserve a snapshot of its state.
10164 @value{GDBN} has a special command for that.
10168 @kindex generate-core-file
10169 @item generate-core-file [@var{file}]
10170 @itemx gcore [@var{file}]
10171 Produce a core dump of the inferior process. The optional argument
10172 @var{file} specifies the file name where to put the core dump. If not
10173 specified, the file name defaults to @file{core.@var{pid}}, where
10174 @var{pid} is the inferior process ID.
10176 Note that this command is implemented only for some systems (as of
10177 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10180 @node Character Sets
10181 @section Character Sets
10182 @cindex character sets
10184 @cindex translating between character sets
10185 @cindex host character set
10186 @cindex target character set
10188 If the program you are debugging uses a different character set to
10189 represent characters and strings than the one @value{GDBN} uses itself,
10190 @value{GDBN} can automatically translate between the character sets for
10191 you. The character set @value{GDBN} uses we call the @dfn{host
10192 character set}; the one the inferior program uses we call the
10193 @dfn{target character set}.
10195 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10196 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10197 remote protocol (@pxref{Remote Debugging}) to debug a program
10198 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10199 then the host character set is Latin-1, and the target character set is
10200 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10201 target-charset EBCDIC-US}, then @value{GDBN} translates between
10202 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10203 character and string literals in expressions.
10205 @value{GDBN} has no way to automatically recognize which character set
10206 the inferior program uses; you must tell it, using the @code{set
10207 target-charset} command, described below.
10209 Here are the commands for controlling @value{GDBN}'s character set
10213 @item set target-charset @var{charset}
10214 @kindex set target-charset
10215 Set the current target character set to @var{charset}. To display the
10216 list of supported target character sets, type
10217 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10219 @item set host-charset @var{charset}
10220 @kindex set host-charset
10221 Set the current host character set to @var{charset}.
10223 By default, @value{GDBN} uses a host character set appropriate to the
10224 system it is running on; you can override that default using the
10225 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10226 automatically determine the appropriate host character set. In this
10227 case, @value{GDBN} uses @samp{UTF-8}.
10229 @value{GDBN} can only use certain character sets as its host character
10230 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10231 @value{GDBN} will list the host character sets it supports.
10233 @item set charset @var{charset}
10234 @kindex set charset
10235 Set the current host and target character sets to @var{charset}. As
10236 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10237 @value{GDBN} will list the names of the character sets that can be used
10238 for both host and target.
10241 @kindex show charset
10242 Show the names of the current host and target character sets.
10244 @item show host-charset
10245 @kindex show host-charset
10246 Show the name of the current host character set.
10248 @item show target-charset
10249 @kindex show target-charset
10250 Show the name of the current target character set.
10252 @item set target-wide-charset @var{charset}
10253 @kindex set target-wide-charset
10254 Set the current target's wide character set to @var{charset}. This is
10255 the character set used by the target's @code{wchar_t} type. To
10256 display the list of supported wide character sets, type
10257 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10259 @item show target-wide-charset
10260 @kindex show target-wide-charset
10261 Show the name of the current target's wide character set.
10264 Here is an example of @value{GDBN}'s character set support in action.
10265 Assume that the following source code has been placed in the file
10266 @file{charset-test.c}:
10272 = @{72, 101, 108, 108, 111, 44, 32, 119,
10273 111, 114, 108, 100, 33, 10, 0@};
10274 char ibm1047_hello[]
10275 = @{200, 133, 147, 147, 150, 107, 64, 166,
10276 150, 153, 147, 132, 90, 37, 0@};
10280 printf ("Hello, world!\n");
10284 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10285 containing the string @samp{Hello, world!} followed by a newline,
10286 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10288 We compile the program, and invoke the debugger on it:
10291 $ gcc -g charset-test.c -o charset-test
10292 $ gdb -nw charset-test
10293 GNU gdb 2001-12-19-cvs
10294 Copyright 2001 Free Software Foundation, Inc.
10299 We can use the @code{show charset} command to see what character sets
10300 @value{GDBN} is currently using to interpret and display characters and
10304 (@value{GDBP}) show charset
10305 The current host and target character set is `ISO-8859-1'.
10309 For the sake of printing this manual, let's use @sc{ascii} as our
10310 initial character set:
10312 (@value{GDBP}) set charset ASCII
10313 (@value{GDBP}) show charset
10314 The current host and target character set is `ASCII'.
10318 Let's assume that @sc{ascii} is indeed the correct character set for our
10319 host system --- in other words, let's assume that if @value{GDBN} prints
10320 characters using the @sc{ascii} character set, our terminal will display
10321 them properly. Since our current target character set is also
10322 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10325 (@value{GDBP}) print ascii_hello
10326 $1 = 0x401698 "Hello, world!\n"
10327 (@value{GDBP}) print ascii_hello[0]
10332 @value{GDBN} uses the target character set for character and string
10333 literals you use in expressions:
10336 (@value{GDBP}) print '+'
10341 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10344 @value{GDBN} relies on the user to tell it which character set the
10345 target program uses. If we print @code{ibm1047_hello} while our target
10346 character set is still @sc{ascii}, we get jibberish:
10349 (@value{GDBP}) print ibm1047_hello
10350 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10351 (@value{GDBP}) print ibm1047_hello[0]
10356 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10357 @value{GDBN} tells us the character sets it supports:
10360 (@value{GDBP}) set target-charset
10361 ASCII EBCDIC-US IBM1047 ISO-8859-1
10362 (@value{GDBP}) set target-charset
10365 We can select @sc{ibm1047} as our target character set, and examine the
10366 program's strings again. Now the @sc{ascii} string is wrong, but
10367 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10368 target character set, @sc{ibm1047}, to the host character set,
10369 @sc{ascii}, and they display correctly:
10372 (@value{GDBP}) set target-charset IBM1047
10373 (@value{GDBP}) show charset
10374 The current host character set is `ASCII'.
10375 The current target character set is `IBM1047'.
10376 (@value{GDBP}) print ascii_hello
10377 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10378 (@value{GDBP}) print ascii_hello[0]
10380 (@value{GDBP}) print ibm1047_hello
10381 $8 = 0x4016a8 "Hello, world!\n"
10382 (@value{GDBP}) print ibm1047_hello[0]
10387 As above, @value{GDBN} uses the target character set for character and
10388 string literals you use in expressions:
10391 (@value{GDBP}) print '+'
10396 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10399 @node Caching Remote Data
10400 @section Caching Data of Remote Targets
10401 @cindex caching data of remote targets
10403 @value{GDBN} caches data exchanged between the debugger and a
10404 remote target (@pxref{Remote Debugging}). Such caching generally improves
10405 performance, because it reduces the overhead of the remote protocol by
10406 bundling memory reads and writes into large chunks. Unfortunately, simply
10407 caching everything would lead to incorrect results, since @value{GDBN}
10408 does not necessarily know anything about volatile values, memory-mapped I/O
10409 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10410 memory can be changed @emph{while} a gdb command is executing.
10411 Therefore, by default, @value{GDBN} only caches data
10412 known to be on the stack@footnote{In non-stop mode, it is moderately
10413 rare for a running thread to modify the stack of a stopped thread
10414 in a way that would interfere with a backtrace, and caching of
10415 stack reads provides a significant speed up of remote backtraces.}.
10416 Other regions of memory can be explicitly marked as
10417 cacheable; see @pxref{Memory Region Attributes}.
10420 @kindex set remotecache
10421 @item set remotecache on
10422 @itemx set remotecache off
10423 This option no longer does anything; it exists for compatibility
10426 @kindex show remotecache
10427 @item show remotecache
10428 Show the current state of the obsolete remotecache flag.
10430 @kindex set stack-cache
10431 @item set stack-cache on
10432 @itemx set stack-cache off
10433 Enable or disable caching of stack accesses. When @code{ON}, use
10434 caching. By default, this option is @code{ON}.
10436 @kindex show stack-cache
10437 @item show stack-cache
10438 Show the current state of data caching for memory accesses.
10440 @kindex info dcache
10441 @item info dcache @r{[}line@r{]}
10442 Print the information about the data cache performance. The
10443 information displayed includes the dcache width and depth, and for
10444 each cache line, its number, address, and how many times it was
10445 referenced. This command is useful for debugging the data cache
10448 If a line number is specified, the contents of that line will be
10451 @item set dcache size @var{size}
10452 @cindex dcache size
10453 @kindex set dcache size
10454 Set maximum number of entries in dcache (dcache depth above).
10456 @item set dcache line-size @var{line-size}
10457 @cindex dcache line-size
10458 @kindex set dcache line-size
10459 Set number of bytes each dcache entry caches (dcache width above).
10460 Must be a power of 2.
10462 @item show dcache size
10463 @kindex show dcache size
10464 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10466 @item show dcache line-size
10467 @kindex show dcache line-size
10468 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10472 @node Searching Memory
10473 @section Search Memory
10474 @cindex searching memory
10476 Memory can be searched for a particular sequence of bytes with the
10477 @code{find} command.
10481 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10482 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10483 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10484 etc. The search begins at address @var{start_addr} and continues for either
10485 @var{len} bytes or through to @var{end_addr} inclusive.
10488 @var{s} and @var{n} are optional parameters.
10489 They may be specified in either order, apart or together.
10492 @item @var{s}, search query size
10493 The size of each search query value.
10499 halfwords (two bytes)
10503 giant words (eight bytes)
10506 All values are interpreted in the current language.
10507 This means, for example, that if the current source language is C/C@t{++}
10508 then searching for the string ``hello'' includes the trailing '\0'.
10510 If the value size is not specified, it is taken from the
10511 value's type in the current language.
10512 This is useful when one wants to specify the search
10513 pattern as a mixture of types.
10514 Note that this means, for example, that in the case of C-like languages
10515 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10516 which is typically four bytes.
10518 @item @var{n}, maximum number of finds
10519 The maximum number of matches to print. The default is to print all finds.
10522 You can use strings as search values. Quote them with double-quotes
10524 The string value is copied into the search pattern byte by byte,
10525 regardless of the endianness of the target and the size specification.
10527 The address of each match found is printed as well as a count of the
10528 number of matches found.
10530 The address of the last value found is stored in convenience variable
10532 A count of the number of matches is stored in @samp{$numfound}.
10534 For example, if stopped at the @code{printf} in this function:
10540 static char hello[] = "hello-hello";
10541 static struct @{ char c; short s; int i; @}
10542 __attribute__ ((packed)) mixed
10543 = @{ 'c', 0x1234, 0x87654321 @};
10544 printf ("%s\n", hello);
10549 you get during debugging:
10552 (gdb) find &hello[0], +sizeof(hello), "hello"
10553 0x804956d <hello.1620+6>
10555 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10556 0x8049567 <hello.1620>
10557 0x804956d <hello.1620+6>
10559 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10560 0x8049567 <hello.1620>
10562 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10563 0x8049560 <mixed.1625>
10565 (gdb) print $numfound
10568 $2 = (void *) 0x8049560
10571 @node Optimized Code
10572 @chapter Debugging Optimized Code
10573 @cindex optimized code, debugging
10574 @cindex debugging optimized code
10576 Almost all compilers support optimization. With optimization
10577 disabled, the compiler generates assembly code that corresponds
10578 directly to your source code, in a simplistic way. As the compiler
10579 applies more powerful optimizations, the generated assembly code
10580 diverges from your original source code. With help from debugging
10581 information generated by the compiler, @value{GDBN} can map from
10582 the running program back to constructs from your original source.
10584 @value{GDBN} is more accurate with optimization disabled. If you
10585 can recompile without optimization, it is easier to follow the
10586 progress of your program during debugging. But, there are many cases
10587 where you may need to debug an optimized version.
10589 When you debug a program compiled with @samp{-g -O}, remember that the
10590 optimizer has rearranged your code; the debugger shows you what is
10591 really there. Do not be too surprised when the execution path does not
10592 exactly match your source file! An extreme example: if you define a
10593 variable, but never use it, @value{GDBN} never sees that
10594 variable---because the compiler optimizes it out of existence.
10596 Some things do not work as well with @samp{-g -O} as with just
10597 @samp{-g}, particularly on machines with instruction scheduling. If in
10598 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10599 please report it to us as a bug (including a test case!).
10600 @xref{Variables}, for more information about debugging optimized code.
10603 * Inline Functions:: How @value{GDBN} presents inlining
10604 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10607 @node Inline Functions
10608 @section Inline Functions
10609 @cindex inline functions, debugging
10611 @dfn{Inlining} is an optimization that inserts a copy of the function
10612 body directly at each call site, instead of jumping to a shared
10613 routine. @value{GDBN} displays inlined functions just like
10614 non-inlined functions. They appear in backtraces. You can view their
10615 arguments and local variables, step into them with @code{step}, skip
10616 them with @code{next}, and escape from them with @code{finish}.
10617 You can check whether a function was inlined by using the
10618 @code{info frame} command.
10620 For @value{GDBN} to support inlined functions, the compiler must
10621 record information about inlining in the debug information ---
10622 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10623 other compilers do also. @value{GDBN} only supports inlined functions
10624 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10625 do not emit two required attributes (@samp{DW_AT_call_file} and
10626 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10627 function calls with earlier versions of @value{NGCC}. It instead
10628 displays the arguments and local variables of inlined functions as
10629 local variables in the caller.
10631 The body of an inlined function is directly included at its call site;
10632 unlike a non-inlined function, there are no instructions devoted to
10633 the call. @value{GDBN} still pretends that the call site and the
10634 start of the inlined function are different instructions. Stepping to
10635 the call site shows the call site, and then stepping again shows
10636 the first line of the inlined function, even though no additional
10637 instructions are executed.
10639 This makes source-level debugging much clearer; you can see both the
10640 context of the call and then the effect of the call. Only stepping by
10641 a single instruction using @code{stepi} or @code{nexti} does not do
10642 this; single instruction steps always show the inlined body.
10644 There are some ways that @value{GDBN} does not pretend that inlined
10645 function calls are the same as normal calls:
10649 Setting breakpoints at the call site of an inlined function may not
10650 work, because the call site does not contain any code. @value{GDBN}
10651 may incorrectly move the breakpoint to the next line of the enclosing
10652 function, after the call. This limitation will be removed in a future
10653 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10654 or inside the inlined function instead.
10657 @value{GDBN} cannot locate the return value of inlined calls after
10658 using the @code{finish} command. This is a limitation of compiler-generated
10659 debugging information; after @code{finish}, you can step to the next line
10660 and print a variable where your program stored the return value.
10664 @node Tail Call Frames
10665 @section Tail Call Frames
10666 @cindex tail call frames, debugging
10668 Function @code{B} can call function @code{C} in its very last statement. In
10669 unoptimized compilation the call of @code{C} is immediately followed by return
10670 instruction at the end of @code{B} code. Optimizing compiler may replace the
10671 call and return in function @code{B} into one jump to function @code{C}
10672 instead. Such use of a jump instruction is called @dfn{tail call}.
10674 During execution of function @code{C}, there will be no indication in the
10675 function call stack frames that it was tail-called from @code{B}. If function
10676 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10677 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10678 some cases @value{GDBN} can determine that @code{C} was tail-called from
10679 @code{B}, and it will then create fictitious call frame for that, with the
10680 return address set up as if @code{B} called @code{C} normally.
10682 This functionality is currently supported only by DWARF 2 debugging format and
10683 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10684 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10687 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10688 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10692 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10694 Stack level 1, frame at 0x7fffffffda30:
10695 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10696 tail call frame, caller of frame at 0x7fffffffda30
10697 source language c++.
10698 Arglist at unknown address.
10699 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10702 The detection of all the possible code path executions can find them ambiguous.
10703 There is no execution history stored (possible @ref{Reverse Execution} is never
10704 used for this purpose) and the last known caller could have reached the known
10705 callee by multiple different jump sequences. In such case @value{GDBN} still
10706 tries to show at least all the unambiguous top tail callers and all the
10707 unambiguous bottom tail calees, if any.
10710 @anchor{set debug entry-values}
10711 @item set debug entry-values
10712 @kindex set debug entry-values
10713 When set to on, enables printing of analysis messages for both frame argument
10714 values at function entry and tail calls. It will show all the possible valid
10715 tail calls code paths it has considered. It will also print the intersection
10716 of them with the final unambiguous (possibly partial or even empty) code path
10719 @item show debug entry-values
10720 @kindex show debug entry-values
10721 Show the current state of analysis messages printing for both frame argument
10722 values at function entry and tail calls.
10725 The analysis messages for tail calls can for example show why the virtual tail
10726 call frame for function @code{c} has not been recognized (due to the indirect
10727 reference by variable @code{x}):
10730 static void __attribute__((noinline, noclone)) c (void);
10731 void (*x) (void) = c;
10732 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10733 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10734 int main (void) @{ x (); return 0; @}
10736 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10737 DW_TAG_GNU_call_site 0x40039a in main
10739 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10742 #1 0x000000000040039a in main () at t.c:5
10745 Another possibility is an ambiguous virtual tail call frames resolution:
10749 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10750 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10751 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10752 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10753 static void __attribute__((noinline, noclone)) b (void)
10754 @{ if (i) c (); else e (); @}
10755 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10756 int main (void) @{ a (); return 0; @}
10758 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10759 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10760 tailcall: reduced: 0x4004d2(a) |
10763 #1 0x00000000004004d2 in a () at t.c:8
10764 #2 0x0000000000400395 in main () at t.c:9
10767 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10768 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10770 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10771 @ifset HAVE_MAKEINFO_CLICK
10772 @set ARROW @click{}
10773 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10774 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10776 @ifclear HAVE_MAKEINFO_CLICK
10778 @set CALLSEQ1B @value{CALLSEQ1A}
10779 @set CALLSEQ2B @value{CALLSEQ2A}
10782 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10783 The code can have possible execution paths @value{CALLSEQ1B} or
10784 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10786 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10787 has found. It then finds another possible calling sequcen - that one is
10788 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10789 printed as the @code{reduced:} calling sequence. That one could have many
10790 futher @code{compare:} and @code{reduced:} statements as long as there remain
10791 any non-ambiguous sequence entries.
10793 For the frame of function @code{b} in both cases there are different possible
10794 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10795 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10796 therefore this one is displayed to the user while the ambiguous frames are
10799 There can be also reasons why printing of frame argument values at function
10804 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10805 static void __attribute__((noinline, noclone)) a (int i);
10806 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10807 static void __attribute__((noinline, noclone)) a (int i)
10808 @{ if (i) b (i - 1); else c (0); @}
10809 int main (void) @{ a (5); return 0; @}
10812 #0 c (i=i@@entry=0) at t.c:2
10813 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10814 function "a" at 0x400420 can call itself via tail calls
10815 i=<optimized out>) at t.c:6
10816 #2 0x000000000040036e in main () at t.c:7
10819 @value{GDBN} cannot find out from the inferior state if and how many times did
10820 function @code{a} call itself (via function @code{b}) as these calls would be
10821 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10822 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10823 prints @code{<optimized out>} instead.
10826 @chapter C Preprocessor Macros
10828 Some languages, such as C and C@t{++}, provide a way to define and invoke
10829 ``preprocessor macros'' which expand into strings of tokens.
10830 @value{GDBN} can evaluate expressions containing macro invocations, show
10831 the result of macro expansion, and show a macro's definition, including
10832 where it was defined.
10834 You may need to compile your program specially to provide @value{GDBN}
10835 with information about preprocessor macros. Most compilers do not
10836 include macros in their debugging information, even when you compile
10837 with the @option{-g} flag. @xref{Compilation}.
10839 A program may define a macro at one point, remove that definition later,
10840 and then provide a different definition after that. Thus, at different
10841 points in the program, a macro may have different definitions, or have
10842 no definition at all. If there is a current stack frame, @value{GDBN}
10843 uses the macros in scope at that frame's source code line. Otherwise,
10844 @value{GDBN} uses the macros in scope at the current listing location;
10847 Whenever @value{GDBN} evaluates an expression, it always expands any
10848 macro invocations present in the expression. @value{GDBN} also provides
10849 the following commands for working with macros explicitly.
10853 @kindex macro expand
10854 @cindex macro expansion, showing the results of preprocessor
10855 @cindex preprocessor macro expansion, showing the results of
10856 @cindex expanding preprocessor macros
10857 @item macro expand @var{expression}
10858 @itemx macro exp @var{expression}
10859 Show the results of expanding all preprocessor macro invocations in
10860 @var{expression}. Since @value{GDBN} simply expands macros, but does
10861 not parse the result, @var{expression} need not be a valid expression;
10862 it can be any string of tokens.
10865 @item macro expand-once @var{expression}
10866 @itemx macro exp1 @var{expression}
10867 @cindex expand macro once
10868 @i{(This command is not yet implemented.)} Show the results of
10869 expanding those preprocessor macro invocations that appear explicitly in
10870 @var{expression}. Macro invocations appearing in that expansion are
10871 left unchanged. This command allows you to see the effect of a
10872 particular macro more clearly, without being confused by further
10873 expansions. Since @value{GDBN} simply expands macros, but does not
10874 parse the result, @var{expression} need not be a valid expression; it
10875 can be any string of tokens.
10878 @cindex macro definition, showing
10879 @cindex definition of a macro, showing
10880 @cindex macros, from debug info
10881 @item info macro [-a|-all] [--] @var{macro}
10882 Show the current definition or all definitions of the named @var{macro},
10883 and describe the source location or compiler command-line where that
10884 definition was established. The optional double dash is to signify the end of
10885 argument processing and the beginning of @var{macro} for non C-like macros where
10886 the macro may begin with a hyphen.
10888 @kindex info macros
10889 @item info macros @var{linespec}
10890 Show all macro definitions that are in effect at the location specified
10891 by @var{linespec}, and describe the source location or compiler
10892 command-line where those definitions were established.
10894 @kindex macro define
10895 @cindex user-defined macros
10896 @cindex defining macros interactively
10897 @cindex macros, user-defined
10898 @item macro define @var{macro} @var{replacement-list}
10899 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10900 Introduce a definition for a preprocessor macro named @var{macro},
10901 invocations of which are replaced by the tokens given in
10902 @var{replacement-list}. The first form of this command defines an
10903 ``object-like'' macro, which takes no arguments; the second form
10904 defines a ``function-like'' macro, which takes the arguments given in
10907 A definition introduced by this command is in scope in every
10908 expression evaluated in @value{GDBN}, until it is removed with the
10909 @code{macro undef} command, described below. The definition overrides
10910 all definitions for @var{macro} present in the program being debugged,
10911 as well as any previous user-supplied definition.
10913 @kindex macro undef
10914 @item macro undef @var{macro}
10915 Remove any user-supplied definition for the macro named @var{macro}.
10916 This command only affects definitions provided with the @code{macro
10917 define} command, described above; it cannot remove definitions present
10918 in the program being debugged.
10922 List all the macros defined using the @code{macro define} command.
10925 @cindex macros, example of debugging with
10926 Here is a transcript showing the above commands in action. First, we
10927 show our source files:
10932 #include "sample.h"
10935 #define ADD(x) (M + x)
10940 printf ("Hello, world!\n");
10942 printf ("We're so creative.\n");
10944 printf ("Goodbye, world!\n");
10951 Now, we compile the program using the @sc{gnu} C compiler,
10952 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10953 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10954 and @option{-gdwarf-4}; we recommend always choosing the most recent
10955 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10956 includes information about preprocessor macros in the debugging
10960 $ gcc -gdwarf-2 -g3 sample.c -o sample
10964 Now, we start @value{GDBN} on our sample program:
10968 GNU gdb 2002-05-06-cvs
10969 Copyright 2002 Free Software Foundation, Inc.
10970 GDB is free software, @dots{}
10974 We can expand macros and examine their definitions, even when the
10975 program is not running. @value{GDBN} uses the current listing position
10976 to decide which macro definitions are in scope:
10979 (@value{GDBP}) list main
10982 5 #define ADD(x) (M + x)
10987 10 printf ("Hello, world!\n");
10989 12 printf ("We're so creative.\n");
10990 (@value{GDBP}) info macro ADD
10991 Defined at /home/jimb/gdb/macros/play/sample.c:5
10992 #define ADD(x) (M + x)
10993 (@value{GDBP}) info macro Q
10994 Defined at /home/jimb/gdb/macros/play/sample.h:1
10995 included at /home/jimb/gdb/macros/play/sample.c:2
10997 (@value{GDBP}) macro expand ADD(1)
10998 expands to: (42 + 1)
10999 (@value{GDBP}) macro expand-once ADD(1)
11000 expands to: once (M + 1)
11004 In the example above, note that @code{macro expand-once} expands only
11005 the macro invocation explicit in the original text --- the invocation of
11006 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11007 which was introduced by @code{ADD}.
11009 Once the program is running, @value{GDBN} uses the macro definitions in
11010 force at the source line of the current stack frame:
11013 (@value{GDBP}) break main
11014 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11016 Starting program: /home/jimb/gdb/macros/play/sample
11018 Breakpoint 1, main () at sample.c:10
11019 10 printf ("Hello, world!\n");
11023 At line 10, the definition of the macro @code{N} at line 9 is in force:
11026 (@value{GDBP}) info macro N
11027 Defined at /home/jimb/gdb/macros/play/sample.c:9
11029 (@value{GDBP}) macro expand N Q M
11030 expands to: 28 < 42
11031 (@value{GDBP}) print N Q M
11036 As we step over directives that remove @code{N}'s definition, and then
11037 give it a new definition, @value{GDBN} finds the definition (or lack
11038 thereof) in force at each point:
11041 (@value{GDBP}) next
11043 12 printf ("We're so creative.\n");
11044 (@value{GDBP}) info macro N
11045 The symbol `N' has no definition as a C/C++ preprocessor macro
11046 at /home/jimb/gdb/macros/play/sample.c:12
11047 (@value{GDBP}) next
11049 14 printf ("Goodbye, world!\n");
11050 (@value{GDBP}) info macro N
11051 Defined at /home/jimb/gdb/macros/play/sample.c:13
11053 (@value{GDBP}) macro expand N Q M
11054 expands to: 1729 < 42
11055 (@value{GDBP}) print N Q M
11060 In addition to source files, macros can be defined on the compilation command
11061 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11062 such a way, @value{GDBN} displays the location of their definition as line zero
11063 of the source file submitted to the compiler.
11066 (@value{GDBP}) info macro __STDC__
11067 Defined at /home/jimb/gdb/macros/play/sample.c:0
11074 @chapter Tracepoints
11075 @c This chapter is based on the documentation written by Michael
11076 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11078 @cindex tracepoints
11079 In some applications, it is not feasible for the debugger to interrupt
11080 the program's execution long enough for the developer to learn
11081 anything helpful about its behavior. If the program's correctness
11082 depends on its real-time behavior, delays introduced by a debugger
11083 might cause the program to change its behavior drastically, or perhaps
11084 fail, even when the code itself is correct. It is useful to be able
11085 to observe the program's behavior without interrupting it.
11087 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11088 specify locations in the program, called @dfn{tracepoints}, and
11089 arbitrary expressions to evaluate when those tracepoints are reached.
11090 Later, using the @code{tfind} command, you can examine the values
11091 those expressions had when the program hit the tracepoints. The
11092 expressions may also denote objects in memory---structures or arrays,
11093 for example---whose values @value{GDBN} should record; while visiting
11094 a particular tracepoint, you may inspect those objects as if they were
11095 in memory at that moment. However, because @value{GDBN} records these
11096 values without interacting with you, it can do so quickly and
11097 unobtrusively, hopefully not disturbing the program's behavior.
11099 The tracepoint facility is currently available only for remote
11100 targets. @xref{Targets}. In addition, your remote target must know
11101 how to collect trace data. This functionality is implemented in the
11102 remote stub; however, none of the stubs distributed with @value{GDBN}
11103 support tracepoints as of this writing. The format of the remote
11104 packets used to implement tracepoints are described in @ref{Tracepoint
11107 It is also possible to get trace data from a file, in a manner reminiscent
11108 of corefiles; you specify the filename, and use @code{tfind} to search
11109 through the file. @xref{Trace Files}, for more details.
11111 This chapter describes the tracepoint commands and features.
11114 * Set Tracepoints::
11115 * Analyze Collected Data::
11116 * Tracepoint Variables::
11120 @node Set Tracepoints
11121 @section Commands to Set Tracepoints
11123 Before running such a @dfn{trace experiment}, an arbitrary number of
11124 tracepoints can be set. A tracepoint is actually a special type of
11125 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11126 standard breakpoint commands. For instance, as with breakpoints,
11127 tracepoint numbers are successive integers starting from one, and many
11128 of the commands associated with tracepoints take the tracepoint number
11129 as their argument, to identify which tracepoint to work on.
11131 For each tracepoint, you can specify, in advance, some arbitrary set
11132 of data that you want the target to collect in the trace buffer when
11133 it hits that tracepoint. The collected data can include registers,
11134 local variables, or global data. Later, you can use @value{GDBN}
11135 commands to examine the values these data had at the time the
11136 tracepoint was hit.
11138 Tracepoints do not support every breakpoint feature. Ignore counts on
11139 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11140 commands when they are hit. Tracepoints may not be thread-specific
11143 @cindex fast tracepoints
11144 Some targets may support @dfn{fast tracepoints}, which are inserted in
11145 a different way (such as with a jump instead of a trap), that is
11146 faster but possibly restricted in where they may be installed.
11148 @cindex static tracepoints
11149 @cindex markers, static tracepoints
11150 @cindex probing markers, static tracepoints
11151 Regular and fast tracepoints are dynamic tracing facilities, meaning
11152 that they can be used to insert tracepoints at (almost) any location
11153 in the target. Some targets may also support controlling @dfn{static
11154 tracepoints} from @value{GDBN}. With static tracing, a set of
11155 instrumentation points, also known as @dfn{markers}, are embedded in
11156 the target program, and can be activated or deactivated by name or
11157 address. These are usually placed at locations which facilitate
11158 investigating what the target is actually doing. @value{GDBN}'s
11159 support for static tracing includes being able to list instrumentation
11160 points, and attach them with @value{GDBN} defined high level
11161 tracepoints that expose the whole range of convenience of
11162 @value{GDBN}'s tracepoints support. Namely, support for collecting
11163 registers values and values of global or local (to the instrumentation
11164 point) variables; tracepoint conditions and trace state variables.
11165 The act of installing a @value{GDBN} static tracepoint on an
11166 instrumentation point, or marker, is referred to as @dfn{probing} a
11167 static tracepoint marker.
11169 @code{gdbserver} supports tracepoints on some target systems.
11170 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11172 This section describes commands to set tracepoints and associated
11173 conditions and actions.
11176 * Create and Delete Tracepoints::
11177 * Enable and Disable Tracepoints::
11178 * Tracepoint Passcounts::
11179 * Tracepoint Conditions::
11180 * Trace State Variables::
11181 * Tracepoint Actions::
11182 * Listing Tracepoints::
11183 * Listing Static Tracepoint Markers::
11184 * Starting and Stopping Trace Experiments::
11185 * Tracepoint Restrictions::
11188 @node Create and Delete Tracepoints
11189 @subsection Create and Delete Tracepoints
11192 @cindex set tracepoint
11194 @item trace @var{location}
11195 The @code{trace} command is very similar to the @code{break} command.
11196 Its argument @var{location} can be a source line, a function name, or
11197 an address in the target program. @xref{Specify Location}. The
11198 @code{trace} command defines a tracepoint, which is a point in the
11199 target program where the debugger will briefly stop, collect some
11200 data, and then allow the program to continue. Setting a tracepoint or
11201 changing its actions takes effect immediately if the remote stub
11202 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11204 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11205 these changes don't take effect until the next @code{tstart}
11206 command, and once a trace experiment is running, further changes will
11207 not have any effect until the next trace experiment starts. In addition,
11208 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11209 address is not yet resolved. (This is similar to pending breakpoints.)
11210 Pending tracepoints are not downloaded to the target and not installed
11211 until they are resolved. The resolution of pending tracepoints requires
11212 @value{GDBN} support---when debugging with the remote target, and
11213 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11214 tracing}), pending tracepoints can not be resolved (and downloaded to
11215 the remote stub) while @value{GDBN} is disconnected.
11217 Here are some examples of using the @code{trace} command:
11220 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11222 (@value{GDBP}) @b{trace +2} // 2 lines forward
11224 (@value{GDBP}) @b{trace my_function} // first source line of function
11226 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11228 (@value{GDBP}) @b{trace *0x2117c4} // an address
11232 You can abbreviate @code{trace} as @code{tr}.
11234 @item trace @var{location} if @var{cond}
11235 Set a tracepoint with condition @var{cond}; evaluate the expression
11236 @var{cond} each time the tracepoint is reached, and collect data only
11237 if the value is nonzero---that is, if @var{cond} evaluates as true.
11238 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11239 information on tracepoint conditions.
11241 @item ftrace @var{location} [ if @var{cond} ]
11242 @cindex set fast tracepoint
11243 @cindex fast tracepoints, setting
11245 The @code{ftrace} command sets a fast tracepoint. For targets that
11246 support them, fast tracepoints will use a more efficient but possibly
11247 less general technique to trigger data collection, such as a jump
11248 instruction instead of a trap, or some sort of hardware support. It
11249 may not be possible to create a fast tracepoint at the desired
11250 location, in which case the command will exit with an explanatory
11253 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11256 On 32-bit x86-architecture systems, fast tracepoints normally need to
11257 be placed at an instruction that is 5 bytes or longer, but can be
11258 placed at 4-byte instructions if the low 64K of memory of the target
11259 program is available to install trampolines. Some Unix-type systems,
11260 such as @sc{gnu}/Linux, exclude low addresses from the program's
11261 address space; but for instance with the Linux kernel it is possible
11262 to let @value{GDBN} use this area by doing a @command{sysctl} command
11263 to set the @code{mmap_min_addr} kernel parameter, as in
11266 sudo sysctl -w vm.mmap_min_addr=32768
11270 which sets the low address to 32K, which leaves plenty of room for
11271 trampolines. The minimum address should be set to a page boundary.
11273 @item strace @var{location} [ if @var{cond} ]
11274 @cindex set static tracepoint
11275 @cindex static tracepoints, setting
11276 @cindex probe static tracepoint marker
11278 The @code{strace} command sets a static tracepoint. For targets that
11279 support it, setting a static tracepoint probes a static
11280 instrumentation point, or marker, found at @var{location}. It may not
11281 be possible to set a static tracepoint at the desired location, in
11282 which case the command will exit with an explanatory message.
11284 @value{GDBN} handles arguments to @code{strace} exactly as for
11285 @code{trace}, with the addition that the user can also specify
11286 @code{-m @var{marker}} as @var{location}. This probes the marker
11287 identified by the @var{marker} string identifier. This identifier
11288 depends on the static tracepoint backend library your program is
11289 using. You can find all the marker identifiers in the @samp{ID} field
11290 of the @code{info static-tracepoint-markers} command output.
11291 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11292 Markers}. For example, in the following small program using the UST
11298 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11303 the marker id is composed of joining the first two arguments to the
11304 @code{trace_mark} call with a slash, which translates to:
11307 (@value{GDBP}) info static-tracepoint-markers
11308 Cnt Enb ID Address What
11309 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11315 so you may probe the marker above with:
11318 (@value{GDBP}) strace -m ust/bar33
11321 Static tracepoints accept an extra collect action --- @code{collect
11322 $_sdata}. This collects arbitrary user data passed in the probe point
11323 call to the tracing library. In the UST example above, you'll see
11324 that the third argument to @code{trace_mark} is a printf-like format
11325 string. The user data is then the result of running that formating
11326 string against the following arguments. Note that @code{info
11327 static-tracepoint-markers} command output lists that format string in
11328 the @samp{Data:} field.
11330 You can inspect this data when analyzing the trace buffer, by printing
11331 the $_sdata variable like any other variable available to
11332 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11335 @cindex last tracepoint number
11336 @cindex recent tracepoint number
11337 @cindex tracepoint number
11338 The convenience variable @code{$tpnum} records the tracepoint number
11339 of the most recently set tracepoint.
11341 @kindex delete tracepoint
11342 @cindex tracepoint deletion
11343 @item delete tracepoint @r{[}@var{num}@r{]}
11344 Permanently delete one or more tracepoints. With no argument, the
11345 default is to delete all tracepoints. Note that the regular
11346 @code{delete} command can remove tracepoints also.
11351 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11353 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11357 You can abbreviate this command as @code{del tr}.
11360 @node Enable and Disable Tracepoints
11361 @subsection Enable and Disable Tracepoints
11363 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11366 @kindex disable tracepoint
11367 @item disable tracepoint @r{[}@var{num}@r{]}
11368 Disable tracepoint @var{num}, or all tracepoints if no argument
11369 @var{num} is given. A disabled tracepoint will have no effect during
11370 a trace experiment, but it is not forgotten. You can re-enable
11371 a disabled tracepoint using the @code{enable tracepoint} command.
11372 If the command is issued during a trace experiment and the debug target
11373 has support for disabling tracepoints during a trace experiment, then the
11374 change will be effective immediately. Otherwise, it will be applied to the
11375 next trace experiment.
11377 @kindex enable tracepoint
11378 @item enable tracepoint @r{[}@var{num}@r{]}
11379 Enable tracepoint @var{num}, or all tracepoints. If this command is
11380 issued during a trace experiment and the debug target supports enabling
11381 tracepoints during a trace experiment, then the enabled tracepoints will
11382 become effective immediately. Otherwise, they will become effective the
11383 next time a trace experiment is run.
11386 @node Tracepoint Passcounts
11387 @subsection Tracepoint Passcounts
11391 @cindex tracepoint pass count
11392 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11393 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11394 automatically stop a trace experiment. If a tracepoint's passcount is
11395 @var{n}, then the trace experiment will be automatically stopped on
11396 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11397 @var{num} is not specified, the @code{passcount} command sets the
11398 passcount of the most recently defined tracepoint. If no passcount is
11399 given, the trace experiment will run until stopped explicitly by the
11405 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11406 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11408 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11409 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11410 (@value{GDBP}) @b{trace foo}
11411 (@value{GDBP}) @b{pass 3}
11412 (@value{GDBP}) @b{trace bar}
11413 (@value{GDBP}) @b{pass 2}
11414 (@value{GDBP}) @b{trace baz}
11415 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11416 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11417 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11418 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11422 @node Tracepoint Conditions
11423 @subsection Tracepoint Conditions
11424 @cindex conditional tracepoints
11425 @cindex tracepoint conditions
11427 The simplest sort of tracepoint collects data every time your program
11428 reaches a specified place. You can also specify a @dfn{condition} for
11429 a tracepoint. A condition is just a Boolean expression in your
11430 programming language (@pxref{Expressions, ,Expressions}). A
11431 tracepoint with a condition evaluates the expression each time your
11432 program reaches it, and data collection happens only if the condition
11435 Tracepoint conditions can be specified when a tracepoint is set, by
11436 using @samp{if} in the arguments to the @code{trace} command.
11437 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11438 also be set or changed at any time with the @code{condition} command,
11439 just as with breakpoints.
11441 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11442 the conditional expression itself. Instead, @value{GDBN} encodes the
11443 expression into an agent expression (@pxref{Agent Expressions})
11444 suitable for execution on the target, independently of @value{GDBN}.
11445 Global variables become raw memory locations, locals become stack
11446 accesses, and so forth.
11448 For instance, suppose you have a function that is usually called
11449 frequently, but should not be called after an error has occurred. You
11450 could use the following tracepoint command to collect data about calls
11451 of that function that happen while the error code is propagating
11452 through the program; an unconditional tracepoint could end up
11453 collecting thousands of useless trace frames that you would have to
11457 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11460 @node Trace State Variables
11461 @subsection Trace State Variables
11462 @cindex trace state variables
11464 A @dfn{trace state variable} is a special type of variable that is
11465 created and managed by target-side code. The syntax is the same as
11466 that for GDB's convenience variables (a string prefixed with ``$''),
11467 but they are stored on the target. They must be created explicitly,
11468 using a @code{tvariable} command. They are always 64-bit signed
11471 Trace state variables are remembered by @value{GDBN}, and downloaded
11472 to the target along with tracepoint information when the trace
11473 experiment starts. There are no intrinsic limits on the number of
11474 trace state variables, beyond memory limitations of the target.
11476 @cindex convenience variables, and trace state variables
11477 Although trace state variables are managed by the target, you can use
11478 them in print commands and expressions as if they were convenience
11479 variables; @value{GDBN} will get the current value from the target
11480 while the trace experiment is running. Trace state variables share
11481 the same namespace as other ``$'' variables, which means that you
11482 cannot have trace state variables with names like @code{$23} or
11483 @code{$pc}, nor can you have a trace state variable and a convenience
11484 variable with the same name.
11488 @item tvariable $@var{name} [ = @var{expression} ]
11490 The @code{tvariable} command creates a new trace state variable named
11491 @code{$@var{name}}, and optionally gives it an initial value of
11492 @var{expression}. @var{expression} is evaluated when this command is
11493 entered; the result will be converted to an integer if possible,
11494 otherwise @value{GDBN} will report an error. A subsequent
11495 @code{tvariable} command specifying the same name does not create a
11496 variable, but instead assigns the supplied initial value to the
11497 existing variable of that name, overwriting any previous initial
11498 value. The default initial value is 0.
11500 @item info tvariables
11501 @kindex info tvariables
11502 List all the trace state variables along with their initial values.
11503 Their current values may also be displayed, if the trace experiment is
11506 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11507 @kindex delete tvariable
11508 Delete the given trace state variables, or all of them if no arguments
11513 @node Tracepoint Actions
11514 @subsection Tracepoint Action Lists
11518 @cindex tracepoint actions
11519 @item actions @r{[}@var{num}@r{]}
11520 This command will prompt for a list of actions to be taken when the
11521 tracepoint is hit. If the tracepoint number @var{num} is not
11522 specified, this command sets the actions for the one that was most
11523 recently defined (so that you can define a tracepoint and then say
11524 @code{actions} without bothering about its number). You specify the
11525 actions themselves on the following lines, one action at a time, and
11526 terminate the actions list with a line containing just @code{end}. So
11527 far, the only defined actions are @code{collect}, @code{teval}, and
11528 @code{while-stepping}.
11530 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11531 Commands, ,Breakpoint Command Lists}), except that only the defined
11532 actions are allowed; any other @value{GDBN} command is rejected.
11534 @cindex remove actions from a tracepoint
11535 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11536 and follow it immediately with @samp{end}.
11539 (@value{GDBP}) @b{collect @var{data}} // collect some data
11541 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11543 (@value{GDBP}) @b{end} // signals the end of actions.
11546 In the following example, the action list begins with @code{collect}
11547 commands indicating the things to be collected when the tracepoint is
11548 hit. Then, in order to single-step and collect additional data
11549 following the tracepoint, a @code{while-stepping} command is used,
11550 followed by the list of things to be collected after each step in a
11551 sequence of single steps. The @code{while-stepping} command is
11552 terminated by its own separate @code{end} command. Lastly, the action
11553 list is terminated by an @code{end} command.
11556 (@value{GDBP}) @b{trace foo}
11557 (@value{GDBP}) @b{actions}
11558 Enter actions for tracepoint 1, one per line:
11561 > while-stepping 12
11562 > collect $pc, arr[i]
11567 @kindex collect @r{(tracepoints)}
11568 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11569 Collect values of the given expressions when the tracepoint is hit.
11570 This command accepts a comma-separated list of any valid expressions.
11571 In addition to global, static, or local variables, the following
11572 special arguments are supported:
11576 Collect all registers.
11579 Collect all function arguments.
11582 Collect all local variables.
11585 Collect the return address. This is helpful if you want to see more
11589 Collects the number of arguments from the static probe at which the
11590 tracepoint is located.
11591 @xref{Static Probe Points}.
11593 @item $_probe_arg@var{n}
11594 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11595 from the static probe at which the tracepoint is located.
11596 @xref{Static Probe Points}.
11599 @vindex $_sdata@r{, collect}
11600 Collect static tracepoint marker specific data. Only available for
11601 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11602 Lists}. On the UST static tracepoints library backend, an
11603 instrumentation point resembles a @code{printf} function call. The
11604 tracing library is able to collect user specified data formatted to a
11605 character string using the format provided by the programmer that
11606 instrumented the program. Other backends have similar mechanisms.
11607 Here's an example of a UST marker call:
11610 const char master_name[] = "$your_name";
11611 trace_mark(channel1, marker1, "hello %s", master_name)
11614 In this case, collecting @code{$_sdata} collects the string
11615 @samp{hello $yourname}. When analyzing the trace buffer, you can
11616 inspect @samp{$_sdata} like any other variable available to
11620 You can give several consecutive @code{collect} commands, each one
11621 with a single argument, or one @code{collect} command with several
11622 arguments separated by commas; the effect is the same.
11624 The optional @var{mods} changes the usual handling of the arguments.
11625 @code{s} requests that pointers to chars be handled as strings, in
11626 particular collecting the contents of the memory being pointed at, up
11627 to the first zero. The upper bound is by default the value of the
11628 @code{print elements} variable; if @code{s} is followed by a decimal
11629 number, that is the upper bound instead. So for instance
11630 @samp{collect/s25 mystr} collects as many as 25 characters at
11633 The command @code{info scope} (@pxref{Symbols, info scope}) is
11634 particularly useful for figuring out what data to collect.
11636 @kindex teval @r{(tracepoints)}
11637 @item teval @var{expr1}, @var{expr2}, @dots{}
11638 Evaluate the given expressions when the tracepoint is hit. This
11639 command accepts a comma-separated list of expressions. The results
11640 are discarded, so this is mainly useful for assigning values to trace
11641 state variables (@pxref{Trace State Variables}) without adding those
11642 values to the trace buffer, as would be the case if the @code{collect}
11645 @kindex while-stepping @r{(tracepoints)}
11646 @item while-stepping @var{n}
11647 Perform @var{n} single-step instruction traces after the tracepoint,
11648 collecting new data after each step. The @code{while-stepping}
11649 command is followed by the list of what to collect while stepping
11650 (followed by its own @code{end} command):
11653 > while-stepping 12
11654 > collect $regs, myglobal
11660 Note that @code{$pc} is not automatically collected by
11661 @code{while-stepping}; you need to explicitly collect that register if
11662 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11665 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11666 @kindex set default-collect
11667 @cindex default collection action
11668 This variable is a list of expressions to collect at each tracepoint
11669 hit. It is effectively an additional @code{collect} action prepended
11670 to every tracepoint action list. The expressions are parsed
11671 individually for each tracepoint, so for instance a variable named
11672 @code{xyz} may be interpreted as a global for one tracepoint, and a
11673 local for another, as appropriate to the tracepoint's location.
11675 @item show default-collect
11676 @kindex show default-collect
11677 Show the list of expressions that are collected by default at each
11682 @node Listing Tracepoints
11683 @subsection Listing Tracepoints
11686 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11687 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11688 @cindex information about tracepoints
11689 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11690 Display information about the tracepoint @var{num}. If you don't
11691 specify a tracepoint number, displays information about all the
11692 tracepoints defined so far. The format is similar to that used for
11693 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11694 command, simply restricting itself to tracepoints.
11696 A tracepoint's listing may include additional information specific to
11701 its passcount as given by the @code{passcount @var{n}} command
11704 the state about installed on target of each location
11708 (@value{GDBP}) @b{info trace}
11709 Num Type Disp Enb Address What
11710 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11712 collect globfoo, $regs
11717 2 tracepoint keep y <MULTIPLE>
11719 2.1 y 0x0804859c in func4 at change-loc.h:35
11720 installed on target
11721 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11722 installed on target
11723 2.3 y <PENDING> set_tracepoint
11724 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11725 not installed on target
11730 This command can be abbreviated @code{info tp}.
11733 @node Listing Static Tracepoint Markers
11734 @subsection Listing Static Tracepoint Markers
11737 @kindex info static-tracepoint-markers
11738 @cindex information about static tracepoint markers
11739 @item info static-tracepoint-markers
11740 Display information about all static tracepoint markers defined in the
11743 For each marker, the following columns are printed:
11747 An incrementing counter, output to help readability. This is not a
11750 The marker ID, as reported by the target.
11751 @item Enabled or Disabled
11752 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11753 that are not enabled.
11755 Where the marker is in your program, as a memory address.
11757 Where the marker is in the source for your program, as a file and line
11758 number. If the debug information included in the program does not
11759 allow @value{GDBN} to locate the source of the marker, this column
11760 will be left blank.
11764 In addition, the following information may be printed for each marker:
11768 User data passed to the tracing library by the marker call. In the
11769 UST backend, this is the format string passed as argument to the
11771 @item Static tracepoints probing the marker
11772 The list of static tracepoints attached to the marker.
11776 (@value{GDBP}) info static-tracepoint-markers
11777 Cnt ID Enb Address What
11778 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11779 Data: number1 %d number2 %d
11780 Probed by static tracepoints: #2
11781 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11787 @node Starting and Stopping Trace Experiments
11788 @subsection Starting and Stopping Trace Experiments
11791 @kindex tstart [ @var{notes} ]
11792 @cindex start a new trace experiment
11793 @cindex collected data discarded
11795 This command starts the trace experiment, and begins collecting data.
11796 It has the side effect of discarding all the data collected in the
11797 trace buffer during the previous trace experiment. If any arguments
11798 are supplied, they are taken as a note and stored with the trace
11799 experiment's state. The notes may be arbitrary text, and are
11800 especially useful with disconnected tracing in a multi-user context;
11801 the notes can explain what the trace is doing, supply user contact
11802 information, and so forth.
11804 @kindex tstop [ @var{notes} ]
11805 @cindex stop a running trace experiment
11807 This command stops the trace experiment. If any arguments are
11808 supplied, they are recorded with the experiment as a note. This is
11809 useful if you are stopping a trace started by someone else, for
11810 instance if the trace is interfering with the system's behavior and
11811 needs to be stopped quickly.
11813 @strong{Note}: a trace experiment and data collection may stop
11814 automatically if any tracepoint's passcount is reached
11815 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11818 @cindex status of trace data collection
11819 @cindex trace experiment, status of
11821 This command displays the status of the current trace data
11825 Here is an example of the commands we described so far:
11828 (@value{GDBP}) @b{trace gdb_c_test}
11829 (@value{GDBP}) @b{actions}
11830 Enter actions for tracepoint #1, one per line.
11831 > collect $regs,$locals,$args
11832 > while-stepping 11
11836 (@value{GDBP}) @b{tstart}
11837 [time passes @dots{}]
11838 (@value{GDBP}) @b{tstop}
11841 @anchor{disconnected tracing}
11842 @cindex disconnected tracing
11843 You can choose to continue running the trace experiment even if
11844 @value{GDBN} disconnects from the target, voluntarily or
11845 involuntarily. For commands such as @code{detach}, the debugger will
11846 ask what you want to do with the trace. But for unexpected
11847 terminations (@value{GDBN} crash, network outage), it would be
11848 unfortunate to lose hard-won trace data, so the variable
11849 @code{disconnected-tracing} lets you decide whether the trace should
11850 continue running without @value{GDBN}.
11853 @item set disconnected-tracing on
11854 @itemx set disconnected-tracing off
11855 @kindex set disconnected-tracing
11856 Choose whether a tracing run should continue to run if @value{GDBN}
11857 has disconnected from the target. Note that @code{detach} or
11858 @code{quit} will ask you directly what to do about a running trace no
11859 matter what this variable's setting, so the variable is mainly useful
11860 for handling unexpected situations, such as loss of the network.
11862 @item show disconnected-tracing
11863 @kindex show disconnected-tracing
11864 Show the current choice for disconnected tracing.
11868 When you reconnect to the target, the trace experiment may or may not
11869 still be running; it might have filled the trace buffer in the
11870 meantime, or stopped for one of the other reasons. If it is running,
11871 it will continue after reconnection.
11873 Upon reconnection, the target will upload information about the
11874 tracepoints in effect. @value{GDBN} will then compare that
11875 information to the set of tracepoints currently defined, and attempt
11876 to match them up, allowing for the possibility that the numbers may
11877 have changed due to creation and deletion in the meantime. If one of
11878 the target's tracepoints does not match any in @value{GDBN}, the
11879 debugger will create a new tracepoint, so that you have a number with
11880 which to specify that tracepoint. This matching-up process is
11881 necessarily heuristic, and it may result in useless tracepoints being
11882 created; you may simply delete them if they are of no use.
11884 @cindex circular trace buffer
11885 If your target agent supports a @dfn{circular trace buffer}, then you
11886 can run a trace experiment indefinitely without filling the trace
11887 buffer; when space runs out, the agent deletes already-collected trace
11888 frames, oldest first, until there is enough room to continue
11889 collecting. This is especially useful if your tracepoints are being
11890 hit too often, and your trace gets terminated prematurely because the
11891 buffer is full. To ask for a circular trace buffer, simply set
11892 @samp{circular-trace-buffer} to on. You can set this at any time,
11893 including during tracing; if the agent can do it, it will change
11894 buffer handling on the fly, otherwise it will not take effect until
11898 @item set circular-trace-buffer on
11899 @itemx set circular-trace-buffer off
11900 @kindex set circular-trace-buffer
11901 Choose whether a tracing run should use a linear or circular buffer
11902 for trace data. A linear buffer will not lose any trace data, but may
11903 fill up prematurely, while a circular buffer will discard old trace
11904 data, but it will have always room for the latest tracepoint hits.
11906 @item show circular-trace-buffer
11907 @kindex show circular-trace-buffer
11908 Show the current choice for the trace buffer. Note that this may not
11909 match the agent's current buffer handling, nor is it guaranteed to
11910 match the setting that might have been in effect during a past run,
11911 for instance if you are looking at frames from a trace file.
11916 @item set trace-buffer-size @var{n}
11917 @itemx set trace-buffer-size unlimited
11918 @kindex set trace-buffer-size
11919 Request that the target use a trace buffer of @var{n} bytes. Not all
11920 targets will honor the request; they may have a compiled-in size for
11921 the trace buffer, or some other limitation. Set to a value of
11922 @code{unlimited} or @code{-1} to let the target use whatever size it
11923 likes. This is also the default.
11925 @item show trace-buffer-size
11926 @kindex show trace-buffer-size
11927 Show the current requested size for the trace buffer. Note that this
11928 will only match the actual size if the target supports size-setting,
11929 and was able to handle the requested size. For instance, if the
11930 target can only change buffer size between runs, this variable will
11931 not reflect the change until the next run starts. Use @code{tstatus}
11932 to get a report of the actual buffer size.
11936 @item set trace-user @var{text}
11937 @kindex set trace-user
11939 @item show trace-user
11940 @kindex show trace-user
11942 @item set trace-notes @var{text}
11943 @kindex set trace-notes
11944 Set the trace run's notes.
11946 @item show trace-notes
11947 @kindex show trace-notes
11948 Show the trace run's notes.
11950 @item set trace-stop-notes @var{text}
11951 @kindex set trace-stop-notes
11952 Set the trace run's stop notes. The handling of the note is as for
11953 @code{tstop} arguments; the set command is convenient way to fix a
11954 stop note that is mistaken or incomplete.
11956 @item show trace-stop-notes
11957 @kindex show trace-stop-notes
11958 Show the trace run's stop notes.
11962 @node Tracepoint Restrictions
11963 @subsection Tracepoint Restrictions
11965 @cindex tracepoint restrictions
11966 There are a number of restrictions on the use of tracepoints. As
11967 described above, tracepoint data gathering occurs on the target
11968 without interaction from @value{GDBN}. Thus the full capabilities of
11969 the debugger are not available during data gathering, and then at data
11970 examination time, you will be limited by only having what was
11971 collected. The following items describe some common problems, but it
11972 is not exhaustive, and you may run into additional difficulties not
11978 Tracepoint expressions are intended to gather objects (lvalues). Thus
11979 the full flexibility of GDB's expression evaluator is not available.
11980 You cannot call functions, cast objects to aggregate types, access
11981 convenience variables or modify values (except by assignment to trace
11982 state variables). Some language features may implicitly call
11983 functions (for instance Objective-C fields with accessors), and therefore
11984 cannot be collected either.
11987 Collection of local variables, either individually or in bulk with
11988 @code{$locals} or @code{$args}, during @code{while-stepping} may
11989 behave erratically. The stepping action may enter a new scope (for
11990 instance by stepping into a function), or the location of the variable
11991 may change (for instance it is loaded into a register). The
11992 tracepoint data recorded uses the location information for the
11993 variables that is correct for the tracepoint location. When the
11994 tracepoint is created, it is not possible, in general, to determine
11995 where the steps of a @code{while-stepping} sequence will advance the
11996 program---particularly if a conditional branch is stepped.
11999 Collection of an incompletely-initialized or partially-destroyed object
12000 may result in something that @value{GDBN} cannot display, or displays
12001 in a misleading way.
12004 When @value{GDBN} displays a pointer to character it automatically
12005 dereferences the pointer to also display characters of the string
12006 being pointed to. However, collecting the pointer during tracing does
12007 not automatically collect the string. You need to explicitly
12008 dereference the pointer and provide size information if you want to
12009 collect not only the pointer, but the memory pointed to. For example,
12010 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12014 It is not possible to collect a complete stack backtrace at a
12015 tracepoint. Instead, you may collect the registers and a few hundred
12016 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12017 (adjust to use the name of the actual stack pointer register on your
12018 target architecture, and the amount of stack you wish to capture).
12019 Then the @code{backtrace} command will show a partial backtrace when
12020 using a trace frame. The number of stack frames that can be examined
12021 depends on the sizes of the frames in the collected stack. Note that
12022 if you ask for a block so large that it goes past the bottom of the
12023 stack, the target agent may report an error trying to read from an
12027 If you do not collect registers at a tracepoint, @value{GDBN} can
12028 infer that the value of @code{$pc} must be the same as the address of
12029 the tracepoint and use that when you are looking at a trace frame
12030 for that tracepoint. However, this cannot work if the tracepoint has
12031 multiple locations (for instance if it was set in a function that was
12032 inlined), or if it has a @code{while-stepping} loop. In those cases
12033 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12038 @node Analyze Collected Data
12039 @section Using the Collected Data
12041 After the tracepoint experiment ends, you use @value{GDBN} commands
12042 for examining the trace data. The basic idea is that each tracepoint
12043 collects a trace @dfn{snapshot} every time it is hit and another
12044 snapshot every time it single-steps. All these snapshots are
12045 consecutively numbered from zero and go into a buffer, and you can
12046 examine them later. The way you examine them is to @dfn{focus} on a
12047 specific trace snapshot. When the remote stub is focused on a trace
12048 snapshot, it will respond to all @value{GDBN} requests for memory and
12049 registers by reading from the buffer which belongs to that snapshot,
12050 rather than from @emph{real} memory or registers of the program being
12051 debugged. This means that @strong{all} @value{GDBN} commands
12052 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12053 behave as if we were currently debugging the program state as it was
12054 when the tracepoint occurred. Any requests for data that are not in
12055 the buffer will fail.
12058 * tfind:: How to select a trace snapshot
12059 * tdump:: How to display all data for a snapshot
12060 * save tracepoints:: How to save tracepoints for a future run
12064 @subsection @code{tfind @var{n}}
12067 @cindex select trace snapshot
12068 @cindex find trace snapshot
12069 The basic command for selecting a trace snapshot from the buffer is
12070 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12071 counting from zero. If no argument @var{n} is given, the next
12072 snapshot is selected.
12074 Here are the various forms of using the @code{tfind} command.
12078 Find the first snapshot in the buffer. This is a synonym for
12079 @code{tfind 0} (since 0 is the number of the first snapshot).
12082 Stop debugging trace snapshots, resume @emph{live} debugging.
12085 Same as @samp{tfind none}.
12088 No argument means find the next trace snapshot.
12091 Find the previous trace snapshot before the current one. This permits
12092 retracing earlier steps.
12094 @item tfind tracepoint @var{num}
12095 Find the next snapshot associated with tracepoint @var{num}. Search
12096 proceeds forward from the last examined trace snapshot. If no
12097 argument @var{num} is given, it means find the next snapshot collected
12098 for the same tracepoint as the current snapshot.
12100 @item tfind pc @var{addr}
12101 Find the next snapshot associated with the value @var{addr} of the
12102 program counter. Search proceeds forward from the last examined trace
12103 snapshot. If no argument @var{addr} is given, it means find the next
12104 snapshot with the same value of PC as the current snapshot.
12106 @item tfind outside @var{addr1}, @var{addr2}
12107 Find the next snapshot whose PC is outside the given range of
12108 addresses (exclusive).
12110 @item tfind range @var{addr1}, @var{addr2}
12111 Find the next snapshot whose PC is between @var{addr1} and
12112 @var{addr2} (inclusive).
12114 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12115 Find the next snapshot associated with the source line @var{n}. If
12116 the optional argument @var{file} is given, refer to line @var{n} in
12117 that source file. Search proceeds forward from the last examined
12118 trace snapshot. If no argument @var{n} is given, it means find the
12119 next line other than the one currently being examined; thus saying
12120 @code{tfind line} repeatedly can appear to have the same effect as
12121 stepping from line to line in a @emph{live} debugging session.
12124 The default arguments for the @code{tfind} commands are specifically
12125 designed to make it easy to scan through the trace buffer. For
12126 instance, @code{tfind} with no argument selects the next trace
12127 snapshot, and @code{tfind -} with no argument selects the previous
12128 trace snapshot. So, by giving one @code{tfind} command, and then
12129 simply hitting @key{RET} repeatedly you can examine all the trace
12130 snapshots in order. Or, by saying @code{tfind -} and then hitting
12131 @key{RET} repeatedly you can examine the snapshots in reverse order.
12132 The @code{tfind line} command with no argument selects the snapshot
12133 for the next source line executed. The @code{tfind pc} command with
12134 no argument selects the next snapshot with the same program counter
12135 (PC) as the current frame. The @code{tfind tracepoint} command with
12136 no argument selects the next trace snapshot collected by the same
12137 tracepoint as the current one.
12139 In addition to letting you scan through the trace buffer manually,
12140 these commands make it easy to construct @value{GDBN} scripts that
12141 scan through the trace buffer and print out whatever collected data
12142 you are interested in. Thus, if we want to examine the PC, FP, and SP
12143 registers from each trace frame in the buffer, we can say this:
12146 (@value{GDBP}) @b{tfind start}
12147 (@value{GDBP}) @b{while ($trace_frame != -1)}
12148 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12149 $trace_frame, $pc, $sp, $fp
12153 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12154 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12155 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12156 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12157 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12158 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12159 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12160 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12161 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12162 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12163 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12166 Or, if we want to examine the variable @code{X} at each source line in
12170 (@value{GDBP}) @b{tfind start}
12171 (@value{GDBP}) @b{while ($trace_frame != -1)}
12172 > printf "Frame %d, X == %d\n", $trace_frame, X
12182 @subsection @code{tdump}
12184 @cindex dump all data collected at tracepoint
12185 @cindex tracepoint data, display
12187 This command takes no arguments. It prints all the data collected at
12188 the current trace snapshot.
12191 (@value{GDBP}) @b{trace 444}
12192 (@value{GDBP}) @b{actions}
12193 Enter actions for tracepoint #2, one per line:
12194 > collect $regs, $locals, $args, gdb_long_test
12197 (@value{GDBP}) @b{tstart}
12199 (@value{GDBP}) @b{tfind line 444}
12200 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12202 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12204 (@value{GDBP}) @b{tdump}
12205 Data collected at tracepoint 2, trace frame 1:
12206 d0 0xc4aa0085 -995491707
12210 d4 0x71aea3d 119204413
12213 d7 0x380035 3670069
12214 a0 0x19e24a 1696330
12215 a1 0x3000668 50333288
12217 a3 0x322000 3284992
12218 a4 0x3000698 50333336
12219 a5 0x1ad3cc 1758156
12220 fp 0x30bf3c 0x30bf3c
12221 sp 0x30bf34 0x30bf34
12223 pc 0x20b2c8 0x20b2c8
12227 p = 0x20e5b4 "gdb-test"
12234 gdb_long_test = 17 '\021'
12239 @code{tdump} works by scanning the tracepoint's current collection
12240 actions and printing the value of each expression listed. So
12241 @code{tdump} can fail, if after a run, you change the tracepoint's
12242 actions to mention variables that were not collected during the run.
12244 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12245 uses the collected value of @code{$pc} to distinguish between trace
12246 frames that were collected at the tracepoint hit, and frames that were
12247 collected while stepping. This allows it to correctly choose whether
12248 to display the basic list of collections, or the collections from the
12249 body of the while-stepping loop. However, if @code{$pc} was not collected,
12250 then @code{tdump} will always attempt to dump using the basic collection
12251 list, and may fail if a while-stepping frame does not include all the
12252 same data that is collected at the tracepoint hit.
12253 @c This is getting pretty arcane, example would be good.
12255 @node save tracepoints
12256 @subsection @code{save tracepoints @var{filename}}
12257 @kindex save tracepoints
12258 @kindex save-tracepoints
12259 @cindex save tracepoints for future sessions
12261 This command saves all current tracepoint definitions together with
12262 their actions and passcounts, into a file @file{@var{filename}}
12263 suitable for use in a later debugging session. To read the saved
12264 tracepoint definitions, use the @code{source} command (@pxref{Command
12265 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12266 alias for @w{@code{save tracepoints}}
12268 @node Tracepoint Variables
12269 @section Convenience Variables for Tracepoints
12270 @cindex tracepoint variables
12271 @cindex convenience variables for tracepoints
12274 @vindex $trace_frame
12275 @item (int) $trace_frame
12276 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12277 snapshot is selected.
12279 @vindex $tracepoint
12280 @item (int) $tracepoint
12281 The tracepoint for the current trace snapshot.
12283 @vindex $trace_line
12284 @item (int) $trace_line
12285 The line number for the current trace snapshot.
12287 @vindex $trace_file
12288 @item (char []) $trace_file
12289 The source file for the current trace snapshot.
12291 @vindex $trace_func
12292 @item (char []) $trace_func
12293 The name of the function containing @code{$tracepoint}.
12296 Note: @code{$trace_file} is not suitable for use in @code{printf},
12297 use @code{output} instead.
12299 Here's a simple example of using these convenience variables for
12300 stepping through all the trace snapshots and printing some of their
12301 data. Note that these are not the same as trace state variables,
12302 which are managed by the target.
12305 (@value{GDBP}) @b{tfind start}
12307 (@value{GDBP}) @b{while $trace_frame != -1}
12308 > output $trace_file
12309 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12315 @section Using Trace Files
12316 @cindex trace files
12318 In some situations, the target running a trace experiment may no
12319 longer be available; perhaps it crashed, or the hardware was needed
12320 for a different activity. To handle these cases, you can arrange to
12321 dump the trace data into a file, and later use that file as a source
12322 of trace data, via the @code{target tfile} command.
12327 @item tsave [ -r ] @var{filename}
12328 @itemx tsave [-ctf] @var{dirname}
12329 Save the trace data to @var{filename}. By default, this command
12330 assumes that @var{filename} refers to the host filesystem, so if
12331 necessary @value{GDBN} will copy raw trace data up from the target and
12332 then save it. If the target supports it, you can also supply the
12333 optional argument @code{-r} (``remote'') to direct the target to save
12334 the data directly into @var{filename} in its own filesystem, which may be
12335 more efficient if the trace buffer is very large. (Note, however, that
12336 @code{target tfile} can only read from files accessible to the host.)
12337 By default, this command will save trace frame in tfile format.
12338 You can supply the optional argument @code{-ctf} to save date in CTF
12339 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12340 that can be shared by multiple debugging and tracing tools. Please go to
12341 @indicateurl{http://www.efficios.com/ctf} to get more information.
12343 @kindex target tfile
12347 @item target tfile @var{filename}
12348 @itemx target ctf @var{dirname}
12349 Use the file named @var{filename} or directory named @var{dirname} as
12350 a source of trace data. Commands that examine data work as they do with
12351 a live target, but it is not possible to run any new trace experiments.
12352 @code{tstatus} will report the state of the trace run at the moment
12353 the data was saved, as well as the current trace frame you are examining.
12354 @var{filename} or @var{dirname} must be on a filesystem accessible to
12358 (@value{GDBP}) target ctf ctf.ctf
12359 (@value{GDBP}) tfind
12360 Found trace frame 0, tracepoint 2
12361 39 ++a; /* set tracepoint 1 here */
12362 (@value{GDBP}) tdump
12363 Data collected at tracepoint 2, trace frame 0:
12367 c = @{"123", "456", "789", "123", "456", "789"@}
12368 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12376 @chapter Debugging Programs That Use Overlays
12379 If your program is too large to fit completely in your target system's
12380 memory, you can sometimes use @dfn{overlays} to work around this
12381 problem. @value{GDBN} provides some support for debugging programs that
12385 * How Overlays Work:: A general explanation of overlays.
12386 * Overlay Commands:: Managing overlays in @value{GDBN}.
12387 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12388 mapped by asking the inferior.
12389 * Overlay Sample Program:: A sample program using overlays.
12392 @node How Overlays Work
12393 @section How Overlays Work
12394 @cindex mapped overlays
12395 @cindex unmapped overlays
12396 @cindex load address, overlay's
12397 @cindex mapped address
12398 @cindex overlay area
12400 Suppose you have a computer whose instruction address space is only 64
12401 kilobytes long, but which has much more memory which can be accessed by
12402 other means: special instructions, segment registers, or memory
12403 management hardware, for example. Suppose further that you want to
12404 adapt a program which is larger than 64 kilobytes to run on this system.
12406 One solution is to identify modules of your program which are relatively
12407 independent, and need not call each other directly; call these modules
12408 @dfn{overlays}. Separate the overlays from the main program, and place
12409 their machine code in the larger memory. Place your main program in
12410 instruction memory, but leave at least enough space there to hold the
12411 largest overlay as well.
12413 Now, to call a function located in an overlay, you must first copy that
12414 overlay's machine code from the large memory into the space set aside
12415 for it in the instruction memory, and then jump to its entry point
12418 @c NB: In the below the mapped area's size is greater or equal to the
12419 @c size of all overlays. This is intentional to remind the developer
12420 @c that overlays don't necessarily need to be the same size.
12424 Data Instruction Larger
12425 Address Space Address Space Address Space
12426 +-----------+ +-----------+ +-----------+
12428 +-----------+ +-----------+ +-----------+<-- overlay 1
12429 | program | | main | .----| overlay 1 | load address
12430 | variables | | program | | +-----------+
12431 | and heap | | | | | |
12432 +-----------+ | | | +-----------+<-- overlay 2
12433 | | +-----------+ | | | load address
12434 +-----------+ | | | .-| overlay 2 |
12436 mapped --->+-----------+ | | +-----------+
12437 address | | | | | |
12438 | overlay | <-' | | |
12439 | area | <---' +-----------+<-- overlay 3
12440 | | <---. | | load address
12441 +-----------+ `--| overlay 3 |
12448 @anchor{A code overlay}A code overlay
12452 The diagram (@pxref{A code overlay}) shows a system with separate data
12453 and instruction address spaces. To map an overlay, the program copies
12454 its code from the larger address space to the instruction address space.
12455 Since the overlays shown here all use the same mapped address, only one
12456 may be mapped at a time. For a system with a single address space for
12457 data and instructions, the diagram would be similar, except that the
12458 program variables and heap would share an address space with the main
12459 program and the overlay area.
12461 An overlay loaded into instruction memory and ready for use is called a
12462 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12463 instruction memory. An overlay not present (or only partially present)
12464 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12465 is its address in the larger memory. The mapped address is also called
12466 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12467 called the @dfn{load memory address}, or @dfn{LMA}.
12469 Unfortunately, overlays are not a completely transparent way to adapt a
12470 program to limited instruction memory. They introduce a new set of
12471 global constraints you must keep in mind as you design your program:
12476 Before calling or returning to a function in an overlay, your program
12477 must make sure that overlay is actually mapped. Otherwise, the call or
12478 return will transfer control to the right address, but in the wrong
12479 overlay, and your program will probably crash.
12482 If the process of mapping an overlay is expensive on your system, you
12483 will need to choose your overlays carefully to minimize their effect on
12484 your program's performance.
12487 The executable file you load onto your system must contain each
12488 overlay's instructions, appearing at the overlay's load address, not its
12489 mapped address. However, each overlay's instructions must be relocated
12490 and its symbols defined as if the overlay were at its mapped address.
12491 You can use GNU linker scripts to specify different load and relocation
12492 addresses for pieces of your program; see @ref{Overlay Description,,,
12493 ld.info, Using ld: the GNU linker}.
12496 The procedure for loading executable files onto your system must be able
12497 to load their contents into the larger address space as well as the
12498 instruction and data spaces.
12502 The overlay system described above is rather simple, and could be
12503 improved in many ways:
12508 If your system has suitable bank switch registers or memory management
12509 hardware, you could use those facilities to make an overlay's load area
12510 contents simply appear at their mapped address in instruction space.
12511 This would probably be faster than copying the overlay to its mapped
12512 area in the usual way.
12515 If your overlays are small enough, you could set aside more than one
12516 overlay area, and have more than one overlay mapped at a time.
12519 You can use overlays to manage data, as well as instructions. In
12520 general, data overlays are even less transparent to your design than
12521 code overlays: whereas code overlays only require care when you call or
12522 return to functions, data overlays require care every time you access
12523 the data. Also, if you change the contents of a data overlay, you
12524 must copy its contents back out to its load address before you can copy a
12525 different data overlay into the same mapped area.
12530 @node Overlay Commands
12531 @section Overlay Commands
12533 To use @value{GDBN}'s overlay support, each overlay in your program must
12534 correspond to a separate section of the executable file. The section's
12535 virtual memory address and load memory address must be the overlay's
12536 mapped and load addresses. Identifying overlays with sections allows
12537 @value{GDBN} to determine the appropriate address of a function or
12538 variable, depending on whether the overlay is mapped or not.
12540 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12541 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12546 Disable @value{GDBN}'s overlay support. When overlay support is
12547 disabled, @value{GDBN} assumes that all functions and variables are
12548 always present at their mapped addresses. By default, @value{GDBN}'s
12549 overlay support is disabled.
12551 @item overlay manual
12552 @cindex manual overlay debugging
12553 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12554 relies on you to tell it which overlays are mapped, and which are not,
12555 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12556 commands described below.
12558 @item overlay map-overlay @var{overlay}
12559 @itemx overlay map @var{overlay}
12560 @cindex map an overlay
12561 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12562 be the name of the object file section containing the overlay. When an
12563 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12564 functions and variables at their mapped addresses. @value{GDBN} assumes
12565 that any other overlays whose mapped ranges overlap that of
12566 @var{overlay} are now unmapped.
12568 @item overlay unmap-overlay @var{overlay}
12569 @itemx overlay unmap @var{overlay}
12570 @cindex unmap an overlay
12571 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12572 must be the name of the object file section containing the overlay.
12573 When an overlay is unmapped, @value{GDBN} assumes it can find the
12574 overlay's functions and variables at their load addresses.
12577 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12578 consults a data structure the overlay manager maintains in the inferior
12579 to see which overlays are mapped. For details, see @ref{Automatic
12580 Overlay Debugging}.
12582 @item overlay load-target
12583 @itemx overlay load
12584 @cindex reloading the overlay table
12585 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12586 re-reads the table @value{GDBN} automatically each time the inferior
12587 stops, so this command should only be necessary if you have changed the
12588 overlay mapping yourself using @value{GDBN}. This command is only
12589 useful when using automatic overlay debugging.
12591 @item overlay list-overlays
12592 @itemx overlay list
12593 @cindex listing mapped overlays
12594 Display a list of the overlays currently mapped, along with their mapped
12595 addresses, load addresses, and sizes.
12599 Normally, when @value{GDBN} prints a code address, it includes the name
12600 of the function the address falls in:
12603 (@value{GDBP}) print main
12604 $3 = @{int ()@} 0x11a0 <main>
12607 When overlay debugging is enabled, @value{GDBN} recognizes code in
12608 unmapped overlays, and prints the names of unmapped functions with
12609 asterisks around them. For example, if @code{foo} is a function in an
12610 unmapped overlay, @value{GDBN} prints it this way:
12613 (@value{GDBP}) overlay list
12614 No sections are mapped.
12615 (@value{GDBP}) print foo
12616 $5 = @{int (int)@} 0x100000 <*foo*>
12619 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12623 (@value{GDBP}) overlay list
12624 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12625 mapped at 0x1016 - 0x104a
12626 (@value{GDBP}) print foo
12627 $6 = @{int (int)@} 0x1016 <foo>
12630 When overlay debugging is enabled, @value{GDBN} can find the correct
12631 address for functions and variables in an overlay, whether or not the
12632 overlay is mapped. This allows most @value{GDBN} commands, like
12633 @code{break} and @code{disassemble}, to work normally, even on unmapped
12634 code. However, @value{GDBN}'s breakpoint support has some limitations:
12638 @cindex breakpoints in overlays
12639 @cindex overlays, setting breakpoints in
12640 You can set breakpoints in functions in unmapped overlays, as long as
12641 @value{GDBN} can write to the overlay at its load address.
12643 @value{GDBN} can not set hardware or simulator-based breakpoints in
12644 unmapped overlays. However, if you set a breakpoint at the end of your
12645 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12646 you are using manual overlay management), @value{GDBN} will re-set its
12647 breakpoints properly.
12651 @node Automatic Overlay Debugging
12652 @section Automatic Overlay Debugging
12653 @cindex automatic overlay debugging
12655 @value{GDBN} can automatically track which overlays are mapped and which
12656 are not, given some simple co-operation from the overlay manager in the
12657 inferior. If you enable automatic overlay debugging with the
12658 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12659 looks in the inferior's memory for certain variables describing the
12660 current state of the overlays.
12662 Here are the variables your overlay manager must define to support
12663 @value{GDBN}'s automatic overlay debugging:
12667 @item @code{_ovly_table}:
12668 This variable must be an array of the following structures:
12673 /* The overlay's mapped address. */
12676 /* The size of the overlay, in bytes. */
12677 unsigned long size;
12679 /* The overlay's load address. */
12682 /* Non-zero if the overlay is currently mapped;
12684 unsigned long mapped;
12688 @item @code{_novlys}:
12689 This variable must be a four-byte signed integer, holding the total
12690 number of elements in @code{_ovly_table}.
12694 To decide whether a particular overlay is mapped or not, @value{GDBN}
12695 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12696 @code{lma} members equal the VMA and LMA of the overlay's section in the
12697 executable file. When @value{GDBN} finds a matching entry, it consults
12698 the entry's @code{mapped} member to determine whether the overlay is
12701 In addition, your overlay manager may define a function called
12702 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12703 will silently set a breakpoint there. If the overlay manager then
12704 calls this function whenever it has changed the overlay table, this
12705 will enable @value{GDBN} to accurately keep track of which overlays
12706 are in program memory, and update any breakpoints that may be set
12707 in overlays. This will allow breakpoints to work even if the
12708 overlays are kept in ROM or other non-writable memory while they
12709 are not being executed.
12711 @node Overlay Sample Program
12712 @section Overlay Sample Program
12713 @cindex overlay example program
12715 When linking a program which uses overlays, you must place the overlays
12716 at their load addresses, while relocating them to run at their mapped
12717 addresses. To do this, you must write a linker script (@pxref{Overlay
12718 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12719 since linker scripts are specific to a particular host system, target
12720 architecture, and target memory layout, this manual cannot provide
12721 portable sample code demonstrating @value{GDBN}'s overlay support.
12723 However, the @value{GDBN} source distribution does contain an overlaid
12724 program, with linker scripts for a few systems, as part of its test
12725 suite. The program consists of the following files from
12726 @file{gdb/testsuite/gdb.base}:
12730 The main program file.
12732 A simple overlay manager, used by @file{overlays.c}.
12737 Overlay modules, loaded and used by @file{overlays.c}.
12740 Linker scripts for linking the test program on the @code{d10v-elf}
12741 and @code{m32r-elf} targets.
12744 You can build the test program using the @code{d10v-elf} GCC
12745 cross-compiler like this:
12748 $ d10v-elf-gcc -g -c overlays.c
12749 $ d10v-elf-gcc -g -c ovlymgr.c
12750 $ d10v-elf-gcc -g -c foo.c
12751 $ d10v-elf-gcc -g -c bar.c
12752 $ d10v-elf-gcc -g -c baz.c
12753 $ d10v-elf-gcc -g -c grbx.c
12754 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12755 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12758 The build process is identical for any other architecture, except that
12759 you must substitute the appropriate compiler and linker script for the
12760 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12764 @chapter Using @value{GDBN} with Different Languages
12767 Although programming languages generally have common aspects, they are
12768 rarely expressed in the same manner. For instance, in ANSI C,
12769 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12770 Modula-2, it is accomplished by @code{p^}. Values can also be
12771 represented (and displayed) differently. Hex numbers in C appear as
12772 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12774 @cindex working language
12775 Language-specific information is built into @value{GDBN} for some languages,
12776 allowing you to express operations like the above in your program's
12777 native language, and allowing @value{GDBN} to output values in a manner
12778 consistent with the syntax of your program's native language. The
12779 language you use to build expressions is called the @dfn{working
12783 * Setting:: Switching between source languages
12784 * Show:: Displaying the language
12785 * Checks:: Type and range checks
12786 * Supported Languages:: Supported languages
12787 * Unsupported Languages:: Unsupported languages
12791 @section Switching Between Source Languages
12793 There are two ways to control the working language---either have @value{GDBN}
12794 set it automatically, or select it manually yourself. You can use the
12795 @code{set language} command for either purpose. On startup, @value{GDBN}
12796 defaults to setting the language automatically. The working language is
12797 used to determine how expressions you type are interpreted, how values
12800 In addition to the working language, every source file that
12801 @value{GDBN} knows about has its own working language. For some object
12802 file formats, the compiler might indicate which language a particular
12803 source file is in. However, most of the time @value{GDBN} infers the
12804 language from the name of the file. The language of a source file
12805 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12806 show each frame appropriately for its own language. There is no way to
12807 set the language of a source file from within @value{GDBN}, but you can
12808 set the language associated with a filename extension. @xref{Show, ,
12809 Displaying the Language}.
12811 This is most commonly a problem when you use a program, such
12812 as @code{cfront} or @code{f2c}, that generates C but is written in
12813 another language. In that case, make the
12814 program use @code{#line} directives in its C output; that way
12815 @value{GDBN} will know the correct language of the source code of the original
12816 program, and will display that source code, not the generated C code.
12819 * Filenames:: Filename extensions and languages.
12820 * Manually:: Setting the working language manually
12821 * Automatically:: Having @value{GDBN} infer the source language
12825 @subsection List of Filename Extensions and Languages
12827 If a source file name ends in one of the following extensions, then
12828 @value{GDBN} infers that its language is the one indicated.
12846 C@t{++} source file
12852 Objective-C source file
12856 Fortran source file
12859 Modula-2 source file
12863 Assembler source file. This actually behaves almost like C, but
12864 @value{GDBN} does not skip over function prologues when stepping.
12867 In addition, you may set the language associated with a filename
12868 extension. @xref{Show, , Displaying the Language}.
12871 @subsection Setting the Working Language
12873 If you allow @value{GDBN} to set the language automatically,
12874 expressions are interpreted the same way in your debugging session and
12877 @kindex set language
12878 If you wish, you may set the language manually. To do this, issue the
12879 command @samp{set language @var{lang}}, where @var{lang} is the name of
12880 a language, such as
12881 @code{c} or @code{modula-2}.
12882 For a list of the supported languages, type @samp{set language}.
12884 Setting the language manually prevents @value{GDBN} from updating the working
12885 language automatically. This can lead to confusion if you try
12886 to debug a program when the working language is not the same as the
12887 source language, when an expression is acceptable to both
12888 languages---but means different things. For instance, if the current
12889 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12897 might not have the effect you intended. In C, this means to add
12898 @code{b} and @code{c} and place the result in @code{a}. The result
12899 printed would be the value of @code{a}. In Modula-2, this means to compare
12900 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12902 @node Automatically
12903 @subsection Having @value{GDBN} Infer the Source Language
12905 To have @value{GDBN} set the working language automatically, use
12906 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12907 then infers the working language. That is, when your program stops in a
12908 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12909 working language to the language recorded for the function in that
12910 frame. If the language for a frame is unknown (that is, if the function
12911 or block corresponding to the frame was defined in a source file that
12912 does not have a recognized extension), the current working language is
12913 not changed, and @value{GDBN} issues a warning.
12915 This may not seem necessary for most programs, which are written
12916 entirely in one source language. However, program modules and libraries
12917 written in one source language can be used by a main program written in
12918 a different source language. Using @samp{set language auto} in this
12919 case frees you from having to set the working language manually.
12922 @section Displaying the Language
12924 The following commands help you find out which language is the
12925 working language, and also what language source files were written in.
12928 @item show language
12929 @kindex show language
12930 Display the current working language. This is the
12931 language you can use with commands such as @code{print} to
12932 build and compute expressions that may involve variables in your program.
12935 @kindex info frame@r{, show the source language}
12936 Display the source language for this frame. This language becomes the
12937 working language if you use an identifier from this frame.
12938 @xref{Frame Info, ,Information about a Frame}, to identify the other
12939 information listed here.
12942 @kindex info source@r{, show the source language}
12943 Display the source language of this source file.
12944 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12945 information listed here.
12948 In unusual circumstances, you may have source files with extensions
12949 not in the standard list. You can then set the extension associated
12950 with a language explicitly:
12953 @item set extension-language @var{ext} @var{language}
12954 @kindex set extension-language
12955 Tell @value{GDBN} that source files with extension @var{ext} are to be
12956 assumed as written in the source language @var{language}.
12958 @item info extensions
12959 @kindex info extensions
12960 List all the filename extensions and the associated languages.
12964 @section Type and Range Checking
12966 Some languages are designed to guard you against making seemingly common
12967 errors through a series of compile- and run-time checks. These include
12968 checking the type of arguments to functions and operators and making
12969 sure mathematical overflows are caught at run time. Checks such as
12970 these help to ensure a program's correctness once it has been compiled
12971 by eliminating type mismatches and providing active checks for range
12972 errors when your program is running.
12974 By default @value{GDBN} checks for these errors according to the
12975 rules of the current source language. Although @value{GDBN} does not check
12976 the statements in your program, it can check expressions entered directly
12977 into @value{GDBN} for evaluation via the @code{print} command, for example.
12980 * Type Checking:: An overview of type checking
12981 * Range Checking:: An overview of range checking
12984 @cindex type checking
12985 @cindex checks, type
12986 @node Type Checking
12987 @subsection An Overview of Type Checking
12989 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12990 arguments to operators and functions have to be of the correct type,
12991 otherwise an error occurs. These checks prevent type mismatch
12992 errors from ever causing any run-time problems. For example,
12995 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12997 (@value{GDBP}) print obj.my_method (0)
13000 (@value{GDBP}) print obj.my_method (0x1234)
13001 Cannot resolve method klass::my_method to any overloaded instance
13004 The second example fails because in C@t{++} the integer constant
13005 @samp{0x1234} is not type-compatible with the pointer parameter type.
13007 For the expressions you use in @value{GDBN} commands, you can tell
13008 @value{GDBN} to not enforce strict type checking or
13009 to treat any mismatches as errors and abandon the expression;
13010 When type checking is disabled, @value{GDBN} successfully evaluates
13011 expressions like the second example above.
13013 Even if type checking is off, there may be other reasons
13014 related to type that prevent @value{GDBN} from evaluating an expression.
13015 For instance, @value{GDBN} does not know how to add an @code{int} and
13016 a @code{struct foo}. These particular type errors have nothing to do
13017 with the language in use and usually arise from expressions which make
13018 little sense to evaluate anyway.
13020 @value{GDBN} provides some additional commands for controlling type checking:
13022 @kindex set check type
13023 @kindex show check type
13025 @item set check type on
13026 @itemx set check type off
13027 Set strict type checking on or off. If any type mismatches occur in
13028 evaluating an expression while type checking is on, @value{GDBN} prints a
13029 message and aborts evaluation of the expression.
13031 @item show check type
13032 Show the current setting of type checking and whether @value{GDBN}
13033 is enforcing strict type checking rules.
13036 @cindex range checking
13037 @cindex checks, range
13038 @node Range Checking
13039 @subsection An Overview of Range Checking
13041 In some languages (such as Modula-2), it is an error to exceed the
13042 bounds of a type; this is enforced with run-time checks. Such range
13043 checking is meant to ensure program correctness by making sure
13044 computations do not overflow, or indices on an array element access do
13045 not exceed the bounds of the array.
13047 For expressions you use in @value{GDBN} commands, you can tell
13048 @value{GDBN} to treat range errors in one of three ways: ignore them,
13049 always treat them as errors and abandon the expression, or issue
13050 warnings but evaluate the expression anyway.
13052 A range error can result from numerical overflow, from exceeding an
13053 array index bound, or when you type a constant that is not a member
13054 of any type. Some languages, however, do not treat overflows as an
13055 error. In many implementations of C, mathematical overflow causes the
13056 result to ``wrap around'' to lower values---for example, if @var{m} is
13057 the largest integer value, and @var{s} is the smallest, then
13060 @var{m} + 1 @result{} @var{s}
13063 This, too, is specific to individual languages, and in some cases
13064 specific to individual compilers or machines. @xref{Supported Languages, ,
13065 Supported Languages}, for further details on specific languages.
13067 @value{GDBN} provides some additional commands for controlling the range checker:
13069 @kindex set check range
13070 @kindex show check range
13072 @item set check range auto
13073 Set range checking on or off based on the current working language.
13074 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13077 @item set check range on
13078 @itemx set check range off
13079 Set range checking on or off, overriding the default setting for the
13080 current working language. A warning is issued if the setting does not
13081 match the language default. If a range error occurs and range checking is on,
13082 then a message is printed and evaluation of the expression is aborted.
13084 @item set check range warn
13085 Output messages when the @value{GDBN} range checker detects a range error,
13086 but attempt to evaluate the expression anyway. Evaluating the
13087 expression may still be impossible for other reasons, such as accessing
13088 memory that the process does not own (a typical example from many Unix
13092 Show the current setting of the range checker, and whether or not it is
13093 being set automatically by @value{GDBN}.
13096 @node Supported Languages
13097 @section Supported Languages
13099 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13100 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13101 @c This is false ...
13102 Some @value{GDBN} features may be used in expressions regardless of the
13103 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13104 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13105 ,Expressions}) can be used with the constructs of any supported
13108 The following sections detail to what degree each source language is
13109 supported by @value{GDBN}. These sections are not meant to be language
13110 tutorials or references, but serve only as a reference guide to what the
13111 @value{GDBN} expression parser accepts, and what input and output
13112 formats should look like for different languages. There are many good
13113 books written on each of these languages; please look to these for a
13114 language reference or tutorial.
13117 * C:: C and C@t{++}
13120 * Objective-C:: Objective-C
13121 * OpenCL C:: OpenCL C
13122 * Fortran:: Fortran
13124 * Modula-2:: Modula-2
13129 @subsection C and C@t{++}
13131 @cindex C and C@t{++}
13132 @cindex expressions in C or C@t{++}
13134 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13135 to both languages. Whenever this is the case, we discuss those languages
13139 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13140 @cindex @sc{gnu} C@t{++}
13141 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13142 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13143 effectively, you must compile your C@t{++} programs with a supported
13144 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13145 compiler (@code{aCC}).
13148 * C Operators:: C and C@t{++} operators
13149 * C Constants:: C and C@t{++} constants
13150 * C Plus Plus Expressions:: C@t{++} expressions
13151 * C Defaults:: Default settings for C and C@t{++}
13152 * C Checks:: C and C@t{++} type and range checks
13153 * Debugging C:: @value{GDBN} and C
13154 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13155 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13159 @subsubsection C and C@t{++} Operators
13161 @cindex C and C@t{++} operators
13163 Operators must be defined on values of specific types. For instance,
13164 @code{+} is defined on numbers, but not on structures. Operators are
13165 often defined on groups of types.
13167 For the purposes of C and C@t{++}, the following definitions hold:
13172 @emph{Integral types} include @code{int} with any of its storage-class
13173 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13176 @emph{Floating-point types} include @code{float}, @code{double}, and
13177 @code{long double} (if supported by the target platform).
13180 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13183 @emph{Scalar types} include all of the above.
13188 The following operators are supported. They are listed here
13189 in order of increasing precedence:
13193 The comma or sequencing operator. Expressions in a comma-separated list
13194 are evaluated from left to right, with the result of the entire
13195 expression being the last expression evaluated.
13198 Assignment. The value of an assignment expression is the value
13199 assigned. Defined on scalar types.
13202 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13203 and translated to @w{@code{@var{a} = @var{a op b}}}.
13204 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13205 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13206 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13209 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13210 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13214 Logical @sc{or}. Defined on integral types.
13217 Logical @sc{and}. Defined on integral types.
13220 Bitwise @sc{or}. Defined on integral types.
13223 Bitwise exclusive-@sc{or}. Defined on integral types.
13226 Bitwise @sc{and}. Defined on integral types.
13229 Equality and inequality. Defined on scalar types. The value of these
13230 expressions is 0 for false and non-zero for true.
13232 @item <@r{, }>@r{, }<=@r{, }>=
13233 Less than, greater than, less than or equal, greater than or equal.
13234 Defined on scalar types. The value of these expressions is 0 for false
13235 and non-zero for true.
13238 left shift, and right shift. Defined on integral types.
13241 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13244 Addition and subtraction. Defined on integral types, floating-point types and
13247 @item *@r{, }/@r{, }%
13248 Multiplication, division, and modulus. Multiplication and division are
13249 defined on integral and floating-point types. Modulus is defined on
13253 Increment and decrement. When appearing before a variable, the
13254 operation is performed before the variable is used in an expression;
13255 when appearing after it, the variable's value is used before the
13256 operation takes place.
13259 Pointer dereferencing. Defined on pointer types. Same precedence as
13263 Address operator. Defined on variables. Same precedence as @code{++}.
13265 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13266 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13267 to examine the address
13268 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13272 Negative. Defined on integral and floating-point types. Same
13273 precedence as @code{++}.
13276 Logical negation. Defined on integral types. Same precedence as
13280 Bitwise complement operator. Defined on integral types. Same precedence as
13285 Structure member, and pointer-to-structure member. For convenience,
13286 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13287 pointer based on the stored type information.
13288 Defined on @code{struct} and @code{union} data.
13291 Dereferences of pointers to members.
13294 Array indexing. @code{@var{a}[@var{i}]} is defined as
13295 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13298 Function parameter list. Same precedence as @code{->}.
13301 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13302 and @code{class} types.
13305 Doubled colons also represent the @value{GDBN} scope operator
13306 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13310 If an operator is redefined in the user code, @value{GDBN} usually
13311 attempts to invoke the redefined version instead of using the operator's
13312 predefined meaning.
13315 @subsubsection C and C@t{++} Constants
13317 @cindex C and C@t{++} constants
13319 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13324 Integer constants are a sequence of digits. Octal constants are
13325 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13326 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13327 @samp{l}, specifying that the constant should be treated as a
13331 Floating point constants are a sequence of digits, followed by a decimal
13332 point, followed by a sequence of digits, and optionally followed by an
13333 exponent. An exponent is of the form:
13334 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13335 sequence of digits. The @samp{+} is optional for positive exponents.
13336 A floating-point constant may also end with a letter @samp{f} or
13337 @samp{F}, specifying that the constant should be treated as being of
13338 the @code{float} (as opposed to the default @code{double}) type; or with
13339 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13343 Enumerated constants consist of enumerated identifiers, or their
13344 integral equivalents.
13347 Character constants are a single character surrounded by single quotes
13348 (@code{'}), or a number---the ordinal value of the corresponding character
13349 (usually its @sc{ascii} value). Within quotes, the single character may
13350 be represented by a letter or by @dfn{escape sequences}, which are of
13351 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13352 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13353 @samp{@var{x}} is a predefined special character---for example,
13354 @samp{\n} for newline.
13356 Wide character constants can be written by prefixing a character
13357 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13358 form of @samp{x}. The target wide character set is used when
13359 computing the value of this constant (@pxref{Character Sets}).
13362 String constants are a sequence of character constants surrounded by
13363 double quotes (@code{"}). Any valid character constant (as described
13364 above) may appear. Double quotes within the string must be preceded by
13365 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13368 Wide string constants can be written by prefixing a string constant
13369 with @samp{L}, as in C. The target wide character set is used when
13370 computing the value of this constant (@pxref{Character Sets}).
13373 Pointer constants are an integral value. You can also write pointers
13374 to constants using the C operator @samp{&}.
13377 Array constants are comma-separated lists surrounded by braces @samp{@{}
13378 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13379 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13380 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13383 @node C Plus Plus Expressions
13384 @subsubsection C@t{++} Expressions
13386 @cindex expressions in C@t{++}
13387 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13389 @cindex debugging C@t{++} programs
13390 @cindex C@t{++} compilers
13391 @cindex debug formats and C@t{++}
13392 @cindex @value{NGCC} and C@t{++}
13394 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13395 the proper compiler and the proper debug format. Currently,
13396 @value{GDBN} works best when debugging C@t{++} code that is compiled
13397 with the most recent version of @value{NGCC} possible. The DWARF
13398 debugging format is preferred; @value{NGCC} defaults to this on most
13399 popular platforms. Other compilers and/or debug formats are likely to
13400 work badly or not at all when using @value{GDBN} to debug C@t{++}
13401 code. @xref{Compilation}.
13406 @cindex member functions
13408 Member function calls are allowed; you can use expressions like
13411 count = aml->GetOriginal(x, y)
13414 @vindex this@r{, inside C@t{++} member functions}
13415 @cindex namespace in C@t{++}
13417 While a member function is active (in the selected stack frame), your
13418 expressions have the same namespace available as the member function;
13419 that is, @value{GDBN} allows implicit references to the class instance
13420 pointer @code{this} following the same rules as C@t{++}. @code{using}
13421 declarations in the current scope are also respected by @value{GDBN}.
13423 @cindex call overloaded functions
13424 @cindex overloaded functions, calling
13425 @cindex type conversions in C@t{++}
13427 You can call overloaded functions; @value{GDBN} resolves the function
13428 call to the right definition, with some restrictions. @value{GDBN} does not
13429 perform overload resolution involving user-defined type conversions,
13430 calls to constructors, or instantiations of templates that do not exist
13431 in the program. It also cannot handle ellipsis argument lists or
13434 It does perform integral conversions and promotions, floating-point
13435 promotions, arithmetic conversions, pointer conversions, conversions of
13436 class objects to base classes, and standard conversions such as those of
13437 functions or arrays to pointers; it requires an exact match on the
13438 number of function arguments.
13440 Overload resolution is always performed, unless you have specified
13441 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13442 ,@value{GDBN} Features for C@t{++}}.
13444 You must specify @code{set overload-resolution off} in order to use an
13445 explicit function signature to call an overloaded function, as in
13447 p 'foo(char,int)'('x', 13)
13450 The @value{GDBN} command-completion facility can simplify this;
13451 see @ref{Completion, ,Command Completion}.
13453 @cindex reference declarations
13455 @value{GDBN} understands variables declared as C@t{++} references; you can use
13456 them in expressions just as you do in C@t{++} source---they are automatically
13459 In the parameter list shown when @value{GDBN} displays a frame, the values of
13460 reference variables are not displayed (unlike other variables); this
13461 avoids clutter, since references are often used for large structures.
13462 The @emph{address} of a reference variable is always shown, unless
13463 you have specified @samp{set print address off}.
13466 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13467 expressions can use it just as expressions in your program do. Since
13468 one scope may be defined in another, you can use @code{::} repeatedly if
13469 necessary, for example in an expression like
13470 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13471 resolving name scope by reference to source files, in both C and C@t{++}
13472 debugging (@pxref{Variables, ,Program Variables}).
13475 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13480 @subsubsection C and C@t{++} Defaults
13482 @cindex C and C@t{++} defaults
13484 If you allow @value{GDBN} to set range checking automatically, it
13485 defaults to @code{off} whenever the working language changes to
13486 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13487 selects the working language.
13489 If you allow @value{GDBN} to set the language automatically, it
13490 recognizes source files whose names end with @file{.c}, @file{.C}, or
13491 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13492 these files, it sets the working language to C or C@t{++}.
13493 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13494 for further details.
13497 @subsubsection C and C@t{++} Type and Range Checks
13499 @cindex C and C@t{++} checks
13501 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13502 checking is used. However, if you turn type checking off, @value{GDBN}
13503 will allow certain non-standard conversions, such as promoting integer
13504 constants to pointers.
13506 Range checking, if turned on, is done on mathematical operations. Array
13507 indices are not checked, since they are often used to index a pointer
13508 that is not itself an array.
13511 @subsubsection @value{GDBN} and C
13513 The @code{set print union} and @code{show print union} commands apply to
13514 the @code{union} type. When set to @samp{on}, any @code{union} that is
13515 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13516 appears as @samp{@{...@}}.
13518 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13519 with pointers and a memory allocation function. @xref{Expressions,
13522 @node Debugging C Plus Plus
13523 @subsubsection @value{GDBN} Features for C@t{++}
13525 @cindex commands for C@t{++}
13527 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13528 designed specifically for use with C@t{++}. Here is a summary:
13531 @cindex break in overloaded functions
13532 @item @r{breakpoint menus}
13533 When you want a breakpoint in a function whose name is overloaded,
13534 @value{GDBN} has the capability to display a menu of possible breakpoint
13535 locations to help you specify which function definition you want.
13536 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13538 @cindex overloading in C@t{++}
13539 @item rbreak @var{regex}
13540 Setting breakpoints using regular expressions is helpful for setting
13541 breakpoints on overloaded functions that are not members of any special
13543 @xref{Set Breaks, ,Setting Breakpoints}.
13545 @cindex C@t{++} exception handling
13547 @itemx catch rethrow
13549 Debug C@t{++} exception handling using these commands. @xref{Set
13550 Catchpoints, , Setting Catchpoints}.
13552 @cindex inheritance
13553 @item ptype @var{typename}
13554 Print inheritance relationships as well as other information for type
13556 @xref{Symbols, ,Examining the Symbol Table}.
13558 @item info vtbl @var{expression}.
13559 The @code{info vtbl} command can be used to display the virtual
13560 method tables of the object computed by @var{expression}. This shows
13561 one entry per virtual table; there may be multiple virtual tables when
13562 multiple inheritance is in use.
13564 @cindex C@t{++} symbol display
13565 @item set print demangle
13566 @itemx show print demangle
13567 @itemx set print asm-demangle
13568 @itemx show print asm-demangle
13569 Control whether C@t{++} symbols display in their source form, both when
13570 displaying code as C@t{++} source and when displaying disassemblies.
13571 @xref{Print Settings, ,Print Settings}.
13573 @item set print object
13574 @itemx show print object
13575 Choose whether to print derived (actual) or declared types of objects.
13576 @xref{Print Settings, ,Print Settings}.
13578 @item set print vtbl
13579 @itemx show print vtbl
13580 Control the format for printing virtual function tables.
13581 @xref{Print Settings, ,Print Settings}.
13582 (The @code{vtbl} commands do not work on programs compiled with the HP
13583 ANSI C@t{++} compiler (@code{aCC}).)
13585 @kindex set overload-resolution
13586 @cindex overloaded functions, overload resolution
13587 @item set overload-resolution on
13588 Enable overload resolution for C@t{++} expression evaluation. The default
13589 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13590 and searches for a function whose signature matches the argument types,
13591 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13592 Expressions, ,C@t{++} Expressions}, for details).
13593 If it cannot find a match, it emits a message.
13595 @item set overload-resolution off
13596 Disable overload resolution for C@t{++} expression evaluation. For
13597 overloaded functions that are not class member functions, @value{GDBN}
13598 chooses the first function of the specified name that it finds in the
13599 symbol table, whether or not its arguments are of the correct type. For
13600 overloaded functions that are class member functions, @value{GDBN}
13601 searches for a function whose signature @emph{exactly} matches the
13604 @kindex show overload-resolution
13605 @item show overload-resolution
13606 Show the current setting of overload resolution.
13608 @item @r{Overloaded symbol names}
13609 You can specify a particular definition of an overloaded symbol, using
13610 the same notation that is used to declare such symbols in C@t{++}: type
13611 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13612 also use the @value{GDBN} command-line word completion facilities to list the
13613 available choices, or to finish the type list for you.
13614 @xref{Completion,, Command Completion}, for details on how to do this.
13617 @node Decimal Floating Point
13618 @subsubsection Decimal Floating Point format
13619 @cindex decimal floating point format
13621 @value{GDBN} can examine, set and perform computations with numbers in
13622 decimal floating point format, which in the C language correspond to the
13623 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13624 specified by the extension to support decimal floating-point arithmetic.
13626 There are two encodings in use, depending on the architecture: BID (Binary
13627 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13628 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13631 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13632 to manipulate decimal floating point numbers, it is not possible to convert
13633 (using a cast, for example) integers wider than 32-bit to decimal float.
13635 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13636 point computations, error checking in decimal float operations ignores
13637 underflow, overflow and divide by zero exceptions.
13639 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13640 to inspect @code{_Decimal128} values stored in floating point registers.
13641 See @ref{PowerPC,,PowerPC} for more details.
13647 @value{GDBN} can be used to debug programs written in D and compiled with
13648 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13649 specific feature --- dynamic arrays.
13654 @cindex Go (programming language)
13655 @value{GDBN} can be used to debug programs written in Go and compiled with
13656 @file{gccgo} or @file{6g} compilers.
13658 Here is a summary of the Go-specific features and restrictions:
13661 @cindex current Go package
13662 @item The current Go package
13663 The name of the current package does not need to be specified when
13664 specifying global variables and functions.
13666 For example, given the program:
13670 var myglob = "Shall we?"
13676 When stopped inside @code{main} either of these work:
13680 (gdb) p main.myglob
13683 @cindex builtin Go types
13684 @item Builtin Go types
13685 The @code{string} type is recognized by @value{GDBN} and is printed
13688 @cindex builtin Go functions
13689 @item Builtin Go functions
13690 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13691 function and handles it internally.
13693 @cindex restrictions on Go expressions
13694 @item Restrictions on Go expressions
13695 All Go operators are supported except @code{&^}.
13696 The Go @code{_} ``blank identifier'' is not supported.
13697 Automatic dereferencing of pointers is not supported.
13701 @subsection Objective-C
13703 @cindex Objective-C
13704 This section provides information about some commands and command
13705 options that are useful for debugging Objective-C code. See also
13706 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13707 few more commands specific to Objective-C support.
13710 * Method Names in Commands::
13711 * The Print Command with Objective-C::
13714 @node Method Names in Commands
13715 @subsubsection Method Names in Commands
13717 The following commands have been extended to accept Objective-C method
13718 names as line specifications:
13720 @kindex clear@r{, and Objective-C}
13721 @kindex break@r{, and Objective-C}
13722 @kindex info line@r{, and Objective-C}
13723 @kindex jump@r{, and Objective-C}
13724 @kindex list@r{, and Objective-C}
13728 @item @code{info line}
13733 A fully qualified Objective-C method name is specified as
13736 -[@var{Class} @var{methodName}]
13739 where the minus sign is used to indicate an instance method and a
13740 plus sign (not shown) is used to indicate a class method. The class
13741 name @var{Class} and method name @var{methodName} are enclosed in
13742 brackets, similar to the way messages are specified in Objective-C
13743 source code. For example, to set a breakpoint at the @code{create}
13744 instance method of class @code{Fruit} in the program currently being
13748 break -[Fruit create]
13751 To list ten program lines around the @code{initialize} class method,
13755 list +[NSText initialize]
13758 In the current version of @value{GDBN}, the plus or minus sign is
13759 required. In future versions of @value{GDBN}, the plus or minus
13760 sign will be optional, but you can use it to narrow the search. It
13761 is also possible to specify just a method name:
13767 You must specify the complete method name, including any colons. If
13768 your program's source files contain more than one @code{create} method,
13769 you'll be presented with a numbered list of classes that implement that
13770 method. Indicate your choice by number, or type @samp{0} to exit if
13773 As another example, to clear a breakpoint established at the
13774 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13777 clear -[NSWindow makeKeyAndOrderFront:]
13780 @node The Print Command with Objective-C
13781 @subsubsection The Print Command With Objective-C
13782 @cindex Objective-C, print objects
13783 @kindex print-object
13784 @kindex po @r{(@code{print-object})}
13786 The print command has also been extended to accept methods. For example:
13789 print -[@var{object} hash]
13792 @cindex print an Objective-C object description
13793 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13795 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13796 and print the result. Also, an additional command has been added,
13797 @code{print-object} or @code{po} for short, which is meant to print
13798 the description of an object. However, this command may only work
13799 with certain Objective-C libraries that have a particular hook
13800 function, @code{_NSPrintForDebugger}, defined.
13803 @subsection OpenCL C
13806 This section provides information about @value{GDBN}s OpenCL C support.
13809 * OpenCL C Datatypes::
13810 * OpenCL C Expressions::
13811 * OpenCL C Operators::
13814 @node OpenCL C Datatypes
13815 @subsubsection OpenCL C Datatypes
13817 @cindex OpenCL C Datatypes
13818 @value{GDBN} supports the builtin scalar and vector datatypes specified
13819 by OpenCL 1.1. In addition the half- and double-precision floating point
13820 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13821 extensions are also known to @value{GDBN}.
13823 @node OpenCL C Expressions
13824 @subsubsection OpenCL C Expressions
13826 @cindex OpenCL C Expressions
13827 @value{GDBN} supports accesses to vector components including the access as
13828 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13829 supported by @value{GDBN} can be used as well.
13831 @node OpenCL C Operators
13832 @subsubsection OpenCL C Operators
13834 @cindex OpenCL C Operators
13835 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13839 @subsection Fortran
13840 @cindex Fortran-specific support in @value{GDBN}
13842 @value{GDBN} can be used to debug programs written in Fortran, but it
13843 currently supports only the features of Fortran 77 language.
13845 @cindex trailing underscore, in Fortran symbols
13846 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13847 among them) append an underscore to the names of variables and
13848 functions. When you debug programs compiled by those compilers, you
13849 will need to refer to variables and functions with a trailing
13853 * Fortran Operators:: Fortran operators and expressions
13854 * Fortran Defaults:: Default settings for Fortran
13855 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13858 @node Fortran Operators
13859 @subsubsection Fortran Operators and Expressions
13861 @cindex Fortran operators and expressions
13863 Operators must be defined on values of specific types. For instance,
13864 @code{+} is defined on numbers, but not on characters or other non-
13865 arithmetic types. Operators are often defined on groups of types.
