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. If you do not define @code{SHELL},
2015 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2016 use of any shell with the @code{set startup-with-shell} command (see
2019 @item The @emph{environment.}
2020 Your program normally inherits its environment from @value{GDBN}, but you can
2021 use the @value{GDBN} commands @code{set environment} and @code{unset
2022 environment} to change parts of the environment that affect
2023 your program. @xref{Environment, ,Your Program's Environment}.
2025 @item The @emph{working directory.}
2026 Your program inherits its working directory from @value{GDBN}. You can set
2027 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2028 @xref{Working Directory, ,Your Program's Working Directory}.
2030 @item The @emph{standard input and output.}
2031 Your program normally uses the same device for standard input and
2032 standard output as @value{GDBN} is using. You can redirect input and output
2033 in the @code{run} command line, or you can use the @code{tty} command to
2034 set a different device for your program.
2035 @xref{Input/Output, ,Your Program's Input and Output}.
2038 @emph{Warning:} While input and output redirection work, you cannot use
2039 pipes to pass the output of the program you are debugging to another
2040 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2044 When you issue the @code{run} command, your program begins to execute
2045 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2046 of how to arrange for your program to stop. Once your program has
2047 stopped, you may call functions in your program, using the @code{print}
2048 or @code{call} commands. @xref{Data, ,Examining Data}.
2050 If the modification time of your symbol file has changed since the last
2051 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2052 table, and reads it again. When it does this, @value{GDBN} tries to retain
2053 your current breakpoints.
2058 @cindex run to main procedure
2059 The name of the main procedure can vary from language to language.
2060 With C or C@t{++}, the main procedure name is always @code{main}, but
2061 other languages such as Ada do not require a specific name for their
2062 main procedure. The debugger provides a convenient way to start the
2063 execution of the program and to stop at the beginning of the main
2064 procedure, depending on the language used.
2066 The @samp{start} command does the equivalent of setting a temporary
2067 breakpoint at the beginning of the main procedure and then invoking
2068 the @samp{run} command.
2070 @cindex elaboration phase
2071 Some programs contain an @dfn{elaboration} phase where some startup code is
2072 executed before the main procedure is called. This depends on the
2073 languages used to write your program. In C@t{++}, for instance,
2074 constructors for static and global objects are executed before
2075 @code{main} is called. It is therefore possible that the debugger stops
2076 before reaching the main procedure. However, the temporary breakpoint
2077 will remain to halt execution.
2079 Specify the arguments to give to your program as arguments to the
2080 @samp{start} command. These arguments will be given verbatim to the
2081 underlying @samp{run} command. Note that the same arguments will be
2082 reused if no argument is provided during subsequent calls to
2083 @samp{start} or @samp{run}.
2085 It is sometimes necessary to debug the program during elaboration. In
2086 these cases, using the @code{start} command would stop the execution of
2087 your program too late, as the program would have already completed the
2088 elaboration phase. Under these circumstances, insert breakpoints in your
2089 elaboration code before running your program.
2091 @kindex set exec-wrapper
2092 @item set exec-wrapper @var{wrapper}
2093 @itemx show exec-wrapper
2094 @itemx unset exec-wrapper
2095 When @samp{exec-wrapper} is set, the specified wrapper is used to
2096 launch programs for debugging. @value{GDBN} starts your program
2097 with a shell command of the form @kbd{exec @var{wrapper}
2098 @var{program}}. Quoting is added to @var{program} and its
2099 arguments, but not to @var{wrapper}, so you should add quotes if
2100 appropriate for your shell. The wrapper runs until it executes
2101 your program, and then @value{GDBN} takes control.
2103 You can use any program that eventually calls @code{execve} with
2104 its arguments as a wrapper. Several standard Unix utilities do
2105 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2106 with @code{exec "$@@"} will also work.
2108 For example, you can use @code{env} to pass an environment variable to
2109 the debugged program, without setting the variable in your shell's
2113 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2117 This command is available when debugging locally on most targets, excluding
2118 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2120 @kindex set startup-with-shell
2121 @item set startup-with-shell
2122 @itemx set startup-with-shell on
2123 @itemx set startup-with-shell off
2124 @itemx show set startup-with-shell
2125 On Unix systems, by default, if a shell is available on your target,
2126 @value{GDBN}) uses it to start your program. Arguments of the
2127 @code{run} command are passed to the shell, which does variable
2128 substitution, expands wildcard characters and performs redirection of
2129 I/O. In some circumstances, it may be useful to disable such use of a
2130 shell, for example, when debugging the shell itself or diagnosing
2131 startup failures such as:
2135 Starting program: ./a.out
2136 During startup program terminated with signal SIGSEGV, Segmentation fault.
2140 which indicates the shell or the wrapper specified with
2141 @samp{exec-wrapper} crashed, not your program. Most often, this is
2142 caused by something odd in your shell's non-interactive mode
2143 initialization file---such as @file{.cshrc} for C-shell,
2144 $@file{.zshenv} for the Z shell, or the file specified in the
2145 @samp{BASH_ENV} environment variable for BASH.
2147 @kindex set disable-randomization
2148 @item set disable-randomization
2149 @itemx set disable-randomization on
2150 This option (enabled by default in @value{GDBN}) will turn off the native
2151 randomization of the virtual address space of the started program. This option
2152 is useful for multiple debugging sessions to make the execution better
2153 reproducible and memory addresses reusable across debugging sessions.
2155 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2156 On @sc{gnu}/Linux you can get the same behavior using
2159 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2162 @item set disable-randomization off
2163 Leave the behavior of the started executable unchanged. Some bugs rear their
2164 ugly heads only when the program is loaded at certain addresses. If your bug
2165 disappears when you run the program under @value{GDBN}, that might be because
2166 @value{GDBN} by default disables the address randomization on platforms, such
2167 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2168 disable-randomization off} to try to reproduce such elusive bugs.
2170 On targets where it is available, virtual address space randomization
2171 protects the programs against certain kinds of security attacks. In these
2172 cases the attacker needs to know the exact location of a concrete executable
2173 code. Randomizing its location makes it impossible to inject jumps misusing
2174 a code at its expected addresses.
2176 Prelinking shared libraries provides a startup performance advantage but it
2177 makes addresses in these libraries predictable for privileged processes by
2178 having just unprivileged access at the target system. Reading the shared
2179 library binary gives enough information for assembling the malicious code
2180 misusing it. Still even a prelinked shared library can get loaded at a new
2181 random address just requiring the regular relocation process during the
2182 startup. Shared libraries not already prelinked are always loaded at
2183 a randomly chosen address.
2185 Position independent executables (PIE) contain position independent code
2186 similar to the shared libraries and therefore such executables get loaded at
2187 a randomly chosen address upon startup. PIE executables always load even
2188 already prelinked shared libraries at a random address. You can build such
2189 executable using @command{gcc -fPIE -pie}.
2191 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2192 (as long as the randomization is enabled).
2194 @item show disable-randomization
2195 Show the current setting of the explicit disable of the native randomization of
2196 the virtual address space of the started program.
2201 @section Your Program's Arguments
2203 @cindex arguments (to your program)
2204 The arguments to your program can be specified by the arguments of the
2206 They are passed to a shell, which expands wildcard characters and
2207 performs redirection of I/O, and thence to your program. Your
2208 @code{SHELL} environment variable (if it exists) specifies what shell
2209 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2210 the default shell (@file{/bin/sh} on Unix).
2212 On non-Unix systems, the program is usually invoked directly by
2213 @value{GDBN}, which emulates I/O redirection via the appropriate system
2214 calls, and the wildcard characters are expanded by the startup code of
2215 the program, not by the shell.
2217 @code{run} with no arguments uses the same arguments used by the previous
2218 @code{run}, or those set by the @code{set args} command.
2223 Specify the arguments to be used the next time your program is run. If
2224 @code{set args} has no arguments, @code{run} executes your program
2225 with no arguments. Once you have run your program with arguments,
2226 using @code{set args} before the next @code{run} is the only way to run
2227 it again without arguments.
2231 Show the arguments to give your program when it is started.
2235 @section Your Program's Environment
2237 @cindex environment (of your program)
2238 The @dfn{environment} consists of a set of environment variables and
2239 their values. Environment variables conventionally record such things as
2240 your user name, your home directory, your terminal type, and your search
2241 path for programs to run. Usually you set up environment variables with
2242 the shell and they are inherited by all the other programs you run. When
2243 debugging, it can be useful to try running your program with a modified
2244 environment without having to start @value{GDBN} over again.
2248 @item path @var{directory}
2249 Add @var{directory} to the front of the @code{PATH} environment variable
2250 (the search path for executables) that will be passed to your program.
2251 The value of @code{PATH} used by @value{GDBN} does not change.
2252 You may specify several directory names, separated by whitespace or by a
2253 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2254 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2255 is moved to the front, so it is searched sooner.
2257 You can use the string @samp{$cwd} to refer to whatever is the current
2258 working directory at the time @value{GDBN} searches the path. If you
2259 use @samp{.} instead, it refers to the directory where you executed the
2260 @code{path} command. @value{GDBN} replaces @samp{.} in the
2261 @var{directory} argument (with the current path) before adding
2262 @var{directory} to the search path.
2263 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2264 @c document that, since repeating it would be a no-op.
2268 Display the list of search paths for executables (the @code{PATH}
2269 environment variable).
2271 @kindex show environment
2272 @item show environment @r{[}@var{varname}@r{]}
2273 Print the value of environment variable @var{varname} to be given to
2274 your program when it starts. If you do not supply @var{varname},
2275 print the names and values of all environment variables to be given to
2276 your program. You can abbreviate @code{environment} as @code{env}.
2278 @kindex set environment
2279 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2280 Set environment variable @var{varname} to @var{value}. The value
2281 changes for your program only, not for @value{GDBN} itself. @var{value} may
2282 be any string; the values of environment variables are just strings, and
2283 any interpretation is supplied by your program itself. The @var{value}
2284 parameter is optional; if it is eliminated, the variable is set to a
2286 @c "any string" here does not include leading, trailing
2287 @c blanks. Gnu asks: does anyone care?
2289 For example, this command:
2296 tells the debugged program, when subsequently run, that its user is named
2297 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2298 are not actually required.)
2300 @kindex unset environment
2301 @item unset environment @var{varname}
2302 Remove variable @var{varname} from the environment to be passed to your
2303 program. This is different from @samp{set env @var{varname} =};
2304 @code{unset environment} removes the variable from the environment,
2305 rather than assigning it an empty value.
2308 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2309 the shell indicated by your @code{SHELL} environment variable if it
2310 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2311 names a shell that runs an initialization file when started
2312 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2313 for the Z shell, or the file specified in the @samp{BASH_ENV}
2314 environment variable for BASH---any variables you set in that file
2315 affect your program. You may wish to move setting of environment
2316 variables to files that are only run when you sign on, such as
2317 @file{.login} or @file{.profile}.
2319 @node Working Directory
2320 @section Your Program's Working Directory
2322 @cindex working directory (of your program)
2323 Each time you start your program with @code{run}, it inherits its
2324 working directory from the current working directory of @value{GDBN}.
2325 The @value{GDBN} working directory is initially whatever it inherited
2326 from its parent process (typically the shell), but you can specify a new
2327 working directory in @value{GDBN} with the @code{cd} command.
2329 The @value{GDBN} working directory also serves as a default for the commands
2330 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2335 @cindex change working directory
2336 @item cd @r{[}@var{directory}@r{]}
2337 Set the @value{GDBN} working directory to @var{directory}. If not
2338 given, @var{directory} uses @file{'~'}.
2342 Print the @value{GDBN} working directory.
2345 It is generally impossible to find the current working directory of
2346 the process being debugged (since a program can change its directory
2347 during its run). If you work on a system where @value{GDBN} is
2348 configured with the @file{/proc} support, you can use the @code{info
2349 proc} command (@pxref{SVR4 Process Information}) to find out the
2350 current working directory of the debuggee.
2353 @section Your Program's Input and Output
2358 By default, the program you run under @value{GDBN} does input and output to
2359 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2360 to its own terminal modes to interact with you, but it records the terminal
2361 modes your program was using and switches back to them when you continue
2362 running your program.
2365 @kindex info terminal
2367 Displays information recorded by @value{GDBN} about the terminal modes your
2371 You can redirect your program's input and/or output using shell
2372 redirection with the @code{run} command. For example,
2379 starts your program, diverting its output to the file @file{outfile}.
2382 @cindex controlling terminal
2383 Another way to specify where your program should do input and output is
2384 with the @code{tty} command. This command accepts a file name as
2385 argument, and causes this file to be the default for future @code{run}
2386 commands. It also resets the controlling terminal for the child
2387 process, for future @code{run} commands. For example,
2394 directs that processes started with subsequent @code{run} commands
2395 default to do input and output on the terminal @file{/dev/ttyb} and have
2396 that as their controlling terminal.
2398 An explicit redirection in @code{run} overrides the @code{tty} command's
2399 effect on the input/output device, but not its effect on the controlling
2402 When you use the @code{tty} command or redirect input in the @code{run}
2403 command, only the input @emph{for your program} is affected. The input
2404 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2405 for @code{set inferior-tty}.
2407 @cindex inferior tty
2408 @cindex set inferior controlling terminal
2409 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2410 display the name of the terminal that will be used for future runs of your
2414 @item set inferior-tty /dev/ttyb
2415 @kindex set inferior-tty
2416 Set the tty for the program being debugged to /dev/ttyb.
2418 @item show inferior-tty
2419 @kindex show inferior-tty
2420 Show the current tty for the program being debugged.
2424 @section Debugging an Already-running Process
2429 @item attach @var{process-id}
2430 This command attaches to a running process---one that was started
2431 outside @value{GDBN}. (@code{info files} shows your active
2432 targets.) The command takes as argument a process ID. The usual way to
2433 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2434 or with the @samp{jobs -l} shell command.
2436 @code{attach} does not repeat if you press @key{RET} a second time after
2437 executing the command.
2440 To use @code{attach}, your program must be running in an environment
2441 which supports processes; for example, @code{attach} does not work for
2442 programs on bare-board targets that lack an operating system. You must
2443 also have permission to send the process a signal.
2445 When you use @code{attach}, the debugger finds the program running in
2446 the process first by looking in the current working directory, then (if
2447 the program is not found) by using the source file search path
2448 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2449 the @code{file} command to load the program. @xref{Files, ,Commands to
2452 The first thing @value{GDBN} does after arranging to debug the specified
2453 process is to stop it. You can examine and modify an attached process
2454 with all the @value{GDBN} commands that are ordinarily available when
2455 you start processes with @code{run}. You can insert breakpoints; you
2456 can step and continue; you can modify storage. If you would rather the
2457 process continue running, you may use the @code{continue} command after
2458 attaching @value{GDBN} to the process.
2463 When you have finished debugging the attached process, you can use the
2464 @code{detach} command to release it from @value{GDBN} control. Detaching
2465 the process continues its execution. After the @code{detach} command,
2466 that process and @value{GDBN} become completely independent once more, and you
2467 are ready to @code{attach} another process or start one with @code{run}.
2468 @code{detach} does not repeat if you press @key{RET} again after
2469 executing the command.
2472 If you exit @value{GDBN} while you have an attached process, you detach
2473 that process. If you use the @code{run} command, you kill that process.
2474 By default, @value{GDBN} asks for confirmation if you try to do either of these
2475 things; you can control whether or not you need to confirm by using the
2476 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2480 @section Killing the Child Process
2485 Kill the child process in which your program is running under @value{GDBN}.
2488 This command is useful if you wish to debug a core dump instead of a
2489 running process. @value{GDBN} ignores any core dump file while your program
2492 On some operating systems, a program cannot be executed outside @value{GDBN}
2493 while you have breakpoints set on it inside @value{GDBN}. You can use the
2494 @code{kill} command in this situation to permit running your program
2495 outside the debugger.
2497 The @code{kill} command is also useful if you wish to recompile and
2498 relink your program, since on many systems it is impossible to modify an
2499 executable file while it is running in a process. In this case, when you
2500 next type @code{run}, @value{GDBN} notices that the file has changed, and
2501 reads the symbol table again (while trying to preserve your current
2502 breakpoint settings).
2504 @node Inferiors and Programs
2505 @section Debugging Multiple Inferiors and Programs
2507 @value{GDBN} lets you run and debug multiple programs in a single
2508 session. In addition, @value{GDBN} on some systems may let you run
2509 several programs simultaneously (otherwise you have to exit from one
2510 before starting another). In the most general case, you can have
2511 multiple threads of execution in each of multiple processes, launched
2512 from multiple executables.
2515 @value{GDBN} represents the state of each program execution with an
2516 object called an @dfn{inferior}. An inferior typically corresponds to
2517 a process, but is more general and applies also to targets that do not
2518 have processes. Inferiors may be created before a process runs, and
2519 may be retained after a process exits. Inferiors have unique
2520 identifiers that are different from process ids. Usually each
2521 inferior will also have its own distinct address space, although some
2522 embedded targets may have several inferiors running in different parts
2523 of a single address space. Each inferior may in turn have multiple
2524 threads running in it.
2526 To find out what inferiors exist at any moment, use @w{@code{info
2530 @kindex info inferiors
2531 @item info inferiors
2532 Print a list of all inferiors currently being managed by @value{GDBN}.
2534 @value{GDBN} displays for each inferior (in this order):
2538 the inferior number assigned by @value{GDBN}
2541 the target system's inferior identifier
2544 the name of the executable the inferior is running.
2549 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2550 indicates the current inferior.
2554 @c end table here to get a little more width for example
2557 (@value{GDBP}) info inferiors
2558 Num Description Executable
2559 2 process 2307 hello
2560 * 1 process 3401 goodbye
2563 To switch focus between inferiors, use the @code{inferior} command:
2566 @kindex inferior @var{infno}
2567 @item inferior @var{infno}
2568 Make inferior number @var{infno} the current inferior. The argument
2569 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2570 in the first field of the @samp{info inferiors} display.
2574 You can get multiple executables into a debugging session via the
2575 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2576 systems @value{GDBN} can add inferiors to the debug session
2577 automatically by following calls to @code{fork} and @code{exec}. To
2578 remove inferiors from the debugging session use the
2579 @w{@code{remove-inferiors}} command.
2582 @kindex add-inferior
2583 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2584 Adds @var{n} inferiors to be run using @var{executable} as the
2585 executable. @var{n} defaults to 1. If no executable is specified,
2586 the inferiors begins empty, with no program. You can still assign or
2587 change the program assigned to the inferior at any time by using the
2588 @code{file} command with the executable name as its argument.
2590 @kindex clone-inferior
2591 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2592 Adds @var{n} inferiors ready to execute the same program as inferior
2593 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2594 number of the current inferior. This is a convenient command when you
2595 want to run another instance of the inferior you are debugging.
2598 (@value{GDBP}) info inferiors
2599 Num Description Executable
2600 * 1 process 29964 helloworld
2601 (@value{GDBP}) clone-inferior
2604 (@value{GDBP}) info inferiors
2605 Num Description Executable
2607 * 1 process 29964 helloworld
2610 You can now simply switch focus to inferior 2 and run it.
2612 @kindex remove-inferiors
2613 @item remove-inferiors @var{infno}@dots{}
2614 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2615 possible to remove an inferior that is running with this command. For
2616 those, use the @code{kill} or @code{detach} command first.
2620 To quit debugging one of the running inferiors that is not the current
2621 inferior, you can either detach from it by using the @w{@code{detach
2622 inferior}} command (allowing it to run independently), or kill it
2623 using the @w{@code{kill inferiors}} command:
2626 @kindex detach inferiors @var{infno}@dots{}
2627 @item detach inferior @var{infno}@dots{}
2628 Detach from the inferior or inferiors identified by @value{GDBN}
2629 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2630 still stays on the list of inferiors shown by @code{info inferiors},
2631 but its Description will show @samp{<null>}.
2633 @kindex kill inferiors @var{infno}@dots{}
2634 @item kill inferiors @var{infno}@dots{}
2635 Kill the inferior or inferiors identified by @value{GDBN} inferior
2636 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2637 stays on the list of inferiors shown by @code{info inferiors}, but its
2638 Description will show @samp{<null>}.
2641 After the successful completion of a command such as @code{detach},
2642 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2643 a normal process exit, the inferior is still valid and listed with
2644 @code{info inferiors}, ready to be restarted.
2647 To be notified when inferiors are started or exit under @value{GDBN}'s
2648 control use @w{@code{set print inferior-events}}:
2651 @kindex set print inferior-events
2652 @cindex print messages on inferior start and exit
2653 @item set print inferior-events
2654 @itemx set print inferior-events on
2655 @itemx set print inferior-events off
2656 The @code{set print inferior-events} command allows you to enable or
2657 disable printing of messages when @value{GDBN} notices that new
2658 inferiors have started or that inferiors have exited or have been
2659 detached. By default, these messages will not be printed.
2661 @kindex show print inferior-events
2662 @item show print inferior-events
2663 Show whether messages will be printed when @value{GDBN} detects that
2664 inferiors have started, exited or have been detached.
2667 Many commands will work the same with multiple programs as with a
2668 single program: e.g., @code{print myglobal} will simply display the
2669 value of @code{myglobal} in the current inferior.
2672 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2673 get more info about the relationship of inferiors, programs, address
2674 spaces in a debug session. You can do that with the @w{@code{maint
2675 info program-spaces}} command.
2678 @kindex maint info program-spaces
2679 @item maint info program-spaces
2680 Print a list of all program spaces currently being managed by
2683 @value{GDBN} displays for each program space (in this order):
2687 the program space number assigned by @value{GDBN}
2690 the name of the executable loaded into the program space, with e.g.,
2691 the @code{file} command.
2696 An asterisk @samp{*} preceding the @value{GDBN} program space number
2697 indicates the current program space.
2699 In addition, below each program space line, @value{GDBN} prints extra
2700 information that isn't suitable to display in tabular form. For
2701 example, the list of inferiors bound to the program space.
2704 (@value{GDBP}) maint info program-spaces
2707 Bound inferiors: ID 1 (process 21561)
2711 Here we can see that no inferior is running the program @code{hello},
2712 while @code{process 21561} is running the program @code{goodbye}. On
2713 some targets, it is possible that multiple inferiors are bound to the
2714 same program space. The most common example is that of debugging both
2715 the parent and child processes of a @code{vfork} call. For example,
2718 (@value{GDBP}) maint info program-spaces
2721 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2724 Here, both inferior 2 and inferior 1 are running in the same program
2725 space as a result of inferior 1 having executed a @code{vfork} call.
2729 @section Debugging Programs with Multiple Threads
2731 @cindex threads of execution
2732 @cindex multiple threads
2733 @cindex switching threads
2734 In some operating systems, such as HP-UX and Solaris, a single program
2735 may have more than one @dfn{thread} of execution. The precise semantics
2736 of threads differ from one operating system to another, but in general
2737 the threads of a single program are akin to multiple processes---except
2738 that they share one address space (that is, they can all examine and
2739 modify the same variables). On the other hand, each thread has its own
2740 registers and execution stack, and perhaps private memory.
2742 @value{GDBN} provides these facilities for debugging multi-thread
2746 @item automatic notification of new threads
2747 @item @samp{thread @var{threadno}}, a command to switch among threads
2748 @item @samp{info threads}, a command to inquire about existing threads
2749 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2750 a command to apply a command to a list of threads
2751 @item thread-specific breakpoints
2752 @item @samp{set print thread-events}, which controls printing of
2753 messages on thread start and exit.
2754 @item @samp{set libthread-db-search-path @var{path}}, which lets
2755 the user specify which @code{libthread_db} to use if the default choice
2756 isn't compatible with the program.
2760 @emph{Warning:} These facilities are not yet available on every
2761 @value{GDBN} configuration where the operating system supports threads.
2762 If your @value{GDBN} does not support threads, these commands have no
2763 effect. For example, a system without thread support shows no output
2764 from @samp{info threads}, and always rejects the @code{thread} command,
2768 (@value{GDBP}) info threads
2769 (@value{GDBP}) thread 1
2770 Thread ID 1 not known. Use the "info threads" command to
2771 see the IDs of currently known threads.
2773 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2774 @c doesn't support threads"?
2777 @cindex focus of debugging
2778 @cindex current thread
2779 The @value{GDBN} thread debugging facility allows you to observe all
2780 threads while your program runs---but whenever @value{GDBN} takes
2781 control, one thread in particular is always the focus of debugging.
2782 This thread is called the @dfn{current thread}. Debugging commands show
2783 program information from the perspective of the current thread.
2785 @cindex @code{New} @var{systag} message
2786 @cindex thread identifier (system)
2787 @c FIXME-implementors!! It would be more helpful if the [New...] message
2788 @c included GDB's numeric thread handle, so you could just go to that
2789 @c thread without first checking `info threads'.
2790 Whenever @value{GDBN} detects a new thread in your program, it displays
2791 the target system's identification for the thread with a message in the
2792 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2793 whose form varies depending on the particular system. For example, on
2794 @sc{gnu}/Linux, you might see
2797 [New Thread 0x41e02940 (LWP 25582)]
2801 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2802 the @var{systag} is simply something like @samp{process 368}, with no
2805 @c FIXME!! (1) Does the [New...] message appear even for the very first
2806 @c thread of a program, or does it only appear for the
2807 @c second---i.e.@: when it becomes obvious we have a multithread
2809 @c (2) *Is* there necessarily a first thread always? Or do some
2810 @c multithread systems permit starting a program with multiple
2811 @c threads ab initio?
2813 @cindex thread number
2814 @cindex thread identifier (GDB)
2815 For debugging purposes, @value{GDBN} associates its own thread
2816 number---always a single integer---with each thread in your program.
2819 @kindex info threads
2820 @item info threads @r{[}@var{id}@dots{}@r{]}
2821 Display a summary of all threads currently in your program. Optional
2822 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2823 means to print information only about the specified thread or threads.
2824 @value{GDBN} displays for each thread (in this order):
2828 the thread number assigned by @value{GDBN}
2831 the target system's thread identifier (@var{systag})
2834 the thread's name, if one is known. A thread can either be named by
2835 the user (see @code{thread name}, below), or, in some cases, by the
2839 the current stack frame summary for that thread
2843 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2844 indicates the current thread.
2848 @c end table here to get a little more width for example
2851 (@value{GDBP}) info threads
2853 3 process 35 thread 27 0x34e5 in sigpause ()
2854 2 process 35 thread 23 0x34e5 in sigpause ()
2855 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2859 On Solaris, you can display more information about user threads with a
2860 Solaris-specific command:
2863 @item maint info sol-threads
2864 @kindex maint info sol-threads
2865 @cindex thread info (Solaris)
2866 Display info on Solaris user threads.
2870 @kindex thread @var{threadno}
2871 @item thread @var{threadno}
2872 Make thread number @var{threadno} the current thread. The command
2873 argument @var{threadno} is the internal @value{GDBN} thread number, as
2874 shown in the first field of the @samp{info threads} display.
2875 @value{GDBN} responds by displaying the system identifier of the thread
2876 you selected, and its current stack frame summary:
2879 (@value{GDBP}) thread 2
2880 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2881 #0 some_function (ignore=0x0) at example.c:8
2882 8 printf ("hello\n");
2886 As with the @samp{[New @dots{}]} message, the form of the text after
2887 @samp{Switching to} depends on your system's conventions for identifying
2890 @vindex $_thread@r{, convenience variable}
2891 The debugger convenience variable @samp{$_thread} contains the number
2892 of the current thread. You may find this useful in writing breakpoint
2893 conditional expressions, command scripts, and so forth. See
2894 @xref{Convenience Vars,, Convenience Variables}, for general
2895 information on convenience variables.
2897 @kindex thread apply
2898 @cindex apply command to several threads
2899 @item thread apply [@var{threadno} | all] @var{command}
2900 The @code{thread apply} command allows you to apply the named
2901 @var{command} to one or more threads. Specify the numbers of the
2902 threads that you want affected with the command argument
2903 @var{threadno}. It can be a single thread number, one of the numbers
2904 shown in the first field of the @samp{info threads} display; or it
2905 could be a range of thread numbers, as in @code{2-4}. To apply a
2906 command to all threads, type @kbd{thread apply all @var{command}}.
2909 @cindex name a thread
2910 @item thread name [@var{name}]
2911 This command assigns a name to the current thread. If no argument is
2912 given, any existing user-specified name is removed. The thread name
2913 appears in the @samp{info threads} display.
2915 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2916 determine the name of the thread as given by the OS. On these
2917 systems, a name specified with @samp{thread name} will override the
2918 system-give name, and removing the user-specified name will cause
2919 @value{GDBN} to once again display the system-specified name.
2922 @cindex search for a thread
2923 @item thread find [@var{regexp}]
2924 Search for and display thread ids whose name or @var{systag}
2925 matches the supplied regular expression.
2927 As well as being the complement to the @samp{thread name} command,
2928 this command also allows you to identify a thread by its target
2929 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2933 (@value{GDBN}) thread find 26688
2934 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2935 (@value{GDBN}) info thread 4
2937 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2940 @kindex set print thread-events
2941 @cindex print messages on thread start and exit
2942 @item set print thread-events
2943 @itemx set print thread-events on
2944 @itemx set print thread-events off
2945 The @code{set print thread-events} command allows you to enable or
2946 disable printing of messages when @value{GDBN} notices that new threads have
2947 started or that threads have exited. By default, these messages will
2948 be printed if detection of these events is supported by the target.
2949 Note that these messages cannot be disabled on all targets.
2951 @kindex show print thread-events
2952 @item show print thread-events
2953 Show whether messages will be printed when @value{GDBN} detects that threads
2954 have started and exited.
2957 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2958 more information about how @value{GDBN} behaves when you stop and start
2959 programs with multiple threads.
2961 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2962 watchpoints in programs with multiple threads.
2964 @anchor{set libthread-db-search-path}
2966 @kindex set libthread-db-search-path
2967 @cindex search path for @code{libthread_db}
2968 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2969 If this variable is set, @var{path} is a colon-separated list of
2970 directories @value{GDBN} will use to search for @code{libthread_db}.
2971 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2972 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2973 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2976 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2977 @code{libthread_db} library to obtain information about threads in the
2978 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2979 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2980 specific thread debugging library loading is enabled
2981 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2983 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2984 refers to the default system directories that are
2985 normally searched for loading shared libraries. The @samp{$sdir} entry
2986 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2987 (@pxref{libthread_db.so.1 file}).
2989 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2990 refers to the directory from which @code{libpthread}
2991 was loaded in the inferior process.
2993 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2994 @value{GDBN} attempts to initialize it with the current inferior process.
2995 If this initialization fails (which could happen because of a version
2996 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2997 will unload @code{libthread_db}, and continue with the next directory.
2998 If none of @code{libthread_db} libraries initialize successfully,
2999 @value{GDBN} will issue a warning and thread debugging will be disabled.
3001 Setting @code{libthread-db-search-path} is currently implemented
3002 only on some platforms.
3004 @kindex show libthread-db-search-path
3005 @item show libthread-db-search-path
3006 Display current libthread_db search path.
3008 @kindex set debug libthread-db
3009 @kindex show debug libthread-db
3010 @cindex debugging @code{libthread_db}
3011 @item set debug libthread-db
3012 @itemx show debug libthread-db
3013 Turns on or off display of @code{libthread_db}-related events.
3014 Use @code{1} to enable, @code{0} to disable.
3018 @section Debugging Forks
3020 @cindex fork, debugging programs which call
3021 @cindex multiple processes
3022 @cindex processes, multiple
3023 On most systems, @value{GDBN} has no special support for debugging
3024 programs which create additional processes using the @code{fork}
3025 function. When a program forks, @value{GDBN} will continue to debug the
3026 parent process and the child process will run unimpeded. If you have
3027 set a breakpoint in any code which the child then executes, the child
3028 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3029 will cause it to terminate.
3031 However, if you want to debug the child process there is a workaround
3032 which isn't too painful. Put a call to @code{sleep} in the code which
3033 the child process executes after the fork. It may be useful to sleep
3034 only if a certain environment variable is set, or a certain file exists,
3035 so that the delay need not occur when you don't want to run @value{GDBN}
3036 on the child. While the child is sleeping, use the @code{ps} program to
3037 get its process ID. Then tell @value{GDBN} (a new invocation of
3038 @value{GDBN} if you are also debugging the parent process) to attach to
3039 the child process (@pxref{Attach}). From that point on you can debug
3040 the child process just like any other process which you attached to.
3042 On some systems, @value{GDBN} provides support for debugging programs that
3043 create additional processes using the @code{fork} or @code{vfork} functions.
3044 Currently, the only platforms with this feature are HP-UX (11.x and later
3045 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3047 By default, when a program forks, @value{GDBN} will continue to debug
3048 the parent process and the child process will run unimpeded.
3050 If you want to follow the child process instead of the parent process,
3051 use the command @w{@code{set follow-fork-mode}}.
3054 @kindex set follow-fork-mode
3055 @item set follow-fork-mode @var{mode}
3056 Set the debugger response to a program call of @code{fork} or
3057 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3058 process. The @var{mode} argument can be:
3062 The original process is debugged after a fork. The child process runs
3063 unimpeded. This is the default.
3066 The new process is debugged after a fork. The parent process runs
3071 @kindex show follow-fork-mode
3072 @item show follow-fork-mode
3073 Display the current debugger response to a @code{fork} or @code{vfork} call.
3076 @cindex debugging multiple processes
3077 On Linux, if you want to debug both the parent and child processes, use the
3078 command @w{@code{set detach-on-fork}}.
3081 @kindex set detach-on-fork
3082 @item set detach-on-fork @var{mode}
3083 Tells gdb whether to detach one of the processes after a fork, or
3084 retain debugger control over them both.
3088 The child process (or parent process, depending on the value of
3089 @code{follow-fork-mode}) will be detached and allowed to run
3090 independently. This is the default.
3093 Both processes will be held under the control of @value{GDBN}.
3094 One process (child or parent, depending on the value of
3095 @code{follow-fork-mode}) is debugged as usual, while the other
3100 @kindex show detach-on-fork
3101 @item show detach-on-fork
3102 Show whether detach-on-fork mode is on/off.
3105 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3106 will retain control of all forked processes (including nested forks).
3107 You can list the forked processes under the control of @value{GDBN} by
3108 using the @w{@code{info inferiors}} command, and switch from one fork
3109 to another by using the @code{inferior} command (@pxref{Inferiors and
3110 Programs, ,Debugging Multiple Inferiors and Programs}).
3112 To quit debugging one of the forked processes, you can either detach
3113 from it by using the @w{@code{detach inferiors}} command (allowing it
3114 to run independently), or kill it using the @w{@code{kill inferiors}}
3115 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3118 If you ask to debug a child process and a @code{vfork} is followed by an
3119 @code{exec}, @value{GDBN} executes the new target up to the first
3120 breakpoint in the new target. If you have a breakpoint set on
3121 @code{main} in your original program, the breakpoint will also be set on
3122 the child process's @code{main}.
3124 On some systems, when a child process is spawned by @code{vfork}, you
3125 cannot debug the child or parent until an @code{exec} call completes.
3127 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3128 call executes, the new target restarts. To restart the parent
3129 process, use the @code{file} command with the parent executable name
3130 as its argument. By default, after an @code{exec} call executes,
3131 @value{GDBN} discards the symbols of the previous executable image.
3132 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3136 @kindex set follow-exec-mode
3137 @item set follow-exec-mode @var{mode}
3139 Set debugger response to a program call of @code{exec}. An
3140 @code{exec} call replaces the program image of a process.
3142 @code{follow-exec-mode} can be:
3146 @value{GDBN} creates a new inferior and rebinds the process to this
3147 new inferior. The program the process was running before the
3148 @code{exec} call can be restarted afterwards by restarting the
3154 (@value{GDBP}) info inferiors
3156 Id Description Executable
3159 process 12020 is executing new program: prog2
3160 Program exited normally.
3161 (@value{GDBP}) info inferiors
3162 Id Description Executable
3168 @value{GDBN} keeps the process bound to the same inferior. The new
3169 executable image replaces the previous executable loaded in the
3170 inferior. Restarting the inferior after the @code{exec} call, with
3171 e.g., the @code{run} command, restarts the executable the process was
3172 running after the @code{exec} call. This is the default mode.
3177 (@value{GDBP}) info inferiors
3178 Id Description Executable
3181 process 12020 is executing new program: prog2
3182 Program exited normally.
3183 (@value{GDBP}) info inferiors
3184 Id Description Executable
3191 You can use the @code{catch} command to make @value{GDBN} stop whenever
3192 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3193 Catchpoints, ,Setting Catchpoints}.
3195 @node Checkpoint/Restart
3196 @section Setting a @emph{Bookmark} to Return to Later
3201 @cindex snapshot of a process
3202 @cindex rewind program state
3204 On certain operating systems@footnote{Currently, only
3205 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3206 program's state, called a @dfn{checkpoint}, and come back to it
3209 Returning to a checkpoint effectively undoes everything that has
3210 happened in the program since the @code{checkpoint} was saved. This
3211 includes changes in memory, registers, and even (within some limits)
3212 system state. Effectively, it is like going back in time to the
3213 moment when the checkpoint was saved.
3215 Thus, if you're stepping thru a program and you think you're
3216 getting close to the point where things go wrong, you can save
3217 a checkpoint. Then, if you accidentally go too far and miss
3218 the critical statement, instead of having to restart your program
3219 from the beginning, you can just go back to the checkpoint and
3220 start again from there.
3222 This can be especially useful if it takes a lot of time or
3223 steps to reach the point where you think the bug occurs.
3225 To use the @code{checkpoint}/@code{restart} method of debugging:
3230 Save a snapshot of the debugged program's current execution state.
3231 The @code{checkpoint} command takes no arguments, but each checkpoint
3232 is assigned a small integer id, similar to a breakpoint id.
3234 @kindex info checkpoints
3235 @item info checkpoints
3236 List the checkpoints that have been saved in the current debugging
3237 session. For each checkpoint, the following information will be
3244 @item Source line, or label
3247 @kindex restart @var{checkpoint-id}
3248 @item restart @var{checkpoint-id}
3249 Restore the program state that was saved as checkpoint number
3250 @var{checkpoint-id}. All program variables, registers, stack frames
3251 etc.@: will be returned to the values that they had when the checkpoint
3252 was saved. In essence, gdb will ``wind back the clock'' to the point
3253 in time when the checkpoint was saved.
3255 Note that breakpoints, @value{GDBN} variables, command history etc.
3256 are not affected by restoring a checkpoint. In general, a checkpoint
3257 only restores things that reside in the program being debugged, not in
3260 @kindex delete checkpoint @var{checkpoint-id}
3261 @item delete checkpoint @var{checkpoint-id}
3262 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3266 Returning to a previously saved checkpoint will restore the user state
3267 of the program being debugged, plus a significant subset of the system
3268 (OS) state, including file pointers. It won't ``un-write'' data from
3269 a file, but it will rewind the file pointer to the previous location,
3270 so that the previously written data can be overwritten. For files
3271 opened in read mode, the pointer will also be restored so that the
3272 previously read data can be read again.
3274 Of course, characters that have been sent to a printer (or other
3275 external device) cannot be ``snatched back'', and characters received
3276 from eg.@: a serial device can be removed from internal program buffers,
3277 but they cannot be ``pushed back'' into the serial pipeline, ready to
3278 be received again. Similarly, the actual contents of files that have
3279 been changed cannot be restored (at this time).
3281 However, within those constraints, you actually can ``rewind'' your
3282 program to a previously saved point in time, and begin debugging it
3283 again --- and you can change the course of events so as to debug a
3284 different execution path this time.
3286 @cindex checkpoints and process id
3287 Finally, there is one bit of internal program state that will be
3288 different when you return to a checkpoint --- the program's process
3289 id. Each checkpoint will have a unique process id (or @var{pid}),
3290 and each will be different from the program's original @var{pid}.
3291 If your program has saved a local copy of its process id, this could
3292 potentially pose a problem.
3294 @subsection A Non-obvious Benefit of Using Checkpoints
3296 On some systems such as @sc{gnu}/Linux, address space randomization
3297 is performed on new processes for security reasons. This makes it
3298 difficult or impossible to set a breakpoint, or watchpoint, on an
3299 absolute address if you have to restart the program, since the
3300 absolute location of a symbol will change from one execution to the
3303 A checkpoint, however, is an @emph{identical} copy of a process.
3304 Therefore if you create a checkpoint at (eg.@:) the start of main,
3305 and simply return to that checkpoint instead of restarting the
3306 process, you can avoid the effects of address randomization and
3307 your symbols will all stay in the same place.
3310 @chapter Stopping and Continuing
3312 The principal purposes of using a debugger are so that you can stop your
3313 program before it terminates; or so that, if your program runs into
3314 trouble, you can investigate and find out why.
3316 Inside @value{GDBN}, your program may stop for any of several reasons,
3317 such as a signal, a breakpoint, or reaching a new line after a
3318 @value{GDBN} command such as @code{step}. You may then examine and
3319 change variables, set new breakpoints or remove old ones, and then
3320 continue execution. Usually, the messages shown by @value{GDBN} provide
3321 ample explanation of the status of your program---but you can also
3322 explicitly request this information at any time.
3325 @kindex info program
3327 Display information about the status of your program: whether it is
3328 running or not, what process it is, and why it stopped.
3332 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3333 * Continuing and Stepping:: Resuming execution
3334 * Skipping Over Functions and Files::
3335 Skipping over functions and files
3337 * Thread Stops:: Stopping and starting multi-thread programs
3341 @section Breakpoints, Watchpoints, and Catchpoints
3344 A @dfn{breakpoint} makes your program stop whenever a certain point in
3345 the program is reached. For each breakpoint, you can add conditions to
3346 control in finer detail whether your program stops. You can set
3347 breakpoints with the @code{break} command and its variants (@pxref{Set
3348 Breaks, ,Setting Breakpoints}), to specify the place where your program
3349 should stop by line number, function name or exact address in the
3352 On some systems, you can set breakpoints in shared libraries before
3353 the executable is run. There is a minor limitation on HP-UX systems:
3354 you must wait until the executable is run in order to set breakpoints
3355 in shared library routines that are not called directly by the program
3356 (for example, routines that are arguments in a @code{pthread_create}
3360 @cindex data breakpoints
3361 @cindex memory tracing
3362 @cindex breakpoint on memory address
3363 @cindex breakpoint on variable modification
3364 A @dfn{watchpoint} is a special breakpoint that stops your program
3365 when the value of an expression changes. The expression may be a value
3366 of a variable, or it could involve values of one or more variables
3367 combined by operators, such as @samp{a + b}. This is sometimes called
3368 @dfn{data breakpoints}. You must use a different command to set
3369 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3370 from that, you can manage a watchpoint like any other breakpoint: you
3371 enable, disable, and delete both breakpoints and watchpoints using the
3374 You can arrange to have values from your program displayed automatically
3375 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3379 @cindex breakpoint on events
3380 A @dfn{catchpoint} is another special breakpoint that stops your program
3381 when a certain kind of event occurs, such as the throwing of a C@t{++}
3382 exception or the loading of a library. As with watchpoints, you use a
3383 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3384 Catchpoints}), but aside from that, you can manage a catchpoint like any
3385 other breakpoint. (To stop when your program receives a signal, use the
3386 @code{handle} command; see @ref{Signals, ,Signals}.)
3388 @cindex breakpoint numbers
3389 @cindex numbers for breakpoints
3390 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3391 catchpoint when you create it; these numbers are successive integers
3392 starting with one. In many of the commands for controlling various
3393 features of breakpoints you use the breakpoint number to say which
3394 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3395 @dfn{disabled}; if disabled, it has no effect on your program until you
3398 @cindex breakpoint ranges
3399 @cindex ranges of breakpoints
3400 Some @value{GDBN} commands accept a range of breakpoints on which to
3401 operate. A breakpoint range is either a single breakpoint number, like
3402 @samp{5}, or two such numbers, in increasing order, separated by a
3403 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3404 all breakpoints in that range are operated on.
3407 * Set Breaks:: Setting breakpoints
3408 * Set Watchpoints:: Setting watchpoints
3409 * Set Catchpoints:: Setting catchpoints
3410 * Delete Breaks:: Deleting breakpoints
3411 * Disabling:: Disabling breakpoints
3412 * Conditions:: Break conditions
3413 * Break Commands:: Breakpoint command lists
3414 * Dynamic Printf:: Dynamic printf
3415 * Save Breakpoints:: How to save breakpoints in a file
3416 * Static Probe Points:: Listing static probe points
3417 * Error in Breakpoints:: ``Cannot insert breakpoints''
3418 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3422 @subsection Setting Breakpoints
3424 @c FIXME LMB what does GDB do if no code on line of breakpt?
3425 @c consider in particular declaration with/without initialization.
3427 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3430 @kindex b @r{(@code{break})}
3431 @vindex $bpnum@r{, convenience variable}
3432 @cindex latest breakpoint
3433 Breakpoints are set with the @code{break} command (abbreviated
3434 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3435 number of the breakpoint you've set most recently; see @ref{Convenience
3436 Vars,, Convenience Variables}, for a discussion of what you can do with
3437 convenience variables.
3440 @item break @var{location}
3441 Set a breakpoint at the given @var{location}, which can specify a
3442 function name, a line number, or an address of an instruction.
3443 (@xref{Specify Location}, for a list of all the possible ways to
3444 specify a @var{location}.) The breakpoint will stop your program just
3445 before it executes any of the code in the specified @var{location}.
3447 When using source languages that permit overloading of symbols, such as
3448 C@t{++}, a function name may refer to more than one possible place to break.
3449 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3452 It is also possible to insert a breakpoint that will stop the program
3453 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3454 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3457 When called without any arguments, @code{break} sets a breakpoint at
3458 the next instruction to be executed in the selected stack frame
3459 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3460 innermost, this makes your program stop as soon as control
3461 returns to that frame. This is similar to the effect of a
3462 @code{finish} command in the frame inside the selected frame---except
3463 that @code{finish} does not leave an active breakpoint. If you use
3464 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3465 the next time it reaches the current location; this may be useful
3468 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3469 least one instruction has been executed. If it did not do this, you
3470 would be unable to proceed past a breakpoint without first disabling the
3471 breakpoint. This rule applies whether or not the breakpoint already
3472 existed when your program stopped.
3474 @item break @dots{} if @var{cond}
3475 Set a breakpoint with condition @var{cond}; evaluate the expression
3476 @var{cond} each time the breakpoint is reached, and stop only if the
3477 value is nonzero---that is, if @var{cond} evaluates as true.
3478 @samp{@dots{}} stands for one of the possible arguments described
3479 above (or no argument) specifying where to break. @xref{Conditions,
3480 ,Break Conditions}, for more information on breakpoint conditions.
3483 @item tbreak @var{args}
3484 Set a breakpoint enabled only for one stop. @var{args} are the
3485 same as for the @code{break} command, and the breakpoint is set in the same
3486 way, but the breakpoint is automatically deleted after the first time your
3487 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3490 @cindex hardware breakpoints
3491 @item hbreak @var{args}
3492 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3493 @code{break} command and the breakpoint is set in the same way, but the
3494 breakpoint requires hardware support and some target hardware may not
3495 have this support. The main purpose of this is EPROM/ROM code
3496 debugging, so you can set a breakpoint at an instruction without
3497 changing the instruction. This can be used with the new trap-generation
3498 provided by SPARClite DSU and most x86-based targets. These targets
3499 will generate traps when a program accesses some data or instruction
3500 address that is assigned to the debug registers. However the hardware
3501 breakpoint registers can take a limited number of breakpoints. For
3502 example, on the DSU, only two data breakpoints can be set at a time, and
3503 @value{GDBN} will reject this command if more than two are used. Delete
3504 or disable unused hardware breakpoints before setting new ones
3505 (@pxref{Disabling, ,Disabling Breakpoints}).
3506 @xref{Conditions, ,Break Conditions}.
3507 For remote targets, you can restrict the number of hardware
3508 breakpoints @value{GDBN} will use, see @ref{set remote
3509 hardware-breakpoint-limit}.
3512 @item thbreak @var{args}
3513 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3514 are the same as for the @code{hbreak} command and the breakpoint is set in
3515 the same way. However, like the @code{tbreak} command,
3516 the breakpoint is automatically deleted after the
3517 first time your program stops there. Also, like the @code{hbreak}
3518 command, the breakpoint requires hardware support and some target hardware
3519 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3520 See also @ref{Conditions, ,Break Conditions}.
3523 @cindex regular expression
3524 @cindex breakpoints at functions matching a regexp
3525 @cindex set breakpoints in many functions
3526 @item rbreak @var{regex}
3527 Set breakpoints on all functions matching the regular expression
3528 @var{regex}. This command sets an unconditional breakpoint on all
3529 matches, printing a list of all breakpoints it set. Once these
3530 breakpoints are set, they are treated just like the breakpoints set with
3531 the @code{break} command. You can delete them, disable them, or make
3532 them conditional the same way as any other breakpoint.
3534 The syntax of the regular expression is the standard one used with tools
3535 like @file{grep}. Note that this is different from the syntax used by
3536 shells, so for instance @code{foo*} matches all functions that include
3537 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3538 @code{.*} leading and trailing the regular expression you supply, so to
3539 match only functions that begin with @code{foo}, use @code{^foo}.
3541 @cindex non-member C@t{++} functions, set breakpoint in
3542 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3543 breakpoints on overloaded functions that are not members of any special
3546 @cindex set breakpoints on all functions
3547 The @code{rbreak} command can be used to set breakpoints in
3548 @strong{all} the functions in a program, like this:
3551 (@value{GDBP}) rbreak .
3554 @item rbreak @var{file}:@var{regex}
3555 If @code{rbreak} is called with a filename qualification, it limits
3556 the search for functions matching the given regular expression to the
3557 specified @var{file}. This can be used, for example, to set breakpoints on
3558 every function in a given file:
3561 (@value{GDBP}) rbreak file.c:.
3564 The colon separating the filename qualifier from the regex may
3565 optionally be surrounded by spaces.
3567 @kindex info breakpoints
3568 @cindex @code{$_} and @code{info breakpoints}
3569 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3570 @itemx info break @r{[}@var{n}@dots{}@r{]}
3571 Print a table of all breakpoints, watchpoints, and catchpoints set and
3572 not deleted. Optional argument @var{n} means print information only
3573 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3574 For each breakpoint, following columns are printed:
3577 @item Breakpoint Numbers
3579 Breakpoint, watchpoint, or catchpoint.
3581 Whether the breakpoint is marked to be disabled or deleted when hit.
3582 @item Enabled or Disabled
3583 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3584 that are not enabled.
3586 Where the breakpoint is in your program, as a memory address. For a
3587 pending breakpoint whose address is not yet known, this field will
3588 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3589 library that has the symbol or line referred by breakpoint is loaded.
3590 See below for details. A breakpoint with several locations will
3591 have @samp{<MULTIPLE>} in this field---see below for details.
3593 Where the breakpoint is in the source for your program, as a file and
3594 line number. For a pending breakpoint, the original string passed to
3595 the breakpoint command will be listed as it cannot be resolved until
3596 the appropriate shared library is loaded in the future.
3600 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3601 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3602 @value{GDBN} on the host's side. If it is ``target'', then the condition
3603 is evaluated by the target. The @code{info break} command shows
3604 the condition on the line following the affected breakpoint, together with
3605 its condition evaluation mode in between parentheses.
3607 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3608 allowed to have a condition specified for it. The condition is not parsed for
3609 validity until a shared library is loaded that allows the pending
3610 breakpoint to resolve to a valid location.
3613 @code{info break} with a breakpoint
3614 number @var{n} as argument lists only that breakpoint. The
3615 convenience variable @code{$_} and the default examining-address for
3616 the @code{x} command are set to the address of the last breakpoint
3617 listed (@pxref{Memory, ,Examining Memory}).
3620 @code{info break} displays a count of the number of times the breakpoint
3621 has been hit. This is especially useful in conjunction with the
3622 @code{ignore} command. You can ignore a large number of breakpoint
3623 hits, look at the breakpoint info to see how many times the breakpoint
3624 was hit, and then run again, ignoring one less than that number. This
3625 will get you quickly to the last hit of that breakpoint.
3628 For a breakpoints with an enable count (xref) greater than 1,
3629 @code{info break} also displays that count.
3633 @value{GDBN} allows you to set any number of breakpoints at the same place in
3634 your program. There is nothing silly or meaningless about this. When
3635 the breakpoints are conditional, this is even useful
3636 (@pxref{Conditions, ,Break Conditions}).
3638 @cindex multiple locations, breakpoints
3639 @cindex breakpoints, multiple locations
3640 It is possible that a breakpoint corresponds to several locations
3641 in your program. Examples of this situation are:
3645 Multiple functions in the program may have the same name.
3648 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3649 instances of the function body, used in different cases.
3652 For a C@t{++} template function, a given line in the function can
3653 correspond to any number of instantiations.
3656 For an inlined function, a given source line can correspond to
3657 several places where that function is inlined.
3660 In all those cases, @value{GDBN} will insert a breakpoint at all
3661 the relevant locations.
3663 A breakpoint with multiple locations is displayed in the breakpoint
3664 table using several rows---one header row, followed by one row for
3665 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3666 address column. The rows for individual locations contain the actual
3667 addresses for locations, and show the functions to which those
3668 locations belong. The number column for a location is of the form
3669 @var{breakpoint-number}.@var{location-number}.
3674 Num Type Disp Enb Address What
3675 1 breakpoint keep y <MULTIPLE>
3677 breakpoint already hit 1 time
3678 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3679 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3682 Each location can be individually enabled or disabled by passing
3683 @var{breakpoint-number}.@var{location-number} as argument to the
3684 @code{enable} and @code{disable} commands. Note that you cannot
3685 delete the individual locations from the list, you can only delete the
3686 entire list of locations that belong to their parent breakpoint (with
3687 the @kbd{delete @var{num}} command, where @var{num} is the number of
3688 the parent breakpoint, 1 in the above example). Disabling or enabling
3689 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3690 that belong to that breakpoint.
3692 @cindex pending breakpoints
3693 It's quite common to have a breakpoint inside a shared library.
3694 Shared libraries can be loaded and unloaded explicitly,
3695 and possibly repeatedly, as the program is executed. To support
3696 this use case, @value{GDBN} updates breakpoint locations whenever
3697 any shared library is loaded or unloaded. Typically, you would
3698 set a breakpoint in a shared library at the beginning of your
3699 debugging session, when the library is not loaded, and when the
3700 symbols from the library are not available. When you try to set
3701 breakpoint, @value{GDBN} will ask you if you want to set
3702 a so called @dfn{pending breakpoint}---breakpoint whose address
3703 is not yet resolved.
3705 After the program is run, whenever a new shared library is loaded,
3706 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3707 shared library contains the symbol or line referred to by some
3708 pending breakpoint, that breakpoint is resolved and becomes an
3709 ordinary breakpoint. When a library is unloaded, all breakpoints
3710 that refer to its symbols or source lines become pending again.
3712 This logic works for breakpoints with multiple locations, too. For
3713 example, if you have a breakpoint in a C@t{++} template function, and
3714 a newly loaded shared library has an instantiation of that template,
3715 a new location is added to the list of locations for the breakpoint.
3717 Except for having unresolved address, pending breakpoints do not
3718 differ from regular breakpoints. You can set conditions or commands,
3719 enable and disable them and perform other breakpoint operations.
3721 @value{GDBN} provides some additional commands for controlling what
3722 happens when the @samp{break} command cannot resolve breakpoint
3723 address specification to an address:
3725 @kindex set breakpoint pending
3726 @kindex show breakpoint pending
3728 @item set breakpoint pending auto
3729 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3730 location, it queries you whether a pending breakpoint should be created.
3732 @item set breakpoint pending on
3733 This indicates that an unrecognized breakpoint location should automatically
3734 result in a pending breakpoint being created.
3736 @item set breakpoint pending off
3737 This indicates that pending breakpoints are not to be created. Any
3738 unrecognized breakpoint location results in an error. This setting does
3739 not affect any pending breakpoints previously created.
3741 @item show breakpoint pending
3742 Show the current behavior setting for creating pending breakpoints.
3745 The settings above only affect the @code{break} command and its
3746 variants. Once breakpoint is set, it will be automatically updated
3747 as shared libraries are loaded and unloaded.
3749 @cindex automatic hardware breakpoints
3750 For some targets, @value{GDBN} can automatically decide if hardware or
3751 software breakpoints should be used, depending on whether the
3752 breakpoint address is read-only or read-write. This applies to
3753 breakpoints set with the @code{break} command as well as to internal
3754 breakpoints set by commands like @code{next} and @code{finish}. For
3755 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3758 You can control this automatic behaviour with the following commands::
3760 @kindex set breakpoint auto-hw
3761 @kindex show breakpoint auto-hw
3763 @item set breakpoint auto-hw on
3764 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3765 will try to use the target memory map to decide if software or hardware
3766 breakpoint must be used.
3768 @item set breakpoint auto-hw off
3769 This indicates @value{GDBN} should not automatically select breakpoint
3770 type. If the target provides a memory map, @value{GDBN} will warn when
3771 trying to set software breakpoint at a read-only address.
3774 @value{GDBN} normally implements breakpoints by replacing the program code
3775 at the breakpoint address with a special instruction, which, when
3776 executed, given control to the debugger. By default, the program
3777 code is so modified only when the program is resumed. As soon as
3778 the program stops, @value{GDBN} restores the original instructions. This
3779 behaviour guards against leaving breakpoints inserted in the
3780 target should gdb abrubptly disconnect. However, with slow remote
3781 targets, inserting and removing breakpoint can reduce the performance.
3782 This behavior can be controlled with the following commands::
3784 @kindex set breakpoint always-inserted
3785 @kindex show breakpoint always-inserted
3787 @item set breakpoint always-inserted off
3788 All breakpoints, including newly added by the user, are inserted in
3789 the target only when the target is resumed. All breakpoints are
3790 removed from the target when it stops.
3792 @item set breakpoint always-inserted on
3793 Causes all breakpoints to be inserted in the target at all times. If
3794 the user adds a new breakpoint, or changes an existing breakpoint, the
3795 breakpoints in the target are updated immediately. A breakpoint is
3796 removed from the target only when breakpoint itself is removed.
3798 @cindex non-stop mode, and @code{breakpoint always-inserted}
3799 @item set breakpoint always-inserted auto
3800 This is the default mode. If @value{GDBN} is controlling the inferior
3801 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3802 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3803 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3804 @code{breakpoint always-inserted} mode is off.
3807 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3808 when a breakpoint breaks. If the condition is true, then the process being
3809 debugged stops, otherwise the process is resumed.
3811 If the target supports evaluating conditions on its end, @value{GDBN} may
3812 download the breakpoint, together with its conditions, to it.
3814 This feature can be controlled via the following commands:
3816 @kindex set breakpoint condition-evaluation
3817 @kindex show breakpoint condition-evaluation
3819 @item set breakpoint condition-evaluation host
3820 This option commands @value{GDBN} to evaluate the breakpoint
3821 conditions on the host's side. Unconditional breakpoints are sent to
3822 the target which in turn receives the triggers and reports them back to GDB
3823 for condition evaluation. This is the standard evaluation mode.
3825 @item set breakpoint condition-evaluation target
3826 This option commands @value{GDBN} to download breakpoint conditions
3827 to the target at the moment of their insertion. The target
3828 is responsible for evaluating the conditional expression and reporting
3829 breakpoint stop events back to @value{GDBN} whenever the condition
3830 is true. Due to limitations of target-side evaluation, some conditions
3831 cannot be evaluated there, e.g., conditions that depend on local data
3832 that is only known to the host. Examples include
3833 conditional expressions involving convenience variables, complex types
3834 that cannot be handled by the agent expression parser and expressions
3835 that are too long to be sent over to the target, specially when the
3836 target is a remote system. In these cases, the conditions will be
3837 evaluated by @value{GDBN}.
3839 @item set breakpoint condition-evaluation auto
3840 This is the default mode. If the target supports evaluating breakpoint
3841 conditions on its end, @value{GDBN} will download breakpoint conditions to
3842 the target (limitations mentioned previously apply). If the target does
3843 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3844 to evaluating all these conditions on the host's side.
3848 @cindex negative breakpoint numbers
3849 @cindex internal @value{GDBN} breakpoints
3850 @value{GDBN} itself sometimes sets breakpoints in your program for
3851 special purposes, such as proper handling of @code{longjmp} (in C
3852 programs). These internal breakpoints are assigned negative numbers,
3853 starting with @code{-1}; @samp{info breakpoints} does not display them.
3854 You can see these breakpoints with the @value{GDBN} maintenance command
3855 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3858 @node Set Watchpoints
3859 @subsection Setting Watchpoints
3861 @cindex setting watchpoints
3862 You can use a watchpoint to stop execution whenever the value of an
3863 expression changes, without having to predict a particular place where
3864 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3865 The expression may be as simple as the value of a single variable, or
3866 as complex as many variables combined by operators. Examples include:
3870 A reference to the value of a single variable.
3873 An address cast to an appropriate data type. For example,
3874 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3875 address (assuming an @code{int} occupies 4 bytes).
3878 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3879 expression can use any operators valid in the program's native
3880 language (@pxref{Languages}).
3883 You can set a watchpoint on an expression even if the expression can
3884 not be evaluated yet. For instance, you can set a watchpoint on
3885 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3886 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3887 the expression produces a valid value. If the expression becomes
3888 valid in some other way than changing a variable (e.g.@: if the memory
3889 pointed to by @samp{*global_ptr} becomes readable as the result of a
3890 @code{malloc} call), @value{GDBN} may not stop until the next time
3891 the expression changes.
3893 @cindex software watchpoints
3894 @cindex hardware watchpoints
3895 Depending on your system, watchpoints may be implemented in software or
3896 hardware. @value{GDBN} does software watchpointing by single-stepping your
3897 program and testing the variable's value each time, which is hundreds of
3898 times slower than normal execution. (But this may still be worth it, to
3899 catch errors where you have no clue what part of your program is the
3902 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3903 x86-based targets, @value{GDBN} includes support for hardware
3904 watchpoints, which do not slow down the running of your program.
3908 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3909 Set a watchpoint for an expression. @value{GDBN} will break when the
3910 expression @var{expr} is written into by the program and its value
3911 changes. The simplest (and the most popular) use of this command is
3912 to watch the value of a single variable:
3915 (@value{GDBP}) watch foo
3918 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3919 argument, @value{GDBN} breaks only when the thread identified by
3920 @var{threadnum} changes the value of @var{expr}. If any other threads
3921 change the value of @var{expr}, @value{GDBN} will not break. Note
3922 that watchpoints restricted to a single thread in this way only work
3923 with Hardware Watchpoints.
3925 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3926 (see below). The @code{-location} argument tells @value{GDBN} to
3927 instead watch the memory referred to by @var{expr}. In this case,
3928 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3929 and watch the memory at that address. The type of the result is used
3930 to determine the size of the watched memory. If the expression's
3931 result does not have an address, then @value{GDBN} will print an
3934 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3935 of masked watchpoints, if the current architecture supports this
3936 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3937 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3938 to an address to watch. The mask specifies that some bits of an address
3939 (the bits which are reset in the mask) should be ignored when matching
3940 the address accessed by the inferior against the watchpoint address.
3941 Thus, a masked watchpoint watches many addresses simultaneously---those
3942 addresses whose unmasked bits are identical to the unmasked bits in the
3943 watchpoint address. The @code{mask} argument implies @code{-location}.
3947 (@value{GDBP}) watch foo mask 0xffff00ff
3948 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3952 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3953 Set a watchpoint that will break when the value of @var{expr} is read
3957 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3958 Set a watchpoint that will break when @var{expr} is either read from
3959 or written into by the program.
3961 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3962 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3963 This command prints a list of watchpoints, using the same format as
3964 @code{info break} (@pxref{Set Breaks}).
3967 If you watch for a change in a numerically entered address you need to
3968 dereference it, as the address itself is just a constant number which will
3969 never change. @value{GDBN} refuses to create a watchpoint that watches
3970 a never-changing value:
3973 (@value{GDBP}) watch 0x600850
3974 Cannot watch constant value 0x600850.
3975 (@value{GDBP}) watch *(int *) 0x600850
3976 Watchpoint 1: *(int *) 6293584
3979 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3980 watchpoints execute very quickly, and the debugger reports a change in
3981 value at the exact instruction where the change occurs. If @value{GDBN}
3982 cannot set a hardware watchpoint, it sets a software watchpoint, which
3983 executes more slowly and reports the change in value at the next
3984 @emph{statement}, not the instruction, after the change occurs.
3986 @cindex use only software watchpoints
3987 You can force @value{GDBN} to use only software watchpoints with the
3988 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3989 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3990 the underlying system supports them. (Note that hardware-assisted
3991 watchpoints that were set @emph{before} setting
3992 @code{can-use-hw-watchpoints} to zero will still use the hardware
3993 mechanism of watching expression values.)
3996 @item set can-use-hw-watchpoints
3997 @kindex set can-use-hw-watchpoints
3998 Set whether or not to use hardware watchpoints.
4000 @item show can-use-hw-watchpoints
4001 @kindex show can-use-hw-watchpoints
4002 Show the current mode of using hardware watchpoints.
4005 For remote targets, you can restrict the number of hardware
4006 watchpoints @value{GDBN} will use, see @ref{set remote
4007 hardware-breakpoint-limit}.
4009 When you issue the @code{watch} command, @value{GDBN} reports
4012 Hardware watchpoint @var{num}: @var{expr}
4016 if it was able to set a hardware watchpoint.
4018 Currently, the @code{awatch} and @code{rwatch} commands can only set
4019 hardware watchpoints, because accesses to data that don't change the
4020 value of the watched expression cannot be detected without examining
4021 every instruction as it is being executed, and @value{GDBN} does not do
4022 that currently. If @value{GDBN} finds that it is unable to set a
4023 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4024 will print a message like this:
4027 Expression cannot be implemented with read/access watchpoint.
4030 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4031 data type of the watched expression is wider than what a hardware
4032 watchpoint on the target machine can handle. For example, some systems
4033 can only watch regions that are up to 4 bytes wide; on such systems you
4034 cannot set hardware watchpoints for an expression that yields a
4035 double-precision floating-point number (which is typically 8 bytes
4036 wide). As a work-around, it might be possible to break the large region
4037 into a series of smaller ones and watch them with separate watchpoints.
4039 If you set too many hardware watchpoints, @value{GDBN} might be unable
4040 to insert all of them when you resume the execution of your program.
4041 Since the precise number of active watchpoints is unknown until such
4042 time as the program is about to be resumed, @value{GDBN} might not be
4043 able to warn you about this when you set the watchpoints, and the
4044 warning will be printed only when the program is resumed:
4047 Hardware watchpoint @var{num}: Could not insert watchpoint
4051 If this happens, delete or disable some of the watchpoints.
4053 Watching complex expressions that reference many variables can also
4054 exhaust the resources available for hardware-assisted watchpoints.
4055 That's because @value{GDBN} needs to watch every variable in the
4056 expression with separately allocated resources.
4058 If you call a function interactively using @code{print} or @code{call},
4059 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4060 kind of breakpoint or the call completes.
4062 @value{GDBN} automatically deletes watchpoints that watch local
4063 (automatic) variables, or expressions that involve such variables, when
4064 they go out of scope, that is, when the execution leaves the block in
4065 which these variables were defined. In particular, when the program
4066 being debugged terminates, @emph{all} local variables go out of scope,
4067 and so only watchpoints that watch global variables remain set. If you
4068 rerun the program, you will need to set all such watchpoints again. One
4069 way of doing that would be to set a code breakpoint at the entry to the
4070 @code{main} function and when it breaks, set all the watchpoints.
4072 @cindex watchpoints and threads
4073 @cindex threads and watchpoints
4074 In multi-threaded programs, watchpoints will detect changes to the
4075 watched expression from every thread.
4078 @emph{Warning:} In multi-threaded programs, software watchpoints
4079 have only limited usefulness. If @value{GDBN} creates a software
4080 watchpoint, it can only watch the value of an expression @emph{in a
4081 single thread}. If you are confident that the expression can only
4082 change due to the current thread's activity (and if you are also
4083 confident that no other thread can become current), then you can use
4084 software watchpoints as usual. However, @value{GDBN} may not notice
4085 when a non-current thread's activity changes the expression. (Hardware
4086 watchpoints, in contrast, watch an expression in all threads.)
4089 @xref{set remote hardware-watchpoint-limit}.
4091 @node Set Catchpoints
4092 @subsection Setting Catchpoints
4093 @cindex catchpoints, setting
4094 @cindex exception handlers
4095 @cindex event handling
4097 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4098 kinds of program events, such as C@t{++} exceptions or the loading of a
4099 shared library. Use the @code{catch} command to set a catchpoint.
4103 @item catch @var{event}
4104 Stop when @var{event} occurs. @var{event} can be any of the following:
4107 @item throw @r{[}@var{regexp}@r{]}
4108 @itemx rethrow @r{[}@var{regexp}@r{]}
4109 @itemx catch @r{[}@var{regexp}@r{]}
4110 @cindex stop on C@t{++} exceptions
4111 The throwing, re-throwing, or catching of a C@t{++} exception.
4113 If @var{regexp} is given, then only exceptions whose type matches the
4114 regular expression will be caught.
4116 @vindex $_exception@r{, convenience variable}
4117 The convenience variable @code{$_exception} is available at an
4118 exception-related catchpoint, on some systems. This holds the
4119 exception being thrown.
4121 There are currently some limitations to C@t{++} exception handling in
4126 The support for these commands is system-dependent. Currently, only
4127 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4131 The regular expression feature and the @code{$_exception} convenience
4132 variable rely on the presence of some SDT probes in @code{libstdc++}.
4133 If these probes are not present, then these features cannot be used.
4134 These probes were first available in the GCC 4.8 release, but whether
4135 or not they are available in your GCC also depends on how it was
4139 The @code{$_exception} convenience variable is only valid at the
4140 instruction at which an exception-related catchpoint is set.
4143 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4144 location in the system library which implements runtime exception
4145 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4146 (@pxref{Selection}) to get to your code.
4149 If you call a function interactively, @value{GDBN} normally returns
4150 control to you when the function has finished executing. If the call
4151 raises an exception, however, the call may bypass the mechanism that
4152 returns control to you and cause your program either to abort or to
4153 simply continue running until it hits a breakpoint, catches a signal
4154 that @value{GDBN} is listening for, or exits. This is the case even if
4155 you set a catchpoint for the exception; catchpoints on exceptions are
4156 disabled within interactive calls. @xref{Calling}, for information on
4157 controlling this with @code{set unwind-on-terminating-exception}.
4160 You cannot raise an exception interactively.
4163 You cannot install an exception handler interactively.
4167 @cindex Ada exception catching
4168 @cindex catch Ada exceptions
4169 An Ada exception being raised. If an exception name is specified
4170 at the end of the command (eg @code{catch exception Program_Error}),
4171 the debugger will stop only when this specific exception is raised.
4172 Otherwise, the debugger stops execution when any Ada exception is raised.
4174 When inserting an exception catchpoint on a user-defined exception whose
4175 name is identical to one of the exceptions defined by the language, the
4176 fully qualified name must be used as the exception name. Otherwise,
4177 @value{GDBN} will assume that it should stop on the pre-defined exception
4178 rather than the user-defined one. For instance, assuming an exception
4179 called @code{Constraint_Error} is defined in package @code{Pck}, then
4180 the command to use to catch such exceptions is @kbd{catch exception
4181 Pck.Constraint_Error}.
4183 @item exception unhandled
4184 An exception that was raised but is not handled by the program.
4187 A failed Ada assertion.
4190 @cindex break on fork/exec
4191 A call to @code{exec}. This is currently only available for HP-UX
4195 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4196 @cindex break on a system call.
4197 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4198 syscall is a mechanism for application programs to request a service
4199 from the operating system (OS) or one of the OS system services.
4200 @value{GDBN} can catch some or all of the syscalls issued by the
4201 debuggee, and show the related information for each syscall. If no
4202 argument is specified, calls to and returns from all system calls
4205 @var{name} can be any system call name that is valid for the
4206 underlying OS. Just what syscalls are valid depends on the OS. On
4207 GNU and Unix systems, you can find the full list of valid syscall
4208 names on @file{/usr/include/asm/unistd.h}.
4210 @c For MS-Windows, the syscall names and the corresponding numbers
4211 @c can be found, e.g., on this URL:
4212 @c http://www.metasploit.com/users/opcode/syscalls.html
4213 @c but we don't support Windows syscalls yet.
4215 Normally, @value{GDBN} knows in advance which syscalls are valid for
4216 each OS, so you can use the @value{GDBN} command-line completion
4217 facilities (@pxref{Completion,, command completion}) to list the
4220 You may also specify the system call numerically. A syscall's
4221 number is the value passed to the OS's syscall dispatcher to
4222 identify the requested service. When you specify the syscall by its
4223 name, @value{GDBN} uses its database of syscalls to convert the name
4224 into the corresponding numeric code, but using the number directly
4225 may be useful if @value{GDBN}'s database does not have the complete
4226 list of syscalls on your system (e.g., because @value{GDBN} lags
4227 behind the OS upgrades).
4229 The example below illustrates how this command works if you don't provide
4233 (@value{GDBP}) catch syscall
4234 Catchpoint 1 (syscall)
4236 Starting program: /tmp/catch-syscall
4238 Catchpoint 1 (call to syscall 'close'), \
4239 0xffffe424 in __kernel_vsyscall ()
4243 Catchpoint 1 (returned from syscall 'close'), \
4244 0xffffe424 in __kernel_vsyscall ()
4248 Here is an example of catching a system call by name:
4251 (@value{GDBP}) catch syscall chroot
4252 Catchpoint 1 (syscall 'chroot' [61])
4254 Starting program: /tmp/catch-syscall
4256 Catchpoint 1 (call to syscall 'chroot'), \
4257 0xffffe424 in __kernel_vsyscall ()
4261 Catchpoint 1 (returned from syscall 'chroot'), \
4262 0xffffe424 in __kernel_vsyscall ()
4266 An example of specifying a system call numerically. In the case
4267 below, the syscall number has a corresponding entry in the XML
4268 file, so @value{GDBN} finds its name and prints it:
4271 (@value{GDBP}) catch syscall 252
4272 Catchpoint 1 (syscall(s) 'exit_group')
4274 Starting program: /tmp/catch-syscall
4276 Catchpoint 1 (call to syscall 'exit_group'), \
4277 0xffffe424 in __kernel_vsyscall ()
4281 Program exited normally.
4285 However, there can be situations when there is no corresponding name
4286 in XML file for that syscall number. In this case, @value{GDBN} prints
4287 a warning message saying that it was not able to find the syscall name,
4288 but the catchpoint will be set anyway. See the example below:
4291 (@value{GDBP}) catch syscall 764
4292 warning: The number '764' does not represent a known syscall.
4293 Catchpoint 2 (syscall 764)
4297 If you configure @value{GDBN} using the @samp{--without-expat} option,
4298 it will not be able to display syscall names. Also, if your
4299 architecture does not have an XML file describing its system calls,
4300 you will not be able to see the syscall names. It is important to
4301 notice that these two features are used for accessing the syscall
4302 name database. In either case, you will see a warning like this:
4305 (@value{GDBP}) catch syscall
4306 warning: Could not open "syscalls/i386-linux.xml"
4307 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4308 GDB will not be able to display syscall names.
4309 Catchpoint 1 (syscall)
4313 Of course, the file name will change depending on your architecture and system.
4315 Still using the example above, you can also try to catch a syscall by its
4316 number. In this case, you would see something like:
4319 (@value{GDBP}) catch syscall 252
4320 Catchpoint 1 (syscall(s) 252)
4323 Again, in this case @value{GDBN} would not be able to display syscall's names.
4326 A call to @code{fork}. This is currently only available for HP-UX
4330 A call to @code{vfork}. This is currently only available for HP-UX
4333 @item load @r{[}regexp@r{]}
4334 @itemx unload @r{[}regexp@r{]}
4335 The loading or unloading of a shared library. If @var{regexp} is
4336 given, then the catchpoint will stop only if the regular expression
4337 matches one of the affected libraries.
4339 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4340 The delivery of a signal.
4342 With no arguments, this catchpoint will catch any signal that is not
4343 used internally by @value{GDBN}, specifically, all signals except
4344 @samp{SIGTRAP} and @samp{SIGINT}.
4346 With the argument @samp{all}, all signals, including those used by
4347 @value{GDBN}, will be caught. This argument cannot be used with other
4350 Otherwise, the arguments are a list of signal names as given to
4351 @code{handle} (@pxref{Signals}). Only signals specified in this list
4354 One reason that @code{catch signal} can be more useful than
4355 @code{handle} is that you can attach commands and conditions to the
4358 When a signal is caught by a catchpoint, the signal's @code{stop} and
4359 @code{print} settings, as specified by @code{handle}, are ignored.
4360 However, whether the signal is still delivered to the inferior depends
4361 on the @code{pass} setting; this can be changed in the catchpoint's
4366 @item tcatch @var{event}
4367 Set a catchpoint that is enabled only for one stop. The catchpoint is
4368 automatically deleted after the first time the event is caught.
4372 Use the @code{info break} command to list the current catchpoints.
4376 @subsection Deleting Breakpoints
4378 @cindex clearing breakpoints, watchpoints, catchpoints
4379 @cindex deleting breakpoints, watchpoints, catchpoints
4380 It is often necessary to eliminate a breakpoint, watchpoint, or
4381 catchpoint once it has done its job and you no longer want your program
4382 to stop there. This is called @dfn{deleting} the breakpoint. A
4383 breakpoint that has been deleted no longer exists; it is forgotten.
4385 With the @code{clear} command you can delete breakpoints according to
4386 where they are in your program. With the @code{delete} command you can
4387 delete individual breakpoints, watchpoints, or catchpoints by specifying
4388 their breakpoint numbers.
4390 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4391 automatically ignores breakpoints on the first instruction to be executed
4392 when you continue execution without changing the execution address.
4397 Delete any breakpoints at the next instruction to be executed in the
4398 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4399 the innermost frame is selected, this is a good way to delete a
4400 breakpoint where your program just stopped.
4402 @item clear @var{location}
4403 Delete any breakpoints set at the specified @var{location}.
4404 @xref{Specify Location}, for the various forms of @var{location}; the
4405 most useful ones are listed below:
4408 @item clear @var{function}
4409 @itemx clear @var{filename}:@var{function}
4410 Delete any breakpoints set at entry to the named @var{function}.
4412 @item clear @var{linenum}
4413 @itemx clear @var{filename}:@var{linenum}
4414 Delete any breakpoints set at or within the code of the specified
4415 @var{linenum} of the specified @var{filename}.
4418 @cindex delete breakpoints
4420 @kindex d @r{(@code{delete})}
4421 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4422 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4423 ranges specified as arguments. If no argument is specified, delete all
4424 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4425 confirm off}). You can abbreviate this command as @code{d}.
4429 @subsection Disabling Breakpoints
4431 @cindex enable/disable a breakpoint
4432 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4433 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4434 it had been deleted, but remembers the information on the breakpoint so
4435 that you can @dfn{enable} it again later.
4437 You disable and enable breakpoints, watchpoints, and catchpoints with
4438 the @code{enable} and @code{disable} commands, optionally specifying
4439 one or more breakpoint numbers as arguments. Use @code{info break} to
4440 print a list of all breakpoints, watchpoints, and catchpoints if you
4441 do not know which numbers to use.
4443 Disabling and enabling a breakpoint that has multiple locations
4444 affects all of its locations.
4446 A breakpoint, watchpoint, or catchpoint can have any of several
4447 different states of enablement:
4451 Enabled. The breakpoint stops your program. A breakpoint set
4452 with the @code{break} command starts out in this state.
4454 Disabled. The breakpoint has no effect on your program.
4456 Enabled once. The breakpoint stops your program, but then becomes
4459 Enabled for a count. The breakpoint stops your program for the next
4460 N times, then becomes disabled.
4462 Enabled for deletion. The breakpoint stops your program, but
4463 immediately after it does so it is deleted permanently. A breakpoint
4464 set with the @code{tbreak} command starts out in this state.