13869 The exponentiation operator. It raises the first operand to the power
13873 The range operator. Normally used in the form of array(low:high) to
13874 represent a section of array.
13877 The access component operator. Normally used to access elements in derived
13878 types. Also suitable for unions. As unions aren't part of regular Fortran,
13879 this can only happen when accessing a register that uses a gdbarch-defined
13883 @node Fortran Defaults
13884 @subsubsection Fortran Defaults
13886 @cindex Fortran Defaults
13888 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13889 default uses case-insensitive matches for Fortran symbols. You can
13890 change that with the @samp{set case-insensitive} command, see
13891 @ref{Symbols}, for the details.
13893 @node Special Fortran Commands
13894 @subsubsection Special Fortran Commands
13896 @cindex Special Fortran commands
13898 @value{GDBN} has some commands to support Fortran-specific features,
13899 such as displaying common blocks.
13902 @cindex @code{COMMON} blocks, Fortran
13903 @kindex info common
13904 @item info common @r{[}@var{common-name}@r{]}
13905 This command prints the values contained in the Fortran @code{COMMON}
13906 block whose name is @var{common-name}. With no argument, the names of
13907 all @code{COMMON} blocks visible at the current program location are
13914 @cindex Pascal support in @value{GDBN}, limitations
13915 Debugging Pascal programs which use sets, subranges, file variables, or
13916 nested functions does not currently work. @value{GDBN} does not support
13917 entering expressions, printing values, or similar features using Pascal
13920 The Pascal-specific command @code{set print pascal_static-members}
13921 controls whether static members of Pascal objects are displayed.
13922 @xref{Print Settings, pascal_static-members}.
13925 @subsection Modula-2
13927 @cindex Modula-2, @value{GDBN} support
13929 The extensions made to @value{GDBN} to support Modula-2 only support
13930 output from the @sc{gnu} Modula-2 compiler (which is currently being
13931 developed). Other Modula-2 compilers are not currently supported, and
13932 attempting to debug executables produced by them is most likely
13933 to give an error as @value{GDBN} reads in the executable's symbol
13936 @cindex expressions in Modula-2
13938 * M2 Operators:: Built-in operators
13939 * Built-In Func/Proc:: Built-in functions and procedures
13940 * M2 Constants:: Modula-2 constants
13941 * M2 Types:: Modula-2 types
13942 * M2 Defaults:: Default settings for Modula-2
13943 * Deviations:: Deviations from standard Modula-2
13944 * M2 Checks:: Modula-2 type and range checks
13945 * M2 Scope:: The scope operators @code{::} and @code{.}
13946 * GDB/M2:: @value{GDBN} and Modula-2
13950 @subsubsection Operators
13951 @cindex Modula-2 operators
13953 Operators must be defined on values of specific types. For instance,
13954 @code{+} is defined on numbers, but not on structures. Operators are
13955 often defined on groups of types. For the purposes of Modula-2, the
13956 following definitions hold:
13961 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13965 @emph{Character types} consist of @code{CHAR} and its subranges.
13968 @emph{Floating-point types} consist of @code{REAL}.
13971 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13975 @emph{Scalar types} consist of all of the above.
13978 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13981 @emph{Boolean types} consist of @code{BOOLEAN}.
13985 The following operators are supported, and appear in order of
13986 increasing precedence:
13990 Function argument or array index separator.
13993 Assignment. The value of @var{var} @code{:=} @var{value} is
13997 Less than, greater than on integral, floating-point, or enumerated
14001 Less than or equal to, greater than or equal to
14002 on integral, floating-point and enumerated types, or set inclusion on
14003 set types. Same precedence as @code{<}.
14005 @item =@r{, }<>@r{, }#
14006 Equality and two ways of expressing inequality, valid on scalar types.
14007 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14008 available for inequality, since @code{#} conflicts with the script
14012 Set membership. Defined on set types and the types of their members.
14013 Same precedence as @code{<}.
14016 Boolean disjunction. Defined on boolean types.
14019 Boolean conjunction. Defined on boolean types.
14022 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14025 Addition and subtraction on integral and floating-point types, or union
14026 and difference on set types.
14029 Multiplication on integral and floating-point types, or set intersection
14033 Division on floating-point types, or symmetric set difference on set
14034 types. Same precedence as @code{*}.
14037 Integer division and remainder. Defined on integral types. Same
14038 precedence as @code{*}.
14041 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14044 Pointer dereferencing. Defined on pointer types.
14047 Boolean negation. Defined on boolean types. Same precedence as
14051 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14052 precedence as @code{^}.
14055 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14058 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14062 @value{GDBN} and Modula-2 scope operators.
14066 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14067 treats the use of the operator @code{IN}, or the use of operators
14068 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14069 @code{<=}, and @code{>=} on sets as an error.
14073 @node Built-In Func/Proc
14074 @subsubsection Built-in Functions and Procedures
14075 @cindex Modula-2 built-ins
14077 Modula-2 also makes available several built-in procedures and functions.
14078 In describing these, the following metavariables are used:
14083 represents an @code{ARRAY} variable.
14086 represents a @code{CHAR} constant or variable.
14089 represents a variable or constant of integral type.
14092 represents an identifier that belongs to a set. Generally used in the
14093 same function with the metavariable @var{s}. The type of @var{s} should
14094 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14097 represents a variable or constant of integral or floating-point type.
14100 represents a variable or constant of floating-point type.
14106 represents a variable.
14109 represents a variable or constant of one of many types. See the
14110 explanation of the function for details.
14113 All Modula-2 built-in procedures also return a result, described below.
14117 Returns the absolute value of @var{n}.
14120 If @var{c} is a lower case letter, it returns its upper case
14121 equivalent, otherwise it returns its argument.
14124 Returns the character whose ordinal value is @var{i}.
14127 Decrements the value in the variable @var{v} by one. Returns the new value.
14129 @item DEC(@var{v},@var{i})
14130 Decrements the value in the variable @var{v} by @var{i}. Returns the
14133 @item EXCL(@var{m},@var{s})
14134 Removes the element @var{m} from the set @var{s}. Returns the new
14137 @item FLOAT(@var{i})
14138 Returns the floating point equivalent of the integer @var{i}.
14140 @item HIGH(@var{a})
14141 Returns the index of the last member of @var{a}.
14144 Increments the value in the variable @var{v} by one. Returns the new value.
14146 @item INC(@var{v},@var{i})
14147 Increments the value in the variable @var{v} by @var{i}. Returns the
14150 @item INCL(@var{m},@var{s})
14151 Adds the element @var{m} to the set @var{s} if it is not already
14152 there. Returns the new set.
14155 Returns the maximum value of the type @var{t}.
14158 Returns the minimum value of the type @var{t}.
14161 Returns boolean TRUE if @var{i} is an odd number.
14164 Returns the ordinal value of its argument. For example, the ordinal
14165 value of a character is its @sc{ascii} value (on machines supporting the
14166 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14167 integral, character and enumerated types.
14169 @item SIZE(@var{x})
14170 Returns the size of its argument. @var{x} can be a variable or a type.
14172 @item TRUNC(@var{r})
14173 Returns the integral part of @var{r}.
14175 @item TSIZE(@var{x})
14176 Returns the size of its argument. @var{x} can be a variable or a type.
14178 @item VAL(@var{t},@var{i})
14179 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14183 @emph{Warning:} Sets and their operations are not yet supported, so
14184 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14188 @cindex Modula-2 constants
14190 @subsubsection Constants
14192 @value{GDBN} allows you to express the constants of Modula-2 in the following
14198 Integer constants are simply a sequence of digits. When used in an
14199 expression, a constant is interpreted to be type-compatible with the
14200 rest of the expression. Hexadecimal integers are specified by a
14201 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14204 Floating point constants appear as a sequence of digits, followed by a
14205 decimal point and another sequence of digits. An optional exponent can
14206 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14207 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14208 digits of the floating point constant must be valid decimal (base 10)
14212 Character constants consist of a single character enclosed by a pair of
14213 like quotes, either single (@code{'}) or double (@code{"}). They may
14214 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14215 followed by a @samp{C}.
14218 String constants consist of a sequence of characters enclosed by a
14219 pair of like quotes, either single (@code{'}) or double (@code{"}).
14220 Escape sequences in the style of C are also allowed. @xref{C
14221 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14225 Enumerated constants consist of an enumerated identifier.
14228 Boolean constants consist of the identifiers @code{TRUE} and
14232 Pointer constants consist of integral values only.
14235 Set constants are not yet supported.
14239 @subsubsection Modula-2 Types
14240 @cindex Modula-2 types
14242 Currently @value{GDBN} can print the following data types in Modula-2
14243 syntax: array types, record types, set types, pointer types, procedure
14244 types, enumerated types, subrange types and base types. You can also
14245 print the contents of variables declared using these type.
14246 This section gives a number of simple source code examples together with
14247 sample @value{GDBN} sessions.
14249 The first example contains the following section of code:
14258 and you can request @value{GDBN} to interrogate the type and value of
14259 @code{r} and @code{s}.
14262 (@value{GDBP}) print s
14264 (@value{GDBP}) ptype s
14266 (@value{GDBP}) print r
14268 (@value{GDBP}) ptype r
14273 Likewise if your source code declares @code{s} as:
14277 s: SET ['A'..'Z'] ;
14281 then you may query the type of @code{s} by:
14284 (@value{GDBP}) ptype s
14285 type = SET ['A'..'Z']
14289 Note that at present you cannot interactively manipulate set
14290 expressions using the debugger.
14292 The following example shows how you might declare an array in Modula-2
14293 and how you can interact with @value{GDBN} to print its type and contents:
14297 s: ARRAY [-10..10] OF CHAR ;
14301 (@value{GDBP}) ptype s
14302 ARRAY [-10..10] OF CHAR
14305 Note that the array handling is not yet complete and although the type
14306 is printed correctly, expression handling still assumes that all
14307 arrays have a lower bound of zero and not @code{-10} as in the example
14310 Here are some more type related Modula-2 examples:
14314 colour = (blue, red, yellow, green) ;
14315 t = [blue..yellow] ;
14323 The @value{GDBN} interaction shows how you can query the data type
14324 and value of a variable.
14327 (@value{GDBP}) print s
14329 (@value{GDBP}) ptype t
14330 type = [blue..yellow]
14334 In this example a Modula-2 array is declared and its contents
14335 displayed. Observe that the contents are written in the same way as
14336 their @code{C} counterparts.
14340 s: ARRAY [1..5] OF CARDINAL ;
14346 (@value{GDBP}) print s
14347 $1 = @{1, 0, 0, 0, 0@}
14348 (@value{GDBP}) ptype s
14349 type = ARRAY [1..5] OF CARDINAL
14352 The Modula-2 language interface to @value{GDBN} also understands
14353 pointer types as shown in this example:
14357 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14364 and you can request that @value{GDBN} describes the type of @code{s}.
14367 (@value{GDBP}) ptype s
14368 type = POINTER TO ARRAY [1..5] OF CARDINAL
14371 @value{GDBN} handles compound types as we can see in this example.
14372 Here we combine array types, record types, pointer types and subrange
14383 myarray = ARRAY myrange OF CARDINAL ;
14384 myrange = [-2..2] ;
14386 s: POINTER TO ARRAY myrange OF foo ;
14390 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14394 (@value{GDBP}) ptype s
14395 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14398 f3 : ARRAY [-2..2] OF CARDINAL;
14403 @subsubsection Modula-2 Defaults
14404 @cindex Modula-2 defaults
14406 If type and range checking are set automatically by @value{GDBN}, they
14407 both default to @code{on} whenever the working language changes to
14408 Modula-2. This happens regardless of whether you or @value{GDBN}
14409 selected the working language.
14411 If you allow @value{GDBN} to set the language automatically, then entering
14412 code compiled from a file whose name ends with @file{.mod} sets the
14413 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14414 Infer the Source Language}, for further details.
14417 @subsubsection Deviations from Standard Modula-2
14418 @cindex Modula-2, deviations from
14420 A few changes have been made to make Modula-2 programs easier to debug.
14421 This is done primarily via loosening its type strictness:
14425 Unlike in standard Modula-2, pointer constants can be formed by
14426 integers. This allows you to modify pointer variables during
14427 debugging. (In standard Modula-2, the actual address contained in a
14428 pointer variable is hidden from you; it can only be modified
14429 through direct assignment to another pointer variable or expression that
14430 returned a pointer.)
14433 C escape sequences can be used in strings and characters to represent
14434 non-printable characters. @value{GDBN} prints out strings with these
14435 escape sequences embedded. Single non-printable characters are
14436 printed using the @samp{CHR(@var{nnn})} format.
14439 The assignment operator (@code{:=}) returns the value of its right-hand
14443 All built-in procedures both modify @emph{and} return their argument.
14447 @subsubsection Modula-2 Type and Range Checks
14448 @cindex Modula-2 checks
14451 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14454 @c FIXME remove warning when type/range checks added
14456 @value{GDBN} considers two Modula-2 variables type equivalent if:
14460 They are of types that have been declared equivalent via a @code{TYPE
14461 @var{t1} = @var{t2}} statement
14464 They have been declared on the same line. (Note: This is true of the
14465 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14468 As long as type checking is enabled, any attempt to combine variables
14469 whose types are not equivalent is an error.
14471 Range checking is done on all mathematical operations, assignment, array
14472 index bounds, and all built-in functions and procedures.
14475 @subsubsection The Scope Operators @code{::} and @code{.}
14477 @cindex @code{.}, Modula-2 scope operator
14478 @cindex colon, doubled as scope operator
14480 @vindex colon-colon@r{, in Modula-2}
14481 @c Info cannot handle :: but TeX can.
14484 @vindex ::@r{, in Modula-2}
14487 There are a few subtle differences between the Modula-2 scope operator
14488 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14493 @var{module} . @var{id}
14494 @var{scope} :: @var{id}
14498 where @var{scope} is the name of a module or a procedure,
14499 @var{module} the name of a module, and @var{id} is any declared
14500 identifier within your program, except another module.
14502 Using the @code{::} operator makes @value{GDBN} search the scope
14503 specified by @var{scope} for the identifier @var{id}. If it is not
14504 found in the specified scope, then @value{GDBN} searches all scopes
14505 enclosing the one specified by @var{scope}.
14507 Using the @code{.} operator makes @value{GDBN} search the current scope for
14508 the identifier specified by @var{id} that was imported from the
14509 definition module specified by @var{module}. With this operator, it is
14510 an error if the identifier @var{id} was not imported from definition
14511 module @var{module}, or if @var{id} is not an identifier in
14515 @subsubsection @value{GDBN} and Modula-2
14517 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14518 Five subcommands of @code{set print} and @code{show print} apply
14519 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14520 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14521 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14522 analogue in Modula-2.
14524 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14525 with any language, is not useful with Modula-2. Its
14526 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14527 created in Modula-2 as they can in C or C@t{++}. However, because an
14528 address can be specified by an integral constant, the construct
14529 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14531 @cindex @code{#} in Modula-2
14532 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14533 interpreted as the beginning of a comment. Use @code{<>} instead.
14539 The extensions made to @value{GDBN} for Ada only support
14540 output from the @sc{gnu} Ada (GNAT) compiler.
14541 Other Ada compilers are not currently supported, and
14542 attempting to debug executables produced by them is most likely
14546 @cindex expressions in Ada
14548 * Ada Mode Intro:: General remarks on the Ada syntax
14549 and semantics supported by Ada mode
14551 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14552 * Additions to Ada:: Extensions of the Ada expression syntax.
14553 * Stopping Before Main Program:: Debugging the program during elaboration.
14554 * Ada Tasks:: Listing and setting breakpoints in tasks.
14555 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14556 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14558 * Ada Glitches:: Known peculiarities of Ada mode.
14561 @node Ada Mode Intro
14562 @subsubsection Introduction
14563 @cindex Ada mode, general
14565 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14566 syntax, with some extensions.
14567 The philosophy behind the design of this subset is
14571 That @value{GDBN} should provide basic literals and access to operations for
14572 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14573 leaving more sophisticated computations to subprograms written into the
14574 program (which therefore may be called from @value{GDBN}).
14577 That type safety and strict adherence to Ada language restrictions
14578 are not particularly important to the @value{GDBN} user.
14581 That brevity is important to the @value{GDBN} user.
14584 Thus, for brevity, the debugger acts as if all names declared in
14585 user-written packages are directly visible, even if they are not visible
14586 according to Ada rules, thus making it unnecessary to fully qualify most
14587 names with their packages, regardless of context. Where this causes
14588 ambiguity, @value{GDBN} asks the user's intent.
14590 The debugger will start in Ada mode if it detects an Ada main program.
14591 As for other languages, it will enter Ada mode when stopped in a program that
14592 was translated from an Ada source file.
14594 While in Ada mode, you may use `@t{--}' for comments. This is useful
14595 mostly for documenting command files. The standard @value{GDBN} comment
14596 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14597 middle (to allow based literals).
14599 The debugger supports limited overloading. Given a subprogram call in which
14600 the function symbol has multiple definitions, it will use the number of
14601 actual parameters and some information about their types to attempt to narrow
14602 the set of definitions. It also makes very limited use of context, preferring
14603 procedures to functions in the context of the @code{call} command, and
14604 functions to procedures elsewhere.
14606 @node Omissions from Ada
14607 @subsubsection Omissions from Ada
14608 @cindex Ada, omissions from
14610 Here are the notable omissions from the subset:
14614 Only a subset of the attributes are supported:
14618 @t{'First}, @t{'Last}, and @t{'Length}
14619 on array objects (not on types and subtypes).
14622 @t{'Min} and @t{'Max}.
14625 @t{'Pos} and @t{'Val}.
14631 @t{'Range} on array objects (not subtypes), but only as the right
14632 operand of the membership (@code{in}) operator.
14635 @t{'Access}, @t{'Unchecked_Access}, and
14636 @t{'Unrestricted_Access} (a GNAT extension).
14644 @code{Characters.Latin_1} are not available and
14645 concatenation is not implemented. Thus, escape characters in strings are
14646 not currently available.
14649 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14650 equality of representations. They will generally work correctly
14651 for strings and arrays whose elements have integer or enumeration types.
14652 They may not work correctly for arrays whose element
14653 types have user-defined equality, for arrays of real values
14654 (in particular, IEEE-conformant floating point, because of negative
14655 zeroes and NaNs), and for arrays whose elements contain unused bits with
14656 indeterminate values.
14659 The other component-by-component array operations (@code{and}, @code{or},
14660 @code{xor}, @code{not}, and relational tests other than equality)
14661 are not implemented.
14664 @cindex array aggregates (Ada)
14665 @cindex record aggregates (Ada)
14666 @cindex aggregates (Ada)
14667 There is limited support for array and record aggregates. They are
14668 permitted only on the right sides of assignments, as in these examples:
14671 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14672 (@value{GDBP}) set An_Array := (1, others => 0)
14673 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14674 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14675 (@value{GDBP}) set A_Record := (1, "Peter", True);
14676 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14680 discriminant's value by assigning an aggregate has an
14681 undefined effect if that discriminant is used within the record.
14682 However, you can first modify discriminants by directly assigning to
14683 them (which normally would not be allowed in Ada), and then performing an
14684 aggregate assignment. For example, given a variable @code{A_Rec}
14685 declared to have a type such as:
14688 type Rec (Len : Small_Integer := 0) is record
14690 Vals : IntArray (1 .. Len);
14694 you can assign a value with a different size of @code{Vals} with two
14698 (@value{GDBP}) set A_Rec.Len := 4
14699 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14702 As this example also illustrates, @value{GDBN} is very loose about the usual
14703 rules concerning aggregates. You may leave out some of the
14704 components of an array or record aggregate (such as the @code{Len}
14705 component in the assignment to @code{A_Rec} above); they will retain their
14706 original values upon assignment. You may freely use dynamic values as
14707 indices in component associations. You may even use overlapping or
14708 redundant component associations, although which component values are
14709 assigned in such cases is not defined.
14712 Calls to dispatching subprograms are not implemented.
14715 The overloading algorithm is much more limited (i.e., less selective)
14716 than that of real Ada. It makes only limited use of the context in
14717 which a subexpression appears to resolve its meaning, and it is much
14718 looser in its rules for allowing type matches. As a result, some
14719 function calls will be ambiguous, and the user will be asked to choose
14720 the proper resolution.
14723 The @code{new} operator is not implemented.
14726 Entry calls are not implemented.
14729 Aside from printing, arithmetic operations on the native VAX floating-point
14730 formats are not supported.
14733 It is not possible to slice a packed array.
14736 The names @code{True} and @code{False}, when not part of a qualified name,
14737 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14739 Should your program
14740 redefine these names in a package or procedure (at best a dubious practice),
14741 you will have to use fully qualified names to access their new definitions.
14744 @node Additions to Ada
14745 @subsubsection Additions to Ada
14746 @cindex Ada, deviations from
14748 As it does for other languages, @value{GDBN} makes certain generic
14749 extensions to Ada (@pxref{Expressions}):
14753 If the expression @var{E} is a variable residing in memory (typically
14754 a local variable or array element) and @var{N} is a positive integer,
14755 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14756 @var{N}-1 adjacent variables following it in memory as an array. In
14757 Ada, this operator is generally not necessary, since its prime use is
14758 in displaying parts of an array, and slicing will usually do this in
14759 Ada. However, there are occasional uses when debugging programs in
14760 which certain debugging information has been optimized away.
14763 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14764 appears in function or file @var{B}.'' When @var{B} is a file name,
14765 you must typically surround it in single quotes.
14768 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14769 @var{type} that appears at address @var{addr}.''
14772 A name starting with @samp{$} is a convenience variable
14773 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14776 In addition, @value{GDBN} provides a few other shortcuts and outright
14777 additions specific to Ada:
14781 The assignment statement is allowed as an expression, returning
14782 its right-hand operand as its value. Thus, you may enter
14785 (@value{GDBP}) set x := y + 3
14786 (@value{GDBP}) print A(tmp := y + 1)
14790 The semicolon is allowed as an ``operator,'' returning as its value
14791 the value of its right-hand operand.
14792 This allows, for example,
14793 complex conditional breaks:
14796 (@value{GDBP}) break f
14797 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14801 Rather than use catenation and symbolic character names to introduce special
14802 characters into strings, one may instead use a special bracket notation,
14803 which is also used to print strings. A sequence of characters of the form
14804 @samp{["@var{XX}"]} within a string or character literal denotes the
14805 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14806 sequence of characters @samp{["""]} also denotes a single quotation mark
14807 in strings. For example,
14809 "One line.["0a"]Next line.["0a"]"
14812 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14816 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14817 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14821 (@value{GDBP}) print 'max(x, y)
14825 When printing arrays, @value{GDBN} uses positional notation when the
14826 array has a lower bound of 1, and uses a modified named notation otherwise.
14827 For example, a one-dimensional array of three integers with a lower bound
14828 of 3 might print as
14835 That is, in contrast to valid Ada, only the first component has a @code{=>}
14839 You may abbreviate attributes in expressions with any unique,
14840 multi-character subsequence of
14841 their names (an exact match gets preference).
14842 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14843 in place of @t{a'length}.
14846 @cindex quoting Ada internal identifiers
14847 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14848 to lower case. The GNAT compiler uses upper-case characters for
14849 some of its internal identifiers, which are normally of no interest to users.
14850 For the rare occasions when you actually have to look at them,
14851 enclose them in angle brackets to avoid the lower-case mapping.
14854 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14858 Printing an object of class-wide type or dereferencing an
14859 access-to-class-wide value will display all the components of the object's
14860 specific type (as indicated by its run-time tag). Likewise, component
14861 selection on such a value will operate on the specific type of the
14866 @node Stopping Before Main Program
14867 @subsubsection Stopping at the Very Beginning
14869 @cindex breakpointing Ada elaboration code
14870 It is sometimes necessary to debug the program during elaboration, and
14871 before reaching the main procedure.
14872 As defined in the Ada Reference
14873 Manual, the elaboration code is invoked from a procedure called
14874 @code{adainit}. To run your program up to the beginning of
14875 elaboration, simply use the following two commands:
14876 @code{tbreak adainit} and @code{run}.
14879 @subsubsection Extensions for Ada Tasks
14880 @cindex Ada, tasking
14882 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14883 @value{GDBN} provides the following task-related commands:
14888 This command shows a list of current Ada tasks, as in the following example:
14895 (@value{GDBP}) info tasks
14896 ID TID P-ID Pri State Name
14897 1 8088000 0 15 Child Activation Wait main_task
14898 2 80a4000 1 15 Accept Statement b
14899 3 809a800 1 15 Child Activation Wait a
14900 * 4 80ae800 3 15 Runnable c
14905 In this listing, the asterisk before the last task indicates it to be the
14906 task currently being inspected.
14910 Represents @value{GDBN}'s internal task number.
14916 The parent's task ID (@value{GDBN}'s internal task number).
14919 The base priority of the task.
14922 Current state of the task.
14926 The task has been created but has not been activated. It cannot be
14930 The task is not blocked for any reason known to Ada. (It may be waiting
14931 for a mutex, though.) It is conceptually "executing" in normal mode.
14934 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14935 that were waiting on terminate alternatives have been awakened and have
14936 terminated themselves.
14938 @item Child Activation Wait
14939 The task is waiting for created tasks to complete activation.
14941 @item Accept Statement
14942 The task is waiting on an accept or selective wait statement.
14944 @item Waiting on entry call
14945 The task is waiting on an entry call.
14947 @item Async Select Wait
14948 The task is waiting to start the abortable part of an asynchronous
14952 The task is waiting on a select statement with only a delay
14955 @item Child Termination Wait
14956 The task is sleeping having completed a master within itself, and is
14957 waiting for the tasks dependent on that master to become terminated or
14958 waiting on a terminate Phase.
14960 @item Wait Child in Term Alt
14961 The task is sleeping waiting for tasks on terminate alternatives to
14962 finish terminating.
14964 @item Accepting RV with @var{taskno}
14965 The task is accepting a rendez-vous with the task @var{taskno}.
14969 Name of the task in the program.
14973 @kindex info task @var{taskno}
14974 @item info task @var{taskno}
14975 This command shows detailled informations on the specified task, as in
14976 the following example:
14981 (@value{GDBP}) info tasks
14982 ID TID P-ID Pri State Name
14983 1 8077880 0 15 Child Activation Wait main_task
14984 * 2 807c468 1 15 Runnable task_1
14985 (@value{GDBP}) info task 2
14986 Ada Task: 0x807c468
14989 Parent: 1 (main_task)
14995 @kindex task@r{ (Ada)}
14996 @cindex current Ada task ID
14997 This command prints the ID of the current task.
15003 (@value{GDBP}) info tasks
15004 ID TID P-ID Pri State Name
15005 1 8077870 0 15 Child Activation Wait main_task
15006 * 2 807c458 1 15 Runnable t
15007 (@value{GDBP}) task
15008 [Current task is 2]
15011 @item task @var{taskno}
15012 @cindex Ada task switching
15013 This command is like the @code{thread @var{threadno}}
15014 command (@pxref{Threads}). It switches the context of debugging
15015 from the current task to the given task.
15021 (@value{GDBP}) info tasks
15022 ID TID P-ID Pri State Name
15023 1 8077870 0 15 Child Activation Wait main_task
15024 * 2 807c458 1 15 Runnable t
15025 (@value{GDBP}) task 1
15026 [Switching to task 1]
15027 #0 0x8067726 in pthread_cond_wait ()
15029 #0 0x8067726 in pthread_cond_wait ()
15030 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15031 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15032 #3 0x806153e in system.tasking.stages.activate_tasks ()
15033 #4 0x804aacc in un () at un.adb:5
15036 @item break @var{linespec} task @var{taskno}
15037 @itemx break @var{linespec} task @var{taskno} if @dots{}
15038 @cindex breakpoints and tasks, in Ada
15039 @cindex task breakpoints, in Ada
15040 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15041 These commands are like the @code{break @dots{} thread @dots{}}
15042 command (@pxref{Thread Stops}).
15043 @var{linespec} specifies source lines, as described
15044 in @ref{Specify Location}.
15046 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15047 to specify that you only want @value{GDBN} to stop the program when a
15048 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15049 numeric task identifiers assigned by @value{GDBN}, shown in the first
15050 column of the @samp{info tasks} display.
15052 If you do not specify @samp{task @var{taskno}} when you set a
15053 breakpoint, the breakpoint applies to @emph{all} tasks of your
15056 You can use the @code{task} qualifier on conditional breakpoints as
15057 well; in this case, place @samp{task @var{taskno}} before the
15058 breakpoint condition (before the @code{if}).
15066 (@value{GDBP}) info tasks
15067 ID TID P-ID Pri State Name
15068 1 140022020 0 15 Child Activation Wait main_task
15069 2 140045060 1 15 Accept/Select Wait t2
15070 3 140044840 1 15 Runnable t1
15071 * 4 140056040 1 15 Runnable t3
15072 (@value{GDBP}) b 15 task 2
15073 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15074 (@value{GDBP}) cont
15079 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15081 (@value{GDBP}) info tasks
15082 ID TID P-ID Pri State Name
15083 1 140022020 0 15 Child Activation Wait main_task
15084 * 2 140045060 1 15 Runnable t2
15085 3 140044840 1 15 Runnable t1
15086 4 140056040 1 15 Delay Sleep t3
15090 @node Ada Tasks and Core Files
15091 @subsubsection Tasking Support when Debugging Core Files
15092 @cindex Ada tasking and core file debugging
15094 When inspecting a core file, as opposed to debugging a live program,
15095 tasking support may be limited or even unavailable, depending on
15096 the platform being used.
15097 For instance, on x86-linux, the list of tasks is available, but task
15098 switching is not supported. On Tru64, however, task switching will work
15101 On certain platforms, including Tru64, the debugger needs to perform some
15102 memory writes in order to provide Ada tasking support. When inspecting
15103 a core file, this means that the core file must be opened with read-write
15104 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15105 Under these circumstances, you should make a backup copy of the core
15106 file before inspecting it with @value{GDBN}.
15108 @node Ravenscar Profile
15109 @subsubsection Tasking Support when using the Ravenscar Profile
15110 @cindex Ravenscar Profile
15112 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15113 specifically designed for systems with safety-critical real-time
15117 @kindex set ravenscar task-switching on
15118 @cindex task switching with program using Ravenscar Profile
15119 @item set ravenscar task-switching on
15120 Allows task switching when debugging a program that uses the Ravenscar
15121 Profile. This is the default.
15123 @kindex set ravenscar task-switching off
15124 @item set ravenscar task-switching off
15125 Turn off task switching when debugging a program that uses the Ravenscar
15126 Profile. This is mostly intended to disable the code that adds support
15127 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15128 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15129 To be effective, this command should be run before the program is started.
15131 @kindex show ravenscar task-switching
15132 @item show ravenscar task-switching
15133 Show whether it is possible to switch from task to task in a program
15134 using the Ravenscar Profile.
15139 @subsubsection Known Peculiarities of Ada Mode
15140 @cindex Ada, problems
15142 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15143 we know of several problems with and limitations of Ada mode in
15145 some of which will be fixed with planned future releases of the debugger
15146 and the GNU Ada compiler.
15150 Static constants that the compiler chooses not to materialize as objects in
15151 storage are invisible to the debugger.
15154 Named parameter associations in function argument lists are ignored (the
15155 argument lists are treated as positional).
15158 Many useful library packages are currently invisible to the debugger.
15161 Fixed-point arithmetic, conversions, input, and output is carried out using
15162 floating-point arithmetic, and may give results that only approximate those on
15166 The GNAT compiler never generates the prefix @code{Standard} for any of
15167 the standard symbols defined by the Ada language. @value{GDBN} knows about
15168 this: it will strip the prefix from names when you use it, and will never
15169 look for a name you have so qualified among local symbols, nor match against
15170 symbols in other packages or subprograms. If you have
15171 defined entities anywhere in your program other than parameters and
15172 local variables whose simple names match names in @code{Standard},
15173 GNAT's lack of qualification here can cause confusion. When this happens,
15174 you can usually resolve the confusion
15175 by qualifying the problematic names with package
15176 @code{Standard} explicitly.
15179 Older versions of the compiler sometimes generate erroneous debugging
15180 information, resulting in the debugger incorrectly printing the value
15181 of affected entities. In some cases, the debugger is able to work
15182 around an issue automatically. In other cases, the debugger is able
15183 to work around the issue, but the work-around has to be specifically
15186 @kindex set ada trust-PAD-over-XVS
15187 @kindex show ada trust-PAD-over-XVS
15190 @item set ada trust-PAD-over-XVS on
15191 Configure GDB to strictly follow the GNAT encoding when computing the
15192 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15193 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15194 a complete description of the encoding used by the GNAT compiler).
15195 This is the default.
15197 @item set ada trust-PAD-over-XVS off
15198 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15199 sometimes prints the wrong value for certain entities, changing @code{ada
15200 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15201 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15202 @code{off}, but this incurs a slight performance penalty, so it is
15203 recommended to leave this setting to @code{on} unless necessary.
15207 @node Unsupported Languages
15208 @section Unsupported Languages
15210 @cindex unsupported languages
15211 @cindex minimal language
15212 In addition to the other fully-supported programming languages,
15213 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15214 It does not represent a real programming language, but provides a set
15215 of capabilities close to what the C or assembly languages provide.
15216 This should allow most simple operations to be performed while debugging
15217 an application that uses a language currently not supported by @value{GDBN}.
15219 If the language is set to @code{auto}, @value{GDBN} will automatically
15220 select this language if the current frame corresponds to an unsupported
15224 @chapter Examining the Symbol Table
15226 The commands described in this chapter allow you to inquire about the
15227 symbols (names of variables, functions and types) defined in your
15228 program. This information is inherent in the text of your program and
15229 does not change as your program executes. @value{GDBN} finds it in your
15230 program's symbol table, in the file indicated when you started @value{GDBN}
15231 (@pxref{File Options, ,Choosing Files}), or by one of the
15232 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15234 @cindex symbol names
15235 @cindex names of symbols
15236 @cindex quoting names
15237 Occasionally, you may need to refer to symbols that contain unusual
15238 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15239 most frequent case is in referring to static variables in other
15240 source files (@pxref{Variables,,Program Variables}). File names
15241 are recorded in object files as debugging symbols, but @value{GDBN} would
15242 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15243 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15244 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15251 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15254 @cindex case-insensitive symbol names
15255 @cindex case sensitivity in symbol names
15256 @kindex set case-sensitive
15257 @item set case-sensitive on
15258 @itemx set case-sensitive off
15259 @itemx set case-sensitive auto
15260 Normally, when @value{GDBN} looks up symbols, it matches their names
15261 with case sensitivity determined by the current source language.
15262 Occasionally, you may wish to control that. The command @code{set
15263 case-sensitive} lets you do that by specifying @code{on} for
15264 case-sensitive matches or @code{off} for case-insensitive ones. If
15265 you specify @code{auto}, case sensitivity is reset to the default
15266 suitable for the source language. The default is case-sensitive
15267 matches for all languages except for Fortran, for which the default is
15268 case-insensitive matches.
15270 @kindex show case-sensitive
15271 @item show case-sensitive
15272 This command shows the current setting of case sensitivity for symbols
15275 @kindex set print type methods
15276 @item set print type methods
15277 @itemx set print type methods on
15278 @itemx set print type methods off
15279 Normally, when @value{GDBN} prints a class, it displays any methods
15280 declared in that class. You can control this behavior either by
15281 passing the appropriate flag to @code{ptype}, or using @command{set
15282 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15283 display the methods; this is the default. Specifying @code{off} will
15284 cause @value{GDBN} to omit the methods.
15286 @kindex show print type methods
15287 @item show print type methods
15288 This command shows the current setting of method display when printing
15291 @kindex set print type typedefs
15292 @item set print type typedefs
15293 @itemx set print type typedefs on
15294 @itemx set print type typedefs off
15296 Normally, when @value{GDBN} prints a class, it displays any typedefs
15297 defined in that class. You can control this behavior either by
15298 passing the appropriate flag to @code{ptype}, or using @command{set
15299 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15300 display the typedef definitions; this is the default. Specifying
15301 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15302 Note that this controls whether the typedef definition itself is
15303 printed, not whether typedef names are substituted when printing other
15306 @kindex show print type typedefs
15307 @item show print type typedefs
15308 This command shows the current setting of typedef display when
15311 @kindex info address
15312 @cindex address of a symbol
15313 @item info address @var{symbol}
15314 Describe where the data for @var{symbol} is stored. For a register
15315 variable, this says which register it is kept in. For a non-register
15316 local variable, this prints the stack-frame offset at which the variable
15319 Note the contrast with @samp{print &@var{symbol}}, which does not work
15320 at all for a register variable, and for a stack local variable prints
15321 the exact address of the current instantiation of the variable.
15323 @kindex info symbol
15324 @cindex symbol from address
15325 @cindex closest symbol and offset for an address
15326 @item info symbol @var{addr}
15327 Print the name of a symbol which is stored at the address @var{addr}.
15328 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15329 nearest symbol and an offset from it:
15332 (@value{GDBP}) info symbol 0x54320
15333 _initialize_vx + 396 in section .text
15337 This is the opposite of the @code{info address} command. You can use
15338 it to find out the name of a variable or a function given its address.
15340 For dynamically linked executables, the name of executable or shared
15341 library containing the symbol is also printed:
15344 (@value{GDBP}) info symbol 0x400225
15345 _start + 5 in section .text of /tmp/a.out
15346 (@value{GDBP}) info symbol 0x2aaaac2811cf
15347 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15351 @item whatis[/@var{flags}] [@var{arg}]
15352 Print the data type of @var{arg}, which can be either an expression
15353 or a name of a data type. With no argument, print the data type of
15354 @code{$}, the last value in the value history.
15356 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15357 is not actually evaluated, and any side-effecting operations (such as
15358 assignments or function calls) inside it do not take place.
15360 If @var{arg} is a variable or an expression, @code{whatis} prints its
15361 literal type as it is used in the source code. If the type was
15362 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15363 the data type underlying the @code{typedef}. If the type of the
15364 variable or the expression is a compound data type, such as
15365 @code{struct} or @code{class}, @code{whatis} never prints their
15366 fields or methods. It just prints the @code{struct}/@code{class}
15367 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15368 such a compound data type, use @code{ptype}.
15370 If @var{arg} is a type name that was defined using @code{typedef},
15371 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15372 Unrolling means that @code{whatis} will show the underlying type used
15373 in the @code{typedef} declaration of @var{arg}. However, if that
15374 underlying type is also a @code{typedef}, @code{whatis} will not
15377 For C code, the type names may also have the form @samp{class
15378 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15379 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15381 @var{flags} can be used to modify how the type is displayed.
15382 Available flags are:
15386 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15387 parameters and typedefs defined in a class when printing the class'
15388 members. The @code{/r} flag disables this.
15391 Do not print methods defined in the class.
15394 Print methods defined in the class. This is the default, but the flag
15395 exists in case you change the default with @command{set print type methods}.
15398 Do not print typedefs defined in the class. Note that this controls
15399 whether the typedef definition itself is printed, not whether typedef
15400 names are substituted when printing other types.
15403 Print typedefs defined in the class. This is the default, but the flag
15404 exists in case you change the default with @command{set print type typedefs}.
15408 @item ptype[/@var{flags}] [@var{arg}]
15409 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15410 detailed description of the type, instead of just the name of the type.
15411 @xref{Expressions, ,Expressions}.
15413 Contrary to @code{whatis}, @code{ptype} always unrolls any
15414 @code{typedef}s in its argument declaration, whether the argument is
15415 a variable, expression, or a data type. This means that @code{ptype}
15416 of a variable or an expression will not print literally its type as
15417 present in the source code---use @code{whatis} for that. @code{typedef}s at
15418 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15419 fields, methods and inner @code{class typedef}s of @code{struct}s,
15420 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15422 For example, for this variable declaration:
15425 typedef double real_t;
15426 struct complex @{ real_t real; double imag; @};
15427 typedef struct complex complex_t;
15429 real_t *real_pointer_var;
15433 the two commands give this output:
15437 (@value{GDBP}) whatis var
15439 (@value{GDBP}) ptype var
15440 type = struct complex @{
15444 (@value{GDBP}) whatis complex_t
15445 type = struct complex
15446 (@value{GDBP}) whatis struct complex
15447 type = struct complex
15448 (@value{GDBP}) ptype struct complex
15449 type = struct complex @{
15453 (@value{GDBP}) whatis real_pointer_var
15455 (@value{GDBP}) ptype real_pointer_var
15461 As with @code{whatis}, using @code{ptype} without an argument refers to
15462 the type of @code{$}, the last value in the value history.
15464 @cindex incomplete type
15465 Sometimes, programs use opaque data types or incomplete specifications
15466 of complex data structure. If the debug information included in the
15467 program does not allow @value{GDBN} to display a full declaration of
15468 the data type, it will say @samp{<incomplete type>}. For example,
15469 given these declarations:
15473 struct foo *fooptr;
15477 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15480 (@value{GDBP}) ptype foo
15481 $1 = <incomplete type>
15485 ``Incomplete type'' is C terminology for data types that are not
15486 completely specified.
15489 @item info types @var{regexp}
15491 Print a brief description of all types whose names match the regular
15492 expression @var{regexp} (or all types in your program, if you supply
15493 no argument). Each complete typename is matched as though it were a
15494 complete line; thus, @samp{i type value} gives information on all
15495 types in your program whose names include the string @code{value}, but
15496 @samp{i type ^value$} gives information only on types whose complete
15497 name is @code{value}.
15499 This command differs from @code{ptype} in two ways: first, like
15500 @code{whatis}, it does not print a detailed description; second, it
15501 lists all source files where a type is defined.
15503 @kindex info type-printers
15504 @item info type-printers
15505 Versions of @value{GDBN} that ship with Python scripting enabled may
15506 have ``type printers'' available. When using @command{ptype} or
15507 @command{whatis}, these printers are consulted when the name of a type
15508 is needed. @xref{Type Printing API}, for more information on writing
15511 @code{info type-printers} displays all the available type printers.
15513 @kindex enable type-printer
15514 @kindex disable type-printer
15515 @item enable type-printer @var{name}@dots{}
15516 @item disable type-printer @var{name}@dots{}
15517 These commands can be used to enable or disable type printers.
15520 @cindex local variables
15521 @item info scope @var{location}
15522 List all the variables local to a particular scope. This command
15523 accepts a @var{location} argument---a function name, a source line, or
15524 an address preceded by a @samp{*}, and prints all the variables local
15525 to the scope defined by that location. (@xref{Specify Location}, for
15526 details about supported forms of @var{location}.) For example:
15529 (@value{GDBP}) @b{info scope command_line_handler}
15530 Scope for command_line_handler:
15531 Symbol rl is an argument at stack/frame offset 8, length 4.
15532 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15533 Symbol linelength is in static storage at address 0x150a1c, length 4.
15534 Symbol p is a local variable in register $esi, length 4.
15535 Symbol p1 is a local variable in register $ebx, length 4.
15536 Symbol nline is a local variable in register $edx, length 4.
15537 Symbol repeat is a local variable at frame offset -8, length 4.
15541 This command is especially useful for determining what data to collect
15542 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15545 @kindex info source
15547 Show information about the current source file---that is, the source file for
15548 the function containing the current point of execution:
15551 the name of the source file, and the directory containing it,
15553 the directory it was compiled in,
15555 its length, in lines,
15557 which programming language it is written in,
15559 whether the executable includes debugging information for that file, and
15560 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15562 whether the debugging information includes information about
15563 preprocessor macros.
15567 @kindex info sources
15569 Print the names of all source files in your program for which there is
15570 debugging information, organized into two lists: files whose symbols
15571 have already been read, and files whose symbols will be read when needed.
15573 @kindex info functions
15574 @item info functions
15575 Print the names and data types of all defined functions.
15577 @item info functions @var{regexp}
15578 Print the names and data types of all defined functions
15579 whose names contain a match for regular expression @var{regexp}.
15580 Thus, @samp{info fun step} finds all functions whose names
15581 include @code{step}; @samp{info fun ^step} finds those whose names
15582 start with @code{step}. If a function name contains characters
15583 that conflict with the regular expression language (e.g.@:
15584 @samp{operator*()}), they may be quoted with a backslash.
15586 @kindex info variables
15587 @item info variables
15588 Print the names and data types of all variables that are defined
15589 outside of functions (i.e.@: excluding local variables).
15591 @item info variables @var{regexp}
15592 Print the names and data types of all variables (except for local
15593 variables) whose names contain a match for regular expression
15596 @kindex info classes
15597 @cindex Objective-C, classes and selectors
15599 @itemx info classes @var{regexp}
15600 Display all Objective-C classes in your program, or
15601 (with the @var{regexp} argument) all those matching a particular regular
15604 @kindex info selectors
15605 @item info selectors
15606 @itemx info selectors @var{regexp}
15607 Display all Objective-C selectors in your program, or
15608 (with the @var{regexp} argument) all those matching a particular regular
15612 This was never implemented.
15613 @kindex info methods
15615 @itemx info methods @var{regexp}
15616 The @code{info methods} command permits the user to examine all defined
15617 methods within C@t{++} program, or (with the @var{regexp} argument) a
15618 specific set of methods found in the various C@t{++} classes. Many
15619 C@t{++} classes provide a large number of methods. Thus, the output
15620 from the @code{ptype} command can be overwhelming and hard to use. The
15621 @code{info-methods} command filters the methods, printing only those
15622 which match the regular-expression @var{regexp}.
15625 @cindex opaque data types
15626 @kindex set opaque-type-resolution
15627 @item set opaque-type-resolution on
15628 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15629 declared as a pointer to a @code{struct}, @code{class}, or
15630 @code{union}---for example, @code{struct MyType *}---that is used in one
15631 source file although the full declaration of @code{struct MyType} is in
15632 another source file. The default is on.
15634 A change in the setting of this subcommand will not take effect until
15635 the next time symbols for a file are loaded.
15637 @item set opaque-type-resolution off
15638 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15639 is printed as follows:
15641 @{<no data fields>@}
15644 @kindex show opaque-type-resolution
15645 @item show opaque-type-resolution
15646 Show whether opaque types are resolved or not.
15648 @kindex maint print symbols
15649 @cindex symbol dump
15650 @kindex maint print psymbols
15651 @cindex partial symbol dump
15652 @item maint print symbols @var{filename}
15653 @itemx maint print psymbols @var{filename}
15654 @itemx maint print msymbols @var{filename}
15655 Write a dump of debugging symbol data into the file @var{filename}.
15656 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15657 symbols with debugging data are included. If you use @samp{maint print
15658 symbols}, @value{GDBN} includes all the symbols for which it has already
15659 collected full details: that is, @var{filename} reflects symbols for
15660 only those files whose symbols @value{GDBN} has read. You can use the
15661 command @code{info sources} to find out which files these are. If you
15662 use @samp{maint print psymbols} instead, the dump shows information about
15663 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15664 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15665 @samp{maint print msymbols} dumps just the minimal symbol information
15666 required for each object file from which @value{GDBN} has read some symbols.
15667 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15668 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15670 @kindex maint info symtabs
15671 @kindex maint info psymtabs
15672 @cindex listing @value{GDBN}'s internal symbol tables
15673 @cindex symbol tables, listing @value{GDBN}'s internal
15674 @cindex full symbol tables, listing @value{GDBN}'s internal
15675 @cindex partial symbol tables, listing @value{GDBN}'s internal
15676 @item maint info symtabs @r{[} @var{regexp} @r{]}
15677 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15679 List the @code{struct symtab} or @code{struct partial_symtab}
15680 structures whose names match @var{regexp}. If @var{regexp} is not
15681 given, list them all. The output includes expressions which you can
15682 copy into a @value{GDBN} debugging this one to examine a particular
15683 structure in more detail. For example:
15686 (@value{GDBP}) maint info psymtabs dwarf2read
15687 @{ objfile /home/gnu/build/gdb/gdb
15688 ((struct objfile *) 0x82e69d0)
15689 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15690 ((struct partial_symtab *) 0x8474b10)
15693 text addresses 0x814d3c8 -- 0x8158074
15694 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15695 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15696 dependencies (none)
15699 (@value{GDBP}) maint info symtabs
15703 We see that there is one partial symbol table whose filename contains
15704 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15705 and we see that @value{GDBN} has not read in any symtabs yet at all.
15706 If we set a breakpoint on a function, that will cause @value{GDBN} to
15707 read the symtab for the compilation unit containing that function:
15710 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15711 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15713 (@value{GDBP}) maint info symtabs
15714 @{ objfile /home/gnu/build/gdb/gdb
15715 ((struct objfile *) 0x82e69d0)
15716 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15717 ((struct symtab *) 0x86c1f38)
15720 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15721 linetable ((struct linetable *) 0x8370fa0)
15722 debugformat DWARF 2
15731 @chapter Altering Execution
15733 Once you think you have found an error in your program, you might want to
15734 find out for certain whether correcting the apparent error would lead to
15735 correct results in the rest of the run. You can find the answer by
15736 experiment, using the @value{GDBN} features for altering execution of the
15739 For example, you can store new values into variables or memory
15740 locations, give your program a signal, restart it at a different
15741 address, or even return prematurely from a function.
15744 * Assignment:: Assignment to variables
15745 * Jumping:: Continuing at a different address
15746 * Signaling:: Giving your program a signal
15747 * Returning:: Returning from a function
15748 * Calling:: Calling your program's functions
15749 * Patching:: Patching your program
15753 @section Assignment to Variables
15756 @cindex setting variables
15757 To alter the value of a variable, evaluate an assignment expression.
15758 @xref{Expressions, ,Expressions}. For example,
15765 stores the value 4 into the variable @code{x}, and then prints the
15766 value of the assignment expression (which is 4).
15767 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15768 information on operators in supported languages.
15770 @kindex set variable
15771 @cindex variables, setting
15772 If you are not interested in seeing the value of the assignment, use the
15773 @code{set} command instead of the @code{print} command. @code{set} is
15774 really the same as @code{print} except that the expression's value is
15775 not printed and is not put in the value history (@pxref{Value History,
15776 ,Value History}). The expression is evaluated only for its effects.
15778 If the beginning of the argument string of the @code{set} command
15779 appears identical to a @code{set} subcommand, use the @code{set
15780 variable} command instead of just @code{set}. This command is identical
15781 to @code{set} except for its lack of subcommands. For example, if your
15782 program has a variable @code{width}, you get an error if you try to set
15783 a new value with just @samp{set width=13}, because @value{GDBN} has the
15784 command @code{set width}:
15787 (@value{GDBP}) whatis width
15789 (@value{GDBP}) p width
15791 (@value{GDBP}) set width=47
15792 Invalid syntax in expression.
15796 The invalid expression, of course, is @samp{=47}. In
15797 order to actually set the program's variable @code{width}, use
15800 (@value{GDBP}) set var width=47
15803 Because the @code{set} command has many subcommands that can conflict
15804 with the names of program variables, it is a good idea to use the
15805 @code{set variable} command instead of just @code{set}. For example, if
15806 your program has a variable @code{g}, you run into problems if you try
15807 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15808 the command @code{set gnutarget}, abbreviated @code{set g}:
15812 (@value{GDBP}) whatis g
15816 (@value{GDBP}) set g=4
15820 The program being debugged has been started already.
15821 Start it from the beginning? (y or n) y
15822 Starting program: /home/smith/cc_progs/a.out
15823 "/home/smith/cc_progs/a.out": can't open to read symbols:
15824 Invalid bfd target.
15825 (@value{GDBP}) show g
15826 The current BFD target is "=4".
15831 The program variable @code{g} did not change, and you silently set the
15832 @code{gnutarget} to an invalid value. In order to set the variable
15836 (@value{GDBP}) set var g=4
15839 @value{GDBN} allows more implicit conversions in assignments than C; you can
15840 freely store an integer value into a pointer variable or vice versa,
15841 and you can convert any structure to any other structure that is the
15842 same length or shorter.
15843 @comment FIXME: how do structs align/pad in these conversions?
15844 @comment /doc@cygnus.com 18dec1990
15846 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15847 construct to generate a value of specified type at a specified address
15848 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15849 to memory location @code{0x83040} as an integer (which implies a certain size
15850 and representation in memory), and
15853 set @{int@}0x83040 = 4
15857 stores the value 4 into that memory location.
15860 @section Continuing at a Different Address
15862 Ordinarily, when you continue your program, you do so at the place where
15863 it stopped, with the @code{continue} command. You can instead continue at
15864 an address of your own choosing, with the following commands:
15868 @kindex j @r{(@code{jump})}
15869 @item jump @var{linespec}
15870 @itemx j @var{linespec}
15871 @itemx jump @var{location}
15872 @itemx j @var{location}
15873 Resume execution at line @var{linespec} or at address given by
15874 @var{location}. Execution stops again immediately if there is a
15875 breakpoint there. @xref{Specify Location}, for a description of the
15876 different forms of @var{linespec} and @var{location}. It is common
15877 practice to use the @code{tbreak} command in conjunction with
15878 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15880 The @code{jump} command does not change the current stack frame, or
15881 the stack pointer, or the contents of any memory location or any
15882 register other than the program counter. If line @var{linespec} is in
15883 a different function from the one currently executing, the results may
15884 be bizarre if the two functions expect different patterns of arguments or
15885 of local variables. For this reason, the @code{jump} command requests
15886 confirmation if the specified line is not in the function currently
15887 executing. However, even bizarre results are predictable if you are
15888 well acquainted with the machine-language code of your program.
15891 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15892 On many systems, you can get much the same effect as the @code{jump}
15893 command by storing a new value into the register @code{$pc}. The
15894 difference is that this does not start your program running; it only
15895 changes the address of where it @emph{will} run when you continue. For
15903 makes the next @code{continue} command or stepping command execute at
15904 address @code{0x485}, rather than at the address where your program stopped.
15905 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15907 The most common occasion to use the @code{jump} command is to back
15908 up---perhaps with more breakpoints set---over a portion of a program
15909 that has already executed, in order to examine its execution in more
15914 @section Giving your Program a Signal
15915 @cindex deliver a signal to a program
15919 @item signal @var{signal}
15920 Resume execution where your program stopped, but immediately give it the
15921 signal @var{signal}. @var{signal} can be the name or the number of a
15922 signal. For example, on many systems @code{signal 2} and @code{signal
15923 SIGINT} are both ways of sending an interrupt signal.
15925 Alternatively, if @var{signal} is zero, continue execution without
15926 giving a signal. This is useful when your program stopped on account of
15927 a signal and would ordinarily see the signal when resumed with the
15928 @code{continue} command; @samp{signal 0} causes it to resume without a
15931 @code{signal} does not repeat when you press @key{RET} a second time
15932 after executing the command.
15936 Invoking the @code{signal} command is not the same as invoking the
15937 @code{kill} utility from the shell. Sending a signal with @code{kill}
15938 causes @value{GDBN} to decide what to do with the signal depending on
15939 the signal handling tables (@pxref{Signals}). The @code{signal} command
15940 passes the signal directly to your program.
15944 @section Returning from a Function
15947 @cindex returning from a function
15950 @itemx return @var{expression}
15951 You can cancel execution of a function call with the @code{return}
15952 command. If you give an
15953 @var{expression} argument, its value is used as the function's return
15957 When you use @code{return}, @value{GDBN} discards the selected stack frame
15958 (and all frames within it). You can think of this as making the
15959 discarded frame return prematurely. If you wish to specify a value to
15960 be returned, give that value as the argument to @code{return}.
15962 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15963 Frame}), and any other frames inside of it, leaving its caller as the
15964 innermost remaining frame. That frame becomes selected. The
15965 specified value is stored in the registers used for returning values
15968 The @code{return} command does not resume execution; it leaves the
15969 program stopped in the state that would exist if the function had just
15970 returned. In contrast, the @code{finish} command (@pxref{Continuing
15971 and Stepping, ,Continuing and Stepping}) resumes execution until the
15972 selected stack frame returns naturally.
15974 @value{GDBN} needs to know how the @var{expression} argument should be set for
15975 the inferior. The concrete registers assignment depends on the OS ABI and the
15976 type being returned by the selected stack frame. For example it is common for
15977 OS ABI to return floating point values in FPU registers while integer values in
15978 CPU registers. Still some ABIs return even floating point values in CPU
15979 registers. Larger integer widths (such as @code{long long int}) also have
15980 specific placement rules. @value{GDBN} already knows the OS ABI from its
15981 current target so it needs to find out also the type being returned to make the
15982 assignment into the right register(s).
15984 Normally, the selected stack frame has debug info. @value{GDBN} will always
15985 use the debug info instead of the implicit type of @var{expression} when the
15986 debug info is available. For example, if you type @kbd{return -1}, and the
15987 function in the current stack frame is declared to return a @code{long long
15988 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15989 into a @code{long long int}:
15992 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15994 (@value{GDBP}) return -1
15995 Make func return now? (y or n) y
15996 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15997 43 printf ("result=%lld\n", func ());
16001 However, if the selected stack frame does not have a debug info, e.g., if the
16002 function was compiled without debug info, @value{GDBN} has to find out the type
16003 to return from user. Specifying a different type by mistake may set the value
16004 in different inferior registers than the caller code expects. For example,
16005 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16006 of a @code{long long int} result for a debug info less function (on 32-bit
16007 architectures). Therefore the user is required to specify the return type by
16008 an appropriate cast explicitly:
16011 Breakpoint 2, 0x0040050b in func ()
16012 (@value{GDBP}) return -1
16013 Return value type not available for selected stack frame.
16014 Please use an explicit cast of the value to return.
16015 (@value{GDBP}) return (long long int) -1
16016 Make selected stack frame return now? (y or n) y
16017 #0 0x00400526 in main ()
16022 @section Calling Program Functions
16025 @cindex calling functions
16026 @cindex inferior functions, calling
16027 @item print @var{expr}
16028 Evaluate the expression @var{expr} and display the resulting value.
16029 @var{expr} may include calls to functions in the program being
16033 @item call @var{expr}
16034 Evaluate the expression @var{expr} without displaying @code{void}
16037 You can use this variant of the @code{print} command if you want to
16038 execute a function from your program that does not return anything
16039 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16040 with @code{void} returned values that @value{GDBN} will otherwise
16041 print. If the result is not void, it is printed and saved in the
16045 It is possible for the function you call via the @code{print} or
16046 @code{call} command to generate a signal (e.g., if there's a bug in
16047 the function, or if you passed it incorrect arguments). What happens
16048 in that case is controlled by the @code{set unwindonsignal} command.
16050 Similarly, with a C@t{++} program it is possible for the function you
16051 call via the @code{print} or @code{call} command to generate an
16052 exception that is not handled due to the constraints of the dummy
16053 frame. In this case, any exception that is raised in the frame, but has
16054 an out-of-frame exception handler will not be found. GDB builds a
16055 dummy-frame for the inferior function call, and the unwinder cannot
16056 seek for exception handlers outside of this dummy-frame. What happens
16057 in that case is controlled by the
16058 @code{set unwind-on-terminating-exception} command.
16061 @item set unwindonsignal
16062 @kindex set unwindonsignal
16063 @cindex unwind stack in called functions
16064 @cindex call dummy stack unwinding
16065 Set unwinding of the stack if a signal is received while in a function
16066 that @value{GDBN} called in the program being debugged. If set to on,
16067 @value{GDBN} unwinds the stack it created for the call and restores
16068 the context to what it was before the call. If set to off (the
16069 default), @value{GDBN} stops in the frame where the signal was
16072 @item show unwindonsignal
16073 @kindex show unwindonsignal
16074 Show the current setting of stack unwinding in the functions called by
16077 @item set unwind-on-terminating-exception
16078 @kindex set unwind-on-terminating-exception
16079 @cindex unwind stack in called functions with unhandled exceptions
16080 @cindex call dummy stack unwinding on unhandled exception.
16081 Set unwinding of the stack if a C@t{++} exception is raised, but left
16082 unhandled while in a function that @value{GDBN} called in the program being
16083 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16084 it created for the call and restores the context to what it was before
16085 the call. If set to off, @value{GDBN} the exception is delivered to
16086 the default C@t{++} exception handler and the inferior terminated.
16088 @item show unwind-on-terminating-exception
16089 @kindex show unwind-on-terminating-exception
16090 Show the current setting of stack unwinding in the functions called by
16095 @cindex weak alias functions
16096 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16097 for another function. In such case, @value{GDBN} might not pick up
16098 the type information, including the types of the function arguments,
16099 which causes @value{GDBN} to call the inferior function incorrectly.
16100 As a result, the called function will function erroneously and may
16101 even crash. A solution to that is to use the name of the aliased
16105 @section Patching Programs
16107 @cindex patching binaries
16108 @cindex writing into executables
16109 @cindex writing into corefiles
16111 By default, @value{GDBN} opens the file containing your program's
16112 executable code (or the corefile) read-only. This prevents accidental
16113 alterations to machine code; but it also prevents you from intentionally
16114 patching your program's binary.
16116 If you'd like to be able to patch the binary, you can specify that
16117 explicitly with the @code{set write} command. For example, you might
16118 want to turn on internal debugging flags, or even to make emergency
16124 @itemx set write off
16125 If you specify @samp{set write on}, @value{GDBN} opens executable and
16126 core files for both reading and writing; if you specify @kbd{set write
16127 off} (the default), @value{GDBN} opens them read-only.
16129 If you have already loaded a file, you must load it again (using the
16130 @code{exec-file} or @code{core-file} command) after changing @code{set
16131 write}, for your new setting to take effect.
16135 Display whether executable files and core files are opened for writing
16136 as well as reading.
16140 @chapter @value{GDBN} Files
16142 @value{GDBN} needs to know the file name of the program to be debugged,
16143 both in order to read its symbol table and in order to start your
16144 program. To debug a core dump of a previous run, you must also tell
16145 @value{GDBN} the name of the core dump file.
16148 * Files:: Commands to specify files
16149 * Separate Debug Files:: Debugging information in separate files
16150 * MiniDebugInfo:: Debugging information in a special section
16151 * Index Files:: Index files speed up GDB
16152 * Symbol Errors:: Errors reading symbol files
16153 * Data Files:: GDB data files
16157 @section Commands to Specify Files
16159 @cindex symbol table
16160 @cindex core dump file
16162 You may want to specify executable and core dump file names. The usual
16163 way to do this is at start-up time, using the arguments to
16164 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16165 Out of @value{GDBN}}).
16167 Occasionally it is necessary to change to a different file during a
16168 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16169 specify a file you want to use. Or you are debugging a remote target
16170 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16171 Program}). In these situations the @value{GDBN} commands to specify
16172 new files are useful.
16175 @cindex executable file
16177 @item file @var{filename}
16178 Use @var{filename} as the program to be debugged. It is read for its
16179 symbols and for the contents of pure memory. It is also the program
16180 executed when you use the @code{run} command. If you do not specify a
16181 directory and the file is not found in the @value{GDBN} working directory,
16182 @value{GDBN} uses the environment variable @code{PATH} as a list of
16183 directories to search, just as the shell does when looking for a program
16184 to run. You can change the value of this variable, for both @value{GDBN}
16185 and your program, using the @code{path} command.
16187 @cindex unlinked object files
16188 @cindex patching object files
16189 You can load unlinked object @file{.o} files into @value{GDBN} using
16190 the @code{file} command. You will not be able to ``run'' an object
16191 file, but you can disassemble functions and inspect variables. Also,
16192 if the underlying BFD functionality supports it, you could use
16193 @kbd{gdb -write} to patch object files using this technique. Note
16194 that @value{GDBN} can neither interpret nor modify relocations in this
16195 case, so branches and some initialized variables will appear to go to
16196 the wrong place. But this feature is still handy from time to time.
16199 @code{file} with no argument makes @value{GDBN} discard any information it
16200 has on both executable file and the symbol table.
16203 @item exec-file @r{[} @var{filename} @r{]}
16204 Specify that the program to be run (but not the symbol table) is found
16205 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16206 if necessary to locate your program. Omitting @var{filename} means to
16207 discard information on the executable file.
16209 @kindex symbol-file
16210 @item symbol-file @r{[} @var{filename} @r{]}
16211 Read symbol table information from file @var{filename}. @code{PATH} is
16212 searched when necessary. Use the @code{file} command to get both symbol
16213 table and program to run from the same file.
16215 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16216 program's symbol table.
16218 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16219 some breakpoints and auto-display expressions. This is because they may
16220 contain pointers to the internal data recording symbols and data types,
16221 which are part of the old symbol table data being discarded inside
16224 @code{symbol-file} does not repeat if you press @key{RET} again after
16227 When @value{GDBN} is configured for a particular environment, it
16228 understands debugging information in whatever format is the standard
16229 generated for that environment; you may use either a @sc{gnu} compiler, or
16230 other compilers that adhere to the local conventions.
16231 Best results are usually obtained from @sc{gnu} compilers; for example,
16232 using @code{@value{NGCC}} you can generate debugging information for
16235 For most kinds of object files, with the exception of old SVR3 systems
16236 using COFF, the @code{symbol-file} command does not normally read the
16237 symbol table in full right away. Instead, it scans the symbol table
16238 quickly to find which source files and which symbols are present. The
16239 details are read later, one source file at a time, as they are needed.
16241 The purpose of this two-stage reading strategy is to make @value{GDBN}
16242 start up faster. For the most part, it is invisible except for
16243 occasional pauses while the symbol table details for a particular source
16244 file are being read. (The @code{set verbose} command can turn these
16245 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16246 Warnings and Messages}.)
16248 We have not implemented the two-stage strategy for COFF yet. When the
16249 symbol table is stored in COFF format, @code{symbol-file} reads the
16250 symbol table data in full right away. Note that ``stabs-in-COFF''
16251 still does the two-stage strategy, since the debug info is actually
16255 @cindex reading symbols immediately
16256 @cindex symbols, reading immediately
16257 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16258 @itemx file @r{[} -readnow @r{]} @var{filename}
16259 You can override the @value{GDBN} two-stage strategy for reading symbol
16260 tables by using the @samp{-readnow} option with any of the commands that
16261 load symbol table information, if you want to be sure @value{GDBN} has the
16262 entire symbol table available.
16264 @c FIXME: for now no mention of directories, since this seems to be in
16265 @c flux. 13mar1992 status is that in theory GDB would look either in
16266 @c current dir or in same dir as myprog; but issues like competing
16267 @c GDB's, or clutter in system dirs, mean that in practice right now
16268 @c only current dir is used. FFish says maybe a special GDB hierarchy
16269 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16273 @item core-file @r{[}@var{filename}@r{]}
16275 Specify the whereabouts of a core dump file to be used as the ``contents
16276 of memory''. Traditionally, core files contain only some parts of the
16277 address space of the process that generated them; @value{GDBN} can access the
16278 executable file itself for other parts.
16280 @code{core-file} with no argument specifies that no core file is
16283 Note that the core file is ignored when your program is actually running
16284 under @value{GDBN}. So, if you have been running your program and you
16285 wish to debug a core file instead, you must kill the subprocess in which
16286 the program is running. To do this, use the @code{kill} command
16287 (@pxref{Kill Process, ,Killing the Child Process}).
16289 @kindex add-symbol-file
16290 @cindex dynamic linking
16291 @item add-symbol-file @var{filename} @var{address}
16292 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16293 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16294 The @code{add-symbol-file} command reads additional symbol table
16295 information from the file @var{filename}. You would use this command
16296 when @var{filename} has been dynamically loaded (by some other means)
16297 into the program that is running. @var{address} should be the memory
16298 address at which the file has been loaded; @value{GDBN} cannot figure
16299 this out for itself. You can additionally specify an arbitrary number
16300 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16301 section name and base address for that section. You can specify any
16302 @var{address} as an expression.
16304 The symbol table of the file @var{filename} is added to the symbol table
16305 originally read with the @code{symbol-file} command. You can use the
16306 @code{add-symbol-file} command any number of times; the new symbol data
16307 thus read keeps adding to the old. To discard all old symbol data
16308 instead, use the @code{symbol-file} command without any arguments.
16310 @cindex relocatable object files, reading symbols from
16311 @cindex object files, relocatable, reading symbols from
16312 @cindex reading symbols from relocatable object files
16313 @cindex symbols, reading from relocatable object files
16314 @cindex @file{.o} files, reading symbols from
16315 Although @var{filename} is typically a shared library file, an
16316 executable file, or some other object file which has been fully
16317 relocated for loading into a process, you can also load symbolic
16318 information from relocatable @file{.o} files, as long as:
16322 the file's symbolic information refers only to linker symbols defined in
16323 that file, not to symbols defined by other object files,
16325 every section the file's symbolic information refers to has actually
16326 been loaded into the inferior, as it appears in the file, and
16328 you can determine the address at which every section was loaded, and
16329 provide these to the @code{add-symbol-file} command.
16333 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16334 relocatable files into an already running program; such systems
16335 typically make the requirements above easy to meet. However, it's
16336 important to recognize that many native systems use complex link
16337 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16338 assembly, for example) that make the requirements difficult to meet. In
16339 general, one cannot assume that using @code{add-symbol-file} to read a
16340 relocatable object file's symbolic information will have the same effect
16341 as linking the relocatable object file into the program in the normal
16344 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16346 @kindex add-symbol-file-from-memory
16347 @cindex @code{syscall DSO}
16348 @cindex load symbols from memory
16349 @item add-symbol-file-from-memory @var{address}
16350 Load symbols from the given @var{address} in a dynamically loaded
16351 object file whose image is mapped directly into the inferior's memory.
16352 For example, the Linux kernel maps a @code{syscall DSO} into each
16353 process's address space; this DSO provides kernel-specific code for
16354 some system calls. The argument can be any expression whose
16355 evaluation yields the address of the file's shared object file header.
16356 For this command to work, you must have used @code{symbol-file} or
16357 @code{exec-file} commands in advance.
16359 @kindex add-shared-symbol-files
16361 @item add-shared-symbol-files @var{library-file}
16362 @itemx assf @var{library-file}
16363 The @code{add-shared-symbol-files} command can currently be used only
16364 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16365 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16366 @value{GDBN} automatically looks for shared libraries, however if
16367 @value{GDBN} does not find yours, you can invoke
16368 @code{add-shared-symbol-files}. It takes one argument: the shared
16369 library's file name. @code{assf} is a shorthand alias for
16370 @code{add-shared-symbol-files}.
16373 @item section @var{section} @var{addr}
16374 The @code{section} command changes the base address of the named
16375 @var{section} of the exec file to @var{addr}. This can be used if the
16376 exec file does not contain section addresses, (such as in the
16377 @code{a.out} format), or when the addresses specified in the file
16378 itself are wrong. Each section must be changed separately. The
16379 @code{info files} command, described below, lists all the sections and
16383 @kindex info target
16386 @code{info files} and @code{info target} are synonymous; both print the
16387 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16388 including the names of the executable and core dump files currently in
16389 use by @value{GDBN}, and the files from which symbols were loaded. The
16390 command @code{help target} lists all possible targets rather than
16393 @kindex maint info sections
16394 @item maint info sections
16395 Another command that can give you extra information about program sections
16396 is @code{maint info sections}. In addition to the section information
16397 displayed by @code{info files}, this command displays the flags and file
16398 offset of each section in the executable and core dump files. In addition,
16399 @code{maint info sections} provides the following command options (which
16400 may be arbitrarily combined):
16404 Display sections for all loaded object files, including shared libraries.
16405 @item @var{sections}
16406 Display info only for named @var{sections}.
16407 @item @var{section-flags}
16408 Display info only for sections for which @var{section-flags} are true.
16409 The section flags that @value{GDBN} currently knows about are:
16412 Section will have space allocated in the process when loaded.
16413 Set for all sections except those containing debug information.
16415 Section will be loaded from the file into the child process memory.
16416 Set for pre-initialized code and data, clear for @code{.bss} sections.
16418 Section needs to be relocated before loading.
16420 Section cannot be modified by the child process.
16422 Section contains executable code only.
16424 Section contains data only (no executable code).
16426 Section will reside in ROM.
16428 Section contains data for constructor/destructor lists.
16430 Section is not empty.
16432 An instruction to the linker to not output the section.
16433 @item COFF_SHARED_LIBRARY
16434 A notification to the linker that the section contains
16435 COFF shared library information.
16437 Section contains common symbols.
16440 @kindex set trust-readonly-sections
16441 @cindex read-only sections
16442 @item set trust-readonly-sections on
16443 Tell @value{GDBN} that readonly sections in your object file
16444 really are read-only (i.e.@: that their contents will not change).
16445 In that case, @value{GDBN} can fetch values from these sections
16446 out of the object file, rather than from the target program.
16447 For some targets (notably embedded ones), this can be a significant
16448 enhancement to debugging performance.
16450 The default is off.
16452 @item set trust-readonly-sections off
16453 Tell @value{GDBN} not to trust readonly sections. This means that
16454 the contents of the section might change while the program is running,
16455 and must therefore be fetched from the target when needed.
16457 @item show trust-readonly-sections
16458 Show the current setting of trusting readonly sections.
16461 All file-specifying commands allow both absolute and relative file names
16462 as arguments. @value{GDBN} always converts the file name to an absolute file
16463 name and remembers it that way.
16465 @cindex shared libraries
16466 @anchor{Shared Libraries}
16467 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16468 and IBM RS/6000 AIX shared libraries.
16470 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16471 shared libraries. @xref{Expat}.
16473 @value{GDBN} automatically loads symbol definitions from shared libraries
16474 when you use the @code{run} command, or when you examine a core file.
16475 (Before you issue the @code{run} command, @value{GDBN} does not understand
16476 references to a function in a shared library, however---unless you are
16477 debugging a core file).
16479 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16480 automatically loads the symbols at the time of the @code{shl_load} call.
16482 @c FIXME: some @value{GDBN} release may permit some refs to undef
16483 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16484 @c FIXME...lib; check this from time to time when updating manual
16486 There are times, however, when you may wish to not automatically load
16487 symbol definitions from shared libraries, such as when they are
16488 particularly large or there are many of them.
16490 To control the automatic loading of shared library symbols, use the
16494 @kindex set auto-solib-add
16495 @item set auto-solib-add @var{mode}
16496 If @var{mode} is @code{on}, symbols from all shared object libraries
16497 will be loaded automatically when the inferior begins execution, you
16498 attach to an independently started inferior, or when the dynamic linker
16499 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16500 is @code{off}, symbols must be loaded manually, using the
16501 @code{sharedlibrary} command. The default value is @code{on}.
16503 @cindex memory used for symbol tables
16504 If your program uses lots of shared libraries with debug info that
16505 takes large amounts of memory, you can decrease the @value{GDBN}
16506 memory footprint by preventing it from automatically loading the
16507 symbols from shared libraries. To that end, type @kbd{set
16508 auto-solib-add off} before running the inferior, then load each
16509 library whose debug symbols you do need with @kbd{sharedlibrary
16510 @var{regexp}}, where @var{regexp} is a regular expression that matches
16511 the libraries whose symbols you want to be loaded.
16513 @kindex show auto-solib-add
16514 @item show auto-solib-add
16515 Display the current autoloading mode.
16518 @cindex load shared library
16519 To explicitly load shared library symbols, use the @code{sharedlibrary}
16523 @kindex info sharedlibrary
16525 @item info share @var{regex}
16526 @itemx info sharedlibrary @var{regex}
16527 Print the names of the shared libraries which are currently loaded
16528 that match @var{regex}. If @var{regex} is omitted then print
16529 all shared libraries that are loaded.
16531 @kindex sharedlibrary
16533 @item sharedlibrary @var{regex}
16534 @itemx share @var{regex}
16535 Load shared object library symbols for files matching a
16536 Unix regular expression.
16537 As with files loaded automatically, it only loads shared libraries
16538 required by your program for a core file or after typing @code{run}. If
16539 @var{regex} is omitted all shared libraries required by your program are
16542 @item nosharedlibrary
16543 @kindex nosharedlibrary
16544 @cindex unload symbols from shared libraries
16545 Unload all shared object library symbols. This discards all symbols
16546 that have been loaded from all shared libraries. Symbols from shared
16547 libraries that were loaded by explicit user requests are not
16551 Sometimes you may wish that @value{GDBN} stops and gives you control
16552 when any of shared library events happen. The best way to do this is
16553 to use @code{catch load} and @code{catch unload} (@pxref{Set
16556 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16557 command for this. This command exists for historical reasons. It is
16558 less useful than setting a catchpoint, because it does not allow for
16559 conditions or commands as a catchpoint does.
16562 @item set stop-on-solib-events
16563 @kindex set stop-on-solib-events
16564 This command controls whether @value{GDBN} should give you control
16565 when the dynamic linker notifies it about some shared library event.
16566 The most common event of interest is loading or unloading of a new
16569 @item show stop-on-solib-events
16570 @kindex show stop-on-solib-events
16571 Show whether @value{GDBN} stops and gives you control when shared
16572 library events happen.
16575 Shared libraries are also supported in many cross or remote debugging
16576 configurations. @value{GDBN} needs to have access to the target's libraries;
16577 this can be accomplished either by providing copies of the libraries
16578 on the host system, or by asking @value{GDBN} to automatically retrieve the
16579 libraries from the target. If copies of the target libraries are
16580 provided, they need to be the same as the target libraries, although the
16581 copies on the target can be stripped as long as the copies on the host are
16584 @cindex where to look for shared libraries
16585 For remote debugging, you need to tell @value{GDBN} where the target
16586 libraries are, so that it can load the correct copies---otherwise, it
16587 may try to load the host's libraries. @value{GDBN} has two variables
16588 to specify the search directories for target libraries.
16591 @cindex prefix for shared library file names
16592 @cindex system root, alternate
16593 @kindex set solib-absolute-prefix
16594 @kindex set sysroot
16595 @item set sysroot @var{path}
16596 Use @var{path} as the system root for the program being debugged. Any
16597 absolute shared library paths will be prefixed with @var{path}; many
16598 runtime loaders store the absolute paths to the shared library in the
16599 target program's memory. If you use @code{set sysroot} to find shared
16600 libraries, they need to be laid out in the same way that they are on
16601 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16604 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16605 retrieve the target libraries from the remote system. This is only
16606 supported when using a remote target that supports the @code{remote get}
16607 command (@pxref{File Transfer,,Sending files to a remote system}).
16608 The part of @var{path} following the initial @file{remote:}
16609 (if present) is used as system root prefix on the remote file system.
16610 @footnote{If you want to specify a local system root using a directory
16611 that happens to be named @file{remote:}, you need to use some equivalent
16612 variant of the name like @file{./remote:}.}
16614 For targets with an MS-DOS based filesystem, such as MS-Windows and
16615 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16616 absolute file name with @var{path}. But first, on Unix hosts,
16617 @value{GDBN} converts all backslash directory separators into forward
16618 slashes, because the backslash is not a directory separator on Unix:
16621 c:\foo\bar.dll @result{} c:/foo/bar.dll
16624 Then, @value{GDBN} attempts prefixing the target file name with
16625 @var{path}, and looks for the resulting file name in the host file
16629 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16632 If that does not find the shared library, @value{GDBN} tries removing
16633 the @samp{:} character from the drive spec, both for convenience, and,
16634 for the case of the host file system not supporting file names with
16638 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16641 This makes it possible to have a system root that mirrors a target
16642 with more than one drive. E.g., you may want to setup your local
16643 copies of the target system shared libraries like so (note @samp{c} vs
16647 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16648 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16649 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16653 and point the system root at @file{/path/to/sysroot}, so that
16654 @value{GDBN} can find the correct copies of both
16655 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16657 If that still does not find the shared library, @value{GDBN} tries
16658 removing the whole drive spec from the target file name:
16661 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16664 This last lookup makes it possible to not care about the drive name,
16665 if you don't want or need to.
16667 The @code{set solib-absolute-prefix} command is an alias for @code{set
16670 @cindex default system root
16671 @cindex @samp{--with-sysroot}
16672 You can set the default system root by using the configure-time
16673 @samp{--with-sysroot} option. If the system root is inside
16674 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16675 @samp{--exec-prefix}), then the default system root will be updated
16676 automatically if the installed @value{GDBN} is moved to a new
16679 @kindex show sysroot
16681 Display the current shared library prefix.
16683 @kindex set solib-search-path
16684 @item set solib-search-path @var{path}
16685 If this variable is set, @var{path} is a colon-separated list of
16686 directories to search for shared libraries. @samp{solib-search-path}
16687 is used after @samp{sysroot} fails to locate the library, or if the
16688 path to the library is relative instead of absolute. If you want to
16689 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16690 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16691 finding your host's libraries. @samp{sysroot} is preferred; setting
16692 it to a nonexistent directory may interfere with automatic loading
16693 of shared library symbols.
16695 @kindex show solib-search-path
16696 @item show solib-search-path
16697 Display the current shared library search path.
16699 @cindex DOS file-name semantics of file names.
16700 @kindex set target-file-system-kind (unix|dos-based|auto)
16701 @kindex show target-file-system-kind
16702 @item set target-file-system-kind @var{kind}
16703 Set assumed file system kind for target reported file names.
16705 Shared library file names as reported by the target system may not
16706 make sense as is on the system @value{GDBN} is running on. For
16707 example, when remote debugging a target that has MS-DOS based file
16708 system semantics, from a Unix host, the target may be reporting to
16709 @value{GDBN} a list of loaded shared libraries with file names such as
16710 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16711 drive letters, so the @samp{c:\} prefix is not normally understood as
16712 indicating an absolute file name, and neither is the backslash
16713 normally considered a directory separator character. In that case,
16714 the native file system would interpret this whole absolute file name
16715 as a relative file name with no directory components. This would make
16716 it impossible to point @value{GDBN} at a copy of the remote target's
16717 shared libraries on the host using @code{set sysroot}, and impractical
16718 with @code{set solib-search-path}. Setting
16719 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16720 to interpret such file names similarly to how the target would, and to
16721 map them to file names valid on @value{GDBN}'s native file system
16722 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16723 to one of the supported file system kinds. In that case, @value{GDBN}
16724 tries to determine the appropriate file system variant based on the
16725 current target's operating system (@pxref{ABI, ,Configuring the
16726 Current ABI}). The supported file system settings are:
16730 Instruct @value{GDBN} to assume the target file system is of Unix
16731 kind. Only file names starting the forward slash (@samp{/}) character
16732 are considered absolute, and the directory separator character is also
16736 Instruct @value{GDBN} to assume the target file system is DOS based.
16737 File names starting with either a forward slash, or a drive letter
16738 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16739 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16740 considered directory separators.
16743 Instruct @value{GDBN} to use the file system kind associated with the
16744 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16745 This is the default.
16749 @cindex file name canonicalization
16750 @cindex base name differences
16751 When processing file names provided by the user, @value{GDBN}
16752 frequently needs to compare them to the file names recorded in the
16753 program's debug info. Normally, @value{GDBN} compares just the
16754 @dfn{base names} of the files as strings, which is reasonably fast
16755 even for very large programs. (The base name of a file is the last
16756 portion of its name, after stripping all the leading directories.)
16757 This shortcut in comparison is based upon the assumption that files
16758 cannot have more than one base name. This is usually true, but
16759 references to files that use symlinks or similar filesystem
16760 facilities violate that assumption. If your program records files
16761 using such facilities, or if you provide file names to @value{GDBN}
16762 using symlinks etc., you can set @code{basenames-may-differ} to
16763 @code{true} to instruct @value{GDBN} to completely canonicalize each
16764 pair of file names it needs to compare. This will make file-name
16765 comparisons accurate, but at a price of a significant slowdown.
16768 @item set basenames-may-differ
16769 @kindex set basenames-may-differ
16770 Set whether a source file may have multiple base names.
16772 @item show basenames-may-differ
16773 @kindex show basenames-may-differ
16774 Show whether a source file may have multiple base names.
16777 @node Separate Debug Files
16778 @section Debugging Information in Separate Files
16779 @cindex separate debugging information files
16780 @cindex debugging information in separate files
16781 @cindex @file{.debug} subdirectories
16782 @cindex debugging information directory, global
16783 @cindex global debugging information directories
16784 @cindex build ID, and separate debugging files
16785 @cindex @file{.build-id} directory
16787 @value{GDBN} allows you to put a program's debugging information in a
16788 file separate from the executable itself, in a way that allows
16789 @value{GDBN} to find and load the debugging information automatically.
16790 Since debugging information can be very large---sometimes larger
16791 than the executable code itself---some systems distribute debugging
16792 information for their executables in separate files, which users can
16793 install only when they need to debug a problem.
16795 @value{GDBN} supports two ways of specifying the separate debug info
16800 The executable contains a @dfn{debug link} that specifies the name of
16801 the separate debug info file. The separate debug file's name is
16802 usually @file{@var{executable}.debug}, where @var{executable} is the
16803 name of the corresponding executable file without leading directories
16804 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16805 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16806 checksum for the debug file, which @value{GDBN} uses to validate that
16807 the executable and the debug file came from the same build.
16810 The executable contains a @dfn{build ID}, a unique bit string that is
16811 also present in the corresponding debug info file. (This is supported
16812 only on some operating systems, notably those which use the ELF format
16813 for binary files and the @sc{gnu} Binutils.) For more details about
16814 this feature, see the description of the @option{--build-id}
16815 command-line option in @ref{Options, , Command Line Options, ld.info,
16816 The GNU Linker}. The debug info file's name is not specified
16817 explicitly by the build ID, but can be computed from the build ID, see
16821 Depending on the way the debug info file is specified, @value{GDBN}
16822 uses two different methods of looking for the debug file:
16826 For the ``debug link'' method, @value{GDBN} looks up the named file in
16827 the directory of the executable file, then in a subdirectory of that
16828 directory named @file{.debug}, and finally under each one of the global debug
16829 directories, in a subdirectory whose name is identical to the leading
16830 directories of the executable's absolute file name.
16833 For the ``build ID'' method, @value{GDBN} looks in the
16834 @file{.build-id} subdirectory of each one of the global debug directories for
16835 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16836 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16837 are the rest of the bit string. (Real build ID strings are 32 or more
16838 hex characters, not 10.)
16841 So, for example, suppose you ask @value{GDBN} to debug
16842 @file{/usr/bin/ls}, which has a debug link that specifies the
16843 file @file{ls.debug}, and a build ID whose value in hex is
16844 @code{abcdef1234}. If the list of the global debug directories includes
16845 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16846 debug information files, in the indicated order:
16850 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16852 @file{/usr/bin/ls.debug}
16854 @file{/usr/bin/.debug/ls.debug}
16856 @file{/usr/lib/debug/usr/bin/ls.debug}.
16859 @anchor{debug-file-directory}
16860 Global debugging info directories default to what is set by @value{GDBN}
16861 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16862 you can also set the global debugging info directories, and view the list
16863 @value{GDBN} is currently using.
16867 @kindex set debug-file-directory
16868 @item set debug-file-directory @var{directories}
16869 Set the directories which @value{GDBN} searches for separate debugging
16870 information files to @var{directory}. Multiple path components can be set
16871 concatenating them by a path separator.
16873 @kindex show debug-file-directory
16874 @item show debug-file-directory
16875 Show the directories @value{GDBN} searches for separate debugging
16880 @cindex @code{.gnu_debuglink} sections
16881 @cindex debug link sections
16882 A debug link is a special section of the executable file named
16883 @code{.gnu_debuglink}. The section must contain:
16887 A filename, with any leading directory components removed, followed by
16890 zero to three bytes of padding, as needed to reach the next four-byte
16891 boundary within the section, and
16893 a four-byte CRC checksum, stored in the same endianness used for the
16894 executable file itself. The checksum is computed on the debugging
16895 information file's full contents by the function given below, passing
16896 zero as the @var{crc} argument.
16899 Any executable file format can carry a debug link, as long as it can
16900 contain a section named @code{.gnu_debuglink} with the contents
16903 @cindex @code{.note.gnu.build-id} sections
16904 @cindex build ID sections
16905 The build ID is a special section in the executable file (and in other
16906 ELF binary files that @value{GDBN} may consider). This section is
16907 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16908 It contains unique identification for the built files---the ID remains
16909 the same across multiple builds of the same build tree. The default
16910 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16911 content for the build ID string. The same section with an identical
16912 value is present in the original built binary with symbols, in its
16913 stripped variant, and in the separate debugging information file.
16915 The debugging information file itself should be an ordinary
16916 executable, containing a full set of linker symbols, sections, and
16917 debugging information. The sections of the debugging information file
16918 should have the same names, addresses, and sizes as the original file,
16919 but they need not contain any data---much like a @code{.bss} section
16920 in an ordinary executable.
16922 The @sc{gnu} binary utilities (Binutils) package includes the
16923 @samp{objcopy} utility that can produce
16924 the separated executable / debugging information file pairs using the
16925 following commands:
16928 @kbd{objcopy --only-keep-debug foo foo.debug}
16933 These commands remove the debugging
16934 information from the executable file @file{foo} and place it in the file
16935 @file{foo.debug}. You can use the first, second or both methods to link the
16940 The debug link method needs the following additional command to also leave
16941 behind a debug link in @file{foo}:
16944 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16947 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16948 a version of the @code{strip} command such that the command @kbd{strip foo -f
16949 foo.debug} has the same functionality as the two @code{objcopy} commands and
16950 the @code{ln -s} command above, together.
16953 Build ID gets embedded into the main executable using @code{ld --build-id} or
16954 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16955 compatibility fixes for debug files separation are present in @sc{gnu} binary
16956 utilities (Binutils) package since version 2.18.
16961 @cindex CRC algorithm definition
16962 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16963 IEEE 802.3 using the polynomial:
16965 @c TexInfo requires naked braces for multi-digit exponents for Tex
16966 @c output, but this causes HTML output to barf. HTML has to be set using
16967 @c raw commands. So we end up having to specify this equation in 2
16972 <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>
16973 + <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
16979 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16980 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16984 The function is computed byte at a time, taking the least
16985 significant bit of each byte first. The initial pattern
16986 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16987 the final result is inverted to ensure trailing zeros also affect the
16990 @emph{Note:} This is the same CRC polynomial as used in handling the
16991 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16992 , @value{GDBN} Remote Serial Protocol}). However in the
16993 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16994 significant bit first, and the result is not inverted, so trailing
16995 zeros have no effect on the CRC value.
16997 To complete the description, we show below the code of the function
16998 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16999 initially supplied @code{crc} argument means that an initial call to
17000 this function passing in zero will start computing the CRC using
17003 @kindex gnu_debuglink_crc32
17006 gnu_debuglink_crc32 (unsigned long crc,
17007 unsigned char *buf, size_t len)
17009 static const unsigned long crc32_table[256] =
17011 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17012 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17013 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17014 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17015 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17016 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17017 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17018 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17019 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17020 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17021 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17022 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17023 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17024 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17025 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17026 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17027 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17028 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17029 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17030 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17031 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17032 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17033 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17034 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17035 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17036 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17037 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17038 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17039 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17040 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17041 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17042 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17043 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17044 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17045 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17046 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17047 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17048 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17049 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17050 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17051 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17052 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17053 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17054 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17055 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17056 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17057 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17058 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17059 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17060 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17061 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17064 unsigned char *end;
17066 crc = ~crc & 0xffffffff;
17067 for (end = buf + len; buf < end; ++buf)
17068 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17069 return ~crc & 0xffffffff;
17074 This computation does not apply to the ``build ID'' method.
17076 @node MiniDebugInfo
17077 @section Debugging information in a special section
17078 @cindex separate debug sections
17079 @cindex @samp{.gnu_debugdata} section
17081 Some systems ship pre-built executables and libraries that have a
17082 special @samp{.gnu_debugdata} section. This feature is called
17083 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17084 is used to supply extra symbols for backtraces.
17086 The intent of this section is to provide extra minimal debugging
17087 information for use in simple backtraces. It is not intended to be a
17088 replacement for full separate debugging information (@pxref{Separate
17089 Debug Files}). The example below shows the intended use; however,
17090 @value{GDBN} does not currently put restrictions on what sort of
17091 debugging information might be included in the section.
17093 @value{GDBN} has support for this extension. If the section exists,
17094 then it is used provided that no other source of debugging information
17095 can be found, and that @value{GDBN} was configured with LZMA support.
17097 This section can be easily created using @command{objcopy} and other
17098 standard utilities:
17101 # Extract the dynamic symbols from the main binary, there is no need
17102 # to also have these in the normal symbol table
17103 nm -D @var{binary} --format=posix --defined-only \
17104 | awk '@{ print $1 @}' | sort > dynsyms
17106 # Extract all the text (i.e. function) symbols from the debuginfo .
17107 nm @var{binary} --format=posix --defined-only \
17108 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17111 # Keep all the function symbols not already in the dynamic symbol
17113 comm -13 dynsyms funcsyms > keep_symbols
17115 # Copy the full debuginfo, keeping only a minimal set of symbols and
17116 # removing some unnecessary sections.
17117 objcopy -S --remove-section .gdb_index --remove-section .comment \
17118 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17120 # Inject the compressed data into the .gnu_debugdata section of the
17123 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17127 @section Index Files Speed Up @value{GDBN}
17128 @cindex index files
17129 @cindex @samp{.gdb_index} section
17131 When @value{GDBN} finds a symbol file, it scans the symbols in the
17132 file in order to construct an internal symbol table. This lets most
17133 @value{GDBN} operations work quickly---at the cost of a delay early
17134 on. For large programs, this delay can be quite lengthy, so
17135 @value{GDBN} provides a way to build an index, which speeds up
17138 The index is stored as a section in the symbol file. @value{GDBN} can
17139 write the index to a file, then you can put it into the symbol file
17140 using @command{objcopy}.
17142 To create an index file, use the @code{save gdb-index} command:
17145 @item save gdb-index @var{directory}
17146 @kindex save gdb-index
17147 Create an index file for each symbol file currently known by
17148 @value{GDBN}. Each file is named after its corresponding symbol file,
17149 with @samp{.gdb-index} appended, and is written into the given
17153 Once you have created an index file you can merge it into your symbol
17154 file, here named @file{symfile}, using @command{objcopy}:
17157 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17158 --set-section-flags .gdb_index=readonly symfile symfile
17161 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17162 sections that have been deprecated. Usually they are deprecated because
17163 they are missing a new feature or have performance issues.
17164 To tell @value{GDBN} to use a deprecated index section anyway
17165 specify @code{set use-deprecated-index-sections on}.
17166 The default is @code{off}.
17167 This can speed up startup, but may result in some functionality being lost.
17168 @xref{Index Section Format}.
17170 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17171 must be done before gdb reads the file. The following will not work:
17174 $ gdb -ex "set use-deprecated-index-sections on" <program>
17177 Instead you must do, for example,
17180 $ gdb -iex "set use-deprecated-index-sections on" <program>
17183 There are currently some limitation on indices. They only work when
17184 for DWARF debugging information, not stabs. And, they do not
17185 currently work for programs using Ada.
17187 @node Symbol Errors
17188 @section Errors Reading Symbol Files
17190 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17191 such as symbol types it does not recognize, or known bugs in compiler
17192 output. By default, @value{GDBN} does not notify you of such problems, since
17193 they are relatively common and primarily of interest to people
17194 debugging compilers. If you are interested in seeing information
17195 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17196 only one message about each such type of problem, no matter how many
17197 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17198 to see how many times the problems occur, with the @code{set
17199 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17202 The messages currently printed, and their meanings, include:
17205 @item inner block not inside outer block in @var{symbol}
17207 The symbol information shows where symbol scopes begin and end
17208 (such as at the start of a function or a block of statements). This
17209 error indicates that an inner scope block is not fully contained
17210 in its outer scope blocks.
17212 @value{GDBN} circumvents the problem by treating the inner block as if it had
17213 the same scope as the outer block. In the error message, @var{symbol}
17214 may be shown as ``@code{(don't know)}'' if the outer block is not a
17217 @item block at @var{address} out of order
17219 The symbol information for symbol scope blocks should occur in
17220 order of increasing addresses. This error indicates that it does not
17223 @value{GDBN} does not circumvent this problem, and has trouble
17224 locating symbols in the source file whose symbols it is reading. (You
17225 can often determine what source file is affected by specifying
17226 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17229 @item bad block start address patched
17231 The symbol information for a symbol scope block has a start address
17232 smaller than the address of the preceding source line. This is known
17233 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17235 @value{GDBN} circumvents the problem by treating the symbol scope block as
17236 starting on the previous source line.
17238 @item bad string table offset in symbol @var{n}
17241 Symbol number @var{n} contains a pointer into the string table which is
17242 larger than the size of the string table.
17244 @value{GDBN} circumvents the problem by considering the symbol to have the
17245 name @code{foo}, which may cause other problems if many symbols end up
17248 @item unknown symbol type @code{0x@var{nn}}
17250 The symbol information contains new data types that @value{GDBN} does
17251 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17252 uncomprehended information, in hexadecimal.
17254 @value{GDBN} circumvents the error by ignoring this symbol information.
17255 This usually allows you to debug your program, though certain symbols
17256 are not accessible. If you encounter such a problem and feel like
17257 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17258 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17259 and examine @code{*bufp} to see the symbol.
17261 @item stub type has NULL name
17263 @value{GDBN} could not find the full definition for a struct or class.
17265 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17266 The symbol information for a C@t{++} member function is missing some
17267 information that recent versions of the compiler should have output for
17270 @item info mismatch between compiler and debugger
17272 @value{GDBN} could not parse a type specification output by the compiler.
17277 @section GDB Data Files
17279 @cindex prefix for data files
17280 @value{GDBN} will sometimes read an auxiliary data file. These files
17281 are kept in a directory known as the @dfn{data directory}.
17283 You can set the data directory's name, and view the name @value{GDBN}
17284 is currently using.
17287 @kindex set data-directory
17288 @item set data-directory @var{directory}
17289 Set the directory which @value{GDBN} searches for auxiliary data files
17290 to @var{directory}.
17292 @kindex show data-directory
17293 @item show data-directory
17294 Show the directory @value{GDBN} searches for auxiliary data files.
17297 @cindex default data directory
17298 @cindex @samp{--with-gdb-datadir}
17299 You can set the default data directory by using the configure-time
17300 @samp{--with-gdb-datadir} option. If the data directory is inside
17301 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17302 @samp{--exec-prefix}), then the default data directory will be updated
17303 automatically if the installed @value{GDBN} is moved to a new
17306 The data directory may also be specified with the
17307 @code{--data-directory} command line option.
17308 @xref{Mode Options}.
17311 @chapter Specifying a Debugging Target
17313 @cindex debugging target
17314 A @dfn{target} is the execution environment occupied by your program.
17316 Often, @value{GDBN} runs in the same host environment as your program;
17317 in that case, the debugging target is specified as a side effect when
17318 you use the @code{file} or @code{core} commands. When you need more
17319 flexibility---for example, running @value{GDBN} on a physically separate
17320 host, or controlling a standalone system over a serial port or a
17321 realtime system over a TCP/IP connection---you can use the @code{target}
17322 command to specify one of the target types configured for @value{GDBN}
17323 (@pxref{Target Commands, ,Commands for Managing Targets}).
17325 @cindex target architecture
17326 It is possible to build @value{GDBN} for several different @dfn{target
17327 architectures}. When @value{GDBN} is built like that, you can choose
17328 one of the available architectures with the @kbd{set architecture}
17332 @kindex set architecture
17333 @kindex show architecture
17334 @item set architecture @var{arch}
17335 This command sets the current target architecture to @var{arch}. The
17336 value of @var{arch} can be @code{"auto"}, in addition to one of the
17337 supported architectures.
17339 @item show architecture
17340 Show the current target architecture.
17342 @item set processor
17344 @kindex set processor
17345 @kindex show processor
17346 These are alias commands for, respectively, @code{set architecture}
17347 and @code{show architecture}.
17351 * Active Targets:: Active targets
17352 * Target Commands:: Commands for managing targets
17353 * Byte Order:: Choosing target byte order
17356 @node Active Targets
17357 @section Active Targets
17359 @cindex stacking targets
17360 @cindex active targets
17361 @cindex multiple targets
17363 There are multiple classes of targets such as: processes, executable files or
17364 recording sessions. Core files belong to the process class, making core file
17365 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17366 on multiple active targets, one in each class. This allows you to (for
17367 example) start a process and inspect its activity, while still having access to
17368 the executable file after the process finishes. Or if you start process
17369 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17370 presented a virtual layer of the recording target, while the process target
17371 remains stopped at the chronologically last point of the process execution.
17373 Use the @code{core-file} and @code{exec-file} commands to select a new core
17374 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17375 specify as a target a process that is already running, use the @code{attach}
17376 command (@pxref{Attach, ,Debugging an Already-running Process}).
17378 @node Target Commands
17379 @section Commands for Managing Targets
17382 @item target @var{type} @var{parameters}
17383 Connects the @value{GDBN} host environment to a target machine or
17384 process. A target is typically a protocol for talking to debugging
17385 facilities. You use the argument @var{type} to specify the type or
17386 protocol of the target machine.
17388 Further @var{parameters} are interpreted by the target protocol, but
17389 typically include things like device names or host names to connect
17390 with, process numbers, and baud rates.
17392 The @code{target} command does not repeat if you press @key{RET} again
17393 after executing the command.
17395 @kindex help target
17397 Displays the names of all targets available. To display targets
17398 currently selected, use either @code{info target} or @code{info files}
17399 (@pxref{Files, ,Commands to Specify Files}).
17401 @item help target @var{name}
17402 Describe a particular target, including any parameters necessary to
17405 @kindex set gnutarget
17406 @item set gnutarget @var{args}
17407 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17408 knows whether it is reading an @dfn{executable},
17409 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17410 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17411 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17414 @emph{Warning:} To specify a file format with @code{set gnutarget},
17415 you must know the actual BFD name.
17419 @xref{Files, , Commands to Specify Files}.
17421 @kindex show gnutarget
17422 @item show gnutarget
17423 Use the @code{show gnutarget} command to display what file format
17424 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17425 @value{GDBN} will determine the file format for each file automatically,
17426 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17429 @cindex common targets
17430 Here are some common targets (available, or not, depending on the GDB
17435 @item target exec @var{program}
17436 @cindex executable file target
17437 An executable file. @samp{target exec @var{program}} is the same as
17438 @samp{exec-file @var{program}}.
17440 @item target core @var{filename}
17441 @cindex core dump file target
17442 A core dump file. @samp{target core @var{filename}} is the same as
17443 @samp{core-file @var{filename}}.
17445 @item target remote @var{medium}
17446 @cindex remote target
17447 A remote system connected to @value{GDBN} via a serial line or network
17448 connection. This command tells @value{GDBN} to use its own remote
17449 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17451 For example, if you have a board connected to @file{/dev/ttya} on the
17452 machine running @value{GDBN}, you could say:
17455 target remote /dev/ttya
17458 @code{target remote} supports the @code{load} command. This is only
17459 useful if you have some other way of getting the stub to the target
17460 system, and you can put it somewhere in memory where it won't get
17461 clobbered by the download.
17463 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17464 @cindex built-in simulator target
17465 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17473 works; however, you cannot assume that a specific memory map, device
17474 drivers, or even basic I/O is available, although some simulators do
17475 provide these. For info about any processor-specific simulator details,
17476 see the appropriate section in @ref{Embedded Processors, ,Embedded
17481 Some configurations may include these targets as well:
17485 @item target nrom @var{dev}
17486 @cindex NetROM ROM emulator target
17487 NetROM ROM emulator. This target only supports downloading.
17491 Different targets are available on different configurations of @value{GDBN};
17492 your configuration may have more or fewer targets.
17494 Many remote targets require you to download the executable's code once
17495 you've successfully established a connection. You may wish to control
17496 various aspects of this process.
17501 @kindex set hash@r{, for remote monitors}
17502 @cindex hash mark while downloading
17503 This command controls whether a hash mark @samp{#} is displayed while
17504 downloading a file to the remote monitor. If on, a hash mark is
17505 displayed after each S-record is successfully downloaded to the
17509 @kindex show hash@r{, for remote monitors}
17510 Show the current status of displaying the hash mark.
17512 @item set debug monitor
17513 @kindex set debug monitor
17514 @cindex display remote monitor communications
17515 Enable or disable display of communications messages between
17516 @value{GDBN} and the remote monitor.
17518 @item show debug monitor
17519 @kindex show debug monitor
17520 Show the current status of displaying communications between
17521 @value{GDBN} and the remote monitor.
17526 @kindex load @var{filename}
17527 @item load @var{filename}
17529 Depending on what remote debugging facilities are configured into
17530 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17531 is meant to make @var{filename} (an executable) available for debugging
17532 on the remote system---by downloading, or dynamic linking, for example.
17533 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17534 the @code{add-symbol-file} command.
17536 If your @value{GDBN} does not have a @code{load} command, attempting to
17537 execute it gets the error message ``@code{You can't do that when your
17538 target is @dots{}}''
17540 The file is loaded at whatever address is specified in the executable.
17541 For some object file formats, you can specify the load address when you
17542 link the program; for other formats, like a.out, the object file format
17543 specifies a fixed address.
17544 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17546 Depending on the remote side capabilities, @value{GDBN} may be able to
17547 load programs into flash memory.
17549 @code{load} does not repeat if you press @key{RET} again after using it.
17553 @section Choosing Target Byte Order
17555 @cindex choosing target byte order
17556 @cindex target byte order
17558 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17559 offer the ability to run either big-endian or little-endian byte
17560 orders. Usually the executable or symbol will include a bit to
17561 designate the endian-ness, and you will not need to worry about
17562 which to use. However, you may still find it useful to adjust
17563 @value{GDBN}'s idea of processor endian-ness manually.
17567 @item set endian big
17568 Instruct @value{GDBN} to assume the target is big-endian.
17570 @item set endian little
17571 Instruct @value{GDBN} to assume the target is little-endian.
17573 @item set endian auto
17574 Instruct @value{GDBN} to use the byte order associated with the
17578 Display @value{GDBN}'s current idea of the target byte order.
17582 Note that these commands merely adjust interpretation of symbolic
17583 data on the host, and that they have absolutely no effect on the
17587 @node Remote Debugging
17588 @chapter Debugging Remote Programs
17589 @cindex remote debugging
17591 If you are trying to debug a program running on a machine that cannot run
17592 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17593 For example, you might use remote debugging on an operating system kernel,
17594 or on a small system which does not have a general purpose operating system
17595 powerful enough to run a full-featured debugger.
17597 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17598 to make this work with particular debugging targets. In addition,
17599 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17600 but not specific to any particular target system) which you can use if you
17601 write the remote stubs---the code that runs on the remote system to
17602 communicate with @value{GDBN}.
17604 Other remote targets may be available in your
17605 configuration of @value{GDBN}; use @code{help target} to list them.
17608 * Connecting:: Connecting to a remote target
17609 * File Transfer:: Sending files to a remote system
17610 * Server:: Using the gdbserver program
17611 * Remote Configuration:: Remote configuration
17612 * Remote Stub:: Implementing a remote stub
17616 @section Connecting to a Remote Target
17618 On the @value{GDBN} host machine, you will need an unstripped copy of
17619 your program, since @value{GDBN} needs symbol and debugging information.
17620 Start up @value{GDBN} as usual, using the name of the local copy of your
17621 program as the first argument.
17623 @cindex @code{target remote}
17624 @value{GDBN} can communicate with the target over a serial line, or
17625 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17626 each case, @value{GDBN} uses the same protocol for debugging your
17627 program; only the medium carrying the debugging packets varies. The
17628 @code{target remote} command establishes a connection to the target.
17629 Its arguments indicate which medium to use:
17633 @item target remote @var{serial-device}
17634 @cindex serial line, @code{target remote}
17635 Use @var{serial-device} to communicate with the target. For example,
17636 to use a serial line connected to the device named @file{/dev/ttyb}:
17639 target remote /dev/ttyb
17642 If you're using a serial line, you may want to give @value{GDBN} the
17643 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17644 (@pxref{Remote Configuration, set remotebaud}) before the
17645 @code{target} command.
17647 @item target remote @code{@var{host}:@var{port}}
17648 @itemx target remote @code{tcp:@var{host}:@var{port}}
17649 @cindex @acronym{TCP} port, @code{target remote}
17650 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17651 The @var{host} may be either a host name or a numeric @acronym{IP}
17652 address; @var{port} must be a decimal number. The @var{host} could be
17653 the target machine itself, if it is directly connected to the net, or
17654 it might be a terminal server which in turn has a serial line to the
17657 For example, to connect to port 2828 on a terminal server named
17661 target remote manyfarms:2828
17664 If your remote target is actually running on the same machine as your
17665 debugger session (e.g.@: a simulator for your target running on the
17666 same host), you can omit the hostname. For example, to connect to
17667 port 1234 on your local machine:
17670 target remote :1234
17674 Note that the colon is still required here.
17676 @item target remote @code{udp:@var{host}:@var{port}}
17677 @cindex @acronym{UDP} port, @code{target remote}
17678 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17679 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17682 target remote udp:manyfarms:2828
17685 When using a @acronym{UDP} connection for remote debugging, you should
17686 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17687 can silently drop packets on busy or unreliable networks, which will
17688 cause havoc with your debugging session.
17690 @item target remote | @var{command}
17691 @cindex pipe, @code{target remote} to
17692 Run @var{command} in the background and communicate with it using a
17693 pipe. The @var{command} is a shell command, to be parsed and expanded
17694 by the system's command shell, @code{/bin/sh}; it should expect remote
17695 protocol packets on its standard input, and send replies on its
17696 standard output. You could use this to run a stand-alone simulator
17697 that speaks the remote debugging protocol, to make net connections
17698 using programs like @code{ssh}, or for other similar tricks.
17700 If @var{command} closes its standard output (perhaps by exiting),
17701 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17702 program has already exited, this will have no effect.)
17706 Once the connection has been established, you can use all the usual
17707 commands to examine and change data. The remote program is already
17708 running; you can use @kbd{step} and @kbd{continue}, and you do not
17709 need to use @kbd{run}.
17711 @cindex interrupting remote programs
17712 @cindex remote programs, interrupting
17713 Whenever @value{GDBN} is waiting for the remote program, if you type the
17714 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17715 program. This may or may not succeed, depending in part on the hardware
17716 and the serial drivers the remote system uses. If you type the
17717 interrupt character once again, @value{GDBN} displays this prompt:
17720 Interrupted while waiting for the program.
17721 Give up (and stop debugging it)? (y or n)
17724 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17725 (If you decide you want to try again later, you can use @samp{target
17726 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17727 goes back to waiting.
17730 @kindex detach (remote)
17732 When you have finished debugging the remote program, you can use the
17733 @code{detach} command to release it from @value{GDBN} control.
17734 Detaching from the target normally resumes its execution, but the results
17735 will depend on your particular remote stub. After the @code{detach}
17736 command, @value{GDBN} is free to connect to another target.
17740 The @code{disconnect} command behaves like @code{detach}, except that
17741 the target is generally not resumed. It will wait for @value{GDBN}
17742 (this instance or another one) to connect and continue debugging. After
17743 the @code{disconnect} command, @value{GDBN} is again free to connect to
17746 @cindex send command to remote monitor
17747 @cindex extend @value{GDBN} for remote targets
17748 @cindex add new commands for external monitor
17750 @item monitor @var{cmd}
17751 This command allows you to send arbitrary commands directly to the
17752 remote monitor. Since @value{GDBN} doesn't care about the commands it
17753 sends like this, this command is the way to extend @value{GDBN}---you
17754 can add new commands that only the external monitor will understand
17758 @node File Transfer
17759 @section Sending files to a remote system
17760 @cindex remote target, file transfer
17761 @cindex file transfer
17762 @cindex sending files to remote systems
17764 Some remote targets offer the ability to transfer files over the same
17765 connection used to communicate with @value{GDBN}. This is convenient
17766 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17767 running @code{gdbserver} over a network interface. For other targets,
17768 e.g.@: embedded devices with only a single serial port, this may be
17769 the only way to upload or download files.
17771 Not all remote targets support these commands.
17775 @item remote put @var{hostfile} @var{targetfile}
17776 Copy file @var{hostfile} from the host system (the machine running
17777 @value{GDBN}) to @var{targetfile} on the target system.
17780 @item remote get @var{targetfile} @var{hostfile}
17781 Copy file @var{targetfile} from the target system to @var{hostfile}
17782 on the host system.
17784 @kindex remote delete
17785 @item remote delete @var{targetfile}
17786 Delete @var{targetfile} from the target system.
17791 @section Using the @code{gdbserver} Program
17794 @cindex remote connection without stubs
17795 @code{gdbserver} is a control program for Unix-like systems, which
17796 allows you to connect your program with a remote @value{GDBN} via
17797 @code{target remote}---but without linking in the usual debugging stub.
17799 @code{gdbserver} is not a complete replacement for the debugging stubs,
17800 because it requires essentially the same operating-system facilities
17801 that @value{GDBN} itself does. In fact, a system that can run
17802 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17803 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17804 because it is a much smaller program than @value{GDBN} itself. It is
17805 also easier to port than all of @value{GDBN}, so you may be able to get
17806 started more quickly on a new system by using @code{gdbserver}.
17807 Finally, if you develop code for real-time systems, you may find that
17808 the tradeoffs involved in real-time operation make it more convenient to
17809 do as much development work as possible on another system, for example
17810 by cross-compiling. You can use @code{gdbserver} to make a similar
17811 choice for debugging.
17813 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17814 or a TCP connection, using the standard @value{GDBN} remote serial
17818 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17819 Do not run @code{gdbserver} connected to any public network; a
17820 @value{GDBN} connection to @code{gdbserver} provides access to the
17821 target system with the same privileges as the user running
17825 @subsection Running @code{gdbserver}
17826 @cindex arguments, to @code{gdbserver}
17827 @cindex @code{gdbserver}, command-line arguments
17829 Run @code{gdbserver} on the target system. You need a copy of the
17830 program you want to debug, including any libraries it requires.
17831 @code{gdbserver} does not need your program's symbol table, so you can
17832 strip the program if necessary to save space. @value{GDBN} on the host
17833 system does all the symbol handling.
17835 To use the server, you must tell it how to communicate with @value{GDBN};
17836 the name of your program; and the arguments for your program. The usual
17840 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17843 @var{comm} is either a device name (to use a serial line), or a TCP
17844 hostname and portnumber, or @code{-} or @code{stdio} to use
17845 stdin/stdout of @code{gdbserver}.
17846 For example, to debug Emacs with the argument
17847 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17851 target> gdbserver /dev/com1 emacs foo.txt
17854 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17857 To use a TCP connection instead of a serial line:
17860 target> gdbserver host:2345 emacs foo.txt
17863 The only difference from the previous example is the first argument,
17864 specifying that you are communicating with the host @value{GDBN} via
17865 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17866 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17867 (Currently, the @samp{host} part is ignored.) You can choose any number
17868 you want for the port number as long as it does not conflict with any
17869 TCP ports already in use on the target system (for example, @code{23} is
17870 reserved for @code{telnet}).@footnote{If you choose a port number that
17871 conflicts with another service, @code{gdbserver} prints an error message
17872 and exits.} You must use the same port number with the host @value{GDBN}
17873 @code{target remote} command.
17875 The @code{stdio} connection is useful when starting @code{gdbserver}
17879 (gdb) target remote | ssh -T hostname gdbserver - hello
17882 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17883 and we don't want escape-character handling. Ssh does this by default when
17884 a command is provided, the flag is provided to make it explicit.
17885 You could elide it if you want to.
17887 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17888 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17889 display through a pipe connected to gdbserver.
17890 Both @code{stdout} and @code{stderr} use the same pipe.
17892 @subsubsection Attaching to a Running Program
17893 @cindex attach to a program, @code{gdbserver}
17894 @cindex @option{--attach}, @code{gdbserver} option
17896 On some targets, @code{gdbserver} can also attach to running programs.
17897 This is accomplished via the @code{--attach} argument. The syntax is:
17900 target> gdbserver --attach @var{comm} @var{pid}
17903 @var{pid} is the process ID of a currently running process. It isn't necessary
17904 to point @code{gdbserver} at a binary for the running process.
17907 You can debug processes by name instead of process ID if your target has the
17908 @code{pidof} utility:
17911 target> gdbserver --attach @var{comm} `pidof @var{program}`
17914 In case more than one copy of @var{program} is running, or @var{program}
17915 has multiple threads, most versions of @code{pidof} support the
17916 @code{-s} option to only return the first process ID.
17918 @subsubsection Multi-Process Mode for @code{gdbserver}
17919 @cindex @code{gdbserver}, multiple processes
17920 @cindex multiple processes with @code{gdbserver}
17922 When you connect to @code{gdbserver} using @code{target remote},
17923 @code{gdbserver} debugs the specified program only once. When the
17924 program exits, or you detach from it, @value{GDBN} closes the connection
17925 and @code{gdbserver} exits.
17927 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17928 enters multi-process mode. When the debugged program exits, or you
17929 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17930 though no program is running. The @code{run} and @code{attach}
17931 commands instruct @code{gdbserver} to run or attach to a new program.
17932 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17933 remote exec-file}) to select the program to run. Command line
17934 arguments are supported, except for wildcard expansion and I/O
17935 redirection (@pxref{Arguments}).
17937 @cindex @option{--multi}, @code{gdbserver} option
17938 To start @code{gdbserver} without supplying an initial command to run
17939 or process ID to attach, use the @option{--multi} command line option.
17940 Then you can connect using @kbd{target extended-remote} and start
17941 the program you want to debug.
17943 In multi-process mode @code{gdbserver} does not automatically exit unless you
17944 use the option @option{--once}. You can terminate it by using
17945 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17946 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17947 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17948 @option{--multi} option to @code{gdbserver} has no influence on that.
17950 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17952 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17954 @code{gdbserver} normally terminates after all of its debugged processes have
17955 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17956 extended-remote}, @code{gdbserver} stays running even with no processes left.
17957 @value{GDBN} normally terminates the spawned debugged process on its exit,
17958 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17959 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17960 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17961 stays running even in the @kbd{target remote} mode.
17963 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17964 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17965 completeness, at most one @value{GDBN} can be connected at a time.
17967 @cindex @option{--once}, @code{gdbserver} option
17968 By default, @code{gdbserver} keeps the listening TCP port open, so that
17969 additional connections are possible. However, if you start @code{gdbserver}
17970 with the @option{--once} option, it will stop listening for any further
17971 connection attempts after connecting to the first @value{GDBN} session. This
17972 means no further connections to @code{gdbserver} will be possible after the
17973 first one. It also means @code{gdbserver} will terminate after the first
17974 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17975 connections and even in the @kbd{target extended-remote} mode. The
17976 @option{--once} option allows reusing the same port number for connecting to
17977 multiple instances of @code{gdbserver} running on the same host, since each
17978 instance closes its port after the first connection.
17980 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17982 @cindex @option{--debug}, @code{gdbserver} option
17983 The @option{--debug} option tells @code{gdbserver} to display extra
17984 status information about the debugging process.
17985 @cindex @option{--remote-debug}, @code{gdbserver} option
17986 The @option{--remote-debug} option tells @code{gdbserver} to display
17987 remote protocol debug output. These options are intended for
17988 @code{gdbserver} development and for bug reports to the developers.
17990 @cindex @option{--wrapper}, @code{gdbserver} option
17991 The @option{--wrapper} option specifies a wrapper to launch programs
17992 for debugging. The option should be followed by the name of the
17993 wrapper, then any command-line arguments to pass to the wrapper, then
17994 @kbd{--} indicating the end of the wrapper arguments.
17996 @code{gdbserver} runs the specified wrapper program with a combined
17997 command line including the wrapper arguments, then the name of the
17998 program to debug, then any arguments to the program. The wrapper
17999 runs until it executes your program, and then @value{GDBN} gains control.
18001 You can use any program that eventually calls @code{execve} with
18002 its arguments as a wrapper. Several standard Unix utilities do
18003 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18004 with @code{exec "$@@"} will also work.
18006 For example, you can use @code{env} to pass an environment variable to
18007 the debugged program, without setting the variable in @code{gdbserver}'s
18011 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18014 @subsection Connecting to @code{gdbserver}
18016 Run @value{GDBN} on the host system.
18018 First make sure you have the necessary symbol files. Load symbols for
18019 your application using the @code{file} command before you connect. Use
18020 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18021 was compiled with the correct sysroot using @code{--with-sysroot}).
18023 The symbol file and target libraries must exactly match the executable
18024 and libraries on the target, with one exception: the files on the host
18025 system should not be stripped, even if the files on the target system
18026 are. Mismatched or missing files will lead to confusing results
18027 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18028 files may also prevent @code{gdbserver} from debugging multi-threaded
18031 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18032 For TCP connections, you must start up @code{gdbserver} prior to using
18033 the @code{target remote} command. Otherwise you may get an error whose
18034 text depends on the host system, but which usually looks something like
18035 @samp{Connection refused}. Don't use the @code{load}
18036 command in @value{GDBN} when using @code{gdbserver}, since the program is
18037 already on the target.
18039 @subsection Monitor Commands for @code{gdbserver}
18040 @cindex monitor commands, for @code{gdbserver}
18041 @anchor{Monitor Commands for gdbserver}
18043 During a @value{GDBN} session using @code{gdbserver}, you can use the
18044 @code{monitor} command to send special requests to @code{gdbserver}.
18045 Here are the available commands.
18049 List the available monitor commands.
18051 @item monitor set debug 0
18052 @itemx monitor set debug 1
18053 Disable or enable general debugging messages.
18055 @item monitor set remote-debug 0
18056 @itemx monitor set remote-debug 1
18057 Disable or enable specific debugging messages associated with the remote
18058 protocol (@pxref{Remote Protocol}).
18060 @item monitor set libthread-db-search-path [PATH]
18061 @cindex gdbserver, search path for @code{libthread_db}
18062 When this command is issued, @var{path} is a colon-separated list of
18063 directories to search for @code{libthread_db} (@pxref{Threads,,set
18064 libthread-db-search-path}). If you omit @var{path},
18065 @samp{libthread-db-search-path} will be reset to its default value.
18067 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18068 not supported in @code{gdbserver}.
18071 Tell gdbserver to exit immediately. This command should be followed by
18072 @code{disconnect} to close the debugging session. @code{gdbserver} will
18073 detach from any attached processes and kill any processes it created.
18074 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18075 of a multi-process mode debug session.
18079 @subsection Tracepoints support in @code{gdbserver}
18080 @cindex tracepoints support in @code{gdbserver}
18082 On some targets, @code{gdbserver} supports tracepoints, fast
18083 tracepoints and static tracepoints.
18085 For fast or static tracepoints to work, a special library called the
18086 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18087 This library is built and distributed as an integral part of
18088 @code{gdbserver}. In addition, support for static tracepoints
18089 requires building the in-process agent library with static tracepoints
18090 support. At present, the UST (LTTng Userspace Tracer,
18091 @url{http://lttng.org/ust}) tracing engine is supported. This support
18092 is automatically available if UST development headers are found in the
18093 standard include path when @code{gdbserver} is built, or if
18094 @code{gdbserver} was explicitly configured using @option{--with-ust}
18095 to point at such headers. You can explicitly disable the support
18096 using @option{--with-ust=no}.
18098 There are several ways to load the in-process agent in your program:
18101 @item Specifying it as dependency at link time
18103 You can link your program dynamically with the in-process agent
18104 library. On most systems, this is accomplished by adding
18105 @code{-linproctrace} to the link command.
18107 @item Using the system's preloading mechanisms
18109 You can force loading the in-process agent at startup time by using
18110 your system's support for preloading shared libraries. Many Unixes
18111 support the concept of preloading user defined libraries. In most
18112 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18113 in the environment. See also the description of @code{gdbserver}'s
18114 @option{--wrapper} command line option.
18116 @item Using @value{GDBN} to force loading the agent at run time
18118 On some systems, you can force the inferior to load a shared library,
18119 by calling a dynamic loader function in the inferior that takes care
18120 of dynamically looking up and loading a shared library. On most Unix
18121 systems, the function is @code{dlopen}. You'll use the @code{call}
18122 command for that. For example:
18125 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18128 Note that on most Unix systems, for the @code{dlopen} function to be
18129 available, the program needs to be linked with @code{-ldl}.
18132 On systems that have a userspace dynamic loader, like most Unix
18133 systems, when you connect to @code{gdbserver} using @code{target
18134 remote}, you'll find that the program is stopped at the dynamic
18135 loader's entry point, and no shared library has been loaded in the
18136 program's address space yet, including the in-process agent. In that
18137 case, before being able to use any of the fast or static tracepoints
18138 features, you need to let the loader run and load the shared
18139 libraries. The simplest way to do that is to run the program to the
18140 main procedure. E.g., if debugging a C or C@t{++} program, start
18141 @code{gdbserver} like so:
18144 $ gdbserver :9999 myprogram
18147 Start GDB and connect to @code{gdbserver} like so, and run to main:
18151 (@value{GDBP}) target remote myhost:9999
18152 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18153 (@value{GDBP}) b main
18154 (@value{GDBP}) continue
18157 The in-process tracing agent library should now be loaded into the
18158 process; you can confirm it with the @code{info sharedlibrary}
18159 command, which will list @file{libinproctrace.so} as loaded in the
18160 process. You are now ready to install fast tracepoints, list static
18161 tracepoint markers, probe static tracepoints markers, and start
18164 @node Remote Configuration
18165 @section Remote Configuration
18168 @kindex show remote
18169 This section documents the configuration options available when
18170 debugging remote programs. For the options related to the File I/O
18171 extensions of the remote protocol, see @ref{system,
18172 system-call-allowed}.
18175 @item set remoteaddresssize @var{bits}
18176 @cindex address size for remote targets
18177 @cindex bits in remote address
18178 Set the maximum size of address in a memory packet to the specified
18179 number of bits. @value{GDBN} will mask off the address bits above
18180 that number, when it passes addresses to the remote target. The
18181 default value is the number of bits in the target's address.
18183 @item show remoteaddresssize
18184 Show the current value of remote address size in bits.
18186 @item set remotebaud @var{n}
18187 @cindex baud rate for remote targets
18188 Set the baud rate for the remote serial I/O to @var{n} baud. The
18189 value is used to set the speed of the serial port used for debugging
18192 @item show remotebaud
18193 Show the current speed of the remote connection.
18195 @item set remotebreak
18196 @cindex interrupt remote programs
18197 @cindex BREAK signal instead of Ctrl-C
18198 @anchor{set remotebreak}
18199 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18200 when you type @kbd{Ctrl-c} to interrupt the program running
18201 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18202 character instead. The default is off, since most remote systems
18203 expect to see @samp{Ctrl-C} as the interrupt signal.
18205 @item show remotebreak
18206 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18207 interrupt the remote program.
18209 @item set remoteflow on
18210 @itemx set remoteflow off
18211 @kindex set remoteflow
18212 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18213 on the serial port used to communicate to the remote target.
18215 @item show remoteflow
18216 @kindex show remoteflow
18217 Show the current setting of hardware flow control.
18219 @item set remotelogbase @var{base}
18220 Set the base (a.k.a.@: radix) of logging serial protocol
18221 communications to @var{base}. Supported values of @var{base} are:
18222 @code{ascii}, @code{octal}, and @code{hex}. The default is
18225 @item show remotelogbase
18226 Show the current setting of the radix for logging remote serial
18229 @item set remotelogfile @var{file}
18230 @cindex record serial communications on file
18231 Record remote serial communications on the named @var{file}. The
18232 default is not to record at all.
18234 @item show remotelogfile.
18235 Show the current setting of the file name on which to record the
18236 serial communications.
18238 @item set remotetimeout @var{num}
18239 @cindex timeout for serial communications
18240 @cindex remote timeout
18241 Set the timeout limit to wait for the remote target to respond to
18242 @var{num} seconds. The default is 2 seconds.
18244 @item show remotetimeout
18245 Show the current number of seconds to wait for the remote target
18248 @cindex limit hardware breakpoints and watchpoints
18249 @cindex remote target, limit break- and watchpoints
18250 @anchor{set remote hardware-watchpoint-limit}
18251 @anchor{set remote hardware-breakpoint-limit}
18252 @item set remote hardware-watchpoint-limit @var{limit}
18253 @itemx set remote hardware-breakpoint-limit @var{limit}
18254 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18255 watchpoints. A limit of -1, the default, is treated as unlimited.
18257 @cindex limit hardware watchpoints length
18258 @cindex remote target, limit watchpoints length
18259 @anchor{set remote hardware-watchpoint-length-limit}
18260 @item set remote hardware-watchpoint-length-limit @var{limit}
18261 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18262 a remote hardware watchpoint. A limit of -1, the default, is treated
18265 @item show remote hardware-watchpoint-length-limit
18266 Show the current limit (in bytes) of the maximum length of
18267 a remote hardware watchpoint.
18269 @item set remote exec-file @var{filename}
18270 @itemx show remote exec-file
18271 @anchor{set remote exec-file}
18272 @cindex executable file, for remote target
18273 Select the file used for @code{run} with @code{target
18274 extended-remote}. This should be set to a filename valid on the
18275 target system. If it is not set, the target will use a default
18276 filename (e.g.@: the last program run).
18278 @item set remote interrupt-sequence
18279 @cindex interrupt remote programs
18280 @cindex select Ctrl-C, BREAK or BREAK-g
18281 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18282 @samp{BREAK-g} as the
18283 sequence to the remote target in order to interrupt the execution.
18284 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18285 is high level of serial line for some certain time.
18286 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18287 It is @code{BREAK} signal followed by character @code{g}.
18289 @item show interrupt-sequence
18290 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18291 is sent by @value{GDBN} to interrupt the remote program.
18292 @code{BREAK-g} is BREAK signal followed by @code{g} and
18293 also known as Magic SysRq g.
18295 @item set remote interrupt-on-connect
18296 @cindex send interrupt-sequence on start
18297 Specify whether interrupt-sequence is sent to remote target when
18298 @value{GDBN} connects to it. This is mostly needed when you debug
18299 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18300 which is known as Magic SysRq g in order to connect @value{GDBN}.
18302 @item show interrupt-on-connect
18303 Show whether interrupt-sequence is sent
18304 to remote target when @value{GDBN} connects to it.
18308 @item set tcp auto-retry on
18309 @cindex auto-retry, for remote TCP target
18310 Enable auto-retry for remote TCP connections. This is useful if the remote
18311 debugging agent is launched in parallel with @value{GDBN}; there is a race
18312 condition because the agent may not become ready to accept the connection
18313 before @value{GDBN} attempts to connect. When auto-retry is
18314 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18315 to establish the connection using the timeout specified by
18316 @code{set tcp connect-timeout}.
18318 @item set tcp auto-retry off
18319 Do not auto-retry failed TCP connections.
18321 @item show tcp auto-retry
18322 Show the current auto-retry setting.
18324 @item set tcp connect-timeout @var{seconds}
18325 @itemx set tcp connect-timeout unlimited
18326 @cindex connection timeout, for remote TCP target
18327 @cindex timeout, for remote target connection
18328 Set the timeout for establishing a TCP connection to the remote target to
18329 @var{seconds}. The timeout affects both polling to retry failed connections
18330 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18331 that are merely slow to complete, and represents an approximate cumulative
18332 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18333 @value{GDBN} will keep attempting to establish a connection forever,
18334 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18336 @item show tcp connect-timeout
18337 Show the current connection timeout setting.
18340 @cindex remote packets, enabling and disabling
18341 The @value{GDBN} remote protocol autodetects the packets supported by
18342 your debugging stub. If you need to override the autodetection, you
18343 can use these commands to enable or disable individual packets. Each
18344 packet can be set to @samp{on} (the remote target supports this
18345 packet), @samp{off} (the remote target does not support this packet),
18346 or @samp{auto} (detect remote target support for this packet). They
18347 all default to @samp{auto}. For more information about each packet,
18348 see @ref{Remote Protocol}.
18350 During normal use, you should not have to use any of these commands.
18351 If you do, that may be a bug in your remote debugging stub, or a bug
18352 in @value{GDBN}. You may want to report the problem to the
18353 @value{GDBN} developers.
18355 For each packet @var{name}, the command to enable or disable the
18356 packet is @code{set remote @var{name}-packet}. The available settings
18359 @multitable @columnfractions 0.28 0.32 0.25
18362 @tab Related Features
18364 @item @code{fetch-register}
18366 @tab @code{info registers}
18368 @item @code{set-register}
18372 @item @code{binary-download}
18374 @tab @code{load}, @code{set}
18376 @item @code{read-aux-vector}
18377 @tab @code{qXfer:auxv:read}
18378 @tab @code{info auxv}
18380 @item @code{symbol-lookup}
18381 @tab @code{qSymbol}
18382 @tab Detecting multiple threads
18384 @item @code{attach}
18385 @tab @code{vAttach}
18388 @item @code{verbose-resume}
18390 @tab Stepping or resuming multiple threads
18396 @item @code{software-breakpoint}
18400 @item @code{hardware-breakpoint}
18404 @item @code{write-watchpoint}
18408 @item @code{read-watchpoint}
18412 @item @code{access-watchpoint}
18416 @item @code{target-features}
18417 @tab @code{qXfer:features:read}
18418 @tab @code{set architecture}
18420 @item @code{library-info}
18421 @tab @code{qXfer:libraries:read}
18422 @tab @code{info sharedlibrary}
18424 @item @code{memory-map}
18425 @tab @code{qXfer:memory-map:read}
18426 @tab @code{info mem}
18428 @item @code{read-sdata-object}
18429 @tab @code{qXfer:sdata:read}
18430 @tab @code{print $_sdata}
18432 @item @code{read-spu-object}
18433 @tab @code{qXfer:spu:read}
18434 @tab @code{info spu}
18436 @item @code{write-spu-object}
18437 @tab @code{qXfer:spu:write}
18438 @tab @code{info spu}
18440 @item @code{read-siginfo-object}
18441 @tab @code{qXfer:siginfo:read}
18442 @tab @code{print $_siginfo}
18444 @item @code{write-siginfo-object}
18445 @tab @code{qXfer:siginfo:write}
18446 @tab @code{set $_siginfo}
18448 @item @code{threads}
18449 @tab @code{qXfer:threads:read}
18450 @tab @code{info threads}
18452 @item @code{get-thread-local-@*storage-address}
18453 @tab @code{qGetTLSAddr}
18454 @tab Displaying @code{__thread} variables
18456 @item @code{get-thread-information-block-address}
18457 @tab @code{qGetTIBAddr}
18458 @tab Display MS-Windows Thread Information Block.
18460 @item @code{search-memory}
18461 @tab @code{qSearch:memory}
18464 @item @code{supported-packets}
18465 @tab @code{qSupported}
18466 @tab Remote communications parameters
18468 @item @code{pass-signals}
18469 @tab @code{QPassSignals}
18470 @tab @code{handle @var{signal}}
18472 @item @code{program-signals}
18473 @tab @code{QProgramSignals}
18474 @tab @code{handle @var{signal}}
18476 @item @code{hostio-close-packet}
18477 @tab @code{vFile:close}
18478 @tab @code{remote get}, @code{remote put}
18480 @item @code{hostio-open-packet}
18481 @tab @code{vFile:open}
18482 @tab @code{remote get}, @code{remote put}
18484 @item @code{hostio-pread-packet}
18485 @tab @code{vFile:pread}
18486 @tab @code{remote get}, @code{remote put}
18488 @item @code{hostio-pwrite-packet}
18489 @tab @code{vFile:pwrite}
18490 @tab @code{remote get}, @code{remote put}
18492 @item @code{hostio-unlink-packet}
18493 @tab @code{vFile:unlink}
18494 @tab @code{remote delete}
18496 @item @code{hostio-readlink-packet}
18497 @tab @code{vFile:readlink}
18500 @item @code{noack-packet}
18501 @tab @code{QStartNoAckMode}
18502 @tab Packet acknowledgment
18504 @item @code{osdata}
18505 @tab @code{qXfer:osdata:read}
18506 @tab @code{info os}
18508 @item @code{query-attached}
18509 @tab @code{qAttached}
18510 @tab Querying remote process attach state.
18512 @item @code{trace-buffer-size}
18513 @tab @code{QTBuffer:size}
18514 @tab @code{set trace-buffer-size}
18516 @item @code{trace-status}
18517 @tab @code{qTStatus}
18518 @tab @code{tstatus}
18520 @item @code{traceframe-info}
18521 @tab @code{qXfer:traceframe-info:read}
18522 @tab Traceframe info
18524 @item @code{install-in-trace}
18525 @tab @code{InstallInTrace}
18526 @tab Install tracepoint in tracing
18528 @item @code{disable-randomization}
18529 @tab @code{QDisableRandomization}
18530 @tab @code{set disable-randomization}
18532 @item @code{conditional-breakpoints-packet}
18533 @tab @code{Z0 and Z1}
18534 @tab @code{Support for target-side breakpoint condition evaluation}
18538 @section Implementing a Remote Stub
18540 @cindex debugging stub, example
18541 @cindex remote stub, example
18542 @cindex stub example, remote debugging
18543 The stub files provided with @value{GDBN} implement the target side of the
18544 communication protocol, and the @value{GDBN} side is implemented in the
18545 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18546 these subroutines to communicate, and ignore the details. (If you're
18547 implementing your own stub file, you can still ignore the details: start
18548 with one of the existing stub files. @file{sparc-stub.c} is the best
18549 organized, and therefore the easiest to read.)
18551 @cindex remote serial debugging, overview
18552 To debug a program running on another machine (the debugging
18553 @dfn{target} machine), you must first arrange for all the usual
18554 prerequisites for the program to run by itself. For example, for a C
18559 A startup routine to set up the C runtime environment; these usually
18560 have a name like @file{crt0}. The startup routine may be supplied by
18561 your hardware supplier, or you may have to write your own.
18564 A C subroutine library to support your program's
18565 subroutine calls, notably managing input and output.
18568 A way of getting your program to the other machine---for example, a
18569 download program. These are often supplied by the hardware
18570 manufacturer, but you may have to write your own from hardware
18574 The next step is to arrange for your program to use a serial port to
18575 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18576 machine). In general terms, the scheme looks like this:
18580 @value{GDBN} already understands how to use this protocol; when everything
18581 else is set up, you can simply use the @samp{target remote} command
18582 (@pxref{Targets,,Specifying a Debugging Target}).
18584 @item On the target,
18585 you must link with your program a few special-purpose subroutines that
18586 implement the @value{GDBN} remote serial protocol. The file containing these
18587 subroutines is called a @dfn{debugging stub}.
18589 On certain remote targets, you can use an auxiliary program
18590 @code{gdbserver} instead of linking a stub into your program.
18591 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18594 The debugging stub is specific to the architecture of the remote
18595 machine; for example, use @file{sparc-stub.c} to debug programs on
18598 @cindex remote serial stub list
18599 These working remote stubs are distributed with @value{GDBN}:
18604 @cindex @file{i386-stub.c}
18607 For Intel 386 and compatible architectures.
18610 @cindex @file{m68k-stub.c}
18611 @cindex Motorola 680x0
18613 For Motorola 680x0 architectures.
18616 @cindex @file{sh-stub.c}
18619 For Renesas SH architectures.
18622 @cindex @file{sparc-stub.c}
18624 For @sc{sparc} architectures.
18626 @item sparcl-stub.c
18627 @cindex @file{sparcl-stub.c}
18630 For Fujitsu @sc{sparclite} architectures.
18634 The @file{README} file in the @value{GDBN} distribution may list other
18635 recently added stubs.
18638 * Stub Contents:: What the stub can do for you
18639 * Bootstrapping:: What you must do for the stub
18640 * Debug Session:: Putting it all together
18643 @node Stub Contents
18644 @subsection What the Stub Can Do for You
18646 @cindex remote serial stub
18647 The debugging stub for your architecture supplies these three
18651 @item set_debug_traps
18652 @findex set_debug_traps
18653 @cindex remote serial stub, initialization
18654 This routine arranges for @code{handle_exception} to run when your
18655 program stops. You must call this subroutine explicitly in your
18656 program's startup code.
18658 @item handle_exception
18659 @findex handle_exception
18660 @cindex remote serial stub, main routine
18661 This is the central workhorse, but your program never calls it
18662 explicitly---the setup code arranges for @code{handle_exception} to
18663 run when a trap is triggered.
18665 @code{handle_exception} takes control when your program stops during
18666 execution (for example, on a breakpoint), and mediates communications
18667 with @value{GDBN} on the host machine. This is where the communications
18668 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18669 representative on the target machine. It begins by sending summary
18670 information on the state of your program, then continues to execute,
18671 retrieving and transmitting any information @value{GDBN} needs, until you
18672 execute a @value{GDBN} command that makes your program resume; at that point,
18673 @code{handle_exception} returns control to your own code on the target
18677 @cindex @code{breakpoint} subroutine, remote
18678 Use this auxiliary subroutine to make your program contain a
18679 breakpoint. Depending on the particular situation, this may be the only
18680 way for @value{GDBN} to get control. For instance, if your target
18681 machine has some sort of interrupt button, you won't need to call this;
18682 pressing the interrupt button transfers control to
18683 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18684 simply receiving characters on the serial port may also trigger a trap;
18685 again, in that situation, you don't need to call @code{breakpoint} from
18686 your own program---simply running @samp{target remote} from the host
18687 @value{GDBN} session gets control.
18689 Call @code{breakpoint} if none of these is true, or if you simply want
18690 to make certain your program stops at a predetermined point for the
18691 start of your debugging session.
18694 @node Bootstrapping
18695 @subsection What You Must Do for the Stub
18697 @cindex remote stub, support routines
18698 The debugging stubs that come with @value{GDBN} are set up for a particular
18699 chip architecture, but they have no information about the rest of your
18700 debugging target machine.
18702 First of all you need to tell the stub how to communicate with the
18706 @item int getDebugChar()
18707 @findex getDebugChar
18708 Write this subroutine to read a single character from the serial port.
18709 It may be identical to @code{getchar} for your target system; a
18710 different name is used to allow you to distinguish the two if you wish.
18712 @item void putDebugChar(int)
18713 @findex putDebugChar
18714 Write this subroutine to write a single character to the serial port.
18715 It may be identical to @code{putchar} for your target system; a
18716 different name is used to allow you to distinguish the two if you wish.
18719 @cindex control C, and remote debugging
18720 @cindex interrupting remote targets
18721 If you want @value{GDBN} to be able to stop your program while it is
18722 running, you need to use an interrupt-driven serial driver, and arrange
18723 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18724 character). That is the character which @value{GDBN} uses to tell the
18725 remote system to stop.
18727 Getting the debugging target to return the proper status to @value{GDBN}
18728 probably requires changes to the standard stub; one quick and dirty way
18729 is to just execute a breakpoint instruction (the ``dirty'' part is that
18730 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18732 Other routines you need to supply are:
18735 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18736 @findex exceptionHandler
18737 Write this function to install @var{exception_address} in the exception
18738 handling tables. You need to do this because the stub does not have any
18739 way of knowing what the exception handling tables on your target system
18740 are like (for example, the processor's table might be in @sc{rom},
18741 containing entries which point to a table in @sc{ram}).
18742 @var{exception_number} is the exception number which should be changed;
18743 its meaning is architecture-dependent (for example, different numbers
18744 might represent divide by zero, misaligned access, etc). When this
18745 exception occurs, control should be transferred directly to
18746 @var{exception_address}, and the processor state (stack, registers,
18747 and so on) should be just as it is when a processor exception occurs. So if
18748 you want to use a jump instruction to reach @var{exception_address}, it
18749 should be a simple jump, not a jump to subroutine.
18751 For the 386, @var{exception_address} should be installed as an interrupt
18752 gate so that interrupts are masked while the handler runs. The gate
18753 should be at privilege level 0 (the most privileged level). The
18754 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18755 help from @code{exceptionHandler}.
18757 @item void flush_i_cache()
18758 @findex flush_i_cache
18759 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18760 instruction cache, if any, on your target machine. If there is no
18761 instruction cache, this subroutine may be a no-op.
18763 On target machines that have instruction caches, @value{GDBN} requires this
18764 function to make certain that the state of your program is stable.
18768 You must also make sure this library routine is available:
18771 @item void *memset(void *, int, int)
18773 This is the standard library function @code{memset} that sets an area of
18774 memory to a known value. If you have one of the free versions of
18775 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18776 either obtain it from your hardware manufacturer, or write your own.
18779 If you do not use the GNU C compiler, you may need other standard
18780 library subroutines as well; this varies from one stub to another,
18781 but in general the stubs are likely to use any of the common library
18782 subroutines which @code{@value{NGCC}} generates as inline code.
18785 @node Debug Session
18786 @subsection Putting it All Together
18788 @cindex remote serial debugging summary
18789 In summary, when your program is ready to debug, you must follow these
18794 Make sure you have defined the supporting low-level routines
18795 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18797 @code{getDebugChar}, @code{putDebugChar},
18798 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18802 Insert these lines in your program's startup code, before the main
18803 procedure is called:
18810 On some machines, when a breakpoint trap is raised, the hardware
18811 automatically makes the PC point to the instruction after the
18812 breakpoint. If your machine doesn't do that, you may need to adjust
18813 @code{handle_exception} to arrange for it to return to the instruction
18814 after the breakpoint on this first invocation, so that your program
18815 doesn't keep hitting the initial breakpoint instead of making
18819 For the 680x0 stub only, you need to provide a variable called
18820 @code{exceptionHook}. Normally you just use:
18823 void (*exceptionHook)() = 0;
18827 but if before calling @code{set_debug_traps}, you set it to point to a
18828 function in your program, that function is called when
18829 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18830 error). The function indicated by @code{exceptionHook} is called with
18831 one parameter: an @code{int} which is the exception number.
18834 Compile and link together: your program, the @value{GDBN} debugging stub for
18835 your target architecture, and the supporting subroutines.
18838 Make sure you have a serial connection between your target machine and
18839 the @value{GDBN} host, and identify the serial port on the host.
18842 @c The "remote" target now provides a `load' command, so we should
18843 @c document that. FIXME.
18844 Download your program to your target machine (or get it there by
18845 whatever means the manufacturer provides), and start it.
18848 Start @value{GDBN} on the host, and connect to the target
18849 (@pxref{Connecting,,Connecting to a Remote Target}).
18853 @node Configurations
18854 @chapter Configuration-Specific Information
18856 While nearly all @value{GDBN} commands are available for all native and
18857 cross versions of the debugger, there are some exceptions. This chapter
18858 describes things that are only available in certain configurations.
18860 There are three major categories of configurations: native
18861 configurations, where the host and target are the same, embedded
18862 operating system configurations, which are usually the same for several
18863 different processor architectures, and bare embedded processors, which
18864 are quite different from each other.
18869 * Embedded Processors::
18876 This section describes details specific to particular native
18881 * BSD libkvm Interface:: Debugging BSD kernel memory images
18882 * SVR4 Process Information:: SVR4 process information
18883 * DJGPP Native:: Features specific to the DJGPP port
18884 * Cygwin Native:: Features specific to the Cygwin port
18885 * Hurd Native:: Features specific to @sc{gnu} Hurd
18886 * Darwin:: Features specific to Darwin
18892 On HP-UX systems, if you refer to a function or variable name that
18893 begins with a dollar sign, @value{GDBN} searches for a user or system
18894 name first, before it searches for a convenience variable.
18897 @node BSD libkvm Interface
18898 @subsection BSD libkvm Interface
18901 @cindex kernel memory image
18902 @cindex kernel crash dump
18904 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18905 interface that provides a uniform interface for accessing kernel virtual
18906 memory images, including live systems and crash dumps. @value{GDBN}
18907 uses this interface to allow you to debug live kernels and kernel crash
18908 dumps on many native BSD configurations. This is implemented as a
18909 special @code{kvm} debugging target. For debugging a live system, load
18910 the currently running kernel into @value{GDBN} and connect to the
18914 (@value{GDBP}) @b{target kvm}
18917 For debugging crash dumps, provide the file name of the crash dump as an
18921 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18924 Once connected to the @code{kvm} target, the following commands are
18930 Set current context from the @dfn{Process Control Block} (PCB) address.
18933 Set current context from proc address. This command isn't available on
18934 modern FreeBSD systems.
18937 @node SVR4 Process Information
18938 @subsection SVR4 Process Information
18940 @cindex examine process image
18941 @cindex process info via @file{/proc}
18943 Many versions of SVR4 and compatible systems provide a facility called
18944 @samp{/proc} that can be used to examine the image of a running
18945 process using file-system subroutines.
18947 If @value{GDBN} is configured for an operating system with this
18948 facility, the command @code{info proc} is available to report
18949 information about the process running your program, or about any
18950 process running on your system. This includes, as of this writing,
18951 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18952 not HP-UX, for example.
18954 This command may also work on core files that were created on a system
18955 that has the @samp{/proc} facility.
18961 @itemx info proc @var{process-id}
18962 Summarize available information about any running process. If a
18963 process ID is specified by @var{process-id}, display information about
18964 that process; otherwise display information about the program being
18965 debugged. The summary includes the debugged process ID, the command
18966 line used to invoke it, its current working directory, and its
18967 executable file's absolute file name.
18969 On some systems, @var{process-id} can be of the form
18970 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18971 within a process. If the optional @var{pid} part is missing, it means
18972 a thread from the process being debugged (the leading @samp{/} still
18973 needs to be present, or else @value{GDBN} will interpret the number as
18974 a process ID rather than a thread ID).
18976 @item info proc cmdline
18977 @cindex info proc cmdline
18978 Show the original command line of the process. This command is
18979 specific to @sc{gnu}/Linux.
18981 @item info proc cwd
18982 @cindex info proc cwd
18983 Show the current working directory of the process. This command is
18984 specific to @sc{gnu}/Linux.
18986 @item info proc exe
18987 @cindex info proc exe
18988 Show the name of executable of the process. This command is specific
18991 @item info proc mappings
18992 @cindex memory address space mappings
18993 Report the memory address space ranges accessible in the program, with
18994 information on whether the process has read, write, or execute access
18995 rights to each range. On @sc{gnu}/Linux systems, each memory range
18996 includes the object file which is mapped to that range, instead of the
18997 memory access rights to that range.
18999 @item info proc stat
19000 @itemx info proc status
19001 @cindex process detailed status information
19002 These subcommands are specific to @sc{gnu}/Linux systems. They show
19003 the process-related information, including the user ID and group ID;
19004 how many threads are there in the process; its virtual memory usage;
19005 the signals that are pending, blocked, and ignored; its TTY; its
19006 consumption of system and user time; its stack size; its @samp{nice}
19007 value; etc. For more information, see the @samp{proc} man page
19008 (type @kbd{man 5 proc} from your shell prompt).
19010 @item info proc all
19011 Show all the information about the process described under all of the
19012 above @code{info proc} subcommands.
19015 @comment These sub-options of 'info proc' were not included when
19016 @comment procfs.c was re-written. Keep their descriptions around
19017 @comment against the day when someone finds the time to put them back in.
19018 @kindex info proc times
19019 @item info proc times
19020 Starting time, user CPU time, and system CPU time for your program and
19023 @kindex info proc id
19025 Report on the process IDs related to your program: its own process ID,
19026 the ID of its parent, the process group ID, and the session ID.
19029 @item set procfs-trace
19030 @kindex set procfs-trace
19031 @cindex @code{procfs} API calls
19032 This command enables and disables tracing of @code{procfs} API calls.
19034 @item show procfs-trace
19035 @kindex show procfs-trace
19036 Show the current state of @code{procfs} API call tracing.
19038 @item set procfs-file @var{file}
19039 @kindex set procfs-file
19040 Tell @value{GDBN} to write @code{procfs} API trace to the named
19041 @var{file}. @value{GDBN} appends the trace info to the previous
19042 contents of the file. The default is to display the trace on the
19045 @item show procfs-file
19046 @kindex show procfs-file
19047 Show the file to which @code{procfs} API trace is written.
19049 @item proc-trace-entry
19050 @itemx proc-trace-exit
19051 @itemx proc-untrace-entry
19052 @itemx proc-untrace-exit
19053 @kindex proc-trace-entry
19054 @kindex proc-trace-exit
19055 @kindex proc-untrace-entry
19056 @kindex proc-untrace-exit
19057 These commands enable and disable tracing of entries into and exits
19058 from the @code{syscall} interface.
19061 @kindex info pidlist
19062 @cindex process list, QNX Neutrino
19063 For QNX Neutrino only, this command displays the list of all the
19064 processes and all the threads within each process.
19067 @kindex info meminfo
19068 @cindex mapinfo list, QNX Neutrino
19069 For QNX Neutrino only, this command displays the list of all mapinfos.
19073 @subsection Features for Debugging @sc{djgpp} Programs
19074 @cindex @sc{djgpp} debugging
19075 @cindex native @sc{djgpp} debugging
19076 @cindex MS-DOS-specific commands
19079 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19080 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19081 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19082 top of real-mode DOS systems and their emulations.
19084 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19085 defines a few commands specific to the @sc{djgpp} port. This
19086 subsection describes those commands.
19091 This is a prefix of @sc{djgpp}-specific commands which print
19092 information about the target system and important OS structures.
19095 @cindex MS-DOS system info
19096 @cindex free memory information (MS-DOS)
19097 @item info dos sysinfo
19098 This command displays assorted information about the underlying
19099 platform: the CPU type and features, the OS version and flavor, the
19100 DPMI version, and the available conventional and DPMI memory.
19105 @cindex segment descriptor tables
19106 @cindex descriptor tables display
19108 @itemx info dos ldt
19109 @itemx info dos idt
19110 These 3 commands display entries from, respectively, Global, Local,
19111 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19112 tables are data structures which store a descriptor for each segment
19113 that is currently in use. The segment's selector is an index into a
19114 descriptor table; the table entry for that index holds the
19115 descriptor's base address and limit, and its attributes and access
19118 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19119 segment (used for both data and the stack), and a DOS segment (which
19120 allows access to DOS/BIOS data structures and absolute addresses in
19121 conventional memory). However, the DPMI host will usually define
19122 additional segments in order to support the DPMI environment.
19124 @cindex garbled pointers
19125 These commands allow to display entries from the descriptor tables.
19126 Without an argument, all entries from the specified table are
19127 displayed. An argument, which should be an integer expression, means
19128 display a single entry whose index is given by the argument. For
19129 example, here's a convenient way to display information about the
19130 debugged program's data segment:
19133 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19134 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19138 This comes in handy when you want to see whether a pointer is outside
19139 the data segment's limit (i.e.@: @dfn{garbled}).
19141 @cindex page tables display (MS-DOS)
19143 @itemx info dos pte
19144 These two commands display entries from, respectively, the Page
19145 Directory and the Page Tables. Page Directories and Page Tables are
19146 data structures which control how virtual memory addresses are mapped
19147 into physical addresses. A Page Table includes an entry for every
19148 page of memory that is mapped into the program's address space; there
19149 may be several Page Tables, each one holding up to 4096 entries. A
19150 Page Directory has up to 4096 entries, one each for every Page Table
19151 that is currently in use.
19153 Without an argument, @kbd{info dos pde} displays the entire Page
19154 Directory, and @kbd{info dos pte} displays all the entries in all of
19155 the Page Tables. An argument, an integer expression, given to the
19156 @kbd{info dos pde} command means display only that entry from the Page
19157 Directory table. An argument given to the @kbd{info dos pte} command
19158 means display entries from a single Page Table, the one pointed to by
19159 the specified entry in the Page Directory.
19161 @cindex direct memory access (DMA) on MS-DOS
19162 These commands are useful when your program uses @dfn{DMA} (Direct
19163 Memory Access), which needs physical addresses to program the DMA
19166 These commands are supported only with some DPMI servers.
19168 @cindex physical address from linear address
19169 @item info dos address-pte @var{addr}
19170 This command displays the Page Table entry for a specified linear
19171 address. The argument @var{addr} is a linear address which should
19172 already have the appropriate segment's base address added to it,
19173 because this command accepts addresses which may belong to @emph{any}
19174 segment. For example, here's how to display the Page Table entry for
19175 the page where a variable @code{i} is stored:
19178 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19179 @exdent @code{Page Table entry for address 0x11a00d30:}
19180 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19184 This says that @code{i} is stored at offset @code{0xd30} from the page
19185 whose physical base address is @code{0x02698000}, and shows all the
19186 attributes of that page.
19188 Note that you must cast the addresses of variables to a @code{char *},
19189 since otherwise the value of @code{__djgpp_base_address}, the base
19190 address of all variables and functions in a @sc{djgpp} program, will
19191 be added using the rules of C pointer arithmetics: if @code{i} is
19192 declared an @code{int}, @value{GDBN} will add 4 times the value of
19193 @code{__djgpp_base_address} to the address of @code{i}.
19195 Here's another example, it displays the Page Table entry for the
19199 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19200 @exdent @code{Page Table entry for address 0x29110:}
19201 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19205 (The @code{+ 3} offset is because the transfer buffer's address is the
19206 3rd member of the @code{_go32_info_block} structure.) The output
19207 clearly shows that this DPMI server maps the addresses in conventional
19208 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19209 linear (@code{0x29110}) addresses are identical.
19211 This command is supported only with some DPMI servers.
19214 @cindex DOS serial data link, remote debugging
19215 In addition to native debugging, the DJGPP port supports remote
19216 debugging via a serial data link. The following commands are specific
19217 to remote serial debugging in the DJGPP port of @value{GDBN}.
19220 @kindex set com1base
19221 @kindex set com1irq
19222 @kindex set com2base
19223 @kindex set com2irq
19224 @kindex set com3base
19225 @kindex set com3irq
19226 @kindex set com4base
19227 @kindex set com4irq
19228 @item set com1base @var{addr}
19229 This command sets the base I/O port address of the @file{COM1} serial
19232 @item set com1irq @var{irq}
19233 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19234 for the @file{COM1} serial port.
19236 There are similar commands @samp{set com2base}, @samp{set com3irq},
19237 etc.@: for setting the port address and the @code{IRQ} lines for the
19240 @kindex show com1base
19241 @kindex show com1irq
19242 @kindex show com2base
19243 @kindex show com2irq
19244 @kindex show com3base
19245 @kindex show com3irq
19246 @kindex show com4base
19247 @kindex show com4irq
19248 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19249 display the current settings of the base address and the @code{IRQ}
19250 lines used by the COM ports.
19253 @kindex info serial
19254 @cindex DOS serial port status
19255 This command prints the status of the 4 DOS serial ports. For each
19256 port, it prints whether it's active or not, its I/O base address and
19257 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19258 counts of various errors encountered so far.
19262 @node Cygwin Native
19263 @subsection Features for Debugging MS Windows PE Executables
19264 @cindex MS Windows debugging
19265 @cindex native Cygwin debugging
19266 @cindex Cygwin-specific commands
19268 @value{GDBN} supports native debugging of MS Windows programs, including
19269 DLLs with and without symbolic debugging information.
19271 @cindex Ctrl-BREAK, MS-Windows
19272 @cindex interrupt debuggee on MS-Windows
19273 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19274 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19275 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19276 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19277 sequence, which can be used to interrupt the debuggee even if it
19280 There are various additional Cygwin-specific commands, described in
19281 this section. Working with DLLs that have no debugging symbols is
19282 described in @ref{Non-debug DLL Symbols}.
19287 This is a prefix of MS Windows-specific commands which print
19288 information about the target system and important OS structures.
19290 @item info w32 selector
19291 This command displays information returned by
19292 the Win32 API @code{GetThreadSelectorEntry} function.
19293 It takes an optional argument that is evaluated to
19294 a long value to give the information about this given selector.
19295 Without argument, this command displays information
19296 about the six segment registers.
19298 @item info w32 thread-information-block
19299 This command displays thread specific information stored in the
19300 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19301 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19305 This is a Cygwin-specific alias of @code{info shared}.
19307 @kindex dll-symbols
19309 This command loads symbols from a dll similarly to
19310 add-sym command but without the need to specify a base address.
19312 @kindex set cygwin-exceptions
19313 @cindex debugging the Cygwin DLL
19314 @cindex Cygwin DLL, debugging
19315 @item set cygwin-exceptions @var{mode}
19316 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19317 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19318 @value{GDBN} will delay recognition of exceptions, and may ignore some
19319 exceptions which seem to be caused by internal Cygwin DLL
19320 ``bookkeeping''. This option is meant primarily for debugging the
19321 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19322 @value{GDBN} users with false @code{SIGSEGV} signals.
19324 @kindex show cygwin-exceptions
19325 @item show cygwin-exceptions
19326 Displays whether @value{GDBN} will break on exceptions that happen
19327 inside the Cygwin DLL itself.
19329 @kindex set new-console
19330 @item set new-console @var{mode}
19331 If @var{mode} is @code{on} the debuggee will
19332 be started in a new console on next start.
19333 If @var{mode} is @code{off}, the debuggee will
19334 be started in the same console as the debugger.
19336 @kindex show new-console
19337 @item show new-console
19338 Displays whether a new console is used
19339 when the debuggee is started.
19341 @kindex set new-group
19342 @item set new-group @var{mode}
19343 This boolean value controls whether the debuggee should
19344 start a new group or stay in the same group as the debugger.
19345 This affects the way the Windows OS handles
19348 @kindex show new-group
19349 @item show new-group
19350 Displays current value of new-group boolean.
19352 @kindex set debugevents
19353 @item set debugevents
19354 This boolean value adds debug output concerning kernel events related
19355 to the debuggee seen by the debugger. This includes events that
19356 signal thread and process creation and exit, DLL loading and
19357 unloading, console interrupts, and debugging messages produced by the
19358 Windows @code{OutputDebugString} API call.
19360 @kindex set debugexec
19361 @item set debugexec
19362 This boolean value adds debug output concerning execute events
19363 (such as resume thread) seen by the debugger.
19365 @kindex set debugexceptions
19366 @item set debugexceptions
19367 This boolean value adds debug output concerning exceptions in the
19368 debuggee seen by the debugger.
19370 @kindex set debugmemory
19371 @item set debugmemory
19372 This boolean value adds debug output concerning debuggee memory reads
19373 and writes by the debugger.
19377 This boolean values specifies whether the debuggee is called
19378 via a shell or directly (default value is on).
19382 Displays if the debuggee will be started with a shell.
19387 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19390 @node Non-debug DLL Symbols
19391 @subsubsection Support for DLLs without Debugging Symbols
19392 @cindex DLLs with no debugging symbols
19393 @cindex Minimal symbols and DLLs
19395 Very often on windows, some of the DLLs that your program relies on do
19396 not include symbolic debugging information (for example,
19397 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19398 symbols in a DLL, it relies on the minimal amount of symbolic
19399 information contained in the DLL's export table. This section
19400 describes working with such symbols, known internally to @value{GDBN} as
19401 ``minimal symbols''.
19403 Note that before the debugged program has started execution, no DLLs
19404 will have been loaded. The easiest way around this problem is simply to
19405 start the program --- either by setting a breakpoint or letting the
19406 program run once to completion. It is also possible to force
19407 @value{GDBN} to load a particular DLL before starting the executable ---
19408 see the shared library information in @ref{Files}, or the
19409 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19410 explicitly loading symbols from a DLL with no debugging information will
19411 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19412 which may adversely affect symbol lookup performance.
19414 @subsubsection DLL Name Prefixes
19416 In keeping with the naming conventions used by the Microsoft debugging
19417 tools, DLL export symbols are made available with a prefix based on the
19418 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19419 also entered into the symbol table, so @code{CreateFileA} is often
19420 sufficient. In some cases there will be name clashes within a program
19421 (particularly if the executable itself includes full debugging symbols)
19422 necessitating the use of the fully qualified name when referring to the
19423 contents of the DLL. Use single-quotes around the name to avoid the
19424 exclamation mark (``!'') being interpreted as a language operator.
19426 Note that the internal name of the DLL may be all upper-case, even
19427 though the file name of the DLL is lower-case, or vice-versa. Since
19428 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19429 some confusion. If in doubt, try the @code{info functions} and
19430 @code{info variables} commands or even @code{maint print msymbols}
19431 (@pxref{Symbols}). Here's an example:
19434 (@value{GDBP}) info function CreateFileA
19435 All functions matching regular expression "CreateFileA":
19437 Non-debugging symbols:
19438 0x77e885f4 CreateFileA
19439 0x77e885f4 KERNEL32!CreateFileA
19443 (@value{GDBP}) info function !
19444 All functions matching regular expression "!":
19446 Non-debugging symbols:
19447 0x6100114c cygwin1!__assert
19448 0x61004034 cygwin1!_dll_crt0@@0
19449 0x61004240 cygwin1!dll_crt0(per_process *)
19453 @subsubsection Working with Minimal Symbols
19455 Symbols extracted from a DLL's export table do not contain very much
19456 type information. All that @value{GDBN} can do is guess whether a symbol
19457 refers to a function or variable depending on the linker section that
19458 contains the symbol. Also note that the actual contents of the memory
19459 contained in a DLL are not available unless the program is running. This
19460 means that you cannot examine the contents of a variable or disassemble
19461 a function within a DLL without a running program.
19463 Variables are generally treated as pointers and dereferenced
19464 automatically. For this reason, it is often necessary to prefix a
19465 variable name with the address-of operator (``&'') and provide explicit
19466 type information in the command. Here's an example of the type of
19470 (@value{GDBP}) print 'cygwin1!__argv'
19475 (@value{GDBP}) x 'cygwin1!__argv'
19476 0x10021610: "\230y\""
19479 And two possible solutions:
19482 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19483 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19487 (@value{GDBP}) x/2x &'cygwin1!__argv'
19488 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19489 (@value{GDBP}) x/x 0x10021608
19490 0x10021608: 0x0022fd98
19491 (@value{GDBP}) x/s 0x0022fd98
19492 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19495 Setting a break point within a DLL is possible even before the program
19496 starts execution. However, under these circumstances, @value{GDBN} can't
19497 examine the initial instructions of the function in order to skip the
19498 function's frame set-up code. You can work around this by using ``*&''
19499 to set the breakpoint at a raw memory address:
19502 (@value{GDBP}) break *&'python22!PyOS_Readline'
19503 Breakpoint 1 at 0x1e04eff0
19506 The author of these extensions is not entirely convinced that setting a
19507 break point within a shared DLL like @file{kernel32.dll} is completely
19511 @subsection Commands Specific to @sc{gnu} Hurd Systems
19512 @cindex @sc{gnu} Hurd debugging
19514 This subsection describes @value{GDBN} commands specific to the
19515 @sc{gnu} Hurd native debugging.
19520 @kindex set signals@r{, Hurd command}
19521 @kindex set sigs@r{, Hurd command}
19522 This command toggles the state of inferior signal interception by
19523 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19524 affected by this command. @code{sigs} is a shorthand alias for
19529 @kindex show signals@r{, Hurd command}
19530 @kindex show sigs@r{, Hurd command}
19531 Show the current state of intercepting inferior's signals.
19533 @item set signal-thread
19534 @itemx set sigthread
19535 @kindex set signal-thread
19536 @kindex set sigthread
19537 This command tells @value{GDBN} which thread is the @code{libc} signal
19538 thread. That thread is run when a signal is delivered to a running
19539 process. @code{set sigthread} is the shorthand alias of @code{set
19542 @item show signal-thread
19543 @itemx show sigthread
19544 @kindex show signal-thread
19545 @kindex show sigthread
19546 These two commands show which thread will run when the inferior is
19547 delivered a signal.
19550 @kindex set stopped@r{, Hurd command}
19551 This commands tells @value{GDBN} that the inferior process is stopped,
19552 as with the @code{SIGSTOP} signal. The stopped process can be
19553 continued by delivering a signal to it.
19556 @kindex show stopped@r{, Hurd command}
19557 This command shows whether @value{GDBN} thinks the debuggee is
19560 @item set exceptions
19561 @kindex set exceptions@r{, Hurd command}
19562 Use this command to turn off trapping of exceptions in the inferior.
19563 When exception trapping is off, neither breakpoints nor
19564 single-stepping will work. To restore the default, set exception
19567 @item show exceptions
19568 @kindex show exceptions@r{, Hurd command}
19569 Show the current state of trapping exceptions in the inferior.
19571 @item set task pause
19572 @kindex set task@r{, Hurd commands}
19573 @cindex task attributes (@sc{gnu} Hurd)
19574 @cindex pause current task (@sc{gnu} Hurd)
19575 This command toggles task suspension when @value{GDBN} has control.
19576 Setting it to on takes effect immediately, and the task is suspended
19577 whenever @value{GDBN} gets control. Setting it to off will take
19578 effect the next time the inferior is continued. If this option is set
19579 to off, you can use @code{set thread default pause on} or @code{set
19580 thread pause on} (see below) to pause individual threads.
19582 @item show task pause
19583 @kindex show task@r{, Hurd commands}
19584 Show the current state of task suspension.
19586 @item set task detach-suspend-count
19587 @cindex task suspend count
19588 @cindex detach from task, @sc{gnu} Hurd
19589 This command sets the suspend count the task will be left with when
19590 @value{GDBN} detaches from it.
19592 @item show task detach-suspend-count
19593 Show the suspend count the task will be left with when detaching.
19595 @item set task exception-port
19596 @itemx set task excp
19597 @cindex task exception port, @sc{gnu} Hurd
19598 This command sets the task exception port to which @value{GDBN} will
19599 forward exceptions. The argument should be the value of the @dfn{send
19600 rights} of the task. @code{set task excp} is a shorthand alias.
19602 @item set noninvasive
19603 @cindex noninvasive task options
19604 This command switches @value{GDBN} to a mode that is the least
19605 invasive as far as interfering with the inferior is concerned. This
19606 is the same as using @code{set task pause}, @code{set exceptions}, and
19607 @code{set signals} to values opposite to the defaults.
19609 @item info send-rights
19610 @itemx info receive-rights
19611 @itemx info port-rights
19612 @itemx info port-sets
19613 @itemx info dead-names
19616 @cindex send rights, @sc{gnu} Hurd
19617 @cindex receive rights, @sc{gnu} Hurd
19618 @cindex port rights, @sc{gnu} Hurd
19619 @cindex port sets, @sc{gnu} Hurd
19620 @cindex dead names, @sc{gnu} Hurd
19621 These commands display information about, respectively, send rights,
19622 receive rights, port rights, port sets, and dead names of a task.
19623 There are also shorthand aliases: @code{info ports} for @code{info
19624 port-rights} and @code{info psets} for @code{info port-sets}.
19626 @item set thread pause
19627 @kindex set thread@r{, Hurd command}
19628 @cindex thread properties, @sc{gnu} Hurd
19629 @cindex pause current thread (@sc{gnu} Hurd)
19630 This command toggles current thread suspension when @value{GDBN} has
19631 control. Setting it to on takes effect immediately, and the current
19632 thread is suspended whenever @value{GDBN} gets control. Setting it to
19633 off will take effect the next time the inferior is continued.
19634 Normally, this command has no effect, since when @value{GDBN} has
19635 control, the whole task is suspended. However, if you used @code{set
19636 task pause off} (see above), this command comes in handy to suspend
19637 only the current thread.
19639 @item show thread pause
19640 @kindex show thread@r{, Hurd command}
19641 This command shows the state of current thread suspension.
19643 @item set thread run
19644 This command sets whether the current thread is allowed to run.
19646 @item show thread run
19647 Show whether the current thread is allowed to run.
19649 @item set thread detach-suspend-count
19650 @cindex thread suspend count, @sc{gnu} Hurd
19651 @cindex detach from thread, @sc{gnu} Hurd
19652 This command sets the suspend count @value{GDBN} will leave on a
19653 thread when detaching. This number is relative to the suspend count
19654 found by @value{GDBN} when it notices the thread; use @code{set thread
19655 takeover-suspend-count} to force it to an absolute value.
19657 @item show thread detach-suspend-count
19658 Show the suspend count @value{GDBN} will leave on the thread when
19661 @item set thread exception-port
19662 @itemx set thread excp
19663 Set the thread exception port to which to forward exceptions. This
19664 overrides the port set by @code{set task exception-port} (see above).
19665 @code{set thread excp} is the shorthand alias.
19667 @item set thread takeover-suspend-count
19668 Normally, @value{GDBN}'s thread suspend counts are relative to the
19669 value @value{GDBN} finds when it notices each thread. This command
19670 changes the suspend counts to be absolute instead.
19672 @item set thread default
19673 @itemx show thread default
19674 @cindex thread default settings, @sc{gnu} Hurd
19675 Each of the above @code{set thread} commands has a @code{set thread
19676 default} counterpart (e.g., @code{set thread default pause}, @code{set
19677 thread default exception-port}, etc.). The @code{thread default}
19678 variety of commands sets the default thread properties for all
19679 threads; you can then change the properties of individual threads with
19680 the non-default commands.
19687 @value{GDBN} provides the following commands specific to the Darwin target:
19690 @item set debug darwin @var{num}
19691 @kindex set debug darwin
19692 When set to a non zero value, enables debugging messages specific to
19693 the Darwin support. Higher values produce more verbose output.
19695 @item show debug darwin
19696 @kindex show debug darwin
19697 Show the current state of Darwin messages.
19699 @item set debug mach-o @var{num}
19700 @kindex set debug mach-o
19701 When set to a non zero value, enables debugging messages while
19702 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19703 file format used on Darwin for object and executable files.) Higher
19704 values produce more verbose output. This is a command to diagnose
19705 problems internal to @value{GDBN} and should not be needed in normal
19708 @item show debug mach-o
19709 @kindex show debug mach-o
19710 Show the current state of Mach-O file messages.
19712 @item set mach-exceptions on
19713 @itemx set mach-exceptions off
19714 @kindex set mach-exceptions
19715 On Darwin, faults are first reported as a Mach exception and are then
19716 mapped to a Posix signal. Use this command to turn on trapping of
19717 Mach exceptions in the inferior. This might be sometimes useful to
19718 better understand the cause of a fault. The default is off.
19720 @item show mach-exceptions
19721 @kindex show mach-exceptions
19722 Show the current state of exceptions trapping.
19727 @section Embedded Operating Systems
19729 This section describes configurations involving the debugging of
19730 embedded operating systems that are available for several different
19734 * VxWorks:: Using @value{GDBN} with VxWorks
19737 @value{GDBN} includes the ability to debug programs running on
19738 various real-time operating systems.
19741 @subsection Using @value{GDBN} with VxWorks
19747 @kindex target vxworks
19748 @item target vxworks @var{machinename}
19749 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19750 is the target system's machine name or IP address.
19754 On VxWorks, @code{load} links @var{filename} dynamically on the
19755 current target system as well as adding its symbols in @value{GDBN}.
19757 @value{GDBN} enables developers to spawn and debug tasks running on networked
19758 VxWorks targets from a Unix host. Already-running tasks spawned from
19759 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19760 both the Unix host and on the VxWorks target. The program
19761 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19762 installed with the name @code{vxgdb}, to distinguish it from a
19763 @value{GDBN} for debugging programs on the host itself.)
19766 @item VxWorks-timeout @var{args}
19767 @kindex vxworks-timeout
19768 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19769 This option is set by the user, and @var{args} represents the number of
19770 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19771 your VxWorks target is a slow software simulator or is on the far side
19772 of a thin network line.
19775 The following information on connecting to VxWorks was current when
19776 this manual was produced; newer releases of VxWorks may use revised
19779 @findex INCLUDE_RDB
19780 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19781 to include the remote debugging interface routines in the VxWorks
19782 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19783 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19784 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19785 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19786 information on configuring and remaking VxWorks, see the manufacturer's
19788 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19790 Once you have included @file{rdb.a} in your VxWorks system image and set
19791 your Unix execution search path to find @value{GDBN}, you are ready to
19792 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19793 @code{vxgdb}, depending on your installation).
19795 @value{GDBN} comes up showing the prompt:
19802 * VxWorks Connection:: Connecting to VxWorks
19803 * VxWorks Download:: VxWorks download
19804 * VxWorks Attach:: Running tasks
19807 @node VxWorks Connection
19808 @subsubsection Connecting to VxWorks
19810 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19811 network. To connect to a target whose host name is ``@code{tt}'', type:
19814 (vxgdb) target vxworks tt
19818 @value{GDBN} displays messages like these:
19821 Attaching remote machine across net...
19826 @value{GDBN} then attempts to read the symbol tables of any object modules
19827 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19828 these files by searching the directories listed in the command search
19829 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19830 to find an object file, it displays a message such as:
19833 prog.o: No such file or directory.
19836 When this happens, add the appropriate directory to the search path with
19837 the @value{GDBN} command @code{path}, and execute the @code{target}
19840 @node VxWorks Download
19841 @subsubsection VxWorks Download
19843 @cindex download to VxWorks
19844 If you have connected to the VxWorks target and you want to debug an
19845 object that has not yet been loaded, you can use the @value{GDBN}
19846 @code{load} command to download a file from Unix to VxWorks
19847 incrementally. The object file given as an argument to the @code{load}
19848 command is actually opened twice: first by the VxWorks target in order
19849 to download the code, then by @value{GDBN} in order to read the symbol
19850 table. This can lead to problems if the current working directories on
19851 the two systems differ. If both systems have NFS mounted the same
19852 filesystems, you can avoid these problems by using absolute paths.
19853 Otherwise, it is simplest to set the working directory on both systems
19854 to the directory in which the object file resides, and then to reference
19855 the file by its name, without any path. For instance, a program
19856 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19857 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19858 program, type this on VxWorks:
19861 -> cd "@var{vxpath}/vw/demo/rdb"
19865 Then, in @value{GDBN}, type:
19868 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19869 (vxgdb) load prog.o
19872 @value{GDBN} displays a response similar to this:
19875 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19878 You can also use the @code{load} command to reload an object module
19879 after editing and recompiling the corresponding source file. Note that
19880 this makes @value{GDBN} delete all currently-defined breakpoints,
19881 auto-displays, and convenience variables, and to clear the value
19882 history. (This is necessary in order to preserve the integrity of
19883 debugger's data structures that reference the target system's symbol
19886 @node VxWorks Attach
19887 @subsubsection Running Tasks
19889 @cindex running VxWorks tasks
19890 You can also attach to an existing task using the @code{attach} command as
19894 (vxgdb) attach @var{task}
19898 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19899 or suspended when you attach to it. Running tasks are suspended at
19900 the time of attachment.
19902 @node Embedded Processors
19903 @section Embedded Processors
19905 This section goes into details specific to particular embedded
19908 @cindex send command to simulator
19909 Whenever a specific embedded processor has a simulator, @value{GDBN}
19910 allows to send an arbitrary command to the simulator.
19913 @item sim @var{command}
19914 @kindex sim@r{, a command}
19915 Send an arbitrary @var{command} string to the simulator. Consult the
19916 documentation for the specific simulator in use for information about
19917 acceptable commands.
19923 * M32R/D:: Renesas M32R/D
19924 * M68K:: Motorola M68K
19925 * MicroBlaze:: Xilinx MicroBlaze
19926 * MIPS Embedded:: MIPS Embedded
19927 * PowerPC Embedded:: PowerPC Embedded
19928 * PA:: HP PA Embedded
19929 * Sparclet:: Tsqware Sparclet
19930 * Sparclite:: Fujitsu Sparclite
19931 * Z8000:: Zilog Z8000
19934 * Super-H:: Renesas Super-H
19943 @item target rdi @var{dev}
19944 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19945 use this target to communicate with both boards running the Angel
19946 monitor, or with the EmbeddedICE JTAG debug device.
19949 @item target rdp @var{dev}
19954 @value{GDBN} provides the following ARM-specific commands:
19957 @item set arm disassembler
19959 This commands selects from a list of disassembly styles. The
19960 @code{"std"} style is the standard style.
19962 @item show arm disassembler
19964 Show the current disassembly style.
19966 @item set arm apcs32
19967 @cindex ARM 32-bit mode
19968 This command toggles ARM operation mode between 32-bit and 26-bit.
19970 @item show arm apcs32
19971 Display the current usage of the ARM 32-bit mode.
19973 @item set arm fpu @var{fputype}
19974 This command sets the ARM floating-point unit (FPU) type. The
19975 argument @var{fputype} can be one of these:
19979 Determine the FPU type by querying the OS ABI.
19981 Software FPU, with mixed-endian doubles on little-endian ARM
19984 GCC-compiled FPA co-processor.
19986 Software FPU with pure-endian doubles.
19992 Show the current type of the FPU.
19995 This command forces @value{GDBN} to use the specified ABI.
19998 Show the currently used ABI.
20000 @item set arm fallback-mode (arm|thumb|auto)
20001 @value{GDBN} uses the symbol table, when available, to determine
20002 whether instructions are ARM or Thumb. This command controls
20003 @value{GDBN}'s default behavior when the symbol table is not
20004 available. The default is @samp{auto}, which causes @value{GDBN} to
20005 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20008 @item show arm fallback-mode
20009 Show the current fallback instruction mode.
20011 @item set arm force-mode (arm|thumb|auto)
20012 This command overrides use of the symbol table to determine whether
20013 instructions are ARM or Thumb. The default is @samp{auto}, which
20014 causes @value{GDBN} to use the symbol table and then the setting
20015 of @samp{set arm fallback-mode}.
20017 @item show arm force-mode
20018 Show the current forced instruction mode.
20020 @item set debug arm
20021 Toggle whether to display ARM-specific debugging messages from the ARM
20022 target support subsystem.
20024 @item show debug arm
20025 Show whether ARM-specific debugging messages are enabled.
20028 The following commands are available when an ARM target is debugged
20029 using the RDI interface:
20032 @item rdilogfile @r{[}@var{file}@r{]}
20034 @cindex ADP (Angel Debugger Protocol) logging
20035 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20036 With an argument, sets the log file to the specified @var{file}. With
20037 no argument, show the current log file name. The default log file is
20040 @item rdilogenable @r{[}@var{arg}@r{]}
20041 @kindex rdilogenable
20042 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20043 enables logging, with an argument 0 or @code{"no"} disables it. With
20044 no arguments displays the current setting. When logging is enabled,
20045 ADP packets exchanged between @value{GDBN} and the RDI target device
20046 are logged to a file.
20048 @item set rdiromatzero
20049 @kindex set rdiromatzero
20050 @cindex ROM at zero address, RDI
20051 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20052 vector catching is disabled, so that zero address can be used. If off
20053 (the default), vector catching is enabled. For this command to take
20054 effect, it needs to be invoked prior to the @code{target rdi} command.
20056 @item show rdiromatzero
20057 @kindex show rdiromatzero
20058 Show the current setting of ROM at zero address.
20060 @item set rdiheartbeat
20061 @kindex set rdiheartbeat
20062 @cindex RDI heartbeat
20063 Enable or disable RDI heartbeat packets. It is not recommended to
20064 turn on this option, since it confuses ARM and EPI JTAG interface, as
20065 well as the Angel monitor.
20067 @item show rdiheartbeat
20068 @kindex show rdiheartbeat
20069 Show the setting of RDI heartbeat packets.
20073 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20074 The @value{GDBN} ARM simulator accepts the following optional arguments.
20077 @item --swi-support=@var{type}
20078 Tell the simulator which SWI interfaces to support.
20079 @var{type} may be a comma separated list of the following values.
20080 The default value is @code{all}.
20093 @subsection Renesas M32R/D and M32R/SDI
20096 @kindex target m32r
20097 @item target m32r @var{dev}
20098 Renesas M32R/D ROM monitor.
20100 @kindex target m32rsdi
20101 @item target m32rsdi @var{dev}
20102 Renesas M32R SDI server, connected via parallel port to the board.
20105 The following @value{GDBN} commands are specific to the M32R monitor:
20108 @item set download-path @var{path}
20109 @kindex set download-path
20110 @cindex find downloadable @sc{srec} files (M32R)
20111 Set the default path for finding downloadable @sc{srec} files.
20113 @item show download-path
20114 @kindex show download-path
20115 Show the default path for downloadable @sc{srec} files.
20117 @item set board-address @var{addr}
20118 @kindex set board-address
20119 @cindex M32-EVA target board address
20120 Set the IP address for the M32R-EVA target board.
20122 @item show board-address
20123 @kindex show board-address
20124 Show the current IP address of the target board.
20126 @item set server-address @var{addr}
20127 @kindex set server-address
20128 @cindex download server address (M32R)
20129 Set the IP address for the download server, which is the @value{GDBN}'s
20132 @item show server-address
20133 @kindex show server-address
20134 Display the IP address of the download server.
20136 @item upload @r{[}@var{file}@r{]}
20137 @kindex upload@r{, M32R}
20138 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20139 upload capability. If no @var{file} argument is given, the current
20140 executable file is uploaded.
20142 @item tload @r{[}@var{file}@r{]}
20143 @kindex tload@r{, M32R}
20144 Test the @code{upload} command.
20147 The following commands are available for M32R/SDI:
20152 @cindex reset SDI connection, M32R
20153 This command resets the SDI connection.
20157 This command shows the SDI connection status.
20160 @kindex debug_chaos
20161 @cindex M32R/Chaos debugging
20162 Instructs the remote that M32R/Chaos debugging is to be used.
20164 @item use_debug_dma
20165 @kindex use_debug_dma
20166 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20169 @kindex use_mon_code
20170 Instructs the remote to use the MON_CODE method of accessing memory.
20173 @kindex use_ib_break
20174 Instructs the remote to set breakpoints by IB break.
20176 @item use_dbt_break
20177 @kindex use_dbt_break
20178 Instructs the remote to set breakpoints by DBT.
20184 The Motorola m68k configuration includes ColdFire support, and a
20185 target command for the following ROM monitor.
20189 @kindex target dbug
20190 @item target dbug @var{dev}
20191 dBUG ROM monitor for Motorola ColdFire.
20196 @subsection MicroBlaze
20197 @cindex Xilinx MicroBlaze
20198 @cindex XMD, Xilinx Microprocessor Debugger
20200 The MicroBlaze is a soft-core processor supported on various Xilinx
20201 FPGAs, such as Spartan or Virtex series. Boards with these processors
20202 usually have JTAG ports which connect to a host system running the Xilinx
20203 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20204 This host system is used to download the configuration bitstream to
20205 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20206 communicates with the target board using the JTAG interface and
20207 presents a @code{gdbserver} interface to the board. By default
20208 @code{xmd} uses port @code{1234}. (While it is possible to change
20209 this default port, it requires the use of undocumented @code{xmd}
20210 commands. Contact Xilinx support if you need to do this.)
20212 Use these GDB commands to connect to the MicroBlaze target processor.
20215 @item target remote :1234
20216 Use this command to connect to the target if you are running @value{GDBN}
20217 on the same system as @code{xmd}.
20219 @item target remote @var{xmd-host}:1234
20220 Use this command to connect to the target if it is connected to @code{xmd}
20221 running on a different system named @var{xmd-host}.
20224 Use this command to download a program to the MicroBlaze target.
20226 @item set debug microblaze @var{n}
20227 Enable MicroBlaze-specific debugging messages if non-zero.
20229 @item show debug microblaze @var{n}
20230 Show MicroBlaze-specific debugging level.
20233 @node MIPS Embedded
20234 @subsection @acronym{MIPS} Embedded
20236 @cindex @acronym{MIPS} boards
20237 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20238 @acronym{MIPS} board attached to a serial line. This is available when
20239 you configure @value{GDBN} with @samp{--target=mips-elf}.
20242 Use these @value{GDBN} commands to specify the connection to your target board:
20245 @item target mips @var{port}
20246 @kindex target mips @var{port}
20247 To run a program on the board, start up @code{@value{GDBP}} with the
20248 name of your program as the argument. To connect to the board, use the
20249 command @samp{target mips @var{port}}, where @var{port} is the name of
20250 the serial port connected to the board. If the program has not already
20251 been downloaded to the board, you may use the @code{load} command to
20252 download it. You can then use all the usual @value{GDBN} commands.
20254 For example, this sequence connects to the target board through a serial
20255 port, and loads and runs a program called @var{prog} through the
20259 host$ @value{GDBP} @var{prog}
20260 @value{GDBN} is free software and @dots{}
20261 (@value{GDBP}) target mips /dev/ttyb
20262 (@value{GDBP}) load @var{prog}
20266 @item target mips @var{hostname}:@var{portnumber}
20267 On some @value{GDBN} host configurations, you can specify a TCP
20268 connection (for instance, to a serial line managed by a terminal
20269 concentrator) instead of a serial port, using the syntax
20270 @samp{@var{hostname}:@var{portnumber}}.
20272 @item target pmon @var{port}
20273 @kindex target pmon @var{port}
20276 @item target ddb @var{port}
20277 @kindex target ddb @var{port}
20278 NEC's DDB variant of PMON for Vr4300.
20280 @item target lsi @var{port}
20281 @kindex target lsi @var{port}
20282 LSI variant of PMON.
20284 @kindex target r3900
20285 @item target r3900 @var{dev}
20286 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20288 @kindex target array
20289 @item target array @var{dev}
20290 Array Tech LSI33K RAID controller board.
20296 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20299 @item set mipsfpu double
20300 @itemx set mipsfpu single
20301 @itemx set mipsfpu none
20302 @itemx set mipsfpu auto
20303 @itemx show mipsfpu
20304 @kindex set mipsfpu
20305 @kindex show mipsfpu
20306 @cindex @acronym{MIPS} remote floating point
20307 @cindex floating point, @acronym{MIPS} remote
20308 If your target board does not support the @acronym{MIPS} floating point
20309 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20310 need this, you may wish to put the command in your @value{GDBN} init
20311 file). This tells @value{GDBN} how to find the return value of
20312 functions which return floating point values. It also allows
20313 @value{GDBN} to avoid saving the floating point registers when calling
20314 functions on the board. If you are using a floating point coprocessor
20315 with only single precision floating point support, as on the @sc{r4650}
20316 processor, use the command @samp{set mipsfpu single}. The default
20317 double precision floating point coprocessor may be selected using
20318 @samp{set mipsfpu double}.
20320 In previous versions the only choices were double precision or no
20321 floating point, so @samp{set mipsfpu on} will select double precision
20322 and @samp{set mipsfpu off} will select no floating point.
20324 As usual, you can inquire about the @code{mipsfpu} variable with
20325 @samp{show mipsfpu}.
20327 @item set timeout @var{seconds}
20328 @itemx set retransmit-timeout @var{seconds}
20329 @itemx show timeout
20330 @itemx show retransmit-timeout
20331 @cindex @code{timeout}, @acronym{MIPS} protocol
20332 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20333 @kindex set timeout
20334 @kindex show timeout
20335 @kindex set retransmit-timeout
20336 @kindex show retransmit-timeout
20337 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20338 remote protocol, with the @code{set timeout @var{seconds}} command. The
20339 default is 5 seconds. Similarly, you can control the timeout used while
20340 waiting for an acknowledgment of a packet with the @code{set
20341 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20342 You can inspect both values with @code{show timeout} and @code{show
20343 retransmit-timeout}. (These commands are @emph{only} available when
20344 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20346 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20347 is waiting for your program to stop. In that case, @value{GDBN} waits
20348 forever because it has no way of knowing how long the program is going
20349 to run before stopping.
20351 @item set syn-garbage-limit @var{num}
20352 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20353 @cindex synchronize with remote @acronym{MIPS} target
20354 Limit the maximum number of characters @value{GDBN} should ignore when
20355 it tries to synchronize with the remote target. The default is 10
20356 characters. Setting the limit to -1 means there's no limit.
20358 @item show syn-garbage-limit
20359 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20360 Show the current limit on the number of characters to ignore when
20361 trying to synchronize with the remote system.
20363 @item set monitor-prompt @var{prompt}
20364 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20365 @cindex remote monitor prompt
20366 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20367 remote monitor. The default depends on the target:
20377 @item show monitor-prompt
20378 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20379 Show the current strings @value{GDBN} expects as the prompt from the
20382 @item set monitor-warnings
20383 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20384 Enable or disable monitor warnings about hardware breakpoints. This
20385 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20386 display warning messages whose codes are returned by the @code{lsi}
20387 PMON monitor for breakpoint commands.
20389 @item show monitor-warnings
20390 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20391 Show the current setting of printing monitor warnings.
20393 @item pmon @var{command}
20394 @kindex pmon@r{, @acronym{MIPS} remote}
20395 @cindex send PMON command
20396 This command allows sending an arbitrary @var{command} string to the
20397 monitor. The monitor must be in debug mode for this to work.
20400 @node PowerPC Embedded
20401 @subsection PowerPC Embedded
20403 @cindex DVC register
20404 @value{GDBN} supports using the DVC (Data Value Compare) register to
20405 implement in hardware simple hardware watchpoint conditions of the form:
20408 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20409 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20412 The DVC register will be automatically used when @value{GDBN} detects
20413 such pattern in a condition expression, and the created watchpoint uses one
20414 debug register (either the @code{exact-watchpoints} option is on and the
20415 variable is scalar, or the variable has a length of one byte). This feature
20416 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20419 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20420 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20421 in which case watchpoints using only one debug register are created when
20422 watching variables of scalar types.
20424 You can create an artificial array to watch an arbitrary memory
20425 region using one of the following commands (@pxref{Expressions}):
20428 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20429 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20432 PowerPC embedded processors support masked watchpoints. See the discussion
20433 about the @code{mask} argument in @ref{Set Watchpoints}.
20435 @cindex ranged breakpoint
20436 PowerPC embedded processors support hardware accelerated
20437 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20438 the inferior whenever it executes an instruction at any address within
20439 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20440 use the @code{break-range} command.
20442 @value{GDBN} provides the following PowerPC-specific commands:
20445 @kindex break-range
20446 @item break-range @var{start-location}, @var{end-location}
20447 Set a breakpoint for an address range.
20448 @var{start-location} and @var{end-location} can specify a function name,
20449 a line number, an offset of lines from the current line or from the start
20450 location, or an address of an instruction (see @ref{Specify Location},
20451 for a list of all the possible ways to specify a @var{location}.)
20452 The breakpoint will stop execution of the inferior whenever it
20453 executes an instruction at any address within the specified range,
20454 (including @var{start-location} and @var{end-location}.)
20456 @kindex set powerpc
20457 @item set powerpc soft-float
20458 @itemx show powerpc soft-float
20459 Force @value{GDBN} to use (or not use) a software floating point calling
20460 convention. By default, @value{GDBN} selects the calling convention based
20461 on the selected architecture and the provided executable file.
20463 @item set powerpc vector-abi
20464 @itemx show powerpc vector-abi
20465 Force @value{GDBN} to use the specified calling convention for vector
20466 arguments and return values. The valid options are @samp{auto};
20467 @samp{generic}, to avoid vector registers even if they are present;
20468 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20469 registers. By default, @value{GDBN} selects the calling convention
20470 based on the selected architecture and the provided executable file.
20472 @item set powerpc exact-watchpoints
20473 @itemx show powerpc exact-watchpoints
20474 Allow @value{GDBN} to use only one debug register when watching a variable
20475 of scalar type, thus assuming that the variable is accessed through the
20476 address of its first byte.
20478 @kindex target dink32
20479 @item target dink32 @var{dev}
20480 DINK32 ROM monitor.
20482 @kindex target ppcbug
20483 @item target ppcbug @var{dev}
20484 @kindex target ppcbug1
20485 @item target ppcbug1 @var{dev}
20486 PPCBUG ROM monitor for PowerPC.
20489 @item target sds @var{dev}
20490 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20493 @cindex SDS protocol
20494 The following commands specific to the SDS protocol are supported
20498 @item set sdstimeout @var{nsec}
20499 @kindex set sdstimeout
20500 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20501 default is 2 seconds.
20503 @item show sdstimeout
20504 @kindex show sdstimeout
20505 Show the current value of the SDS timeout.
20507 @item sds @var{command}
20508 @kindex sds@r{, a command}
20509 Send the specified @var{command} string to the SDS monitor.
20514 @subsection HP PA Embedded
20518 @kindex target op50n
20519 @item target op50n @var{dev}
20520 OP50N monitor, running on an OKI HPPA board.
20522 @kindex target w89k
20523 @item target w89k @var{dev}
20524 W89K monitor, running on a Winbond HPPA board.
20529 @subsection Tsqware Sparclet
20533 @value{GDBN} enables developers to debug tasks running on
20534 Sparclet targets from a Unix host.
20535 @value{GDBN} uses code that runs on
20536 both the Unix host and on the Sparclet target. The program
20537 @code{@value{GDBP}} is installed and executed on the Unix host.
20540 @item remotetimeout @var{args}
20541 @kindex remotetimeout
20542 @value{GDBN} supports the option @code{remotetimeout}.
20543 This option is set by the user, and @var{args} represents the number of
20544 seconds @value{GDBN} waits for responses.
20547 @cindex compiling, on Sparclet
20548 When compiling for debugging, include the options @samp{-g} to get debug
20549 information and @samp{-Ttext} to relocate the program to where you wish to
20550 load it on the target. You may also want to add the options @samp{-n} or
20551 @samp{-N} in order to reduce the size of the sections. Example:
20554 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20557 You can use @code{objdump} to verify that the addresses are what you intended:
20560 sparclet-aout-objdump --headers --syms prog
20563 @cindex running, on Sparclet
20565 your Unix execution search path to find @value{GDBN}, you are ready to
20566 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20567 (or @code{sparclet-aout-gdb}, depending on your installation).
20569 @value{GDBN} comes up showing the prompt:
20576 * Sparclet File:: Setting the file to debug
20577 * Sparclet Connection:: Connecting to Sparclet
20578 * Sparclet Download:: Sparclet download
20579 * Sparclet Execution:: Running and debugging
20582 @node Sparclet File
20583 @subsubsection Setting File to Debug
20585 The @value{GDBN} command @code{file} lets you choose with program to debug.
20588 (gdbslet) file prog
20592 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20593 @value{GDBN} locates
20594 the file by searching the directories listed in the command search
20596 If the file was compiled with debug information (option @samp{-g}), source
20597 files will be searched as well.
20598 @value{GDBN} locates
20599 the source files by searching the directories listed in the directory search
20600 path (@pxref{Environment, ,Your Program's Environment}).
20602 to find a file, it displays a message such as:
20605 prog: No such file or directory.
20608 When this happens, add the appropriate directories to the search paths with
20609 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20610 @code{target} command again.
20612 @node Sparclet Connection
20613 @subsubsection Connecting to Sparclet
20615 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20616 To connect to a target on serial port ``@code{ttya}'', type:
20619 (gdbslet) target sparclet /dev/ttya
20620 Remote target sparclet connected to /dev/ttya
20621 main () at ../prog.c:3
20625 @value{GDBN} displays messages like these:
20631 @node Sparclet Download
20632 @subsubsection Sparclet Download
20634 @cindex download to Sparclet
20635 Once connected to the Sparclet target,
20636 you can use the @value{GDBN}
20637 @code{load} command to download the file from the host to the target.
20638 The file name and load offset should be given as arguments to the @code{load}
20640 Since the file format is aout, the program must be loaded to the starting
20641 address. You can use @code{objdump} to find out what this value is. The load
20642 offset is an offset which is added to the VMA (virtual memory address)
20643 of each of the file's sections.
20644 For instance, if the program
20645 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20646 and bss at 0x12010170, in @value{GDBN}, type:
20649 (gdbslet) load prog 0x12010000
20650 Loading section .text, size 0xdb0 vma 0x12010000
20653 If the code is loaded at a different address then what the program was linked
20654 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20655 to tell @value{GDBN} where to map the symbol table.
20657 @node Sparclet Execution
20658 @subsubsection Running and Debugging
20660 @cindex running and debugging Sparclet programs
20661 You can now begin debugging the task using @value{GDBN}'s execution control
20662 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20663 manual for the list of commands.
20667 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20669 Starting program: prog
20670 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20671 3 char *symarg = 0;
20673 4 char *execarg = "hello!";
20678 @subsection Fujitsu Sparclite
20682 @kindex target sparclite
20683 @item target sparclite @var{dev}
20684 Fujitsu sparclite boards, used only for the purpose of loading.
20685 You must use an additional command to debug the program.
20686 For example: target remote @var{dev} using @value{GDBN} standard
20692 @subsection Zilog Z8000
20695 @cindex simulator, Z8000
20696 @cindex Zilog Z8000 simulator
20698 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20701 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20702 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20703 segmented variant). The simulator recognizes which architecture is
20704 appropriate by inspecting the object code.
20707 @item target sim @var{args}
20709 @kindex target sim@r{, with Z8000}
20710 Debug programs on a simulated CPU. If the simulator supports setup
20711 options, specify them via @var{args}.
20715 After specifying this target, you can debug programs for the simulated
20716 CPU in the same style as programs for your host computer; use the
20717 @code{file} command to load a new program image, the @code{run} command
20718 to run your program, and so on.
20720 As well as making available all the usual machine registers
20721 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20722 additional items of information as specially named registers:
20727 Counts clock-ticks in the simulator.
20730 Counts instructions run in the simulator.
20733 Execution time in 60ths of a second.
20737 You can refer to these values in @value{GDBN} expressions with the usual
20738 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20739 conditional breakpoint that suspends only after at least 5000
20740 simulated clock ticks.
20743 @subsection Atmel AVR
20746 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20747 following AVR-specific commands:
20750 @item info io_registers
20751 @kindex info io_registers@r{, AVR}
20752 @cindex I/O registers (Atmel AVR)
20753 This command displays information about the AVR I/O registers. For
20754 each register, @value{GDBN} prints its number and value.
20761 When configured for debugging CRIS, @value{GDBN} provides the
20762 following CRIS-specific commands:
20765 @item set cris-version @var{ver}
20766 @cindex CRIS version
20767 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20768 The CRIS version affects register names and sizes. This command is useful in
20769 case autodetection of the CRIS version fails.
20771 @item show cris-version
20772 Show the current CRIS version.
20774 @item set cris-dwarf2-cfi
20775 @cindex DWARF-2 CFI and CRIS
20776 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20777 Change to @samp{off} when using @code{gcc-cris} whose version is below
20780 @item show cris-dwarf2-cfi
20781 Show the current state of using DWARF-2 CFI.
20783 @item set cris-mode @var{mode}
20785 Set the current CRIS mode to @var{mode}. It should only be changed when
20786 debugging in guru mode, in which case it should be set to
20787 @samp{guru} (the default is @samp{normal}).
20789 @item show cris-mode
20790 Show the current CRIS mode.
20794 @subsection Renesas Super-H
20797 For the Renesas Super-H processor, @value{GDBN} provides these
20801 @item set sh calling-convention @var{convention}
20802 @kindex set sh calling-convention
20803 Set the calling-convention used when calling functions from @value{GDBN}.
20804 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20805 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20806 convention. If the DWARF-2 information of the called function specifies
20807 that the function follows the Renesas calling convention, the function
20808 is called using the Renesas calling convention. If the calling convention
20809 is set to @samp{renesas}, the Renesas calling convention is always used,
20810 regardless of the DWARF-2 information. This can be used to override the
20811 default of @samp{gcc} if debug information is missing, or the compiler
20812 does not emit the DWARF-2 calling convention entry for a function.
20814 @item show sh calling-convention
20815 @kindex show sh calling-convention
20816 Show the current calling convention setting.
20821 @node Architectures
20822 @section Architectures
20824 This section describes characteristics of architectures that affect
20825 all uses of @value{GDBN} with the architecture, both native and cross.
20832 * HPPA:: HP PA architecture
20833 * SPU:: Cell Broadband Engine SPU architecture
20838 @subsection AArch64
20839 @cindex AArch64 support
20841 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20842 following special commands:
20845 @item set debug aarch64
20846 @kindex set debug aarch64
20847 This command determines whether AArch64 architecture-specific debugging
20848 messages are to be displayed.
20850 @item show debug aarch64
20851 Show whether AArch64 debugging messages are displayed.
20856 @subsection x86 Architecture-specific Issues
20859 @item set struct-convention @var{mode}
20860 @kindex set struct-convention
20861 @cindex struct return convention
20862 @cindex struct/union returned in registers
20863 Set the convention used by the inferior to return @code{struct}s and
20864 @code{union}s from functions to @var{mode}. Possible values of
20865 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20866 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20867 are returned on the stack, while @code{"reg"} means that a
20868 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20869 be returned in a register.
20871 @item show struct-convention
20872 @kindex show struct-convention
20873 Show the current setting of the convention to return @code{struct}s
20880 See the following section.
20883 @subsection @acronym{MIPS}
20885 @cindex stack on Alpha
20886 @cindex stack on @acronym{MIPS}
20887 @cindex Alpha stack
20888 @cindex @acronym{MIPS} stack
20889 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20890 sometimes requires @value{GDBN} to search backward in the object code to
20891 find the beginning of a function.
20893 @cindex response time, @acronym{MIPS} debugging
20894 To improve response time (especially for embedded applications, where
20895 @value{GDBN} may be restricted to a slow serial line for this search)
20896 you may want to limit the size of this search, using one of these
20900 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20901 @item set heuristic-fence-post @var{limit}
20902 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20903 search for the beginning of a function. A value of @var{0} (the
20904 default) means there is no limit. However, except for @var{0}, the
20905 larger the limit the more bytes @code{heuristic-fence-post} must search
20906 and therefore the longer it takes to run. You should only need to use
20907 this command when debugging a stripped executable.
20909 @item show heuristic-fence-post
20910 Display the current limit.
20914 These commands are available @emph{only} when @value{GDBN} is configured
20915 for debugging programs on Alpha or @acronym{MIPS} processors.
20917 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20921 @item set mips abi @var{arg}
20922 @kindex set mips abi
20923 @cindex set ABI for @acronym{MIPS}
20924 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20925 values of @var{arg} are:
20929 The default ABI associated with the current binary (this is the
20939 @item show mips abi
20940 @kindex show mips abi
20941 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20943 @item set mips compression @var{arg}
20944 @kindex set mips compression
20945 @cindex code compression, @acronym{MIPS}
20946 Tell @value{GDBN} which @acronym{MIPS} compressed
20947 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20948 inferior. @value{GDBN} uses this for code disassembly and other
20949 internal interpretation purposes. This setting is only referred to
20950 when no executable has been associated with the debugging session or
20951 the executable does not provide information about the encoding it uses.
20952 Otherwise this setting is automatically updated from information
20953 provided by the executable.
20955 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20956 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20957 executables containing @acronym{MIPS16} code frequently are not
20958 identified as such.
20960 This setting is ``sticky''; that is, it retains its value across
20961 debugging sessions until reset either explicitly with this command or
20962 implicitly from an executable.
20964 The compiler and/or assembler typically add symbol table annotations to
20965 identify functions compiled for the @acronym{MIPS16} or
20966 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20967 are present, @value{GDBN} uses them in preference to the global
20968 compressed @acronym{ISA} encoding setting.
20970 @item show mips compression
20971 @kindex show mips compression
20972 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20973 @value{GDBN} to debug the inferior.
20976 @itemx show mipsfpu
20977 @xref{MIPS Embedded, set mipsfpu}.
20979 @item set mips mask-address @var{arg}
20980 @kindex set mips mask-address
20981 @cindex @acronym{MIPS} addresses, masking
20982 This command determines whether the most-significant 32 bits of 64-bit
20983 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20984 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20985 setting, which lets @value{GDBN} determine the correct value.
20987 @item show mips mask-address
20988 @kindex show mips mask-address
20989 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20992 @item set remote-mips64-transfers-32bit-regs
20993 @kindex set remote-mips64-transfers-32bit-regs
20994 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20995 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20996 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20997 and 64 bits for other registers, set this option to @samp{on}.
20999 @item show remote-mips64-transfers-32bit-regs
21000 @kindex show remote-mips64-transfers-32bit-regs
21001 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21003 @item set debug mips
21004 @kindex set debug mips
21005 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21006 target code in @value{GDBN}.
21008 @item show debug mips
21009 @kindex show debug mips
21010 Show the current setting of @acronym{MIPS} debugging messages.
21016 @cindex HPPA support
21018 When @value{GDBN} is debugging the HP PA architecture, it provides the
21019 following special commands:
21022 @item set debug hppa
21023 @kindex set debug hppa
21024 This command determines whether HPPA architecture-specific debugging
21025 messages are to be displayed.
21027 @item show debug hppa
21028 Show whether HPPA debugging messages are displayed.
21030 @item maint print unwind @var{address}
21031 @kindex maint print unwind@r{, HPPA}
21032 This command displays the contents of the unwind table entry at the
21033 given @var{address}.
21039 @subsection Cell Broadband Engine SPU architecture
21040 @cindex Cell Broadband Engine
21043 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21044 it provides the following special commands:
21047 @item info spu event
21049 Display SPU event facility status. Shows current event mask
21050 and pending event status.
21052 @item info spu signal
21053 Display SPU signal notification facility status. Shows pending
21054 signal-control word and signal notification mode of both signal
21055 notification channels.
21057 @item info spu mailbox
21058 Display SPU mailbox facility status. Shows all pending entries,
21059 in order of processing, in each of the SPU Write Outbound,
21060 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21063 Display MFC DMA status. Shows all pending commands in the MFC
21064 DMA queue. For each entry, opcode, tag, class IDs, effective
21065 and local store addresses and transfer size are shown.
21067 @item info spu proxydma
21068 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21069 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21070 and local store addresses and transfer size are shown.
21074 When @value{GDBN} is debugging a combined PowerPC/SPU application
21075 on the Cell Broadband Engine, it provides in addition the following
21079 @item set spu stop-on-load @var{arg}
21081 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21082 will give control to the user when a new SPE thread enters its @code{main}
21083 function. The default is @code{off}.
21085 @item show spu stop-on-load
21087 Show whether to stop for new SPE threads.
21089 @item set spu auto-flush-cache @var{arg}
21090 Set whether to automatically flush the software-managed cache. When set to
21091 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21092 cache to be flushed whenever SPE execution stops. This provides a consistent
21093 view of PowerPC memory that is accessed via the cache. If an application
21094 does not use the software-managed cache, this option has no effect.
21096 @item show spu auto-flush-cache
21097 Show whether to automatically flush the software-managed cache.
21102 @subsection PowerPC
21103 @cindex PowerPC architecture
21105 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21106 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21107 numbers stored in the floating point registers. These values must be stored
21108 in two consecutive registers, always starting at an even register like
21109 @code{f0} or @code{f2}.
21111 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21112 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21113 @code{f2} and @code{f3} for @code{$dl1} and so on.
21115 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21116 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21119 @node Controlling GDB
21120 @chapter Controlling @value{GDBN}
21122 You can alter the way @value{GDBN} interacts with you by using the
21123 @code{set} command. For commands controlling how @value{GDBN} displays
21124 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21129 * Editing:: Command editing
21130 * Command History:: Command history
21131 * Screen Size:: Screen size
21132 * Numbers:: Numbers
21133 * ABI:: Configuring the current ABI
21134 * Auto-loading:: Automatically loading associated files
21135 * Messages/Warnings:: Optional warnings and messages
21136 * Debugging Output:: Optional messages about internal happenings
21137 * Other Misc Settings:: Other Miscellaneous Settings
21145 @value{GDBN} indicates its readiness to read a command by printing a string
21146 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21147 can change the prompt string with the @code{set prompt} command. For
21148 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21149 the prompt in one of the @value{GDBN} sessions so that you can always tell
21150 which one you are talking to.
21152 @emph{Note:} @code{set prompt} does not add a space for you after the
21153 prompt you set. This allows you to set a prompt which ends in a space
21154 or a prompt that does not.
21158 @item set prompt @var{newprompt}
21159 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21161 @kindex show prompt
21163 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21166 Versions of @value{GDBN} that ship with Python scripting enabled have
21167 prompt extensions. The commands for interacting with these extensions
21171 @kindex set extended-prompt
21172 @item set extended-prompt @var{prompt}
21173 Set an extended prompt that allows for substitutions.
21174 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21175 substitution. Any escape sequences specified as part of the prompt
21176 string are replaced with the corresponding strings each time the prompt
21182 set extended-prompt Current working directory: \w (gdb)
21185 Note that when an extended-prompt is set, it takes control of the
21186 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21188 @kindex show extended-prompt
21189 @item show extended-prompt
21190 Prints the extended prompt. Any escape sequences specified as part of
21191 the prompt string with @code{set extended-prompt}, are replaced with the
21192 corresponding strings each time the prompt is displayed.
21196 @section Command Editing
21198 @cindex command line editing
21200 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21201 @sc{gnu} library provides consistent behavior for programs which provide a
21202 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21203 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21204 substitution, and a storage and recall of command history across
21205 debugging sessions.
21207 You may control the behavior of command line editing in @value{GDBN} with the
21208 command @code{set}.
21211 @kindex set editing
21214 @itemx set editing on
21215 Enable command line editing (enabled by default).
21217 @item set editing off
21218 Disable command line editing.
21220 @kindex show editing
21222 Show whether command line editing is enabled.
21225 @ifset SYSTEM_READLINE
21226 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21228 @ifclear SYSTEM_READLINE
21229 @xref{Command Line Editing},
21231 for more details about the Readline
21232 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21233 encouraged to read that chapter.
21235 @node Command History
21236 @section Command History
21237 @cindex command history
21239 @value{GDBN} can keep track of the commands you type during your
21240 debugging sessions, so that you can be certain of precisely what
21241 happened. Use these commands to manage the @value{GDBN} command
21244 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21245 package, to provide the history facility.
21246 @ifset SYSTEM_READLINE
21247 @xref{Using History Interactively, , , history, GNU History Library},
21249 @ifclear SYSTEM_READLINE
21250 @xref{Using History Interactively},
21252 for the detailed description of the History library.
21254 To issue a command to @value{GDBN} without affecting certain aspects of
21255 the state which is seen by users, prefix it with @samp{server }
21256 (@pxref{Server Prefix}). This
21257 means that this command will not affect the command history, nor will it
21258 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21259 pressed on a line by itself.
21261 @cindex @code{server}, command prefix
21262 The server prefix does not affect the recording of values into the value
21263 history; to print a value without recording it into the value history,
21264 use the @code{output} command instead of the @code{print} command.
21266 Here is the description of @value{GDBN} commands related to command
21270 @cindex history substitution
21271 @cindex history file
21272 @kindex set history filename
21273 @cindex @env{GDBHISTFILE}, environment variable
21274 @item set history filename @var{fname}
21275 Set the name of the @value{GDBN} command history file to @var{fname}.
21276 This is the file where @value{GDBN} reads an initial command history
21277 list, and where it writes the command history from this session when it
21278 exits. You can access this list through history expansion or through
21279 the history command editing characters listed below. This file defaults
21280 to the value of the environment variable @code{GDBHISTFILE}, or to
21281 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21284 @cindex save command history
21285 @kindex set history save
21286 @item set history save
21287 @itemx set history save on
21288 Record command history in a file, whose name may be specified with the
21289 @code{set history filename} command. By default, this option is disabled.
21291 @item set history save off
21292 Stop recording command history in a file.
21294 @cindex history size
21295 @kindex set history size
21296 @cindex @env{HISTSIZE}, environment variable
21297 @item set history size @var{size}
21298 @itemx set history size unlimited
21299 Set the number of commands which @value{GDBN} keeps in its history list.
21300 This defaults to the value of the environment variable
21301 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21302 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21303 history list is unlimited.
21306 History expansion assigns special meaning to the character @kbd{!}.
21307 @ifset SYSTEM_READLINE
21308 @xref{Event Designators, , , history, GNU History Library},
21310 @ifclear SYSTEM_READLINE
21311 @xref{Event Designators},
21315 @cindex history expansion, turn on/off
21316 Since @kbd{!} is also the logical not operator in C, history expansion
21317 is off by default. If you decide to enable history expansion with the
21318 @code{set history expansion on} command, you may sometimes need to
21319 follow @kbd{!} (when it is used as logical not, in an expression) with
21320 a space or a tab to prevent it from being expanded. The readline
21321 history facilities do not attempt substitution on the strings
21322 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21324 The commands to control history expansion are:
21327 @item set history expansion on
21328 @itemx set history expansion
21329 @kindex set history expansion
21330 Enable history expansion. History expansion is off by default.
21332 @item set history expansion off
21333 Disable history expansion.
21336 @kindex show history
21338 @itemx show history filename
21339 @itemx show history save
21340 @itemx show history size
21341 @itemx show history expansion
21342 These commands display the state of the @value{GDBN} history parameters.
21343 @code{show history} by itself displays all four states.
21348 @kindex show commands
21349 @cindex show last commands
21350 @cindex display command history
21351 @item show commands
21352 Display the last ten commands in the command history.
21354 @item show commands @var{n}
21355 Print ten commands centered on command number @var{n}.
21357 @item show commands +
21358 Print ten commands just after the commands last printed.
21362 @section Screen Size
21363 @cindex size of screen
21364 @cindex pauses in output
21366 Certain commands to @value{GDBN} may produce large amounts of
21367 information output to the screen. To help you read all of it,
21368 @value{GDBN} pauses and asks you for input at the end of each page of
21369 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21370 to discard the remaining output. Also, the screen width setting
21371 determines when to wrap lines of output. Depending on what is being
21372 printed, @value{GDBN} tries to break the line at a readable place,
21373 rather than simply letting it overflow onto the following line.
21375 Normally @value{GDBN} knows the size of the screen from the terminal
21376 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21377 together with the value of the @code{TERM} environment variable and the
21378 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21379 you can override it with the @code{set height} and @code{set
21386 @kindex show height
21387 @item set height @var{lpp}
21388 @itemx set height unlimited
21390 @itemx set width @var{cpl}
21391 @itemx set width unlimited
21393 These @code{set} commands specify a screen height of @var{lpp} lines and
21394 a screen width of @var{cpl} characters. The associated @code{show}
21395 commands display the current settings.
21397 If you specify a height of either @code{unlimited} or zero lines,
21398 @value{GDBN} does not pause during output no matter how long the
21399 output is. This is useful if output is to a file or to an editor
21402 Likewise, you can specify @samp{set width unlimited} or @samp{set
21403 width 0} to prevent @value{GDBN} from wrapping its output.
21405 @item set pagination on
21406 @itemx set pagination off
21407 @kindex set pagination
21408 Turn the output pagination on or off; the default is on. Turning
21409 pagination off is the alternative to @code{set height unlimited}. Note that
21410 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21411 Options, -batch}) also automatically disables pagination.
21413 @item show pagination
21414 @kindex show pagination
21415 Show the current pagination mode.
21420 @cindex number representation
21421 @cindex entering numbers
21423 You can always enter numbers in octal, decimal, or hexadecimal in
21424 @value{GDBN} by the usual conventions: octal numbers begin with
21425 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21426 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21427 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21428 10; likewise, the default display for numbers---when no particular
21429 format is specified---is base 10. You can change the default base for
21430 both input and output with the commands described below.
21433 @kindex set input-radix
21434 @item set input-radix @var{base}
21435 Set the default base for numeric input. Supported choices
21436 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21437 specified either unambiguously or using the current input radix; for
21441 set input-radix 012
21442 set input-radix 10.
21443 set input-radix 0xa
21447 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21448 leaves the input radix unchanged, no matter what it was, since
21449 @samp{10}, being without any leading or trailing signs of its base, is
21450 interpreted in the current radix. Thus, if the current radix is 16,
21451 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21454 @kindex set output-radix
21455 @item set output-radix @var{base}
21456 Set the default base for numeric display. Supported choices
21457 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21458 specified either unambiguously or using the current input radix.
21460 @kindex show input-radix
21461 @item show input-radix
21462 Display the current default base for numeric input.
21464 @kindex show output-radix
21465 @item show output-radix
21466 Display the current default base for numeric display.
21468 @item set radix @r{[}@var{base}@r{]}
21472 These commands set and show the default base for both input and output
21473 of numbers. @code{set radix} sets the radix of input and output to
21474 the same base; without an argument, it resets the radix back to its
21475 default value of 10.
21480 @section Configuring the Current ABI
21482 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21483 application automatically. However, sometimes you need to override its
21484 conclusions. Use these commands to manage @value{GDBN}'s view of the
21490 @cindex Newlib OS ABI and its influence on the longjmp handling
21492 One @value{GDBN} configuration can debug binaries for multiple operating
21493 system targets, either via remote debugging or native emulation.
21494 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21495 but you can override its conclusion using the @code{set osabi} command.
21496 One example where this is useful is in debugging of binaries which use
21497 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21498 not have the same identifying marks that the standard C library for your
21501 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21502 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21503 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21504 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21508 Show the OS ABI currently in use.
21511 With no argument, show the list of registered available OS ABI's.
21513 @item set osabi @var{abi}
21514 Set the current OS ABI to @var{abi}.
21517 @cindex float promotion
21519 Generally, the way that an argument of type @code{float} is passed to a
21520 function depends on whether the function is prototyped. For a prototyped
21521 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21522 according to the architecture's convention for @code{float}. For unprototyped
21523 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21524 @code{double} and then passed.
21526 Unfortunately, some forms of debug information do not reliably indicate whether
21527 a function is prototyped. If @value{GDBN} calls a function that is not marked
21528 as prototyped, it consults @kbd{set coerce-float-to-double}.
21531 @kindex set coerce-float-to-double
21532 @item set coerce-float-to-double
21533 @itemx set coerce-float-to-double on
21534 Arguments of type @code{float} will be promoted to @code{double} when passed
21535 to an unprototyped function. This is the default setting.