4467 You can use the following commands to enable or disable breakpoints,
4468 watchpoints, and catchpoints:
4472 @kindex dis @r{(@code{disable})}
4473 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4474 Disable the specified breakpoints---or all breakpoints, if none are
4475 listed. A disabled breakpoint has no effect but is not forgotten. All
4476 options such as ignore-counts, conditions and commands are remembered in
4477 case the breakpoint is enabled again later. You may abbreviate
4478 @code{disable} as @code{dis}.
4481 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4482 Enable the specified breakpoints (or all defined breakpoints). They
4483 become effective once again in stopping your program.
4485 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4486 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4487 of these breakpoints immediately after stopping your program.
4489 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4490 Enable the specified breakpoints temporarily. @value{GDBN} records
4491 @var{count} with each of the specified breakpoints, and decrements a
4492 breakpoint's count when it is hit. When any count reaches 0,
4493 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4494 count (@pxref{Conditions, ,Break Conditions}), that will be
4495 decremented to 0 before @var{count} is affected.
4497 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4498 Enable the specified breakpoints to work once, then die. @value{GDBN}
4499 deletes any of these breakpoints as soon as your program stops there.
4500 Breakpoints set by the @code{tbreak} command start out in this state.
4503 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4504 @c confusing: tbreak is also initially enabled.
4505 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4506 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4507 subsequently, they become disabled or enabled only when you use one of
4508 the commands above. (The command @code{until} can set and delete a
4509 breakpoint of its own, but it does not change the state of your other
4510 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4514 @subsection Break Conditions
4515 @cindex conditional breakpoints
4516 @cindex breakpoint conditions
4518 @c FIXME what is scope of break condition expr? Context where wanted?
4519 @c in particular for a watchpoint?
4520 The simplest sort of breakpoint breaks every time your program reaches a
4521 specified place. You can also specify a @dfn{condition} for a
4522 breakpoint. A condition is just a Boolean expression in your
4523 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4524 a condition evaluates the expression each time your program reaches it,
4525 and your program stops only if the condition is @emph{true}.
4527 This is the converse of using assertions for program validation; in that
4528 situation, you want to stop when the assertion is violated---that is,
4529 when the condition is false. In C, if you want to test an assertion expressed
4530 by the condition @var{assert}, you should set the condition
4531 @samp{! @var{assert}} on the appropriate breakpoint.
4533 Conditions are also accepted for watchpoints; you may not need them,
4534 since a watchpoint is inspecting the value of an expression anyhow---but
4535 it might be simpler, say, to just set a watchpoint on a variable name,
4536 and specify a condition that tests whether the new value is an interesting
4539 Break conditions can have side effects, and may even call functions in
4540 your program. This can be useful, for example, to activate functions
4541 that log program progress, or to use your own print functions to
4542 format special data structures. The effects are completely predictable
4543 unless there is another enabled breakpoint at the same address. (In
4544 that case, @value{GDBN} might see the other breakpoint first and stop your
4545 program without checking the condition of this one.) Note that
4546 breakpoint commands are usually more convenient and flexible than break
4548 purpose of performing side effects when a breakpoint is reached
4549 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4551 Breakpoint conditions can also be evaluated on the target's side if
4552 the target supports it. Instead of evaluating the conditions locally,
4553 @value{GDBN} encodes the expression into an agent expression
4554 (@pxref{Agent Expressions}) suitable for execution on the target,
4555 independently of @value{GDBN}. Global variables become raw memory
4556 locations, locals become stack accesses, and so forth.
4558 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4559 when its condition evaluates to true. This mechanism may provide faster
4560 response times depending on the performance characteristics of the target
4561 since it does not need to keep @value{GDBN} informed about
4562 every breakpoint trigger, even those with false conditions.
4564 Break conditions can be specified when a breakpoint is set, by using
4565 @samp{if} in the arguments to the @code{break} command. @xref{Set
4566 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4567 with the @code{condition} command.
4569 You can also use the @code{if} keyword with the @code{watch} command.
4570 The @code{catch} command does not recognize the @code{if} keyword;
4571 @code{condition} is the only way to impose a further condition on a
4576 @item condition @var{bnum} @var{expression}
4577 Specify @var{expression} as the break condition for breakpoint,
4578 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4579 breakpoint @var{bnum} stops your program only if the value of
4580 @var{expression} is true (nonzero, in C). When you use
4581 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4582 syntactic correctness, and to determine whether symbols in it have
4583 referents in the context of your breakpoint. If @var{expression} uses
4584 symbols not referenced in the context of the breakpoint, @value{GDBN}
4585 prints an error message:
4588 No symbol "foo" in current context.
4593 not actually evaluate @var{expression} at the time the @code{condition}
4594 command (or a command that sets a breakpoint with a condition, like
4595 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4597 @item condition @var{bnum}
4598 Remove the condition from breakpoint number @var{bnum}. It becomes
4599 an ordinary unconditional breakpoint.
4602 @cindex ignore count (of breakpoint)
4603 A special case of a breakpoint condition is to stop only when the
4604 breakpoint has been reached a certain number of times. This is so
4605 useful that there is a special way to do it, using the @dfn{ignore
4606 count} of the breakpoint. Every breakpoint has an ignore count, which
4607 is an integer. Most of the time, the ignore count is zero, and
4608 therefore has no effect. But if your program reaches a breakpoint whose
4609 ignore count is positive, then instead of stopping, it just decrements
4610 the ignore count by one and continues. As a result, if the ignore count
4611 value is @var{n}, the breakpoint does not stop the next @var{n} times
4612 your program reaches it.
4616 @item ignore @var{bnum} @var{count}
4617 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4618 The next @var{count} times the breakpoint is reached, your program's
4619 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4622 To make the breakpoint stop the next time it is reached, specify
4625 When you use @code{continue} to resume execution of your program from a
4626 breakpoint, you can specify an ignore count directly as an argument to
4627 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4628 Stepping,,Continuing and Stepping}.
4630 If a breakpoint has a positive ignore count and a condition, the
4631 condition is not checked. Once the ignore count reaches zero,
4632 @value{GDBN} resumes checking the condition.
4634 You could achieve the effect of the ignore count with a condition such
4635 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4636 is decremented each time. @xref{Convenience Vars, ,Convenience
4640 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4643 @node Break Commands
4644 @subsection Breakpoint Command Lists
4646 @cindex breakpoint commands
4647 You can give any breakpoint (or watchpoint or catchpoint) a series of
4648 commands to execute when your program stops due to that breakpoint. For
4649 example, you might want to print the values of certain expressions, or
4650 enable other breakpoints.
4654 @kindex end@r{ (breakpoint commands)}
4655 @item commands @r{[}@var{range}@dots{}@r{]}
4656 @itemx @dots{} @var{command-list} @dots{}
4658 Specify a list of commands for the given breakpoints. The commands
4659 themselves appear on the following lines. Type a line containing just
4660 @code{end} to terminate the commands.
4662 To remove all commands from a breakpoint, type @code{commands} and
4663 follow it immediately with @code{end}; that is, give no commands.
4665 With no argument, @code{commands} refers to the last breakpoint,
4666 watchpoint, or catchpoint set (not to the breakpoint most recently
4667 encountered). If the most recent breakpoints were set with a single
4668 command, then the @code{commands} will apply to all the breakpoints
4669 set by that command. This applies to breakpoints set by
4670 @code{rbreak}, and also applies when a single @code{break} command
4671 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4675 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4676 disabled within a @var{command-list}.
4678 You can use breakpoint commands to start your program up again. Simply
4679 use the @code{continue} command, or @code{step}, or any other command
4680 that resumes execution.
4682 Any other commands in the command list, after a command that resumes
4683 execution, are ignored. This is because any time you resume execution
4684 (even with a simple @code{next} or @code{step}), you may encounter
4685 another breakpoint---which could have its own command list, leading to
4686 ambiguities about which list to execute.
4689 If the first command you specify in a command list is @code{silent}, the
4690 usual message about stopping at a breakpoint is not printed. This may
4691 be desirable for breakpoints that are to print a specific message and
4692 then continue. If none of the remaining commands print anything, you
4693 see no sign that the breakpoint was reached. @code{silent} is
4694 meaningful only at the beginning of a breakpoint command list.
4696 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4697 print precisely controlled output, and are often useful in silent
4698 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4700 For example, here is how you could use breakpoint commands to print the
4701 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4707 printf "x is %d\n",x
4712 One application for breakpoint commands is to compensate for one bug so
4713 you can test for another. Put a breakpoint just after the erroneous line
4714 of code, give it a condition to detect the case in which something
4715 erroneous has been done, and give it commands to assign correct values
4716 to any variables that need them. End with the @code{continue} command
4717 so that your program does not stop, and start with the @code{silent}
4718 command so that no output is produced. Here is an example:
4729 @node Dynamic Printf
4730 @subsection Dynamic Printf
4732 @cindex dynamic printf
4734 The dynamic printf command @code{dprintf} combines a breakpoint with
4735 formatted printing of your program's data to give you the effect of
4736 inserting @code{printf} calls into your program on-the-fly, without
4737 having to recompile it.
4739 In its most basic form, the output goes to the GDB console. However,
4740 you can set the variable @code{dprintf-style} for alternate handling.
4741 For instance, you can ask to format the output by calling your
4742 program's @code{printf} function. This has the advantage that the
4743 characters go to the program's output device, so they can recorded in
4744 redirects to files and so forth.
4746 If you are doing remote debugging with a stub or agent, you can also
4747 ask to have the printf handled by the remote agent. In addition to
4748 ensuring that the output goes to the remote program's device along
4749 with any other output the program might produce, you can also ask that
4750 the dprintf remain active even after disconnecting from the remote
4751 target. Using the stub/agent is also more efficient, as it can do
4752 everything without needing to communicate with @value{GDBN}.
4756 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4757 Whenever execution reaches @var{location}, print the values of one or
4758 more @var{expressions} under the control of the string @var{template}.
4759 To print several values, separate them with commas.
4761 @item set dprintf-style @var{style}
4762 Set the dprintf output to be handled in one of several different
4763 styles enumerated below. A change of style affects all existing
4764 dynamic printfs immediately. (If you need individual control over the
4765 print commands, simply define normal breakpoints with
4766 explicitly-supplied command lists.)
4769 @kindex dprintf-style gdb
4770 Handle the output using the @value{GDBN} @code{printf} command.
4773 @kindex dprintf-style call
4774 Handle the output by calling a function in your program (normally
4778 @kindex dprintf-style agent
4779 Have the remote debugging agent (such as @code{gdbserver}) handle
4780 the output itself. This style is only available for agents that
4781 support running commands on the target.
4783 @item set dprintf-function @var{function}
4784 Set the function to call if the dprintf style is @code{call}. By
4785 default its value is @code{printf}. You may set it to any expression.
4786 that @value{GDBN} can evaluate to a function, as per the @code{call}
4789 @item set dprintf-channel @var{channel}
4790 Set a ``channel'' for dprintf. If set to a non-empty value,
4791 @value{GDBN} will evaluate it as an expression and pass the result as
4792 a first argument to the @code{dprintf-function}, in the manner of
4793 @code{fprintf} and similar functions. Otherwise, the dprintf format
4794 string will be the first argument, in the manner of @code{printf}.
4796 As an example, if you wanted @code{dprintf} output to go to a logfile
4797 that is a standard I/O stream assigned to the variable @code{mylog},
4798 you could do the following:
4801 (gdb) set dprintf-style call
4802 (gdb) set dprintf-function fprintf
4803 (gdb) set dprintf-channel mylog
4804 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4805 Dprintf 1 at 0x123456: file main.c, line 25.
4807 1 dprintf keep y 0x00123456 in main at main.c:25
4808 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4813 Note that the @code{info break} displays the dynamic printf commands
4814 as normal breakpoint commands; you can thus easily see the effect of
4815 the variable settings.
4817 @item set disconnected-dprintf on
4818 @itemx set disconnected-dprintf off
4819 @kindex set disconnected-dprintf
4820 Choose whether @code{dprintf} commands should continue to run if
4821 @value{GDBN} has disconnected from the target. This only applies
4822 if the @code{dprintf-style} is @code{agent}.
4824 @item show disconnected-dprintf off
4825 @kindex show disconnected-dprintf
4826 Show the current choice for disconnected @code{dprintf}.
4830 @value{GDBN} does not check the validity of function and channel,
4831 relying on you to supply values that are meaningful for the contexts
4832 in which they are being used. For instance, the function and channel
4833 may be the values of local variables, but if that is the case, then
4834 all enabled dynamic prints must be at locations within the scope of
4835 those locals. If evaluation fails, @value{GDBN} will report an error.
4837 @node Save Breakpoints
4838 @subsection How to save breakpoints to a file
4840 To save breakpoint definitions to a file use the @w{@code{save
4841 breakpoints}} command.
4844 @kindex save breakpoints
4845 @cindex save breakpoints to a file for future sessions
4846 @item save breakpoints [@var{filename}]
4847 This command saves all current breakpoint definitions together with
4848 their commands and ignore counts, into a file @file{@var{filename}}
4849 suitable for use in a later debugging session. This includes all
4850 types of breakpoints (breakpoints, watchpoints, catchpoints,
4851 tracepoints). To read the saved breakpoint definitions, use the
4852 @code{source} command (@pxref{Command Files}). Note that watchpoints
4853 with expressions involving local variables may fail to be recreated
4854 because it may not be possible to access the context where the
4855 watchpoint is valid anymore. Because the saved breakpoint definitions
4856 are simply a sequence of @value{GDBN} commands that recreate the
4857 breakpoints, you can edit the file in your favorite editing program,
4858 and remove the breakpoint definitions you're not interested in, or
4859 that can no longer be recreated.
4862 @node Static Probe Points
4863 @subsection Static Probe Points
4865 @cindex static probe point, SystemTap
4866 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4867 for Statically Defined Tracing, and the probes are designed to have a tiny
4868 runtime code and data footprint, and no dynamic relocations. They are
4869 usable from assembly, C and C@t{++} languages. See
4870 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4871 for a good reference on how the @acronym{SDT} probes are implemented.
4873 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4874 @acronym{SDT} probes are supported on ELF-compatible systems. See
4875 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4876 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4877 in your applications.
4879 @cindex semaphores on static probe points
4880 Some probes have an associated semaphore variable; for instance, this
4881 happens automatically if you defined your probe using a DTrace-style
4882 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4883 automatically enable it when you specify a breakpoint using the
4884 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4885 location by some other method (e.g., @code{break file:line}), then
4886 @value{GDBN} will not automatically set the semaphore.
4888 You can examine the available static static probes using @code{info
4889 probes}, with optional arguments:
4893 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4894 If given, @var{provider} is a regular expression used to match against provider
4895 names when selecting which probes to list. If omitted, probes by all
4896 probes from all providers are listed.
4898 If given, @var{name} is a regular expression to match against probe names
4899 when selecting which probes to list. If omitted, probe names are not
4900 considered when deciding whether to display them.
4902 If given, @var{objfile} is a regular expression used to select which
4903 object files (executable or shared libraries) to examine. If not
4904 given, all object files are considered.
4906 @item info probes all
4907 List the available static probes, from all types.
4910 @vindex $_probe_arg@r{, convenience variable}
4911 A probe may specify up to twelve arguments. These are available at the
4912 point at which the probe is defined---that is, when the current PC is
4913 at the probe's location. The arguments are available using the
4914 convenience variables (@pxref{Convenience Vars})
4915 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4916 an integer of the appropriate size; types are not preserved. The
4917 convenience variable @code{$_probe_argc} holds the number of arguments
4918 at the current probe point.
4920 These variables are always available, but attempts to access them at
4921 any location other than a probe point will cause @value{GDBN} to give
4925 @c @ifclear BARETARGET
4926 @node Error in Breakpoints
4927 @subsection ``Cannot insert breakpoints''
4929 If you request too many active hardware-assisted breakpoints and
4930 watchpoints, you will see this error message:
4932 @c FIXME: the precise wording of this message may change; the relevant
4933 @c source change is not committed yet (Sep 3, 1999).
4935 Stopped; cannot insert breakpoints.
4936 You may have requested too many hardware breakpoints and watchpoints.
4940 This message is printed when you attempt to resume the program, since
4941 only then @value{GDBN} knows exactly how many hardware breakpoints and
4942 watchpoints it needs to insert.
4944 When this message is printed, you need to disable or remove some of the
4945 hardware-assisted breakpoints and watchpoints, and then continue.
4947 @node Breakpoint-related Warnings
4948 @subsection ``Breakpoint address adjusted...''
4949 @cindex breakpoint address adjusted
4951 Some processor architectures place constraints on the addresses at
4952 which breakpoints may be placed. For architectures thus constrained,
4953 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4954 with the constraints dictated by the architecture.
4956 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4957 a VLIW architecture in which a number of RISC-like instructions may be
4958 bundled together for parallel execution. The FR-V architecture
4959 constrains the location of a breakpoint instruction within such a
4960 bundle to the instruction with the lowest address. @value{GDBN}
4961 honors this constraint by adjusting a breakpoint's address to the
4962 first in the bundle.
4964 It is not uncommon for optimized code to have bundles which contain
4965 instructions from different source statements, thus it may happen that
4966 a breakpoint's address will be adjusted from one source statement to
4967 another. Since this adjustment may significantly alter @value{GDBN}'s
4968 breakpoint related behavior from what the user expects, a warning is
4969 printed when the breakpoint is first set and also when the breakpoint
4972 A warning like the one below is printed when setting a breakpoint
4973 that's been subject to address adjustment:
4976 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4979 Such warnings are printed both for user settable and @value{GDBN}'s
4980 internal breakpoints. If you see one of these warnings, you should
4981 verify that a breakpoint set at the adjusted address will have the
4982 desired affect. If not, the breakpoint in question may be removed and
4983 other breakpoints may be set which will have the desired behavior.
4984 E.g., it may be sufficient to place the breakpoint at a later
4985 instruction. A conditional breakpoint may also be useful in some
4986 cases to prevent the breakpoint from triggering too often.
4988 @value{GDBN} will also issue a warning when stopping at one of these
4989 adjusted breakpoints:
4992 warning: Breakpoint 1 address previously adjusted from 0x00010414
4996 When this warning is encountered, it may be too late to take remedial
4997 action except in cases where the breakpoint is hit earlier or more
4998 frequently than expected.
5000 @node Continuing and Stepping
5001 @section Continuing and Stepping
5005 @cindex resuming execution
5006 @dfn{Continuing} means resuming program execution until your program
5007 completes normally. In contrast, @dfn{stepping} means executing just
5008 one more ``step'' of your program, where ``step'' may mean either one
5009 line of source code, or one machine instruction (depending on what
5010 particular command you use). Either when continuing or when stepping,
5011 your program may stop even sooner, due to a breakpoint or a signal. (If
5012 it stops due to a signal, you may want to use @code{handle}, or use
5013 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5017 @kindex c @r{(@code{continue})}
5018 @kindex fg @r{(resume foreground execution)}
5019 @item continue @r{[}@var{ignore-count}@r{]}
5020 @itemx c @r{[}@var{ignore-count}@r{]}
5021 @itemx fg @r{[}@var{ignore-count}@r{]}
5022 Resume program execution, at the address where your program last stopped;
5023 any breakpoints set at that address are bypassed. The optional argument
5024 @var{ignore-count} allows you to specify a further number of times to
5025 ignore a breakpoint at this location; its effect is like that of
5026 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5028 The argument @var{ignore-count} is meaningful only when your program
5029 stopped due to a breakpoint. At other times, the argument to
5030 @code{continue} is ignored.
5032 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5033 debugged program is deemed to be the foreground program) are provided
5034 purely for convenience, and have exactly the same behavior as
5038 To resume execution at a different place, you can use @code{return}
5039 (@pxref{Returning, ,Returning from a Function}) to go back to the
5040 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5041 Different Address}) to go to an arbitrary location in your program.
5043 A typical technique for using stepping is to set a breakpoint
5044 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5045 beginning of the function or the section of your program where a problem
5046 is believed to lie, run your program until it stops at that breakpoint,
5047 and then step through the suspect area, examining the variables that are
5048 interesting, until you see the problem happen.
5052 @kindex s @r{(@code{step})}
5054 Continue running your program until control reaches a different source
5055 line, then stop it and return control to @value{GDBN}. This command is
5056 abbreviated @code{s}.
5059 @c "without debugging information" is imprecise; actually "without line
5060 @c numbers in the debugging information". (gcc -g1 has debugging info but
5061 @c not line numbers). But it seems complex to try to make that
5062 @c distinction here.
5063 @emph{Warning:} If you use the @code{step} command while control is
5064 within a function that was compiled without debugging information,
5065 execution proceeds until control reaches a function that does have
5066 debugging information. Likewise, it will not step into a function which
5067 is compiled without debugging information. To step through functions
5068 without debugging information, use the @code{stepi} command, described
5072 The @code{step} command only stops at the first instruction of a source
5073 line. This prevents the multiple stops that could otherwise occur in
5074 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5075 to stop if a function that has debugging information is called within
5076 the line. In other words, @code{step} @emph{steps inside} any functions
5077 called within the line.
5079 Also, the @code{step} command only enters a function if there is line
5080 number information for the function. Otherwise it acts like the
5081 @code{next} command. This avoids problems when using @code{cc -gl}
5082 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5083 was any debugging information about the routine.
5085 @item step @var{count}
5086 Continue running as in @code{step}, but do so @var{count} times. If a
5087 breakpoint is reached, or a signal not related to stepping occurs before
5088 @var{count} steps, stepping stops right away.
5091 @kindex n @r{(@code{next})}
5092 @item next @r{[}@var{count}@r{]}
5093 Continue to the next source line in the current (innermost) stack frame.
5094 This is similar to @code{step}, but function calls that appear within
5095 the line of code are executed without stopping. Execution stops when
5096 control reaches a different line of code at the original stack level
5097 that was executing when you gave the @code{next} command. This command
5098 is abbreviated @code{n}.
5100 An argument @var{count} is a repeat count, as for @code{step}.
5103 @c FIX ME!! Do we delete this, or is there a way it fits in with
5104 @c the following paragraph? --- Vctoria
5106 @c @code{next} within a function that lacks debugging information acts like
5107 @c @code{step}, but any function calls appearing within the code of the
5108 @c function are executed without stopping.
5110 The @code{next} command only stops at the first instruction of a
5111 source line. This prevents multiple stops that could otherwise occur in
5112 @code{switch} statements, @code{for} loops, etc.
5114 @kindex set step-mode
5116 @cindex functions without line info, and stepping
5117 @cindex stepping into functions with no line info
5118 @itemx set step-mode on
5119 The @code{set step-mode on} command causes the @code{step} command to
5120 stop at the first instruction of a function which contains no debug line
5121 information rather than stepping over it.
5123 This is useful in cases where you may be interested in inspecting the
5124 machine instructions of a function which has no symbolic info and do not
5125 want @value{GDBN} to automatically skip over this function.
5127 @item set step-mode off
5128 Causes the @code{step} command to step over any functions which contains no
5129 debug information. This is the default.
5131 @item show step-mode
5132 Show whether @value{GDBN} will stop in or step over functions without
5133 source line debug information.
5136 @kindex fin @r{(@code{finish})}
5138 Continue running until just after function in the selected stack frame
5139 returns. Print the returned value (if any). This command can be
5140 abbreviated as @code{fin}.
5142 Contrast this with the @code{return} command (@pxref{Returning,
5143 ,Returning from a Function}).
5146 @kindex u @r{(@code{until})}
5147 @cindex run until specified location
5150 Continue running until a source line past the current line, in the
5151 current stack frame, is reached. This command is used to avoid single
5152 stepping through a loop more than once. It is like the @code{next}
5153 command, except that when @code{until} encounters a jump, it
5154 automatically continues execution until the program counter is greater
5155 than the address of the jump.
5157 This means that when you reach the end of a loop after single stepping
5158 though it, @code{until} makes your program continue execution until it
5159 exits the loop. In contrast, a @code{next} command at the end of a loop
5160 simply steps back to the beginning of the loop, which forces you to step
5161 through the next iteration.
5163 @code{until} always stops your program if it attempts to exit the current
5166 @code{until} may produce somewhat counterintuitive results if the order
5167 of machine code does not match the order of the source lines. For
5168 example, in the following excerpt from a debugging session, the @code{f}
5169 (@code{frame}) command shows that execution is stopped at line
5170 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5174 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5176 (@value{GDBP}) until
5177 195 for ( ; argc > 0; NEXTARG) @{
5180 This happened because, for execution efficiency, the compiler had
5181 generated code for the loop closure test at the end, rather than the
5182 start, of the loop---even though the test in a C @code{for}-loop is
5183 written before the body of the loop. The @code{until} command appeared
5184 to step back to the beginning of the loop when it advanced to this
5185 expression; however, it has not really gone to an earlier
5186 statement---not in terms of the actual machine code.
5188 @code{until} with no argument works by means of single
5189 instruction stepping, and hence is slower than @code{until} with an
5192 @item until @var{location}
5193 @itemx u @var{location}
5194 Continue running your program until either the specified location is
5195 reached, or the current stack frame returns. @var{location} is any of
5196 the forms described in @ref{Specify Location}.
5197 This form of the command uses temporary breakpoints, and
5198 hence is quicker than @code{until} without an argument. The specified
5199 location is actually reached only if it is in the current frame. This
5200 implies that @code{until} can be used to skip over recursive function
5201 invocations. For instance in the code below, if the current location is
5202 line @code{96}, issuing @code{until 99} will execute the program up to
5203 line @code{99} in the same invocation of factorial, i.e., after the inner
5204 invocations have returned.
5207 94 int factorial (int value)
5209 96 if (value > 1) @{
5210 97 value *= factorial (value - 1);
5217 @kindex advance @var{location}
5218 @item advance @var{location}
5219 Continue running the program up to the given @var{location}. An argument is
5220 required, which should be of one of the forms described in
5221 @ref{Specify Location}.
5222 Execution will also stop upon exit from the current stack
5223 frame. This command is similar to @code{until}, but @code{advance} will
5224 not skip over recursive function calls, and the target location doesn't
5225 have to be in the same frame as the current one.
5229 @kindex si @r{(@code{stepi})}
5231 @itemx stepi @var{arg}
5233 Execute one machine instruction, then stop and return to the debugger.
5235 It is often useful to do @samp{display/i $pc} when stepping by machine
5236 instructions. This makes @value{GDBN} automatically display the next
5237 instruction to be executed, each time your program stops. @xref{Auto
5238 Display,, Automatic Display}.
5240 An argument is a repeat count, as in @code{step}.
5244 @kindex ni @r{(@code{nexti})}
5246 @itemx nexti @var{arg}
5248 Execute one machine instruction, but if it is a function call,
5249 proceed until the function returns.
5251 An argument is a repeat count, as in @code{next}.
5255 @anchor{range stepping}
5256 @cindex range stepping
5257 @cindex target-assisted range stepping
5258 By default, and if available, @value{GDBN} makes use of
5259 target-assisted @dfn{range stepping}. In other words, whenever you
5260 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5261 tells the target to step the corresponding range of instruction
5262 addresses instead of issuing multiple single-steps. This speeds up
5263 line stepping, particularly for remote targets. Ideally, there should
5264 be no reason you would want to turn range stepping off. However, it's
5265 possible that a bug in the debug info, a bug in the remote stub (for
5266 remote targets), or even a bug in @value{GDBN} could make line
5267 stepping behave incorrectly when target-assisted range stepping is
5268 enabled. You can use the following command to turn off range stepping
5272 @kindex set range-stepping
5273 @kindex show range-stepping
5274 @item set range-stepping
5275 @itemx show range-stepping
5276 Control whether range stepping is enabled.
5278 If @code{on}, and the target supports it, @value{GDBN} tells the
5279 target to step a range of addresses itself, instead of issuing
5280 multiple single-steps. If @code{off}, @value{GDBN} always issues
5281 single-steps, even if range stepping is supported by the target. The
5282 default is @code{on}.
5286 @node Skipping Over Functions and Files
5287 @section Skipping Over Functions and Files
5288 @cindex skipping over functions and files
5290 The program you are debugging may contain some functions which are
5291 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5292 skip a function or all functions in a file when stepping.
5294 For example, consider the following C function:
5305 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5306 are not interested in stepping through @code{boring}. If you run @code{step}
5307 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5308 step over both @code{foo} and @code{boring}!
5310 One solution is to @code{step} into @code{boring} and use the @code{finish}
5311 command to immediately exit it. But this can become tedious if @code{boring}
5312 is called from many places.
5314 A more flexible solution is to execute @kbd{skip boring}. This instructs
5315 @value{GDBN} never to step into @code{boring}. Now when you execute
5316 @code{step} at line 103, you'll step over @code{boring} and directly into
5319 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5320 example, @code{skip file boring.c}.
5323 @kindex skip function
5324 @item skip @r{[}@var{linespec}@r{]}
5325 @itemx skip function @r{[}@var{linespec}@r{]}
5326 After running this command, the function named by @var{linespec} or the
5327 function containing the line named by @var{linespec} will be skipped over when
5328 stepping. @xref{Specify Location}.
5330 If you do not specify @var{linespec}, the function you're currently debugging
5333 (If you have a function called @code{file} that you want to skip, use
5334 @kbd{skip function file}.)
5337 @item skip file @r{[}@var{filename}@r{]}
5338 After running this command, any function whose source lives in @var{filename}
5339 will be skipped over when stepping.
5341 If you do not specify @var{filename}, functions whose source lives in the file
5342 you're currently debugging will be skipped.
5345 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5346 These are the commands for managing your list of skips:
5350 @item info skip @r{[}@var{range}@r{]}
5351 Print details about the specified skip(s). If @var{range} is not specified,
5352 print a table with details about all functions and files marked for skipping.
5353 @code{info skip} prints the following information about each skip:
5357 A number identifying this skip.
5359 The type of this skip, either @samp{function} or @samp{file}.
5360 @item Enabled or Disabled
5361 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5363 For function skips, this column indicates the address in memory of the function
5364 being skipped. If you've set a function skip on a function which has not yet
5365 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5366 which has the function is loaded, @code{info skip} will show the function's
5369 For file skips, this field contains the filename being skipped. For functions
5370 skips, this field contains the function name and its line number in the file
5371 where it is defined.
5375 @item skip delete @r{[}@var{range}@r{]}
5376 Delete the specified skip(s). If @var{range} is not specified, delete all
5380 @item skip enable @r{[}@var{range}@r{]}
5381 Enable the specified skip(s). If @var{range} is not specified, enable all
5384 @kindex skip disable
5385 @item skip disable @r{[}@var{range}@r{]}
5386 Disable the specified skip(s). If @var{range} is not specified, disable all
5395 A signal is an asynchronous event that can happen in a program. The
5396 operating system defines the possible kinds of signals, and gives each
5397 kind a name and a number. For example, in Unix @code{SIGINT} is the
5398 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5399 @code{SIGSEGV} is the signal a program gets from referencing a place in
5400 memory far away from all the areas in use; @code{SIGALRM} occurs when
5401 the alarm clock timer goes off (which happens only if your program has
5402 requested an alarm).
5404 @cindex fatal signals
5405 Some signals, including @code{SIGALRM}, are a normal part of the
5406 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5407 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5408 program has not specified in advance some other way to handle the signal.
5409 @code{SIGINT} does not indicate an error in your program, but it is normally
5410 fatal so it can carry out the purpose of the interrupt: to kill the program.
5412 @value{GDBN} has the ability to detect any occurrence of a signal in your
5413 program. You can tell @value{GDBN} in advance what to do for each kind of
5416 @cindex handling signals
5417 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5418 @code{SIGALRM} be silently passed to your program
5419 (so as not to interfere with their role in the program's functioning)
5420 but to stop your program immediately whenever an error signal happens.
5421 You can change these settings with the @code{handle} command.
5424 @kindex info signals
5428 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5429 handle each one. You can use this to see the signal numbers of all
5430 the defined types of signals.
5432 @item info signals @var{sig}
5433 Similar, but print information only about the specified signal number.
5435 @code{info handle} is an alias for @code{info signals}.
5437 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5438 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5439 for details about this command.
5442 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5443 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5444 can be the number of a signal or its name (with or without the
5445 @samp{SIG} at the beginning); a list of signal numbers of the form
5446 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5447 known signals. Optional arguments @var{keywords}, described below,
5448 say what change to make.
5452 The keywords allowed by the @code{handle} command can be abbreviated.
5453 Their full names are:
5457 @value{GDBN} should not stop your program when this signal happens. It may
5458 still print a message telling you that the signal has come in.
5461 @value{GDBN} should stop your program when this signal happens. This implies
5462 the @code{print} keyword as well.
5465 @value{GDBN} should print a message when this signal happens.
5468 @value{GDBN} should not mention the occurrence of the signal at all. This
5469 implies the @code{nostop} keyword as well.
5473 @value{GDBN} should allow your program to see this signal; your program
5474 can handle the signal, or else it may terminate if the signal is fatal
5475 and not handled. @code{pass} and @code{noignore} are synonyms.
5479 @value{GDBN} should not allow your program to see this signal.
5480 @code{nopass} and @code{ignore} are synonyms.
5484 When a signal stops your program, the signal is not visible to the
5486 continue. Your program sees the signal then, if @code{pass} is in
5487 effect for the signal in question @emph{at that time}. In other words,
5488 after @value{GDBN} reports a signal, you can use the @code{handle}
5489 command with @code{pass} or @code{nopass} to control whether your
5490 program sees that signal when you continue.
5492 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5493 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5494 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5497 You can also use the @code{signal} command to prevent your program from
5498 seeing a signal, or cause it to see a signal it normally would not see,
5499 or to give it any signal at any time. For example, if your program stopped
5500 due to some sort of memory reference error, you might store correct
5501 values into the erroneous variables and continue, hoping to see more
5502 execution; but your program would probably terminate immediately as
5503 a result of the fatal signal once it saw the signal. To prevent this,
5504 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5507 @cindex extra signal information
5508 @anchor{extra signal information}
5510 On some targets, @value{GDBN} can inspect extra signal information
5511 associated with the intercepted signal, before it is actually
5512 delivered to the program being debugged. This information is exported
5513 by the convenience variable @code{$_siginfo}, and consists of data
5514 that is passed by the kernel to the signal handler at the time of the
5515 receipt of a signal. The data type of the information itself is
5516 target dependent. You can see the data type using the @code{ptype
5517 $_siginfo} command. On Unix systems, it typically corresponds to the
5518 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5521 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5522 referenced address that raised a segmentation fault.
5526 (@value{GDBP}) continue
5527 Program received signal SIGSEGV, Segmentation fault.
5528 0x0000000000400766 in main ()
5530 (@value{GDBP}) ptype $_siginfo
5537 struct @{...@} _kill;
5538 struct @{...@} _timer;
5540 struct @{...@} _sigchld;
5541 struct @{...@} _sigfault;
5542 struct @{...@} _sigpoll;
5545 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5549 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5550 $1 = (void *) 0x7ffff7ff7000
5554 Depending on target support, @code{$_siginfo} may also be writable.
5557 @section Stopping and Starting Multi-thread Programs
5559 @cindex stopped threads
5560 @cindex threads, stopped
5562 @cindex continuing threads
5563 @cindex threads, continuing
5565 @value{GDBN} supports debugging programs with multiple threads
5566 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5567 are two modes of controlling execution of your program within the
5568 debugger. In the default mode, referred to as @dfn{all-stop mode},
5569 when any thread in your program stops (for example, at a breakpoint
5570 or while being stepped), all other threads in the program are also stopped by
5571 @value{GDBN}. On some targets, @value{GDBN} also supports
5572 @dfn{non-stop mode}, in which other threads can continue to run freely while
5573 you examine the stopped thread in the debugger.
5576 * All-Stop Mode:: All threads stop when GDB takes control
5577 * Non-Stop Mode:: Other threads continue to execute
5578 * Background Execution:: Running your program asynchronously
5579 * Thread-Specific Breakpoints:: Controlling breakpoints
5580 * Interrupted System Calls:: GDB may interfere with system calls
5581 * Observer Mode:: GDB does not alter program behavior
5585 @subsection All-Stop Mode
5587 @cindex all-stop mode
5589 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5590 @emph{all} threads of execution stop, not just the current thread. This
5591 allows you to examine the overall state of the program, including
5592 switching between threads, without worrying that things may change
5595 Conversely, whenever you restart the program, @emph{all} threads start
5596 executing. @emph{This is true even when single-stepping} with commands
5597 like @code{step} or @code{next}.
5599 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5600 Since thread scheduling is up to your debugging target's operating
5601 system (not controlled by @value{GDBN}), other threads may
5602 execute more than one statement while the current thread completes a
5603 single step. Moreover, in general other threads stop in the middle of a
5604 statement, rather than at a clean statement boundary, when the program
5607 You might even find your program stopped in another thread after
5608 continuing or even single-stepping. This happens whenever some other
5609 thread runs into a breakpoint, a signal, or an exception before the
5610 first thread completes whatever you requested.
5612 @cindex automatic thread selection
5613 @cindex switching threads automatically
5614 @cindex threads, automatic switching
5615 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5616 signal, it automatically selects the thread where that breakpoint or
5617 signal happened. @value{GDBN} alerts you to the context switch with a
5618 message such as @samp{[Switching to Thread @var{n}]} to identify the
5621 On some OSes, you can modify @value{GDBN}'s default behavior by
5622 locking the OS scheduler to allow only a single thread to run.
5625 @item set scheduler-locking @var{mode}
5626 @cindex scheduler locking mode
5627 @cindex lock scheduler
5628 Set the scheduler locking mode. If it is @code{off}, then there is no
5629 locking and any thread may run at any time. If @code{on}, then only the
5630 current thread may run when the inferior is resumed. The @code{step}
5631 mode optimizes for single-stepping; it prevents other threads
5632 from preempting the current thread while you are stepping, so that
5633 the focus of debugging does not change unexpectedly.
5634 Other threads only rarely (or never) get a chance to run
5635 when you step. They are more likely to run when you @samp{next} over a
5636 function call, and they are completely free to run when you use commands
5637 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5638 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5639 the current thread away from the thread that you are debugging.
5641 @item show scheduler-locking
5642 Display the current scheduler locking mode.
5645 @cindex resume threads of multiple processes simultaneously
5646 By default, when you issue one of the execution commands such as
5647 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5648 threads of the current inferior to run. For example, if @value{GDBN}
5649 is attached to two inferiors, each with two threads, the
5650 @code{continue} command resumes only the two threads of the current
5651 inferior. This is useful, for example, when you debug a program that
5652 forks and you want to hold the parent stopped (so that, for instance,
5653 it doesn't run to exit), while you debug the child. In other
5654 situations, you may not be interested in inspecting the current state
5655 of any of the processes @value{GDBN} is attached to, and you may want
5656 to resume them all until some breakpoint is hit. In the latter case,
5657 you can instruct @value{GDBN} to allow all threads of all the
5658 inferiors to run with the @w{@code{set schedule-multiple}} command.
5661 @kindex set schedule-multiple
5662 @item set schedule-multiple
5663 Set the mode for allowing threads of multiple processes to be resumed
5664 when an execution command is issued. When @code{on}, all threads of
5665 all processes are allowed to run. When @code{off}, only the threads
5666 of the current process are resumed. The default is @code{off}. The
5667 @code{scheduler-locking} mode takes precedence when set to @code{on},
5668 or while you are stepping and set to @code{step}.
5670 @item show schedule-multiple
5671 Display the current mode for resuming the execution of threads of
5676 @subsection Non-Stop Mode
5678 @cindex non-stop mode
5680 @c This section is really only a place-holder, and needs to be expanded
5681 @c with more details.
5683 For some multi-threaded targets, @value{GDBN} supports an optional
5684 mode of operation in which you can examine stopped program threads in
5685 the debugger while other threads continue to execute freely. This
5686 minimizes intrusion when debugging live systems, such as programs
5687 where some threads have real-time constraints or must continue to
5688 respond to external events. This is referred to as @dfn{non-stop} mode.
5690 In non-stop mode, when a thread stops to report a debugging event,
5691 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5692 threads as well, in contrast to the all-stop mode behavior. Additionally,
5693 execution commands such as @code{continue} and @code{step} apply by default
5694 only to the current thread in non-stop mode, rather than all threads as
5695 in all-stop mode. This allows you to control threads explicitly in
5696 ways that are not possible in all-stop mode --- for example, stepping
5697 one thread while allowing others to run freely, stepping
5698 one thread while holding all others stopped, or stepping several threads
5699 independently and simultaneously.
5701 To enter non-stop mode, use this sequence of commands before you run
5702 or attach to your program:
5705 # Enable the async interface.
5708 # If using the CLI, pagination breaks non-stop.
5711 # Finally, turn it on!
5715 You can use these commands to manipulate the non-stop mode setting:
5718 @kindex set non-stop
5719 @item set non-stop on
5720 Enable selection of non-stop mode.
5721 @item set non-stop off
5722 Disable selection of non-stop mode.
5723 @kindex show non-stop
5725 Show the current non-stop enablement setting.
5728 Note these commands only reflect whether non-stop mode is enabled,
5729 not whether the currently-executing program is being run in non-stop mode.
5730 In particular, the @code{set non-stop} preference is only consulted when
5731 @value{GDBN} starts or connects to the target program, and it is generally
5732 not possible to switch modes once debugging has started. Furthermore,
5733 since not all targets support non-stop mode, even when you have enabled
5734 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5737 In non-stop mode, all execution commands apply only to the current thread
5738 by default. That is, @code{continue} only continues one thread.
5739 To continue all threads, issue @code{continue -a} or @code{c -a}.
5741 You can use @value{GDBN}'s background execution commands
5742 (@pxref{Background Execution}) to run some threads in the background
5743 while you continue to examine or step others from @value{GDBN}.
5744 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5745 always executed asynchronously in non-stop mode.
5747 Suspending execution is done with the @code{interrupt} command when
5748 running in the background, or @kbd{Ctrl-c} during foreground execution.
5749 In all-stop mode, this stops the whole process;
5750 but in non-stop mode the interrupt applies only to the current thread.
5751 To stop the whole program, use @code{interrupt -a}.
5753 Other execution commands do not currently support the @code{-a} option.
5755 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5756 that thread current, as it does in all-stop mode. This is because the
5757 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5758 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5759 changed to a different thread just as you entered a command to operate on the
5760 previously current thread.
5762 @node Background Execution
5763 @subsection Background Execution
5765 @cindex foreground execution
5766 @cindex background execution
5767 @cindex asynchronous execution
5768 @cindex execution, foreground, background and asynchronous
5770 @value{GDBN}'s execution commands have two variants: the normal
5771 foreground (synchronous) behavior, and a background
5772 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5773 the program to report that some thread has stopped before prompting for
5774 another command. In background execution, @value{GDBN} immediately gives
5775 a command prompt so that you can issue other commands while your program runs.
5777 You need to explicitly enable asynchronous mode before you can use
5778 background execution commands. You can use these commands to
5779 manipulate the asynchronous mode setting:
5782 @kindex set target-async
5783 @item set target-async on
5784 Enable asynchronous mode.
5785 @item set target-async off
5786 Disable asynchronous mode.
5787 @kindex show target-async
5788 @item show target-async
5789 Show the current target-async setting.
5792 If the target doesn't support async mode, @value{GDBN} issues an error
5793 message if you attempt to use the background execution commands.
5795 To specify background execution, add a @code{&} to the command. For example,
5796 the background form of the @code{continue} command is @code{continue&}, or
5797 just @code{c&}. The execution commands that accept background execution
5803 @xref{Starting, , Starting your Program}.
5807 @xref{Attach, , Debugging an Already-running Process}.
5811 @xref{Continuing and Stepping, step}.
5815 @xref{Continuing and Stepping, stepi}.
5819 @xref{Continuing and Stepping, next}.
5823 @xref{Continuing and Stepping, nexti}.
5827 @xref{Continuing and Stepping, continue}.
5831 @xref{Continuing and Stepping, finish}.
5835 @xref{Continuing and Stepping, until}.
5839 Background execution is especially useful in conjunction with non-stop
5840 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5841 However, you can also use these commands in the normal all-stop mode with
5842 the restriction that you cannot issue another execution command until the
5843 previous one finishes. Examples of commands that are valid in all-stop
5844 mode while the program is running include @code{help} and @code{info break}.
5846 You can interrupt your program while it is running in the background by
5847 using the @code{interrupt} command.
5854 Suspend execution of the running program. In all-stop mode,
5855 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5856 only the current thread. To stop the whole program in non-stop mode,
5857 use @code{interrupt -a}.
5860 @node Thread-Specific Breakpoints
5861 @subsection Thread-Specific Breakpoints
5863 When your program has multiple threads (@pxref{Threads,, Debugging
5864 Programs with Multiple Threads}), you can choose whether to set
5865 breakpoints on all threads, or on a particular thread.
5868 @cindex breakpoints and threads
5869 @cindex thread breakpoints
5870 @kindex break @dots{} thread @var{threadno}
5871 @item break @var{linespec} thread @var{threadno}
5872 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5873 @var{linespec} specifies source lines; there are several ways of
5874 writing them (@pxref{Specify Location}), but the effect is always to
5875 specify some source line.
5877 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5878 to specify that you only want @value{GDBN} to stop the program when a
5879 particular thread reaches this breakpoint. @var{threadno} is one of the
5880 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5881 column of the @samp{info threads} display.
5883 If you do not specify @samp{thread @var{threadno}} when you set a
5884 breakpoint, the breakpoint applies to @emph{all} threads of your
5887 You can use the @code{thread} qualifier on conditional breakpoints as
5888 well; in this case, place @samp{thread @var{threadno}} before or
5889 after the breakpoint condition, like this:
5892 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5897 Thread-specific breakpoints are automatically deleted when
5898 @value{GDBN} detects the corresponding thread is no longer in the
5899 thread list. For example:
5903 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5906 There are several ways for a thread to disappear, such as a regular
5907 thread exit, but also when you detach from the process with the
5908 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5909 Process}), or if @value{GDBN} loses the remote connection
5910 (@pxref{Remote Debugging}), etc. Note that with some targets,
5911 @value{GDBN} is only able to detect a thread has exited when the user
5912 explictly asks for the thread list with the @code{info threads}
5915 @node Interrupted System Calls
5916 @subsection Interrupted System Calls
5918 @cindex thread breakpoints and system calls
5919 @cindex system calls and thread breakpoints
5920 @cindex premature return from system calls
5921 There is an unfortunate side effect when using @value{GDBN} to debug
5922 multi-threaded programs. If one thread stops for a
5923 breakpoint, or for some other reason, and another thread is blocked in a
5924 system call, then the system call may return prematurely. This is a
5925 consequence of the interaction between multiple threads and the signals
5926 that @value{GDBN} uses to implement breakpoints and other events that
5929 To handle this problem, your program should check the return value of
5930 each system call and react appropriately. This is good programming
5933 For example, do not write code like this:
5939 The call to @code{sleep} will return early if a different thread stops
5940 at a breakpoint or for some other reason.
5942 Instead, write this:
5947 unslept = sleep (unslept);
5950 A system call is allowed to return early, so the system is still
5951 conforming to its specification. But @value{GDBN} does cause your
5952 multi-threaded program to behave differently than it would without
5955 Also, @value{GDBN} uses internal breakpoints in the thread library to
5956 monitor certain events such as thread creation and thread destruction.
5957 When such an event happens, a system call in another thread may return
5958 prematurely, even though your program does not appear to stop.
5961 @subsection Observer Mode
5963 If you want to build on non-stop mode and observe program behavior
5964 without any chance of disruption by @value{GDBN}, you can set
5965 variables to disable all of the debugger's attempts to modify state,
5966 whether by writing memory, inserting breakpoints, etc. These operate
5967 at a low level, intercepting operations from all commands.
5969 When all of these are set to @code{off}, then @value{GDBN} is said to
5970 be @dfn{observer mode}. As a convenience, the variable
5971 @code{observer} can be set to disable these, plus enable non-stop
5974 Note that @value{GDBN} will not prevent you from making nonsensical
5975 combinations of these settings. For instance, if you have enabled
5976 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5977 then breakpoints that work by writing trap instructions into the code
5978 stream will still not be able to be placed.
5983 @item set observer on
5984 @itemx set observer off
5985 When set to @code{on}, this disables all the permission variables
5986 below (except for @code{insert-fast-tracepoints}), plus enables
5987 non-stop debugging. Setting this to @code{off} switches back to
5988 normal debugging, though remaining in non-stop mode.
5991 Show whether observer mode is on or off.
5993 @kindex may-write-registers
5994 @item set may-write-registers on
5995 @itemx set may-write-registers off
5996 This controls whether @value{GDBN} will attempt to alter the values of
5997 registers, such as with assignment expressions in @code{print}, or the
5998 @code{jump} command. It defaults to @code{on}.
6000 @item show may-write-registers
6001 Show the current permission to write registers.
6003 @kindex may-write-memory
6004 @item set may-write-memory on
6005 @itemx set may-write-memory off
6006 This controls whether @value{GDBN} will attempt to alter the contents
6007 of memory, such as with assignment expressions in @code{print}. It
6008 defaults to @code{on}.
6010 @item show may-write-memory
6011 Show the current permission to write memory.
6013 @kindex may-insert-breakpoints
6014 @item set may-insert-breakpoints on
6015 @itemx set may-insert-breakpoints off
6016 This controls whether @value{GDBN} will attempt to insert breakpoints.
6017 This affects all breakpoints, including internal breakpoints defined
6018 by @value{GDBN}. It defaults to @code{on}.
6020 @item show may-insert-breakpoints
6021 Show the current permission to insert breakpoints.
6023 @kindex may-insert-tracepoints
6024 @item set may-insert-tracepoints on
6025 @itemx set may-insert-tracepoints off
6026 This controls whether @value{GDBN} will attempt to insert (regular)
6027 tracepoints at the beginning of a tracing experiment. It affects only
6028 non-fast tracepoints, fast tracepoints being under the control of
6029 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6031 @item show may-insert-tracepoints
6032 Show the current permission to insert tracepoints.
6034 @kindex may-insert-fast-tracepoints
6035 @item set may-insert-fast-tracepoints on
6036 @itemx set may-insert-fast-tracepoints off
6037 This controls whether @value{GDBN} will attempt to insert fast
6038 tracepoints at the beginning of a tracing experiment. It affects only
6039 fast tracepoints, regular (non-fast) tracepoints being under the
6040 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6042 @item show may-insert-fast-tracepoints
6043 Show the current permission to insert fast tracepoints.
6045 @kindex may-interrupt
6046 @item set may-interrupt on
6047 @itemx set may-interrupt off
6048 This controls whether @value{GDBN} will attempt to interrupt or stop
6049 program execution. When this variable is @code{off}, the
6050 @code{interrupt} command will have no effect, nor will
6051 @kbd{Ctrl-c}. It defaults to @code{on}.
6053 @item show may-interrupt
6054 Show the current permission to interrupt or stop the program.
6058 @node Reverse Execution
6059 @chapter Running programs backward
6060 @cindex reverse execution
6061 @cindex running programs backward
6063 When you are debugging a program, it is not unusual to realize that
6064 you have gone too far, and some event of interest has already happened.
6065 If the target environment supports it, @value{GDBN} can allow you to
6066 ``rewind'' the program by running it backward.
6068 A target environment that supports reverse execution should be able
6069 to ``undo'' the changes in machine state that have taken place as the
6070 program was executing normally. Variables, registers etc.@: should
6071 revert to their previous values. Obviously this requires a great
6072 deal of sophistication on the part of the target environment; not
6073 all target environments can support reverse execution.
6075 When a program is executed in reverse, the instructions that
6076 have most recently been executed are ``un-executed'', in reverse
6077 order. The program counter runs backward, following the previous
6078 thread of execution in reverse. As each instruction is ``un-executed'',
6079 the values of memory and/or registers that were changed by that
6080 instruction are reverted to their previous states. After executing
6081 a piece of source code in reverse, all side effects of that code
6082 should be ``undone'', and all variables should be returned to their
6083 prior values@footnote{
6084 Note that some side effects are easier to undo than others. For instance,
6085 memory and registers are relatively easy, but device I/O is hard. Some
6086 targets may be able undo things like device I/O, and some may not.
6088 The contract between @value{GDBN} and the reverse executing target
6089 requires only that the target do something reasonable when
6090 @value{GDBN} tells it to execute backwards, and then report the
6091 results back to @value{GDBN}. Whatever the target reports back to
6092 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6093 assumes that the memory and registers that the target reports are in a
6094 consistant state, but @value{GDBN} accepts whatever it is given.
6097 If you are debugging in a target environment that supports
6098 reverse execution, @value{GDBN} provides the following commands.
6101 @kindex reverse-continue
6102 @kindex rc @r{(@code{reverse-continue})}
6103 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6104 @itemx rc @r{[}@var{ignore-count}@r{]}
6105 Beginning at the point where your program last stopped, start executing
6106 in reverse. Reverse execution will stop for breakpoints and synchronous
6107 exceptions (signals), just like normal execution. Behavior of
6108 asynchronous signals depends on the target environment.
6110 @kindex reverse-step
6111 @kindex rs @r{(@code{step})}
6112 @item reverse-step @r{[}@var{count}@r{]}
6113 Run the program backward until control reaches the start of a
6114 different source line; then stop it, and return control to @value{GDBN}.
6116 Like the @code{step} command, @code{reverse-step} will only stop
6117 at the beginning of a source line. It ``un-executes'' the previously
6118 executed source line. If the previous source line included calls to
6119 debuggable functions, @code{reverse-step} will step (backward) into
6120 the called function, stopping at the beginning of the @emph{last}
6121 statement in the called function (typically a return statement).
6123 Also, as with the @code{step} command, if non-debuggable functions are
6124 called, @code{reverse-step} will run thru them backward without stopping.
6126 @kindex reverse-stepi
6127 @kindex rsi @r{(@code{reverse-stepi})}
6128 @item reverse-stepi @r{[}@var{count}@r{]}
6129 Reverse-execute one machine instruction. Note that the instruction
6130 to be reverse-executed is @emph{not} the one pointed to by the program
6131 counter, but the instruction executed prior to that one. For instance,
6132 if the last instruction was a jump, @code{reverse-stepi} will take you
6133 back from the destination of the jump to the jump instruction itself.
6135 @kindex reverse-next
6136 @kindex rn @r{(@code{reverse-next})}
6137 @item reverse-next @r{[}@var{count}@r{]}
6138 Run backward to the beginning of the previous line executed in
6139 the current (innermost) stack frame. If the line contains function
6140 calls, they will be ``un-executed'' without stopping. Starting from
6141 the first line of a function, @code{reverse-next} will take you back
6142 to the caller of that function, @emph{before} the function was called,
6143 just as the normal @code{next} command would take you from the last
6144 line of a function back to its return to its caller
6145 @footnote{Unless the code is too heavily optimized.}.
6147 @kindex reverse-nexti
6148 @kindex rni @r{(@code{reverse-nexti})}
6149 @item reverse-nexti @r{[}@var{count}@r{]}
6150 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6151 in reverse, except that called functions are ``un-executed'' atomically.
6152 That is, if the previously executed instruction was a return from
6153 another function, @code{reverse-nexti} will continue to execute
6154 in reverse until the call to that function (from the current stack
6157 @kindex reverse-finish
6158 @item reverse-finish
6159 Just as the @code{finish} command takes you to the point where the
6160 current function returns, @code{reverse-finish} takes you to the point
6161 where it was called. Instead of ending up at the end of the current
6162 function invocation, you end up at the beginning.
6164 @kindex set exec-direction
6165 @item set exec-direction
6166 Set the direction of target execution.
6167 @item set exec-direction reverse
6168 @cindex execute forward or backward in time
6169 @value{GDBN} will perform all execution commands in reverse, until the
6170 exec-direction mode is changed to ``forward''. Affected commands include
6171 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6172 command cannot be used in reverse mode.
6173 @item set exec-direction forward
6174 @value{GDBN} will perform all execution commands in the normal fashion.
6175 This is the default.
6179 @node Process Record and Replay
6180 @chapter Recording Inferior's Execution and Replaying It
6181 @cindex process record and replay
6182 @cindex recording inferior's execution and replaying it
6184 On some platforms, @value{GDBN} provides a special @dfn{process record
6185 and replay} target that can record a log of the process execution, and
6186 replay it later with both forward and reverse execution commands.
6189 When this target is in use, if the execution log includes the record
6190 for the next instruction, @value{GDBN} will debug in @dfn{replay
6191 mode}. In the replay mode, the inferior does not really execute code
6192 instructions. Instead, all the events that normally happen during
6193 code execution are taken from the execution log. While code is not
6194 really executed in replay mode, the values of registers (including the
6195 program counter register) and the memory of the inferior are still
6196 changed as they normally would. Their contents are taken from the
6200 If the record for the next instruction is not in the execution log,
6201 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6202 inferior executes normally, and @value{GDBN} records the execution log
6205 The process record and replay target supports reverse execution
6206 (@pxref{Reverse Execution}), even if the platform on which the
6207 inferior runs does not. However, the reverse execution is limited in
6208 this case by the range of the instructions recorded in the execution
6209 log. In other words, reverse execution on platforms that don't
6210 support it directly can only be done in the replay mode.
6212 When debugging in the reverse direction, @value{GDBN} will work in
6213 replay mode as long as the execution log includes the record for the
6214 previous instruction; otherwise, it will work in record mode, if the
6215 platform supports reverse execution, or stop if not.
6217 For architecture environments that support process record and replay,
6218 @value{GDBN} provides the following commands:
6221 @kindex target record
6222 @kindex target record-full
6223 @kindex target record-btrace
6226 @kindex record btrace
6230 @item record @var{method}
6231 This command starts the process record and replay target. The
6232 recording method can be specified as parameter. Without a parameter
6233 the command uses the @code{full} recording method. The following
6234 recording methods are available:
6238 Full record/replay recording using @value{GDBN}'s software record and
6239 replay implementation. This method allows replaying and reverse
6243 Hardware-supported instruction recording. This method does not allow
6244 replaying and reverse execution.
6246 This recording method may not be available on all processors.
6249 The process record and replay target can only debug a process that is
6250 already running. Therefore, you need first to start the process with
6251 the @kbd{run} or @kbd{start} commands, and then start the recording
6252 with the @kbd{record @var{method}} command.
6254 Both @code{record @var{method}} and @code{rec @var{method}} are
6255 aliases of @code{target record-@var{method}}.
6257 @cindex displaced stepping, and process record and replay
6258 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6259 will be automatically disabled when process record and replay target
6260 is started. That's because the process record and replay target
6261 doesn't support displaced stepping.
6263 @cindex non-stop mode, and process record and replay
6264 @cindex asynchronous execution, and process record and replay
6265 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6266 the asynchronous execution mode (@pxref{Background Execution}), not
6267 all recording methods are available. The @code{full} recording method
6268 does not support these two modes.
6273 Stop the process record and replay target. When process record and
6274 replay target stops, the entire execution log will be deleted and the
6275 inferior will either be terminated, or will remain in its final state.
6277 When you stop the process record and replay target in record mode (at
6278 the end of the execution log), the inferior will be stopped at the
6279 next instruction that would have been recorded. In other words, if
6280 you record for a while and then stop recording, the inferior process
6281 will be left in the same state as if the recording never happened.
6283 On the other hand, if the process record and replay target is stopped
6284 while in replay mode (that is, not at the end of the execution log,
6285 but at some earlier point), the inferior process will become ``live''
6286 at that earlier state, and it will then be possible to continue the
6287 usual ``live'' debugging of the process from that state.
6289 When the inferior process exits, or @value{GDBN} detaches from it,
6290 process record and replay target will automatically stop itself.
6294 Go to a specific location in the execution log. There are several
6295 ways to specify the location to go to:
6298 @item record goto begin
6299 @itemx record goto start
6300 Go to the beginning of the execution log.
6302 @item record goto end
6303 Go to the end of the execution log.
6305 @item record goto @var{n}
6306 Go to instruction number @var{n} in the execution log.
6310 @item record save @var{filename}
6311 Save the execution log to a file @file{@var{filename}}.
6312 Default filename is @file{gdb_record.@var{process_id}}, where
6313 @var{process_id} is the process ID of the inferior.
6315 This command may not be available for all recording methods.
6317 @kindex record restore
6318 @item record restore @var{filename}
6319 Restore the execution log from a file @file{@var{filename}}.
6320 File must have been created with @code{record save}.
6322 @kindex set record full
6323 @item set record full insn-number-max @var{limit}
6324 @itemx set record full insn-number-max unlimited
6325 Set the limit of instructions to be recorded for the @code{full}
6326 recording method. Default value is 200000.
6328 If @var{limit} is a positive number, then @value{GDBN} will start
6329 deleting instructions from the log once the number of the record
6330 instructions becomes greater than @var{limit}. For every new recorded
6331 instruction, @value{GDBN} will delete the earliest recorded
6332 instruction to keep the number of recorded instructions at the limit.
6333 (Since deleting recorded instructions loses information, @value{GDBN}
6334 lets you control what happens when the limit is reached, by means of
6335 the @code{stop-at-limit} option, described below.)
6337 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6338 delete recorded instructions from the execution log. The number of
6339 recorded instructions is limited only by the available memory.
6341 @kindex show record full
6342 @item show record full insn-number-max
6343 Show the limit of instructions to be recorded with the @code{full}
6346 @item set record full stop-at-limit
6347 Control the behavior of the @code{full} recording method when the
6348 number of recorded instructions reaches the limit. If ON (the
6349 default), @value{GDBN} will stop when the limit is reached for the
6350 first time and ask you whether you want to stop the inferior or
6351 continue running it and recording the execution log. If you decide
6352 to continue recording, each new recorded instruction will cause the
6353 oldest one to be deleted.
6355 If this option is OFF, @value{GDBN} will automatically delete the
6356 oldest record to make room for each new one, without asking.
6358 @item show record full stop-at-limit
6359 Show the current setting of @code{stop-at-limit}.
6361 @item set record full memory-query
6362 Control the behavior when @value{GDBN} is unable to record memory
6363 changes caused by an instruction for the @code{full} recording method.
6364 If ON, @value{GDBN} will query whether to stop the inferior in that
6367 If this option is OFF (the default), @value{GDBN} will automatically
6368 ignore the effect of such instructions on memory. Later, when
6369 @value{GDBN} replays this execution log, it will mark the log of this
6370 instruction as not accessible, and it will not affect the replay
6373 @item show record full memory-query
6374 Show the current setting of @code{memory-query}.
6378 Show various statistics about the recording depending on the recording
6383 For the @code{full} recording method, it shows the state of process
6384 record and its in-memory execution log buffer, including:
6388 Whether in record mode or replay mode.
6390 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6392 Highest recorded instruction number.
6394 Current instruction about to be replayed (if in replay mode).
6396 Number of instructions contained in the execution log.
6398 Maximum number of instructions that may be contained in the execution log.
6402 For the @code{btrace} recording method, it shows the number of
6403 instructions that have been recorded and the number of blocks of
6404 sequential control-flow that is formed by the recorded instructions.
6407 @kindex record delete
6410 When record target runs in replay mode (``in the past''), delete the
6411 subsequent execution log and begin to record a new execution log starting
6412 from the current address. This means you will abandon the previously
6413 recorded ``future'' and begin recording a new ``future''.
6415 @kindex record instruction-history
6416 @kindex rec instruction-history
6417 @item record instruction-history
6418 Disassembles instructions from the recorded execution log. By
6419 default, ten instructions are disassembled. This can be changed using
6420 the @code{set record instruction-history-size} command. Instructions
6421 are printed in execution order. There are several ways to specify
6422 what part of the execution log to disassemble:
6425 @item record instruction-history @var{insn}
6426 Disassembles ten instructions starting from instruction number
6429 @item record instruction-history @var{insn}, +/-@var{n}
6430 Disassembles @var{n} instructions around instruction number
6431 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6432 @var{n} instructions after instruction number @var{insn}. If
6433 @var{n} is preceded with @code{-}, disassembles @var{n}
6434 instructions before instruction number @var{insn}.
6436 @item record instruction-history
6437 Disassembles ten more instructions after the last disassembly.
6439 @item record instruction-history -
6440 Disassembles ten more instructions before the last disassembly.
6442 @item record instruction-history @var{begin} @var{end}
6443 Disassembles instructions beginning with instruction number
6444 @var{begin} until instruction number @var{end}. The instruction
6445 number @var{end} is not included.
6448 This command may not be available for all recording methods.
6451 @item set record instruction-history-size @var{size}
6452 @itemx set record instruction-history-size unlimited
6453 Define how many instructions to disassemble in the @code{record
6454 instruction-history} command. The default value is 10.
6455 A @var{size} of @code{unlimited} means unlimited instructions.
6458 @item show record instruction-history-size
6459 Show how many instructions to disassemble in the @code{record
6460 instruction-history} command.
6462 @kindex record function-call-history
6463 @kindex rec function-call-history
6464 @item record function-call-history
6465 Prints the execution history at function granularity. It prints one
6466 line for each sequence of instructions that belong to the same
6467 function giving the name of that function, the source lines
6468 for this instruction sequence (if the @code{/l} modifier is
6469 specified), and the instructions numbers that form the sequence (if
6470 the @code{/i} modifier is specified).
6473 (@value{GDBP}) @b{list 1, 10}
6484 (@value{GDBP}) @b{record function-call-history /l}
6490 By default, ten lines are printed. This can be changed using the
6491 @code{set record function-call-history-size} command. Functions are
6492 printed in execution order. There are several ways to specify what
6496 @item record function-call-history @var{func}
6497 Prints ten functions starting from function number @var{func}.
6499 @item record function-call-history @var{func}, +/-@var{n}
6500 Prints @var{n} functions around function number @var{func}. If
6501 @var{n} is preceded with @code{+}, prints @var{n} functions after
6502 function number @var{func}. If @var{n} is preceded with @code{-},
6503 prints @var{n} functions before function number @var{func}.
6505 @item record function-call-history
6506 Prints ten more functions after the last ten-line print.
6508 @item record function-call-history -
6509 Prints ten more functions before the last ten-line print.
6511 @item record function-call-history @var{begin} @var{end}
6512 Prints functions beginning with function number @var{begin} until
6513 function number @var{end}. The function number @var{end} is not
6517 This command may not be available for all recording methods.
6519 @item set record function-call-history-size @var{size}
6520 @itemx set record function-call-history-size unlimited
6521 Define how many lines to print in the
6522 @code{record function-call-history} command. The default value is 10.
6523 A size of @code{unlimited} means unlimited lines.
6525 @item show record function-call-history-size
6526 Show how many lines to print in the
6527 @code{record function-call-history} command.
6532 @chapter Examining the Stack
6534 When your program has stopped, the first thing you need to know is where it
6535 stopped and how it got there.
6538 Each time your program performs a function call, information about the call
6540 That information includes the location of the call in your program,
6541 the arguments of the call,
6542 and the local variables of the function being called.
6543 The information is saved in a block of data called a @dfn{stack frame}.
6544 The stack frames are allocated in a region of memory called the @dfn{call
6547 When your program stops, the @value{GDBN} commands for examining the
6548 stack allow you to see all of this information.
6550 @cindex selected frame
6551 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6552 @value{GDBN} commands refer implicitly to the selected frame. In
6553 particular, whenever you ask @value{GDBN} for the value of a variable in
6554 your program, the value is found in the selected frame. There are
6555 special @value{GDBN} commands to select whichever frame you are
6556 interested in. @xref{Selection, ,Selecting a Frame}.
6558 When your program stops, @value{GDBN} automatically selects the
6559 currently executing frame and describes it briefly, similar to the
6560 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6563 * Frames:: Stack frames
6564 * Backtrace:: Backtraces
6565 * Frame Filter Management:: Managing frame filters
6566 * Selection:: Selecting a frame
6567 * Frame Info:: Information on a frame
6572 @section Stack Frames
6574 @cindex frame, definition
6576 The call stack is divided up into contiguous pieces called @dfn{stack
6577 frames}, or @dfn{frames} for short; each frame is the data associated
6578 with one call to one function. The frame contains the arguments given
6579 to the function, the function's local variables, and the address at
6580 which the function is executing.
6582 @cindex initial frame
6583 @cindex outermost frame
6584 @cindex innermost frame
6585 When your program is started, the stack has only one frame, that of the
6586 function @code{main}. This is called the @dfn{initial} frame or the
6587 @dfn{outermost} frame. Each time a function is called, a new frame is
6588 made. Each time a function returns, the frame for that function invocation
6589 is eliminated. If a function is recursive, there can be many frames for
6590 the same function. The frame for the function in which execution is
6591 actually occurring is called the @dfn{innermost} frame. This is the most
6592 recently created of all the stack frames that still exist.
6594 @cindex frame pointer
6595 Inside your program, stack frames are identified by their addresses. A
6596 stack frame consists of many bytes, each of which has its own address; each
6597 kind of computer has a convention for choosing one byte whose
6598 address serves as the address of the frame. Usually this address is kept
6599 in a register called the @dfn{frame pointer register}
6600 (@pxref{Registers, $fp}) while execution is going on in that frame.
6602 @cindex frame number
6603 @value{GDBN} assigns numbers to all existing stack frames, starting with
6604 zero for the innermost frame, one for the frame that called it,
6605 and so on upward. These numbers do not really exist in your program;
6606 they are assigned by @value{GDBN} to give you a way of designating stack
6607 frames in @value{GDBN} commands.
6609 @c The -fomit-frame-pointer below perennially causes hbox overflow
6610 @c underflow problems.
6611 @cindex frameless execution
6612 Some compilers provide a way to compile functions so that they operate
6613 without stack frames. (For example, the @value{NGCC} option
6615 @samp{-fomit-frame-pointer}
6617 generates functions without a frame.)
6618 This is occasionally done with heavily used library functions to save
6619 the frame setup time. @value{GDBN} has limited facilities for dealing
6620 with these function invocations. If the innermost function invocation
6621 has no stack frame, @value{GDBN} nevertheless regards it as though
6622 it had a separate frame, which is numbered zero as usual, allowing
6623 correct tracing of the function call chain. However, @value{GDBN} has
6624 no provision for frameless functions elsewhere in the stack.
6627 @kindex frame@r{, command}
6628 @cindex current stack frame
6629 @item frame @var{args}
6630 The @code{frame} command allows you to move from one stack frame to another,
6631 and to print the stack frame you select. @var{args} may be either the
6632 address of the frame or the stack frame number. Without an argument,
6633 @code{frame} prints the current stack frame.
6635 @kindex select-frame
6636 @cindex selecting frame silently
6638 The @code{select-frame} command allows you to move from one stack frame
6639 to another without printing the frame. This is the silent version of
6647 @cindex call stack traces
6648 A backtrace is a summary of how your program got where it is. It shows one
6649 line per frame, for many frames, starting with the currently executing
6650 frame (frame zero), followed by its caller (frame one), and on up the
6653 @anchor{backtrace-command}
6656 @kindex bt @r{(@code{backtrace})}
6659 Print a backtrace of the entire stack: one line per frame for all
6660 frames in the stack.
6662 You can stop the backtrace at any time by typing the system interrupt
6663 character, normally @kbd{Ctrl-c}.
6665 @item backtrace @var{n}
6667 Similar, but print only the innermost @var{n} frames.
6669 @item backtrace -@var{n}
6671 Similar, but print only the outermost @var{n} frames.
6673 @item backtrace full
6675 @itemx bt full @var{n}
6676 @itemx bt full -@var{n}
6677 Print the values of the local variables also. @var{n} specifies the
6678 number of frames to print, as described above.
6680 @item backtrace no-filters
6681 @itemx bt no-filters
6682 @itemx bt no-filters @var{n}
6683 @itemx bt no-filters -@var{n}
6684 @itemx bt no-filters full
6685 @itemx bt no-filters full @var{n}
6686 @itemx bt no-filters full -@var{n}
6687 Do not run Python frame filters on this backtrace. @xref{Frame
6688 Filter API}, for more information. Additionally use @ref{disable
6689 frame-filter all} to turn off all frame filters. This is only
6690 relevant when @value{GDBN} has been configured with @code{Python}
6696 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6697 are additional aliases for @code{backtrace}.
6699 @cindex multiple threads, backtrace
6700 In a multi-threaded program, @value{GDBN} by default shows the
6701 backtrace only for the current thread. To display the backtrace for
6702 several or all of the threads, use the command @code{thread apply}
6703 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6704 apply all backtrace}, @value{GDBN} will display the backtrace for all
6705 the threads; this is handy when you debug a core dump of a
6706 multi-threaded program.
6708 Each line in the backtrace shows the frame number and the function name.
6709 The program counter value is also shown---unless you use @code{set
6710 print address off}. The backtrace also shows the source file name and
6711 line number, as well as the arguments to the function. The program
6712 counter value is omitted if it is at the beginning of the code for that
6715 Here is an example of a backtrace. It was made with the command
6716 @samp{bt 3}, so it shows the innermost three frames.
6720 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6722 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6723 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6725 (More stack frames follow...)
6730 The display for frame zero does not begin with a program counter
6731 value, indicating that your program has stopped at the beginning of the
6732 code for line @code{993} of @code{builtin.c}.
6735 The value of parameter @code{data} in frame 1 has been replaced by
6736 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6737 only if it is a scalar (integer, pointer, enumeration, etc). See command
6738 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6739 on how to configure the way function parameter values are printed.
6741 @cindex optimized out, in backtrace
6742 @cindex function call arguments, optimized out
6743 If your program was compiled with optimizations, some compilers will
6744 optimize away arguments passed to functions if those arguments are
6745 never used after the call. Such optimizations generate code that
6746 passes arguments through registers, but doesn't store those arguments
6747 in the stack frame. @value{GDBN} has no way of displaying such
6748 arguments in stack frames other than the innermost one. Here's what
6749 such a backtrace might look like:
6753 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6755 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6756 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6758 (More stack frames follow...)
6763 The values of arguments that were not saved in their stack frames are
6764 shown as @samp{<optimized out>}.
6766 If you need to display the values of such optimized-out arguments,
6767 either deduce that from other variables whose values depend on the one
6768 you are interested in, or recompile without optimizations.
6770 @cindex backtrace beyond @code{main} function
6771 @cindex program entry point
6772 @cindex startup code, and backtrace
6773 Most programs have a standard user entry point---a place where system
6774 libraries and startup code transition into user code. For C this is
6775 @code{main}@footnote{
6776 Note that embedded programs (the so-called ``free-standing''
6777 environment) are not required to have a @code{main} function as the
6778 entry point. They could even have multiple entry points.}.
6779 When @value{GDBN} finds the entry function in a backtrace
6780 it will terminate the backtrace, to avoid tracing into highly
6781 system-specific (and generally uninteresting) code.
6783 If you need to examine the startup code, or limit the number of levels
6784 in a backtrace, you can change this behavior:
6787 @item set backtrace past-main
6788 @itemx set backtrace past-main on
6789 @kindex set backtrace
6790 Backtraces will continue past the user entry point.
6792 @item set backtrace past-main off
6793 Backtraces will stop when they encounter the user entry point. This is the
6796 @item show backtrace past-main
6797 @kindex show backtrace
6798 Display the current user entry point backtrace policy.
6800 @item set backtrace past-entry
6801 @itemx set backtrace past-entry on
6802 Backtraces will continue past the internal entry point of an application.
6803 This entry point is encoded by the linker when the application is built,
6804 and is likely before the user entry point @code{main} (or equivalent) is called.
6806 @item set backtrace past-entry off
6807 Backtraces will stop when they encounter the internal entry point of an
6808 application. This is the default.
6810 @item show backtrace past-entry
6811 Display the current internal entry point backtrace policy.
6813 @item set backtrace limit @var{n}
6814 @itemx set backtrace limit 0
6815 @itemx set backtrace limit unlimited
6816 @cindex backtrace limit
6817 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6818 or zero means unlimited levels.
6820 @item show backtrace limit
6821 Display the current limit on backtrace levels.
6824 You can control how file names are displayed.
6827 @item set filename-display
6828 @itemx set filename-display relative
6829 @cindex filename-display
6830 Display file names relative to the compilation directory. This is the default.
6832 @item set filename-display basename
6833 Display only basename of a filename.
6835 @item set filename-display absolute
6836 Display an absolute filename.
6838 @item show filename-display
6839 Show the current way to display filenames.
6842 @node Frame Filter Management
6843 @section Management of Frame Filters.
6844 @cindex managing frame filters
6846 Frame filters are Python based utilities to manage and decorate the
6847 output of frames. @xref{Frame Filter API}, for further information.
6849 Managing frame filters is performed by several commands available
6850 within @value{GDBN}, detailed here.
6853 @kindex info frame-filter
6854 @item info frame-filter
6855 Print a list of installed frame filters from all dictionaries, showing
6856 their name, priority and enabled status.
6858 @kindex disable frame-filter
6859 @anchor{disable frame-filter all}
6860 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6861 Disable a frame filter in the dictionary matching
6862 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6863 @var{filter-dictionary} may be @code{all}, @code{global},
6864 @code{progspace} or the name of the object file where the frame filter
6865 dictionary resides. When @code{all} is specified, all frame filters
6866 across all dictionaries are disabled. @var{filter-name} is the name
6867 of the frame filter and is used when @code{all} is not the option for
6868 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6869 may be enabled again later.
6871 @kindex enable frame-filter
6872 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6873 Enable a frame filter in the dictionary matching
6874 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6875 @var{filter-dictionary} may be @code{all}, @code{global},
6876 @code{progspace} or the name of the object file where the frame filter
6877 dictionary resides. When @code{all} is specified, all frame filters across
6878 all dictionaries are enabled. @var{filter-name} is the name of the frame
6879 filter and is used when @code{all} is not the option for
6880 @var{filter-dictionary}.
6885 (gdb) info frame-filter
6887 global frame-filters:
6888 Priority Enabled Name
6889 1000 No PrimaryFunctionFilter
6892 progspace /build/test frame-filters:
6893 Priority Enabled Name
6894 100 Yes ProgspaceFilter
6896 objfile /build/test frame-filters:
6897 Priority Enabled Name
6898 999 Yes BuildProgra Filter
6900 (gdb) disable frame-filter /build/test BuildProgramFilter
6901 (gdb) info frame-filter
6903 global frame-filters:
6904 Priority Enabled Name
6905 1000 No PrimaryFunctionFilter
6908 progspace /build/test frame-filters:
6909 Priority Enabled Name
6910 100 Yes ProgspaceFilter
6912 objfile /build/test frame-filters:
6913 Priority Enabled Name
6914 999 No BuildProgramFilter
6916 (gdb) enable frame-filter global PrimaryFunctionFilter
6917 (gdb) info frame-filter
6919 global frame-filters:
6920 Priority Enabled Name
6921 1000 Yes PrimaryFunctionFilter
6924 progspace /build/test frame-filters:
6925 Priority Enabled Name
6926 100 Yes ProgspaceFilter
6928 objfile /build/test frame-filters:
6929 Priority Enabled Name
6930 999 No BuildProgramFilter
6933 @kindex set frame-filter priority
6934 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6935 Set the @var{priority} of a frame filter in the dictionary matching
6936 @var{filter-dictionary}, and the frame filter name matching
6937 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6938 @code{progspace} or the name of the object file where the frame filter
6939 dictionary resides. @var{priority} is an integer.
6941 @kindex show frame-filter priority
6942 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6943 Show the @var{priority} of a frame filter in the dictionary matching
6944 @var{filter-dictionary}, and the frame filter name matching
6945 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6946 @code{progspace} or the name of the object file where the frame filter
6952 (gdb) info frame-filter
6954 global frame-filters:
6955 Priority Enabled Name
6956 1000 Yes PrimaryFunctionFilter
6959 progspace /build/test frame-filters:
6960 Priority Enabled Name
6961 100 Yes ProgspaceFilter
6963 objfile /build/test frame-filters:
6964 Priority Enabled Name
6965 999 No BuildProgramFilter
6967 (gdb) set frame-filter priority global Reverse 50
6968 (gdb) info frame-filter
6970 global frame-filters:
6971 Priority Enabled Name
6972 1000 Yes PrimaryFunctionFilter
6975 progspace /build/test frame-filters:
6976 Priority Enabled Name
6977 100 Yes ProgspaceFilter
6979 objfile /build/test frame-filters:
6980 Priority Enabled Name
6981 999 No BuildProgramFilter
6986 @section Selecting a Frame
6988 Most commands for examining the stack and other data in your program work on
6989 whichever stack frame is selected at the moment. Here are the commands for
6990 selecting a stack frame; all of them finish by printing a brief description
6991 of the stack frame just selected.
6994 @kindex frame@r{, selecting}
6995 @kindex f @r{(@code{frame})}
6998 Select frame number @var{n}. Recall that frame zero is the innermost
6999 (currently executing) frame, frame one is the frame that called the
7000 innermost one, and so on. The highest-numbered frame is the one for
7003 @item frame @var{addr}
7005 Select the frame at address @var{addr}. This is useful mainly if the
7006 chaining of stack frames has been damaged by a bug, making it
7007 impossible for @value{GDBN} to assign numbers properly to all frames. In
7008 addition, this can be useful when your program has multiple stacks and
7009 switches between them.
7011 On the SPARC architecture, @code{frame} needs two addresses to
7012 select an arbitrary frame: a frame pointer and a stack pointer.
7014 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7015 pointer and a program counter.
7017 On the 29k architecture, it needs three addresses: a register stack
7018 pointer, a program counter, and a memory stack pointer.
7022 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7023 advances toward the outermost frame, to higher frame numbers, to frames
7024 that have existed longer. @var{n} defaults to one.
7027 @kindex do @r{(@code{down})}
7029 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7030 advances toward the innermost frame, to lower frame numbers, to frames
7031 that were created more recently. @var{n} defaults to one. You may
7032 abbreviate @code{down} as @code{do}.
7035 All of these commands end by printing two lines of output describing the
7036 frame. The first line shows the frame number, the function name, the
7037 arguments, and the source file and line number of execution in that
7038 frame. The second line shows the text of that source line.
7046 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7048 10 read_input_file (argv[i]);
7052 After such a printout, the @code{list} command with no arguments
7053 prints ten lines centered on the point of execution in the frame.
7054 You can also edit the program at the point of execution with your favorite
7055 editing program by typing @code{edit}.
7056 @xref{List, ,Printing Source Lines},
7060 @kindex down-silently
7062 @item up-silently @var{n}
7063 @itemx down-silently @var{n}
7064 These two commands are variants of @code{up} and @code{down},
7065 respectively; they differ in that they do their work silently, without
7066 causing display of the new frame. They are intended primarily for use
7067 in @value{GDBN} command scripts, where the output might be unnecessary and
7072 @section Information About a Frame
7074 There are several other commands to print information about the selected
7080 When used without any argument, this command does not change which
7081 frame is selected, but prints a brief description of the currently
7082 selected stack frame. It can be abbreviated @code{f}. With an
7083 argument, this command is used to select a stack frame.
7084 @xref{Selection, ,Selecting a Frame}.
7087 @kindex info f @r{(@code{info frame})}
7090 This command prints a verbose description of the selected stack frame,
7095 the address of the frame
7097 the address of the next frame down (called by this frame)
7099 the address of the next frame up (caller of this frame)
7101 the language in which the source code corresponding to this frame is written
7103 the address of the frame's arguments
7105 the address of the frame's local variables
7107 the program counter saved in it (the address of execution in the caller frame)
7109 which registers were saved in the frame
7112 @noindent The verbose description is useful when
7113 something has gone wrong that has made the stack format fail to fit
7114 the usual conventions.
7116 @item info frame @var{addr}
7117 @itemx info f @var{addr}
7118 Print a verbose description of the frame at address @var{addr}, without
7119 selecting that frame. The selected frame remains unchanged by this
7120 command. This requires the same kind of address (more than one for some
7121 architectures) that you specify in the @code{frame} command.
7122 @xref{Selection, ,Selecting a Frame}.
7126 Print the arguments of the selected frame, each on a separate line.
7130 Print the local variables of the selected frame, each on a separate
7131 line. These are all variables (declared either static or automatic)
7132 accessible at the point of execution of the selected frame.
7138 @chapter Examining Source Files
7140 @value{GDBN} can print parts of your program's source, since the debugging
7141 information recorded in the program tells @value{GDBN} what source files were
7142 used to build it. When your program stops, @value{GDBN} spontaneously prints
7143 the line where it stopped. Likewise, when you select a stack frame
7144 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7145 execution in that frame has stopped. You can print other portions of
7146 source files by explicit command.
7148 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7149 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7150 @value{GDBN} under @sc{gnu} Emacs}.
7153 * List:: Printing source lines
7154 * Specify Location:: How to specify code locations
7155 * Edit:: Editing source files
7156 * Search:: Searching source files
7157 * Source Path:: Specifying source directories
7158 * Machine Code:: Source and machine code
7162 @section Printing Source Lines
7165 @kindex l @r{(@code{list})}
7166 To print lines from a source file, use the @code{list} command
7167 (abbreviated @code{l}). By default, ten lines are printed.
7168 There are several ways to specify what part of the file you want to
7169 print; see @ref{Specify Location}, for the full list.
7171 Here are the forms of the @code{list} command most commonly used:
7174 @item list @var{linenum}
7175 Print lines centered around line number @var{linenum} in the
7176 current source file.
7178 @item list @var{function}
7179 Print lines centered around the beginning of function
7183 Print more lines. If the last lines printed were printed with a
7184 @code{list} command, this prints lines following the last lines
7185 printed; however, if the last line printed was a solitary line printed
7186 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7187 Stack}), this prints lines centered around that line.
7190 Print lines just before the lines last printed.
7193 @cindex @code{list}, how many lines to display
7194 By default, @value{GDBN} prints ten source lines with any of these forms of
7195 the @code{list} command. You can change this using @code{set listsize}:
7198 @kindex set listsize
7199 @item set listsize @var{count}
7200 @itemx set listsize unlimited
7201 Make the @code{list} command display @var{count} source lines (unless
7202 the @code{list} argument explicitly specifies some other number).
7203 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7205 @kindex show listsize
7207 Display the number of lines that @code{list} prints.
7210 Repeating a @code{list} command with @key{RET} discards the argument,
7211 so it is equivalent to typing just @code{list}. This is more useful
7212 than listing the same lines again. An exception is made for an
7213 argument of @samp{-}; that argument is preserved in repetition so that
7214 each repetition moves up in the source file.
7216 In general, the @code{list} command expects you to supply zero, one or two
7217 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7218 of writing them (@pxref{Specify Location}), but the effect is always
7219 to specify some source line.
7221 Here is a complete description of the possible arguments for @code{list}:
7224 @item list @var{linespec}
7225 Print lines centered around the line specified by @var{linespec}.
7227 @item list @var{first},@var{last}
7228 Print lines from @var{first} to @var{last}. Both arguments are
7229 linespecs. When a @code{list} command has two linespecs, and the
7230 source file of the second linespec is omitted, this refers to
7231 the same source file as the first linespec.
7233 @item list ,@var{last}
7234 Print lines ending with @var{last}.
7236 @item list @var{first},
7237 Print lines starting with @var{first}.
7240 Print lines just after the lines last printed.
7243 Print lines just before the lines last printed.
7246 As described in the preceding table.
7249 @node Specify Location
7250 @section Specifying a Location
7251 @cindex specifying location
7254 Several @value{GDBN} commands accept arguments that specify a location
7255 of your program's code. Since @value{GDBN} is a source-level
7256 debugger, a location usually specifies some line in the source code;
7257 for that reason, locations are also known as @dfn{linespecs}.
7259 Here are all the different ways of specifying a code location that
7260 @value{GDBN} understands:
7264 Specifies the line number @var{linenum} of the current source file.
7267 @itemx +@var{offset}
7268 Specifies the line @var{offset} lines before or after the @dfn{current
7269 line}. For the @code{list} command, the current line is the last one
7270 printed; for the breakpoint commands, this is the line at which
7271 execution stopped in the currently selected @dfn{stack frame}
7272 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7273 used as the second of the two linespecs in a @code{list} command,
7274 this specifies the line @var{offset} lines up or down from the first
7277 @item @var{filename}:@var{linenum}
7278 Specifies the line @var{linenum} in the source file @var{filename}.
7279 If @var{filename} is a relative file name, then it will match any
7280 source file name with the same trailing components. For example, if
7281 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7282 name of @file{/build/trunk/gcc/expr.c}, but not
7283 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7285 @item @var{function}
7286 Specifies the line that begins the body of the function @var{function}.
7287 For example, in C, this is the line with the open brace.
7289 @item @var{function}:@var{label}
7290 Specifies the line where @var{label} appears in @var{function}.
7292 @item @var{filename}:@var{function}
7293 Specifies the line that begins the body of the function @var{function}
7294 in the file @var{filename}. You only need the file name with a
7295 function name to avoid ambiguity when there are identically named
7296 functions in different source files.
7299 Specifies the line at which the label named @var{label} appears.
7300 @value{GDBN} searches for the label in the function corresponding to
7301 the currently selected stack frame. If there is no current selected
7302 stack frame (for instance, if the inferior is not running), then
7303 @value{GDBN} will not search for a label.
7305 @item *@var{address}
7306 Specifies the program address @var{address}. For line-oriented
7307 commands, such as @code{list} and @code{edit}, this specifies a source
7308 line that contains @var{address}. For @code{break} and other
7309 breakpoint oriented commands, this can be used to set breakpoints in
7310 parts of your program which do not have debugging information or
7313 Here @var{address} may be any expression valid in the current working
7314 language (@pxref{Languages, working language}) that specifies a code
7315 address. In addition, as a convenience, @value{GDBN} extends the
7316 semantics of expressions used in locations to cover the situations
7317 that frequently happen during debugging. Here are the various forms
7321 @item @var{expression}
7322 Any expression valid in the current working language.
7324 @item @var{funcaddr}
7325 An address of a function or procedure derived from its name. In C,
7326 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7327 simply the function's name @var{function} (and actually a special case
7328 of a valid expression). In Pascal and Modula-2, this is
7329 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7330 (although the Pascal form also works).
7332 This form specifies the address of the function's first instruction,
7333 before the stack frame and arguments have been set up.
7335 @item '@var{filename}'::@var{funcaddr}
7336 Like @var{funcaddr} above, but also specifies the name of the source
7337 file explicitly. This is useful if the name of the function does not
7338 specify the function unambiguously, e.g., if there are several
7339 functions with identical names in different source files.
7342 @cindex breakpoint at static probe point
7343 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7344 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7345 applications to embed static probes. @xref{Static Probe Points}, for more
7346 information on finding and using static probes. This form of linespec
7347 specifies the location of such a static probe.
7349 If @var{objfile} is given, only probes coming from that shared library
7350 or executable matching @var{objfile} as a regular expression are considered.
7351 If @var{provider} is given, then only probes from that provider are considered.
7352 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7353 each one of those probes.
7359 @section Editing Source Files
7360 @cindex editing source files
7363 @kindex e @r{(@code{edit})}
7364 To edit the lines in a source file, use the @code{edit} command.
7365 The editing program of your choice
7366 is invoked with the current line set to
7367 the active line in the program.
7368 Alternatively, there are several ways to specify what part of the file you
7369 want to print if you want to see other parts of the program:
7372 @item edit @var{location}
7373 Edit the source file specified by @code{location}. Editing starts at
7374 that @var{location}, e.g., at the specified source line of the
7375 specified file. @xref{Specify Location}, for all the possible forms
7376 of the @var{location} argument; here are the forms of the @code{edit}
7377 command most commonly used:
7380 @item edit @var{number}
7381 Edit the current source file with @var{number} as the active line number.
7383 @item edit @var{function}
7384 Edit the file containing @var{function} at the beginning of its definition.
7389 @subsection Choosing your Editor
7390 You can customize @value{GDBN} to use any editor you want
7392 The only restriction is that your editor (say @code{ex}), recognizes the
7393 following command-line syntax:
7395 ex +@var{number} file
7397 The optional numeric value +@var{number} specifies the number of the line in
7398 the file where to start editing.}.
7399 By default, it is @file{@value{EDITOR}}, but you can change this
7400 by setting the environment variable @code{EDITOR} before using
7401 @value{GDBN}. For example, to configure @value{GDBN} to use the
7402 @code{vi} editor, you could use these commands with the @code{sh} shell:
7408 or in the @code{csh} shell,
7410 setenv EDITOR /usr/bin/vi
7415 @section Searching Source Files
7416 @cindex searching source files
7418 There are two commands for searching through the current source file for a
7423 @kindex forward-search
7424 @kindex fo @r{(@code{forward-search})}
7425 @item forward-search @var{regexp}
7426 @itemx search @var{regexp}
7427 The command @samp{forward-search @var{regexp}} checks each line,
7428 starting with the one following the last line listed, for a match for
7429 @var{regexp}. It lists the line that is found. You can use the
7430 synonym @samp{search @var{regexp}} or abbreviate the command name as
7433 @kindex reverse-search
7434 @item reverse-search @var{regexp}
7435 The command @samp{reverse-search @var{regexp}} checks each line, starting
7436 with the one before the last line listed and going backward, for a match
7437 for @var{regexp}. It lists the line that is found. You can abbreviate
7438 this command as @code{rev}.
7442 @section Specifying Source Directories
7445 @cindex directories for source files
7446 Executable programs sometimes do not record the directories of the source
7447 files from which they were compiled, just the names. Even when they do,
7448 the directories could be moved between the compilation and your debugging
7449 session. @value{GDBN} has a list of directories to search for source files;
7450 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7451 it tries all the directories in the list, in the order they are present
7452 in the list, until it finds a file with the desired name.
7454 For example, suppose an executable references the file
7455 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7456 @file{/mnt/cross}. The file is first looked up literally; if this
7457 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7458 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7459 message is printed. @value{GDBN} does not look up the parts of the
7460 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7461 Likewise, the subdirectories of the source path are not searched: if
7462 the source path is @file{/mnt/cross}, and the binary refers to
7463 @file{foo.c}, @value{GDBN} would not find it under
7464 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7466 Plain file names, relative file names with leading directories, file
7467 names containing dots, etc.@: are all treated as described above; for
7468 instance, if the source path is @file{/mnt/cross}, and the source file
7469 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7470 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7471 that---@file{/mnt/cross/foo.c}.
7473 Note that the executable search path is @emph{not} used to locate the
7476 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7477 any information it has cached about where source files are found and where
7478 each line is in the file.
7482 When you start @value{GDBN}, its source path includes only @samp{cdir}
7483 and @samp{cwd}, in that order.
7484 To add other directories, use the @code{directory} command.
7486 The search path is used to find both program source files and @value{GDBN}
7487 script files (read using the @samp{-command} option and @samp{source} command).
7489 In addition to the source path, @value{GDBN} provides a set of commands
7490 that manage a list of source path substitution rules. A @dfn{substitution
7491 rule} specifies how to rewrite source directories stored in the program's
7492 debug information in case the sources were moved to a different
7493 directory between compilation and debugging. A rule is made of
7494 two strings, the first specifying what needs to be rewritten in
7495 the path, and the second specifying how it should be rewritten.
7496 In @ref{set substitute-path}, we name these two parts @var{from} and
7497 @var{to} respectively. @value{GDBN} does a simple string replacement
7498 of @var{from} with @var{to} at the start of the directory part of the
7499 source file name, and uses that result instead of the original file
7500 name to look up the sources.
7502 Using the previous example, suppose the @file{foo-1.0} tree has been
7503 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7504 @value{GDBN} to replace @file{/usr/src} in all source path names with
7505 @file{/mnt/cross}. The first lookup will then be
7506 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7507 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7508 substitution rule, use the @code{set substitute-path} command
7509 (@pxref{set substitute-path}).
7511 To avoid unexpected substitution results, a rule is applied only if the
7512 @var{from} part of the directory name ends at a directory separator.
7513 For instance, a rule substituting @file{/usr/source} into
7514 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7515 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7516 is applied only at the beginning of the directory name, this rule will
7517 not be applied to @file{/root/usr/source/baz.c} either.
7519 In many cases, you can achieve the same result using the @code{directory}
7520 command. However, @code{set substitute-path} can be more efficient in
7521 the case where the sources are organized in a complex tree with multiple
7522 subdirectories. With the @code{directory} command, you need to add each
7523 subdirectory of your project. If you moved the entire tree while
7524 preserving its internal organization, then @code{set substitute-path}
7525 allows you to direct the debugger to all the sources with one single
7528 @code{set substitute-path} is also more than just a shortcut command.
7529 The source path is only used if the file at the original location no
7530 longer exists. On the other hand, @code{set substitute-path} modifies
7531 the debugger behavior to look at the rewritten location instead. So, if
7532 for any reason a source file that is not relevant to your executable is
7533 located at the original location, a substitution rule is the only
7534 method available to point @value{GDBN} at the new location.
7536 @cindex @samp{--with-relocated-sources}
7537 @cindex default source path substitution
7538 You can configure a default source path substitution rule by
7539 configuring @value{GDBN} with the
7540 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7541 should be the name of a directory under @value{GDBN}'s configured
7542 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7543 directory names in debug information under @var{dir} will be adjusted
7544 automatically if the installed @value{GDBN} is moved to a new
7545 location. This is useful if @value{GDBN}, libraries or executables
7546 with debug information and corresponding source code are being moved
7550 @item directory @var{dirname} @dots{}
7551 @item dir @var{dirname} @dots{}
7552 Add directory @var{dirname} to the front of the source path. Several
7553 directory names may be given to this command, separated by @samp{:}
7554 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7555 part of absolute file names) or
7556 whitespace. You may specify a directory that is already in the source
7557 path; this moves it forward, so @value{GDBN} searches it sooner.
7561 @vindex $cdir@r{, convenience variable}
7562 @vindex $cwd@r{, convenience variable}
7563 @cindex compilation directory
7564 @cindex current directory
7565 @cindex working directory
7566 @cindex directory, current
7567 @cindex directory, compilation
7568 You can use the string @samp{$cdir} to refer to the compilation
7569 directory (if one is recorded), and @samp{$cwd} to refer to the current
7570 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7571 tracks the current working directory as it changes during your @value{GDBN}
7572 session, while the latter is immediately expanded to the current
7573 directory at the time you add an entry to the source path.
7576 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7578 @c RET-repeat for @code{directory} is explicitly disabled, but since
7579 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7581 @item set directories @var{path-list}
7582 @kindex set directories
7583 Set the source path to @var{path-list}.
7584 @samp{$cdir:$cwd} are added if missing.
7586 @item show directories
7587 @kindex show directories
7588 Print the source path: show which directories it contains.
7590 @anchor{set substitute-path}
7591 @item set substitute-path @var{from} @var{to}
7592 @kindex set substitute-path
7593 Define a source path substitution rule, and add it at the end of the
7594 current list of existing substitution rules. If a rule with the same
7595 @var{from} was already defined, then the old rule is also deleted.
7597 For example, if the file @file{/foo/bar/baz.c} was moved to
7598 @file{/mnt/cross/baz.c}, then the command
7601 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7605 will tell @value{GDBN} to replace @samp{/usr/src} with
7606 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7607 @file{baz.c} even though it was moved.
7609 In the case when more than one substitution rule have been defined,
7610 the rules are evaluated one by one in the order where they have been
7611 defined. The first one matching, if any, is selected to perform
7614 For instance, if we had entered the following commands:
7617 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7618 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7622 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7623 @file{/mnt/include/defs.h} by using the first rule. However, it would
7624 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7625 @file{/mnt/src/lib/foo.c}.
7628 @item unset substitute-path [path]
7629 @kindex unset substitute-path
7630 If a path is specified, search the current list of substitution rules
7631 for a rule that would rewrite that path. Delete that rule if found.
7632 A warning is emitted by the debugger if no rule could be found.
7634 If no path is specified, then all substitution rules are deleted.
7636 @item show substitute-path [path]
7637 @kindex show substitute-path
7638 If a path is specified, then print the source path substitution rule
7639 which would rewrite that path, if any.
7641 If no path is specified, then print all existing source path substitution
7646 If your source path is cluttered with directories that are no longer of
7647 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7648 versions of source. You can correct the situation as follows:
7652 Use @code{directory} with no argument to reset the source path to its default value.
7655 Use @code{directory} with suitable arguments to reinstall the
7656 directories you want in the source path. You can add all the
7657 directories in one command.
7661 @section Source and Machine Code
7662 @cindex source line and its code address
7664 You can use the command @code{info line} to map source lines to program
7665 addresses (and vice versa), and the command @code{disassemble} to display
7666 a range of addresses as machine instructions. You can use the command
7667 @code{set disassemble-next-line} to set whether to disassemble next
7668 source line when execution stops. When run under @sc{gnu} Emacs
7669 mode, the @code{info line} command causes the arrow to point to the
7670 line specified. Also, @code{info line} prints addresses in symbolic form as
7675 @item info line @var{linespec}
7676 Print the starting and ending addresses of the compiled code for
7677 source line @var{linespec}. You can specify source lines in any of
7678 the ways documented in @ref{Specify Location}.
7681 For example, we can use @code{info line} to discover the location of
7682 the object code for the first line of function
7683 @code{m4_changequote}:
7685 @c FIXME: I think this example should also show the addresses in
7686 @c symbolic form, as they usually would be displayed.
7688 (@value{GDBP}) info line m4_changequote
7689 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7693 @cindex code address and its source line
7694 We can also inquire (using @code{*@var{addr}} as the form for
7695 @var{linespec}) what source line covers a particular address:
7697 (@value{GDBP}) info line *0x63ff
7698 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7701 @cindex @code{$_} and @code{info line}
7702 @cindex @code{x} command, default address
7703 @kindex x@r{(examine), and} info line
7704 After @code{info line}, the default address for the @code{x} command
7705 is changed to the starting address of the line, so that @samp{x/i} is
7706 sufficient to begin examining the machine code (@pxref{Memory,
7707 ,Examining Memory}). Also, this address is saved as the value of the
7708 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7713 @cindex assembly instructions
7714 @cindex instructions, assembly
7715 @cindex machine instructions
7716 @cindex listing machine instructions
7718 @itemx disassemble /m
7719 @itemx disassemble /r
7720 This specialized command dumps a range of memory as machine
7721 instructions. It can also print mixed source+disassembly by specifying
7722 the @code{/m} modifier and print the raw instructions in hex as well as
7723 in symbolic form by specifying the @code{/r}.
7724 The default memory range is the function surrounding the
7725 program counter of the selected frame. A single argument to this
7726 command is a program counter value; @value{GDBN} dumps the function
7727 surrounding this value. When two arguments are given, they should
7728 be separated by a comma, possibly surrounded by whitespace. The
7729 arguments specify a range of addresses to dump, in one of two forms:
7732 @item @var{start},@var{end}
7733 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7734 @item @var{start},+@var{length}
7735 the addresses from @var{start} (inclusive) to
7736 @code{@var{start}+@var{length}} (exclusive).
7740 When 2 arguments are specified, the name of the function is also
7741 printed (since there could be several functions in the given range).
7743 The argument(s) can be any expression yielding a numeric value, such as
7744 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7746 If the range of memory being disassembled contains current program counter,
7747 the instruction at that location is shown with a @code{=>} marker.
7750 The following example shows the disassembly of a range of addresses of
7751 HP PA-RISC 2.0 code:
7754 (@value{GDBP}) disas 0x32c4, 0x32e4
7755 Dump of assembler code from 0x32c4 to 0x32e4:
7756 0x32c4 <main+204>: addil 0,dp
7757 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7758 0x32cc <main+212>: ldil 0x3000,r31
7759 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7760 0x32d4 <main+220>: ldo 0(r31),rp
7761 0x32d8 <main+224>: addil -0x800,dp
7762 0x32dc <main+228>: ldo 0x588(r1),r26
7763 0x32e0 <main+232>: ldil 0x3000,r31
7764 End of assembler dump.
7767 Here is an example showing mixed source+assembly for Intel x86, when the
7768 program is stopped just after function prologue:
7771 (@value{GDBP}) disas /m main
7772 Dump of assembler code for function main:
7774 0x08048330 <+0>: push %ebp
7775 0x08048331 <+1>: mov %esp,%ebp
7776 0x08048333 <+3>: sub $0x8,%esp
7777 0x08048336 <+6>: and $0xfffffff0,%esp
7778 0x08048339 <+9>: sub $0x10,%esp
7780 6 printf ("Hello.\n");
7781 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7782 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7786 0x08048348 <+24>: mov $0x0,%eax
7787 0x0804834d <+29>: leave
7788 0x0804834e <+30>: ret
7790 End of assembler dump.
7793 Here is another example showing raw instructions in hex for AMD x86-64,
7796 (gdb) disas /r 0x400281,+10
7797 Dump of assembler code from 0x400281 to 0x40028b:
7798 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7799 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7800 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7801 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7802 End of assembler dump.
7805 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7806 So, for example, if you want to disassemble function @code{bar}
7807 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7808 and not @samp{disassemble foo.c:bar}.
7810 Some architectures have more than one commonly-used set of instruction
7811 mnemonics or other syntax.
7813 For programs that were dynamically linked and use shared libraries,
7814 instructions that call functions or branch to locations in the shared
7815 libraries might show a seemingly bogus location---it's actually a
7816 location of the relocation table. On some architectures, @value{GDBN}
7817 might be able to resolve these to actual function names.
7820 @kindex set disassembly-flavor
7821 @cindex Intel disassembly flavor
7822 @cindex AT&T disassembly flavor
7823 @item set disassembly-flavor @var{instruction-set}
7824 Select the instruction set to use when disassembling the
7825 program via the @code{disassemble} or @code{x/i} commands.
7827 Currently this command is only defined for the Intel x86 family. You
7828 can set @var{instruction-set} to either @code{intel} or @code{att}.
7829 The default is @code{att}, the AT&T flavor used by default by Unix
7830 assemblers for x86-based targets.
7832 @kindex show disassembly-flavor
7833 @item show disassembly-flavor
7834 Show the current setting of the disassembly flavor.
7838 @kindex set disassemble-next-line
7839 @kindex show disassemble-next-line
7840 @item set disassemble-next-line
7841 @itemx show disassemble-next-line
7842 Control whether or not @value{GDBN} will disassemble the next source
7843 line or instruction when execution stops. If ON, @value{GDBN} will
7844 display disassembly of the next source line when execution of the
7845 program being debugged stops. This is @emph{in addition} to
7846 displaying the source line itself, which @value{GDBN} always does if
7847 possible. If the next source line cannot be displayed for some reason
7848 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7849 info in the debug info), @value{GDBN} will display disassembly of the
7850 next @emph{instruction} instead of showing the next source line. If
7851 AUTO, @value{GDBN} will display disassembly of next instruction only
7852 if the source line cannot be displayed. This setting causes
7853 @value{GDBN} to display some feedback when you step through a function
7854 with no line info or whose source file is unavailable. The default is
7855 OFF, which means never display the disassembly of the next line or
7861 @chapter Examining Data
7863 @cindex printing data
7864 @cindex examining data
7867 The usual way to examine data in your program is with the @code{print}
7868 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7869 evaluates and prints the value of an expression of the language your
7870 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7871 Different Languages}). It may also print the expression using a
7872 Python-based pretty-printer (@pxref{Pretty Printing}).
7875 @item print @var{expr}
7876 @itemx print /@var{f} @var{expr}
7877 @var{expr} is an expression (in the source language). By default the
7878 value of @var{expr} is printed in a format appropriate to its data type;
7879 you can choose a different format by specifying @samp{/@var{f}}, where
7880 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7884 @itemx print /@var{f}
7885 @cindex reprint the last value
7886 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7887 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7888 conveniently inspect the same value in an alternative format.
7891 A more low-level way of examining data is with the @code{x} command.
7892 It examines data in memory at a specified address and prints it in a
7893 specified format. @xref{Memory, ,Examining Memory}.
7895 If you are interested in information about types, or about how the
7896 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7897 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7900 @cindex exploring hierarchical data structures
7902 Another way of examining values of expressions and type information is
7903 through the Python extension command @code{explore} (available only if
7904 the @value{GDBN} build is configured with @code{--with-python}). It
7905 offers an interactive way to start at the highest level (or, the most
7906 abstract level) of the data type of an expression (or, the data type
7907 itself) and explore all the way down to leaf scalar values/fields
7908 embedded in the higher level data types.
7911 @item explore @var{arg}
7912 @var{arg} is either an expression (in the source language), or a type
7913 visible in the current context of the program being debugged.
7916 The working of the @code{explore} command can be illustrated with an
7917 example. If a data type @code{struct ComplexStruct} is defined in your
7927 struct ComplexStruct
7929 struct SimpleStruct *ss_p;
7935 followed by variable declarations as
7938 struct SimpleStruct ss = @{ 10, 1.11 @};
7939 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7943 then, the value of the variable @code{cs} can be explored using the
7944 @code{explore} command as follows.
7948 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7949 the following fields:
7951 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7952 arr = <Enter 1 to explore this field of type `int [10]'>
7954 Enter the field number of choice:
7958 Since the fields of @code{cs} are not scalar values, you are being
7959 prompted to chose the field you want to explore. Let's say you choose
7960 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7961 pointer, you will be asked if it is pointing to a single value. From
7962 the declaration of @code{cs} above, it is indeed pointing to a single
7963 value, hence you enter @code{y}. If you enter @code{n}, then you will
7964 be asked if it were pointing to an array of values, in which case this
7965 field will be explored as if it were an array.
7968 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7969 Continue exploring it as a pointer to a single value [y/n]: y
7970 The value of `*(cs.ss_p)' is a struct/class of type `struct
7971 SimpleStruct' with the following fields:
7973 i = 10 .. (Value of type `int')
7974 d = 1.1100000000000001 .. (Value of type `double')
7976 Press enter to return to parent value:
7980 If the field @code{arr} of @code{cs} was chosen for exploration by
7981 entering @code{1} earlier, then since it is as array, you will be
7982 prompted to enter the index of the element in the array that you want
7986 `cs.arr' is an array of `int'.
7987 Enter the index of the element you want to explore in `cs.arr': 5
7989 `(cs.arr)[5]' is a scalar value of type `int'.
7993 Press enter to return to parent value:
7996 In general, at any stage of exploration, you can go deeper towards the
7997 leaf values by responding to the prompts appropriately, or hit the
7998 return key to return to the enclosing data structure (the @i{higher}
7999 level data structure).
8001 Similar to exploring values, you can use the @code{explore} command to
8002 explore types. Instead of specifying a value (which is typically a
8003 variable name or an expression valid in the current context of the
8004 program being debugged), you specify a type name. If you consider the
8005 same example as above, your can explore the type
8006 @code{struct ComplexStruct} by passing the argument
8007 @code{struct ComplexStruct} to the @code{explore} command.
8010 (gdb) explore struct ComplexStruct
8014 By responding to the prompts appropriately in the subsequent interactive
8015 session, you can explore the type @code{struct ComplexStruct} in a
8016 manner similar to how the value @code{cs} was explored in the above
8019 The @code{explore} command also has two sub-commands,
8020 @code{explore value} and @code{explore type}. The former sub-command is
8021 a way to explicitly specify that value exploration of the argument is
8022 being invoked, while the latter is a way to explicitly specify that type
8023 exploration of the argument is being invoked.
8026 @item explore value @var{expr}
8027 @cindex explore value
8028 This sub-command of @code{explore} explores the value of the
8029 expression @var{expr} (if @var{expr} is an expression valid in the
8030 current context of the program being debugged). The behavior of this
8031 command is identical to that of the behavior of the @code{explore}
8032 command being passed the argument @var{expr}.
8034 @item explore type @var{arg}
8035 @cindex explore type
8036 This sub-command of @code{explore} explores the type of @var{arg} (if
8037 @var{arg} is a type visible in the current context of program being
8038 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8039 is an expression valid in the current context of the program being
8040 debugged). If @var{arg} is a type, then the behavior of this command is
8041 identical to that of the @code{explore} command being passed the
8042 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8043 this command will be identical to that of the @code{explore} command
8044 being passed the type of @var{arg} as the argument.
8048 * Expressions:: Expressions
8049 * Ambiguous Expressions:: Ambiguous Expressions
8050 * Variables:: Program variables
8051 * Arrays:: Artificial arrays
8052 * Output Formats:: Output formats
8053 * Memory:: Examining memory
8054 * Auto Display:: Automatic display
8055 * Print Settings:: Print settings
8056 * Pretty Printing:: Python pretty printing
8057 * Value History:: Value history
8058 * Convenience Vars:: Convenience variables
8059 * Convenience Funs:: Convenience functions
8060 * Registers:: Registers
8061 * Floating Point Hardware:: Floating point hardware
8062 * Vector Unit:: Vector Unit
8063 * OS Information:: Auxiliary data provided by operating system
8064 * Memory Region Attributes:: Memory region attributes
8065 * Dump/Restore Files:: Copy between memory and a file
8066 * Core File Generation:: Cause a program dump its core
8067 * Character Sets:: Debugging programs that use a different
8068 character set than GDB does
8069 * Caching Remote Data:: Data caching for remote targets
8070 * Searching Memory:: Searching memory for a sequence of bytes
8074 @section Expressions
8077 @code{print} and many other @value{GDBN} commands accept an expression and
8078 compute its value. Any kind of constant, variable or operator defined
8079 by the programming language you are using is valid in an expression in
8080 @value{GDBN}. This includes conditional expressions, function calls,
8081 casts, and string constants. It also includes preprocessor macros, if
8082 you compiled your program to include this information; see
8085 @cindex arrays in expressions
8086 @value{GDBN} supports array constants in expressions input by
8087 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8088 you can use the command @code{print @{1, 2, 3@}} to create an array
8089 of three integers. If you pass an array to a function or assign it
8090 to a program variable, @value{GDBN} copies the array to memory that
8091 is @code{malloc}ed in the target program.
8093 Because C is so widespread, most of the expressions shown in examples in
8094 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8095 Languages}, for information on how to use expressions in other
8098 In this section, we discuss operators that you can use in @value{GDBN}
8099 expressions regardless of your programming language.
8101 @cindex casts, in expressions
8102 Casts are supported in all languages, not just in C, because it is so
8103 useful to cast a number into a pointer in order to examine a structure
8104 at that address in memory.
8105 @c FIXME: casts supported---Mod2 true?
8107 @value{GDBN} supports these operators, in addition to those common
8108 to programming languages:
8112 @samp{@@} is a binary operator for treating parts of memory as arrays.
8113 @xref{Arrays, ,Artificial Arrays}, for more information.
8116 @samp{::} allows you to specify a variable in terms of the file or
8117 function where it is defined. @xref{Variables, ,Program Variables}.
8119 @cindex @{@var{type}@}
8120 @cindex type casting memory
8121 @cindex memory, viewing as typed object
8122 @cindex casts, to view memory
8123 @item @{@var{type}@} @var{addr}
8124 Refers to an object of type @var{type} stored at address @var{addr} in
8125 memory. @var{addr} may be any expression whose value is an integer or
8126 pointer (but parentheses are required around binary operators, just as in
8127 a cast). This construct is allowed regardless of what kind of data is
8128 normally supposed to reside at @var{addr}.
8131 @node Ambiguous Expressions
8132 @section Ambiguous Expressions
8133 @cindex ambiguous expressions
8135 Expressions can sometimes contain some ambiguous elements. For instance,
8136 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8137 a single function name to be defined several times, for application in
8138 different contexts. This is called @dfn{overloading}. Another example
8139 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8140 templates and is typically instantiated several times, resulting in
8141 the same function name being defined in different contexts.
8143 In some cases and depending on the language, it is possible to adjust
8144 the expression to remove the ambiguity. For instance in C@t{++}, you
8145 can specify the signature of the function you want to break on, as in
8146 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8147 qualified name of your function often makes the expression unambiguous
8150 When an ambiguity that needs to be resolved is detected, the debugger
8151 has the capability to display a menu of numbered choices for each
8152 possibility, and then waits for the selection with the prompt @samp{>}.
8153 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8154 aborts the current command. If the command in which the expression was
8155 used allows more than one choice to be selected, the next option in the
8156 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8159 For example, the following session excerpt shows an attempt to set a
8160 breakpoint at the overloaded symbol @code{String::after}.
8161 We choose three particular definitions of that function name:
8163 @c FIXME! This is likely to change to show arg type lists, at least
8166 (@value{GDBP}) b String::after
8169 [2] file:String.cc; line number:867
8170 [3] file:String.cc; line number:860
8171 [4] file:String.cc; line number:875
8172 [5] file:String.cc; line number:853
8173 [6] file:String.cc; line number:846
8174 [7] file:String.cc; line number:735
8176 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8177 Breakpoint 2 at 0xb344: file String.cc, line 875.
8178 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8179 Multiple breakpoints were set.
8180 Use the "delete" command to delete unwanted
8187 @kindex set multiple-symbols
8188 @item set multiple-symbols @var{mode}
8189 @cindex multiple-symbols menu
8191 This option allows you to adjust the debugger behavior when an expression
8194 By default, @var{mode} is set to @code{all}. If the command with which
8195 the expression is used allows more than one choice, then @value{GDBN}
8196 automatically selects all possible choices. For instance, inserting
8197 a breakpoint on a function using an ambiguous name results in a breakpoint
8198 inserted on each possible match. However, if a unique choice must be made,
8199 then @value{GDBN} uses the menu to help you disambiguate the expression.
8200 For instance, printing the address of an overloaded function will result
8201 in the use of the menu.
8203 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8204 when an ambiguity is detected.
8206 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8207 an error due to the ambiguity and the command is aborted.
8209 @kindex show multiple-symbols
8210 @item show multiple-symbols
8211 Show the current value of the @code{multiple-symbols} setting.
8215 @section Program Variables
8217 The most common kind of expression to use is the name of a variable
8220 Variables in expressions are understood in the selected stack frame
8221 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8225 global (or file-static)
8232 visible according to the scope rules of the
8233 programming language from the point of execution in that frame
8236 @noindent This means that in the function
8251 you can examine and use the variable @code{a} whenever your program is
8252 executing within the function @code{foo}, but you can only use or
8253 examine the variable @code{b} while your program is executing inside
8254 the block where @code{b} is declared.
8256 @cindex variable name conflict
8257 There is an exception: you can refer to a variable or function whose
8258 scope is a single source file even if the current execution point is not
8259 in this file. But it is possible to have more than one such variable or
8260 function with the same name (in different source files). If that
8261 happens, referring to that name has unpredictable effects. If you wish,
8262 you can specify a static variable in a particular function or file by
8263 using the colon-colon (@code{::}) notation:
8265 @cindex colon-colon, context for variables/functions
8267 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8268 @cindex @code{::}, context for variables/functions
8271 @var{file}::@var{variable}
8272 @var{function}::@var{variable}
8276 Here @var{file} or @var{function} is the name of the context for the
8277 static @var{variable}. In the case of file names, you can use quotes to
8278 make sure @value{GDBN} parses the file name as a single word---for example,
8279 to print a global value of @code{x} defined in @file{f2.c}:
8282 (@value{GDBP}) p 'f2.c'::x
8285 The @code{::} notation is normally used for referring to
8286 static variables, since you typically disambiguate uses of local variables
8287 in functions by selecting the appropriate frame and using the
8288 simple name of the variable. However, you may also use this notation
8289 to refer to local variables in frames enclosing the selected frame:
8298 process (a); /* Stop here */
8309 For example, if there is a breakpoint at the commented line,
8310 here is what you might see
8311 when the program stops after executing the call @code{bar(0)}:
8316 (@value{GDBP}) p bar::a
8319 #2 0x080483d0 in foo (a=5) at foobar.c:12
8322 (@value{GDBP}) p bar::a
8326 @cindex C@t{++} scope resolution
8327 These uses of @samp{::} are very rarely in conflict with the very similar
8328 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8329 scope resolution operator in @value{GDBN} expressions.
8330 @c FIXME: Um, so what happens in one of those rare cases where it's in
8333 @cindex wrong values
8334 @cindex variable values, wrong
8335 @cindex function entry/exit, wrong values of variables
8336 @cindex optimized code, wrong values of variables
8338 @emph{Warning:} Occasionally, a local variable may appear to have the
8339 wrong value at certain points in a function---just after entry to a new
8340 scope, and just before exit.
8342 You may see this problem when you are stepping by machine instructions.
8343 This is because, on most machines, it takes more than one instruction to
8344 set up a stack frame (including local variable definitions); if you are
8345 stepping by machine instructions, variables may appear to have the wrong
8346 values until the stack frame is completely built. On exit, it usually
8347 also takes more than one machine instruction to destroy a stack frame;
8348 after you begin stepping through that group of instructions, local
8349 variable definitions may be gone.
8351 This may also happen when the compiler does significant optimizations.
8352 To be sure of always seeing accurate values, turn off all optimization
8355 @cindex ``No symbol "foo" in current context''
8356 Another possible effect of compiler optimizations is to optimize
8357 unused variables out of existence, or assign variables to registers (as
8358 opposed to memory addresses). Depending on the support for such cases
8359 offered by the debug info format used by the compiler, @value{GDBN}
8360 might not be able to display values for such local variables. If that
8361 happens, @value{GDBN} will print a message like this:
8364 No symbol "foo" in current context.
8367 To solve such problems, either recompile without optimizations, or use a
8368 different debug info format, if the compiler supports several such
8369 formats. @xref{Compilation}, for more information on choosing compiler
8370 options. @xref{C, ,C and C@t{++}}, for more information about debug
8371 info formats that are best suited to C@t{++} programs.
8373 If you ask to print an object whose contents are unknown to
8374 @value{GDBN}, e.g., because its data type is not completely specified
8375 by the debug information, @value{GDBN} will say @samp{<incomplete
8376 type>}. @xref{Symbols, incomplete type}, for more about this.
8378 If you append @kbd{@@entry} string to a function parameter name you get its
8379 value at the time the function got called. If the value is not available an
8380 error message is printed. Entry values are available only with some compilers.
8381 Entry values are normally also printed at the function parameter list according
8382 to @ref{set print entry-values}.
8385 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8391 (gdb) print i@@entry
8395 Strings are identified as arrays of @code{char} values without specified
8396 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8397 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8398 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8399 defines literal string type @code{"char"} as @code{char} without a sign.
8404 signed char var1[] = "A";
8407 You get during debugging
8412 $2 = @{65 'A', 0 '\0'@}
8416 @section Artificial Arrays
8418 @cindex artificial array
8420 @kindex @@@r{, referencing memory as an array}
8421 It is often useful to print out several successive objects of the
8422 same type in memory; a section of an array, or an array of
8423 dynamically determined size for which only a pointer exists in the
8426 You can do this by referring to a contiguous span of memory as an
8427 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8428 operand of @samp{@@} should be the first element of the desired array
8429 and be an individual object. The right operand should be the desired length
8430 of the array. The result is an array value whose elements are all of
8431 the type of the left argument. The first element is actually the left
8432 argument; the second element comes from bytes of memory immediately
8433 following those that hold the first element, and so on. Here is an
8434 example. If a program says
8437 int *array = (int *) malloc (len * sizeof (int));
8441 you can print the contents of @code{array} with
8447 The left operand of @samp{@@} must reside in memory. Array values made
8448 with @samp{@@} in this way behave just like other arrays in terms of
8449 subscripting, and are coerced to pointers when used in expressions.
8450 Artificial arrays most often appear in expressions via the value history
8451 (@pxref{Value History, ,Value History}), after printing one out.
8453 Another way to create an artificial array is to use a cast.
8454 This re-interprets a value as if it were an array.
8455 The value need not be in memory:
8457 (@value{GDBP}) p/x (short[2])0x12345678
8458 $1 = @{0x1234, 0x5678@}
8461 As a convenience, if you leave the array length out (as in
8462 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8463 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8465 (@value{GDBP}) p/x (short[])0x12345678
8466 $2 = @{0x1234, 0x5678@}
8469 Sometimes the artificial array mechanism is not quite enough; in
8470 moderately complex data structures, the elements of interest may not
8471 actually be adjacent---for example, if you are interested in the values
8472 of pointers in an array. One useful work-around in this situation is
8473 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8474 Variables}) as a counter in an expression that prints the first
8475 interesting value, and then repeat that expression via @key{RET}. For
8476 instance, suppose you have an array @code{dtab} of pointers to
8477 structures, and you are interested in the values of a field @code{fv}
8478 in each structure. Here is an example of what you might type:
8488 @node Output Formats
8489 @section Output Formats
8491 @cindex formatted output
8492 @cindex output formats
8493 By default, @value{GDBN} prints a value according to its data type. Sometimes
8494 this is not what you want. For example, you might want to print a number
8495 in hex, or a pointer in decimal. Or you might want to view data in memory
8496 at a certain address as a character string or as an instruction. To do
8497 these things, specify an @dfn{output format} when you print a value.
8499 The simplest use of output formats is to say how to print a value
8500 already computed. This is done by starting the arguments of the
8501 @code{print} command with a slash and a format letter. The format
8502 letters supported are:
8506 Regard the bits of the value as an integer, and print the integer in
8510 Print as integer in signed decimal.
8513 Print as integer in unsigned decimal.
8516 Print as integer in octal.
8519 Print as integer in binary. The letter @samp{t} stands for ``two''.
8520 @footnote{@samp{b} cannot be used because these format letters are also
8521 used with the @code{x} command, where @samp{b} stands for ``byte'';
8522 see @ref{Memory,,Examining Memory}.}
8525 @cindex unknown address, locating
8526 @cindex locate address
8527 Print as an address, both absolute in hexadecimal and as an offset from
8528 the nearest preceding symbol. You can use this format used to discover
8529 where (in what function) an unknown address is located:
8532 (@value{GDBP}) p/a 0x54320
8533 $3 = 0x54320 <_initialize_vx+396>
8537 The command @code{info symbol 0x54320} yields similar results.
8538 @xref{Symbols, info symbol}.
8541 Regard as an integer and print it as a character constant. This
8542 prints both the numerical value and its character representation. The
8543 character representation is replaced with the octal escape @samp{\nnn}
8544 for characters outside the 7-bit @sc{ascii} range.
8546 Without this format, @value{GDBN} displays @code{char},
8547 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8548 constants. Single-byte members of vectors are displayed as integer
8552 Regard the bits of the value as a floating point number and print
8553 using typical floating point syntax.
8556 @cindex printing strings
8557 @cindex printing byte arrays
8558 Regard as a string, if possible. With this format, pointers to single-byte
8559 data are displayed as null-terminated strings and arrays of single-byte data
8560 are displayed as fixed-length strings. Other values are displayed in their
8563 Without this format, @value{GDBN} displays pointers to and arrays of
8564 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8565 strings. Single-byte members of a vector are displayed as an integer
8569 Like @samp{x} formatting, the value is treated as an integer and
8570 printed as hexadecimal, but leading zeros are printed to pad the value
8571 to the size of the integer type.
8574 @cindex raw printing
8575 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8576 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8577 Printing}). This typically results in a higher-level display of the
8578 value's contents. The @samp{r} format bypasses any Python
8579 pretty-printer which might exist.
8582 For example, to print the program counter in hex (@pxref{Registers}), type
8589 Note that no space is required before the slash; this is because command
8590 names in @value{GDBN} cannot contain a slash.
8592 To reprint the last value in the value history with a different format,
8593 you can use the @code{print} command with just a format and no
8594 expression. For example, @samp{p/x} reprints the last value in hex.
8597 @section Examining Memory
8599 You can use the command @code{x} (for ``examine'') to examine memory in
8600 any of several formats, independently of your program's data types.
8602 @cindex examining memory
8604 @kindex x @r{(examine memory)}
8605 @item x/@var{nfu} @var{addr}
8608 Use the @code{x} command to examine memory.
8611 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8612 much memory to display and how to format it; @var{addr} is an
8613 expression giving the address where you want to start displaying memory.
8614 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8615 Several commands set convenient defaults for @var{addr}.
8618 @item @var{n}, the repeat count
8619 The repeat count is a decimal integer; the default is 1. It specifies
8620 how much memory (counting by units @var{u}) to display.
8621 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8624 @item @var{f}, the display format
8625 The display format is one of the formats used by @code{print}
8626 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8627 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8628 The default is @samp{x} (hexadecimal) initially. The default changes
8629 each time you use either @code{x} or @code{print}.
8631 @item @var{u}, the unit size
8632 The unit size is any of
8638 Halfwords (two bytes).
8640 Words (four bytes). This is the initial default.
8642 Giant words (eight bytes).
8645 Each time you specify a unit size with @code{x}, that size becomes the
8646 default unit the next time you use @code{x}. For the @samp{i} format,
8647 the unit size is ignored and is normally not written. For the @samp{s} format,
8648 the unit size defaults to @samp{b}, unless it is explicitly given.
8649 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8650 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8651 Note that the results depend on the programming language of the
8652 current compilation unit. If the language is C, the @samp{s}
8653 modifier will use the UTF-16 encoding while @samp{w} will use
8654 UTF-32. The encoding is set by the programming language and cannot
8657 @item @var{addr}, starting display address
8658 @var{addr} is the address where you want @value{GDBN} to begin displaying
8659 memory. The expression need not have a pointer value (though it may);
8660 it is always interpreted as an integer address of a byte of memory.
8661 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8662 @var{addr} is usually just after the last address examined---but several
8663 other commands also set the default address: @code{info breakpoints} (to
8664 the address of the last breakpoint listed), @code{info line} (to the
8665 starting address of a line), and @code{print} (if you use it to display
8666 a value from memory).
8669 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8670 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8671 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8672 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8673 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8675 Since the letters indicating unit sizes are all distinct from the
8676 letters specifying output formats, you do not have to remember whether
8677 unit size or format comes first; either order works. The output
8678 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8679 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8681 Even though the unit size @var{u} is ignored for the formats @samp{s}
8682 and @samp{i}, you might still want to use a count @var{n}; for example,
8683 @samp{3i} specifies that you want to see three machine instructions,
8684 including any operands. For convenience, especially when used with
8685 the @code{display} command, the @samp{i} format also prints branch delay
8686 slot instructions, if any, beyond the count specified, which immediately
8687 follow the last instruction that is within the count. The command
8688 @code{disassemble} gives an alternative way of inspecting machine
8689 instructions; see @ref{Machine Code,,Source and Machine Code}.
8691 All the defaults for the arguments to @code{x} are designed to make it
8692 easy to continue scanning memory with minimal specifications each time
8693 you use @code{x}. For example, after you have inspected three machine
8694 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8695 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8696 the repeat count @var{n} is used again; the other arguments default as
8697 for successive uses of @code{x}.
8699 When examining machine instructions, the instruction at current program
8700 counter is shown with a @code{=>} marker. For example:
8703 (@value{GDBP}) x/5i $pc-6
8704 0x804837f <main+11>: mov %esp,%ebp
8705 0x8048381 <main+13>: push %ecx
8706 0x8048382 <main+14>: sub $0x4,%esp
8707 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8708 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8711 @cindex @code{$_}, @code{$__}, and value history
8712 The addresses and contents printed by the @code{x} command are not saved
8713 in the value history because there is often too much of them and they
8714 would get in the way. Instead, @value{GDBN} makes these values available for
8715 subsequent use in expressions as values of the convenience variables
8716 @code{$_} and @code{$__}. After an @code{x} command, the last address
8717 examined is available for use in expressions in the convenience variable
8718 @code{$_}. The contents of that address, as examined, are available in
8719 the convenience variable @code{$__}.
8721 If the @code{x} command has a repeat count, the address and contents saved
8722 are from the last memory unit printed; this is not the same as the last
8723 address printed if several units were printed on the last line of output.
8725 @cindex remote memory comparison
8726 @cindex verify remote memory image
8727 When you are debugging a program running on a remote target machine
8728 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8729 remote machine's memory against the executable file you downloaded to
8730 the target. The @code{compare-sections} command is provided for such
8734 @kindex compare-sections
8735 @item compare-sections @r{[}@var{section-name}@r{]}
8736 Compare the data of a loadable section @var{section-name} in the
8737 executable file of the program being debugged with the same section in
8738 the remote machine's memory, and report any mismatches. With no
8739 arguments, compares all loadable sections. This command's
8740 availability depends on the target's support for the @code{"qCRC"}
8745 @section Automatic Display
8746 @cindex automatic display
8747 @cindex display of expressions
8749 If you find that you want to print the value of an expression frequently
8750 (to see how it changes), you might want to add it to the @dfn{automatic
8751 display list} so that @value{GDBN} prints its value each time your program stops.
8752 Each expression added to the list is given a number to identify it;
8753 to remove an expression from the list, you specify that number.
8754 The automatic display looks like this:
8758 3: bar[5] = (struct hack *) 0x3804
8762 This display shows item numbers, expressions and their current values. As with
8763 displays you request manually using @code{x} or @code{print}, you can
8764 specify the output format you prefer; in fact, @code{display} decides
8765 whether to use @code{print} or @code{x} depending your format
8766 specification---it uses @code{x} if you specify either the @samp{i}
8767 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8771 @item display @var{expr}
8772 Add the expression @var{expr} to the list of expressions to display
8773 each time your program stops. @xref{Expressions, ,Expressions}.
8775 @code{display} does not repeat if you press @key{RET} again after using it.
8777 @item display/@var{fmt} @var{expr}
8778 For @var{fmt} specifying only a display format and not a size or
8779 count, add the expression @var{expr} to the auto-display list but
8780 arrange to display it each time in the specified format @var{fmt}.
8781 @xref{Output Formats,,Output Formats}.
8783 @item display/@var{fmt} @var{addr}
8784 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8785 number of units, add the expression @var{addr} as a memory address to
8786 be examined each time your program stops. Examining means in effect
8787 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8790 For example, @samp{display/i $pc} can be helpful, to see the machine
8791 instruction about to be executed each time execution stops (@samp{$pc}
8792 is a common name for the program counter; @pxref{Registers, ,Registers}).
8795 @kindex delete display
8797 @item undisplay @var{dnums}@dots{}
8798 @itemx delete display @var{dnums}@dots{}
8799 Remove items from the list of expressions to display. Specify the
8800 numbers of the displays that you want affected with the command
8801 argument @var{dnums}. It can be a single display number, one of the
8802 numbers shown in the first field of the @samp{info display} display;
8803 or it could be a range of display numbers, as in @code{2-4}.
8805 @code{undisplay} does not repeat if you press @key{RET} after using it.
8806 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8808 @kindex disable display
8809 @item disable display @var{dnums}@dots{}
8810 Disable the display of item numbers @var{dnums}. A disabled display
8811 item is not printed automatically, but is not forgotten. It may be
8812 enabled again later. Specify the numbers of the displays that you
8813 want affected with the command argument @var{dnums}. It can be a
8814 single display number, one of the numbers shown in the first field of
8815 the @samp{info display} display; or it could be a range of display
8816 numbers, as in @code{2-4}.
8818 @kindex enable display
8819 @item enable display @var{dnums}@dots{}
8820 Enable display of item numbers @var{dnums}. It becomes effective once
8821 again in auto display of its expression, until you specify otherwise.
8822 Specify the numbers of the displays that you want affected with the
8823 command argument @var{dnums}. It can be a single display number, one
8824 of the numbers shown in the first field of the @samp{info display}
8825 display; or it could be a range of display numbers, as in @code{2-4}.
8828 Display the current values of the expressions on the list, just as is
8829 done when your program stops.
8831 @kindex info display
8833 Print the list of expressions previously set up to display
8834 automatically, each one with its item number, but without showing the
8835 values. This includes disabled expressions, which are marked as such.
8836 It also includes expressions which would not be displayed right now
8837 because they refer to automatic variables not currently available.
8840 @cindex display disabled out of scope
8841 If a display expression refers to local variables, then it does not make
8842 sense outside the lexical context for which it was set up. Such an
8843 expression is disabled when execution enters a context where one of its
8844 variables is not defined. For example, if you give the command
8845 @code{display last_char} while inside a function with an argument
8846 @code{last_char}, @value{GDBN} displays this argument while your program
8847 continues to stop inside that function. When it stops elsewhere---where
8848 there is no variable @code{last_char}---the display is disabled
8849 automatically. The next time your program stops where @code{last_char}
8850 is meaningful, you can enable the display expression once again.
8852 @node Print Settings
8853 @section Print Settings
8855 @cindex format options
8856 @cindex print settings
8857 @value{GDBN} provides the following ways to control how arrays, structures,
8858 and symbols are printed.
8861 These settings are useful for debugging programs in any language:
8865 @item set print address
8866 @itemx set print address on
8867 @cindex print/don't print memory addresses
8868 @value{GDBN} prints memory addresses showing the location of stack
8869 traces, structure values, pointer values, breakpoints, and so forth,
8870 even when it also displays the contents of those addresses. The default
8871 is @code{on}. For example, this is what a stack frame display looks like with
8872 @code{set print address on}:
8877 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8879 530 if (lquote != def_lquote)
8883 @item set print address off
8884 Do not print addresses when displaying their contents. For example,
8885 this is the same stack frame displayed with @code{set print address off}:
8889 (@value{GDBP}) set print addr off
8891 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8892 530 if (lquote != def_lquote)
8896 You can use @samp{set print address off} to eliminate all machine
8897 dependent displays from the @value{GDBN} interface. For example, with
8898 @code{print address off}, you should get the same text for backtraces on
8899 all machines---whether or not they involve pointer arguments.
8902 @item show print address
8903 Show whether or not addresses are to be printed.
8906 When @value{GDBN} prints a symbolic address, it normally prints the
8907 closest earlier symbol plus an offset. If that symbol does not uniquely
8908 identify the address (for example, it is a name whose scope is a single
8909 source file), you may need to clarify. One way to do this is with
8910 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8911 you can set @value{GDBN} to print the source file and line number when
8912 it prints a symbolic address:
8915 @item set print symbol-filename on
8916 @cindex source file and line of a symbol
8917 @cindex symbol, source file and line
8918 Tell @value{GDBN} to print the source file name and line number of a
8919 symbol in the symbolic form of an address.
8921 @item set print symbol-filename off
8922 Do not print source file name and line number of a symbol. This is the
8925 @item show print symbol-filename
8926 Show whether or not @value{GDBN} will print the source file name and
8927 line number of a symbol in the symbolic form of an address.
8930 Another situation where it is helpful to show symbol filenames and line
8931 numbers is when disassembling code; @value{GDBN} shows you the line
8932 number and source file that corresponds to each instruction.
8934 Also, you may wish to see the symbolic form only if the address being
8935 printed is reasonably close to the closest earlier symbol:
8938 @item set print max-symbolic-offset @var{max-offset}
8939 @itemx set print max-symbolic-offset unlimited
8940 @cindex maximum value for offset of closest symbol
8941 Tell @value{GDBN} to only display the symbolic form of an address if the
8942 offset between the closest earlier symbol and the address is less than
8943 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8944 to always print the symbolic form of an address if any symbol precedes
8945 it. Zero is equivalent to @code{unlimited}.
8947 @item show print max-symbolic-offset
8948 Ask how large the maximum offset is that @value{GDBN} prints in a
8952 @cindex wild pointer, interpreting
8953 @cindex pointer, finding referent
8954 If you have a pointer and you are not sure where it points, try
8955 @samp{set print symbol-filename on}. Then you can determine the name
8956 and source file location of the variable where it points, using
8957 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8958 For example, here @value{GDBN} shows that a variable @code{ptt} points
8959 at another variable @code{t}, defined in @file{hi2.c}:
8962 (@value{GDBP}) set print symbol-filename on
8963 (@value{GDBP}) p/a ptt
8964 $4 = 0xe008 <t in hi2.c>
8968 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8969 does not show the symbol name and filename of the referent, even with
8970 the appropriate @code{set print} options turned on.
8973 You can also enable @samp{/a}-like formatting all the time using
8974 @samp{set print symbol on}:
8977 @item set print symbol on
8978 Tell @value{GDBN} to print the symbol corresponding to an address, if
8981 @item set print symbol off
8982 Tell @value{GDBN} not to print the symbol corresponding to an
8983 address. In this mode, @value{GDBN} will still print the symbol
8984 corresponding to pointers to functions. This is the default.
8986 @item show print symbol
8987 Show whether @value{GDBN} will display the symbol corresponding to an
8991 Other settings control how different kinds of objects are printed:
8994 @item set print array
8995 @itemx set print array on
8996 @cindex pretty print arrays
8997 Pretty print arrays. This format is more convenient to read,
8998 but uses more space. The default is off.
9000 @item set print array off
9001 Return to compressed format for arrays.
9003 @item show print array
9004 Show whether compressed or pretty format is selected for displaying
9007 @cindex print array indexes
9008 @item set print array-indexes
9009 @itemx set print array-indexes on
9010 Print the index of each element when displaying arrays. May be more
9011 convenient to locate a given element in the array or quickly find the
9012 index of a given element in that printed array. The default is off.
9014 @item set print array-indexes off
9015 Stop printing element indexes when displaying arrays.
9017 @item show print array-indexes
9018 Show whether the index of each element is printed when displaying
9021 @item set print elements @var{number-of-elements}
9022 @itemx set print elements unlimited
9023 @cindex number of array elements to print
9024 @cindex limit on number of printed array elements
9025 Set a limit on how many elements of an array @value{GDBN} will print.
9026 If @value{GDBN} is printing a large array, it stops printing after it has
9027 printed the number of elements set by the @code{set print elements} command.
9028 This limit also applies to the display of strings.
9029 When @value{GDBN} starts, this limit is set to 200.
9030 Setting @var{number-of-elements} to @code{unlimited} or zero means
9031 that the number of elements to print is unlimited.
9033 @item show print elements
9034 Display the number of elements of a large array that @value{GDBN} will print.
9035 If the number is 0, then the printing is unlimited.
9037 @item set print frame-arguments @var{value}
9038 @kindex set print frame-arguments
9039 @cindex printing frame argument values
9040 @cindex print all frame argument values
9041 @cindex print frame argument values for scalars only
9042 @cindex do not print frame argument values
9043 This command allows to control how the values of arguments are printed
9044 when the debugger prints a frame (@pxref{Frames}). The possible
9049 The values of all arguments are printed.
9052 Print the value of an argument only if it is a scalar. The value of more
9053 complex arguments such as arrays, structures, unions, etc, is replaced
9054 by @code{@dots{}}. This is the default. Here is an example where
9055 only scalar arguments are shown:
9058 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9063 None of the argument values are printed. Instead, the value of each argument
9064 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9067 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9072 By default, only scalar arguments are printed. This command can be used
9073 to configure the debugger to print the value of all arguments, regardless
9074 of their type. However, it is often advantageous to not print the value
9075 of more complex parameters. For instance, it reduces the amount of
9076 information printed in each frame, making the backtrace more readable.
9077 Also, it improves performance when displaying Ada frames, because
9078 the computation of large arguments can sometimes be CPU-intensive,
9079 especially in large applications. Setting @code{print frame-arguments}
9080 to @code{scalars} (the default) or @code{none} avoids this computation,
9081 thus speeding up the display of each Ada frame.
9083 @item show print frame-arguments
9084 Show how the value of arguments should be displayed when printing a frame.
9086 @item set print raw frame-arguments on
9087 Print frame arguments in raw, non pretty-printed, form.
9089 @item set print raw frame-arguments off
9090 Print frame arguments in pretty-printed form, if there is a pretty-printer
9091 for the value (@pxref{Pretty Printing}),
9092 otherwise print the value in raw form.
9093 This is the default.
9095 @item show print raw frame-arguments
9096 Show whether to print frame arguments in raw form.
9098 @anchor{set print entry-values}
9099 @item set print entry-values @var{value}
9100 @kindex set print entry-values
9101 Set printing of frame argument values at function entry. In some cases
9102 @value{GDBN} can determine the value of function argument which was passed by
9103 the function caller, even if the value was modified inside the called function
9104 and therefore is different. With optimized code, the current value could be
9105 unavailable, but the entry value may still be known.
9107 The default value is @code{default} (see below for its description). Older
9108 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9109 this feature will behave in the @code{default} setting the same way as with the
9112 This functionality is currently supported only by DWARF 2 debugging format and
9113 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9114 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9117 The @var{value} parameter can be one of the following:
9121 Print only actual parameter values, never print values from function entry
9125 #0 different (val=6)
9126 #0 lost (val=<optimized out>)
9128 #0 invalid (val=<optimized out>)
9132 Print only parameter values from function entry point. The actual parameter
9133 values are never printed.
9135 #0 equal (val@@entry=5)
9136 #0 different (val@@entry=5)
9137 #0 lost (val@@entry=5)
9138 #0 born (val@@entry=<optimized out>)
9139 #0 invalid (val@@entry=<optimized out>)
9143 Print only parameter values from function entry point. If value from function
9144 entry point is not known while the actual value is known, print the actual
9145 value for such parameter.
9147 #0 equal (val@@entry=5)
9148 #0 different (val@@entry=5)
9149 #0 lost (val@@entry=5)
9151 #0 invalid (val@@entry=<optimized out>)
9155 Print actual parameter values. If actual parameter value is not known while
9156 value from function entry point is known, print the entry point value for such
9160 #0 different (val=6)
9161 #0 lost (val@@entry=5)
9163 #0 invalid (val=<optimized out>)
9167 Always print both the actual parameter value and its value from function entry
9168 point, even if values of one or both are not available due to compiler
9171 #0 equal (val=5, val@@entry=5)
9172 #0 different (val=6, val@@entry=5)
9173 #0 lost (val=<optimized out>, val@@entry=5)
9174 #0 born (val=10, val@@entry=<optimized out>)
9175 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9179 Print the actual parameter value if it is known and also its value from
9180 function entry point if it is known. If neither is known, print for the actual
9181 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9182 values are known and identical, print the shortened
9183 @code{param=param@@entry=VALUE} notation.
9185 #0 equal (val=val@@entry=5)
9186 #0 different (val=6, val@@entry=5)
9187 #0 lost (val@@entry=5)
9189 #0 invalid (val=<optimized out>)
9193 Always print the actual parameter value. Print also its value from function
9194 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9195 if both values are known and identical, print the shortened
9196 @code{param=param@@entry=VALUE} notation.
9198 #0 equal (val=val@@entry=5)
9199 #0 different (val=6, val@@entry=5)
9200 #0 lost (val=<optimized out>, val@@entry=5)
9202 #0 invalid (val=<optimized out>)
9206 For analysis messages on possible failures of frame argument values at function
9207 entry resolution see @ref{set debug entry-values}.
9209 @item show print entry-values
9210 Show the method being used for printing of frame argument values at function
9213 @item set print repeats @var{number-of-repeats}
9214 @itemx set print repeats unlimited
9215 @cindex repeated array elements
9216 Set the threshold for suppressing display of repeated array
9217 elements. When the number of consecutive identical elements of an
9218 array exceeds the threshold, @value{GDBN} prints the string
9219 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9220 identical repetitions, instead of displaying the identical elements
9221 themselves. Setting the threshold to @code{unlimited} or zero will
9222 cause all elements to be individually printed. The default threshold
9225 @item show print repeats
9226 Display the current threshold for printing repeated identical
9229 @item set print null-stop
9230 @cindex @sc{null} elements in arrays
9231 Cause @value{GDBN} to stop printing the characters of an array when the first
9232 @sc{null} is encountered. This is useful when large arrays actually
9233 contain only short strings.
9236 @item show print null-stop
9237 Show whether @value{GDBN} stops printing an array on the first
9238 @sc{null} character.
9240 @item set print pretty on
9241 @cindex print structures in indented form
9242 @cindex indentation in structure display
9243 Cause @value{GDBN} to print structures in an indented format with one member
9244 per line, like this:
9259 @item set print pretty off
9260 Cause @value{GDBN} to print structures in a compact format, like this:
9264 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9265 meat = 0x54 "Pork"@}
9270 This is the default format.
9272 @item show print pretty
9273 Show which format @value{GDBN} is using to print structures.
9275 @item set print sevenbit-strings on
9276 @cindex eight-bit characters in strings
9277 @cindex octal escapes in strings
9278 Print using only seven-bit characters; if this option is set,
9279 @value{GDBN} displays any eight-bit characters (in strings or
9280 character values) using the notation @code{\}@var{nnn}. This setting is
9281 best if you are working in English (@sc{ascii}) and you use the
9282 high-order bit of characters as a marker or ``meta'' bit.
9284 @item set print sevenbit-strings off
9285 Print full eight-bit characters. This allows the use of more
9286 international character sets, and is the default.
9288 @item show print sevenbit-strings
9289 Show whether or not @value{GDBN} is printing only seven-bit characters.
9291 @item set print union on
9292 @cindex unions in structures, printing
9293 Tell @value{GDBN} to print unions which are contained in structures
9294 and other unions. This is the default setting.
9296 @item set print union off
9297 Tell @value{GDBN} not to print unions which are contained in
9298 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9301 @item show print union
9302 Ask @value{GDBN} whether or not it will print unions which are contained in
9303 structures and other unions.
9305 For example, given the declarations
9308 typedef enum @{Tree, Bug@} Species;
9309 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9310 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9321 struct thing foo = @{Tree, @{Acorn@}@};
9325 with @code{set print union on} in effect @samp{p foo} would print
9328 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9332 and with @code{set print union off} in effect it would print
9335 $1 = @{it = Tree, form = @{...@}@}
9339 @code{set print union} affects programs written in C-like languages
9345 These settings are of interest when debugging C@t{++} programs:
9348 @cindex demangling C@t{++} names
9349 @item set print demangle
9350 @itemx set print demangle on
9351 Print C@t{++} names in their source form rather than in the encoded
9352 (``mangled'') form passed to the assembler and linker for type-safe
9353 linkage. The default is on.
9355 @item show print demangle
9356 Show whether C@t{++} names are printed in mangled or demangled form.
9358 @item set print asm-demangle
9359 @itemx set print asm-demangle on
9360 Print C@t{++} names in their source form rather than their mangled form, even
9361 in assembler code printouts such as instruction disassemblies.
9364 @item show print asm-demangle
9365 Show whether C@t{++} names in assembly listings are printed in mangled
9368 @cindex C@t{++} symbol decoding style
9369 @cindex symbol decoding style, C@t{++}
9370 @kindex set demangle-style
9371 @item set demangle-style @var{style}
9372 Choose among several encoding schemes used by different compilers to
9373 represent C@t{++} names. The choices for @var{style} are currently:
9377 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9378 This is the default.
9381 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9384 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9387 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9390 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9391 @strong{Warning:} this setting alone is not sufficient to allow
9392 debugging @code{cfront}-generated executables. @value{GDBN} would
9393 require further enhancement to permit that.
9396 If you omit @var{style}, you will see a list of possible formats.
9398 @item show demangle-style
9399 Display the encoding style currently in use for decoding C@t{++} symbols.
9401 @item set print object
9402 @itemx set print object on
9403 @cindex derived type of an object, printing
9404 @cindex display derived types
9405 When displaying a pointer to an object, identify the @emph{actual}
9406 (derived) type of the object rather than the @emph{declared} type, using
9407 the virtual function table. Note that the virtual function table is
9408 required---this feature can only work for objects that have run-time
9409 type identification; a single virtual method in the object's declared
9410 type is sufficient. Note that this setting is also taken into account when
9411 working with variable objects via MI (@pxref{GDB/MI}).
9413 @item set print object off
9414 Display only the declared type of objects, without reference to the
9415 virtual function table. This is the default setting.
9417 @item show print object
9418 Show whether actual, or declared, object types are displayed.
9420 @item set print static-members
9421 @itemx set print static-members on
9422 @cindex static members of C@t{++} objects
9423 Print static members when displaying a C@t{++} object. The default is on.
9425 @item set print static-members off
9426 Do not print static members when displaying a C@t{++} object.
9428 @item show print static-members
9429 Show whether C@t{++} static members are printed or not.
9431 @item set print pascal_static-members
9432 @itemx set print pascal_static-members on
9433 @cindex static members of Pascal objects
9434 @cindex Pascal objects, static members display
9435 Print static members when displaying a Pascal object. The default is on.
9437 @item set print pascal_static-members off
9438 Do not print static members when displaying a Pascal object.
9440 @item show print pascal_static-members
9441 Show whether Pascal static members are printed or not.
9443 @c These don't work with HP ANSI C++ yet.
9444 @item set print vtbl
9445 @itemx set print vtbl on
9446 @cindex pretty print C@t{++} virtual function tables
9447 @cindex virtual functions (C@t{++}) display
9448 @cindex VTBL display
9449 Pretty print C@t{++} virtual function tables. The default is off.
9450 (The @code{vtbl} commands do not work on programs compiled with the HP
9451 ANSI C@t{++} compiler (@code{aCC}).)
9453 @item set print vtbl off
9454 Do not pretty print C@t{++} virtual function tables.
9456 @item show print vtbl
9457 Show whether C@t{++} virtual function tables are pretty printed, or not.
9460 @node Pretty Printing
9461 @section Pretty Printing
9463 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9464 Python code. It greatly simplifies the display of complex objects. This
9465 mechanism works for both MI and the CLI.
9468 * Pretty-Printer Introduction:: Introduction to pretty-printers
9469 * Pretty-Printer Example:: An example pretty-printer
9470 * Pretty-Printer Commands:: Pretty-printer commands
9473 @node Pretty-Printer Introduction
9474 @subsection Pretty-Printer Introduction
9476 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9477 registered for the value. If there is then @value{GDBN} invokes the
9478 pretty-printer to print the value. Otherwise the value is printed normally.
9480 Pretty-printers are normally named. This makes them easy to manage.
9481 The @samp{info pretty-printer} command will list all the installed
9482 pretty-printers with their names.
9483 If a pretty-printer can handle multiple data types, then its
9484 @dfn{subprinters} are the printers for the individual data types.
9485 Each such subprinter has its own name.
9486 The format of the name is @var{printer-name};@var{subprinter-name}.
9488 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9489 Typically they are automatically loaded and registered when the corresponding
9490 debug information is loaded, thus making them available without having to
9491 do anything special.
9493 There are three places where a pretty-printer can be registered.
9497 Pretty-printers registered globally are available when debugging
9501 Pretty-printers registered with a program space are available only
9502 when debugging that program.
9503 @xref{Progspaces In Python}, for more details on program spaces in Python.
9506 Pretty-printers registered with an objfile are loaded and unloaded
9507 with the corresponding objfile (e.g., shared library).
9508 @xref{Objfiles In Python}, for more details on objfiles in Python.
9511 @xref{Selecting Pretty-Printers}, for further information on how
9512 pretty-printers are selected,
9514 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9517 @node Pretty-Printer Example
9518 @subsection Pretty-Printer Example
9520 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9523 (@value{GDBP}) print s
9525 static npos = 4294967295,
9527 <std::allocator<char>> = @{
9528 <__gnu_cxx::new_allocator<char>> = @{
9529 <No data fields>@}, <No data fields>
9531 members of std::basic_string<char, std::char_traits<char>,
9532 std::allocator<char> >::_Alloc_hider:
9533 _M_p = 0x804a014 "abcd"
9538 With a pretty-printer for @code{std::string} only the contents are printed:
9541 (@value{GDBP}) print s
9545 @node Pretty-Printer Commands
9546 @subsection Pretty-Printer Commands
9547 @cindex pretty-printer commands
9550 @kindex info pretty-printer
9551 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9552 Print the list of installed pretty-printers.
9553 This includes disabled pretty-printers, which are marked as such.
9555 @var{object-regexp} is a regular expression matching the objects
9556 whose pretty-printers to list.
9557 Objects can be @code{global}, the program space's file
9558 (@pxref{Progspaces In Python}),
9559 and the object files within that program space (@pxref{Objfiles In Python}).
9560 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9561 looks up a printer from these three objects.
9563 @var{name-regexp} is a regular expression matching the name of the printers
9566 @kindex disable pretty-printer
9567 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9568 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9569 A disabled pretty-printer is not forgotten, it may be enabled again later.
9571 @kindex enable pretty-printer
9572 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9573 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9578 Suppose we have three pretty-printers installed: one from library1.so
9579 named @code{foo} that prints objects of type @code{foo}, and
9580 another from library2.so named @code{bar} that prints two types of objects,
9581 @code{bar1} and @code{bar2}.
9584 (gdb) info pretty-printer
9591 (gdb) info pretty-printer library2
9596 (gdb) disable pretty-printer library1
9598 2 of 3 printers enabled
9599 (gdb) info pretty-printer
9606 (gdb) disable pretty-printer library2 bar:bar1
9608 1 of 3 printers enabled
9609 (gdb) info pretty-printer library2
9616 (gdb) disable pretty-printer library2 bar
9618 0 of 3 printers enabled
9619 (gdb) info pretty-printer library2
9628 Note that for @code{bar} the entire printer can be disabled,
9629 as can each individual subprinter.
9632 @section Value History
9634 @cindex value history
9635 @cindex history of values printed by @value{GDBN}
9636 Values printed by the @code{print} command are saved in the @value{GDBN}
9637 @dfn{value history}. This allows you to refer to them in other expressions.
9638 Values are kept until the symbol table is re-read or discarded
9639 (for example with the @code{file} or @code{symbol-file} commands).
9640 When the symbol table changes, the value history is discarded,
9641 since the values may contain pointers back to the types defined in the
9646 @cindex history number
9647 The values printed are given @dfn{history numbers} by which you can
9648 refer to them. These are successive integers starting with one.
9649 @code{print} shows you the history number assigned to a value by
9650 printing @samp{$@var{num} = } before the value; here @var{num} is the
9653 To refer to any previous value, use @samp{$} followed by the value's
9654 history number. The way @code{print} labels its output is designed to
9655 remind you of this. Just @code{$} refers to the most recent value in
9656 the history, and @code{$$} refers to the value before that.
9657 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9658 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9659 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9661 For example, suppose you have just printed a pointer to a structure and
9662 want to see the contents of the structure. It suffices to type
9668 If you have a chain of structures where the component @code{next} points
9669 to the next one, you can print the contents of the next one with this:
9676 You can print successive links in the chain by repeating this
9677 command---which you can do by just typing @key{RET}.
9679 Note that the history records values, not expressions. If the value of
9680 @code{x} is 4 and you type these commands:
9688 then the value recorded in the value history by the @code{print} command
9689 remains 4 even though the value of @code{x} has changed.
9694 Print the last ten values in the value history, with their item numbers.
9695 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9696 values} does not change the history.
9698 @item show values @var{n}
9699 Print ten history values centered on history item number @var{n}.
9702 Print ten history values just after the values last printed. If no more
9703 values are available, @code{show values +} produces no display.
9706 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9707 same effect as @samp{show values +}.
9709 @node Convenience Vars
9710 @section Convenience Variables
9712 @cindex convenience variables
9713 @cindex user-defined variables
9714 @value{GDBN} provides @dfn{convenience variables} that you can use within
9715 @value{GDBN} to hold on to a value and refer to it later. These variables
9716 exist entirely within @value{GDBN}; they are not part of your program, and
9717 setting a convenience variable has no direct effect on further execution
9718 of your program. That is why you can use them freely.
9720 Convenience variables are prefixed with @samp{$}. Any name preceded by
9721 @samp{$} can be used for a convenience variable, unless it is one of
9722 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9723 (Value history references, in contrast, are @emph{numbers} preceded
9724 by @samp{$}. @xref{Value History, ,Value History}.)
9726 You can save a value in a convenience variable with an assignment
9727 expression, just as you would set a variable in your program.
9731 set $foo = *object_ptr
9735 would save in @code{$foo} the value contained in the object pointed to by
9738 Using a convenience variable for the first time creates it, but its
9739 value is @code{void} until you assign a new value. You can alter the
9740 value with another assignment at any time.
9742 Convenience variables have no fixed types. You can assign a convenience
9743 variable any type of value, including structures and arrays, even if
9744 that variable already has a value of a different type. The convenience
9745 variable, when used as an expression, has the type of its current value.
9748 @kindex show convenience
9749 @cindex show all user variables and functions
9750 @item show convenience
9751 Print a list of convenience variables used so far, and their values,
9752 as well as a list of the convenience functions.
9753 Abbreviated @code{show conv}.
9755 @kindex init-if-undefined
9756 @cindex convenience variables, initializing
9757 @item init-if-undefined $@var{variable} = @var{expression}
9758 Set a convenience variable if it has not already been set. This is useful
9759 for user-defined commands that keep some state. It is similar, in concept,
9760 to using local static variables with initializers in C (except that
9761 convenience variables are global). It can also be used to allow users to
9762 override default values used in a command script.