21537 @item set coerce-float-to-double off
21538 Arguments of type @code{float} will be passed directly to unprototyped
21541 @kindex show coerce-float-to-double
21542 @item show coerce-float-to-double
21543 Show the current setting of promoting @code{float} to @code{double}.
21547 @kindex show cp-abi
21548 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21549 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21550 used to build your application. @value{GDBN} only fully supports
21551 programs with a single C@t{++} ABI; if your program contains code using
21552 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21553 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21554 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21555 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21556 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21557 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21562 Show the C@t{++} ABI currently in use.
21565 With no argument, show the list of supported C@t{++} ABI's.
21567 @item set cp-abi @var{abi}
21568 @itemx set cp-abi auto
21569 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21573 @section Automatically loading associated files
21574 @cindex auto-loading
21576 @value{GDBN} sometimes reads files with commands and settings automatically,
21577 without being explicitly told so by the user. We call this feature
21578 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21579 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21580 results or introduce security risks (e.g., if the file comes from untrusted
21583 Note that loading of these associated files (including the local @file{.gdbinit}
21584 file) requires accordingly configured @code{auto-load safe-path}
21585 (@pxref{Auto-loading safe path}).
21587 For these reasons, @value{GDBN} includes commands and options to let you
21588 control when to auto-load files and which files should be auto-loaded.
21591 @anchor{set auto-load off}
21592 @kindex set auto-load off
21593 @item set auto-load off
21594 Globally disable loading of all auto-loaded files.
21595 You may want to use this command with the @samp{-iex} option
21596 (@pxref{Option -init-eval-command}) such as:
21598 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21601 Be aware that system init file (@pxref{System-wide configuration})
21602 and init files from your home directory (@pxref{Home Directory Init File})
21603 still get read (as they come from generally trusted directories).
21604 To prevent @value{GDBN} from auto-loading even those init files, use the
21605 @option{-nx} option (@pxref{Mode Options}), in addition to
21606 @code{set auto-load no}.
21608 @anchor{show auto-load}
21609 @kindex show auto-load
21610 @item show auto-load
21611 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21615 (gdb) show auto-load
21616 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21617 libthread-db: Auto-loading of inferior specific libthread_db is on.
21618 local-gdbinit: Auto-loading of .gdbinit script from current directory
21620 python-scripts: Auto-loading of Python scripts is on.
21621 safe-path: List of directories from which it is safe to auto-load files
21622 is $debugdir:$datadir/auto-load.
21623 scripts-directory: List of directories from which to load auto-loaded scripts
21624 is $debugdir:$datadir/auto-load.
21627 @anchor{info auto-load}
21628 @kindex info auto-load
21629 @item info auto-load
21630 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21634 (gdb) info auto-load
21637 Yes /home/user/gdb/gdb-gdb.gdb
21638 libthread-db: No auto-loaded libthread-db.
21639 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21643 Yes /home/user/gdb/gdb-gdb.py
21647 These are various kinds of files @value{GDBN} can automatically load:
21651 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21653 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21655 @xref{dotdebug_gdb_scripts section},
21656 controlled by @ref{set auto-load python-scripts}.
21658 @xref{Init File in the Current Directory},
21659 controlled by @ref{set auto-load local-gdbinit}.
21661 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21664 These are @value{GDBN} control commands for the auto-loading:
21666 @multitable @columnfractions .5 .5
21667 @item @xref{set auto-load off}.
21668 @tab Disable auto-loading globally.
21669 @item @xref{show auto-load}.
21670 @tab Show setting of all kinds of files.
21671 @item @xref{info auto-load}.
21672 @tab Show state of all kinds of files.
21673 @item @xref{set auto-load gdb-scripts}.
21674 @tab Control for @value{GDBN} command scripts.
21675 @item @xref{show auto-load gdb-scripts}.
21676 @tab Show setting of @value{GDBN} command scripts.
21677 @item @xref{info auto-load gdb-scripts}.
21678 @tab Show state of @value{GDBN} command scripts.
21679 @item @xref{set auto-load python-scripts}.
21680 @tab Control for @value{GDBN} Python scripts.
21681 @item @xref{show auto-load python-scripts}.
21682 @tab Show setting of @value{GDBN} Python scripts.
21683 @item @xref{info auto-load python-scripts}.
21684 @tab Show state of @value{GDBN} Python scripts.
21685 @item @xref{set auto-load scripts-directory}.
21686 @tab Control for @value{GDBN} auto-loaded scripts location.
21687 @item @xref{show auto-load scripts-directory}.
21688 @tab Show @value{GDBN} auto-loaded scripts location.
21689 @item @xref{set auto-load local-gdbinit}.
21690 @tab Control for init file in the current directory.
21691 @item @xref{show auto-load local-gdbinit}.
21692 @tab Show setting of init file in the current directory.
21693 @item @xref{info auto-load local-gdbinit}.
21694 @tab Show state of init file in the current directory.
21695 @item @xref{set auto-load libthread-db}.
21696 @tab Control for thread debugging library.
21697 @item @xref{show auto-load libthread-db}.
21698 @tab Show setting of thread debugging library.
21699 @item @xref{info auto-load libthread-db}.
21700 @tab Show state of thread debugging library.
21701 @item @xref{set auto-load safe-path}.
21702 @tab Control directories trusted for automatic loading.
21703 @item @xref{show auto-load safe-path}.
21704 @tab Show directories trusted for automatic loading.
21705 @item @xref{add-auto-load-safe-path}.
21706 @tab Add directory trusted for automatic loading.
21710 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21711 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21712 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21713 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21714 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21715 @xref{Python Auto-loading}.
21718 @node Init File in the Current Directory
21719 @subsection Automatically loading init file in the current directory
21720 @cindex auto-loading init file in the current directory
21722 By default, @value{GDBN} reads and executes the canned sequences of commands
21723 from init file (if any) in the current working directory,
21724 see @ref{Init File in the Current Directory during Startup}.
21726 Note that loading of this local @file{.gdbinit} file also requires accordingly
21727 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21730 @anchor{set auto-load local-gdbinit}
21731 @kindex set auto-load local-gdbinit
21732 @item set auto-load local-gdbinit [on|off]
21733 Enable or disable the auto-loading of canned sequences of commands
21734 (@pxref{Sequences}) found in init file in the current directory.
21736 @anchor{show auto-load local-gdbinit}
21737 @kindex show auto-load local-gdbinit
21738 @item show auto-load local-gdbinit
21739 Show whether auto-loading of canned sequences of commands from init file in the
21740 current directory is enabled or disabled.
21742 @anchor{info auto-load local-gdbinit}
21743 @kindex info auto-load local-gdbinit
21744 @item info auto-load local-gdbinit
21745 Print whether canned sequences of commands from init file in the
21746 current directory have been auto-loaded.
21749 @node libthread_db.so.1 file
21750 @subsection Automatically loading thread debugging library
21751 @cindex auto-loading libthread_db.so.1
21753 This feature is currently present only on @sc{gnu}/Linux native hosts.
21755 @value{GDBN} reads in some cases thread debugging library from places specific
21756 to the inferior (@pxref{set libthread-db-search-path}).
21758 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21759 without checking this @samp{set auto-load libthread-db} switch as system
21760 libraries have to be trusted in general. In all other cases of
21761 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21762 auto-load libthread-db} is enabled before trying to open such thread debugging
21765 Note that loading of this debugging library also requires accordingly configured
21766 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21769 @anchor{set auto-load libthread-db}
21770 @kindex set auto-load libthread-db
21771 @item set auto-load libthread-db [on|off]
21772 Enable or disable the auto-loading of inferior specific thread debugging library.
21774 @anchor{show auto-load libthread-db}
21775 @kindex show auto-load libthread-db
21776 @item show auto-load libthread-db
21777 Show whether auto-loading of inferior specific thread debugging library is
21778 enabled or disabled.
21780 @anchor{info auto-load libthread-db}
21781 @kindex info auto-load libthread-db
21782 @item info auto-load libthread-db
21783 Print the list of all loaded inferior specific thread debugging libraries and
21784 for each such library print list of inferior @var{pid}s using it.
21787 @node objfile-gdb.gdb file
21788 @subsection The @file{@var{objfile}-gdb.gdb} file
21789 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21791 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21792 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21793 auto-load gdb-scripts} is set to @samp{on}.
21795 Note that loading of this script file also requires accordingly configured
21796 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21798 For more background refer to the similar Python scripts auto-loading
21799 description (@pxref{objfile-gdb.py file}).
21802 @anchor{set auto-load gdb-scripts}
21803 @kindex set auto-load gdb-scripts
21804 @item set auto-load gdb-scripts [on|off]
21805 Enable or disable the auto-loading of canned sequences of commands scripts.
21807 @anchor{show auto-load gdb-scripts}
21808 @kindex show auto-load gdb-scripts
21809 @item show auto-load gdb-scripts
21810 Show whether auto-loading of canned sequences of commands scripts is enabled or
21813 @anchor{info auto-load gdb-scripts}
21814 @kindex info auto-load gdb-scripts
21815 @cindex print list of auto-loaded canned sequences of commands scripts
21816 @item info auto-load gdb-scripts [@var{regexp}]
21817 Print the list of all canned sequences of commands scripts that @value{GDBN}
21821 If @var{regexp} is supplied only canned sequences of commands scripts with
21822 matching names are printed.
21824 @node Auto-loading safe path
21825 @subsection Security restriction for auto-loading
21826 @cindex auto-loading safe-path
21828 As the files of inferior can come from untrusted source (such as submitted by
21829 an application user) @value{GDBN} does not always load any files automatically.
21830 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21831 directories trusted for loading files not explicitly requested by user.
21832 Each directory can also be a shell wildcard pattern.
21834 If the path is not set properly you will see a warning and the file will not
21839 Reading symbols from /home/user/gdb/gdb...done.
21840 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21841 declined by your `auto-load safe-path' set
21842 to "$debugdir:$datadir/auto-load".
21843 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21844 declined by your `auto-load safe-path' set
21845 to "$debugdir:$datadir/auto-load".
21849 To instruct @value{GDBN} to go ahead and use the init files anyway,
21850 invoke @value{GDBN} like this:
21853 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
21856 The list of trusted directories is controlled by the following commands:
21859 @anchor{set auto-load safe-path}
21860 @kindex set auto-load safe-path
21861 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21862 Set the list of directories (and their subdirectories) trusted for automatic
21863 loading and execution of scripts. You can also enter a specific trusted file.
21864 Each directory can also be a shell wildcard pattern; wildcards do not match
21865 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21866 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21867 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21868 its default value as specified during @value{GDBN} compilation.
21870 The list of directories uses path separator (@samp{:} on GNU and Unix
21871 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21872 to the @env{PATH} environment variable.
21874 @anchor{show auto-load safe-path}
21875 @kindex show auto-load safe-path
21876 @item show auto-load safe-path
21877 Show the list of directories trusted for automatic loading and execution of
21880 @anchor{add-auto-load-safe-path}
21881 @kindex add-auto-load-safe-path
21882 @item add-auto-load-safe-path
21883 Add an entry (or list of entries) the list of directories trusted for automatic
21884 loading and execution of scripts. Multiple entries may be delimited by the
21885 host platform path separator in use.
21888 This variable defaults to what @code{--with-auto-load-dir} has been configured
21889 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21890 substitution applies the same as for @ref{set auto-load scripts-directory}.
21891 The default @code{set auto-load safe-path} value can be also overriden by
21892 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21894 Setting this variable to @file{/} disables this security protection,
21895 corresponding @value{GDBN} configuration option is
21896 @option{--without-auto-load-safe-path}.
21897 This variable is supposed to be set to the system directories writable by the
21898 system superuser only. Users can add their source directories in init files in
21899 their home directories (@pxref{Home Directory Init File}). See also deprecated
21900 init file in the current directory
21901 (@pxref{Init File in the Current Directory during Startup}).
21903 To force @value{GDBN} to load the files it declined to load in the previous
21904 example, you could use one of the following ways:
21907 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21908 Specify this trusted directory (or a file) as additional component of the list.
21909 You have to specify also any existing directories displayed by
21910 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21912 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21913 Specify this directory as in the previous case but just for a single
21914 @value{GDBN} session.
21916 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21917 Disable auto-loading safety for a single @value{GDBN} session.
21918 This assumes all the files you debug during this @value{GDBN} session will come
21919 from trusted sources.
21921 @item @kbd{./configure --without-auto-load-safe-path}
21922 During compilation of @value{GDBN} you may disable any auto-loading safety.
21923 This assumes all the files you will ever debug with this @value{GDBN} come from
21927 On the other hand you can also explicitly forbid automatic files loading which
21928 also suppresses any such warning messages:
21931 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21932 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21934 @item @file{~/.gdbinit}: @samp{set auto-load no}
21935 Disable auto-loading globally for the user
21936 (@pxref{Home Directory Init File}). While it is improbable, you could also
21937 use system init file instead (@pxref{System-wide configuration}).
21940 This setting applies to the file names as entered by user. If no entry matches
21941 @value{GDBN} tries as a last resort to also resolve all the file names into
21942 their canonical form (typically resolving symbolic links) and compare the
21943 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21944 own before starting the comparison so a canonical form of directories is
21945 recommended to be entered.
21947 @node Auto-loading verbose mode
21948 @subsection Displaying files tried for auto-load
21949 @cindex auto-loading verbose mode
21951 For better visibility of all the file locations where you can place scripts to
21952 be auto-loaded with inferior --- or to protect yourself against accidental
21953 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21954 all the files attempted to be loaded. Both existing and non-existing files may
21957 For example the list of directories from which it is safe to auto-load files
21958 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21959 may not be too obvious while setting it up.
21962 (gdb) set debug auto-load on
21963 (gdb) file ~/src/t/true
21964 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21965 for objfile "/tmp/true".
21966 auto-load: Updating directories of "/usr:/opt".
21967 auto-load: Using directory "/usr".
21968 auto-load: Using directory "/opt".
21969 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21970 by your `auto-load safe-path' set to "/usr:/opt".
21974 @anchor{set debug auto-load}
21975 @kindex set debug auto-load
21976 @item set debug auto-load [on|off]
21977 Set whether to print the filenames attempted to be auto-loaded.
21979 @anchor{show debug auto-load}
21980 @kindex show debug auto-load
21981 @item show debug auto-load
21982 Show whether printing of the filenames attempted to be auto-loaded is turned
21986 @node Messages/Warnings
21987 @section Optional Warnings and Messages
21989 @cindex verbose operation
21990 @cindex optional warnings
21991 By default, @value{GDBN} is silent about its inner workings. If you are
21992 running on a slow machine, you may want to use the @code{set verbose}
21993 command. This makes @value{GDBN} tell you when it does a lengthy
21994 internal operation, so you will not think it has crashed.
21996 Currently, the messages controlled by @code{set verbose} are those
21997 which announce that the symbol table for a source file is being read;
21998 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22001 @kindex set verbose
22002 @item set verbose on
22003 Enables @value{GDBN} output of certain informational messages.
22005 @item set verbose off
22006 Disables @value{GDBN} output of certain informational messages.
22008 @kindex show verbose
22010 Displays whether @code{set verbose} is on or off.
22013 By default, if @value{GDBN} encounters bugs in the symbol table of an
22014 object file, it is silent; but if you are debugging a compiler, you may
22015 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22020 @kindex set complaints
22021 @item set complaints @var{limit}
22022 Permits @value{GDBN} to output @var{limit} complaints about each type of
22023 unusual symbols before becoming silent about the problem. Set
22024 @var{limit} to zero to suppress all complaints; set it to a large number
22025 to prevent complaints from being suppressed.
22027 @kindex show complaints
22028 @item show complaints
22029 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22033 @anchor{confirmation requests}
22034 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22035 lot of stupid questions to confirm certain commands. For example, if
22036 you try to run a program which is already running:
22040 The program being debugged has been started already.
22041 Start it from the beginning? (y or n)
22044 If you are willing to unflinchingly face the consequences of your own
22045 commands, you can disable this ``feature'':
22049 @kindex set confirm
22051 @cindex confirmation
22052 @cindex stupid questions
22053 @item set confirm off
22054 Disables confirmation requests. Note that running @value{GDBN} with
22055 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22056 automatically disables confirmation requests.
22058 @item set confirm on
22059 Enables confirmation requests (the default).
22061 @kindex show confirm
22063 Displays state of confirmation requests.
22067 @cindex command tracing
22068 If you need to debug user-defined commands or sourced files you may find it
22069 useful to enable @dfn{command tracing}. In this mode each command will be
22070 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22071 quantity denoting the call depth of each command.
22074 @kindex set trace-commands
22075 @cindex command scripts, debugging
22076 @item set trace-commands on
22077 Enable command tracing.
22078 @item set trace-commands off
22079 Disable command tracing.
22080 @item show trace-commands
22081 Display the current state of command tracing.
22084 @node Debugging Output
22085 @section Optional Messages about Internal Happenings
22086 @cindex optional debugging messages
22088 @value{GDBN} has commands that enable optional debugging messages from
22089 various @value{GDBN} subsystems; normally these commands are of
22090 interest to @value{GDBN} maintainers, or when reporting a bug. This
22091 section documents those commands.
22094 @kindex set exec-done-display
22095 @item set exec-done-display
22096 Turns on or off the notification of asynchronous commands'
22097 completion. When on, @value{GDBN} will print a message when an
22098 asynchronous command finishes its execution. The default is off.
22099 @kindex show exec-done-display
22100 @item show exec-done-display
22101 Displays the current setting of asynchronous command completion
22104 @cindex ARM AArch64
22105 @item set debug aarch64
22106 Turns on or off display of debugging messages related to ARM AArch64.
22107 The default is off.
22109 @item show debug aarch64
22110 Displays the current state of displaying debugging messages related to
22112 @cindex gdbarch debugging info
22113 @cindex architecture debugging info
22114 @item set debug arch
22115 Turns on or off display of gdbarch debugging info. The default is off
22116 @item show debug arch
22117 Displays the current state of displaying gdbarch debugging info.
22118 @item set debug aix-thread
22119 @cindex AIX threads
22120 Display debugging messages about inner workings of the AIX thread
22122 @item show debug aix-thread
22123 Show the current state of AIX thread debugging info display.
22124 @item set debug check-physname
22126 Check the results of the ``physname'' computation. When reading DWARF
22127 debugging information for C@t{++}, @value{GDBN} attempts to compute
22128 each entity's name. @value{GDBN} can do this computation in two
22129 different ways, depending on exactly what information is present.
22130 When enabled, this setting causes @value{GDBN} to compute the names
22131 both ways and display any discrepancies.
22132 @item show debug check-physname
22133 Show the current state of ``physname'' checking.
22134 @item set debug coff-pe-read
22135 @cindex COFF/PE exported symbols
22136 Control display of debugging messages related to reading of COFF/PE
22137 exported symbols. The default is off.
22138 @item show debug coff-pe-read
22139 Displays the current state of displaying debugging messages related to
22140 reading of COFF/PE exported symbols.
22141 @item set debug dwarf2-die
22142 @cindex DWARF2 DIEs
22143 Dump DWARF2 DIEs after they are read in.
22144 The value is the number of nesting levels to print.
22145 A value of zero turns off the display.
22146 @item show debug dwarf2-die
22147 Show the current state of DWARF2 DIE debugging.
22148 @item set debug dwarf2-read
22149 @cindex DWARF2 Reading
22150 Turns on or off display of debugging messages related to reading
22151 DWARF debug info. The default is off.
22152 @item show debug dwarf2-read
22153 Show the current state of DWARF2 reader debugging.
22154 @item set debug displaced
22155 @cindex displaced stepping debugging info
22156 Turns on or off display of @value{GDBN} debugging info for the
22157 displaced stepping support. The default is off.
22158 @item show debug displaced
22159 Displays the current state of displaying @value{GDBN} debugging info
22160 related to displaced stepping.
22161 @item set debug event
22162 @cindex event debugging info
22163 Turns on or off display of @value{GDBN} event debugging info. The
22165 @item show debug event
22166 Displays the current state of displaying @value{GDBN} event debugging
22168 @item set debug expression
22169 @cindex expression debugging info
22170 Turns on or off display of debugging info about @value{GDBN}
22171 expression parsing. The default is off.
22172 @item show debug expression
22173 Displays the current state of displaying debugging info about
22174 @value{GDBN} expression parsing.
22175 @item set debug frame
22176 @cindex frame debugging info
22177 Turns on or off display of @value{GDBN} frame debugging info. The
22179 @item show debug frame
22180 Displays the current state of displaying @value{GDBN} frame debugging
22182 @item set debug gnu-nat
22183 @cindex @sc{gnu}/Hurd debug messages
22184 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22185 @item show debug gnu-nat
22186 Show the current state of @sc{gnu}/Hurd debugging messages.
22187 @item set debug infrun
22188 @cindex inferior debugging info
22189 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22190 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22191 for implementing operations such as single-stepping the inferior.
22192 @item show debug infrun
22193 Displays the current state of @value{GDBN} inferior debugging.
22194 @item set debug jit
22195 @cindex just-in-time compilation, debugging messages
22196 Turns on or off debugging messages from JIT debug support.
22197 @item show debug jit
22198 Displays the current state of @value{GDBN} JIT debugging.
22199 @item set debug lin-lwp
22200 @cindex @sc{gnu}/Linux LWP debug messages
22201 @cindex Linux lightweight processes
22202 Turns on or off debugging messages from the Linux LWP debug support.
22203 @item show debug lin-lwp
22204 Show the current state of Linux LWP debugging messages.
22205 @item set debug mach-o
22206 @cindex Mach-O symbols processing
22207 Control display of debugging messages related to Mach-O symbols
22208 processing. The default is off.
22209 @item show debug mach-o
22210 Displays the current state of displaying debugging messages related to
22211 reading of COFF/PE exported symbols.
22212 @item set debug notification
22213 @cindex remote async notification debugging info
22214 Turns on or off debugging messages about remote async notification.
22215 The default is off.
22216 @item show debug notification
22217 Displays the current state of remote async notification debugging messages.
22218 @item set debug observer
22219 @cindex observer debugging info
22220 Turns on or off display of @value{GDBN} observer debugging. This
22221 includes info such as the notification of observable events.
22222 @item show debug observer
22223 Displays the current state of observer debugging.
22224 @item set debug overload
22225 @cindex C@t{++} overload debugging info
22226 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22227 info. This includes info such as ranking of functions, etc. The default
22229 @item show debug overload
22230 Displays the current state of displaying @value{GDBN} C@t{++} overload
22232 @cindex expression parser, debugging info
22233 @cindex debug expression parser
22234 @item set debug parser
22235 Turns on or off the display of expression parser debugging output.
22236 Internally, this sets the @code{yydebug} variable in the expression
22237 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22238 details. The default is off.
22239 @item show debug parser
22240 Show the current state of expression parser debugging.
22241 @cindex packets, reporting on stdout
22242 @cindex serial connections, debugging
22243 @cindex debug remote protocol
22244 @cindex remote protocol debugging
22245 @cindex display remote packets
22246 @item set debug remote
22247 Turns on or off display of reports on all packets sent back and forth across
22248 the serial line to the remote machine. The info is printed on the
22249 @value{GDBN} standard output stream. The default is off.
22250 @item show debug remote
22251 Displays the state of display of remote packets.
22252 @item set debug serial
22253 Turns on or off display of @value{GDBN} serial debugging info. The
22255 @item show debug serial
22256 Displays the current state of displaying @value{GDBN} serial debugging
22258 @item set debug solib-frv
22259 @cindex FR-V shared-library debugging
22260 Turns on or off debugging messages for FR-V shared-library code.
22261 @item show debug solib-frv
22262 Display the current state of FR-V shared-library code debugging
22264 @item set debug symtab-create
22265 @cindex symbol table creation
22266 Turns on or off display of debugging messages related to symbol table creation.
22267 The default is off.
22268 @item show debug symtab-create
22269 Show the current state of symbol table creation debugging.
22270 @item set debug target
22271 @cindex target debugging info
22272 Turns on or off display of @value{GDBN} target debugging info. This info
22273 includes what is going on at the target level of GDB, as it happens. The
22274 default is 0. Set it to 1 to track events, and to 2 to also track the
22275 value of large memory transfers. Changes to this flag do not take effect
22276 until the next time you connect to a target or use the @code{run} command.
22277 @item show debug target
22278 Displays the current state of displaying @value{GDBN} target debugging
22280 @item set debug timestamp
22281 @cindex timestampping debugging info
22282 Turns on or off display of timestamps with @value{GDBN} debugging info.
22283 When enabled, seconds and microseconds are displayed before each debugging
22285 @item show debug timestamp
22286 Displays the current state of displaying timestamps with @value{GDBN}
22288 @item set debugvarobj
22289 @cindex variable object debugging info
22290 Turns on or off display of @value{GDBN} variable object debugging
22291 info. The default is off.
22292 @item show debugvarobj
22293 Displays the current state of displaying @value{GDBN} variable object
22295 @item set debug xml
22296 @cindex XML parser debugging
22297 Turns on or off debugging messages for built-in XML parsers.
22298 @item show debug xml
22299 Displays the current state of XML debugging messages.
22302 @node Other Misc Settings
22303 @section Other Miscellaneous Settings
22304 @cindex miscellaneous settings
22307 @kindex set interactive-mode
22308 @item set interactive-mode
22309 If @code{on}, forces @value{GDBN} to assume that GDB was started
22310 in a terminal. In practice, this means that @value{GDBN} should wait
22311 for the user to answer queries generated by commands entered at
22312 the command prompt. If @code{off}, forces @value{GDBN} to operate
22313 in the opposite mode, and it uses the default answers to all queries.
22314 If @code{auto} (the default), @value{GDBN} tries to determine whether
22315 its standard input is a terminal, and works in interactive-mode if it
22316 is, non-interactively otherwise.
22318 In the vast majority of cases, the debugger should be able to guess
22319 correctly which mode should be used. But this setting can be useful
22320 in certain specific cases, such as running a MinGW @value{GDBN}
22321 inside a cygwin window.
22323 @kindex show interactive-mode
22324 @item show interactive-mode
22325 Displays whether the debugger is operating in interactive mode or not.
22328 @node Extending GDB
22329 @chapter Extending @value{GDBN}
22330 @cindex extending GDB
22332 @value{GDBN} provides three mechanisms for extension. The first is based
22333 on composition of @value{GDBN} commands, the second is based on the
22334 Python scripting language, and the third is for defining new aliases of
22337 To facilitate the use of the first two extensions, @value{GDBN} is capable
22338 of evaluating the contents of a file. When doing so, @value{GDBN}
22339 can recognize which scripting language is being used by looking at
22340 the filename extension. Files with an unrecognized filename extension
22341 are always treated as a @value{GDBN} Command Files.
22342 @xref{Command Files,, Command files}.
22344 You can control how @value{GDBN} evaluates these files with the following
22348 @kindex set script-extension
22349 @kindex show script-extension
22350 @item set script-extension off
22351 All scripts are always evaluated as @value{GDBN} Command Files.
22353 @item set script-extension soft
22354 The debugger determines the scripting language based on filename
22355 extension. If this scripting language is supported, @value{GDBN}
22356 evaluates the script using that language. Otherwise, it evaluates
22357 the file as a @value{GDBN} Command File.
22359 @item set script-extension strict
22360 The debugger determines the scripting language based on filename
22361 extension, and evaluates the script using that language. If the
22362 language is not supported, then the evaluation fails.
22364 @item show script-extension
22365 Display the current value of the @code{script-extension} option.
22370 * Sequences:: Canned Sequences of Commands
22371 * Python:: Scripting @value{GDBN} using Python
22372 * Aliases:: Creating new spellings of existing commands
22376 @section Canned Sequences of Commands
22378 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22379 Command Lists}), @value{GDBN} provides two ways to store sequences of
22380 commands for execution as a unit: user-defined commands and command
22384 * Define:: How to define your own commands
22385 * Hooks:: Hooks for user-defined commands
22386 * Command Files:: How to write scripts of commands to be stored in a file
22387 * Output:: Commands for controlled output
22391 @subsection User-defined Commands
22393 @cindex user-defined command
22394 @cindex arguments, to user-defined commands
22395 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22396 which you assign a new name as a command. This is done with the
22397 @code{define} command. User commands may accept up to 10 arguments
22398 separated by whitespace. Arguments are accessed within the user command
22399 via @code{$arg0@dots{}$arg9}. A trivial example:
22403 print $arg0 + $arg1 + $arg2
22408 To execute the command use:
22415 This defines the command @code{adder}, which prints the sum of
22416 its three arguments. Note the arguments are text substitutions, so they may
22417 reference variables, use complex expressions, or even perform inferior
22420 @cindex argument count in user-defined commands
22421 @cindex how many arguments (user-defined commands)
22422 In addition, @code{$argc} may be used to find out how many arguments have
22423 been passed. This expands to a number in the range 0@dots{}10.
22428 print $arg0 + $arg1
22431 print $arg0 + $arg1 + $arg2
22439 @item define @var{commandname}
22440 Define a command named @var{commandname}. If there is already a command
22441 by that name, you are asked to confirm that you want to redefine it.
22442 @var{commandname} may be a bare command name consisting of letters,
22443 numbers, dashes, and underscores. It may also start with any predefined
22444 prefix command. For example, @samp{define target my-target} creates
22445 a user-defined @samp{target my-target} command.
22447 The definition of the command is made up of other @value{GDBN} command lines,
22448 which are given following the @code{define} command. The end of these
22449 commands is marked by a line containing @code{end}.
22452 @kindex end@r{ (user-defined commands)}
22453 @item document @var{commandname}
22454 Document the user-defined command @var{commandname}, so that it can be
22455 accessed by @code{help}. The command @var{commandname} must already be
22456 defined. This command reads lines of documentation just as @code{define}
22457 reads the lines of the command definition, ending with @code{end}.
22458 After the @code{document} command is finished, @code{help} on command
22459 @var{commandname} displays the documentation you have written.
22461 You may use the @code{document} command again to change the
22462 documentation of a command. Redefining the command with @code{define}
22463 does not change the documentation.
22465 @kindex dont-repeat
22466 @cindex don't repeat command
22468 Used inside a user-defined command, this tells @value{GDBN} that this
22469 command should not be repeated when the user hits @key{RET}
22470 (@pxref{Command Syntax, repeat last command}).
22472 @kindex help user-defined
22473 @item help user-defined
22474 List all user-defined commands and all python commands defined in class
22475 COMAND_USER. The first line of the documentation or docstring is
22480 @itemx show user @var{commandname}
22481 Display the @value{GDBN} commands used to define @var{commandname} (but
22482 not its documentation). If no @var{commandname} is given, display the
22483 definitions for all user-defined commands.
22484 This does not work for user-defined python commands.
22486 @cindex infinite recursion in user-defined commands
22487 @kindex show max-user-call-depth
22488 @kindex set max-user-call-depth
22489 @item show max-user-call-depth
22490 @itemx set max-user-call-depth
22491 The value of @code{max-user-call-depth} controls how many recursion
22492 levels are allowed in user-defined commands before @value{GDBN} suspects an
22493 infinite recursion and aborts the command.
22494 This does not apply to user-defined python commands.
22497 In addition to the above commands, user-defined commands frequently
22498 use control flow commands, described in @ref{Command Files}.
22500 When user-defined commands are executed, the
22501 commands of the definition are not printed. An error in any command
22502 stops execution of the user-defined command.
22504 If used interactively, commands that would ask for confirmation proceed
22505 without asking when used inside a user-defined command. Many @value{GDBN}
22506 commands that normally print messages to say what they are doing omit the
22507 messages when used in a user-defined command.
22510 @subsection User-defined Command Hooks
22511 @cindex command hooks
22512 @cindex hooks, for commands
22513 @cindex hooks, pre-command
22516 You may define @dfn{hooks}, which are a special kind of user-defined
22517 command. Whenever you run the command @samp{foo}, if the user-defined
22518 command @samp{hook-foo} exists, it is executed (with no arguments)
22519 before that command.
22521 @cindex hooks, post-command
22523 A hook may also be defined which is run after the command you executed.
22524 Whenever you run the command @samp{foo}, if the user-defined command
22525 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22526 that command. Post-execution hooks may exist simultaneously with
22527 pre-execution hooks, for the same command.
22529 It is valid for a hook to call the command which it hooks. If this
22530 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22532 @c It would be nice if hookpost could be passed a parameter indicating
22533 @c if the command it hooks executed properly or not. FIXME!
22535 @kindex stop@r{, a pseudo-command}
22536 In addition, a pseudo-command, @samp{stop} exists. Defining
22537 (@samp{hook-stop}) makes the associated commands execute every time
22538 execution stops in your program: before breakpoint commands are run,
22539 displays are printed, or the stack frame is printed.
22541 For example, to ignore @code{SIGALRM} signals while
22542 single-stepping, but treat them normally during normal execution,
22547 handle SIGALRM nopass
22551 handle SIGALRM pass
22554 define hook-continue
22555 handle SIGALRM pass
22559 As a further example, to hook at the beginning and end of the @code{echo}
22560 command, and to add extra text to the beginning and end of the message,
22568 define hookpost-echo
22572 (@value{GDBP}) echo Hello World
22573 <<<---Hello World--->>>
22578 You can define a hook for any single-word command in @value{GDBN}, but
22579 not for command aliases; you should define a hook for the basic command
22580 name, e.g.@: @code{backtrace} rather than @code{bt}.
22581 @c FIXME! So how does Joe User discover whether a command is an alias
22583 You can hook a multi-word command by adding @code{hook-} or
22584 @code{hookpost-} to the last word of the command, e.g.@:
22585 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22587 If an error occurs during the execution of your hook, execution of
22588 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22589 (before the command that you actually typed had a chance to run).
22591 If you try to define a hook which does not match any known command, you
22592 get a warning from the @code{define} command.
22594 @node Command Files
22595 @subsection Command Files
22597 @cindex command files
22598 @cindex scripting commands
22599 A command file for @value{GDBN} is a text file made of lines that are
22600 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22601 also be included. An empty line in a command file does nothing; it
22602 does not mean to repeat the last command, as it would from the
22605 You can request the execution of a command file with the @code{source}
22606 command. Note that the @code{source} command is also used to evaluate
22607 scripts that are not Command Files. The exact behavior can be configured
22608 using the @code{script-extension} setting.
22609 @xref{Extending GDB,, Extending GDB}.
22613 @cindex execute commands from a file
22614 @item source [-s] [-v] @var{filename}
22615 Execute the command file @var{filename}.
22618 The lines in a command file are generally executed sequentially,
22619 unless the order of execution is changed by one of the
22620 @emph{flow-control commands} described below. The commands are not
22621 printed as they are executed. An error in any command terminates
22622 execution of the command file and control is returned to the console.
22624 @value{GDBN} first searches for @var{filename} in the current directory.
22625 If the file is not found there, and @var{filename} does not specify a
22626 directory, then @value{GDBN} also looks for the file on the source search path
22627 (specified with the @samp{directory} command);
22628 except that @file{$cdir} is not searched because the compilation directory
22629 is not relevant to scripts.
22631 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22632 on the search path even if @var{filename} specifies a directory.
22633 The search is done by appending @var{filename} to each element of the
22634 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22635 and the search path contains @file{/home/user} then @value{GDBN} will
22636 look for the script @file{/home/user/mylib/myscript}.
22637 The search is also done if @var{filename} is an absolute path.
22638 For example, if @var{filename} is @file{/tmp/myscript} and
22639 the search path contains @file{/home/user} then @value{GDBN} will
22640 look for the script @file{/home/user/tmp/myscript}.
22641 For DOS-like systems, if @var{filename} contains a drive specification,
22642 it is stripped before concatenation. For example, if @var{filename} is
22643 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22644 will look for the script @file{c:/tmp/myscript}.
22646 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22647 each command as it is executed. The option must be given before
22648 @var{filename}, and is interpreted as part of the filename anywhere else.
22650 Commands that would ask for confirmation if used interactively proceed
22651 without asking when used in a command file. Many @value{GDBN} commands that
22652 normally print messages to say what they are doing omit the messages
22653 when called from command files.
22655 @value{GDBN} also accepts command input from standard input. In this
22656 mode, normal output goes to standard output and error output goes to
22657 standard error. Errors in a command file supplied on standard input do
22658 not terminate execution of the command file---execution continues with
22662 gdb < cmds > log 2>&1
22665 (The syntax above will vary depending on the shell used.) This example
22666 will execute commands from the file @file{cmds}. All output and errors
22667 would be directed to @file{log}.
22669 Since commands stored on command files tend to be more general than
22670 commands typed interactively, they frequently need to deal with
22671 complicated situations, such as different or unexpected values of
22672 variables and symbols, changes in how the program being debugged is
22673 built, etc. @value{GDBN} provides a set of flow-control commands to
22674 deal with these complexities. Using these commands, you can write
22675 complex scripts that loop over data structures, execute commands
22676 conditionally, etc.
22683 This command allows to include in your script conditionally executed
22684 commands. The @code{if} command takes a single argument, which is an
22685 expression to evaluate. It is followed by a series of commands that
22686 are executed only if the expression is true (its value is nonzero).
22687 There can then optionally be an @code{else} line, followed by a series
22688 of commands that are only executed if the expression was false. The
22689 end of the list is marked by a line containing @code{end}.
22693 This command allows to write loops. Its syntax is similar to
22694 @code{if}: the command takes a single argument, which is an expression
22695 to evaluate, and must be followed by the commands to execute, one per
22696 line, terminated by an @code{end}. These commands are called the
22697 @dfn{body} of the loop. The commands in the body of @code{while} are
22698 executed repeatedly as long as the expression evaluates to true.
22702 This command exits the @code{while} loop in whose body it is included.
22703 Execution of the script continues after that @code{while}s @code{end}
22706 @kindex loop_continue
22707 @item loop_continue
22708 This command skips the execution of the rest of the body of commands
22709 in the @code{while} loop in whose body it is included. Execution
22710 branches to the beginning of the @code{while} loop, where it evaluates
22711 the controlling expression.
22713 @kindex end@r{ (if/else/while commands)}
22715 Terminate the block of commands that are the body of @code{if},
22716 @code{else}, or @code{while} flow-control commands.
22721 @subsection Commands for Controlled Output
22723 During the execution of a command file or a user-defined command, normal
22724 @value{GDBN} output is suppressed; the only output that appears is what is
22725 explicitly printed by the commands in the definition. This section
22726 describes three commands useful for generating exactly the output you
22731 @item echo @var{text}
22732 @c I do not consider backslash-space a standard C escape sequence
22733 @c because it is not in ANSI.
22734 Print @var{text}. Nonprinting characters can be included in
22735 @var{text} using C escape sequences, such as @samp{\n} to print a
22736 newline. @strong{No newline is printed unless you specify one.}
22737 In addition to the standard C escape sequences, a backslash followed
22738 by a space stands for a space. This is useful for displaying a
22739 string with spaces at the beginning or the end, since leading and
22740 trailing spaces are otherwise trimmed from all arguments.
22741 To print @samp{@w{ }and foo =@w{ }}, use the command
22742 @samp{echo \@w{ }and foo = \@w{ }}.
22744 A backslash at the end of @var{text} can be used, as in C, to continue
22745 the command onto subsequent lines. For example,
22748 echo This is some text\n\
22749 which is continued\n\
22750 onto several lines.\n
22753 produces the same output as
22756 echo This is some text\n
22757 echo which is continued\n
22758 echo onto several lines.\n
22762 @item output @var{expression}
22763 Print the value of @var{expression} and nothing but that value: no
22764 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22765 value history either. @xref{Expressions, ,Expressions}, for more information
22768 @item output/@var{fmt} @var{expression}
22769 Print the value of @var{expression} in format @var{fmt}. You can use
22770 the same formats as for @code{print}. @xref{Output Formats,,Output
22771 Formats}, for more information.
22774 @item printf @var{template}, @var{expressions}@dots{}
22775 Print the values of one or more @var{expressions} under the control of
22776 the string @var{template}. To print several values, make
22777 @var{expressions} be a comma-separated list of individual expressions,
22778 which may be either numbers or pointers. Their values are printed as
22779 specified by @var{template}, exactly as a C program would do by
22780 executing the code below:
22783 printf (@var{template}, @var{expressions}@dots{});
22786 As in @code{C} @code{printf}, ordinary characters in @var{template}
22787 are printed verbatim, while @dfn{conversion specification} introduced
22788 by the @samp{%} character cause subsequent @var{expressions} to be
22789 evaluated, their values converted and formatted according to type and
22790 style information encoded in the conversion specifications, and then
22793 For example, you can print two values in hex like this:
22796 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22799 @code{printf} supports all the standard @code{C} conversion
22800 specifications, including the flags and modifiers between the @samp{%}
22801 character and the conversion letter, with the following exceptions:
22805 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22808 The modifier @samp{*} is not supported for specifying precision or
22812 The @samp{'} flag (for separation of digits into groups according to
22813 @code{LC_NUMERIC'}) is not supported.
22816 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22820 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22823 The conversion letters @samp{a} and @samp{A} are not supported.
22827 Note that the @samp{ll} type modifier is supported only if the
22828 underlying @code{C} implementation used to build @value{GDBN} supports
22829 the @code{long long int} type, and the @samp{L} type modifier is
22830 supported only if @code{long double} type is available.
22832 As in @code{C}, @code{printf} supports simple backslash-escape
22833 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22834 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22835 single character. Octal and hexadecimal escape sequences are not
22838 Additionally, @code{printf} supports conversion specifications for DFP
22839 (@dfn{Decimal Floating Point}) types using the following length modifiers
22840 together with a floating point specifier.
22845 @samp{H} for printing @code{Decimal32} types.
22848 @samp{D} for printing @code{Decimal64} types.
22851 @samp{DD} for printing @code{Decimal128} types.
22854 If the underlying @code{C} implementation used to build @value{GDBN} has
22855 support for the three length modifiers for DFP types, other modifiers
22856 such as width and precision will also be available for @value{GDBN} to use.
22858 In case there is no such @code{C} support, no additional modifiers will be
22859 available and the value will be printed in the standard way.
22861 Here's an example of printing DFP types using the above conversion letters:
22863 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22867 @item eval @var{template}, @var{expressions}@dots{}
22868 Convert the values of one or more @var{expressions} under the control of
22869 the string @var{template} to a command line, and call it.
22874 @section Scripting @value{GDBN} using Python
22875 @cindex python scripting
22876 @cindex scripting with python
22878 You can script @value{GDBN} using the @uref{http://www.python.org/,
22879 Python programming language}. This feature is available only if
22880 @value{GDBN} was configured using @option{--with-python}.
22882 @cindex python directory
22883 Python scripts used by @value{GDBN} should be installed in
22884 @file{@var{data-directory}/python}, where @var{data-directory} is
22885 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22886 This directory, known as the @dfn{python directory},
22887 is automatically added to the Python Search Path in order to allow
22888 the Python interpreter to locate all scripts installed at this location.
22890 Additionally, @value{GDBN} commands and convenience functions which
22891 are written in Python and are located in the
22892 @file{@var{data-directory}/python/gdb/command} or
22893 @file{@var{data-directory}/python/gdb/function} directories are
22894 automatically imported when @value{GDBN} starts.
22897 * Python Commands:: Accessing Python from @value{GDBN}.
22898 * Python API:: Accessing @value{GDBN} from Python.
22899 * Python Auto-loading:: Automatically loading Python code.
22900 * Python modules:: Python modules provided by @value{GDBN}.
22903 @node Python Commands
22904 @subsection Python Commands
22905 @cindex python commands
22906 @cindex commands to access python
22908 @value{GDBN} provides two commands for accessing the Python interpreter,
22909 and one related setting:
22912 @kindex python-interactive
22914 @item python-interactive @r{[}@var{command}@r{]}
22915 @itemx pi @r{[}@var{command}@r{]}
22916 Without an argument, the @code{python-interactive} command can be used
22917 to start an interactive Python prompt. To return to @value{GDBN},
22918 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22920 Alternatively, a single-line Python command can be given as an
22921 argument and evaluated. If the command is an expression, the result
22922 will be printed; otherwise, nothing will be printed. For example:
22925 (@value{GDBP}) python-interactive 2 + 3
22931 @item python @r{[}@var{command}@r{]}
22932 @itemx py @r{[}@var{command}@r{]}
22933 The @code{python} command can be used to evaluate Python code.
22935 If given an argument, the @code{python} command will evaluate the
22936 argument as a Python command. For example:
22939 (@value{GDBP}) python print 23
22943 If you do not provide an argument to @code{python}, it will act as a
22944 multi-line command, like @code{define}. In this case, the Python
22945 script is made up of subsequent command lines, given after the
22946 @code{python} command. This command list is terminated using a line
22947 containing @code{end}. For example:
22950 (@value{GDBP}) python
22952 End with a line saying just "end".
22958 @kindex set python print-stack
22959 @item set python print-stack
22960 By default, @value{GDBN} will print only the message component of a
22961 Python exception when an error occurs in a Python script. This can be
22962 controlled using @code{set python print-stack}: if @code{full}, then
22963 full Python stack printing is enabled; if @code{none}, then Python stack
22964 and message printing is disabled; if @code{message}, the default, only
22965 the message component of the error is printed.
22968 It is also possible to execute a Python script from the @value{GDBN}
22972 @item source @file{script-name}
22973 The script name must end with @samp{.py} and @value{GDBN} must be configured
22974 to recognize the script language based on filename extension using
22975 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22977 @item python execfile ("script-name")
22978 This method is based on the @code{execfile} Python built-in function,
22979 and thus is always available.
22983 @subsection Python API
22985 @cindex programming in python
22987 You can get quick online help for @value{GDBN}'s Python API by issuing
22988 the command @w{@kbd{python help (gdb)}}.
22990 Functions and methods which have two or more optional arguments allow
22991 them to be specified using keyword syntax. This allows passing some
22992 optional arguments while skipping others. Example:
22993 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
22996 * Basic Python:: Basic Python Functions.
22997 * Exception Handling:: How Python exceptions are translated.
22998 * Values From Inferior:: Python representation of values.
22999 * Types In Python:: Python representation of types.
23000 * Pretty Printing API:: Pretty-printing values.
23001 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23002 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23003 * Type Printing API:: Pretty-printing types.
23004 * Inferiors In Python:: Python representation of inferiors (processes)
23005 * Events In Python:: Listening for events from @value{GDBN}.
23006 * Threads In Python:: Accessing inferior threads from Python.
23007 * Commands In Python:: Implementing new commands in Python.
23008 * Parameters In Python:: Adding new @value{GDBN} parameters.
23009 * Functions In Python:: Writing new convenience functions.
23010 * Progspaces In Python:: Program spaces.
23011 * Objfiles In Python:: Object files.
23012 * Frames In Python:: Accessing inferior stack frames from Python.
23013 * Blocks In Python:: Accessing frame blocks from Python.
23014 * Symbols In Python:: Python representation of symbols.
23015 * Symbol Tables In Python:: Python representation of symbol tables.
23016 * Breakpoints In Python:: Manipulating breakpoints using Python.
23017 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23019 * Lazy Strings In Python:: Python representation of lazy strings.
23020 * Architectures In Python:: Python representation of architectures.
23024 @subsubsection Basic Python
23026 @cindex python stdout
23027 @cindex python pagination
23028 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23029 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23030 A Python program which outputs to one of these streams may have its
23031 output interrupted by the user (@pxref{Screen Size}). In this
23032 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23034 Some care must be taken when writing Python code to run in
23035 @value{GDBN}. Two things worth noting in particular:
23039 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23040 Python code must not override these, or even change the options using
23041 @code{sigaction}. If your program changes the handling of these
23042 signals, @value{GDBN} will most likely stop working correctly. Note
23043 that it is unfortunately common for GUI toolkits to install a
23044 @code{SIGCHLD} handler.
23047 @value{GDBN} takes care to mark its internal file descriptors as
23048 close-on-exec. However, this cannot be done in a thread-safe way on
23049 all platforms. Your Python programs should be aware of this and
23050 should both create new file descriptors with the close-on-exec flag
23051 set and arrange to close unneeded file descriptors before starting a
23055 @cindex python functions
23056 @cindex python module
23058 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23059 methods and classes added by @value{GDBN} are placed in this module.
23060 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23061 use in all scripts evaluated by the @code{python} command.
23063 @findex gdb.PYTHONDIR
23064 @defvar gdb.PYTHONDIR
23065 A string containing the python directory (@pxref{Python}).
23068 @findex gdb.execute
23069 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23070 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23071 If a GDB exception happens while @var{command} runs, it is
23072 translated as described in @ref{Exception Handling,,Exception Handling}.
23074 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23075 command as having originated from the user invoking it interactively.
23076 It must be a boolean value. If omitted, it defaults to @code{False}.
23078 By default, any output produced by @var{command} is sent to
23079 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23080 @code{True}, then output will be collected by @code{gdb.execute} and
23081 returned as a string. The default is @code{False}, in which case the
23082 return value is @code{None}. If @var{to_string} is @code{True}, the
23083 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23084 and height, and its pagination will be disabled; @pxref{Screen Size}.
23087 @findex gdb.breakpoints
23088 @defun gdb.breakpoints ()
23089 Return a sequence holding all of @value{GDBN}'s breakpoints.
23090 @xref{Breakpoints In Python}, for more information.
23093 @findex gdb.parameter
23094 @defun gdb.parameter (parameter)
23095 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23096 string naming the parameter to look up; @var{parameter} may contain
23097 spaces if the parameter has a multi-part name. For example,
23098 @samp{print object} is a valid parameter name.
23100 If the named parameter does not exist, this function throws a
23101 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23102 parameter's value is converted to a Python value of the appropriate
23103 type, and returned.
23106 @findex gdb.history
23107 @defun gdb.history (number)
23108 Return a value from @value{GDBN}'s value history (@pxref{Value
23109 History}). @var{number} indicates which history element to return.
23110 If @var{number} is negative, then @value{GDBN} will take its absolute value
23111 and count backward from the last element (i.e., the most recent element) to
23112 find the value to return. If @var{number} is zero, then @value{GDBN} will
23113 return the most recent element. If the element specified by @var{number}
23114 doesn't exist in the value history, a @code{gdb.error} exception will be
23117 If no exception is raised, the return value is always an instance of
23118 @code{gdb.Value} (@pxref{Values From Inferior}).
23121 @findex gdb.parse_and_eval
23122 @defun gdb.parse_and_eval (expression)
23123 Parse @var{expression} as an expression in the current language,
23124 evaluate it, and return the result as a @code{gdb.Value}.
23125 @var{expression} must be a string.
23127 This function can be useful when implementing a new command
23128 (@pxref{Commands In Python}), as it provides a way to parse the
23129 command's argument as an expression. It is also useful simply to
23130 compute values, for example, it is the only way to get the value of a
23131 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23134 @findex gdb.find_pc_line
23135 @defun gdb.find_pc_line (pc)
23136 Return the @code{gdb.Symtab_and_line} object corresponding to the
23137 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23138 value of @var{pc} is passed as an argument, then the @code{symtab} and
23139 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23140 will be @code{None} and 0 respectively.
23143 @findex gdb.post_event
23144 @defun gdb.post_event (event)
23145 Put @var{event}, a callable object taking no arguments, into
23146 @value{GDBN}'s internal event queue. This callable will be invoked at
23147 some later point, during @value{GDBN}'s event processing. Events
23148 posted using @code{post_event} will be run in the order in which they
23149 were posted; however, there is no way to know when they will be
23150 processed relative to other events inside @value{GDBN}.
23152 @value{GDBN} is not thread-safe. If your Python program uses multiple
23153 threads, you must be careful to only call @value{GDBN}-specific
23154 functions in the main @value{GDBN} thread. @code{post_event} ensures
23158 (@value{GDBP}) python
23162 > def __init__(self, message):
23163 > self.message = message;
23164 > def __call__(self):
23165 > gdb.write(self.message)
23167 >class MyThread1 (threading.Thread):
23169 > gdb.post_event(Writer("Hello "))
23171 >class MyThread2 (threading.Thread):
23173 > gdb.post_event(Writer("World\n"))
23175 >MyThread1().start()
23176 >MyThread2().start()
23178 (@value{GDBP}) Hello World
23183 @defun gdb.write (string @r{[}, stream{]})
23184 Print a string to @value{GDBN}'s paginated output stream. The
23185 optional @var{stream} determines the stream to print to. The default
23186 stream is @value{GDBN}'s standard output stream. Possible stream
23193 @value{GDBN}'s standard output stream.
23198 @value{GDBN}'s standard error stream.
23203 @value{GDBN}'s log stream (@pxref{Logging Output}).
23206 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23207 call this function and will automatically direct the output to the
23212 @defun gdb.flush ()
23213 Flush the buffer of a @value{GDBN} paginated stream so that the
23214 contents are displayed immediately. @value{GDBN} will flush the
23215 contents of a stream automatically when it encounters a newline in the
23216 buffer. The optional @var{stream} determines the stream to flush. The
23217 default stream is @value{GDBN}'s standard output stream. Possible
23224 @value{GDBN}'s standard output stream.
23229 @value{GDBN}'s standard error stream.
23234 @value{GDBN}'s log stream (@pxref{Logging Output}).
23238 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23239 call this function for the relevant stream.
23242 @findex gdb.target_charset
23243 @defun gdb.target_charset ()
23244 Return the name of the current target character set (@pxref{Character
23245 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23246 that @samp{auto} is never returned.
23249 @findex gdb.target_wide_charset
23250 @defun gdb.target_wide_charset ()
23251 Return the name of the current target wide character set
23252 (@pxref{Character Sets}). This differs from
23253 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23257 @findex gdb.solib_name
23258 @defun gdb.solib_name (address)
23259 Return the name of the shared library holding the given @var{address}
23260 as a string, or @code{None}.
23263 @findex gdb.decode_line
23264 @defun gdb.decode_line @r{[}expression@r{]}
23265 Return locations of the line specified by @var{expression}, or of the
23266 current line if no argument was given. This function returns a Python
23267 tuple containing two elements. The first element contains a string
23268 holding any unparsed section of @var{expression} (or @code{None} if
23269 the expression has been fully parsed). The second element contains
23270 either @code{None} or another tuple that contains all the locations
23271 that match the expression represented as @code{gdb.Symtab_and_line}
23272 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23273 provided, it is decoded the way that @value{GDBN}'s inbuilt
23274 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23277 @defun gdb.prompt_hook (current_prompt)
23278 @anchor{prompt_hook}
23280 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23281 assigned to this operation before a prompt is displayed by
23284 The parameter @code{current_prompt} contains the current @value{GDBN}
23285 prompt. This method must return a Python string, or @code{None}. If
23286 a string is returned, the @value{GDBN} prompt will be set to that
23287 string. If @code{None} is returned, @value{GDBN} will continue to use
23288 the current prompt.
23290 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23291 such as those used by readline for command input, and annotation
23292 related prompts are prohibited from being changed.
23295 @node Exception Handling
23296 @subsubsection Exception Handling
23297 @cindex python exceptions
23298 @cindex exceptions, python
23300 When executing the @code{python} command, Python exceptions
23301 uncaught within the Python code are translated to calls to
23302 @value{GDBN} error-reporting mechanism. If the command that called
23303 @code{python} does not handle the error, @value{GDBN} will
23304 terminate it and print an error message containing the Python
23305 exception name, the associated value, and the Python call stack
23306 backtrace at the point where the exception was raised. Example:
23309 (@value{GDBP}) python print foo
23310 Traceback (most recent call last):
23311 File "<string>", line 1, in <module>
23312 NameError: name 'foo' is not defined
23315 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23316 Python code are converted to Python exceptions. The type of the
23317 Python exception depends on the error.
23321 This is the base class for most exceptions generated by @value{GDBN}.
23322 It is derived from @code{RuntimeError}, for compatibility with earlier
23323 versions of @value{GDBN}.
23325 If an error occurring in @value{GDBN} does not fit into some more
23326 specific category, then the generated exception will have this type.
23328 @item gdb.MemoryError
23329 This is a subclass of @code{gdb.error} which is thrown when an
23330 operation tried to access invalid memory in the inferior.
23332 @item KeyboardInterrupt
23333 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23334 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23337 In all cases, your exception handler will see the @value{GDBN} error
23338 message as its value and the Python call stack backtrace at the Python
23339 statement closest to where the @value{GDBN} error occured as the
23342 @findex gdb.GdbError
23343 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23344 it is useful to be able to throw an exception that doesn't cause a
23345 traceback to be printed. For example, the user may have invoked the
23346 command incorrectly. Use the @code{gdb.GdbError} exception
23347 to handle this case. Example:
23351 >class HelloWorld (gdb.Command):
23352 > """Greet the whole world."""
23353 > def __init__ (self):
23354 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23355 > def invoke (self, args, from_tty):
23356 > argv = gdb.string_to_argv (args)
23357 > if len (argv) != 0:
23358 > raise gdb.GdbError ("hello-world takes no arguments")
23359 > print "Hello, World!"
23362 (gdb) hello-world 42
23363 hello-world takes no arguments
23366 @node Values From Inferior
23367 @subsubsection Values From Inferior
23368 @cindex values from inferior, with Python
23369 @cindex python, working with values from inferior
23371 @cindex @code{gdb.Value}
23372 @value{GDBN} provides values it obtains from the inferior program in
23373 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23374 for its internal bookkeeping of the inferior's values, and for
23375 fetching values when necessary.
23377 Inferior values that are simple scalars can be used directly in
23378 Python expressions that are valid for the value's data type. Here's
23379 an example for an integer or floating-point value @code{some_val}:
23386 As result of this, @code{bar} will also be a @code{gdb.Value} object
23387 whose values are of the same type as those of @code{some_val}.
23389 Inferior values that are structures or instances of some class can
23390 be accessed using the Python @dfn{dictionary syntax}. For example, if
23391 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23392 can access its @code{foo} element with:
23395 bar = some_val['foo']
23398 Again, @code{bar} will also be a @code{gdb.Value} object.
23400 A @code{gdb.Value} that represents a function can be executed via
23401 inferior function call. Any arguments provided to the call must match
23402 the function's prototype, and must be provided in the order specified
23405 For example, @code{some_val} is a @code{gdb.Value} instance
23406 representing a function that takes two integers as arguments. To
23407 execute this function, call it like so:
23410 result = some_val (10,20)
23413 Any values returned from a function call will be stored as a
23416 The following attributes are provided:
23418 @defvar Value.address
23419 If this object is addressable, this read-only attribute holds a
23420 @code{gdb.Value} object representing the address. Otherwise,
23421 this attribute holds @code{None}.
23424 @cindex optimized out value in Python
23425 @defvar Value.is_optimized_out
23426 This read-only boolean attribute is true if the compiler optimized out
23427 this value, thus it is not available for fetching from the inferior.
23431 The type of this @code{gdb.Value}. The value of this attribute is a
23432 @code{gdb.Type} object (@pxref{Types In Python}).
23435 @defvar Value.dynamic_type
23436 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23437 type information (@acronym{RTTI}) to determine the dynamic type of the
23438 value. If this value is of class type, it will return the class in
23439 which the value is embedded, if any. If this value is of pointer or
23440 reference to a class type, it will compute the dynamic type of the
23441 referenced object, and return a pointer or reference to that type,
23442 respectively. In all other cases, it will return the value's static
23445 Note that this feature will only work when debugging a C@t{++} program
23446 that includes @acronym{RTTI} for the object in question. Otherwise,
23447 it will just return the static type of the value as in @kbd{ptype foo}
23448 (@pxref{Symbols, ptype}).
23451 @defvar Value.is_lazy
23452 The value of this read-only boolean attribute is @code{True} if this
23453 @code{gdb.Value} has not yet been fetched from the inferior.
23454 @value{GDBN} does not fetch values until necessary, for efficiency.
23458 myval = gdb.parse_and_eval ('somevar')
23461 The value of @code{somevar} is not fetched at this time. It will be
23462 fetched when the value is needed, or when the @code{fetch_lazy}
23466 The following methods are provided:
23468 @defun Value.__init__ (@var{val})
23469 Many Python values can be converted directly to a @code{gdb.Value} via
23470 this object initializer. Specifically:
23473 @item Python boolean
23474 A Python boolean is converted to the boolean type from the current
23477 @item Python integer
23478 A Python integer is converted to the C @code{long} type for the
23479 current architecture.
23482 A Python long is converted to the C @code{long long} type for the
23483 current architecture.
23486 A Python float is converted to the C @code{double} type for the
23487 current architecture.
23489 @item Python string
23490 A Python string is converted to a target string, using the current
23493 @item @code{gdb.Value}
23494 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23496 @item @code{gdb.LazyString}
23497 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23498 Python}), then the lazy string's @code{value} method is called, and
23499 its result is used.
23503 @defun Value.cast (type)
23504 Return a new instance of @code{gdb.Value} that is the result of
23505 casting this instance to the type described by @var{type}, which must
23506 be a @code{gdb.Type} object. If the cast cannot be performed for some
23507 reason, this method throws an exception.
23510 @defun Value.dereference ()
23511 For pointer data types, this method returns a new @code{gdb.Value} object
23512 whose contents is the object pointed to by the pointer. For example, if
23513 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23520 then you can use the corresponding @code{gdb.Value} to access what
23521 @code{foo} points to like this:
23524 bar = foo.dereference ()
23527 The result @code{bar} will be a @code{gdb.Value} object holding the
23528 value pointed to by @code{foo}.
23530 A similar function @code{Value.referenced_value} exists which also
23531 returns @code{gdb.Value} objects corresonding to the values pointed to
23532 by pointer values (and additionally, values referenced by reference
23533 values). However, the behavior of @code{Value.dereference}
23534 differs from @code{Value.referenced_value} by the fact that the
23535 behavior of @code{Value.dereference} is identical to applying the C
23536 unary operator @code{*} on a given value. For example, consider a
23537 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23541 typedef int *intptr;
23545 intptr &ptrref = ptr;
23548 Though @code{ptrref} is a reference value, one can apply the method
23549 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23550 to it and obtain a @code{gdb.Value} which is identical to that
23551 corresponding to @code{val}. However, if you apply the method
23552 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23553 object identical to that corresponding to @code{ptr}.
23556 py_ptrref = gdb.parse_and_eval ("ptrref")
23557 py_val = py_ptrref.dereference ()
23558 py_ptr = py_ptrref.referenced_value ()
23561 The @code{gdb.Value} object @code{py_val} is identical to that
23562 corresponding to @code{val}, and @code{py_ptr} is identical to that
23563 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23564 be applied whenever the C unary operator @code{*} can be applied
23565 to the corresponding C value. For those cases where applying both
23566 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23567 the results obtained need not be identical (as we have seen in the above
23568 example). The results are however identical when applied on
23569 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23570 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23573 @defun Value.referenced_value ()
23574 For pointer or reference data types, this method returns a new
23575 @code{gdb.Value} object corresponding to the value referenced by the
23576 pointer/reference value. For pointer data types,
23577 @code{Value.dereference} and @code{Value.referenced_value} produce
23578 identical results. The difference between these methods is that
23579 @code{Value.dereference} cannot get the values referenced by reference
23580 values. For example, consider a reference to an @code{int}, declared
23581 in your C@t{++} program as
23589 then applying @code{Value.dereference} to the @code{gdb.Value} object
23590 corresponding to @code{ref} will result in an error, while applying
23591 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23592 identical to that corresponding to @code{val}.
23595 py_ref = gdb.parse_and_eval ("ref")
23596 er_ref = py_ref.dereference () # Results in error
23597 py_val = py_ref.referenced_value () # Returns the referenced value
23600 The @code{gdb.Value} object @code{py_val} is identical to that
23601 corresponding to @code{val}.
23604 @defun Value.dynamic_cast (type)
23605 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23606 operator were used. Consult a C@t{++} reference for details.
23609 @defun Value.reinterpret_cast (type)
23610 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23611 operator were used. Consult a C@t{++} reference for details.
23614 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23615 If this @code{gdb.Value} represents a string, then this method
23616 converts the contents to a Python string. Otherwise, this method will
23617 throw an exception.
23619 Strings are recognized in a language-specific way; whether a given
23620 @code{gdb.Value} represents a string is determined by the current
23623 For C-like languages, a value is a string if it is a pointer to or an
23624 array of characters or ints. The string is assumed to be terminated
23625 by a zero of the appropriate width. However if the optional length
23626 argument is given, the string will be converted to that given length,
23627 ignoring any embedded zeros that the string may contain.
23629 If the optional @var{encoding} argument is given, it must be a string
23630 naming the encoding of the string in the @code{gdb.Value}, such as
23631 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23632 the same encodings as the corresponding argument to Python's
23633 @code{string.decode} method, and the Python codec machinery will be used
23634 to convert the string. If @var{encoding} is not given, or if
23635 @var{encoding} is the empty string, then either the @code{target-charset}
23636 (@pxref{Character Sets}) will be used, or a language-specific encoding
23637 will be used, if the current language is able to supply one.
23639 The optional @var{errors} argument is the same as the corresponding
23640 argument to Python's @code{string.decode} method.
23642 If the optional @var{length} argument is given, the string will be
23643 fetched and converted to the given length.
23646 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23647 If this @code{gdb.Value} represents a string, then this method
23648 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23649 In Python}). Otherwise, this method will throw an exception.
23651 If the optional @var{encoding} argument is given, it must be a string
23652 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23653 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23654 @var{encoding} argument is an encoding that @value{GDBN} does
23655 recognize, @value{GDBN} will raise an error.
23657 When a lazy string is printed, the @value{GDBN} encoding machinery is
23658 used to convert the string during printing. If the optional
23659 @var{encoding} argument is not provided, or is an empty string,
23660 @value{GDBN} will automatically select the encoding most suitable for
23661 the string type. For further information on encoding in @value{GDBN}
23662 please see @ref{Character Sets}.
23664 If the optional @var{length} argument is given, the string will be
23665 fetched and encoded to the length of characters specified. If
23666 the @var{length} argument is not provided, the string will be fetched
23667 and encoded until a null of appropriate width is found.
23670 @defun Value.fetch_lazy ()
23671 If the @code{gdb.Value} object is currently a lazy value
23672 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23673 fetched from the inferior. Any errors that occur in the process
23674 will produce a Python exception.
23676 If the @code{gdb.Value} object is not a lazy value, this method
23679 This method does not return a value.
23683 @node Types In Python
23684 @subsubsection Types In Python
23685 @cindex types in Python
23686 @cindex Python, working with types
23689 @value{GDBN} represents types from the inferior using the class
23692 The following type-related functions are available in the @code{gdb}
23695 @findex gdb.lookup_type
23696 @defun gdb.lookup_type (name @r{[}, block@r{]})
23697 This function looks up a type by name. @var{name} is the name of the
23698 type to look up. It must be a string.
23700 If @var{block} is given, then @var{name} is looked up in that scope.
23701 Otherwise, it is searched for globally.
23703 Ordinarily, this function will return an instance of @code{gdb.Type}.
23704 If the named type cannot be found, it will throw an exception.
23707 If the type is a structure or class type, or an enum type, the fields
23708 of that type can be accessed using the Python @dfn{dictionary syntax}.
23709 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23710 a structure type, you can access its @code{foo} field with:
23713 bar = some_type['foo']
23716 @code{bar} will be a @code{gdb.Field} object; see below under the
23717 description of the @code{Type.fields} method for a description of the
23718 @code{gdb.Field} class.
23720 An instance of @code{Type} has the following attributes:
23723 The type code for this type. The type code will be one of the
23724 @code{TYPE_CODE_} constants defined below.
23727 @defvar Type.sizeof
23728 The size of this type, in target @code{char} units. Usually, a
23729 target's @code{char} type will be an 8-bit byte. However, on some
23730 unusual platforms, this type may have a different size.
23734 The tag name for this type. The tag name is the name after
23735 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23736 languages have this concept. If this type has no tag name, then
23737 @code{None} is returned.
23740 The following methods are provided:
23742 @defun Type.fields ()
23743 For structure and union types, this method returns the fields. Range
23744 types have two fields, the minimum and maximum values. Enum types
23745 have one field per enum constant. Function and method types have one
23746 field per parameter. The base types of C@t{++} classes are also
23747 represented as fields. If the type has no fields, or does not fit
23748 into one of these categories, an empty sequence will be returned.
23750 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23753 This attribute is not available for @code{static} fields (as in
23754 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23755 position of the field. For @code{enum} fields, the value is the
23756 enumeration member's integer representation.
23759 The name of the field, or @code{None} for anonymous fields.
23762 This is @code{True} if the field is artificial, usually meaning that
23763 it was provided by the compiler and not the user. This attribute is
23764 always provided, and is @code{False} if the field is not artificial.
23766 @item is_base_class
23767 This is @code{True} if the field represents a base class of a C@t{++}
23768 structure. This attribute is always provided, and is @code{False}
23769 if the field is not a base class of the type that is the argument of
23770 @code{fields}, or if that type was not a C@t{++} class.
23773 If the field is packed, or is a bitfield, then this will have a
23774 non-zero value, which is the size of the field in bits. Otherwise,
23775 this will be zero; in this case the field's size is given by its type.
23778 The type of the field. This is usually an instance of @code{Type},
23779 but it can be @code{None} in some situations.
23783 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23784 Return a new @code{gdb.Type} object which represents an array of this
23785 type. If one argument is given, it is the inclusive upper bound of
23786 the array; in this case the lower bound is zero. If two arguments are
23787 given, the first argument is the lower bound of the array, and the
23788 second argument is the upper bound of the array. An array's length
23789 must not be negative, but the bounds can be.
23792 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23793 Return a new @code{gdb.Type} object which represents a vector of this
23794 type. If one argument is given, it is the inclusive upper bound of
23795 the vector; in this case the lower bound is zero. If two arguments are
23796 given, the first argument is the lower bound of the vector, and the
23797 second argument is the upper bound of the vector. A vector's length
23798 must not be negative, but the bounds can be.
23800 The difference between an @code{array} and a @code{vector} is that
23801 arrays behave like in C: when used in expressions they decay to a pointer
23802 to the first element whereas vectors are treated as first class values.
23805 @defun Type.const ()
23806 Return a new @code{gdb.Type} object which represents a
23807 @code{const}-qualified variant of this type.
23810 @defun Type.volatile ()
23811 Return a new @code{gdb.Type} object which represents a
23812 @code{volatile}-qualified variant of this type.
23815 @defun Type.unqualified ()
23816 Return a new @code{gdb.Type} object which represents an unqualified
23817 variant of this type. That is, the result is neither @code{const} nor
23821 @defun Type.range ()
23822 Return a Python @code{Tuple} object that contains two elements: the
23823 low bound of the argument type and the high bound of that type. If
23824 the type does not have a range, @value{GDBN} will raise a
23825 @code{gdb.error} exception (@pxref{Exception Handling}).
23828 @defun Type.reference ()
23829 Return a new @code{gdb.Type} object which represents a reference to this
23833 @defun Type.pointer ()
23834 Return a new @code{gdb.Type} object which represents a pointer to this
23838 @defun Type.strip_typedefs ()
23839 Return a new @code{gdb.Type} that represents the real type,
23840 after removing all layers of typedefs.
23843 @defun Type.target ()
23844 Return a new @code{gdb.Type} object which represents the target type
23847 For a pointer type, the target type is the type of the pointed-to
23848 object. For an array type (meaning C-like arrays), the target type is
23849 the type of the elements of the array. For a function or method type,
23850 the target type is the type of the return value. For a complex type,
23851 the target type is the type of the elements. For a typedef, the
23852 target type is the aliased type.
23854 If the type does not have a target, this method will throw an
23858 @defun Type.template_argument (n @r{[}, block@r{]})
23859 If this @code{gdb.Type} is an instantiation of a template, this will
23860 return a new @code{gdb.Type} which represents the type of the
23861 @var{n}th template argument.
23863 If this @code{gdb.Type} is not a template type, this will throw an
23864 exception. Ordinarily, only C@t{++} code will have template types.
23866 If @var{block} is given, then @var{name} is looked up in that scope.
23867 Otherwise, it is searched for globally.
23871 Each type has a code, which indicates what category this type falls
23872 into. The available type categories are represented by constants
23873 defined in the @code{gdb} module:
23876 @findex TYPE_CODE_PTR
23877 @findex gdb.TYPE_CODE_PTR
23878 @item gdb.TYPE_CODE_PTR
23879 The type is a pointer.
23881 @findex TYPE_CODE_ARRAY
23882 @findex gdb.TYPE_CODE_ARRAY
23883 @item gdb.TYPE_CODE_ARRAY
23884 The type is an array.
23886 @findex TYPE_CODE_STRUCT
23887 @findex gdb.TYPE_CODE_STRUCT
23888 @item gdb.TYPE_CODE_STRUCT
23889 The type is a structure.
23891 @findex TYPE_CODE_UNION
23892 @findex gdb.TYPE_CODE_UNION
23893 @item gdb.TYPE_CODE_UNION
23894 The type is a union.
23896 @findex TYPE_CODE_ENUM
23897 @findex gdb.TYPE_CODE_ENUM
23898 @item gdb.TYPE_CODE_ENUM
23899 The type is an enum.
23901 @findex TYPE_CODE_FLAGS
23902 @findex gdb.TYPE_CODE_FLAGS
23903 @item gdb.TYPE_CODE_FLAGS
23904 A bit flags type, used for things such as status registers.
23906 @findex TYPE_CODE_FUNC
23907 @findex gdb.TYPE_CODE_FUNC
23908 @item gdb.TYPE_CODE_FUNC
23909 The type is a function.
23911 @findex TYPE_CODE_INT
23912 @findex gdb.TYPE_CODE_INT
23913 @item gdb.TYPE_CODE_INT
23914 The type is an integer type.
23916 @findex TYPE_CODE_FLT
23917 @findex gdb.TYPE_CODE_FLT
23918 @item gdb.TYPE_CODE_FLT
23919 A floating point type.
23921 @findex TYPE_CODE_VOID
23922 @findex gdb.TYPE_CODE_VOID
23923 @item gdb.TYPE_CODE_VOID
23924 The special type @code{void}.
23926 @findex TYPE_CODE_SET
23927 @findex gdb.TYPE_CODE_SET
23928 @item gdb.TYPE_CODE_SET
23931 @findex TYPE_CODE_RANGE
23932 @findex gdb.TYPE_CODE_RANGE
23933 @item gdb.TYPE_CODE_RANGE
23934 A range type, that is, an integer type with bounds.
23936 @findex TYPE_CODE_STRING
23937 @findex gdb.TYPE_CODE_STRING
23938 @item gdb.TYPE_CODE_STRING
23939 A string type. Note that this is only used for certain languages with
23940 language-defined string types; C strings are not represented this way.
23942 @findex TYPE_CODE_BITSTRING
23943 @findex gdb.TYPE_CODE_BITSTRING
23944 @item gdb.TYPE_CODE_BITSTRING
23945 A string of bits. It is deprecated.
23947 @findex TYPE_CODE_ERROR
23948 @findex gdb.TYPE_CODE_ERROR
23949 @item gdb.TYPE_CODE_ERROR
23950 An unknown or erroneous type.
23952 @findex TYPE_CODE_METHOD
23953 @findex gdb.TYPE_CODE_METHOD
23954 @item gdb.TYPE_CODE_METHOD
23955 A method type, as found in C@t{++} or Java.
23957 @findex TYPE_CODE_METHODPTR
23958 @findex gdb.TYPE_CODE_METHODPTR
23959 @item gdb.TYPE_CODE_METHODPTR
23960 A pointer-to-member-function.
23962 @findex TYPE_CODE_MEMBERPTR
23963 @findex gdb.TYPE_CODE_MEMBERPTR
23964 @item gdb.TYPE_CODE_MEMBERPTR
23965 A pointer-to-member.
23967 @findex TYPE_CODE_REF
23968 @findex gdb.TYPE_CODE_REF
23969 @item gdb.TYPE_CODE_REF
23972 @findex TYPE_CODE_CHAR
23973 @findex gdb.TYPE_CODE_CHAR
23974 @item gdb.TYPE_CODE_CHAR
23977 @findex TYPE_CODE_BOOL
23978 @findex gdb.TYPE_CODE_BOOL
23979 @item gdb.TYPE_CODE_BOOL
23982 @findex TYPE_CODE_COMPLEX
23983 @findex gdb.TYPE_CODE_COMPLEX
23984 @item gdb.TYPE_CODE_COMPLEX
23985 A complex float type.
23987 @findex TYPE_CODE_TYPEDEF
23988 @findex gdb.TYPE_CODE_TYPEDEF
23989 @item gdb.TYPE_CODE_TYPEDEF
23990 A typedef to some other type.
23992 @findex TYPE_CODE_NAMESPACE
23993 @findex gdb.TYPE_CODE_NAMESPACE
23994 @item gdb.TYPE_CODE_NAMESPACE
23995 A C@t{++} namespace.
23997 @findex TYPE_CODE_DECFLOAT
23998 @findex gdb.TYPE_CODE_DECFLOAT
23999 @item gdb.TYPE_CODE_DECFLOAT
24000 A decimal floating point type.
24002 @findex TYPE_CODE_INTERNAL_FUNCTION
24003 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24004 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24005 A function internal to @value{GDBN}. This is the type used to represent
24006 convenience functions.
24009 Further support for types is provided in the @code{gdb.types}
24010 Python module (@pxref{gdb.types}).
24012 @node Pretty Printing API
24013 @subsubsection Pretty Printing API
24015 An example output is provided (@pxref{Pretty Printing}).
24017 A pretty-printer is just an object that holds a value and implements a
24018 specific interface, defined here.
24020 @defun pretty_printer.children (self)
24021 @value{GDBN} will call this method on a pretty-printer to compute the
24022 children of the pretty-printer's value.
24024 This method must return an object conforming to the Python iterator
24025 protocol. Each item returned by the iterator must be a tuple holding
24026 two elements. The first element is the ``name'' of the child; the
24027 second element is the child's value. The value can be any Python
24028 object which is convertible to a @value{GDBN} value.
24030 This method is optional. If it does not exist, @value{GDBN} will act
24031 as though the value has no children.
24034 @defun pretty_printer.display_hint (self)
24035 The CLI may call this method and use its result to change the
24036 formatting of a value. The result will also be supplied to an MI
24037 consumer as a @samp{displayhint} attribute of the variable being
24040 This method is optional. If it does exist, this method must return a
24043 Some display hints are predefined by @value{GDBN}:
24047 Indicate that the object being printed is ``array-like''. The CLI
24048 uses this to respect parameters such as @code{set print elements} and
24049 @code{set print array}.
24052 Indicate that the object being printed is ``map-like'', and that the
24053 children of this value can be assumed to alternate between keys and
24057 Indicate that the object being printed is ``string-like''. If the
24058 printer's @code{to_string} method returns a Python string of some
24059 kind, then @value{GDBN} will call its internal language-specific
24060 string-printing function to format the string. For the CLI this means
24061 adding quotation marks, possibly escaping some characters, respecting
24062 @code{set print elements}, and the like.
24066 @defun pretty_printer.to_string (self)
24067 @value{GDBN} will call this method to display the string
24068 representation of the value passed to the object's constructor.
24070 When printing from the CLI, if the @code{to_string} method exists,
24071 then @value{GDBN} will prepend its result to the values returned by
24072 @code{children}. Exactly how this formatting is done is dependent on
24073 the display hint, and may change as more hints are added. Also,
24074 depending on the print settings (@pxref{Print Settings}), the CLI may
24075 print just the result of @code{to_string} in a stack trace, omitting
24076 the result of @code{children}.
24078 If this method returns a string, it is printed verbatim.
24080 Otherwise, if this method returns an instance of @code{gdb.Value},
24081 then @value{GDBN} prints this value. This may result in a call to
24082 another pretty-printer.
24084 If instead the method returns a Python value which is convertible to a
24085 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24086 the resulting value. Again, this may result in a call to another
24087 pretty-printer. Python scalars (integers, floats, and booleans) and
24088 strings are convertible to @code{gdb.Value}; other types are not.
24090 Finally, if this method returns @code{None} then no further operations
24091 are peformed in this method and nothing is printed.
24093 If the result is not one of these types, an exception is raised.
24096 @value{GDBN} provides a function which can be used to look up the
24097 default pretty-printer for a @code{gdb.Value}:
24099 @findex gdb.default_visualizer
24100 @defun gdb.default_visualizer (value)
24101 This function takes a @code{gdb.Value} object as an argument. If a
24102 pretty-printer for this value exists, then it is returned. If no such
24103 printer exists, then this returns @code{None}.
24106 @node Selecting Pretty-Printers
24107 @subsubsection Selecting Pretty-Printers
24109 The Python list @code{gdb.pretty_printers} contains an array of
24110 functions or callable objects that have been registered via addition
24111 as a pretty-printer. Printers in this list are called @code{global}
24112 printers, they're available when debugging all inferiors.
24113 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24114 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24117 Each function on these lists is passed a single @code{gdb.Value}
24118 argument and should return a pretty-printer object conforming to the
24119 interface definition above (@pxref{Pretty Printing API}). If a function
24120 cannot create a pretty-printer for the value, it should return
24123 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24124 @code{gdb.Objfile} in the current program space and iteratively calls
24125 each enabled lookup routine in the list for that @code{gdb.Objfile}
24126 until it receives a pretty-printer object.
24127 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24128 searches the pretty-printer list of the current program space,
24129 calling each enabled function until an object is returned.
24130 After these lists have been exhausted, it tries the global
24131 @code{gdb.pretty_printers} list, again calling each enabled function until an
24132 object is returned.
24134 The order in which the objfiles are searched is not specified. For a
24135 given list, functions are always invoked from the head of the list,
24136 and iterated over sequentially until the end of the list, or a printer
24137 object is returned.
24139 For various reasons a pretty-printer may not work.
24140 For example, the underlying data structure may have changed and
24141 the pretty-printer is out of date.
24143 The consequences of a broken pretty-printer are severe enough that
24144 @value{GDBN} provides support for enabling and disabling individual
24145 printers. For example, if @code{print frame-arguments} is on,
24146 a backtrace can become highly illegible if any argument is printed
24147 with a broken printer.
24149 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24150 attribute to the registered function or callable object. If this attribute
24151 is present and its value is @code{False}, the printer is disabled, otherwise
24152 the printer is enabled.
24154 @node Writing a Pretty-Printer
24155 @subsubsection Writing a Pretty-Printer
24156 @cindex writing a pretty-printer
24158 A pretty-printer consists of two parts: a lookup function to detect
24159 if the type is supported, and the printer itself.
24161 Here is an example showing how a @code{std::string} printer might be
24162 written. @xref{Pretty Printing API}, for details on the API this class
24166 class StdStringPrinter(object):
24167 "Print a std::string"
24169 def __init__(self, val):
24172 def to_string(self):
24173 return self.val['_M_dataplus']['_M_p']
24175 def display_hint(self):
24179 And here is an example showing how a lookup function for the printer
24180 example above might be written.
24183 def str_lookup_function(val):
24184 lookup_tag = val.type.tag
24185 if lookup_tag == None:
24187 regex = re.compile("^std::basic_string<char,.*>$")
24188 if regex.match(lookup_tag):
24189 return StdStringPrinter(val)
24193 The example lookup function extracts the value's type, and attempts to
24194 match it to a type that it can pretty-print. If it is a type the
24195 printer can pretty-print, it will return a printer object. If not, it
24196 returns @code{None}.
24198 We recommend that you put your core pretty-printers into a Python
24199 package. If your pretty-printers are for use with a library, we
24200 further recommend embedding a version number into the package name.
24201 This practice will enable @value{GDBN} to load multiple versions of
24202 your pretty-printers at the same time, because they will have
24205 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24206 can be evaluated multiple times without changing its meaning. An
24207 ideal auto-load file will consist solely of @code{import}s of your
24208 printer modules, followed by a call to a register pretty-printers with
24209 the current objfile.
24211 Taken as a whole, this approach will scale nicely to multiple
24212 inferiors, each potentially using a different library version.
24213 Embedding a version number in the Python package name will ensure that
24214 @value{GDBN} is able to load both sets of printers simultaneously.
24215 Then, because the search for pretty-printers is done by objfile, and
24216 because your auto-loaded code took care to register your library's
24217 printers with a specific objfile, @value{GDBN} will find the correct
24218 printers for the specific version of the library used by each
24221 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24222 this code might appear in @code{gdb.libstdcxx.v6}:
24225 def register_printers(objfile):
24226 objfile.pretty_printers.append(str_lookup_function)
24230 And then the corresponding contents of the auto-load file would be:
24233 import gdb.libstdcxx.v6
24234 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24237 The previous example illustrates a basic pretty-printer.
24238 There are a few things that can be improved on.
24239 The printer doesn't have a name, making it hard to identify in a
24240 list of installed printers. The lookup function has a name, but
24241 lookup functions can have arbitrary, even identical, names.
24243 Second, the printer only handles one type, whereas a library typically has
24244 several types. One could install a lookup function for each desired type
24245 in the library, but one could also have a single lookup function recognize
24246 several types. The latter is the conventional way this is handled.
24247 If a pretty-printer can handle multiple data types, then its
24248 @dfn{subprinters} are the printers for the individual data types.
24250 The @code{gdb.printing} module provides a formal way of solving these
24251 problems (@pxref{gdb.printing}).
24252 Here is another example that handles multiple types.
24254 These are the types we are going to pretty-print:
24257 struct foo @{ int a, b; @};
24258 struct bar @{ struct foo x, y; @};
24261 Here are the printers:
24265 """Print a foo object."""
24267 def __init__(self, val):
24270 def to_string(self):
24271 return ("a=<" + str(self.val["a"]) +
24272 "> b=<" + str(self.val["b"]) + ">")
24275 """Print a bar object."""
24277 def __init__(self, val):
24280 def to_string(self):
24281 return ("x=<" + str(self.val["x"]) +
24282 "> y=<" + str(self.val["y"]) + ">")
24285 This example doesn't need a lookup function, that is handled by the
24286 @code{gdb.printing} module. Instead a function is provided to build up
24287 the object that handles the lookup.
24290 import gdb.printing
24292 def build_pretty_printer():
24293 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24295 pp.add_printer('foo', '^foo$', fooPrinter)
24296 pp.add_printer('bar', '^bar$', barPrinter)
24300 And here is the autoload support:
24303 import gdb.printing
24305 gdb.printing.register_pretty_printer(
24306 gdb.current_objfile(),
24307 my_library.build_pretty_printer())
24310 Finally, when this printer is loaded into @value{GDBN}, here is the
24311 corresponding output of @samp{info pretty-printer}:
24314 (gdb) info pretty-printer
24321 @node Type Printing API
24322 @subsubsection Type Printing API
24323 @cindex type printing API for Python
24325 @value{GDBN} provides a way for Python code to customize type display.
24326 This is mainly useful for substituting canonical typedef names for
24329 @cindex type printer
24330 A @dfn{type printer} is just a Python object conforming to a certain
24331 protocol. A simple base class implementing the protocol is provided;
24332 see @ref{gdb.types}. A type printer must supply at least:
24334 @defivar type_printer enabled
24335 A boolean which is True if the printer is enabled, and False
24336 otherwise. This is manipulated by the @code{enable type-printer}
24337 and @code{disable type-printer} commands.
24340 @defivar type_printer name
24341 The name of the type printer. This must be a string. This is used by
24342 the @code{enable type-printer} and @code{disable type-printer}
24346 @defmethod type_printer instantiate (self)
24347 This is called by @value{GDBN} at the start of type-printing. It is
24348 only called if the type printer is enabled. This method must return a
24349 new object that supplies a @code{recognize} method, as described below.
24353 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24354 will compute a list of type recognizers. This is done by iterating
24355 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24356 followed by the per-progspace type printers (@pxref{Progspaces In
24357 Python}), and finally the global type printers.
24359 @value{GDBN} will call the @code{instantiate} method of each enabled
24360 type printer. If this method returns @code{None}, then the result is
24361 ignored; otherwise, it is appended to the list of recognizers.
24363 Then, when @value{GDBN} is going to display a type name, it iterates
24364 over the list of recognizers. For each one, it calls the recognition
24365 function, stopping if the function returns a non-@code{None} value.
24366 The recognition function is defined as:
24368 @defmethod type_recognizer recognize (self, type)
24369 If @var{type} is not recognized, return @code{None}. Otherwise,
24370 return a string which is to be printed as the name of @var{type}.
24371 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24375 @value{GDBN} uses this two-pass approach so that type printers can
24376 efficiently cache information without holding on to it too long. For
24377 example, it can be convenient to look up type information in a type
24378 printer and hold it for a recognizer's lifetime; if a single pass were
24379 done then type printers would have to make use of the event system in
24380 order to avoid holding information that could become stale as the
24383 @node Inferiors In Python
24384 @subsubsection Inferiors In Python
24385 @cindex inferiors in Python
24387 @findex gdb.Inferior
24388 Programs which are being run under @value{GDBN} are called inferiors
24389 (@pxref{Inferiors and Programs}). Python scripts can access
24390 information about and manipulate inferiors controlled by @value{GDBN}
24391 via objects of the @code{gdb.Inferior} class.
24393 The following inferior-related functions are available in the @code{gdb}
24396 @defun gdb.inferiors ()
24397 Return a tuple containing all inferior objects.
24400 @defun gdb.selected_inferior ()
24401 Return an object representing the current inferior.
24404 A @code{gdb.Inferior} object has the following attributes:
24406 @defvar Inferior.num
24407 ID of inferior, as assigned by GDB.
24410 @defvar Inferior.pid
24411 Process ID of the inferior, as assigned by the underlying operating
24415 @defvar Inferior.was_attached
24416 Boolean signaling whether the inferior was created using `attach', or
24417 started by @value{GDBN} itself.
24420 A @code{gdb.Inferior} object has the following methods:
24422 @defun Inferior.is_valid ()
24423 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24424 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24425 if the inferior no longer exists within @value{GDBN}. All other
24426 @code{gdb.Inferior} methods will throw an exception if it is invalid
24427 at the time the method is called.
24430 @defun Inferior.threads ()
24431 This method returns a tuple holding all the threads which are valid
24432 when it is called. If there are no valid threads, the method will
24433 return an empty tuple.
24436 @findex Inferior.read_memory
24437 @defun Inferior.read_memory (address, length)
24438 Read @var{length} bytes of memory from the inferior, starting at
24439 @var{address}. Returns a buffer object, which behaves much like an array
24440 or a string. It can be modified and given to the
24441 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24442 value is a @code{memoryview} object.
24445 @findex Inferior.write_memory
24446 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24447 Write the contents of @var{buffer} to the inferior, starting at
24448 @var{address}. The @var{buffer} parameter must be a Python object
24449 which supports the buffer protocol, i.e., a string, an array or the
24450 object returned from @code{Inferior.read_memory}. If given, @var{length}
24451 determines the number of bytes from @var{buffer} to be written.
24454 @findex gdb.search_memory
24455 @defun Inferior.search_memory (address, length, pattern)
24456 Search a region of the inferior memory starting at @var{address} with
24457 the given @var{length} using the search pattern supplied in
24458 @var{pattern}. The @var{pattern} parameter must be a Python object
24459 which supports the buffer protocol, i.e., a string, an array or the
24460 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24461 containing the address where the pattern was found, or @code{None} if
24462 the pattern could not be found.
24465 @node Events In Python
24466 @subsubsection Events In Python
24467 @cindex inferior events in Python
24469 @value{GDBN} provides a general event facility so that Python code can be
24470 notified of various state changes, particularly changes that occur in
24473 An @dfn{event} is just an object that describes some state change. The
24474 type of the object and its attributes will vary depending on the details
24475 of the change. All the existing events are described below.
24477 In order to be notified of an event, you must register an event handler
24478 with an @dfn{event registry}. An event registry is an object in the
24479 @code{gdb.events} module which dispatches particular events. A registry
24480 provides methods to register and unregister event handlers:
24482 @defun EventRegistry.connect (object)
24483 Add the given callable @var{object} to the registry. This object will be
24484 called when an event corresponding to this registry occurs.
24487 @defun EventRegistry.disconnect (object)
24488 Remove the given @var{object} from the registry. Once removed, the object
24489 will no longer receive notifications of events.
24492 Here is an example:
24495 def exit_handler (event):
24496 print "event type: exit"
24497 print "exit code: %d" % (event.exit_code)
24499 gdb.events.exited.connect (exit_handler)
24502 In the above example we connect our handler @code{exit_handler} to the
24503 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24504 called when the inferior exits. The argument @dfn{event} in this example is
24505 of type @code{gdb.ExitedEvent}. As you can see in the example the
24506 @code{ExitedEvent} object has an attribute which indicates the exit code of
24509 The following is a listing of the event registries that are available and
24510 details of the events they emit:
24515 Emits @code{gdb.ThreadEvent}.
24517 Some events can be thread specific when @value{GDBN} is running in non-stop
24518 mode. When represented in Python, these events all extend
24519 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24520 events which are emitted by this or other modules might extend this event.
24521 Examples of these events are @code{gdb.BreakpointEvent} and
24522 @code{gdb.ContinueEvent}.
24524 @defvar ThreadEvent.inferior_thread
24525 In non-stop mode this attribute will be set to the specific thread which was
24526 involved in the emitted event. Otherwise, it will be set to @code{None}.
24529 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24531 This event indicates that the inferior has been continued after a stop. For
24532 inherited attribute refer to @code{gdb.ThreadEvent} above.
24534 @item events.exited
24535 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24536 @code{events.ExitedEvent} has two attributes:
24537 @defvar ExitedEvent.exit_code
24538 An integer representing the exit code, if available, which the inferior
24539 has returned. (The exit code could be unavailable if, for example,
24540 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24541 the attribute does not exist.
24543 @defvar ExitedEvent inferior
24544 A reference to the inferior which triggered the @code{exited} event.
24548 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24550 Indicates that the inferior has stopped. All events emitted by this registry
24551 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24552 will indicate the stopped thread when @value{GDBN} is running in non-stop
24553 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24555 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24557 This event indicates that the inferior or one of its threads has received as
24558 signal. @code{gdb.SignalEvent} has the following attributes:
24560 @defvar SignalEvent.stop_signal
24561 A string representing the signal received by the inferior. A list of possible
24562 signal values can be obtained by running the command @code{info signals} in
24563 the @value{GDBN} command prompt.
24566 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24568 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24569 been hit, and has the following attributes:
24571 @defvar BreakpointEvent.breakpoints
24572 A sequence containing references to all the breakpoints (type
24573 @code{gdb.Breakpoint}) that were hit.
24574 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24576 @defvar BreakpointEvent.breakpoint
24577 A reference to the first breakpoint that was hit.
24578 This function is maintained for backward compatibility and is now deprecated
24579 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24582 @item events.new_objfile
24583 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24584 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24586 @defvar NewObjFileEvent.new_objfile
24587 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24588 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24593 @node Threads In Python
24594 @subsubsection Threads In Python
24595 @cindex threads in python
24597 @findex gdb.InferiorThread
24598 Python scripts can access information about, and manipulate inferior threads
24599 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24601 The following thread-related functions are available in the @code{gdb}
24604 @findex gdb.selected_thread
24605 @defun gdb.selected_thread ()
24606 This function returns the thread object for the selected thread. If there
24607 is no selected thread, this will return @code{None}.
24610 A @code{gdb.InferiorThread} object has the following attributes:
24612 @defvar InferiorThread.name
24613 The name of the thread. If the user specified a name using
24614 @code{thread name}, then this returns that name. Otherwise, if an
24615 OS-supplied name is available, then it is returned. Otherwise, this
24616 returns @code{None}.
24618 This attribute can be assigned to. The new value must be a string
24619 object, which sets the new name, or @code{None}, which removes any
24620 user-specified thread name.
24623 @defvar InferiorThread.num
24624 ID of the thread, as assigned by GDB.
24627 @defvar InferiorThread.ptid
24628 ID of the thread, as assigned by the operating system. This attribute is a
24629 tuple containing three integers. The first is the Process ID (PID); the second
24630 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24631 Either the LWPID or TID may be 0, which indicates that the operating system
24632 does not use that identifier.
24635 A @code{gdb.InferiorThread} object has the following methods:
24637 @defun InferiorThread.is_valid ()
24638 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24639 @code{False} if not. A @code{gdb.InferiorThread} object will become
24640 invalid if the thread exits, or the inferior that the thread belongs
24641 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24642 exception if it is invalid at the time the method is called.
24645 @defun InferiorThread.switch ()
24646 This changes @value{GDBN}'s currently selected thread to the one represented
24650 @defun InferiorThread.is_stopped ()
24651 Return a Boolean indicating whether the thread is stopped.
24654 @defun InferiorThread.is_running ()
24655 Return a Boolean indicating whether the thread is running.
24658 @defun InferiorThread.is_exited ()
24659 Return a Boolean indicating whether the thread is exited.
24662 @node Commands In Python
24663 @subsubsection Commands In Python
24665 @cindex commands in python
24666 @cindex python commands
24667 You can implement new @value{GDBN} CLI commands in Python. A CLI
24668 command is implemented using an instance of the @code{gdb.Command}
24669 class, most commonly using a subclass.
24671 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24672 The object initializer for @code{Command} registers the new command
24673 with @value{GDBN}. This initializer is normally invoked from the
24674 subclass' own @code{__init__} method.
24676 @var{name} is the name of the command. If @var{name} consists of
24677 multiple words, then the initial words are looked for as prefix
24678 commands. In this case, if one of the prefix commands does not exist,
24679 an exception is raised.
24681 There is no support for multi-line commands.
24683 @var{command_class} should be one of the @samp{COMMAND_} constants
24684 defined below. This argument tells @value{GDBN} how to categorize the
24685 new command in the help system.
24687 @var{completer_class} is an optional argument. If given, it should be
24688 one of the @samp{COMPLETE_} constants defined below. This argument
24689 tells @value{GDBN} how to perform completion for this command. If not
24690 given, @value{GDBN} will attempt to complete using the object's
24691 @code{complete} method (see below); if no such method is found, an
24692 error will occur when completion is attempted.
24694 @var{prefix} is an optional argument. If @code{True}, then the new
24695 command is a prefix command; sub-commands of this command may be
24698 The help text for the new command is taken from the Python
24699 documentation string for the command's class, if there is one. If no
24700 documentation string is provided, the default value ``This command is
24701 not documented.'' is used.
24704 @cindex don't repeat Python command
24705 @defun Command.dont_repeat ()
24706 By default, a @value{GDBN} command is repeated when the user enters a
24707 blank line at the command prompt. A command can suppress this
24708 behavior by invoking the @code{dont_repeat} method. This is similar
24709 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24712 @defun Command.invoke (argument, from_tty)
24713 This method is called by @value{GDBN} when this command is invoked.
24715 @var{argument} is a string. It is the argument to the command, after
24716 leading and trailing whitespace has been stripped.
24718 @var{from_tty} is a boolean argument. When true, this means that the
24719 command was entered by the user at the terminal; when false it means
24720 that the command came from elsewhere.
24722 If this method throws an exception, it is turned into a @value{GDBN}
24723 @code{error} call. Otherwise, the return value is ignored.
24725 @findex gdb.string_to_argv
24726 To break @var{argument} up into an argv-like string use
24727 @code{gdb.string_to_argv}. This function behaves identically to
24728 @value{GDBN}'s internal argument lexer @code{buildargv}.
24729 It is recommended to use this for consistency.
24730 Arguments are separated by spaces and may be quoted.
24734 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24735 ['1', '2 "3', '4 "5', "6 '7"]
24740 @cindex completion of Python commands
24741 @defun Command.complete (text, word)
24742 This method is called by @value{GDBN} when the user attempts
24743 completion on this command. All forms of completion are handled by
24744 this method, that is, the @key{TAB} and @key{M-?} key bindings
24745 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24748 The arguments @var{text} and @var{word} are both strings. @var{text}
24749 holds the complete command line up to the cursor's location.
24750 @var{word} holds the last word of the command line; this is computed
24751 using a word-breaking heuristic.
24753 The @code{complete} method can return several values:
24756 If the return value is a sequence, the contents of the sequence are
24757 used as the completions. It is up to @code{complete} to ensure that the
24758 contents actually do complete the word. A zero-length sequence is
24759 allowed, it means that there were no completions available. Only
24760 string elements of the sequence are used; other elements in the
24761 sequence are ignored.
24764 If the return value is one of the @samp{COMPLETE_} constants defined
24765 below, then the corresponding @value{GDBN}-internal completion
24766 function is invoked, and its result is used.
24769 All other results are treated as though there were no available
24774 When a new command is registered, it must be declared as a member of
24775 some general class of commands. This is used to classify top-level
24776 commands in the on-line help system; note that prefix commands are not
24777 listed under their own category but rather that of their top-level
24778 command. The available classifications are represented by constants
24779 defined in the @code{gdb} module:
24782 @findex COMMAND_NONE
24783 @findex gdb.COMMAND_NONE
24784 @item gdb.COMMAND_NONE
24785 The command does not belong to any particular class. A command in
24786 this category will not be displayed in any of the help categories.
24788 @findex COMMAND_RUNNING
24789 @findex gdb.COMMAND_RUNNING
24790 @item gdb.COMMAND_RUNNING
24791 The command is related to running the inferior. For example,
24792 @code{start}, @code{step}, and @code{continue} are in this category.
24793 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24794 commands in this category.
24796 @findex COMMAND_DATA
24797 @findex gdb.COMMAND_DATA
24798 @item gdb.COMMAND_DATA
24799 The command is related to data or variables. For example,
24800 @code{call}, @code{find}, and @code{print} are in this category. Type
24801 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24804 @findex COMMAND_STACK
24805 @findex gdb.COMMAND_STACK
24806 @item gdb.COMMAND_STACK
24807 The command has to do with manipulation of the stack. For example,
24808 @code{backtrace}, @code{frame}, and @code{return} are in this
24809 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24810 list of commands in this category.
24812 @findex COMMAND_FILES
24813 @findex gdb.COMMAND_FILES
24814 @item gdb.COMMAND_FILES
24815 This class is used for file-related commands. For example,
24816 @code{file}, @code{list} and @code{section} are in this category.
24817 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24818 commands in this category.
24820 @findex COMMAND_SUPPORT
24821 @findex gdb.COMMAND_SUPPORT
24822 @item gdb.COMMAND_SUPPORT
24823 This should be used for ``support facilities'', generally meaning
24824 things that are useful to the user when interacting with @value{GDBN},
24825 but not related to the state of the inferior. For example,
24826 @code{help}, @code{make}, and @code{shell} are in this category. Type
24827 @kbd{help support} at the @value{GDBN} prompt to see a list of
24828 commands in this category.
24830 @findex COMMAND_STATUS
24831 @findex gdb.COMMAND_STATUS
24832 @item gdb.COMMAND_STATUS
24833 The command is an @samp{info}-related command, that is, related to the
24834 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24835 and @code{show} are in this category. Type @kbd{help status} at the
24836 @value{GDBN} prompt to see a list of commands in this category.
24838 @findex COMMAND_BREAKPOINTS
24839 @findex gdb.COMMAND_BREAKPOINTS
24840 @item gdb.COMMAND_BREAKPOINTS
24841 The command has to do with breakpoints. For example, @code{break},
24842 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24843 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24846 @findex COMMAND_TRACEPOINTS
24847 @findex gdb.COMMAND_TRACEPOINTS
24848 @item gdb.COMMAND_TRACEPOINTS
24849 The command has to do with tracepoints. For example, @code{trace},
24850 @code{actions}, and @code{tfind} are in this category. Type
24851 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24852 commands in this category.
24854 @findex COMMAND_USER
24855 @findex gdb.COMMAND_USER
24856 @item gdb.COMMAND_USER
24857 The command is a general purpose command for the user, and typically
24858 does not fit in one of the other categories.
24859 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24860 a list of commands in this category, as well as the list of gdb macros
24861 (@pxref{Sequences}).
24863 @findex COMMAND_OBSCURE
24864 @findex gdb.COMMAND_OBSCURE
24865 @item gdb.COMMAND_OBSCURE
24866 The command is only used in unusual circumstances, or is not of
24867 general interest to users. For example, @code{checkpoint},
24868 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24869 obscure} at the @value{GDBN} prompt to see a list of commands in this
24872 @findex COMMAND_MAINTENANCE
24873 @findex gdb.COMMAND_MAINTENANCE
24874 @item gdb.COMMAND_MAINTENANCE
24875 The command is only useful to @value{GDBN} maintainers. The
24876 @code{maintenance} and @code{flushregs} commands are in this category.
24877 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24878 commands in this category.
24881 A new command can use a predefined completion function, either by
24882 specifying it via an argument at initialization, or by returning it
24883 from the @code{complete} method. These predefined completion
24884 constants are all defined in the @code{gdb} module:
24887 @findex COMPLETE_NONE
24888 @findex gdb.COMPLETE_NONE
24889 @item gdb.COMPLETE_NONE
24890 This constant means that no completion should be done.
24892 @findex COMPLETE_FILENAME
24893 @findex gdb.COMPLETE_FILENAME
24894 @item gdb.COMPLETE_FILENAME
24895 This constant means that filename completion should be performed.
24897 @findex COMPLETE_LOCATION
24898 @findex gdb.COMPLETE_LOCATION
24899 @item gdb.COMPLETE_LOCATION
24900 This constant means that location completion should be done.
24901 @xref{Specify Location}.
24903 @findex COMPLETE_COMMAND
24904 @findex gdb.COMPLETE_COMMAND
24905 @item gdb.COMPLETE_COMMAND
24906 This constant means that completion should examine @value{GDBN}
24909 @findex COMPLETE_SYMBOL
24910 @findex gdb.COMPLETE_SYMBOL
24911 @item gdb.COMPLETE_SYMBOL
24912 This constant means that completion should be done using symbol names
24916 The following code snippet shows how a trivial CLI command can be
24917 implemented in Python:
24920 class HelloWorld (gdb.Command):
24921 """Greet the whole world."""
24923 def __init__ (self):
24924 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24926 def invoke (self, arg, from_tty):
24927 print "Hello, World!"
24932 The last line instantiates the class, and is necessary to trigger the
24933 registration of the command with @value{GDBN}. Depending on how the
24934 Python code is read into @value{GDBN}, you may need to import the
24935 @code{gdb} module explicitly.
24937 @node Parameters In Python
24938 @subsubsection Parameters In Python
24940 @cindex parameters in python
24941 @cindex python parameters
24942 @tindex gdb.Parameter
24944 You can implement new @value{GDBN} parameters using Python. A new
24945 parameter is implemented as an instance of the @code{gdb.Parameter}
24948 Parameters are exposed to the user via the @code{set} and
24949 @code{show} commands. @xref{Help}.
24951 There are many parameters that already exist and can be set in
24952 @value{GDBN}. Two examples are: @code{set follow fork} and
24953 @code{set charset}. Setting these parameters influences certain
24954 behavior in @value{GDBN}. Similarly, you can define parameters that
24955 can be used to influence behavior in custom Python scripts and commands.
24957 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24958 The object initializer for @code{Parameter} registers the new
24959 parameter with @value{GDBN}. This initializer is normally invoked
24960 from the subclass' own @code{__init__} method.
24962 @var{name} is the name of the new parameter. If @var{name} consists
24963 of multiple words, then the initial words are looked for as prefix
24964 parameters. An example of this can be illustrated with the
24965 @code{set print} set of parameters. If @var{name} is
24966 @code{print foo}, then @code{print} will be searched as the prefix
24967 parameter. In this case the parameter can subsequently be accessed in
24968 @value{GDBN} as @code{set print foo}.
24970 If @var{name} consists of multiple words, and no prefix parameter group
24971 can be found, an exception is raised.
24973 @var{command-class} should be one of the @samp{COMMAND_} constants
24974 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24975 categorize the new parameter in the help system.
24977 @var{parameter-class} should be one of the @samp{PARAM_} constants
24978 defined below. This argument tells @value{GDBN} the type of the new
24979 parameter; this information is used for input validation and
24982 If @var{parameter-class} is @code{PARAM_ENUM}, then
24983 @var{enum-sequence} must be a sequence of strings. These strings
24984 represent the possible values for the parameter.
24986 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24987 of a fourth argument will cause an exception to be thrown.
24989 The help text for the new parameter is taken from the Python
24990 documentation string for the parameter's class, if there is one. If
24991 there is no documentation string, a default value is used.
24994 @defvar Parameter.set_doc
24995 If this attribute exists, and is a string, then its value is used as
24996 the help text for this parameter's @code{set} command. The value is
24997 examined when @code{Parameter.__init__} is invoked; subsequent changes
25001 @defvar Parameter.show_doc
25002 If this attribute exists, and is a string, then its value is used as
25003 the help text for this parameter's @code{show} command. The value is
25004 examined when @code{Parameter.__init__} is invoked; subsequent changes
25008 @defvar Parameter.value
25009 The @code{value} attribute holds the underlying value of the
25010 parameter. It can be read and assigned to just as any other
25011 attribute. @value{GDBN} does validation when assignments are made.
25014 There are two methods that should be implemented in any
25015 @code{Parameter} class. These are:
25017 @defun Parameter.get_set_string (self)
25018 @value{GDBN} will call this method when a @var{parameter}'s value has
25019 been changed via the @code{set} API (for example, @kbd{set foo off}).
25020 The @code{value} attribute has already been populated with the new
25021 value and may be used in output. This method must return a string.
25024 @defun Parameter.get_show_string (self, svalue)
25025 @value{GDBN} will call this method when a @var{parameter}'s
25026 @code{show} API has been invoked (for example, @kbd{show foo}). The
25027 argument @code{svalue} receives the string representation of the
25028 current value. This method must return a string.
25031 When a new parameter is defined, its type must be specified. The
25032 available types are represented by constants defined in the @code{gdb}
25036 @findex PARAM_BOOLEAN
25037 @findex gdb.PARAM_BOOLEAN
25038 @item gdb.PARAM_BOOLEAN
25039 The value is a plain boolean. The Python boolean values, @code{True}
25040 and @code{False} are the only valid values.
25042 @findex PARAM_AUTO_BOOLEAN
25043 @findex gdb.PARAM_AUTO_BOOLEAN
25044 @item gdb.PARAM_AUTO_BOOLEAN
25045 The value has three possible states: true, false, and @samp{auto}. In
25046 Python, true and false are represented using boolean constants, and
25047 @samp{auto} is represented using @code{None}.
25049 @findex PARAM_UINTEGER
25050 @findex gdb.PARAM_UINTEGER
25051 @item gdb.PARAM_UINTEGER
25052 The value is an unsigned integer. The value of 0 should be
25053 interpreted to mean ``unlimited''.
25055 @findex PARAM_INTEGER
25056 @findex gdb.PARAM_INTEGER
25057 @item gdb.PARAM_INTEGER
25058 The value is a signed integer. The value of 0 should be interpreted
25059 to mean ``unlimited''.
25061 @findex PARAM_STRING
25062 @findex gdb.PARAM_STRING
25063 @item gdb.PARAM_STRING
25064 The value is a string. When the user modifies the string, any escape
25065 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25066 translated into corresponding characters and encoded into the current
25069 @findex PARAM_STRING_NOESCAPE
25070 @findex gdb.PARAM_STRING_NOESCAPE
25071 @item gdb.PARAM_STRING_NOESCAPE
25072 The value is a string. When the user modifies the string, escapes are
25073 passed through untranslated.
25075 @findex PARAM_OPTIONAL_FILENAME
25076 @findex gdb.PARAM_OPTIONAL_FILENAME
25077 @item gdb.PARAM_OPTIONAL_FILENAME
25078 The value is a either a filename (a string), or @code{None}.
25080 @findex PARAM_FILENAME
25081 @findex gdb.PARAM_FILENAME
25082 @item gdb.PARAM_FILENAME
25083 The value is a filename. This is just like
25084 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25086 @findex PARAM_ZINTEGER
25087 @findex gdb.PARAM_ZINTEGER
25088 @item gdb.PARAM_ZINTEGER
25089 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25090 is interpreted as itself.
25093 @findex gdb.PARAM_ENUM
25094 @item gdb.PARAM_ENUM
25095 The value is a string, which must be one of a collection string
25096 constants provided when the parameter is created.
25099 @node Functions In Python
25100 @subsubsection Writing new convenience functions
25102 @cindex writing convenience functions
25103 @cindex convenience functions in python
25104 @cindex python convenience functions
25105 @tindex gdb.Function
25107 You can implement new convenience functions (@pxref{Convenience Vars})
25108 in Python. A convenience function is an instance of a subclass of the
25109 class @code{gdb.Function}.
25111 @defun Function.__init__ (name)
25112 The initializer for @code{Function} registers the new function with
25113 @value{GDBN}. The argument @var{name} is the name of the function,
25114 a string. The function will be visible to the user as a convenience
25115 variable of type @code{internal function}, whose name is the same as
25116 the given @var{name}.
25118 The documentation for the new function is taken from the documentation
25119 string for the new class.
25122 @defun Function.invoke (@var{*args})
25123 When a convenience function is evaluated, its arguments are converted
25124 to instances of @code{gdb.Value}, and then the function's
25125 @code{invoke} method is called. Note that @value{GDBN} does not
25126 predetermine the arity of convenience functions. Instead, all
25127 available arguments are passed to @code{invoke}, following the
25128 standard Python calling convention. In particular, a convenience
25129 function can have default values for parameters without ill effect.
25131 The return value of this method is used as its value in the enclosing
25132 expression. If an ordinary Python value is returned, it is converted
25133 to a @code{gdb.Value} following the usual rules.
25136 The following code snippet shows how a trivial convenience function can
25137 be implemented in Python:
25140 class Greet (gdb.Function):
25141 """Return string to greet someone.
25142 Takes a name as argument."""
25144 def __init__ (self):
25145 super (Greet, self).__init__ ("greet")
25147 def invoke (self, name):
25148 return "Hello, %s!" % name.string ()
25153 The last line instantiates the class, and is necessary to trigger the
25154 registration of the function with @value{GDBN}. Depending on how the
25155 Python code is read into @value{GDBN}, you may need to import the
25156 @code{gdb} module explicitly.
25158 Now you can use the function in an expression:
25161 (gdb) print $greet("Bob")
25165 @node Progspaces In Python
25166 @subsubsection Program Spaces In Python
25168 @cindex progspaces in python
25169 @tindex gdb.Progspace
25171 A program space, or @dfn{progspace}, represents a symbolic view
25172 of an address space.
25173 It consists of all of the objfiles of the program.
25174 @xref{Objfiles In Python}.
25175 @xref{Inferiors and Programs, program spaces}, for more details
25176 about program spaces.
25178 The following progspace-related functions are available in the
25181 @findex gdb.current_progspace
25182 @defun gdb.current_progspace ()
25183 This function returns the program space of the currently selected inferior.
25184 @xref{Inferiors and Programs}.
25187 @findex gdb.progspaces
25188 @defun gdb.progspaces ()
25189 Return a sequence of all the progspaces currently known to @value{GDBN}.
25192 Each progspace is represented by an instance of the @code{gdb.Progspace}
25195 @defvar Progspace.filename
25196 The file name of the progspace as a string.
25199 @defvar Progspace.pretty_printers
25200 The @code{pretty_printers} attribute is a list of functions. It is
25201 used to look up pretty-printers. A @code{Value} is passed to each
25202 function in order; if the function returns @code{None}, then the
25203 search continues. Otherwise, the return value should be an object
25204 which is used to format the value. @xref{Pretty Printing API}, for more
25208 @defvar Progspace.type_printers
25209 The @code{type_printers} attribute is a list of type printer objects.
25210 @xref{Type Printing API}, for more information.
25213 @node Objfiles In Python
25214 @subsubsection Objfiles In Python
25216 @cindex objfiles in python
25217 @tindex gdb.Objfile
25219 @value{GDBN} loads symbols for an inferior from various
25220 symbol-containing files (@pxref{Files}). These include the primary
25221 executable file, any shared libraries used by the inferior, and any
25222 separate debug info files (@pxref{Separate Debug Files}).
25223 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25225 The following objfile-related functions are available in the
25228 @findex gdb.current_objfile
25229 @defun gdb.current_objfile ()
25230 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25231 sets the ``current objfile'' to the corresponding objfile. This
25232 function returns the current objfile. If there is no current objfile,
25233 this function returns @code{None}.
25236 @findex gdb.objfiles
25237 @defun gdb.objfiles ()
25238 Return a sequence of all the objfiles current known to @value{GDBN}.
25239 @xref{Objfiles In Python}.
25242 Each objfile is represented by an instance of the @code{gdb.Objfile}
25245 @defvar Objfile.filename
25246 The file name of the objfile as a string.
25249 @defvar Objfile.pretty_printers
25250 The @code{pretty_printers} attribute is a list of functions. It is
25251 used to look up pretty-printers. A @code{Value} is passed to each
25252 function in order; if the function returns @code{None}, then the
25253 search continues. Otherwise, the return value should be an object
25254 which is used to format the value. @xref{Pretty Printing API}, for more
25258 @defvar Objfile.type_printers
25259 The @code{type_printers} attribute is a list of type printer objects.
25260 @xref{Type Printing API}, for more information.
25263 A @code{gdb.Objfile} object has the following methods:
25265 @defun Objfile.is_valid ()
25266 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25267 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25268 if the object file it refers to is not loaded in @value{GDBN} any
25269 longer. All other @code{gdb.Objfile} methods will throw an exception
25270 if it is invalid at the time the method is called.
25273 @node Frames In Python
25274 @subsubsection Accessing inferior stack frames from Python.
25276 @cindex frames in python
25277 When the debugged program stops, @value{GDBN} is able to analyze its call
25278 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25279 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25280 while its corresponding frame exists in the inferior's stack. If you try
25281 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25282 exception (@pxref{Exception Handling}).
25284 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25288 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25292 The following frame-related functions are available in the @code{gdb} module:
25294 @findex gdb.selected_frame
25295 @defun gdb.selected_frame ()
25296 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25299 @findex gdb.newest_frame
25300 @defun gdb.newest_frame ()
25301 Return the newest frame object for the selected thread.
25304 @defun gdb.frame_stop_reason_string (reason)
25305 Return a string explaining the reason why @value{GDBN} stopped unwinding
25306 frames, as expressed by the given @var{reason} code (an integer, see the
25307 @code{unwind_stop_reason} method further down in this section).
25310 A @code{gdb.Frame} object has the following methods:
25312 @defun Frame.is_valid ()
25313 Returns true if the @code{gdb.Frame} object is valid, false if not.
25314 A frame object can become invalid if the frame it refers to doesn't
25315 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25316 an exception if it is invalid at the time the method is called.
25319 @defun Frame.name ()
25320 Returns the function name of the frame, or @code{None} if it can't be
25324 @defun Frame.architecture ()
25325 Returns the @code{gdb.Architecture} object corresponding to the frame's
25326 architecture. @xref{Architectures In Python}.
25329 @defun Frame.type ()
25330 Returns the type of the frame. The value can be one of:
25332 @item gdb.NORMAL_FRAME
25333 An ordinary stack frame.
25335 @item gdb.DUMMY_FRAME
25336 A fake stack frame that was created by @value{GDBN} when performing an
25337 inferior function call.
25339 @item gdb.INLINE_FRAME
25340 A frame representing an inlined function. The function was inlined
25341 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25343 @item gdb.TAILCALL_FRAME
25344 A frame representing a tail call. @xref{Tail Call Frames}.
25346 @item gdb.SIGTRAMP_FRAME
25347 A signal trampoline frame. This is the frame created by the OS when
25348 it calls into a signal handler.
25350 @item gdb.ARCH_FRAME
25351 A fake stack frame representing a cross-architecture call.
25353 @item gdb.SENTINEL_FRAME
25354 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25359 @defun Frame.unwind_stop_reason ()
25360 Return an integer representing the reason why it's not possible to find
25361 more frames toward the outermost frame. Use
25362 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25363 function to a string. The value can be one of:
25366 @item gdb.FRAME_UNWIND_NO_REASON
25367 No particular reason (older frames should be available).
25369 @item gdb.FRAME_UNWIND_NULL_ID
25370 The previous frame's analyzer returns an invalid result.
25372 @item gdb.FRAME_UNWIND_OUTERMOST
25373 This frame is the outermost.
25375 @item gdb.FRAME_UNWIND_UNAVAILABLE
25376 Cannot unwind further, because that would require knowing the
25377 values of registers or memory that have not been collected.
25379 @item gdb.FRAME_UNWIND_INNER_ID
25380 This frame ID looks like it ought to belong to a NEXT frame,
25381 but we got it for a PREV frame. Normally, this is a sign of
25382 unwinder failure. It could also indicate stack corruption.
25384 @item gdb.FRAME_UNWIND_SAME_ID
25385 This frame has the same ID as the previous one. That means
25386 that unwinding further would almost certainly give us another
25387 frame with exactly the same ID, so break the chain. Normally,
25388 this is a sign of unwinder failure. It could also indicate
25391 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25392 The frame unwinder did not find any saved PC, but we needed
25393 one to unwind further.
25395 @item gdb.FRAME_UNWIND_FIRST_ERROR
25396 Any stop reason greater or equal to this value indicates some kind
25397 of error. This special value facilitates writing code that tests
25398 for errors in unwinding in a way that will work correctly even if
25399 the list of the other values is modified in future @value{GDBN}
25400 versions. Using it, you could write:
25402 reason = gdb.selected_frame().unwind_stop_reason ()
25403 reason_str = gdb.frame_stop_reason_string (reason)
25404 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25405 print "An error occured: %s" % reason_str
25412 Returns the frame's resume address.
25415 @defun Frame.block ()
25416 Return the frame's code block. @xref{Blocks In Python}.
25419 @defun Frame.function ()
25420 Return the symbol for the function corresponding to this frame.
25421 @xref{Symbols In Python}.
25424 @defun Frame.older ()
25425 Return the frame that called this frame.
25428 @defun Frame.newer ()
25429 Return the frame called by this frame.
25432 @defun Frame.find_sal ()
25433 Return the frame's symtab and line object.
25434 @xref{Symbol Tables In Python}.
25437 @defun Frame.read_var (variable @r{[}, block@r{]})
25438 Return the value of @var{variable} in this frame. If the optional
25439 argument @var{block} is provided, search for the variable from that
25440 block; otherwise start at the frame's current block (which is
25441 determined by the frame's current program counter). @var{variable}
25442 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25443 @code{gdb.Block} object.
25446 @defun Frame.select ()
25447 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25451 @node Blocks In Python
25452 @subsubsection Accessing frame blocks from Python.
25454 @cindex blocks in python
25457 Within each frame, @value{GDBN} maintains information on each block
25458 stored in that frame. These blocks are organized hierarchically, and
25459 are represented individually in Python as a @code{gdb.Block}.
25460 Please see @ref{Frames In Python}, for a more in-depth discussion on
25461 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25462 detailed technical information on @value{GDBN}'s book-keeping of the
25465 A @code{gdb.Block} is iterable. The iterator returns the symbols
25466 (@pxref{Symbols In Python}) local to the block. Python programs
25467 should not assume that a specific block object will always contain a
25468 given symbol, since changes in @value{GDBN} features and
25469 infrastructure may cause symbols move across blocks in a symbol
25472 The following block-related functions are available in the @code{gdb}
25475 @findex gdb.block_for_pc
25476 @defun gdb.block_for_pc (pc)
25477 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25478 block cannot be found for the @var{pc} value specified, the function
25479 will return @code{None}.
25482 A @code{gdb.Block} object has the following methods:
25484 @defun Block.is_valid ()
25485 Returns @code{True} if the @code{gdb.Block} object is valid,
25486 @code{False} if not. A block object can become invalid if the block it
25487 refers to doesn't exist anymore in the inferior. All other
25488 @code{gdb.Block} methods will throw an exception if it is invalid at
25489 the time the method is called. The block's validity is also checked
25490 during iteration over symbols of the block.
25493 A @code{gdb.Block} object has the following attributes:
25495 @defvar Block.start
25496 The start address of the block. This attribute is not writable.
25500 The end address of the block. This attribute is not writable.
25503 @defvar Block.function
25504 The name of the block represented as a @code{gdb.Symbol}. If the
25505 block is not named, then this attribute holds @code{None}. This
25506 attribute is not writable.
25509 @defvar Block.superblock
25510 The block containing this block. If this parent block does not exist,
25511 this attribute holds @code{None}. This attribute is not writable.
25514 @defvar Block.global_block
25515 The global block associated with this block. This attribute is not
25519 @defvar Block.static_block
25520 The static block associated with this block. This attribute is not
25524 @defvar Block.is_global
25525 @code{True} if the @code{gdb.Block} object is a global block,
25526 @code{False} if not. This attribute is not
25530 @defvar Block.is_static
25531 @code{True} if the @code{gdb.Block} object is a static block,
25532 @code{False} if not. This attribute is not writable.
25535 @node Symbols In Python
25536 @subsubsection Python representation of Symbols.
25538 @cindex symbols in python
25541 @value{GDBN} represents every variable, function and type as an
25542 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25543 Similarly, Python represents these symbols in @value{GDBN} with the
25544 @code{gdb.Symbol} object.
25546 The following symbol-related functions are available in the @code{gdb}
25549 @findex gdb.lookup_symbol
25550 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25551 This function searches for a symbol by name. The search scope can be
25552 restricted to the parameters defined in the optional domain and block
25555 @var{name} is the name of the symbol. It must be a string. The
25556 optional @var{block} argument restricts the search to symbols visible
25557 in that @var{block}. The @var{block} argument must be a
25558 @code{gdb.Block} object. If omitted, the block for the current frame
25559 is used. The optional @var{domain} argument restricts
25560 the search to the domain type. The @var{domain} argument must be a
25561 domain constant defined in the @code{gdb} module and described later
25564 The result is a tuple of two elements.
25565 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25567 If the symbol is found, the second element is @code{True} if the symbol
25568 is a field of a method's object (e.g., @code{this} in C@t{++}),
25569 otherwise it is @code{False}.
25570 If the symbol is not found, the second element is @code{False}.
25573 @findex gdb.lookup_global_symbol
25574 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25575 This function searches for a global symbol by name.
25576 The search scope can be restricted to by the domain argument.
25578 @var{name} is the name of the symbol. It must be a string.
25579 The optional @var{domain} argument restricts the search to the domain type.
25580 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25581 module and described later in this chapter.
25583 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25587 A @code{gdb.Symbol} object has the following attributes:
25589 @defvar Symbol.type
25590 The type of the symbol or @code{None} if no type is recorded.
25591 This attribute is represented as a @code{gdb.Type} object.
25592 @xref{Types In Python}. This attribute is not writable.
25595 @defvar Symbol.symtab
25596 The symbol table in which the symbol appears. This attribute is
25597 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25598 Python}. This attribute is not writable.
25601 @defvar Symbol.line
25602 The line number in the source code at which the symbol was defined.
25603 This is an integer.
25606 @defvar Symbol.name
25607 The name of the symbol as a string. This attribute is not writable.
25610 @defvar Symbol.linkage_name
25611 The name of the symbol, as used by the linker (i.e., may be mangled).
25612 This attribute is not writable.
25615 @defvar Symbol.print_name
25616 The name of the symbol in a form suitable for output. This is either
25617 @code{name} or @code{linkage_name}, depending on whether the user
25618 asked @value{GDBN} to display demangled or mangled names.
25621 @defvar Symbol.addr_class
25622 The address class of the symbol. This classifies how to find the value
25623 of a symbol. Each address class is a constant defined in the
25624 @code{gdb} module and described later in this chapter.
25627 @defvar Symbol.needs_frame
25628 This is @code{True} if evaluating this symbol's value requires a frame
25629 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25630 local variables will require a frame, but other symbols will not.
25633 @defvar Symbol.is_argument
25634 @code{True} if the symbol is an argument of a function.
25637 @defvar Symbol.is_constant
25638 @code{True} if the symbol is a constant.
25641 @defvar Symbol.is_function
25642 @code{True} if the symbol is a function or a method.
25645 @defvar Symbol.is_variable
25646 @code{True} if the symbol is a variable.
25649 A @code{gdb.Symbol} object has the following methods:
25651 @defun Symbol.is_valid ()
25652 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25653 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25654 the symbol it refers to does not exist in @value{GDBN} any longer.
25655 All other @code{gdb.Symbol} methods will throw an exception if it is
25656 invalid at the time the method is called.
25659 @defun Symbol.value (@r{[}frame@r{]})
25660 Compute the value of the symbol, as a @code{gdb.Value}. For
25661 functions, this computes the address of the function, cast to the
25662 appropriate type. If the symbol requires a frame in order to compute
25663 its value, then @var{frame} must be given. If @var{frame} is not
25664 given, or if @var{frame} is invalid, then this method will throw an
25668 The available domain categories in @code{gdb.Symbol} are represented
25669 as constants in the @code{gdb} module:
25672 @findex SYMBOL_UNDEF_DOMAIN
25673 @findex gdb.SYMBOL_UNDEF_DOMAIN
25674 @item gdb.SYMBOL_UNDEF_DOMAIN
25675 This is used when a domain has not been discovered or none of the
25676 following domains apply. This usually indicates an error either
25677 in the symbol information or in @value{GDBN}'s handling of symbols.
25678 @findex SYMBOL_VAR_DOMAIN
25679 @findex gdb.SYMBOL_VAR_DOMAIN
25680 @item gdb.SYMBOL_VAR_DOMAIN
25681 This domain contains variables, function names, typedef names and enum
25683 @findex SYMBOL_STRUCT_DOMAIN
25684 @findex gdb.SYMBOL_STRUCT_DOMAIN
25685 @item gdb.SYMBOL_STRUCT_DOMAIN
25686 This domain holds struct, union and enum type names.
25687 @findex SYMBOL_LABEL_DOMAIN
25688 @findex gdb.SYMBOL_LABEL_DOMAIN
25689 @item gdb.SYMBOL_LABEL_DOMAIN
25690 This domain contains names of labels (for gotos).
25691 @findex SYMBOL_VARIABLES_DOMAIN
25692 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25693 @item gdb.SYMBOL_VARIABLES_DOMAIN
25694 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25695 contains everything minus functions and types.
25696 @findex SYMBOL_FUNCTIONS_DOMAIN
25697 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25698 @item gdb.SYMBOL_FUNCTION_DOMAIN
25699 This domain contains all functions.
25700 @findex SYMBOL_TYPES_DOMAIN
25701 @findex gdb.SYMBOL_TYPES_DOMAIN
25702 @item gdb.SYMBOL_TYPES_DOMAIN
25703 This domain contains all types.
25706 The available address class categories in @code{gdb.Symbol} are represented
25707 as constants in the @code{gdb} module:
25710 @findex SYMBOL_LOC_UNDEF
25711 @findex gdb.SYMBOL_LOC_UNDEF
25712 @item gdb.SYMBOL_LOC_UNDEF
25713 If this is returned by address class, it indicates an error either in
25714 the symbol information or in @value{GDBN}'s handling of symbols.
25715 @findex SYMBOL_LOC_CONST
25716 @findex gdb.SYMBOL_LOC_CONST
25717 @item gdb.SYMBOL_LOC_CONST
25718 Value is constant int.
25719 @findex SYMBOL_LOC_STATIC
25720 @findex gdb.SYMBOL_LOC_STATIC
25721 @item gdb.SYMBOL_LOC_STATIC
25722 Value is at a fixed address.
25723 @findex SYMBOL_LOC_REGISTER
25724 @findex gdb.SYMBOL_LOC_REGISTER
25725 @item gdb.SYMBOL_LOC_REGISTER
25726 Value is in a register.
25727 @findex SYMBOL_LOC_ARG
25728 @findex gdb.SYMBOL_LOC_ARG
25729 @item gdb.SYMBOL_LOC_ARG
25730 Value is an argument. This value is at the offset stored within the
25731 symbol inside the frame's argument list.
25732 @findex SYMBOL_LOC_REF_ARG
25733 @findex gdb.SYMBOL_LOC_REF_ARG
25734 @item gdb.SYMBOL_LOC_REF_ARG
25735 Value address is stored in the frame's argument list. Just like
25736 @code{LOC_ARG} except that the value's address is stored at the
25737 offset, not the value itself.
25738 @findex SYMBOL_LOC_REGPARM_ADDR
25739 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25740 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25741 Value is a specified register. Just like @code{LOC_REGISTER} except
25742 the register holds the address of the argument instead of the argument
25744 @findex SYMBOL_LOC_LOCAL
25745 @findex gdb.SYMBOL_LOC_LOCAL
25746 @item gdb.SYMBOL_LOC_LOCAL
25747 Value is a local variable.
25748 @findex SYMBOL_LOC_TYPEDEF
25749 @findex gdb.SYMBOL_LOC_TYPEDEF
25750 @item gdb.SYMBOL_LOC_TYPEDEF
25751 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25753 @findex SYMBOL_LOC_BLOCK
25754 @findex gdb.SYMBOL_LOC_BLOCK
25755 @item gdb.SYMBOL_LOC_BLOCK
25757 @findex SYMBOL_LOC_CONST_BYTES
25758 @findex gdb.SYMBOL_LOC_CONST_BYTES
25759 @item gdb.SYMBOL_LOC_CONST_BYTES
25760 Value is a byte-sequence.
25761 @findex SYMBOL_LOC_UNRESOLVED
25762 @findex gdb.SYMBOL_LOC_UNRESOLVED
25763 @item gdb.SYMBOL_LOC_UNRESOLVED
25764 Value is at a fixed address, but the address of the variable has to be
25765 determined from the minimal symbol table whenever the variable is
25767 @findex SYMBOL_LOC_OPTIMIZED_OUT
25768 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25769 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25770 The value does not actually exist in the program.
25771 @findex SYMBOL_LOC_COMPUTED
25772 @findex gdb.SYMBOL_LOC_COMPUTED
25773 @item gdb.SYMBOL_LOC_COMPUTED
25774 The value's address is a computed location.
25777 @node Symbol Tables In Python
25778 @subsubsection Symbol table representation in Python.
25780 @cindex symbol tables in python
25782 @tindex gdb.Symtab_and_line
25784 Access to symbol table data maintained by @value{GDBN} on the inferior
25785 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25786 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25787 from the @code{find_sal} method in @code{gdb.Frame} object.
25788 @xref{Frames In Python}.
25790 For more information on @value{GDBN}'s symbol table management, see
25791 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25793 A @code{gdb.Symtab_and_line} object has the following attributes:
25795 @defvar Symtab_and_line.symtab
25796 The symbol table object (@code{gdb.Symtab}) for this frame.
25797 This attribute is not writable.
25800 @defvar Symtab_and_line.pc
25801 Indicates the start of the address range occupied by code for the
25802 current source line. This attribute is not writable.
25805 @defvar Symtab_and_line.last
25806 Indicates the end of the address range occupied by code for the current
25807 source line. This attribute is not writable.
25810 @defvar Symtab_and_line.line
25811 Indicates the current line number for this object. This
25812 attribute is not writable.
25815 A @code{gdb.Symtab_and_line} object has the following methods:
25817 @defun Symtab_and_line.is_valid ()
25818 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25819 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25820 invalid if the Symbol table and line object it refers to does not
25821 exist in @value{GDBN} any longer. All other
25822 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25823 invalid at the time the method is called.
25826 A @code{gdb.Symtab} object has the following attributes:
25828 @defvar Symtab.filename
25829 The symbol table's source filename. This attribute is not writable.
25832 @defvar Symtab.objfile
25833 The symbol table's backing object file. @xref{Objfiles In Python}.
25834 This attribute is not writable.
25837 A @code{gdb.Symtab} object has the following methods:
25839 @defun Symtab.is_valid ()
25840 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25841 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25842 the symbol table it refers to does not exist in @value{GDBN} any
25843 longer. All other @code{gdb.Symtab} methods will throw an exception
25844 if it is invalid at the time the method is called.
25847 @defun Symtab.fullname ()
25848 Return the symbol table's source absolute file name.
25851 @defun Symtab.global_block ()
25852 Return the global block of the underlying symbol table.
25853 @xref{Blocks In Python}.
25856 @defun Symtab.static_block ()
25857 Return the static block of the underlying symbol table.
25858 @xref{Blocks In Python}.
25861 @node Breakpoints In Python
25862 @subsubsection Manipulating breakpoints using Python
25864 @cindex breakpoints in python
25865 @tindex gdb.Breakpoint
25867 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25870 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25871 Create a new breakpoint. @var{spec} is a string naming the
25872 location of the breakpoint, or an expression that defines a
25873 watchpoint. The contents can be any location recognized by the
25874 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25875 command. The optional @var{type} denotes the breakpoint to create
25876 from the types defined later in this chapter. This argument can be
25877 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25878 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25879 allows the breakpoint to become invisible to the user. The breakpoint
25880 will neither be reported when created, nor will it be listed in the
25881 output from @code{info breakpoints} (but will be listed with the
25882 @code{maint info breakpoints} command). The optional @var{wp_class}
25883 argument defines the class of watchpoint to create, if @var{type} is
25884 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25885 assumed to be a @code{gdb.WP_WRITE} class.
25888 @defun Breakpoint.stop (self)
25889 The @code{gdb.Breakpoint} class can be sub-classed and, in
25890 particular, you may choose to implement the @code{stop} method.
25891 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25892 it will be called when the inferior reaches any location of a
25893 breakpoint which instantiates that sub-class. If the method returns
25894 @code{True}, the inferior will be stopped at the location of the
25895 breakpoint, otherwise the inferior will continue.
25897 If there are multiple breakpoints at the same location with a
25898 @code{stop} method, each one will be called regardless of the
25899 return status of the previous. This ensures that all @code{stop}
25900 methods have a chance to execute at that location. In this scenario
25901 if one of the methods returns @code{True} but the others return
25902 @code{False}, the inferior will still be stopped.
25904 You should not alter the execution state of the inferior (i.e.@:, step,
25905 next, etc.), alter the current frame context (i.e.@:, change the current
25906 active frame), or alter, add or delete any breakpoint. As a general
25907 rule, you should not alter any data within @value{GDBN} or the inferior
25910 Example @code{stop} implementation:
25913 class MyBreakpoint (gdb.Breakpoint):
25915 inf_val = gdb.parse_and_eval("foo")
25922 The available watchpoint types represented by constants are defined in the
25927 @findex gdb.WP_READ
25929 Read only watchpoint.
25932 @findex gdb.WP_WRITE
25934 Write only watchpoint.
25937 @findex gdb.WP_ACCESS
25938 @item gdb.WP_ACCESS
25939 Read/Write watchpoint.
25942 @defun Breakpoint.is_valid ()
25943 Return @code{True} if this @code{Breakpoint} object is valid,
25944 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25945 if the user deletes the breakpoint. In this case, the object still
25946 exists, but the underlying breakpoint does not. In the cases of
25947 watchpoint scope, the watchpoint remains valid even if execution of the
25948 inferior leaves the scope of that watchpoint.
25951 @defun Breakpoint.delete
25952 Permanently deletes the @value{GDBN} breakpoint. This also
25953 invalidates the Python @code{Breakpoint} object. Any further access
25954 to this object's attributes or methods will raise an error.
25957 @defvar Breakpoint.enabled
25958 This attribute is @code{True} if the breakpoint is enabled, and
25959 @code{False} otherwise. This attribute is writable.
25962 @defvar Breakpoint.silent
25963 This attribute is @code{True} if the breakpoint is silent, and
25964 @code{False} otherwise. This attribute is writable.
25966 Note that a breakpoint can also be silent if it has commands and the
25967 first command is @code{silent}. This is not reported by the
25968 @code{silent} attribute.
25971 @defvar Breakpoint.thread
25972 If the breakpoint is thread-specific, this attribute holds the thread
25973 id. If the breakpoint is not thread-specific, this attribute is
25974 @code{None}. This attribute is writable.
25977 @defvar Breakpoint.task
25978 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25979 id. If the breakpoint is not task-specific (or the underlying
25980 language is not Ada), this attribute is @code{None}. This attribute
25984 @defvar Breakpoint.ignore_count
25985 This attribute holds the ignore count for the breakpoint, an integer.
25986 This attribute is writable.
25989 @defvar Breakpoint.number
25990 This attribute holds the breakpoint's number --- the identifier used by
25991 the user to manipulate the breakpoint. This attribute is not writable.
25994 @defvar Breakpoint.type
25995 This attribute holds the breakpoint's type --- the identifier used to
25996 determine the actual breakpoint type or use-case. This attribute is not
26000 @defvar Breakpoint.visible
26001 This attribute tells whether the breakpoint is visible to the user
26002 when set, or when the @samp{info breakpoints} command is run. This
26003 attribute is not writable.
26006 The available types are represented by constants defined in the @code{gdb}
26010 @findex BP_BREAKPOINT
26011 @findex gdb.BP_BREAKPOINT
26012 @item gdb.BP_BREAKPOINT
26013 Normal code breakpoint.
26015 @findex BP_WATCHPOINT
26016 @findex gdb.BP_WATCHPOINT
26017 @item gdb.BP_WATCHPOINT
26018 Watchpoint breakpoint.
26020 @findex BP_HARDWARE_WATCHPOINT
26021 @findex gdb.BP_HARDWARE_WATCHPOINT
26022 @item gdb.BP_HARDWARE_WATCHPOINT
26023 Hardware assisted watchpoint.
26025 @findex BP_READ_WATCHPOINT
26026 @findex gdb.BP_READ_WATCHPOINT
26027 @item gdb.BP_READ_WATCHPOINT
26028 Hardware assisted read watchpoint.
26030 @findex BP_ACCESS_WATCHPOINT
26031 @findex gdb.BP_ACCESS_WATCHPOINT
26032 @item gdb.BP_ACCESS_WATCHPOINT
26033 Hardware assisted access watchpoint.
26036 @defvar Breakpoint.hit_count
26037 This attribute holds the hit count for the breakpoint, an integer.
26038 This attribute is writable, but currently it can only be set to zero.
26041 @defvar Breakpoint.location
26042 This attribute holds the location of the breakpoint, as specified by
26043 the user. It is a string. If the breakpoint does not have a location
26044 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26045 attribute is not writable.
26048 @defvar Breakpoint.expression
26049 This attribute holds a breakpoint expression, as specified by
26050 the user. It is a string. If the breakpoint does not have an
26051 expression (the breakpoint is not a watchpoint) the attribute's value
26052 is @code{None}. This attribute is not writable.
26055 @defvar Breakpoint.condition
26056 This attribute holds the condition of the breakpoint, as specified by
26057 the user. It is a string. If there is no condition, this attribute's
26058 value is @code{None}. This attribute is writable.
26061 @defvar Breakpoint.commands
26062 This attribute holds the commands attached to the breakpoint. If
26063 there are commands, this attribute's value is a string holding all the
26064 commands, separated by newlines. If there are no commands, this
26065 attribute is @code{None}. This attribute is not writable.
26068 @node Finish Breakpoints in Python
26069 @subsubsection Finish Breakpoints
26071 @cindex python finish breakpoints
26072 @tindex gdb.FinishBreakpoint
26074 A finish breakpoint is a temporary breakpoint set at the return address of
26075 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26076 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26077 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26078 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26079 Finish breakpoints are thread specific and must be create with the right
26082 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26083 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26084 object @var{frame}. If @var{frame} is not provided, this defaults to the
26085 newest frame. The optional @var{internal} argument allows the breakpoint to
26086 become invisible to the user. @xref{Breakpoints In Python}, for further
26087 details about this argument.
26090 @defun FinishBreakpoint.out_of_scope (self)
26091 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26092 @code{return} command, @dots{}), a function may not properly terminate, and
26093 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26094 situation, the @code{out_of_scope} callback will be triggered.
26096 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26100 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26102 print "normal finish"
26105 def out_of_scope ():
26106 print "abnormal finish"
26110 @defvar FinishBreakpoint.return_value
26111 When @value{GDBN} is stopped at a finish breakpoint and the frame
26112 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26113 attribute will contain a @code{gdb.Value} object corresponding to the return
26114 value of the function. The value will be @code{None} if the function return
26115 type is @code{void} or if the return value was not computable. This attribute
26119 @node Lazy Strings In Python
26120 @subsubsection Python representation of lazy strings.
26122 @cindex lazy strings in python
26123 @tindex gdb.LazyString
26125 A @dfn{lazy string} is a string whose contents is not retrieved or
26126 encoded until it is needed.
26128 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26129 @code{address} that points to a region of memory, an @code{encoding}
26130 that will be used to encode that region of memory, and a @code{length}
26131 to delimit the region of memory that represents the string. The
26132 difference between a @code{gdb.LazyString} and a string wrapped within
26133 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26134 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26135 retrieved and encoded during printing, while a @code{gdb.Value}
26136 wrapping a string is immediately retrieved and encoded on creation.
26138 A @code{gdb.LazyString} object has the following functions:
26140 @defun LazyString.value ()
26141 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26142 will point to the string in memory, but will lose all the delayed
26143 retrieval, encoding and handling that @value{GDBN} applies to a
26144 @code{gdb.LazyString}.
26147 @defvar LazyString.address
26148 This attribute holds the address of the string. This attribute is not
26152 @defvar LazyString.length
26153 This attribute holds the length of the string in characters. If the
26154 length is -1, then the string will be fetched and encoded up to the
26155 first null of appropriate width. This attribute is not writable.
26158 @defvar LazyString.encoding
26159 This attribute holds the encoding that will be applied to the string
26160 when the string is printed by @value{GDBN}. If the encoding is not
26161 set, or contains an empty string, then @value{GDBN} will select the
26162 most appropriate encoding when the string is printed. This attribute
26166 @defvar LazyString.type
26167 This attribute holds the type that is represented by the lazy string's
26168 type. For a lazy string this will always be a pointer type. To
26169 resolve this to the lazy string's character type, use the type's
26170 @code{target} method. @xref{Types In Python}. This attribute is not
26174 @node Architectures In Python
26175 @subsubsection Python representation of architectures
26176 @cindex Python architectures
26178 @value{GDBN} uses architecture specific parameters and artifacts in a
26179 number of its various computations. An architecture is represented
26180 by an instance of the @code{gdb.Architecture} class.
26182 A @code{gdb.Architecture} class has the following methods:
26184 @defun Architecture.name ()
26185 Return the name (string value) of the architecture.
26188 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26189 Return a list of disassembled instructions starting from the memory
26190 address @var{start_pc}. The optional arguments @var{end_pc} and
26191 @var{count} determine the number of instructions in the returned list.
26192 If both the optional arguments @var{end_pc} and @var{count} are
26193 specified, then a list of at most @var{count} disassembled instructions
26194 whose start address falls in the closed memory address interval from
26195 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26196 specified, but @var{count} is specified, then @var{count} number of
26197 instructions starting from the address @var{start_pc} are returned. If
26198 @var{count} is not specified but @var{end_pc} is specified, then all
26199 instructions whose start address falls in the closed memory address
26200 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26201 @var{end_pc} nor @var{count} are specified, then a single instruction at
26202 @var{start_pc} is returned. For all of these cases, each element of the
26203 returned list is a Python @code{dict} with the following string keys:
26208 The value corresponding to this key is a Python long integer capturing
26209 the memory address of the instruction.
26212 The value corresponding to this key is a string value which represents
26213 the instruction with assembly language mnemonics. The assembly
26214 language flavor used is the same as that specified by the current CLI
26215 variable @code{disassembly-flavor}. @xref{Machine Code}.
26218 The value corresponding to this key is the length (integer value) of the
26219 instruction in bytes.
26224 @node Python Auto-loading
26225 @subsection Python Auto-loading
26226 @cindex Python auto-loading
26228 When a new object file is read (for example, due to the @code{file}
26229 command, or because the inferior has loaded a shared library),
26230 @value{GDBN} will look for Python support scripts in several ways:
26231 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26232 and @code{.debug_gdb_scripts} section
26233 (@pxref{dotdebug_gdb_scripts section}).
26235 The auto-loading feature is useful for supplying application-specific
26236 debugging commands and scripts.
26238 Auto-loading can be enabled or disabled,
26239 and the list of auto-loaded scripts can be printed.
26242 @anchor{set auto-load python-scripts}
26243 @kindex set auto-load python-scripts
26244 @item set auto-load python-scripts [on|off]
26245 Enable or disable the auto-loading of Python scripts.
26247 @anchor{show auto-load python-scripts}
26248 @kindex show auto-load python-scripts
26249 @item show auto-load python-scripts
26250 Show whether auto-loading of Python scripts is enabled or disabled.
26252 @anchor{info auto-load python-scripts}
26253 @kindex info auto-load python-scripts
26254 @cindex print list of auto-loaded Python scripts
26255 @item info auto-load python-scripts [@var{regexp}]
26256 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26258 Also printed is the list of Python scripts that were mentioned in
26259 the @code{.debug_gdb_scripts} section and were not found
26260 (@pxref{dotdebug_gdb_scripts section}).
26261 This is useful because their names are not printed when @value{GDBN}
26262 tries to load them and fails. There may be many of them, and printing
26263 an error message for each one is problematic.
26265 If @var{regexp} is supplied only Python scripts with matching names are printed.
26270 (gdb) info auto-load python-scripts
26272 Yes py-section-script.py
26273 full name: /tmp/py-section-script.py
26274 No my-foo-pretty-printers.py
26278 When reading an auto-loaded file, @value{GDBN} sets the
26279 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26280 function (@pxref{Objfiles In Python}). This can be useful for
26281 registering objfile-specific pretty-printers.
26284 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26285 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26286 * Which flavor to choose?::
26289 @node objfile-gdb.py file
26290 @subsubsection The @file{@var{objfile}-gdb.py} file
26291 @cindex @file{@var{objfile}-gdb.py}
26293 When a new object file is read, @value{GDBN} looks for
26294 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26295 where @var{objfile} is the object file's real name, formed by ensuring
26296 that the file name is absolute, following all symlinks, and resolving
26297 @code{.} and @code{..} components. If this file exists and is
26298 readable, @value{GDBN} will evaluate it as a Python script.
26300 If this file does not exist, then @value{GDBN} will look for
26301 @var{script-name} file in all of the directories as specified below.
26303 Note that loading of this script file also requires accordingly configured
26304 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26306 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26307 scripts normally according to its @file{.exe} filename. But if no scripts are
26308 found @value{GDBN} also tries script filenames matching the object file without
26309 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26310 is attempted on any platform. This makes the script filenames compatible
26311 between Unix and MS-Windows hosts.
26314 @anchor{set auto-load scripts-directory}
26315 @kindex set auto-load scripts-directory
26316 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26317 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26318 may be delimited by the host platform path separator in use
26319 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26321 Each entry here needs to be covered also by the security setting
26322 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26324 @anchor{with-auto-load-dir}
26325 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26326 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26327 configuration option @option{--with-auto-load-dir}.
26329 Any reference to @file{$debugdir} will get replaced by
26330 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26331 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26332 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26333 @file{$datadir} must be placed as a directory component --- either alone or
26334 delimited by @file{/} or @file{\} directory separators, depending on the host
26337 The list of directories uses path separator (@samp{:} on GNU and Unix
26338 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26339 to the @env{PATH} environment variable.
26341 @anchor{show auto-load scripts-directory}
26342 @kindex show auto-load scripts-directory
26343 @item show auto-load scripts-directory
26344 Show @value{GDBN} auto-loaded scripts location.
26347 @value{GDBN} does not track which files it has already auto-loaded this way.
26348 @value{GDBN} will load the associated script every time the corresponding
26349 @var{objfile} is opened.
26350 So your @file{-gdb.py} file should be careful to avoid errors if it
26351 is evaluated more than once.
26353 @node dotdebug_gdb_scripts section
26354 @subsubsection The @code{.debug_gdb_scripts} section
26355 @cindex @code{.debug_gdb_scripts} section
26357 For systems using file formats like ELF and COFF,
26358 when @value{GDBN} loads a new object file
26359 it will look for a special section named @samp{.debug_gdb_scripts}.
26360 If this section exists, its contents is a list of names of scripts to load.
26362 @value{GDBN} will look for each specified script file first in the
26363 current directory and then along the source search path
26364 (@pxref{Source Path, ,Specifying Source Directories}),
26365 except that @file{$cdir} is not searched, since the compilation
26366 directory is not relevant to scripts.
26368 Entries can be placed in section @code{.debug_gdb_scripts} with,
26369 for example, this GCC macro:
26372 /* Note: The "MS" section flags are to remove duplicates. */
26373 #define DEFINE_GDB_SCRIPT(script_name) \
26375 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26377 .asciz \"" script_name "\"\n\
26383 Then one can reference the macro in a header or source file like this:
26386 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26389 The script name may include directories if desired.
26391 Note that loading of this script file also requires accordingly configured
26392 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26394 If the macro is put in a header, any application or library
26395 using this header will get a reference to the specified script.
26397 @node Which flavor to choose?
26398 @subsubsection Which flavor to choose?
26400 Given the multiple ways of auto-loading Python scripts, it might not always
26401 be clear which one to choose. This section provides some guidance.
26403 Benefits of the @file{-gdb.py} way:
26407 Can be used with file formats that don't support multiple sections.
26410 Ease of finding scripts for public libraries.
26412 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26413 in the source search path.
26414 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26415 isn't a source directory in which to find the script.
26418 Doesn't require source code additions.
26421 Benefits of the @code{.debug_gdb_scripts} way:
26425 Works with static linking.
26427 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26428 trigger their loading. When an application is statically linked the only
26429 objfile available is the executable, and it is cumbersome to attach all the
26430 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26433 Works with classes that are entirely inlined.
26435 Some classes can be entirely inlined, and thus there may not be an associated
26436 shared library to attach a @file{-gdb.py} script to.
26439 Scripts needn't be copied out of the source tree.
26441 In some circumstances, apps can be built out of large collections of internal
26442 libraries, and the build infrastructure necessary to install the
26443 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26444 cumbersome. It may be easier to specify the scripts in the
26445 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26446 top of the source tree to the source search path.
26449 @node Python modules
26450 @subsection Python modules
26451 @cindex python modules
26453 @value{GDBN} comes with several modules to assist writing Python code.
26456 * gdb.printing:: Building and registering pretty-printers.
26457 * gdb.types:: Utilities for working with types.
26458 * gdb.prompt:: Utilities for prompt value substitution.
26462 @subsubsection gdb.printing
26463 @cindex gdb.printing
26465 This module provides a collection of utilities for working with
26469 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26470 This class specifies the API that makes @samp{info pretty-printer},
26471 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26472 Pretty-printers should generally inherit from this class.
26474 @item SubPrettyPrinter (@var{name})
26475 For printers that handle multiple types, this class specifies the
26476 corresponding API for the subprinters.
26478 @item RegexpCollectionPrettyPrinter (@var{name})
26479 Utility class for handling multiple printers, all recognized via
26480 regular expressions.
26481 @xref{Writing a Pretty-Printer}, for an example.
26483 @item FlagEnumerationPrinter (@var{name})
26484 A pretty-printer which handles printing of @code{enum} values. Unlike
26485 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26486 work properly when there is some overlap between the enumeration
26487 constants. @var{name} is the name of the printer and also the name of
26488 the @code{enum} type to look up.
26490 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26491 Register @var{printer} with the pretty-printer list of @var{obj}.
26492 If @var{replace} is @code{True} then any existing copy of the printer
26493 is replaced. Otherwise a @code{RuntimeError} exception is raised
26494 if a printer with the same name already exists.
26498 @subsubsection gdb.types
26501 This module provides a collection of utilities for working with
26502 @code{gdb.Type} objects.
26505 @item get_basic_type (@var{type})
26506 Return @var{type} with const and volatile qualifiers stripped,
26507 and with typedefs and C@t{++} references converted to the underlying type.
26512 typedef const int const_int;
26514 const_int& foo_ref (foo);
26515 int main () @{ return 0; @}
26522 (gdb) python import gdb.types
26523 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26524 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26528 @item has_field (@var{type}, @var{field})
26529 Return @code{True} if @var{type}, assumed to be a type with fields
26530 (e.g., a structure or union), has field @var{field}.
26532 @item make_enum_dict (@var{enum_type})
26533 Return a Python @code{dictionary} type produced from @var{enum_type}.
26535 @item deep_items (@var{type})
26536 Returns a Python iterator similar to the standard
26537 @code{gdb.Type.iteritems} method, except that the iterator returned
26538 by @code{deep_items} will recursively traverse anonymous struct or
26539 union fields. For example:
26553 Then in @value{GDBN}:
26555 (@value{GDBP}) python import gdb.types
26556 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26557 (@value{GDBP}) python print struct_a.keys ()
26559 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26560 @{['a', 'b0', 'b1']@}
26563 @item get_type_recognizers ()
26564 Return a list of the enabled type recognizers for the current context.
26565 This is called by @value{GDBN} during the type-printing process
26566 (@pxref{Type Printing API}).
26568 @item apply_type_recognizers (recognizers, type_obj)
26569 Apply the type recognizers, @var{recognizers}, to the type object
26570 @var{type_obj}. If any recognizer returns a string, return that
26571 string. Otherwise, return @code{None}. This is called by
26572 @value{GDBN} during the type-printing process (@pxref{Type Printing
26575 @item register_type_printer (locus, printer)
26576 This is a convenience function to register a type printer.
26577 @var{printer} is the type printer to register. It must implement the
26578 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26579 which case the printer is registered with that objfile; a
26580 @code{gdb.Progspace}, in which case the printer is registered with
26581 that progspace; or @code{None}, in which case the printer is
26582 registered globally.
26585 This is a base class that implements the type printer protocol. Type
26586 printers are encouraged, but not required, to derive from this class.
26587 It defines a constructor:
26589 @defmethod TypePrinter __init__ (self, name)
26590 Initialize the type printer with the given name. The new printer
26591 starts in the enabled state.
26597 @subsubsection gdb.prompt
26600 This module provides a method for prompt value-substitution.
26603 @item substitute_prompt (@var{string})
26604 Return @var{string} with escape sequences substituted by values. Some
26605 escape sequences take arguments. You can specify arguments inside
26606 ``@{@}'' immediately following the escape sequence.
26608 The escape sequences you can pass to this function are:
26612 Substitute a backslash.
26614 Substitute an ESC character.
26616 Substitute the selected frame; an argument names a frame parameter.
26618 Substitute a newline.
26620 Substitute a parameter's value; the argument names the parameter.
26622 Substitute a carriage return.
26624 Substitute the selected thread; an argument names a thread parameter.
26626 Substitute the version of GDB.
26628 Substitute the current working directory.
26630 Begin a sequence of non-printing characters. These sequences are
26631 typically used with the ESC character, and are not counted in the string
26632 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26633 blue-colored ``(gdb)'' prompt where the length is five.
26635 End a sequence of non-printing characters.
26641 substitute_prompt (``frame: \f,
26642 print arguments: \p@{print frame-arguments@}'')
26645 @exdent will return the string:
26648 "frame: main, print arguments: scalars"
26653 @section Creating new spellings of existing commands
26654 @cindex aliases for commands
26656 It is often useful to define alternate spellings of existing commands.
26657 For example, if a new @value{GDBN} command defined in Python has
26658 a long name to type, it is handy to have an abbreviated version of it
26659 that involves less typing.
26661 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26662 of the @samp{step} command even though it is otherwise an ambiguous
26663 abbreviation of other commands like @samp{set} and @samp{show}.
26665 Aliases are also used to provide shortened or more common versions
26666 of multi-word commands. For example, @value{GDBN} provides the
26667 @samp{tty} alias of the @samp{set inferior-tty} command.
26669 You can define a new alias with the @samp{alias} command.
26674 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26678 @var{ALIAS} specifies the name of the new alias.
26679 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26682 @var{COMMAND} specifies the name of an existing command
26683 that is being aliased.
26685 The @samp{-a} option specifies that the new alias is an abbreviation
26686 of the command. Abbreviations are not shown in command
26687 lists displayed by the @samp{help} command.
26689 The @samp{--} option specifies the end of options,
26690 and is useful when @var{ALIAS} begins with a dash.
26692 Here is a simple example showing how to make an abbreviation
26693 of a command so that there is less to type.
26694 Suppose you were tired of typing @samp{disas}, the current
26695 shortest unambiguous abbreviation of the @samp{disassemble} command
26696 and you wanted an even shorter version named @samp{di}.
26697 The following will accomplish this.
26700 (gdb) alias -a di = disas
26703 Note that aliases are different from user-defined commands.
26704 With a user-defined command, you also need to write documentation
26705 for it with the @samp{document} command.
26706 An alias automatically picks up the documentation of the existing command.
26708 Here is an example where we make @samp{elms} an abbreviation of
26709 @samp{elements} in the @samp{set print elements} command.
26710 This is to show that you can make an abbreviation of any part
26714 (gdb) alias -a set print elms = set print elements
26715 (gdb) alias -a show print elms = show print elements
26716 (gdb) set p elms 20
26718 Limit on string chars or array elements to print is 200.
26721 Note that if you are defining an alias of a @samp{set} command,
26722 and you want to have an alias for the corresponding @samp{show}
26723 command, then you need to define the latter separately.
26725 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26726 @var{ALIAS}, just as they are normally.
26729 (gdb) alias -a set pr elms = set p ele
26732 Finally, here is an example showing the creation of a one word
26733 alias for a more complex command.
26734 This creates alias @samp{spe} of the command @samp{set print elements}.
26737 (gdb) alias spe = set print elements
26742 @chapter Command Interpreters
26743 @cindex command interpreters
26745 @value{GDBN} supports multiple command interpreters, and some command
26746 infrastructure to allow users or user interface writers to switch
26747 between interpreters or run commands in other interpreters.
26749 @value{GDBN} currently supports two command interpreters, the console
26750 interpreter (sometimes called the command-line interpreter or @sc{cli})
26751 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26752 describes both of these interfaces in great detail.
26754 By default, @value{GDBN} will start with the console interpreter.
26755 However, the user may choose to start @value{GDBN} with another
26756 interpreter by specifying the @option{-i} or @option{--interpreter}
26757 startup options. Defined interpreters include:
26761 @cindex console interpreter
26762 The traditional console or command-line interpreter. This is the most often
26763 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26764 @value{GDBN} will use this interpreter.
26767 @cindex mi interpreter
26768 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26769 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26770 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26774 @cindex mi2 interpreter
26775 The current @sc{gdb/mi} interface.
26778 @cindex mi1 interpreter
26779 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26783 @cindex invoke another interpreter
26784 The interpreter being used by @value{GDBN} may not be dynamically
26785 switched at runtime. Although possible, this could lead to a very
26786 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26787 enters the command "interpreter-set console" in a console view,
26788 @value{GDBN} would switch to using the console interpreter, rendering
26789 the IDE inoperable!
26791 @kindex interpreter-exec
26792 Although you may only choose a single interpreter at startup, you may execute
26793 commands in any interpreter from the current interpreter using the appropriate
26794 command. If you are running the console interpreter, simply use the
26795 @code{interpreter-exec} command:
26798 interpreter-exec mi "-data-list-register-names"
26801 @sc{gdb/mi} has a similar command, although it is only available in versions of
26802 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26805 @chapter @value{GDBN} Text User Interface
26807 @cindex Text User Interface
26810 * TUI Overview:: TUI overview
26811 * TUI Keys:: TUI key bindings
26812 * TUI Single Key Mode:: TUI single key mode
26813 * TUI Commands:: TUI-specific commands
26814 * TUI Configuration:: TUI configuration variables
26817 The @value{GDBN} Text User Interface (TUI) is a terminal
26818 interface which uses the @code{curses} library to show the source
26819 file, the assembly output, the program registers and @value{GDBN}
26820 commands in separate text windows. The TUI mode is supported only
26821 on platforms where a suitable version of the @code{curses} library
26824 The TUI mode is enabled by default when you invoke @value{GDBN} as
26825 @samp{@value{GDBP} -tui}.
26826 You can also switch in and out of TUI mode while @value{GDBN} runs by
26827 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26828 @xref{TUI Keys, ,TUI Key Bindings}.
26831 @section TUI Overview
26833 In TUI mode, @value{GDBN} can display several text windows:
26837 This window is the @value{GDBN} command window with the @value{GDBN}
26838 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26839 managed using readline.
26842 The source window shows the source file of the program. The current
26843 line and active breakpoints are displayed in this window.
26846 The assembly window shows the disassembly output of the program.
26849 This window shows the processor registers. Registers are highlighted
26850 when their values change.
26853 The source and assembly windows show the current program position
26854 by highlighting the current line and marking it with a @samp{>} marker.
26855 Breakpoints are indicated with two markers. The first marker
26856 indicates the breakpoint type:
26860 Breakpoint which was hit at least once.
26863 Breakpoint which was never hit.
26866 Hardware breakpoint which was hit at least once.
26869 Hardware breakpoint which was never hit.
26872 The second marker indicates whether the breakpoint is enabled or not:
26876 Breakpoint is enabled.
26879 Breakpoint is disabled.
26882 The source, assembly and register windows are updated when the current
26883 thread changes, when the frame changes, or when the program counter
26886 These windows are not all visible at the same time. The command
26887 window is always visible. The others can be arranged in several
26898 source and assembly,
26901 source and registers, or
26904 assembly and registers.
26907 A status line above the command window shows the following information:
26911 Indicates the current @value{GDBN} target.
26912 (@pxref{Targets, ,Specifying a Debugging Target}).
26915 Gives the current process or thread number.
26916 When no process is being debugged, this field is set to @code{No process}.
26919 Gives the current function name for the selected frame.
26920 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26921 When there is no symbol corresponding to the current program counter,
26922 the string @code{??} is displayed.
26925 Indicates the current line number for the selected frame.
26926 When the current line number is not known, the string @code{??} is displayed.
26929 Indicates the current program counter address.
26933 @section TUI Key Bindings
26934 @cindex TUI key bindings
26936 The TUI installs several key bindings in the readline keymaps
26937 @ifset SYSTEM_READLINE
26938 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26940 @ifclear SYSTEM_READLINE
26941 (@pxref{Command Line Editing}).
26943 The following key bindings are installed for both TUI mode and the
26944 @value{GDBN} standard mode.
26953 Enter or leave the TUI mode. When leaving the TUI mode,
26954 the curses window management stops and @value{GDBN} operates using
26955 its standard mode, writing on the terminal directly. When reentering
26956 the TUI mode, control is given back to the curses windows.
26957 The screen is then refreshed.
26961 Use a TUI layout with only one window. The layout will
26962 either be @samp{source} or @samp{assembly}. When the TUI mode
26963 is not active, it will switch to the TUI mode.
26965 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26969 Use a TUI layout with at least two windows. When the current
26970 layout already has two windows, the next layout with two windows is used.
26971 When a new layout is chosen, one window will always be common to the
26972 previous layout and the new one.
26974 Think of it as the Emacs @kbd{C-x 2} binding.
26978 Change the active window. The TUI associates several key bindings
26979 (like scrolling and arrow keys) with the active window. This command
26980 gives the focus to the next TUI window.
26982 Think of it as the Emacs @kbd{C-x o} binding.
26986 Switch in and out of the TUI SingleKey mode that binds single
26987 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26990 The following key bindings only work in the TUI mode:
26995 Scroll the active window one page up.
26999 Scroll the active window one page down.
27003 Scroll the active window one line up.
27007 Scroll the active window one line down.
27011 Scroll the active window one column left.
27015 Scroll the active window one column right.
27019 Refresh the screen.
27022 Because the arrow keys scroll the active window in the TUI mode, they
27023 are not available for their normal use by readline unless the command
27024 window has the focus. When another window is active, you must use
27025 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27026 and @kbd{C-f} to control the command window.
27028 @node TUI Single Key Mode
27029 @section TUI Single Key Mode
27030 @cindex TUI single key mode
27032 The TUI also provides a @dfn{SingleKey} mode, which binds several
27033 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27034 switch into this mode, where the following key bindings are used:
27037 @kindex c @r{(SingleKey TUI key)}
27041 @kindex d @r{(SingleKey TUI key)}
27045 @kindex f @r{(SingleKey TUI key)}
27049 @kindex n @r{(SingleKey TUI key)}
27053 @kindex q @r{(SingleKey TUI key)}
27055 exit the SingleKey mode.
27057 @kindex r @r{(SingleKey TUI key)}
27061 @kindex s @r{(SingleKey TUI key)}
27065 @kindex u @r{(SingleKey TUI key)}
27069 @kindex v @r{(SingleKey TUI key)}
27073 @kindex w @r{(SingleKey TUI key)}
27078 Other keys temporarily switch to the @value{GDBN} command prompt.
27079 The key that was pressed is inserted in the editing buffer so that
27080 it is possible to type most @value{GDBN} commands without interaction
27081 with the TUI SingleKey mode. Once the command is entered the TUI
27082 SingleKey mode is restored. The only way to permanently leave
27083 this mode is by typing @kbd{q} or @kbd{C-x s}.
27087 @section TUI-specific Commands
27088 @cindex TUI commands
27090 The TUI has specific commands to control the text windows.
27091 These commands are always available, even when @value{GDBN} is not in
27092 the TUI mode. When @value{GDBN} is in the standard mode, most
27093 of these commands will automatically switch to the TUI mode.
27095 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27096 terminal, or @value{GDBN} has been started with the machine interface
27097 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27098 these commands will fail with an error, because it would not be
27099 possible or desirable to enable curses window management.
27104 List and give the size of all displayed windows.
27108 Display the next layout.
27111 Display the previous layout.
27114 Display the source window only.
27117 Display the assembly window only.
27120 Display the source and assembly window.
27123 Display the register window together with the source or assembly window.
27127 Make the next window active for scrolling.
27130 Make the previous window active for scrolling.
27133 Make the source window active for scrolling.
27136 Make the assembly window active for scrolling.
27139 Make the register window active for scrolling.
27142 Make the command window active for scrolling.
27146 Refresh the screen. This is similar to typing @kbd{C-L}.
27148 @item tui reg float
27150 Show the floating point registers in the register window.
27152 @item tui reg general
27153 Show the general registers in the register window.
27156 Show the next register group. The list of register groups as well as
27157 their order is target specific. The predefined register groups are the
27158 following: @code{general}, @code{float}, @code{system}, @code{vector},
27159 @code{all}, @code{save}, @code{restore}.
27161 @item tui reg system
27162 Show the system registers in the register window.
27166 Update the source window and the current execution point.
27168 @item winheight @var{name} +@var{count}
27169 @itemx winheight @var{name} -@var{count}
27171 Change the height of the window @var{name} by @var{count}
27172 lines. Positive counts increase the height, while negative counts
27175 @item tabset @var{nchars}
27177 Set the width of tab stops to be @var{nchars} characters.
27180 @node TUI Configuration
27181 @section TUI Configuration Variables
27182 @cindex TUI configuration variables
27184 Several configuration variables control the appearance of TUI windows.
27187 @item set tui border-kind @var{kind}
27188 @kindex set tui border-kind
27189 Select the border appearance for the source, assembly and register windows.
27190 The possible values are the following:
27193 Use a space character to draw the border.
27196 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27199 Use the Alternate Character Set to draw the border. The border is
27200 drawn using character line graphics if the terminal supports them.
27203 @item set tui border-mode @var{mode}
27204 @kindex set tui border-mode
27205 @itemx set tui active-border-mode @var{mode}
27206 @kindex set tui active-border-mode
27207 Select the display attributes for the borders of the inactive windows
27208 or the active window. The @var{mode} can be one of the following:
27211 Use normal attributes to display the border.
27217 Use reverse video mode.
27220 Use half bright mode.
27222 @item half-standout
27223 Use half bright and standout mode.
27226 Use extra bright or bold mode.
27228 @item bold-standout
27229 Use extra bright or bold and standout mode.
27234 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27237 @cindex @sc{gnu} Emacs
27238 A special interface allows you to use @sc{gnu} Emacs to view (and
27239 edit) the source files for the program you are debugging with
27242 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27243 executable file you want to debug as an argument. This command starts
27244 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27245 created Emacs buffer.
27246 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27248 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27253 All ``terminal'' input and output goes through an Emacs buffer, called
27256 This applies both to @value{GDBN} commands and their output, and to the input
27257 and output done by the program you are debugging.
27259 This is useful because it means that you can copy the text of previous
27260 commands and input them again; you can even use parts of the output
27263 All the facilities of Emacs' Shell mode are available for interacting
27264 with your program. In particular, you can send signals the usual
27265 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27269 @value{GDBN} displays source code through Emacs.
27271 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27272 source file for that frame and puts an arrow (@samp{=>}) at the
27273 left margin of the current line. Emacs uses a separate buffer for
27274 source display, and splits the screen to show both your @value{GDBN} session
27277 Explicit @value{GDBN} @code{list} or search commands still produce output as
27278 usual, but you probably have no reason to use them from Emacs.
27281 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27282 a graphical mode, enabled by default, which provides further buffers
27283 that can control the execution and describe the state of your program.
27284 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27286 If you specify an absolute file name when prompted for the @kbd{M-x
27287 gdb} argument, then Emacs sets your current working directory to where
27288 your program resides. If you only specify the file name, then Emacs
27289 sets your current working directory to the directory associated
27290 with the previous buffer. In this case, @value{GDBN} may find your
27291 program by searching your environment's @code{PATH} variable, but on
27292 some operating systems it might not find the source. So, although the
27293 @value{GDBN} input and output session proceeds normally, the auxiliary
27294 buffer does not display the current source and line of execution.
27296 The initial working directory of @value{GDBN} is printed on the top
27297 line of the GUD buffer and this serves as a default for the commands
27298 that specify files for @value{GDBN} to operate on. @xref{Files,
27299 ,Commands to Specify Files}.
27301 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27302 need to call @value{GDBN} by a different name (for example, if you
27303 keep several configurations around, with different names) you can
27304 customize the Emacs variable @code{gud-gdb-command-name} to run the
27307 In the GUD buffer, you can use these special Emacs commands in
27308 addition to the standard Shell mode commands:
27312 Describe the features of Emacs' GUD Mode.
27315 Execute to another source line, like the @value{GDBN} @code{step} command; also
27316 update the display window to show the current file and location.
27319 Execute to next source line in this function, skipping all function
27320 calls, like the @value{GDBN} @code{next} command. Then update the display window
27321 to show the current file and location.
27324 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27325 display window accordingly.
27328 Execute until exit from the selected stack frame, like the @value{GDBN}
27329 @code{finish} command.
27332 Continue execution of your program, like the @value{GDBN} @code{continue}
27336 Go up the number of frames indicated by the numeric argument
27337 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27338 like the @value{GDBN} @code{up} command.
27341 Go down the number of frames indicated by the numeric argument, like the
27342 @value{GDBN} @code{down} command.
27345 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27346 tells @value{GDBN} to set a breakpoint on the source line point is on.
27348 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27349 separate frame which shows a backtrace when the GUD buffer is current.
27350 Move point to any frame in the stack and type @key{RET} to make it
27351 become the current frame and display the associated source in the
27352 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27353 selected frame become the current one. In graphical mode, the
27354 speedbar displays watch expressions.
27356 If you accidentally delete the source-display buffer, an easy way to get
27357 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27358 request a frame display; when you run under Emacs, this recreates
27359 the source buffer if necessary to show you the context of the current
27362 The source files displayed in Emacs are in ordinary Emacs buffers
27363 which are visiting the source files in the usual way. You can edit
27364 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27365 communicates with Emacs in terms of line numbers. If you add or
27366 delete lines from the text, the line numbers that @value{GDBN} knows cease
27367 to correspond properly with the code.
27369 A more detailed description of Emacs' interaction with @value{GDBN} is
27370 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27374 @chapter The @sc{gdb/mi} Interface
27376 @unnumberedsec Function and Purpose
27378 @cindex @sc{gdb/mi}, its purpose
27379 @sc{gdb/mi} is a line based machine oriented text interface to
27380 @value{GDBN} and is activated by specifying using the
27381 @option{--interpreter} command line option (@pxref{Mode Options}). It
27382 is specifically intended to support the development of systems which
27383 use the debugger as just one small component of a larger system.
27385 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27386 in the form of a reference manual.
27388 Note that @sc{gdb/mi} is still under construction, so some of the
27389 features described below are incomplete and subject to change
27390 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27392 @unnumberedsec Notation and Terminology
27394 @cindex notational conventions, for @sc{gdb/mi}
27395 This chapter uses the following notation:
27399 @code{|} separates two alternatives.
27402 @code{[ @var{something} ]} indicates that @var{something} is optional:
27403 it may or may not be given.
27406 @code{( @var{group} )*} means that @var{group} inside the parentheses
27407 may repeat zero or more times.
27410 @code{( @var{group} )+} means that @var{group} inside the parentheses
27411 may repeat one or more times.
27414 @code{"@var{string}"} means a literal @var{string}.
27418 @heading Dependencies
27422 * GDB/MI General Design::
27423 * GDB/MI Command Syntax::
27424 * GDB/MI Compatibility with CLI::
27425 * GDB/MI Development and Front Ends::
27426 * GDB/MI Output Records::
27427 * GDB/MI Simple Examples::
27428 * GDB/MI Command Description Format::
27429 * GDB/MI Breakpoint Commands::
27430 * GDB/MI Catchpoint Commands::
27431 * GDB/MI Program Context::
27432 * GDB/MI Thread Commands::
27433 * GDB/MI Ada Tasking Commands::
27434 * GDB/MI Program Execution::
27435 * GDB/MI Stack Manipulation::
27436 * GDB/MI Variable Objects::
27437 * GDB/MI Data Manipulation::
27438 * GDB/MI Tracepoint Commands::
27439 * GDB/MI Symbol Query::
27440 * GDB/MI File Commands::
27442 * GDB/MI Kod Commands::
27443 * GDB/MI Memory Overlay Commands::
27444 * GDB/MI Signal Handling Commands::
27446 * GDB/MI Target Manipulation::
27447 * GDB/MI File Transfer Commands::
27448 * GDB/MI Miscellaneous Commands::
27451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27452 @node GDB/MI General Design
27453 @section @sc{gdb/mi} General Design
27454 @cindex GDB/MI General Design
27456 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27457 parts---commands sent to @value{GDBN}, responses to those commands
27458 and notifications. Each command results in exactly one response,
27459 indicating either successful completion of the command, or an error.
27460 For the commands that do not resume the target, the response contains the
27461 requested information. For the commands that resume the target, the
27462 response only indicates whether the target was successfully resumed.
27463 Notifications is the mechanism for reporting changes in the state of the
27464 target, or in @value{GDBN} state, that cannot conveniently be associated with
27465 a command and reported as part of that command response.
27467 The important examples of notifications are:
27471 Exec notifications. These are used to report changes in
27472 target state---when a target is resumed, or stopped. It would not
27473 be feasible to include this information in response of resuming
27474 commands, because one resume commands can result in multiple events in
27475 different threads. Also, quite some time may pass before any event
27476 happens in the target, while a frontend needs to know whether the resuming
27477 command itself was successfully executed.
27480 Console output, and status notifications. Console output
27481 notifications are used to report output of CLI commands, as well as
27482 diagnostics for other commands. Status notifications are used to
27483 report the progress of a long-running operation. Naturally, including
27484 this information in command response would mean no output is produced
27485 until the command is finished, which is undesirable.
27488 General notifications. Commands may have various side effects on
27489 the @value{GDBN} or target state beyond their official purpose. For example,
27490 a command may change the selected thread. Although such changes can
27491 be included in command response, using notification allows for more
27492 orthogonal frontend design.
27496 There's no guarantee that whenever an MI command reports an error,
27497 @value{GDBN} or the target are in any specific state, and especially,
27498 the state is not reverted to the state before the MI command was
27499 processed. Therefore, whenever an MI command results in an error,
27500 we recommend that the frontend refreshes all the information shown in
27501 the user interface.
27505 * Context management::
27506 * Asynchronous and non-stop modes::
27510 @node Context management
27511 @subsection Context management
27513 In most cases when @value{GDBN} accesses the target, this access is
27514 done in context of a specific thread and frame (@pxref{Frames}).
27515 Often, even when accessing global data, the target requires that a thread
27516 be specified. The CLI interface maintains the selected thread and frame,
27517 and supplies them to target on each command. This is convenient,
27518 because a command line user would not want to specify that information
27519 explicitly on each command, and because user interacts with
27520 @value{GDBN} via a single terminal, so no confusion is possible as
27521 to what thread and frame are the current ones.
27523 In the case of MI, the concept of selected thread and frame is less
27524 useful. First, a frontend can easily remember this information
27525 itself. Second, a graphical frontend can have more than one window,
27526 each one used for debugging a different thread, and the frontend might
27527 want to access additional threads for internal purposes. This
27528 increases the risk that by relying on implicitly selected thread, the
27529 frontend may be operating on a wrong one. Therefore, each MI command
27530 should explicitly specify which thread and frame to operate on. To
27531 make it possible, each MI command accepts the @samp{--thread} and
27532 @samp{--frame} options, the value to each is @value{GDBN} identifier
27533 for thread and frame to operate on.
27535 Usually, each top-level window in a frontend allows the user to select
27536 a thread and a frame, and remembers the user selection for further
27537 operations. However, in some cases @value{GDBN} may suggest that the
27538 current thread be changed. For example, when stopping on a breakpoint
27539 it is reasonable to switch to the thread where breakpoint is hit. For
27540 another example, if the user issues the CLI @samp{thread} command via
27541 the frontend, it is desirable to change the frontend's selected thread to the
27542 one specified by user. @value{GDBN} communicates the suggestion to
27543 change current thread using the @samp{=thread-selected} notification.
27544 No such notification is available for the selected frame at the moment.
27546 Note that historically, MI shares the selected thread with CLI, so
27547 frontends used the @code{-thread-select} to execute commands in the
27548 right context. However, getting this to work right is cumbersome. The
27549 simplest way is for frontend to emit @code{-thread-select} command
27550 before every command. This doubles the number of commands that need
27551 to be sent. The alternative approach is to suppress @code{-thread-select}
27552 if the selected thread in @value{GDBN} is supposed to be identical to the
27553 thread the frontend wants to operate on. However, getting this
27554 optimization right can be tricky. In particular, if the frontend
27555 sends several commands to @value{GDBN}, and one of the commands changes the
27556 selected thread, then the behaviour of subsequent commands will
27557 change. So, a frontend should either wait for response from such
27558 problematic commands, or explicitly add @code{-thread-select} for
27559 all subsequent commands. No frontend is known to do this exactly
27560 right, so it is suggested to just always pass the @samp{--thread} and
27561 @samp{--frame} options.
27563 @node Asynchronous and non-stop modes
27564 @subsection Asynchronous command execution and non-stop mode
27566 On some targets, @value{GDBN} is capable of processing MI commands
27567 even while the target is running. This is called @dfn{asynchronous
27568 command execution} (@pxref{Background Execution}). The frontend may
27569 specify a preferrence for asynchronous execution using the
27570 @code{-gdb-set target-async 1} command, which should be emitted before
27571 either running the executable or attaching to the target. After the
27572 frontend has started the executable or attached to the target, it can
27573 find if asynchronous execution is enabled using the
27574 @code{-list-target-features} command.
27576 Even if @value{GDBN} can accept a command while target is running,
27577 many commands that access the target do not work when the target is
27578 running. Therefore, asynchronous command execution is most useful
27579 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27580 it is possible to examine the state of one thread, while other threads
27583 When a given thread is running, MI commands that try to access the
27584 target in the context of that thread may not work, or may work only on
27585 some targets. In particular, commands that try to operate on thread's
27586 stack will not work, on any target. Commands that read memory, or
27587 modify breakpoints, may work or not work, depending on the target. Note
27588 that even commands that operate on global state, such as @code{print},
27589 @code{set}, and breakpoint commands, still access the target in the
27590 context of a specific thread, so frontend should try to find a
27591 stopped thread and perform the operation on that thread (using the
27592 @samp{--thread} option).
27594 Which commands will work in the context of a running thread is
27595 highly target dependent. However, the two commands
27596 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27597 to find the state of a thread, will always work.
27599 @node Thread groups
27600 @subsection Thread groups
27601 @value{GDBN} may be used to debug several processes at the same time.
27602 On some platfroms, @value{GDBN} may support debugging of several
27603 hardware systems, each one having several cores with several different
27604 processes running on each core. This section describes the MI
27605 mechanism to support such debugging scenarios.
27607 The key observation is that regardless of the structure of the
27608 target, MI can have a global list of threads, because most commands that
27609 accept the @samp{--thread} option do not need to know what process that
27610 thread belongs to. Therefore, it is not necessary to introduce
27611 neither additional @samp{--process} option, nor an notion of the
27612 current process in the MI interface. The only strictly new feature
27613 that is required is the ability to find how the threads are grouped
27616 To allow the user to discover such grouping, and to support arbitrary
27617 hierarchy of machines/cores/processes, MI introduces the concept of a
27618 @dfn{thread group}. Thread group is a collection of threads and other
27619 thread groups. A thread group always has a string identifier, a type,
27620 and may have additional attributes specific to the type. A new
27621 command, @code{-list-thread-groups}, returns the list of top-level
27622 thread groups, which correspond to processes that @value{GDBN} is
27623 debugging at the moment. By passing an identifier of a thread group
27624 to the @code{-list-thread-groups} command, it is possible to obtain
27625 the members of specific thread group.
27627 To allow the user to easily discover processes, and other objects, he
27628 wishes to debug, a concept of @dfn{available thread group} is
27629 introduced. Available thread group is an thread group that
27630 @value{GDBN} is not debugging, but that can be attached to, using the
27631 @code{-target-attach} command. The list of available top-level thread
27632 groups can be obtained using @samp{-list-thread-groups --available}.
27633 In general, the content of a thread group may be only retrieved only
27634 after attaching to that thread group.
27636 Thread groups are related to inferiors (@pxref{Inferiors and
27637 Programs}). Each inferior corresponds to a thread group of a special
27638 type @samp{process}, and some additional operations are permitted on
27639 such thread groups.
27641 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27642 @node GDB/MI Command Syntax
27643 @section @sc{gdb/mi} Command Syntax
27646 * GDB/MI Input Syntax::
27647 * GDB/MI Output Syntax::
27650 @node GDB/MI Input Syntax
27651 @subsection @sc{gdb/mi} Input Syntax
27653 @cindex input syntax for @sc{gdb/mi}
27654 @cindex @sc{gdb/mi}, input syntax
27656 @item @var{command} @expansion{}
27657 @code{@var{cli-command} | @var{mi-command}}
27659 @item @var{cli-command} @expansion{}
27660 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27661 @var{cli-command} is any existing @value{GDBN} CLI command.
27663 @item @var{mi-command} @expansion{}
27664 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27665 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27667 @item @var{token} @expansion{}
27668 "any sequence of digits"
27670 @item @var{option} @expansion{}
27671 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27673 @item @var{parameter} @expansion{}
27674 @code{@var{non-blank-sequence} | @var{c-string}}
27676 @item @var{operation} @expansion{}
27677 @emph{any of the operations described in this chapter}
27679 @item @var{non-blank-sequence} @expansion{}
27680 @emph{anything, provided it doesn't contain special characters such as
27681 "-", @var{nl}, """ and of course " "}
27683 @item @var{c-string} @expansion{}
27684 @code{""" @var{seven-bit-iso-c-string-content} """}
27686 @item @var{nl} @expansion{}
27695 The CLI commands are still handled by the @sc{mi} interpreter; their
27696 output is described below.
27699 The @code{@var{token}}, when present, is passed back when the command
27703 Some @sc{mi} commands accept optional arguments as part of the parameter
27704 list. Each option is identified by a leading @samp{-} (dash) and may be
27705 followed by an optional argument parameter. Options occur first in the
27706 parameter list and can be delimited from normal parameters using
27707 @samp{--} (this is useful when some parameters begin with a dash).
27714 We want easy access to the existing CLI syntax (for debugging).
27717 We want it to be easy to spot a @sc{mi} operation.
27720 @node GDB/MI Output Syntax
27721 @subsection @sc{gdb/mi} Output Syntax
27723 @cindex output syntax of @sc{gdb/mi}
27724 @cindex @sc{gdb/mi}, output syntax
27725 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27726 followed, optionally, by a single result record. This result record
27727 is for the most recent command. The sequence of output records is
27728 terminated by @samp{(gdb)}.
27730 If an input command was prefixed with a @code{@var{token}} then the
27731 corresponding output for that command will also be prefixed by that same
27735 @item @var{output} @expansion{}
27736 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27738 @item @var{result-record} @expansion{}
27739 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27741 @item @var{out-of-band-record} @expansion{}
27742 @code{@var{async-record} | @var{stream-record}}
27744 @item @var{async-record} @expansion{}
27745 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27747 @item @var{exec-async-output} @expansion{}
27748 @code{[ @var{token} ] "*" @var{async-output}}
27750 @item @var{status-async-output} @expansion{}
27751 @code{[ @var{token} ] "+" @var{async-output}}
27753 @item @var{notify-async-output} @expansion{}
27754 @code{[ @var{token} ] "=" @var{async-output}}
27756 @item @var{async-output} @expansion{}
27757 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27759 @item @var{result-class} @expansion{}
27760 @code{"done" | "running" | "connected" | "error" | "exit"}
27762 @item @var{async-class} @expansion{}
27763 @code{"stopped" | @var{others}} (where @var{others} will be added
27764 depending on the needs---this is still in development).
27766 @item @var{result} @expansion{}
27767 @code{ @var{variable} "=" @var{value}}
27769 @item @var{variable} @expansion{}
27770 @code{ @var{string} }
27772 @item @var{value} @expansion{}
27773 @code{ @var{const} | @var{tuple} | @var{list} }
27775 @item @var{const} @expansion{}
27776 @code{@var{c-string}}
27778 @item @var{tuple} @expansion{}
27779 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27781 @item @var{list} @expansion{}
27782 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27783 @var{result} ( "," @var{result} )* "]" }
27785 @item @var{stream-record} @expansion{}
27786 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27788 @item @var{console-stream-output} @expansion{}
27789 @code{"~" @var{c-string}}
27791 @item @var{target-stream-output} @expansion{}
27792 @code{"@@" @var{c-string}}
27794 @item @var{log-stream-output} @expansion{}
27795 @code{"&" @var{c-string}}
27797 @item @var{nl} @expansion{}
27800 @item @var{token} @expansion{}
27801 @emph{any sequence of digits}.
27809 All output sequences end in a single line containing a period.
27812 The @code{@var{token}} is from the corresponding request. Note that
27813 for all async output, while the token is allowed by the grammar and
27814 may be output by future versions of @value{GDBN} for select async
27815 output messages, it is generally omitted. Frontends should treat
27816 all async output as reporting general changes in the state of the
27817 target and there should be no need to associate async output to any
27821 @cindex status output in @sc{gdb/mi}
27822 @var{status-async-output} contains on-going status information about the
27823 progress of a slow operation. It can be discarded. All status output is
27824 prefixed by @samp{+}.
27827 @cindex async output in @sc{gdb/mi}
27828 @var{exec-async-output} contains asynchronous state change on the target
27829 (stopped, started, disappeared). All async output is prefixed by
27833 @cindex notify output in @sc{gdb/mi}
27834 @var{notify-async-output} contains supplementary information that the
27835 client should handle (e.g., a new breakpoint information). All notify
27836 output is prefixed by @samp{=}.
27839 @cindex console output in @sc{gdb/mi}
27840 @var{console-stream-output} is output that should be displayed as is in the
27841 console. It is the textual response to a CLI command. All the console
27842 output is prefixed by @samp{~}.
27845 @cindex target output in @sc{gdb/mi}
27846 @var{target-stream-output} is the output produced by the target program.
27847 All the target output is prefixed by @samp{@@}.
27850 @cindex log output in @sc{gdb/mi}
27851 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27852 instance messages that should be displayed as part of an error log. All
27853 the log output is prefixed by @samp{&}.
27856 @cindex list output in @sc{gdb/mi}
27857 New @sc{gdb/mi} commands should only output @var{lists} containing
27863 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27864 details about the various output records.
27866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27867 @node GDB/MI Compatibility with CLI
27868 @section @sc{gdb/mi} Compatibility with CLI
27870 @cindex compatibility, @sc{gdb/mi} and CLI
27871 @cindex @sc{gdb/mi}, compatibility with CLI
27873 For the developers convenience CLI commands can be entered directly,
27874 but there may be some unexpected behaviour. For example, commands
27875 that query the user will behave as if the user replied yes, breakpoint
27876 command lists are not executed and some CLI commands, such as
27877 @code{if}, @code{when} and @code{define}, prompt for further input with
27878 @samp{>}, which is not valid MI output.
27880 This feature may be removed at some stage in the future and it is
27881 recommended that front ends use the @code{-interpreter-exec} command
27882 (@pxref{-interpreter-exec}).
27884 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27885 @node GDB/MI Development and Front Ends
27886 @section @sc{gdb/mi} Development and Front Ends
27887 @cindex @sc{gdb/mi} development
27889 The application which takes the MI output and presents the state of the
27890 program being debugged to the user is called a @dfn{front end}.
27892 Although @sc{gdb/mi} is still incomplete, it is currently being used
27893 by a variety of front ends to @value{GDBN}. This makes it difficult
27894 to introduce new functionality without breaking existing usage. This
27895 section tries to minimize the problems by describing how the protocol
27898 Some changes in MI need not break a carefully designed front end, and
27899 for these the MI version will remain unchanged. The following is a
27900 list of changes that may occur within one level, so front ends should
27901 parse MI output in a way that can handle them:
27905 New MI commands may be added.
27908 New fields may be added to the output of any MI command.
27911 The range of values for fields with specified values, e.g.,
27912 @code{in_scope} (@pxref{-var-update}) may be extended.
27914 @c The format of field's content e.g type prefix, may change so parse it
27915 @c at your own risk. Yes, in general?
27917 @c The order of fields may change? Shouldn't really matter but it might
27918 @c resolve inconsistencies.
27921 If the changes are likely to break front ends, the MI version level
27922 will be increased by one. This will allow the front end to parse the
27923 output according to the MI version. Apart from mi0, new versions of
27924 @value{GDBN} will not support old versions of MI and it will be the
27925 responsibility of the front end to work with the new one.
27927 @c Starting with mi3, add a new command -mi-version that prints the MI
27930 The best way to avoid unexpected changes in MI that might break your front
27931 end is to make your project known to @value{GDBN} developers and
27932 follow development on @email{gdb@@sourceware.org} and
27933 @email{gdb-patches@@sourceware.org}.
27934 @cindex mailing lists
27936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27937 @node GDB/MI Output Records
27938 @section @sc{gdb/mi} Output Records
27941 * GDB/MI Result Records::
27942 * GDB/MI Stream Records::
27943 * GDB/MI Async Records::
27944 * GDB/MI Breakpoint Information::
27945 * GDB/MI Frame Information::
27946 * GDB/MI Thread Information::
27947 * GDB/MI Ada Exception Information::
27950 @node GDB/MI Result Records
27951 @subsection @sc{gdb/mi} Result Records
27953 @cindex result records in @sc{gdb/mi}
27954 @cindex @sc{gdb/mi}, result records
27955 In addition to a number of out-of-band notifications, the response to a
27956 @sc{gdb/mi} command includes one of the following result indications:
27960 @item "^done" [ "," @var{results} ]
27961 The synchronous operation was successful, @code{@var{results}} are the return
27966 This result record is equivalent to @samp{^done}. Historically, it
27967 was output instead of @samp{^done} if the command has resumed the
27968 target. This behaviour is maintained for backward compatibility, but
27969 all frontends should treat @samp{^done} and @samp{^running}
27970 identically and rely on the @samp{*running} output record to determine
27971 which threads are resumed.
27975 @value{GDBN} has connected to a remote target.
27977 @item "^error" "," @var{c-string}
27979 The operation failed. The @code{@var{c-string}} contains the corresponding
27984 @value{GDBN} has terminated.
27988 @node GDB/MI Stream Records
27989 @subsection @sc{gdb/mi} Stream Records
27991 @cindex @sc{gdb/mi}, stream records
27992 @cindex stream records in @sc{gdb/mi}
27993 @value{GDBN} internally maintains a number of output streams: the console, the
27994 target, and the log. The output intended for each of these streams is
27995 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27997 Each stream record begins with a unique @dfn{prefix character} which
27998 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27999 Syntax}). In addition to the prefix, each stream record contains a
28000 @code{@var{string-output}}. This is either raw text (with an implicit new
28001 line) or a quoted C string (which does not contain an implicit newline).
28004 @item "~" @var{string-output}
28005 The console output stream contains text that should be displayed in the
28006 CLI console window. It contains the textual responses to CLI commands.
28008 @item "@@" @var{string-output}
28009 The target output stream contains any textual output from the running
28010 target. This is only present when GDB's event loop is truly
28011 asynchronous, which is currently only the case for remote targets.
28013 @item "&" @var{string-output}
28014 The log stream contains debugging messages being produced by @value{GDBN}'s
28018 @node GDB/MI Async Records
28019 @subsection @sc{gdb/mi} Async Records
28021 @cindex async records in @sc{gdb/mi}
28022 @cindex @sc{gdb/mi}, async records
28023 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28024 additional changes that have occurred. Those changes can either be a
28025 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28026 target activity (e.g., target stopped).
28028 The following is the list of possible async records:
28032 @item *running,thread-id="@var{thread}"
28033 The target is now running. The @var{thread} field tells which
28034 specific thread is now running, and can be @samp{all} if all threads
28035 are running. The frontend should assume that no interaction with a
28036 running thread is possible after this notification is produced.
28037 The frontend should not assume that this notification is output
28038 only once for any command. @value{GDBN} may emit this notification
28039 several times, either for different threads, because it cannot resume
28040 all threads together, or even for a single thread, if the thread must
28041 be stepped though some code before letting it run freely.
28043 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28044 The target has stopped. The @var{reason} field can have one of the
28048 @item breakpoint-hit
28049 A breakpoint was reached.
28050 @item watchpoint-trigger
28051 A watchpoint was triggered.
28052 @item read-watchpoint-trigger
28053 A read watchpoint was triggered.
28054 @item access-watchpoint-trigger
28055 An access watchpoint was triggered.
28056 @item function-finished
28057 An -exec-finish or similar CLI command was accomplished.
28058 @item location-reached
28059 An -exec-until or similar CLI command was accomplished.
28060 @item watchpoint-scope
28061 A watchpoint has gone out of scope.
28062 @item end-stepping-range
28063 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28064 similar CLI command was accomplished.
28065 @item exited-signalled
28066 The inferior exited because of a signal.
28068 The inferior exited.
28069 @item exited-normally
28070 The inferior exited normally.
28071 @item signal-received
28072 A signal was received by the inferior.
28074 The inferior has stopped due to a library being loaded or unloaded.
28075 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28076 set or when a @code{catch load} or @code{catch unload} catchpoint is
28077 in use (@pxref{Set Catchpoints}).
28079 The inferior has forked. This is reported when @code{catch fork}
28080 (@pxref{Set Catchpoints}) has been used.
28082 The inferior has vforked. This is reported in when @code{catch vfork}
28083 (@pxref{Set Catchpoints}) has been used.
28084 @item syscall-entry
28085 The inferior entered a system call. This is reported when @code{catch
28086 syscall} (@pxref{Set Catchpoints}) has been used.
28087 @item syscall-entry
28088 The inferior returned from a system call. This is reported when
28089 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28091 The inferior called @code{exec}. This is reported when @code{catch exec}
28092 (@pxref{Set Catchpoints}) has been used.
28095 The @var{id} field identifies the thread that directly caused the stop
28096 -- for example by hitting a breakpoint. Depending on whether all-stop
28097 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28098 stop all threads, or only the thread that directly triggered the stop.
28099 If all threads are stopped, the @var{stopped} field will have the
28100 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28101 field will be a list of thread identifiers. Presently, this list will
28102 always include a single thread, but frontend should be prepared to see
28103 several threads in the list. The @var{core} field reports the
28104 processor core on which the stop event has happened. This field may be absent
28105 if such information is not available.
28107 @item =thread-group-added,id="@var{id}"
28108 @itemx =thread-group-removed,id="@var{id}"
28109 A thread group was either added or removed. The @var{id} field
28110 contains the @value{GDBN} identifier of the thread group. When a thread
28111 group is added, it generally might not be associated with a running
28112 process. When a thread group is removed, its id becomes invalid and
28113 cannot be used in any way.
28115 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28116 A thread group became associated with a running program,
28117 either because the program was just started or the thread group
28118 was attached to a program. The @var{id} field contains the
28119 @value{GDBN} identifier of the thread group. The @var{pid} field
28120 contains process identifier, specific to the operating system.
28122 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28123 A thread group is no longer associated with a running program,
28124 either because the program has exited, or because it was detached
28125 from. The @var{id} field contains the @value{GDBN} identifier of the
28126 thread group. @var{code} is the exit code of the inferior; it exists
28127 only when the inferior exited with some code.
28129 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28130 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28131 A thread either was created, or has exited. The @var{id} field
28132 contains the @value{GDBN} identifier of the thread. The @var{gid}
28133 field identifies the thread group this thread belongs to.
28135 @item =thread-selected,id="@var{id}"
28136 Informs that the selected thread was changed as result of the last
28137 command. This notification is not emitted as result of @code{-thread-select}
28138 command but is emitted whenever an MI command that is not documented
28139 to change the selected thread actually changes it. In particular,
28140 invoking, directly or indirectly (via user-defined command), the CLI
28141 @code{thread} command, will generate this notification.
28143 We suggest that in response to this notification, front ends
28144 highlight the selected thread and cause subsequent commands to apply to
28147 @item =library-loaded,...
28148 Reports that a new library file was loaded by the program. This
28149 notification has 4 fields---@var{id}, @var{target-name},
28150 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28151 opaque identifier of the library. For remote debugging case,
28152 @var{target-name} and @var{host-name} fields give the name of the
28153 library file on the target, and on the host respectively. For native
28154 debugging, both those fields have the same value. The
28155 @var{symbols-loaded} field is emitted only for backward compatibility
28156 and should not be relied on to convey any useful information. The
28157 @var{thread-group} field, if present, specifies the id of the thread
28158 group in whose context the library was loaded. If the field is
28159 absent, it means the library was loaded in the context of all present
28162 @item =library-unloaded,...
28163 Reports that a library was unloaded by the program. This notification
28164 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28165 the same meaning as for the @code{=library-loaded} notification.
28166 The @var{thread-group} field, if present, specifies the id of the
28167 thread group in whose context the library was unloaded. If the field is
28168 absent, it means the library was unloaded in the context of all present
28171 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28172 @itemx =traceframe-changed,end
28173 Reports that the trace frame was changed and its new number is
28174 @var{tfnum}. The number of the tracepoint associated with this trace
28175 frame is @var{tpnum}.
28177 @item =tsv-created,name=@var{name},initial=@var{initial}
28178 Reports that the new trace state variable @var{name} is created with
28179 initial value @var{initial}.
28181 @item =tsv-deleted,name=@var{name}
28182 @itemx =tsv-deleted
28183 Reports that the trace state variable @var{name} is deleted or all
28184 trace state variables are deleted.
28186 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28187 Reports that the trace state variable @var{name} is modified with
28188 the initial value @var{initial}. The current value @var{current} of
28189 trace state variable is optional and is reported if the current
28190 value of trace state variable is known.
28192 @item =breakpoint-created,bkpt=@{...@}
28193 @itemx =breakpoint-modified,bkpt=@{...@}
28194 @itemx =breakpoint-deleted,id=@var{number}
28195 Reports that a breakpoint was created, modified, or deleted,
28196 respectively. Only user-visible breakpoints are reported to the MI
28199 The @var{bkpt} argument is of the same form as returned by the various
28200 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28201 @var{number} is the ordinal number of the breakpoint.
28203 Note that if a breakpoint is emitted in the result record of a
28204 command, then it will not also be emitted in an async record.
28206 @item =record-started,thread-group="@var{id}"
28207 @itemx =record-stopped,thread-group="@var{id}"
28208 Execution log recording was either started or stopped on an
28209 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28210 group corresponding to the affected inferior.
28212 @item =cmd-param-changed,param=@var{param},value=@var{value}
28213 Reports that a parameter of the command @code{set @var{param}} is
28214 changed to @var{value}. In the multi-word @code{set} command,
28215 the @var{param} is the whole parameter list to @code{set} command.
28216 For example, In command @code{set check type on}, @var{param}
28217 is @code{check type} and @var{value} is @code{on}.
28219 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28220 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28221 written in an inferior. The @var{id} is the identifier of the
28222 thread group corresponding to the affected inferior. The optional
28223 @code{type="code"} part is reported if the memory written to holds
28227 @node GDB/MI Breakpoint Information
28228 @subsection @sc{gdb/mi} Breakpoint Information
28230 When @value{GDBN} reports information about a breakpoint, a
28231 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28236 The breakpoint number. For a breakpoint that represents one location
28237 of a multi-location breakpoint, this will be a dotted pair, like
28241 The type of the breakpoint. For ordinary breakpoints this will be
28242 @samp{breakpoint}, but many values are possible.
28245 If the type of the breakpoint is @samp{catchpoint}, then this
28246 indicates the exact type of catchpoint.
28249 This is the breakpoint disposition---either @samp{del}, meaning that
28250 the breakpoint will be deleted at the next stop, or @samp{keep},
28251 meaning that the breakpoint will not be deleted.
28254 This indicates whether the breakpoint is enabled, in which case the
28255 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28256 Note that this is not the same as the field @code{enable}.
28259 The address of the breakpoint. This may be a hexidecimal number,
28260 giving the address; or the string @samp{<PENDING>}, for a pending
28261 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28262 multiple locations. This field will not be present if no address can
28263 be determined. For example, a watchpoint does not have an address.
28266 If known, the function in which the breakpoint appears.
28267 If not known, this field is not present.
28270 The name of the source file which contains this function, if known.
28271 If not known, this field is not present.
28274 The full file name of the source file which contains this function, if
28275 known. If not known, this field is not present.
28278 The line number at which this breakpoint appears, if known.
28279 If not known, this field is not present.
28282 If the source file is not known, this field may be provided. If
28283 provided, this holds the address of the breakpoint, possibly followed
28287 If this breakpoint is pending, this field is present and holds the
28288 text used to set the breakpoint, as entered by the user.
28291 Where this breakpoint's condition is evaluated, either @samp{host} or
28295 If this is a thread-specific breakpoint, then this identifies the
28296 thread in which the breakpoint can trigger.
28299 If this breakpoint is restricted to a particular Ada task, then this
28300 field will hold the task identifier.
28303 If the breakpoint is conditional, this is the condition expression.
28306 The ignore count of the breakpoint.
28309 The enable count of the breakpoint.
28311 @item traceframe-usage
28314 @item static-tracepoint-marker-string-id
28315 For a static tracepoint, the name of the static tracepoint marker.
28318 For a masked watchpoint, this is the mask.
28321 A tracepoint's pass count.
28323 @item original-location
28324 The location of the breakpoint as originally specified by the user.
28325 This field is optional.
28328 The number of times the breakpoint has been hit.
28331 This field is only given for tracepoints. This is either @samp{y},
28332 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28336 Some extra data, the exact contents of which are type-dependent.
28340 For example, here is what the output of @code{-break-insert}
28341 (@pxref{GDB/MI Breakpoint Commands}) might be:
28344 -> -break-insert main
28345 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28346 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28347 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28352 @node GDB/MI Frame Information
28353 @subsection @sc{gdb/mi} Frame Information
28355 Response from many MI commands includes an information about stack
28356 frame. This information is a tuple that may have the following
28361 The level of the stack frame. The innermost frame has the level of
28362 zero. This field is always present.
28365 The name of the function corresponding to the frame. This field may
28366 be absent if @value{GDBN} is unable to determine the function name.
28369 The code address for the frame. This field is always present.
28372 The name of the source files that correspond to the frame's code
28373 address. This field may be absent.
28376 The source line corresponding to the frames' code address. This field
28380 The name of the binary file (either executable or shared library) the
28381 corresponds to the frame's code address. This field may be absent.
28385 @node GDB/MI Thread Information
28386 @subsection @sc{gdb/mi} Thread Information
28388 Whenever @value{GDBN} has to report an information about a thread, it
28389 uses a tuple with the following fields:
28393 The numeric id assigned to the thread by @value{GDBN}. This field is
28397 Target-specific string identifying the thread. This field is always present.
28400 Additional information about the thread provided by the target.
28401 It is supposed to be human-readable and not interpreted by the
28402 frontend. This field is optional.
28405 Either @samp{stopped} or @samp{running}, depending on whether the
28406 thread is presently running. This field is always present.
28409 The value of this field is an integer number of the processor core the
28410 thread was last seen on. This field is optional.
28413 @node GDB/MI Ada Exception Information
28414 @subsection @sc{gdb/mi} Ada Exception Information
28416 Whenever a @code{*stopped} record is emitted because the program
28417 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28418 @value{GDBN} provides the name of the exception that was raised via
28419 the @code{exception-name} field.
28421 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28422 @node GDB/MI Simple Examples
28423 @section Simple Examples of @sc{gdb/mi} Interaction
28424 @cindex @sc{gdb/mi}, simple examples
28426 This subsection presents several simple examples of interaction using
28427 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28428 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28429 the output received from @sc{gdb/mi}.
28431 Note the line breaks shown in the examples are here only for
28432 readability, they don't appear in the real output.
28434 @subheading Setting a Breakpoint
28436 Setting a breakpoint generates synchronous output which contains detailed
28437 information of the breakpoint.
28440 -> -break-insert main
28441 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28442 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28443 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28448 @subheading Program Execution
28450 Program execution generates asynchronous records and MI gives the
28451 reason that execution stopped.
28457 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28458 frame=@{addr="0x08048564",func="main",
28459 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28460 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28465 <- *stopped,reason="exited-normally"
28469 @subheading Quitting @value{GDBN}
28471 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28479 Please note that @samp{^exit} is printed immediately, but it might
28480 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28481 performs necessary cleanups, including killing programs being debugged
28482 or disconnecting from debug hardware, so the frontend should wait till
28483 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28484 fails to exit in reasonable time.
28486 @subheading A Bad Command
28488 Here's what happens if you pass a non-existent command:
28492 <- ^error,msg="Undefined MI command: rubbish"
28497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28498 @node GDB/MI Command Description Format
28499 @section @sc{gdb/mi} Command Description Format
28501 The remaining sections describe blocks of commands. Each block of
28502 commands is laid out in a fashion similar to this section.
28504 @subheading Motivation
28506 The motivation for this collection of commands.
28508 @subheading Introduction
28510 A brief introduction to this collection of commands as a whole.
28512 @subheading Commands
28514 For each command in the block, the following is described:
28516 @subsubheading Synopsis
28519 -command @var{args}@dots{}
28522 @subsubheading Result
28524 @subsubheading @value{GDBN} Command
28526 The corresponding @value{GDBN} CLI command(s), if any.
28528 @subsubheading Example
28530 Example(s) formatted for readability. Some of the described commands have
28531 not been implemented yet and these are labeled N.A.@: (not available).
28534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28535 @node GDB/MI Breakpoint Commands
28536 @section @sc{gdb/mi} Breakpoint Commands
28538 @cindex breakpoint commands for @sc{gdb/mi}
28539 @cindex @sc{gdb/mi}, breakpoint commands
28540 This section documents @sc{gdb/mi} commands for manipulating
28543 @subheading The @code{-break-after} Command
28544 @findex -break-after
28546 @subsubheading Synopsis
28549 -break-after @var{number} @var{count}
28552 The breakpoint number @var{number} is not in effect until it has been
28553 hit @var{count} times. To see how this is reflected in the output of
28554 the @samp{-break-list} command, see the description of the
28555 @samp{-break-list} command below.
28557 @subsubheading @value{GDBN} Command
28559 The corresponding @value{GDBN} command is @samp{ignore}.
28561 @subsubheading Example
28566 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28567 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28568 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28576 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28577 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28578 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28579 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28580 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28581 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28582 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28583 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28584 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28585 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28590 @subheading The @code{-break-catch} Command
28591 @findex -break-catch
28594 @subheading The @code{-break-commands} Command
28595 @findex -break-commands
28597 @subsubheading Synopsis
28600 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28603 Specifies the CLI commands that should be executed when breakpoint
28604 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28605 are the commands. If no command is specified, any previously-set
28606 commands are cleared. @xref{Break Commands}. Typical use of this
28607 functionality is tracing a program, that is, printing of values of
28608 some variables whenever breakpoint is hit and then continuing.
28610 @subsubheading @value{GDBN} Command
28612 The corresponding @value{GDBN} command is @samp{commands}.
28614 @subsubheading Example
28619 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28620 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28621 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28624 -break-commands 1 "print v" "continue"
28629 @subheading The @code{-break-condition} Command
28630 @findex -break-condition
28632 @subsubheading Synopsis
28635 -break-condition @var{number} @var{expr}
28638 Breakpoint @var{number} will stop the program only if the condition in
28639 @var{expr} is true. The condition becomes part of the
28640 @samp{-break-list} output (see the description of the @samp{-break-list}
28643 @subsubheading @value{GDBN} Command
28645 The corresponding @value{GDBN} command is @samp{condition}.
28647 @subsubheading Example
28651 -break-condition 1 1
28655 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28656 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28657 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28658 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28659 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28660 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28661 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28662 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28663 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28664 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28668 @subheading The @code{-break-delete} Command
28669 @findex -break-delete
28671 @subsubheading Synopsis
28674 -break-delete ( @var{breakpoint} )+
28677 Delete the breakpoint(s) whose number(s) are specified in the argument
28678 list. This is obviously reflected in the breakpoint list.
28680 @subsubheading @value{GDBN} Command
28682 The corresponding @value{GDBN} command is @samp{delete}.
28684 @subsubheading Example
28692 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28693 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28694 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28695 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28696 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28697 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28698 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28703 @subheading The @code{-break-disable} Command
28704 @findex -break-disable
28706 @subsubheading Synopsis
28709 -break-disable ( @var{breakpoint} )+
28712 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28713 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28715 @subsubheading @value{GDBN} Command
28717 The corresponding @value{GDBN} command is @samp{disable}.
28719 @subsubheading Example
28727 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28728 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28729 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28730 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28731 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28732 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28733 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28734 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28735 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28736 line="5",thread-groups=["i1"],times="0"@}]@}
28740 @subheading The @code{-break-enable} Command
28741 @findex -break-enable
28743 @subsubheading Synopsis
28746 -break-enable ( @var{breakpoint} )+
28749 Enable (previously disabled) @var{breakpoint}(s).
28751 @subsubheading @value{GDBN} Command
28753 The corresponding @value{GDBN} command is @samp{enable}.
28755 @subsubheading Example
28763 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28764 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28765 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28766 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28767 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28768 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28769 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28770 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28771 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28772 line="5",thread-groups=["i1"],times="0"@}]@}
28776 @subheading The @code{-break-info} Command
28777 @findex -break-info
28779 @subsubheading Synopsis
28782 -break-info @var{breakpoint}
28786 Get information about a single breakpoint.
28788 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28789 Information}, for details on the format of each breakpoint in the
28792 @subsubheading @value{GDBN} Command
28794 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28796 @subsubheading Example
28799 @subheading The @code{-break-insert} Command
28800 @findex -break-insert
28802 @subsubheading Synopsis
28805 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28806 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28807 [ -p @var{thread-id} ] [ @var{location} ]
28811 If specified, @var{location}, can be one of:
28818 @item filename:linenum
28819 @item filename:function
28823 The possible optional parameters of this command are:
28827 Insert a temporary breakpoint.
28829 Insert a hardware breakpoint.
28831 If @var{location} cannot be parsed (for example if it
28832 refers to unknown files or functions), create a pending
28833 breakpoint. Without this flag, @value{GDBN} will report
28834 an error, and won't create a breakpoint, if @var{location}
28837 Create a disabled breakpoint.
28839 Create a tracepoint. @xref{Tracepoints}. When this parameter
28840 is used together with @samp{-h}, a fast tracepoint is created.
28841 @item -c @var{condition}
28842 Make the breakpoint conditional on @var{condition}.
28843 @item -i @var{ignore-count}
28844 Initialize the @var{ignore-count}.
28845 @item -p @var{thread-id}
28846 Restrict the breakpoint to the specified @var{thread-id}.
28849 @subsubheading Result
28851 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28852 resulting breakpoint.
28854 Note: this format is open to change.
28855 @c An out-of-band breakpoint instead of part of the result?
28857 @subsubheading @value{GDBN} Command
28859 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28860 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28862 @subsubheading Example
28867 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28868 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28871 -break-insert -t foo
28872 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28873 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28877 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28878 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28879 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28880 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28881 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28882 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28883 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28884 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28885 addr="0x0001072c", func="main",file="recursive2.c",
28886 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28888 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28889 addr="0x00010774",func="foo",file="recursive2.c",
28890 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28893 @c -break-insert -r foo.*
28894 @c ~int foo(int, int);
28895 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28896 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28901 @subheading The @code{-break-list} Command
28902 @findex -break-list
28904 @subsubheading Synopsis
28910 Displays the list of inserted breakpoints, showing the following fields:
28914 number of the breakpoint
28916 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28918 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28921 is the breakpoint enabled or no: @samp{y} or @samp{n}
28923 memory location at which the breakpoint is set
28925 logical location of the breakpoint, expressed by function name, file
28927 @item Thread-groups
28928 list of thread groups to which this breakpoint applies
28930 number of times the breakpoint has been hit
28933 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28934 @code{body} field is an empty list.
28936 @subsubheading @value{GDBN} Command
28938 The corresponding @value{GDBN} command is @samp{info break}.
28940 @subsubheading Example
28945 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28946 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28947 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28948 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28949 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28950 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28951 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28952 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28953 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28955 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28956 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28957 line="13",thread-groups=["i1"],times="0"@}]@}
28961 Here's an example of the result when there are no breakpoints:
28966 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28967 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28968 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28969 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28970 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28971 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28972 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28977 @subheading The @code{-break-passcount} Command
28978 @findex -break-passcount
28980 @subsubheading Synopsis
28983 -break-passcount @var{tracepoint-number} @var{passcount}
28986 Set the passcount for tracepoint @var{tracepoint-number} to
28987 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28988 is not a tracepoint, error is emitted. This corresponds to CLI
28989 command @samp{passcount}.
28991 @subheading The @code{-break-watch} Command
28992 @findex -break-watch
28994 @subsubheading Synopsis
28997 -break-watch [ -a | -r ]
29000 Create a watchpoint. With the @samp{-a} option it will create an
29001 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29002 read from or on a write to the memory location. With the @samp{-r}
29003 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29004 trigger only when the memory location is accessed for reading. Without
29005 either of the options, the watchpoint created is a regular watchpoint,
29006 i.e., it will trigger when the memory location is accessed for writing.
29007 @xref{Set Watchpoints, , Setting Watchpoints}.
29009 Note that @samp{-break-list} will report a single list of watchpoints and
29010 breakpoints inserted.
29012 @subsubheading @value{GDBN} Command
29014 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29017 @subsubheading Example
29019 Setting a watchpoint on a variable in the @code{main} function:
29024 ^done,wpt=@{number="2",exp="x"@}
29029 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29030 value=@{old="-268439212",new="55"@},
29031 frame=@{func="main",args=[],file="recursive2.c",
29032 fullname="/home/foo/bar/recursive2.c",line="5"@}
29036 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29037 the program execution twice: first for the variable changing value, then
29038 for the watchpoint going out of scope.
29043 ^done,wpt=@{number="5",exp="C"@}
29048 *stopped,reason="watchpoint-trigger",
29049 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29050 frame=@{func="callee4",args=[],
29051 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29052 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29057 *stopped,reason="watchpoint-scope",wpnum="5",
29058 frame=@{func="callee3",args=[@{name="strarg",
29059 value="0x11940 \"A string argument.\""@}],
29060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29061 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29065 Listing breakpoints and watchpoints, at different points in the program
29066 execution. Note that once the watchpoint goes out of scope, it is
29072 ^done,wpt=@{number="2",exp="C"@}
29075 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29076 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29077 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29078 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29079 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29080 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29081 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29082 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29083 addr="0x00010734",func="callee4",
29084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29085 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29087 bkpt=@{number="2",type="watchpoint",disp="keep",
29088 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29093 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29094 value=@{old="-276895068",new="3"@},
29095 frame=@{func="callee4",args=[],
29096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29097 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29100 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29101 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29102 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29103 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29104 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29105 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29106 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29107 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29108 addr="0x00010734",func="callee4",
29109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29110 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29112 bkpt=@{number="2",type="watchpoint",disp="keep",
29113 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29117 ^done,reason="watchpoint-scope",wpnum="2",
29118 frame=@{func="callee3",args=[@{name="strarg",
29119 value="0x11940 \"A string argument.\""@}],
29120 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29121 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29124 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29125 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29126 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29127 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29128 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29129 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29130 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29131 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29132 addr="0x00010734",func="callee4",
29133 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29134 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29135 thread-groups=["i1"],times="1"@}]@}
29140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29141 @node GDB/MI Catchpoint Commands
29142 @section @sc{gdb/mi} Catchpoint Commands
29144 This section documents @sc{gdb/mi} commands for manipulating
29147 @subheading The @code{-catch-load} Command
29148 @findex -catch-load
29150 @subsubheading Synopsis
29153 -catch-load [ -t ] [ -d ] @var{regexp}
29156 Add a catchpoint for library load events. If the @samp{-t} option is used,
29157 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29158 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29159 in a disabled state. The @samp{regexp} argument is a regular
29160 expression used to match the name of the loaded library.