9764 If the variable is already defined then the expression is not evaluated so
9765 any side-effects do not occur.
9768 One of the ways to use a convenience variable is as a counter to be
9769 incremented or a pointer to be advanced. For example, to print
9770 a field from successive elements of an array of structures:
9774 print bar[$i++]->contents
9778 Repeat that command by typing @key{RET}.
9780 Some convenience variables are created automatically by @value{GDBN} and given
9781 values likely to be useful.
9784 @vindex $_@r{, convenience variable}
9786 The variable @code{$_} is automatically set by the @code{x} command to
9787 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9788 commands which provide a default address for @code{x} to examine also
9789 set @code{$_} to that address; these commands include @code{info line}
9790 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9791 except when set by the @code{x} command, in which case it is a pointer
9792 to the type of @code{$__}.
9794 @vindex $__@r{, convenience variable}
9796 The variable @code{$__} is automatically set by the @code{x} command
9797 to the value found in the last address examined. Its type is chosen
9798 to match the format in which the data was printed.
9801 @vindex $_exitcode@r{, convenience variable}
9802 When the program being debugged terminates normally, @value{GDBN}
9803 automatically sets this variable to the exit code of the program, and
9804 resets @code{$_exitsignal} to @code{void}.
9807 @vindex $_exitsignal@r{, convenience variable}
9808 When the program being debugged dies due to an uncaught signal,
9809 @value{GDBN} automatically sets this variable to that signal's number,
9810 and resets @code{$_exitcode} to @code{void}.
9812 To distinguish between whether the program being debugged has exited
9813 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9814 @code{$_exitsignal} is not @code{void}), the convenience function
9815 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9816 Functions}). For example, considering the following source code:
9822 main (int argc, char *argv[])
9829 A valid way of telling whether the program being debugged has exited
9830 or signalled would be:
9833 (@value{GDBP}) define has_exited_or_signalled
9834 Type commands for definition of ``has_exited_or_signalled''.
9835 End with a line saying just ``end''.
9836 >if $_isvoid ($_exitsignal)
9837 >echo The program has exited\n
9839 >echo The program has signalled\n
9845 Program terminated with signal SIGALRM, Alarm clock.
9846 The program no longer exists.
9847 (@value{GDBP}) has_exited_or_signalled
9848 The program has signalled
9851 As can be seen, @value{GDBN} correctly informs that the program being
9852 debugged has signalled, since it calls @code{raise} and raises a
9853 @code{SIGALRM} signal. If the program being debugged had not called
9854 @code{raise}, then @value{GDBN} would report a normal exit:
9857 (@value{GDBP}) has_exited_or_signalled
9858 The program has exited
9862 The variable @code{$_exception} is set to the exception object being
9863 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9866 @itemx $_probe_arg0@dots{}$_probe_arg11
9867 Arguments to a static probe. @xref{Static Probe Points}.
9870 @vindex $_sdata@r{, inspect, convenience variable}
9871 The variable @code{$_sdata} contains extra collected static tracepoint
9872 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9873 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9874 if extra static tracepoint data has not been collected.
9877 @vindex $_siginfo@r{, convenience variable}
9878 The variable @code{$_siginfo} contains extra signal information
9879 (@pxref{extra signal information}). Note that @code{$_siginfo}
9880 could be empty, if the application has not yet received any signals.
9881 For example, it will be empty before you execute the @code{run} command.
9884 @vindex $_tlb@r{, convenience variable}
9885 The variable @code{$_tlb} is automatically set when debugging
9886 applications running on MS-Windows in native mode or connected to
9887 gdbserver that supports the @code{qGetTIBAddr} request.
9888 @xref{General Query Packets}.
9889 This variable contains the address of the thread information block.
9893 On HP-UX systems, if you refer to a function or variable name that
9894 begins with a dollar sign, @value{GDBN} searches for a user or system
9895 name first, before it searches for a convenience variable.
9897 @node Convenience Funs
9898 @section Convenience Functions
9900 @cindex convenience functions
9901 @value{GDBN} also supplies some @dfn{convenience functions}. These
9902 have a syntax similar to convenience variables. A convenience
9903 function can be used in an expression just like an ordinary function;
9904 however, a convenience function is implemented internally to
9907 These functions do not require @value{GDBN} to be configured with
9908 @code{Python} support, which means that they are always available.
9912 @item $_isvoid (@var{expr})
9913 @findex $_isvoid@r{, convenience function}
9914 Return one if the expression @var{expr} is @code{void}. Otherwise it
9917 A @code{void} expression is an expression where the type of the result
9918 is @code{void}. For example, you can examine a convenience variable
9919 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9923 (@value{GDBP}) print $_exitcode
9925 (@value{GDBP}) print $_isvoid ($_exitcode)
9928 Starting program: ./a.out
9929 [Inferior 1 (process 29572) exited normally]
9930 (@value{GDBP}) print $_exitcode
9932 (@value{GDBP}) print $_isvoid ($_exitcode)
9936 In the example above, we used @code{$_isvoid} to check whether
9937 @code{$_exitcode} is @code{void} before and after the execution of the
9938 program being debugged. Before the execution there is no exit code to
9939 be examined, therefore @code{$_exitcode} is @code{void}. After the
9940 execution the program being debugged returned zero, therefore
9941 @code{$_exitcode} is zero, which means that it is not @code{void}
9944 The @code{void} expression can also be a call of a function from the
9945 program being debugged. For example, given the following function:
9954 The result of calling it inside @value{GDBN} is @code{void}:
9957 (@value{GDBP}) print foo ()
9959 (@value{GDBP}) print $_isvoid (foo ())
9961 (@value{GDBP}) set $v = foo ()
9962 (@value{GDBP}) print $v
9964 (@value{GDBP}) print $_isvoid ($v)
9970 These functions require @value{GDBN} to be configured with
9971 @code{Python} support.
9975 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9976 @findex $_memeq@r{, convenience function}
9977 Returns one if the @var{length} bytes at the addresses given by
9978 @var{buf1} and @var{buf2} are equal.
9979 Otherwise it returns zero.
9981 @item $_regex(@var{str}, @var{regex})
9982 @findex $_regex@r{, convenience function}
9983 Returns one if the string @var{str} matches the regular expression
9984 @var{regex}. Otherwise it returns zero.
9985 The syntax of the regular expression is that specified by @code{Python}'s
9986 regular expression support.
9988 @item $_streq(@var{str1}, @var{str2})
9989 @findex $_streq@r{, convenience function}
9990 Returns one if the strings @var{str1} and @var{str2} are equal.
9991 Otherwise it returns zero.
9993 @item $_strlen(@var{str})
9994 @findex $_strlen@r{, convenience function}
9995 Returns the length of string @var{str}.
9999 @value{GDBN} provides the ability to list and get help on
10000 convenience functions.
10003 @item help function
10004 @kindex help function
10005 @cindex show all convenience functions
10006 Print a list of all convenience functions.
10013 You can refer to machine register contents, in expressions, as variables
10014 with names starting with @samp{$}. The names of registers are different
10015 for each machine; use @code{info registers} to see the names used on
10019 @kindex info registers
10020 @item info registers
10021 Print the names and values of all registers except floating-point
10022 and vector registers (in the selected stack frame).
10024 @kindex info all-registers
10025 @cindex floating point registers
10026 @item info all-registers
10027 Print the names and values of all registers, including floating-point
10028 and vector registers (in the selected stack frame).
10030 @item info registers @var{regname} @dots{}
10031 Print the @dfn{relativized} value of each specified register @var{regname}.
10032 As discussed in detail below, register values are normally relative to
10033 the selected stack frame. @var{regname} may be any register name valid on
10034 the machine you are using, with or without the initial @samp{$}.
10037 @cindex stack pointer register
10038 @cindex program counter register
10039 @cindex process status register
10040 @cindex frame pointer register
10041 @cindex standard registers
10042 @value{GDBN} has four ``standard'' register names that are available (in
10043 expressions) on most machines---whenever they do not conflict with an
10044 architecture's canonical mnemonics for registers. The register names
10045 @code{$pc} and @code{$sp} are used for the program counter register and
10046 the stack pointer. @code{$fp} is used for a register that contains a
10047 pointer to the current stack frame, and @code{$ps} is used for a
10048 register that contains the processor status. For example,
10049 you could print the program counter in hex with
10056 or print the instruction to be executed next with
10063 or add four to the stack pointer@footnote{This is a way of removing
10064 one word from the stack, on machines where stacks grow downward in
10065 memory (most machines, nowadays). This assumes that the innermost
10066 stack frame is selected; setting @code{$sp} is not allowed when other
10067 stack frames are selected. To pop entire frames off the stack,
10068 regardless of machine architecture, use @code{return};
10069 see @ref{Returning, ,Returning from a Function}.} with
10075 Whenever possible, these four standard register names are available on
10076 your machine even though the machine has different canonical mnemonics,
10077 so long as there is no conflict. The @code{info registers} command
10078 shows the canonical names. For example, on the SPARC, @code{info
10079 registers} displays the processor status register as @code{$psr} but you
10080 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10081 is an alias for the @sc{eflags} register.
10083 @value{GDBN} always considers the contents of an ordinary register as an
10084 integer when the register is examined in this way. Some machines have
10085 special registers which can hold nothing but floating point; these
10086 registers are considered to have floating point values. There is no way
10087 to refer to the contents of an ordinary register as floating point value
10088 (although you can @emph{print} it as a floating point value with
10089 @samp{print/f $@var{regname}}).
10091 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10092 means that the data format in which the register contents are saved by
10093 the operating system is not the same one that your program normally
10094 sees. For example, the registers of the 68881 floating point
10095 coprocessor are always saved in ``extended'' (raw) format, but all C
10096 programs expect to work with ``double'' (virtual) format. In such
10097 cases, @value{GDBN} normally works with the virtual format only (the format
10098 that makes sense for your program), but the @code{info registers} command
10099 prints the data in both formats.
10101 @cindex SSE registers (x86)
10102 @cindex MMX registers (x86)
10103 Some machines have special registers whose contents can be interpreted
10104 in several different ways. For example, modern x86-based machines
10105 have SSE and MMX registers that can hold several values packed
10106 together in several different formats. @value{GDBN} refers to such
10107 registers in @code{struct} notation:
10110 (@value{GDBP}) print $xmm1
10112 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10113 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10114 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10115 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10116 v4_int32 = @{0, 20657912, 11, 13@},
10117 v2_int64 = @{88725056443645952, 55834574859@},
10118 uint128 = 0x0000000d0000000b013b36f800000000
10123 To set values of such registers, you need to tell @value{GDBN} which
10124 view of the register you wish to change, as if you were assigning
10125 value to a @code{struct} member:
10128 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10131 Normally, register values are relative to the selected stack frame
10132 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10133 value that the register would contain if all stack frames farther in
10134 were exited and their saved registers restored. In order to see the
10135 true contents of hardware registers, you must select the innermost
10136 frame (with @samp{frame 0}).
10138 @cindex caller-saved registers
10139 @cindex call-clobbered registers
10140 @cindex volatile registers
10141 @cindex <not saved> values
10142 Usually ABIs reserve some registers as not needed to be saved by the
10143 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10144 registers). It may therefore not be possible for @value{GDBN} to know
10145 the value a register had before the call (in other words, in the outer
10146 frame), if the register value has since been changed by the callee.
10147 @value{GDBN} tries to deduce where the inner frame saved
10148 (``callee-saved'') registers, from the debug info, unwind info, or the
10149 machine code generated by your compiler. If some register is not
10150 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10151 its own knowledge of the ABI, or because the debug/unwind info
10152 explicitly says the register's value is undefined), @value{GDBN}
10153 displays @w{@samp{<not saved>}} as the register's value. With targets
10154 that @value{GDBN} has no knowledge of the register saving convention,
10155 if a register was not saved by the callee, then its value and location
10156 in the outer frame are assumed to be the same of the inner frame.
10157 This is usually harmless, because if the register is call-clobbered,
10158 the caller either does not care what is in the register after the
10159 call, or has code to restore the value that it does care about. Note,
10160 however, that if you change such a register in the outer frame, you
10161 may also be affecting the inner frame. Also, the more ``outer'' the
10162 frame is you're looking at, the more likely a call-clobbered
10163 register's value is to be wrong, in the sense that it doesn't actually
10164 represent the value the register had just before the call.
10166 @node Floating Point Hardware
10167 @section Floating Point Hardware
10168 @cindex floating point
10170 Depending on the configuration, @value{GDBN} may be able to give
10171 you more information about the status of the floating point hardware.
10176 Display hardware-dependent information about the floating
10177 point unit. The exact contents and layout vary depending on the
10178 floating point chip. Currently, @samp{info float} is supported on
10179 the ARM and x86 machines.
10183 @section Vector Unit
10184 @cindex vector unit
10186 Depending on the configuration, @value{GDBN} may be able to give you
10187 more information about the status of the vector unit.
10190 @kindex info vector
10192 Display information about the vector unit. The exact contents and
10193 layout vary depending on the hardware.
10196 @node OS Information
10197 @section Operating System Auxiliary Information
10198 @cindex OS information
10200 @value{GDBN} provides interfaces to useful OS facilities that can help
10201 you debug your program.
10203 @cindex auxiliary vector
10204 @cindex vector, auxiliary
10205 Some operating systems supply an @dfn{auxiliary vector} to programs at
10206 startup. This is akin to the arguments and environment that you
10207 specify for a program, but contains a system-dependent variety of
10208 binary values that tell system libraries important details about the
10209 hardware, operating system, and process. Each value's purpose is
10210 identified by an integer tag; the meanings are well-known but system-specific.
10211 Depending on the configuration and operating system facilities,
10212 @value{GDBN} may be able to show you this information. For remote
10213 targets, this functionality may further depend on the remote stub's
10214 support of the @samp{qXfer:auxv:read} packet, see
10215 @ref{qXfer auxiliary vector read}.
10220 Display the auxiliary vector of the inferior, which can be either a
10221 live process or a core dump file. @value{GDBN} prints each tag value
10222 numerically, and also shows names and text descriptions for recognized
10223 tags. Some values in the vector are numbers, some bit masks, and some
10224 pointers to strings or other data. @value{GDBN} displays each value in the
10225 most appropriate form for a recognized tag, and in hexadecimal for
10226 an unrecognized tag.
10229 On some targets, @value{GDBN} can access operating system-specific
10230 information and show it to you. The types of information available
10231 will differ depending on the type of operating system running on the
10232 target. The mechanism used to fetch the data is described in
10233 @ref{Operating System Information}. For remote targets, this
10234 functionality depends on the remote stub's support of the
10235 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10239 @item info os @var{infotype}
10241 Display OS information of the requested type.
10243 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10245 @anchor{linux info os infotypes}
10247 @kindex info os processes
10249 Display the list of processes on the target. For each process,
10250 @value{GDBN} prints the process identifier, the name of the user, the
10251 command corresponding to the process, and the list of processor cores
10252 that the process is currently running on. (To understand what these
10253 properties mean, for this and the following info types, please consult
10254 the general @sc{gnu}/Linux documentation.)
10256 @kindex info os procgroups
10258 Display the list of process groups on the target. For each process,
10259 @value{GDBN} prints the identifier of the process group that it belongs
10260 to, the command corresponding to the process group leader, the process
10261 identifier, and the command line of the process. The list is sorted
10262 first by the process group identifier, then by the process identifier,
10263 so that processes belonging to the same process group are grouped together
10264 and the process group leader is listed first.
10266 @kindex info os threads
10268 Display the list of threads running on the target. For each thread,
10269 @value{GDBN} prints the identifier of the process that the thread
10270 belongs to, the command of the process, the thread identifier, and the
10271 processor core that it is currently running on. The main thread of a
10272 process is not listed.
10274 @kindex info os files
10276 Display the list of open file descriptors on the target. For each
10277 file descriptor, @value{GDBN} prints the identifier of the process
10278 owning the descriptor, the command of the owning process, the value
10279 of the descriptor, and the target of the descriptor.
10281 @kindex info os sockets
10283 Display the list of Internet-domain sockets on the target. For each
10284 socket, @value{GDBN} prints the address and port of the local and
10285 remote endpoints, the current state of the connection, the creator of
10286 the socket, the IP address family of the socket, and the type of the
10289 @kindex info os shm
10291 Display the list of all System V shared-memory regions on the target.
10292 For each shared-memory region, @value{GDBN} prints the region key,
10293 the shared-memory identifier, the access permissions, the size of the
10294 region, the process that created the region, the process that last
10295 attached to or detached from the region, the current number of live
10296 attaches to the region, and the times at which the region was last
10297 attached to, detach from, and changed.
10299 @kindex info os semaphores
10301 Display the list of all System V semaphore sets on the target. For each
10302 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10303 set identifier, the access permissions, the number of semaphores in the
10304 set, the user and group of the owner and creator of the semaphore set,
10305 and the times at which the semaphore set was operated upon and changed.
10307 @kindex info os msg
10309 Display the list of all System V message queues on the target. For each
10310 message queue, @value{GDBN} prints the message queue key, the message
10311 queue identifier, the access permissions, the current number of bytes
10312 on the queue, the current number of messages on the queue, the processes
10313 that last sent and received a message on the queue, the user and group
10314 of the owner and creator of the message queue, the times at which a
10315 message was last sent and received on the queue, and the time at which
10316 the message queue was last changed.
10318 @kindex info os modules
10320 Display the list of all loaded kernel modules on the target. For each
10321 module, @value{GDBN} prints the module name, the size of the module in
10322 bytes, the number of times the module is used, the dependencies of the
10323 module, the status of the module, and the address of the loaded module
10328 If @var{infotype} is omitted, then list the possible values for
10329 @var{infotype} and the kind of OS information available for each
10330 @var{infotype}. If the target does not return a list of possible
10331 types, this command will report an error.
10334 @node Memory Region Attributes
10335 @section Memory Region Attributes
10336 @cindex memory region attributes
10338 @dfn{Memory region attributes} allow you to describe special handling
10339 required by regions of your target's memory. @value{GDBN} uses
10340 attributes to determine whether to allow certain types of memory
10341 accesses; whether to use specific width accesses; and whether to cache
10342 target memory. By default the description of memory regions is
10343 fetched from the target (if the current target supports this), but the
10344 user can override the fetched regions.
10346 Defined memory regions can be individually enabled and disabled. When a
10347 memory region is disabled, @value{GDBN} uses the default attributes when
10348 accessing memory in that region. Similarly, if no memory regions have
10349 been defined, @value{GDBN} uses the default attributes when accessing
10352 When a memory region is defined, it is given a number to identify it;
10353 to enable, disable, or remove a memory region, you specify that number.
10357 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10358 Define a memory region bounded by @var{lower} and @var{upper} with
10359 attributes @var{attributes}@dots{}, and add it to the list of regions
10360 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10361 case: it is treated as the target's maximum memory address.
10362 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10365 Discard any user changes to the memory regions and use target-supplied
10366 regions, if available, or no regions if the target does not support.
10369 @item delete mem @var{nums}@dots{}
10370 Remove memory regions @var{nums}@dots{} from the list of regions
10371 monitored by @value{GDBN}.
10373 @kindex disable mem
10374 @item disable mem @var{nums}@dots{}
10375 Disable monitoring of memory regions @var{nums}@dots{}.
10376 A disabled memory region is not forgotten.
10377 It may be enabled again later.
10380 @item enable mem @var{nums}@dots{}
10381 Enable monitoring of memory regions @var{nums}@dots{}.
10385 Print a table of all defined memory regions, with the following columns
10389 @item Memory Region Number
10390 @item Enabled or Disabled.
10391 Enabled memory regions are marked with @samp{y}.
10392 Disabled memory regions are marked with @samp{n}.
10395 The address defining the inclusive lower bound of the memory region.
10398 The address defining the exclusive upper bound of the memory region.
10401 The list of attributes set for this memory region.
10406 @subsection Attributes
10408 @subsubsection Memory Access Mode
10409 The access mode attributes set whether @value{GDBN} may make read or
10410 write accesses to a memory region.
10412 While these attributes prevent @value{GDBN} from performing invalid
10413 memory accesses, they do nothing to prevent the target system, I/O DMA,
10414 etc.@: from accessing memory.
10418 Memory is read only.
10420 Memory is write only.
10422 Memory is read/write. This is the default.
10425 @subsubsection Memory Access Size
10426 The access size attribute tells @value{GDBN} to use specific sized
10427 accesses in the memory region. Often memory mapped device registers
10428 require specific sized accesses. If no access size attribute is
10429 specified, @value{GDBN} may use accesses of any size.
10433 Use 8 bit memory accesses.
10435 Use 16 bit memory accesses.
10437 Use 32 bit memory accesses.
10439 Use 64 bit memory accesses.
10442 @c @subsubsection Hardware/Software Breakpoints
10443 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10444 @c will use hardware or software breakpoints for the internal breakpoints
10445 @c used by the step, next, finish, until, etc. commands.
10449 @c Always use hardware breakpoints
10450 @c @item swbreak (default)
10453 @subsubsection Data Cache
10454 The data cache attributes set whether @value{GDBN} will cache target
10455 memory. While this generally improves performance by reducing debug
10456 protocol overhead, it can lead to incorrect results because @value{GDBN}
10457 does not know about volatile variables or memory mapped device
10462 Enable @value{GDBN} to cache target memory.
10464 Disable @value{GDBN} from caching target memory. This is the default.
10467 @subsection Memory Access Checking
10468 @value{GDBN} can be instructed to refuse accesses to memory that is
10469 not explicitly described. This can be useful if accessing such
10470 regions has undesired effects for a specific target, or to provide
10471 better error checking. The following commands control this behaviour.
10474 @kindex set mem inaccessible-by-default
10475 @item set mem inaccessible-by-default [on|off]
10476 If @code{on} is specified, make @value{GDBN} treat memory not
10477 explicitly described by the memory ranges as non-existent and refuse accesses
10478 to such memory. The checks are only performed if there's at least one
10479 memory range defined. If @code{off} is specified, make @value{GDBN}
10480 treat the memory not explicitly described by the memory ranges as RAM.
10481 The default value is @code{on}.
10482 @kindex show mem inaccessible-by-default
10483 @item show mem inaccessible-by-default
10484 Show the current handling of accesses to unknown memory.
10488 @c @subsubsection Memory Write Verification
10489 @c The memory write verification attributes set whether @value{GDBN}
10490 @c will re-reads data after each write to verify the write was successful.
10494 @c @item noverify (default)
10497 @node Dump/Restore Files
10498 @section Copy Between Memory and a File
10499 @cindex dump/restore files
10500 @cindex append data to a file
10501 @cindex dump data to a file
10502 @cindex restore data from a file
10504 You can use the commands @code{dump}, @code{append}, and
10505 @code{restore} to copy data between target memory and a file. The
10506 @code{dump} and @code{append} commands write data to a file, and the
10507 @code{restore} command reads data from a file back into the inferior's
10508 memory. Files may be in binary, Motorola S-record, Intel hex, or
10509 Tektronix Hex format; however, @value{GDBN} can only append to binary
10515 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10516 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10517 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10518 or the value of @var{expr}, to @var{filename} in the given format.
10520 The @var{format} parameter may be any one of:
10527 Motorola S-record format.
10529 Tektronix Hex format.
10532 @value{GDBN} uses the same definitions of these formats as the
10533 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10534 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10538 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10539 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10540 Append the contents of memory from @var{start_addr} to @var{end_addr},
10541 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10542 (@value{GDBN} can only append data to files in raw binary form.)
10545 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10546 Restore the contents of file @var{filename} into memory. The
10547 @code{restore} command can automatically recognize any known @sc{bfd}
10548 file format, except for raw binary. To restore a raw binary file you
10549 must specify the optional keyword @code{binary} after the filename.
10551 If @var{bias} is non-zero, its value will be added to the addresses
10552 contained in the file. Binary files always start at address zero, so
10553 they will be restored at address @var{bias}. Other bfd files have
10554 a built-in location; they will be restored at offset @var{bias}
10555 from that location.
10557 If @var{start} and/or @var{end} are non-zero, then only data between
10558 file offset @var{start} and file offset @var{end} will be restored.
10559 These offsets are relative to the addresses in the file, before
10560 the @var{bias} argument is applied.
10564 @node Core File Generation
10565 @section How to Produce a Core File from Your Program
10566 @cindex dump core from inferior
10568 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10569 image of a running process and its process status (register values
10570 etc.). Its primary use is post-mortem debugging of a program that
10571 crashed while it ran outside a debugger. A program that crashes
10572 automatically produces a core file, unless this feature is disabled by
10573 the user. @xref{Files}, for information on invoking @value{GDBN} in
10574 the post-mortem debugging mode.
10576 Occasionally, you may wish to produce a core file of the program you
10577 are debugging in order to preserve a snapshot of its state.
10578 @value{GDBN} has a special command for that.
10582 @kindex generate-core-file
10583 @item generate-core-file [@var{file}]
10584 @itemx gcore [@var{file}]
10585 Produce a core dump of the inferior process. The optional argument
10586 @var{file} specifies the file name where to put the core dump. If not
10587 specified, the file name defaults to @file{core.@var{pid}}, where
10588 @var{pid} is the inferior process ID.
10590 Note that this command is implemented only for some systems (as of
10591 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10594 @node Character Sets
10595 @section Character Sets
10596 @cindex character sets
10598 @cindex translating between character sets
10599 @cindex host character set
10600 @cindex target character set
10602 If the program you are debugging uses a different character set to
10603 represent characters and strings than the one @value{GDBN} uses itself,
10604 @value{GDBN} can automatically translate between the character sets for
10605 you. The character set @value{GDBN} uses we call the @dfn{host
10606 character set}; the one the inferior program uses we call the
10607 @dfn{target character set}.
10609 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10610 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10611 remote protocol (@pxref{Remote Debugging}) to debug a program
10612 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10613 then the host character set is Latin-1, and the target character set is
10614 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10615 target-charset EBCDIC-US}, then @value{GDBN} translates between
10616 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10617 character and string literals in expressions.
10619 @value{GDBN} has no way to automatically recognize which character set
10620 the inferior program uses; you must tell it, using the @code{set
10621 target-charset} command, described below.
10623 Here are the commands for controlling @value{GDBN}'s character set
10627 @item set target-charset @var{charset}
10628 @kindex set target-charset
10629 Set the current target character set to @var{charset}. To display the
10630 list of supported target character sets, type
10631 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10633 @item set host-charset @var{charset}
10634 @kindex set host-charset
10635 Set the current host character set to @var{charset}.
10637 By default, @value{GDBN} uses a host character set appropriate to the
10638 system it is running on; you can override that default using the
10639 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10640 automatically determine the appropriate host character set. In this
10641 case, @value{GDBN} uses @samp{UTF-8}.
10643 @value{GDBN} can only use certain character sets as its host character
10644 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10645 @value{GDBN} will list the host character sets it supports.
10647 @item set charset @var{charset}
10648 @kindex set charset
10649 Set the current host and target character sets to @var{charset}. As
10650 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10651 @value{GDBN} will list the names of the character sets that can be used
10652 for both host and target.
10655 @kindex show charset
10656 Show the names of the current host and target character sets.
10658 @item show host-charset
10659 @kindex show host-charset
10660 Show the name of the current host character set.
10662 @item show target-charset
10663 @kindex show target-charset
10664 Show the name of the current target character set.
10666 @item set target-wide-charset @var{charset}
10667 @kindex set target-wide-charset
10668 Set the current target's wide character set to @var{charset}. This is
10669 the character set used by the target's @code{wchar_t} type. To
10670 display the list of supported wide character sets, type
10671 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10673 @item show target-wide-charset
10674 @kindex show target-wide-charset
10675 Show the name of the current target's wide character set.
10678 Here is an example of @value{GDBN}'s character set support in action.
10679 Assume that the following source code has been placed in the file
10680 @file{charset-test.c}:
10686 = @{72, 101, 108, 108, 111, 44, 32, 119,
10687 111, 114, 108, 100, 33, 10, 0@};
10688 char ibm1047_hello[]
10689 = @{200, 133, 147, 147, 150, 107, 64, 166,
10690 150, 153, 147, 132, 90, 37, 0@};
10694 printf ("Hello, world!\n");
10698 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10699 containing the string @samp{Hello, world!} followed by a newline,
10700 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10702 We compile the program, and invoke the debugger on it:
10705 $ gcc -g charset-test.c -o charset-test
10706 $ gdb -nw charset-test
10707 GNU gdb 2001-12-19-cvs
10708 Copyright 2001 Free Software Foundation, Inc.
10713 We can use the @code{show charset} command to see what character sets
10714 @value{GDBN} is currently using to interpret and display characters and
10718 (@value{GDBP}) show charset
10719 The current host and target character set is `ISO-8859-1'.
10723 For the sake of printing this manual, let's use @sc{ascii} as our
10724 initial character set:
10726 (@value{GDBP}) set charset ASCII
10727 (@value{GDBP}) show charset
10728 The current host and target character set is `ASCII'.
10732 Let's assume that @sc{ascii} is indeed the correct character set for our
10733 host system --- in other words, let's assume that if @value{GDBN} prints
10734 characters using the @sc{ascii} character set, our terminal will display
10735 them properly. Since our current target character set is also
10736 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10739 (@value{GDBP}) print ascii_hello
10740 $1 = 0x401698 "Hello, world!\n"
10741 (@value{GDBP}) print ascii_hello[0]
10746 @value{GDBN} uses the target character set for character and string
10747 literals you use in expressions:
10750 (@value{GDBP}) print '+'
10755 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10758 @value{GDBN} relies on the user to tell it which character set the
10759 target program uses. If we print @code{ibm1047_hello} while our target
10760 character set is still @sc{ascii}, we get jibberish:
10763 (@value{GDBP}) print ibm1047_hello
10764 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10765 (@value{GDBP}) print ibm1047_hello[0]
10770 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10771 @value{GDBN} tells us the character sets it supports:
10774 (@value{GDBP}) set target-charset
10775 ASCII EBCDIC-US IBM1047 ISO-8859-1
10776 (@value{GDBP}) set target-charset
10779 We can select @sc{ibm1047} as our target character set, and examine the
10780 program's strings again. Now the @sc{ascii} string is wrong, but
10781 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10782 target character set, @sc{ibm1047}, to the host character set,
10783 @sc{ascii}, and they display correctly:
10786 (@value{GDBP}) set target-charset IBM1047
10787 (@value{GDBP}) show charset
10788 The current host character set is `ASCII'.
10789 The current target character set is `IBM1047'.
10790 (@value{GDBP}) print ascii_hello
10791 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10792 (@value{GDBP}) print ascii_hello[0]
10794 (@value{GDBP}) print ibm1047_hello
10795 $8 = 0x4016a8 "Hello, world!\n"
10796 (@value{GDBP}) print ibm1047_hello[0]
10801 As above, @value{GDBN} uses the target character set for character and
10802 string literals you use in expressions:
10805 (@value{GDBP}) print '+'
10810 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10813 @node Caching Remote Data
10814 @section Caching Data of Remote Targets
10815 @cindex caching data of remote targets
10817 @value{GDBN} caches data exchanged between the debugger and a
10818 remote target (@pxref{Remote Debugging}). Such caching generally improves
10819 performance, because it reduces the overhead of the remote protocol by
10820 bundling memory reads and writes into large chunks. Unfortunately, simply
10821 caching everything would lead to incorrect results, since @value{GDBN}
10822 does not necessarily know anything about volatile values, memory-mapped I/O
10823 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10824 memory can be changed @emph{while} a gdb command is executing.
10825 Therefore, by default, @value{GDBN} only caches data
10826 known to be on the stack@footnote{In non-stop mode, it is moderately
10827 rare for a running thread to modify the stack of a stopped thread
10828 in a way that would interfere with a backtrace, and caching of
10829 stack reads provides a significant speed up of remote backtraces.}.
10830 Other regions of memory can be explicitly marked as
10831 cacheable; see @pxref{Memory Region Attributes}.
10834 @kindex set remotecache
10835 @item set remotecache on
10836 @itemx set remotecache off
10837 This option no longer does anything; it exists for compatibility
10840 @kindex show remotecache
10841 @item show remotecache
10842 Show the current state of the obsolete remotecache flag.
10844 @kindex set stack-cache
10845 @item set stack-cache on
10846 @itemx set stack-cache off
10847 Enable or disable caching of stack accesses. When @code{ON}, use
10848 caching. By default, this option is @code{ON}.
10850 @kindex show stack-cache
10851 @item show stack-cache
10852 Show the current state of data caching for memory accesses.
10854 @kindex info dcache
10855 @item info dcache @r{[}line@r{]}
10856 Print the information about the data cache performance. The
10857 information displayed includes the dcache width and depth, and for
10858 each cache line, its number, address, and how many times it was
10859 referenced. This command is useful for debugging the data cache
10862 If a line number is specified, the contents of that line will be
10865 @item set dcache size @var{size}
10866 @cindex dcache size
10867 @kindex set dcache size
10868 Set maximum number of entries in dcache (dcache depth above).
10870 @item set dcache line-size @var{line-size}
10871 @cindex dcache line-size
10872 @kindex set dcache line-size
10873 Set number of bytes each dcache entry caches (dcache width above).
10874 Must be a power of 2.
10876 @item show dcache size
10877 @kindex show dcache size
10878 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10880 @item show dcache line-size
10881 @kindex show dcache line-size
10882 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10886 @node Searching Memory
10887 @section Search Memory
10888 @cindex searching memory
10890 Memory can be searched for a particular sequence of bytes with the
10891 @code{find} command.
10895 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10896 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10897 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10898 etc. The search begins at address @var{start_addr} and continues for either
10899 @var{len} bytes or through to @var{end_addr} inclusive.
10902 @var{s} and @var{n} are optional parameters.
10903 They may be specified in either order, apart or together.
10906 @item @var{s}, search query size
10907 The size of each search query value.
10913 halfwords (two bytes)
10917 giant words (eight bytes)
10920 All values are interpreted in the current language.
10921 This means, for example, that if the current source language is C/C@t{++}
10922 then searching for the string ``hello'' includes the trailing '\0'.
10924 If the value size is not specified, it is taken from the
10925 value's type in the current language.
10926 This is useful when one wants to specify the search
10927 pattern as a mixture of types.
10928 Note that this means, for example, that in the case of C-like languages
10929 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10930 which is typically four bytes.
10932 @item @var{n}, maximum number of finds
10933 The maximum number of matches to print. The default is to print all finds.
10936 You can use strings as search values. Quote them with double-quotes
10938 The string value is copied into the search pattern byte by byte,
10939 regardless of the endianness of the target and the size specification.
10941 The address of each match found is printed as well as a count of the
10942 number of matches found.
10944 The address of the last value found is stored in convenience variable
10946 A count of the number of matches is stored in @samp{$numfound}.
10948 For example, if stopped at the @code{printf} in this function:
10954 static char hello[] = "hello-hello";
10955 static struct @{ char c; short s; int i; @}
10956 __attribute__ ((packed)) mixed
10957 = @{ 'c', 0x1234, 0x87654321 @};
10958 printf ("%s\n", hello);
10963 you get during debugging:
10966 (gdb) find &hello[0], +sizeof(hello), "hello"
10967 0x804956d <hello.1620+6>
10969 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10970 0x8049567 <hello.1620>
10971 0x804956d <hello.1620+6>
10973 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10974 0x8049567 <hello.1620>
10976 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10977 0x8049560 <mixed.1625>
10979 (gdb) print $numfound
10982 $2 = (void *) 0x8049560
10985 @node Optimized Code
10986 @chapter Debugging Optimized Code
10987 @cindex optimized code, debugging
10988 @cindex debugging optimized code
10990 Almost all compilers support optimization. With optimization
10991 disabled, the compiler generates assembly code that corresponds
10992 directly to your source code, in a simplistic way. As the compiler
10993 applies more powerful optimizations, the generated assembly code
10994 diverges from your original source code. With help from debugging
10995 information generated by the compiler, @value{GDBN} can map from
10996 the running program back to constructs from your original source.
10998 @value{GDBN} is more accurate with optimization disabled. If you
10999 can recompile without optimization, it is easier to follow the
11000 progress of your program during debugging. But, there are many cases
11001 where you may need to debug an optimized version.
11003 When you debug a program compiled with @samp{-g -O}, remember that the
11004 optimizer has rearranged your code; the debugger shows you what is
11005 really there. Do not be too surprised when the execution path does not
11006 exactly match your source file! An extreme example: if you define a
11007 variable, but never use it, @value{GDBN} never sees that
11008 variable---because the compiler optimizes it out of existence.
11010 Some things do not work as well with @samp{-g -O} as with just
11011 @samp{-g}, particularly on machines with instruction scheduling. If in
11012 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11013 please report it to us as a bug (including a test case!).
11014 @xref{Variables}, for more information about debugging optimized code.
11017 * Inline Functions:: How @value{GDBN} presents inlining
11018 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11021 @node Inline Functions
11022 @section Inline Functions
11023 @cindex inline functions, debugging
11025 @dfn{Inlining} is an optimization that inserts a copy of the function
11026 body directly at each call site, instead of jumping to a shared
11027 routine. @value{GDBN} displays inlined functions just like
11028 non-inlined functions. They appear in backtraces. You can view their
11029 arguments and local variables, step into them with @code{step}, skip
11030 them with @code{next}, and escape from them with @code{finish}.
11031 You can check whether a function was inlined by using the
11032 @code{info frame} command.
11034 For @value{GDBN} to support inlined functions, the compiler must
11035 record information about inlining in the debug information ---
11036 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11037 other compilers do also. @value{GDBN} only supports inlined functions
11038 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11039 do not emit two required attributes (@samp{DW_AT_call_file} and
11040 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11041 function calls with earlier versions of @value{NGCC}. It instead
11042 displays the arguments and local variables of inlined functions as
11043 local variables in the caller.
11045 The body of an inlined function is directly included at its call site;
11046 unlike a non-inlined function, there are no instructions devoted to
11047 the call. @value{GDBN} still pretends that the call site and the
11048 start of the inlined function are different instructions. Stepping to
11049 the call site shows the call site, and then stepping again shows
11050 the first line of the inlined function, even though no additional
11051 instructions are executed.
11053 This makes source-level debugging much clearer; you can see both the
11054 context of the call and then the effect of the call. Only stepping by
11055 a single instruction using @code{stepi} or @code{nexti} does not do
11056 this; single instruction steps always show the inlined body.
11058 There are some ways that @value{GDBN} does not pretend that inlined
11059 function calls are the same as normal calls:
11063 Setting breakpoints at the call site of an inlined function may not
11064 work, because the call site does not contain any code. @value{GDBN}
11065 may incorrectly move the breakpoint to the next line of the enclosing
11066 function, after the call. This limitation will be removed in a future
11067 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11068 or inside the inlined function instead.
11071 @value{GDBN} cannot locate the return value of inlined calls after
11072 using the @code{finish} command. This is a limitation of compiler-generated
11073 debugging information; after @code{finish}, you can step to the next line
11074 and print a variable where your program stored the return value.
11078 @node Tail Call Frames
11079 @section Tail Call Frames
11080 @cindex tail call frames, debugging
11082 Function @code{B} can call function @code{C} in its very last statement. In
11083 unoptimized compilation the call of @code{C} is immediately followed by return
11084 instruction at the end of @code{B} code. Optimizing compiler may replace the
11085 call and return in function @code{B} into one jump to function @code{C}
11086 instead. Such use of a jump instruction is called @dfn{tail call}.
11088 During execution of function @code{C}, there will be no indication in the
11089 function call stack frames that it was tail-called from @code{B}. If function
11090 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11091 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11092 some cases @value{GDBN} can determine that @code{C} was tail-called from
11093 @code{B}, and it will then create fictitious call frame for that, with the
11094 return address set up as if @code{B} called @code{C} normally.
11096 This functionality is currently supported only by DWARF 2 debugging format and
11097 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11098 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11101 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11102 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11106 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11108 Stack level 1, frame at 0x7fffffffda30:
11109 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11110 tail call frame, caller of frame at 0x7fffffffda30
11111 source language c++.
11112 Arglist at unknown address.
11113 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11116 The detection of all the possible code path executions can find them ambiguous.
11117 There is no execution history stored (possible @ref{Reverse Execution} is never
11118 used for this purpose) and the last known caller could have reached the known
11119 callee by multiple different jump sequences. In such case @value{GDBN} still
11120 tries to show at least all the unambiguous top tail callers and all the
11121 unambiguous bottom tail calees, if any.
11124 @anchor{set debug entry-values}
11125 @item set debug entry-values
11126 @kindex set debug entry-values
11127 When set to on, enables printing of analysis messages for both frame argument
11128 values at function entry and tail calls. It will show all the possible valid
11129 tail calls code paths it has considered. It will also print the intersection
11130 of them with the final unambiguous (possibly partial or even empty) code path
11133 @item show debug entry-values
11134 @kindex show debug entry-values
11135 Show the current state of analysis messages printing for both frame argument
11136 values at function entry and tail calls.
11139 The analysis messages for tail calls can for example show why the virtual tail
11140 call frame for function @code{c} has not been recognized (due to the indirect
11141 reference by variable @code{x}):
11144 static void __attribute__((noinline, noclone)) c (void);
11145 void (*x) (void) = c;
11146 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11147 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11148 int main (void) @{ x (); return 0; @}
11150 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11151 DW_TAG_GNU_call_site 0x40039a in main
11153 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11156 #1 0x000000000040039a in main () at t.c:5
11159 Another possibility is an ambiguous virtual tail call frames resolution:
11163 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11164 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11165 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11166 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11167 static void __attribute__((noinline, noclone)) b (void)
11168 @{ if (i) c (); else e (); @}
11169 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11170 int main (void) @{ a (); return 0; @}
11172 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11173 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11174 tailcall: reduced: 0x4004d2(a) |
11177 #1 0x00000000004004d2 in a () at t.c:8
11178 #2 0x0000000000400395 in main () at t.c:9
11181 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11182 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11184 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11185 @ifset HAVE_MAKEINFO_CLICK
11186 @set ARROW @click{}
11187 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11188 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11190 @ifclear HAVE_MAKEINFO_CLICK
11192 @set CALLSEQ1B @value{CALLSEQ1A}
11193 @set CALLSEQ2B @value{CALLSEQ2A}
11196 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11197 The code can have possible execution paths @value{CALLSEQ1B} or
11198 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11200 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11201 has found. It then finds another possible calling sequcen - that one is
11202 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11203 printed as the @code{reduced:} calling sequence. That one could have many
11204 futher @code{compare:} and @code{reduced:} statements as long as there remain
11205 any non-ambiguous sequence entries.
11207 For the frame of function @code{b} in both cases there are different possible
11208 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11209 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11210 therefore this one is displayed to the user while the ambiguous frames are
11213 There can be also reasons why printing of frame argument values at function
11218 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11219 static void __attribute__((noinline, noclone)) a (int i);
11220 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11221 static void __attribute__((noinline, noclone)) a (int i)
11222 @{ if (i) b (i - 1); else c (0); @}
11223 int main (void) @{ a (5); return 0; @}
11226 #0 c (i=i@@entry=0) at t.c:2
11227 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11228 function "a" at 0x400420 can call itself via tail calls
11229 i=<optimized out>) at t.c:6
11230 #2 0x000000000040036e in main () at t.c:7
11233 @value{GDBN} cannot find out from the inferior state if and how many times did
11234 function @code{a} call itself (via function @code{b}) as these calls would be
11235 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11236 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11237 prints @code{<optimized out>} instead.
11240 @chapter C Preprocessor Macros
11242 Some languages, such as C and C@t{++}, provide a way to define and invoke
11243 ``preprocessor macros'' which expand into strings of tokens.
11244 @value{GDBN} can evaluate expressions containing macro invocations, show
11245 the result of macro expansion, and show a macro's definition, including
11246 where it was defined.
11248 You may need to compile your program specially to provide @value{GDBN}
11249 with information about preprocessor macros. Most compilers do not
11250 include macros in their debugging information, even when you compile
11251 with the @option{-g} flag. @xref{Compilation}.
11253 A program may define a macro at one point, remove that definition later,
11254 and then provide a different definition after that. Thus, at different
11255 points in the program, a macro may have different definitions, or have
11256 no definition at all. If there is a current stack frame, @value{GDBN}
11257 uses the macros in scope at that frame's source code line. Otherwise,
11258 @value{GDBN} uses the macros in scope at the current listing location;
11261 Whenever @value{GDBN} evaluates an expression, it always expands any
11262 macro invocations present in the expression. @value{GDBN} also provides
11263 the following commands for working with macros explicitly.
11267 @kindex macro expand
11268 @cindex macro expansion, showing the results of preprocessor
11269 @cindex preprocessor macro expansion, showing the results of
11270 @cindex expanding preprocessor macros
11271 @item macro expand @var{expression}
11272 @itemx macro exp @var{expression}
11273 Show the results of expanding all preprocessor macro invocations in
11274 @var{expression}. Since @value{GDBN} simply expands macros, but does
11275 not parse the result, @var{expression} need not be a valid expression;
11276 it can be any string of tokens.
11279 @item macro expand-once @var{expression}
11280 @itemx macro exp1 @var{expression}
11281 @cindex expand macro once
11282 @i{(This command is not yet implemented.)} Show the results of
11283 expanding those preprocessor macro invocations that appear explicitly in
11284 @var{expression}. Macro invocations appearing in that expansion are
11285 left unchanged. This command allows you to see the effect of a
11286 particular macro more clearly, without being confused by further
11287 expansions. Since @value{GDBN} simply expands macros, but does not
11288 parse the result, @var{expression} need not be a valid expression; it
11289 can be any string of tokens.
11292 @cindex macro definition, showing
11293 @cindex definition of a macro, showing
11294 @cindex macros, from debug info
11295 @item info macro [-a|-all] [--] @var{macro}
11296 Show the current definition or all definitions of the named @var{macro},
11297 and describe the source location or compiler command-line where that
11298 definition was established. The optional double dash is to signify the end of
11299 argument processing and the beginning of @var{macro} for non C-like macros where
11300 the macro may begin with a hyphen.
11302 @kindex info macros
11303 @item info macros @var{linespec}
11304 Show all macro definitions that are in effect at the location specified
11305 by @var{linespec}, and describe the source location or compiler
11306 command-line where those definitions were established.
11308 @kindex macro define
11309 @cindex user-defined macros
11310 @cindex defining macros interactively
11311 @cindex macros, user-defined
11312 @item macro define @var{macro} @var{replacement-list}
11313 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11314 Introduce a definition for a preprocessor macro named @var{macro},
11315 invocations of which are replaced by the tokens given in
11316 @var{replacement-list}. The first form of this command defines an
11317 ``object-like'' macro, which takes no arguments; the second form
11318 defines a ``function-like'' macro, which takes the arguments given in
11321 A definition introduced by this command is in scope in every
11322 expression evaluated in @value{GDBN}, until it is removed with the
11323 @code{macro undef} command, described below. The definition overrides
11324 all definitions for @var{macro} present in the program being debugged,
11325 as well as any previous user-supplied definition.
11327 @kindex macro undef
11328 @item macro undef @var{macro}
11329 Remove any user-supplied definition for the macro named @var{macro}.
11330 This command only affects definitions provided with the @code{macro
11331 define} command, described above; it cannot remove definitions present
11332 in the program being debugged.
11336 List all the macros defined using the @code{macro define} command.
11339 @cindex macros, example of debugging with
11340 Here is a transcript showing the above commands in action. First, we
11341 show our source files:
11346 #include "sample.h"
11349 #define ADD(x) (M + x)
11354 printf ("Hello, world!\n");
11356 printf ("We're so creative.\n");
11358 printf ("Goodbye, world!\n");
11365 Now, we compile the program using the @sc{gnu} C compiler,
11366 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11367 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11368 and @option{-gdwarf-4}; we recommend always choosing the most recent
11369 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11370 includes information about preprocessor macros in the debugging
11374 $ gcc -gdwarf-2 -g3 sample.c -o sample
11378 Now, we start @value{GDBN} on our sample program:
11382 GNU gdb 2002-05-06-cvs
11383 Copyright 2002 Free Software Foundation, Inc.
11384 GDB is free software, @dots{}
11388 We can expand macros and examine their definitions, even when the
11389 program is not running. @value{GDBN} uses the current listing position
11390 to decide which macro definitions are in scope:
11393 (@value{GDBP}) list main
11396 5 #define ADD(x) (M + x)
11401 10 printf ("Hello, world!\n");
11403 12 printf ("We're so creative.\n");
11404 (@value{GDBP}) info macro ADD
11405 Defined at /home/jimb/gdb/macros/play/sample.c:5
11406 #define ADD(x) (M + x)
11407 (@value{GDBP}) info macro Q
11408 Defined at /home/jimb/gdb/macros/play/sample.h:1
11409 included at /home/jimb/gdb/macros/play/sample.c:2
11411 (@value{GDBP}) macro expand ADD(1)
11412 expands to: (42 + 1)
11413 (@value{GDBP}) macro expand-once ADD(1)
11414 expands to: once (M + 1)
11418 In the example above, note that @code{macro expand-once} expands only
11419 the macro invocation explicit in the original text --- the invocation of
11420 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11421 which was introduced by @code{ADD}.
11423 Once the program is running, @value{GDBN} uses the macro definitions in
11424 force at the source line of the current stack frame:
11427 (@value{GDBP}) break main
11428 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11430 Starting program: /home/jimb/gdb/macros/play/sample
11432 Breakpoint 1, main () at sample.c:10
11433 10 printf ("Hello, world!\n");
11437 At line 10, the definition of the macro @code{N} at line 9 is in force:
11440 (@value{GDBP}) info macro N
11441 Defined at /home/jimb/gdb/macros/play/sample.c:9
11443 (@value{GDBP}) macro expand N Q M
11444 expands to: 28 < 42
11445 (@value{GDBP}) print N Q M
11450 As we step over directives that remove @code{N}'s definition, and then
11451 give it a new definition, @value{GDBN} finds the definition (or lack
11452 thereof) in force at each point:
11455 (@value{GDBP}) next
11457 12 printf ("We're so creative.\n");
11458 (@value{GDBP}) info macro N
11459 The symbol `N' has no definition as a C/C++ preprocessor macro
11460 at /home/jimb/gdb/macros/play/sample.c:12
11461 (@value{GDBP}) next
11463 14 printf ("Goodbye, world!\n");
11464 (@value{GDBP}) info macro N
11465 Defined at /home/jimb/gdb/macros/play/sample.c:13
11467 (@value{GDBP}) macro expand N Q M
11468 expands to: 1729 < 42
11469 (@value{GDBP}) print N Q M
11474 In addition to source files, macros can be defined on the compilation command
11475 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11476 such a way, @value{GDBN} displays the location of their definition as line zero
11477 of the source file submitted to the compiler.
11480 (@value{GDBP}) info macro __STDC__
11481 Defined at /home/jimb/gdb/macros/play/sample.c:0
11488 @chapter Tracepoints
11489 @c This chapter is based on the documentation written by Michael
11490 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11492 @cindex tracepoints
11493 In some applications, it is not feasible for the debugger to interrupt
11494 the program's execution long enough for the developer to learn
11495 anything helpful about its behavior. If the program's correctness
11496 depends on its real-time behavior, delays introduced by a debugger
11497 might cause the program to change its behavior drastically, or perhaps
11498 fail, even when the code itself is correct. It is useful to be able
11499 to observe the program's behavior without interrupting it.
11501 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11502 specify locations in the program, called @dfn{tracepoints}, and
11503 arbitrary expressions to evaluate when those tracepoints are reached.
11504 Later, using the @code{tfind} command, you can examine the values
11505 those expressions had when the program hit the tracepoints. The
11506 expressions may also denote objects in memory---structures or arrays,
11507 for example---whose values @value{GDBN} should record; while visiting
11508 a particular tracepoint, you may inspect those objects as if they were
11509 in memory at that moment. However, because @value{GDBN} records these
11510 values without interacting with you, it can do so quickly and
11511 unobtrusively, hopefully not disturbing the program's behavior.
11513 The tracepoint facility is currently available only for remote
11514 targets. @xref{Targets}. In addition, your remote target must know
11515 how to collect trace data. This functionality is implemented in the
11516 remote stub; however, none of the stubs distributed with @value{GDBN}
11517 support tracepoints as of this writing. The format of the remote
11518 packets used to implement tracepoints are described in @ref{Tracepoint
11521 It is also possible to get trace data from a file, in a manner reminiscent
11522 of corefiles; you specify the filename, and use @code{tfind} to search
11523 through the file. @xref{Trace Files}, for more details.
11525 This chapter describes the tracepoint commands and features.
11528 * Set Tracepoints::
11529 * Analyze Collected Data::
11530 * Tracepoint Variables::
11534 @node Set Tracepoints
11535 @section Commands to Set Tracepoints
11537 Before running such a @dfn{trace experiment}, an arbitrary number of
11538 tracepoints can be set. A tracepoint is actually a special type of
11539 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11540 standard breakpoint commands. For instance, as with breakpoints,
11541 tracepoint numbers are successive integers starting from one, and many
11542 of the commands associated with tracepoints take the tracepoint number
11543 as their argument, to identify which tracepoint to work on.
11545 For each tracepoint, you can specify, in advance, some arbitrary set
11546 of data that you want the target to collect in the trace buffer when
11547 it hits that tracepoint. The collected data can include registers,
11548 local variables, or global data. Later, you can use @value{GDBN}
11549 commands to examine the values these data had at the time the
11550 tracepoint was hit.
11552 Tracepoints do not support every breakpoint feature. Ignore counts on
11553 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11554 commands when they are hit. Tracepoints may not be thread-specific
11557 @cindex fast tracepoints
11558 Some targets may support @dfn{fast tracepoints}, which are inserted in
11559 a different way (such as with a jump instead of a trap), that is
11560 faster but possibly restricted in where they may be installed.
11562 @cindex static tracepoints
11563 @cindex markers, static tracepoints
11564 @cindex probing markers, static tracepoints
11565 Regular and fast tracepoints are dynamic tracing facilities, meaning
11566 that they can be used to insert tracepoints at (almost) any location
11567 in the target. Some targets may also support controlling @dfn{static
11568 tracepoints} from @value{GDBN}. With static tracing, a set of
11569 instrumentation points, also known as @dfn{markers}, are embedded in
11570 the target program, and can be activated or deactivated by name or
11571 address. These are usually placed at locations which facilitate
11572 investigating what the target is actually doing. @value{GDBN}'s
11573 support for static tracing includes being able to list instrumentation
11574 points, and attach them with @value{GDBN} defined high level
11575 tracepoints that expose the whole range of convenience of
11576 @value{GDBN}'s tracepoints support. Namely, support for collecting
11577 registers values and values of global or local (to the instrumentation
11578 point) variables; tracepoint conditions and trace state variables.
11579 The act of installing a @value{GDBN} static tracepoint on an
11580 instrumentation point, or marker, is referred to as @dfn{probing} a
11581 static tracepoint marker.
11583 @code{gdbserver} supports tracepoints on some target systems.
11584 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11586 This section describes commands to set tracepoints and associated
11587 conditions and actions.
11590 * Create and Delete Tracepoints::
11591 * Enable and Disable Tracepoints::
11592 * Tracepoint Passcounts::
11593 * Tracepoint Conditions::
11594 * Trace State Variables::
11595 * Tracepoint Actions::
11596 * Listing Tracepoints::
11597 * Listing Static Tracepoint Markers::
11598 * Starting and Stopping Trace Experiments::
11599 * Tracepoint Restrictions::
11602 @node Create and Delete Tracepoints
11603 @subsection Create and Delete Tracepoints
11606 @cindex set tracepoint
11608 @item trace @var{location}
11609 The @code{trace} command is very similar to the @code{break} command.
11610 Its argument @var{location} can be a source line, a function name, or
11611 an address in the target program. @xref{Specify Location}. The
11612 @code{trace} command defines a tracepoint, which is a point in the
11613 target program where the debugger will briefly stop, collect some
11614 data, and then allow the program to continue. Setting a tracepoint or
11615 changing its actions takes effect immediately if the remote stub
11616 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11618 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11619 these changes don't take effect until the next @code{tstart}
11620 command, and once a trace experiment is running, further changes will
11621 not have any effect until the next trace experiment starts. In addition,
11622 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11623 address is not yet resolved. (This is similar to pending breakpoints.)
11624 Pending tracepoints are not downloaded to the target and not installed
11625 until they are resolved. The resolution of pending tracepoints requires
11626 @value{GDBN} support---when debugging with the remote target, and
11627 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11628 tracing}), pending tracepoints can not be resolved (and downloaded to
11629 the remote stub) while @value{GDBN} is disconnected.
11631 Here are some examples of using the @code{trace} command:
11634 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11636 (@value{GDBP}) @b{trace +2} // 2 lines forward
11638 (@value{GDBP}) @b{trace my_function} // first source line of function
11640 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11642 (@value{GDBP}) @b{trace *0x2117c4} // an address
11646 You can abbreviate @code{trace} as @code{tr}.
11648 @item trace @var{location} if @var{cond}
11649 Set a tracepoint with condition @var{cond}; evaluate the expression
11650 @var{cond} each time the tracepoint is reached, and collect data only
11651 if the value is nonzero---that is, if @var{cond} evaluates as true.
11652 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11653 information on tracepoint conditions.
11655 @item ftrace @var{location} [ if @var{cond} ]
11656 @cindex set fast tracepoint
11657 @cindex fast tracepoints, setting
11659 The @code{ftrace} command sets a fast tracepoint. For targets that
11660 support them, fast tracepoints will use a more efficient but possibly
11661 less general technique to trigger data collection, such as a jump
11662 instruction instead of a trap, or some sort of hardware support. It
11663 may not be possible to create a fast tracepoint at the desired
11664 location, in which case the command will exit with an explanatory
11667 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11670 On 32-bit x86-architecture systems, fast tracepoints normally need to
11671 be placed at an instruction that is 5 bytes or longer, but can be
11672 placed at 4-byte instructions if the low 64K of memory of the target
11673 program is available to install trampolines. Some Unix-type systems,
11674 such as @sc{gnu}/Linux, exclude low addresses from the program's
11675 address space; but for instance with the Linux kernel it is possible
11676 to let @value{GDBN} use this area by doing a @command{sysctl} command
11677 to set the @code{mmap_min_addr} kernel parameter, as in
11680 sudo sysctl -w vm.mmap_min_addr=32768
11684 which sets the low address to 32K, which leaves plenty of room for
11685 trampolines. The minimum address should be set to a page boundary.
11687 @item strace @var{location} [ if @var{cond} ]
11688 @cindex set static tracepoint
11689 @cindex static tracepoints, setting
11690 @cindex probe static tracepoint marker
11692 The @code{strace} command sets a static tracepoint. For targets that
11693 support it, setting a static tracepoint probes a static
11694 instrumentation point, or marker, found at @var{location}. It may not
11695 be possible to set a static tracepoint at the desired location, in
11696 which case the command will exit with an explanatory message.
11698 @value{GDBN} handles arguments to @code{strace} exactly as for
11699 @code{trace}, with the addition that the user can also specify
11700 @code{-m @var{marker}} as @var{location}. This probes the marker
11701 identified by the @var{marker} string identifier. This identifier
11702 depends on the static tracepoint backend library your program is
11703 using. You can find all the marker identifiers in the @samp{ID} field
11704 of the @code{info static-tracepoint-markers} command output.
11705 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11706 Markers}. For example, in the following small program using the UST
11712 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11717 the marker id is composed of joining the first two arguments to the
11718 @code{trace_mark} call with a slash, which translates to:
11721 (@value{GDBP}) info static-tracepoint-markers
11722 Cnt Enb ID Address What
11723 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11729 so you may probe the marker above with:
11732 (@value{GDBP}) strace -m ust/bar33
11735 Static tracepoints accept an extra collect action --- @code{collect
11736 $_sdata}. This collects arbitrary user data passed in the probe point
11737 call to the tracing library. In the UST example above, you'll see
11738 that the third argument to @code{trace_mark} is a printf-like format
11739 string. The user data is then the result of running that formating
11740 string against the following arguments. Note that @code{info
11741 static-tracepoint-markers} command output lists that format string in
11742 the @samp{Data:} field.
11744 You can inspect this data when analyzing the trace buffer, by printing
11745 the $_sdata variable like any other variable available to
11746 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11749 @cindex last tracepoint number
11750 @cindex recent tracepoint number
11751 @cindex tracepoint number
11752 The convenience variable @code{$tpnum} records the tracepoint number
11753 of the most recently set tracepoint.
11755 @kindex delete tracepoint
11756 @cindex tracepoint deletion
11757 @item delete tracepoint @r{[}@var{num}@r{]}
11758 Permanently delete one or more tracepoints. With no argument, the
11759 default is to delete all tracepoints. Note that the regular
11760 @code{delete} command can remove tracepoints also.
11765 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11767 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11771 You can abbreviate this command as @code{del tr}.
11774 @node Enable and Disable Tracepoints
11775 @subsection Enable and Disable Tracepoints
11777 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11780 @kindex disable tracepoint
11781 @item disable tracepoint @r{[}@var{num}@r{]}
11782 Disable tracepoint @var{num}, or all tracepoints if no argument
11783 @var{num} is given. A disabled tracepoint will have no effect during
11784 a trace experiment, but it is not forgotten. You can re-enable
11785 a disabled tracepoint using the @code{enable tracepoint} command.
11786 If the command is issued during a trace experiment and the debug target
11787 has support for disabling tracepoints during a trace experiment, then the
11788 change will be effective immediately. Otherwise, it will be applied to the
11789 next trace experiment.
11791 @kindex enable tracepoint
11792 @item enable tracepoint @r{[}@var{num}@r{]}
11793 Enable tracepoint @var{num}, or all tracepoints. If this command is
11794 issued during a trace experiment and the debug target supports enabling
11795 tracepoints during a trace experiment, then the enabled tracepoints will
11796 become effective immediately. Otherwise, they will become effective the
11797 next time a trace experiment is run.
11800 @node Tracepoint Passcounts
11801 @subsection Tracepoint Passcounts
11805 @cindex tracepoint pass count
11806 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11807 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11808 automatically stop a trace experiment. If a tracepoint's passcount is
11809 @var{n}, then the trace experiment will be automatically stopped on
11810 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11811 @var{num} is not specified, the @code{passcount} command sets the
11812 passcount of the most recently defined tracepoint. If no passcount is
11813 given, the trace experiment will run until stopped explicitly by the
11819 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11820 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11822 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11823 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11824 (@value{GDBP}) @b{trace foo}
11825 (@value{GDBP}) @b{pass 3}
11826 (@value{GDBP}) @b{trace bar}
11827 (@value{GDBP}) @b{pass 2}
11828 (@value{GDBP}) @b{trace baz}
11829 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11830 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11831 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11832 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11836 @node Tracepoint Conditions
11837 @subsection Tracepoint Conditions
11838 @cindex conditional tracepoints
11839 @cindex tracepoint conditions
11841 The simplest sort of tracepoint collects data every time your program
11842 reaches a specified place. You can also specify a @dfn{condition} for
11843 a tracepoint. A condition is just a Boolean expression in your
11844 programming language (@pxref{Expressions, ,Expressions}). A
11845 tracepoint with a condition evaluates the expression each time your
11846 program reaches it, and data collection happens only if the condition
11849 Tracepoint conditions can be specified when a tracepoint is set, by
11850 using @samp{if} in the arguments to the @code{trace} command.
11851 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11852 also be set or changed at any time with the @code{condition} command,
11853 just as with breakpoints.
11855 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11856 the conditional expression itself. Instead, @value{GDBN} encodes the
11857 expression into an agent expression (@pxref{Agent Expressions})
11858 suitable for execution on the target, independently of @value{GDBN}.
11859 Global variables become raw memory locations, locals become stack
11860 accesses, and so forth.
11862 For instance, suppose you have a function that is usually called
11863 frequently, but should not be called after an error has occurred. You
11864 could use the following tracepoint command to collect data about calls
11865 of that function that happen while the error code is propagating
11866 through the program; an unconditional tracepoint could end up
11867 collecting thousands of useless trace frames that you would have to
11871 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11874 @node Trace State Variables
11875 @subsection Trace State Variables
11876 @cindex trace state variables
11878 A @dfn{trace state variable} is a special type of variable that is
11879 created and managed by target-side code. The syntax is the same as
11880 that for GDB's convenience variables (a string prefixed with ``$''),
11881 but they are stored on the target. They must be created explicitly,
11882 using a @code{tvariable} command. They are always 64-bit signed
11885 Trace state variables are remembered by @value{GDBN}, and downloaded
11886 to the target along with tracepoint information when the trace
11887 experiment starts. There are no intrinsic limits on the number of
11888 trace state variables, beyond memory limitations of the target.
11890 @cindex convenience variables, and trace state variables
11891 Although trace state variables are managed by the target, you can use
11892 them in print commands and expressions as if they were convenience
11893 variables; @value{GDBN} will get the current value from the target
11894 while the trace experiment is running. Trace state variables share
11895 the same namespace as other ``$'' variables, which means that you
11896 cannot have trace state variables with names like @code{$23} or
11897 @code{$pc}, nor can you have a trace state variable and a convenience
11898 variable with the same name.
11902 @item tvariable $@var{name} [ = @var{expression} ]
11904 The @code{tvariable} command creates a new trace state variable named
11905 @code{$@var{name}}, and optionally gives it an initial value of
11906 @var{expression}. @var{expression} is evaluated when this command is
11907 entered; the result will be converted to an integer if possible,
11908 otherwise @value{GDBN} will report an error. A subsequent
11909 @code{tvariable} command specifying the same name does not create a
11910 variable, but instead assigns the supplied initial value to the
11911 existing variable of that name, overwriting any previous initial
11912 value. The default initial value is 0.
11914 @item info tvariables
11915 @kindex info tvariables
11916 List all the trace state variables along with their initial values.
11917 Their current values may also be displayed, if the trace experiment is
11920 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11921 @kindex delete tvariable
11922 Delete the given trace state variables, or all of them if no arguments
11927 @node Tracepoint Actions
11928 @subsection Tracepoint Action Lists
11932 @cindex tracepoint actions
11933 @item actions @r{[}@var{num}@r{]}
11934 This command will prompt for a list of actions to be taken when the
11935 tracepoint is hit. If the tracepoint number @var{num} is not
11936 specified, this command sets the actions for the one that was most
11937 recently defined (so that you can define a tracepoint and then say
11938 @code{actions} without bothering about its number). You specify the
11939 actions themselves on the following lines, one action at a time, and
11940 terminate the actions list with a line containing just @code{end}. So
11941 far, the only defined actions are @code{collect}, @code{teval}, and
11942 @code{while-stepping}.
11944 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11945 Commands, ,Breakpoint Command Lists}), except that only the defined
11946 actions are allowed; any other @value{GDBN} command is rejected.
11948 @cindex remove actions from a tracepoint
11949 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11950 and follow it immediately with @samp{end}.
11953 (@value{GDBP}) @b{collect @var{data}} // collect some data
11955 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11957 (@value{GDBP}) @b{end} // signals the end of actions.
11960 In the following example, the action list begins with @code{collect}
11961 commands indicating the things to be collected when the tracepoint is
11962 hit. Then, in order to single-step and collect additional data
11963 following the tracepoint, a @code{while-stepping} command is used,
11964 followed by the list of things to be collected after each step in a
11965 sequence of single steps. The @code{while-stepping} command is
11966 terminated by its own separate @code{end} command. Lastly, the action
11967 list is terminated by an @code{end} command.
11970 (@value{GDBP}) @b{trace foo}
11971 (@value{GDBP}) @b{actions}
11972 Enter actions for tracepoint 1, one per line:
11975 > while-stepping 12
11976 > collect $pc, arr[i]
11981 @kindex collect @r{(tracepoints)}
11982 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11983 Collect values of the given expressions when the tracepoint is hit.
11984 This command accepts a comma-separated list of any valid expressions.
11985 In addition to global, static, or local variables, the following
11986 special arguments are supported:
11990 Collect all registers.
11993 Collect all function arguments.
11996 Collect all local variables.
11999 Collect the return address. This is helpful if you want to see more
12003 Collects the number of arguments from the static probe at which the
12004 tracepoint is located.
12005 @xref{Static Probe Points}.
12007 @item $_probe_arg@var{n}
12008 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12009 from the static probe at which the tracepoint is located.
12010 @xref{Static Probe Points}.
12013 @vindex $_sdata@r{, collect}
12014 Collect static tracepoint marker specific data. Only available for
12015 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12016 Lists}. On the UST static tracepoints library backend, an
12017 instrumentation point resembles a @code{printf} function call. The
12018 tracing library is able to collect user specified data formatted to a
12019 character string using the format provided by the programmer that
12020 instrumented the program. Other backends have similar mechanisms.
12021 Here's an example of a UST marker call:
12024 const char master_name[] = "$your_name";
12025 trace_mark(channel1, marker1, "hello %s", master_name)
12028 In this case, collecting @code{$_sdata} collects the string
12029 @samp{hello $yourname}. When analyzing the trace buffer, you can
12030 inspect @samp{$_sdata} like any other variable available to
12034 You can give several consecutive @code{collect} commands, each one
12035 with a single argument, or one @code{collect} command with several
12036 arguments separated by commas; the effect is the same.
12038 The optional @var{mods} changes the usual handling of the arguments.
12039 @code{s} requests that pointers to chars be handled as strings, in
12040 particular collecting the contents of the memory being pointed at, up
12041 to the first zero. The upper bound is by default the value of the
12042 @code{print elements} variable; if @code{s} is followed by a decimal
12043 number, that is the upper bound instead. So for instance
12044 @samp{collect/s25 mystr} collects as many as 25 characters at
12047 The command @code{info scope} (@pxref{Symbols, info scope}) is
12048 particularly useful for figuring out what data to collect.
12050 @kindex teval @r{(tracepoints)}
12051 @item teval @var{expr1}, @var{expr2}, @dots{}
12052 Evaluate the given expressions when the tracepoint is hit. This
12053 command accepts a comma-separated list of expressions. The results
12054 are discarded, so this is mainly useful for assigning values to trace
12055 state variables (@pxref{Trace State Variables}) without adding those
12056 values to the trace buffer, as would be the case if the @code{collect}
12059 @kindex while-stepping @r{(tracepoints)}
12060 @item while-stepping @var{n}
12061 Perform @var{n} single-step instruction traces after the tracepoint,
12062 collecting new data after each step. The @code{while-stepping}
12063 command is followed by the list of what to collect while stepping
12064 (followed by its own @code{end} command):
12067 > while-stepping 12
12068 > collect $regs, myglobal
12074 Note that @code{$pc} is not automatically collected by
12075 @code{while-stepping}; you need to explicitly collect that register if
12076 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12079 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12080 @kindex set default-collect
12081 @cindex default collection action
12082 This variable is a list of expressions to collect at each tracepoint
12083 hit. It is effectively an additional @code{collect} action prepended
12084 to every tracepoint action list. The expressions are parsed
12085 individually for each tracepoint, so for instance a variable named
12086 @code{xyz} may be interpreted as a global for one tracepoint, and a
12087 local for another, as appropriate to the tracepoint's location.
12089 @item show default-collect
12090 @kindex show default-collect
12091 Show the list of expressions that are collected by default at each
12096 @node Listing Tracepoints
12097 @subsection Listing Tracepoints
12100 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12101 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12102 @cindex information about tracepoints
12103 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12104 Display information about the tracepoint @var{num}. If you don't
12105 specify a tracepoint number, displays information about all the
12106 tracepoints defined so far. The format is similar to that used for
12107 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12108 command, simply restricting itself to tracepoints.
12110 A tracepoint's listing may include additional information specific to
12115 its passcount as given by the @code{passcount @var{n}} command
12118 the state about installed on target of each location
12122 (@value{GDBP}) @b{info trace}
12123 Num Type Disp Enb Address What
12124 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12126 collect globfoo, $regs
12131 2 tracepoint keep y <MULTIPLE>
12133 2.1 y 0x0804859c in func4 at change-loc.h:35
12134 installed on target
12135 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12136 installed on target
12137 2.3 y <PENDING> set_tracepoint
12138 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12139 not installed on target
12144 This command can be abbreviated @code{info tp}.
12147 @node Listing Static Tracepoint Markers
12148 @subsection Listing Static Tracepoint Markers
12151 @kindex info static-tracepoint-markers
12152 @cindex information about static tracepoint markers
12153 @item info static-tracepoint-markers
12154 Display information about all static tracepoint markers defined in the
12157 For each marker, the following columns are printed:
12161 An incrementing counter, output to help readability. This is not a
12164 The marker ID, as reported by the target.
12165 @item Enabled or Disabled
12166 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12167 that are not enabled.
12169 Where the marker is in your program, as a memory address.
12171 Where the marker is in the source for your program, as a file and line
12172 number. If the debug information included in the program does not
12173 allow @value{GDBN} to locate the source of the marker, this column
12174 will be left blank.
12178 In addition, the following information may be printed for each marker:
12182 User data passed to the tracing library by the marker call. In the
12183 UST backend, this is the format string passed as argument to the
12185 @item Static tracepoints probing the marker
12186 The list of static tracepoints attached to the marker.
12190 (@value{GDBP}) info static-tracepoint-markers
12191 Cnt ID Enb Address What
12192 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12193 Data: number1 %d number2 %d
12194 Probed by static tracepoints: #2
12195 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12201 @node Starting and Stopping Trace Experiments
12202 @subsection Starting and Stopping Trace Experiments
12205 @kindex tstart [ @var{notes} ]
12206 @cindex start a new trace experiment
12207 @cindex collected data discarded
12209 This command starts the trace experiment, and begins collecting data.
12210 It has the side effect of discarding all the data collected in the
12211 trace buffer during the previous trace experiment. If any arguments
12212 are supplied, they are taken as a note and stored with the trace
12213 experiment's state. The notes may be arbitrary text, and are
12214 especially useful with disconnected tracing in a multi-user context;
12215 the notes can explain what the trace is doing, supply user contact
12216 information, and so forth.
12218 @kindex tstop [ @var{notes} ]
12219 @cindex stop a running trace experiment
12221 This command stops the trace experiment. If any arguments are
12222 supplied, they are recorded with the experiment as a note. This is
12223 useful if you are stopping a trace started by someone else, for
12224 instance if the trace is interfering with the system's behavior and
12225 needs to be stopped quickly.
12227 @strong{Note}: a trace experiment and data collection may stop
12228 automatically if any tracepoint's passcount is reached
12229 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12232 @cindex status of trace data collection
12233 @cindex trace experiment, status of
12235 This command displays the status of the current trace data
12239 Here is an example of the commands we described so far:
12242 (@value{GDBP}) @b{trace gdb_c_test}
12243 (@value{GDBP}) @b{actions}
12244 Enter actions for tracepoint #1, one per line.
12245 > collect $regs,$locals,$args
12246 > while-stepping 11
12250 (@value{GDBP}) @b{tstart}
12251 [time passes @dots{}]
12252 (@value{GDBP}) @b{tstop}
12255 @anchor{disconnected tracing}
12256 @cindex disconnected tracing
12257 You can choose to continue running the trace experiment even if
12258 @value{GDBN} disconnects from the target, voluntarily or
12259 involuntarily. For commands such as @code{detach}, the debugger will
12260 ask what you want to do with the trace. But for unexpected
12261 terminations (@value{GDBN} crash, network outage), it would be
12262 unfortunate to lose hard-won trace data, so the variable
12263 @code{disconnected-tracing} lets you decide whether the trace should
12264 continue running without @value{GDBN}.
12267 @item set disconnected-tracing on
12268 @itemx set disconnected-tracing off
12269 @kindex set disconnected-tracing
12270 Choose whether a tracing run should continue to run if @value{GDBN}
12271 has disconnected from the target. Note that @code{detach} or
12272 @code{quit} will ask you directly what to do about a running trace no
12273 matter what this variable's setting, so the variable is mainly useful
12274 for handling unexpected situations, such as loss of the network.
12276 @item show disconnected-tracing
12277 @kindex show disconnected-tracing
12278 Show the current choice for disconnected tracing.
12282 When you reconnect to the target, the trace experiment may or may not
12283 still be running; it might have filled the trace buffer in the
12284 meantime, or stopped for one of the other reasons. If it is running,
12285 it will continue after reconnection.
12287 Upon reconnection, the target will upload information about the
12288 tracepoints in effect. @value{GDBN} will then compare that
12289 information to the set of tracepoints currently defined, and attempt
12290 to match them up, allowing for the possibility that the numbers may
12291 have changed due to creation and deletion in the meantime. If one of
12292 the target's tracepoints does not match any in @value{GDBN}, the
12293 debugger will create a new tracepoint, so that you have a number with
12294 which to specify that tracepoint. This matching-up process is
12295 necessarily heuristic, and it may result in useless tracepoints being
12296 created; you may simply delete them if they are of no use.
12298 @cindex circular trace buffer
12299 If your target agent supports a @dfn{circular trace buffer}, then you
12300 can run a trace experiment indefinitely without filling the trace
12301 buffer; when space runs out, the agent deletes already-collected trace
12302 frames, oldest first, until there is enough room to continue
12303 collecting. This is especially useful if your tracepoints are being
12304 hit too often, and your trace gets terminated prematurely because the
12305 buffer is full. To ask for a circular trace buffer, simply set
12306 @samp{circular-trace-buffer} to on. You can set this at any time,
12307 including during tracing; if the agent can do it, it will change
12308 buffer handling on the fly, otherwise it will not take effect until
12312 @item set circular-trace-buffer on
12313 @itemx set circular-trace-buffer off
12314 @kindex set circular-trace-buffer
12315 Choose whether a tracing run should use a linear or circular buffer
12316 for trace data. A linear buffer will not lose any trace data, but may
12317 fill up prematurely, while a circular buffer will discard old trace
12318 data, but it will have always room for the latest tracepoint hits.
12320 @item show circular-trace-buffer
12321 @kindex show circular-trace-buffer
12322 Show the current choice for the trace buffer. Note that this may not
12323 match the agent's current buffer handling, nor is it guaranteed to
12324 match the setting that might have been in effect during a past run,
12325 for instance if you are looking at frames from a trace file.
12330 @item set trace-buffer-size @var{n}
12331 @itemx set trace-buffer-size unlimited
12332 @kindex set trace-buffer-size
12333 Request that the target use a trace buffer of @var{n} bytes. Not all
12334 targets will honor the request; they may have a compiled-in size for
12335 the trace buffer, or some other limitation. Set to a value of
12336 @code{unlimited} or @code{-1} to let the target use whatever size it
12337 likes. This is also the default.
12339 @item show trace-buffer-size
12340 @kindex show trace-buffer-size
12341 Show the current requested size for the trace buffer. Note that this
12342 will only match the actual size if the target supports size-setting,
12343 and was able to handle the requested size. For instance, if the
12344 target can only change buffer size between runs, this variable will
12345 not reflect the change until the next run starts. Use @code{tstatus}
12346 to get a report of the actual buffer size.
12350 @item set trace-user @var{text}
12351 @kindex set trace-user
12353 @item show trace-user
12354 @kindex show trace-user
12356 @item set trace-notes @var{text}
12357 @kindex set trace-notes
12358 Set the trace run's notes.
12360 @item show trace-notes
12361 @kindex show trace-notes
12362 Show the trace run's notes.
12364 @item set trace-stop-notes @var{text}
12365 @kindex set trace-stop-notes
12366 Set the trace run's stop notes. The handling of the note is as for
12367 @code{tstop} arguments; the set command is convenient way to fix a
12368 stop note that is mistaken or incomplete.
12370 @item show trace-stop-notes
12371 @kindex show trace-stop-notes
12372 Show the trace run's stop notes.
12376 @node Tracepoint Restrictions
12377 @subsection Tracepoint Restrictions
12379 @cindex tracepoint restrictions
12380 There are a number of restrictions on the use of tracepoints. As
12381 described above, tracepoint data gathering occurs on the target
12382 without interaction from @value{GDBN}. Thus the full capabilities of
12383 the debugger are not available during data gathering, and then at data
12384 examination time, you will be limited by only having what was
12385 collected. The following items describe some common problems, but it
12386 is not exhaustive, and you may run into additional difficulties not
12392 Tracepoint expressions are intended to gather objects (lvalues). Thus
12393 the full flexibility of GDB's expression evaluator is not available.
12394 You cannot call functions, cast objects to aggregate types, access
12395 convenience variables or modify values (except by assignment to trace
12396 state variables). Some language features may implicitly call
12397 functions (for instance Objective-C fields with accessors), and therefore
12398 cannot be collected either.
12401 Collection of local variables, either individually or in bulk with
12402 @code{$locals} or @code{$args}, during @code{while-stepping} may
12403 behave erratically. The stepping action may enter a new scope (for
12404 instance by stepping into a function), or the location of the variable
12405 may change (for instance it is loaded into a register). The
12406 tracepoint data recorded uses the location information for the
12407 variables that is correct for the tracepoint location. When the
12408 tracepoint is created, it is not possible, in general, to determine
12409 where the steps of a @code{while-stepping} sequence will advance the
12410 program---particularly if a conditional branch is stepped.
12413 Collection of an incompletely-initialized or partially-destroyed object
12414 may result in something that @value{GDBN} cannot display, or displays
12415 in a misleading way.
12418 When @value{GDBN} displays a pointer to character it automatically
12419 dereferences the pointer to also display characters of the string
12420 being pointed to. However, collecting the pointer during tracing does
12421 not automatically collect the string. You need to explicitly
12422 dereference the pointer and provide size information if you want to
12423 collect not only the pointer, but the memory pointed to. For example,
12424 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12428 It is not possible to collect a complete stack backtrace at a
12429 tracepoint. Instead, you may collect the registers and a few hundred
12430 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12431 (adjust to use the name of the actual stack pointer register on your
12432 target architecture, and the amount of stack you wish to capture).
12433 Then the @code{backtrace} command will show a partial backtrace when
12434 using a trace frame. The number of stack frames that can be examined
12435 depends on the sizes of the frames in the collected stack. Note that
12436 if you ask for a block so large that it goes past the bottom of the
12437 stack, the target agent may report an error trying to read from an
12441 If you do not collect registers at a tracepoint, @value{GDBN} can
12442 infer that the value of @code{$pc} must be the same as the address of
12443 the tracepoint and use that when you are looking at a trace frame
12444 for that tracepoint. However, this cannot work if the tracepoint has
12445 multiple locations (for instance if it was set in a function that was
12446 inlined), or if it has a @code{while-stepping} loop. In those cases
12447 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12452 @node Analyze Collected Data
12453 @section Using the Collected Data
12455 After the tracepoint experiment ends, you use @value{GDBN} commands
12456 for examining the trace data. The basic idea is that each tracepoint
12457 collects a trace @dfn{snapshot} every time it is hit and another
12458 snapshot every time it single-steps. All these snapshots are
12459 consecutively numbered from zero and go into a buffer, and you can
12460 examine them later. The way you examine them is to @dfn{focus} on a
12461 specific trace snapshot. When the remote stub is focused on a trace
12462 snapshot, it will respond to all @value{GDBN} requests for memory and
12463 registers by reading from the buffer which belongs to that snapshot,
12464 rather than from @emph{real} memory or registers of the program being
12465 debugged. This means that @strong{all} @value{GDBN} commands
12466 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12467 behave as if we were currently debugging the program state as it was
12468 when the tracepoint occurred. Any requests for data that are not in
12469 the buffer will fail.
12472 * tfind:: How to select a trace snapshot
12473 * tdump:: How to display all data for a snapshot
12474 * save tracepoints:: How to save tracepoints for a future run
12478 @subsection @code{tfind @var{n}}
12481 @cindex select trace snapshot
12482 @cindex find trace snapshot
12483 The basic command for selecting a trace snapshot from the buffer is
12484 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12485 counting from zero. If no argument @var{n} is given, the next
12486 snapshot is selected.
12488 Here are the various forms of using the @code{tfind} command.
12492 Find the first snapshot in the buffer. This is a synonym for
12493 @code{tfind 0} (since 0 is the number of the first snapshot).
12496 Stop debugging trace snapshots, resume @emph{live} debugging.
12499 Same as @samp{tfind none}.
12502 No argument means find the next trace snapshot.
12505 Find the previous trace snapshot before the current one. This permits
12506 retracing earlier steps.
12508 @item tfind tracepoint @var{num}
12509 Find the next snapshot associated with tracepoint @var{num}. Search
12510 proceeds forward from the last examined trace snapshot. If no
12511 argument @var{num} is given, it means find the next snapshot collected
12512 for the same tracepoint as the current snapshot.
12514 @item tfind pc @var{addr}
12515 Find the next snapshot associated with the value @var{addr} of the
12516 program counter. Search proceeds forward from the last examined trace
12517 snapshot. If no argument @var{addr} is given, it means find the next
12518 snapshot with the same value of PC as the current snapshot.
12520 @item tfind outside @var{addr1}, @var{addr2}
12521 Find the next snapshot whose PC is outside the given range of
12522 addresses (exclusive).
12524 @item tfind range @var{addr1}, @var{addr2}
12525 Find the next snapshot whose PC is between @var{addr1} and
12526 @var{addr2} (inclusive).
12528 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12529 Find the next snapshot associated with the source line @var{n}. If
12530 the optional argument @var{file} is given, refer to line @var{n} in
12531 that source file. Search proceeds forward from the last examined
12532 trace snapshot. If no argument @var{n} is given, it means find the
12533 next line other than the one currently being examined; thus saying
12534 @code{tfind line} repeatedly can appear to have the same effect as
12535 stepping from line to line in a @emph{live} debugging session.
12538 The default arguments for the @code{tfind} commands are specifically
12539 designed to make it easy to scan through the trace buffer. For
12540 instance, @code{tfind} with no argument selects the next trace
12541 snapshot, and @code{tfind -} with no argument selects the previous
12542 trace snapshot. So, by giving one @code{tfind} command, and then
12543 simply hitting @key{RET} repeatedly you can examine all the trace
12544 snapshots in order. Or, by saying @code{tfind -} and then hitting
12545 @key{RET} repeatedly you can examine the snapshots in reverse order.
12546 The @code{tfind line} command with no argument selects the snapshot
12547 for the next source line executed. The @code{tfind pc} command with
12548 no argument selects the next snapshot with the same program counter
12549 (PC) as the current frame. The @code{tfind tracepoint} command with
12550 no argument selects the next trace snapshot collected by the same
12551 tracepoint as the current one.
12553 In addition to letting you scan through the trace buffer manually,
12554 these commands make it easy to construct @value{GDBN} scripts that
12555 scan through the trace buffer and print out whatever collected data
12556 you are interested in. Thus, if we want to examine the PC, FP, and SP
12557 registers from each trace frame in the buffer, we can say this:
12560 (@value{GDBP}) @b{tfind start}
12561 (@value{GDBP}) @b{while ($trace_frame != -1)}
12562 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12563 $trace_frame, $pc, $sp, $fp
12567 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12568 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12569 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12570 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12571 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12572 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12573 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12574 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12575 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12576 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12577 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12580 Or, if we want to examine the variable @code{X} at each source line in
12584 (@value{GDBP}) @b{tfind start}
12585 (@value{GDBP}) @b{while ($trace_frame != -1)}
12586 > printf "Frame %d, X == %d\n", $trace_frame, X
12596 @subsection @code{tdump}
12598 @cindex dump all data collected at tracepoint
12599 @cindex tracepoint data, display
12601 This command takes no arguments. It prints all the data collected at
12602 the current trace snapshot.
12605 (@value{GDBP}) @b{trace 444}
12606 (@value{GDBP}) @b{actions}
12607 Enter actions for tracepoint #2, one per line:
12608 > collect $regs, $locals, $args, gdb_long_test
12611 (@value{GDBP}) @b{tstart}
12613 (@value{GDBP}) @b{tfind line 444}
12614 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12616 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12618 (@value{GDBP}) @b{tdump}
12619 Data collected at tracepoint 2, trace frame 1:
12620 d0 0xc4aa0085 -995491707
12624 d4 0x71aea3d 119204413
12627 d7 0x380035 3670069
12628 a0 0x19e24a 1696330
12629 a1 0x3000668 50333288
12631 a3 0x322000 3284992
12632 a4 0x3000698 50333336
12633 a5 0x1ad3cc 1758156
12634 fp 0x30bf3c 0x30bf3c
12635 sp 0x30bf34 0x30bf34
12637 pc 0x20b2c8 0x20b2c8
12641 p = 0x20e5b4 "gdb-test"
12648 gdb_long_test = 17 '\021'
12653 @code{tdump} works by scanning the tracepoint's current collection
12654 actions and printing the value of each expression listed. So
12655 @code{tdump} can fail, if after a run, you change the tracepoint's
12656 actions to mention variables that were not collected during the run.
12658 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12659 uses the collected value of @code{$pc} to distinguish between trace
12660 frames that were collected at the tracepoint hit, and frames that were
12661 collected while stepping. This allows it to correctly choose whether
12662 to display the basic list of collections, or the collections from the
12663 body of the while-stepping loop. However, if @code{$pc} was not collected,
12664 then @code{tdump} will always attempt to dump using the basic collection
12665 list, and may fail if a while-stepping frame does not include all the
12666 same data that is collected at the tracepoint hit.
12667 @c This is getting pretty arcane, example would be good.
12669 @node save tracepoints
12670 @subsection @code{save tracepoints @var{filename}}
12671 @kindex save tracepoints
12672 @kindex save-tracepoints
12673 @cindex save tracepoints for future sessions
12675 This command saves all current tracepoint definitions together with
12676 their actions and passcounts, into a file @file{@var{filename}}
12677 suitable for use in a later debugging session. To read the saved
12678 tracepoint definitions, use the @code{source} command (@pxref{Command
12679 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12680 alias for @w{@code{save tracepoints}}
12682 @node Tracepoint Variables
12683 @section Convenience Variables for Tracepoints
12684 @cindex tracepoint variables
12685 @cindex convenience variables for tracepoints
12688 @vindex $trace_frame
12689 @item (int) $trace_frame
12690 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12691 snapshot is selected.
12693 @vindex $tracepoint
12694 @item (int) $tracepoint
12695 The tracepoint for the current trace snapshot.
12697 @vindex $trace_line
12698 @item (int) $trace_line
12699 The line number for the current trace snapshot.
12701 @vindex $trace_file
12702 @item (char []) $trace_file
12703 The source file for the current trace snapshot.
12705 @vindex $trace_func
12706 @item (char []) $trace_func
12707 The name of the function containing @code{$tracepoint}.
12710 Note: @code{$trace_file} is not suitable for use in @code{printf},
12711 use @code{output} instead.
12713 Here's a simple example of using these convenience variables for
12714 stepping through all the trace snapshots and printing some of their
12715 data. Note that these are not the same as trace state variables,
12716 which are managed by the target.
12719 (@value{GDBP}) @b{tfind start}
12721 (@value{GDBP}) @b{while $trace_frame != -1}
12722 > output $trace_file
12723 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12729 @section Using Trace Files
12730 @cindex trace files
12732 In some situations, the target running a trace experiment may no
12733 longer be available; perhaps it crashed, or the hardware was needed
12734 for a different activity. To handle these cases, you can arrange to
12735 dump the trace data into a file, and later use that file as a source
12736 of trace data, via the @code{target tfile} command.
12741 @item tsave [ -r ] @var{filename}
12742 @itemx tsave [-ctf] @var{dirname}
12743 Save the trace data to @var{filename}. By default, this command
12744 assumes that @var{filename} refers to the host filesystem, so if
12745 necessary @value{GDBN} will copy raw trace data up from the target and
12746 then save it. If the target supports it, you can also supply the
12747 optional argument @code{-r} (``remote'') to direct the target to save
12748 the data directly into @var{filename} in its own filesystem, which may be
12749 more efficient if the trace buffer is very large. (Note, however, that
12750 @code{target tfile} can only read from files accessible to the host.)
12751 By default, this command will save trace frame in tfile format.
12752 You can supply the optional argument @code{-ctf} to save date in CTF
12753 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12754 that can be shared by multiple debugging and tracing tools. Please go to
12755 @indicateurl{http://www.efficios.com/ctf} to get more information.
12757 @kindex target tfile
12761 @item target tfile @var{filename}
12762 @itemx target ctf @var{dirname}
12763 Use the file named @var{filename} or directory named @var{dirname} as
12764 a source of trace data. Commands that examine data work as they do with
12765 a live target, but it is not possible to run any new trace experiments.
12766 @code{tstatus} will report the state of the trace run at the moment
12767 the data was saved, as well as the current trace frame you are examining.
12768 @var{filename} or @var{dirname} must be on a filesystem accessible to
12772 (@value{GDBP}) target ctf ctf.ctf
12773 (@value{GDBP}) tfind
12774 Found trace frame 0, tracepoint 2
12775 39 ++a; /* set tracepoint 1 here */
12776 (@value{GDBP}) tdump
12777 Data collected at tracepoint 2, trace frame 0:
12781 c = @{"123", "456", "789", "123", "456", "789"@}
12782 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12790 @chapter Debugging Programs That Use Overlays
12793 If your program is too large to fit completely in your target system's
12794 memory, you can sometimes use @dfn{overlays} to work around this
12795 problem. @value{GDBN} provides some support for debugging programs that
12799 * How Overlays Work:: A general explanation of overlays.
12800 * Overlay Commands:: Managing overlays in @value{GDBN}.
12801 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12802 mapped by asking the inferior.
12803 * Overlay Sample Program:: A sample program using overlays.
12806 @node How Overlays Work
12807 @section How Overlays Work
12808 @cindex mapped overlays
12809 @cindex unmapped overlays
12810 @cindex load address, overlay's
12811 @cindex mapped address
12812 @cindex overlay area
12814 Suppose you have a computer whose instruction address space is only 64
12815 kilobytes long, but which has much more memory which can be accessed by
12816 other means: special instructions, segment registers, or memory
12817 management hardware, for example. Suppose further that you want to
12818 adapt a program which is larger than 64 kilobytes to run on this system.
12820 One solution is to identify modules of your program which are relatively
12821 independent, and need not call each other directly; call these modules
12822 @dfn{overlays}. Separate the overlays from the main program, and place
12823 their machine code in the larger memory. Place your main program in
12824 instruction memory, but leave at least enough space there to hold the
12825 largest overlay as well.
12827 Now, to call a function located in an overlay, you must first copy that
12828 overlay's machine code from the large memory into the space set aside
12829 for it in the instruction memory, and then jump to its entry point
12832 @c NB: In the below the mapped area's size is greater or equal to the
12833 @c size of all overlays. This is intentional to remind the developer
12834 @c that overlays don't necessarily need to be the same size.
12838 Data Instruction Larger
12839 Address Space Address Space Address Space
12840 +-----------+ +-----------+ +-----------+
12842 +-----------+ +-----------+ +-----------+<-- overlay 1
12843 | program | | main | .----| overlay 1 | load address
12844 | variables | | program | | +-----------+
12845 | and heap | | | | | |
12846 +-----------+ | | | +-----------+<-- overlay 2
12847 | | +-----------+ | | | load address
12848 +-----------+ | | | .-| overlay 2 |
12850 mapped --->+-----------+ | | +-----------+
12851 address | | | | | |
12852 | overlay | <-' | | |
12853 | area | <---' +-----------+<-- overlay 3
12854 | | <---. | | load address
12855 +-----------+ `--| overlay 3 |
12862 @anchor{A code overlay}A code overlay
12866 The diagram (@pxref{A code overlay}) shows a system with separate data
12867 and instruction address spaces. To map an overlay, the program copies
12868 its code from the larger address space to the instruction address space.
12869 Since the overlays shown here all use the same mapped address, only one
12870 may be mapped at a time. For a system with a single address space for
12871 data and instructions, the diagram would be similar, except that the
12872 program variables and heap would share an address space with the main
12873 program and the overlay area.
12875 An overlay loaded into instruction memory and ready for use is called a
12876 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12877 instruction memory. An overlay not present (or only partially present)
12878 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12879 is its address in the larger memory. The mapped address is also called
12880 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12881 called the @dfn{load memory address}, or @dfn{LMA}.
12883 Unfortunately, overlays are not a completely transparent way to adapt a
12884 program to limited instruction memory. They introduce a new set of
12885 global constraints you must keep in mind as you design your program:
12890 Before calling or returning to a function in an overlay, your program
12891 must make sure that overlay is actually mapped. Otherwise, the call or
12892 return will transfer control to the right address, but in the wrong
12893 overlay, and your program will probably crash.
12896 If the process of mapping an overlay is expensive on your system, you
12897 will need to choose your overlays carefully to minimize their effect on
12898 your program's performance.
12901 The executable file you load onto your system must contain each
12902 overlay's instructions, appearing at the overlay's load address, not its
12903 mapped address. However, each overlay's instructions must be relocated
12904 and its symbols defined as if the overlay were at its mapped address.
12905 You can use GNU linker scripts to specify different load and relocation
12906 addresses for pieces of your program; see @ref{Overlay Description,,,
12907 ld.info, Using ld: the GNU linker}.
12910 The procedure for loading executable files onto your system must be able
12911 to load their contents into the larger address space as well as the
12912 instruction and data spaces.
12916 The overlay system described above is rather simple, and could be
12917 improved in many ways:
12922 If your system has suitable bank switch registers or memory management
12923 hardware, you could use those facilities to make an overlay's load area
12924 contents simply appear at their mapped address in instruction space.
12925 This would probably be faster than copying the overlay to its mapped
12926 area in the usual way.
12929 If your overlays are small enough, you could set aside more than one
12930 overlay area, and have more than one overlay mapped at a time.
12933 You can use overlays to manage data, as well as instructions. In
12934 general, data overlays are even less transparent to your design than
12935 code overlays: whereas code overlays only require care when you call or
12936 return to functions, data overlays require care every time you access
12937 the data. Also, if you change the contents of a data overlay, you
12938 must copy its contents back out to its load address before you can copy a
12939 different data overlay into the same mapped area.
12944 @node Overlay Commands
12945 @section Overlay Commands
12947 To use @value{GDBN}'s overlay support, each overlay in your program must
12948 correspond to a separate section of the executable file. The section's
12949 virtual memory address and load memory address must be the overlay's
12950 mapped and load addresses. Identifying overlays with sections allows
12951 @value{GDBN} to determine the appropriate address of a function or
12952 variable, depending on whether the overlay is mapped or not.
12954 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12955 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12960 Disable @value{GDBN}'s overlay support. When overlay support is
12961 disabled, @value{GDBN} assumes that all functions and variables are
12962 always present at their mapped addresses. By default, @value{GDBN}'s
12963 overlay support is disabled.
12965 @item overlay manual
12966 @cindex manual overlay debugging
12967 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12968 relies on you to tell it which overlays are mapped, and which are not,
12969 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12970 commands described below.
12972 @item overlay map-overlay @var{overlay}
12973 @itemx overlay map @var{overlay}
12974 @cindex map an overlay
12975 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12976 be the name of the object file section containing the overlay. When an
12977 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12978 functions and variables at their mapped addresses. @value{GDBN} assumes
12979 that any other overlays whose mapped ranges overlap that of
12980 @var{overlay} are now unmapped.
12982 @item overlay unmap-overlay @var{overlay}
12983 @itemx overlay unmap @var{overlay}
12984 @cindex unmap an overlay
12985 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12986 must be the name of the object file section containing the overlay.
12987 When an overlay is unmapped, @value{GDBN} assumes it can find the
12988 overlay's functions and variables at their load addresses.
12991 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12992 consults a data structure the overlay manager maintains in the inferior
12993 to see which overlays are mapped. For details, see @ref{Automatic
12994 Overlay Debugging}.
12996 @item overlay load-target
12997 @itemx overlay load
12998 @cindex reloading the overlay table
12999 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13000 re-reads the table @value{GDBN} automatically each time the inferior
13001 stops, so this command should only be necessary if you have changed the
13002 overlay mapping yourself using @value{GDBN}. This command is only
13003 useful when using automatic overlay debugging.
13005 @item overlay list-overlays
13006 @itemx overlay list
13007 @cindex listing mapped overlays
13008 Display a list of the overlays currently mapped, along with their mapped
13009 addresses, load addresses, and sizes.
13013 Normally, when @value{GDBN} prints a code address, it includes the name
13014 of the function the address falls in:
13017 (@value{GDBP}) print main
13018 $3 = @{int ()@} 0x11a0 <main>
13021 When overlay debugging is enabled, @value{GDBN} recognizes code in
13022 unmapped overlays, and prints the names of unmapped functions with
13023 asterisks around them. For example, if @code{foo} is a function in an
13024 unmapped overlay, @value{GDBN} prints it this way:
13027 (@value{GDBP}) overlay list
13028 No sections are mapped.
13029 (@value{GDBP}) print foo
13030 $5 = @{int (int)@} 0x100000 <*foo*>
13033 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13037 (@value{GDBP}) overlay list
13038 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13039 mapped at 0x1016 - 0x104a
13040 (@value{GDBP}) print foo
13041 $6 = @{int (int)@} 0x1016 <foo>
13044 When overlay debugging is enabled, @value{GDBN} can find the correct
13045 address for functions and variables in an overlay, whether or not the
13046 overlay is mapped. This allows most @value{GDBN} commands, like
13047 @code{break} and @code{disassemble}, to work normally, even on unmapped
13048 code. However, @value{GDBN}'s breakpoint support has some limitations:
13052 @cindex breakpoints in overlays
13053 @cindex overlays, setting breakpoints in
13054 You can set breakpoints in functions in unmapped overlays, as long as
13055 @value{GDBN} can write to the overlay at its load address.
13057 @value{GDBN} can not set hardware or simulator-based breakpoints in
13058 unmapped overlays. However, if you set a breakpoint at the end of your
13059 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13060 you are using manual overlay management), @value{GDBN} will re-set its
13061 breakpoints properly.
13065 @node Automatic Overlay Debugging
13066 @section Automatic Overlay Debugging
13067 @cindex automatic overlay debugging
13069 @value{GDBN} can automatically track which overlays are mapped and which
13070 are not, given some simple co-operation from the overlay manager in the
13071 inferior. If you enable automatic overlay debugging with the
13072 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13073 looks in the inferior's memory for certain variables describing the
13074 current state of the overlays.
13076 Here are the variables your overlay manager must define to support
13077 @value{GDBN}'s automatic overlay debugging:
13081 @item @code{_ovly_table}:
13082 This variable must be an array of the following structures:
13087 /* The overlay's mapped address. */
13090 /* The size of the overlay, in bytes. */
13091 unsigned long size;
13093 /* The overlay's load address. */
13096 /* Non-zero if the overlay is currently mapped;
13098 unsigned long mapped;
13102 @item @code{_novlys}:
13103 This variable must be a four-byte signed integer, holding the total
13104 number of elements in @code{_ovly_table}.
13108 To decide whether a particular overlay is mapped or not, @value{GDBN}
13109 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13110 @code{lma} members equal the VMA and LMA of the overlay's section in the
13111 executable file. When @value{GDBN} finds a matching entry, it consults
13112 the entry's @code{mapped} member to determine whether the overlay is
13115 In addition, your overlay manager may define a function called
13116 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13117 will silently set a breakpoint there. If the overlay manager then
13118 calls this function whenever it has changed the overlay table, this
13119 will enable @value{GDBN} to accurately keep track of which overlays
13120 are in program memory, and update any breakpoints that may be set
13121 in overlays. This will allow breakpoints to work even if the
13122 overlays are kept in ROM or other non-writable memory while they
13123 are not being executed.
13125 @node Overlay Sample Program
13126 @section Overlay Sample Program
13127 @cindex overlay example program
13129 When linking a program which uses overlays, you must place the overlays
13130 at their load addresses, while relocating them to run at their mapped
13131 addresses. To do this, you must write a linker script (@pxref{Overlay
13132 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13133 since linker scripts are specific to a particular host system, target
13134 architecture, and target memory layout, this manual cannot provide
13135 portable sample code demonstrating @value{GDBN}'s overlay support.
13137 However, the @value{GDBN} source distribution does contain an overlaid
13138 program, with linker scripts for a few systems, as part of its test
13139 suite. The program consists of the following files from
13140 @file{gdb/testsuite/gdb.base}:
13144 The main program file.
13146 A simple overlay manager, used by @file{overlays.c}.
13151 Overlay modules, loaded and used by @file{overlays.c}.
13154 Linker scripts for linking the test program on the @code{d10v-elf}
13155 and @code{m32r-elf} targets.
13158 You can build the test program using the @code{d10v-elf} GCC
13159 cross-compiler like this:
13162 $ d10v-elf-gcc -g -c overlays.c
13163 $ d10v-elf-gcc -g -c ovlymgr.c
13164 $ d10v-elf-gcc -g -c foo.c
13165 $ d10v-elf-gcc -g -c bar.c
13166 $ d10v-elf-gcc -g -c baz.c
13167 $ d10v-elf-gcc -g -c grbx.c
13168 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13169 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13172 The build process is identical for any other architecture, except that
13173 you must substitute the appropriate compiler and linker script for the
13174 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13178 @chapter Using @value{GDBN} with Different Languages
13181 Although programming languages generally have common aspects, they are
13182 rarely expressed in the same manner. For instance, in ANSI C,
13183 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13184 Modula-2, it is accomplished by @code{p^}. Values can also be
13185 represented (and displayed) differently. Hex numbers in C appear as
13186 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13188 @cindex working language
13189 Language-specific information is built into @value{GDBN} for some languages,
13190 allowing you to express operations like the above in your program's
13191 native language, and allowing @value{GDBN} to output values in a manner
13192 consistent with the syntax of your program's native language. The
13193 language you use to build expressions is called the @dfn{working
13197 * Setting:: Switching between source languages
13198 * Show:: Displaying the language
13199 * Checks:: Type and range checks
13200 * Supported Languages:: Supported languages
13201 * Unsupported Languages:: Unsupported languages
13205 @section Switching Between Source Languages
13207 There are two ways to control the working language---either have @value{GDBN}
13208 set it automatically, or select it manually yourself. You can use the
13209 @code{set language} command for either purpose. On startup, @value{GDBN}
13210 defaults to setting the language automatically. The working language is
13211 used to determine how expressions you type are interpreted, how values
13214 In addition to the working language, every source file that
13215 @value{GDBN} knows about has its own working language. For some object
13216 file formats, the compiler might indicate which language a particular
13217 source file is in. However, most of the time @value{GDBN} infers the
13218 language from the name of the file. The language of a source file
13219 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13220 show each frame appropriately for its own language. There is no way to
13221 set the language of a source file from within @value{GDBN}, but you can
13222 set the language associated with a filename extension. @xref{Show, ,
13223 Displaying the Language}.
13225 This is most commonly a problem when you use a program, such
13226 as @code{cfront} or @code{f2c}, that generates C but is written in
13227 another language. In that case, make the
13228 program use @code{#line} directives in its C output; that way
13229 @value{GDBN} will know the correct language of the source code of the original
13230 program, and will display that source code, not the generated C code.
13233 * Filenames:: Filename extensions and languages.
13234 * Manually:: Setting the working language manually
13235 * Automatically:: Having @value{GDBN} infer the source language
13239 @subsection List of Filename Extensions and Languages
13241 If a source file name ends in one of the following extensions, then
13242 @value{GDBN} infers that its language is the one indicated.
13260 C@t{++} source file
13266 Objective-C source file
13270 Fortran source file
13273 Modula-2 source file
13277 Assembler source file. This actually behaves almost like C, but
13278 @value{GDBN} does not skip over function prologues when stepping.
13281 In addition, you may set the language associated with a filename
13282 extension. @xref{Show, , Displaying the Language}.
13285 @subsection Setting the Working Language
13287 If you allow @value{GDBN} to set the language automatically,
13288 expressions are interpreted the same way in your debugging session and
13291 @kindex set language
13292 If you wish, you may set the language manually. To do this, issue the
13293 command @samp{set language @var{lang}}, where @var{lang} is the name of
13294 a language, such as
13295 @code{c} or @code{modula-2}.
13296 For a list of the supported languages, type @samp{set language}.
13298 Setting the language manually prevents @value{GDBN} from updating the working
13299 language automatically. This can lead to confusion if you try
13300 to debug a program when the working language is not the same as the
13301 source language, when an expression is acceptable to both
13302 languages---but means different things. For instance, if the current
13303 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13311 might not have the effect you intended. In C, this means to add
13312 @code{b} and @code{c} and place the result in @code{a}. The result
13313 printed would be the value of @code{a}. In Modula-2, this means to compare
13314 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13316 @node Automatically
13317 @subsection Having @value{GDBN} Infer the Source Language
13319 To have @value{GDBN} set the working language automatically, use
13320 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13321 then infers the working language. That is, when your program stops in a
13322 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13323 working language to the language recorded for the function in that
13324 frame. If the language for a frame is unknown (that is, if the function
13325 or block corresponding to the frame was defined in a source file that
13326 does not have a recognized extension), the current working language is
13327 not changed, and @value{GDBN} issues a warning.
13329 This may not seem necessary for most programs, which are written
13330 entirely in one source language. However, program modules and libraries
13331 written in one source language can be used by a main program written in
13332 a different source language. Using @samp{set language auto} in this
13333 case frees you from having to set the working language manually.
13336 @section Displaying the Language
13338 The following commands help you find out which language is the
13339 working language, and also what language source files were written in.
13342 @item show language
13343 @anchor{show language}
13344 @kindex show language
13345 Display the current working language. This is the
13346 language you can use with commands such as @code{print} to
13347 build and compute expressions that may involve variables in your program.
13350 @kindex info frame@r{, show the source language}
13351 Display the source language for this frame. This language becomes the
13352 working language if you use an identifier from this frame.
13353 @xref{Frame Info, ,Information about a Frame}, to identify the other
13354 information listed here.
13357 @kindex info source@r{, show the source language}
13358 Display the source language of this source file.
13359 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13360 information listed here.
13363 In unusual circumstances, you may have source files with extensions
13364 not in the standard list. You can then set the extension associated
13365 with a language explicitly:
13368 @item set extension-language @var{ext} @var{language}
13369 @kindex set extension-language
13370 Tell @value{GDBN} that source files with extension @var{ext} are to be
13371 assumed as written in the source language @var{language}.
13373 @item info extensions
13374 @kindex info extensions
13375 List all the filename extensions and the associated languages.
13379 @section Type and Range Checking
13381 Some languages are designed to guard you against making seemingly common
13382 errors through a series of compile- and run-time checks. These include
13383 checking the type of arguments to functions and operators and making
13384 sure mathematical overflows are caught at run time. Checks such as
13385 these help to ensure a program's correctness once it has been compiled
13386 by eliminating type mismatches and providing active checks for range
13387 errors when your program is running.
13389 By default @value{GDBN} checks for these errors according to the
13390 rules of the current source language. Although @value{GDBN} does not check
13391 the statements in your program, it can check expressions entered directly
13392 into @value{GDBN} for evaluation via the @code{print} command, for example.
13395 * Type Checking:: An overview of type checking
13396 * Range Checking:: An overview of range checking
13399 @cindex type checking
13400 @cindex checks, type
13401 @node Type Checking
13402 @subsection An Overview of Type Checking
13404 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13405 arguments to operators and functions have to be of the correct type,
13406 otherwise an error occurs. These checks prevent type mismatch
13407 errors from ever causing any run-time problems. For example,
13410 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13412 (@value{GDBP}) print obj.my_method (0)
13415 (@value{GDBP}) print obj.my_method (0x1234)
13416 Cannot resolve method klass::my_method to any overloaded instance
13419 The second example fails because in C@t{++} the integer constant
13420 @samp{0x1234} is not type-compatible with the pointer parameter type.
13422 For the expressions you use in @value{GDBN} commands, you can tell
13423 @value{GDBN} to not enforce strict type checking or
13424 to treat any mismatches as errors and abandon the expression;
13425 When type checking is disabled, @value{GDBN} successfully evaluates
13426 expressions like the second example above.
13428 Even if type checking is off, there may be other reasons
13429 related to type that prevent @value{GDBN} from evaluating an expression.
13430 For instance, @value{GDBN} does not know how to add an @code{int} and
13431 a @code{struct foo}. These particular type errors have nothing to do
13432 with the language in use and usually arise from expressions which make
13433 little sense to evaluate anyway.
13435 @value{GDBN} provides some additional commands for controlling type checking:
13437 @kindex set check type
13438 @kindex show check type
13440 @item set check type on
13441 @itemx set check type off
13442 Set strict type checking on or off. If any type mismatches occur in
13443 evaluating an expression while type checking is on, @value{GDBN} prints a
13444 message and aborts evaluation of the expression.
13446 @item show check type
13447 Show the current setting of type checking and whether @value{GDBN}
13448 is enforcing strict type checking rules.
13451 @cindex range checking
13452 @cindex checks, range
13453 @node Range Checking
13454 @subsection An Overview of Range Checking
13456 In some languages (such as Modula-2), it is an error to exceed the
13457 bounds of a type; this is enforced with run-time checks. Such range
13458 checking is meant to ensure program correctness by making sure
13459 computations do not overflow, or indices on an array element access do
13460 not exceed the bounds of the array.
13462 For expressions you use in @value{GDBN} commands, you can tell
13463 @value{GDBN} to treat range errors in one of three ways: ignore them,
13464 always treat them as errors and abandon the expression, or issue
13465 warnings but evaluate the expression anyway.
13467 A range error can result from numerical overflow, from exceeding an
13468 array index bound, or when you type a constant that is not a member
13469 of any type. Some languages, however, do not treat overflows as an
13470 error. In many implementations of C, mathematical overflow causes the
13471 result to ``wrap around'' to lower values---for example, if @var{m} is
13472 the largest integer value, and @var{s} is the smallest, then
13475 @var{m} + 1 @result{} @var{s}
13478 This, too, is specific to individual languages, and in some cases
13479 specific to individual compilers or machines. @xref{Supported Languages, ,
13480 Supported Languages}, for further details on specific languages.
13482 @value{GDBN} provides some additional commands for controlling the range checker:
13484 @kindex set check range
13485 @kindex show check range
13487 @item set check range auto
13488 Set range checking on or off based on the current working language.
13489 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13492 @item set check range on
13493 @itemx set check range off
13494 Set range checking on or off, overriding the default setting for the
13495 current working language. A warning is issued if the setting does not
13496 match the language default. If a range error occurs and range checking is on,
13497 then a message is printed and evaluation of the expression is aborted.
13499 @item set check range warn
13500 Output messages when the @value{GDBN} range checker detects a range error,
13501 but attempt to evaluate the expression anyway. Evaluating the
13502 expression may still be impossible for other reasons, such as accessing
13503 memory that the process does not own (a typical example from many Unix
13507 Show the current setting of the range checker, and whether or not it is
13508 being set automatically by @value{GDBN}.
13511 @node Supported Languages
13512 @section Supported Languages
13514 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13515 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13516 @c This is false ...
13517 Some @value{GDBN} features may be used in expressions regardless of the
13518 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13519 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13520 ,Expressions}) can be used with the constructs of any supported
13523 The following sections detail to what degree each source language is
13524 supported by @value{GDBN}. These sections are not meant to be language
13525 tutorials or references, but serve only as a reference guide to what the
13526 @value{GDBN} expression parser accepts, and what input and output
13527 formats should look like for different languages. There are many good
13528 books written on each of these languages; please look to these for a
13529 language reference or tutorial.
13532 * C:: C and C@t{++}
13535 * Objective-C:: Objective-C
13536 * OpenCL C:: OpenCL C
13537 * Fortran:: Fortran
13539 * Modula-2:: Modula-2
13544 @subsection C and C@t{++}
13546 @cindex C and C@t{++}
13547 @cindex expressions in C or C@t{++}
13549 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13550 to both languages. Whenever this is the case, we discuss those languages
13554 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13555 @cindex @sc{gnu} C@t{++}
13556 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13557 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13558 effectively, you must compile your C@t{++} programs with a supported
13559 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13560 compiler (@code{aCC}).
13563 * C Operators:: C and C@t{++} operators
13564 * C Constants:: C and C@t{++} constants
13565 * C Plus Plus Expressions:: C@t{++} expressions
13566 * C Defaults:: Default settings for C and C@t{++}
13567 * C Checks:: C and C@t{++} type and range checks
13568 * Debugging C:: @value{GDBN} and C
13569 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13570 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13574 @subsubsection C and C@t{++} Operators
13576 @cindex C and C@t{++} operators
13578 Operators must be defined on values of specific types. For instance,
13579 @code{+} is defined on numbers, but not on structures. Operators are
13580 often defined on groups of types.
13582 For the purposes of C and C@t{++}, the following definitions hold:
13587 @emph{Integral types} include @code{int} with any of its storage-class
13588 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13591 @emph{Floating-point types} include @code{float}, @code{double}, and
13592 @code{long double} (if supported by the target platform).
13595 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13598 @emph{Scalar types} include all of the above.
13603 The following operators are supported. They are listed here
13604 in order of increasing precedence:
13608 The comma or sequencing operator. Expressions in a comma-separated list
13609 are evaluated from left to right, with the result of the entire
13610 expression being the last expression evaluated.
13613 Assignment. The value of an assignment expression is the value
13614 assigned. Defined on scalar types.
13617 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13618 and translated to @w{@code{@var{a} = @var{a op b}}}.
13619 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13620 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13621 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13624 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13625 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13629 Logical @sc{or}. Defined on integral types.
13632 Logical @sc{and}. Defined on integral types.
13635 Bitwise @sc{or}. Defined on integral types.
13638 Bitwise exclusive-@sc{or}. Defined on integral types.
13641 Bitwise @sc{and}. Defined on integral types.
13644 Equality and inequality. Defined on scalar types. The value of these
13645 expressions is 0 for false and non-zero for true.
13647 @item <@r{, }>@r{, }<=@r{, }>=
13648 Less than, greater than, less than or equal, greater than or equal.
13649 Defined on scalar types. The value of these expressions is 0 for false
13650 and non-zero for true.
13653 left shift, and right shift. Defined on integral types.
13656 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13659 Addition and subtraction. Defined on integral types, floating-point types and
13662 @item *@r{, }/@r{, }%
13663 Multiplication, division, and modulus. Multiplication and division are
13664 defined on integral and floating-point types. Modulus is defined on
13668 Increment and decrement. When appearing before a variable, the
13669 operation is performed before the variable is used in an expression;
13670 when appearing after it, the variable's value is used before the
13671 operation takes place.
13674 Pointer dereferencing. Defined on pointer types. Same precedence as
13678 Address operator. Defined on variables. Same precedence as @code{++}.
13680 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13681 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13682 to examine the address
13683 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13687 Negative. Defined on integral and floating-point types. Same
13688 precedence as @code{++}.
13691 Logical negation. Defined on integral types. Same precedence as
13695 Bitwise complement operator. Defined on integral types. Same precedence as
13700 Structure member, and pointer-to-structure member. For convenience,
13701 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13702 pointer based on the stored type information.
13703 Defined on @code{struct} and @code{union} data.
13706 Dereferences of pointers to members.
13709 Array indexing. @code{@var{a}[@var{i}]} is defined as
13710 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13713 Function parameter list. Same precedence as @code{->}.
13716 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13717 and @code{class} types.
13720 Doubled colons also represent the @value{GDBN} scope operator
13721 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13725 If an operator is redefined in the user code, @value{GDBN} usually
13726 attempts to invoke the redefined version instead of using the operator's
13727 predefined meaning.
13730 @subsubsection C and C@t{++} Constants
13732 @cindex C and C@t{++} constants
13734 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13739 Integer constants are a sequence of digits. Octal constants are
13740 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13741 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13742 @samp{l}, specifying that the constant should be treated as a
13746 Floating point constants are a sequence of digits, followed by a decimal
13747 point, followed by a sequence of digits, and optionally followed by an
13748 exponent. An exponent is of the form:
13749 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13750 sequence of digits. The @samp{+} is optional for positive exponents.
13751 A floating-point constant may also end with a letter @samp{f} or
13752 @samp{F}, specifying that the constant should be treated as being of
13753 the @code{float} (as opposed to the default @code{double}) type; or with
13754 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13758 Enumerated constants consist of enumerated identifiers, or their
13759 integral equivalents.
13762 Character constants are a single character surrounded by single quotes
13763 (@code{'}), or a number---the ordinal value of the corresponding character
13764 (usually its @sc{ascii} value). Within quotes, the single character may
13765 be represented by a letter or by @dfn{escape sequences}, which are of
13766 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13767 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13768 @samp{@var{x}} is a predefined special character---for example,
13769 @samp{\n} for newline.
13771 Wide character constants can be written by prefixing a character
13772 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13773 form of @samp{x}. The target wide character set is used when
13774 computing the value of this constant (@pxref{Character Sets}).
13777 String constants are a sequence of character constants surrounded by
13778 double quotes (@code{"}). Any valid character constant (as described
13779 above) may appear. Double quotes within the string must be preceded by
13780 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13783 Wide string constants can be written by prefixing a string constant
13784 with @samp{L}, as in C. The target wide character set is used when
13785 computing the value of this constant (@pxref{Character Sets}).
13788 Pointer constants are an integral value. You can also write pointers
13789 to constants using the C operator @samp{&}.
13792 Array constants are comma-separated lists surrounded by braces @samp{@{}
13793 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13794 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13795 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13798 @node C Plus Plus Expressions
13799 @subsubsection C@t{++} Expressions
13801 @cindex expressions in C@t{++}
13802 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13804 @cindex debugging C@t{++} programs
13805 @cindex C@t{++} compilers
13806 @cindex debug formats and C@t{++}
13807 @cindex @value{NGCC} and C@t{++}
13809 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13810 the proper compiler and the proper debug format. Currently,
13811 @value{GDBN} works best when debugging C@t{++} code that is compiled
13812 with the most recent version of @value{NGCC} possible. The DWARF
13813 debugging format is preferred; @value{NGCC} defaults to this on most
13814 popular platforms. Other compilers and/or debug formats are likely to
13815 work badly or not at all when using @value{GDBN} to debug C@t{++}
13816 code. @xref{Compilation}.
13821 @cindex member functions
13823 Member function calls are allowed; you can use expressions like
13826 count = aml->GetOriginal(x, y)
13829 @vindex this@r{, inside C@t{++} member functions}
13830 @cindex namespace in C@t{++}
13832 While a member function is active (in the selected stack frame), your
13833 expressions have the same namespace available as the member function;
13834 that is, @value{GDBN} allows implicit references to the class instance
13835 pointer @code{this} following the same rules as C@t{++}. @code{using}
13836 declarations in the current scope are also respected by @value{GDBN}.
13838 @cindex call overloaded functions
13839 @cindex overloaded functions, calling
13840 @cindex type conversions in C@t{++}
13842 You can call overloaded functions; @value{GDBN} resolves the function
13843 call to the right definition, with some restrictions. @value{GDBN} does not
13844 perform overload resolution involving user-defined type conversions,
13845 calls to constructors, or instantiations of templates that do not exist
13846 in the program. It also cannot handle ellipsis argument lists or
13849 It does perform integral conversions and promotions, floating-point
13850 promotions, arithmetic conversions, pointer conversions, conversions of
13851 class objects to base classes, and standard conversions such as those of
13852 functions or arrays to pointers; it requires an exact match on the
13853 number of function arguments.
13855 Overload resolution is always performed, unless you have specified
13856 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13857 ,@value{GDBN} Features for C@t{++}}.
13859 You must specify @code{set overload-resolution off} in order to use an
13860 explicit function signature to call an overloaded function, as in
13862 p 'foo(char,int)'('x', 13)
13865 The @value{GDBN} command-completion facility can simplify this;
13866 see @ref{Completion, ,Command Completion}.
13868 @cindex reference declarations
13870 @value{GDBN} understands variables declared as C@t{++} references; you can use
13871 them in expressions just as you do in C@t{++} source---they are automatically
13874 In the parameter list shown when @value{GDBN} displays a frame, the values of
13875 reference variables are not displayed (unlike other variables); this
13876 avoids clutter, since references are often used for large structures.
13877 The @emph{address} of a reference variable is always shown, unless
13878 you have specified @samp{set print address off}.
13881 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13882 expressions can use it just as expressions in your program do. Since
13883 one scope may be defined in another, you can use @code{::} repeatedly if
13884 necessary, for example in an expression like
13885 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13886 resolving name scope by reference to source files, in both C and C@t{++}
13887 debugging (@pxref{Variables, ,Program Variables}).
13890 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13895 @subsubsection C and C@t{++} Defaults
13897 @cindex C and C@t{++} defaults
13899 If you allow @value{GDBN} to set range checking automatically, it
13900 defaults to @code{off} whenever the working language changes to
13901 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13902 selects the working language.
13904 If you allow @value{GDBN} to set the language automatically, it
13905 recognizes source files whose names end with @file{.c}, @file{.C}, or
13906 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13907 these files, it sets the working language to C or C@t{++}.
13908 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13909 for further details.
13912 @subsubsection C and C@t{++} Type and Range Checks
13914 @cindex C and C@t{++} checks
13916 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13917 checking is used. However, if you turn type checking off, @value{GDBN}
13918 will allow certain non-standard conversions, such as promoting integer
13919 constants to pointers.
13921 Range checking, if turned on, is done on mathematical operations. Array
13922 indices are not checked, since they are often used to index a pointer
13923 that is not itself an array.
13926 @subsubsection @value{GDBN} and C
13928 The @code{set print union} and @code{show print union} commands apply to
13929 the @code{union} type. When set to @samp{on}, any @code{union} that is
13930 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13931 appears as @samp{@{...@}}.
13933 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13934 with pointers and a memory allocation function. @xref{Expressions,
13937 @node Debugging C Plus Plus
13938 @subsubsection @value{GDBN} Features for C@t{++}
13940 @cindex commands for C@t{++}
13942 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13943 designed specifically for use with C@t{++}. Here is a summary:
13946 @cindex break in overloaded functions
13947 @item @r{breakpoint menus}
13948 When you want a breakpoint in a function whose name is overloaded,
13949 @value{GDBN} has the capability to display a menu of possible breakpoint
13950 locations to help you specify which function definition you want.
13951 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13953 @cindex overloading in C@t{++}
13954 @item rbreak @var{regex}
13955 Setting breakpoints using regular expressions is helpful for setting
13956 breakpoints on overloaded functions that are not members of any special
13958 @xref{Set Breaks, ,Setting Breakpoints}.
13960 @cindex C@t{++} exception handling
13962 @itemx catch rethrow
13964 Debug C@t{++} exception handling using these commands. @xref{Set
13965 Catchpoints, , Setting Catchpoints}.
13967 @cindex inheritance
13968 @item ptype @var{typename}
13969 Print inheritance relationships as well as other information for type
13971 @xref{Symbols, ,Examining the Symbol Table}.
13973 @item info vtbl @var{expression}.
13974 The @code{info vtbl} command can be used to display the virtual
13975 method tables of the object computed by @var{expression}. This shows
13976 one entry per virtual table; there may be multiple virtual tables when
13977 multiple inheritance is in use.
13979 @cindex C@t{++} symbol display
13980 @item set print demangle
13981 @itemx show print demangle
13982 @itemx set print asm-demangle
13983 @itemx show print asm-demangle
13984 Control whether C@t{++} symbols display in their source form, both when
13985 displaying code as C@t{++} source and when displaying disassemblies.
13986 @xref{Print Settings, ,Print Settings}.
13988 @item set print object
13989 @itemx show print object
13990 Choose whether to print derived (actual) or declared types of objects.
13991 @xref{Print Settings, ,Print Settings}.
13993 @item set print vtbl
13994 @itemx show print vtbl
13995 Control the format for printing virtual function tables.
13996 @xref{Print Settings, ,Print Settings}.
13997 (The @code{vtbl} commands do not work on programs compiled with the HP
13998 ANSI C@t{++} compiler (@code{aCC}).)
14000 @kindex set overload-resolution
14001 @cindex overloaded functions, overload resolution
14002 @item set overload-resolution on
14003 Enable overload resolution for C@t{++} expression evaluation. The default
14004 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14005 and searches for a function whose signature matches the argument types,
14006 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14007 Expressions, ,C@t{++} Expressions}, for details).
14008 If it cannot find a match, it emits a message.
14010 @item set overload-resolution off
14011 Disable overload resolution for C@t{++} expression evaluation. For
14012 overloaded functions that are not class member functions, @value{GDBN}
14013 chooses the first function of the specified name that it finds in the
14014 symbol table, whether or not its arguments are of the correct type. For
14015 overloaded functions that are class member functions, @value{GDBN}
14016 searches for a function whose signature @emph{exactly} matches the
14019 @kindex show overload-resolution
14020 @item show overload-resolution
14021 Show the current setting of overload resolution.
14023 @item @r{Overloaded symbol names}
14024 You can specify a particular definition of an overloaded symbol, using
14025 the same notation that is used to declare such symbols in C@t{++}: type
14026 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14027 also use the @value{GDBN} command-line word completion facilities to list the
14028 available choices, or to finish the type list for you.
14029 @xref{Completion,, Command Completion}, for details on how to do this.
14032 @node Decimal Floating Point
14033 @subsubsection Decimal Floating Point format
14034 @cindex decimal floating point format
14036 @value{GDBN} can examine, set and perform computations with numbers in
14037 decimal floating point format, which in the C language correspond to the
14038 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14039 specified by the extension to support decimal floating-point arithmetic.
14041 There are two encodings in use, depending on the architecture: BID (Binary
14042 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14043 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14046 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14047 to manipulate decimal floating point numbers, it is not possible to convert
14048 (using a cast, for example) integers wider than 32-bit to decimal float.
14050 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14051 point computations, error checking in decimal float operations ignores
14052 underflow, overflow and divide by zero exceptions.
14054 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14055 to inspect @code{_Decimal128} values stored in floating point registers.
14056 See @ref{PowerPC,,PowerPC} for more details.
14062 @value{GDBN} can be used to debug programs written in D and compiled with
14063 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14064 specific feature --- dynamic arrays.
14069 @cindex Go (programming language)
14070 @value{GDBN} can be used to debug programs written in Go and compiled with
14071 @file{gccgo} or @file{6g} compilers.
14073 Here is a summary of the Go-specific features and restrictions:
14076 @cindex current Go package
14077 @item The current Go package
14078 The name of the current package does not need to be specified when
14079 specifying global variables and functions.
14081 For example, given the program:
14085 var myglob = "Shall we?"
14091 When stopped inside @code{main} either of these work:
14095 (gdb) p main.myglob
14098 @cindex builtin Go types
14099 @item Builtin Go types
14100 The @code{string} type is recognized by @value{GDBN} and is printed
14103 @cindex builtin Go functions
14104 @item Builtin Go functions
14105 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14106 function and handles it internally.
14108 @cindex restrictions on Go expressions
14109 @item Restrictions on Go expressions
14110 All Go operators are supported except @code{&^}.
14111 The Go @code{_} ``blank identifier'' is not supported.
14112 Automatic dereferencing of pointers is not supported.
14116 @subsection Objective-C
14118 @cindex Objective-C
14119 This section provides information about some commands and command
14120 options that are useful for debugging Objective-C code. See also
14121 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14122 few more commands specific to Objective-C support.
14125 * Method Names in Commands::
14126 * The Print Command with Objective-C::
14129 @node Method Names in Commands
14130 @subsubsection Method Names in Commands
14132 The following commands have been extended to accept Objective-C method
14133 names as line specifications:
14135 @kindex clear@r{, and Objective-C}
14136 @kindex break@r{, and Objective-C}
14137 @kindex info line@r{, and Objective-C}
14138 @kindex jump@r{, and Objective-C}
14139 @kindex list@r{, and Objective-C}
14143 @item @code{info line}
14148 A fully qualified Objective-C method name is specified as
14151 -[@var{Class} @var{methodName}]
14154 where the minus sign is used to indicate an instance method and a
14155 plus sign (not shown) is used to indicate a class method. The class
14156 name @var{Class} and method name @var{methodName} are enclosed in
14157 brackets, similar to the way messages are specified in Objective-C
14158 source code. For example, to set a breakpoint at the @code{create}
14159 instance method of class @code{Fruit} in the program currently being
14163 break -[Fruit create]
14166 To list ten program lines around the @code{initialize} class method,
14170 list +[NSText initialize]
14173 In the current version of @value{GDBN}, the plus or minus sign is
14174 required. In future versions of @value{GDBN}, the plus or minus
14175 sign will be optional, but you can use it to narrow the search. It
14176 is also possible to specify just a method name:
14182 You must specify the complete method name, including any colons. If
14183 your program's source files contain more than one @code{create} method,
14184 you'll be presented with a numbered list of classes that implement that
14185 method. Indicate your choice by number, or type @samp{0} to exit if
14188 As another example, to clear a breakpoint established at the
14189 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14192 clear -[NSWindow makeKeyAndOrderFront:]
14195 @node The Print Command with Objective-C
14196 @subsubsection The Print Command With Objective-C
14197 @cindex Objective-C, print objects
14198 @kindex print-object
14199 @kindex po @r{(@code{print-object})}
14201 The print command has also been extended to accept methods. For example:
14204 print -[@var{object} hash]
14207 @cindex print an Objective-C object description
14208 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14210 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14211 and print the result. Also, an additional command has been added,
14212 @code{print-object} or @code{po} for short, which is meant to print
14213 the description of an object. However, this command may only work
14214 with certain Objective-C libraries that have a particular hook
14215 function, @code{_NSPrintForDebugger}, defined.
14218 @subsection OpenCL C
14221 This section provides information about @value{GDBN}s OpenCL C support.
14224 * OpenCL C Datatypes::
14225 * OpenCL C Expressions::
14226 * OpenCL C Operators::
14229 @node OpenCL C Datatypes
14230 @subsubsection OpenCL C Datatypes
14232 @cindex OpenCL C Datatypes
14233 @value{GDBN} supports the builtin scalar and vector datatypes specified
14234 by OpenCL 1.1. In addition the half- and double-precision floating point
14235 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14236 extensions are also known to @value{GDBN}.
14238 @node OpenCL C Expressions
14239 @subsubsection OpenCL C Expressions
14241 @cindex OpenCL C Expressions
14242 @value{GDBN} supports accesses to vector components including the access as
14243 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14244 supported by @value{GDBN} can be used as well.
14246 @node OpenCL C Operators
14247 @subsubsection OpenCL C Operators
14249 @cindex OpenCL C Operators
14250 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14254 @subsection Fortran
14255 @cindex Fortran-specific support in @value{GDBN}
14257 @value{GDBN} can be used to debug programs written in Fortran, but it
14258 currently supports only the features of Fortran 77 language.
14260 @cindex trailing underscore, in Fortran symbols
14261 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14262 among them) append an underscore to the names of variables and
14263 functions. When you debug programs compiled by those compilers, you
14264 will need to refer to variables and functions with a trailing
14268 * Fortran Operators:: Fortran operators and expressions
14269 * Fortran Defaults:: Default settings for Fortran
14270 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14273 @node Fortran Operators
14274 @subsubsection Fortran Operators and Expressions
14276 @cindex Fortran operators and expressions
14278 Operators must be defined on values of specific types. For instance,
14279 @code{+} is defined on numbers, but not on characters or other non-
14280 arithmetic types. Operators are often defined on groups of types.
14284 The exponentiation operator. It raises the first operand to the power
14288 The range operator. Normally used in the form of array(low:high) to
14289 represent a section of array.
14292 The access component operator. Normally used to access elements in derived
14293 types. Also suitable for unions. As unions aren't part of regular Fortran,
14294 this can only happen when accessing a register that uses a gdbarch-defined
14298 @node Fortran Defaults
14299 @subsubsection Fortran Defaults
14301 @cindex Fortran Defaults
14303 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14304 default uses case-insensitive matches for Fortran symbols. You can
14305 change that with the @samp{set case-insensitive} command, see
14306 @ref{Symbols}, for the details.
14308 @node Special Fortran Commands
14309 @subsubsection Special Fortran Commands
14311 @cindex Special Fortran commands
14313 @value{GDBN} has some commands to support Fortran-specific features,
14314 such as displaying common blocks.
14317 @cindex @code{COMMON} blocks, Fortran
14318 @kindex info common
14319 @item info common @r{[}@var{common-name}@r{]}
14320 This command prints the values contained in the Fortran @code{COMMON}
14321 block whose name is @var{common-name}. With no argument, the names of
14322 all @code{COMMON} blocks visible at the current program location are
14329 @cindex Pascal support in @value{GDBN}, limitations
14330 Debugging Pascal programs which use sets, subranges, file variables, or
14331 nested functions does not currently work. @value{GDBN} does not support
14332 entering expressions, printing values, or similar features using Pascal
14335 The Pascal-specific command @code{set print pascal_static-members}
14336 controls whether static members of Pascal objects are displayed.
14337 @xref{Print Settings, pascal_static-members}.
14340 @subsection Modula-2
14342 @cindex Modula-2, @value{GDBN} support
14344 The extensions made to @value{GDBN} to support Modula-2 only support
14345 output from the @sc{gnu} Modula-2 compiler (which is currently being
14346 developed). Other Modula-2 compilers are not currently supported, and
14347 attempting to debug executables produced by them is most likely
14348 to give an error as @value{GDBN} reads in the executable's symbol
14351 @cindex expressions in Modula-2
14353 * M2 Operators:: Built-in operators
14354 * Built-In Func/Proc:: Built-in functions and procedures
14355 * M2 Constants:: Modula-2 constants
14356 * M2 Types:: Modula-2 types
14357 * M2 Defaults:: Default settings for Modula-2
14358 * Deviations:: Deviations from standard Modula-2
14359 * M2 Checks:: Modula-2 type and range checks
14360 * M2 Scope:: The scope operators @code{::} and @code{.}
14361 * GDB/M2:: @value{GDBN} and Modula-2
14365 @subsubsection Operators
14366 @cindex Modula-2 operators
14368 Operators must be defined on values of specific types. For instance,
14369 @code{+} is defined on numbers, but not on structures. Operators are
14370 often defined on groups of types. For the purposes of Modula-2, the
14371 following definitions hold:
14376 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14380 @emph{Character types} consist of @code{CHAR} and its subranges.
14383 @emph{Floating-point types} consist of @code{REAL}.
14386 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14390 @emph{Scalar types} consist of all of the above.
14393 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14396 @emph{Boolean types} consist of @code{BOOLEAN}.
14400 The following operators are supported, and appear in order of
14401 increasing precedence:
14405 Function argument or array index separator.
14408 Assignment. The value of @var{var} @code{:=} @var{value} is
14412 Less than, greater than on integral, floating-point, or enumerated
14416 Less than or equal to, greater than or equal to
14417 on integral, floating-point and enumerated types, or set inclusion on
14418 set types. Same precedence as @code{<}.
14420 @item =@r{, }<>@r{, }#
14421 Equality and two ways of expressing inequality, valid on scalar types.
14422 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14423 available for inequality, since @code{#} conflicts with the script
14427 Set membership. Defined on set types and the types of their members.
14428 Same precedence as @code{<}.
14431 Boolean disjunction. Defined on boolean types.
14434 Boolean conjunction. Defined on boolean types.
14437 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14440 Addition and subtraction on integral and floating-point types, or union
14441 and difference on set types.
14444 Multiplication on integral and floating-point types, or set intersection
14448 Division on floating-point types, or symmetric set difference on set
14449 types. Same precedence as @code{*}.
14452 Integer division and remainder. Defined on integral types. Same
14453 precedence as @code{*}.
14456 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14459 Pointer dereferencing. Defined on pointer types.
14462 Boolean negation. Defined on boolean types. Same precedence as
14466 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14467 precedence as @code{^}.
14470 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14473 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14477 @value{GDBN} and Modula-2 scope operators.
14481 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14482 treats the use of the operator @code{IN}, or the use of operators
14483 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14484 @code{<=}, and @code{>=} on sets as an error.
14488 @node Built-In Func/Proc
14489 @subsubsection Built-in Functions and Procedures
14490 @cindex Modula-2 built-ins
14492 Modula-2 also makes available several built-in procedures and functions.
14493 In describing these, the following metavariables are used:
14498 represents an @code{ARRAY} variable.
14501 represents a @code{CHAR} constant or variable.
14504 represents a variable or constant of integral type.
14507 represents an identifier that belongs to a set. Generally used in the
14508 same function with the metavariable @var{s}. The type of @var{s} should
14509 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14512 represents a variable or constant of integral or floating-point type.
14515 represents a variable or constant of floating-point type.
14521 represents a variable.
14524 represents a variable or constant of one of many types. See the
14525 explanation of the function for details.
14528 All Modula-2 built-in procedures also return a result, described below.
14532 Returns the absolute value of @var{n}.
14535 If @var{c} is a lower case letter, it returns its upper case
14536 equivalent, otherwise it returns its argument.
14539 Returns the character whose ordinal value is @var{i}.
14542 Decrements the value in the variable @var{v} by one. Returns the new value.
14544 @item DEC(@var{v},@var{i})
14545 Decrements the value in the variable @var{v} by @var{i}. Returns the
14548 @item EXCL(@var{m},@var{s})
14549 Removes the element @var{m} from the set @var{s}. Returns the new
14552 @item FLOAT(@var{i})
14553 Returns the floating point equivalent of the integer @var{i}.
14555 @item HIGH(@var{a})
14556 Returns the index of the last member of @var{a}.
14559 Increments the value in the variable @var{v} by one. Returns the new value.
14561 @item INC(@var{v},@var{i})
14562 Increments the value in the variable @var{v} by @var{i}. Returns the
14565 @item INCL(@var{m},@var{s})
14566 Adds the element @var{m} to the set @var{s} if it is not already
14567 there. Returns the new set.
14570 Returns the maximum value of the type @var{t}.
14573 Returns the minimum value of the type @var{t}.
14576 Returns boolean TRUE if @var{i} is an odd number.
14579 Returns the ordinal value of its argument. For example, the ordinal
14580 value of a character is its @sc{ascii} value (on machines supporting the
14581 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14582 integral, character and enumerated types.
14584 @item SIZE(@var{x})
14585 Returns the size of its argument. @var{x} can be a variable or a type.
14587 @item TRUNC(@var{r})
14588 Returns the integral part of @var{r}.
14590 @item TSIZE(@var{x})
14591 Returns the size of its argument. @var{x} can be a variable or a type.
14593 @item VAL(@var{t},@var{i})
14594 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14598 @emph{Warning:} Sets and their operations are not yet supported, so
14599 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14603 @cindex Modula-2 constants
14605 @subsubsection Constants
14607 @value{GDBN} allows you to express the constants of Modula-2 in the following
14613 Integer constants are simply a sequence of digits. When used in an
14614 expression, a constant is interpreted to be type-compatible with the
14615 rest of the expression. Hexadecimal integers are specified by a
14616 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14619 Floating point constants appear as a sequence of digits, followed by a
14620 decimal point and another sequence of digits. An optional exponent can
14621 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14622 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14623 digits of the floating point constant must be valid decimal (base 10)
14627 Character constants consist of a single character enclosed by a pair of
14628 like quotes, either single (@code{'}) or double (@code{"}). They may
14629 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14630 followed by a @samp{C}.
14633 String constants consist of a sequence of characters enclosed by a
14634 pair of like quotes, either single (@code{'}) or double (@code{"}).
14635 Escape sequences in the style of C are also allowed. @xref{C
14636 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14640 Enumerated constants consist of an enumerated identifier.
14643 Boolean constants consist of the identifiers @code{TRUE} and
14647 Pointer constants consist of integral values only.
14650 Set constants are not yet supported.
14654 @subsubsection Modula-2 Types
14655 @cindex Modula-2 types
14657 Currently @value{GDBN} can print the following data types in Modula-2
14658 syntax: array types, record types, set types, pointer types, procedure
14659 types, enumerated types, subrange types and base types. You can also
14660 print the contents of variables declared using these type.
14661 This section gives a number of simple source code examples together with
14662 sample @value{GDBN} sessions.
14664 The first example contains the following section of code:
14673 and you can request @value{GDBN} to interrogate the type and value of
14674 @code{r} and @code{s}.
14677 (@value{GDBP}) print s
14679 (@value{GDBP}) ptype s
14681 (@value{GDBP}) print r
14683 (@value{GDBP}) ptype r
14688 Likewise if your source code declares @code{s} as:
14692 s: SET ['A'..'Z'] ;
14696 then you may query the type of @code{s} by:
14699 (@value{GDBP}) ptype s
14700 type = SET ['A'..'Z']
14704 Note that at present you cannot interactively manipulate set
14705 expressions using the debugger.
14707 The following example shows how you might declare an array in Modula-2
14708 and how you can interact with @value{GDBN} to print its type and contents:
14712 s: ARRAY [-10..10] OF CHAR ;
14716 (@value{GDBP}) ptype s
14717 ARRAY [-10..10] OF CHAR
14720 Note that the array handling is not yet complete and although the type
14721 is printed correctly, expression handling still assumes that all
14722 arrays have a lower bound of zero and not @code{-10} as in the example
14725 Here are some more type related Modula-2 examples:
14729 colour = (blue, red, yellow, green) ;
14730 t = [blue..yellow] ;
14738 The @value{GDBN} interaction shows how you can query the data type
14739 and value of a variable.
14742 (@value{GDBP}) print s
14744 (@value{GDBP}) ptype t
14745 type = [blue..yellow]
14749 In this example a Modula-2 array is declared and its contents
14750 displayed. Observe that the contents are written in the same way as
14751 their @code{C} counterparts.
14755 s: ARRAY [1..5] OF CARDINAL ;
14761 (@value{GDBP}) print s
14762 $1 = @{1, 0, 0, 0, 0@}
14763 (@value{GDBP}) ptype s
14764 type = ARRAY [1..5] OF CARDINAL
14767 The Modula-2 language interface to @value{GDBN} also understands
14768 pointer types as shown in this example:
14772 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14779 and you can request that @value{GDBN} describes the type of @code{s}.
14782 (@value{GDBP}) ptype s
14783 type = POINTER TO ARRAY [1..5] OF CARDINAL
14786 @value{GDBN} handles compound types as we can see in this example.
14787 Here we combine array types, record types, pointer types and subrange
14798 myarray = ARRAY myrange OF CARDINAL ;
14799 myrange = [-2..2] ;
14801 s: POINTER TO ARRAY myrange OF foo ;
14805 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14809 (@value{GDBP}) ptype s
14810 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14813 f3 : ARRAY [-2..2] OF CARDINAL;
14818 @subsubsection Modula-2 Defaults
14819 @cindex Modula-2 defaults
14821 If type and range checking are set automatically by @value{GDBN}, they
14822 both default to @code{on} whenever the working language changes to
14823 Modula-2. This happens regardless of whether you or @value{GDBN}
14824 selected the working language.
14826 If you allow @value{GDBN} to set the language automatically, then entering
14827 code compiled from a file whose name ends with @file{.mod} sets the
14828 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14829 Infer the Source Language}, for further details.
14832 @subsubsection Deviations from Standard Modula-2
14833 @cindex Modula-2, deviations from
14835 A few changes have been made to make Modula-2 programs easier to debug.
14836 This is done primarily via loosening its type strictness:
14840 Unlike in standard Modula-2, pointer constants can be formed by
14841 integers. This allows you to modify pointer variables during
14842 debugging. (In standard Modula-2, the actual address contained in a
14843 pointer variable is hidden from you; it can only be modified
14844 through direct assignment to another pointer variable or expression that
14845 returned a pointer.)
14848 C escape sequences can be used in strings and characters to represent
14849 non-printable characters. @value{GDBN} prints out strings with these
14850 escape sequences embedded. Single non-printable characters are
14851 printed using the @samp{CHR(@var{nnn})} format.
14854 The assignment operator (@code{:=}) returns the value of its right-hand
14858 All built-in procedures both modify @emph{and} return their argument.
14862 @subsubsection Modula-2 Type and Range Checks
14863 @cindex Modula-2 checks
14866 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14869 @c FIXME remove warning when type/range checks added
14871 @value{GDBN} considers two Modula-2 variables type equivalent if:
14875 They are of types that have been declared equivalent via a @code{TYPE
14876 @var{t1} = @var{t2}} statement
14879 They have been declared on the same line. (Note: This is true of the
14880 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14883 As long as type checking is enabled, any attempt to combine variables
14884 whose types are not equivalent is an error.
14886 Range checking is done on all mathematical operations, assignment, array
14887 index bounds, and all built-in functions and procedures.
14890 @subsubsection The Scope Operators @code{::} and @code{.}
14892 @cindex @code{.}, Modula-2 scope operator
14893 @cindex colon, doubled as scope operator
14895 @vindex colon-colon@r{, in Modula-2}
14896 @c Info cannot handle :: but TeX can.
14899 @vindex ::@r{, in Modula-2}
14902 There are a few subtle differences between the Modula-2 scope operator
14903 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14908 @var{module} . @var{id}
14909 @var{scope} :: @var{id}
14913 where @var{scope} is the name of a module or a procedure,
14914 @var{module} the name of a module, and @var{id} is any declared
14915 identifier within your program, except another module.
14917 Using the @code{::} operator makes @value{GDBN} search the scope
14918 specified by @var{scope} for the identifier @var{id}. If it is not
14919 found in the specified scope, then @value{GDBN} searches all scopes
14920 enclosing the one specified by @var{scope}.
14922 Using the @code{.} operator makes @value{GDBN} search the current scope for
14923 the identifier specified by @var{id} that was imported from the
14924 definition module specified by @var{module}. With this operator, it is
14925 an error if the identifier @var{id} was not imported from definition
14926 module @var{module}, or if @var{id} is not an identifier in
14930 @subsubsection @value{GDBN} and Modula-2
14932 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14933 Five subcommands of @code{set print} and @code{show print} apply
14934 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14935 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14936 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14937 analogue in Modula-2.
14939 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14940 with any language, is not useful with Modula-2. Its
14941 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14942 created in Modula-2 as they can in C or C@t{++}. However, because an
14943 address can be specified by an integral constant, the construct
14944 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14946 @cindex @code{#} in Modula-2
14947 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14948 interpreted as the beginning of a comment. Use @code{<>} instead.
14954 The extensions made to @value{GDBN} for Ada only support
14955 output from the @sc{gnu} Ada (GNAT) compiler.
14956 Other Ada compilers are not currently supported, and
14957 attempting to debug executables produced by them is most likely
14961 @cindex expressions in Ada
14963 * Ada Mode Intro:: General remarks on the Ada syntax
14964 and semantics supported by Ada mode
14966 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14967 * Additions to Ada:: Extensions of the Ada expression syntax.
14968 * Stopping Before Main Program:: Debugging the program during elaboration.
14969 * Ada Exceptions:: Ada Exceptions
14970 * Ada Tasks:: Listing and setting breakpoints in tasks.
14971 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14972 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14974 * Ada Glitches:: Known peculiarities of Ada mode.
14977 @node Ada Mode Intro
14978 @subsubsection Introduction
14979 @cindex Ada mode, general
14981 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14982 syntax, with some extensions.
14983 The philosophy behind the design of this subset is
14987 That @value{GDBN} should provide basic literals and access to operations for
14988 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14989 leaving more sophisticated computations to subprograms written into the
14990 program (which therefore may be called from @value{GDBN}).
14993 That type safety and strict adherence to Ada language restrictions
14994 are not particularly important to the @value{GDBN} user.
14997 That brevity is important to the @value{GDBN} user.
15000 Thus, for brevity, the debugger acts as if all names declared in
15001 user-written packages are directly visible, even if they are not visible
15002 according to Ada rules, thus making it unnecessary to fully qualify most
15003 names with their packages, regardless of context. Where this causes
15004 ambiguity, @value{GDBN} asks the user's intent.
15006 The debugger will start in Ada mode if it detects an Ada main program.
15007 As for other languages, it will enter Ada mode when stopped in a program that
15008 was translated from an Ada source file.
15010 While in Ada mode, you may use `@t{--}' for comments. This is useful
15011 mostly for documenting command files. The standard @value{GDBN} comment
15012 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15013 middle (to allow based literals).
15015 The debugger supports limited overloading. Given a subprogram call in which
15016 the function symbol has multiple definitions, it will use the number of
15017 actual parameters and some information about their types to attempt to narrow
15018 the set of definitions. It also makes very limited use of context, preferring
15019 procedures to functions in the context of the @code{call} command, and
15020 functions to procedures elsewhere.
15022 @node Omissions from Ada
15023 @subsubsection Omissions from Ada
15024 @cindex Ada, omissions from
15026 Here are the notable omissions from the subset:
15030 Only a subset of the attributes are supported:
15034 @t{'First}, @t{'Last}, and @t{'Length}
15035 on array objects (not on types and subtypes).
15038 @t{'Min} and @t{'Max}.
15041 @t{'Pos} and @t{'Val}.
15047 @t{'Range} on array objects (not subtypes), but only as the right
15048 operand of the membership (@code{in}) operator.
15051 @t{'Access}, @t{'Unchecked_Access}, and
15052 @t{'Unrestricted_Access} (a GNAT extension).
15060 @code{Characters.Latin_1} are not available and
15061 concatenation is not implemented. Thus, escape characters in strings are
15062 not currently available.
15065 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15066 equality of representations. They will generally work correctly
15067 for strings and arrays whose elements have integer or enumeration types.
15068 They may not work correctly for arrays whose element
15069 types have user-defined equality, for arrays of real values
15070 (in particular, IEEE-conformant floating point, because of negative
15071 zeroes and NaNs), and for arrays whose elements contain unused bits with
15072 indeterminate values.
15075 The other component-by-component array operations (@code{and}, @code{or},
15076 @code{xor}, @code{not}, and relational tests other than equality)
15077 are not implemented.
15080 @cindex array aggregates (Ada)
15081 @cindex record aggregates (Ada)
15082 @cindex aggregates (Ada)
15083 There is limited support for array and record aggregates. They are
15084 permitted only on the right sides of assignments, as in these examples:
15087 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15088 (@value{GDBP}) set An_Array := (1, others => 0)
15089 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15090 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15091 (@value{GDBP}) set A_Record := (1, "Peter", True);
15092 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15096 discriminant's value by assigning an aggregate has an
15097 undefined effect if that discriminant is used within the record.
15098 However, you can first modify discriminants by directly assigning to
15099 them (which normally would not be allowed in Ada), and then performing an
15100 aggregate assignment. For example, given a variable @code{A_Rec}
15101 declared to have a type such as:
15104 type Rec (Len : Small_Integer := 0) is record
15106 Vals : IntArray (1 .. Len);
15110 you can assign a value with a different size of @code{Vals} with two
15114 (@value{GDBP}) set A_Rec.Len := 4
15115 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15118 As this example also illustrates, @value{GDBN} is very loose about the usual
15119 rules concerning aggregates. You may leave out some of the
15120 components of an array or record aggregate (such as the @code{Len}
15121 component in the assignment to @code{A_Rec} above); they will retain their
15122 original values upon assignment. You may freely use dynamic values as
15123 indices in component associations. You may even use overlapping or
15124 redundant component associations, although which component values are
15125 assigned in such cases is not defined.
15128 Calls to dispatching subprograms are not implemented.
15131 The overloading algorithm is much more limited (i.e., less selective)
15132 than that of real Ada. It makes only limited use of the context in
15133 which a subexpression appears to resolve its meaning, and it is much
15134 looser in its rules for allowing type matches. As a result, some
15135 function calls will be ambiguous, and the user will be asked to choose
15136 the proper resolution.
15139 The @code{new} operator is not implemented.
15142 Entry calls are not implemented.
15145 Aside from printing, arithmetic operations on the native VAX floating-point
15146 formats are not supported.
15149 It is not possible to slice a packed array.
15152 The names @code{True} and @code{False}, when not part of a qualified name,
15153 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15155 Should your program
15156 redefine these names in a package or procedure (at best a dubious practice),
15157 you will have to use fully qualified names to access their new definitions.
15160 @node Additions to Ada
15161 @subsubsection Additions to Ada
15162 @cindex Ada, deviations from
15164 As it does for other languages, @value{GDBN} makes certain generic
15165 extensions to Ada (@pxref{Expressions}):
15169 If the expression @var{E} is a variable residing in memory (typically
15170 a local variable or array element) and @var{N} is a positive integer,
15171 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15172 @var{N}-1 adjacent variables following it in memory as an array. In
15173 Ada, this operator is generally not necessary, since its prime use is
15174 in displaying parts of an array, and slicing will usually do this in
15175 Ada. However, there are occasional uses when debugging programs in
15176 which certain debugging information has been optimized away.
15179 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15180 appears in function or file @var{B}.'' When @var{B} is a file name,
15181 you must typically surround it in single quotes.
15184 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15185 @var{type} that appears at address @var{addr}.''
15188 A name starting with @samp{$} is a convenience variable
15189 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15192 In addition, @value{GDBN} provides a few other shortcuts and outright
15193 additions specific to Ada:
15197 The assignment statement is allowed as an expression, returning
15198 its right-hand operand as its value. Thus, you may enter
15201 (@value{GDBP}) set x := y + 3
15202 (@value{GDBP}) print A(tmp := y + 1)
15206 The semicolon is allowed as an ``operator,'' returning as its value
15207 the value of its right-hand operand.
15208 This allows, for example,
15209 complex conditional breaks:
15212 (@value{GDBP}) break f
15213 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15217 Rather than use catenation and symbolic character names to introduce special
15218 characters into strings, one may instead use a special bracket notation,
15219 which is also used to print strings. A sequence of characters of the form
15220 @samp{["@var{XX}"]} within a string or character literal denotes the
15221 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15222 sequence of characters @samp{["""]} also denotes a single quotation mark
15223 in strings. For example,
15225 "One line.["0a"]Next line.["0a"]"
15228 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15232 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15233 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15237 (@value{GDBP}) print 'max(x, y)
15241 When printing arrays, @value{GDBN} uses positional notation when the
15242 array has a lower bound of 1, and uses a modified named notation otherwise.
15243 For example, a one-dimensional array of three integers with a lower bound
15244 of 3 might print as
15251 That is, in contrast to valid Ada, only the first component has a @code{=>}
15255 You may abbreviate attributes in expressions with any unique,
15256 multi-character subsequence of
15257 their names (an exact match gets preference).
15258 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15259 in place of @t{a'length}.
15262 @cindex quoting Ada internal identifiers
15263 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15264 to lower case. The GNAT compiler uses upper-case characters for
15265 some of its internal identifiers, which are normally of no interest to users.
15266 For the rare occasions when you actually have to look at them,
15267 enclose them in angle brackets to avoid the lower-case mapping.
15270 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15274 Printing an object of class-wide type or dereferencing an
15275 access-to-class-wide value will display all the components of the object's
15276 specific type (as indicated by its run-time tag). Likewise, component
15277 selection on such a value will operate on the specific type of the
15282 @node Stopping Before Main Program
15283 @subsubsection Stopping at the Very Beginning
15285 @cindex breakpointing Ada elaboration code
15286 It is sometimes necessary to debug the program during elaboration, and
15287 before reaching the main procedure.
15288 As defined in the Ada Reference
15289 Manual, the elaboration code is invoked from a procedure called
15290 @code{adainit}. To run your program up to the beginning of
15291 elaboration, simply use the following two commands:
15292 @code{tbreak adainit} and @code{run}.
15294 @node Ada Exceptions
15295 @subsubsection Ada Exceptions
15297 A command is provided to list all Ada exceptions:
15300 @kindex info exceptions
15301 @item info exceptions
15302 @itemx info exceptions @var{regexp}
15303 The @code{info exceptions} command allows you to list all Ada exceptions
15304 defined within the program being debugged, as well as their addresses.
15305 With a regular expression, @var{regexp}, as argument, only those exceptions
15306 whose names match @var{regexp} are listed.
15309 Below is a small example, showing how the command can be used, first
15310 without argument, and next with a regular expression passed as an
15314 (@value{GDBP}) info exceptions
15315 All defined Ada exceptions:
15316 constraint_error: 0x613da0
15317 program_error: 0x613d20
15318 storage_error: 0x613ce0
15319 tasking_error: 0x613ca0
15320 const.aint_global_e: 0x613b00
15321 (@value{GDBP}) info exceptions const.aint
15322 All Ada exceptions matching regular expression "const.aint":
15323 constraint_error: 0x613da0
15324 const.aint_global_e: 0x613b00
15327 It is also possible to ask @value{GDBN} to stop your program's execution
15328 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15331 @subsubsection Extensions for Ada Tasks
15332 @cindex Ada, tasking
15334 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15335 @value{GDBN} provides the following task-related commands:
15340 This command shows a list of current Ada tasks, as in the following example:
15347 (@value{GDBP}) info tasks
15348 ID TID P-ID Pri State Name
15349 1 8088000 0 15 Child Activation Wait main_task
15350 2 80a4000 1 15 Accept Statement b
15351 3 809a800 1 15 Child Activation Wait a
15352 * 4 80ae800 3 15 Runnable c
15357 In this listing, the asterisk before the last task indicates it to be the
15358 task currently being inspected.