29163 @subsubheading @value{GDBN} Command
29165 The corresponding @value{GDBN} command is @samp{catch load}.
29167 @subsubheading Example
29170 -catch-load -t foo.so
29171 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29172 what="load of library matching foo.so",catch-type="load",times="0"@}
29177 @subheading The @code{-catch-unload} Command
29178 @findex -catch-unload
29180 @subsubheading Synopsis
29183 -catch-unload [ -t ] [ -d ] @var{regexp}
29186 Add a catchpoint for library unload events. If the @samp{-t} option is
29187 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29188 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29189 created in a disabled state. The @samp{regexp} argument is a regular
29190 expression used to match the name of the unloaded library.
29192 @subsubheading @value{GDBN} Command
29194 The corresponding @value{GDBN} command is @samp{catch unload}.
29196 @subsubheading Example
29199 -catch-unload -d bar.so
29200 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29201 what="load of library matching bar.so",catch-type="unload",times="0"@}
29206 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29207 @node GDB/MI Program Context
29208 @section @sc{gdb/mi} Program Context
29210 @subheading The @code{-exec-arguments} Command
29211 @findex -exec-arguments
29214 @subsubheading Synopsis
29217 -exec-arguments @var{args}
29220 Set the inferior program arguments, to be used in the next
29223 @subsubheading @value{GDBN} Command
29225 The corresponding @value{GDBN} command is @samp{set args}.
29227 @subsubheading Example
29231 -exec-arguments -v word
29238 @subheading The @code{-exec-show-arguments} Command
29239 @findex -exec-show-arguments
29241 @subsubheading Synopsis
29244 -exec-show-arguments
29247 Print the arguments of the program.
29249 @subsubheading @value{GDBN} Command
29251 The corresponding @value{GDBN} command is @samp{show args}.
29253 @subsubheading Example
29258 @subheading The @code{-environment-cd} Command
29259 @findex -environment-cd
29261 @subsubheading Synopsis
29264 -environment-cd @var{pathdir}
29267 Set @value{GDBN}'s working directory.
29269 @subsubheading @value{GDBN} Command
29271 The corresponding @value{GDBN} command is @samp{cd}.
29273 @subsubheading Example
29277 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29283 @subheading The @code{-environment-directory} Command
29284 @findex -environment-directory
29286 @subsubheading Synopsis
29289 -environment-directory [ -r ] [ @var{pathdir} ]+
29292 Add directories @var{pathdir} to beginning of search path for source files.
29293 If the @samp{-r} option is used, the search path is reset to the default
29294 search path. If directories @var{pathdir} are supplied in addition to the
29295 @samp{-r} option, the search path is first reset and then addition
29297 Multiple directories may be specified, separated by blanks. Specifying
29298 multiple directories in a single command
29299 results in the directories added to the beginning of the
29300 search path in the same order they were presented in the command.
29301 If blanks are needed as
29302 part of a directory name, double-quotes should be used around
29303 the name. In the command output, the path will show up separated
29304 by the system directory-separator character. The directory-separator
29305 character must not be used
29306 in any directory name.
29307 If no directories are specified, the current search path is displayed.
29309 @subsubheading @value{GDBN} Command
29311 The corresponding @value{GDBN} command is @samp{dir}.
29313 @subsubheading Example
29317 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29318 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29320 -environment-directory ""
29321 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29323 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29324 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29326 -environment-directory -r
29327 ^done,source-path="$cdir:$cwd"
29332 @subheading The @code{-environment-path} Command
29333 @findex -environment-path
29335 @subsubheading Synopsis
29338 -environment-path [ -r ] [ @var{pathdir} ]+
29341 Add directories @var{pathdir} to beginning of search path for object files.
29342 If the @samp{-r} option is used, the search path is reset to the original
29343 search path that existed at gdb start-up. If directories @var{pathdir} are
29344 supplied in addition to the
29345 @samp{-r} option, the search path is first reset and then addition
29347 Multiple directories may be specified, separated by blanks. Specifying
29348 multiple directories in a single command
29349 results in the directories added to the beginning of the
29350 search path in the same order they were presented in the command.
29351 If blanks are needed as
29352 part of a directory name, double-quotes should be used around
29353 the name. In the command output, the path will show up separated
29354 by the system directory-separator character. The directory-separator
29355 character must not be used
29356 in any directory name.
29357 If no directories are specified, the current path is displayed.
29360 @subsubheading @value{GDBN} Command
29362 The corresponding @value{GDBN} command is @samp{path}.
29364 @subsubheading Example
29369 ^done,path="/usr/bin"
29371 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29372 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29374 -environment-path -r /usr/local/bin
29375 ^done,path="/usr/local/bin:/usr/bin"
29380 @subheading The @code{-environment-pwd} Command
29381 @findex -environment-pwd
29383 @subsubheading Synopsis
29389 Show the current working directory.
29391 @subsubheading @value{GDBN} Command
29393 The corresponding @value{GDBN} command is @samp{pwd}.
29395 @subsubheading Example
29400 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29405 @node GDB/MI Thread Commands
29406 @section @sc{gdb/mi} Thread Commands
29409 @subheading The @code{-thread-info} Command
29410 @findex -thread-info
29412 @subsubheading Synopsis
29415 -thread-info [ @var{thread-id} ]
29418 Reports information about either a specific thread, if
29419 the @var{thread-id} parameter is present, or about all
29420 threads. When printing information about all threads,
29421 also reports the current thread.
29423 @subsubheading @value{GDBN} Command
29425 The @samp{info thread} command prints the same information
29428 @subsubheading Result
29430 The result is a list of threads. The following attributes are
29431 defined for a given thread:
29435 This field exists only for the current thread. It has the value @samp{*}.
29438 The identifier that @value{GDBN} uses to refer to the thread.
29441 The identifier that the target uses to refer to the thread.
29444 Extra information about the thread, in a target-specific format. This
29448 The name of the thread. If the user specified a name using the
29449 @code{thread name} command, then this name is given. Otherwise, if
29450 @value{GDBN} can extract the thread name from the target, then that
29451 name is given. If @value{GDBN} cannot find the thread name, then this
29455 The stack frame currently executing in the thread.
29458 The thread's state. The @samp{state} field may have the following
29463 The thread is stopped. Frame information is available for stopped
29467 The thread is running. There's no frame information for running
29473 If @value{GDBN} can find the CPU core on which this thread is running,
29474 then this field is the core identifier. This field is optional.
29478 @subsubheading Example
29483 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29484 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29485 args=[]@},state="running"@},
29486 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29487 frame=@{level="0",addr="0x0804891f",func="foo",
29488 args=[@{name="i",value="10"@}],
29489 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29490 state="running"@}],
29491 current-thread-id="1"
29495 @subheading The @code{-thread-list-ids} Command
29496 @findex -thread-list-ids
29498 @subsubheading Synopsis
29504 Produces a list of the currently known @value{GDBN} thread ids. At the
29505 end of the list it also prints the total number of such threads.
29507 This command is retained for historical reasons, the
29508 @code{-thread-info} command should be used instead.
29510 @subsubheading @value{GDBN} Command
29512 Part of @samp{info threads} supplies the same information.
29514 @subsubheading Example
29519 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29520 current-thread-id="1",number-of-threads="3"
29525 @subheading The @code{-thread-select} Command
29526 @findex -thread-select
29528 @subsubheading Synopsis
29531 -thread-select @var{threadnum}
29534 Make @var{threadnum} the current thread. It prints the number of the new
29535 current thread, and the topmost frame for that thread.
29537 This command is deprecated in favor of explicitly using the
29538 @samp{--thread} option to each command.
29540 @subsubheading @value{GDBN} Command
29542 The corresponding @value{GDBN} command is @samp{thread}.
29544 @subsubheading Example
29551 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29552 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29556 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29557 number-of-threads="3"
29560 ^done,new-thread-id="3",
29561 frame=@{level="0",func="vprintf",
29562 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29563 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29568 @node GDB/MI Ada Tasking Commands
29569 @section @sc{gdb/mi} Ada Tasking Commands
29571 @subheading The @code{-ada-task-info} Command
29572 @findex -ada-task-info
29574 @subsubheading Synopsis
29577 -ada-task-info [ @var{task-id} ]
29580 Reports information about either a specific Ada task, if the
29581 @var{task-id} parameter is present, or about all Ada tasks.
29583 @subsubheading @value{GDBN} Command
29585 The @samp{info tasks} command prints the same information
29586 about all Ada tasks (@pxref{Ada Tasks}).
29588 @subsubheading Result
29590 The result is a table of Ada tasks. The following columns are
29591 defined for each Ada task:
29595 This field exists only for the current thread. It has the value @samp{*}.
29598 The identifier that @value{GDBN} uses to refer to the Ada task.
29601 The identifier that the target uses to refer to the Ada task.
29604 The identifier of the thread corresponding to the Ada task.
29606 This field should always exist, as Ada tasks are always implemented
29607 on top of a thread. But if @value{GDBN} cannot find this corresponding
29608 thread for any reason, the field is omitted.
29611 This field exists only when the task was created by another task.
29612 In this case, it provides the ID of the parent task.
29615 The base priority of the task.
29618 The current state of the task. For a detailed description of the
29619 possible states, see @ref{Ada Tasks}.
29622 The name of the task.
29626 @subsubheading Example
29630 ^done,tasks=@{nr_rows="3",nr_cols="8",
29631 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29632 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29633 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29634 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29635 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29636 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29637 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29638 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29639 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29640 state="Child Termination Wait",name="main_task"@}]@}
29644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29645 @node GDB/MI Program Execution
29646 @section @sc{gdb/mi} Program Execution
29648 These are the asynchronous commands which generate the out-of-band
29649 record @samp{*stopped}. Currently @value{GDBN} only really executes
29650 asynchronously with remote targets and this interaction is mimicked in
29653 @subheading The @code{-exec-continue} Command
29654 @findex -exec-continue
29656 @subsubheading Synopsis
29659 -exec-continue [--reverse] [--all|--thread-group N]
29662 Resumes the execution of the inferior program, which will continue
29663 to execute until it reaches a debugger stop event. If the
29664 @samp{--reverse} option is specified, execution resumes in reverse until
29665 it reaches a stop event. Stop events may include
29668 breakpoints or watchpoints
29670 signals or exceptions
29672 the end of the process (or its beginning under @samp{--reverse})
29674 the end or beginning of a replay log if one is being used.
29676 In all-stop mode (@pxref{All-Stop
29677 Mode}), may resume only one thread, or all threads, depending on the
29678 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29679 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29680 ignored in all-stop mode. If the @samp{--thread-group} options is
29681 specified, then all threads in that thread group are resumed.
29683 @subsubheading @value{GDBN} Command
29685 The corresponding @value{GDBN} corresponding is @samp{continue}.
29687 @subsubheading Example
29694 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29695 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29701 @subheading The @code{-exec-finish} Command
29702 @findex -exec-finish
29704 @subsubheading Synopsis
29707 -exec-finish [--reverse]
29710 Resumes the execution of the inferior program until the current
29711 function is exited. Displays the results returned by the function.
29712 If the @samp{--reverse} option is specified, resumes the reverse
29713 execution of the inferior program until the point where current
29714 function was called.
29716 @subsubheading @value{GDBN} Command
29718 The corresponding @value{GDBN} command is @samp{finish}.
29720 @subsubheading Example
29722 Function returning @code{void}.
29729 *stopped,reason="function-finished",frame=@{func="main",args=[],
29730 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29734 Function returning other than @code{void}. The name of the internal
29735 @value{GDBN} variable storing the result is printed, together with the
29742 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29743 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29744 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29745 gdb-result-var="$1",return-value="0"
29750 @subheading The @code{-exec-interrupt} Command
29751 @findex -exec-interrupt
29753 @subsubheading Synopsis
29756 -exec-interrupt [--all|--thread-group N]
29759 Interrupts the background execution of the target. Note how the token
29760 associated with the stop message is the one for the execution command
29761 that has been interrupted. The token for the interrupt itself only
29762 appears in the @samp{^done} output. If the user is trying to
29763 interrupt a non-running program, an error message will be printed.
29765 Note that when asynchronous execution is enabled, this command is
29766 asynchronous just like other execution commands. That is, first the
29767 @samp{^done} response will be printed, and the target stop will be
29768 reported after that using the @samp{*stopped} notification.
29770 In non-stop mode, only the context thread is interrupted by default.
29771 All threads (in all inferiors) will be interrupted if the
29772 @samp{--all} option is specified. If the @samp{--thread-group}
29773 option is specified, all threads in that group will be interrupted.
29775 @subsubheading @value{GDBN} Command
29777 The corresponding @value{GDBN} command is @samp{interrupt}.
29779 @subsubheading Example
29790 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29791 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29792 fullname="/home/foo/bar/try.c",line="13"@}
29797 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29801 @subheading The @code{-exec-jump} Command
29804 @subsubheading Synopsis
29807 -exec-jump @var{location}
29810 Resumes execution of the inferior program at the location specified by
29811 parameter. @xref{Specify Location}, for a description of the
29812 different forms of @var{location}.
29814 @subsubheading @value{GDBN} Command
29816 The corresponding @value{GDBN} command is @samp{jump}.
29818 @subsubheading Example
29821 -exec-jump foo.c:10
29822 *running,thread-id="all"
29827 @subheading The @code{-exec-next} Command
29830 @subsubheading Synopsis
29833 -exec-next [--reverse]
29836 Resumes execution of the inferior program, stopping when the beginning
29837 of the next source line is reached.
29839 If the @samp{--reverse} option is specified, resumes reverse execution
29840 of the inferior program, stopping at the beginning of the previous
29841 source line. If you issue this command on the first line of a
29842 function, it will take you back to the caller of that function, to the
29843 source line where the function was called.
29846 @subsubheading @value{GDBN} Command
29848 The corresponding @value{GDBN} command is @samp{next}.
29850 @subsubheading Example
29856 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29861 @subheading The @code{-exec-next-instruction} Command
29862 @findex -exec-next-instruction
29864 @subsubheading Synopsis
29867 -exec-next-instruction [--reverse]
29870 Executes one machine instruction. If the instruction is a function
29871 call, continues until the function returns. If the program stops at an
29872 instruction in the middle of a source line, the address will be
29875 If the @samp{--reverse} option is specified, resumes reverse execution
29876 of the inferior program, stopping at the previous instruction. If the
29877 previously executed instruction was a return from another function,
29878 it will continue to execute in reverse until the call to that function
29879 (from the current stack frame) is reached.
29881 @subsubheading @value{GDBN} Command
29883 The corresponding @value{GDBN} command is @samp{nexti}.
29885 @subsubheading Example
29889 -exec-next-instruction
29893 *stopped,reason="end-stepping-range",
29894 addr="0x000100d4",line="5",file="hello.c"
29899 @subheading The @code{-exec-return} Command
29900 @findex -exec-return
29902 @subsubheading Synopsis
29908 Makes current function return immediately. Doesn't execute the inferior.
29909 Displays the new current frame.
29911 @subsubheading @value{GDBN} Command
29913 The corresponding @value{GDBN} command is @samp{return}.
29915 @subsubheading Example
29919 200-break-insert callee4
29920 200^done,bkpt=@{number="1",addr="0x00010734",
29921 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29926 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29927 frame=@{func="callee4",args=[],
29928 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29929 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29935 111^done,frame=@{level="0",func="callee3",
29936 args=[@{name="strarg",
29937 value="0x11940 \"A string argument.\""@}],
29938 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29939 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29944 @subheading The @code{-exec-run} Command
29947 @subsubheading Synopsis
29950 -exec-run [--all | --thread-group N]
29953 Starts execution of the inferior from the beginning. The inferior
29954 executes until either a breakpoint is encountered or the program
29955 exits. In the latter case the output will include an exit code, if
29956 the program has exited exceptionally.
29958 When no option is specified, the current inferior is started. If the
29959 @samp{--thread-group} option is specified, it should refer to a thread
29960 group of type @samp{process}, and that thread group will be started.
29961 If the @samp{--all} option is specified, then all inferiors will be started.
29963 @subsubheading @value{GDBN} Command
29965 The corresponding @value{GDBN} command is @samp{run}.
29967 @subsubheading Examples
29972 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29977 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29978 frame=@{func="main",args=[],file="recursive2.c",
29979 fullname="/home/foo/bar/recursive2.c",line="4"@}
29984 Program exited normally:
29992 *stopped,reason="exited-normally"
29997 Program exited exceptionally:
30005 *stopped,reason="exited",exit-code="01"
30009 Another way the program can terminate is if it receives a signal such as
30010 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30014 *stopped,reason="exited-signalled",signal-name="SIGINT",
30015 signal-meaning="Interrupt"
30019 @c @subheading -exec-signal
30022 @subheading The @code{-exec-step} Command
30025 @subsubheading Synopsis
30028 -exec-step [--reverse]
30031 Resumes execution of the inferior program, stopping when the beginning
30032 of the next source line is reached, if the next source line is not a
30033 function call. If it is, stop at the first instruction of the called
30034 function. If the @samp{--reverse} option is specified, resumes reverse
30035 execution of the inferior program, stopping at the beginning of the
30036 previously executed source line.
30038 @subsubheading @value{GDBN} Command
30040 The corresponding @value{GDBN} command is @samp{step}.
30042 @subsubheading Example
30044 Stepping into a function:
30050 *stopped,reason="end-stepping-range",
30051 frame=@{func="foo",args=[@{name="a",value="10"@},
30052 @{name="b",value="0"@}],file="recursive2.c",
30053 fullname="/home/foo/bar/recursive2.c",line="11"@}
30063 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30068 @subheading The @code{-exec-step-instruction} Command
30069 @findex -exec-step-instruction
30071 @subsubheading Synopsis
30074 -exec-step-instruction [--reverse]
30077 Resumes the inferior which executes one machine instruction. If the
30078 @samp{--reverse} option is specified, resumes reverse execution of the
30079 inferior program, stopping at the previously executed instruction.
30080 The output, once @value{GDBN} has stopped, will vary depending on
30081 whether we have stopped in the middle of a source line or not. In the
30082 former case, the address at which the program stopped will be printed
30085 @subsubheading @value{GDBN} Command
30087 The corresponding @value{GDBN} command is @samp{stepi}.
30089 @subsubheading Example
30093 -exec-step-instruction
30097 *stopped,reason="end-stepping-range",
30098 frame=@{func="foo",args=[],file="try.c",
30099 fullname="/home/foo/bar/try.c",line="10"@}
30101 -exec-step-instruction
30105 *stopped,reason="end-stepping-range",
30106 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30107 fullname="/home/foo/bar/try.c",line="10"@}
30112 @subheading The @code{-exec-until} Command
30113 @findex -exec-until
30115 @subsubheading Synopsis
30118 -exec-until [ @var{location} ]
30121 Executes the inferior until the @var{location} specified in the
30122 argument is reached. If there is no argument, the inferior executes
30123 until a source line greater than the current one is reached. The
30124 reason for stopping in this case will be @samp{location-reached}.
30126 @subsubheading @value{GDBN} Command
30128 The corresponding @value{GDBN} command is @samp{until}.
30130 @subsubheading Example
30134 -exec-until recursive2.c:6
30138 *stopped,reason="location-reached",frame=@{func="main",args=[],
30139 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30144 @subheading -file-clear
30145 Is this going away????
30148 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30149 @node GDB/MI Stack Manipulation
30150 @section @sc{gdb/mi} Stack Manipulation Commands
30153 @subheading The @code{-stack-info-frame} Command
30154 @findex -stack-info-frame
30156 @subsubheading Synopsis
30162 Get info on the selected frame.
30164 @subsubheading @value{GDBN} Command
30166 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30167 (without arguments).
30169 @subsubheading Example
30174 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30175 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30176 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30180 @subheading The @code{-stack-info-depth} Command
30181 @findex -stack-info-depth
30183 @subsubheading Synopsis
30186 -stack-info-depth [ @var{max-depth} ]
30189 Return the depth of the stack. If the integer argument @var{max-depth}
30190 is specified, do not count beyond @var{max-depth} frames.
30192 @subsubheading @value{GDBN} Command
30194 There's no equivalent @value{GDBN} command.
30196 @subsubheading Example
30198 For a stack with frame levels 0 through 11:
30205 -stack-info-depth 4
30208 -stack-info-depth 12
30211 -stack-info-depth 11
30214 -stack-info-depth 13
30219 @subheading The @code{-stack-list-arguments} Command
30220 @findex -stack-list-arguments
30222 @subsubheading Synopsis
30225 -stack-list-arguments @var{print-values}
30226 [ @var{low-frame} @var{high-frame} ]
30229 Display a list of the arguments for the frames between @var{low-frame}
30230 and @var{high-frame} (inclusive). If @var{low-frame} and
30231 @var{high-frame} are not provided, list the arguments for the whole
30232 call stack. If the two arguments are equal, show the single frame
30233 at the corresponding level. It is an error if @var{low-frame} is
30234 larger than the actual number of frames. On the other hand,
30235 @var{high-frame} may be larger than the actual number of frames, in
30236 which case only existing frames will be returned.
30238 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30239 the variables; if it is 1 or @code{--all-values}, print also their
30240 values; and if it is 2 or @code{--simple-values}, print the name,
30241 type and value for simple data types, and the name and type for arrays,
30242 structures and unions.
30244 Use of this command to obtain arguments in a single frame is
30245 deprecated in favor of the @samp{-stack-list-variables} command.
30247 @subsubheading @value{GDBN} Command
30249 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30250 @samp{gdb_get_args} command which partially overlaps with the
30251 functionality of @samp{-stack-list-arguments}.
30253 @subsubheading Example
30260 frame=@{level="0",addr="0x00010734",func="callee4",
30261 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30262 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30263 frame=@{level="1",addr="0x0001076c",func="callee3",
30264 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30265 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30266 frame=@{level="2",addr="0x0001078c",func="callee2",
30267 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30268 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30269 frame=@{level="3",addr="0x000107b4",func="callee1",
30270 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30271 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30272 frame=@{level="4",addr="0x000107e0",func="main",
30273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30276 -stack-list-arguments 0
30279 frame=@{level="0",args=[]@},
30280 frame=@{level="1",args=[name="strarg"]@},
30281 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30282 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30283 frame=@{level="4",args=[]@}]
30285 -stack-list-arguments 1
30288 frame=@{level="0",args=[]@},
30290 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30291 frame=@{level="2",args=[
30292 @{name="intarg",value="2"@},
30293 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30294 @{frame=@{level="3",args=[
30295 @{name="intarg",value="2"@},
30296 @{name="strarg",value="0x11940 \"A string argument.\""@},
30297 @{name="fltarg",value="3.5"@}]@},
30298 frame=@{level="4",args=[]@}]
30300 -stack-list-arguments 0 2 2
30301 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30303 -stack-list-arguments 1 2 2
30304 ^done,stack-args=[frame=@{level="2",
30305 args=[@{name="intarg",value="2"@},
30306 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30310 @c @subheading -stack-list-exception-handlers
30313 @subheading The @code{-stack-list-frames} Command
30314 @findex -stack-list-frames
30316 @subsubheading Synopsis
30319 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30322 List the frames currently on the stack. For each frame it displays the
30327 The frame number, 0 being the topmost frame, i.e., the innermost function.
30329 The @code{$pc} value for that frame.
30333 File name of the source file where the function lives.
30334 @item @var{fullname}
30335 The full file name of the source file where the function lives.
30337 Line number corresponding to the @code{$pc}.
30339 The shared library where this function is defined. This is only given
30340 if the frame's function is not known.
30343 If invoked without arguments, this command prints a backtrace for the
30344 whole stack. If given two integer arguments, it shows the frames whose
30345 levels are between the two arguments (inclusive). If the two arguments
30346 are equal, it shows the single frame at the corresponding level. It is
30347 an error if @var{low-frame} is larger than the actual number of
30348 frames. On the other hand, @var{high-frame} may be larger than the
30349 actual number of frames, in which case only existing frames will be returned.
30351 @subsubheading @value{GDBN} Command
30353 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30355 @subsubheading Example
30357 Full stack backtrace:
30363 [frame=@{level="0",addr="0x0001076c",func="foo",
30364 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30365 frame=@{level="1",addr="0x000107a4",func="foo",
30366 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30367 frame=@{level="2",addr="0x000107a4",func="foo",
30368 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30369 frame=@{level="3",addr="0x000107a4",func="foo",
30370 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30371 frame=@{level="4",addr="0x000107a4",func="foo",
30372 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30373 frame=@{level="5",addr="0x000107a4",func="foo",
30374 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30375 frame=@{level="6",addr="0x000107a4",func="foo",
30376 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30377 frame=@{level="7",addr="0x000107a4",func="foo",
30378 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30379 frame=@{level="8",addr="0x000107a4",func="foo",
30380 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30381 frame=@{level="9",addr="0x000107a4",func="foo",
30382 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30383 frame=@{level="10",addr="0x000107a4",func="foo",
30384 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30385 frame=@{level="11",addr="0x00010738",func="main",
30386 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30390 Show frames between @var{low_frame} and @var{high_frame}:
30394 -stack-list-frames 3 5
30396 [frame=@{level="3",addr="0x000107a4",func="foo",
30397 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30398 frame=@{level="4",addr="0x000107a4",func="foo",
30399 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30400 frame=@{level="5",addr="0x000107a4",func="foo",
30401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30405 Show a single frame:
30409 -stack-list-frames 3 3
30411 [frame=@{level="3",addr="0x000107a4",func="foo",
30412 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30417 @subheading The @code{-stack-list-locals} Command
30418 @findex -stack-list-locals
30420 @subsubheading Synopsis
30423 -stack-list-locals @var{print-values}
30426 Display the local variable names for the selected frame. If
30427 @var{print-values} is 0 or @code{--no-values}, print only the names of
30428 the variables; if it is 1 or @code{--all-values}, print also their
30429 values; and if it is 2 or @code{--simple-values}, print the name,
30430 type and value for simple data types, and the name and type for arrays,
30431 structures and unions. In this last case, a frontend can immediately
30432 display the value of simple data types and create variable objects for
30433 other data types when the user wishes to explore their values in
30436 This command is deprecated in favor of the
30437 @samp{-stack-list-variables} command.
30439 @subsubheading @value{GDBN} Command
30441 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30443 @subsubheading Example
30447 -stack-list-locals 0
30448 ^done,locals=[name="A",name="B",name="C"]
30450 -stack-list-locals --all-values
30451 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30452 @{name="C",value="@{1, 2, 3@}"@}]
30453 -stack-list-locals --simple-values
30454 ^done,locals=[@{name="A",type="int",value="1"@},
30455 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30459 @subheading The @code{-stack-list-variables} Command
30460 @findex -stack-list-variables
30462 @subsubheading Synopsis
30465 -stack-list-variables @var{print-values}
30468 Display the names of local variables and function arguments for the selected frame. If
30469 @var{print-values} is 0 or @code{--no-values}, print only the names of
30470 the variables; if it is 1 or @code{--all-values}, print also their
30471 values; and if it is 2 or @code{--simple-values}, print the name,
30472 type and value for simple data types, and the name and type for arrays,
30473 structures and unions.
30475 @subsubheading Example
30479 -stack-list-variables --thread 1 --frame 0 --all-values
30480 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30485 @subheading The @code{-stack-select-frame} Command
30486 @findex -stack-select-frame
30488 @subsubheading Synopsis
30491 -stack-select-frame @var{framenum}
30494 Change the selected frame. Select a different frame @var{framenum} on
30497 This command in deprecated in favor of passing the @samp{--frame}
30498 option to every command.
30500 @subsubheading @value{GDBN} Command
30502 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30503 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30505 @subsubheading Example
30509 -stack-select-frame 2
30514 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30515 @node GDB/MI Variable Objects
30516 @section @sc{gdb/mi} Variable Objects
30520 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30522 For the implementation of a variable debugger window (locals, watched
30523 expressions, etc.), we are proposing the adaptation of the existing code
30524 used by @code{Insight}.
30526 The two main reasons for that are:
30530 It has been proven in practice (it is already on its second generation).
30533 It will shorten development time (needless to say how important it is
30537 The original interface was designed to be used by Tcl code, so it was
30538 slightly changed so it could be used through @sc{gdb/mi}. This section
30539 describes the @sc{gdb/mi} operations that will be available and gives some
30540 hints about their use.
30542 @emph{Note}: In addition to the set of operations described here, we
30543 expect the @sc{gui} implementation of a variable window to require, at
30544 least, the following operations:
30547 @item @code{-gdb-show} @code{output-radix}
30548 @item @code{-stack-list-arguments}
30549 @item @code{-stack-list-locals}
30550 @item @code{-stack-select-frame}
30555 @subheading Introduction to Variable Objects
30557 @cindex variable objects in @sc{gdb/mi}
30559 Variable objects are "object-oriented" MI interface for examining and
30560 changing values of expressions. Unlike some other MI interfaces that
30561 work with expressions, variable objects are specifically designed for
30562 simple and efficient presentation in the frontend. A variable object
30563 is identified by string name. When a variable object is created, the
30564 frontend specifies the expression for that variable object. The
30565 expression can be a simple variable, or it can be an arbitrary complex
30566 expression, and can even involve CPU registers. After creating a
30567 variable object, the frontend can invoke other variable object
30568 operations---for example to obtain or change the value of a variable
30569 object, or to change display format.
30571 Variable objects have hierarchical tree structure. Any variable object
30572 that corresponds to a composite type, such as structure in C, has
30573 a number of child variable objects, for example corresponding to each
30574 element of a structure. A child variable object can itself have
30575 children, recursively. Recursion ends when we reach
30576 leaf variable objects, which always have built-in types. Child variable
30577 objects are created only by explicit request, so if a frontend
30578 is not interested in the children of a particular variable object, no
30579 child will be created.
30581 For a leaf variable object it is possible to obtain its value as a
30582 string, or set the value from a string. String value can be also
30583 obtained for a non-leaf variable object, but it's generally a string
30584 that only indicates the type of the object, and does not list its
30585 contents. Assignment to a non-leaf variable object is not allowed.
30587 A frontend does not need to read the values of all variable objects each time
30588 the program stops. Instead, MI provides an update command that lists all
30589 variable objects whose values has changed since the last update
30590 operation. This considerably reduces the amount of data that must
30591 be transferred to the frontend. As noted above, children variable
30592 objects are created on demand, and only leaf variable objects have a
30593 real value. As result, gdb will read target memory only for leaf
30594 variables that frontend has created.
30596 The automatic update is not always desirable. For example, a frontend
30597 might want to keep a value of some expression for future reference,
30598 and never update it. For another example, fetching memory is
30599 relatively slow for embedded targets, so a frontend might want
30600 to disable automatic update for the variables that are either not
30601 visible on the screen, or ``closed''. This is possible using so
30602 called ``frozen variable objects''. Such variable objects are never
30603 implicitly updated.
30605 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30606 fixed variable object, the expression is parsed when the variable
30607 object is created, including associating identifiers to specific
30608 variables. The meaning of expression never changes. For a floating
30609 variable object the values of variables whose names appear in the
30610 expressions are re-evaluated every time in the context of the current
30611 frame. Consider this example:
30616 struct work_state state;
30623 If a fixed variable object for the @code{state} variable is created in
30624 this function, and we enter the recursive call, the variable
30625 object will report the value of @code{state} in the top-level
30626 @code{do_work} invocation. On the other hand, a floating variable
30627 object will report the value of @code{state} in the current frame.
30629 If an expression specified when creating a fixed variable object
30630 refers to a local variable, the variable object becomes bound to the
30631 thread and frame in which the variable object is created. When such
30632 variable object is updated, @value{GDBN} makes sure that the
30633 thread/frame combination the variable object is bound to still exists,
30634 and re-evaluates the variable object in context of that thread/frame.
30636 The following is the complete set of @sc{gdb/mi} operations defined to
30637 access this functionality:
30639 @multitable @columnfractions .4 .6
30640 @item @strong{Operation}
30641 @tab @strong{Description}
30643 @item @code{-enable-pretty-printing}
30644 @tab enable Python-based pretty-printing
30645 @item @code{-var-create}
30646 @tab create a variable object
30647 @item @code{-var-delete}
30648 @tab delete the variable object and/or its children
30649 @item @code{-var-set-format}
30650 @tab set the display format of this variable
30651 @item @code{-var-show-format}
30652 @tab show the display format of this variable
30653 @item @code{-var-info-num-children}
30654 @tab tells how many children this object has
30655 @item @code{-var-list-children}
30656 @tab return a list of the object's children
30657 @item @code{-var-info-type}
30658 @tab show the type of this variable object
30659 @item @code{-var-info-expression}
30660 @tab print parent-relative expression that this variable object represents
30661 @item @code{-var-info-path-expression}
30662 @tab print full expression that this variable object represents
30663 @item @code{-var-show-attributes}
30664 @tab is this variable editable? does it exist here?
30665 @item @code{-var-evaluate-expression}
30666 @tab get the value of this variable
30667 @item @code{-var-assign}
30668 @tab set the value of this variable
30669 @item @code{-var-update}
30670 @tab update the variable and its children
30671 @item @code{-var-set-frozen}
30672 @tab set frozeness attribute
30673 @item @code{-var-set-update-range}
30674 @tab set range of children to display on update
30677 In the next subsection we describe each operation in detail and suggest
30678 how it can be used.
30680 @subheading Description And Use of Operations on Variable Objects
30682 @subheading The @code{-enable-pretty-printing} Command
30683 @findex -enable-pretty-printing
30686 -enable-pretty-printing
30689 @value{GDBN} allows Python-based visualizers to affect the output of the
30690 MI variable object commands. However, because there was no way to
30691 implement this in a fully backward-compatible way, a front end must
30692 request that this functionality be enabled.
30694 Once enabled, this feature cannot be disabled.
30696 Note that if Python support has not been compiled into @value{GDBN},
30697 this command will still succeed (and do nothing).
30699 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30700 may work differently in future versions of @value{GDBN}.
30702 @subheading The @code{-var-create} Command
30703 @findex -var-create
30705 @subsubheading Synopsis
30708 -var-create @{@var{name} | "-"@}
30709 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30712 This operation creates a variable object, which allows the monitoring of
30713 a variable, the result of an expression, a memory cell or a CPU
30716 The @var{name} parameter is the string by which the object can be
30717 referenced. It must be unique. If @samp{-} is specified, the varobj
30718 system will generate a string ``varNNNNNN'' automatically. It will be
30719 unique provided that one does not specify @var{name} of that format.
30720 The command fails if a duplicate name is found.
30722 The frame under which the expression should be evaluated can be
30723 specified by @var{frame-addr}. A @samp{*} indicates that the current
30724 frame should be used. A @samp{@@} indicates that a floating variable
30725 object must be created.
30727 @var{expression} is any expression valid on the current language set (must not
30728 begin with a @samp{*}), or one of the following:
30732 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30735 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30738 @samp{$@var{regname}} --- a CPU register name
30741 @cindex dynamic varobj
30742 A varobj's contents may be provided by a Python-based pretty-printer. In this
30743 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30744 have slightly different semantics in some cases. If the
30745 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30746 will never create a dynamic varobj. This ensures backward
30747 compatibility for existing clients.
30749 @subsubheading Result
30751 This operation returns attributes of the newly-created varobj. These
30756 The name of the varobj.
30759 The number of children of the varobj. This number is not necessarily
30760 reliable for a dynamic varobj. Instead, you must examine the
30761 @samp{has_more} attribute.
30764 The varobj's scalar value. For a varobj whose type is some sort of
30765 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30766 will not be interesting.
30769 The varobj's type. This is a string representation of the type, as
30770 would be printed by the @value{GDBN} CLI. If @samp{print object}
30771 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30772 @emph{actual} (derived) type of the object is shown rather than the
30773 @emph{declared} one.
30776 If a variable object is bound to a specific thread, then this is the
30777 thread's identifier.
30780 For a dynamic varobj, this indicates whether there appear to be any
30781 children available. For a non-dynamic varobj, this will be 0.
30784 This attribute will be present and have the value @samp{1} if the
30785 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30786 then this attribute will not be present.
30789 A dynamic varobj can supply a display hint to the front end. The
30790 value comes directly from the Python pretty-printer object's
30791 @code{display_hint} method. @xref{Pretty Printing API}.
30794 Typical output will look like this:
30797 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30798 has_more="@var{has_more}"
30802 @subheading The @code{-var-delete} Command
30803 @findex -var-delete
30805 @subsubheading Synopsis
30808 -var-delete [ -c ] @var{name}
30811 Deletes a previously created variable object and all of its children.
30812 With the @samp{-c} option, just deletes the children.
30814 Returns an error if the object @var{name} is not found.
30817 @subheading The @code{-var-set-format} Command
30818 @findex -var-set-format
30820 @subsubheading Synopsis
30823 -var-set-format @var{name} @var{format-spec}
30826 Sets the output format for the value of the object @var{name} to be
30829 @anchor{-var-set-format}
30830 The syntax for the @var{format-spec} is as follows:
30833 @var{format-spec} @expansion{}
30834 @{binary | decimal | hexadecimal | octal | natural@}
30837 The natural format is the default format choosen automatically
30838 based on the variable type (like decimal for an @code{int}, hex
30839 for pointers, etc.).
30841 For a variable with children, the format is set only on the
30842 variable itself, and the children are not affected.
30844 @subheading The @code{-var-show-format} Command
30845 @findex -var-show-format
30847 @subsubheading Synopsis
30850 -var-show-format @var{name}
30853 Returns the format used to display the value of the object @var{name}.
30856 @var{format} @expansion{}
30861 @subheading The @code{-var-info-num-children} Command
30862 @findex -var-info-num-children
30864 @subsubheading Synopsis
30867 -var-info-num-children @var{name}
30870 Returns the number of children of a variable object @var{name}:
30876 Note that this number is not completely reliable for a dynamic varobj.
30877 It will return the current number of children, but more children may
30881 @subheading The @code{-var-list-children} Command
30882 @findex -var-list-children
30884 @subsubheading Synopsis
30887 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30889 @anchor{-var-list-children}
30891 Return a list of the children of the specified variable object and
30892 create variable objects for them, if they do not already exist. With
30893 a single argument or if @var{print-values} has a value of 0 or
30894 @code{--no-values}, print only the names of the variables; if
30895 @var{print-values} is 1 or @code{--all-values}, also print their
30896 values; and if it is 2 or @code{--simple-values} print the name and
30897 value for simple data types and just the name for arrays, structures
30900 @var{from} and @var{to}, if specified, indicate the range of children
30901 to report. If @var{from} or @var{to} is less than zero, the range is
30902 reset and all children will be reported. Otherwise, children starting
30903 at @var{from} (zero-based) and up to and excluding @var{to} will be
30906 If a child range is requested, it will only affect the current call to
30907 @code{-var-list-children}, but not future calls to @code{-var-update}.
30908 For this, you must instead use @code{-var-set-update-range}. The
30909 intent of this approach is to enable a front end to implement any
30910 update approach it likes; for example, scrolling a view may cause the
30911 front end to request more children with @code{-var-list-children}, and
30912 then the front end could call @code{-var-set-update-range} with a
30913 different range to ensure that future updates are restricted to just
30916 For each child the following results are returned:
30921 Name of the variable object created for this child.
30924 The expression to be shown to the user by the front end to designate this child.
30925 For example this may be the name of a structure member.
30927 For a dynamic varobj, this value cannot be used to form an
30928 expression. There is no way to do this at all with a dynamic varobj.
30930 For C/C@t{++} structures there are several pseudo children returned to
30931 designate access qualifiers. For these pseudo children @var{exp} is
30932 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30933 type and value are not present.
30935 A dynamic varobj will not report the access qualifying
30936 pseudo-children, regardless of the language. This information is not
30937 available at all with a dynamic varobj.
30940 Number of children this child has. For a dynamic varobj, this will be
30944 The type of the child. If @samp{print object}
30945 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30946 @emph{actual} (derived) type of the object is shown rather than the
30947 @emph{declared} one.
30950 If values were requested, this is the value.
30953 If this variable object is associated with a thread, this is the thread id.
30954 Otherwise this result is not present.
30957 If the variable object is frozen, this variable will be present with a value of 1.
30960 The result may have its own attributes:
30964 A dynamic varobj can supply a display hint to the front end. The
30965 value comes directly from the Python pretty-printer object's
30966 @code{display_hint} method. @xref{Pretty Printing API}.
30969 This is an integer attribute which is nonzero if there are children
30970 remaining after the end of the selected range.
30973 @subsubheading Example
30977 -var-list-children n
30978 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30979 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30981 -var-list-children --all-values n
30982 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30983 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30987 @subheading The @code{-var-info-type} Command
30988 @findex -var-info-type
30990 @subsubheading Synopsis
30993 -var-info-type @var{name}
30996 Returns the type of the specified variable @var{name}. The type is
30997 returned as a string in the same format as it is output by the
31001 type=@var{typename}
31005 @subheading The @code{-var-info-expression} Command
31006 @findex -var-info-expression
31008 @subsubheading Synopsis
31011 -var-info-expression @var{name}
31014 Returns a string that is suitable for presenting this
31015 variable object in user interface. The string is generally
31016 not valid expression in the current language, and cannot be evaluated.
31018 For example, if @code{a} is an array, and variable object
31019 @code{A} was created for @code{a}, then we'll get this output:
31022 (gdb) -var-info-expression A.1
31023 ^done,lang="C",exp="1"
31027 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
31029 Note that the output of the @code{-var-list-children} command also
31030 includes those expressions, so the @code{-var-info-expression} command
31033 @subheading The @code{-var-info-path-expression} Command
31034 @findex -var-info-path-expression
31036 @subsubheading Synopsis
31039 -var-info-path-expression @var{name}
31042 Returns an expression that can be evaluated in the current
31043 context and will yield the same value that a variable object has.
31044 Compare this with the @code{-var-info-expression} command, which
31045 result can be used only for UI presentation. Typical use of
31046 the @code{-var-info-path-expression} command is creating a
31047 watchpoint from a variable object.
31049 This command is currently not valid for children of a dynamic varobj,
31050 and will give an error when invoked on one.
31052 For example, suppose @code{C} is a C@t{++} class, derived from class
31053 @code{Base}, and that the @code{Base} class has a member called
31054 @code{m_size}. Assume a variable @code{c} is has the type of
31055 @code{C} and a variable object @code{C} was created for variable
31056 @code{c}. Then, we'll get this output:
31058 (gdb) -var-info-path-expression C.Base.public.m_size
31059 ^done,path_expr=((Base)c).m_size)
31062 @subheading The @code{-var-show-attributes} Command
31063 @findex -var-show-attributes
31065 @subsubheading Synopsis
31068 -var-show-attributes @var{name}
31071 List attributes of the specified variable object @var{name}:
31074 status=@var{attr} [ ( ,@var{attr} )* ]
31078 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31080 @subheading The @code{-var-evaluate-expression} Command
31081 @findex -var-evaluate-expression
31083 @subsubheading Synopsis
31086 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31089 Evaluates the expression that is represented by the specified variable
31090 object and returns its value as a string. The format of the string
31091 can be specified with the @samp{-f} option. The possible values of
31092 this option are the same as for @code{-var-set-format}
31093 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31094 the current display format will be used. The current display format
31095 can be changed using the @code{-var-set-format} command.
31101 Note that one must invoke @code{-var-list-children} for a variable
31102 before the value of a child variable can be evaluated.
31104 @subheading The @code{-var-assign} Command
31105 @findex -var-assign
31107 @subsubheading Synopsis
31110 -var-assign @var{name} @var{expression}
31113 Assigns the value of @var{expression} to the variable object specified
31114 by @var{name}. The object must be @samp{editable}. If the variable's
31115 value is altered by the assign, the variable will show up in any
31116 subsequent @code{-var-update} list.
31118 @subsubheading Example
31126 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31130 @subheading The @code{-var-update} Command
31131 @findex -var-update
31133 @subsubheading Synopsis
31136 -var-update [@var{print-values}] @{@var{name} | "*"@}
31139 Reevaluate the expressions corresponding to the variable object
31140 @var{name} and all its direct and indirect children, and return the
31141 list of variable objects whose values have changed; @var{name} must
31142 be a root variable object. Here, ``changed'' means that the result of
31143 @code{-var-evaluate-expression} before and after the
31144 @code{-var-update} is different. If @samp{*} is used as the variable
31145 object names, all existing variable objects are updated, except
31146 for frozen ones (@pxref{-var-set-frozen}). The option
31147 @var{print-values} determines whether both names and values, or just
31148 names are printed. The possible values of this option are the same
31149 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31150 recommended to use the @samp{--all-values} option, to reduce the
31151 number of MI commands needed on each program stop.
31153 With the @samp{*} parameter, if a variable object is bound to a
31154 currently running thread, it will not be updated, without any
31157 If @code{-var-set-update-range} was previously used on a varobj, then
31158 only the selected range of children will be reported.
31160 @code{-var-update} reports all the changed varobjs in a tuple named
31163 Each item in the change list is itself a tuple holding:
31167 The name of the varobj.
31170 If values were requested for this update, then this field will be
31171 present and will hold the value of the varobj.
31174 @anchor{-var-update}
31175 This field is a string which may take one of three values:
31179 The variable object's current value is valid.
31182 The variable object does not currently hold a valid value but it may
31183 hold one in the future if its associated expression comes back into
31187 The variable object no longer holds a valid value.
31188 This can occur when the executable file being debugged has changed,
31189 either through recompilation or by using the @value{GDBN} @code{file}
31190 command. The front end should normally choose to delete these variable
31194 In the future new values may be added to this list so the front should
31195 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31198 This is only present if the varobj is still valid. If the type
31199 changed, then this will be the string @samp{true}; otherwise it will
31202 When a varobj's type changes, its children are also likely to have
31203 become incorrect. Therefore, the varobj's children are automatically
31204 deleted when this attribute is @samp{true}. Also, the varobj's update
31205 range, when set using the @code{-var-set-update-range} command, is
31209 If the varobj's type changed, then this field will be present and will
31212 @item new_num_children
31213 For a dynamic varobj, if the number of children changed, or if the
31214 type changed, this will be the new number of children.
31216 The @samp{numchild} field in other varobj responses is generally not
31217 valid for a dynamic varobj -- it will show the number of children that
31218 @value{GDBN} knows about, but because dynamic varobjs lazily
31219 instantiate their children, this will not reflect the number of
31220 children which may be available.
31222 The @samp{new_num_children} attribute only reports changes to the
31223 number of children known by @value{GDBN}. This is the only way to
31224 detect whether an update has removed children (which necessarily can
31225 only happen at the end of the update range).
31228 The display hint, if any.
31231 This is an integer value, which will be 1 if there are more children
31232 available outside the varobj's update range.
31235 This attribute will be present and have the value @samp{1} if the
31236 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31237 then this attribute will not be present.
31240 If new children were added to a dynamic varobj within the selected
31241 update range (as set by @code{-var-set-update-range}), then they will
31242 be listed in this attribute.
31245 @subsubheading Example
31252 -var-update --all-values var1
31253 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31254 type_changed="false"@}]
31258 @subheading The @code{-var-set-frozen} Command
31259 @findex -var-set-frozen
31260 @anchor{-var-set-frozen}
31262 @subsubheading Synopsis
31265 -var-set-frozen @var{name} @var{flag}
31268 Set the frozenness flag on the variable object @var{name}. The
31269 @var{flag} parameter should be either @samp{1} to make the variable
31270 frozen or @samp{0} to make it unfrozen. If a variable object is
31271 frozen, then neither itself, nor any of its children, are
31272 implicitly updated by @code{-var-update} of
31273 a parent variable or by @code{-var-update *}. Only
31274 @code{-var-update} of the variable itself will update its value and
31275 values of its children. After a variable object is unfrozen, it is
31276 implicitly updated by all subsequent @code{-var-update} operations.
31277 Unfreezing a variable does not update it, only subsequent
31278 @code{-var-update} does.
31280 @subsubheading Example
31284 -var-set-frozen V 1
31289 @subheading The @code{-var-set-update-range} command
31290 @findex -var-set-update-range
31291 @anchor{-var-set-update-range}
31293 @subsubheading Synopsis
31296 -var-set-update-range @var{name} @var{from} @var{to}
31299 Set the range of children to be returned by future invocations of
31300 @code{-var-update}.
31302 @var{from} and @var{to} indicate the range of children to report. If
31303 @var{from} or @var{to} is less than zero, the range is reset and all
31304 children will be reported. Otherwise, children starting at @var{from}
31305 (zero-based) and up to and excluding @var{to} will be reported.
31307 @subsubheading Example
31311 -var-set-update-range V 1 2
31315 @subheading The @code{-var-set-visualizer} command
31316 @findex -var-set-visualizer
31317 @anchor{-var-set-visualizer}
31319 @subsubheading Synopsis
31322 -var-set-visualizer @var{name} @var{visualizer}
31325 Set a visualizer for the variable object @var{name}.
31327 @var{visualizer} is the visualizer to use. The special value
31328 @samp{None} means to disable any visualizer in use.
31330 If not @samp{None}, @var{visualizer} must be a Python expression.
31331 This expression must evaluate to a callable object which accepts a
31332 single argument. @value{GDBN} will call this object with the value of
31333 the varobj @var{name} as an argument (this is done so that the same
31334 Python pretty-printing code can be used for both the CLI and MI).
31335 When called, this object must return an object which conforms to the
31336 pretty-printing interface (@pxref{Pretty Printing API}).
31338 The pre-defined function @code{gdb.default_visualizer} may be used to
31339 select a visualizer by following the built-in process
31340 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31341 a varobj is created, and so ordinarily is not needed.
31343 This feature is only available if Python support is enabled. The MI
31344 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31345 can be used to check this.
31347 @subsubheading Example
31349 Resetting the visualizer:
31353 -var-set-visualizer V None
31357 Reselecting the default (type-based) visualizer:
31361 -var-set-visualizer V gdb.default_visualizer
31365 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31366 can be used to instantiate this class for a varobj:
31370 -var-set-visualizer V "lambda val: SomeClass()"
31374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31375 @node GDB/MI Data Manipulation
31376 @section @sc{gdb/mi} Data Manipulation
31378 @cindex data manipulation, in @sc{gdb/mi}
31379 @cindex @sc{gdb/mi}, data manipulation
31380 This section describes the @sc{gdb/mi} commands that manipulate data:
31381 examine memory and registers, evaluate expressions, etc.
31383 @c REMOVED FROM THE INTERFACE.
31384 @c @subheading -data-assign
31385 @c Change the value of a program variable. Plenty of side effects.
31386 @c @subsubheading GDB Command
31388 @c @subsubheading Example
31391 @subheading The @code{-data-disassemble} Command
31392 @findex -data-disassemble
31394 @subsubheading Synopsis
31398 [ -s @var{start-addr} -e @var{end-addr} ]
31399 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31407 @item @var{start-addr}
31408 is the beginning address (or @code{$pc})
31409 @item @var{end-addr}
31411 @item @var{filename}
31412 is the name of the file to disassemble
31413 @item @var{linenum}
31414 is the line number to disassemble around
31416 is the number of disassembly lines to be produced. If it is -1,
31417 the whole function will be disassembled, in case no @var{end-addr} is
31418 specified. If @var{end-addr} is specified as a non-zero value, and
31419 @var{lines} is lower than the number of disassembly lines between
31420 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31421 displayed; if @var{lines} is higher than the number of lines between
31422 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31425 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31426 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31427 mixed source and disassembly with raw opcodes).
31430 @subsubheading Result
31432 The result of the @code{-data-disassemble} command will be a list named
31433 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31434 used with the @code{-data-disassemble} command.
31436 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31441 The address at which this instruction was disassembled.
31444 The name of the function this instruction is within.
31447 The decimal offset in bytes from the start of @samp{func-name}.
31450 The text disassembly for this @samp{address}.
31453 This field is only present for mode 2. This contains the raw opcode
31454 bytes for the @samp{inst} field.
31458 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31459 @samp{src_and_asm_line}, each of which has the following fields:
31463 The line number within @samp{file}.
31466 The file name from the compilation unit. This might be an absolute
31467 file name or a relative file name depending on the compile command
31471 Absolute file name of @samp{file}. It is converted to a canonical form
31472 using the source file search path
31473 (@pxref{Source Path, ,Specifying Source Directories})
31474 and after resolving all the symbolic links.
31476 If the source file is not found this field will contain the path as
31477 present in the debug information.
31479 @item line_asm_insn
31480 This is a list of tuples containing the disassembly for @samp{line} in
31481 @samp{file}. The fields of each tuple are the same as for
31482 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31483 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31488 Note that whatever included in the @samp{inst} field, is not
31489 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31492 @subsubheading @value{GDBN} Command
31494 The corresponding @value{GDBN} command is @samp{disassemble}.
31496 @subsubheading Example
31498 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31502 -data-disassemble -s $pc -e "$pc + 20" -- 0
31505 @{address="0x000107c0",func-name="main",offset="4",
31506 inst="mov 2, %o0"@},
31507 @{address="0x000107c4",func-name="main",offset="8",
31508 inst="sethi %hi(0x11800), %o2"@},
31509 @{address="0x000107c8",func-name="main",offset="12",
31510 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31511 @{address="0x000107cc",func-name="main",offset="16",
31512 inst="sethi %hi(0x11800), %o2"@},
31513 @{address="0x000107d0",func-name="main",offset="20",
31514 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31518 Disassemble the whole @code{main} function. Line 32 is part of
31522 -data-disassemble -f basics.c -l 32 -- 0
31524 @{address="0x000107bc",func-name="main",offset="0",
31525 inst="save %sp, -112, %sp"@},
31526 @{address="0x000107c0",func-name="main",offset="4",
31527 inst="mov 2, %o0"@},
31528 @{address="0x000107c4",func-name="main",offset="8",
31529 inst="sethi %hi(0x11800), %o2"@},
31531 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31532 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31536 Disassemble 3 instructions from the start of @code{main}:
31540 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31542 @{address="0x000107bc",func-name="main",offset="0",
31543 inst="save %sp, -112, %sp"@},
31544 @{address="0x000107c0",func-name="main",offset="4",
31545 inst="mov 2, %o0"@},
31546 @{address="0x000107c4",func-name="main",offset="8",
31547 inst="sethi %hi(0x11800), %o2"@}]
31551 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31555 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31557 src_and_asm_line=@{line="31",
31558 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31559 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31560 line_asm_insn=[@{address="0x000107bc",
31561 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31562 src_and_asm_line=@{line="32",
31563 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31564 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31565 line_asm_insn=[@{address="0x000107c0",
31566 func-name="main",offset="4",inst="mov 2, %o0"@},
31567 @{address="0x000107c4",func-name="main",offset="8",
31568 inst="sethi %hi(0x11800), %o2"@}]@}]
31573 @subheading The @code{-data-evaluate-expression} Command
31574 @findex -data-evaluate-expression
31576 @subsubheading Synopsis
31579 -data-evaluate-expression @var{expr}
31582 Evaluate @var{expr} as an expression. The expression could contain an
31583 inferior function call. The function call will execute synchronously.
31584 If the expression contains spaces, it must be enclosed in double quotes.
31586 @subsubheading @value{GDBN} Command
31588 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31589 @samp{call}. In @code{gdbtk} only, there's a corresponding
31590 @samp{gdb_eval} command.
31592 @subsubheading Example
31594 In the following example, the numbers that precede the commands are the
31595 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31596 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31600 211-data-evaluate-expression A
31603 311-data-evaluate-expression &A
31604 311^done,value="0xefffeb7c"
31606 411-data-evaluate-expression A+3
31609 511-data-evaluate-expression "A + 3"
31615 @subheading The @code{-data-list-changed-registers} Command
31616 @findex -data-list-changed-registers
31618 @subsubheading Synopsis
31621 -data-list-changed-registers
31624 Display a list of the registers that have changed.
31626 @subsubheading @value{GDBN} Command
31628 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31629 has the corresponding command @samp{gdb_changed_register_list}.
31631 @subsubheading Example
31633 On a PPC MBX board:
31641 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31642 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31645 -data-list-changed-registers
31646 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31647 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31648 "24","25","26","27","28","30","31","64","65","66","67","69"]
31653 @subheading The @code{-data-list-register-names} Command
31654 @findex -data-list-register-names
31656 @subsubheading Synopsis
31659 -data-list-register-names [ ( @var{regno} )+ ]
31662 Show a list of register names for the current target. If no arguments
31663 are given, it shows a list of the names of all the registers. If
31664 integer numbers are given as arguments, it will print a list of the
31665 names of the registers corresponding to the arguments. To ensure
31666 consistency between a register name and its number, the output list may
31667 include empty register names.
31669 @subsubheading @value{GDBN} Command
31671 @value{GDBN} does not have a command which corresponds to
31672 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31673 corresponding command @samp{gdb_regnames}.
31675 @subsubheading Example
31677 For the PPC MBX board:
31680 -data-list-register-names
31681 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31682 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31683 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31684 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31685 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31686 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31687 "", "pc","ps","cr","lr","ctr","xer"]
31689 -data-list-register-names 1 2 3
31690 ^done,register-names=["r1","r2","r3"]
31694 @subheading The @code{-data-list-register-values} Command
31695 @findex -data-list-register-values
31697 @subsubheading Synopsis
31700 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31703 Display the registers' contents. @var{fmt} is the format according to
31704 which the registers' contents are to be returned, followed by an optional
31705 list of numbers specifying the registers to display. A missing list of
31706 numbers indicates that the contents of all the registers must be returned.
31708 Allowed formats for @var{fmt} are:
31725 @subsubheading @value{GDBN} Command
31727 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31728 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31730 @subsubheading Example
31732 For a PPC MBX board (note: line breaks are for readability only, they
31733 don't appear in the actual output):
31737 -data-list-register-values r 64 65
31738 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31739 @{number="65",value="0x00029002"@}]
31741 -data-list-register-values x
31742 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31743 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31744 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31745 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31746 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31747 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31748 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31749 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31750 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31751 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31752 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31753 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31754 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31755 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31756 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31757 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31758 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31759 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31760 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31761 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31762 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31763 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31764 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31765 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31766 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31767 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31768 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31769 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31770 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31771 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31772 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31773 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31774 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31775 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31776 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31777 @{number="69",value="0x20002b03"@}]
31782 @subheading The @code{-data-read-memory} Command
31783 @findex -data-read-memory
31785 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31787 @subsubheading Synopsis
31790 -data-read-memory [ -o @var{byte-offset} ]
31791 @var{address} @var{word-format} @var{word-size}
31792 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31799 @item @var{address}
31800 An expression specifying the address of the first memory word to be
31801 read. Complex expressions containing embedded white space should be
31802 quoted using the C convention.
31804 @item @var{word-format}
31805 The format to be used to print the memory words. The notation is the
31806 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31809 @item @var{word-size}
31810 The size of each memory word in bytes.
31812 @item @var{nr-rows}
31813 The number of rows in the output table.
31815 @item @var{nr-cols}
31816 The number of columns in the output table.
31819 If present, indicates that each row should include an @sc{ascii} dump. The
31820 value of @var{aschar} is used as a padding character when a byte is not a
31821 member of the printable @sc{ascii} character set (printable @sc{ascii}
31822 characters are those whose code is between 32 and 126, inclusively).
31824 @item @var{byte-offset}
31825 An offset to add to the @var{address} before fetching memory.
31828 This command displays memory contents as a table of @var{nr-rows} by
31829 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31830 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31831 (returned as @samp{total-bytes}). Should less than the requested number
31832 of bytes be returned by the target, the missing words are identified
31833 using @samp{N/A}. The number of bytes read from the target is returned
31834 in @samp{nr-bytes} and the starting address used to read memory in
31837 The address of the next/previous row or page is available in
31838 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31841 @subsubheading @value{GDBN} Command
31843 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31844 @samp{gdb_get_mem} memory read command.
31846 @subsubheading Example
31848 Read six bytes of memory starting at @code{bytes+6} but then offset by
31849 @code{-6} bytes. Format as three rows of two columns. One byte per
31850 word. Display each word in hex.
31854 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31855 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31856 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31857 prev-page="0x0000138a",memory=[
31858 @{addr="0x00001390",data=["0x00","0x01"]@},
31859 @{addr="0x00001392",data=["0x02","0x03"]@},
31860 @{addr="0x00001394",data=["0x04","0x05"]@}]
31864 Read two bytes of memory starting at address @code{shorts + 64} and
31865 display as a single word formatted in decimal.
31869 5-data-read-memory shorts+64 d 2 1 1
31870 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31871 next-row="0x00001512",prev-row="0x0000150e",
31872 next-page="0x00001512",prev-page="0x0000150e",memory=[
31873 @{addr="0x00001510",data=["128"]@}]
31877 Read thirty two bytes of memory starting at @code{bytes+16} and format
31878 as eight rows of four columns. Include a string encoding with @samp{x}
31879 used as the non-printable character.
31883 4-data-read-memory bytes+16 x 1 8 4 x
31884 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31885 next-row="0x000013c0",prev-row="0x0000139c",
31886 next-page="0x000013c0",prev-page="0x00001380",memory=[
31887 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31888 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31889 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31890 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31891 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31892 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31893 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31894 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31898 @subheading The @code{-data-read-memory-bytes} Command
31899 @findex -data-read-memory-bytes
31901 @subsubheading Synopsis
31904 -data-read-memory-bytes [ -o @var{byte-offset} ]
31905 @var{address} @var{count}
31912 @item @var{address}
31913 An expression specifying the address of the first memory word to be
31914 read. Complex expressions containing embedded white space should be
31915 quoted using the C convention.
31918 The number of bytes to read. This should be an integer literal.
31920 @item @var{byte-offset}
31921 The offsets in bytes relative to @var{address} at which to start
31922 reading. This should be an integer literal. This option is provided
31923 so that a frontend is not required to first evaluate address and then
31924 perform address arithmetics itself.
31928 This command attempts to read all accessible memory regions in the
31929 specified range. First, all regions marked as unreadable in the memory
31930 map (if one is defined) will be skipped. @xref{Memory Region
31931 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31932 regions. For each one, if reading full region results in an errors,
31933 @value{GDBN} will try to read a subset of the region.
31935 In general, every single byte in the region may be readable or not,
31936 and the only way to read every readable byte is to try a read at
31937 every address, which is not practical. Therefore, @value{GDBN} will
31938 attempt to read all accessible bytes at either beginning or the end
31939 of the region, using a binary division scheme. This heuristic works
31940 well for reading accross a memory map boundary. Note that if a region
31941 has a readable range that is neither at the beginning or the end,
31942 @value{GDBN} will not read it.
31944 The result record (@pxref{GDB/MI Result Records}) that is output of
31945 the command includes a field named @samp{memory} whose content is a
31946 list of tuples. Each tuple represent a successfully read memory block
31947 and has the following fields:
31951 The start address of the memory block, as hexadecimal literal.
31954 The end address of the memory block, as hexadecimal literal.
31957 The offset of the memory block, as hexadecimal literal, relative to
31958 the start address passed to @code{-data-read-memory-bytes}.
31961 The contents of the memory block, in hex.
31967 @subsubheading @value{GDBN} Command
31969 The corresponding @value{GDBN} command is @samp{x}.
31971 @subsubheading Example
31975 -data-read-memory-bytes &a 10
31976 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31978 contents="01000000020000000300"@}]
31983 @subheading The @code{-data-write-memory-bytes} Command
31984 @findex -data-write-memory-bytes
31986 @subsubheading Synopsis
31989 -data-write-memory-bytes @var{address} @var{contents}
31990 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31997 @item @var{address}
31998 An expression specifying the address of the first memory word to be
31999 read. Complex expressions containing embedded white space should be
32000 quoted using the C convention.
32002 @item @var{contents}
32003 The hex-encoded bytes to write.
32006 Optional argument indicating the number of bytes to be written. If @var{count}
32007 is greater than @var{contents}' length, @value{GDBN} will repeatedly
32008 write @var{contents} until it fills @var{count} bytes.
32012 @subsubheading @value{GDBN} Command
32014 There's no corresponding @value{GDBN} command.
32016 @subsubheading Example
32020 -data-write-memory-bytes &a "aabbccdd"
32027 -data-write-memory-bytes &a "aabbccdd" 16e
32032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32033 @node GDB/MI Tracepoint Commands
32034 @section @sc{gdb/mi} Tracepoint Commands
32036 The commands defined in this section implement MI support for
32037 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32039 @subheading The @code{-trace-find} Command
32040 @findex -trace-find
32042 @subsubheading Synopsis
32045 -trace-find @var{mode} [@var{parameters}@dots{}]
32048 Find a trace frame using criteria defined by @var{mode} and
32049 @var{parameters}. The following table lists permissible
32050 modes and their parameters. For details of operation, see @ref{tfind}.
32055 No parameters are required. Stops examining trace frames.
32058 An integer is required as parameter. Selects tracepoint frame with
32061 @item tracepoint-number
32062 An integer is required as parameter. Finds next
32063 trace frame that corresponds to tracepoint with the specified number.
32066 An address is required as parameter. Finds
32067 next trace frame that corresponds to any tracepoint at the specified
32070 @item pc-inside-range
32071 Two addresses are required as parameters. Finds next trace
32072 frame that corresponds to a tracepoint at an address inside the
32073 specified range. Both bounds are considered to be inside the range.
32075 @item pc-outside-range
32076 Two addresses are required as parameters. Finds
32077 next trace frame that corresponds to a tracepoint at an address outside
32078 the specified range. Both bounds are considered to be inside the range.
32081 Line specification is required as parameter. @xref{Specify Location}.
32082 Finds next trace frame that corresponds to a tracepoint at
32083 the specified location.
32087 If @samp{none} was passed as @var{mode}, the response does not
32088 have fields. Otherwise, the response may have the following fields:
32092 This field has either @samp{0} or @samp{1} as the value, depending
32093 on whether a matching tracepoint was found.
32096 The index of the found traceframe. This field is present iff
32097 the @samp{found} field has value of @samp{1}.
32100 The index of the found tracepoint. This field is present iff
32101 the @samp{found} field has value of @samp{1}.
32104 The information about the frame corresponding to the found trace
32105 frame. This field is present only if a trace frame was found.
32106 @xref{GDB/MI Frame Information}, for description of this field.
32110 @subsubheading @value{GDBN} Command
32112 The corresponding @value{GDBN} command is @samp{tfind}.
32114 @subheading -trace-define-variable
32115 @findex -trace-define-variable
32117 @subsubheading Synopsis
32120 -trace-define-variable @var{name} [ @var{value} ]
32123 Create trace variable @var{name} if it does not exist. If
32124 @var{value} is specified, sets the initial value of the specified
32125 trace variable to that value. Note that the @var{name} should start
32126 with the @samp{$} character.
32128 @subsubheading @value{GDBN} Command
32130 The corresponding @value{GDBN} command is @samp{tvariable}.
32132 @subheading -trace-list-variables
32133 @findex -trace-list-variables
32135 @subsubheading Synopsis
32138 -trace-list-variables
32141 Return a table of all defined trace variables. Each element of the
32142 table has the following fields:
32146 The name of the trace variable. This field is always present.
32149 The initial value. This is a 64-bit signed integer. This
32150 field is always present.
32153 The value the trace variable has at the moment. This is a 64-bit
32154 signed integer. This field is absent iff current value is
32155 not defined, for example if the trace was never run, or is
32160 @subsubheading @value{GDBN} Command
32162 The corresponding @value{GDBN} command is @samp{tvariables}.
32164 @subsubheading Example
32168 -trace-list-variables
32169 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32170 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32171 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32172 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32173 body=[variable=@{name="$trace_timestamp",initial="0"@}
32174 variable=@{name="$foo",initial="10",current="15"@}]@}
32178 @subheading -trace-save
32179 @findex -trace-save
32181 @subsubheading Synopsis
32184 -trace-save [-r ] @var{filename}
32187 Saves the collected trace data to @var{filename}. Without the
32188 @samp{-r} option, the data is downloaded from the target and saved
32189 in a local file. With the @samp{-r} option the target is asked
32190 to perform the save.
32192 @subsubheading @value{GDBN} Command
32194 The corresponding @value{GDBN} command is @samp{tsave}.
32197 @subheading -trace-start
32198 @findex -trace-start
32200 @subsubheading Synopsis
32206 Starts a tracing experiments. The result of this command does not
32209 @subsubheading @value{GDBN} Command
32211 The corresponding @value{GDBN} command is @samp{tstart}.
32213 @subheading -trace-status
32214 @findex -trace-status
32216 @subsubheading Synopsis
32222 Obtains the status of a tracing experiment. The result may include
32223 the following fields:
32228 May have a value of either @samp{0}, when no tracing operations are
32229 supported, @samp{1}, when all tracing operations are supported, or
32230 @samp{file} when examining trace file. In the latter case, examining
32231 of trace frame is possible but new tracing experiement cannot be
32232 started. This field is always present.
32235 May have a value of either @samp{0} or @samp{1} depending on whether
32236 tracing experiement is in progress on target. This field is present
32237 if @samp{supported} field is not @samp{0}.
32240 Report the reason why the tracing was stopped last time. This field
32241 may be absent iff tracing was never stopped on target yet. The
32242 value of @samp{request} means the tracing was stopped as result of
32243 the @code{-trace-stop} command. The value of @samp{overflow} means
32244 the tracing buffer is full. The value of @samp{disconnection} means
32245 tracing was automatically stopped when @value{GDBN} has disconnected.
32246 The value of @samp{passcount} means tracing was stopped when a
32247 tracepoint was passed a maximal number of times for that tracepoint.
32248 This field is present if @samp{supported} field is not @samp{0}.
32250 @item stopping-tracepoint
32251 The number of tracepoint whose passcount as exceeded. This field is
32252 present iff the @samp{stop-reason} field has the value of
32256 @itemx frames-created
32257 The @samp{frames} field is a count of the total number of trace frames
32258 in the trace buffer, while @samp{frames-created} is the total created
32259 during the run, including ones that were discarded, such as when a
32260 circular trace buffer filled up. Both fields are optional.
32264 These fields tell the current size of the tracing buffer and the
32265 remaining space. These fields are optional.
32268 The value of the circular trace buffer flag. @code{1} means that the
32269 trace buffer is circular and old trace frames will be discarded if
32270 necessary to make room, @code{0} means that the trace buffer is linear
32274 The value of the disconnected tracing flag. @code{1} means that
32275 tracing will continue after @value{GDBN} disconnects, @code{0} means
32276 that the trace run will stop.
32279 The filename of the trace file being examined. This field is
32280 optional, and only present when examining a trace file.
32284 @subsubheading @value{GDBN} Command
32286 The corresponding @value{GDBN} command is @samp{tstatus}.
32288 @subheading -trace-stop
32289 @findex -trace-stop
32291 @subsubheading Synopsis
32297 Stops a tracing experiment. The result of this command has the same
32298 fields as @code{-trace-status}, except that the @samp{supported} and
32299 @samp{running} fields are not output.
32301 @subsubheading @value{GDBN} Command
32303 The corresponding @value{GDBN} command is @samp{tstop}.
32306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32307 @node GDB/MI Symbol Query
32308 @section @sc{gdb/mi} Symbol Query Commands
32312 @subheading The @code{-symbol-info-address} Command
32313 @findex -symbol-info-address
32315 @subsubheading Synopsis
32318 -symbol-info-address @var{symbol}
32321 Describe where @var{symbol} is stored.
32323 @subsubheading @value{GDBN} Command
32325 The corresponding @value{GDBN} command is @samp{info address}.
32327 @subsubheading Example
32331 @subheading The @code{-symbol-info-file} Command
32332 @findex -symbol-info-file
32334 @subsubheading Synopsis
32340 Show the file for the symbol.
32342 @subsubheading @value{GDBN} Command
32344 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32345 @samp{gdb_find_file}.
32347 @subsubheading Example
32351 @subheading The @code{-symbol-info-function} Command
32352 @findex -symbol-info-function
32354 @subsubheading Synopsis
32357 -symbol-info-function
32360 Show which function the symbol lives in.
32362 @subsubheading @value{GDBN} Command
32364 @samp{gdb_get_function} in @code{gdbtk}.
32366 @subsubheading Example
32370 @subheading The @code{-symbol-info-line} Command
32371 @findex -symbol-info-line
32373 @subsubheading Synopsis
32379 Show the core addresses of the code for a source line.
32381 @subsubheading @value{GDBN} Command
32383 The corresponding @value{GDBN} command is @samp{info line}.
32384 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32386 @subsubheading Example
32390 @subheading The @code{-symbol-info-symbol} Command
32391 @findex -symbol-info-symbol
32393 @subsubheading Synopsis
32396 -symbol-info-symbol @var{addr}
32399 Describe what symbol is at location @var{addr}.
32401 @subsubheading @value{GDBN} Command
32403 The corresponding @value{GDBN} command is @samp{info symbol}.
32405 @subsubheading Example
32409 @subheading The @code{-symbol-list-functions} Command
32410 @findex -symbol-list-functions
32412 @subsubheading Synopsis
32415 -symbol-list-functions
32418 List the functions in the executable.
32420 @subsubheading @value{GDBN} Command
32422 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32423 @samp{gdb_search} in @code{gdbtk}.
32425 @subsubheading Example
32430 @subheading The @code{-symbol-list-lines} Command
32431 @findex -symbol-list-lines
32433 @subsubheading Synopsis
32436 -symbol-list-lines @var{filename}
32439 Print the list of lines that contain code and their associated program
32440 addresses for the given source filename. The entries are sorted in
32441 ascending PC order.
32443 @subsubheading @value{GDBN} Command
32445 There is no corresponding @value{GDBN} command.
32447 @subsubheading Example
32450 -symbol-list-lines basics.c
32451 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32457 @subheading The @code{-symbol-list-types} Command
32458 @findex -symbol-list-types
32460 @subsubheading Synopsis
32466 List all the type names.
32468 @subsubheading @value{GDBN} Command
32470 The corresponding commands are @samp{info types} in @value{GDBN},
32471 @samp{gdb_search} in @code{gdbtk}.
32473 @subsubheading Example
32477 @subheading The @code{-symbol-list-variables} Command
32478 @findex -symbol-list-variables
32480 @subsubheading Synopsis
32483 -symbol-list-variables
32486 List all the global and static variable names.
32488 @subsubheading @value{GDBN} Command
32490 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32492 @subsubheading Example
32496 @subheading The @code{-symbol-locate} Command
32497 @findex -symbol-locate
32499 @subsubheading Synopsis
32505 @subsubheading @value{GDBN} Command
32507 @samp{gdb_loc} in @code{gdbtk}.
32509 @subsubheading Example
32513 @subheading The @code{-symbol-type} Command
32514 @findex -symbol-type
32516 @subsubheading Synopsis
32519 -symbol-type @var{variable}
32522 Show type of @var{variable}.
32524 @subsubheading @value{GDBN} Command
32526 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32527 @samp{gdb_obj_variable}.
32529 @subsubheading Example
32534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32535 @node GDB/MI File Commands
32536 @section @sc{gdb/mi} File Commands
32538 This section describes the GDB/MI commands to specify executable file names
32539 and to read in and obtain symbol table information.
32541 @subheading The @code{-file-exec-and-symbols} Command
32542 @findex -file-exec-and-symbols
32544 @subsubheading Synopsis
32547 -file-exec-and-symbols @var{file}
32550 Specify the executable file to be debugged. This file is the one from
32551 which the symbol table is also read. If no file is specified, the
32552 command clears the executable and symbol information. If breakpoints
32553 are set when using this command with no arguments, @value{GDBN} will produce
32554 error messages. Otherwise, no output is produced, except a completion
32557 @subsubheading @value{GDBN} Command
32559 The corresponding @value{GDBN} command is @samp{file}.
32561 @subsubheading Example
32565 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32571 @subheading The @code{-file-exec-file} Command
32572 @findex -file-exec-file
32574 @subsubheading Synopsis
32577 -file-exec-file @var{file}
32580 Specify the executable file to be debugged. Unlike
32581 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32582 from this file. If used without argument, @value{GDBN} clears the information
32583 about the executable file. No output is produced, except a completion
32586 @subsubheading @value{GDBN} Command
32588 The corresponding @value{GDBN} command is @samp{exec-file}.
32590 @subsubheading Example
32594 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32601 @subheading The @code{-file-list-exec-sections} Command
32602 @findex -file-list-exec-sections
32604 @subsubheading Synopsis
32607 -file-list-exec-sections
32610 List the sections of the current executable file.
32612 @subsubheading @value{GDBN} Command
32614 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32615 information as this command. @code{gdbtk} has a corresponding command
32616 @samp{gdb_load_info}.
32618 @subsubheading Example
32623 @subheading The @code{-file-list-exec-source-file} Command
32624 @findex -file-list-exec-source-file
32626 @subsubheading Synopsis
32629 -file-list-exec-source-file
32632 List the line number, the current source file, and the absolute path
32633 to the current source file for the current executable. The macro
32634 information field has a value of @samp{1} or @samp{0} depending on
32635 whether or not the file includes preprocessor macro information.
32637 @subsubheading @value{GDBN} Command
32639 The @value{GDBN} equivalent is @samp{info source}
32641 @subsubheading Example
32645 123-file-list-exec-source-file
32646 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32651 @subheading The @code{-file-list-exec-source-files} Command
32652 @findex -file-list-exec-source-files
32654 @subsubheading Synopsis
32657 -file-list-exec-source-files
32660 List the source files for the current executable.
32662 It will always output both the filename and fullname (absolute file
32663 name) of a source file.
32665 @subsubheading @value{GDBN} Command
32667 The @value{GDBN} equivalent is @samp{info sources}.
32668 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32670 @subsubheading Example
32673 -file-list-exec-source-files
32675 @{file=foo.c,fullname=/home/foo.c@},
32676 @{file=/home/bar.c,fullname=/home/bar.c@},
32677 @{file=gdb_could_not_find_fullpath.c@}]
32682 @subheading The @code{-file-list-shared-libraries} Command
32683 @findex -file-list-shared-libraries
32685 @subsubheading Synopsis
32688 -file-list-shared-libraries
32691 List the shared libraries in the program.
32693 @subsubheading @value{GDBN} Command
32695 The corresponding @value{GDBN} command is @samp{info shared}.
32697 @subsubheading Example
32701 @subheading The @code{-file-list-symbol-files} Command
32702 @findex -file-list-symbol-files
32704 @subsubheading Synopsis
32707 -file-list-symbol-files
32712 @subsubheading @value{GDBN} Command
32714 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32716 @subsubheading Example
32721 @subheading The @code{-file-symbol-file} Command
32722 @findex -file-symbol-file
32724 @subsubheading Synopsis
32727 -file-symbol-file @var{file}
32730 Read symbol table info from the specified @var{file} argument. When
32731 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32732 produced, except for a completion notification.
32734 @subsubheading @value{GDBN} Command
32736 The corresponding @value{GDBN} command is @samp{symbol-file}.
32738 @subsubheading Example
32742 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32749 @node GDB/MI Memory Overlay Commands
32750 @section @sc{gdb/mi} Memory Overlay Commands
32752 The memory overlay commands are not implemented.
32754 @c @subheading -overlay-auto
32756 @c @subheading -overlay-list-mapping-state
32758 @c @subheading -overlay-list-overlays
32760 @c @subheading -overlay-map
32762 @c @subheading -overlay-off
32764 @c @subheading -overlay-on
32766 @c @subheading -overlay-unmap
32768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32769 @node GDB/MI Signal Handling Commands
32770 @section @sc{gdb/mi} Signal Handling Commands
32772 Signal handling commands are not implemented.
32774 @c @subheading -signal-handle
32776 @c @subheading -signal-list-handle-actions
32778 @c @subheading -signal-list-signal-types
32782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32783 @node GDB/MI Target Manipulation
32784 @section @sc{gdb/mi} Target Manipulation Commands
32787 @subheading The @code{-target-attach} Command
32788 @findex -target-attach
32790 @subsubheading Synopsis
32793 -target-attach @var{pid} | @var{gid} | @var{file}
32796 Attach to a process @var{pid} or a file @var{file} outside of
32797 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32798 group, the id previously returned by
32799 @samp{-list-thread-groups --available} must be used.
32801 @subsubheading @value{GDBN} Command
32803 The corresponding @value{GDBN} command is @samp{attach}.
32805 @subsubheading Example
32809 =thread-created,id="1"
32810 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32816 @subheading The @code{-target-compare-sections} Command
32817 @findex -target-compare-sections
32819 @subsubheading Synopsis
32822 -target-compare-sections [ @var{section} ]
32825 Compare data of section @var{section} on target to the exec file.
32826 Without the argument, all sections are compared.
32828 @subsubheading @value{GDBN} Command
32830 The @value{GDBN} equivalent is @samp{compare-sections}.
32832 @subsubheading Example
32837 @subheading The @code{-target-detach} Command
32838 @findex -target-detach
32840 @subsubheading Synopsis
32843 -target-detach [ @var{pid} | @var{gid} ]
32846 Detach from the remote target which normally resumes its execution.
32847 If either @var{pid} or @var{gid} is specified, detaches from either
32848 the specified process, or specified thread group. There's no output.
32850 @subsubheading @value{GDBN} Command
32852 The corresponding @value{GDBN} command is @samp{detach}.
32854 @subsubheading Example
32864 @subheading The @code{-target-disconnect} Command
32865 @findex -target-disconnect
32867 @subsubheading Synopsis
32873 Disconnect from the remote target. There's no output and the target is
32874 generally not resumed.
32876 @subsubheading @value{GDBN} Command
32878 The corresponding @value{GDBN} command is @samp{disconnect}.
32880 @subsubheading Example
32890 @subheading The @code{-target-download} Command
32891 @findex -target-download
32893 @subsubheading Synopsis
32899 Loads the executable onto the remote target.
32900 It prints out an update message every half second, which includes the fields:
32904 The name of the section.
32906 The size of what has been sent so far for that section.
32908 The size of the section.
32910 The total size of what was sent so far (the current and the previous sections).
32912 The size of the overall executable to download.
32916 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32917 @sc{gdb/mi} Output Syntax}).
32919 In addition, it prints the name and size of the sections, as they are
32920 downloaded. These messages include the following fields:
32924 The name of the section.
32926 The size of the section.
32928 The size of the overall executable to download.
32932 At the end, a summary is printed.
32934 @subsubheading @value{GDBN} Command
32936 The corresponding @value{GDBN} command is @samp{load}.
32938 @subsubheading Example
32940 Note: each status message appears on a single line. Here the messages
32941 have been broken down so that they can fit onto a page.
32946 +download,@{section=".text",section-size="6668",total-size="9880"@}
32947 +download,@{section=".text",section-sent="512",section-size="6668",
32948 total-sent="512",total-size="9880"@}
32949 +download,@{section=".text",section-sent="1024",section-size="6668",
32950 total-sent="1024",total-size="9880"@}
32951 +download,@{section=".text",section-sent="1536",section-size="6668",
32952 total-sent="1536",total-size="9880"@}
32953 +download,@{section=".text",section-sent="2048",section-size="6668",
32954 total-sent="2048",total-size="9880"@}
32955 +download,@{section=".text",section-sent="2560",section-size="6668",
32956 total-sent="2560",total-size="9880"@}
32957 +download,@{section=".text",section-sent="3072",section-size="6668",
32958 total-sent="3072",total-size="9880"@}
32959 +download,@{section=".text",section-sent="3584",section-size="6668",
32960 total-sent="3584",total-size="9880"@}
32961 +download,@{section=".text",section-sent="4096",section-size="6668",
32962 total-sent="4096",total-size="9880"@}
32963 +download,@{section=".text",section-sent="4608",section-size="6668",
32964 total-sent="4608",total-size="9880"@}
32965 +download,@{section=".text",section-sent="5120",section-size="6668",
32966 total-sent="5120",total-size="9880"@}
32967 +download,@{section=".text",section-sent="5632",section-size="6668",
32968 total-sent="5632",total-size="9880"@}
32969 +download,@{section=".text",section-sent="6144",section-size="6668",
32970 total-sent="6144",total-size="9880"@}
32971 +download,@{section=".text",section-sent="6656",section-size="6668",
32972 total-sent="6656",total-size="9880"@}
32973 +download,@{section=".init",section-size="28",total-size="9880"@}
32974 +download,@{section=".fini",section-size="28",total-size="9880"@}
32975 +download,@{section=".data",section-size="3156",total-size="9880"@}
32976 +download,@{section=".data",section-sent="512",section-size="3156",
32977 total-sent="7236",total-size="9880"@}
32978 +download,@{section=".data",section-sent="1024",section-size="3156",
32979 total-sent="7748",total-size="9880"@}
32980 +download,@{section=".data",section-sent="1536",section-size="3156",
32981 total-sent="8260",total-size="9880"@}
32982 +download,@{section=".data",section-sent="2048",section-size="3156",
32983 total-sent="8772",total-size="9880"@}
32984 +download,@{section=".data",section-sent="2560",section-size="3156",
32985 total-sent="9284",total-size="9880"@}
32986 +download,@{section=".data",section-sent="3072",section-size="3156",
32987 total-sent="9796",total-size="9880"@}
32988 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32995 @subheading The @code{-target-exec-status} Command
32996 @findex -target-exec-status
32998 @subsubheading Synopsis
33001 -target-exec-status
33004 Provide information on the state of the target (whether it is running or
33005 not, for instance).
33007 @subsubheading @value{GDBN} Command
33009 There's no equivalent @value{GDBN} command.
33011 @subsubheading Example
33015 @subheading The @code{-target-list-available-targets} Command
33016 @findex -target-list-available-targets
33018 @subsubheading Synopsis
33021 -target-list-available-targets
33024 List the possible targets to connect to.
33026 @subsubheading @value{GDBN} Command
33028 The corresponding @value{GDBN} command is @samp{help target}.
33030 @subsubheading Example
33034 @subheading The @code{-target-list-current-targets} Command
33035 @findex -target-list-current-targets
33037 @subsubheading Synopsis
33040 -target-list-current-targets
33043 Describe the current target.
33045 @subsubheading @value{GDBN} Command
33047 The corresponding information is printed by @samp{info file} (among
33050 @subsubheading Example
33054 @subheading The @code{-target-list-parameters} Command
33055 @findex -target-list-parameters
33057 @subsubheading Synopsis
33060 -target-list-parameters
33066 @subsubheading @value{GDBN} Command
33070 @subsubheading Example
33074 @subheading The @code{-target-select} Command
33075 @findex -target-select
33077 @subsubheading Synopsis
33080 -target-select @var{type} @var{parameters @dots{}}
33083 Connect @value{GDBN} to the remote target. This command takes two args:
33087 The type of target, for instance @samp{remote}, etc.
33088 @item @var{parameters}
33089 Device names, host names and the like. @xref{Target Commands, ,
33090 Commands for Managing Targets}, for more details.
33093 The output is a connection notification, followed by the address at
33094 which the target program is, in the following form:
33097 ^connected,addr="@var{address}",func="@var{function name}",
33098 args=[@var{arg list}]
33101 @subsubheading @value{GDBN} Command
33103 The corresponding @value{GDBN} command is @samp{target}.
33105 @subsubheading Example
33109 -target-select remote /dev/ttya
33110 ^connected,addr="0xfe00a300",func="??",args=[]
33114 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33115 @node GDB/MI File Transfer Commands
33116 @section @sc{gdb/mi} File Transfer Commands
33119 @subheading The @code{-target-file-put} Command
33120 @findex -target-file-put
33122 @subsubheading Synopsis
33125 -target-file-put @var{hostfile} @var{targetfile}
33128 Copy file @var{hostfile} from the host system (the machine running
33129 @value{GDBN}) to @var{targetfile} on the target system.
33131 @subsubheading @value{GDBN} Command
33133 The corresponding @value{GDBN} command is @samp{remote put}.
33135 @subsubheading Example
33139 -target-file-put localfile remotefile
33145 @subheading The @code{-target-file-get} Command
33146 @findex -target-file-get
33148 @subsubheading Synopsis
33151 -target-file-get @var{targetfile} @var{hostfile}
33154 Copy file @var{targetfile} from the target system to @var{hostfile}
33155 on the host system.
33157 @subsubheading @value{GDBN} Command
33159 The corresponding @value{GDBN} command is @samp{remote get}.
33161 @subsubheading Example
33165 -target-file-get remotefile localfile
33171 @subheading The @code{-target-file-delete} Command
33172 @findex -target-file-delete
33174 @subsubheading Synopsis
33177 -target-file-delete @var{targetfile}
33180 Delete @var{targetfile} from the target system.
33182 @subsubheading @value{GDBN} Command
33184 The corresponding @value{GDBN} command is @samp{remote delete}.
33186 @subsubheading Example
33190 -target-file-delete remotefile
33196 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33197 @node GDB/MI Miscellaneous Commands
33198 @section Miscellaneous @sc{gdb/mi} Commands
33200 @c @subheading -gdb-complete
33202 @subheading The @code{-gdb-exit} Command
33205 @subsubheading Synopsis
33211 Exit @value{GDBN} immediately.
33213 @subsubheading @value{GDBN} Command
33215 Approximately corresponds to @samp{quit}.
33217 @subsubheading Example
33227 @subheading The @code{-exec-abort} Command
33228 @findex -exec-abort
33230 @subsubheading Synopsis
33236 Kill the inferior running program.
33238 @subsubheading @value{GDBN} Command
33240 The corresponding @value{GDBN} command is @samp{kill}.
33242 @subsubheading Example
33247 @subheading The @code{-gdb-set} Command
33250 @subsubheading Synopsis
33256 Set an internal @value{GDBN} variable.
33257 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33259 @subsubheading @value{GDBN} Command
33261 The corresponding @value{GDBN} command is @samp{set}.
33263 @subsubheading Example
33273 @subheading The @code{-gdb-show} Command
33276 @subsubheading Synopsis
33282 Show the current value of a @value{GDBN} variable.
33284 @subsubheading @value{GDBN} Command
33286 The corresponding @value{GDBN} command is @samp{show}.
33288 @subsubheading Example
33297 @c @subheading -gdb-source
33300 @subheading The @code{-gdb-version} Command
33301 @findex -gdb-version
33303 @subsubheading Synopsis
33309 Show version information for @value{GDBN}. Used mostly in testing.
33311 @subsubheading @value{GDBN} Command
33313 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33314 default shows this information when you start an interactive session.
33316 @subsubheading Example
33318 @c This example modifies the actual output from GDB to avoid overfull
33324 ~Copyright 2000 Free Software Foundation, Inc.
33325 ~GDB is free software, covered by the GNU General Public License, and
33326 ~you are welcome to change it and/or distribute copies of it under
33327 ~ certain conditions.
33328 ~Type "show copying" to see the conditions.
33329 ~There is absolutely no warranty for GDB. Type "show warranty" for
33331 ~This GDB was configured as
33332 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33337 @subheading The @code{-list-features} Command
33338 @findex -list-features
33340 Returns a list of particular features of the MI protocol that
33341 this version of gdb implements. A feature can be a command,
33342 or a new field in an output of some command, or even an
33343 important bugfix. While a frontend can sometimes detect presence
33344 of a feature at runtime, it is easier to perform detection at debugger
33347 The command returns a list of strings, with each string naming an
33348 available feature. Each returned string is just a name, it does not
33349 have any internal structure. The list of possible feature names
33355 (gdb) -list-features
33356 ^done,result=["feature1","feature2"]
33359 The current list of features is:
33362 @item frozen-varobjs
33363 Indicates support for the @code{-var-set-frozen} command, as well
33364 as possible presense of the @code{frozen} field in the output
33365 of @code{-varobj-create}.
33366 @item pending-breakpoints
33367 Indicates support for the @option{-f} option to the @code{-break-insert}
33370 Indicates Python scripting support, Python-based
33371 pretty-printing commands, and possible presence of the
33372 @samp{display_hint} field in the output of @code{-var-list-children}
33374 Indicates support for the @code{-thread-info} command.
33375 @item data-read-memory-bytes
33376 Indicates support for the @code{-data-read-memory-bytes} and the
33377 @code{-data-write-memory-bytes} commands.
33378 @item breakpoint-notifications
33379 Indicates that changes to breakpoints and breakpoints created via the
33380 CLI will be announced via async records.
33381 @item ada-task-info
33382 Indicates support for the @code{-ada-task-info} command.
33385 @subheading The @code{-list-target-features} Command
33386 @findex -list-target-features
33388 Returns a list of particular features that are supported by the
33389 target. Those features affect the permitted MI commands, but
33390 unlike the features reported by the @code{-list-features} command, the
33391 features depend on which target GDB is using at the moment. Whenever
33392 a target can change, due to commands such as @code{-target-select},
33393 @code{-target-attach} or @code{-exec-run}, the list of target features
33394 may change, and the frontend should obtain it again.
33398 (gdb) -list-features
33399 ^done,result=["async"]
33402 The current list of features is:
33406 Indicates that the target is capable of asynchronous command
33407 execution, which means that @value{GDBN} will accept further commands
33408 while the target is running.
33411 Indicates that the target is capable of reverse execution.
33412 @xref{Reverse Execution}, for more information.
33416 @subheading The @code{-list-thread-groups} Command
33417 @findex -list-thread-groups
33419 @subheading Synopsis
33422 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33425 Lists thread groups (@pxref{Thread groups}). When a single thread
33426 group is passed as the argument, lists the children of that group.
33427 When several thread group are passed, lists information about those
33428 thread groups. Without any parameters, lists information about all
33429 top-level thread groups.
33431 Normally, thread groups that are being debugged are reported.
33432 With the @samp{--available} option, @value{GDBN} reports thread groups
33433 available on the target.
33435 The output of this command may have either a @samp{threads} result or
33436 a @samp{groups} result. The @samp{thread} result has a list of tuples
33437 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33438 Information}). The @samp{groups} result has a list of tuples as value,
33439 each tuple describing a thread group. If top-level groups are
33440 requested (that is, no parameter is passed), or when several groups
33441 are passed, the output always has a @samp{groups} result. The format
33442 of the @samp{group} result is described below.
33444 To reduce the number of roundtrips it's possible to list thread groups
33445 together with their children, by passing the @samp{--recurse} option
33446 and the recursion depth. Presently, only recursion depth of 1 is
33447 permitted. If this option is present, then every reported thread group
33448 will also include its children, either as @samp{group} or
33449 @samp{threads} field.
33451 In general, any combination of option and parameters is permitted, with
33452 the following caveats:
33456 When a single thread group is passed, the output will typically
33457 be the @samp{threads} result. Because threads may not contain
33458 anything, the @samp{recurse} option will be ignored.
33461 When the @samp{--available} option is passed, limited information may
33462 be available. In particular, the list of threads of a process might
33463 be inaccessible. Further, specifying specific thread groups might
33464 not give any performance advantage over listing all thread groups.
33465 The frontend should assume that @samp{-list-thread-groups --available}
33466 is always an expensive operation and cache the results.
33470 The @samp{groups} result is a list of tuples, where each tuple may
33471 have the following fields:
33475 Identifier of the thread group. This field is always present.
33476 The identifier is an opaque string; frontends should not try to
33477 convert it to an integer, even though it might look like one.
33480 The type of the thread group. At present, only @samp{process} is a
33484 The target-specific process identifier. This field is only present
33485 for thread groups of type @samp{process} and only if the process exists.
33488 The number of children this thread group has. This field may be
33489 absent for an available thread group.
33492 This field has a list of tuples as value, each tuple describing a
33493 thread. It may be present if the @samp{--recurse} option is
33494 specified, and it's actually possible to obtain the threads.
33497 This field is a list of integers, each identifying a core that one
33498 thread of the group is running on. This field may be absent if
33499 such information is not available.
33502 The name of the executable file that corresponds to this thread group.
33503 The field is only present for thread groups of type @samp{process},
33504 and only if there is a corresponding executable file.
33508 @subheading Example
33512 -list-thread-groups
33513 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33514 -list-thread-groups 17
33515 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33516 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33517 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33518 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33519 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33520 -list-thread-groups --available
33521 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33522 -list-thread-groups --available --recurse 1
33523 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33524 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33525 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33526 -list-thread-groups --available --recurse 1 17 18
33527 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33528 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33529 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33532 @subheading The @code{-info-os} Command
33535 @subsubheading Synopsis
33538 -info-os [ @var{type} ]
33541 If no argument is supplied, the command returns a table of available
33542 operating-system-specific information types. If one of these types is
33543 supplied as an argument @var{type}, then the command returns a table
33544 of data of that type.
33546 The types of information available depend on the target operating
33549 @subsubheading @value{GDBN} Command
33551 The corresponding @value{GDBN} command is @samp{info os}.
33553 @subsubheading Example
33555 When run on a @sc{gnu}/Linux system, the output will look something
33561 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33562 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33563 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33564 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33565 body=[item=@{col0="processes",col1="Listing of all processes",
33566 col2="Processes"@},
33567 item=@{col0="procgroups",col1="Listing of all process groups",
33568 col2="Process groups"@},
33569 item=@{col0="threads",col1="Listing of all threads",
33571 item=@{col0="files",col1="Listing of all file descriptors",
33572 col2="File descriptors"@},
33573 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33575 item=@{col0="shm",col1="Listing of all shared-memory regions",
33576 col2="Shared-memory regions"@},
33577 item=@{col0="semaphores",col1="Listing of all semaphores",
33578 col2="Semaphores"@},
33579 item=@{col0="msg",col1="Listing of all message queues",
33580 col2="Message queues"@},
33581 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33582 col2="Kernel modules"@}]@}
33585 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33586 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33587 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33588 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33589 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33590 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33591 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33592 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33594 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33595 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33599 (Note that the MI output here includes a @code{"Title"} column that
33600 does not appear in command-line @code{info os}; this column is useful
33601 for MI clients that want to enumerate the types of data, such as in a
33602 popup menu, but is needless clutter on the command line, and
33603 @code{info os} omits it.)
33605 @subheading The @code{-add-inferior} Command
33606 @findex -add-inferior
33608 @subheading Synopsis
33614 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33615 inferior is not associated with any executable. Such association may
33616 be established with the @samp{-file-exec-and-symbols} command
33617 (@pxref{GDB/MI File Commands}). The command response has a single
33618 field, @samp{thread-group}, whose value is the identifier of the
33619 thread group corresponding to the new inferior.
33621 @subheading Example
33626 ^done,thread-group="i3"
33629 @subheading The @code{-interpreter-exec} Command
33630 @findex -interpreter-exec
33632 @subheading Synopsis
33635 -interpreter-exec @var{interpreter} @var{command}
33637 @anchor{-interpreter-exec}
33639 Execute the specified @var{command} in the given @var{interpreter}.
33641 @subheading @value{GDBN} Command
33643 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33645 @subheading Example
33649 -interpreter-exec console "break main"
33650 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33651 &"During symbol reading, bad structure-type format.\n"
33652 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33657 @subheading The @code{-inferior-tty-set} Command
33658 @findex -inferior-tty-set
33660 @subheading Synopsis
33663 -inferior-tty-set /dev/pts/1
33666 Set terminal for future runs of the program being debugged.
33668 @subheading @value{GDBN} Command
33670 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33672 @subheading Example
33676 -inferior-tty-set /dev/pts/1
33681 @subheading The @code{-inferior-tty-show} Command
33682 @findex -inferior-tty-show
33684 @subheading Synopsis
33690 Show terminal for future runs of program being debugged.
33692 @subheading @value{GDBN} Command
33694 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33696 @subheading Example
33700 -inferior-tty-set /dev/pts/1
33704 ^done,inferior_tty_terminal="/dev/pts/1"
33708 @subheading The @code{-enable-timings} Command
33709 @findex -enable-timings
33711 @subheading Synopsis
33714 -enable-timings [yes | no]
33717 Toggle the printing of the wallclock, user and system times for an MI
33718 command as a field in its output. This command is to help frontend
33719 developers optimize the performance of their code. No argument is
33720 equivalent to @samp{yes}.
33722 @subheading @value{GDBN} Command
33726 @subheading Example
33734 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33735 addr="0x080484ed",func="main",file="myprog.c",
33736 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33738 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33746 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33747 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33748 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33749 fullname="/home/nickrob/myprog.c",line="73"@}
33754 @chapter @value{GDBN} Annotations
33756 This chapter describes annotations in @value{GDBN}. Annotations were
33757 designed to interface @value{GDBN} to graphical user interfaces or other
33758 similar programs which want to interact with @value{GDBN} at a
33759 relatively high level.
33761 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33765 This is Edition @value{EDITION}, @value{DATE}.
33769 * Annotations Overview:: What annotations are; the general syntax.
33770 * Server Prefix:: Issuing a command without affecting user state.
33771 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33772 * Errors:: Annotations for error messages.
33773 * Invalidation:: Some annotations describe things now invalid.
33774 * Annotations for Running::
33775 Whether the program is running, how it stopped, etc.
33776 * Source Annotations:: Annotations describing source code.
33779 @node Annotations Overview
33780 @section What is an Annotation?
33781 @cindex annotations
33783 Annotations start with a newline character, two @samp{control-z}
33784 characters, and the name of the annotation. If there is no additional
33785 information associated with this annotation, the name of the annotation
33786 is followed immediately by a newline. If there is additional
33787 information, the name of the annotation is followed by a space, the
33788 additional information, and a newline. The additional information
33789 cannot contain newline characters.
33791 Any output not beginning with a newline and two @samp{control-z}
33792 characters denotes literal output from @value{GDBN}. Currently there is
33793 no need for @value{GDBN} to output a newline followed by two
33794 @samp{control-z} characters, but if there was such a need, the
33795 annotations could be extended with an @samp{escape} annotation which
33796 means those three characters as output.
33798 The annotation @var{level}, which is specified using the
33799 @option{--annotate} command line option (@pxref{Mode Options}), controls
33800 how much information @value{GDBN} prints together with its prompt,
33801 values of expressions, source lines, and other types of output. Level 0
33802 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33803 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33804 for programs that control @value{GDBN}, and level 2 annotations have
33805 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33806 Interface, annotate, GDB's Obsolete Annotations}).
33809 @kindex set annotate
33810 @item set annotate @var{level}
33811 The @value{GDBN} command @code{set annotate} sets the level of
33812 annotations to the specified @var{level}.
33814 @item show annotate
33815 @kindex show annotate
33816 Show the current annotation level.
33819 This chapter describes level 3 annotations.
33821 A simple example of starting up @value{GDBN} with annotations is:
33824 $ @kbd{gdb --annotate=3}
33826 Copyright 2003 Free Software Foundation, Inc.
33827 GDB is free software, covered by the GNU General Public License,
33828 and you are welcome to change it and/or distribute copies of it
33829 under certain conditions.
33830 Type "show copying" to see the conditions.
33831 There is absolutely no warranty for GDB. Type "show warranty"
33833 This GDB was configured as "i386-pc-linux-gnu"
33844 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33845 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33846 denotes a @samp{control-z} character) are annotations; the rest is
33847 output from @value{GDBN}.
33849 @node Server Prefix
33850 @section The Server Prefix
33851 @cindex server prefix
33853 If you prefix a command with @samp{server } then it will not affect
33854 the command history, nor will it affect @value{GDBN}'s notion of which
33855 command to repeat if @key{RET} is pressed on a line by itself. This
33856 means that commands can be run behind a user's back by a front-end in
33857 a transparent manner.
33859 The @code{server } prefix does not affect the recording of values into
33860 the value history; to print a value without recording it into the
33861 value history, use the @code{output} command instead of the
33862 @code{print} command.
33864 Using this prefix also disables confirmation requests
33865 (@pxref{confirmation requests}).
33868 @section Annotation for @value{GDBN} Input
33870 @cindex annotations for prompts
33871 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33872 to know when to send output, when the output from a given command is
33875 Different kinds of input each have a different @dfn{input type}. Each
33876 input type has three annotations: a @code{pre-} annotation, which
33877 denotes the beginning of any prompt which is being output, a plain
33878 annotation, which denotes the end of the prompt, and then a @code{post-}
33879 annotation which denotes the end of any echo which may (or may not) be
33880 associated with the input. For example, the @code{prompt} input type
33881 features the following annotations:
33889 The input types are
33892 @findex pre-prompt annotation
33893 @findex prompt annotation
33894 @findex post-prompt annotation
33896 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33898 @findex pre-commands annotation
33899 @findex commands annotation
33900 @findex post-commands annotation
33902 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33903 command. The annotations are repeated for each command which is input.
33905 @findex pre-overload-choice annotation
33906 @findex overload-choice annotation
33907 @findex post-overload-choice annotation
33908 @item overload-choice
33909 When @value{GDBN} wants the user to select between various overloaded functions.
33911 @findex pre-query annotation
33912 @findex query annotation
33913 @findex post-query annotation
33915 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33917 @findex pre-prompt-for-continue annotation
33918 @findex prompt-for-continue annotation
33919 @findex post-prompt-for-continue annotation
33920 @item prompt-for-continue
33921 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33922 expect this to work well; instead use @code{set height 0} to disable
33923 prompting. This is because the counting of lines is buggy in the
33924 presence of annotations.
33929 @cindex annotations for errors, warnings and interrupts
33931 @findex quit annotation
33936 This annotation occurs right before @value{GDBN} responds to an interrupt.
33938 @findex error annotation
33943 This annotation occurs right before @value{GDBN} responds to an error.
33945 Quit and error annotations indicate that any annotations which @value{GDBN} was
33946 in the middle of may end abruptly. For example, if a
33947 @code{value-history-begin} annotation is followed by a @code{error}, one
33948 cannot expect to receive the matching @code{value-history-end}. One
33949 cannot expect not to receive it either, however; an error annotation
33950 does not necessarily mean that @value{GDBN} is immediately returning all the way
33953 @findex error-begin annotation
33954 A quit or error annotation may be preceded by
33960 Any output between that and the quit or error annotation is the error
33963 Warning messages are not yet annotated.
33964 @c If we want to change that, need to fix warning(), type_error(),
33965 @c range_error(), and possibly other places.
33968 @section Invalidation Notices
33970 @cindex annotations for invalidation messages
33971 The following annotations say that certain pieces of state may have
33975 @findex frames-invalid annotation
33976 @item ^Z^Zframes-invalid
33978 The frames (for example, output from the @code{backtrace} command) may
33981 @findex breakpoints-invalid annotation
33982 @item ^Z^Zbreakpoints-invalid
33984 The breakpoints may have changed. For example, the user just added or
33985 deleted a breakpoint.
33988 @node Annotations for Running
33989 @section Running the Program
33990 @cindex annotations for running programs
33992 @findex starting annotation
33993 @findex stopping annotation
33994 When the program starts executing due to a @value{GDBN} command such as
33995 @code{step} or @code{continue},
34001 is output. When the program stops,
34007 is output. Before the @code{stopped} annotation, a variety of
34008 annotations describe how the program stopped.
34011 @findex exited annotation
34012 @item ^Z^Zexited @var{exit-status}
34013 The program exited, and @var{exit-status} is the exit status (zero for
34014 successful exit, otherwise nonzero).
34016 @findex signalled annotation
34017 @findex signal-name annotation
34018 @findex signal-name-end annotation
34019 @findex signal-string annotation
34020 @findex signal-string-end annotation
34021 @item ^Z^Zsignalled
34022 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34023 annotation continues:
34029 ^Z^Zsignal-name-end
34033 ^Z^Zsignal-string-end
34038 where @var{name} is the name of the signal, such as @code{SIGILL} or
34039 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34040 as @code{Illegal Instruction} or @code{Segmentation fault}.
34041 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34042 user's benefit and have no particular format.
34044 @findex signal annotation
34046 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34047 just saying that the program received the signal, not that it was
34048 terminated with it.
34050 @findex breakpoint annotation
34051 @item ^Z^Zbreakpoint @var{number}
34052 The program hit breakpoint number @var{number}.
34054 @findex watchpoint annotation
34055 @item ^Z^Zwatchpoint @var{number}
34056 The program hit watchpoint number @var{number}.
34059 @node Source Annotations
34060 @section Displaying Source
34061 @cindex annotations for source display
34063 @findex source annotation
34064 The following annotation is used instead of displaying source code:
34067 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34070 where @var{filename} is an absolute file name indicating which source
34071 file, @var{line} is the line number within that file (where 1 is the
34072 first line in the file), @var{character} is the character position
34073 within the file (where 0 is the first character in the file) (for most
34074 debug formats this will necessarily point to the beginning of a line),
34075 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34076 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34077 @var{addr} is the address in the target program associated with the
34078 source which is being displayed. @var{addr} is in the form @samp{0x}
34079 followed by one or more lowercase hex digits (note that this does not
34080 depend on the language).
34082 @node JIT Interface
34083 @chapter JIT Compilation Interface
34084 @cindex just-in-time compilation
34085 @cindex JIT compilation interface
34087 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34088 interface. A JIT compiler is a program or library that generates native
34089 executable code at runtime and executes it, usually in order to achieve good
34090 performance while maintaining platform independence.
34092 Programs that use JIT compilation are normally difficult to debug because
34093 portions of their code are generated at runtime, instead of being loaded from
34094 object files, which is where @value{GDBN} normally finds the program's symbols
34095 and debug information. In order to debug programs that use JIT compilation,
34096 @value{GDBN} has an interface that allows the program to register in-memory
34097 symbol files with @value{GDBN} at runtime.
34099 If you are using @value{GDBN} to debug a program that uses this interface, then
34100 it should work transparently so long as you have not stripped the binary. If
34101 you are developing a JIT compiler, then the interface is documented in the rest
34102 of this chapter. At this time, the only known client of this interface is the
34105 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34106 JIT compiler communicates with @value{GDBN} by writing data into a global
34107 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34108 attaches, it reads a linked list of symbol files from the global variable to
34109 find existing code, and puts a breakpoint in the function so that it can find
34110 out about additional code.
34113 * Declarations:: Relevant C struct declarations
34114 * Registering Code:: Steps to register code
34115 * Unregistering Code:: Steps to unregister code
34116 * Custom Debug Info:: Emit debug information in a custom format
34120 @section JIT Declarations
34122 These are the relevant struct declarations that a C program should include to
34123 implement the interface:
34133 struct jit_code_entry
34135 struct jit_code_entry *next_entry;
34136 struct jit_code_entry *prev_entry;
34137 const char *symfile_addr;
34138 uint64_t symfile_size;
34141 struct jit_descriptor
34144 /* This type should be jit_actions_t, but we use uint32_t
34145 to be explicit about the bitwidth. */
34146 uint32_t action_flag;
34147 struct jit_code_entry *relevant_entry;
34148 struct jit_code_entry *first_entry;
34151 /* GDB puts a breakpoint in this function. */
34152 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34154 /* Make sure to specify the version statically, because the
34155 debugger may check the version before we can set it. */
34156 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34159 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34160 modifications to this global data properly, which can easily be done by putting
34161 a global mutex around modifications to these structures.
34163 @node Registering Code
34164 @section Registering Code
34166 To register code with @value{GDBN}, the JIT should follow this protocol:
34170 Generate an object file in memory with symbols and other desired debug
34171 information. The file must include the virtual addresses of the sections.
34174 Create a code entry for the file, which gives the start and size of the symbol
34178 Add it to the linked list in the JIT descriptor.
34181 Point the relevant_entry field of the descriptor at the entry.
34184 Set @code{action_flag} to @code{JIT_REGISTER} and call
34185 @code{__jit_debug_register_code}.
34188 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34189 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34190 new code. However, the linked list must still be maintained in order to allow
34191 @value{GDBN} to attach to a running process and still find the symbol files.
34193 @node Unregistering Code
34194 @section Unregistering Code
34196 If code is freed, then the JIT should use the following protocol:
34200 Remove the code entry corresponding to the code from the linked list.
34203 Point the @code{relevant_entry} field of the descriptor at the code entry.
34206 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34207 @code{__jit_debug_register_code}.
34210 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34211 and the JIT will leak the memory used for the associated symbol files.
34213 @node Custom Debug Info
34214 @section Custom Debug Info
34215 @cindex custom JIT debug info
34216 @cindex JIT debug info reader
34218 Generating debug information in platform-native file formats (like ELF
34219 or COFF) may be an overkill for JIT compilers; especially if all the
34220 debug info is used for is displaying a meaningful backtrace. The
34221 issue can be resolved by having the JIT writers decide on a debug info
34222 format and also provide a reader that parses the debug info generated
34223 by the JIT compiler. This section gives a brief overview on writing
34224 such a parser. More specific details can be found in the source file
34225 @file{gdb/jit-reader.in}, which is also installed as a header at
34226 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34228 The reader is implemented as a shared object (so this functionality is
34229 not available on platforms which don't allow loading shared objects at
34230 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34231 @code{jit-reader-unload} are provided, to be used to load and unload
34232 the readers from a preconfigured directory. Once loaded, the shared
34233 object is used the parse the debug information emitted by the JIT
34237 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34238 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34241 @node Using JIT Debug Info Readers
34242 @subsection Using JIT Debug Info Readers
34243 @kindex jit-reader-load
34244 @kindex jit-reader-unload
34246 Readers can be loaded and unloaded using the @code{jit-reader-load}
34247 and @code{jit-reader-unload} commands.
34250 @item jit-reader-load @var{reader}
34251 Load the JIT reader named @var{reader}. @var{reader} is a shared
34252 object specified as either an absolute or a relative file name. In
34253 the latter case, @value{GDBN} will try to load the reader from a
34254 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34255 system (here @var{libdir} is the system library directory, often
34256 @file{/usr/local/lib}).
34258 Only one reader can be active at a time; trying to load a second
34259 reader when one is already loaded will result in @value{GDBN}
34260 reporting an error. A new JIT reader can be loaded by first unloading
34261 the current one using @code{jit-reader-unload} and then invoking
34262 @code{jit-reader-load}.
34264 @item jit-reader-unload
34265 Unload the currently loaded JIT reader.
34269 @node Writing JIT Debug Info Readers
34270 @subsection Writing JIT Debug Info Readers
34271 @cindex writing JIT debug info readers
34273 As mentioned, a reader is essentially a shared object conforming to a
34274 certain ABI. This ABI is described in @file{jit-reader.h}.
34276 @file{jit-reader.h} defines the structures, macros and functions
34277 required to write a reader. It is installed (along with
34278 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34279 the system include directory.
34281 Readers need to be released under a GPL compatible license. A reader
34282 can be declared as released under such a license by placing the macro
34283 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34285 The entry point for readers is the symbol @code{gdb_init_reader},
34286 which is expected to be a function with the prototype
34288 @findex gdb_init_reader
34290 extern struct gdb_reader_funcs *gdb_init_reader (void);
34293 @cindex @code{struct gdb_reader_funcs}
34295 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34296 functions. These functions are executed to read the debug info
34297 generated by the JIT compiler (@code{read}), to unwind stack frames
34298 (@code{unwind}) and to create canonical frame IDs
34299 (@code{get_Frame_id}). It also has a callback that is called when the
34300 reader is being unloaded (@code{destroy}). The struct looks like this
34303 struct gdb_reader_funcs
34305 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34306 int reader_version;
34308 /* For use by the reader. */
34311 gdb_read_debug_info *read;
34312 gdb_unwind_frame *unwind;
34313 gdb_get_frame_id *get_frame_id;
34314 gdb_destroy_reader *destroy;
34318 @cindex @code{struct gdb_symbol_callbacks}
34319 @cindex @code{struct gdb_unwind_callbacks}
34321 The callbacks are provided with another set of callbacks by
34322 @value{GDBN} to do their job. For @code{read}, these callbacks are
34323 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34324 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34325 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34326 files and new symbol tables inside those object files. @code{struct
34327 gdb_unwind_callbacks} has callbacks to read registers off the current
34328 frame and to write out the values of the registers in the previous
34329 frame. Both have a callback (@code{target_read}) to read bytes off the
34330 target's address space.
34332 @node In-Process Agent
34333 @chapter In-Process Agent
34334 @cindex debugging agent
34335 The traditional debugging model is conceptually low-speed, but works fine,
34336 because most bugs can be reproduced in debugging-mode execution. However,
34337 as multi-core or many-core processors are becoming mainstream, and
34338 multi-threaded programs become more and more popular, there should be more
34339 and more bugs that only manifest themselves at normal-mode execution, for
34340 example, thread races, because debugger's interference with the program's
34341 timing may conceal the bugs. On the other hand, in some applications,
34342 it is not feasible for the debugger to interrupt the program's execution
34343 long enough for the developer to learn anything helpful about its behavior.
34344 If the program's correctness depends on its real-time behavior, delays
34345 introduced by a debugger might cause the program to fail, even when the
34346 code itself is correct. It is useful to be able to observe the program's
34347 behavior without interrupting it.
34349 Therefore, traditional debugging model is too intrusive to reproduce
34350 some bugs. In order to reduce the interference with the program, we can
34351 reduce the number of operations performed by debugger. The
34352 @dfn{In-Process Agent}, a shared library, is running within the same
34353 process with inferior, and is able to perform some debugging operations
34354 itself. As a result, debugger is only involved when necessary, and
34355 performance of debugging can be improved accordingly. Note that
34356 interference with program can be reduced but can't be removed completely,
34357 because the in-process agent will still stop or slow down the program.
34359 The in-process agent can interpret and execute Agent Expressions
34360 (@pxref{Agent Expressions}) during performing debugging operations. The
34361 agent expressions can be used for different purposes, such as collecting
34362 data in tracepoints, and condition evaluation in breakpoints.
34364 @anchor{Control Agent}
34365 You can control whether the in-process agent is used as an aid for
34366 debugging with the following commands:
34369 @kindex set agent on
34371 Causes the in-process agent to perform some operations on behalf of the
34372 debugger. Just which operations requested by the user will be done
34373 by the in-process agent depends on the its capabilities. For example,
34374 if you request to evaluate breakpoint conditions in the in-process agent,
34375 and the in-process agent has such capability as well, then breakpoint
34376 conditions will be evaluated in the in-process agent.
34378 @kindex set agent off
34379 @item set agent off
34380 Disables execution of debugging operations by the in-process agent. All
34381 of the operations will be performed by @value{GDBN}.
34385 Display the current setting of execution of debugging operations by
34386 the in-process agent.
34390 * In-Process Agent Protocol::
34393 @node In-Process Agent Protocol
34394 @section In-Process Agent Protocol
34395 @cindex in-process agent protocol
34397 The in-process agent is able to communicate with both @value{GDBN} and
34398 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34399 used for communications between @value{GDBN} or GDBserver and the IPA.
34400 In general, @value{GDBN} or GDBserver sends commands
34401 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34402 in-process agent replies back with the return result of the command, or
34403 some other information. The data sent to in-process agent is composed
34404 of primitive data types, such as 4-byte or 8-byte type, and composite
34405 types, which are called objects (@pxref{IPA Protocol Objects}).
34408 * IPA Protocol Objects::
34409 * IPA Protocol Commands::
34412 @node IPA Protocol Objects
34413 @subsection IPA Protocol Objects
34414 @cindex ipa protocol objects
34416 The commands sent to and results received from agent may contain some
34417 complex data types called @dfn{objects}.
34419 The in-process agent is running on the same machine with @value{GDBN}
34420 or GDBserver, so it doesn't have to handle as much differences between
34421 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34422 However, there are still some differences of two ends in two processes:
34426 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34427 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34429 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34430 GDBserver is compiled with one, and in-process agent is compiled with
34434 Here are the IPA Protocol Objects:
34438 agent expression object. It represents an agent expression
34439 (@pxref{Agent Expressions}).
34440 @anchor{agent expression object}
34442 tracepoint action object. It represents a tracepoint action
34443 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34444 memory, static trace data and to evaluate expression.
34445 @anchor{tracepoint action object}
34447 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34448 @anchor{tracepoint object}
34452 The following table describes important attributes of each IPA protocol
34455 @multitable @columnfractions .30 .20 .50
34456 @headitem Name @tab Size @tab Description
34457 @item @emph{agent expression object} @tab @tab
34458 @item length @tab 4 @tab length of bytes code
34459 @item byte code @tab @var{length} @tab contents of byte code
34460 @item @emph{tracepoint action for collecting memory} @tab @tab
34461 @item 'M' @tab 1 @tab type of tracepoint action
34462 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34463 address of the lowest byte to collect, otherwise @var{addr} is the offset
34464 of @var{basereg} for memory collecting.
34465 @item len @tab 8 @tab length of memory for collecting
34466 @item basereg @tab 4 @tab the register number containing the starting
34467 memory address for collecting.
34468 @item @emph{tracepoint action for collecting registers} @tab @tab
34469 @item 'R' @tab 1 @tab type of tracepoint action
34470 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34471 @item 'L' @tab 1 @tab type of tracepoint action
34472 @item @emph{tracepoint action for expression evaluation} @tab @tab
34473 @item 'X' @tab 1 @tab type of tracepoint action
34474 @item agent expression @tab length of @tab @ref{agent expression object}
34475 @item @emph{tracepoint object} @tab @tab
34476 @item number @tab 4 @tab number of tracepoint
34477 @item address @tab 8 @tab address of tracepoint inserted on
34478 @item type @tab 4 @tab type of tracepoint
34479 @item enabled @tab 1 @tab enable or disable of tracepoint
34480 @item step_count @tab 8 @tab step
34481 @item pass_count @tab 8 @tab pass
34482 @item numactions @tab 4 @tab number of tracepoint actions
34483 @item hit count @tab 8 @tab hit count
34484 @item trace frame usage @tab 8 @tab trace frame usage
34485 @item compiled_cond @tab 8 @tab compiled condition
34486 @item orig_size @tab 8 @tab orig size
34487 @item condition @tab 4 if condition is NULL otherwise length of
34488 @ref{agent expression object}
34489 @tab zero if condition is NULL, otherwise is
34490 @ref{agent expression object}
34491 @item actions @tab variable
34492 @tab numactions number of @ref{tracepoint action object}
34495 @node IPA Protocol Commands
34496 @subsection IPA Protocol Commands
34497 @cindex ipa protocol commands
34499 The spaces in each command are delimiters to ease reading this commands
34500 specification. They don't exist in real commands.
34504 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34505 Installs a new fast tracepoint described by @var{tracepoint_object}
34506 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34507 head of @dfn{jumppad}, which is used to jump to data collection routine
34512 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34513 @var{target_address} is address of tracepoint in the inferior.
34514 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34515 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34516 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34517 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34524 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34525 is about to kill inferiors.
34533 @item probe_marker_at:@var{address}
34534 Asks in-process agent to probe the marker at @var{address}.
34541 @item unprobe_marker_at:@var{address}
34542 Asks in-process agent to unprobe the marker at @var{address}.
34546 @chapter Reporting Bugs in @value{GDBN}
34547 @cindex bugs in @value{GDBN}
34548 @cindex reporting bugs in @value{GDBN}
34550 Your bug reports play an essential role in making @value{GDBN} reliable.
34552 Reporting a bug may help you by bringing a solution to your problem, or it
34553 may not. But in any case the principal function of a bug report is to help
34554 the entire community by making the next version of @value{GDBN} work better. Bug
34555 reports are your contribution to the maintenance of @value{GDBN}.
34557 In order for a bug report to serve its purpose, you must include the
34558 information that enables us to fix the bug.
34561 * Bug Criteria:: Have you found a bug?
34562 * Bug Reporting:: How to report bugs
34566 @section Have You Found a Bug?
34567 @cindex bug criteria
34569 If you are not sure whether you have found a bug, here are some guidelines:
34572 @cindex fatal signal
34573 @cindex debugger crash
34574 @cindex crash of debugger
34576 If the debugger gets a fatal signal, for any input whatever, that is a
34577 @value{GDBN} bug. Reliable debuggers never crash.
34579 @cindex error on valid input
34581 If @value{GDBN} produces an error message for valid input, that is a
34582 bug. (Note that if you're cross debugging, the problem may also be
34583 somewhere in the connection to the target.)
34585 @cindex invalid input
34587 If @value{GDBN} does not produce an error message for invalid input,
34588 that is a bug. However, you should note that your idea of
34589 ``invalid input'' might be our idea of ``an extension'' or ``support
34590 for traditional practice''.
34593 If you are an experienced user of debugging tools, your suggestions
34594 for improvement of @value{GDBN} are welcome in any case.
34597 @node Bug Reporting
34598 @section How to Report Bugs
34599 @cindex bug reports
34600 @cindex @value{GDBN} bugs, reporting
34602 A number of companies and individuals offer support for @sc{gnu} products.
34603 If you obtained @value{GDBN} from a support organization, we recommend you
34604 contact that organization first.
34606 You can find contact information for many support companies and
34607 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34609 @c should add a web page ref...
34612 @ifset BUGURL_DEFAULT
34613 In any event, we also recommend that you submit bug reports for
34614 @value{GDBN}. The preferred method is to submit them directly using
34615 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34616 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34619 @strong{Do not send bug reports to @samp{info-gdb}, or to
34620 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34621 not want to receive bug reports. Those that do have arranged to receive
34624 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34625 serves as a repeater. The mailing list and the newsgroup carry exactly
34626 the same messages. Often people think of posting bug reports to the
34627 newsgroup instead of mailing them. This appears to work, but it has one
34628 problem which can be crucial: a newsgroup posting often lacks a mail
34629 path back to the sender. Thus, if we need to ask for more information,
34630 we may be unable to reach you. For this reason, it is better to send
34631 bug reports to the mailing list.
34633 @ifclear BUGURL_DEFAULT
34634 In any event, we also recommend that you submit bug reports for
34635 @value{GDBN} to @value{BUGURL}.
34639 The fundamental principle of reporting bugs usefully is this:
34640 @strong{report all the facts}. If you are not sure whether to state a
34641 fact or leave it out, state it!
34643 Often people omit facts because they think they know what causes the
34644 problem and assume that some details do not matter. Thus, you might
34645 assume that the name of the variable you use in an example does not matter.
34646 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34647 stray memory reference which happens to fetch from the location where that
34648 name is stored in memory; perhaps, if the name were different, the contents
34649 of that location would fool the debugger into doing the right thing despite
34650 the bug. Play it safe and give a specific, complete example. That is the
34651 easiest thing for you to do, and the most helpful.
34653 Keep in mind that the purpose of a bug report is to enable us to fix the
34654 bug. It may be that the bug has been reported previously, but neither
34655 you nor we can know that unless your bug report is complete and
34658 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34659 bell?'' Those bug reports are useless, and we urge everyone to
34660 @emph{refuse to respond to them} except to chide the sender to report
34663 To enable us to fix the bug, you should include all these things:
34667 The version of @value{GDBN}. @value{GDBN} announces it if you start
34668 with no arguments; you can also print it at any time using @code{show
34671 Without this, we will not know whether there is any point in looking for
34672 the bug in the current version of @value{GDBN}.
34675 The type of machine you are using, and the operating system name and
34679 The details of the @value{GDBN} build-time configuration.
34680 @value{GDBN} shows these details if you invoke it with the
34681 @option{--configuration} command-line option, or if you type
34682 @code{show configuration} at @value{GDBN}'s prompt.
34685 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34686 ``@value{GCC}--2.8.1''.
34689 What compiler (and its version) was used to compile the program you are
34690 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34691 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34692 to get this information; for other compilers, see the documentation for
34696 The command arguments you gave the compiler to compile your example and
34697 observe the bug. For example, did you use @samp{-O}? To guarantee
34698 you will not omit something important, list them all. A copy of the
34699 Makefile (or the output from make) is sufficient.
34701 If we were to try to guess the arguments, we would probably guess wrong
34702 and then we might not encounter the bug.
34705 A complete input script, and all necessary source files, that will
34709 A description of what behavior you observe that you believe is
34710 incorrect. For example, ``It gets a fatal signal.''
34712 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34713 will certainly notice it. But if the bug is incorrect output, we might
34714 not notice unless it is glaringly wrong. You might as well not give us
34715 a chance to make a mistake.
34717 Even if the problem you experience is a fatal signal, you should still
34718 say so explicitly. Suppose something strange is going on, such as, your
34719 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34720 the C library on your system. (This has happened!) Your copy might
34721 crash and ours would not. If you told us to expect a crash, then when
34722 ours fails to crash, we would know that the bug was not happening for
34723 us. If you had not told us to expect a crash, then we would not be able
34724 to draw any conclusion from our observations.
34727 @cindex recording a session script
34728 To collect all this information, you can use a session recording program
34729 such as @command{script}, which is available on many Unix systems.
34730 Just run your @value{GDBN} session inside @command{script} and then
34731 include the @file{typescript} file with your bug report.
34733 Another way to record a @value{GDBN} session is to run @value{GDBN}
34734 inside Emacs and then save the entire buffer to a file.
34737 If you wish to suggest changes to the @value{GDBN} source, send us context
34738 diffs. If you even discuss something in the @value{GDBN} source, refer to
34739 it by context, not by line number.
34741 The line numbers in our development sources will not match those in your
34742 sources. Your line numbers would convey no useful information to us.
34746 Here are some things that are not necessary:
34750 A description of the envelope of the bug.
34752 Often people who encounter a bug spend a lot of time investigating
34753 which changes to the input file will make the bug go away and which
34754 changes will not affect it.
34756 This is often time consuming and not very useful, because the way we
34757 will find the bug is by running a single example under the debugger
34758 with breakpoints, not by pure deduction from a series of examples.
34759 We recommend that you save your time for something else.
34761 Of course, if you can find a simpler example to report @emph{instead}
34762 of the original one, that is a convenience for us. Errors in the
34763 output will be easier to spot, running under the debugger will take
34764 less time, and so on.
34766 However, simplification is not vital; if you do not want to do this,
34767 report the bug anyway and send us the entire test case you used.
34770 A patch for the bug.
34772 A patch for the bug does help us if it is a good one. But do not omit
34773 the necessary information, such as the test case, on the assumption that
34774 a patch is all we need. We might see problems with your patch and decide
34775 to fix the problem another way, or we might not understand it at all.
34777 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34778 construct an example that will make the program follow a certain path
34779 through the code. If you do not send us the example, we will not be able
34780 to construct one, so we will not be able to verify that the bug is fixed.
34782 And if we cannot understand what bug you are trying to fix, or why your
34783 patch should be an improvement, we will not install it. A test case will
34784 help us to understand.
34787 A guess about what the bug is or what it depends on.
34789 Such guesses are usually wrong. Even we cannot guess right about such
34790 things without first using the debugger to find the facts.
34793 @c The readline documentation is distributed with the readline code
34794 @c and consists of the two following files:
34797 @c Use -I with makeinfo to point to the appropriate directory,
34798 @c environment var TEXINPUTS with TeX.
34799 @ifclear SYSTEM_READLINE
34800 @include rluser.texi
34801 @include hsuser.texi
34805 @appendix In Memoriam
34807 The @value{GDBN} project mourns the loss of the following long-time
34812 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34813 to Free Software in general. Outside of @value{GDBN}, he was known in
34814 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34816 @item Michael Snyder
34817 Michael was one of the Global Maintainers of the @value{GDBN} project,
34818 with contributions recorded as early as 1996, until 2011. In addition
34819 to his day to day participation, he was a large driving force behind
34820 adding Reverse Debugging to @value{GDBN}.
34823 Beyond their technical contributions to the project, they were also
34824 enjoyable members of the Free Software Community. We will miss them.
34826 @node Formatting Documentation
34827 @appendix Formatting Documentation
34829 @cindex @value{GDBN} reference card
34830 @cindex reference card
34831 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34832 for printing with PostScript or Ghostscript, in the @file{gdb}
34833 subdirectory of the main source directory@footnote{In
34834 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34835 release.}. If you can use PostScript or Ghostscript with your printer,
34836 you can print the reference card immediately with @file{refcard.ps}.
34838 The release also includes the source for the reference card. You
34839 can format it, using @TeX{}, by typing:
34845 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34846 mode on US ``letter'' size paper;
34847 that is, on a sheet 11 inches wide by 8.5 inches
34848 high. You will need to specify this form of printing as an option to
34849 your @sc{dvi} output program.
34851 @cindex documentation
34853 All the documentation for @value{GDBN} comes as part of the machine-readable
34854 distribution. The documentation is written in Texinfo format, which is
34855 a documentation system that uses a single source file to produce both
34856 on-line information and a printed manual. You can use one of the Info
34857 formatting commands to create the on-line version of the documentation
34858 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34860 @value{GDBN} includes an already formatted copy of the on-line Info
34861 version of this manual in the @file{gdb} subdirectory. The main Info
34862 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34863 subordinate files matching @samp{gdb.info*} in the same directory. If
34864 necessary, you can print out these files, or read them with any editor;
34865 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34866 Emacs or the standalone @code{info} program, available as part of the
34867 @sc{gnu} Texinfo distribution.
34869 If you want to format these Info files yourself, you need one of the
34870 Info formatting programs, such as @code{texinfo-format-buffer} or
34873 If you have @code{makeinfo} installed, and are in the top level
34874 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34875 version @value{GDBVN}), you can make the Info file by typing:
34882 If you want to typeset and print copies of this manual, you need @TeX{},
34883 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34884 Texinfo definitions file.
34886 @TeX{} is a typesetting program; it does not print files directly, but
34887 produces output files called @sc{dvi} files. To print a typeset
34888 document, you need a program to print @sc{dvi} files. If your system
34889 has @TeX{} installed, chances are it has such a program. The precise
34890 command to use depends on your system; @kbd{lpr -d} is common; another
34891 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34892 require a file name without any extension or a @samp{.dvi} extension.
34894 @TeX{} also requires a macro definitions file called
34895 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34896 written in Texinfo format. On its own, @TeX{} cannot either read or
34897 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34898 and is located in the @file{gdb-@var{version-number}/texinfo}
34901 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34902 typeset and print this manual. First switch to the @file{gdb}
34903 subdirectory of the main source directory (for example, to
34904 @file{gdb-@value{GDBVN}/gdb}) and type:
34910 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34912 @node Installing GDB
34913 @appendix Installing @value{GDBN}
34914 @cindex installation
34917 * Requirements:: Requirements for building @value{GDBN}
34918 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34919 * Separate Objdir:: Compiling @value{GDBN} in another directory
34920 * Config Names:: Specifying names for hosts and targets
34921 * Configure Options:: Summary of options for configure
34922 * System-wide configuration:: Having a system-wide init file
34926 @section Requirements for Building @value{GDBN}
34927 @cindex building @value{GDBN}, requirements for
34929 Building @value{GDBN} requires various tools and packages to be available.
34930 Other packages will be used only if they are found.
34932 @heading Tools/Packages Necessary for Building @value{GDBN}
34934 @item ISO C90 compiler
34935 @value{GDBN} is written in ISO C90. It should be buildable with any
34936 working C90 compiler, e.g.@: GCC.
34940 @heading Tools/Packages Optional for Building @value{GDBN}
34944 @value{GDBN} can use the Expat XML parsing library. This library may be
34945 included with your operating system distribution; if it is not, you
34946 can get the latest version from @url{http://expat.sourceforge.net}.
34947 The @file{configure} script will search for this library in several
34948 standard locations; if it is installed in an unusual path, you can
34949 use the @option{--with-libexpat-prefix} option to specify its location.
34955 Remote protocol memory maps (@pxref{Memory Map Format})
34957 Target descriptions (@pxref{Target Descriptions})
34959 Remote shared library lists (@xref{Library List Format},
34960 or alternatively @pxref{Library List Format for SVR4 Targets})
34962 MS-Windows shared libraries (@pxref{Shared Libraries})
34964 Traceframe info (@pxref{Traceframe Info Format})
34966 Branch trace (@pxref{Branch Trace Format})
34970 @cindex compressed debug sections
34971 @value{GDBN} will use the @samp{zlib} library, if available, to read
34972 compressed debug sections. Some linkers, such as GNU gold, are capable
34973 of producing binaries with compressed debug sections. If @value{GDBN}
34974 is compiled with @samp{zlib}, it will be able to read the debug
34975 information in such binaries.
34977 The @samp{zlib} library is likely included with your operating system
34978 distribution; if it is not, you can get the latest version from
34979 @url{http://zlib.net}.
34982 @value{GDBN}'s features related to character sets (@pxref{Character
34983 Sets}) require a functioning @code{iconv} implementation. If you are
34984 on a GNU system, then this is provided by the GNU C Library. Some
34985 other systems also provide a working @code{iconv}.
34987 If @value{GDBN} is using the @code{iconv} program which is installed
34988 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34989 This is done with @option{--with-iconv-bin} which specifies the
34990 directory that contains the @code{iconv} program.
34992 On systems without @code{iconv}, you can install GNU Libiconv. If you
34993 have previously installed Libiconv, you can use the
34994 @option{--with-libiconv-prefix} option to configure.
34996 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34997 arrange to build Libiconv if a directory named @file{libiconv} appears
34998 in the top-most source directory. If Libiconv is built this way, and
34999 if the operating system does not provide a suitable @code{iconv}
35000 implementation, then the just-built library will automatically be used
35001 by @value{GDBN}. One easy way to set this up is to download GNU
35002 Libiconv, unpack it, and then rename the directory holding the
35003 Libiconv source code to @samp{libiconv}.
35006 @node Running Configure
35007 @section Invoking the @value{GDBN} @file{configure} Script
35008 @cindex configuring @value{GDBN}
35009 @value{GDBN} comes with a @file{configure} script that automates the process
35010 of preparing @value{GDBN} for installation; you can then use @code{make} to
35011 build the @code{gdb} program.
35013 @c irrelevant in info file; it's as current as the code it lives with.
35014 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35015 look at the @file{README} file in the sources; we may have improved the
35016 installation procedures since publishing this manual.}
35019 The @value{GDBN} distribution includes all the source code you need for
35020 @value{GDBN} in a single directory, whose name is usually composed by
35021 appending the version number to @samp{gdb}.
35023 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35024 @file{gdb-@value{GDBVN}} directory. That directory contains:
35027 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35028 script for configuring @value{GDBN} and all its supporting libraries
35030 @item gdb-@value{GDBVN}/gdb
35031 the source specific to @value{GDBN} itself
35033 @item gdb-@value{GDBVN}/bfd
35034 source for the Binary File Descriptor library
35036 @item gdb-@value{GDBVN}/include
35037 @sc{gnu} include files
35039 @item gdb-@value{GDBVN}/libiberty
35040 source for the @samp{-liberty} free software library
35042 @item gdb-@value{GDBVN}/opcodes
35043 source for the library of opcode tables and disassemblers
35045 @item gdb-@value{GDBVN}/readline
35046 source for the @sc{gnu} command-line interface
35048 @item gdb-@value{GDBVN}/glob
35049 source for the @sc{gnu} filename pattern-matching subroutine
35051 @item gdb-@value{GDBVN}/mmalloc
35052 source for the @sc{gnu} memory-mapped malloc package
35055 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35056 from the @file{gdb-@var{version-number}} source directory, which in
35057 this example is the @file{gdb-@value{GDBVN}} directory.
35059 First switch to the @file{gdb-@var{version-number}} source directory
35060 if you are not already in it; then run @file{configure}. Pass the
35061 identifier for the platform on which @value{GDBN} will run as an
35067 cd gdb-@value{GDBVN}
35068 ./configure @var{host}
35073 where @var{host} is an identifier such as @samp{sun4} or
35074 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35075 (You can often leave off @var{host}; @file{configure} tries to guess the
35076 correct value by examining your system.)
35078 Running @samp{configure @var{host}} and then running @code{make} builds the
35079 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35080 libraries, then @code{gdb} itself. The configured source files, and the
35081 binaries, are left in the corresponding source directories.
35084 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35085 system does not recognize this automatically when you run a different
35086 shell, you may need to run @code{sh} on it explicitly:
35089 sh configure @var{host}
35092 If you run @file{configure} from a directory that contains source
35093 directories for multiple libraries or programs, such as the
35094 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35096 creates configuration files for every directory level underneath (unless
35097 you tell it not to, with the @samp{--norecursion} option).
35099 You should run the @file{configure} script from the top directory in the
35100 source tree, the @file{gdb-@var{version-number}} directory. If you run
35101 @file{configure} from one of the subdirectories, you will configure only
35102 that subdirectory. That is usually not what you want. In particular,
35103 if you run the first @file{configure} from the @file{gdb} subdirectory
35104 of the @file{gdb-@var{version-number}} directory, you will omit the
35105 configuration of @file{bfd}, @file{readline}, and other sibling
35106 directories of the @file{gdb} subdirectory. This leads to build errors
35107 about missing include files such as @file{bfd/bfd.h}.
35109 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35110 However, you should make sure that the shell on your path (named by
35111 the @samp{SHELL} environment variable) is publicly readable. Remember
35112 that @value{GDBN} uses the shell to start your program---some systems refuse to
35113 let @value{GDBN} debug child processes whose programs are not readable.
35115 @node Separate Objdir
35116 @section Compiling @value{GDBN} in Another Directory
35118 If you want to run @value{GDBN} versions for several host or target machines,
35119 you need a different @code{gdb} compiled for each combination of
35120 host and target. @file{configure} is designed to make this easy by
35121 allowing you to generate each configuration in a separate subdirectory,
35122 rather than in the source directory. If your @code{make} program
35123 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35124 @code{make} in each of these directories builds the @code{gdb}
35125 program specified there.
35127 To build @code{gdb} in a separate directory, run @file{configure}
35128 with the @samp{--srcdir} option to specify where to find the source.
35129 (You also need to specify a path to find @file{configure}
35130 itself from your working directory. If the path to @file{configure}
35131 would be the same as the argument to @samp{--srcdir}, you can leave out
35132 the @samp{--srcdir} option; it is assumed.)
35134 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35135 separate directory for a Sun 4 like this:
35139 cd gdb-@value{GDBVN}
35142 ../gdb-@value{GDBVN}/configure sun4
35147 When @file{configure} builds a configuration using a remote source
35148 directory, it creates a tree for the binaries with the same structure
35149 (and using the same names) as the tree under the source directory. In
35150 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35151 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35152 @file{gdb-sun4/gdb}.
35154 Make sure that your path to the @file{configure} script has just one
35155 instance of @file{gdb} in it. If your path to @file{configure} looks
35156 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35157 one subdirectory of @value{GDBN}, not the whole package. This leads to
35158 build errors about missing include files such as @file{bfd/bfd.h}.
35160 One popular reason to build several @value{GDBN} configurations in separate
35161 directories is to configure @value{GDBN} for cross-compiling (where
35162 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35163 programs that run on another machine---the @dfn{target}).
35164 You specify a cross-debugging target by
35165 giving the @samp{--target=@var{target}} option to @file{configure}.
35167 When you run @code{make} to build a program or library, you must run
35168 it in a configured directory---whatever directory you were in when you
35169 called @file{configure} (or one of its subdirectories).
35171 The @code{Makefile} that @file{configure} generates in each source
35172 directory also runs recursively. If you type @code{make} in a source
35173 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35174 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35175 will build all the required libraries, and then build GDB.
35177 When you have multiple hosts or targets configured in separate
35178 directories, you can run @code{make} on them in parallel (for example,
35179 if they are NFS-mounted on each of the hosts); they will not interfere
35183 @section Specifying Names for Hosts and Targets
35185 The specifications used for hosts and targets in the @file{configure}
35186 script are based on a three-part naming scheme, but some short predefined
35187 aliases are also supported. The full naming scheme encodes three pieces
35188 of information in the following pattern:
35191 @var{architecture}-@var{vendor}-@var{os}
35194 For example, you can use the alias @code{sun4} as a @var{host} argument,
35195 or as the value for @var{target} in a @code{--target=@var{target}}
35196 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35198 The @file{configure} script accompanying @value{GDBN} does not provide
35199 any query facility to list all supported host and target names or
35200 aliases. @file{configure} calls the Bourne shell script
35201 @code{config.sub} to map abbreviations to full names; you can read the
35202 script, if you wish, or you can use it to test your guesses on
35203 abbreviations---for example:
35206 % sh config.sub i386-linux
35208 % sh config.sub alpha-linux
35209 alpha-unknown-linux-gnu
35210 % sh config.sub hp9k700
35212 % sh config.sub sun4
35213 sparc-sun-sunos4.1.1
35214 % sh config.sub sun3
35215 m68k-sun-sunos4.1.1
35216 % sh config.sub i986v
35217 Invalid configuration `i986v': machine `i986v' not recognized
35221 @code{config.sub} is also distributed in the @value{GDBN} source
35222 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35224 @node Configure Options
35225 @section @file{configure} Options
35227 Here is a summary of the @file{configure} options and arguments that
35228 are most often useful for building @value{GDBN}. @file{configure} also has
35229 several other options not listed here. @inforef{What Configure
35230 Does,,configure.info}, for a full explanation of @file{configure}.
35233 configure @r{[}--help@r{]}
35234 @r{[}--prefix=@var{dir}@r{]}
35235 @r{[}--exec-prefix=@var{dir}@r{]}
35236 @r{[}--srcdir=@var{dirname}@r{]}
35237 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35238 @r{[}--target=@var{target}@r{]}
35243 You may introduce options with a single @samp{-} rather than
35244 @samp{--} if you prefer; but you may abbreviate option names if you use
35249 Display a quick summary of how to invoke @file{configure}.
35251 @item --prefix=@var{dir}
35252 Configure the source to install programs and files under directory
35255 @item --exec-prefix=@var{dir}
35256 Configure the source to install programs under directory
35259 @c avoid splitting the warning from the explanation:
35261 @item --srcdir=@var{dirname}
35262 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35263 @code{make} that implements the @code{VPATH} feature.}@*
35264 Use this option to make configurations in directories separate from the
35265 @value{GDBN} source directories. Among other things, you can use this to
35266 build (or maintain) several configurations simultaneously, in separate
35267 directories. @file{configure} writes configuration-specific files in
35268 the current directory, but arranges for them to use the source in the
35269 directory @var{dirname}. @file{configure} creates directories under
35270 the working directory in parallel to the source directories below
35273 @item --norecursion
35274 Configure only the directory level where @file{configure} is executed; do not
35275 propagate configuration to subdirectories.
35277 @item --target=@var{target}
35278 Configure @value{GDBN} for cross-debugging programs running on the specified
35279 @var{target}. Without this option, @value{GDBN} is configured to debug
35280 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35282 There is no convenient way to generate a list of all available targets.
35284 @item @var{host} @dots{}
35285 Configure @value{GDBN} to run on the specified @var{host}.
35287 There is no convenient way to generate a list of all available hosts.
35290 There are many other options available as well, but they are generally
35291 needed for special purposes only.
35293 @node System-wide configuration
35294 @section System-wide configuration and settings
35295 @cindex system-wide init file
35297 @value{GDBN} can be configured to have a system-wide init file;
35298 this file will be read and executed at startup (@pxref{Startup, , What
35299 @value{GDBN} does during startup}).
35301 Here is the corresponding configure option:
35304 @item --with-system-gdbinit=@var{file}
35305 Specify that the default location of the system-wide init file is
35309 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35310 it may be subject to relocation. Two possible cases:
35314 If the default location of this init file contains @file{$prefix},
35315 it will be subject to relocation. Suppose that the configure options
35316 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35317 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35318 init file is looked for as @file{$install/etc/gdbinit} instead of
35319 @file{$prefix/etc/gdbinit}.
35322 By contrast, if the default location does not contain the prefix,
35323 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35324 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35325 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35326 wherever @value{GDBN} is installed.
35329 If the configured location of the system-wide init file (as given by the
35330 @option{--with-system-gdbinit} option at configure time) is in the
35331 data-directory (as specified by @option{--with-gdb-datadir} at configure
35332 time) or in one of its subdirectories, then @value{GDBN} will look for the
35333 system-wide init file in the directory specified by the
35334 @option{--data-directory} command-line option.
35335 Note that the system-wide init file is only read once, during @value{GDBN}
35336 initialization. If the data-directory is changed after @value{GDBN} has
35337 started with the @code{set data-directory} command, the file will not be
35340 @node Maintenance Commands
35341 @appendix Maintenance Commands
35342 @cindex maintenance commands
35343 @cindex internal commands
35345 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35346 includes a number of commands intended for @value{GDBN} developers,
35347 that are not documented elsewhere in this manual. These commands are
35348 provided here for reference. (For commands that turn on debugging
35349 messages, see @ref{Debugging Output}.)
35352 @kindex maint agent
35353 @kindex maint agent-eval
35354 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35355 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35356 Translate the given @var{expression} into remote agent bytecodes.
35357 This command is useful for debugging the Agent Expression mechanism
35358 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35359 expression useful for data collection, such as by tracepoints, while
35360 @samp{maint agent-eval} produces an expression that evaluates directly
35361 to a result. For instance, a collection expression for @code{globa +
35362 globb} will include bytecodes to record four bytes of memory at each
35363 of the addresses of @code{globa} and @code{globb}, while discarding
35364 the result of the addition, while an evaluation expression will do the
35365 addition and return the sum.
35366 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35367 If not, generate remote agent bytecode for current frame PC address.
35369 @kindex maint agent-printf
35370 @item maint agent-printf @var{format},@var{expr},...
35371 Translate the given format string and list of argument expressions
35372 into remote agent bytecodes and display them as a disassembled list.
35373 This command is useful for debugging the agent version of dynamic
35374 printf (@pxref{Dynamic Printf}).
35376 @kindex maint info breakpoints
35377 @item @anchor{maint info breakpoints}maint info breakpoints
35378 Using the same format as @samp{info breakpoints}, display both the
35379 breakpoints you've set explicitly, and those @value{GDBN} is using for
35380 internal purposes. Internal breakpoints are shown with negative
35381 breakpoint numbers. The type column identifies what kind of breakpoint
35386 Normal, explicitly set breakpoint.
35389 Normal, explicitly set watchpoint.
35392 Internal breakpoint, used to handle correctly stepping through
35393 @code{longjmp} calls.
35395 @item longjmp resume
35396 Internal breakpoint at the target of a @code{longjmp}.
35399 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35402 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35405 Shared library events.
35409 @kindex maint info bfds
35410 @item maint info bfds
35411 This prints information about each @code{bfd} object that is known to
35412 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35414 @kindex set displaced-stepping
35415 @kindex show displaced-stepping
35416 @cindex displaced stepping support
35417 @cindex out-of-line single-stepping
35418 @item set displaced-stepping
35419 @itemx show displaced-stepping
35420 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35421 if the target supports it. Displaced stepping is a way to single-step
35422 over breakpoints without removing them from the inferior, by executing
35423 an out-of-line copy of the instruction that was originally at the
35424 breakpoint location. It is also known as out-of-line single-stepping.
35427 @item set displaced-stepping on
35428 If the target architecture supports it, @value{GDBN} will use
35429 displaced stepping to step over breakpoints.
35431 @item set displaced-stepping off
35432 @value{GDBN} will not use displaced stepping to step over breakpoints,
35433 even if such is supported by the target architecture.
35435 @cindex non-stop mode, and @samp{set displaced-stepping}
35436 @item set displaced-stepping auto
35437 This is the default mode. @value{GDBN} will use displaced stepping
35438 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35439 architecture supports displaced stepping.
35442 @kindex maint check-symtabs
35443 @item maint check-symtabs
35444 Check the consistency of psymtabs and symtabs.
35446 @kindex maint cplus first_component
35447 @item maint cplus first_component @var{name}
35448 Print the first C@t{++} class/namespace component of @var{name}.
35450 @kindex maint cplus namespace
35451 @item maint cplus namespace
35452 Print the list of possible C@t{++} namespaces.
35454 @kindex maint demangle
35455 @item maint demangle @var{name}
35456 Demangle a C@t{++} or Objective-C mangled @var{name}.
35458 @kindex maint deprecate
35459 @kindex maint undeprecate
35460 @cindex deprecated commands
35461 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35462 @itemx maint undeprecate @var{command}
35463 Deprecate or undeprecate the named @var{command}. Deprecated commands
35464 cause @value{GDBN} to issue a warning when you use them. The optional
35465 argument @var{replacement} says which newer command should be used in
35466 favor of the deprecated one; if it is given, @value{GDBN} will mention
35467 the replacement as part of the warning.
35469 @kindex maint dump-me
35470 @item maint dump-me
35471 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35472 Cause a fatal signal in the debugger and force it to dump its core.
35473 This is supported only on systems which support aborting a program
35474 with the @code{SIGQUIT} signal.
35476 @kindex maint internal-error
35477 @kindex maint internal-warning
35478 @item maint internal-error @r{[}@var{message-text}@r{]}
35479 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35480 Cause @value{GDBN} to call the internal function @code{internal_error}
35481 or @code{internal_warning} and hence behave as though an internal error
35482 or internal warning has been detected. In addition to reporting the
35483 internal problem, these functions give the user the opportunity to
35484 either quit @value{GDBN} or create a core file of the current
35485 @value{GDBN} session.
35487 These commands take an optional parameter @var{message-text} that is
35488 used as the text of the error or warning message.
35490 Here's an example of using @code{internal-error}:
35493 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35494 @dots{}/maint.c:121: internal-error: testing, 1, 2
35495 A problem internal to GDB has been detected. Further
35496 debugging may prove unreliable.
35497 Quit this debugging session? (y or n) @kbd{n}
35498 Create a core file? (y or n) @kbd{n}
35502 @cindex @value{GDBN} internal error
35503 @cindex internal errors, control of @value{GDBN} behavior
35505 @kindex maint set internal-error
35506 @kindex maint show internal-error
35507 @kindex maint set internal-warning
35508 @kindex maint show internal-warning
35509 @item maint set internal-error @var{action} [ask|yes|no]
35510 @itemx maint show internal-error @var{action}
35511 @itemx maint set internal-warning @var{action} [ask|yes|no]
35512 @itemx maint show internal-warning @var{action}
35513 When @value{GDBN} reports an internal problem (error or warning) it
35514 gives the user the opportunity to both quit @value{GDBN} and create a
35515 core file of the current @value{GDBN} session. These commands let you
35516 override the default behaviour for each particular @var{action},
35517 described in the table below.
35521 You can specify that @value{GDBN} should always (yes) or never (no)
35522 quit. The default is to ask the user what to do.
35525 You can specify that @value{GDBN} should always (yes) or never (no)
35526 create a core file. The default is to ask the user what to do.
35529 @kindex maint packet
35530 @item maint packet @var{text}
35531 If @value{GDBN} is talking to an inferior via the serial protocol,
35532 then this command sends the string @var{text} to the inferior, and
35533 displays the response packet. @value{GDBN} supplies the initial
35534 @samp{$} character, the terminating @samp{#} character, and the
35537 @kindex maint print architecture
35538 @item maint print architecture @r{[}@var{file}@r{]}
35539 Print the entire architecture configuration. The optional argument
35540 @var{file} names the file where the output goes.
35542 @kindex maint print c-tdesc
35543 @item maint print c-tdesc
35544 Print the current target description (@pxref{Target Descriptions}) as
35545 a C source file. The created source file can be used in @value{GDBN}
35546 when an XML parser is not available to parse the description.
35548 @kindex maint print dummy-frames
35549 @item maint print dummy-frames
35550 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35553 (@value{GDBP}) @kbd{b add}
35555 (@value{GDBP}) @kbd{print add(2,3)}
35556 Breakpoint 2, add (a=2, b=3) at @dots{}
35558 The program being debugged stopped while in a function called from GDB.
35560 (@value{GDBP}) @kbd{maint print dummy-frames}
35561 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35562 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35563 call_lo=0x01014000 call_hi=0x01014001
35567 Takes an optional file parameter.
35569 @kindex maint print registers
35570 @kindex maint print raw-registers
35571 @kindex maint print cooked-registers
35572 @kindex maint print register-groups
35573 @kindex maint print remote-registers
35574 @item maint print registers @r{[}@var{file}@r{]}
35575 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35576 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35577 @itemx maint print register-groups @r{[}@var{file}@r{]}
35578 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35579 Print @value{GDBN}'s internal register data structures.
35581 The command @code{maint print raw-registers} includes the contents of
35582 the raw register cache; the command @code{maint print
35583 cooked-registers} includes the (cooked) value of all registers,
35584 including registers which aren't available on the target nor visible
35585 to user; the command @code{maint print register-groups} includes the
35586 groups that each register is a member of; and the command @code{maint
35587 print remote-registers} includes the remote target's register numbers
35588 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35589 @value{GDBN} Internals}.
35591 These commands take an optional parameter, a file name to which to
35592 write the information.
35594 @kindex maint print reggroups
35595 @item maint print reggroups @r{[}@var{file}@r{]}
35596 Print @value{GDBN}'s internal register group data structures. The
35597 optional argument @var{file} tells to what file to write the
35600 The register groups info looks like this:
35603 (@value{GDBP}) @kbd{maint print reggroups}
35616 This command forces @value{GDBN} to flush its internal register cache.
35618 @kindex maint print objfiles
35619 @cindex info for known object files
35620 @item maint print objfiles
35621 Print a dump of all known object files. For each object file, this
35622 command prints its name, address in memory, and all of its psymtabs
35625 @kindex maint print section-scripts
35626 @cindex info for known .debug_gdb_scripts-loaded scripts
35627 @item maint print section-scripts [@var{regexp}]
35628 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35629 If @var{regexp} is specified, only print scripts loaded by object files
35630 matching @var{regexp}.
35631 For each script, this command prints its name as specified in the objfile,
35632 and the full path if known.
35633 @xref{dotdebug_gdb_scripts section}.
35635 @kindex maint print statistics
35636 @cindex bcache statistics
35637 @item maint print statistics
35638 This command prints, for each object file in the program, various data
35639 about that object file followed by the byte cache (@dfn{bcache})
35640 statistics for the object file. The objfile data includes the number
35641 of minimal, partial, full, and stabs symbols, the number of types
35642 defined by the objfile, the number of as yet unexpanded psym tables,
35643 the number of line tables and string tables, and the amount of memory
35644 used by the various tables. The bcache statistics include the counts,
35645 sizes, and counts of duplicates of all and unique objects, max,
35646 average, and median entry size, total memory used and its overhead and
35647 savings, and various measures of the hash table size and chain
35650 @kindex maint print target-stack
35651 @cindex target stack description
35652 @item maint print target-stack
35653 A @dfn{target} is an interface between the debugger and a particular
35654 kind of file or process. Targets can be stacked in @dfn{strata},
35655 so that more than one target can potentially respond to a request.
35656 In particular, memory accesses will walk down the stack of targets
35657 until they find a target that is interested in handling that particular
35660 This command prints a short description of each layer that was pushed on
35661 the @dfn{target stack}, starting from the top layer down to the bottom one.
35663 @kindex maint print type
35664 @cindex type chain of a data type
35665 @item maint print type @var{expr}
35666 Print the type chain for a type specified by @var{expr}. The argument
35667 can be either a type name or a symbol. If it is a symbol, the type of
35668 that symbol is described. The type chain produced by this command is
35669 a recursive definition of the data type as stored in @value{GDBN}'s
35670 data structures, including its flags and contained types.
35672 @kindex maint set dwarf2 always-disassemble
35673 @kindex maint show dwarf2 always-disassemble
35674 @item maint set dwarf2 always-disassemble
35675 @item maint show dwarf2 always-disassemble
35676 Control the behavior of @code{info address} when using DWARF debugging
35679 The default is @code{off}, which means that @value{GDBN} should try to
35680 describe a variable's location in an easily readable format. When
35681 @code{on}, @value{GDBN} will instead display the DWARF location
35682 expression in an assembly-like format. Note that some locations are
35683 too complex for @value{GDBN} to describe simply; in this case you will
35684 always see the disassembly form.
35686 Here is an example of the resulting disassembly:
35689 (gdb) info addr argc
35690 Symbol "argc" is a complex DWARF expression:
35694 For more information on these expressions, see
35695 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35697 @kindex maint set dwarf2 max-cache-age
35698 @kindex maint show dwarf2 max-cache-age
35699 @item maint set dwarf2 max-cache-age
35700 @itemx maint show dwarf2 max-cache-age
35701 Control the DWARF 2 compilation unit cache.
35703 @cindex DWARF 2 compilation units cache
35704 In object files with inter-compilation-unit references, such as those
35705 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35706 reader needs to frequently refer to previously read compilation units.
35707 This setting controls how long a compilation unit will remain in the
35708 cache if it is not referenced. A higher limit means that cached
35709 compilation units will be stored in memory longer, and more total
35710 memory will be used. Setting it to zero disables caching, which will
35711 slow down @value{GDBN} startup, but reduce memory consumption.
35713 @kindex maint set profile
35714 @kindex maint show profile
35715 @cindex profiling GDB
35716 @item maint set profile
35717 @itemx maint show profile
35718 Control profiling of @value{GDBN}.
35720 Profiling will be disabled until you use the @samp{maint set profile}
35721 command to enable it. When you enable profiling, the system will begin
35722 collecting timing and execution count data; when you disable profiling or
35723 exit @value{GDBN}, the results will be written to a log file. Remember that
35724 if you use profiling, @value{GDBN} will overwrite the profiling log file
35725 (often called @file{gmon.out}). If you have a record of important profiling
35726 data in a @file{gmon.out} file, be sure to move it to a safe location.
35728 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35729 compiled with the @samp{-pg} compiler option.
35731 @kindex maint set show-debug-regs
35732 @kindex maint show show-debug-regs
35733 @cindex hardware debug registers
35734 @item maint set show-debug-regs
35735 @itemx maint show show-debug-regs
35736 Control whether to show variables that mirror the hardware debug
35737 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35738 enabled, the debug registers values are shown when @value{GDBN} inserts or
35739 removes a hardware breakpoint or watchpoint, and when the inferior
35740 triggers a hardware-assisted breakpoint or watchpoint.
35742 @kindex maint set show-all-tib
35743 @kindex maint show show-all-tib
35744 @item maint set show-all-tib
35745 @itemx maint show show-all-tib
35746 Control whether to show all non zero areas within a 1k block starting
35747 at thread local base, when using the @samp{info w32 thread-information-block}
35750 @kindex maint set per-command
35751 @kindex maint show per-command
35752 @item maint set per-command
35753 @itemx maint show per-command
35754 @cindex resources used by commands
35756 @value{GDBN} can display the resources used by each command.
35757 This is useful in debugging performance problems.
35760 @item maint set per-command space [on|off]
35761 @itemx maint show per-command space
35762 Enable or disable the printing of the memory used by GDB for each command.
35763 If enabled, @value{GDBN} will display how much memory each command
35764 took, following the command's own output.
35765 This can also be requested by invoking @value{GDBN} with the
35766 @option{--statistics} command-line switch (@pxref{Mode Options}).
35768 @item maint set per-command time [on|off]
35769 @itemx maint show per-command time
35770 Enable or disable the printing of the execution time of @value{GDBN}
35772 If enabled, @value{GDBN} will display how much time it
35773 took to execute each command, following the command's own output.
35774 Both CPU time and wallclock time are printed.
35775 Printing both is useful when trying to determine whether the cost is
35776 CPU or, e.g., disk/network latency.
35777 Note that the CPU time printed is for @value{GDBN} only, it does not include
35778 the execution time of the inferior because there's no mechanism currently
35779 to compute how much time was spent by @value{GDBN} and how much time was
35780 spent by the program been debugged.
35781 This can also be requested by invoking @value{GDBN} with the
35782 @option{--statistics} command-line switch (@pxref{Mode Options}).
35784 @item maint set per-command symtab [on|off]
35785 @itemx maint show per-command symtab
35786 Enable or disable the printing of basic symbol table statistics
35788 If enabled, @value{GDBN} will display the following information:
35792 number of symbol tables
35794 number of primary symbol tables
35796 number of blocks in the blockvector
35800 @kindex maint space
35801 @cindex memory used by commands
35802 @item maint space @var{value}
35803 An alias for @code{maint set per-command space}.
35804 A non-zero value enables it, zero disables it.
35807 @cindex time of command execution
35808 @item maint time @var{value}
35809 An alias for @code{maint set per-command time}.
35810 A non-zero value enables it, zero disables it.
35812 @kindex maint translate-address
35813 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35814 Find the symbol stored at the location specified by the address
35815 @var{addr} and an optional section name @var{section}. If found,
35816 @value{GDBN} prints the name of the closest symbol and an offset from
35817 the symbol's location to the specified address. This is similar to
35818 the @code{info address} command (@pxref{Symbols}), except that this
35819 command also allows to find symbols in other sections.
35821 If section was not specified, the section in which the symbol was found
35822 is also printed. For dynamically linked executables, the name of
35823 executable or shared library containing the symbol is printed as well.
35827 The following command is useful for non-interactive invocations of
35828 @value{GDBN}, such as in the test suite.
35831 @item set watchdog @var{nsec}
35832 @kindex set watchdog
35833 @cindex watchdog timer
35834 @cindex timeout for commands
35835 Set the maximum number of seconds @value{GDBN} will wait for the
35836 target operation to finish. If this time expires, @value{GDBN}
35837 reports and error and the command is aborted.
35839 @item show watchdog
35840 Show the current setting of the target wait timeout.
35843 @node Remote Protocol
35844 @appendix @value{GDBN} Remote Serial Protocol
35849 * Stop Reply Packets::
35850 * General Query Packets::
35851 * Architecture-Specific Protocol Details::
35852 * Tracepoint Packets::
35853 * Host I/O Packets::
35855 * Notification Packets::
35856 * Remote Non-Stop::
35857 * Packet Acknowledgment::
35859 * File-I/O Remote Protocol Extension::
35860 * Library List Format::
35861 * Library List Format for SVR4 Targets::
35862 * Memory Map Format::
35863 * Thread List Format::
35864 * Traceframe Info Format::
35865 * Branch Trace Format::
35871 There may be occasions when you need to know something about the
35872 protocol---for example, if there is only one serial port to your target
35873 machine, you might want your program to do something special if it
35874 recognizes a packet meant for @value{GDBN}.
35876 In the examples below, @samp{->} and @samp{<-} are used to indicate
35877 transmitted and received data, respectively.
35879 @cindex protocol, @value{GDBN} remote serial
35880 @cindex serial protocol, @value{GDBN} remote
35881 @cindex remote serial protocol
35882 All @value{GDBN} commands and responses (other than acknowledgments
35883 and notifications, see @ref{Notification Packets}) are sent as a
35884 @var{packet}. A @var{packet} is introduced with the character
35885 @samp{$}, the actual @var{packet-data}, and the terminating character
35886 @samp{#} followed by a two-digit @var{checksum}:
35889 @code{$}@var{packet-data}@code{#}@var{checksum}
35893 @cindex checksum, for @value{GDBN} remote
35895 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35896 characters between the leading @samp{$} and the trailing @samp{#} (an
35897 eight bit unsigned checksum).
35899 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35900 specification also included an optional two-digit @var{sequence-id}:
35903 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35906 @cindex sequence-id, for @value{GDBN} remote
35908 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35909 has never output @var{sequence-id}s. Stubs that handle packets added
35910 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35912 When either the host or the target machine receives a packet, the first
35913 response expected is an acknowledgment: either @samp{+} (to indicate
35914 the package was received correctly) or @samp{-} (to request
35918 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35923 The @samp{+}/@samp{-} acknowledgments can be disabled
35924 once a connection is established.
35925 @xref{Packet Acknowledgment}, for details.
35927 The host (@value{GDBN}) sends @var{command}s, and the target (the
35928 debugging stub incorporated in your program) sends a @var{response}. In
35929 the case of step and continue @var{command}s, the response is only sent
35930 when the operation has completed, and the target has again stopped all
35931 threads in all attached processes. This is the default all-stop mode
35932 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35933 execution mode; see @ref{Remote Non-Stop}, for details.
35935 @var{packet-data} consists of a sequence of characters with the
35936 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35939 @cindex remote protocol, field separator
35940 Fields within the packet should be separated using @samp{,} @samp{;} or
35941 @samp{:}. Except where otherwise noted all numbers are represented in
35942 @sc{hex} with leading zeros suppressed.
35944 Implementors should note that prior to @value{GDBN} 5.0, the character
35945 @samp{:} could not appear as the third character in a packet (as it
35946 would potentially conflict with the @var{sequence-id}).
35948 @cindex remote protocol, binary data
35949 @anchor{Binary Data}
35950 Binary data in most packets is encoded either as two hexadecimal
35951 digits per byte of binary data. This allowed the traditional remote
35952 protocol to work over connections which were only seven-bit clean.
35953 Some packets designed more recently assume an eight-bit clean
35954 connection, and use a more efficient encoding to send and receive
35957 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35958 as an escape character. Any escaped byte is transmitted as the escape
35959 character followed by the original character XORed with @code{0x20}.
35960 For example, the byte @code{0x7d} would be transmitted as the two
35961 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35962 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35963 @samp{@}}) must always be escaped. Responses sent by the stub
35964 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35965 is not interpreted as the start of a run-length encoded sequence
35968 Response @var{data} can be run-length encoded to save space.
35969 Run-length encoding replaces runs of identical characters with one
35970 instance of the repeated character, followed by a @samp{*} and a
35971 repeat count. The repeat count is itself sent encoded, to avoid
35972 binary characters in @var{data}: a value of @var{n} is sent as
35973 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35974 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35975 code 32) for a repeat count of 3. (This is because run-length
35976 encoding starts to win for counts 3 or more.) Thus, for example,
35977 @samp{0* } is a run-length encoding of ``0000'': the space character
35978 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35981 The printable characters @samp{#} and @samp{$} or with a numeric value
35982 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35983 seven repeats (@samp{$}) can be expanded using a repeat count of only
35984 five (@samp{"}). For example, @samp{00000000} can be encoded as
35987 The error response returned for some packets includes a two character
35988 error number. That number is not well defined.
35990 @cindex empty response, for unsupported packets
35991 For any @var{command} not supported by the stub, an empty response
35992 (@samp{$#00}) should be returned. That way it is possible to extend the
35993 protocol. A newer @value{GDBN} can tell if a packet is supported based
35996 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35997 commands for register access, and the @samp{m} and @samp{M} commands
35998 for memory access. Stubs that only control single-threaded targets
35999 can implement run control with the @samp{c} (continue), and @samp{s}
36000 (step) commands. Stubs that support multi-threading targets should
36001 support the @samp{vCont} command. All other commands are optional.
36006 The following table provides a complete list of all currently defined
36007 @var{command}s and their corresponding response @var{data}.
36008 @xref{File-I/O Remote Protocol Extension}, for details about the File
36009 I/O extension of the remote protocol.
36011 Each packet's description has a template showing the packet's overall
36012 syntax, followed by an explanation of the packet's meaning. We
36013 include spaces in some of the templates for clarity; these are not
36014 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36015 separate its components. For example, a template like @samp{foo
36016 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36017 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36018 @var{baz}. @value{GDBN} does not transmit a space character between the
36019 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36022 @cindex @var{thread-id}, in remote protocol
36023 @anchor{thread-id syntax}
36024 Several packets and replies include a @var{thread-id} field to identify
36025 a thread. Normally these are positive numbers with a target-specific
36026 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36027 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36030 In addition, the remote protocol supports a multiprocess feature in
36031 which the @var{thread-id} syntax is extended to optionally include both
36032 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36033 The @var{pid} (process) and @var{tid} (thread) components each have the
36034 format described above: a positive number with target-specific
36035 interpretation formatted as a big-endian hex string, literal @samp{-1}
36036 to indicate all processes or threads (respectively), or @samp{0} to
36037 indicate an arbitrary process or thread. Specifying just a process, as
36038 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36039 error to specify all processes but a specific thread, such as
36040 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36041 for those packets and replies explicitly documented to include a process
36042 ID, rather than a @var{thread-id}.
36044 The multiprocess @var{thread-id} syntax extensions are only used if both
36045 @value{GDBN} and the stub report support for the @samp{multiprocess}
36046 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36049 Note that all packet forms beginning with an upper- or lower-case
36050 letter, other than those described here, are reserved for future use.
36052 Here are the packet descriptions.
36057 @cindex @samp{!} packet
36058 @anchor{extended mode}
36059 Enable extended mode. In extended mode, the remote server is made
36060 persistent. The @samp{R} packet is used to restart the program being
36066 The remote target both supports and has enabled extended mode.
36070 @cindex @samp{?} packet
36071 Indicate the reason the target halted. The reply is the same as for
36072 step and continue. This packet has a special interpretation when the
36073 target is in non-stop mode; see @ref{Remote Non-Stop}.
36076 @xref{Stop Reply Packets}, for the reply specifications.
36078 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36079 @cindex @samp{A} packet
36080 Initialized @code{argv[]} array passed into program. @var{arglen}
36081 specifies the number of bytes in the hex encoded byte stream
36082 @var{arg}. See @code{gdbserver} for more details.
36087 The arguments were set.
36093 @cindex @samp{b} packet
36094 (Don't use this packet; its behavior is not well-defined.)
36095 Change the serial line speed to @var{baud}.
36097 JTC: @emph{When does the transport layer state change? When it's
36098 received, or after the ACK is transmitted. In either case, there are
36099 problems if the command or the acknowledgment packet is dropped.}
36101 Stan: @emph{If people really wanted to add something like this, and get
36102 it working for the first time, they ought to modify ser-unix.c to send
36103 some kind of out-of-band message to a specially-setup stub and have the
36104 switch happen "in between" packets, so that from remote protocol's point
36105 of view, nothing actually happened.}
36107 @item B @var{addr},@var{mode}
36108 @cindex @samp{B} packet
36109 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36110 breakpoint at @var{addr}.
36112 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36113 (@pxref{insert breakpoint or watchpoint packet}).
36115 @cindex @samp{bc} packet
36118 Backward continue. Execute the target system in reverse. No parameter.
36119 @xref{Reverse Execution}, for more information.
36122 @xref{Stop Reply Packets}, for the reply specifications.
36124 @cindex @samp{bs} packet
36127 Backward single step. Execute one instruction in reverse. No parameter.
36128 @xref{Reverse Execution}, for more information.
36131 @xref{Stop Reply Packets}, for the reply specifications.
36133 @item c @r{[}@var{addr}@r{]}
36134 @cindex @samp{c} packet
36135 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36136 resume at current address.
36138 This packet is deprecated for multi-threading support. @xref{vCont
36142 @xref{Stop Reply Packets}, for the reply specifications.
36144 @item C @var{sig}@r{[};@var{addr}@r{]}
36145 @cindex @samp{C} packet
36146 Continue with signal @var{sig} (hex signal number). If
36147 @samp{;@var{addr}} is omitted, resume at same address.
36149 This packet is deprecated for multi-threading support. @xref{vCont
36153 @xref{Stop Reply Packets}, for the reply specifications.
36156 @cindex @samp{d} packet
36159 Don't use this packet; instead, define a general set packet
36160 (@pxref{General Query Packets}).
36164 @cindex @samp{D} packet
36165 The first form of the packet is used to detach @value{GDBN} from the
36166 remote system. It is sent to the remote target
36167 before @value{GDBN} disconnects via the @code{detach} command.
36169 The second form, including a process ID, is used when multiprocess
36170 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36171 detach only a specific process. The @var{pid} is specified as a
36172 big-endian hex string.
36182 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36183 @cindex @samp{F} packet
36184 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36185 This is part of the File-I/O protocol extension. @xref{File-I/O
36186 Remote Protocol Extension}, for the specification.
36189 @anchor{read registers packet}
36190 @cindex @samp{g} packet
36191 Read general registers.
36195 @item @var{XX@dots{}}
36196 Each byte of register data is described by two hex digits. The bytes
36197 with the register are transmitted in target byte order. The size of
36198 each register and their position within the @samp{g} packet are
36199 determined by the @value{GDBN} internal gdbarch functions
36200 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36201 specification of several standard @samp{g} packets is specified below.
36203 When reading registers from a trace frame (@pxref{Analyze Collected
36204 Data,,Using the Collected Data}), the stub may also return a string of
36205 literal @samp{x}'s in place of the register data digits, to indicate
36206 that the corresponding register has not been collected, thus its value
36207 is unavailable. For example, for an architecture with 4 registers of
36208 4 bytes each, the following reply indicates to @value{GDBN} that
36209 registers 0 and 2 have not been collected, while registers 1 and 3
36210 have been collected, and both have zero value:
36214 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36221 @item G @var{XX@dots{}}
36222 @cindex @samp{G} packet
36223 Write general registers. @xref{read registers packet}, for a
36224 description of the @var{XX@dots{}} data.
36234 @item H @var{op} @var{thread-id}
36235 @cindex @samp{H} packet
36236 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36237 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36238 it should be @samp{c} for step and continue operations (note that this
36239 is deprecated, supporting the @samp{vCont} command is a better
36240 option), @samp{g} for other operations. The thread designator
36241 @var{thread-id} has the format and interpretation described in
36242 @ref{thread-id syntax}.
36253 @c 'H': How restrictive (or permissive) is the thread model. If a
36254 @c thread is selected and stopped, are other threads allowed
36255 @c to continue to execute? As I mentioned above, I think the
36256 @c semantics of each command when a thread is selected must be
36257 @c described. For example:
36259 @c 'g': If the stub supports threads and a specific thread is
36260 @c selected, returns the register block from that thread;
36261 @c otherwise returns current registers.
36263 @c 'G' If the stub supports threads and a specific thread is
36264 @c selected, sets the registers of the register block of
36265 @c that thread; otherwise sets current registers.
36267 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36268 @anchor{cycle step packet}
36269 @cindex @samp{i} packet
36270 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36271 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36272 step starting at that address.
36275 @cindex @samp{I} packet
36276 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36280 @cindex @samp{k} packet
36283 FIXME: @emph{There is no description of how to operate when a specific
36284 thread context has been selected (i.e.@: does 'k' kill only that
36287 @item m @var{addr},@var{length}
36288 @cindex @samp{m} packet
36289 Read @var{length} bytes of memory starting at address @var{addr}.
36290 Note that @var{addr} may not be aligned to any particular boundary.
36292 The stub need not use any particular size or alignment when gathering
36293 data from memory for the response; even if @var{addr} is word-aligned
36294 and @var{length} is a multiple of the word size, the stub is free to
36295 use byte accesses, or not. For this reason, this packet may not be
36296 suitable for accessing memory-mapped I/O devices.
36297 @cindex alignment of remote memory accesses
36298 @cindex size of remote memory accesses
36299 @cindex memory, alignment and size of remote accesses
36303 @item @var{XX@dots{}}
36304 Memory contents; each byte is transmitted as a two-digit hexadecimal
36305 number. The reply may contain fewer bytes than requested if the
36306 server was able to read only part of the region of memory.
36311 @item M @var{addr},@var{length}:@var{XX@dots{}}
36312 @cindex @samp{M} packet
36313 Write @var{length} bytes of memory starting at address @var{addr}.
36314 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36315 hexadecimal number.
36322 for an error (this includes the case where only part of the data was
36327 @cindex @samp{p} packet
36328 Read the value of register @var{n}; @var{n} is in hex.
36329 @xref{read registers packet}, for a description of how the returned
36330 register value is encoded.
36334 @item @var{XX@dots{}}
36335 the register's value
36339 Indicating an unrecognized @var{query}.
36342 @item P @var{n@dots{}}=@var{r@dots{}}
36343 @anchor{write register packet}
36344 @cindex @samp{P} packet
36345 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36346 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36347 digits for each byte in the register (target byte order).
36357 @item q @var{name} @var{params}@dots{}
36358 @itemx Q @var{name} @var{params}@dots{}
36359 @cindex @samp{q} packet
36360 @cindex @samp{Q} packet
36361 General query (@samp{q}) and set (@samp{Q}). These packets are
36362 described fully in @ref{General Query Packets}.
36365 @cindex @samp{r} packet
36366 Reset the entire system.
36368 Don't use this packet; use the @samp{R} packet instead.
36371 @cindex @samp{R} packet
36372 Restart the program being debugged. @var{XX}, while needed, is ignored.
36373 This packet is only available in extended mode (@pxref{extended mode}).
36375 The @samp{R} packet has no reply.
36377 @item s @r{[}@var{addr}@r{]}
36378 @cindex @samp{s} packet
36379 Single step. @var{addr} is the address at which to resume. If
36380 @var{addr} is omitted, resume at same address.
36382 This packet is deprecated for multi-threading support. @xref{vCont
36386 @xref{Stop Reply Packets}, for the reply specifications.
36388 @item S @var{sig}@r{[};@var{addr}@r{]}
36389 @anchor{step with signal packet}
36390 @cindex @samp{S} packet
36391 Step with signal. This is analogous to the @samp{C} packet, but
36392 requests a single-step, rather than a normal resumption of execution.
36394 This packet is deprecated for multi-threading support. @xref{vCont
36398 @xref{Stop Reply Packets}, for the reply specifications.
36400 @item t @var{addr}:@var{PP},@var{MM}
36401 @cindex @samp{t} packet
36402 Search backwards starting at address @var{addr} for a match with pattern
36403 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36404 @var{addr} must be at least 3 digits.
36406 @item T @var{thread-id}
36407 @cindex @samp{T} packet
36408 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36413 thread is still alive
36419 Packets starting with @samp{v} are identified by a multi-letter name,
36420 up to the first @samp{;} or @samp{?} (or the end of the packet).
36422 @item vAttach;@var{pid}
36423 @cindex @samp{vAttach} packet
36424 Attach to a new process with the specified process ID @var{pid}.
36425 The process ID is a
36426 hexadecimal integer identifying the process. In all-stop mode, all
36427 threads in the attached process are stopped; in non-stop mode, it may be
36428 attached without being stopped if that is supported by the target.
36430 @c In non-stop mode, on a successful vAttach, the stub should set the
36431 @c current thread to a thread of the newly-attached process. After
36432 @c attaching, GDB queries for the attached process's thread ID with qC.
36433 @c Also note that, from a user perspective, whether or not the
36434 @c target is stopped on attach in non-stop mode depends on whether you
36435 @c use the foreground or background version of the attach command, not
36436 @c on what vAttach does; GDB does the right thing with respect to either
36437 @c stopping or restarting threads.
36439 This packet is only available in extended mode (@pxref{extended mode}).
36445 @item @r{Any stop packet}
36446 for success in all-stop mode (@pxref{Stop Reply Packets})
36448 for success in non-stop mode (@pxref{Remote Non-Stop})
36451 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36452 @cindex @samp{vCont} packet
36453 @anchor{vCont packet}
36454 Resume the inferior, specifying different actions for each thread.
36455 If an action is specified with no @var{thread-id}, then it is applied to any
36456 threads that don't have a specific action specified; if no default action is
36457 specified then other threads should remain stopped in all-stop mode and
36458 in their current state in non-stop mode.
36459 Specifying multiple
36460 default actions is an error; specifying no actions is also an error.
36461 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36463 Currently supported actions are:
36469 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36473 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36478 The optional argument @var{addr} normally associated with the
36479 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36480 not supported in @samp{vCont}.
36482 The @samp{t} action is only relevant in non-stop mode
36483 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36484 A stop reply should be generated for any affected thread not already stopped.
36485 When a thread is stopped by means of a @samp{t} action,
36486 the corresponding stop reply should indicate that the thread has stopped with
36487 signal @samp{0}, regardless of whether the target uses some other signal
36488 as an implementation detail.
36490 The stub must support @samp{vCont} if it reports support for
36491 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36492 this case @samp{vCont} actions can be specified to apply to all threads
36493 in a process by using the @samp{p@var{pid}.-1} form of the
36497 @xref{Stop Reply Packets}, for the reply specifications.
36500 @cindex @samp{vCont?} packet
36501 Request a list of actions supported by the @samp{vCont} packet.
36505 @item vCont@r{[};@var{action}@dots{}@r{]}
36506 The @samp{vCont} packet is supported. Each @var{action} is a supported
36507 command in the @samp{vCont} packet.
36509 The @samp{vCont} packet is not supported.
36512 @item vFile:@var{operation}:@var{parameter}@dots{}
36513 @cindex @samp{vFile} packet
36514 Perform a file operation on the target system. For details,
36515 see @ref{Host I/O Packets}.
36517 @item vFlashErase:@var{addr},@var{length}
36518 @cindex @samp{vFlashErase} packet
36519 Direct the stub to erase @var{length} bytes of flash starting at
36520 @var{addr}. The region may enclose any number of flash blocks, but
36521 its start and end must fall on block boundaries, as indicated by the
36522 flash block size appearing in the memory map (@pxref{Memory Map
36523 Format}). @value{GDBN} groups flash memory programming operations
36524 together, and sends a @samp{vFlashDone} request after each group; the
36525 stub is allowed to delay erase operation until the @samp{vFlashDone}
36526 packet is received.
36536 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36537 @cindex @samp{vFlashWrite} packet
36538 Direct the stub to write data to flash address @var{addr}. The data
36539 is passed in binary form using the same encoding as for the @samp{X}
36540 packet (@pxref{Binary Data}). The memory ranges specified by
36541 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36542 not overlap, and must appear in order of increasing addresses
36543 (although @samp{vFlashErase} packets for higher addresses may already
36544 have been received; the ordering is guaranteed only between
36545 @samp{vFlashWrite} packets). If a packet writes to an address that was
36546 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36547 target-specific method, the results are unpredictable.
36555 for vFlashWrite addressing non-flash memory
36561 @cindex @samp{vFlashDone} packet
36562 Indicate to the stub that flash programming operation is finished.
36563 The stub is permitted to delay or batch the effects of a group of
36564 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36565 @samp{vFlashDone} packet is received. The contents of the affected
36566 regions of flash memory are unpredictable until the @samp{vFlashDone}
36567 request is completed.
36569 @item vKill;@var{pid}
36570 @cindex @samp{vKill} packet
36571 Kill the process with the specified process ID. @var{pid} is a
36572 hexadecimal integer identifying the process. This packet is used in
36573 preference to @samp{k} when multiprocess protocol extensions are
36574 supported; see @ref{multiprocess extensions}.
36584 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36585 @cindex @samp{vRun} packet
36586 Run the program @var{filename}, passing it each @var{argument} on its
36587 command line. The file and arguments are hex-encoded strings. If
36588 @var{filename} is an empty string, the stub may use a default program
36589 (e.g.@: the last program run). The program is created in the stopped
36592 @c FIXME: What about non-stop mode?
36594 This packet is only available in extended mode (@pxref{extended mode}).
36600 @item @r{Any stop packet}
36601 for success (@pxref{Stop Reply Packets})
36605 @cindex @samp{vStopped} packet
36606 @xref{Notification Packets}.
36608 @item X @var{addr},@var{length}:@var{XX@dots{}}
36610 @cindex @samp{X} packet
36611 Write data to memory, where the data is transmitted in binary.
36612 @var{addr} is address, @var{length} is number of bytes,
36613 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36623 @item z @var{type},@var{addr},@var{kind}
36624 @itemx Z @var{type},@var{addr},@var{kind}
36625 @anchor{insert breakpoint or watchpoint packet}
36626 @cindex @samp{z} packet
36627 @cindex @samp{Z} packets
36628 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36629 watchpoint starting at address @var{address} of kind @var{kind}.
36631 Each breakpoint and watchpoint packet @var{type} is documented
36634 @emph{Implementation notes: A remote target shall return an empty string
36635 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36636 remote target shall support either both or neither of a given
36637 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36638 avoid potential problems with duplicate packets, the operations should
36639 be implemented in an idempotent way.}
36641 @item z0,@var{addr},@var{kind}
36642 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36643 @cindex @samp{z0} packet
36644 @cindex @samp{Z0} packet
36645 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36646 @var{addr} of type @var{kind}.
36648 A memory breakpoint is implemented by replacing the instruction at
36649 @var{addr} with a software breakpoint or trap instruction. The
36650 @var{kind} is target-specific and typically indicates the size of
36651 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36652 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36653 architectures have additional meanings for @var{kind};
36654 @var{cond_list} is an optional list of conditional expressions in bytecode
36655 form that should be evaluated on the target's side. These are the
36656 conditions that should be taken into consideration when deciding if
36657 the breakpoint trigger should be reported back to @var{GDBN}.
36659 The @var{cond_list} parameter is comprised of a series of expressions,
36660 concatenated without separators. Each expression has the following form:
36664 @item X @var{len},@var{expr}
36665 @var{len} is the length of the bytecode expression and @var{expr} is the
36666 actual conditional expression in bytecode form.
36670 The optional @var{cmd_list} parameter introduces commands that may be
36671 run on the target, rather than being reported back to @value{GDBN}.
36672 The parameter starts with a numeric flag @var{persist}; if the flag is
36673 nonzero, then the breakpoint may remain active and the commands
36674 continue to be run even when @value{GDBN} disconnects from the target.
36675 Following this flag is a series of expressions concatenated with no
36676 separators. Each expression has the following form:
36680 @item X @var{len},@var{expr}
36681 @var{len} is the length of the bytecode expression and @var{expr} is the
36682 actual conditional expression in bytecode form.
36686 see @ref{Architecture-Specific Protocol Details}.
36688 @emph{Implementation note: It is possible for a target to copy or move
36689 code that contains memory breakpoints (e.g., when implementing
36690 overlays). The behavior of this packet, in the presence of such a
36691 target, is not defined.}
36703 @item z1,@var{addr},@var{kind}
36704 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36705 @cindex @samp{z1} packet
36706 @cindex @samp{Z1} packet
36707 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36708 address @var{addr}.
36710 A hardware breakpoint is implemented using a mechanism that is not
36711 dependant on being able to modify the target's memory. @var{kind}
36712 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36714 @emph{Implementation note: A hardware breakpoint is not affected by code
36727 @item z2,@var{addr},@var{kind}
36728 @itemx Z2,@var{addr},@var{kind}
36729 @cindex @samp{z2} packet
36730 @cindex @samp{Z2} packet
36731 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36732 @var{kind} is interpreted as the number of bytes to watch.
36744 @item z3,@var{addr},@var{kind}
36745 @itemx Z3,@var{addr},@var{kind}
36746 @cindex @samp{z3} packet
36747 @cindex @samp{Z3} packet
36748 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36749 @var{kind} is interpreted as the number of bytes to watch.
36761 @item z4,@var{addr},@var{kind}
36762 @itemx Z4,@var{addr},@var{kind}
36763 @cindex @samp{z4} packet
36764 @cindex @samp{Z4} packet
36765 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36766 @var{kind} is interpreted as the number of bytes to watch.
36780 @node Stop Reply Packets
36781 @section Stop Reply Packets
36782 @cindex stop reply packets
36784 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36785 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36786 receive any of the below as a reply. Except for @samp{?}
36787 and @samp{vStopped}, that reply is only returned
36788 when the target halts. In the below the exact meaning of @dfn{signal
36789 number} is defined by the header @file{include/gdb/signals.h} in the
36790 @value{GDBN} source code.
36792 As in the description of request packets, we include spaces in the
36793 reply templates for clarity; these are not part of the reply packet's
36794 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36800 The program received signal number @var{AA} (a two-digit hexadecimal
36801 number). This is equivalent to a @samp{T} response with no
36802 @var{n}:@var{r} pairs.
36804 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36805 @cindex @samp{T} packet reply
36806 The program received signal number @var{AA} (a two-digit hexadecimal
36807 number). This is equivalent to an @samp{S} response, except that the
36808 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36809 and other information directly in the stop reply packet, reducing
36810 round-trip latency. Single-step and breakpoint traps are reported
36811 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36815 If @var{n} is a hexadecimal number, it is a register number, and the
36816 corresponding @var{r} gives that register's value. @var{r} is a
36817 series of bytes in target byte order, with each byte given by a
36818 two-digit hex number.
36821 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36822 the stopped thread, as specified in @ref{thread-id syntax}.
36825 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36826 the core on which the stop event was detected.
36829 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36830 specific event that stopped the target. The currently defined stop
36831 reasons are listed below. @var{aa} should be @samp{05}, the trap
36832 signal. At most one stop reason should be present.
36835 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36836 and go on to the next; this allows us to extend the protocol in the
36840 The currently defined stop reasons are:
36846 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36849 @cindex shared library events, remote reply
36851 The packet indicates that the loaded libraries have changed.
36852 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36853 list of loaded libraries. @var{r} is ignored.
36855 @cindex replay log events, remote reply
36857 The packet indicates that the target cannot continue replaying
36858 logged execution events, because it has reached the end (or the
36859 beginning when executing backward) of the log. The value of @var{r}
36860 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36861 for more information.
36865 @itemx W @var{AA} ; process:@var{pid}
36866 The process exited, and @var{AA} is the exit status. This is only
36867 applicable to certain targets.
36869 The second form of the response, including the process ID of the exited
36870 process, can be used only when @value{GDBN} has reported support for
36871 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36872 The @var{pid} is formatted as a big-endian hex string.
36875 @itemx X @var{AA} ; process:@var{pid}
36876 The process terminated with signal @var{AA}.
36878 The second form of the response, including the process ID of the
36879 terminated process, can be used only when @value{GDBN} has reported
36880 support for multiprocess protocol extensions; see @ref{multiprocess
36881 extensions}. The @var{pid} is formatted as a big-endian hex string.
36883 @item O @var{XX}@dots{}
36884 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36885 written as the program's console output. This can happen at any time
36886 while the program is running and the debugger should continue to wait
36887 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36889 @item F @var{call-id},@var{parameter}@dots{}
36890 @var{call-id} is the identifier which says which host system call should
36891 be called. This is just the name of the function. Translation into the
36892 correct system call is only applicable as it's defined in @value{GDBN}.
36893 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36896 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36897 this very system call.
36899 The target replies with this packet when it expects @value{GDBN} to
36900 call a host system call on behalf of the target. @value{GDBN} replies
36901 with an appropriate @samp{F} packet and keeps up waiting for the next
36902 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36903 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36904 Protocol Extension}, for more details.
36908 @node General Query Packets
36909 @section General Query Packets
36910 @cindex remote query requests
36912 Packets starting with @samp{q} are @dfn{general query packets};
36913 packets starting with @samp{Q} are @dfn{general set packets}. General
36914 query and set packets are a semi-unified form for retrieving and
36915 sending information to and from the stub.
36917 The initial letter of a query or set packet is followed by a name
36918 indicating what sort of thing the packet applies to. For example,
36919 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36920 definitions with the stub. These packet names follow some
36925 The name must not contain commas, colons or semicolons.
36927 Most @value{GDBN} query and set packets have a leading upper case
36930 The names of custom vendor packets should use a company prefix, in
36931 lower case, followed by a period. For example, packets designed at
36932 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36933 foos) or @samp{Qacme.bar} (for setting bars).
36936 The name of a query or set packet should be separated from any
36937 parameters by a @samp{:}; the parameters themselves should be
36938 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36939 full packet name, and check for a separator or the end of the packet,
36940 in case two packet names share a common prefix. New packets should not begin
36941 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36942 packets predate these conventions, and have arguments without any terminator
36943 for the packet name; we suspect they are in widespread use in places that
36944 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36945 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36948 Like the descriptions of the other packets, each description here
36949 has a template showing the packet's overall syntax, followed by an
36950 explanation of the packet's meaning. We include spaces in some of the
36951 templates for clarity; these are not part of the packet's syntax. No
36952 @value{GDBN} packet uses spaces to separate its components.
36954 Here are the currently defined query and set packets:
36960 Turn on or off the agent as a helper to perform some debugging operations
36961 delegated from @value{GDBN} (@pxref{Control Agent}).
36963 @item QAllow:@var{op}:@var{val}@dots{}
36964 @cindex @samp{QAllow} packet
36965 Specify which operations @value{GDBN} expects to request of the
36966 target, as a semicolon-separated list of operation name and value
36967 pairs. Possible values for @var{op} include @samp{WriteReg},
36968 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36969 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36970 indicating that @value{GDBN} will not request the operation, or 1,
36971 indicating that it may. (The target can then use this to set up its
36972 own internals optimally, for instance if the debugger never expects to
36973 insert breakpoints, it may not need to install its own trap handler.)
36976 @cindex current thread, remote request
36977 @cindex @samp{qC} packet
36978 Return the current thread ID.
36982 @item QC @var{thread-id}
36983 Where @var{thread-id} is a thread ID as documented in
36984 @ref{thread-id syntax}.
36985 @item @r{(anything else)}
36986 Any other reply implies the old thread ID.
36989 @item qCRC:@var{addr},@var{length}
36990 @cindex CRC of memory block, remote request
36991 @cindex @samp{qCRC} packet
36992 Compute the CRC checksum of a block of memory using CRC-32 defined in
36993 IEEE 802.3. The CRC is computed byte at a time, taking the most
36994 significant bit of each byte first. The initial pattern code
36995 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36997 @emph{Note:} This is the same CRC used in validating separate debug
36998 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36999 Files}). However the algorithm is slightly different. When validating
37000 separate debug files, the CRC is computed taking the @emph{least}
37001 significant bit of each byte first, and the final result is inverted to
37002 detect trailing zeros.
37007 An error (such as memory fault)
37008 @item C @var{crc32}
37009 The specified memory region's checksum is @var{crc32}.
37012 @item QDisableRandomization:@var{value}
37013 @cindex disable address space randomization, remote request
37014 @cindex @samp{QDisableRandomization} packet
37015 Some target operating systems will randomize the virtual address space
37016 of the inferior process as a security feature, but provide a feature
37017 to disable such randomization, e.g.@: to allow for a more deterministic
37018 debugging experience. On such systems, this packet with a @var{value}
37019 of 1 directs the target to disable address space randomization for
37020 processes subsequently started via @samp{vRun} packets, while a packet
37021 with a @var{value} of 0 tells the target to enable address space
37024 This packet is only available in extended mode (@pxref{extended mode}).
37029 The request succeeded.
37032 An error occurred. @var{nn} are hex digits.
37035 An empty reply indicates that @samp{QDisableRandomization} is not supported
37039 This packet is not probed by default; the remote stub must request it,
37040 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37041 This should only be done on targets that actually support disabling
37042 address space randomization.
37045 @itemx qsThreadInfo
37046 @cindex list active threads, remote request
37047 @cindex @samp{qfThreadInfo} packet
37048 @cindex @samp{qsThreadInfo} packet
37049 Obtain a list of all active thread IDs from the target (OS). Since there
37050 may be too many active threads to fit into one reply packet, this query
37051 works iteratively: it may require more than one query/reply sequence to
37052 obtain the entire list of threads. The first query of the sequence will
37053 be the @samp{qfThreadInfo} query; subsequent queries in the
37054 sequence will be the @samp{qsThreadInfo} query.
37056 NOTE: This packet replaces the @samp{qL} query (see below).
37060 @item m @var{thread-id}
37062 @item m @var{thread-id},@var{thread-id}@dots{}
37063 a comma-separated list of thread IDs
37065 (lower case letter @samp{L}) denotes end of list.
37068 In response to each query, the target will reply with a list of one or
37069 more thread IDs, separated by commas.
37070 @value{GDBN} will respond to each reply with a request for more thread
37071 ids (using the @samp{qs} form of the query), until the target responds
37072 with @samp{l} (lower-case ell, for @dfn{last}).
37073 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37076 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37077 @cindex get thread-local storage address, remote request
37078 @cindex @samp{qGetTLSAddr} packet
37079 Fetch the address associated with thread local storage specified
37080 by @var{thread-id}, @var{offset}, and @var{lm}.
37082 @var{thread-id} is the thread ID associated with the
37083 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37085 @var{offset} is the (big endian, hex encoded) offset associated with the
37086 thread local variable. (This offset is obtained from the debug
37087 information associated with the variable.)
37089 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37090 load module associated with the thread local storage. For example,
37091 a @sc{gnu}/Linux system will pass the link map address of the shared
37092 object associated with the thread local storage under consideration.
37093 Other operating environments may choose to represent the load module
37094 differently, so the precise meaning of this parameter will vary.
37098 @item @var{XX}@dots{}
37099 Hex encoded (big endian) bytes representing the address of the thread
37100 local storage requested.
37103 An error occurred. @var{nn} are hex digits.
37106 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37109 @item qGetTIBAddr:@var{thread-id}
37110 @cindex get thread information block address
37111 @cindex @samp{qGetTIBAddr} packet
37112 Fetch address of the Windows OS specific Thread Information Block.
37114 @var{thread-id} is the thread ID associated with the thread.
37118 @item @var{XX}@dots{}
37119 Hex encoded (big endian) bytes representing the linear address of the
37120 thread information block.
37123 An error occured. This means that either the thread was not found, or the
37124 address could not be retrieved.
37127 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37130 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37131 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37132 digit) is one to indicate the first query and zero to indicate a
37133 subsequent query; @var{threadcount} (two hex digits) is the maximum
37134 number of threads the response packet can contain; and @var{nextthread}
37135 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37136 returned in the response as @var{argthread}.
37138 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37142 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37143 Where: @var{count} (two hex digits) is the number of threads being
37144 returned; @var{done} (one hex digit) is zero to indicate more threads
37145 and one indicates no further threads; @var{argthreadid} (eight hex
37146 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37147 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37148 digits). See @code{remote.c:parse_threadlist_response()}.
37152 @cindex section offsets, remote request
37153 @cindex @samp{qOffsets} packet
37154 Get section offsets that the target used when relocating the downloaded
37159 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37160 Relocate the @code{Text} section by @var{xxx} from its original address.
37161 Relocate the @code{Data} section by @var{yyy} from its original address.
37162 If the object file format provides segment information (e.g.@: @sc{elf}
37163 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37164 segments by the supplied offsets.
37166 @emph{Note: while a @code{Bss} offset may be included in the response,
37167 @value{GDBN} ignores this and instead applies the @code{Data} offset
37168 to the @code{Bss} section.}
37170 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37171 Relocate the first segment of the object file, which conventionally
37172 contains program code, to a starting address of @var{xxx}. If
37173 @samp{DataSeg} is specified, relocate the second segment, which
37174 conventionally contains modifiable data, to a starting address of
37175 @var{yyy}. @value{GDBN} will report an error if the object file
37176 does not contain segment information, or does not contain at least
37177 as many segments as mentioned in the reply. Extra segments are
37178 kept at fixed offsets relative to the last relocated segment.
37181 @item qP @var{mode} @var{thread-id}
37182 @cindex thread information, remote request
37183 @cindex @samp{qP} packet
37184 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37185 encoded 32 bit mode; @var{thread-id} is a thread ID
37186 (@pxref{thread-id syntax}).
37188 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37191 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37195 @cindex non-stop mode, remote request
37196 @cindex @samp{QNonStop} packet
37198 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37199 @xref{Remote Non-Stop}, for more information.
37204 The request succeeded.
37207 An error occurred. @var{nn} are hex digits.
37210 An empty reply indicates that @samp{QNonStop} is not supported by
37214 This packet is not probed by default; the remote stub must request it,
37215 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37216 Use of this packet is controlled by the @code{set non-stop} command;
37217 @pxref{Non-Stop Mode}.
37219 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37220 @cindex pass signals to inferior, remote request
37221 @cindex @samp{QPassSignals} packet
37222 @anchor{QPassSignals}
37223 Each listed @var{signal} should be passed directly to the inferior process.
37224 Signals are numbered identically to continue packets and stop replies
37225 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37226 strictly greater than the previous item. These signals do not need to stop
37227 the inferior, or be reported to @value{GDBN}. All other signals should be
37228 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37229 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37230 new list. This packet improves performance when using @samp{handle
37231 @var{signal} nostop noprint pass}.
37236 The request succeeded.
37239 An error occurred. @var{nn} are hex digits.
37242 An empty reply indicates that @samp{QPassSignals} is not supported by
37246 Use of this packet is controlled by the @code{set remote pass-signals}
37247 command (@pxref{Remote Configuration, set remote pass-signals}).
37248 This packet is not probed by default; the remote stub must request it,
37249 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37251 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37252 @cindex signals the inferior may see, remote request
37253 @cindex @samp{QProgramSignals} packet
37254 @anchor{QProgramSignals}
37255 Each listed @var{signal} may be delivered to the inferior process.
37256 Others should be silently discarded.
37258 In some cases, the remote stub may need to decide whether to deliver a
37259 signal to the program or not without @value{GDBN} involvement. One
37260 example of that is while detaching --- the program's threads may have
37261 stopped for signals that haven't yet had a chance of being reported to
37262 @value{GDBN}, and so the remote stub can use the signal list specified
37263 by this packet to know whether to deliver or ignore those pending
37266 This does not influence whether to deliver a signal as requested by a
37267 resumption packet (@pxref{vCont packet}).
37269 Signals are numbered identically to continue packets and stop replies
37270 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37271 strictly greater than the previous item. Multiple
37272 @samp{QProgramSignals} packets do not combine; any earlier
37273 @samp{QProgramSignals} list is completely replaced by the new list.
37278 The request succeeded.
37281 An error occurred. @var{nn} are hex digits.
37284 An empty reply indicates that @samp{QProgramSignals} is not supported
37288 Use of this packet is controlled by the @code{set remote program-signals}
37289 command (@pxref{Remote Configuration, set remote program-signals}).
37290 This packet is not probed by default; the remote stub must request it,
37291 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37293 @item qRcmd,@var{command}
37294 @cindex execute remote command, remote request
37295 @cindex @samp{qRcmd} packet
37296 @var{command} (hex encoded) is passed to the local interpreter for
37297 execution. Invalid commands should be reported using the output
37298 string. Before the final result packet, the target may also respond
37299 with a number of intermediate @samp{O@var{output}} console output
37300 packets. @emph{Implementors should note that providing access to a
37301 stubs's interpreter may have security implications}.
37306 A command response with no output.
37308 A command response with the hex encoded output string @var{OUTPUT}.
37310 Indicate a badly formed request.
37312 An empty reply indicates that @samp{qRcmd} is not recognized.
37315 (Note that the @code{qRcmd} packet's name is separated from the
37316 command by a @samp{,}, not a @samp{:}, contrary to the naming
37317 conventions above. Please don't use this packet as a model for new
37320 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37321 @cindex searching memory, in remote debugging
37323 @cindex @samp{qSearch:memory} packet
37325 @cindex @samp{qSearch memory} packet
37326 @anchor{qSearch memory}
37327 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37328 @var{address} and @var{length} are encoded in hex.
37329 @var{search-pattern} is a sequence of bytes, hex encoded.
37334 The pattern was not found.
37336 The pattern was found at @var{address}.
37338 A badly formed request or an error was encountered while searching memory.
37340 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37343 @item QStartNoAckMode
37344 @cindex @samp{QStartNoAckMode} packet
37345 @anchor{QStartNoAckMode}
37346 Request that the remote stub disable the normal @samp{+}/@samp{-}
37347 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37352 The stub has switched to no-acknowledgment mode.
37353 @value{GDBN} acknowledges this reponse,
37354 but neither the stub nor @value{GDBN} shall send or expect further
37355 @samp{+}/@samp{-} acknowledgments in the current connection.
37357 An empty reply indicates that the stub does not support no-acknowledgment mode.
37360 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37361 @cindex supported packets, remote query
37362 @cindex features of the remote protocol
37363 @cindex @samp{qSupported} packet
37364 @anchor{qSupported}
37365 Tell the remote stub about features supported by @value{GDBN}, and
37366 query the stub for features it supports. This packet allows
37367 @value{GDBN} and the remote stub to take advantage of each others'
37368 features. @samp{qSupported} also consolidates multiple feature probes
37369 at startup, to improve @value{GDBN} performance---a single larger
37370 packet performs better than multiple smaller probe packets on
37371 high-latency links. Some features may enable behavior which must not
37372 be on by default, e.g.@: because it would confuse older clients or
37373 stubs. Other features may describe packets which could be
37374 automatically probed for, but are not. These features must be
37375 reported before @value{GDBN} will use them. This ``default
37376 unsupported'' behavior is not appropriate for all packets, but it
37377 helps to keep the initial connection time under control with new
37378 versions of @value{GDBN} which support increasing numbers of packets.
37382 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37383 The stub supports or does not support each returned @var{stubfeature},
37384 depending on the form of each @var{stubfeature} (see below for the
37387 An empty reply indicates that @samp{qSupported} is not recognized,
37388 or that no features needed to be reported to @value{GDBN}.
37391 The allowed forms for each feature (either a @var{gdbfeature} in the
37392 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37396 @item @var{name}=@var{value}
37397 The remote protocol feature @var{name} is supported, and associated
37398 with the specified @var{value}. The format of @var{value} depends
37399 on the feature, but it must not include a semicolon.
37401 The remote protocol feature @var{name} is supported, and does not
37402 need an associated value.
37404 The remote protocol feature @var{name} is not supported.
37406 The remote protocol feature @var{name} may be supported, and
37407 @value{GDBN} should auto-detect support in some other way when it is
37408 needed. This form will not be used for @var{gdbfeature} notifications,
37409 but may be used for @var{stubfeature} responses.
37412 Whenever the stub receives a @samp{qSupported} request, the
37413 supplied set of @value{GDBN} features should override any previous
37414 request. This allows @value{GDBN} to put the stub in a known
37415 state, even if the stub had previously been communicating with
37416 a different version of @value{GDBN}.
37418 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37423 This feature indicates whether @value{GDBN} supports multiprocess
37424 extensions to the remote protocol. @value{GDBN} does not use such
37425 extensions unless the stub also reports that it supports them by
37426 including @samp{multiprocess+} in its @samp{qSupported} reply.
37427 @xref{multiprocess extensions}, for details.
37430 This feature indicates that @value{GDBN} supports the XML target
37431 description. If the stub sees @samp{xmlRegisters=} with target
37432 specific strings separated by a comma, it will report register
37436 This feature indicates whether @value{GDBN} supports the
37437 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37438 instruction reply packet}).
37441 Stubs should ignore any unknown values for
37442 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37443 packet supports receiving packets of unlimited length (earlier
37444 versions of @value{GDBN} may reject overly long responses). Additional values
37445 for @var{gdbfeature} may be defined in the future to let the stub take
37446 advantage of new features in @value{GDBN}, e.g.@: incompatible
37447 improvements in the remote protocol---the @samp{multiprocess} feature is
37448 an example of such a feature. The stub's reply should be independent
37449 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37450 describes all the features it supports, and then the stub replies with
37451 all the features it supports.
37453 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37454 responses, as long as each response uses one of the standard forms.
37456 Some features are flags. A stub which supports a flag feature
37457 should respond with a @samp{+} form response. Other features
37458 require values, and the stub should respond with an @samp{=}
37461 Each feature has a default value, which @value{GDBN} will use if
37462 @samp{qSupported} is not available or if the feature is not mentioned
37463 in the @samp{qSupported} response. The default values are fixed; a
37464 stub is free to omit any feature responses that match the defaults.
37466 Not all features can be probed, but for those which can, the probing
37467 mechanism is useful: in some cases, a stub's internal
37468 architecture may not allow the protocol layer to know some information
37469 about the underlying target in advance. This is especially common in
37470 stubs which may be configured for multiple targets.
37472 These are the currently defined stub features and their properties:
37474 @multitable @columnfractions 0.35 0.2 0.12 0.2
37475 @c NOTE: The first row should be @headitem, but we do not yet require
37476 @c a new enough version of Texinfo (4.7) to use @headitem.
37478 @tab Value Required
37482 @item @samp{PacketSize}
37487 @item @samp{qXfer:auxv:read}
37492 @item @samp{qXfer:btrace:read}
37497 @item @samp{qXfer:features:read}
37502 @item @samp{qXfer:libraries:read}
37507 @item @samp{qXfer:memory-map:read}
37512 @item @samp{qXfer:sdata:read}
37517 @item @samp{qXfer:spu:read}
37522 @item @samp{qXfer:spu:write}
37527 @item @samp{qXfer:siginfo:read}
37532 @item @samp{qXfer:siginfo:write}
37537 @item @samp{qXfer:threads:read}
37542 @item @samp{qXfer:traceframe-info:read}
37547 @item @samp{qXfer:uib:read}
37552 @item @samp{qXfer:fdpic:read}
37557 @item @samp{Qbtrace:off}
37562 @item @samp{Qbtrace:bts}
37567 @item @samp{QNonStop}
37572 @item @samp{QPassSignals}
37577 @item @samp{QStartNoAckMode}
37582 @item @samp{multiprocess}
37587 @item @samp{ConditionalBreakpoints}
37592 @item @samp{ConditionalTracepoints}
37597 @item @samp{ReverseContinue}
37602 @item @samp{ReverseStep}
37607 @item @samp{TracepointSource}
37612 @item @samp{QAgent}
37617 @item @samp{QAllow}
37622 @item @samp{QDisableRandomization}
37627 @item @samp{EnableDisableTracepoints}
37632 @item @samp{QTBuffer:size}
37637 @item @samp{tracenz}
37642 @item @samp{BreakpointCommands}
37649 These are the currently defined stub features, in more detail:
37652 @cindex packet size, remote protocol
37653 @item PacketSize=@var{bytes}
37654 The remote stub can accept packets up to at least @var{bytes} in
37655 length. @value{GDBN} will send packets up to this size for bulk
37656 transfers, and will never send larger packets. This is a limit on the
37657 data characters in the packet, including the frame and checksum.
37658 There is no trailing NUL byte in a remote protocol packet; if the stub
37659 stores packets in a NUL-terminated format, it should allow an extra
37660 byte in its buffer for the NUL. If this stub feature is not supported,
37661 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37663 @item qXfer:auxv:read
37664 The remote stub understands the @samp{qXfer:auxv:read} packet
37665 (@pxref{qXfer auxiliary vector read}).
37667 @item qXfer:btrace:read
37668 The remote stub understands the @samp{qXfer:btrace:read}
37669 packet (@pxref{qXfer btrace read}).
37671 @item qXfer:features:read
37672 The remote stub understands the @samp{qXfer:features:read} packet
37673 (@pxref{qXfer target description read}).
37675 @item qXfer:libraries:read
37676 The remote stub understands the @samp{qXfer:libraries:read} packet
37677 (@pxref{qXfer library list read}).
37679 @item qXfer:libraries-svr4:read
37680 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37681 (@pxref{qXfer svr4 library list read}).
37683 @item qXfer:memory-map:read
37684 The remote stub understands the @samp{qXfer:memory-map:read} packet
37685 (@pxref{qXfer memory map read}).
37687 @item qXfer:sdata:read
37688 The remote stub understands the @samp{qXfer:sdata:read} packet
37689 (@pxref{qXfer sdata read}).
37691 @item qXfer:spu:read
37692 The remote stub understands the @samp{qXfer:spu:read} packet
37693 (@pxref{qXfer spu read}).
37695 @item qXfer:spu:write
37696 The remote stub understands the @samp{qXfer:spu:write} packet
37697 (@pxref{qXfer spu write}).
37699 @item qXfer:siginfo:read
37700 The remote stub understands the @samp{qXfer:siginfo:read} packet
37701 (@pxref{qXfer siginfo read}).
37703 @item qXfer:siginfo:write
37704 The remote stub understands the @samp{qXfer:siginfo:write} packet
37705 (@pxref{qXfer siginfo write}).
37707 @item qXfer:threads:read
37708 The remote stub understands the @samp{qXfer:threads:read} packet
37709 (@pxref{qXfer threads read}).
37711 @item qXfer:traceframe-info:read
37712 The remote stub understands the @samp{qXfer:traceframe-info:read}
37713 packet (@pxref{qXfer traceframe info read}).
37715 @item qXfer:uib:read
37716 The remote stub understands the @samp{qXfer:uib:read}
37717 packet (@pxref{qXfer unwind info block}).
37719 @item qXfer:fdpic:read
37720 The remote stub understands the @samp{qXfer:fdpic:read}
37721 packet (@pxref{qXfer fdpic loadmap read}).
37724 The remote stub understands the @samp{QNonStop} packet
37725 (@pxref{QNonStop}).
37728 The remote stub understands the @samp{QPassSignals} packet
37729 (@pxref{QPassSignals}).
37731 @item QStartNoAckMode
37732 The remote stub understands the @samp{QStartNoAckMode} packet and
37733 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37736 @anchor{multiprocess extensions}
37737 @cindex multiprocess extensions, in remote protocol
37738 The remote stub understands the multiprocess extensions to the remote
37739 protocol syntax. The multiprocess extensions affect the syntax of
37740 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37741 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37742 replies. Note that reporting this feature indicates support for the
37743 syntactic extensions only, not that the stub necessarily supports
37744 debugging of more than one process at a time. The stub must not use
37745 multiprocess extensions in packet replies unless @value{GDBN} has also
37746 indicated it supports them in its @samp{qSupported} request.
37748 @item qXfer:osdata:read
37749 The remote stub understands the @samp{qXfer:osdata:read} packet
37750 ((@pxref{qXfer osdata read}).
37752 @item ConditionalBreakpoints
37753 The target accepts and implements evaluation of conditional expressions
37754 defined for breakpoints. The target will only report breakpoint triggers
37755 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37757 @item ConditionalTracepoints
37758 The remote stub accepts and implements conditional expressions defined
37759 for tracepoints (@pxref{Tracepoint Conditions}).
37761 @item ReverseContinue
37762 The remote stub accepts and implements the reverse continue packet
37766 The remote stub accepts and implements the reverse step packet
37769 @item TracepointSource
37770 The remote stub understands the @samp{QTDPsrc} packet that supplies
37771 the source form of tracepoint definitions.
37774 The remote stub understands the @samp{QAgent} packet.
37777 The remote stub understands the @samp{QAllow} packet.
37779 @item QDisableRandomization
37780 The remote stub understands the @samp{QDisableRandomization} packet.
37782 @item StaticTracepoint
37783 @cindex static tracepoints, in remote protocol
37784 The remote stub supports static tracepoints.
37786 @item InstallInTrace
37787 @anchor{install tracepoint in tracing}
37788 The remote stub supports installing tracepoint in tracing.
37790 @item EnableDisableTracepoints
37791 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37792 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37793 to be enabled and disabled while a trace experiment is running.
37795 @item QTBuffer:size
37796 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37797 packet that allows to change the size of the trace buffer.
37800 @cindex string tracing, in remote protocol
37801 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37802 See @ref{Bytecode Descriptions} for details about the bytecode.
37804 @item BreakpointCommands
37805 @cindex breakpoint commands, in remote protocol
37806 The remote stub supports running a breakpoint's command list itself,
37807 rather than reporting the hit to @value{GDBN}.
37810 The remote stub understands the @samp{Qbtrace:off} packet.
37813 The remote stub understands the @samp{Qbtrace:bts} packet.
37818 @cindex symbol lookup, remote request
37819 @cindex @samp{qSymbol} packet
37820 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37821 requests. Accept requests from the target for the values of symbols.
37826 The target does not need to look up any (more) symbols.
37827 @item qSymbol:@var{sym_name}
37828 The target requests the value of symbol @var{sym_name} (hex encoded).
37829 @value{GDBN} may provide the value by using the
37830 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37834 @item qSymbol:@var{sym_value}:@var{sym_name}
37835 Set the value of @var{sym_name} to @var{sym_value}.
37837 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37838 target has previously requested.
37840 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37841 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37847 The target does not need to look up any (more) symbols.
37848 @item qSymbol:@var{sym_name}
37849 The target requests the value of a new symbol @var{sym_name} (hex
37850 encoded). @value{GDBN} will continue to supply the values of symbols
37851 (if available), until the target ceases to request them.
37856 @itemx QTDisconnected
37863 @itemx qTMinFTPILen
37865 @xref{Tracepoint Packets}.
37867 @item qThreadExtraInfo,@var{thread-id}
37868 @cindex thread attributes info, remote request
37869 @cindex @samp{qThreadExtraInfo} packet
37870 Obtain a printable string description of a thread's attributes from
37871 the target OS. @var{thread-id} is a thread ID;
37872 see @ref{thread-id syntax}. This
37873 string may contain anything that the target OS thinks is interesting
37874 for @value{GDBN} to tell the user about the thread. The string is
37875 displayed in @value{GDBN}'s @code{info threads} display. Some
37876 examples of possible thread extra info strings are @samp{Runnable}, or
37877 @samp{Blocked on Mutex}.
37881 @item @var{XX}@dots{}
37882 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37883 comprising the printable string containing the extra information about
37884 the thread's attributes.
37887 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37888 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37889 conventions above. Please don't use this packet as a model for new
37908 @xref{Tracepoint Packets}.
37910 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37911 @cindex read special object, remote request
37912 @cindex @samp{qXfer} packet
37913 @anchor{qXfer read}
37914 Read uninterpreted bytes from the target's special data area
37915 identified by the keyword @var{object}. Request @var{length} bytes
37916 starting at @var{offset} bytes into the data. The content and
37917 encoding of @var{annex} is specific to @var{object}; it can supply
37918 additional details about what data to access.
37920 Here are the specific requests of this form defined so far. All
37921 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37922 formats, listed below.
37925 @item qXfer:auxv:read::@var{offset},@var{length}
37926 @anchor{qXfer auxiliary vector read}
37927 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37928 auxiliary vector}. Note @var{annex} must be empty.
37930 This packet is not probed by default; the remote stub must request it,
37931 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37933 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37934 @anchor{qXfer btrace read}
37936 Return a description of the current branch trace.
37937 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37938 packet may have one of the following values:
37942 Returns all available branch trace.
37945 Returns all available branch trace if the branch trace changed since
37946 the last read request.
37949 This packet is not probed by default; the remote stub must request it
37950 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37952 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37953 @anchor{qXfer target description read}
37954 Access the @dfn{target description}. @xref{Target Descriptions}. The
37955 annex specifies which XML document to access. The main description is
37956 always loaded from the @samp{target.xml} annex.