15362 Represents @value{GDBN}'s internal task number.
15368 The parent's task ID (@value{GDBN}'s internal task number).
15371 The base priority of the task.
15374 Current state of the task.
15378 The task has been created but has not been activated. It cannot be
15382 The task is not blocked for any reason known to Ada. (It may be waiting
15383 for a mutex, though.) It is conceptually "executing" in normal mode.
15386 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15387 that were waiting on terminate alternatives have been awakened and have
15388 terminated themselves.
15390 @item Child Activation Wait
15391 The task is waiting for created tasks to complete activation.
15393 @item Accept Statement
15394 The task is waiting on an accept or selective wait statement.
15396 @item Waiting on entry call
15397 The task is waiting on an entry call.
15399 @item Async Select Wait
15400 The task is waiting to start the abortable part of an asynchronous
15404 The task is waiting on a select statement with only a delay
15407 @item Child Termination Wait
15408 The task is sleeping having completed a master within itself, and is
15409 waiting for the tasks dependent on that master to become terminated or
15410 waiting on a terminate Phase.
15412 @item Wait Child in Term Alt
15413 The task is sleeping waiting for tasks on terminate alternatives to
15414 finish terminating.
15416 @item Accepting RV with @var{taskno}
15417 The task is accepting a rendez-vous with the task @var{taskno}.
15421 Name of the task in the program.
15425 @kindex info task @var{taskno}
15426 @item info task @var{taskno}
15427 This command shows detailled informations on the specified task, as in
15428 the following example:
15433 (@value{GDBP}) info tasks
15434 ID TID P-ID Pri State Name
15435 1 8077880 0 15 Child Activation Wait main_task
15436 * 2 807c468 1 15 Runnable task_1
15437 (@value{GDBP}) info task 2
15438 Ada Task: 0x807c468
15441 Parent: 1 (main_task)
15447 @kindex task@r{ (Ada)}
15448 @cindex current Ada task ID
15449 This command prints the ID of the current task.
15455 (@value{GDBP}) info tasks
15456 ID TID P-ID Pri State Name
15457 1 8077870 0 15 Child Activation Wait main_task
15458 * 2 807c458 1 15 Runnable t
15459 (@value{GDBP}) task
15460 [Current task is 2]
15463 @item task @var{taskno}
15464 @cindex Ada task switching
15465 This command is like the @code{thread @var{threadno}}
15466 command (@pxref{Threads}). It switches the context of debugging
15467 from the current task to the given task.
15473 (@value{GDBP}) info tasks
15474 ID TID P-ID Pri State Name
15475 1 8077870 0 15 Child Activation Wait main_task
15476 * 2 807c458 1 15 Runnable t
15477 (@value{GDBP}) task 1
15478 [Switching to task 1]
15479 #0 0x8067726 in pthread_cond_wait ()
15481 #0 0x8067726 in pthread_cond_wait ()
15482 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15483 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15484 #3 0x806153e in system.tasking.stages.activate_tasks ()
15485 #4 0x804aacc in un () at un.adb:5
15488 @item break @var{linespec} task @var{taskno}
15489 @itemx break @var{linespec} task @var{taskno} if @dots{}
15490 @cindex breakpoints and tasks, in Ada
15491 @cindex task breakpoints, in Ada
15492 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15493 These commands are like the @code{break @dots{} thread @dots{}}
15494 command (@pxref{Thread Stops}).
15495 @var{linespec} specifies source lines, as described
15496 in @ref{Specify Location}.
15498 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15499 to specify that you only want @value{GDBN} to stop the program when a
15500 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15501 numeric task identifiers assigned by @value{GDBN}, shown in the first
15502 column of the @samp{info tasks} display.
15504 If you do not specify @samp{task @var{taskno}} when you set a
15505 breakpoint, the breakpoint applies to @emph{all} tasks of your
15508 You can use the @code{task} qualifier on conditional breakpoints as
15509 well; in this case, place @samp{task @var{taskno}} before the
15510 breakpoint condition (before the @code{if}).
15518 (@value{GDBP}) info tasks
15519 ID TID P-ID Pri State Name
15520 1 140022020 0 15 Child Activation Wait main_task
15521 2 140045060 1 15 Accept/Select Wait t2
15522 3 140044840 1 15 Runnable t1
15523 * 4 140056040 1 15 Runnable t3
15524 (@value{GDBP}) b 15 task 2
15525 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15526 (@value{GDBP}) cont
15531 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15533 (@value{GDBP}) info tasks
15534 ID TID P-ID Pri State Name
15535 1 140022020 0 15 Child Activation Wait main_task
15536 * 2 140045060 1 15 Runnable t2
15537 3 140044840 1 15 Runnable t1
15538 4 140056040 1 15 Delay Sleep t3
15542 @node Ada Tasks and Core Files
15543 @subsubsection Tasking Support when Debugging Core Files
15544 @cindex Ada tasking and core file debugging
15546 When inspecting a core file, as opposed to debugging a live program,
15547 tasking support may be limited or even unavailable, depending on
15548 the platform being used.
15549 For instance, on x86-linux, the list of tasks is available, but task
15550 switching is not supported. On Tru64, however, task switching will work
15553 On certain platforms, including Tru64, the debugger needs to perform some
15554 memory writes in order to provide Ada tasking support. When inspecting
15555 a core file, this means that the core file must be opened with read-write
15556 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15557 Under these circumstances, you should make a backup copy of the core
15558 file before inspecting it with @value{GDBN}.
15560 @node Ravenscar Profile
15561 @subsubsection Tasking Support when using the Ravenscar Profile
15562 @cindex Ravenscar Profile
15564 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15565 specifically designed for systems with safety-critical real-time
15569 @kindex set ravenscar task-switching on
15570 @cindex task switching with program using Ravenscar Profile
15571 @item set ravenscar task-switching on
15572 Allows task switching when debugging a program that uses the Ravenscar
15573 Profile. This is the default.
15575 @kindex set ravenscar task-switching off
15576 @item set ravenscar task-switching off
15577 Turn off task switching when debugging a program that uses the Ravenscar
15578 Profile. This is mostly intended to disable the code that adds support
15579 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15580 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15581 To be effective, this command should be run before the program is started.
15583 @kindex show ravenscar task-switching
15584 @item show ravenscar task-switching
15585 Show whether it is possible to switch from task to task in a program
15586 using the Ravenscar Profile.
15591 @subsubsection Known Peculiarities of Ada Mode
15592 @cindex Ada, problems
15594 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15595 we know of several problems with and limitations of Ada mode in
15597 some of which will be fixed with planned future releases of the debugger
15598 and the GNU Ada compiler.
15602 Static constants that the compiler chooses not to materialize as objects in
15603 storage are invisible to the debugger.
15606 Named parameter associations in function argument lists are ignored (the
15607 argument lists are treated as positional).
15610 Many useful library packages are currently invisible to the debugger.
15613 Fixed-point arithmetic, conversions, input, and output is carried out using
15614 floating-point arithmetic, and may give results that only approximate those on
15618 The GNAT compiler never generates the prefix @code{Standard} for any of
15619 the standard symbols defined by the Ada language. @value{GDBN} knows about
15620 this: it will strip the prefix from names when you use it, and will never
15621 look for a name you have so qualified among local symbols, nor match against
15622 symbols in other packages or subprograms. If you have
15623 defined entities anywhere in your program other than parameters and
15624 local variables whose simple names match names in @code{Standard},
15625 GNAT's lack of qualification here can cause confusion. When this happens,
15626 you can usually resolve the confusion
15627 by qualifying the problematic names with package
15628 @code{Standard} explicitly.
15631 Older versions of the compiler sometimes generate erroneous debugging
15632 information, resulting in the debugger incorrectly printing the value
15633 of affected entities. In some cases, the debugger is able to work
15634 around an issue automatically. In other cases, the debugger is able
15635 to work around the issue, but the work-around has to be specifically
15638 @kindex set ada trust-PAD-over-XVS
15639 @kindex show ada trust-PAD-over-XVS
15642 @item set ada trust-PAD-over-XVS on
15643 Configure GDB to strictly follow the GNAT encoding when computing the
15644 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15645 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15646 a complete description of the encoding used by the GNAT compiler).
15647 This is the default.
15649 @item set ada trust-PAD-over-XVS off
15650 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15651 sometimes prints the wrong value for certain entities, changing @code{ada
15652 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15653 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15654 @code{off}, but this incurs a slight performance penalty, so it is
15655 recommended to leave this setting to @code{on} unless necessary.
15659 @node Unsupported Languages
15660 @section Unsupported Languages
15662 @cindex unsupported languages
15663 @cindex minimal language
15664 In addition to the other fully-supported programming languages,
15665 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15666 It does not represent a real programming language, but provides a set
15667 of capabilities close to what the C or assembly languages provide.
15668 This should allow most simple operations to be performed while debugging
15669 an application that uses a language currently not supported by @value{GDBN}.
15671 If the language is set to @code{auto}, @value{GDBN} will automatically
15672 select this language if the current frame corresponds to an unsupported
15676 @chapter Examining the Symbol Table
15678 The commands described in this chapter allow you to inquire about the
15679 symbols (names of variables, functions and types) defined in your
15680 program. This information is inherent in the text of your program and
15681 does not change as your program executes. @value{GDBN} finds it in your
15682 program's symbol table, in the file indicated when you started @value{GDBN}
15683 (@pxref{File Options, ,Choosing Files}), or by one of the
15684 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15686 @cindex symbol names
15687 @cindex names of symbols
15688 @cindex quoting names
15689 Occasionally, you may need to refer to symbols that contain unusual
15690 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15691 most frequent case is in referring to static variables in other
15692 source files (@pxref{Variables,,Program Variables}). File names
15693 are recorded in object files as debugging symbols, but @value{GDBN} would
15694 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15695 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15696 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15703 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15706 @cindex case-insensitive symbol names
15707 @cindex case sensitivity in symbol names
15708 @kindex set case-sensitive
15709 @item set case-sensitive on
15710 @itemx set case-sensitive off
15711 @itemx set case-sensitive auto
15712 Normally, when @value{GDBN} looks up symbols, it matches their names
15713 with case sensitivity determined by the current source language.
15714 Occasionally, you may wish to control that. The command @code{set
15715 case-sensitive} lets you do that by specifying @code{on} for
15716 case-sensitive matches or @code{off} for case-insensitive ones. If
15717 you specify @code{auto}, case sensitivity is reset to the default
15718 suitable for the source language. The default is case-sensitive
15719 matches for all languages except for Fortran, for which the default is
15720 case-insensitive matches.
15722 @kindex show case-sensitive
15723 @item show case-sensitive
15724 This command shows the current setting of case sensitivity for symbols
15727 @kindex set print type methods
15728 @item set print type methods
15729 @itemx set print type methods on
15730 @itemx set print type methods off
15731 Normally, when @value{GDBN} prints a class, it displays any methods
15732 declared in that class. You can control this behavior either by
15733 passing the appropriate flag to @code{ptype}, or using @command{set
15734 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15735 display the methods; this is the default. Specifying @code{off} will
15736 cause @value{GDBN} to omit the methods.
15738 @kindex show print type methods
15739 @item show print type methods
15740 This command shows the current setting of method display when printing
15743 @kindex set print type typedefs
15744 @item set print type typedefs
15745 @itemx set print type typedefs on
15746 @itemx set print type typedefs off
15748 Normally, when @value{GDBN} prints a class, it displays any typedefs
15749 defined in that class. You can control this behavior either by
15750 passing the appropriate flag to @code{ptype}, or using @command{set
15751 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15752 display the typedef definitions; this is the default. Specifying
15753 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15754 Note that this controls whether the typedef definition itself is
15755 printed, not whether typedef names are substituted when printing other
15758 @kindex show print type typedefs
15759 @item show print type typedefs
15760 This command shows the current setting of typedef display when
15763 @kindex info address
15764 @cindex address of a symbol
15765 @item info address @var{symbol}
15766 Describe where the data for @var{symbol} is stored. For a register
15767 variable, this says which register it is kept in. For a non-register
15768 local variable, this prints the stack-frame offset at which the variable
15771 Note the contrast with @samp{print &@var{symbol}}, which does not work
15772 at all for a register variable, and for a stack local variable prints
15773 the exact address of the current instantiation of the variable.
15775 @kindex info symbol
15776 @cindex symbol from address
15777 @cindex closest symbol and offset for an address
15778 @item info symbol @var{addr}
15779 Print the name of a symbol which is stored at the address @var{addr}.
15780 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15781 nearest symbol and an offset from it:
15784 (@value{GDBP}) info symbol 0x54320
15785 _initialize_vx + 396 in section .text
15789 This is the opposite of the @code{info address} command. You can use
15790 it to find out the name of a variable or a function given its address.
15792 For dynamically linked executables, the name of executable or shared
15793 library containing the symbol is also printed:
15796 (@value{GDBP}) info symbol 0x400225
15797 _start + 5 in section .text of /tmp/a.out
15798 (@value{GDBP}) info symbol 0x2aaaac2811cf
15799 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15803 @item whatis[/@var{flags}] [@var{arg}]
15804 Print the data type of @var{arg}, which can be either an expression
15805 or a name of a data type. With no argument, print the data type of
15806 @code{$}, the last value in the value history.
15808 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15809 is not actually evaluated, and any side-effecting operations (such as
15810 assignments or function calls) inside it do not take place.
15812 If @var{arg} is a variable or an expression, @code{whatis} prints its
15813 literal type as it is used in the source code. If the type was
15814 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15815 the data type underlying the @code{typedef}. If the type of the
15816 variable or the expression is a compound data type, such as
15817 @code{struct} or @code{class}, @code{whatis} never prints their
15818 fields or methods. It just prints the @code{struct}/@code{class}
15819 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15820 such a compound data type, use @code{ptype}.
15822 If @var{arg} is a type name that was defined using @code{typedef},
15823 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15824 Unrolling means that @code{whatis} will show the underlying type used
15825 in the @code{typedef} declaration of @var{arg}. However, if that
15826 underlying type is also a @code{typedef}, @code{whatis} will not
15829 For C code, the type names may also have the form @samp{class
15830 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15831 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15833 @var{flags} can be used to modify how the type is displayed.
15834 Available flags are:
15838 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15839 parameters and typedefs defined in a class when printing the class'
15840 members. The @code{/r} flag disables this.
15843 Do not print methods defined in the class.
15846 Print methods defined in the class. This is the default, but the flag
15847 exists in case you change the default with @command{set print type methods}.
15850 Do not print typedefs defined in the class. Note that this controls
15851 whether the typedef definition itself is printed, not whether typedef
15852 names are substituted when printing other types.
15855 Print typedefs defined in the class. This is the default, but the flag
15856 exists in case you change the default with @command{set print type typedefs}.
15860 @item ptype[/@var{flags}] [@var{arg}]
15861 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15862 detailed description of the type, instead of just the name of the type.
15863 @xref{Expressions, ,Expressions}.
15865 Contrary to @code{whatis}, @code{ptype} always unrolls any
15866 @code{typedef}s in its argument declaration, whether the argument is
15867 a variable, expression, or a data type. This means that @code{ptype}
15868 of a variable or an expression will not print literally its type as
15869 present in the source code---use @code{whatis} for that. @code{typedef}s at
15870 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15871 fields, methods and inner @code{class typedef}s of @code{struct}s,
15872 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15874 For example, for this variable declaration:
15877 typedef double real_t;
15878 struct complex @{ real_t real; double imag; @};
15879 typedef struct complex complex_t;
15881 real_t *real_pointer_var;
15885 the two commands give this output:
15889 (@value{GDBP}) whatis var
15891 (@value{GDBP}) ptype var
15892 type = struct complex @{
15896 (@value{GDBP}) whatis complex_t
15897 type = struct complex
15898 (@value{GDBP}) whatis struct complex
15899 type = struct complex
15900 (@value{GDBP}) ptype struct complex
15901 type = struct complex @{
15905 (@value{GDBP}) whatis real_pointer_var
15907 (@value{GDBP}) ptype real_pointer_var
15913 As with @code{whatis}, using @code{ptype} without an argument refers to
15914 the type of @code{$}, the last value in the value history.
15916 @cindex incomplete type
15917 Sometimes, programs use opaque data types or incomplete specifications
15918 of complex data structure. If the debug information included in the
15919 program does not allow @value{GDBN} to display a full declaration of
15920 the data type, it will say @samp{<incomplete type>}. For example,
15921 given these declarations:
15925 struct foo *fooptr;
15929 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15932 (@value{GDBP}) ptype foo
15933 $1 = <incomplete type>
15937 ``Incomplete type'' is C terminology for data types that are not
15938 completely specified.
15941 @item info types @var{regexp}
15943 Print a brief description of all types whose names match the regular
15944 expression @var{regexp} (or all types in your program, if you supply
15945 no argument). Each complete typename is matched as though it were a
15946 complete line; thus, @samp{i type value} gives information on all
15947 types in your program whose names include the string @code{value}, but
15948 @samp{i type ^value$} gives information only on types whose complete
15949 name is @code{value}.
15951 This command differs from @code{ptype} in two ways: first, like
15952 @code{whatis}, it does not print a detailed description; second, it
15953 lists all source files where a type is defined.
15955 @kindex info type-printers
15956 @item info type-printers
15957 Versions of @value{GDBN} that ship with Python scripting enabled may
15958 have ``type printers'' available. When using @command{ptype} or
15959 @command{whatis}, these printers are consulted when the name of a type
15960 is needed. @xref{Type Printing API}, for more information on writing
15963 @code{info type-printers} displays all the available type printers.
15965 @kindex enable type-printer
15966 @kindex disable type-printer
15967 @item enable type-printer @var{name}@dots{}
15968 @item disable type-printer @var{name}@dots{}
15969 These commands can be used to enable or disable type printers.
15972 @cindex local variables
15973 @item info scope @var{location}
15974 List all the variables local to a particular scope. This command
15975 accepts a @var{location} argument---a function name, a source line, or
15976 an address preceded by a @samp{*}, and prints all the variables local
15977 to the scope defined by that location. (@xref{Specify Location}, for
15978 details about supported forms of @var{location}.) For example:
15981 (@value{GDBP}) @b{info scope command_line_handler}
15982 Scope for command_line_handler:
15983 Symbol rl is an argument at stack/frame offset 8, length 4.
15984 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15985 Symbol linelength is in static storage at address 0x150a1c, length 4.
15986 Symbol p is a local variable in register $esi, length 4.
15987 Symbol p1 is a local variable in register $ebx, length 4.
15988 Symbol nline is a local variable in register $edx, length 4.
15989 Symbol repeat is a local variable at frame offset -8, length 4.
15993 This command is especially useful for determining what data to collect
15994 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15997 @kindex info source
15999 Show information about the current source file---that is, the source file for
16000 the function containing the current point of execution:
16003 the name of the source file, and the directory containing it,
16005 the directory it was compiled in,
16007 its length, in lines,
16009 which programming language it is written in,
16011 whether the executable includes debugging information for that file, and
16012 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16014 whether the debugging information includes information about
16015 preprocessor macros.
16019 @kindex info sources
16021 Print the names of all source files in your program for which there is
16022 debugging information, organized into two lists: files whose symbols
16023 have already been read, and files whose symbols will be read when needed.
16025 @kindex info functions
16026 @item info functions
16027 Print the names and data types of all defined functions.
16029 @item info functions @var{regexp}
16030 Print the names and data types of all defined functions
16031 whose names contain a match for regular expression @var{regexp}.
16032 Thus, @samp{info fun step} finds all functions whose names
16033 include @code{step}; @samp{info fun ^step} finds those whose names
16034 start with @code{step}. If a function name contains characters
16035 that conflict with the regular expression language (e.g.@:
16036 @samp{operator*()}), they may be quoted with a backslash.
16038 @kindex info variables
16039 @item info variables
16040 Print the names and data types of all variables that are defined
16041 outside of functions (i.e.@: excluding local variables).
16043 @item info variables @var{regexp}
16044 Print the names and data types of all variables (except for local
16045 variables) whose names contain a match for regular expression
16048 @kindex info classes
16049 @cindex Objective-C, classes and selectors
16051 @itemx info classes @var{regexp}
16052 Display all Objective-C classes in your program, or
16053 (with the @var{regexp} argument) all those matching a particular regular
16056 @kindex info selectors
16057 @item info selectors
16058 @itemx info selectors @var{regexp}
16059 Display all Objective-C selectors in your program, or
16060 (with the @var{regexp} argument) all those matching a particular regular
16064 This was never implemented.
16065 @kindex info methods
16067 @itemx info methods @var{regexp}
16068 The @code{info methods} command permits the user to examine all defined
16069 methods within C@t{++} program, or (with the @var{regexp} argument) a
16070 specific set of methods found in the various C@t{++} classes. Many
16071 C@t{++} classes provide a large number of methods. Thus, the output
16072 from the @code{ptype} command can be overwhelming and hard to use. The
16073 @code{info-methods} command filters the methods, printing only those
16074 which match the regular-expression @var{regexp}.
16077 @cindex opaque data types
16078 @kindex set opaque-type-resolution
16079 @item set opaque-type-resolution on
16080 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16081 declared as a pointer to a @code{struct}, @code{class}, or
16082 @code{union}---for example, @code{struct MyType *}---that is used in one
16083 source file although the full declaration of @code{struct MyType} is in
16084 another source file. The default is on.
16086 A change in the setting of this subcommand will not take effect until
16087 the next time symbols for a file are loaded.
16089 @item set opaque-type-resolution off
16090 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16091 is printed as follows:
16093 @{<no data fields>@}
16096 @kindex show opaque-type-resolution
16097 @item show opaque-type-resolution
16098 Show whether opaque types are resolved or not.
16100 @kindex maint print symbols
16101 @cindex symbol dump
16102 @kindex maint print psymbols
16103 @cindex partial symbol dump
16104 @kindex maint print msymbols
16105 @cindex minimal symbol dump
16106 @item maint print symbols @var{filename}
16107 @itemx maint print psymbols @var{filename}
16108 @itemx maint print msymbols @var{filename}
16109 Write a dump of debugging symbol data into the file @var{filename}.
16110 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16111 symbols with debugging data are included. If you use @samp{maint print
16112 symbols}, @value{GDBN} includes all the symbols for which it has already
16113 collected full details: that is, @var{filename} reflects symbols for
16114 only those files whose symbols @value{GDBN} has read. You can use the
16115 command @code{info sources} to find out which files these are. If you
16116 use @samp{maint print psymbols} instead, the dump shows information about
16117 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16118 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16119 @samp{maint print msymbols} dumps just the minimal symbol information
16120 required for each object file from which @value{GDBN} has read some symbols.
16121 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16122 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16124 @kindex maint info symtabs
16125 @kindex maint info psymtabs
16126 @cindex listing @value{GDBN}'s internal symbol tables
16127 @cindex symbol tables, listing @value{GDBN}'s internal
16128 @cindex full symbol tables, listing @value{GDBN}'s internal
16129 @cindex partial symbol tables, listing @value{GDBN}'s internal
16130 @item maint info symtabs @r{[} @var{regexp} @r{]}
16131 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16133 List the @code{struct symtab} or @code{struct partial_symtab}
16134 structures whose names match @var{regexp}. If @var{regexp} is not
16135 given, list them all. The output includes expressions which you can
16136 copy into a @value{GDBN} debugging this one to examine a particular
16137 structure in more detail. For example:
16140 (@value{GDBP}) maint info psymtabs dwarf2read
16141 @{ objfile /home/gnu/build/gdb/gdb
16142 ((struct objfile *) 0x82e69d0)
16143 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16144 ((struct partial_symtab *) 0x8474b10)
16147 text addresses 0x814d3c8 -- 0x8158074
16148 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16149 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16150 dependencies (none)
16153 (@value{GDBP}) maint info symtabs
16157 We see that there is one partial symbol table whose filename contains
16158 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16159 and we see that @value{GDBN} has not read in any symtabs yet at all.
16160 If we set a breakpoint on a function, that will cause @value{GDBN} to
16161 read the symtab for the compilation unit containing that function:
16164 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16165 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16167 (@value{GDBP}) maint info symtabs
16168 @{ objfile /home/gnu/build/gdb/gdb
16169 ((struct objfile *) 0x82e69d0)
16170 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16171 ((struct symtab *) 0x86c1f38)
16174 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16175 linetable ((struct linetable *) 0x8370fa0)
16176 debugformat DWARF 2
16185 @chapter Altering Execution
16187 Once you think you have found an error in your program, you might want to
16188 find out for certain whether correcting the apparent error would lead to
16189 correct results in the rest of the run. You can find the answer by
16190 experiment, using the @value{GDBN} features for altering execution of the
16193 For example, you can store new values into variables or memory
16194 locations, give your program a signal, restart it at a different
16195 address, or even return prematurely from a function.
16198 * Assignment:: Assignment to variables
16199 * Jumping:: Continuing at a different address
16200 * Signaling:: Giving your program a signal
16201 * Returning:: Returning from a function
16202 * Calling:: Calling your program's functions
16203 * Patching:: Patching your program
16207 @section Assignment to Variables
16210 @cindex setting variables
16211 To alter the value of a variable, evaluate an assignment expression.
16212 @xref{Expressions, ,Expressions}. For example,
16219 stores the value 4 into the variable @code{x}, and then prints the
16220 value of the assignment expression (which is 4).
16221 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16222 information on operators in supported languages.
16224 @kindex set variable
16225 @cindex variables, setting
16226 If you are not interested in seeing the value of the assignment, use the
16227 @code{set} command instead of the @code{print} command. @code{set} is
16228 really the same as @code{print} except that the expression's value is
16229 not printed and is not put in the value history (@pxref{Value History,
16230 ,Value History}). The expression is evaluated only for its effects.
16232 If the beginning of the argument string of the @code{set} command
16233 appears identical to a @code{set} subcommand, use the @code{set
16234 variable} command instead of just @code{set}. This command is identical
16235 to @code{set} except for its lack of subcommands. For example, if your
16236 program has a variable @code{width}, you get an error if you try to set
16237 a new value with just @samp{set width=13}, because @value{GDBN} has the
16238 command @code{set width}:
16241 (@value{GDBP}) whatis width
16243 (@value{GDBP}) p width
16245 (@value{GDBP}) set width=47
16246 Invalid syntax in expression.
16250 The invalid expression, of course, is @samp{=47}. In
16251 order to actually set the program's variable @code{width}, use
16254 (@value{GDBP}) set var width=47
16257 Because the @code{set} command has many subcommands that can conflict
16258 with the names of program variables, it is a good idea to use the
16259 @code{set variable} command instead of just @code{set}. For example, if
16260 your program has a variable @code{g}, you run into problems if you try
16261 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16262 the command @code{set gnutarget}, abbreviated @code{set g}:
16266 (@value{GDBP}) whatis g
16270 (@value{GDBP}) set g=4
16274 The program being debugged has been started already.
16275 Start it from the beginning? (y or n) y
16276 Starting program: /home/smith/cc_progs/a.out
16277 "/home/smith/cc_progs/a.out": can't open to read symbols:
16278 Invalid bfd target.
16279 (@value{GDBP}) show g
16280 The current BFD target is "=4".
16285 The program variable @code{g} did not change, and you silently set the
16286 @code{gnutarget} to an invalid value. In order to set the variable
16290 (@value{GDBP}) set var g=4
16293 @value{GDBN} allows more implicit conversions in assignments than C; you can
16294 freely store an integer value into a pointer variable or vice versa,
16295 and you can convert any structure to any other structure that is the
16296 same length or shorter.
16297 @comment FIXME: how do structs align/pad in these conversions?
16298 @comment /doc@cygnus.com 18dec1990
16300 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16301 construct to generate a value of specified type at a specified address
16302 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16303 to memory location @code{0x83040} as an integer (which implies a certain size
16304 and representation in memory), and
16307 set @{int@}0x83040 = 4
16311 stores the value 4 into that memory location.
16314 @section Continuing at a Different Address
16316 Ordinarily, when you continue your program, you do so at the place where
16317 it stopped, with the @code{continue} command. You can instead continue at
16318 an address of your own choosing, with the following commands:
16322 @kindex j @r{(@code{jump})}
16323 @item jump @var{linespec}
16324 @itemx j @var{linespec}
16325 @itemx jump @var{location}
16326 @itemx j @var{location}
16327 Resume execution at line @var{linespec} or at address given by
16328 @var{location}. Execution stops again immediately if there is a
16329 breakpoint there. @xref{Specify Location}, for a description of the
16330 different forms of @var{linespec} and @var{location}. It is common
16331 practice to use the @code{tbreak} command in conjunction with
16332 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16334 The @code{jump} command does not change the current stack frame, or
16335 the stack pointer, or the contents of any memory location or any
16336 register other than the program counter. If line @var{linespec} is in
16337 a different function from the one currently executing, the results may
16338 be bizarre if the two functions expect different patterns of arguments or
16339 of local variables. For this reason, the @code{jump} command requests
16340 confirmation if the specified line is not in the function currently
16341 executing. However, even bizarre results are predictable if you are
16342 well acquainted with the machine-language code of your program.
16345 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16346 On many systems, you can get much the same effect as the @code{jump}
16347 command by storing a new value into the register @code{$pc}. The
16348 difference is that this does not start your program running; it only
16349 changes the address of where it @emph{will} run when you continue. For
16357 makes the next @code{continue} command or stepping command execute at
16358 address @code{0x485}, rather than at the address where your program stopped.
16359 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16361 The most common occasion to use the @code{jump} command is to back
16362 up---perhaps with more breakpoints set---over a portion of a program
16363 that has already executed, in order to examine its execution in more
16368 @section Giving your Program a Signal
16369 @cindex deliver a signal to a program
16373 @item signal @var{signal}
16374 Resume execution where your program stopped, but immediately give it the
16375 signal @var{signal}. @var{signal} can be the name or the number of a
16376 signal. For example, on many systems @code{signal 2} and @code{signal
16377 SIGINT} are both ways of sending an interrupt signal.
16379 Alternatively, if @var{signal} is zero, continue execution without
16380 giving a signal. This is useful when your program stopped on account of
16381 a signal and would ordinarily see the signal when resumed with the
16382 @code{continue} command; @samp{signal 0} causes it to resume without a
16385 @code{signal} does not repeat when you press @key{RET} a second time
16386 after executing the command.
16390 Invoking the @code{signal} command is not the same as invoking the
16391 @code{kill} utility from the shell. Sending a signal with @code{kill}
16392 causes @value{GDBN} to decide what to do with the signal depending on
16393 the signal handling tables (@pxref{Signals}). The @code{signal} command
16394 passes the signal directly to your program.
16398 @section Returning from a Function
16401 @cindex returning from a function
16404 @itemx return @var{expression}
16405 You can cancel execution of a function call with the @code{return}
16406 command. If you give an
16407 @var{expression} argument, its value is used as the function's return
16411 When you use @code{return}, @value{GDBN} discards the selected stack frame
16412 (and all frames within it). You can think of this as making the
16413 discarded frame return prematurely. If you wish to specify a value to
16414 be returned, give that value as the argument to @code{return}.
16416 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16417 Frame}), and any other frames inside of it, leaving its caller as the
16418 innermost remaining frame. That frame becomes selected. The
16419 specified value is stored in the registers used for returning values
16422 The @code{return} command does not resume execution; it leaves the
16423 program stopped in the state that would exist if the function had just
16424 returned. In contrast, the @code{finish} command (@pxref{Continuing
16425 and Stepping, ,Continuing and Stepping}) resumes execution until the
16426 selected stack frame returns naturally.
16428 @value{GDBN} needs to know how the @var{expression} argument should be set for
16429 the inferior. The concrete registers assignment depends on the OS ABI and the
16430 type being returned by the selected stack frame. For example it is common for
16431 OS ABI to return floating point values in FPU registers while integer values in
16432 CPU registers. Still some ABIs return even floating point values in CPU
16433 registers. Larger integer widths (such as @code{long long int}) also have
16434 specific placement rules. @value{GDBN} already knows the OS ABI from its
16435 current target so it needs to find out also the type being returned to make the
16436 assignment into the right register(s).
16438 Normally, the selected stack frame has debug info. @value{GDBN} will always
16439 use the debug info instead of the implicit type of @var{expression} when the
16440 debug info is available. For example, if you type @kbd{return -1}, and the
16441 function in the current stack frame is declared to return a @code{long long
16442 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16443 into a @code{long long int}:
16446 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16448 (@value{GDBP}) return -1
16449 Make func return now? (y or n) y
16450 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16451 43 printf ("result=%lld\n", func ());
16455 However, if the selected stack frame does not have a debug info, e.g., if the
16456 function was compiled without debug info, @value{GDBN} has to find out the type
16457 to return from user. Specifying a different type by mistake may set the value
16458 in different inferior registers than the caller code expects. For example,
16459 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16460 of a @code{long long int} result for a debug info less function (on 32-bit
16461 architectures). Therefore the user is required to specify the return type by
16462 an appropriate cast explicitly:
16465 Breakpoint 2, 0x0040050b in func ()
16466 (@value{GDBP}) return -1
16467 Return value type not available for selected stack frame.
16468 Please use an explicit cast of the value to return.
16469 (@value{GDBP}) return (long long int) -1
16470 Make selected stack frame return now? (y or n) y
16471 #0 0x00400526 in main ()
16476 @section Calling Program Functions
16479 @cindex calling functions
16480 @cindex inferior functions, calling
16481 @item print @var{expr}
16482 Evaluate the expression @var{expr} and display the resulting value.
16483 @var{expr} may include calls to functions in the program being
16487 @item call @var{expr}
16488 Evaluate the expression @var{expr} without displaying @code{void}
16491 You can use this variant of the @code{print} command if you want to
16492 execute a function from your program that does not return anything
16493 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16494 with @code{void} returned values that @value{GDBN} will otherwise
16495 print. If the result is not void, it is printed and saved in the
16499 It is possible for the function you call via the @code{print} or
16500 @code{call} command to generate a signal (e.g., if there's a bug in
16501 the function, or if you passed it incorrect arguments). What happens
16502 in that case is controlled by the @code{set unwindonsignal} command.
16504 Similarly, with a C@t{++} program it is possible for the function you
16505 call via the @code{print} or @code{call} command to generate an
16506 exception that is not handled due to the constraints of the dummy
16507 frame. In this case, any exception that is raised in the frame, but has
16508 an out-of-frame exception handler will not be found. GDB builds a
16509 dummy-frame for the inferior function call, and the unwinder cannot
16510 seek for exception handlers outside of this dummy-frame. What happens
16511 in that case is controlled by the
16512 @code{set unwind-on-terminating-exception} command.
16515 @item set unwindonsignal
16516 @kindex set unwindonsignal
16517 @cindex unwind stack in called functions
16518 @cindex call dummy stack unwinding
16519 Set unwinding of the stack if a signal is received while in a function
16520 that @value{GDBN} called in the program being debugged. If set to on,
16521 @value{GDBN} unwinds the stack it created for the call and restores
16522 the context to what it was before the call. If set to off (the
16523 default), @value{GDBN} stops in the frame where the signal was
16526 @item show unwindonsignal
16527 @kindex show unwindonsignal
16528 Show the current setting of stack unwinding in the functions called by
16531 @item set unwind-on-terminating-exception
16532 @kindex set unwind-on-terminating-exception
16533 @cindex unwind stack in called functions with unhandled exceptions
16534 @cindex call dummy stack unwinding on unhandled exception.
16535 Set unwinding of the stack if a C@t{++} exception is raised, but left
16536 unhandled while in a function that @value{GDBN} called in the program being
16537 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16538 it created for the call and restores the context to what it was before
16539 the call. If set to off, @value{GDBN} the exception is delivered to
16540 the default C@t{++} exception handler and the inferior terminated.
16542 @item show unwind-on-terminating-exception
16543 @kindex show unwind-on-terminating-exception
16544 Show the current setting of stack unwinding in the functions called by
16549 @cindex weak alias functions
16550 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16551 for another function. In such case, @value{GDBN} might not pick up
16552 the type information, including the types of the function arguments,
16553 which causes @value{GDBN} to call the inferior function incorrectly.
16554 As a result, the called function will function erroneously and may
16555 even crash. A solution to that is to use the name of the aliased
16559 @section Patching Programs
16561 @cindex patching binaries
16562 @cindex writing into executables
16563 @cindex writing into corefiles
16565 By default, @value{GDBN} opens the file containing your program's
16566 executable code (or the corefile) read-only. This prevents accidental
16567 alterations to machine code; but it also prevents you from intentionally
16568 patching your program's binary.
16570 If you'd like to be able to patch the binary, you can specify that
16571 explicitly with the @code{set write} command. For example, you might
16572 want to turn on internal debugging flags, or even to make emergency
16578 @itemx set write off
16579 If you specify @samp{set write on}, @value{GDBN} opens executable and
16580 core files for both reading and writing; if you specify @kbd{set write
16581 off} (the default), @value{GDBN} opens them read-only.
16583 If you have already loaded a file, you must load it again (using the
16584 @code{exec-file} or @code{core-file} command) after changing @code{set
16585 write}, for your new setting to take effect.
16589 Display whether executable files and core files are opened for writing
16590 as well as reading.
16594 @chapter @value{GDBN} Files
16596 @value{GDBN} needs to know the file name of the program to be debugged,
16597 both in order to read its symbol table and in order to start your
16598 program. To debug a core dump of a previous run, you must also tell
16599 @value{GDBN} the name of the core dump file.
16602 * Files:: Commands to specify files
16603 * Separate Debug Files:: Debugging information in separate files
16604 * MiniDebugInfo:: Debugging information in a special section
16605 * Index Files:: Index files speed up GDB
16606 * Symbol Errors:: Errors reading symbol files
16607 * Data Files:: GDB data files
16611 @section Commands to Specify Files
16613 @cindex symbol table
16614 @cindex core dump file
16616 You may want to specify executable and core dump file names. The usual
16617 way to do this is at start-up time, using the arguments to
16618 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16619 Out of @value{GDBN}}).
16621 Occasionally it is necessary to change to a different file during a
16622 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16623 specify a file you want to use. Or you are debugging a remote target
16624 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16625 Program}). In these situations the @value{GDBN} commands to specify
16626 new files are useful.
16629 @cindex executable file
16631 @item file @var{filename}
16632 Use @var{filename} as the program to be debugged. It is read for its
16633 symbols and for the contents of pure memory. It is also the program
16634 executed when you use the @code{run} command. If you do not specify a
16635 directory and the file is not found in the @value{GDBN} working directory,
16636 @value{GDBN} uses the environment variable @code{PATH} as a list of
16637 directories to search, just as the shell does when looking for a program
16638 to run. You can change the value of this variable, for both @value{GDBN}
16639 and your program, using the @code{path} command.
16641 @cindex unlinked object files
16642 @cindex patching object files
16643 You can load unlinked object @file{.o} files into @value{GDBN} using
16644 the @code{file} command. You will not be able to ``run'' an object
16645 file, but you can disassemble functions and inspect variables. Also,
16646 if the underlying BFD functionality supports it, you could use
16647 @kbd{gdb -write} to patch object files using this technique. Note
16648 that @value{GDBN} can neither interpret nor modify relocations in this
16649 case, so branches and some initialized variables will appear to go to
16650 the wrong place. But this feature is still handy from time to time.
16653 @code{file} with no argument makes @value{GDBN} discard any information it
16654 has on both executable file and the symbol table.
16657 @item exec-file @r{[} @var{filename} @r{]}
16658 Specify that the program to be run (but not the symbol table) is found
16659 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16660 if necessary to locate your program. Omitting @var{filename} means to
16661 discard information on the executable file.
16663 @kindex symbol-file
16664 @item symbol-file @r{[} @var{filename} @r{]}
16665 Read symbol table information from file @var{filename}. @code{PATH} is
16666 searched when necessary. Use the @code{file} command to get both symbol
16667 table and program to run from the same file.
16669 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16670 program's symbol table.
16672 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16673 some breakpoints and auto-display expressions. This is because they may
16674 contain pointers to the internal data recording symbols and data types,
16675 which are part of the old symbol table data being discarded inside
16678 @code{symbol-file} does not repeat if you press @key{RET} again after
16681 When @value{GDBN} is configured for a particular environment, it
16682 understands debugging information in whatever format is the standard
16683 generated for that environment; you may use either a @sc{gnu} compiler, or
16684 other compilers that adhere to the local conventions.
16685 Best results are usually obtained from @sc{gnu} compilers; for example,
16686 using @code{@value{NGCC}} you can generate debugging information for
16689 For most kinds of object files, with the exception of old SVR3 systems
16690 using COFF, the @code{symbol-file} command does not normally read the
16691 symbol table in full right away. Instead, it scans the symbol table
16692 quickly to find which source files and which symbols are present. The
16693 details are read later, one source file at a time, as they are needed.
16695 The purpose of this two-stage reading strategy is to make @value{GDBN}
16696 start up faster. For the most part, it is invisible except for
16697 occasional pauses while the symbol table details for a particular source
16698 file are being read. (The @code{set verbose} command can turn these
16699 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16700 Warnings and Messages}.)
16702 We have not implemented the two-stage strategy for COFF yet. When the
16703 symbol table is stored in COFF format, @code{symbol-file} reads the
16704 symbol table data in full right away. Note that ``stabs-in-COFF''
16705 still does the two-stage strategy, since the debug info is actually
16709 @cindex reading symbols immediately
16710 @cindex symbols, reading immediately
16711 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16712 @itemx file @r{[} -readnow @r{]} @var{filename}
16713 You can override the @value{GDBN} two-stage strategy for reading symbol
16714 tables by using the @samp{-readnow} option with any of the commands that
16715 load symbol table information, if you want to be sure @value{GDBN} has the
16716 entire symbol table available.
16718 @c FIXME: for now no mention of directories, since this seems to be in
16719 @c flux. 13mar1992 status is that in theory GDB would look either in
16720 @c current dir or in same dir as myprog; but issues like competing
16721 @c GDB's, or clutter in system dirs, mean that in practice right now
16722 @c only current dir is used. FFish says maybe a special GDB hierarchy
16723 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16727 @item core-file @r{[}@var{filename}@r{]}
16729 Specify the whereabouts of a core dump file to be used as the ``contents
16730 of memory''. Traditionally, core files contain only some parts of the
16731 address space of the process that generated them; @value{GDBN} can access the
16732 executable file itself for other parts.
16734 @code{core-file} with no argument specifies that no core file is
16737 Note that the core file is ignored when your program is actually running
16738 under @value{GDBN}. So, if you have been running your program and you
16739 wish to debug a core file instead, you must kill the subprocess in which
16740 the program is running. To do this, use the @code{kill} command
16741 (@pxref{Kill Process, ,Killing the Child Process}).
16743 @kindex add-symbol-file
16744 @cindex dynamic linking
16745 @item add-symbol-file @var{filename} @var{address}
16746 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16747 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16748 The @code{add-symbol-file} command reads additional symbol table
16749 information from the file @var{filename}. You would use this command
16750 when @var{filename} has been dynamically loaded (by some other means)
16751 into the program that is running. @var{address} should be the memory
16752 address at which the file has been loaded; @value{GDBN} cannot figure
16753 this out for itself. You can additionally specify an arbitrary number
16754 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16755 section name and base address for that section. You can specify any
16756 @var{address} as an expression.
16758 The symbol table of the file @var{filename} is added to the symbol table
16759 originally read with the @code{symbol-file} command. You can use the
16760 @code{add-symbol-file} command any number of times; the new symbol data
16761 thus read is kept in addition to the old.
16763 Changes can be reverted using the command @code{remove-symbol-file}.
16765 @cindex relocatable object files, reading symbols from
16766 @cindex object files, relocatable, reading symbols from
16767 @cindex reading symbols from relocatable object files
16768 @cindex symbols, reading from relocatable object files
16769 @cindex @file{.o} files, reading symbols from
16770 Although @var{filename} is typically a shared library file, an
16771 executable file, or some other object file which has been fully
16772 relocated for loading into a process, you can also load symbolic
16773 information from relocatable @file{.o} files, as long as:
16777 the file's symbolic information refers only to linker symbols defined in
16778 that file, not to symbols defined by other object files,
16780 every section the file's symbolic information refers to has actually
16781 been loaded into the inferior, as it appears in the file, and
16783 you can determine the address at which every section was loaded, and
16784 provide these to the @code{add-symbol-file} command.
16788 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16789 relocatable files into an already running program; such systems
16790 typically make the requirements above easy to meet. However, it's
16791 important to recognize that many native systems use complex link
16792 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16793 assembly, for example) that make the requirements difficult to meet. In
16794 general, one cannot assume that using @code{add-symbol-file} to read a
16795 relocatable object file's symbolic information will have the same effect
16796 as linking the relocatable object file into the program in the normal
16799 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16801 @kindex remove-symbol-file
16802 @item remove-symbol-file @var{filename}
16803 @item remove-symbol-file -a @var{address}
16804 Remove a symbol file added via the @code{add-symbol-file} command. The
16805 file to remove can be identified by its @var{filename} or by an @var{address}
16806 that lies within the boundaries of this symbol file in memory. Example:
16809 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16810 add symbol table from file "/home/user/gdb/mylib.so" at
16811 .text_addr = 0x7ffff7ff9480
16813 Reading symbols from /home/user/gdb/mylib.so...done.
16814 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16815 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16820 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16822 @kindex add-symbol-file-from-memory
16823 @cindex @code{syscall DSO}
16824 @cindex load symbols from memory
16825 @item add-symbol-file-from-memory @var{address}
16826 Load symbols from the given @var{address} in a dynamically loaded
16827 object file whose image is mapped directly into the inferior's memory.
16828 For example, the Linux kernel maps a @code{syscall DSO} into each
16829 process's address space; this DSO provides kernel-specific code for
16830 some system calls. The argument can be any expression whose
16831 evaluation yields the address of the file's shared object file header.
16832 For this command to work, you must have used @code{symbol-file} or
16833 @code{exec-file} commands in advance.
16835 @kindex add-shared-symbol-files
16837 @item add-shared-symbol-files @var{library-file}
16838 @itemx assf @var{library-file}
16839 The @code{add-shared-symbol-files} command can currently be used only
16840 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16841 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16842 @value{GDBN} automatically looks for shared libraries, however if
16843 @value{GDBN} does not find yours, you can invoke
16844 @code{add-shared-symbol-files}. It takes one argument: the shared
16845 library's file name. @code{assf} is a shorthand alias for
16846 @code{add-shared-symbol-files}.
16849 @item section @var{section} @var{addr}
16850 The @code{section} command changes the base address of the named
16851 @var{section} of the exec file to @var{addr}. This can be used if the
16852 exec file does not contain section addresses, (such as in the
16853 @code{a.out} format), or when the addresses specified in the file
16854 itself are wrong. Each section must be changed separately. The
16855 @code{info files} command, described below, lists all the sections and
16859 @kindex info target
16862 @code{info files} and @code{info target} are synonymous; both print the
16863 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16864 including the names of the executable and core dump files currently in
16865 use by @value{GDBN}, and the files from which symbols were loaded. The
16866 command @code{help target} lists all possible targets rather than
16869 @kindex maint info sections
16870 @item maint info sections
16871 Another command that can give you extra information about program sections
16872 is @code{maint info sections}. In addition to the section information
16873 displayed by @code{info files}, this command displays the flags and file
16874 offset of each section in the executable and core dump files. In addition,
16875 @code{maint info sections} provides the following command options (which
16876 may be arbitrarily combined):
16880 Display sections for all loaded object files, including shared libraries.
16881 @item @var{sections}
16882 Display info only for named @var{sections}.
16883 @item @var{section-flags}
16884 Display info only for sections for which @var{section-flags} are true.
16885 The section flags that @value{GDBN} currently knows about are:
16888 Section will have space allocated in the process when loaded.
16889 Set for all sections except those containing debug information.
16891 Section will be loaded from the file into the child process memory.
16892 Set for pre-initialized code and data, clear for @code{.bss} sections.
16894 Section needs to be relocated before loading.
16896 Section cannot be modified by the child process.
16898 Section contains executable code only.
16900 Section contains data only (no executable code).
16902 Section will reside in ROM.
16904 Section contains data for constructor/destructor lists.
16906 Section is not empty.
16908 An instruction to the linker to not output the section.
16909 @item COFF_SHARED_LIBRARY
16910 A notification to the linker that the section contains
16911 COFF shared library information.
16913 Section contains common symbols.
16916 @kindex set trust-readonly-sections
16917 @cindex read-only sections
16918 @item set trust-readonly-sections on
16919 Tell @value{GDBN} that readonly sections in your object file
16920 really are read-only (i.e.@: that their contents will not change).
16921 In that case, @value{GDBN} can fetch values from these sections
16922 out of the object file, rather than from the target program.
16923 For some targets (notably embedded ones), this can be a significant
16924 enhancement to debugging performance.
16926 The default is off.
16928 @item set trust-readonly-sections off
16929 Tell @value{GDBN} not to trust readonly sections. This means that
16930 the contents of the section might change while the program is running,
16931 and must therefore be fetched from the target when needed.
16933 @item show trust-readonly-sections
16934 Show the current setting of trusting readonly sections.
16937 All file-specifying commands allow both absolute and relative file names
16938 as arguments. @value{GDBN} always converts the file name to an absolute file
16939 name and remembers it that way.
16941 @cindex shared libraries
16942 @anchor{Shared Libraries}
16943 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16944 and IBM RS/6000 AIX shared libraries.
16946 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16947 shared libraries. @xref{Expat}.
16949 @value{GDBN} automatically loads symbol definitions from shared libraries
16950 when you use the @code{run} command, or when you examine a core file.
16951 (Before you issue the @code{run} command, @value{GDBN} does not understand
16952 references to a function in a shared library, however---unless you are
16953 debugging a core file).
16955 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16956 automatically loads the symbols at the time of the @code{shl_load} call.
16958 @c FIXME: some @value{GDBN} release may permit some refs to undef
16959 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16960 @c FIXME...lib; check this from time to time when updating manual
16962 There are times, however, when you may wish to not automatically load
16963 symbol definitions from shared libraries, such as when they are
16964 particularly large or there are many of them.
16966 To control the automatic loading of shared library symbols, use the
16970 @kindex set auto-solib-add
16971 @item set auto-solib-add @var{mode}
16972 If @var{mode} is @code{on}, symbols from all shared object libraries
16973 will be loaded automatically when the inferior begins execution, you
16974 attach to an independently started inferior, or when the dynamic linker
16975 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16976 is @code{off}, symbols must be loaded manually, using the
16977 @code{sharedlibrary} command. The default value is @code{on}.
16979 @cindex memory used for symbol tables
16980 If your program uses lots of shared libraries with debug info that
16981 takes large amounts of memory, you can decrease the @value{GDBN}
16982 memory footprint by preventing it from automatically loading the
16983 symbols from shared libraries. To that end, type @kbd{set
16984 auto-solib-add off} before running the inferior, then load each
16985 library whose debug symbols you do need with @kbd{sharedlibrary
16986 @var{regexp}}, where @var{regexp} is a regular expression that matches
16987 the libraries whose symbols you want to be loaded.
16989 @kindex show auto-solib-add
16990 @item show auto-solib-add
16991 Display the current autoloading mode.
16994 @cindex load shared library
16995 To explicitly load shared library symbols, use the @code{sharedlibrary}
16999 @kindex info sharedlibrary
17001 @item info share @var{regex}
17002 @itemx info sharedlibrary @var{regex}
17003 Print the names of the shared libraries which are currently loaded
17004 that match @var{regex}. If @var{regex} is omitted then print
17005 all shared libraries that are loaded.
17007 @kindex sharedlibrary
17009 @item sharedlibrary @var{regex}
17010 @itemx share @var{regex}
17011 Load shared object library symbols for files matching a
17012 Unix regular expression.
17013 As with files loaded automatically, it only loads shared libraries
17014 required by your program for a core file or after typing @code{run}. If
17015 @var{regex} is omitted all shared libraries required by your program are
17018 @item nosharedlibrary
17019 @kindex nosharedlibrary
17020 @cindex unload symbols from shared libraries
17021 Unload all shared object library symbols. This discards all symbols
17022 that have been loaded from all shared libraries. Symbols from shared
17023 libraries that were loaded by explicit user requests are not
17027 Sometimes you may wish that @value{GDBN} stops and gives you control
17028 when any of shared library events happen. The best way to do this is
17029 to use @code{catch load} and @code{catch unload} (@pxref{Set
17032 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17033 command for this. This command exists for historical reasons. It is
17034 less useful than setting a catchpoint, because it does not allow for
17035 conditions or commands as a catchpoint does.
17038 @item set stop-on-solib-events
17039 @kindex set stop-on-solib-events
17040 This command controls whether @value{GDBN} should give you control
17041 when the dynamic linker notifies it about some shared library event.
17042 The most common event of interest is loading or unloading of a new
17045 @item show stop-on-solib-events
17046 @kindex show stop-on-solib-events
17047 Show whether @value{GDBN} stops and gives you control when shared
17048 library events happen.
17051 Shared libraries are also supported in many cross or remote debugging
17052 configurations. @value{GDBN} needs to have access to the target's libraries;
17053 this can be accomplished either by providing copies of the libraries
17054 on the host system, or by asking @value{GDBN} to automatically retrieve the
17055 libraries from the target. If copies of the target libraries are
17056 provided, they need to be the same as the target libraries, although the
17057 copies on the target can be stripped as long as the copies on the host are
17060 @cindex where to look for shared libraries
17061 For remote debugging, you need to tell @value{GDBN} where the target
17062 libraries are, so that it can load the correct copies---otherwise, it
17063 may try to load the host's libraries. @value{GDBN} has two variables
17064 to specify the search directories for target libraries.
17067 @cindex prefix for shared library file names
17068 @cindex system root, alternate
17069 @kindex set solib-absolute-prefix
17070 @kindex set sysroot
17071 @item set sysroot @var{path}
17072 Use @var{path} as the system root for the program being debugged. Any
17073 absolute shared library paths will be prefixed with @var{path}; many
17074 runtime loaders store the absolute paths to the shared library in the
17075 target program's memory. If you use @code{set sysroot} to find shared
17076 libraries, they need to be laid out in the same way that they are on
17077 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17080 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17081 retrieve the target libraries from the remote system. This is only
17082 supported when using a remote target that supports the @code{remote get}
17083 command (@pxref{File Transfer,,Sending files to a remote system}).
17084 The part of @var{path} following the initial @file{remote:}
17085 (if present) is used as system root prefix on the remote file system.
17086 @footnote{If you want to specify a local system root using a directory
17087 that happens to be named @file{remote:}, you need to use some equivalent
17088 variant of the name like @file{./remote:}.}
17090 For targets with an MS-DOS based filesystem, such as MS-Windows and
17091 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17092 absolute file name with @var{path}. But first, on Unix hosts,
17093 @value{GDBN} converts all backslash directory separators into forward
17094 slashes, because the backslash is not a directory separator on Unix:
17097 c:\foo\bar.dll @result{} c:/foo/bar.dll
17100 Then, @value{GDBN} attempts prefixing the target file name with
17101 @var{path}, and looks for the resulting file name in the host file
17105 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17108 If that does not find the shared library, @value{GDBN} tries removing
17109 the @samp{:} character from the drive spec, both for convenience, and,
17110 for the case of the host file system not supporting file names with
17114 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17117 This makes it possible to have a system root that mirrors a target
17118 with more than one drive. E.g., you may want to setup your local
17119 copies of the target system shared libraries like so (note @samp{c} vs
17123 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17124 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17125 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17129 and point the system root at @file{/path/to/sysroot}, so that
17130 @value{GDBN} can find the correct copies of both
17131 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17133 If that still does not find the shared library, @value{GDBN} tries
17134 removing the whole drive spec from the target file name:
17137 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17140 This last lookup makes it possible to not care about the drive name,
17141 if you don't want or need to.
17143 The @code{set solib-absolute-prefix} command is an alias for @code{set
17146 @cindex default system root
17147 @cindex @samp{--with-sysroot}
17148 You can set the default system root by using the configure-time
17149 @samp{--with-sysroot} option. If the system root is inside
17150 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17151 @samp{--exec-prefix}), then the default system root will be updated
17152 automatically if the installed @value{GDBN} is moved to a new
17155 @kindex show sysroot
17157 Display the current shared library prefix.
17159 @kindex set solib-search-path
17160 @item set solib-search-path @var{path}
17161 If this variable is set, @var{path} is a colon-separated list of
17162 directories to search for shared libraries. @samp{solib-search-path}
17163 is used after @samp{sysroot} fails to locate the library, or if the
17164 path to the library is relative instead of absolute. If you want to
17165 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17166 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17167 finding your host's libraries. @samp{sysroot} is preferred; setting
17168 it to a nonexistent directory may interfere with automatic loading
17169 of shared library symbols.
17171 @kindex show solib-search-path
17172 @item show solib-search-path
17173 Display the current shared library search path.
17175 @cindex DOS file-name semantics of file names.
17176 @kindex set target-file-system-kind (unix|dos-based|auto)
17177 @kindex show target-file-system-kind
17178 @item set target-file-system-kind @var{kind}
17179 Set assumed file system kind for target reported file names.
17181 Shared library file names as reported by the target system may not
17182 make sense as is on the system @value{GDBN} is running on. For
17183 example, when remote debugging a target that has MS-DOS based file
17184 system semantics, from a Unix host, the target may be reporting to
17185 @value{GDBN} a list of loaded shared libraries with file names such as
17186 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17187 drive letters, so the @samp{c:\} prefix is not normally understood as
17188 indicating an absolute file name, and neither is the backslash
17189 normally considered a directory separator character. In that case,
17190 the native file system would interpret this whole absolute file name
17191 as a relative file name with no directory components. This would make
17192 it impossible to point @value{GDBN} at a copy of the remote target's
17193 shared libraries on the host using @code{set sysroot}, and impractical
17194 with @code{set solib-search-path}. Setting
17195 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17196 to interpret such file names similarly to how the target would, and to
17197 map them to file names valid on @value{GDBN}'s native file system
17198 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17199 to one of the supported file system kinds. In that case, @value{GDBN}
17200 tries to determine the appropriate file system variant based on the
17201 current target's operating system (@pxref{ABI, ,Configuring the
17202 Current ABI}). The supported file system settings are:
17206 Instruct @value{GDBN} to assume the target file system is of Unix
17207 kind. Only file names starting the forward slash (@samp{/}) character
17208 are considered absolute, and the directory separator character is also
17212 Instruct @value{GDBN} to assume the target file system is DOS based.
17213 File names starting with either a forward slash, or a drive letter
17214 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17215 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17216 considered directory separators.
17219 Instruct @value{GDBN} to use the file system kind associated with the
17220 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17221 This is the default.
17225 @cindex file name canonicalization
17226 @cindex base name differences
17227 When processing file names provided by the user, @value{GDBN}
17228 frequently needs to compare them to the file names recorded in the
17229 program's debug info. Normally, @value{GDBN} compares just the
17230 @dfn{base names} of the files as strings, which is reasonably fast
17231 even for very large programs. (The base name of a file is the last
17232 portion of its name, after stripping all the leading directories.)
17233 This shortcut in comparison is based upon the assumption that files
17234 cannot have more than one base name. This is usually true, but
17235 references to files that use symlinks or similar filesystem
17236 facilities violate that assumption. If your program records files
17237 using such facilities, or if you provide file names to @value{GDBN}
17238 using symlinks etc., you can set @code{basenames-may-differ} to
17239 @code{true} to instruct @value{GDBN} to completely canonicalize each
17240 pair of file names it needs to compare. This will make file-name
17241 comparisons accurate, but at a price of a significant slowdown.
17244 @item set basenames-may-differ
17245 @kindex set basenames-may-differ
17246 Set whether a source file may have multiple base names.
17248 @item show basenames-may-differ
17249 @kindex show basenames-may-differ
17250 Show whether a source file may have multiple base names.
17253 @node Separate Debug Files
17254 @section Debugging Information in Separate Files
17255 @cindex separate debugging information files
17256 @cindex debugging information in separate files
17257 @cindex @file{.debug} subdirectories
17258 @cindex debugging information directory, global
17259 @cindex global debugging information directories
17260 @cindex build ID, and separate debugging files
17261 @cindex @file{.build-id} directory
17263 @value{GDBN} allows you to put a program's debugging information in a
17264 file separate from the executable itself, in a way that allows
17265 @value{GDBN} to find and load the debugging information automatically.
17266 Since debugging information can be very large---sometimes larger
17267 than the executable code itself---some systems distribute debugging
17268 information for their executables in separate files, which users can
17269 install only when they need to debug a problem.
17271 @value{GDBN} supports two ways of specifying the separate debug info
17276 The executable contains a @dfn{debug link} that specifies the name of
17277 the separate debug info file. The separate debug file's name is
17278 usually @file{@var{executable}.debug}, where @var{executable} is the
17279 name of the corresponding executable file without leading directories
17280 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17281 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17282 checksum for the debug file, which @value{GDBN} uses to validate that
17283 the executable and the debug file came from the same build.
17286 The executable contains a @dfn{build ID}, a unique bit string that is
17287 also present in the corresponding debug info file. (This is supported
17288 only on some operating systems, notably those which use the ELF format
17289 for binary files and the @sc{gnu} Binutils.) For more details about
17290 this feature, see the description of the @option{--build-id}
17291 command-line option in @ref{Options, , Command Line Options, ld.info,
17292 The GNU Linker}. The debug info file's name is not specified
17293 explicitly by the build ID, but can be computed from the build ID, see
17297 Depending on the way the debug info file is specified, @value{GDBN}
17298 uses two different methods of looking for the debug file:
17302 For the ``debug link'' method, @value{GDBN} looks up the named file in
17303 the directory of the executable file, then in a subdirectory of that
17304 directory named @file{.debug}, and finally under each one of the global debug
17305 directories, in a subdirectory whose name is identical to the leading
17306 directories of the executable's absolute file name.
17309 For the ``build ID'' method, @value{GDBN} looks in the
17310 @file{.build-id} subdirectory of each one of the global debug directories for
17311 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17312 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17313 are the rest of the bit string. (Real build ID strings are 32 or more
17314 hex characters, not 10.)
17317 So, for example, suppose you ask @value{GDBN} to debug
17318 @file{/usr/bin/ls}, which has a debug link that specifies the
17319 file @file{ls.debug}, and a build ID whose value in hex is
17320 @code{abcdef1234}. If the list of the global debug directories includes
17321 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17322 debug information files, in the indicated order:
17326 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17328 @file{/usr/bin/ls.debug}
17330 @file{/usr/bin/.debug/ls.debug}
17332 @file{/usr/lib/debug/usr/bin/ls.debug}.
17335 @anchor{debug-file-directory}
17336 Global debugging info directories default to what is set by @value{GDBN}
17337 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17338 you can also set the global debugging info directories, and view the list
17339 @value{GDBN} is currently using.
17343 @kindex set debug-file-directory
17344 @item set debug-file-directory @var{directories}
17345 Set the directories which @value{GDBN} searches for separate debugging
17346 information files to @var{directory}. Multiple path components can be set
17347 concatenating them by a path separator.
17349 @kindex show debug-file-directory
17350 @item show debug-file-directory
17351 Show the directories @value{GDBN} searches for separate debugging
17356 @cindex @code{.gnu_debuglink} sections
17357 @cindex debug link sections
17358 A debug link is a special section of the executable file named
17359 @code{.gnu_debuglink}. The section must contain:
17363 A filename, with any leading directory components removed, followed by
17366 zero to three bytes of padding, as needed to reach the next four-byte
17367 boundary within the section, and
17369 a four-byte CRC checksum, stored in the same endianness used for the
17370 executable file itself. The checksum is computed on the debugging
17371 information file's full contents by the function given below, passing
17372 zero as the @var{crc} argument.
17375 Any executable file format can carry a debug link, as long as it can
17376 contain a section named @code{.gnu_debuglink} with the contents
17379 @cindex @code{.note.gnu.build-id} sections
17380 @cindex build ID sections
17381 The build ID is a special section in the executable file (and in other
17382 ELF binary files that @value{GDBN} may consider). This section is
17383 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17384 It contains unique identification for the built files---the ID remains
17385 the same across multiple builds of the same build tree. The default
17386 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17387 content for the build ID string. The same section with an identical
17388 value is present in the original built binary with symbols, in its
17389 stripped variant, and in the separate debugging information file.
17391 The debugging information file itself should be an ordinary
17392 executable, containing a full set of linker symbols, sections, and
17393 debugging information. The sections of the debugging information file
17394 should have the same names, addresses, and sizes as the original file,
17395 but they need not contain any data---much like a @code{.bss} section
17396 in an ordinary executable.
17398 The @sc{gnu} binary utilities (Binutils) package includes the
17399 @samp{objcopy} utility that can produce
17400 the separated executable / debugging information file pairs using the
17401 following commands:
17404 @kbd{objcopy --only-keep-debug foo foo.debug}
17409 These commands remove the debugging
17410 information from the executable file @file{foo} and place it in the file
17411 @file{foo.debug}. You can use the first, second or both methods to link the
17416 The debug link method needs the following additional command to also leave
17417 behind a debug link in @file{foo}:
17420 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17423 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17424 a version of the @code{strip} command such that the command @kbd{strip foo -f
17425 foo.debug} has the same functionality as the two @code{objcopy} commands and
17426 the @code{ln -s} command above, together.
17429 Build ID gets embedded into the main executable using @code{ld --build-id} or
17430 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17431 compatibility fixes for debug files separation are present in @sc{gnu} binary
17432 utilities (Binutils) package since version 2.18.
17437 @cindex CRC algorithm definition
17438 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17439 IEEE 802.3 using the polynomial:
17441 @c TexInfo requires naked braces for multi-digit exponents for Tex
17442 @c output, but this causes HTML output to barf. HTML has to be set using
17443 @c raw commands. So we end up having to specify this equation in 2
17448 <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>
17449 + <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
17455 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17456 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17460 The function is computed byte at a time, taking the least
17461 significant bit of each byte first. The initial pattern
17462 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17463 the final result is inverted to ensure trailing zeros also affect the
17466 @emph{Note:} This is the same CRC polynomial as used in handling the
17467 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17468 , @value{GDBN} Remote Serial Protocol}). However in the
17469 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17470 significant bit first, and the result is not inverted, so trailing
17471 zeros have no effect on the CRC value.
17473 To complete the description, we show below the code of the function
17474 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17475 initially supplied @code{crc} argument means that an initial call to
17476 this function passing in zero will start computing the CRC using
17479 @kindex gnu_debuglink_crc32
17482 gnu_debuglink_crc32 (unsigned long crc,
17483 unsigned char *buf, size_t len)
17485 static const unsigned long crc32_table[256] =
17487 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17488 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17489 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17490 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17491 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17492 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17493 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17494 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17495 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17496 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17497 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17498 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17499 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17500 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17501 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17502 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17503 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17504 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17505 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17506 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17507 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17508 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17509 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17510 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17511 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17512 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17513 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17514 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17515 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17516 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17517 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17518 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17519 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17520 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17521 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17522 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17523 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17524 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17525 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17526 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17527 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17528 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17529 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17530 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17531 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17532 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17533 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17534 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17535 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17536 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17537 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17540 unsigned char *end;
17542 crc = ~crc & 0xffffffff;
17543 for (end = buf + len; buf < end; ++buf)
17544 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17545 return ~crc & 0xffffffff;
17550 This computation does not apply to the ``build ID'' method.
17552 @node MiniDebugInfo
17553 @section Debugging information in a special section
17554 @cindex separate debug sections
17555 @cindex @samp{.gnu_debugdata} section
17557 Some systems ship pre-built executables and libraries that have a
17558 special @samp{.gnu_debugdata} section. This feature is called
17559 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17560 is used to supply extra symbols for backtraces.
17562 The intent of this section is to provide extra minimal debugging
17563 information for use in simple backtraces. It is not intended to be a
17564 replacement for full separate debugging information (@pxref{Separate
17565 Debug Files}). The example below shows the intended use; however,
17566 @value{GDBN} does not currently put restrictions on what sort of
17567 debugging information might be included in the section.
17569 @value{GDBN} has support for this extension. If the section exists,
17570 then it is used provided that no other source of debugging information
17571 can be found, and that @value{GDBN} was configured with LZMA support.
17573 This section can be easily created using @command{objcopy} and other
17574 standard utilities:
17577 # Extract the dynamic symbols from the main binary, there is no need
17578 # to also have these in the normal symbol table.
17579 nm -D @var{binary} --format=posix --defined-only \
17580 | awk '@{ print $1 @}' | sort > dynsyms
17582 # Extract all the text (i.e. function) symbols from the debuginfo.
17583 # (Note that we actually also accept "D" symbols, for the benefit
17584 # of platforms like PowerPC64 that use function descriptors.)
17585 nm @var{binary} --format=posix --defined-only \
17586 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17589 # Keep all the function symbols not already in the dynamic symbol
17591 comm -13 dynsyms funcsyms > keep_symbols
17593 # Separate full debug info into debug binary.
17594 objcopy --only-keep-debug @var{binary} debug
17596 # Copy the full debuginfo, keeping only a minimal set of symbols and
17597 # removing some unnecessary sections.
17598 objcopy -S --remove-section .gdb_index --remove-section .comment \
17599 --keep-symbols=keep_symbols debug mini_debuginfo
17601 # Drop the full debug info from the original binary.
17602 strip --strip-all -R .comment @var{binary}
17604 # Inject the compressed data into the .gnu_debugdata section of the
17607 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17611 @section Index Files Speed Up @value{GDBN}
17612 @cindex index files
17613 @cindex @samp{.gdb_index} section
17615 When @value{GDBN} finds a symbol file, it scans the symbols in the
17616 file in order to construct an internal symbol table. This lets most
17617 @value{GDBN} operations work quickly---at the cost of a delay early
17618 on. For large programs, this delay can be quite lengthy, so
17619 @value{GDBN} provides a way to build an index, which speeds up
17622 The index is stored as a section in the symbol file. @value{GDBN} can
17623 write the index to a file, then you can put it into the symbol file
17624 using @command{objcopy}.
17626 To create an index file, use the @code{save gdb-index} command:
17629 @item save gdb-index @var{directory}
17630 @kindex save gdb-index
17631 Create an index file for each symbol file currently known by
17632 @value{GDBN}. Each file is named after its corresponding symbol file,
17633 with @samp{.gdb-index} appended, and is written into the given
17637 Once you have created an index file you can merge it into your symbol
17638 file, here named @file{symfile}, using @command{objcopy}:
17641 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17642 --set-section-flags .gdb_index=readonly symfile symfile
17645 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17646 sections that have been deprecated. Usually they are deprecated because
17647 they are missing a new feature or have performance issues.
17648 To tell @value{GDBN} to use a deprecated index section anyway
17649 specify @code{set use-deprecated-index-sections on}.
17650 The default is @code{off}.
17651 This can speed up startup, but may result in some functionality being lost.
17652 @xref{Index Section Format}.
17654 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17655 must be done before gdb reads the file. The following will not work:
17658 $ gdb -ex "set use-deprecated-index-sections on" <program>
17661 Instead you must do, for example,
17664 $ gdb -iex "set use-deprecated-index-sections on" <program>
17667 There are currently some limitation on indices. They only work when
17668 for DWARF debugging information, not stabs. And, they do not
17669 currently work for programs using Ada.
17671 @node Symbol Errors
17672 @section Errors Reading Symbol Files
17674 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17675 such as symbol types it does not recognize, or known bugs in compiler
17676 output. By default, @value{GDBN} does not notify you of such problems, since
17677 they are relatively common and primarily of interest to people
17678 debugging compilers. If you are interested in seeing information
17679 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17680 only one message about each such type of problem, no matter how many
17681 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17682 to see how many times the problems occur, with the @code{set
17683 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17686 The messages currently printed, and their meanings, include:
17689 @item inner block not inside outer block in @var{symbol}
17691 The symbol information shows where symbol scopes begin and end
17692 (such as at the start of a function or a block of statements). This
17693 error indicates that an inner scope block is not fully contained
17694 in its outer scope blocks.
17696 @value{GDBN} circumvents the problem by treating the inner block as if it had
17697 the same scope as the outer block. In the error message, @var{symbol}
17698 may be shown as ``@code{(don't know)}'' if the outer block is not a
17701 @item block at @var{address} out of order
17703 The symbol information for symbol scope blocks should occur in
17704 order of increasing addresses. This error indicates that it does not
17707 @value{GDBN} does not circumvent this problem, and has trouble
17708 locating symbols in the source file whose symbols it is reading. (You
17709 can often determine what source file is affected by specifying
17710 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17713 @item bad block start address patched
17715 The symbol information for a symbol scope block has a start address
17716 smaller than the address of the preceding source line. This is known
17717 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17719 @value{GDBN} circumvents the problem by treating the symbol scope block as
17720 starting on the previous source line.
17722 @item bad string table offset in symbol @var{n}
17725 Symbol number @var{n} contains a pointer into the string table which is
17726 larger than the size of the string table.
17728 @value{GDBN} circumvents the problem by considering the symbol to have the
17729 name @code{foo}, which may cause other problems if many symbols end up
17732 @item unknown symbol type @code{0x@var{nn}}
17734 The symbol information contains new data types that @value{GDBN} does
17735 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17736 uncomprehended information, in hexadecimal.
17738 @value{GDBN} circumvents the error by ignoring this symbol information.
17739 This usually allows you to debug your program, though certain symbols
17740 are not accessible. If you encounter such a problem and feel like
17741 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17742 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17743 and examine @code{*bufp} to see the symbol.
17745 @item stub type has NULL name
17747 @value{GDBN} could not find the full definition for a struct or class.
17749 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17750 The symbol information for a C@t{++} member function is missing some
17751 information that recent versions of the compiler should have output for
17754 @item info mismatch between compiler and debugger
17756 @value{GDBN} could not parse a type specification output by the compiler.
17761 @section GDB Data Files
17763 @cindex prefix for data files
17764 @value{GDBN} will sometimes read an auxiliary data file. These files
17765 are kept in a directory known as the @dfn{data directory}.
17767 You can set the data directory's name, and view the name @value{GDBN}
17768 is currently using.
17771 @kindex set data-directory
17772 @item set data-directory @var{directory}
17773 Set the directory which @value{GDBN} searches for auxiliary data files
17774 to @var{directory}.
17776 @kindex show data-directory
17777 @item show data-directory
17778 Show the directory @value{GDBN} searches for auxiliary data files.
17781 @cindex default data directory
17782 @cindex @samp{--with-gdb-datadir}
17783 You can set the default data directory by using the configure-time
17784 @samp{--with-gdb-datadir} option. If the data directory is inside
17785 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17786 @samp{--exec-prefix}), then the default data directory will be updated
17787 automatically if the installed @value{GDBN} is moved to a new
17790 The data directory may also be specified with the
17791 @code{--data-directory} command line option.
17792 @xref{Mode Options}.
17795 @chapter Specifying a Debugging Target
17797 @cindex debugging target
17798 A @dfn{target} is the execution environment occupied by your program.
17800 Often, @value{GDBN} runs in the same host environment as your program;
17801 in that case, the debugging target is specified as a side effect when
17802 you use the @code{file} or @code{core} commands. When you need more
17803 flexibility---for example, running @value{GDBN} on a physically separate
17804 host, or controlling a standalone system over a serial port or a
17805 realtime system over a TCP/IP connection---you can use the @code{target}
17806 command to specify one of the target types configured for @value{GDBN}
17807 (@pxref{Target Commands, ,Commands for Managing Targets}).
17809 @cindex target architecture
17810 It is possible to build @value{GDBN} for several different @dfn{target
17811 architectures}. When @value{GDBN} is built like that, you can choose
17812 one of the available architectures with the @kbd{set architecture}
17816 @kindex set architecture
17817 @kindex show architecture
17818 @item set architecture @var{arch}
17819 This command sets the current target architecture to @var{arch}. The
17820 value of @var{arch} can be @code{"auto"}, in addition to one of the
17821 supported architectures.
17823 @item show architecture
17824 Show the current target architecture.
17826 @item set processor
17828 @kindex set processor
17829 @kindex show processor
17830 These are alias commands for, respectively, @code{set architecture}
17831 and @code{show architecture}.
17835 * Active Targets:: Active targets
17836 * Target Commands:: Commands for managing targets
17837 * Byte Order:: Choosing target byte order
17840 @node Active Targets
17841 @section Active Targets
17843 @cindex stacking targets
17844 @cindex active targets
17845 @cindex multiple targets
17847 There are multiple classes of targets such as: processes, executable files or
17848 recording sessions. Core files belong to the process class, making core file
17849 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17850 on multiple active targets, one in each class. This allows you to (for
17851 example) start a process and inspect its activity, while still having access to
17852 the executable file after the process finishes. Or if you start process
17853 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17854 presented a virtual layer of the recording target, while the process target
17855 remains stopped at the chronologically last point of the process execution.
17857 Use the @code{core-file} and @code{exec-file} commands to select a new core
17858 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17859 specify as a target a process that is already running, use the @code{attach}
17860 command (@pxref{Attach, ,Debugging an Already-running Process}).
17862 @node Target Commands
17863 @section Commands for Managing Targets
17866 @item target @var{type} @var{parameters}
17867 Connects the @value{GDBN} host environment to a target machine or
17868 process. A target is typically a protocol for talking to debugging
17869 facilities. You use the argument @var{type} to specify the type or
17870 protocol of the target machine.
17872 Further @var{parameters} are interpreted by the target protocol, but
17873 typically include things like device names or host names to connect
17874 with, process numbers, and baud rates.
17876 The @code{target} command does not repeat if you press @key{RET} again
17877 after executing the command.
17879 @kindex help target
17881 Displays the names of all targets available. To display targets
17882 currently selected, use either @code{info target} or @code{info files}
17883 (@pxref{Files, ,Commands to Specify Files}).
17885 @item help target @var{name}
17886 Describe a particular target, including any parameters necessary to
17889 @kindex set gnutarget
17890 @item set gnutarget @var{args}
17891 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17892 knows whether it is reading an @dfn{executable},
17893 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17894 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17895 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17898 @emph{Warning:} To specify a file format with @code{set gnutarget},
17899 you must know the actual BFD name.
17903 @xref{Files, , Commands to Specify Files}.
17905 @kindex show gnutarget
17906 @item show gnutarget
17907 Use the @code{show gnutarget} command to display what file format
17908 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17909 @value{GDBN} will determine the file format for each file automatically,
17910 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17913 @cindex common targets
17914 Here are some common targets (available, or not, depending on the GDB
17919 @item target exec @var{program}
17920 @cindex executable file target
17921 An executable file. @samp{target exec @var{program}} is the same as
17922 @samp{exec-file @var{program}}.
17924 @item target core @var{filename}
17925 @cindex core dump file target
17926 A core dump file. @samp{target core @var{filename}} is the same as
17927 @samp{core-file @var{filename}}.
17929 @item target remote @var{medium}
17930 @cindex remote target
17931 A remote system connected to @value{GDBN} via a serial line or network
17932 connection. This command tells @value{GDBN} to use its own remote
17933 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17935 For example, if you have a board connected to @file{/dev/ttya} on the
17936 machine running @value{GDBN}, you could say:
17939 target remote /dev/ttya
17942 @code{target remote} supports the @code{load} command. This is only
17943 useful if you have some other way of getting the stub to the target
17944 system, and you can put it somewhere in memory where it won't get
17945 clobbered by the download.
17947 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17948 @cindex built-in simulator target
17949 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17957 works; however, you cannot assume that a specific memory map, device
17958 drivers, or even basic I/O is available, although some simulators do
17959 provide these. For info about any processor-specific simulator details,
17960 see the appropriate section in @ref{Embedded Processors, ,Embedded
17965 Different targets are available on different configurations of @value{GDBN};
17966 your configuration may have more or fewer targets.
17968 Many remote targets require you to download the executable's code once
17969 you've successfully established a connection. You may wish to control
17970 various aspects of this process.
17975 @kindex set hash@r{, for remote monitors}
17976 @cindex hash mark while downloading
17977 This command controls whether a hash mark @samp{#} is displayed while
17978 downloading a file to the remote monitor. If on, a hash mark is
17979 displayed after each S-record is successfully downloaded to the
17983 @kindex show hash@r{, for remote monitors}
17984 Show the current status of displaying the hash mark.
17986 @item set debug monitor
17987 @kindex set debug monitor
17988 @cindex display remote monitor communications
17989 Enable or disable display of communications messages between
17990 @value{GDBN} and the remote monitor.
17992 @item show debug monitor
17993 @kindex show debug monitor
17994 Show the current status of displaying communications between
17995 @value{GDBN} and the remote monitor.
18000 @kindex load @var{filename}
18001 @item load @var{filename}
18003 Depending on what remote debugging facilities are configured into
18004 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18005 is meant to make @var{filename} (an executable) available for debugging
18006 on the remote system---by downloading, or dynamic linking, for example.
18007 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18008 the @code{add-symbol-file} command.
18010 If your @value{GDBN} does not have a @code{load} command, attempting to
18011 execute it gets the error message ``@code{You can't do that when your
18012 target is @dots{}}''
18014 The file is loaded at whatever address is specified in the executable.
18015 For some object file formats, you can specify the load address when you
18016 link the program; for other formats, like a.out, the object file format
18017 specifies a fixed address.
18018 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18020 Depending on the remote side capabilities, @value{GDBN} may be able to
18021 load programs into flash memory.
18023 @code{load} does not repeat if you press @key{RET} again after using it.
18027 @section Choosing Target Byte Order
18029 @cindex choosing target byte order
18030 @cindex target byte order
18032 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18033 offer the ability to run either big-endian or little-endian byte
18034 orders. Usually the executable or symbol will include a bit to
18035 designate the endian-ness, and you will not need to worry about
18036 which to use. However, you may still find it useful to adjust
18037 @value{GDBN}'s idea of processor endian-ness manually.
18041 @item set endian big
18042 Instruct @value{GDBN} to assume the target is big-endian.
18044 @item set endian little
18045 Instruct @value{GDBN} to assume the target is little-endian.
18047 @item set endian auto
18048 Instruct @value{GDBN} to use the byte order associated with the
18052 Display @value{GDBN}'s current idea of the target byte order.
18056 Note that these commands merely adjust interpretation of symbolic
18057 data on the host, and that they have absolutely no effect on the
18061 @node Remote Debugging
18062 @chapter Debugging Remote Programs
18063 @cindex remote debugging
18065 If you are trying to debug a program running on a machine that cannot run
18066 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18067 For example, you might use remote debugging on an operating system kernel,
18068 or on a small system which does not have a general purpose operating system
18069 powerful enough to run a full-featured debugger.
18071 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18072 to make this work with particular debugging targets. In addition,
18073 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18074 but not specific to any particular target system) which you can use if you
18075 write the remote stubs---the code that runs on the remote system to
18076 communicate with @value{GDBN}.
18078 Other remote targets may be available in your
18079 configuration of @value{GDBN}; use @code{help target} to list them.
18082 * Connecting:: Connecting to a remote target
18083 * File Transfer:: Sending files to a remote system
18084 * Server:: Using the gdbserver program
18085 * Remote Configuration:: Remote configuration
18086 * Remote Stub:: Implementing a remote stub
18090 @section Connecting to a Remote Target
18092 On the @value{GDBN} host machine, you will need an unstripped copy of
18093 your program, since @value{GDBN} needs symbol and debugging information.
18094 Start up @value{GDBN} as usual, using the name of the local copy of your
18095 program as the first argument.
18097 @cindex @code{target remote}
18098 @value{GDBN} can communicate with the target over a serial line, or
18099 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18100 each case, @value{GDBN} uses the same protocol for debugging your
18101 program; only the medium carrying the debugging packets varies. The
18102 @code{target remote} command establishes a connection to the target.
18103 Its arguments indicate which medium to use:
18107 @item target remote @var{serial-device}
18108 @cindex serial line, @code{target remote}
18109 Use @var{serial-device} to communicate with the target. For example,
18110 to use a serial line connected to the device named @file{/dev/ttyb}:
18113 target remote /dev/ttyb
18116 If you're using a serial line, you may want to give @value{GDBN} the
18117 @samp{--baud} option, or use the @code{set serial baud} command
18118 (@pxref{Remote Configuration, set serial baud}) before the
18119 @code{target} command.
18121 @item target remote @code{@var{host}:@var{port}}
18122 @itemx target remote @code{tcp:@var{host}:@var{port}}
18123 @cindex @acronym{TCP} port, @code{target remote}
18124 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18125 The @var{host} may be either a host name or a numeric @acronym{IP}
18126 address; @var{port} must be a decimal number. The @var{host} could be
18127 the target machine itself, if it is directly connected to the net, or
18128 it might be a terminal server which in turn has a serial line to the
18131 For example, to connect to port 2828 on a terminal server named
18135 target remote manyfarms:2828
18138 If your remote target is actually running on the same machine as your
18139 debugger session (e.g.@: a simulator for your target running on the
18140 same host), you can omit the hostname. For example, to connect to
18141 port 1234 on your local machine:
18144 target remote :1234
18148 Note that the colon is still required here.
18150 @item target remote @code{udp:@var{host}:@var{port}}
18151 @cindex @acronym{UDP} port, @code{target remote}
18152 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18153 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18156 target remote udp:manyfarms:2828
18159 When using a @acronym{UDP} connection for remote debugging, you should
18160 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18161 can silently drop packets on busy or unreliable networks, which will
18162 cause havoc with your debugging session.
18164 @item target remote | @var{command}
18165 @cindex pipe, @code{target remote} to
18166 Run @var{command} in the background and communicate with it using a
18167 pipe. The @var{command} is a shell command, to be parsed and expanded
18168 by the system's command shell, @code{/bin/sh}; it should expect remote
18169 protocol packets on its standard input, and send replies on its
18170 standard output. You could use this to run a stand-alone simulator
18171 that speaks the remote debugging protocol, to make net connections
18172 using programs like @code{ssh}, or for other similar tricks.
18174 If @var{command} closes its standard output (perhaps by exiting),
18175 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18176 program has already exited, this will have no effect.)
18180 Once the connection has been established, you can use all the usual
18181 commands to examine and change data. The remote program is already
18182 running; you can use @kbd{step} and @kbd{continue}, and you do not
18183 need to use @kbd{run}.
18185 @cindex interrupting remote programs
18186 @cindex remote programs, interrupting
18187 Whenever @value{GDBN} is waiting for the remote program, if you type the
18188 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18189 program. This may or may not succeed, depending in part on the hardware
18190 and the serial drivers the remote system uses. If you type the
18191 interrupt character once again, @value{GDBN} displays this prompt:
18194 Interrupted while waiting for the program.
18195 Give up (and stop debugging it)? (y or n)
18198 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18199 (If you decide you want to try again later, you can use @samp{target
18200 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18201 goes back to waiting.
18204 @kindex detach (remote)
18206 When you have finished debugging the remote program, you can use the
18207 @code{detach} command to release it from @value{GDBN} control.
18208 Detaching from the target normally resumes its execution, but the results
18209 will depend on your particular remote stub. After the @code{detach}
18210 command, @value{GDBN} is free to connect to another target.
18214 The @code{disconnect} command behaves like @code{detach}, except that
18215 the target is generally not resumed. It will wait for @value{GDBN}
18216 (this instance or another one) to connect and continue debugging. After
18217 the @code{disconnect} command, @value{GDBN} is again free to connect to
18220 @cindex send command to remote monitor
18221 @cindex extend @value{GDBN} for remote targets
18222 @cindex add new commands for external monitor
18224 @item monitor @var{cmd}
18225 This command allows you to send arbitrary commands directly to the
18226 remote monitor. Since @value{GDBN} doesn't care about the commands it
18227 sends like this, this command is the way to extend @value{GDBN}---you
18228 can add new commands that only the external monitor will understand
18232 @node File Transfer
18233 @section Sending files to a remote system
18234 @cindex remote target, file transfer
18235 @cindex file transfer
18236 @cindex sending files to remote systems
18238 Some remote targets offer the ability to transfer files over the same
18239 connection used to communicate with @value{GDBN}. This is convenient
18240 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18241 running @code{gdbserver} over a network interface. For other targets,
18242 e.g.@: embedded devices with only a single serial port, this may be
18243 the only way to upload or download files.
18245 Not all remote targets support these commands.
18249 @item remote put @var{hostfile} @var{targetfile}
18250 Copy file @var{hostfile} from the host system (the machine running
18251 @value{GDBN}) to @var{targetfile} on the target system.
18254 @item remote get @var{targetfile} @var{hostfile}
18255 Copy file @var{targetfile} from the target system to @var{hostfile}
18256 on the host system.
18258 @kindex remote delete
18259 @item remote delete @var{targetfile}
18260 Delete @var{targetfile} from the target system.
18265 @section Using the @code{gdbserver} Program
18268 @cindex remote connection without stubs
18269 @code{gdbserver} is a control program for Unix-like systems, which
18270 allows you to connect your program with a remote @value{GDBN} via
18271 @code{target remote}---but without linking in the usual debugging stub.
18273 @code{gdbserver} is not a complete replacement for the debugging stubs,
18274 because it requires essentially the same operating-system facilities
18275 that @value{GDBN} itself does. In fact, a system that can run
18276 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18277 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18278 because it is a much smaller program than @value{GDBN} itself. It is
18279 also easier to port than all of @value{GDBN}, so you may be able to get
18280 started more quickly on a new system by using @code{gdbserver}.
18281 Finally, if you develop code for real-time systems, you may find that
18282 the tradeoffs involved in real-time operation make it more convenient to
18283 do as much development work as possible on another system, for example
18284 by cross-compiling. You can use @code{gdbserver} to make a similar
18285 choice for debugging.
18287 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18288 or a TCP connection, using the standard @value{GDBN} remote serial
18292 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18293 Do not run @code{gdbserver} connected to any public network; a
18294 @value{GDBN} connection to @code{gdbserver} provides access to the
18295 target system with the same privileges as the user running
18299 @subsection Running @code{gdbserver}
18300 @cindex arguments, to @code{gdbserver}
18301 @cindex @code{gdbserver}, command-line arguments
18303 Run @code{gdbserver} on the target system. You need a copy of the
18304 program you want to debug, including any libraries it requires.
18305 @code{gdbserver} does not need your program's symbol table, so you can
18306 strip the program if necessary to save space. @value{GDBN} on the host
18307 system does all the symbol handling.
18309 To use the server, you must tell it how to communicate with @value{GDBN};
18310 the name of your program; and the arguments for your program. The usual
18314 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18317 @var{comm} is either a device name (to use a serial line), or a TCP
18318 hostname and portnumber, or @code{-} or @code{stdio} to use
18319 stdin/stdout of @code{gdbserver}.
18320 For example, to debug Emacs with the argument
18321 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18325 target> gdbserver /dev/com1 emacs foo.txt
18328 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18331 To use a TCP connection instead of a serial line:
18334 target> gdbserver host:2345 emacs foo.txt
18337 The only difference from the previous example is the first argument,
18338 specifying that you are communicating with the host @value{GDBN} via
18339 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18340 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18341 (Currently, the @samp{host} part is ignored.) You can choose any number
18342 you want for the port number as long as it does not conflict with any
18343 TCP ports already in use on the target system (for example, @code{23} is
18344 reserved for @code{telnet}).@footnote{If you choose a port number that
18345 conflicts with another service, @code{gdbserver} prints an error message
18346 and exits.} You must use the same port number with the host @value{GDBN}
18347 @code{target remote} command.
18349 The @code{stdio} connection is useful when starting @code{gdbserver}
18353 (gdb) target remote | ssh -T hostname gdbserver - hello
18356 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18357 and we don't want escape-character handling. Ssh does this by default when
18358 a command is provided, the flag is provided to make it explicit.
18359 You could elide it if you want to.
18361 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18362 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18363 display through a pipe connected to gdbserver.
18364 Both @code{stdout} and @code{stderr} use the same pipe.
18366 @subsubsection Attaching to a Running Program
18367 @cindex attach to a program, @code{gdbserver}
18368 @cindex @option{--attach}, @code{gdbserver} option
18370 On some targets, @code{gdbserver} can also attach to running programs.
18371 This is accomplished via the @code{--attach} argument. The syntax is:
18374 target> gdbserver --attach @var{comm} @var{pid}
18377 @var{pid} is the process ID of a currently running process. It isn't necessary
18378 to point @code{gdbserver} at a binary for the running process.
18381 You can debug processes by name instead of process ID if your target has the
18382 @code{pidof} utility:
18385 target> gdbserver --attach @var{comm} `pidof @var{program}`
18388 In case more than one copy of @var{program} is running, or @var{program}
18389 has multiple threads, most versions of @code{pidof} support the
18390 @code{-s} option to only return the first process ID.
18392 @subsubsection Multi-Process Mode for @code{gdbserver}
18393 @cindex @code{gdbserver}, multiple processes
18394 @cindex multiple processes with @code{gdbserver}
18396 When you connect to @code{gdbserver} using @code{target remote},
18397 @code{gdbserver} debugs the specified program only once. When the
18398 program exits, or you detach from it, @value{GDBN} closes the connection
18399 and @code{gdbserver} exits.
18401 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18402 enters multi-process mode. When the debugged program exits, or you
18403 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18404 though no program is running. The @code{run} and @code{attach}
18405 commands instruct @code{gdbserver} to run or attach to a new program.
18406 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18407 remote exec-file}) to select the program to run. Command line
18408 arguments are supported, except for wildcard expansion and I/O
18409 redirection (@pxref{Arguments}).
18411 @cindex @option{--multi}, @code{gdbserver} option
18412 To start @code{gdbserver} without supplying an initial command to run
18413 or process ID to attach, use the @option{--multi} command line option.
18414 Then you can connect using @kbd{target extended-remote} and start
18415 the program you want to debug.
18417 In multi-process mode @code{gdbserver} does not automatically exit unless you
18418 use the option @option{--once}. You can terminate it by using
18419 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18420 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18421 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18422 @option{--multi} option to @code{gdbserver} has no influence on that.
18424 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18426 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18428 @code{gdbserver} normally terminates after all of its debugged processes have
18429 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18430 extended-remote}, @code{gdbserver} stays running even with no processes left.
18431 @value{GDBN} normally terminates the spawned debugged process on its exit,
18432 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18433 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18434 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18435 stays running even in the @kbd{target remote} mode.
18437 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18438 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18439 completeness, at most one @value{GDBN} can be connected at a time.
18441 @cindex @option{--once}, @code{gdbserver} option
18442 By default, @code{gdbserver} keeps the listening TCP port open, so that
18443 subsequent connections are possible. However, if you start @code{gdbserver}
18444 with the @option{--once} option, it will stop listening for any further
18445 connection attempts after connecting to the first @value{GDBN} session. This
18446 means no further connections to @code{gdbserver} will be possible after the
18447 first one. It also means @code{gdbserver} will terminate after the first
18448 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18449 connections and even in the @kbd{target extended-remote} mode. The
18450 @option{--once} option allows reusing the same port number for connecting to
18451 multiple instances of @code{gdbserver} running on the same host, since each
18452 instance closes its port after the first connection.
18454 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18456 @cindex @option{--debug}, @code{gdbserver} option
18457 The @option{--debug} option tells @code{gdbserver} to display extra
18458 status information about the debugging process.
18459 @cindex @option{--remote-debug}, @code{gdbserver} option
18460 The @option{--remote-debug} option tells @code{gdbserver} to display
18461 remote protocol debug output. These options are intended for
18462 @code{gdbserver} development and for bug reports to the developers.
18464 @cindex @option{--wrapper}, @code{gdbserver} option
18465 The @option{--wrapper} option specifies a wrapper to launch programs
18466 for debugging. The option should be followed by the name of the
18467 wrapper, then any command-line arguments to pass to the wrapper, then
18468 @kbd{--} indicating the end of the wrapper arguments.
18470 @code{gdbserver} runs the specified wrapper program with a combined
18471 command line including the wrapper arguments, then the name of the
18472 program to debug, then any arguments to the program. The wrapper
18473 runs until it executes your program, and then @value{GDBN} gains control.
18475 You can use any program that eventually calls @code{execve} with
18476 its arguments as a wrapper. Several standard Unix utilities do
18477 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18478 with @code{exec "$@@"} will also work.
18480 For example, you can use @code{env} to pass an environment variable to
18481 the debugged program, without setting the variable in @code{gdbserver}'s
18485 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18488 @subsection Connecting to @code{gdbserver}
18490 Run @value{GDBN} on the host system.
18492 First make sure you have the necessary symbol files. Load symbols for
18493 your application using the @code{file} command before you connect. Use
18494 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18495 was compiled with the correct sysroot using @code{--with-sysroot}).
18497 The symbol file and target libraries must exactly match the executable
18498 and libraries on the target, with one exception: the files on the host
18499 system should not be stripped, even if the files on the target system
18500 are. Mismatched or missing files will lead to confusing results
18501 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18502 files may also prevent @code{gdbserver} from debugging multi-threaded
18505 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18506 For TCP connections, you must start up @code{gdbserver} prior to using
18507 the @code{target remote} command. Otherwise you may get an error whose
18508 text depends on the host system, but which usually looks something like
18509 @samp{Connection refused}. Don't use the @code{load}
18510 command in @value{GDBN} when using @code{gdbserver}, since the program is
18511 already on the target.
18513 @subsection Monitor Commands for @code{gdbserver}
18514 @cindex monitor commands, for @code{gdbserver}
18515 @anchor{Monitor Commands for gdbserver}
18517 During a @value{GDBN} session using @code{gdbserver}, you can use the
18518 @code{monitor} command to send special requests to @code{gdbserver}.
18519 Here are the available commands.
18523 List the available monitor commands.
18525 @item monitor set debug 0
18526 @itemx monitor set debug 1
18527 Disable or enable general debugging messages.
18529 @item monitor set remote-debug 0
18530 @itemx monitor set remote-debug 1
18531 Disable or enable specific debugging messages associated with the remote
18532 protocol (@pxref{Remote Protocol}).
18534 @item monitor set libthread-db-search-path [PATH]
18535 @cindex gdbserver, search path for @code{libthread_db}
18536 When this command is issued, @var{path} is a colon-separated list of
18537 directories to search for @code{libthread_db} (@pxref{Threads,,set
18538 libthread-db-search-path}). If you omit @var{path},
18539 @samp{libthread-db-search-path} will be reset to its default value.
18541 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18542 not supported in @code{gdbserver}.
18545 Tell gdbserver to exit immediately. This command should be followed by
18546 @code{disconnect} to close the debugging session. @code{gdbserver} will
18547 detach from any attached processes and kill any processes it created.
18548 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18549 of a multi-process mode debug session.
18553 @subsection Tracepoints support in @code{gdbserver}
18554 @cindex tracepoints support in @code{gdbserver}
18556 On some targets, @code{gdbserver} supports tracepoints, fast
18557 tracepoints and static tracepoints.
18559 For fast or static tracepoints to work, a special library called the
18560 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18561 This library is built and distributed as an integral part of
18562 @code{gdbserver}. In addition, support for static tracepoints
18563 requires building the in-process agent library with static tracepoints
18564 support. At present, the UST (LTTng Userspace Tracer,
18565 @url{http://lttng.org/ust}) tracing engine is supported. This support
18566 is automatically available if UST development headers are found in the
18567 standard include path when @code{gdbserver} is built, or if
18568 @code{gdbserver} was explicitly configured using @option{--with-ust}
18569 to point at such headers. You can explicitly disable the support
18570 using @option{--with-ust=no}.
18572 There are several ways to load the in-process agent in your program:
18575 @item Specifying it as dependency at link time
18577 You can link your program dynamically with the in-process agent
18578 library. On most systems, this is accomplished by adding
18579 @code{-linproctrace} to the link command.
18581 @item Using the system's preloading mechanisms
18583 You can force loading the in-process agent at startup time by using
18584 your system's support for preloading shared libraries. Many Unixes
18585 support the concept of preloading user defined libraries. In most
18586 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18587 in the environment. See also the description of @code{gdbserver}'s
18588 @option{--wrapper} command line option.
18590 @item Using @value{GDBN} to force loading the agent at run time
18592 On some systems, you can force the inferior to load a shared library,
18593 by calling a dynamic loader function in the inferior that takes care
18594 of dynamically looking up and loading a shared library. On most Unix
18595 systems, the function is @code{dlopen}. You'll use the @code{call}
18596 command for that. For example:
18599 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18602 Note that on most Unix systems, for the @code{dlopen} function to be
18603 available, the program needs to be linked with @code{-ldl}.
18606 On systems that have a userspace dynamic loader, like most Unix
18607 systems, when you connect to @code{gdbserver} using @code{target
18608 remote}, you'll find that the program is stopped at the dynamic
18609 loader's entry point, and no shared library has been loaded in the
18610 program's address space yet, including the in-process agent. In that
18611 case, before being able to use any of the fast or static tracepoints
18612 features, you need to let the loader run and load the shared
18613 libraries. The simplest way to do that is to run the program to the
18614 main procedure. E.g., if debugging a C or C@t{++} program, start
18615 @code{gdbserver} like so:
18618 $ gdbserver :9999 myprogram
18621 Start GDB and connect to @code{gdbserver} like so, and run to main:
18625 (@value{GDBP}) target remote myhost:9999
18626 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18627 (@value{GDBP}) b main
18628 (@value{GDBP}) continue
18631 The in-process tracing agent library should now be loaded into the
18632 process; you can confirm it with the @code{info sharedlibrary}
18633 command, which will list @file{libinproctrace.so} as loaded in the
18634 process. You are now ready to install fast tracepoints, list static
18635 tracepoint markers, probe static tracepoints markers, and start
18638 @node Remote Configuration
18639 @section Remote Configuration
18642 @kindex show remote
18643 This section documents the configuration options available when
18644 debugging remote programs. For the options related to the File I/O
18645 extensions of the remote protocol, see @ref{system,
18646 system-call-allowed}.
18649 @item set remoteaddresssize @var{bits}
18650 @cindex address size for remote targets
18651 @cindex bits in remote address
18652 Set the maximum size of address in a memory packet to the specified
18653 number of bits. @value{GDBN} will mask off the address bits above
18654 that number, when it passes addresses to the remote target. The
18655 default value is the number of bits in the target's address.
18657 @item show remoteaddresssize
18658 Show the current value of remote address size in bits.
18660 @item set serial baud @var{n}
18661 @cindex baud rate for remote targets
18662 Set the baud rate for the remote serial I/O to @var{n} baud. The
18663 value is used to set the speed of the serial port used for debugging
18666 @item show serial baud
18667 Show the current speed of the remote connection.
18669 @item set remotebreak
18670 @cindex interrupt remote programs
18671 @cindex BREAK signal instead of Ctrl-C
18672 @anchor{set remotebreak}
18673 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18674 when you type @kbd{Ctrl-c} to interrupt the program running
18675 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18676 character instead. The default is off, since most remote systems
18677 expect to see @samp{Ctrl-C} as the interrupt signal.
18679 @item show remotebreak
18680 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18681 interrupt the remote program.
18683 @item set remoteflow on
18684 @itemx set remoteflow off
18685 @kindex set remoteflow
18686 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18687 on the serial port used to communicate to the remote target.
18689 @item show remoteflow
18690 @kindex show remoteflow
18691 Show the current setting of hardware flow control.
18693 @item set remotelogbase @var{base}
18694 Set the base (a.k.a.@: radix) of logging serial protocol
18695 communications to @var{base}. Supported values of @var{base} are:
18696 @code{ascii}, @code{octal}, and @code{hex}. The default is
18699 @item show remotelogbase
18700 Show the current setting of the radix for logging remote serial
18703 @item set remotelogfile @var{file}
18704 @cindex record serial communications on file
18705 Record remote serial communications on the named @var{file}. The
18706 default is not to record at all.
18708 @item show remotelogfile.
18709 Show the current setting of the file name on which to record the
18710 serial communications.
18712 @item set remotetimeout @var{num}
18713 @cindex timeout for serial communications
18714 @cindex remote timeout
18715 Set the timeout limit to wait for the remote target to respond to
18716 @var{num} seconds. The default is 2 seconds.
18718 @item show remotetimeout
18719 Show the current number of seconds to wait for the remote target
18722 @cindex limit hardware breakpoints and watchpoints
18723 @cindex remote target, limit break- and watchpoints
18724 @anchor{set remote hardware-watchpoint-limit}
18725 @anchor{set remote hardware-breakpoint-limit}
18726 @item set remote hardware-watchpoint-limit @var{limit}
18727 @itemx set remote hardware-breakpoint-limit @var{limit}
18728 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18729 watchpoints. A limit of -1, the default, is treated as unlimited.
18731 @cindex limit hardware watchpoints length
18732 @cindex remote target, limit watchpoints length
18733 @anchor{set remote hardware-watchpoint-length-limit}
18734 @item set remote hardware-watchpoint-length-limit @var{limit}
18735 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18736 a remote hardware watchpoint. A limit of -1, the default, is treated
18739 @item show remote hardware-watchpoint-length-limit
18740 Show the current limit (in bytes) of the maximum length of
18741 a remote hardware watchpoint.
18743 @item set remote exec-file @var{filename}
18744 @itemx show remote exec-file
18745 @anchor{set remote exec-file}
18746 @cindex executable file, for remote target
18747 Select the file used for @code{run} with @code{target
18748 extended-remote}. This should be set to a filename valid on the
18749 target system. If it is not set, the target will use a default
18750 filename (e.g.@: the last program run).
18752 @item set remote interrupt-sequence
18753 @cindex interrupt remote programs
18754 @cindex select Ctrl-C, BREAK or BREAK-g
18755 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18756 @samp{BREAK-g} as the
18757 sequence to the remote target in order to interrupt the execution.
18758 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18759 is high level of serial line for some certain time.
18760 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18761 It is @code{BREAK} signal followed by character @code{g}.
18763 @item show interrupt-sequence
18764 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18765 is sent by @value{GDBN} to interrupt the remote program.
18766 @code{BREAK-g} is BREAK signal followed by @code{g} and
18767 also known as Magic SysRq g.
18769 @item set remote interrupt-on-connect
18770 @cindex send interrupt-sequence on start
18771 Specify whether interrupt-sequence is sent to remote target when
18772 @value{GDBN} connects to it. This is mostly needed when you debug
18773 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18774 which is known as Magic SysRq g in order to connect @value{GDBN}.
18776 @item show interrupt-on-connect
18777 Show whether interrupt-sequence is sent
18778 to remote target when @value{GDBN} connects to it.
18782 @item set tcp auto-retry on
18783 @cindex auto-retry, for remote TCP target
18784 Enable auto-retry for remote TCP connections. This is useful if the remote
18785 debugging agent is launched in parallel with @value{GDBN}; there is a race
18786 condition because the agent may not become ready to accept the connection
18787 before @value{GDBN} attempts to connect. When auto-retry is
18788 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18789 to establish the connection using the timeout specified by
18790 @code{set tcp connect-timeout}.
18792 @item set tcp auto-retry off
18793 Do not auto-retry failed TCP connections.
18795 @item show tcp auto-retry
18796 Show the current auto-retry setting.
18798 @item set tcp connect-timeout @var{seconds}
18799 @itemx set tcp connect-timeout unlimited
18800 @cindex connection timeout, for remote TCP target
18801 @cindex timeout, for remote target connection
18802 Set the timeout for establishing a TCP connection to the remote target to
18803 @var{seconds}. The timeout affects both polling to retry failed connections
18804 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18805 that are merely slow to complete, and represents an approximate cumulative
18806 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18807 @value{GDBN} will keep attempting to establish a connection forever,
18808 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18810 @item show tcp connect-timeout
18811 Show the current connection timeout setting.
18814 @cindex remote packets, enabling and disabling
18815 The @value{GDBN} remote protocol autodetects the packets supported by
18816 your debugging stub. If you need to override the autodetection, you
18817 can use these commands to enable or disable individual packets. Each
18818 packet can be set to @samp{on} (the remote target supports this
18819 packet), @samp{off} (the remote target does not support this packet),
18820 or @samp{auto} (detect remote target support for this packet). They
18821 all default to @samp{auto}. For more information about each packet,
18822 see @ref{Remote Protocol}.
18824 During normal use, you should not have to use any of these commands.
18825 If you do, that may be a bug in your remote debugging stub, or a bug
18826 in @value{GDBN}. You may want to report the problem to the
18827 @value{GDBN} developers.
18829 For each packet @var{name}, the command to enable or disable the
18830 packet is @code{set remote @var{name}-packet}. The available settings
18833 @multitable @columnfractions 0.28 0.32 0.25
18836 @tab Related Features
18838 @item @code{fetch-register}
18840 @tab @code{info registers}
18842 @item @code{set-register}
18846 @item @code{binary-download}
18848 @tab @code{load}, @code{set}
18850 @item @code{read-aux-vector}
18851 @tab @code{qXfer:auxv:read}
18852 @tab @code{info auxv}
18854 @item @code{symbol-lookup}
18855 @tab @code{qSymbol}
18856 @tab Detecting multiple threads
18858 @item @code{attach}
18859 @tab @code{vAttach}
18862 @item @code{verbose-resume}
18864 @tab Stepping or resuming multiple threads
18870 @item @code{software-breakpoint}
18874 @item @code{hardware-breakpoint}
18878 @item @code{write-watchpoint}
18882 @item @code{read-watchpoint}
18886 @item @code{access-watchpoint}
18890 @item @code{target-features}
18891 @tab @code{qXfer:features:read}
18892 @tab @code{set architecture}
18894 @item @code{library-info}
18895 @tab @code{qXfer:libraries:read}
18896 @tab @code{info sharedlibrary}
18898 @item @code{memory-map}
18899 @tab @code{qXfer:memory-map:read}
18900 @tab @code{info mem}
18902 @item @code{read-sdata-object}
18903 @tab @code{qXfer:sdata:read}
18904 @tab @code{print $_sdata}
18906 @item @code{read-spu-object}
18907 @tab @code{qXfer:spu:read}
18908 @tab @code{info spu}
18910 @item @code{write-spu-object}
18911 @tab @code{qXfer:spu:write}
18912 @tab @code{info spu}
18914 @item @code{read-siginfo-object}
18915 @tab @code{qXfer:siginfo:read}
18916 @tab @code{print $_siginfo}
18918 @item @code{write-siginfo-object}
18919 @tab @code{qXfer:siginfo:write}
18920 @tab @code{set $_siginfo}
18922 @item @code{threads}
18923 @tab @code{qXfer:threads:read}
18924 @tab @code{info threads}
18926 @item @code{get-thread-local-@*storage-address}
18927 @tab @code{qGetTLSAddr}
18928 @tab Displaying @code{__thread} variables
18930 @item @code{get-thread-information-block-address}
18931 @tab @code{qGetTIBAddr}
18932 @tab Display MS-Windows Thread Information Block.
18934 @item @code{search-memory}
18935 @tab @code{qSearch:memory}
18938 @item @code{supported-packets}
18939 @tab @code{qSupported}
18940 @tab Remote communications parameters
18942 @item @code{pass-signals}
18943 @tab @code{QPassSignals}
18944 @tab @code{handle @var{signal}}
18946 @item @code{program-signals}
18947 @tab @code{QProgramSignals}
18948 @tab @code{handle @var{signal}}
18950 @item @code{hostio-close-packet}
18951 @tab @code{vFile:close}
18952 @tab @code{remote get}, @code{remote put}
18954 @item @code{hostio-open-packet}
18955 @tab @code{vFile:open}
18956 @tab @code{remote get}, @code{remote put}
18958 @item @code{hostio-pread-packet}
18959 @tab @code{vFile:pread}
18960 @tab @code{remote get}, @code{remote put}
18962 @item @code{hostio-pwrite-packet}
18963 @tab @code{vFile:pwrite}
18964 @tab @code{remote get}, @code{remote put}
18966 @item @code{hostio-unlink-packet}
18967 @tab @code{vFile:unlink}
18968 @tab @code{remote delete}
18970 @item @code{hostio-readlink-packet}
18971 @tab @code{vFile:readlink}
18974 @item @code{noack-packet}
18975 @tab @code{QStartNoAckMode}
18976 @tab Packet acknowledgment
18978 @item @code{osdata}
18979 @tab @code{qXfer:osdata:read}
18980 @tab @code{info os}
18982 @item @code{query-attached}
18983 @tab @code{qAttached}
18984 @tab Querying remote process attach state.
18986 @item @code{trace-buffer-size}
18987 @tab @code{QTBuffer:size}
18988 @tab @code{set trace-buffer-size}
18990 @item @code{trace-status}
18991 @tab @code{qTStatus}
18992 @tab @code{tstatus}
18994 @item @code{traceframe-info}
18995 @tab @code{qXfer:traceframe-info:read}
18996 @tab Traceframe info
18998 @item @code{install-in-trace}
18999 @tab @code{InstallInTrace}
19000 @tab Install tracepoint in tracing
19002 @item @code{disable-randomization}
19003 @tab @code{QDisableRandomization}
19004 @tab @code{set disable-randomization}
19006 @item @code{conditional-breakpoints-packet}
19007 @tab @code{Z0 and Z1}
19008 @tab @code{Support for target-side breakpoint condition evaluation}
19012 @section Implementing a Remote Stub
19014 @cindex debugging stub, example
19015 @cindex remote stub, example
19016 @cindex stub example, remote debugging
19017 The stub files provided with @value{GDBN} implement the target side of the
19018 communication protocol, and the @value{GDBN} side is implemented in the
19019 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19020 these subroutines to communicate, and ignore the details. (If you're
19021 implementing your own stub file, you can still ignore the details: start
19022 with one of the existing stub files. @file{sparc-stub.c} is the best
19023 organized, and therefore the easiest to read.)
19025 @cindex remote serial debugging, overview
19026 To debug a program running on another machine (the debugging
19027 @dfn{target} machine), you must first arrange for all the usual
19028 prerequisites for the program to run by itself. For example, for a C
19033 A startup routine to set up the C runtime environment; these usually
19034 have a name like @file{crt0}. The startup routine may be supplied by
19035 your hardware supplier, or you may have to write your own.
19038 A C subroutine library to support your program's
19039 subroutine calls, notably managing input and output.
19042 A way of getting your program to the other machine---for example, a
19043 download program. These are often supplied by the hardware
19044 manufacturer, but you may have to write your own from hardware
19048 The next step is to arrange for your program to use a serial port to
19049 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19050 machine). In general terms, the scheme looks like this:
19054 @value{GDBN} already understands how to use this protocol; when everything
19055 else is set up, you can simply use the @samp{target remote} command
19056 (@pxref{Targets,,Specifying a Debugging Target}).
19058 @item On the target,
19059 you must link with your program a few special-purpose subroutines that
19060 implement the @value{GDBN} remote serial protocol. The file containing these
19061 subroutines is called a @dfn{debugging stub}.
19063 On certain remote targets, you can use an auxiliary program
19064 @code{gdbserver} instead of linking a stub into your program.
19065 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19068 The debugging stub is specific to the architecture of the remote
19069 machine; for example, use @file{sparc-stub.c} to debug programs on
19072 @cindex remote serial stub list
19073 These working remote stubs are distributed with @value{GDBN}:
19078 @cindex @file{i386-stub.c}
19081 For Intel 386 and compatible architectures.
19084 @cindex @file{m68k-stub.c}
19085 @cindex Motorola 680x0
19087 For Motorola 680x0 architectures.
19090 @cindex @file{sh-stub.c}
19093 For Renesas SH architectures.
19096 @cindex @file{sparc-stub.c}
19098 For @sc{sparc} architectures.
19100 @item sparcl-stub.c
19101 @cindex @file{sparcl-stub.c}
19104 For Fujitsu @sc{sparclite} architectures.
19108 The @file{README} file in the @value{GDBN} distribution may list other
19109 recently added stubs.
19112 * Stub Contents:: What the stub can do for you
19113 * Bootstrapping:: What you must do for the stub
19114 * Debug Session:: Putting it all together
19117 @node Stub Contents
19118 @subsection What the Stub Can Do for You
19120 @cindex remote serial stub
19121 The debugging stub for your architecture supplies these three
19125 @item set_debug_traps
19126 @findex set_debug_traps
19127 @cindex remote serial stub, initialization
19128 This routine arranges for @code{handle_exception} to run when your
19129 program stops. You must call this subroutine explicitly in your
19130 program's startup code.
19132 @item handle_exception
19133 @findex handle_exception
19134 @cindex remote serial stub, main routine
19135 This is the central workhorse, but your program never calls it
19136 explicitly---the setup code arranges for @code{handle_exception} to
19137 run when a trap is triggered.
19139 @code{handle_exception} takes control when your program stops during
19140 execution (for example, on a breakpoint), and mediates communications
19141 with @value{GDBN} on the host machine. This is where the communications
19142 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19143 representative on the target machine. It begins by sending summary
19144 information on the state of your program, then continues to execute,
19145 retrieving and transmitting any information @value{GDBN} needs, until you
19146 execute a @value{GDBN} command that makes your program resume; at that point,
19147 @code{handle_exception} returns control to your own code on the target
19151 @cindex @code{breakpoint} subroutine, remote
19152 Use this auxiliary subroutine to make your program contain a
19153 breakpoint. Depending on the particular situation, this may be the only
19154 way for @value{GDBN} to get control. For instance, if your target
19155 machine has some sort of interrupt button, you won't need to call this;
19156 pressing the interrupt button transfers control to
19157 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19158 simply receiving characters on the serial port may also trigger a trap;
19159 again, in that situation, you don't need to call @code{breakpoint} from
19160 your own program---simply running @samp{target remote} from the host
19161 @value{GDBN} session gets control.
19163 Call @code{breakpoint} if none of these is true, or if you simply want
19164 to make certain your program stops at a predetermined point for the
19165 start of your debugging session.
19168 @node Bootstrapping
19169 @subsection What You Must Do for the Stub
19171 @cindex remote stub, support routines
19172 The debugging stubs that come with @value{GDBN} are set up for a particular
19173 chip architecture, but they have no information about the rest of your
19174 debugging target machine.
19176 First of all you need to tell the stub how to communicate with the
19180 @item int getDebugChar()
19181 @findex getDebugChar
19182 Write this subroutine to read a single character from the serial port.
19183 It may be identical to @code{getchar} for your target system; a
19184 different name is used to allow you to distinguish the two if you wish.
19186 @item void putDebugChar(int)
19187 @findex putDebugChar
19188 Write this subroutine to write a single character to the serial port.
19189 It may be identical to @code{putchar} for your target system; a
19190 different name is used to allow you to distinguish the two if you wish.
19193 @cindex control C, and remote debugging
19194 @cindex interrupting remote targets
19195 If you want @value{GDBN} to be able to stop your program while it is
19196 running, you need to use an interrupt-driven serial driver, and arrange
19197 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19198 character). That is the character which @value{GDBN} uses to tell the
19199 remote system to stop.
19201 Getting the debugging target to return the proper status to @value{GDBN}
19202 probably requires changes to the standard stub; one quick and dirty way
19203 is to just execute a breakpoint instruction (the ``dirty'' part is that
19204 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19206 Other routines you need to supply are:
19209 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19210 @findex exceptionHandler
19211 Write this function to install @var{exception_address} in the exception
19212 handling tables. You need to do this because the stub does not have any
19213 way of knowing what the exception handling tables on your target system
19214 are like (for example, the processor's table might be in @sc{rom},
19215 containing entries which point to a table in @sc{ram}).
19216 @var{exception_number} is the exception number which should be changed;
19217 its meaning is architecture-dependent (for example, different numbers
19218 might represent divide by zero, misaligned access, etc). When this
19219 exception occurs, control should be transferred directly to
19220 @var{exception_address}, and the processor state (stack, registers,
19221 and so on) should be just as it is when a processor exception occurs. So if
19222 you want to use a jump instruction to reach @var{exception_address}, it
19223 should be a simple jump, not a jump to subroutine.
19225 For the 386, @var{exception_address} should be installed as an interrupt
19226 gate so that interrupts are masked while the handler runs. The gate
19227 should be at privilege level 0 (the most privileged level). The
19228 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19229 help from @code{exceptionHandler}.
19231 @item void flush_i_cache()
19232 @findex flush_i_cache
19233 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19234 instruction cache, if any, on your target machine. If there is no
19235 instruction cache, this subroutine may be a no-op.
19237 On target machines that have instruction caches, @value{GDBN} requires this
19238 function to make certain that the state of your program is stable.
19242 You must also make sure this library routine is available:
19245 @item void *memset(void *, int, int)
19247 This is the standard library function @code{memset} that sets an area of
19248 memory to a known value. If you have one of the free versions of
19249 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19250 either obtain it from your hardware manufacturer, or write your own.
19253 If you do not use the GNU C compiler, you may need other standard
19254 library subroutines as well; this varies from one stub to another,
19255 but in general the stubs are likely to use any of the common library
19256 subroutines which @code{@value{NGCC}} generates as inline code.
19259 @node Debug Session
19260 @subsection Putting it All Together
19262 @cindex remote serial debugging summary
19263 In summary, when your program is ready to debug, you must follow these
19268 Make sure you have defined the supporting low-level routines
19269 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19271 @code{getDebugChar}, @code{putDebugChar},
19272 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19276 Insert these lines in your program's startup code, before the main
19277 procedure is called:
19284 On some machines, when a breakpoint trap is raised, the hardware
19285 automatically makes the PC point to the instruction after the
19286 breakpoint. If your machine doesn't do that, you may need to adjust
19287 @code{handle_exception} to arrange for it to return to the instruction
19288 after the breakpoint on this first invocation, so that your program
19289 doesn't keep hitting the initial breakpoint instead of making
19293 For the 680x0 stub only, you need to provide a variable called
19294 @code{exceptionHook}. Normally you just use:
19297 void (*exceptionHook)() = 0;
19301 but if before calling @code{set_debug_traps}, you set it to point to a
19302 function in your program, that function is called when
19303 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19304 error). The function indicated by @code{exceptionHook} is called with
19305 one parameter: an @code{int} which is the exception number.
19308 Compile and link together: your program, the @value{GDBN} debugging stub for
19309 your target architecture, and the supporting subroutines.
19312 Make sure you have a serial connection between your target machine and
19313 the @value{GDBN} host, and identify the serial port on the host.
19316 @c The "remote" target now provides a `load' command, so we should
19317 @c document that. FIXME.
19318 Download your program to your target machine (or get it there by
19319 whatever means the manufacturer provides), and start it.
19322 Start @value{GDBN} on the host, and connect to the target
19323 (@pxref{Connecting,,Connecting to a Remote Target}).
19327 @node Configurations
19328 @chapter Configuration-Specific Information
19330 While nearly all @value{GDBN} commands are available for all native and
19331 cross versions of the debugger, there are some exceptions. This chapter
19332 describes things that are only available in certain configurations.
19334 There are three major categories of configurations: native
19335 configurations, where the host and target are the same, embedded
19336 operating system configurations, which are usually the same for several
19337 different processor architectures, and bare embedded processors, which
19338 are quite different from each other.
19343 * Embedded Processors::
19350 This section describes details specific to particular native
19355 * BSD libkvm Interface:: Debugging BSD kernel memory images
19356 * SVR4 Process Information:: SVR4 process information
19357 * DJGPP Native:: Features specific to the DJGPP port
19358 * Cygwin Native:: Features specific to the Cygwin port
19359 * Hurd Native:: Features specific to @sc{gnu} Hurd
19360 * Darwin:: Features specific to Darwin
19366 On HP-UX systems, if you refer to a function or variable name that
19367 begins with a dollar sign, @value{GDBN} searches for a user or system
19368 name first, before it searches for a convenience variable.
19371 @node BSD libkvm Interface
19372 @subsection BSD libkvm Interface
19375 @cindex kernel memory image
19376 @cindex kernel crash dump
19378 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19379 interface that provides a uniform interface for accessing kernel virtual
19380 memory images, including live systems and crash dumps. @value{GDBN}
19381 uses this interface to allow you to debug live kernels and kernel crash
19382 dumps on many native BSD configurations. This is implemented as a
19383 special @code{kvm} debugging target. For debugging a live system, load
19384 the currently running kernel into @value{GDBN} and connect to the
19388 (@value{GDBP}) @b{target kvm}
19391 For debugging crash dumps, provide the file name of the crash dump as an
19395 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19398 Once connected to the @code{kvm} target, the following commands are
19404 Set current context from the @dfn{Process Control Block} (PCB) address.
19407 Set current context from proc address. This command isn't available on
19408 modern FreeBSD systems.
19411 @node SVR4 Process Information
19412 @subsection SVR4 Process Information
19414 @cindex examine process image
19415 @cindex process info via @file{/proc}
19417 Many versions of SVR4 and compatible systems provide a facility called
19418 @samp{/proc} that can be used to examine the image of a running
19419 process using file-system subroutines.
19421 If @value{GDBN} is configured for an operating system with this
19422 facility, the command @code{info proc} is available to report
19423 information about the process running your program, or about any
19424 process running on your system. This includes, as of this writing,
19425 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19426 not HP-UX, for example.
19428 This command may also work on core files that were created on a system
19429 that has the @samp{/proc} facility.
19435 @itemx info proc @var{process-id}
19436 Summarize available information about any running process. If a
19437 process ID is specified by @var{process-id}, display information about
19438 that process; otherwise display information about the program being
19439 debugged. The summary includes the debugged process ID, the command
19440 line used to invoke it, its current working directory, and its
19441 executable file's absolute file name.
19443 On some systems, @var{process-id} can be of the form
19444 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19445 within a process. If the optional @var{pid} part is missing, it means
19446 a thread from the process being debugged (the leading @samp{/} still
19447 needs to be present, or else @value{GDBN} will interpret the number as
19448 a process ID rather than a thread ID).
19450 @item info proc cmdline
19451 @cindex info proc cmdline
19452 Show the original command line of the process. This command is
19453 specific to @sc{gnu}/Linux.
19455 @item info proc cwd
19456 @cindex info proc cwd
19457 Show the current working directory of the process. This command is
19458 specific to @sc{gnu}/Linux.
19460 @item info proc exe
19461 @cindex info proc exe
19462 Show the name of executable of the process. This command is specific
19465 @item info proc mappings
19466 @cindex memory address space mappings
19467 Report the memory address space ranges accessible in the program, with
19468 information on whether the process has read, write, or execute access
19469 rights to each range. On @sc{gnu}/Linux systems, each memory range
19470 includes the object file which is mapped to that range, instead of the
19471 memory access rights to that range.
19473 @item info proc stat
19474 @itemx info proc status
19475 @cindex process detailed status information
19476 These subcommands are specific to @sc{gnu}/Linux systems. They show
19477 the process-related information, including the user ID and group ID;
19478 how many threads are there in the process; its virtual memory usage;
19479 the signals that are pending, blocked, and ignored; its TTY; its
19480 consumption of system and user time; its stack size; its @samp{nice}
19481 value; etc. For more information, see the @samp{proc} man page
19482 (type @kbd{man 5 proc} from your shell prompt).
19484 @item info proc all
19485 Show all the information about the process described under all of the
19486 above @code{info proc} subcommands.
19489 @comment These sub-options of 'info proc' were not included when
19490 @comment procfs.c was re-written. Keep their descriptions around
19491 @comment against the day when someone finds the time to put them back in.
19492 @kindex info proc times
19493 @item info proc times
19494 Starting time, user CPU time, and system CPU time for your program and
19497 @kindex info proc id
19499 Report on the process IDs related to your program: its own process ID,
19500 the ID of its parent, the process group ID, and the session ID.
19503 @item set procfs-trace
19504 @kindex set procfs-trace
19505 @cindex @code{procfs} API calls
19506 This command enables and disables tracing of @code{procfs} API calls.
19508 @item show procfs-trace
19509 @kindex show procfs-trace
19510 Show the current state of @code{procfs} API call tracing.
19512 @item set procfs-file @var{file}
19513 @kindex set procfs-file
19514 Tell @value{GDBN} to write @code{procfs} API trace to the named
19515 @var{file}. @value{GDBN} appends the trace info to the previous
19516 contents of the file. The default is to display the trace on the
19519 @item show procfs-file
19520 @kindex show procfs-file
19521 Show the file to which @code{procfs} API trace is written.
19523 @item proc-trace-entry
19524 @itemx proc-trace-exit
19525 @itemx proc-untrace-entry
19526 @itemx proc-untrace-exit
19527 @kindex proc-trace-entry
19528 @kindex proc-trace-exit
19529 @kindex proc-untrace-entry
19530 @kindex proc-untrace-exit
19531 These commands enable and disable tracing of entries into and exits
19532 from the @code{syscall} interface.
19535 @kindex info pidlist
19536 @cindex process list, QNX Neutrino
19537 For QNX Neutrino only, this command displays the list of all the
19538 processes and all the threads within each process.
19541 @kindex info meminfo
19542 @cindex mapinfo list, QNX Neutrino
19543 For QNX Neutrino only, this command displays the list of all mapinfos.
19547 @subsection Features for Debugging @sc{djgpp} Programs
19548 @cindex @sc{djgpp} debugging
19549 @cindex native @sc{djgpp} debugging
19550 @cindex MS-DOS-specific commands
19553 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19554 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19555 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19556 top of real-mode DOS systems and their emulations.
19558 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19559 defines a few commands specific to the @sc{djgpp} port. This
19560 subsection describes those commands.
19565 This is a prefix of @sc{djgpp}-specific commands which print
19566 information about the target system and important OS structures.
19569 @cindex MS-DOS system info
19570 @cindex free memory information (MS-DOS)
19571 @item info dos sysinfo
19572 This command displays assorted information about the underlying
19573 platform: the CPU type and features, the OS version and flavor, the
19574 DPMI version, and the available conventional and DPMI memory.
19579 @cindex segment descriptor tables
19580 @cindex descriptor tables display
19582 @itemx info dos ldt
19583 @itemx info dos idt
19584 These 3 commands display entries from, respectively, Global, Local,
19585 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19586 tables are data structures which store a descriptor for each segment
19587 that is currently in use. The segment's selector is an index into a
19588 descriptor table; the table entry for that index holds the
19589 descriptor's base address and limit, and its attributes and access
19592 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19593 segment (used for both data and the stack), and a DOS segment (which
19594 allows access to DOS/BIOS data structures and absolute addresses in
19595 conventional memory). However, the DPMI host will usually define
19596 additional segments in order to support the DPMI environment.
19598 @cindex garbled pointers
19599 These commands allow to display entries from the descriptor tables.
19600 Without an argument, all entries from the specified table are
19601 displayed. An argument, which should be an integer expression, means
19602 display a single entry whose index is given by the argument. For
19603 example, here's a convenient way to display information about the
19604 debugged program's data segment:
19607 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19608 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19612 This comes in handy when you want to see whether a pointer is outside
19613 the data segment's limit (i.e.@: @dfn{garbled}).
19615 @cindex page tables display (MS-DOS)
19617 @itemx info dos pte
19618 These two commands display entries from, respectively, the Page
19619 Directory and the Page Tables. Page Directories and Page Tables are
19620 data structures which control how virtual memory addresses are mapped
19621 into physical addresses. A Page Table includes an entry for every
19622 page of memory that is mapped into the program's address space; there
19623 may be several Page Tables, each one holding up to 4096 entries. A
19624 Page Directory has up to 4096 entries, one each for every Page Table
19625 that is currently in use.
19627 Without an argument, @kbd{info dos pde} displays the entire Page
19628 Directory, and @kbd{info dos pte} displays all the entries in all of
19629 the Page Tables. An argument, an integer expression, given to the
19630 @kbd{info dos pde} command means display only that entry from the Page
19631 Directory table. An argument given to the @kbd{info dos pte} command
19632 means display entries from a single Page Table, the one pointed to by
19633 the specified entry in the Page Directory.
19635 @cindex direct memory access (DMA) on MS-DOS
19636 These commands are useful when your program uses @dfn{DMA} (Direct
19637 Memory Access), which needs physical addresses to program the DMA
19640 These commands are supported only with some DPMI servers.
19642 @cindex physical address from linear address
19643 @item info dos address-pte @var{addr}
19644 This command displays the Page Table entry for a specified linear
19645 address. The argument @var{addr} is a linear address which should
19646 already have the appropriate segment's base address added to it,
19647 because this command accepts addresses which may belong to @emph{any}
19648 segment. For example, here's how to display the Page Table entry for
19649 the page where a variable @code{i} is stored:
19652 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19653 @exdent @code{Page Table entry for address 0x11a00d30:}
19654 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19658 This says that @code{i} is stored at offset @code{0xd30} from the page
19659 whose physical base address is @code{0x02698000}, and shows all the
19660 attributes of that page.
19662 Note that you must cast the addresses of variables to a @code{char *},
19663 since otherwise the value of @code{__djgpp_base_address}, the base
19664 address of all variables and functions in a @sc{djgpp} program, will
19665 be added using the rules of C pointer arithmetics: if @code{i} is
19666 declared an @code{int}, @value{GDBN} will add 4 times the value of
19667 @code{__djgpp_base_address} to the address of @code{i}.
19669 Here's another example, it displays the Page Table entry for the
19673 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19674 @exdent @code{Page Table entry for address 0x29110:}
19675 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19679 (The @code{+ 3} offset is because the transfer buffer's address is the
19680 3rd member of the @code{_go32_info_block} structure.) The output
19681 clearly shows that this DPMI server maps the addresses in conventional
19682 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19683 linear (@code{0x29110}) addresses are identical.
19685 This command is supported only with some DPMI servers.
19688 @cindex DOS serial data link, remote debugging
19689 In addition to native debugging, the DJGPP port supports remote
19690 debugging via a serial data link. The following commands are specific
19691 to remote serial debugging in the DJGPP port of @value{GDBN}.
19694 @kindex set com1base
19695 @kindex set com1irq
19696 @kindex set com2base
19697 @kindex set com2irq
19698 @kindex set com3base
19699 @kindex set com3irq
19700 @kindex set com4base
19701 @kindex set com4irq
19702 @item set com1base @var{addr}
19703 This command sets the base I/O port address of the @file{COM1} serial
19706 @item set com1irq @var{irq}
19707 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19708 for the @file{COM1} serial port.
19710 There are similar commands @samp{set com2base}, @samp{set com3irq},
19711 etc.@: for setting the port address and the @code{IRQ} lines for the
19714 @kindex show com1base
19715 @kindex show com1irq
19716 @kindex show com2base
19717 @kindex show com2irq
19718 @kindex show com3base
19719 @kindex show com3irq
19720 @kindex show com4base
19721 @kindex show com4irq
19722 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19723 display the current settings of the base address and the @code{IRQ}
19724 lines used by the COM ports.
19727 @kindex info serial
19728 @cindex DOS serial port status
19729 This command prints the status of the 4 DOS serial ports. For each
19730 port, it prints whether it's active or not, its I/O base address and
19731 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19732 counts of various errors encountered so far.
19736 @node Cygwin Native
19737 @subsection Features for Debugging MS Windows PE Executables
19738 @cindex MS Windows debugging
19739 @cindex native Cygwin debugging
19740 @cindex Cygwin-specific commands
19742 @value{GDBN} supports native debugging of MS Windows programs, including
19743 DLLs with and without symbolic debugging information.
19745 @cindex Ctrl-BREAK, MS-Windows
19746 @cindex interrupt debuggee on MS-Windows
19747 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19748 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19749 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19750 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19751 sequence, which can be used to interrupt the debuggee even if it
19754 There are various additional Cygwin-specific commands, described in
19755 this section. Working with DLLs that have no debugging symbols is
19756 described in @ref{Non-debug DLL Symbols}.
19761 This is a prefix of MS Windows-specific commands which print
19762 information about the target system and important OS structures.
19764 @item info w32 selector
19765 This command displays information returned by
19766 the Win32 API @code{GetThreadSelectorEntry} function.
19767 It takes an optional argument that is evaluated to
19768 a long value to give the information about this given selector.
19769 Without argument, this command displays information
19770 about the six segment registers.
19772 @item info w32 thread-information-block
19773 This command displays thread specific information stored in the
19774 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19775 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19779 This is a Cygwin-specific alias of @code{info shared}.
19781 @kindex dll-symbols
19783 This command loads symbols from a dll similarly to
19784 add-sym command but without the need to specify a base address.
19786 @kindex set cygwin-exceptions
19787 @cindex debugging the Cygwin DLL
19788 @cindex Cygwin DLL, debugging
19789 @item set cygwin-exceptions @var{mode}
19790 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19791 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19792 @value{GDBN} will delay recognition of exceptions, and may ignore some
19793 exceptions which seem to be caused by internal Cygwin DLL
19794 ``bookkeeping''. This option is meant primarily for debugging the
19795 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19796 @value{GDBN} users with false @code{SIGSEGV} signals.
19798 @kindex show cygwin-exceptions
19799 @item show cygwin-exceptions
19800 Displays whether @value{GDBN} will break on exceptions that happen
19801 inside the Cygwin DLL itself.
19803 @kindex set new-console
19804 @item set new-console @var{mode}
19805 If @var{mode} is @code{on} the debuggee will
19806 be started in a new console on next start.
19807 If @var{mode} is @code{off}, the debuggee will
19808 be started in the same console as the debugger.
19810 @kindex show new-console
19811 @item show new-console
19812 Displays whether a new console is used
19813 when the debuggee is started.
19815 @kindex set new-group
19816 @item set new-group @var{mode}
19817 This boolean value controls whether the debuggee should
19818 start a new group or stay in the same group as the debugger.
19819 This affects the way the Windows OS handles
19822 @kindex show new-group
19823 @item show new-group
19824 Displays current value of new-group boolean.
19826 @kindex set debugevents
19827 @item set debugevents
19828 This boolean value adds debug output concerning kernel events related
19829 to the debuggee seen by the debugger. This includes events that
19830 signal thread and process creation and exit, DLL loading and
19831 unloading, console interrupts, and debugging messages produced by the
19832 Windows @code{OutputDebugString} API call.
19834 @kindex set debugexec
19835 @item set debugexec
19836 This boolean value adds debug output concerning execute events
19837 (such as resume thread) seen by the debugger.
19839 @kindex set debugexceptions
19840 @item set debugexceptions
19841 This boolean value adds debug output concerning exceptions in the
19842 debuggee seen by the debugger.
19844 @kindex set debugmemory
19845 @item set debugmemory
19846 This boolean value adds debug output concerning debuggee memory reads
19847 and writes by the debugger.
19851 This boolean values specifies whether the debuggee is called
19852 via a shell or directly (default value is on).
19856 Displays if the debuggee will be started with a shell.
19861 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19864 @node Non-debug DLL Symbols
19865 @subsubsection Support for DLLs without Debugging Symbols
19866 @cindex DLLs with no debugging symbols
19867 @cindex Minimal symbols and DLLs
19869 Very often on windows, some of the DLLs that your program relies on do
19870 not include symbolic debugging information (for example,
19871 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19872 symbols in a DLL, it relies on the minimal amount of symbolic
19873 information contained in the DLL's export table. This section
19874 describes working with such symbols, known internally to @value{GDBN} as
19875 ``minimal symbols''.
19877 Note that before the debugged program has started execution, no DLLs
19878 will have been loaded. The easiest way around this problem is simply to
19879 start the program --- either by setting a breakpoint or letting the
19880 program run once to completion. It is also possible to force
19881 @value{GDBN} to load a particular DLL before starting the executable ---
19882 see the shared library information in @ref{Files}, or the
19883 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19884 explicitly loading symbols from a DLL with no debugging information will
19885 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19886 which may adversely affect symbol lookup performance.
19888 @subsubsection DLL Name Prefixes
19890 In keeping with the naming conventions used by the Microsoft debugging
19891 tools, DLL export symbols are made available with a prefix based on the
19892 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19893 also entered into the symbol table, so @code{CreateFileA} is often
19894 sufficient. In some cases there will be name clashes within a program
19895 (particularly if the executable itself includes full debugging symbols)
19896 necessitating the use of the fully qualified name when referring to the
19897 contents of the DLL. Use single-quotes around the name to avoid the
19898 exclamation mark (``!'') being interpreted as a language operator.
19900 Note that the internal name of the DLL may be all upper-case, even
19901 though the file name of the DLL is lower-case, or vice-versa. Since
19902 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19903 some confusion. If in doubt, try the @code{info functions} and
19904 @code{info variables} commands or even @code{maint print msymbols}
19905 (@pxref{Symbols}). Here's an example:
19908 (@value{GDBP}) info function CreateFileA
19909 All functions matching regular expression "CreateFileA":
19911 Non-debugging symbols:
19912 0x77e885f4 CreateFileA
19913 0x77e885f4 KERNEL32!CreateFileA
19917 (@value{GDBP}) info function !
19918 All functions matching regular expression "!":
19920 Non-debugging symbols:
19921 0x6100114c cygwin1!__assert
19922 0x61004034 cygwin1!_dll_crt0@@0
19923 0x61004240 cygwin1!dll_crt0(per_process *)
19927 @subsubsection Working with Minimal Symbols
19929 Symbols extracted from a DLL's export table do not contain very much
19930 type information. All that @value{GDBN} can do is guess whether a symbol
19931 refers to a function or variable depending on the linker section that
19932 contains the symbol. Also note that the actual contents of the memory
19933 contained in a DLL are not available unless the program is running. This
19934 means that you cannot examine the contents of a variable or disassemble
19935 a function within a DLL without a running program.
19937 Variables are generally treated as pointers and dereferenced
19938 automatically. For this reason, it is often necessary to prefix a
19939 variable name with the address-of operator (``&'') and provide explicit
19940 type information in the command. Here's an example of the type of
19944 (@value{GDBP}) print 'cygwin1!__argv'
19949 (@value{GDBP}) x 'cygwin1!__argv'
19950 0x10021610: "\230y\""
19953 And two possible solutions:
19956 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19957 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19961 (@value{GDBP}) x/2x &'cygwin1!__argv'
19962 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19963 (@value{GDBP}) x/x 0x10021608
19964 0x10021608: 0x0022fd98
19965 (@value{GDBP}) x/s 0x0022fd98
19966 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19969 Setting a break point within a DLL is possible even before the program
19970 starts execution. However, under these circumstances, @value{GDBN} can't
19971 examine the initial instructions of the function in order to skip the
19972 function's frame set-up code. You can work around this by using ``*&''
19973 to set the breakpoint at a raw memory address:
19976 (@value{GDBP}) break *&'python22!PyOS_Readline'
19977 Breakpoint 1 at 0x1e04eff0
19980 The author of these extensions is not entirely convinced that setting a
19981 break point within a shared DLL like @file{kernel32.dll} is completely
19985 @subsection Commands Specific to @sc{gnu} Hurd Systems
19986 @cindex @sc{gnu} Hurd debugging
19988 This subsection describes @value{GDBN} commands specific to the
19989 @sc{gnu} Hurd native debugging.
19994 @kindex set signals@r{, Hurd command}
19995 @kindex set sigs@r{, Hurd command}
19996 This command toggles the state of inferior signal interception by
19997 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19998 affected by this command. @code{sigs} is a shorthand alias for
20003 @kindex show signals@r{, Hurd command}
20004 @kindex show sigs@r{, Hurd command}
20005 Show the current state of intercepting inferior's signals.
20007 @item set signal-thread
20008 @itemx set sigthread
20009 @kindex set signal-thread
20010 @kindex set sigthread
20011 This command tells @value{GDBN} which thread is the @code{libc} signal
20012 thread. That thread is run when a signal is delivered to a running
20013 process. @code{set sigthread} is the shorthand alias of @code{set
20016 @item show signal-thread
20017 @itemx show sigthread
20018 @kindex show signal-thread
20019 @kindex show sigthread
20020 These two commands show which thread will run when the inferior is
20021 delivered a signal.
20024 @kindex set stopped@r{, Hurd command}
20025 This commands tells @value{GDBN} that the inferior process is stopped,
20026 as with the @code{SIGSTOP} signal. The stopped process can be
20027 continued by delivering a signal to it.
20030 @kindex show stopped@r{, Hurd command}
20031 This command shows whether @value{GDBN} thinks the debuggee is
20034 @item set exceptions
20035 @kindex set exceptions@r{, Hurd command}
20036 Use this command to turn off trapping of exceptions in the inferior.
20037 When exception trapping is off, neither breakpoints nor
20038 single-stepping will work. To restore the default, set exception
20041 @item show exceptions
20042 @kindex show exceptions@r{, Hurd command}
20043 Show the current state of trapping exceptions in the inferior.
20045 @item set task pause
20046 @kindex set task@r{, Hurd commands}
20047 @cindex task attributes (@sc{gnu} Hurd)
20048 @cindex pause current task (@sc{gnu} Hurd)
20049 This command toggles task suspension when @value{GDBN} has control.
20050 Setting it to on takes effect immediately, and the task is suspended
20051 whenever @value{GDBN} gets control. Setting it to off will take
20052 effect the next time the inferior is continued. If this option is set
20053 to off, you can use @code{set thread default pause on} or @code{set
20054 thread pause on} (see below) to pause individual threads.
20056 @item show task pause
20057 @kindex show task@r{, Hurd commands}
20058 Show the current state of task suspension.
20060 @item set task detach-suspend-count
20061 @cindex task suspend count
20062 @cindex detach from task, @sc{gnu} Hurd
20063 This command sets the suspend count the task will be left with when
20064 @value{GDBN} detaches from it.
20066 @item show task detach-suspend-count
20067 Show the suspend count the task will be left with when detaching.
20069 @item set task exception-port
20070 @itemx set task excp
20071 @cindex task exception port, @sc{gnu} Hurd
20072 This command sets the task exception port to which @value{GDBN} will
20073 forward exceptions. The argument should be the value of the @dfn{send
20074 rights} of the task. @code{set task excp} is a shorthand alias.
20076 @item set noninvasive
20077 @cindex noninvasive task options
20078 This command switches @value{GDBN} to a mode that is the least
20079 invasive as far as interfering with the inferior is concerned. This
20080 is the same as using @code{set task pause}, @code{set exceptions}, and
20081 @code{set signals} to values opposite to the defaults.
20083 @item info send-rights
20084 @itemx info receive-rights
20085 @itemx info port-rights
20086 @itemx info port-sets
20087 @itemx info dead-names
20090 @cindex send rights, @sc{gnu} Hurd
20091 @cindex receive rights, @sc{gnu} Hurd
20092 @cindex port rights, @sc{gnu} Hurd
20093 @cindex port sets, @sc{gnu} Hurd
20094 @cindex dead names, @sc{gnu} Hurd
20095 These commands display information about, respectively, send rights,
20096 receive rights, port rights, port sets, and dead names of a task.
20097 There are also shorthand aliases: @code{info ports} for @code{info
20098 port-rights} and @code{info psets} for @code{info port-sets}.
20100 @item set thread pause
20101 @kindex set thread@r{, Hurd command}
20102 @cindex thread properties, @sc{gnu} Hurd
20103 @cindex pause current thread (@sc{gnu} Hurd)
20104 This command toggles current thread suspension when @value{GDBN} has
20105 control. Setting it to on takes effect immediately, and the current
20106 thread is suspended whenever @value{GDBN} gets control. Setting it to
20107 off will take effect the next time the inferior is continued.
20108 Normally, this command has no effect, since when @value{GDBN} has
20109 control, the whole task is suspended. However, if you used @code{set
20110 task pause off} (see above), this command comes in handy to suspend
20111 only the current thread.
20113 @item show thread pause
20114 @kindex show thread@r{, Hurd command}
20115 This command shows the state of current thread suspension.
20117 @item set thread run
20118 This command sets whether the current thread is allowed to run.
20120 @item show thread run
20121 Show whether the current thread is allowed to run.
20123 @item set thread detach-suspend-count
20124 @cindex thread suspend count, @sc{gnu} Hurd
20125 @cindex detach from thread, @sc{gnu} Hurd
20126 This command sets the suspend count @value{GDBN} will leave on a
20127 thread when detaching. This number is relative to the suspend count
20128 found by @value{GDBN} when it notices the thread; use @code{set thread
20129 takeover-suspend-count} to force it to an absolute value.
20131 @item show thread detach-suspend-count
20132 Show the suspend count @value{GDBN} will leave on the thread when
20135 @item set thread exception-port
20136 @itemx set thread excp
20137 Set the thread exception port to which to forward exceptions. This
20138 overrides the port set by @code{set task exception-port} (see above).
20139 @code{set thread excp} is the shorthand alias.
20141 @item set thread takeover-suspend-count
20142 Normally, @value{GDBN}'s thread suspend counts are relative to the
20143 value @value{GDBN} finds when it notices each thread. This command
20144 changes the suspend counts to be absolute instead.
20146 @item set thread default
20147 @itemx show thread default
20148 @cindex thread default settings, @sc{gnu} Hurd
20149 Each of the above @code{set thread} commands has a @code{set thread
20150 default} counterpart (e.g., @code{set thread default pause}, @code{set
20151 thread default exception-port}, etc.). The @code{thread default}
20152 variety of commands sets the default thread properties for all
20153 threads; you can then change the properties of individual threads with
20154 the non-default commands.
20161 @value{GDBN} provides the following commands specific to the Darwin target:
20164 @item set debug darwin @var{num}
20165 @kindex set debug darwin
20166 When set to a non zero value, enables debugging messages specific to
20167 the Darwin support. Higher values produce more verbose output.
20169 @item show debug darwin
20170 @kindex show debug darwin
20171 Show the current state of Darwin messages.
20173 @item set debug mach-o @var{num}
20174 @kindex set debug mach-o
20175 When set to a non zero value, enables debugging messages while
20176 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20177 file format used on Darwin for object and executable files.) Higher
20178 values produce more verbose output. This is a command to diagnose
20179 problems internal to @value{GDBN} and should not be needed in normal
20182 @item show debug mach-o
20183 @kindex show debug mach-o
20184 Show the current state of Mach-O file messages.
20186 @item set mach-exceptions on
20187 @itemx set mach-exceptions off
20188 @kindex set mach-exceptions
20189 On Darwin, faults are first reported as a Mach exception and are then
20190 mapped to a Posix signal. Use this command to turn on trapping of
20191 Mach exceptions in the inferior. This might be sometimes useful to
20192 better understand the cause of a fault. The default is off.
20194 @item show mach-exceptions
20195 @kindex show mach-exceptions
20196 Show the current state of exceptions trapping.
20201 @section Embedded Operating Systems
20203 This section describes configurations involving the debugging of
20204 embedded operating systems that are available for several different
20208 * VxWorks:: Using @value{GDBN} with VxWorks
20211 @value{GDBN} includes the ability to debug programs running on
20212 various real-time operating systems.
20215 @subsection Using @value{GDBN} with VxWorks
20221 @kindex target vxworks
20222 @item target vxworks @var{machinename}
20223 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20224 is the target system's machine name or IP address.
20228 On VxWorks, @code{load} links @var{filename} dynamically on the
20229 current target system as well as adding its symbols in @value{GDBN}.
20231 @value{GDBN} enables developers to spawn and debug tasks running on networked
20232 VxWorks targets from a Unix host. Already-running tasks spawned from
20233 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20234 both the Unix host and on the VxWorks target. The program
20235 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20236 installed with the name @code{vxgdb}, to distinguish it from a
20237 @value{GDBN} for debugging programs on the host itself.)
20240 @item VxWorks-timeout @var{args}
20241 @kindex vxworks-timeout
20242 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20243 This option is set by the user, and @var{args} represents the number of
20244 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20245 your VxWorks target is a slow software simulator or is on the far side
20246 of a thin network line.
20249 The following information on connecting to VxWorks was current when
20250 this manual was produced; newer releases of VxWorks may use revised
20253 @findex INCLUDE_RDB
20254 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20255 to include the remote debugging interface routines in the VxWorks
20256 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20257 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20258 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20259 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20260 information on configuring and remaking VxWorks, see the manufacturer's
20262 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20264 Once you have included @file{rdb.a} in your VxWorks system image and set
20265 your Unix execution search path to find @value{GDBN}, you are ready to
20266 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20267 @code{vxgdb}, depending on your installation).
20269 @value{GDBN} comes up showing the prompt:
20276 * VxWorks Connection:: Connecting to VxWorks
20277 * VxWorks Download:: VxWorks download
20278 * VxWorks Attach:: Running tasks
20281 @node VxWorks Connection
20282 @subsubsection Connecting to VxWorks
20284 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20285 network. To connect to a target whose host name is ``@code{tt}'', type:
20288 (vxgdb) target vxworks tt
20292 @value{GDBN} displays messages like these:
20295 Attaching remote machine across net...
20300 @value{GDBN} then attempts to read the symbol tables of any object modules
20301 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20302 these files by searching the directories listed in the command search
20303 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20304 to find an object file, it displays a message such as:
20307 prog.o: No such file or directory.
20310 When this happens, add the appropriate directory to the search path with
20311 the @value{GDBN} command @code{path}, and execute the @code{target}
20314 @node VxWorks Download
20315 @subsubsection VxWorks Download
20317 @cindex download to VxWorks
20318 If you have connected to the VxWorks target and you want to debug an
20319 object that has not yet been loaded, you can use the @value{GDBN}
20320 @code{load} command to download a file from Unix to VxWorks
20321 incrementally. The object file given as an argument to the @code{load}
20322 command is actually opened twice: first by the VxWorks target in order
20323 to download the code, then by @value{GDBN} in order to read the symbol
20324 table. This can lead to problems if the current working directories on
20325 the two systems differ. If both systems have NFS mounted the same
20326 filesystems, you can avoid these problems by using absolute paths.
20327 Otherwise, it is simplest to set the working directory on both systems
20328 to the directory in which the object file resides, and then to reference
20329 the file by its name, without any path. For instance, a program
20330 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20331 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20332 program, type this on VxWorks:
20335 -> cd "@var{vxpath}/vw/demo/rdb"
20339 Then, in @value{GDBN}, type:
20342 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20343 (vxgdb) load prog.o
20346 @value{GDBN} displays a response similar to this:
20349 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20352 You can also use the @code{load} command to reload an object module
20353 after editing and recompiling the corresponding source file. Note that
20354 this makes @value{GDBN} delete all currently-defined breakpoints,
20355 auto-displays, and convenience variables, and to clear the value
20356 history. (This is necessary in order to preserve the integrity of
20357 debugger's data structures that reference the target system's symbol
20360 @node VxWorks Attach
20361 @subsubsection Running Tasks
20363 @cindex running VxWorks tasks
20364 You can also attach to an existing task using the @code{attach} command as
20368 (vxgdb) attach @var{task}
20372 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20373 or suspended when you attach to it. Running tasks are suspended at
20374 the time of attachment.
20376 @node Embedded Processors
20377 @section Embedded Processors
20379 This section goes into details specific to particular embedded
20382 @cindex send command to simulator
20383 Whenever a specific embedded processor has a simulator, @value{GDBN}
20384 allows to send an arbitrary command to the simulator.
20387 @item sim @var{command}
20388 @kindex sim@r{, a command}
20389 Send an arbitrary @var{command} string to the simulator. Consult the
20390 documentation for the specific simulator in use for information about
20391 acceptable commands.
20397 * M32R/D:: Renesas M32R/D
20398 * M68K:: Motorola M68K
20399 * MicroBlaze:: Xilinx MicroBlaze
20400 * MIPS Embedded:: MIPS Embedded
20401 * PowerPC Embedded:: PowerPC Embedded
20402 * PA:: HP PA Embedded
20403 * Sparclet:: Tsqware Sparclet
20404 * Sparclite:: Fujitsu Sparclite
20405 * Z8000:: Zilog Z8000
20408 * Super-H:: Renesas Super-H
20417 @item target rdi @var{dev}
20418 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20419 use this target to communicate with both boards running the Angel
20420 monitor, or with the EmbeddedICE JTAG debug device.
20423 @item target rdp @var{dev}
20428 @value{GDBN} provides the following ARM-specific commands:
20431 @item set arm disassembler
20433 This commands selects from a list of disassembly styles. The
20434 @code{"std"} style is the standard style.
20436 @item show arm disassembler
20438 Show the current disassembly style.
20440 @item set arm apcs32
20441 @cindex ARM 32-bit mode
20442 This command toggles ARM operation mode between 32-bit and 26-bit.
20444 @item show arm apcs32
20445 Display the current usage of the ARM 32-bit mode.
20447 @item set arm fpu @var{fputype}
20448 This command sets the ARM floating-point unit (FPU) type. The
20449 argument @var{fputype} can be one of these:
20453 Determine the FPU type by querying the OS ABI.
20455 Software FPU, with mixed-endian doubles on little-endian ARM
20458 GCC-compiled FPA co-processor.
20460 Software FPU with pure-endian doubles.
20466 Show the current type of the FPU.
20469 This command forces @value{GDBN} to use the specified ABI.
20472 Show the currently used ABI.
20474 @item set arm fallback-mode (arm|thumb|auto)
20475 @value{GDBN} uses the symbol table, when available, to determine
20476 whether instructions are ARM or Thumb. This command controls
20477 @value{GDBN}'s default behavior when the symbol table is not
20478 available. The default is @samp{auto}, which causes @value{GDBN} to
20479 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20482 @item show arm fallback-mode
20483 Show the current fallback instruction mode.
20485 @item set arm force-mode (arm|thumb|auto)
20486 This command overrides use of the symbol table to determine whether
20487 instructions are ARM or Thumb. The default is @samp{auto}, which
20488 causes @value{GDBN} to use the symbol table and then the setting
20489 of @samp{set arm fallback-mode}.
20491 @item show arm force-mode
20492 Show the current forced instruction mode.
20494 @item set debug arm
20495 Toggle whether to display ARM-specific debugging messages from the ARM
20496 target support subsystem.
20498 @item show debug arm
20499 Show whether ARM-specific debugging messages are enabled.
20502 The following commands are available when an ARM target is debugged
20503 using the RDI interface:
20506 @item rdilogfile @r{[}@var{file}@r{]}
20508 @cindex ADP (Angel Debugger Protocol) logging
20509 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20510 With an argument, sets the log file to the specified @var{file}. With
20511 no argument, show the current log file name. The default log file is
20514 @item rdilogenable @r{[}@var{arg}@r{]}
20515 @kindex rdilogenable
20516 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20517 enables logging, with an argument 0 or @code{"no"} disables it. With
20518 no arguments displays the current setting. When logging is enabled,
20519 ADP packets exchanged between @value{GDBN} and the RDI target device
20520 are logged to a file.
20522 @item set rdiromatzero
20523 @kindex set rdiromatzero
20524 @cindex ROM at zero address, RDI
20525 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20526 vector catching is disabled, so that zero address can be used. If off
20527 (the default), vector catching is enabled. For this command to take
20528 effect, it needs to be invoked prior to the @code{target rdi} command.
20530 @item show rdiromatzero
20531 @kindex show rdiromatzero
20532 Show the current setting of ROM at zero address.
20534 @item set rdiheartbeat
20535 @kindex set rdiheartbeat
20536 @cindex RDI heartbeat
20537 Enable or disable RDI heartbeat packets. It is not recommended to
20538 turn on this option, since it confuses ARM and EPI JTAG interface, as
20539 well as the Angel monitor.
20541 @item show rdiheartbeat
20542 @kindex show rdiheartbeat
20543 Show the setting of RDI heartbeat packets.
20547 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20548 The @value{GDBN} ARM simulator accepts the following optional arguments.
20551 @item --swi-support=@var{type}
20552 Tell the simulator which SWI interfaces to support.
20553 @var{type} may be a comma separated list of the following values.