37958 This packet is not probed by default; the remote stub must request it,
37959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37961 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37962 @anchor{qXfer library list read}
37963 Access the target's list of loaded libraries. @xref{Library List Format}.
37964 The annex part of the generic @samp{qXfer} packet must be empty
37965 (@pxref{qXfer read}).
37967 Targets which maintain a list of libraries in the program's memory do
37968 not need to implement this packet; it is designed for platforms where
37969 the operating system manages the list of loaded libraries.
37971 This packet is not probed by default; the remote stub must request it,
37972 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37974 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37975 @anchor{qXfer svr4 library list read}
37976 Access the target's list of loaded libraries when the target is an SVR4
37977 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37978 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37980 This packet is optional for better performance on SVR4 targets.
37981 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37983 This packet is not probed by default; the remote stub must request it,
37984 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37986 @item qXfer:memory-map:read::@var{offset},@var{length}
37987 @anchor{qXfer memory map read}
37988 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37989 annex part of the generic @samp{qXfer} packet must be empty
37990 (@pxref{qXfer read}).
37992 This packet is not probed by default; the remote stub must request it,
37993 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37995 @item qXfer:sdata:read::@var{offset},@var{length}
37996 @anchor{qXfer sdata read}
37998 Read contents of the extra collected static tracepoint marker
37999 information. The annex part of the generic @samp{qXfer} packet must
38000 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38003 This packet is not probed by default; the remote stub must request it,
38004 by supplying an appropriate @samp{qSupported} response
38005 (@pxref{qSupported}).
38007 @item qXfer:siginfo:read::@var{offset},@var{length}
38008 @anchor{qXfer siginfo read}
38009 Read contents of the extra signal information on the target
38010 system. The annex part of the generic @samp{qXfer} packet must be
38011 empty (@pxref{qXfer read}).
38013 This packet is not probed by default; the remote stub must request it,
38014 by supplying an appropriate @samp{qSupported} response
38015 (@pxref{qSupported}).
38017 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38018 @anchor{qXfer spu read}
38019 Read contents of an @code{spufs} file on the target system. The
38020 annex specifies which file to read; it must be of the form
38021 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38022 in the target process, and @var{name} identifes the @code{spufs} file
38023 in that context to be accessed.
38025 This packet is not probed by default; the remote stub must request it,
38026 by supplying an appropriate @samp{qSupported} response
38027 (@pxref{qSupported}).
38029 @item qXfer:threads:read::@var{offset},@var{length}
38030 @anchor{qXfer threads read}
38031 Access the list of threads on target. @xref{Thread List Format}. The
38032 annex part of the generic @samp{qXfer} packet must be empty
38033 (@pxref{qXfer read}).
38035 This packet is not probed by default; the remote stub must request it,
38036 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38038 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38039 @anchor{qXfer traceframe info read}
38041 Return a description of the current traceframe's contents.
38042 @xref{Traceframe Info Format}. The annex part of the generic
38043 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38045 This packet is not probed by default; the remote stub must request it,
38046 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38048 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38049 @anchor{qXfer unwind info block}
38051 Return the unwind information block for @var{pc}. This packet is used
38052 on OpenVMS/ia64 to ask the kernel unwind information.
38054 This packet is not probed by default.
38056 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38057 @anchor{qXfer fdpic loadmap read}
38058 Read contents of @code{loadmap}s on the target system. The
38059 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38060 executable @code{loadmap} or interpreter @code{loadmap} to read.
38062 This packet is not probed by default; the remote stub must request it,
38063 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38065 @item qXfer:osdata:read::@var{offset},@var{length}
38066 @anchor{qXfer osdata read}
38067 Access the target's @dfn{operating system information}.
38068 @xref{Operating System Information}.
38075 Data @var{data} (@pxref{Binary Data}) has been read from the
38076 target. There may be more data at a higher address (although
38077 it is permitted to return @samp{m} even for the last valid
38078 block of data, as long as at least one byte of data was read).
38079 @var{data} may have fewer bytes than the @var{length} in the
38083 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38084 There is no more data to be read. @var{data} may have fewer bytes
38085 than the @var{length} in the request.
38088 The @var{offset} in the request is at the end of the data.
38089 There is no more data to be read.
38092 The request was malformed, or @var{annex} was invalid.
38095 The offset was invalid, or there was an error encountered reading the data.
38096 @var{nn} is a hex-encoded @code{errno} value.
38099 An empty reply indicates the @var{object} string was not recognized by
38100 the stub, or that the object does not support reading.
38103 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38104 @cindex write data into object, remote request
38105 @anchor{qXfer write}
38106 Write uninterpreted bytes into the target's special data area
38107 identified by the keyword @var{object}, starting at @var{offset} bytes
38108 into the data. @var{data}@dots{} is the binary-encoded data
38109 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38110 is specific to @var{object}; it can supply additional details about what data
38113 Here are the specific requests of this form defined so far. All
38114 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38115 formats, listed below.
38118 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38119 @anchor{qXfer siginfo write}
38120 Write @var{data} to the extra signal information on the target system.
38121 The annex part of the generic @samp{qXfer} packet must be
38122 empty (@pxref{qXfer write}).
38124 This packet is not probed by default; the remote stub must request it,
38125 by supplying an appropriate @samp{qSupported} response
38126 (@pxref{qSupported}).
38128 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38129 @anchor{qXfer spu write}
38130 Write @var{data} to an @code{spufs} file on the target system. The
38131 annex specifies which file to write; it must be of the form
38132 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38133 in the target process, and @var{name} identifes the @code{spufs} file
38134 in that context to be accessed.
38136 This packet is not probed by default; the remote stub must request it,
38137 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38143 @var{nn} (hex encoded) is the number of bytes written.
38144 This may be fewer bytes than supplied in the request.
38147 The request was malformed, or @var{annex} was invalid.
38150 The offset was invalid, or there was an error encountered writing the data.
38151 @var{nn} is a hex-encoded @code{errno} value.
38154 An empty reply indicates the @var{object} string was not
38155 recognized by the stub, or that the object does not support writing.
38158 @item qXfer:@var{object}:@var{operation}:@dots{}
38159 Requests of this form may be added in the future. When a stub does
38160 not recognize the @var{object} keyword, or its support for
38161 @var{object} does not recognize the @var{operation} keyword, the stub
38162 must respond with an empty packet.
38164 @item qAttached:@var{pid}
38165 @cindex query attached, remote request
38166 @cindex @samp{qAttached} packet
38167 Return an indication of whether the remote server attached to an
38168 existing process or created a new process. When the multiprocess
38169 protocol extensions are supported (@pxref{multiprocess extensions}),
38170 @var{pid} is an integer in hexadecimal format identifying the target
38171 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38172 the query packet will be simplified as @samp{qAttached}.
38174 This query is used, for example, to know whether the remote process
38175 should be detached or killed when a @value{GDBN} session is ended with
38176 the @code{quit} command.
38181 The remote server attached to an existing process.
38183 The remote server created a new process.
38185 A badly formed request or an error was encountered.
38189 Enable branch tracing for the current thread using bts tracing.
38194 Branch tracing has been enabled.
38196 A badly formed request or an error was encountered.
38200 Disable branch tracing for the current thread.
38205 Branch tracing has been disabled.
38207 A badly formed request or an error was encountered.
38212 @node Architecture-Specific Protocol Details
38213 @section Architecture-Specific Protocol Details
38215 This section describes how the remote protocol is applied to specific
38216 target architectures. Also see @ref{Standard Target Features}, for
38217 details of XML target descriptions for each architecture.
38220 * ARM-Specific Protocol Details::
38221 * MIPS-Specific Protocol Details::
38224 @node ARM-Specific Protocol Details
38225 @subsection @acronym{ARM}-specific Protocol Details
38228 * ARM Breakpoint Kinds::
38231 @node ARM Breakpoint Kinds
38232 @subsubsection @acronym{ARM} Breakpoint Kinds
38233 @cindex breakpoint kinds, @acronym{ARM}
38235 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38240 16-bit Thumb mode breakpoint.
38243 32-bit Thumb mode (Thumb-2) breakpoint.
38246 32-bit @acronym{ARM} mode breakpoint.
38250 @node MIPS-Specific Protocol Details
38251 @subsection @acronym{MIPS}-specific Protocol Details
38254 * MIPS Register packet Format::
38255 * MIPS Breakpoint Kinds::
38258 @node MIPS Register packet Format
38259 @subsubsection @acronym{MIPS} Register Packet Format
38260 @cindex register packet format, @acronym{MIPS}
38262 The following @code{g}/@code{G} packets have previously been defined.
38263 In the below, some thirty-two bit registers are transferred as
38264 sixty-four bits. Those registers should be zero/sign extended (which?)
38265 to fill the space allocated. Register bytes are transferred in target
38266 byte order. The two nibbles within a register byte are transferred
38267 most-significant -- least-significant.
38272 All registers are transferred as thirty-two bit quantities in the order:
38273 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38274 registers; fsr; fir; fp.
38277 All registers are transferred as sixty-four bit quantities (including
38278 thirty-two bit registers such as @code{sr}). The ordering is the same
38283 @node MIPS Breakpoint Kinds
38284 @subsubsection @acronym{MIPS} Breakpoint Kinds
38285 @cindex breakpoint kinds, @acronym{MIPS}
38287 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38292 16-bit @acronym{MIPS16} mode breakpoint.
38295 16-bit @acronym{microMIPS} mode breakpoint.
38298 32-bit standard @acronym{MIPS} mode breakpoint.
38301 32-bit @acronym{microMIPS} mode breakpoint.
38305 @node Tracepoint Packets
38306 @section Tracepoint Packets
38307 @cindex tracepoint packets
38308 @cindex packets, tracepoint
38310 Here we describe the packets @value{GDBN} uses to implement
38311 tracepoints (@pxref{Tracepoints}).
38315 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38316 @cindex @samp{QTDP} packet
38317 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38318 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38319 the tracepoint is disabled. @var{step} is the tracepoint's step
38320 count, and @var{pass} is its pass count. If an @samp{F} is present,
38321 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38322 the number of bytes that the target should copy elsewhere to make room
38323 for the tracepoint. If an @samp{X} is present, it introduces a
38324 tracepoint condition, which consists of a hexadecimal length, followed
38325 by a comma and hex-encoded bytes, in a manner similar to action
38326 encodings as described below. If the trailing @samp{-} is present,
38327 further @samp{QTDP} packets will follow to specify this tracepoint's
38333 The packet was understood and carried out.
38335 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38337 The packet was not recognized.
38340 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38341 Define actions to be taken when a tracepoint is hit. @var{n} and
38342 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38343 this tracepoint. This packet may only be sent immediately after
38344 another @samp{QTDP} packet that ended with a @samp{-}. If the
38345 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38346 specifying more actions for this tracepoint.
38348 In the series of action packets for a given tracepoint, at most one
38349 can have an @samp{S} before its first @var{action}. If such a packet
38350 is sent, it and the following packets define ``while-stepping''
38351 actions. Any prior packets define ordinary actions --- that is, those
38352 taken when the tracepoint is first hit. If no action packet has an
38353 @samp{S}, then all the packets in the series specify ordinary
38354 tracepoint actions.
38356 The @samp{@var{action}@dots{}} portion of the packet is a series of
38357 actions, concatenated without separators. Each action has one of the
38363 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38364 a hexadecimal number whose @var{i}'th bit is set if register number
38365 @var{i} should be collected. (The least significant bit is numbered
38366 zero.) Note that @var{mask} may be any number of digits long; it may
38367 not fit in a 32-bit word.
38369 @item M @var{basereg},@var{offset},@var{len}
38370 Collect @var{len} bytes of memory starting at the address in register
38371 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38372 @samp{-1}, then the range has a fixed address: @var{offset} is the
38373 address of the lowest byte to collect. The @var{basereg},
38374 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38375 values (the @samp{-1} value for @var{basereg} is a special case).
38377 @item X @var{len},@var{expr}
38378 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38379 it directs. @var{expr} is an agent expression, as described in
38380 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38381 two-digit hex number in the packet; @var{len} is the number of bytes
38382 in the expression (and thus one-half the number of hex digits in the
38387 Any number of actions may be packed together in a single @samp{QTDP}
38388 packet, as long as the packet does not exceed the maximum packet
38389 length (400 bytes, for many stubs). There may be only one @samp{R}
38390 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38391 actions. Any registers referred to by @samp{M} and @samp{X} actions
38392 must be collected by a preceding @samp{R} action. (The
38393 ``while-stepping'' actions are treated as if they were attached to a
38394 separate tracepoint, as far as these restrictions are concerned.)
38399 The packet was understood and carried out.
38401 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38403 The packet was not recognized.
38406 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38407 @cindex @samp{QTDPsrc} packet
38408 Specify a source string of tracepoint @var{n} at address @var{addr}.
38409 This is useful to get accurate reproduction of the tracepoints
38410 originally downloaded at the beginning of the trace run. @var{type}
38411 is the name of the tracepoint part, such as @samp{cond} for the
38412 tracepoint's conditional expression (see below for a list of types), while
38413 @var{bytes} is the string, encoded in hexadecimal.
38415 @var{start} is the offset of the @var{bytes} within the overall source
38416 string, while @var{slen} is the total length of the source string.
38417 This is intended for handling source strings that are longer than will
38418 fit in a single packet.
38419 @c Add detailed example when this info is moved into a dedicated
38420 @c tracepoint descriptions section.
38422 The available string types are @samp{at} for the location,
38423 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38424 @value{GDBN} sends a separate packet for each command in the action
38425 list, in the same order in which the commands are stored in the list.
38427 The target does not need to do anything with source strings except
38428 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38431 Although this packet is optional, and @value{GDBN} will only send it
38432 if the target replies with @samp{TracepointSource} @xref{General
38433 Query Packets}, it makes both disconnected tracing and trace files
38434 much easier to use. Otherwise the user must be careful that the
38435 tracepoints in effect while looking at trace frames are identical to
38436 the ones in effect during the trace run; even a small discrepancy
38437 could cause @samp{tdump} not to work, or a particular trace frame not
38440 @item QTDV:@var{n}:@var{value}
38441 @cindex define trace state variable, remote request
38442 @cindex @samp{QTDV} packet
38443 Create a new trace state variable, number @var{n}, with an initial
38444 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38445 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38446 the option of not using this packet for initial values of zero; the
38447 target should simply create the trace state variables as they are
38448 mentioned in expressions.
38450 @item QTFrame:@var{n}
38451 @cindex @samp{QTFrame} packet
38452 Select the @var{n}'th tracepoint frame from the buffer, and use the
38453 register and memory contents recorded there to answer subsequent
38454 request packets from @value{GDBN}.
38456 A successful reply from the stub indicates that the stub has found the
38457 requested frame. The response is a series of parts, concatenated
38458 without separators, describing the frame we selected. Each part has
38459 one of the following forms:
38463 The selected frame is number @var{n} in the trace frame buffer;
38464 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38465 was no frame matching the criteria in the request packet.
38468 The selected trace frame records a hit of tracepoint number @var{t};
38469 @var{t} is a hexadecimal number.
38473 @item QTFrame:pc:@var{addr}
38474 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38475 currently selected frame whose PC is @var{addr};
38476 @var{addr} is a hexadecimal number.
38478 @item QTFrame:tdp:@var{t}
38479 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38480 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38481 is a hexadecimal number.
38483 @item QTFrame:range:@var{start}:@var{end}
38484 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38485 currently selected frame whose PC is between @var{start} (inclusive)
38486 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38489 @item QTFrame:outside:@var{start}:@var{end}
38490 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38491 frame @emph{outside} the given range of addresses (exclusive).
38494 @cindex @samp{qTMinFTPILen} packet
38495 This packet requests the minimum length of instruction at which a fast
38496 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38497 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38498 it depends on the target system being able to create trampolines in
38499 the first 64K of memory, which might or might not be possible for that
38500 system. So the reply to this packet will be 4 if it is able to
38507 The minimum instruction length is currently unknown.
38509 The minimum instruction length is @var{length}, where @var{length} is greater
38510 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38511 that a fast tracepoint may be placed on any instruction regardless of size.
38513 An error has occurred.
38515 An empty reply indicates that the request is not supported by the stub.
38519 @cindex @samp{QTStart} packet
38520 Begin the tracepoint experiment. Begin collecting data from
38521 tracepoint hits in the trace frame buffer. This packet supports the
38522 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38523 instruction reply packet}).
38526 @cindex @samp{QTStop} packet
38527 End the tracepoint experiment. Stop collecting trace frames.
38529 @item QTEnable:@var{n}:@var{addr}
38531 @cindex @samp{QTEnable} packet
38532 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38533 experiment. If the tracepoint was previously disabled, then collection
38534 of data from it will resume.
38536 @item QTDisable:@var{n}:@var{addr}
38538 @cindex @samp{QTDisable} packet
38539 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38540 experiment. No more data will be collected from the tracepoint unless
38541 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38544 @cindex @samp{QTinit} packet
38545 Clear the table of tracepoints, and empty the trace frame buffer.
38547 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38548 @cindex @samp{QTro} packet
38549 Establish the given ranges of memory as ``transparent''. The stub
38550 will answer requests for these ranges from memory's current contents,
38551 if they were not collected as part of the tracepoint hit.
38553 @value{GDBN} uses this to mark read-only regions of memory, like those
38554 containing program code. Since these areas never change, they should
38555 still have the same contents they did when the tracepoint was hit, so
38556 there's no reason for the stub to refuse to provide their contents.
38558 @item QTDisconnected:@var{value}
38559 @cindex @samp{QTDisconnected} packet
38560 Set the choice to what to do with the tracing run when @value{GDBN}
38561 disconnects from the target. A @var{value} of 1 directs the target to
38562 continue the tracing run, while 0 tells the target to stop tracing if
38563 @value{GDBN} is no longer in the picture.
38566 @cindex @samp{qTStatus} packet
38567 Ask the stub if there is a trace experiment running right now.
38569 The reply has the form:
38573 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38574 @var{running} is a single digit @code{1} if the trace is presently
38575 running, or @code{0} if not. It is followed by semicolon-separated
38576 optional fields that an agent may use to report additional status.
38580 If the trace is not running, the agent may report any of several
38581 explanations as one of the optional fields:
38586 No trace has been run yet.
38588 @item tstop[:@var{text}]:0
38589 The trace was stopped by a user-originated stop command. The optional
38590 @var{text} field is a user-supplied string supplied as part of the
38591 stop command (for instance, an explanation of why the trace was
38592 stopped manually). It is hex-encoded.
38595 The trace stopped because the trace buffer filled up.
38597 @item tdisconnected:0
38598 The trace stopped because @value{GDBN} disconnected from the target.
38600 @item tpasscount:@var{tpnum}
38601 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38603 @item terror:@var{text}:@var{tpnum}
38604 The trace stopped because tracepoint @var{tpnum} had an error. The
38605 string @var{text} is available to describe the nature of the error
38606 (for instance, a divide by zero in the condition expression).
38607 @var{text} is hex encoded.
38610 The trace stopped for some other reason.
38614 Additional optional fields supply statistical and other information.
38615 Although not required, they are extremely useful for users monitoring
38616 the progress of a trace run. If a trace has stopped, and these
38617 numbers are reported, they must reflect the state of the just-stopped
38622 @item tframes:@var{n}
38623 The number of trace frames in the buffer.
38625 @item tcreated:@var{n}
38626 The total number of trace frames created during the run. This may
38627 be larger than the trace frame count, if the buffer is circular.
38629 @item tsize:@var{n}
38630 The total size of the trace buffer, in bytes.
38632 @item tfree:@var{n}
38633 The number of bytes still unused in the buffer.
38635 @item circular:@var{n}
38636 The value of the circular trace buffer flag. @code{1} means that the
38637 trace buffer is circular and old trace frames will be discarded if
38638 necessary to make room, @code{0} means that the trace buffer is linear
38641 @item disconn:@var{n}
38642 The value of the disconnected tracing flag. @code{1} means that
38643 tracing will continue after @value{GDBN} disconnects, @code{0} means
38644 that the trace run will stop.
38648 @item qTP:@var{tp}:@var{addr}
38649 @cindex tracepoint status, remote request
38650 @cindex @samp{qTP} packet
38651 Ask the stub for the current state of tracepoint number @var{tp} at
38652 address @var{addr}.
38656 @item V@var{hits}:@var{usage}
38657 The tracepoint has been hit @var{hits} times so far during the trace
38658 run, and accounts for @var{usage} in the trace buffer. Note that
38659 @code{while-stepping} steps are not counted as separate hits, but the
38660 steps' space consumption is added into the usage number.
38664 @item qTV:@var{var}
38665 @cindex trace state variable value, remote request
38666 @cindex @samp{qTV} packet
38667 Ask the stub for the value of the trace state variable number @var{var}.
38672 The value of the variable is @var{value}. This will be the current
38673 value of the variable if the user is examining a running target, or a
38674 saved value if the variable was collected in the trace frame that the
38675 user is looking at. Note that multiple requests may result in
38676 different reply values, such as when requesting values while the
38677 program is running.
38680 The value of the variable is unknown. This would occur, for example,
38681 if the user is examining a trace frame in which the requested variable
38686 @cindex @samp{qTfP} packet
38688 @cindex @samp{qTsP} packet
38689 These packets request data about tracepoints that are being used by
38690 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38691 of data, and multiple @code{qTsP} to get additional pieces. Replies
38692 to these packets generally take the form of the @code{QTDP} packets
38693 that define tracepoints. (FIXME add detailed syntax)
38696 @cindex @samp{qTfV} packet
38698 @cindex @samp{qTsV} packet
38699 These packets request data about trace state variables that are on the
38700 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38701 and multiple @code{qTsV} to get additional variables. Replies to
38702 these packets follow the syntax of the @code{QTDV} packets that define
38703 trace state variables.
38709 @cindex @samp{qTfSTM} packet
38710 @cindex @samp{qTsSTM} packet
38711 These packets request data about static tracepoint markers that exist
38712 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38713 first piece of data, and multiple @code{qTsSTM} to get additional
38714 pieces. Replies to these packets take the following form:
38718 @item m @var{address}:@var{id}:@var{extra}
38720 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38721 a comma-separated list of markers
38723 (lower case letter @samp{L}) denotes end of list.
38725 An error occurred. @var{nn} are hex digits.
38727 An empty reply indicates that the request is not supported by the
38731 @var{address} is encoded in hex.
38732 @var{id} and @var{extra} are strings encoded in hex.
38734 In response to each query, the target will reply with a list of one or
38735 more markers, separated by commas. @value{GDBN} will respond to each
38736 reply with a request for more markers (using the @samp{qs} form of the
38737 query), until the target responds with @samp{l} (lower-case ell, for
38740 @item qTSTMat:@var{address}
38742 @cindex @samp{qTSTMat} packet
38743 This packets requests data about static tracepoint markers in the
38744 target program at @var{address}. Replies to this packet follow the
38745 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38746 tracepoint markers.
38748 @item QTSave:@var{filename}
38749 @cindex @samp{QTSave} packet
38750 This packet directs the target to save trace data to the file name
38751 @var{filename} in the target's filesystem. @var{filename} is encoded
38752 as a hex string; the interpretation of the file name (relative vs
38753 absolute, wild cards, etc) is up to the target.
38755 @item qTBuffer:@var{offset},@var{len}
38756 @cindex @samp{qTBuffer} packet
38757 Return up to @var{len} bytes of the current contents of trace buffer,
38758 starting at @var{offset}. The trace buffer is treated as if it were
38759 a contiguous collection of traceframes, as per the trace file format.
38760 The reply consists as many hex-encoded bytes as the target can deliver
38761 in a packet; it is not an error to return fewer than were asked for.
38762 A reply consisting of just @code{l} indicates that no bytes are
38765 @item QTBuffer:circular:@var{value}
38766 This packet directs the target to use a circular trace buffer if
38767 @var{value} is 1, or a linear buffer if the value is 0.
38769 @item QTBuffer:size:@var{size}
38770 @anchor{QTBuffer-size}
38771 @cindex @samp{QTBuffer size} packet
38772 This packet directs the target to make the trace buffer be of size
38773 @var{size} if possible. A value of @code{-1} tells the target to
38774 use whatever size it prefers.
38776 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38777 @cindex @samp{QTNotes} packet
38778 This packet adds optional textual notes to the trace run. Allowable
38779 types include @code{user}, @code{notes}, and @code{tstop}, the
38780 @var{text} fields are arbitrary strings, hex-encoded.
38784 @subsection Relocate instruction reply packet
38785 When installing fast tracepoints in memory, the target may need to
38786 relocate the instruction currently at the tracepoint address to a
38787 different address in memory. For most instructions, a simple copy is
38788 enough, but, for example, call instructions that implicitly push the
38789 return address on the stack, and relative branches or other
38790 PC-relative instructions require offset adjustment, so that the effect
38791 of executing the instruction at a different address is the same as if
38792 it had executed in the original location.
38794 In response to several of the tracepoint packets, the target may also
38795 respond with a number of intermediate @samp{qRelocInsn} request
38796 packets before the final result packet, to have @value{GDBN} handle
38797 this relocation operation. If a packet supports this mechanism, its
38798 documentation will explicitly say so. See for example the above
38799 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38800 format of the request is:
38803 @item qRelocInsn:@var{from};@var{to}
38805 This requests @value{GDBN} to copy instruction at address @var{from}
38806 to address @var{to}, possibly adjusted so that executing the
38807 instruction at @var{to} has the same effect as executing it at
38808 @var{from}. @value{GDBN} writes the adjusted instruction to target
38809 memory starting at @var{to}.
38814 @item qRelocInsn:@var{adjusted_size}
38815 Informs the stub the relocation is complete. @var{adjusted_size} is
38816 the length in bytes of resulting relocated instruction sequence.
38818 A badly formed request was detected, or an error was encountered while
38819 relocating the instruction.
38822 @node Host I/O Packets
38823 @section Host I/O Packets
38824 @cindex Host I/O, remote protocol
38825 @cindex file transfer, remote protocol
38827 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38828 operations on the far side of a remote link. For example, Host I/O is
38829 used to upload and download files to a remote target with its own
38830 filesystem. Host I/O uses the same constant values and data structure
38831 layout as the target-initiated File-I/O protocol. However, the
38832 Host I/O packets are structured differently. The target-initiated
38833 protocol relies on target memory to store parameters and buffers.
38834 Host I/O requests are initiated by @value{GDBN}, and the
38835 target's memory is not involved. @xref{File-I/O Remote Protocol
38836 Extension}, for more details on the target-initiated protocol.
38838 The Host I/O request packets all encode a single operation along with
38839 its arguments. They have this format:
38843 @item vFile:@var{operation}: @var{parameter}@dots{}
38844 @var{operation} is the name of the particular request; the target
38845 should compare the entire packet name up to the second colon when checking
38846 for a supported operation. The format of @var{parameter} depends on
38847 the operation. Numbers are always passed in hexadecimal. Negative
38848 numbers have an explicit minus sign (i.e.@: two's complement is not
38849 used). Strings (e.g.@: filenames) are encoded as a series of
38850 hexadecimal bytes. The last argument to a system call may be a
38851 buffer of escaped binary data (@pxref{Binary Data}).
38855 The valid responses to Host I/O packets are:
38859 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38860 @var{result} is the integer value returned by this operation, usually
38861 non-negative for success and -1 for errors. If an error has occured,
38862 @var{errno} will be included in the result. @var{errno} will have a
38863 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38864 operations which return data, @var{attachment} supplies the data as a
38865 binary buffer. Binary buffers in response packets are escaped in the
38866 normal way (@pxref{Binary Data}). See the individual packet
38867 documentation for the interpretation of @var{result} and
38871 An empty response indicates that this operation is not recognized.
38875 These are the supported Host I/O operations:
38878 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38879 Open a file at @var{pathname} and return a file descriptor for it, or
38880 return -1 if an error occurs. @var{pathname} is a string,
38881 @var{flags} is an integer indicating a mask of open flags
38882 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38883 of mode bits to use if the file is created (@pxref{mode_t Values}).
38884 @xref{open}, for details of the open flags and mode values.
38886 @item vFile:close: @var{fd}
38887 Close the open file corresponding to @var{fd} and return 0, or
38888 -1 if an error occurs.
38890 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38891 Read data from the open file corresponding to @var{fd}. Up to
38892 @var{count} bytes will be read from the file, starting at @var{offset}
38893 relative to the start of the file. The target may read fewer bytes;
38894 common reasons include packet size limits and an end-of-file
38895 condition. The number of bytes read is returned. Zero should only be
38896 returned for a successful read at the end of the file, or if
38897 @var{count} was zero.
38899 The data read should be returned as a binary attachment on success.
38900 If zero bytes were read, the response should include an empty binary
38901 attachment (i.e.@: a trailing semicolon). The return value is the
38902 number of target bytes read; the binary attachment may be longer if
38903 some characters were escaped.
38905 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38906 Write @var{data} (a binary buffer) to the open file corresponding
38907 to @var{fd}. Start the write at @var{offset} from the start of the
38908 file. Unlike many @code{write} system calls, there is no
38909 separate @var{count} argument; the length of @var{data} in the
38910 packet is used. @samp{vFile:write} returns the number of bytes written,
38911 which may be shorter than the length of @var{data}, or -1 if an
38914 @item vFile:unlink: @var{pathname}
38915 Delete the file at @var{pathname} on the target. Return 0,
38916 or -1 if an error occurs. @var{pathname} is a string.
38918 @item vFile:readlink: @var{filename}
38919 Read value of symbolic link @var{filename} on the target. Return
38920 the number of bytes read, or -1 if an error occurs.
38922 The data read should be returned as a binary attachment on success.
38923 If zero bytes were read, the response should include an empty binary
38924 attachment (i.e.@: a trailing semicolon). The return value is the
38925 number of target bytes read; the binary attachment may be longer if
38926 some characters were escaped.
38931 @section Interrupts
38932 @cindex interrupts (remote protocol)
38934 When a program on the remote target is running, @value{GDBN} may
38935 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38936 a @code{BREAK} followed by @code{g},
38937 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38939 The precise meaning of @code{BREAK} is defined by the transport
38940 mechanism and may, in fact, be undefined. @value{GDBN} does not
38941 currently define a @code{BREAK} mechanism for any of the network
38942 interfaces except for TCP, in which case @value{GDBN} sends the
38943 @code{telnet} BREAK sequence.
38945 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38946 transport mechanisms. It is represented by sending the single byte
38947 @code{0x03} without any of the usual packet overhead described in
38948 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38949 transmitted as part of a packet, it is considered to be packet data
38950 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38951 (@pxref{X packet}), used for binary downloads, may include an unescaped
38952 @code{0x03} as part of its packet.
38954 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38955 When Linux kernel receives this sequence from serial port,
38956 it stops execution and connects to gdb.
38958 Stubs are not required to recognize these interrupt mechanisms and the
38959 precise meaning associated with receipt of the interrupt is
38960 implementation defined. If the target supports debugging of multiple
38961 threads and/or processes, it should attempt to interrupt all
38962 currently-executing threads and processes.
38963 If the stub is successful at interrupting the
38964 running program, it should send one of the stop
38965 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38966 of successfully stopping the program in all-stop mode, and a stop reply
38967 for each stopped thread in non-stop mode.
38968 Interrupts received while the
38969 program is stopped are discarded.
38971 @node Notification Packets
38972 @section Notification Packets
38973 @cindex notification packets
38974 @cindex packets, notification
38976 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38977 packets that require no acknowledgment. Both the GDB and the stub
38978 may send notifications (although the only notifications defined at
38979 present are sent by the stub). Notifications carry information
38980 without incurring the round-trip latency of an acknowledgment, and so
38981 are useful for low-impact communications where occasional packet loss
38984 A notification packet has the form @samp{% @var{data} #
38985 @var{checksum}}, where @var{data} is the content of the notification,
38986 and @var{checksum} is a checksum of @var{data}, computed and formatted
38987 as for ordinary @value{GDBN} packets. A notification's @var{data}
38988 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38989 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38990 to acknowledge the notification's receipt or to report its corruption.
38992 Every notification's @var{data} begins with a name, which contains no
38993 colon characters, followed by a colon character.
38995 Recipients should silently ignore corrupted notifications and
38996 notifications they do not understand. Recipients should restart
38997 timeout periods on receipt of a well-formed notification, whether or
38998 not they understand it.
39000 Senders should only send the notifications described here when this
39001 protocol description specifies that they are permitted. In the
39002 future, we may extend the protocol to permit existing notifications in
39003 new contexts; this rule helps older senders avoid confusing newer
39006 (Older versions of @value{GDBN} ignore bytes received until they see
39007 the @samp{$} byte that begins an ordinary packet, so new stubs may
39008 transmit notifications without fear of confusing older clients. There
39009 are no notifications defined for @value{GDBN} to send at the moment, but we
39010 assume that most older stubs would ignore them, as well.)
39012 Each notification is comprised of three parts:
39014 @item @var{name}:@var{event}
39015 The notification packet is sent by the side that initiates the
39016 exchange (currently, only the stub does that), with @var{event}
39017 carrying the specific information about the notification.
39018 @var{name} is the name of the notification.
39020 The acknowledge sent by the other side, usually @value{GDBN}, to
39021 acknowledge the exchange and request the event.
39024 The purpose of an asynchronous notification mechanism is to report to
39025 @value{GDBN} that something interesting happened in the remote stub.
39027 The remote stub may send notification @var{name}:@var{event}
39028 at any time, but @value{GDBN} acknowledges the notification when
39029 appropriate. The notification event is pending before @value{GDBN}
39030 acknowledges. Only one notification at a time may be pending; if
39031 additional events occur before @value{GDBN} has acknowledged the
39032 previous notification, they must be queued by the stub for later
39033 synchronous transmission in response to @var{ack} packets from
39034 @value{GDBN}. Because the notification mechanism is unreliable,
39035 the stub is permitted to resend a notification if it believes
39036 @value{GDBN} may not have received it.
39038 Specifically, notifications may appear when @value{GDBN} is not
39039 otherwise reading input from the stub, or when @value{GDBN} is
39040 expecting to read a normal synchronous response or a
39041 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39042 Notification packets are distinct from any other communication from
39043 the stub so there is no ambiguity.
39045 After receiving a notification, @value{GDBN} shall acknowledge it by
39046 sending a @var{ack} packet as a regular, synchronous request to the
39047 stub. Such acknowledgment is not required to happen immediately, as
39048 @value{GDBN} is permitted to send other, unrelated packets to the
39049 stub first, which the stub should process normally.
39051 Upon receiving a @var{ack} packet, if the stub has other queued
39052 events to report to @value{GDBN}, it shall respond by sending a
39053 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39054 packet to solicit further responses; again, it is permitted to send
39055 other, unrelated packets as well which the stub should process
39058 If the stub receives a @var{ack} packet and there are no additional
39059 @var{event} to report, the stub shall return an @samp{OK} response.
39060 At this point, @value{GDBN} has finished processing a notification
39061 and the stub has completed sending any queued events. @value{GDBN}
39062 won't accept any new notifications until the final @samp{OK} is
39063 received . If further notification events occur, the stub shall send
39064 a new notification, @value{GDBN} shall accept the notification, and
39065 the process shall be repeated.
39067 The process of asynchronous notification can be illustrated by the
39070 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39073 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39075 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39080 The following notifications are defined:
39081 @multitable @columnfractions 0.12 0.12 0.38 0.38
39090 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39091 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39092 for information on how these notifications are acknowledged by
39094 @tab Report an asynchronous stop event in non-stop mode.
39098 @node Remote Non-Stop
39099 @section Remote Protocol Support for Non-Stop Mode
39101 @value{GDBN}'s remote protocol supports non-stop debugging of
39102 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39103 supports non-stop mode, it should report that to @value{GDBN} by including
39104 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39106 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39107 establishing a new connection with the stub. Entering non-stop mode
39108 does not alter the state of any currently-running threads, but targets
39109 must stop all threads in any already-attached processes when entering
39110 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39111 probe the target state after a mode change.
39113 In non-stop mode, when an attached process encounters an event that
39114 would otherwise be reported with a stop reply, it uses the
39115 asynchronous notification mechanism (@pxref{Notification Packets}) to
39116 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39117 in all processes are stopped when a stop reply is sent, in non-stop
39118 mode only the thread reporting the stop event is stopped. That is,
39119 when reporting a @samp{S} or @samp{T} response to indicate completion
39120 of a step operation, hitting a breakpoint, or a fault, only the
39121 affected thread is stopped; any other still-running threads continue
39122 to run. When reporting a @samp{W} or @samp{X} response, all running
39123 threads belonging to other attached processes continue to run.
39125 In non-stop mode, the target shall respond to the @samp{?} packet as
39126 follows. First, any incomplete stop reply notification/@samp{vStopped}
39127 sequence in progress is abandoned. The target must begin a new
39128 sequence reporting stop events for all stopped threads, whether or not
39129 it has previously reported those events to @value{GDBN}. The first
39130 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39131 subsequent stop replies are sent as responses to @samp{vStopped} packets
39132 using the mechanism described above. The target must not send
39133 asynchronous stop reply notifications until the sequence is complete.
39134 If all threads are running when the target receives the @samp{?} packet,
39135 or if the target is not attached to any process, it shall respond
39138 @node Packet Acknowledgment
39139 @section Packet Acknowledgment
39141 @cindex acknowledgment, for @value{GDBN} remote
39142 @cindex packet acknowledgment, for @value{GDBN} remote
39143 By default, when either the host or the target machine receives a packet,
39144 the first response expected is an acknowledgment: either @samp{+} (to indicate
39145 the package was received correctly) or @samp{-} (to request retransmission).
39146 This mechanism allows the @value{GDBN} remote protocol to operate over
39147 unreliable transport mechanisms, such as a serial line.
39149 In cases where the transport mechanism is itself reliable (such as a pipe or
39150 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39151 It may be desirable to disable them in that case to reduce communication
39152 overhead, or for other reasons. This can be accomplished by means of the
39153 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39155 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39156 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39157 and response format still includes the normal checksum, as described in
39158 @ref{Overview}, but the checksum may be ignored by the receiver.
39160 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39161 no-acknowledgment mode, it should report that to @value{GDBN}
39162 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39163 @pxref{qSupported}.
39164 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39165 disabled via the @code{set remote noack-packet off} command
39166 (@pxref{Remote Configuration}),
39167 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39168 Only then may the stub actually turn off packet acknowledgments.
39169 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39170 response, which can be safely ignored by the stub.
39172 Note that @code{set remote noack-packet} command only affects negotiation
39173 between @value{GDBN} and the stub when subsequent connections are made;
39174 it does not affect the protocol acknowledgment state for any current
39176 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39177 new connection is established,
39178 there is also no protocol request to re-enable the acknowledgments
39179 for the current connection, once disabled.
39184 Example sequence of a target being re-started. Notice how the restart
39185 does not get any direct output:
39190 @emph{target restarts}
39193 <- @code{T001:1234123412341234}
39197 Example sequence of a target being stepped by a single instruction:
39200 -> @code{G1445@dots{}}
39205 <- @code{T001:1234123412341234}
39209 <- @code{1455@dots{}}
39213 @node File-I/O Remote Protocol Extension
39214 @section File-I/O Remote Protocol Extension
39215 @cindex File-I/O remote protocol extension
39218 * File-I/O Overview::
39219 * Protocol Basics::
39220 * The F Request Packet::
39221 * The F Reply Packet::
39222 * The Ctrl-C Message::
39224 * List of Supported Calls::
39225 * Protocol-specific Representation of Datatypes::
39227 * File-I/O Examples::
39230 @node File-I/O Overview
39231 @subsection File-I/O Overview
39232 @cindex file-i/o overview
39234 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39235 target to use the host's file system and console I/O to perform various
39236 system calls. System calls on the target system are translated into a
39237 remote protocol packet to the host system, which then performs the needed
39238 actions and returns a response packet to the target system.
39239 This simulates file system operations even on targets that lack file systems.
39241 The protocol is defined to be independent of both the host and target systems.
39242 It uses its own internal representation of datatypes and values. Both
39243 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39244 translating the system-dependent value representations into the internal
39245 protocol representations when data is transmitted.
39247 The communication is synchronous. A system call is possible only when
39248 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39249 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39250 the target is stopped to allow deterministic access to the target's
39251 memory. Therefore File-I/O is not interruptible by target signals. On
39252 the other hand, it is possible to interrupt File-I/O by a user interrupt
39253 (@samp{Ctrl-C}) within @value{GDBN}.
39255 The target's request to perform a host system call does not finish
39256 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39257 after finishing the system call, the target returns to continuing the
39258 previous activity (continue, step). No additional continue or step
39259 request from @value{GDBN} is required.
39262 (@value{GDBP}) continue
39263 <- target requests 'system call X'
39264 target is stopped, @value{GDBN} executes system call
39265 -> @value{GDBN} returns result
39266 ... target continues, @value{GDBN} returns to wait for the target
39267 <- target hits breakpoint and sends a Txx packet
39270 The protocol only supports I/O on the console and to regular files on
39271 the host file system. Character or block special devices, pipes,
39272 named pipes, sockets or any other communication method on the host
39273 system are not supported by this protocol.
39275 File I/O is not supported in non-stop mode.
39277 @node Protocol Basics
39278 @subsection Protocol Basics
39279 @cindex protocol basics, file-i/o
39281 The File-I/O protocol uses the @code{F} packet as the request as well
39282 as reply packet. Since a File-I/O system call can only occur when
39283 @value{GDBN} is waiting for a response from the continuing or stepping target,
39284 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39285 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39286 This @code{F} packet contains all information needed to allow @value{GDBN}
39287 to call the appropriate host system call:
39291 A unique identifier for the requested system call.
39294 All parameters to the system call. Pointers are given as addresses
39295 in the target memory address space. Pointers to strings are given as
39296 pointer/length pair. Numerical values are given as they are.
39297 Numerical control flags are given in a protocol-specific representation.
39301 At this point, @value{GDBN} has to perform the following actions.
39305 If the parameters include pointer values to data needed as input to a
39306 system call, @value{GDBN} requests this data from the target with a
39307 standard @code{m} packet request. This additional communication has to be
39308 expected by the target implementation and is handled as any other @code{m}
39312 @value{GDBN} translates all value from protocol representation to host
39313 representation as needed. Datatypes are coerced into the host types.
39316 @value{GDBN} calls the system call.
39319 It then coerces datatypes back to protocol representation.
39322 If the system call is expected to return data in buffer space specified
39323 by pointer parameters to the call, the data is transmitted to the
39324 target using a @code{M} or @code{X} packet. This packet has to be expected
39325 by the target implementation and is handled as any other @code{M} or @code{X}
39330 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39331 necessary information for the target to continue. This at least contains
39338 @code{errno}, if has been changed by the system call.
39345 After having done the needed type and value coercion, the target continues
39346 the latest continue or step action.
39348 @node The F Request Packet
39349 @subsection The @code{F} Request Packet
39350 @cindex file-i/o request packet
39351 @cindex @code{F} request packet
39353 The @code{F} request packet has the following format:
39356 @item F@var{call-id},@var{parameter@dots{}}
39358 @var{call-id} is the identifier to indicate the host system call to be called.
39359 This is just the name of the function.
39361 @var{parameter@dots{}} are the parameters to the system call.
39362 Parameters are hexadecimal integer values, either the actual values in case
39363 of scalar datatypes, pointers to target buffer space in case of compound
39364 datatypes and unspecified memory areas, or pointer/length pairs in case
39365 of string parameters. These are appended to the @var{call-id} as a
39366 comma-delimited list. All values are transmitted in ASCII
39367 string representation, pointer/length pairs separated by a slash.
39373 @node The F Reply Packet
39374 @subsection The @code{F} Reply Packet
39375 @cindex file-i/o reply packet
39376 @cindex @code{F} reply packet
39378 The @code{F} reply packet has the following format:
39382 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39384 @var{retcode} is the return code of the system call as hexadecimal value.
39386 @var{errno} is the @code{errno} set by the call, in protocol-specific
39388 This parameter can be omitted if the call was successful.
39390 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39391 case, @var{errno} must be sent as well, even if the call was successful.
39392 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39399 or, if the call was interrupted before the host call has been performed:
39406 assuming 4 is the protocol-specific representation of @code{EINTR}.
39411 @node The Ctrl-C Message
39412 @subsection The @samp{Ctrl-C} Message
39413 @cindex ctrl-c message, in file-i/o protocol
39415 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39416 reply packet (@pxref{The F Reply Packet}),
39417 the target should behave as if it had
39418 gotten a break message. The meaning for the target is ``system call
39419 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39420 (as with a break message) and return to @value{GDBN} with a @code{T02}
39423 It's important for the target to know in which
39424 state the system call was interrupted. There are two possible cases:
39428 The system call hasn't been performed on the host yet.
39431 The system call on the host has been finished.
39435 These two states can be distinguished by the target by the value of the
39436 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39437 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39438 on POSIX systems. In any other case, the target may presume that the
39439 system call has been finished --- successfully or not --- and should behave
39440 as if the break message arrived right after the system call.
39442 @value{GDBN} must behave reliably. If the system call has not been called
39443 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39444 @code{errno} in the packet. If the system call on the host has been finished
39445 before the user requests a break, the full action must be finished by
39446 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39447 The @code{F} packet may only be sent when either nothing has happened
39448 or the full action has been completed.
39451 @subsection Console I/O
39452 @cindex console i/o as part of file-i/o
39454 By default and if not explicitly closed by the target system, the file
39455 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39456 on the @value{GDBN} console is handled as any other file output operation
39457 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39458 by @value{GDBN} so that after the target read request from file descriptor
39459 0 all following typing is buffered until either one of the following
39464 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39466 system call is treated as finished.
39469 The user presses @key{RET}. This is treated as end of input with a trailing
39473 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39474 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39478 If the user has typed more characters than fit in the buffer given to
39479 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39480 either another @code{read(0, @dots{})} is requested by the target, or debugging
39481 is stopped at the user's request.
39484 @node List of Supported Calls
39485 @subsection List of Supported Calls
39486 @cindex list of supported file-i/o calls
39503 @unnumberedsubsubsec open
39504 @cindex open, file-i/o system call
39509 int open(const char *pathname, int flags);
39510 int open(const char *pathname, int flags, mode_t mode);
39514 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39517 @var{flags} is the bitwise @code{OR} of the following values:
39521 If the file does not exist it will be created. The host
39522 rules apply as far as file ownership and time stamps
39526 When used with @code{O_CREAT}, if the file already exists it is
39527 an error and open() fails.
39530 If the file already exists and the open mode allows
39531 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39532 truncated to zero length.
39535 The file is opened in append mode.
39538 The file is opened for reading only.
39541 The file is opened for writing only.
39544 The file is opened for reading and writing.
39548 Other bits are silently ignored.
39552 @var{mode} is the bitwise @code{OR} of the following values:
39556 User has read permission.
39559 User has write permission.
39562 Group has read permission.
39565 Group has write permission.
39568 Others have read permission.
39571 Others have write permission.
39575 Other bits are silently ignored.
39578 @item Return value:
39579 @code{open} returns the new file descriptor or -1 if an error
39586 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39589 @var{pathname} refers to a directory.
39592 The requested access is not allowed.
39595 @var{pathname} was too long.
39598 A directory component in @var{pathname} does not exist.
39601 @var{pathname} refers to a device, pipe, named pipe or socket.
39604 @var{pathname} refers to a file on a read-only filesystem and
39605 write access was requested.
39608 @var{pathname} is an invalid pointer value.
39611 No space on device to create the file.
39614 The process already has the maximum number of files open.
39617 The limit on the total number of files open on the system
39621 The call was interrupted by the user.
39627 @unnumberedsubsubsec close
39628 @cindex close, file-i/o system call
39637 @samp{Fclose,@var{fd}}
39639 @item Return value:
39640 @code{close} returns zero on success, or -1 if an error occurred.
39646 @var{fd} isn't a valid open file descriptor.
39649 The call was interrupted by the user.
39655 @unnumberedsubsubsec read
39656 @cindex read, file-i/o system call
39661 int read(int fd, void *buf, unsigned int count);
39665 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39667 @item Return value:
39668 On success, the number of bytes read is returned.
39669 Zero indicates end of file. If count is zero, read
39670 returns zero as well. On error, -1 is returned.
39676 @var{fd} is not a valid file descriptor or is not open for
39680 @var{bufptr} is an invalid pointer value.
39683 The call was interrupted by the user.
39689 @unnumberedsubsubsec write
39690 @cindex write, file-i/o system call
39695 int write(int fd, const void *buf, unsigned int count);
39699 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39701 @item Return value:
39702 On success, the number of bytes written are returned.
39703 Zero indicates nothing was written. On error, -1
39710 @var{fd} is not a valid file descriptor or is not open for
39714 @var{bufptr} is an invalid pointer value.
39717 An attempt was made to write a file that exceeds the
39718 host-specific maximum file size allowed.
39721 No space on device to write the data.
39724 The call was interrupted by the user.
39730 @unnumberedsubsubsec lseek
39731 @cindex lseek, file-i/o system call
39736 long lseek (int fd, long offset, int flag);
39740 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39742 @var{flag} is one of:
39746 The offset is set to @var{offset} bytes.
39749 The offset is set to its current location plus @var{offset}
39753 The offset is set to the size of the file plus @var{offset}
39757 @item Return value:
39758 On success, the resulting unsigned offset in bytes from
39759 the beginning of the file is returned. Otherwise, a
39760 value of -1 is returned.
39766 @var{fd} is not a valid open file descriptor.
39769 @var{fd} is associated with the @value{GDBN} console.
39772 @var{flag} is not a proper value.
39775 The call was interrupted by the user.
39781 @unnumberedsubsubsec rename
39782 @cindex rename, file-i/o system call
39787 int rename(const char *oldpath, const char *newpath);
39791 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39793 @item Return value:
39794 On success, zero is returned. On error, -1 is returned.
39800 @var{newpath} is an existing directory, but @var{oldpath} is not a
39804 @var{newpath} is a non-empty directory.
39807 @var{oldpath} or @var{newpath} is a directory that is in use by some
39811 An attempt was made to make a directory a subdirectory
39815 A component used as a directory in @var{oldpath} or new
39816 path is not a directory. Or @var{oldpath} is a directory
39817 and @var{newpath} exists but is not a directory.
39820 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39823 No access to the file or the path of the file.
39827 @var{oldpath} or @var{newpath} was too long.
39830 A directory component in @var{oldpath} or @var{newpath} does not exist.
39833 The file is on a read-only filesystem.
39836 The device containing the file has no room for the new
39840 The call was interrupted by the user.
39846 @unnumberedsubsubsec unlink
39847 @cindex unlink, file-i/o system call
39852 int unlink(const char *pathname);
39856 @samp{Funlink,@var{pathnameptr}/@var{len}}
39858 @item Return value:
39859 On success, zero is returned. On error, -1 is returned.
39865 No access to the file or the path of the file.
39868 The system does not allow unlinking of directories.
39871 The file @var{pathname} cannot be unlinked because it's
39872 being used by another process.
39875 @var{pathnameptr} is an invalid pointer value.
39878 @var{pathname} was too long.
39881 A directory component in @var{pathname} does not exist.
39884 A component of the path is not a directory.
39887 The file is on a read-only filesystem.
39890 The call was interrupted by the user.
39896 @unnumberedsubsubsec stat/fstat
39897 @cindex fstat, file-i/o system call
39898 @cindex stat, file-i/o system call
39903 int stat(const char *pathname, struct stat *buf);
39904 int fstat(int fd, struct stat *buf);
39908 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39909 @samp{Ffstat,@var{fd},@var{bufptr}}
39911 @item Return value:
39912 On success, zero is returned. On error, -1 is returned.
39918 @var{fd} is not a valid open file.
39921 A directory component in @var{pathname} does not exist or the
39922 path is an empty string.
39925 A component of the path is not a directory.
39928 @var{pathnameptr} is an invalid pointer value.
39931 No access to the file or the path of the file.
39934 @var{pathname} was too long.
39937 The call was interrupted by the user.
39943 @unnumberedsubsubsec gettimeofday
39944 @cindex gettimeofday, file-i/o system call
39949 int gettimeofday(struct timeval *tv, void *tz);
39953 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39955 @item Return value:
39956 On success, 0 is returned, -1 otherwise.
39962 @var{tz} is a non-NULL pointer.
39965 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39971 @unnumberedsubsubsec isatty
39972 @cindex isatty, file-i/o system call
39977 int isatty(int fd);
39981 @samp{Fisatty,@var{fd}}
39983 @item Return value:
39984 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39990 The call was interrupted by the user.
39995 Note that the @code{isatty} call is treated as a special case: it returns
39996 1 to the target if the file descriptor is attached
39997 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39998 would require implementing @code{ioctl} and would be more complex than
40003 @unnumberedsubsubsec system
40004 @cindex system, file-i/o system call
40009 int system(const char *command);
40013 @samp{Fsystem,@var{commandptr}/@var{len}}
40015 @item Return value:
40016 If @var{len} is zero, the return value indicates whether a shell is
40017 available. A zero return value indicates a shell is not available.
40018 For non-zero @var{len}, the value returned is -1 on error and the
40019 return status of the command otherwise. Only the exit status of the
40020 command is returned, which is extracted from the host's @code{system}
40021 return value by calling @code{WEXITSTATUS(retval)}. In case
40022 @file{/bin/sh} could not be executed, 127 is returned.
40028 The call was interrupted by the user.
40033 @value{GDBN} takes over the full task of calling the necessary host calls
40034 to perform the @code{system} call. The return value of @code{system} on
40035 the host is simplified before it's returned
40036 to the target. Any termination signal information from the child process
40037 is discarded, and the return value consists
40038 entirely of the exit status of the called command.
40040 Due to security concerns, the @code{system} call is by default refused
40041 by @value{GDBN}. The user has to allow this call explicitly with the
40042 @code{set remote system-call-allowed 1} command.
40045 @item set remote system-call-allowed
40046 @kindex set remote system-call-allowed
40047 Control whether to allow the @code{system} calls in the File I/O
40048 protocol for the remote target. The default is zero (disabled).
40050 @item show remote system-call-allowed
40051 @kindex show remote system-call-allowed
40052 Show whether the @code{system} calls are allowed in the File I/O
40056 @node Protocol-specific Representation of Datatypes
40057 @subsection Protocol-specific Representation of Datatypes
40058 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40061 * Integral Datatypes::
40063 * Memory Transfer::
40068 @node Integral Datatypes
40069 @unnumberedsubsubsec Integral Datatypes
40070 @cindex integral datatypes, in file-i/o protocol
40072 The integral datatypes used in the system calls are @code{int},
40073 @code{unsigned int}, @code{long}, @code{unsigned long},
40074 @code{mode_t}, and @code{time_t}.
40076 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40077 implemented as 32 bit values in this protocol.
40079 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40081 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40082 in @file{limits.h}) to allow range checking on host and target.
40084 @code{time_t} datatypes are defined as seconds since the Epoch.
40086 All integral datatypes transferred as part of a memory read or write of a
40087 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40090 @node Pointer Values
40091 @unnumberedsubsubsec Pointer Values
40092 @cindex pointer values, in file-i/o protocol
40094 Pointers to target data are transmitted as they are. An exception
40095 is made for pointers to buffers for which the length isn't
40096 transmitted as part of the function call, namely strings. Strings
40097 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40104 which is a pointer to data of length 18 bytes at position 0x1aaf.
40105 The length is defined as the full string length in bytes, including
40106 the trailing null byte. For example, the string @code{"hello world"}
40107 at address 0x123456 is transmitted as
40113 @node Memory Transfer
40114 @unnumberedsubsubsec Memory Transfer
40115 @cindex memory transfer, in file-i/o protocol
40117 Structured data which is transferred using a memory read or write (for
40118 example, a @code{struct stat}) is expected to be in a protocol-specific format
40119 with all scalar multibyte datatypes being big endian. Translation to
40120 this representation needs to be done both by the target before the @code{F}
40121 packet is sent, and by @value{GDBN} before
40122 it transfers memory to the target. Transferred pointers to structured
40123 data should point to the already-coerced data at any time.
40127 @unnumberedsubsubsec struct stat
40128 @cindex struct stat, in file-i/o protocol
40130 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40131 is defined as follows:
40135 unsigned int st_dev; /* device */
40136 unsigned int st_ino; /* inode */
40137 mode_t st_mode; /* protection */
40138 unsigned int st_nlink; /* number of hard links */
40139 unsigned int st_uid; /* user ID of owner */
40140 unsigned int st_gid; /* group ID of owner */
40141 unsigned int st_rdev; /* device type (if inode device) */
40142 unsigned long st_size; /* total size, in bytes */
40143 unsigned long st_blksize; /* blocksize for filesystem I/O */
40144 unsigned long st_blocks; /* number of blocks allocated */
40145 time_t st_atime; /* time of last access */
40146 time_t st_mtime; /* time of last modification */
40147 time_t st_ctime; /* time of last change */
40151 The integral datatypes conform to the definitions given in the
40152 appropriate section (see @ref{Integral Datatypes}, for details) so this
40153 structure is of size 64 bytes.
40155 The values of several fields have a restricted meaning and/or
40161 A value of 0 represents a file, 1 the console.
40164 No valid meaning for the target. Transmitted unchanged.
40167 Valid mode bits are described in @ref{Constants}. Any other
40168 bits have currently no meaning for the target.
40173 No valid meaning for the target. Transmitted unchanged.
40178 These values have a host and file system dependent
40179 accuracy. Especially on Windows hosts, the file system may not
40180 support exact timing values.
40183 The target gets a @code{struct stat} of the above representation and is
40184 responsible for coercing it to the target representation before
40187 Note that due to size differences between the host, target, and protocol
40188 representations of @code{struct stat} members, these members could eventually
40189 get truncated on the target.
40191 @node struct timeval
40192 @unnumberedsubsubsec struct timeval
40193 @cindex struct timeval, in file-i/o protocol
40195 The buffer of type @code{struct timeval} used by the File-I/O protocol
40196 is defined as follows:
40200 time_t tv_sec; /* second */
40201 long tv_usec; /* microsecond */
40205 The integral datatypes conform to the definitions given in the
40206 appropriate section (see @ref{Integral Datatypes}, for details) so this
40207 structure is of size 8 bytes.
40210 @subsection Constants
40211 @cindex constants, in file-i/o protocol
40213 The following values are used for the constants inside of the
40214 protocol. @value{GDBN} and target are responsible for translating these
40215 values before and after the call as needed.
40226 @unnumberedsubsubsec Open Flags
40227 @cindex open flags, in file-i/o protocol
40229 All values are given in hexadecimal representation.
40241 @node mode_t Values
40242 @unnumberedsubsubsec mode_t Values
40243 @cindex mode_t values, in file-i/o protocol
40245 All values are given in octal representation.
40262 @unnumberedsubsubsec Errno Values
40263 @cindex errno values, in file-i/o protocol
40265 All values are given in decimal representation.
40290 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40291 any error value not in the list of supported error numbers.
40294 @unnumberedsubsubsec Lseek Flags
40295 @cindex lseek flags, in file-i/o protocol
40304 @unnumberedsubsubsec Limits
40305 @cindex limits, in file-i/o protocol
40307 All values are given in decimal representation.
40310 INT_MIN -2147483648
40312 UINT_MAX 4294967295
40313 LONG_MIN -9223372036854775808
40314 LONG_MAX 9223372036854775807
40315 ULONG_MAX 18446744073709551615
40318 @node File-I/O Examples
40319 @subsection File-I/O Examples
40320 @cindex file-i/o examples
40322 Example sequence of a write call, file descriptor 3, buffer is at target
40323 address 0x1234, 6 bytes should be written:
40326 <- @code{Fwrite,3,1234,6}
40327 @emph{request memory read from target}
40330 @emph{return "6 bytes written"}
40334 Example sequence of a read call, file descriptor 3, buffer is at target
40335 address 0x1234, 6 bytes should be read:
40338 <- @code{Fread,3,1234,6}
40339 @emph{request memory write to target}
40340 -> @code{X1234,6:XXXXXX}
40341 @emph{return "6 bytes read"}
40345 Example sequence of a read call, call fails on the host due to invalid
40346 file descriptor (@code{EBADF}):
40349 <- @code{Fread,3,1234,6}
40353 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40357 <- @code{Fread,3,1234,6}
40362 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40366 <- @code{Fread,3,1234,6}
40367 -> @code{X1234,6:XXXXXX}
40371 @node Library List Format
40372 @section Library List Format
40373 @cindex library list format, remote protocol
40375 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40376 same process as your application to manage libraries. In this case,
40377 @value{GDBN} can use the loader's symbol table and normal memory
40378 operations to maintain a list of shared libraries. On other
40379 platforms, the operating system manages loaded libraries.
40380 @value{GDBN} can not retrieve the list of currently loaded libraries
40381 through memory operations, so it uses the @samp{qXfer:libraries:read}
40382 packet (@pxref{qXfer library list read}) instead. The remote stub
40383 queries the target's operating system and reports which libraries
40386 The @samp{qXfer:libraries:read} packet returns an XML document which
40387 lists loaded libraries and their offsets. Each library has an
40388 associated name and one or more segment or section base addresses,
40389 which report where the library was loaded in memory.
40391 For the common case of libraries that are fully linked binaries, the
40392 library should have a list of segments. If the target supports
40393 dynamic linking of a relocatable object file, its library XML element
40394 should instead include a list of allocated sections. The segment or
40395 section bases are start addresses, not relocation offsets; they do not
40396 depend on the library's link-time base addresses.
40398 @value{GDBN} must be linked with the Expat library to support XML
40399 library lists. @xref{Expat}.
40401 A simple memory map, with one loaded library relocated by a single
40402 offset, looks like this:
40406 <library name="/lib/libc.so.6">
40407 <segment address="0x10000000"/>
40412 Another simple memory map, with one loaded library with three
40413 allocated sections (.text, .data, .bss), looks like this:
40417 <library name="sharedlib.o">
40418 <section address="0x10000000"/>
40419 <section address="0x20000000"/>
40420 <section address="0x30000000"/>
40425 The format of a library list is described by this DTD:
40428 <!-- library-list: Root element with versioning -->
40429 <!ELEMENT library-list (library)*>
40430 <!ATTLIST library-list version CDATA #FIXED "1.0">
40431 <!ELEMENT library (segment*, section*)>
40432 <!ATTLIST library name CDATA #REQUIRED>
40433 <!ELEMENT segment EMPTY>
40434 <!ATTLIST segment address CDATA #REQUIRED>
40435 <!ELEMENT section EMPTY>
40436 <!ATTLIST section address CDATA #REQUIRED>
40439 In addition, segments and section descriptors cannot be mixed within a
40440 single library element, and you must supply at least one segment or
40441 section for each library.
40443 @node Library List Format for SVR4 Targets
40444 @section Library List Format for SVR4 Targets
40445 @cindex library list format, remote protocol
40447 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40448 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40449 shared libraries. Still a special library list provided by this packet is
40450 more efficient for the @value{GDBN} remote protocol.
40452 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40453 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40454 target, the following parameters are reported:
40458 @code{name}, the absolute file name from the @code{l_name} field of
40459 @code{struct link_map}.
40461 @code{lm} with address of @code{struct link_map} used for TLS
40462 (Thread Local Storage) access.
40464 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40465 @code{struct link_map}. For prelinked libraries this is not an absolute
40466 memory address. It is a displacement of absolute memory address against
40467 address the file was prelinked to during the library load.
40469 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40472 Additionally the single @code{main-lm} attribute specifies address of
40473 @code{struct link_map} used for the main executable. This parameter is used
40474 for TLS access and its presence is optional.
40476 @value{GDBN} must be linked with the Expat library to support XML
40477 SVR4 library lists. @xref{Expat}.
40479 A simple memory map, with two loaded libraries (which do not use prelink),
40483 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40484 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40486 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40488 </library-list-svr>
40491 The format of an SVR4 library list is described by this DTD:
40494 <!-- library-list-svr4: Root element with versioning -->
40495 <!ELEMENT library-list-svr4 (library)*>
40496 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40497 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40498 <!ELEMENT library EMPTY>
40499 <!ATTLIST library name CDATA #REQUIRED>
40500 <!ATTLIST library lm CDATA #REQUIRED>
40501 <!ATTLIST library l_addr CDATA #REQUIRED>
40502 <!ATTLIST library l_ld CDATA #REQUIRED>
40505 @node Memory Map Format
40506 @section Memory Map Format
40507 @cindex memory map format
40509 To be able to write into flash memory, @value{GDBN} needs to obtain a
40510 memory map from the target. This section describes the format of the
40513 The memory map is obtained using the @samp{qXfer:memory-map:read}
40514 (@pxref{qXfer memory map read}) packet and is an XML document that
40515 lists memory regions.
40517 @value{GDBN} must be linked with the Expat library to support XML
40518 memory maps. @xref{Expat}.
40520 The top-level structure of the document is shown below:
40523 <?xml version="1.0"?>
40524 <!DOCTYPE memory-map
40525 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40526 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40532 Each region can be either:
40537 A region of RAM starting at @var{addr} and extending for @var{length}
40541 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40546 A region of read-only memory:
40549 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40554 A region of flash memory, with erasure blocks @var{blocksize}
40558 <memory type="flash" start="@var{addr}" length="@var{length}">
40559 <property name="blocksize">@var{blocksize}</property>
40565 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40566 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40567 packets to write to addresses in such ranges.
40569 The formal DTD for memory map format is given below:
40572 <!-- ................................................... -->
40573 <!-- Memory Map XML DTD ................................ -->
40574 <!-- File: memory-map.dtd .............................. -->
40575 <!-- .................................... .............. -->
40576 <!-- memory-map.dtd -->
40577 <!-- memory-map: Root element with versioning -->
40578 <!ELEMENT memory-map (memory | property)>
40579 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40580 <!ELEMENT memory (property)>
40581 <!-- memory: Specifies a memory region,
40582 and its type, or device. -->
40583 <!ATTLIST memory type CDATA #REQUIRED
40584 start CDATA #REQUIRED
40585 length CDATA #REQUIRED
40586 device CDATA #IMPLIED>
40587 <!-- property: Generic attribute tag -->
40588 <!ELEMENT property (#PCDATA | property)*>
40589 <!ATTLIST property name CDATA #REQUIRED>
40592 @node Thread List Format
40593 @section Thread List Format
40594 @cindex thread list format
40596 To efficiently update the list of threads and their attributes,
40597 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40598 (@pxref{qXfer threads read}) and obtains the XML document with
40599 the following structure:
40602 <?xml version="1.0"?>
40604 <thread id="id" core="0">
40605 ... description ...
40610 Each @samp{thread} element must have the @samp{id} attribute that
40611 identifies the thread (@pxref{thread-id syntax}). The
40612 @samp{core} attribute, if present, specifies which processor core
40613 the thread was last executing on. The content of the of @samp{thread}
40614 element is interpreted as human-readable auxilliary information.
40616 @node Traceframe Info Format
40617 @section Traceframe Info Format
40618 @cindex traceframe info format
40620 To be able to know which objects in the inferior can be examined when
40621 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40622 memory ranges, registers and trace state variables that have been
40623 collected in a traceframe.
40625 This list is obtained using the @samp{qXfer:traceframe-info:read}
40626 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40628 @value{GDBN} must be linked with the Expat library to support XML
40629 traceframe info discovery. @xref{Expat}.
40631 The top-level structure of the document is shown below:
40634 <?xml version="1.0"?>
40635 <!DOCTYPE traceframe-info
40636 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40637 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40643 Each traceframe block can be either:
40648 A region of collected memory starting at @var{addr} and extending for
40649 @var{length} bytes from there:
40652 <memory start="@var{addr}" length="@var{length}"/>
40657 The formal DTD for the traceframe info format is given below:
40660 <!ELEMENT traceframe-info (memory)* >
40661 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40663 <!ELEMENT memory EMPTY>
40664 <!ATTLIST memory start CDATA #REQUIRED
40665 length CDATA #REQUIRED>
40668 @node Branch Trace Format
40669 @section Branch Trace Format
40670 @cindex branch trace format
40672 In order to display the branch trace of an inferior thread,
40673 @value{GDBN} needs to obtain the list of branches. This list is
40674 represented as list of sequential code blocks that are connected via
40675 branches. The code in each block has been executed sequentially.
40677 This list is obtained using the @samp{qXfer:btrace:read}
40678 (@pxref{qXfer btrace read}) packet and is an XML document.
40680 @value{GDBN} must be linked with the Expat library to support XML
40681 traceframe info discovery. @xref{Expat}.
40683 The top-level structure of the document is shown below:
40686 <?xml version="1.0"?>
40688 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40689 "http://sourceware.org/gdb/gdb-btrace.dtd">
40698 A block of sequentially executed instructions starting at @var{begin}
40699 and ending at @var{end}:
40702 <block begin="@var{begin}" end="@var{end}"/>
40707 The formal DTD for the branch trace format is given below:
40710 <!ELEMENT btrace (block)* >
40711 <!ATTLIST btrace version CDATA #FIXED "1.0">
40713 <!ELEMENT block EMPTY>
40714 <!ATTLIST block begin CDATA #REQUIRED
40715 end CDATA #REQUIRED>
40718 @include agentexpr.texi
40720 @node Target Descriptions
40721 @appendix Target Descriptions
40722 @cindex target descriptions
40724 One of the challenges of using @value{GDBN} to debug embedded systems
40725 is that there are so many minor variants of each processor
40726 architecture in use. It is common practice for vendors to start with
40727 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40728 and then make changes to adapt it to a particular market niche. Some
40729 architectures have hundreds of variants, available from dozens of
40730 vendors. This leads to a number of problems:
40734 With so many different customized processors, it is difficult for
40735 the @value{GDBN} maintainers to keep up with the changes.
40737 Since individual variants may have short lifetimes or limited
40738 audiences, it may not be worthwhile to carry information about every
40739 variant in the @value{GDBN} source tree.
40741 When @value{GDBN} does support the architecture of the embedded system
40742 at hand, the task of finding the correct architecture name to give the
40743 @command{set architecture} command can be error-prone.
40746 To address these problems, the @value{GDBN} remote protocol allows a
40747 target system to not only identify itself to @value{GDBN}, but to
40748 actually describe its own features. This lets @value{GDBN} support
40749 processor variants it has never seen before --- to the extent that the
40750 descriptions are accurate, and that @value{GDBN} understands them.
40752 @value{GDBN} must be linked with the Expat library to support XML
40753 target descriptions. @xref{Expat}.
40756 * Retrieving Descriptions:: How descriptions are fetched from a target.
40757 * Target Description Format:: The contents of a target description.
40758 * Predefined Target Types:: Standard types available for target
40760 * Standard Target Features:: Features @value{GDBN} knows about.
40763 @node Retrieving Descriptions
40764 @section Retrieving Descriptions
40766 Target descriptions can be read from the target automatically, or
40767 specified by the user manually. The default behavior is to read the
40768 description from the target. @value{GDBN} retrieves it via the remote
40769 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40770 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40771 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40772 XML document, of the form described in @ref{Target Description
40775 Alternatively, you can specify a file to read for the target description.
40776 If a file is set, the target will not be queried. The commands to
40777 specify a file are:
40780 @cindex set tdesc filename
40781 @item set tdesc filename @var{path}
40782 Read the target description from @var{path}.
40784 @cindex unset tdesc filename
40785 @item unset tdesc filename
40786 Do not read the XML target description from a file. @value{GDBN}
40787 will use the description supplied by the current target.
40789 @cindex show tdesc filename
40790 @item show tdesc filename
40791 Show the filename to read for a target description, if any.
40795 @node Target Description Format
40796 @section Target Description Format
40797 @cindex target descriptions, XML format
40799 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40800 document which complies with the Document Type Definition provided in
40801 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40802 means you can use generally available tools like @command{xmllint} to
40803 check that your feature descriptions are well-formed and valid.
40804 However, to help people unfamiliar with XML write descriptions for
40805 their targets, we also describe the grammar here.
40807 Target descriptions can identify the architecture of the remote target
40808 and (for some architectures) provide information about custom register
40809 sets. They can also identify the OS ABI of the remote target.
40810 @value{GDBN} can use this information to autoconfigure for your
40811 target, or to warn you if you connect to an unsupported target.
40813 Here is a simple target description:
40816 <target version="1.0">
40817 <architecture>i386:x86-64</architecture>
40822 This minimal description only says that the target uses
40823 the x86-64 architecture.
40825 A target description has the following overall form, with [ ] marking
40826 optional elements and @dots{} marking repeatable elements. The elements
40827 are explained further below.
40830 <?xml version="1.0"?>
40831 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40832 <target version="1.0">
40833 @r{[}@var{architecture}@r{]}
40834 @r{[}@var{osabi}@r{]}
40835 @r{[}@var{compatible}@r{]}
40836 @r{[}@var{feature}@dots{}@r{]}
40841 The description is generally insensitive to whitespace and line
40842 breaks, under the usual common-sense rules. The XML version
40843 declaration and document type declaration can generally be omitted
40844 (@value{GDBN} does not require them), but specifying them may be
40845 useful for XML validation tools. The @samp{version} attribute for
40846 @samp{<target>} may also be omitted, but we recommend
40847 including it; if future versions of @value{GDBN} use an incompatible
40848 revision of @file{gdb-target.dtd}, they will detect and report
40849 the version mismatch.
40851 @subsection Inclusion
40852 @cindex target descriptions, inclusion
40855 @cindex <xi:include>
40858 It can sometimes be valuable to split a target description up into
40859 several different annexes, either for organizational purposes, or to
40860 share files between different possible target descriptions. You can
40861 divide a description into multiple files by replacing any element of
40862 the target description with an inclusion directive of the form:
40865 <xi:include href="@var{document}"/>
40869 When @value{GDBN} encounters an element of this form, it will retrieve
40870 the named XML @var{document}, and replace the inclusion directive with
40871 the contents of that document. If the current description was read
40872 using @samp{qXfer}, then so will be the included document;
40873 @var{document} will be interpreted as the name of an annex. If the
40874 current description was read from a file, @value{GDBN} will look for
40875 @var{document} as a file in the same directory where it found the
40876 original description.
40878 @subsection Architecture
40879 @cindex <architecture>
40881 An @samp{<architecture>} element has this form:
40884 <architecture>@var{arch}</architecture>
40887 @var{arch} is one of the architectures from the set accepted by
40888 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40891 @cindex @code{<osabi>}
40893 This optional field was introduced in @value{GDBN} version 7.0.
40894 Previous versions of @value{GDBN} ignore it.
40896 An @samp{<osabi>} element has this form:
40899 <osabi>@var{abi-name}</osabi>
40902 @var{abi-name} is an OS ABI name from the same selection accepted by
40903 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40905 @subsection Compatible Architecture
40906 @cindex @code{<compatible>}
40908 This optional field was introduced in @value{GDBN} version 7.0.
40909 Previous versions of @value{GDBN} ignore it.
40911 A @samp{<compatible>} element has this form:
40914 <compatible>@var{arch}</compatible>
40917 @var{arch} is one of the architectures from the set accepted by
40918 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40920 A @samp{<compatible>} element is used to specify that the target
40921 is able to run binaries in some other than the main target architecture
40922 given by the @samp{<architecture>} element. For example, on the
40923 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40924 or @code{powerpc:common64}, but the system is able to run binaries
40925 in the @code{spu} architecture as well. The way to describe this
40926 capability with @samp{<compatible>} is as follows:
40929 <architecture>powerpc:common</architecture>
40930 <compatible>spu</compatible>
40933 @subsection Features
40936 Each @samp{<feature>} describes some logical portion of the target
40937 system. Features are currently used to describe available CPU
40938 registers and the types of their contents. A @samp{<feature>} element
40942 <feature name="@var{name}">
40943 @r{[}@var{type}@dots{}@r{]}
40949 Each feature's name should be unique within the description. The name
40950 of a feature does not matter unless @value{GDBN} has some special
40951 knowledge of the contents of that feature; if it does, the feature
40952 should have its standard name. @xref{Standard Target Features}.
40956 Any register's value is a collection of bits which @value{GDBN} must
40957 interpret. The default interpretation is a two's complement integer,
40958 but other types can be requested by name in the register description.
40959 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40960 Target Types}), and the description can define additional composite types.
40962 Each type element must have an @samp{id} attribute, which gives
40963 a unique (within the containing @samp{<feature>}) name to the type.
40964 Types must be defined before they are used.
40967 Some targets offer vector registers, which can be treated as arrays
40968 of scalar elements. These types are written as @samp{<vector>} elements,
40969 specifying the array element type, @var{type}, and the number of elements,
40973 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40977 If a register's value is usefully viewed in multiple ways, define it
40978 with a union type containing the useful representations. The
40979 @samp{<union>} element contains one or more @samp{<field>} elements,
40980 each of which has a @var{name} and a @var{type}:
40983 <union id="@var{id}">
40984 <field name="@var{name}" type="@var{type}"/>
40990 If a register's value is composed from several separate values, define
40991 it with a structure type. There are two forms of the @samp{<struct>}
40992 element; a @samp{<struct>} element must either contain only bitfields
40993 or contain no bitfields. If the structure contains only bitfields,
40994 its total size in bytes must be specified, each bitfield must have an
40995 explicit start and end, and bitfields are automatically assigned an
40996 integer type. The field's @var{start} should be less than or
40997 equal to its @var{end}, and zero represents the least significant bit.
41000 <struct id="@var{id}" size="@var{size}">
41001 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
41006 If the structure contains no bitfields, then each field has an
41007 explicit type, and no implicit padding is added.
41010 <struct id="@var{id}">
41011 <field name="@var{name}" type="@var{type}"/>
41017 If a register's value is a series of single-bit flags, define it with
41018 a flags type. The @samp{<flags>} element has an explicit @var{size}
41019 and contains one or more @samp{<field>} elements. Each field has a
41020 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
41024 <flags id="@var{id}" size="@var{size}">
41025 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
41030 @subsection Registers
41033 Each register is represented as an element with this form:
41036 <reg name="@var{name}"
41037 bitsize="@var{size}"
41038 @r{[}regnum="@var{num}"@r{]}
41039 @r{[}save-restore="@var{save-restore}"@r{]}
41040 @r{[}type="@var{type}"@r{]}
41041 @r{[}group="@var{group}"@r{]}/>
41045 The components are as follows:
41050 The register's name; it must be unique within the target description.
41053 The register's size, in bits.
41056 The register's number. If omitted, a register's number is one greater
41057 than that of the previous register (either in the current feature or in
41058 a preceding feature); the first register in the target description
41059 defaults to zero. This register number is used to read or write
41060 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41061 packets, and registers appear in the @code{g} and @code{G} packets
41062 in order of increasing register number.
41065 Whether the register should be preserved across inferior function
41066 calls; this must be either @code{yes} or @code{no}. The default is
41067 @code{yes}, which is appropriate for most registers except for
41068 some system control registers; this is not related to the target's
41072 The type of the register. @var{type} may be a predefined type, a type
41073 defined in the current feature, or one of the special types @code{int}
41074 and @code{float}. @code{int} is an integer type of the correct size
41075 for @var{bitsize}, and @code{float} is a floating point type (in the
41076 architecture's normal floating point format) of the correct size for
41077 @var{bitsize}. The default is @code{int}.
41080 The register group to which this register belongs. @var{group} must
41081 be either @code{general}, @code{float}, or @code{vector}. If no
41082 @var{group} is specified, @value{GDBN} will not display the register
41083 in @code{info registers}.
41087 @node Predefined Target Types
41088 @section Predefined Target Types
41089 @cindex target descriptions, predefined types
41091 Type definitions in the self-description can build up composite types
41092 from basic building blocks, but can not define fundamental types. Instead,
41093 standard identifiers are provided by @value{GDBN} for the fundamental
41094 types. The currently supported types are:
41103 Signed integer types holding the specified number of bits.
41110 Unsigned integer types holding the specified number of bits.
41114 Pointers to unspecified code and data. The program counter and
41115 any dedicated return address register may be marked as code
41116 pointers; printing a code pointer converts it into a symbolic
41117 address. The stack pointer and any dedicated address registers
41118 may be marked as data pointers.
41121 Single precision IEEE floating point.
41124 Double precision IEEE floating point.
41127 The 12-byte extended precision format used by ARM FPA registers.
41130 The 10-byte extended precision format used by x87 registers.
41133 32bit @sc{eflags} register used by x86.
41136 32bit @sc{mxcsr} register used by x86.
41140 @node Standard Target Features
41141 @section Standard Target Features
41142 @cindex target descriptions, standard features
41144 A target description must contain either no registers or all the
41145 target's registers. If the description contains no registers, then
41146 @value{GDBN} will assume a default register layout, selected based on
41147 the architecture. If the description contains any registers, the
41148 default layout will not be used; the standard registers must be
41149 described in the target description, in such a way that @value{GDBN}
41150 can recognize them.
41152 This is accomplished by giving specific names to feature elements
41153 which contain standard registers. @value{GDBN} will look for features
41154 with those names and verify that they contain the expected registers;
41155 if any known feature is missing required registers, or if any required
41156 feature is missing, @value{GDBN} will reject the target
41157 description. You can add additional registers to any of the
41158 standard features --- @value{GDBN} will display them just as if
41159 they were added to an unrecognized feature.
41161 This section lists the known features and their expected contents.
41162 Sample XML documents for these features are included in the
41163 @value{GDBN} source tree, in the directory @file{gdb/features}.
41165 Names recognized by @value{GDBN} should include the name of the
41166 company or organization which selected the name, and the overall
41167 architecture to which the feature applies; so e.g.@: the feature
41168 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41170 The names of registers are not case sensitive for the purpose
41171 of recognizing standard features, but @value{GDBN} will only display
41172 registers using the capitalization used in the description.
41175 * AArch64 Features::
41180 * PowerPC Features::
41185 @node AArch64 Features
41186 @subsection AArch64 Features
41187 @cindex target descriptions, AArch64 features
41189 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41190 targets. It should contain registers @samp{x0} through @samp{x30},
41191 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41193 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41194 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41198 @subsection ARM Features
41199 @cindex target descriptions, ARM features
41201 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41203 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41204 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41206 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41207 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41208 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41211 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41212 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41214 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41215 it should contain at least registers @samp{wR0} through @samp{wR15} and
41216 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41217 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41219 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41220 should contain at least registers @samp{d0} through @samp{d15}. If
41221 they are present, @samp{d16} through @samp{d31} should also be included.
41222 @value{GDBN} will synthesize the single-precision registers from
41223 halves of the double-precision registers.
41225 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41226 need to contain registers; it instructs @value{GDBN} to display the
41227 VFP double-precision registers as vectors and to synthesize the
41228 quad-precision registers from pairs of double-precision registers.
41229 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41230 be present and include 32 double-precision registers.
41232 @node i386 Features
41233 @subsection i386 Features
41234 @cindex target descriptions, i386 features
41236 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41237 targets. It should describe the following registers:
41241 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41243 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41245 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41246 @samp{fs}, @samp{gs}
41248 @samp{st0} through @samp{st7}
41250 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41251 @samp{foseg}, @samp{fooff} and @samp{fop}
41254 The register sets may be different, depending on the target.
41256 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41257 describe registers:
41261 @samp{xmm0} through @samp{xmm7} for i386
41263 @samp{xmm0} through @samp{xmm15} for amd64
41268 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41269 @samp{org.gnu.gdb.i386.sse} feature. It should
41270 describe the upper 128 bits of @sc{ymm} registers:
41274 @samp{ymm0h} through @samp{ymm7h} for i386
41276 @samp{ymm0h} through @samp{ymm15h} for amd64
41279 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41280 describe a single register, @samp{orig_eax}.
41282 @node MIPS Features
41283 @subsection @acronym{MIPS} Features
41284 @cindex target descriptions, @acronym{MIPS} features
41286 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41287 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41288 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41291 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41292 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41293 registers. They may be 32-bit or 64-bit depending on the target.
41295 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41296 it may be optional in a future version of @value{GDBN}. It should
41297 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41298 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41300 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41301 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41302 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41303 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41305 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41306 contain a single register, @samp{restart}, which is used by the
41307 Linux kernel to control restartable syscalls.
41309 @node M68K Features
41310 @subsection M68K Features
41311 @cindex target descriptions, M68K features
41314 @item @samp{org.gnu.gdb.m68k.core}
41315 @itemx @samp{org.gnu.gdb.coldfire.core}
41316 @itemx @samp{org.gnu.gdb.fido.core}
41317 One of those features must be always present.
41318 The feature that is present determines which flavor of m68k is
41319 used. The feature that is present should contain registers
41320 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41321 @samp{sp}, @samp{ps} and @samp{pc}.
41323 @item @samp{org.gnu.gdb.coldfire.fp}
41324 This feature is optional. If present, it should contain registers
41325 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41329 @node PowerPC Features
41330 @subsection PowerPC Features
41331 @cindex target descriptions, PowerPC features
41333 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41334 targets. It should contain registers @samp{r0} through @samp{r31},
41335 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41336 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41338 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41339 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41341 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41342 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41345 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41346 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41347 will combine these registers with the floating point registers
41348 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41349 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41350 through @samp{vs63}, the set of vector registers for POWER7.
41352 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41353 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41354 @samp{spefscr}. SPE targets should provide 32-bit registers in
41355 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41356 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41357 these to present registers @samp{ev0} through @samp{ev31} to the
41360 @node TIC6x Features
41361 @subsection TMS320C6x Features
41362 @cindex target descriptions, TIC6x features
41363 @cindex target descriptions, TMS320C6x features
41364 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41365 targets. It should contain registers @samp{A0} through @samp{A15},
41366 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41368 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41369 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41370 through @samp{B31}.
41372 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41373 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41375 @node Operating System Information
41376 @appendix Operating System Information
41377 @cindex operating system information
41383 Users of @value{GDBN} often wish to obtain information about the state of
41384 the operating system running on the target---for example the list of
41385 processes, or the list of open files. This section describes the
41386 mechanism that makes it possible. This mechanism is similar to the
41387 target features mechanism (@pxref{Target Descriptions}), but focuses
41388 on a different aspect of target.
41390 Operating system information is retrived from the target via the
41391 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41392 read}). The object name in the request should be @samp{osdata}, and
41393 the @var{annex} identifies the data to be fetched.
41396 @appendixsection Process list
41397 @cindex operating system information, process list
41399 When requesting the process list, the @var{annex} field in the
41400 @samp{qXfer} request should be @samp{processes}. The returned data is
41401 an XML document. The formal syntax of this document is defined in
41402 @file{gdb/features/osdata.dtd}.
41404 An example document is:
41407 <?xml version="1.0"?>
41408 <!DOCTYPE target SYSTEM "osdata.dtd">
41409 <osdata type="processes">
41411 <column name="pid">1</column>
41412 <column name="user">root</column>
41413 <column name="command">/sbin/init</column>
41414 <column name="cores">1,2,3</column>
41419 Each item should include a column whose name is @samp{pid}. The value
41420 of that column should identify the process on the target. The
41421 @samp{user} and @samp{command} columns are optional, and will be
41422 displayed by @value{GDBN}. The @samp{cores} column, if present,
41423 should contain a comma-separated list of cores that this process
41424 is running on. Target may provide additional columns,
41425 which @value{GDBN} currently ignores.
41427 @node Trace File Format
41428 @appendix Trace File Format
41429 @cindex trace file format
41431 The trace file comes in three parts: a header, a textual description
41432 section, and a trace frame section with binary data.
41434 The header has the form @code{\x7fTRACE0\n}. The first byte is
41435 @code{0x7f} so as to indicate that the file contains binary data,
41436 while the @code{0} is a version number that may have different values
41439 The description section consists of multiple lines of @sc{ascii} text
41440 separated by newline characters (@code{0xa}). The lines may include a
41441 variety of optional descriptive or context-setting information, such
41442 as tracepoint definitions or register set size. @value{GDBN} will
41443 ignore any line that it does not recognize. An empty line marks the end
41446 @c FIXME add some specific types of data
41448 The trace frame section consists of a number of consecutive frames.
41449 Each frame begins with a two-byte tracepoint number, followed by a
41450 four-byte size giving the amount of data in the frame. The data in
41451 the frame consists of a number of blocks, each introduced by a
41452 character indicating its type (at least register, memory, and trace
41453 state variable). The data in this section is raw binary, not a
41454 hexadecimal or other encoding; its endianness matches the target's
41457 @c FIXME bi-arch may require endianness/arch info in description section
41460 @item R @var{bytes}
41461 Register block. The number and ordering of bytes matches that of a
41462 @code{g} packet in the remote protocol. Note that these are the
41463 actual bytes, in target order and @value{GDBN} register order, not a
41464 hexadecimal encoding.
41466 @item M @var{address} @var{length} @var{bytes}...
41467 Memory block. This is a contiguous block of memory, at the 8-byte
41468 address @var{address}, with a 2-byte length @var{length}, followed by
41469 @var{length} bytes.
41471 @item V @var{number} @var{value}
41472 Trace state variable block. This records the 8-byte signed value
41473 @var{value} of trace state variable numbered @var{number}.
41477 Future enhancements of the trace file format may include additional types
41480 @node Index Section Format
41481 @appendix @code{.gdb_index} section format
41482 @cindex .gdb_index section format
41483 @cindex index section format
41485 This section documents the index section that is created by @code{save
41486 gdb-index} (@pxref{Index Files}). The index section is
41487 DWARF-specific; some knowledge of DWARF is assumed in this
41490 The mapped index file format is designed to be directly
41491 @code{mmap}able on any architecture. In most cases, a datum is
41492 represented using a little-endian 32-bit integer value, called an
41493 @code{offset_type}. Big endian machines must byte-swap the values
41494 before using them. Exceptions to this rule are noted. The data is
41495 laid out such that alignment is always respected.
41497 A mapped index consists of several areas, laid out in order.
41501 The file header. This is a sequence of values, of @code{offset_type}
41502 unless otherwise noted:
41506 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41507 Version 4 uses a different hashing function from versions 5 and 6.
41508 Version 6 includes symbols for inlined functions, whereas versions 4
41509 and 5 do not. Version 7 adds attributes to the CU indices in the
41510 symbol table. Version 8 specifies that symbols from DWARF type units
41511 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41512 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41514 @value{GDBN} will only read version 4, 5, or 6 indices
41515 by specifying @code{set use-deprecated-index-sections on}.
41516 GDB has a workaround for potentially broken version 7 indices so it is
41517 currently not flagged as deprecated.
41520 The offset, from the start of the file, of the CU list.
41523 The offset, from the start of the file, of the types CU list. Note
41524 that this area can be empty, in which case this offset will be equal
41525 to the next offset.
41528 The offset, from the start of the file, of the address area.
41531 The offset, from the start of the file, of the symbol table.
41534 The offset, from the start of the file, of the constant pool.
41538 The CU list. This is a sequence of pairs of 64-bit little-endian
41539 values, sorted by the CU offset. The first element in each pair is
41540 the offset of a CU in the @code{.debug_info} section. The second
41541 element in each pair is the length of that CU. References to a CU
41542 elsewhere in the map are done using a CU index, which is just the
41543 0-based index into this table. Note that if there are type CUs, then
41544 conceptually CUs and type CUs form a single list for the purposes of
41548 The types CU list. This is a sequence of triplets of 64-bit
41549 little-endian values. In a triplet, the first value is the CU offset,
41550 the second value is the type offset in the CU, and the third value is
41551 the type signature. The types CU list is not sorted.
41554 The address area. The address area consists of a sequence of address
41555 entries. Each address entry has three elements:
41559 The low address. This is a 64-bit little-endian value.
41562 The high address. This is a 64-bit little-endian value. Like
41563 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41566 The CU index. This is an @code{offset_type} value.
41570 The symbol table. This is an open-addressed hash table. The size of
41571 the hash table is always a power of 2.
41573 Each slot in the hash table consists of a pair of @code{offset_type}
41574 values. The first value is the offset of the symbol's name in the
41575 constant pool. The second value is the offset of the CU vector in the
41578 If both values are 0, then this slot in the hash table is empty. This
41579 is ok because while 0 is a valid constant pool index, it cannot be a
41580 valid index for both a string and a CU vector.
41582 The hash value for a table entry is computed by applying an
41583 iterative hash function to the symbol's name. Starting with an
41584 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41585 the string is incorporated into the hash using the formula depending on the
41590 The formula is @code{r = r * 67 + c - 113}.
41592 @item Versions 5 to 7
41593 The formula is @code{r = r * 67 + tolower (c) - 113}.
41596 The terminating @samp{\0} is not incorporated into the hash.
41598 The step size used in the hash table is computed via
41599 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41600 value, and @samp{size} is the size of the hash table. The step size
41601 is used to find the next candidate slot when handling a hash
41604 The names of C@t{++} symbols in the hash table are canonicalized. We
41605 don't currently have a simple description of the canonicalization
41606 algorithm; if you intend to create new index sections, you must read
41610 The constant pool. This is simply a bunch of bytes. It is organized
41611 so that alignment is correct: CU vectors are stored first, followed by
41614 A CU vector in the constant pool is a sequence of @code{offset_type}
41615 values. The first value is the number of CU indices in the vector.
41616 Each subsequent value is the index and symbol attributes of a CU in
41617 the CU list. This element in the hash table is used to indicate which
41618 CUs define the symbol and how the symbol is used.
41619 See below for the format of each CU index+attributes entry.
41621 A string in the constant pool is zero-terminated.
41624 Attributes were added to CU index values in @code{.gdb_index} version 7.
41625 If a symbol has multiple uses within a CU then there is one
41626 CU index+attributes value for each use.
41628 The format of each CU index+attributes entry is as follows
41634 This is the index of the CU in the CU list.
41636 These bits are reserved for future purposes and must be zero.
41638 The kind of the symbol in the CU.
41642 This value is reserved and should not be used.
41643 By reserving zero the full @code{offset_type} value is backwards compatible
41644 with previous versions of the index.
41646 The symbol is a type.
41648 The symbol is a variable or an enum value.
41650 The symbol is a function.
41652 Any other kind of symbol.
41654 These values are reserved.
41658 This bit is zero if the value is global and one if it is static.
41660 The determination of whether a symbol is global or static is complicated.
41661 The authorative reference is the file @file{dwarf2read.c} in
41662 @value{GDBN} sources.
41666 This pseudo-code describes the computation of a symbol's kind and
41667 global/static attributes in the index.
41670 is_external = get_attribute (die, DW_AT_external);
41671 language = get_attribute (cu_die, DW_AT_language);
41674 case DW_TAG_typedef:
41675 case DW_TAG_base_type:
41676 case DW_TAG_subrange_type:
41680 case DW_TAG_enumerator:
41682 is_static = (language != CPLUS && language != JAVA);
41684 case DW_TAG_subprogram:
41686 is_static = ! (is_external || language == ADA);
41688 case DW_TAG_constant:
41690 is_static = ! is_external;
41692 case DW_TAG_variable:
41694 is_static = ! is_external;
41696 case DW_TAG_namespace:
41700 case DW_TAG_class_type:
41701 case DW_TAG_interface_type:
41702 case DW_TAG_structure_type:
41703 case DW_TAG_union_type:
41704 case DW_TAG_enumeration_type:
41706 is_static = (language != CPLUS && language != JAVA);
41714 @appendix Manual pages
41718 * gdb man:: The GNU Debugger man page
41719 * gdbserver man:: Remote Server for the GNU Debugger man page
41720 * gcore man:: Generate a core file of a running program
41721 * gdbinit man:: gdbinit scripts
41727 @c man title gdb The GNU Debugger
41729 @c man begin SYNOPSIS gdb
41730 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41731 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41732 [@option{-b}@w{ }@var{bps}]
41733 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41734 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41735 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41736 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41737 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41740 @c man begin DESCRIPTION gdb
41741 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41742 going on ``inside'' another program while it executes -- or what another
41743 program was doing at the moment it crashed.
41745 @value{GDBN} can do four main kinds of things (plus other things in support of
41746 these) to help you catch bugs in the act:
41750 Start your program, specifying anything that might affect its behavior.
41753 Make your program stop on specified conditions.
41756 Examine what has happened, when your program has stopped.
41759 Change things in your program, so you can experiment with correcting the
41760 effects of one bug and go on to learn about another.
41763 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41766 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41767 commands from the terminal until you tell it to exit with the @value{GDBN}
41768 command @code{quit}. You can get online help from @value{GDBN} itself
41769 by using the command @code{help}.
41771 You can run @code{gdb} with no arguments or options; but the most
41772 usual way to start @value{GDBN} is with one argument or two, specifying an
41773 executable program as the argument:
41779 You can also start with both an executable program and a core file specified:
41785 You can, instead, specify a process ID as a second argument, if you want
41786 to debug a running process:
41794 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41795 named @file{1234}; @value{GDBN} does check for a core file first).
41796 With option @option{-p} you can omit the @var{program} filename.
41798 Here are some of the most frequently needed @value{GDBN} commands:
41800 @c pod2man highlights the right hand side of the @item lines.
41802 @item break [@var{file}:]@var{functiop}
41803 Set a breakpoint at @var{function} (in @var{file}).
41805 @item run [@var{arglist}]
41806 Start your program (with @var{arglist}, if specified).
41809 Backtrace: display the program stack.
41811 @item print @var{expr}
41812 Display the value of an expression.
41815 Continue running your program (after stopping, e.g. at a breakpoint).
41818 Execute next program line (after stopping); step @emph{over} any
41819 function calls in the line.
41821 @item edit [@var{file}:]@var{function}
41822 look at the program line where it is presently stopped.
41824 @item list [@var{file}:]@var{function}
41825 type the text of the program in the vicinity of where it is presently stopped.
41828 Execute next program line (after stopping); step @emph{into} any
41829 function calls in the line.
41831 @item help [@var{name}]
41832 Show information about @value{GDBN} command @var{name}, or general information
41833 about using @value{GDBN}.
41836 Exit from @value{GDBN}.
41840 For full details on @value{GDBN},
41841 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41842 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41843 as the @code{gdb} entry in the @code{info} program.
41847 @c man begin OPTIONS gdb
41848 Any arguments other than options specify an executable
41849 file and core file (or process ID); that is, the first argument
41850 encountered with no
41851 associated option flag is equivalent to a @option{-se} option, and the second,
41852 if any, is equivalent to a @option{-c} option if it's the name of a file.
41854 both long and short forms; both are shown here. The long forms are also
41855 recognized if you truncate them, so long as enough of the option is
41856 present to be unambiguous. (If you prefer, you can flag option
41857 arguments with @option{+} rather than @option{-}, though we illustrate the
41858 more usual convention.)
41860 All the options and command line arguments you give are processed
41861 in sequential order. The order makes a difference when the @option{-x}
41867 List all options, with brief explanations.
41869 @item -symbols=@var{file}
41870 @itemx -s @var{file}
41871 Read symbol table from file @var{file}.
41874 Enable writing into executable and core files.
41876 @item -exec=@var{file}
41877 @itemx -e @var{file}
41878 Use file @var{file} as the executable file to execute when
41879 appropriate, and for examining pure data in conjunction with a core
41882 @item -se=@var{file}
41883 Read symbol table from file @var{file} and use it as the executable
41886 @item -core=@var{file}
41887 @itemx -c @var{file}
41888 Use file @var{file} as a core dump to examine.
41890 @item -command=@var{file}
41891 @itemx -x @var{file}
41892 Execute @value{GDBN} commands from file @var{file}.
41894 @item -ex @var{command}
41895 Execute given @value{GDBN} @var{command}.
41897 @item -directory=@var{directory}
41898 @itemx -d @var{directory}
41899 Add @var{directory} to the path to search for source files.
41902 Do not execute commands from @file{~/.gdbinit}.
41906 Do not execute commands from any @file{.gdbinit} initialization files.
41910 ``Quiet''. Do not print the introductory and copyright messages. These
41911 messages are also suppressed in batch mode.
41914 Run in batch mode. Exit with status @code{0} after processing all the command
41915 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41916 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41917 commands in the command files.
41919 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41920 download and run a program on another computer; in order to make this
41921 more useful, the message
41924 Program exited normally.
41928 (which is ordinarily issued whenever a program running under @value{GDBN} control
41929 terminates) is not issued when running in batch mode.
41931 @item -cd=@var{directory}
41932 Run @value{GDBN} using @var{directory} as its working directory,
41933 instead of the current directory.
41937 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41938 @value{GDBN} to output the full file name and line number in a standard,
41939 recognizable fashion each time a stack frame is displayed (which
41940 includes each time the program stops). This recognizable format looks
41941 like two @samp{\032} characters, followed by the file name, line number
41942 and character position separated by colons, and a newline. The
41943 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41944 characters as a signal to display the source code for the frame.
41947 Set the line speed (baud rate or bits per second) of any serial
41948 interface used by @value{GDBN} for remote debugging.
41950 @item -tty=@var{device}
41951 Run using @var{device} for your program's standard input and output.
41955 @c man begin SEEALSO gdb
41957 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41958 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41959 documentation are properly installed at your site, the command
41966 should give you access to the complete manual.
41968 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41969 Richard M. Stallman and Roland H. Pesch, July 1991.
41973 @node gdbserver man
41974 @heading gdbserver man
41976 @c man title gdbserver Remote Server for the GNU Debugger
41978 @c man begin SYNOPSIS gdbserver
41979 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41981 gdbserver --attach @var{comm} @var{pid}
41983 gdbserver --multi @var{comm}
41987 @c man begin DESCRIPTION gdbserver
41988 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41989 than the one which is running the program being debugged.
41992 @subheading Usage (server (target) side)
41995 Usage (server (target) side):
41998 First, you need to have a copy of the program you want to debug put onto
41999 the target system. The program can be stripped to save space if needed, as
42000 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42001 the @value{GDBN} running on the host system.
42003 To use the server, you log on to the target system, and run the @command{gdbserver}
42004 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42005 your program, and (c) its arguments. The general syntax is:
42008 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42011 For example, using a serial port, you might say:
42015 @c @file would wrap it as F</dev/com1>.
42016 target> gdbserver /dev/com1 emacs foo.txt
42019 target> gdbserver @file{/dev/com1} emacs foo.txt
42023 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42024 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42025 waits patiently for the host @value{GDBN} to communicate with it.
42027 To use a TCP connection, you could say:
42030 target> gdbserver host:2345 emacs foo.txt
42033 This says pretty much the same thing as the last example, except that we are
42034 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42035 that we are expecting to see a TCP connection from @code{host} to local TCP port
42036 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42037 want for the port number as long as it does not conflict with any existing TCP
42038 ports on the target system. This same port number must be used in the host
42039 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42040 you chose a port number that conflicts with another service, @command{gdbserver} will
42041 print an error message and exit.
42043 @command{gdbserver} can also attach to running programs.
42044 This is accomplished via the @option{--attach} argument. The syntax is:
42047 target> gdbserver --attach @var{comm} @var{pid}
42050 @var{pid} is the process ID of a currently running process. It isn't
42051 necessary to point @command{gdbserver} at a binary for the running process.
42053 To start @code{gdbserver} without supplying an initial command to run
42054 or process ID to attach, use the @option{--multi} command line option.
42055 In such case you should connect using @kbd{target extended-remote} to start
42056 the program you want to debug.
42059 target> gdbserver --multi @var{comm}
42063 @subheading Usage (host side)
42069 You need an unstripped copy of the target program on your host system, since
42070 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42071 would, with the target program as the first argument. (You may need to use the
42072 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42073 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42074 new command you need to know about is @code{target remote}
42075 (or @code{target extended-remote}). Its argument is either
42076 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42077 descriptor. For example:
42081 @c @file would wrap it as F</dev/ttyb>.
42082 (gdb) target remote /dev/ttyb
42085 (gdb) target remote @file{/dev/ttyb}
42090 communicates with the server via serial line @file{/dev/ttyb}, and:
42093 (gdb) target remote the-target:2345
42097 communicates via a TCP connection to port 2345 on host `the-target', where
42098 you previously started up @command{gdbserver} with the same port number. Note that for
42099 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42100 command, otherwise you may get an error that looks something like
42101 `Connection refused'.
42103 @command{gdbserver} can also debug multiple inferiors at once,
42106 the @value{GDBN} manual in node @code{Inferiors and Programs}
42107 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42110 @ref{Inferiors and Programs}.
42112 In such case use the @code{extended-remote} @value{GDBN} command variant:
42115 (gdb) target extended-remote the-target:2345
42118 The @command{gdbserver} option @option{--multi} may or may not be used in such
42122 @c man begin OPTIONS gdbserver
42123 There are three different modes for invoking @command{gdbserver}:
42128 Debug a specific program specified by its program name:
42131 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42134 The @var{comm} parameter specifies how should the server communicate
42135 with @value{GDBN}; it is either a device name (to use a serial line),
42136 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42137 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42138 debug in @var{prog}. Any remaining arguments will be passed to the
42139 program verbatim. When the program exits, @value{GDBN} will close the
42140 connection, and @code{gdbserver} will exit.
42143 Debug a specific program by specifying the process ID of a running
42147 gdbserver --attach @var{comm} @var{pid}
42150 The @var{comm} parameter is as described above. Supply the process ID
42151 of a running program in @var{pid}; @value{GDBN} will do everything
42152 else. Like with the previous mode, when the process @var{pid} exits,
42153 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42156 Multi-process mode -- debug more than one program/process:
42159 gdbserver --multi @var{comm}
42162 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42163 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42164 close the connection when a process being debugged exits, so you can
42165 debug several processes in the same session.
42168 In each of the modes you may specify these options:
42173 List all options, with brief explanations.
42176 This option causes @command{gdbserver} to print its version number and exit.
42179 @command{gdbserver} will attach to a running program. The syntax is:
42182 target> gdbserver --attach @var{comm} @var{pid}
42185 @var{pid} is the process ID of a currently running process. It isn't
42186 necessary to point @command{gdbserver} at a binary for the running process.
42189 To start @code{gdbserver} without supplying an initial command to run
42190 or process ID to attach, use this command line option.
42191 Then you can connect using @kbd{target extended-remote} and start
42192 the program you want to debug. The syntax is:
42195 target> gdbserver --multi @var{comm}
42199 Instruct @code{gdbserver} to display extra status information about the debugging
42201 This option is intended for @code{gdbserver} development and for bug reports to
42204 @item --remote-debug
42205 Instruct @code{gdbserver} to display remote protocol debug output.
42206 This option is intended for @code{gdbserver} development and for bug reports to
42210 Specify a wrapper to launch programs
42211 for debugging. The option should be followed by the name of the
42212 wrapper, then any command-line arguments to pass to the wrapper, then
42213 @kbd{--} indicating the end of the wrapper arguments.
42216 By default, @command{gdbserver} keeps the listening TCP port open, so that
42217 additional connections are possible. However, if you start @code{gdbserver}
42218 with the @option{--once} option, it will stop listening for any further
42219 connection attempts after connecting to the first @value{GDBN} session.
42221 @c --disable-packet is not documented for users.
42223 @c --disable-randomization and --no-disable-randomization are superseded by
42224 @c QDisableRandomization.
42229 @c man begin SEEALSO gdbserver
42231 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42232 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42233 documentation are properly installed at your site, the command
42239 should give you access to the complete manual.
42241 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42242 Richard M. Stallman and Roland H. Pesch, July 1991.
42249 @c man title gcore Generate a core file of a running program
42252 @c man begin SYNOPSIS gcore
42253 gcore [-o @var{filename}] @var{pid}
42257 @c man begin DESCRIPTION gcore
42258 Generate a core dump of a running program with process ID @var{pid}.
42259 Produced file is equivalent to a kernel produced core file as if the process
42260 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42261 limit). Unlike after a crash, after @command{gcore} the program remains
42262 running without any change.
42265 @c man begin OPTIONS gcore
42267 @item -o @var{filename}
42268 The optional argument
42269 @var{filename} specifies the file name where to put the core dump.
42270 If not specified, the file name defaults to @file{core.@var{pid}},
42271 where @var{pid} is the running program process ID.
42275 @c man begin SEEALSO gcore
42277 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42278 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42279 documentation are properly installed at your site, the command
42286 should give you access to the complete manual.
42288 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42289 Richard M. Stallman and Roland H. Pesch, July 1991.
42296 @c man title gdbinit GDB initialization scripts
42299 @c man begin SYNOPSIS gdbinit
42300 @ifset SYSTEM_GDBINIT
42301 @value{SYSTEM_GDBINIT}
42310 @c man begin DESCRIPTION gdbinit
42311 These files contain @value{GDBN} commands to automatically execute during
42312 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42315 the @value{GDBN} manual in node @code{Sequences}
42316 -- shell command @code{info -f gdb -n Sequences}.
42322 Please read more in
42324 the @value{GDBN} manual in node @code{Startup}
42325 -- shell command @code{info -f gdb -n Startup}.
42332 @ifset SYSTEM_GDBINIT
42333 @item @value{SYSTEM_GDBINIT}
42335 @ifclear SYSTEM_GDBINIT
42336 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42338 System-wide initialization file. It is executed unless user specified
42339 @value{GDBN} option @code{-nx} or @code{-n}.
42342 the @value{GDBN} manual in node @code{System-wide configuration}
42343 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42346 @ref{System-wide configuration}.
42350 User initialization file. It is executed unless user specified
42351 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42354 Initialization file for current directory. It may need to be enabled with
42355 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42358 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42359 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42362 @ref{Init File in the Current Directory}.
42367 @c man begin SEEALSO gdbinit
42369 gdb(1), @code{info -f gdb -n Startup}
42371 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42372 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42373 documentation are properly installed at your site, the command
42379 should give you access to the complete manual.
42381 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42382 Richard M. Stallman and Roland H. Pesch, July 1991.
42388 @node GNU Free Documentation License
42389 @appendix GNU Free Documentation License
42392 @node Concept Index
42393 @unnumbered Concept Index
42397 @node Command and Variable Index
42398 @unnumbered Command, Variable, and Function Index
42403 % I think something like @@colophon should be in texinfo. In the
42405 \long\def\colophon{\hbox to0pt{}\vfill
42406 \centerline{The body of this manual is set in}
42407 \centerline{\fontname\tenrm,}
42408 \centerline{with headings in {\bf\fontname\tenbf}}
42409 \centerline{and examples in {\tt\fontname\tentt}.}
42410 \centerline{{\it\fontname\tenit\/},}
42411 \centerline{{\bf\fontname\tenbf}, and}
42412 \centerline{{\sl\fontname\tensl\/}}
42413 \centerline{are used for emphasis.}\vfill}
42415 % Blame: doc@@cygnus.com, 1991.