20554 The default value is @code{all}.
20567 @subsection Renesas M32R/D and M32R/SDI
20570 @kindex target m32r
20571 @item target m32r @var{dev}
20572 Renesas M32R/D ROM monitor.
20574 @kindex target m32rsdi
20575 @item target m32rsdi @var{dev}
20576 Renesas M32R SDI server, connected via parallel port to the board.
20579 The following @value{GDBN} commands are specific to the M32R monitor:
20582 @item set download-path @var{path}
20583 @kindex set download-path
20584 @cindex find downloadable @sc{srec} files (M32R)
20585 Set the default path for finding downloadable @sc{srec} files.
20587 @item show download-path
20588 @kindex show download-path
20589 Show the default path for downloadable @sc{srec} files.
20591 @item set board-address @var{addr}
20592 @kindex set board-address
20593 @cindex M32-EVA target board address
20594 Set the IP address for the M32R-EVA target board.
20596 @item show board-address
20597 @kindex show board-address
20598 Show the current IP address of the target board.
20600 @item set server-address @var{addr}
20601 @kindex set server-address
20602 @cindex download server address (M32R)
20603 Set the IP address for the download server, which is the @value{GDBN}'s
20606 @item show server-address
20607 @kindex show server-address
20608 Display the IP address of the download server.
20610 @item upload @r{[}@var{file}@r{]}
20611 @kindex upload@r{, M32R}
20612 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20613 upload capability. If no @var{file} argument is given, the current
20614 executable file is uploaded.
20616 @item tload @r{[}@var{file}@r{]}
20617 @kindex tload@r{, M32R}
20618 Test the @code{upload} command.
20621 The following commands are available for M32R/SDI:
20626 @cindex reset SDI connection, M32R
20627 This command resets the SDI connection.
20631 This command shows the SDI connection status.
20634 @kindex debug_chaos
20635 @cindex M32R/Chaos debugging
20636 Instructs the remote that M32R/Chaos debugging is to be used.
20638 @item use_debug_dma
20639 @kindex use_debug_dma
20640 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20643 @kindex use_mon_code
20644 Instructs the remote to use the MON_CODE method of accessing memory.
20647 @kindex use_ib_break
20648 Instructs the remote to set breakpoints by IB break.
20650 @item use_dbt_break
20651 @kindex use_dbt_break
20652 Instructs the remote to set breakpoints by DBT.
20658 The Motorola m68k configuration includes ColdFire support, and a
20659 target command for the following ROM monitor.
20663 @kindex target dbug
20664 @item target dbug @var{dev}
20665 dBUG ROM monitor for Motorola ColdFire.
20670 @subsection MicroBlaze
20671 @cindex Xilinx MicroBlaze
20672 @cindex XMD, Xilinx Microprocessor Debugger
20674 The MicroBlaze is a soft-core processor supported on various Xilinx
20675 FPGAs, such as Spartan or Virtex series. Boards with these processors
20676 usually have JTAG ports which connect to a host system running the Xilinx
20677 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20678 This host system is used to download the configuration bitstream to
20679 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20680 communicates with the target board using the JTAG interface and
20681 presents a @code{gdbserver} interface to the board. By default
20682 @code{xmd} uses port @code{1234}. (While it is possible to change
20683 this default port, it requires the use of undocumented @code{xmd}
20684 commands. Contact Xilinx support if you need to do this.)
20686 Use these GDB commands to connect to the MicroBlaze target processor.
20689 @item target remote :1234
20690 Use this command to connect to the target if you are running @value{GDBN}
20691 on the same system as @code{xmd}.
20693 @item target remote @var{xmd-host}:1234
20694 Use this command to connect to the target if it is connected to @code{xmd}
20695 running on a different system named @var{xmd-host}.
20698 Use this command to download a program to the MicroBlaze target.
20700 @item set debug microblaze @var{n}
20701 Enable MicroBlaze-specific debugging messages if non-zero.
20703 @item show debug microblaze @var{n}
20704 Show MicroBlaze-specific debugging level.
20707 @node MIPS Embedded
20708 @subsection @acronym{MIPS} Embedded
20710 @cindex @acronym{MIPS} boards
20711 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20712 @acronym{MIPS} board attached to a serial line. This is available when
20713 you configure @value{GDBN} with @samp{--target=mips-elf}.
20716 Use these @value{GDBN} commands to specify the connection to your target board:
20719 @item target mips @var{port}
20720 @kindex target mips @var{port}
20721 To run a program on the board, start up @code{@value{GDBP}} with the
20722 name of your program as the argument. To connect to the board, use the
20723 command @samp{target mips @var{port}}, where @var{port} is the name of
20724 the serial port connected to the board. If the program has not already
20725 been downloaded to the board, you may use the @code{load} command to
20726 download it. You can then use all the usual @value{GDBN} commands.
20728 For example, this sequence connects to the target board through a serial
20729 port, and loads and runs a program called @var{prog} through the
20733 host$ @value{GDBP} @var{prog}
20734 @value{GDBN} is free software and @dots{}
20735 (@value{GDBP}) target mips /dev/ttyb
20736 (@value{GDBP}) load @var{prog}
20740 @item target mips @var{hostname}:@var{portnumber}
20741 On some @value{GDBN} host configurations, you can specify a TCP
20742 connection (for instance, to a serial line managed by a terminal
20743 concentrator) instead of a serial port, using the syntax
20744 @samp{@var{hostname}:@var{portnumber}}.
20746 @item target pmon @var{port}
20747 @kindex target pmon @var{port}
20750 @item target ddb @var{port}
20751 @kindex target ddb @var{port}
20752 NEC's DDB variant of PMON for Vr4300.
20754 @item target lsi @var{port}
20755 @kindex target lsi @var{port}
20756 LSI variant of PMON.
20758 @kindex target r3900
20759 @item target r3900 @var{dev}
20760 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20762 @kindex target array
20763 @item target array @var{dev}
20764 Array Tech LSI33K RAID controller board.
20770 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20773 @item set mipsfpu double
20774 @itemx set mipsfpu single
20775 @itemx set mipsfpu none
20776 @itemx set mipsfpu auto
20777 @itemx show mipsfpu
20778 @kindex set mipsfpu
20779 @kindex show mipsfpu
20780 @cindex @acronym{MIPS} remote floating point
20781 @cindex floating point, @acronym{MIPS} remote
20782 If your target board does not support the @acronym{MIPS} floating point
20783 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20784 need this, you may wish to put the command in your @value{GDBN} init
20785 file). This tells @value{GDBN} how to find the return value of
20786 functions which return floating point values. It also allows
20787 @value{GDBN} to avoid saving the floating point registers when calling
20788 functions on the board. If you are using a floating point coprocessor
20789 with only single precision floating point support, as on the @sc{r4650}
20790 processor, use the command @samp{set mipsfpu single}. The default
20791 double precision floating point coprocessor may be selected using
20792 @samp{set mipsfpu double}.
20794 In previous versions the only choices were double precision or no
20795 floating point, so @samp{set mipsfpu on} will select double precision
20796 and @samp{set mipsfpu off} will select no floating point.
20798 As usual, you can inquire about the @code{mipsfpu} variable with
20799 @samp{show mipsfpu}.
20801 @item set timeout @var{seconds}
20802 @itemx set retransmit-timeout @var{seconds}
20803 @itemx show timeout
20804 @itemx show retransmit-timeout
20805 @cindex @code{timeout}, @acronym{MIPS} protocol
20806 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20807 @kindex set timeout
20808 @kindex show timeout
20809 @kindex set retransmit-timeout
20810 @kindex show retransmit-timeout
20811 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20812 remote protocol, with the @code{set timeout @var{seconds}} command. The
20813 default is 5 seconds. Similarly, you can control the timeout used while
20814 waiting for an acknowledgment of a packet with the @code{set
20815 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20816 You can inspect both values with @code{show timeout} and @code{show
20817 retransmit-timeout}. (These commands are @emph{only} available when
20818 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20820 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20821 is waiting for your program to stop. In that case, @value{GDBN} waits
20822 forever because it has no way of knowing how long the program is going
20823 to run before stopping.
20825 @item set syn-garbage-limit @var{num}
20826 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20827 @cindex synchronize with remote @acronym{MIPS} target
20828 Limit the maximum number of characters @value{GDBN} should ignore when
20829 it tries to synchronize with the remote target. The default is 10
20830 characters. Setting the limit to -1 means there's no limit.
20832 @item show syn-garbage-limit
20833 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20834 Show the current limit on the number of characters to ignore when
20835 trying to synchronize with the remote system.
20837 @item set monitor-prompt @var{prompt}
20838 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20839 @cindex remote monitor prompt
20840 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20841 remote monitor. The default depends on the target:
20851 @item show monitor-prompt
20852 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20853 Show the current strings @value{GDBN} expects as the prompt from the
20856 @item set monitor-warnings
20857 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20858 Enable or disable monitor warnings about hardware breakpoints. This
20859 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20860 display warning messages whose codes are returned by the @code{lsi}
20861 PMON monitor for breakpoint commands.
20863 @item show monitor-warnings
20864 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20865 Show the current setting of printing monitor warnings.
20867 @item pmon @var{command}
20868 @kindex pmon@r{, @acronym{MIPS} remote}
20869 @cindex send PMON command
20870 This command allows sending an arbitrary @var{command} string to the
20871 monitor. The monitor must be in debug mode for this to work.
20874 @node PowerPC Embedded
20875 @subsection PowerPC Embedded
20877 @cindex DVC register
20878 @value{GDBN} supports using the DVC (Data Value Compare) register to
20879 implement in hardware simple hardware watchpoint conditions of the form:
20882 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20883 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20886 The DVC register will be automatically used when @value{GDBN} detects
20887 such pattern in a condition expression, and the created watchpoint uses one
20888 debug register (either the @code{exact-watchpoints} option is on and the
20889 variable is scalar, or the variable has a length of one byte). This feature
20890 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20893 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20894 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20895 in which case watchpoints using only one debug register are created when
20896 watching variables of scalar types.
20898 You can create an artificial array to watch an arbitrary memory
20899 region using one of the following commands (@pxref{Expressions}):
20902 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20903 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20906 PowerPC embedded processors support masked watchpoints. See the discussion
20907 about the @code{mask} argument in @ref{Set Watchpoints}.
20909 @cindex ranged breakpoint
20910 PowerPC embedded processors support hardware accelerated
20911 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20912 the inferior whenever it executes an instruction at any address within
20913 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20914 use the @code{break-range} command.
20916 @value{GDBN} provides the following PowerPC-specific commands:
20919 @kindex break-range
20920 @item break-range @var{start-location}, @var{end-location}
20921 Set a breakpoint for an address range.
20922 @var{start-location} and @var{end-location} can specify a function name,
20923 a line number, an offset of lines from the current line or from the start
20924 location, or an address of an instruction (see @ref{Specify Location},
20925 for a list of all the possible ways to specify a @var{location}.)
20926 The breakpoint will stop execution of the inferior whenever it
20927 executes an instruction at any address within the specified range,
20928 (including @var{start-location} and @var{end-location}.)
20930 @kindex set powerpc
20931 @item set powerpc soft-float
20932 @itemx show powerpc soft-float
20933 Force @value{GDBN} to use (or not use) a software floating point calling
20934 convention. By default, @value{GDBN} selects the calling convention based
20935 on the selected architecture and the provided executable file.
20937 @item set powerpc vector-abi
20938 @itemx show powerpc vector-abi
20939 Force @value{GDBN} to use the specified calling convention for vector
20940 arguments and return values. The valid options are @samp{auto};
20941 @samp{generic}, to avoid vector registers even if they are present;
20942 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20943 registers. By default, @value{GDBN} selects the calling convention
20944 based on the selected architecture and the provided executable file.
20946 @item set powerpc exact-watchpoints
20947 @itemx show powerpc exact-watchpoints
20948 Allow @value{GDBN} to use only one debug register when watching a variable
20949 of scalar type, thus assuming that the variable is accessed through the
20950 address of its first byte.
20952 @kindex target dink32
20953 @item target dink32 @var{dev}
20954 DINK32 ROM monitor.
20956 @kindex target ppcbug
20957 @item target ppcbug @var{dev}
20958 @kindex target ppcbug1
20959 @item target ppcbug1 @var{dev}
20960 PPCBUG ROM monitor for PowerPC.
20963 @item target sds @var{dev}
20964 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20967 @cindex SDS protocol
20968 The following commands specific to the SDS protocol are supported
20972 @item set sdstimeout @var{nsec}
20973 @kindex set sdstimeout
20974 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20975 default is 2 seconds.
20977 @item show sdstimeout
20978 @kindex show sdstimeout
20979 Show the current value of the SDS timeout.
20981 @item sds @var{command}
20982 @kindex sds@r{, a command}
20983 Send the specified @var{command} string to the SDS monitor.
20988 @subsection HP PA Embedded
20992 @kindex target op50n
20993 @item target op50n @var{dev}
20994 OP50N monitor, running on an OKI HPPA board.
20996 @kindex target w89k
20997 @item target w89k @var{dev}
20998 W89K monitor, running on a Winbond HPPA board.
21003 @subsection Tsqware Sparclet
21007 @value{GDBN} enables developers to debug tasks running on
21008 Sparclet targets from a Unix host.
21009 @value{GDBN} uses code that runs on
21010 both the Unix host and on the Sparclet target. The program
21011 @code{@value{GDBP}} is installed and executed on the Unix host.
21014 @item remotetimeout @var{args}
21015 @kindex remotetimeout
21016 @value{GDBN} supports the option @code{remotetimeout}.
21017 This option is set by the user, and @var{args} represents the number of
21018 seconds @value{GDBN} waits for responses.
21021 @cindex compiling, on Sparclet
21022 When compiling for debugging, include the options @samp{-g} to get debug
21023 information and @samp{-Ttext} to relocate the program to where you wish to
21024 load it on the target. You may also want to add the options @samp{-n} or
21025 @samp{-N} in order to reduce the size of the sections. Example:
21028 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21031 You can use @code{objdump} to verify that the addresses are what you intended:
21034 sparclet-aout-objdump --headers --syms prog
21037 @cindex running, on Sparclet
21039 your Unix execution search path to find @value{GDBN}, you are ready to
21040 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21041 (or @code{sparclet-aout-gdb}, depending on your installation).
21043 @value{GDBN} comes up showing the prompt:
21050 * Sparclet File:: Setting the file to debug
21051 * Sparclet Connection:: Connecting to Sparclet
21052 * Sparclet Download:: Sparclet download
21053 * Sparclet Execution:: Running and debugging
21056 @node Sparclet File
21057 @subsubsection Setting File to Debug
21059 The @value{GDBN} command @code{file} lets you choose with program to debug.
21062 (gdbslet) file prog
21066 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21067 @value{GDBN} locates
21068 the file by searching the directories listed in the command search
21070 If the file was compiled with debug information (option @samp{-g}), source
21071 files will be searched as well.
21072 @value{GDBN} locates
21073 the source files by searching the directories listed in the directory search
21074 path (@pxref{Environment, ,Your Program's Environment}).
21076 to find a file, it displays a message such as:
21079 prog: No such file or directory.
21082 When this happens, add the appropriate directories to the search paths with
21083 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21084 @code{target} command again.
21086 @node Sparclet Connection
21087 @subsubsection Connecting to Sparclet
21089 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21090 To connect to a target on serial port ``@code{ttya}'', type:
21093 (gdbslet) target sparclet /dev/ttya
21094 Remote target sparclet connected to /dev/ttya
21095 main () at ../prog.c:3
21099 @value{GDBN} displays messages like these:
21105 @node Sparclet Download
21106 @subsubsection Sparclet Download
21108 @cindex download to Sparclet
21109 Once connected to the Sparclet target,
21110 you can use the @value{GDBN}
21111 @code{load} command to download the file from the host to the target.
21112 The file name and load offset should be given as arguments to the @code{load}
21114 Since the file format is aout, the program must be loaded to the starting
21115 address. You can use @code{objdump} to find out what this value is. The load
21116 offset is an offset which is added to the VMA (virtual memory address)
21117 of each of the file's sections.
21118 For instance, if the program
21119 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21120 and bss at 0x12010170, in @value{GDBN}, type:
21123 (gdbslet) load prog 0x12010000
21124 Loading section .text, size 0xdb0 vma 0x12010000
21127 If the code is loaded at a different address then what the program was linked
21128 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21129 to tell @value{GDBN} where to map the symbol table.
21131 @node Sparclet Execution
21132 @subsubsection Running and Debugging
21134 @cindex running and debugging Sparclet programs
21135 You can now begin debugging the task using @value{GDBN}'s execution control
21136 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21137 manual for the list of commands.
21141 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21143 Starting program: prog
21144 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21145 3 char *symarg = 0;
21147 4 char *execarg = "hello!";
21152 @subsection Fujitsu Sparclite
21156 @kindex target sparclite
21157 @item target sparclite @var{dev}
21158 Fujitsu sparclite boards, used only for the purpose of loading.
21159 You must use an additional command to debug the program.
21160 For example: target remote @var{dev} using @value{GDBN} standard
21166 @subsection Zilog Z8000
21169 @cindex simulator, Z8000
21170 @cindex Zilog Z8000 simulator
21172 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21175 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21176 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21177 segmented variant). The simulator recognizes which architecture is
21178 appropriate by inspecting the object code.
21181 @item target sim @var{args}
21183 @kindex target sim@r{, with Z8000}
21184 Debug programs on a simulated CPU. If the simulator supports setup
21185 options, specify them via @var{args}.
21189 After specifying this target, you can debug programs for the simulated
21190 CPU in the same style as programs for your host computer; use the
21191 @code{file} command to load a new program image, the @code{run} command
21192 to run your program, and so on.
21194 As well as making available all the usual machine registers
21195 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21196 additional items of information as specially named registers:
21201 Counts clock-ticks in the simulator.
21204 Counts instructions run in the simulator.
21207 Execution time in 60ths of a second.
21211 You can refer to these values in @value{GDBN} expressions with the usual
21212 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21213 conditional breakpoint that suspends only after at least 5000
21214 simulated clock ticks.
21217 @subsection Atmel AVR
21220 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21221 following AVR-specific commands:
21224 @item info io_registers
21225 @kindex info io_registers@r{, AVR}
21226 @cindex I/O registers (Atmel AVR)
21227 This command displays information about the AVR I/O registers. For
21228 each register, @value{GDBN} prints its number and value.
21235 When configured for debugging CRIS, @value{GDBN} provides the
21236 following CRIS-specific commands:
21239 @item set cris-version @var{ver}
21240 @cindex CRIS version
21241 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21242 The CRIS version affects register names and sizes. This command is useful in
21243 case autodetection of the CRIS version fails.
21245 @item show cris-version
21246 Show the current CRIS version.
21248 @item set cris-dwarf2-cfi
21249 @cindex DWARF-2 CFI and CRIS
21250 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21251 Change to @samp{off} when using @code{gcc-cris} whose version is below
21254 @item show cris-dwarf2-cfi
21255 Show the current state of using DWARF-2 CFI.
21257 @item set cris-mode @var{mode}
21259 Set the current CRIS mode to @var{mode}. It should only be changed when
21260 debugging in guru mode, in which case it should be set to
21261 @samp{guru} (the default is @samp{normal}).
21263 @item show cris-mode
21264 Show the current CRIS mode.
21268 @subsection Renesas Super-H
21271 For the Renesas Super-H processor, @value{GDBN} provides these
21275 @item set sh calling-convention @var{convention}
21276 @kindex set sh calling-convention
21277 Set the calling-convention used when calling functions from @value{GDBN}.
21278 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21279 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21280 convention. If the DWARF-2 information of the called function specifies
21281 that the function follows the Renesas calling convention, the function
21282 is called using the Renesas calling convention. If the calling convention
21283 is set to @samp{renesas}, the Renesas calling convention is always used,
21284 regardless of the DWARF-2 information. This can be used to override the
21285 default of @samp{gcc} if debug information is missing, or the compiler
21286 does not emit the DWARF-2 calling convention entry for a function.
21288 @item show sh calling-convention
21289 @kindex show sh calling-convention
21290 Show the current calling convention setting.
21295 @node Architectures
21296 @section Architectures
21298 This section describes characteristics of architectures that affect
21299 all uses of @value{GDBN} with the architecture, both native and cross.
21306 * HPPA:: HP PA architecture
21307 * SPU:: Cell Broadband Engine SPU architecture
21313 @subsection AArch64
21314 @cindex AArch64 support
21316 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21317 following special commands:
21320 @item set debug aarch64
21321 @kindex set debug aarch64
21322 This command determines whether AArch64 architecture-specific debugging
21323 messages are to be displayed.
21325 @item show debug aarch64
21326 Show whether AArch64 debugging messages are displayed.
21331 @subsection x86 Architecture-specific Issues
21334 @item set struct-convention @var{mode}
21335 @kindex set struct-convention
21336 @cindex struct return convention
21337 @cindex struct/union returned in registers
21338 Set the convention used by the inferior to return @code{struct}s and
21339 @code{union}s from functions to @var{mode}. Possible values of
21340 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21341 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21342 are returned on the stack, while @code{"reg"} means that a
21343 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21344 be returned in a register.
21346 @item show struct-convention
21347 @kindex show struct-convention
21348 Show the current setting of the convention to return @code{struct}s
21355 See the following section.
21358 @subsection @acronym{MIPS}
21360 @cindex stack on Alpha
21361 @cindex stack on @acronym{MIPS}
21362 @cindex Alpha stack
21363 @cindex @acronym{MIPS} stack
21364 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21365 sometimes requires @value{GDBN} to search backward in the object code to
21366 find the beginning of a function.
21368 @cindex response time, @acronym{MIPS} debugging
21369 To improve response time (especially for embedded applications, where
21370 @value{GDBN} may be restricted to a slow serial line for this search)
21371 you may want to limit the size of this search, using one of these
21375 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21376 @item set heuristic-fence-post @var{limit}
21377 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21378 search for the beginning of a function. A value of @var{0} (the
21379 default) means there is no limit. However, except for @var{0}, the
21380 larger the limit the more bytes @code{heuristic-fence-post} must search
21381 and therefore the longer it takes to run. You should only need to use
21382 this command when debugging a stripped executable.
21384 @item show heuristic-fence-post
21385 Display the current limit.
21389 These commands are available @emph{only} when @value{GDBN} is configured
21390 for debugging programs on Alpha or @acronym{MIPS} processors.
21392 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21396 @item set mips abi @var{arg}
21397 @kindex set mips abi
21398 @cindex set ABI for @acronym{MIPS}
21399 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21400 values of @var{arg} are:
21404 The default ABI associated with the current binary (this is the
21414 @item show mips abi
21415 @kindex show mips abi
21416 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21418 @item set mips compression @var{arg}
21419 @kindex set mips compression
21420 @cindex code compression, @acronym{MIPS}
21421 Tell @value{GDBN} which @acronym{MIPS} compressed
21422 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21423 inferior. @value{GDBN} uses this for code disassembly and other
21424 internal interpretation purposes. This setting is only referred to
21425 when no executable has been associated with the debugging session or
21426 the executable does not provide information about the encoding it uses.
21427 Otherwise this setting is automatically updated from information
21428 provided by the executable.
21430 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21431 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21432 executables containing @acronym{MIPS16} code frequently are not
21433 identified as such.
21435 This setting is ``sticky''; that is, it retains its value across
21436 debugging sessions until reset either explicitly with this command or
21437 implicitly from an executable.
21439 The compiler and/or assembler typically add symbol table annotations to
21440 identify functions compiled for the @acronym{MIPS16} or
21441 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21442 are present, @value{GDBN} uses them in preference to the global
21443 compressed @acronym{ISA} encoding setting.
21445 @item show mips compression
21446 @kindex show mips compression
21447 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21448 @value{GDBN} to debug the inferior.
21451 @itemx show mipsfpu
21452 @xref{MIPS Embedded, set mipsfpu}.
21454 @item set mips mask-address @var{arg}
21455 @kindex set mips mask-address
21456 @cindex @acronym{MIPS} addresses, masking
21457 This command determines whether the most-significant 32 bits of 64-bit
21458 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21459 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21460 setting, which lets @value{GDBN} determine the correct value.
21462 @item show mips mask-address
21463 @kindex show mips mask-address
21464 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21467 @item set remote-mips64-transfers-32bit-regs
21468 @kindex set remote-mips64-transfers-32bit-regs
21469 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21470 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21471 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21472 and 64 bits for other registers, set this option to @samp{on}.
21474 @item show remote-mips64-transfers-32bit-regs
21475 @kindex show remote-mips64-transfers-32bit-regs
21476 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21478 @item set debug mips
21479 @kindex set debug mips
21480 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21481 target code in @value{GDBN}.
21483 @item show debug mips
21484 @kindex show debug mips
21485 Show the current setting of @acronym{MIPS} debugging messages.
21491 @cindex HPPA support
21493 When @value{GDBN} is debugging the HP PA architecture, it provides the
21494 following special commands:
21497 @item set debug hppa
21498 @kindex set debug hppa
21499 This command determines whether HPPA architecture-specific debugging
21500 messages are to be displayed.
21502 @item show debug hppa
21503 Show whether HPPA debugging messages are displayed.
21505 @item maint print unwind @var{address}
21506 @kindex maint print unwind@r{, HPPA}
21507 This command displays the contents of the unwind table entry at the
21508 given @var{address}.
21514 @subsection Cell Broadband Engine SPU architecture
21515 @cindex Cell Broadband Engine
21518 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21519 it provides the following special commands:
21522 @item info spu event
21524 Display SPU event facility status. Shows current event mask
21525 and pending event status.
21527 @item info spu signal
21528 Display SPU signal notification facility status. Shows pending
21529 signal-control word and signal notification mode of both signal
21530 notification channels.
21532 @item info spu mailbox
21533 Display SPU mailbox facility status. Shows all pending entries,
21534 in order of processing, in each of the SPU Write Outbound,
21535 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21538 Display MFC DMA status. Shows all pending commands in the MFC
21539 DMA queue. For each entry, opcode, tag, class IDs, effective
21540 and local store addresses and transfer size are shown.
21542 @item info spu proxydma
21543 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21544 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21545 and local store addresses and transfer size are shown.
21549 When @value{GDBN} is debugging a combined PowerPC/SPU application
21550 on the Cell Broadband Engine, it provides in addition the following
21554 @item set spu stop-on-load @var{arg}
21556 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21557 will give control to the user when a new SPE thread enters its @code{main}
21558 function. The default is @code{off}.
21560 @item show spu stop-on-load
21562 Show whether to stop for new SPE threads.
21564 @item set spu auto-flush-cache @var{arg}
21565 Set whether to automatically flush the software-managed cache. When set to
21566 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21567 cache to be flushed whenever SPE execution stops. This provides a consistent
21568 view of PowerPC memory that is accessed via the cache. If an application
21569 does not use the software-managed cache, this option has no effect.
21571 @item show spu auto-flush-cache
21572 Show whether to automatically flush the software-managed cache.
21577 @subsection PowerPC
21578 @cindex PowerPC architecture
21580 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21581 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21582 numbers stored in the floating point registers. These values must be stored
21583 in two consecutive registers, always starting at an even register like
21584 @code{f0} or @code{f2}.
21586 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21587 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21588 @code{f2} and @code{f3} for @code{$dl1} and so on.
21590 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21591 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21594 @subsection Nios II
21595 @cindex Nios II architecture
21597 When @value{GDBN} is debugging the Nios II architecture,
21598 it provides the following special commands:
21602 @item set debug nios2
21603 @kindex set debug nios2
21604 This command turns on and off debugging messages for the Nios II
21605 target code in @value{GDBN}.
21607 @item show debug nios2
21608 @kindex show debug nios2
21609 Show the current setting of Nios II debugging messages.
21612 @node Controlling GDB
21613 @chapter Controlling @value{GDBN}
21615 You can alter the way @value{GDBN} interacts with you by using the
21616 @code{set} command. For commands controlling how @value{GDBN} displays
21617 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21622 * Editing:: Command editing
21623 * Command History:: Command history
21624 * Screen Size:: Screen size
21625 * Numbers:: Numbers
21626 * ABI:: Configuring the current ABI
21627 * Auto-loading:: Automatically loading associated files
21628 * Messages/Warnings:: Optional warnings and messages
21629 * Debugging Output:: Optional messages about internal happenings
21630 * Other Misc Settings:: Other Miscellaneous Settings
21638 @value{GDBN} indicates its readiness to read a command by printing a string
21639 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21640 can change the prompt string with the @code{set prompt} command. For
21641 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21642 the prompt in one of the @value{GDBN} sessions so that you can always tell
21643 which one you are talking to.
21645 @emph{Note:} @code{set prompt} does not add a space for you after the
21646 prompt you set. This allows you to set a prompt which ends in a space
21647 or a prompt that does not.
21651 @item set prompt @var{newprompt}
21652 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21654 @kindex show prompt
21656 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21659 Versions of @value{GDBN} that ship with Python scripting enabled have
21660 prompt extensions. The commands for interacting with these extensions
21664 @kindex set extended-prompt
21665 @item set extended-prompt @var{prompt}
21666 Set an extended prompt that allows for substitutions.
21667 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21668 substitution. Any escape sequences specified as part of the prompt
21669 string are replaced with the corresponding strings each time the prompt
21675 set extended-prompt Current working directory: \w (gdb)
21678 Note that when an extended-prompt is set, it takes control of the
21679 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21681 @kindex show extended-prompt
21682 @item show extended-prompt
21683 Prints the extended prompt. Any escape sequences specified as part of
21684 the prompt string with @code{set extended-prompt}, are replaced with the
21685 corresponding strings each time the prompt is displayed.
21689 @section Command Editing
21691 @cindex command line editing
21693 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21694 @sc{gnu} library provides consistent behavior for programs which provide a
21695 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21696 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21697 substitution, and a storage and recall of command history across
21698 debugging sessions.
21700 You may control the behavior of command line editing in @value{GDBN} with the
21701 command @code{set}.
21704 @kindex set editing
21707 @itemx set editing on
21708 Enable command line editing (enabled by default).
21710 @item set editing off
21711 Disable command line editing.
21713 @kindex show editing
21715 Show whether command line editing is enabled.
21718 @ifset SYSTEM_READLINE
21719 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21721 @ifclear SYSTEM_READLINE
21722 @xref{Command Line Editing},
21724 for more details about the Readline
21725 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21726 encouraged to read that chapter.
21728 @node Command History
21729 @section Command History
21730 @cindex command history
21732 @value{GDBN} can keep track of the commands you type during your
21733 debugging sessions, so that you can be certain of precisely what
21734 happened. Use these commands to manage the @value{GDBN} command
21737 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21738 package, to provide the history facility.
21739 @ifset SYSTEM_READLINE
21740 @xref{Using History Interactively, , , history, GNU History Library},
21742 @ifclear SYSTEM_READLINE
21743 @xref{Using History Interactively},
21745 for the detailed description of the History library.
21747 To issue a command to @value{GDBN} without affecting certain aspects of
21748 the state which is seen by users, prefix it with @samp{server }
21749 (@pxref{Server Prefix}). This
21750 means that this command will not affect the command history, nor will it
21751 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21752 pressed on a line by itself.
21754 @cindex @code{server}, command prefix
21755 The server prefix does not affect the recording of values into the value
21756 history; to print a value without recording it into the value history,
21757 use the @code{output} command instead of the @code{print} command.
21759 Here is the description of @value{GDBN} commands related to command
21763 @cindex history substitution
21764 @cindex history file
21765 @kindex set history filename
21766 @cindex @env{GDBHISTFILE}, environment variable
21767 @item set history filename @var{fname}
21768 Set the name of the @value{GDBN} command history file to @var{fname}.
21769 This is the file where @value{GDBN} reads an initial command history
21770 list, and where it writes the command history from this session when it
21771 exits. You can access this list through history expansion or through
21772 the history command editing characters listed below. This file defaults
21773 to the value of the environment variable @code{GDBHISTFILE}, or to
21774 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21777 @cindex save command history
21778 @kindex set history save
21779 @item set history save
21780 @itemx set history save on
21781 Record command history in a file, whose name may be specified with the
21782 @code{set history filename} command. By default, this option is disabled.
21784 @item set history save off
21785 Stop recording command history in a file.
21787 @cindex history size
21788 @kindex set history size
21789 @cindex @env{HISTSIZE}, environment variable
21790 @item set history size @var{size}
21791 @itemx set history size unlimited
21792 Set the number of commands which @value{GDBN} keeps in its history list.
21793 This defaults to the value of the environment variable
21794 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21795 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21796 history list is unlimited.
21799 History expansion assigns special meaning to the character @kbd{!}.
21800 @ifset SYSTEM_READLINE
21801 @xref{Event Designators, , , history, GNU History Library},
21803 @ifclear SYSTEM_READLINE
21804 @xref{Event Designators},
21808 @cindex history expansion, turn on/off
21809 Since @kbd{!} is also the logical not operator in C, history expansion
21810 is off by default. If you decide to enable history expansion with the
21811 @code{set history expansion on} command, you may sometimes need to
21812 follow @kbd{!} (when it is used as logical not, in an expression) with
21813 a space or a tab to prevent it from being expanded. The readline
21814 history facilities do not attempt substitution on the strings
21815 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21817 The commands to control history expansion are:
21820 @item set history expansion on
21821 @itemx set history expansion
21822 @kindex set history expansion
21823 Enable history expansion. History expansion is off by default.
21825 @item set history expansion off
21826 Disable history expansion.
21829 @kindex show history
21831 @itemx show history filename
21832 @itemx show history save
21833 @itemx show history size
21834 @itemx show history expansion
21835 These commands display the state of the @value{GDBN} history parameters.
21836 @code{show history} by itself displays all four states.
21841 @kindex show commands
21842 @cindex show last commands
21843 @cindex display command history
21844 @item show commands
21845 Display the last ten commands in the command history.
21847 @item show commands @var{n}
21848 Print ten commands centered on command number @var{n}.
21850 @item show commands +
21851 Print ten commands just after the commands last printed.
21855 @section Screen Size
21856 @cindex size of screen
21857 @cindex pauses in output
21859 Certain commands to @value{GDBN} may produce large amounts of
21860 information output to the screen. To help you read all of it,
21861 @value{GDBN} pauses and asks you for input at the end of each page of
21862 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21863 to discard the remaining output. Also, the screen width setting
21864 determines when to wrap lines of output. Depending on what is being
21865 printed, @value{GDBN} tries to break the line at a readable place,
21866 rather than simply letting it overflow onto the following line.
21868 Normally @value{GDBN} knows the size of the screen from the terminal
21869 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21870 together with the value of the @code{TERM} environment variable and the
21871 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21872 you can override it with the @code{set height} and @code{set
21879 @kindex show height
21880 @item set height @var{lpp}
21881 @itemx set height unlimited
21883 @itemx set width @var{cpl}
21884 @itemx set width unlimited
21886 These @code{set} commands specify a screen height of @var{lpp} lines and
21887 a screen width of @var{cpl} characters. The associated @code{show}
21888 commands display the current settings.
21890 If you specify a height of either @code{unlimited} or zero lines,
21891 @value{GDBN} does not pause during output no matter how long the
21892 output is. This is useful if output is to a file or to an editor
21895 Likewise, you can specify @samp{set width unlimited} or @samp{set
21896 width 0} to prevent @value{GDBN} from wrapping its output.
21898 @item set pagination on
21899 @itemx set pagination off
21900 @kindex set pagination
21901 Turn the output pagination on or off; the default is on. Turning
21902 pagination off is the alternative to @code{set height unlimited}. Note that
21903 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21904 Options, -batch}) also automatically disables pagination.
21906 @item show pagination
21907 @kindex show pagination
21908 Show the current pagination mode.
21913 @cindex number representation
21914 @cindex entering numbers
21916 You can always enter numbers in octal, decimal, or hexadecimal in
21917 @value{GDBN} by the usual conventions: octal numbers begin with
21918 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21919 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21920 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21921 10; likewise, the default display for numbers---when no particular
21922 format is specified---is base 10. You can change the default base for
21923 both input and output with the commands described below.
21926 @kindex set input-radix
21927 @item set input-radix @var{base}
21928 Set the default base for numeric input. Supported choices
21929 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21930 specified either unambiguously or using the current input radix; for
21934 set input-radix 012
21935 set input-radix 10.
21936 set input-radix 0xa
21940 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21941 leaves the input radix unchanged, no matter what it was, since
21942 @samp{10}, being without any leading or trailing signs of its base, is
21943 interpreted in the current radix. Thus, if the current radix is 16,
21944 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21947 @kindex set output-radix
21948 @item set output-radix @var{base}
21949 Set the default base for numeric display. Supported choices
21950 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21951 specified either unambiguously or using the current input radix.
21953 @kindex show input-radix
21954 @item show input-radix
21955 Display the current default base for numeric input.
21957 @kindex show output-radix
21958 @item show output-radix
21959 Display the current default base for numeric display.
21961 @item set radix @r{[}@var{base}@r{]}
21965 These commands set and show the default base for both input and output
21966 of numbers. @code{set radix} sets the radix of input and output to
21967 the same base; without an argument, it resets the radix back to its
21968 default value of 10.
21973 @section Configuring the Current ABI
21975 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21976 application automatically. However, sometimes you need to override its
21977 conclusions. Use these commands to manage @value{GDBN}'s view of the
21983 @cindex Newlib OS ABI and its influence on the longjmp handling
21985 One @value{GDBN} configuration can debug binaries for multiple operating
21986 system targets, either via remote debugging or native emulation.
21987 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21988 but you can override its conclusion using the @code{set osabi} command.
21989 One example where this is useful is in debugging of binaries which use
21990 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21991 not have the same identifying marks that the standard C library for your
21994 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21995 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21996 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21997 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22001 Show the OS ABI currently in use.
22004 With no argument, show the list of registered available OS ABI's.
22006 @item set osabi @var{abi}
22007 Set the current OS ABI to @var{abi}.
22010 @cindex float promotion
22012 Generally, the way that an argument of type @code{float} is passed to a
22013 function depends on whether the function is prototyped. For a prototyped
22014 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22015 according to the architecture's convention for @code{float}. For unprototyped
22016 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22017 @code{double} and then passed.
22019 Unfortunately, some forms of debug information do not reliably indicate whether
22020 a function is prototyped. If @value{GDBN} calls a function that is not marked
22021 as prototyped, it consults @kbd{set coerce-float-to-double}.
22024 @kindex set coerce-float-to-double
22025 @item set coerce-float-to-double
22026 @itemx set coerce-float-to-double on
22027 Arguments of type @code{float} will be promoted to @code{double} when passed
22028 to an unprototyped function. This is the default setting.
22030 @item set coerce-float-to-double off
22031 Arguments of type @code{float} will be passed directly to unprototyped
22034 @kindex show coerce-float-to-double
22035 @item show coerce-float-to-double
22036 Show the current setting of promoting @code{float} to @code{double}.
22040 @kindex show cp-abi
22041 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22042 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22043 used to build your application. @value{GDBN} only fully supports
22044 programs with a single C@t{++} ABI; if your program contains code using
22045 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22046 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22047 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22048 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22049 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22050 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22055 Show the C@t{++} ABI currently in use.
22058 With no argument, show the list of supported C@t{++} ABI's.
22060 @item set cp-abi @var{abi}
22061 @itemx set cp-abi auto
22062 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22066 @section Automatically loading associated files
22067 @cindex auto-loading
22069 @value{GDBN} sometimes reads files with commands and settings automatically,
22070 without being explicitly told so by the user. We call this feature
22071 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22072 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22073 results or introduce security risks (e.g., if the file comes from untrusted
22076 Note that loading of these associated files (including the local @file{.gdbinit}
22077 file) requires accordingly configured @code{auto-load safe-path}
22078 (@pxref{Auto-loading safe path}).
22080 For these reasons, @value{GDBN} includes commands and options to let you
22081 control when to auto-load files and which files should be auto-loaded.
22084 @anchor{set auto-load off}
22085 @kindex set auto-load off
22086 @item set auto-load off
22087 Globally disable loading of all auto-loaded files.
22088 You may want to use this command with the @samp{-iex} option
22089 (@pxref{Option -init-eval-command}) such as:
22091 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22094 Be aware that system init file (@pxref{System-wide configuration})
22095 and init files from your home directory (@pxref{Home Directory Init File})
22096 still get read (as they come from generally trusted directories).
22097 To prevent @value{GDBN} from auto-loading even those init files, use the
22098 @option{-nx} option (@pxref{Mode Options}), in addition to
22099 @code{set auto-load no}.
22101 @anchor{show auto-load}
22102 @kindex show auto-load
22103 @item show auto-load
22104 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22108 (gdb) show auto-load
22109 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22110 libthread-db: Auto-loading of inferior specific libthread_db is on.
22111 local-gdbinit: Auto-loading of .gdbinit script from current directory
22113 python-scripts: Auto-loading of Python scripts is on.
22114 safe-path: List of directories from which it is safe to auto-load files
22115 is $debugdir:$datadir/auto-load.
22116 scripts-directory: List of directories from which to load auto-loaded scripts
22117 is $debugdir:$datadir/auto-load.
22120 @anchor{info auto-load}
22121 @kindex info auto-load
22122 @item info auto-load
22123 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22127 (gdb) info auto-load
22130 Yes /home/user/gdb/gdb-gdb.gdb
22131 libthread-db: No auto-loaded libthread-db.
22132 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22136 Yes /home/user/gdb/gdb-gdb.py
22140 These are various kinds of files @value{GDBN} can automatically load:
22144 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22146 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22148 @xref{dotdebug_gdb_scripts section},
22149 controlled by @ref{set auto-load python-scripts}.
22151 @xref{Init File in the Current Directory},
22152 controlled by @ref{set auto-load local-gdbinit}.
22154 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22157 These are @value{GDBN} control commands for the auto-loading:
22159 @multitable @columnfractions .5 .5
22160 @item @xref{set auto-load off}.
22161 @tab Disable auto-loading globally.
22162 @item @xref{show auto-load}.
22163 @tab Show setting of all kinds of files.
22164 @item @xref{info auto-load}.
22165 @tab Show state of all kinds of files.
22166 @item @xref{set auto-load gdb-scripts}.
22167 @tab Control for @value{GDBN} command scripts.
22168 @item @xref{show auto-load gdb-scripts}.
22169 @tab Show setting of @value{GDBN} command scripts.
22170 @item @xref{info auto-load gdb-scripts}.
22171 @tab Show state of @value{GDBN} command scripts.
22172 @item @xref{set auto-load python-scripts}.
22173 @tab Control for @value{GDBN} Python scripts.
22174 @item @xref{show auto-load python-scripts}.
22175 @tab Show setting of @value{GDBN} Python scripts.
22176 @item @xref{info auto-load python-scripts}.
22177 @tab Show state of @value{GDBN} Python scripts.
22178 @item @xref{set auto-load scripts-directory}.
22179 @tab Control for @value{GDBN} auto-loaded scripts location.
22180 @item @xref{show auto-load scripts-directory}.
22181 @tab Show @value{GDBN} auto-loaded scripts location.
22182 @item @xref{set auto-load local-gdbinit}.
22183 @tab Control for init file in the current directory.
22184 @item @xref{show auto-load local-gdbinit}.
22185 @tab Show setting of init file in the current directory.
22186 @item @xref{info auto-load local-gdbinit}.
22187 @tab Show state of init file in the current directory.
22188 @item @xref{set auto-load libthread-db}.
22189 @tab Control for thread debugging library.
22190 @item @xref{show auto-load libthread-db}.
22191 @tab Show setting of thread debugging library.
22192 @item @xref{info auto-load libthread-db}.
22193 @tab Show state of thread debugging library.
22194 @item @xref{set auto-load safe-path}.
22195 @tab Control directories trusted for automatic loading.
22196 @item @xref{show auto-load safe-path}.
22197 @tab Show directories trusted for automatic loading.
22198 @item @xref{add-auto-load-safe-path}.
22199 @tab Add directory trusted for automatic loading.
22203 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22204 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22205 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22206 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22207 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22208 @xref{Python Auto-loading}.
22211 @node Init File in the Current Directory
22212 @subsection Automatically loading init file in the current directory
22213 @cindex auto-loading init file in the current directory
22215 By default, @value{GDBN} reads and executes the canned sequences of commands
22216 from init file (if any) in the current working directory,
22217 see @ref{Init File in the Current Directory during Startup}.
22219 Note that loading of this local @file{.gdbinit} file also requires accordingly
22220 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22223 @anchor{set auto-load local-gdbinit}
22224 @kindex set auto-load local-gdbinit
22225 @item set auto-load local-gdbinit [on|off]
22226 Enable or disable the auto-loading of canned sequences of commands
22227 (@pxref{Sequences}) found in init file in the current directory.
22229 @anchor{show auto-load local-gdbinit}
22230 @kindex show auto-load local-gdbinit
22231 @item show auto-load local-gdbinit
22232 Show whether auto-loading of canned sequences of commands from init file in the
22233 current directory is enabled or disabled.
22235 @anchor{info auto-load local-gdbinit}
22236 @kindex info auto-load local-gdbinit
22237 @item info auto-load local-gdbinit
22238 Print whether canned sequences of commands from init file in the
22239 current directory have been auto-loaded.
22242 @node libthread_db.so.1 file
22243 @subsection Automatically loading thread debugging library
22244 @cindex auto-loading libthread_db.so.1
22246 This feature is currently present only on @sc{gnu}/Linux native hosts.
22248 @value{GDBN} reads in some cases thread debugging library from places specific
22249 to the inferior (@pxref{set libthread-db-search-path}).
22251 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22252 without checking this @samp{set auto-load libthread-db} switch as system
22253 libraries have to be trusted in general. In all other cases of
22254 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22255 auto-load libthread-db} is enabled before trying to open such thread debugging
22258 Note that loading of this debugging library also requires accordingly configured
22259 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22262 @anchor{set auto-load libthread-db}
22263 @kindex set auto-load libthread-db
22264 @item set auto-load libthread-db [on|off]
22265 Enable or disable the auto-loading of inferior specific thread debugging library.
22267 @anchor{show auto-load libthread-db}
22268 @kindex show auto-load libthread-db
22269 @item show auto-load libthread-db
22270 Show whether auto-loading of inferior specific thread debugging library is
22271 enabled or disabled.
22273 @anchor{info auto-load libthread-db}
22274 @kindex info auto-load libthread-db
22275 @item info auto-load libthread-db
22276 Print the list of all loaded inferior specific thread debugging libraries and
22277 for each such library print list of inferior @var{pid}s using it.
22280 @node objfile-gdb.gdb file
22281 @subsection The @file{@var{objfile}-gdb.gdb} file
22282 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22284 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22285 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22286 auto-load gdb-scripts} is set to @samp{on}.
22288 Note that loading of this script file also requires accordingly configured
22289 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22291 For more background refer to the similar Python scripts auto-loading
22292 description (@pxref{objfile-gdb.py file}).
22295 @anchor{set auto-load gdb-scripts}
22296 @kindex set auto-load gdb-scripts
22297 @item set auto-load gdb-scripts [on|off]
22298 Enable or disable the auto-loading of canned sequences of commands scripts.
22300 @anchor{show auto-load gdb-scripts}
22301 @kindex show auto-load gdb-scripts
22302 @item show auto-load gdb-scripts
22303 Show whether auto-loading of canned sequences of commands scripts is enabled or
22306 @anchor{info auto-load gdb-scripts}
22307 @kindex info auto-load gdb-scripts
22308 @cindex print list of auto-loaded canned sequences of commands scripts
22309 @item info auto-load gdb-scripts [@var{regexp}]
22310 Print the list of all canned sequences of commands scripts that @value{GDBN}
22314 If @var{regexp} is supplied only canned sequences of commands scripts with
22315 matching names are printed.
22317 @node Auto-loading safe path
22318 @subsection Security restriction for auto-loading
22319 @cindex auto-loading safe-path
22321 As the files of inferior can come from untrusted source (such as submitted by
22322 an application user) @value{GDBN} does not always load any files automatically.
22323 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22324 directories trusted for loading files not explicitly requested by user.
22325 Each directory can also be a shell wildcard pattern.
22327 If the path is not set properly you will see a warning and the file will not
22332 Reading symbols from /home/user/gdb/gdb...done.
22333 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22334 declined by your `auto-load safe-path' set
22335 to "$debugdir:$datadir/auto-load".
22336 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22337 declined by your `auto-load safe-path' set
22338 to "$debugdir:$datadir/auto-load".
22342 To instruct @value{GDBN} to go ahead and use the init files anyway,
22343 invoke @value{GDBN} like this:
22346 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22349 The list of trusted directories is controlled by the following commands:
22352 @anchor{set auto-load safe-path}
22353 @kindex set auto-load safe-path
22354 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22355 Set the list of directories (and their subdirectories) trusted for automatic
22356 loading and execution of scripts. You can also enter a specific trusted file.
22357 Each directory can also be a shell wildcard pattern; wildcards do not match
22358 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22359 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22360 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22361 its default value as specified during @value{GDBN} compilation.
22363 The list of directories uses path separator (@samp{:} on GNU and Unix
22364 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22365 to the @env{PATH} environment variable.
22367 @anchor{show auto-load safe-path}
22368 @kindex show auto-load safe-path
22369 @item show auto-load safe-path
22370 Show the list of directories trusted for automatic loading and execution of
22373 @anchor{add-auto-load-safe-path}
22374 @kindex add-auto-load-safe-path
22375 @item add-auto-load-safe-path
22376 Add an entry (or list of entries) the list of directories trusted for automatic
22377 loading and execution of scripts. Multiple entries may be delimited by the
22378 host platform path separator in use.
22381 This variable defaults to what @code{--with-auto-load-dir} has been configured
22382 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22383 substitution applies the same as for @ref{set auto-load scripts-directory}.
22384 The default @code{set auto-load safe-path} value can be also overriden by
22385 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22387 Setting this variable to @file{/} disables this security protection,
22388 corresponding @value{GDBN} configuration option is
22389 @option{--without-auto-load-safe-path}.
22390 This variable is supposed to be set to the system directories writable by the
22391 system superuser only. Users can add their source directories in init files in
22392 their home directories (@pxref{Home Directory Init File}). See also deprecated
22393 init file in the current directory
22394 (@pxref{Init File in the Current Directory during Startup}).
22396 To force @value{GDBN} to load the files it declined to load in the previous
22397 example, you could use one of the following ways:
22400 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22401 Specify this trusted directory (or a file) as additional component of the list.
22402 You have to specify also any existing directories displayed by
22403 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22405 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22406 Specify this directory as in the previous case but just for a single
22407 @value{GDBN} session.
22409 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22410 Disable auto-loading safety for a single @value{GDBN} session.
22411 This assumes all the files you debug during this @value{GDBN} session will come
22412 from trusted sources.
22414 @item @kbd{./configure --without-auto-load-safe-path}
22415 During compilation of @value{GDBN} you may disable any auto-loading safety.
22416 This assumes all the files you will ever debug with this @value{GDBN} come from
22420 On the other hand you can also explicitly forbid automatic files loading which
22421 also suppresses any such warning messages:
22424 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22425 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22427 @item @file{~/.gdbinit}: @samp{set auto-load no}
22428 Disable auto-loading globally for the user
22429 (@pxref{Home Directory Init File}). While it is improbable, you could also
22430 use system init file instead (@pxref{System-wide configuration}).
22433 This setting applies to the file names as entered by user. If no entry matches
22434 @value{GDBN} tries as a last resort to also resolve all the file names into
22435 their canonical form (typically resolving symbolic links) and compare the
22436 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22437 own before starting the comparison so a canonical form of directories is
22438 recommended to be entered.
22440 @node Auto-loading verbose mode
22441 @subsection Displaying files tried for auto-load
22442 @cindex auto-loading verbose mode
22444 For better visibility of all the file locations where you can place scripts to
22445 be auto-loaded with inferior --- or to protect yourself against accidental
22446 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22447 all the files attempted to be loaded. Both existing and non-existing files may
22450 For example the list of directories from which it is safe to auto-load files
22451 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22452 may not be too obvious while setting it up.
22455 (gdb) set debug auto-load on
22456 (gdb) file ~/src/t/true
22457 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22458 for objfile "/tmp/true".
22459 auto-load: Updating directories of "/usr:/opt".
22460 auto-load: Using directory "/usr".
22461 auto-load: Using directory "/opt".
22462 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22463 by your `auto-load safe-path' set to "/usr:/opt".
22467 @anchor{set debug auto-load}
22468 @kindex set debug auto-load
22469 @item set debug auto-load [on|off]
22470 Set whether to print the filenames attempted to be auto-loaded.
22472 @anchor{show debug auto-load}
22473 @kindex show debug auto-load
22474 @item show debug auto-load
22475 Show whether printing of the filenames attempted to be auto-loaded is turned
22479 @node Messages/Warnings
22480 @section Optional Warnings and Messages
22482 @cindex verbose operation
22483 @cindex optional warnings
22484 By default, @value{GDBN} is silent about its inner workings. If you are
22485 running on a slow machine, you may want to use the @code{set verbose}
22486 command. This makes @value{GDBN} tell you when it does a lengthy
22487 internal operation, so you will not think it has crashed.
22489 Currently, the messages controlled by @code{set verbose} are those
22490 which announce that the symbol table for a source file is being read;
22491 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22494 @kindex set verbose
22495 @item set verbose on
22496 Enables @value{GDBN} output of certain informational messages.
22498 @item set verbose off
22499 Disables @value{GDBN} output of certain informational messages.
22501 @kindex show verbose
22503 Displays whether @code{set verbose} is on or off.
22506 By default, if @value{GDBN} encounters bugs in the symbol table of an
22507 object file, it is silent; but if you are debugging a compiler, you may
22508 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22513 @kindex set complaints
22514 @item set complaints @var{limit}
22515 Permits @value{GDBN} to output @var{limit} complaints about each type of
22516 unusual symbols before becoming silent about the problem. Set
22517 @var{limit} to zero to suppress all complaints; set it to a large number
22518 to prevent complaints from being suppressed.
22520 @kindex show complaints
22521 @item show complaints
22522 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22526 @anchor{confirmation requests}
22527 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22528 lot of stupid questions to confirm certain commands. For example, if
22529 you try to run a program which is already running:
22533 The program being debugged has been started already.
22534 Start it from the beginning? (y or n)
22537 If you are willing to unflinchingly face the consequences of your own
22538 commands, you can disable this ``feature'':
22542 @kindex set confirm
22544 @cindex confirmation
22545 @cindex stupid questions
22546 @item set confirm off
22547 Disables confirmation requests. Note that running @value{GDBN} with
22548 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22549 automatically disables confirmation requests.
22551 @item set confirm on
22552 Enables confirmation requests (the default).
22554 @kindex show confirm
22556 Displays state of confirmation requests.
22560 @cindex command tracing
22561 If you need to debug user-defined commands or sourced files you may find it
22562 useful to enable @dfn{command tracing}. In this mode each command will be
22563 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22564 quantity denoting the call depth of each command.
22567 @kindex set trace-commands
22568 @cindex command scripts, debugging
22569 @item set trace-commands on
22570 Enable command tracing.
22571 @item set trace-commands off
22572 Disable command tracing.
22573 @item show trace-commands
22574 Display the current state of command tracing.
22577 @node Debugging Output
22578 @section Optional Messages about Internal Happenings
22579 @cindex optional debugging messages
22581 @value{GDBN} has commands that enable optional debugging messages from
22582 various @value{GDBN} subsystems; normally these commands are of
22583 interest to @value{GDBN} maintainers, or when reporting a bug. This
22584 section documents those commands.
22587 @kindex set exec-done-display
22588 @item set exec-done-display
22589 Turns on or off the notification of asynchronous commands'
22590 completion. When on, @value{GDBN} will print a message when an
22591 asynchronous command finishes its execution. The default is off.
22592 @kindex show exec-done-display
22593 @item show exec-done-display
22594 Displays the current setting of asynchronous command completion
22597 @cindex ARM AArch64
22598 @item set debug aarch64
22599 Turns on or off display of debugging messages related to ARM AArch64.
22600 The default is off.
22602 @item show debug aarch64
22603 Displays the current state of displaying debugging messages related to
22605 @cindex gdbarch debugging info
22606 @cindex architecture debugging info
22607 @item set debug arch
22608 Turns on or off display of gdbarch debugging info. The default is off
22609 @item show debug arch
22610 Displays the current state of displaying gdbarch debugging info.
22611 @item set debug aix-solib
22612 @cindex AIX shared library debugging
22613 Control display of debugging messages from the AIX shared library
22614 support module. The default is off.
22615 @item show debug aix-thread
22616 Show the current state of displaying AIX shared library debugging messages.
22617 @item set debug aix-thread
22618 @cindex AIX threads
22619 Display debugging messages about inner workings of the AIX thread
22621 @item show debug aix-thread
22622 Show the current state of AIX thread debugging info display.
22623 @item set debug check-physname
22625 Check the results of the ``physname'' computation. When reading DWARF
22626 debugging information for C@t{++}, @value{GDBN} attempts to compute
22627 each entity's name. @value{GDBN} can do this computation in two
22628 different ways, depending on exactly what information is present.
22629 When enabled, this setting causes @value{GDBN} to compute the names
22630 both ways and display any discrepancies.
22631 @item show debug check-physname
22632 Show the current state of ``physname'' checking.
22633 @item set debug coff-pe-read
22634 @cindex COFF/PE exported symbols
22635 Control display of debugging messages related to reading of COFF/PE
22636 exported symbols. The default is off.
22637 @item show debug coff-pe-read
22638 Displays the current state of displaying debugging messages related to
22639 reading of COFF/PE exported symbols.
22640 @item set debug dwarf2-die
22641 @cindex DWARF2 DIEs
22642 Dump DWARF2 DIEs after they are read in.
22643 The value is the number of nesting levels to print.
22644 A value of zero turns off the display.
22645 @item show debug dwarf2-die
22646 Show the current state of DWARF2 DIE debugging.
22647 @item set debug dwarf2-read
22648 @cindex DWARF2 Reading
22649 Turns on or off display of debugging messages related to reading
22650 DWARF debug info. The default is 0 (off).
22651 A value of 1 provides basic information.
22652 A value greater than 1 provides more verbose information.
22653 @item show debug dwarf2-read
22654 Show the current state of DWARF2 reader debugging.
22655 @item set debug displaced
22656 @cindex displaced stepping debugging info
22657 Turns on or off display of @value{GDBN} debugging info for the
22658 displaced stepping support. The default is off.
22659 @item show debug displaced
22660 Displays the current state of displaying @value{GDBN} debugging info
22661 related to displaced stepping.
22662 @item set debug event
22663 @cindex event debugging info
22664 Turns on or off display of @value{GDBN} event debugging info. The
22666 @item show debug event
22667 Displays the current state of displaying @value{GDBN} event debugging
22669 @item set debug expression
22670 @cindex expression debugging info
22671 Turns on or off display of debugging info about @value{GDBN}
22672 expression parsing. The default is off.
22673 @item show debug expression
22674 Displays the current state of displaying debugging info about
22675 @value{GDBN} expression parsing.
22676 @item set debug frame
22677 @cindex frame debugging info
22678 Turns on or off display of @value{GDBN} frame debugging info. The
22680 @item show debug frame
22681 Displays the current state of displaying @value{GDBN} frame debugging
22683 @item set debug gnu-nat
22684 @cindex @sc{gnu}/Hurd debug messages
22685 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22686 @item show debug gnu-nat
22687 Show the current state of @sc{gnu}/Hurd debugging messages.
22688 @item set debug infrun
22689 @cindex inferior debugging info
22690 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22691 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22692 for implementing operations such as single-stepping the inferior.
22693 @item show debug infrun
22694 Displays the current state of @value{GDBN} inferior debugging.
22695 @item set debug jit
22696 @cindex just-in-time compilation, debugging messages
22697 Turns on or off debugging messages from JIT debug support.
22698 @item show debug jit
22699 Displays the current state of @value{GDBN} JIT debugging.
22700 @item set debug lin-lwp
22701 @cindex @sc{gnu}/Linux LWP debug messages
22702 @cindex Linux lightweight processes
22703 Turns on or off debugging messages from the Linux LWP debug support.
22704 @item show debug lin-lwp
22705 Show the current state of Linux LWP debugging messages.
22706 @item set debug mach-o
22707 @cindex Mach-O symbols processing
22708 Control display of debugging messages related to Mach-O symbols
22709 processing. The default is off.
22710 @item show debug mach-o
22711 Displays the current state of displaying debugging messages related to
22712 reading of COFF/PE exported symbols.
22713 @item set debug notification
22714 @cindex remote async notification debugging info
22715 Turns on or off debugging messages about remote async notification.
22716 The default is off.
22717 @item show debug notification
22718 Displays the current state of remote async notification debugging messages.
22719 @item set debug observer
22720 @cindex observer debugging info
22721 Turns on or off display of @value{GDBN} observer debugging. This
22722 includes info such as the notification of observable events.
22723 @item show debug observer
22724 Displays the current state of observer debugging.
22725 @item set debug overload
22726 @cindex C@t{++} overload debugging info
22727 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22728 info. This includes info such as ranking of functions, etc. The default
22730 @item show debug overload
22731 Displays the current state of displaying @value{GDBN} C@t{++} overload
22733 @cindex expression parser, debugging info
22734 @cindex debug expression parser
22735 @item set debug parser
22736 Turns on or off the display of expression parser debugging output.
22737 Internally, this sets the @code{yydebug} variable in the expression
22738 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22739 details. The default is off.
22740 @item show debug parser
22741 Show the current state of expression parser debugging.
22742 @cindex packets, reporting on stdout
22743 @cindex serial connections, debugging
22744 @cindex debug remote protocol
22745 @cindex remote protocol debugging
22746 @cindex display remote packets
22747 @item set debug remote
22748 Turns on or off display of reports on all packets sent back and forth across
22749 the serial line to the remote machine. The info is printed on the
22750 @value{GDBN} standard output stream. The default is off.
22751 @item show debug remote
22752 Displays the state of display of remote packets.
22753 @item set debug serial
22754 Turns on or off display of @value{GDBN} serial debugging info. The
22756 @item show debug serial
22757 Displays the current state of displaying @value{GDBN} serial debugging
22759 @item set debug solib-frv
22760 @cindex FR-V shared-library debugging
22761 Turns on or off debugging messages for FR-V shared-library code.
22762 @item show debug solib-frv
22763 Display the current state of FR-V shared-library code debugging
22765 @item set debug symfile
22766 @cindex symbol file functions
22767 Turns on or off display of debugging messages related to symbol file functions.
22768 The default is off. @xref{Files}.
22769 @item show debug symfile
22770 Show the current state of symbol file debugging messages.
22771 @item set debug symtab-create
22772 @cindex symbol table creation
22773 Turns on or off display of debugging messages related to symbol table creation.
22774 The default is 0 (off).
22775 A value of 1 provides basic information.
22776 A value greater than 1 provides more verbose information.
22777 @item show debug symtab-create
22778 Show the current state of symbol table creation debugging.
22779 @item set debug target
22780 @cindex target debugging info
22781 Turns on or off display of @value{GDBN} target debugging info. This info
22782 includes what is going on at the target level of GDB, as it happens. The
22783 default is 0. Set it to 1 to track events, and to 2 to also track the
22784 value of large memory transfers. Changes to this flag do not take effect
22785 until the next time you connect to a target or use the @code{run} command.
22786 @item show debug target
22787 Displays the current state of displaying @value{GDBN} target debugging
22789 @item set debug timestamp
22790 @cindex timestampping debugging info
22791 Turns on or off display of timestamps with @value{GDBN} debugging info.
22792 When enabled, seconds and microseconds are displayed before each debugging
22794 @item show debug timestamp
22795 Displays the current state of displaying timestamps with @value{GDBN}
22797 @item set debugvarobj
22798 @cindex variable object debugging info
22799 Turns on or off display of @value{GDBN} variable object debugging
22800 info. The default is off.
22801 @item show debugvarobj
22802 Displays the current state of displaying @value{GDBN} variable object
22804 @item set debug xml
22805 @cindex XML parser debugging
22806 Turns on or off debugging messages for built-in XML parsers.
22807 @item show debug xml
22808 Displays the current state of XML debugging messages.
22811 @node Other Misc Settings
22812 @section Other Miscellaneous Settings
22813 @cindex miscellaneous settings
22816 @kindex set interactive-mode
22817 @item set interactive-mode
22818 If @code{on}, forces @value{GDBN} to assume that GDB was started
22819 in a terminal. In practice, this means that @value{GDBN} should wait
22820 for the user to answer queries generated by commands entered at
22821 the command prompt. If @code{off}, forces @value{GDBN} to operate
22822 in the opposite mode, and it uses the default answers to all queries.
22823 If @code{auto} (the default), @value{GDBN} tries to determine whether
22824 its standard input is a terminal, and works in interactive-mode if it
22825 is, non-interactively otherwise.
22827 In the vast majority of cases, the debugger should be able to guess
22828 correctly which mode should be used. But this setting can be useful
22829 in certain specific cases, such as running a MinGW @value{GDBN}
22830 inside a cygwin window.
22832 @kindex show interactive-mode
22833 @item show interactive-mode
22834 Displays whether the debugger is operating in interactive mode or not.
22837 @node Extending GDB
22838 @chapter Extending @value{GDBN}
22839 @cindex extending GDB
22841 @value{GDBN} provides three mechanisms for extension. The first is based
22842 on composition of @value{GDBN} commands, the second is based on the
22843 Python scripting language, and the third is for defining new aliases of
22846 To facilitate the use of the first two extensions, @value{GDBN} is capable
22847 of evaluating the contents of a file. When doing so, @value{GDBN}
22848 can recognize which scripting language is being used by looking at
22849 the filename extension. Files with an unrecognized filename extension
22850 are always treated as a @value{GDBN} Command Files.
22851 @xref{Command Files,, Command files}.
22853 You can control how @value{GDBN} evaluates these files with the following
22857 @kindex set script-extension
22858 @kindex show script-extension
22859 @item set script-extension off
22860 All scripts are always evaluated as @value{GDBN} Command Files.
22862 @item set script-extension soft
22863 The debugger determines the scripting language based on filename
22864 extension. If this scripting language is supported, @value{GDBN}
22865 evaluates the script using that language. Otherwise, it evaluates
22866 the file as a @value{GDBN} Command File.
22868 @item set script-extension strict
22869 The debugger determines the scripting language based on filename
22870 extension, and evaluates the script using that language. If the
22871 language is not supported, then the evaluation fails.
22873 @item show script-extension
22874 Display the current value of the @code{script-extension} option.
22879 * Sequences:: Canned Sequences of Commands
22880 * Python:: Scripting @value{GDBN} using Python
22881 * Aliases:: Creating new spellings of existing commands
22885 @section Canned Sequences of Commands
22887 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22888 Command Lists}), @value{GDBN} provides two ways to store sequences of
22889 commands for execution as a unit: user-defined commands and command
22893 * Define:: How to define your own commands
22894 * Hooks:: Hooks for user-defined commands
22895 * Command Files:: How to write scripts of commands to be stored in a file
22896 * Output:: Commands for controlled output
22900 @subsection User-defined Commands
22902 @cindex user-defined command
22903 @cindex arguments, to user-defined commands
22904 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22905 which you assign a new name as a command. This is done with the
22906 @code{define} command. User commands may accept up to 10 arguments
22907 separated by whitespace. Arguments are accessed within the user command
22908 via @code{$arg0@dots{}$arg9}. A trivial example:
22912 print $arg0 + $arg1 + $arg2
22917 To execute the command use:
22924 This defines the command @code{adder}, which prints the sum of
22925 its three arguments. Note the arguments are text substitutions, so they may
22926 reference variables, use complex expressions, or even perform inferior
22929 @cindex argument count in user-defined commands
22930 @cindex how many arguments (user-defined commands)
22931 In addition, @code{$argc} may be used to find out how many arguments have
22932 been passed. This expands to a number in the range 0@dots{}10.
22937 print $arg0 + $arg1
22940 print $arg0 + $arg1 + $arg2
22948 @item define @var{commandname}
22949 Define a command named @var{commandname}. If there is already a command
22950 by that name, you are asked to confirm that you want to redefine it.
22951 @var{commandname} may be a bare command name consisting of letters,
22952 numbers, dashes, and underscores. It may also start with any predefined
22953 prefix command. For example, @samp{define target my-target} creates
22954 a user-defined @samp{target my-target} command.
22956 The definition of the command is made up of other @value{GDBN} command lines,
22957 which are given following the @code{define} command. The end of these
22958 commands is marked by a line containing @code{end}.
22961 @kindex end@r{ (user-defined commands)}
22962 @item document @var{commandname}
22963 Document the user-defined command @var{commandname}, so that it can be
22964 accessed by @code{help}. The command @var{commandname} must already be
22965 defined. This command reads lines of documentation just as @code{define}
22966 reads the lines of the command definition, ending with @code{end}.
22967 After the @code{document} command is finished, @code{help} on command
22968 @var{commandname} displays the documentation you have written.
22970 You may use the @code{document} command again to change the
22971 documentation of a command. Redefining the command with @code{define}
22972 does not change the documentation.
22974 @kindex dont-repeat
22975 @cindex don't repeat command
22977 Used inside a user-defined command, this tells @value{GDBN} that this
22978 command should not be repeated when the user hits @key{RET}
22979 (@pxref{Command Syntax, repeat last command}).
22981 @kindex help user-defined
22982 @item help user-defined
22983 List all user-defined commands and all python commands defined in class
22984 COMAND_USER. The first line of the documentation or docstring is
22989 @itemx show user @var{commandname}
22990 Display the @value{GDBN} commands used to define @var{commandname} (but
22991 not its documentation). If no @var{commandname} is given, display the
22992 definitions for all user-defined commands.
22993 This does not work for user-defined python commands.
22995 @cindex infinite recursion in user-defined commands
22996 @kindex show max-user-call-depth
22997 @kindex set max-user-call-depth
22998 @item show max-user-call-depth
22999 @itemx set max-user-call-depth
23000 The value of @code{max-user-call-depth} controls how many recursion
23001 levels are allowed in user-defined commands before @value{GDBN} suspects an
23002 infinite recursion and aborts the command.
23003 This does not apply to user-defined python commands.
23006 In addition to the above commands, user-defined commands frequently
23007 use control flow commands, described in @ref{Command Files}.
23009 When user-defined commands are executed, the
23010 commands of the definition are not printed. An error in any command
23011 stops execution of the user-defined command.
23013 If used interactively, commands that would ask for confirmation proceed
23014 without asking when used inside a user-defined command. Many @value{GDBN}
23015 commands that normally print messages to say what they are doing omit the
23016 messages when used in a user-defined command.
23019 @subsection User-defined Command Hooks
23020 @cindex command hooks
23021 @cindex hooks, for commands
23022 @cindex hooks, pre-command
23025 You may define @dfn{hooks}, which are a special kind of user-defined
23026 command. Whenever you run the command @samp{foo}, if the user-defined
23027 command @samp{hook-foo} exists, it is executed (with no arguments)
23028 before that command.
23030 @cindex hooks, post-command
23032 A hook may also be defined which is run after the command you executed.
23033 Whenever you run the command @samp{foo}, if the user-defined command
23034 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23035 that command. Post-execution hooks may exist simultaneously with
23036 pre-execution hooks, for the same command.
23038 It is valid for a hook to call the command which it hooks. If this
23039 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23041 @c It would be nice if hookpost could be passed a parameter indicating
23042 @c if the command it hooks executed properly or not. FIXME!
23044 @kindex stop@r{, a pseudo-command}
23045 In addition, a pseudo-command, @samp{stop} exists. Defining
23046 (@samp{hook-stop}) makes the associated commands execute every time
23047 execution stops in your program: before breakpoint commands are run,
23048 displays are printed, or the stack frame is printed.
23050 For example, to ignore @code{SIGALRM} signals while
23051 single-stepping, but treat them normally during normal execution,
23056 handle SIGALRM nopass
23060 handle SIGALRM pass
23063 define hook-continue
23064 handle SIGALRM pass
23068 As a further example, to hook at the beginning and end of the @code{echo}
23069 command, and to add extra text to the beginning and end of the message,
23077 define hookpost-echo
23081 (@value{GDBP}) echo Hello World
23082 <<<---Hello World--->>>
23087 You can define a hook for any single-word command in @value{GDBN}, but
23088 not for command aliases; you should define a hook for the basic command
23089 name, e.g.@: @code{backtrace} rather than @code{bt}.
23090 @c FIXME! So how does Joe User discover whether a command is an alias
23092 You can hook a multi-word command by adding @code{hook-} or
23093 @code{hookpost-} to the last word of the command, e.g.@:
23094 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23096 If an error occurs during the execution of your hook, execution of
23097 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23098 (before the command that you actually typed had a chance to run).
23100 If you try to define a hook which does not match any known command, you
23101 get a warning from the @code{define} command.
23103 @node Command Files
23104 @subsection Command Files
23106 @cindex command files
23107 @cindex scripting commands
23108 A command file for @value{GDBN} is a text file made of lines that are
23109 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23110 also be included. An empty line in a command file does nothing; it
23111 does not mean to repeat the last command, as it would from the
23114 You can request the execution of a command file with the @code{source}
23115 command. Note that the @code{source} command is also used to evaluate
23116 scripts that are not Command Files. The exact behavior can be configured
23117 using the @code{script-extension} setting.
23118 @xref{Extending GDB,, Extending GDB}.
23122 @cindex execute commands from a file
23123 @item source [-s] [-v] @var{filename}
23124 Execute the command file @var{filename}.
23127 The lines in a command file are generally executed sequentially,
23128 unless the order of execution is changed by one of the
23129 @emph{flow-control commands} described below. The commands are not
23130 printed as they are executed. An error in any command terminates
23131 execution of the command file and control is returned to the console.
23133 @value{GDBN} first searches for @var{filename} in the current directory.
23134 If the file is not found there, and @var{filename} does not specify a
23135 directory, then @value{GDBN} also looks for the file on the source search path
23136 (specified with the @samp{directory} command);
23137 except that @file{$cdir} is not searched because the compilation directory
23138 is not relevant to scripts.
23140 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23141 on the search path even if @var{filename} specifies a directory.
23142 The search is done by appending @var{filename} to each element of the
23143 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23144 and the search path contains @file{/home/user} then @value{GDBN} will
23145 look for the script @file{/home/user/mylib/myscript}.
23146 The search is also done if @var{filename} is an absolute path.
23147 For example, if @var{filename} is @file{/tmp/myscript} and
23148 the search path contains @file{/home/user} then @value{GDBN} will
23149 look for the script @file{/home/user/tmp/myscript}.
23150 For DOS-like systems, if @var{filename} contains a drive specification,
23151 it is stripped before concatenation. For example, if @var{filename} is
23152 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23153 will look for the script @file{c:/tmp/myscript}.
23155 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23156 each command as it is executed. The option must be given before
23157 @var{filename}, and is interpreted as part of the filename anywhere else.
23159 Commands that would ask for confirmation if used interactively proceed
23160 without asking when used in a command file. Many @value{GDBN} commands that
23161 normally print messages to say what they are doing omit the messages
23162 when called from command files.
23164 @value{GDBN} also accepts command input from standard input. In this
23165 mode, normal output goes to standard output and error output goes to
23166 standard error. Errors in a command file supplied on standard input do
23167 not terminate execution of the command file---execution continues with
23171 gdb < cmds > log 2>&1
23174 (The syntax above will vary depending on the shell used.) This example
23175 will execute commands from the file @file{cmds}. All output and errors
23176 would be directed to @file{log}.
23178 Since commands stored on command files tend to be more general than
23179 commands typed interactively, they frequently need to deal with
23180 complicated situations, such as different or unexpected values of
23181 variables and symbols, changes in how the program being debugged is
23182 built, etc. @value{GDBN} provides a set of flow-control commands to
23183 deal with these complexities. Using these commands, you can write
23184 complex scripts that loop over data structures, execute commands
23185 conditionally, etc.
23192 This command allows to include in your script conditionally executed
23193 commands. The @code{if} command takes a single argument, which is an
23194 expression to evaluate. It is followed by a series of commands that
23195 are executed only if the expression is true (its value is nonzero).
23196 There can then optionally be an @code{else} line, followed by a series
23197 of commands that are only executed if the expression was false. The
23198 end of the list is marked by a line containing @code{end}.
23202 This command allows to write loops. Its syntax is similar to
23203 @code{if}: the command takes a single argument, which is an expression
23204 to evaluate, and must be followed by the commands to execute, one per
23205 line, terminated by an @code{end}. These commands are called the
23206 @dfn{body} of the loop. The commands in the body of @code{while} are
23207 executed repeatedly as long as the expression evaluates to true.
23211 This command exits the @code{while} loop in whose body it is included.
23212 Execution of the script continues after that @code{while}s @code{end}
23215 @kindex loop_continue
23216 @item loop_continue
23217 This command skips the execution of the rest of the body of commands
23218 in the @code{while} loop in whose body it is included. Execution
23219 branches to the beginning of the @code{while} loop, where it evaluates
23220 the controlling expression.
23222 @kindex end@r{ (if/else/while commands)}
23224 Terminate the block of commands that are the body of @code{if},
23225 @code{else}, or @code{while} flow-control commands.
23230 @subsection Commands for Controlled Output
23232 During the execution of a command file or a user-defined command, normal
23233 @value{GDBN} output is suppressed; the only output that appears is what is
23234 explicitly printed by the commands in the definition. This section
23235 describes three commands useful for generating exactly the output you
23240 @item echo @var{text}
23241 @c I do not consider backslash-space a standard C escape sequence
23242 @c because it is not in ANSI.
23243 Print @var{text}. Nonprinting characters can be included in
23244 @var{text} using C escape sequences, such as @samp{\n} to print a
23245 newline. @strong{No newline is printed unless you specify one.}
23246 In addition to the standard C escape sequences, a backslash followed
23247 by a space stands for a space. This is useful for displaying a
23248 string with spaces at the beginning or the end, since leading and
23249 trailing spaces are otherwise trimmed from all arguments.
23250 To print @samp{@w{ }and foo =@w{ }}, use the command
23251 @samp{echo \@w{ }and foo = \@w{ }}.
23253 A backslash at the end of @var{text} can be used, as in C, to continue
23254 the command onto subsequent lines. For example,
23257 echo This is some text\n\
23258 which is continued\n\
23259 onto several lines.\n
23262 produces the same output as
23265 echo This is some text\n
23266 echo which is continued\n
23267 echo onto several lines.\n
23271 @item output @var{expression}
23272 Print the value of @var{expression} and nothing but that value: no
23273 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23274 value history either. @xref{Expressions, ,Expressions}, for more information
23277 @item output/@var{fmt} @var{expression}
23278 Print the value of @var{expression} in format @var{fmt}. You can use
23279 the same formats as for @code{print}. @xref{Output Formats,,Output
23280 Formats}, for more information.
23283 @item printf @var{template}, @var{expressions}@dots{}
23284 Print the values of one or more @var{expressions} under the control of
23285 the string @var{template}. To print several values, make
23286 @var{expressions} be a comma-separated list of individual expressions,
23287 which may be either numbers or pointers. Their values are printed as
23288 specified by @var{template}, exactly as a C program would do by
23289 executing the code below:
23292 printf (@var{template}, @var{expressions}@dots{});
23295 As in @code{C} @code{printf}, ordinary characters in @var{template}
23296 are printed verbatim, while @dfn{conversion specification} introduced
23297 by the @samp{%} character cause subsequent @var{expressions} to be
23298 evaluated, their values converted and formatted according to type and
23299 style information encoded in the conversion specifications, and then
23302 For example, you can print two values in hex like this:
23305 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23308 @code{printf} supports all the standard @code{C} conversion
23309 specifications, including the flags and modifiers between the @samp{%}
23310 character and the conversion letter, with the following exceptions:
23314 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23317 The modifier @samp{*} is not supported for specifying precision or
23321 The @samp{'} flag (for separation of digits into groups according to
23322 @code{LC_NUMERIC'}) is not supported.
23325 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23329 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23332 The conversion letters @samp{a} and @samp{A} are not supported.
23336 Note that the @samp{ll} type modifier is supported only if the
23337 underlying @code{C} implementation used to build @value{GDBN} supports
23338 the @code{long long int} type, and the @samp{L} type modifier is
23339 supported only if @code{long double} type is available.
23341 As in @code{C}, @code{printf} supports simple backslash-escape
23342 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23343 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23344 single character. Octal and hexadecimal escape sequences are not
23347 Additionally, @code{printf} supports conversion specifications for DFP
23348 (@dfn{Decimal Floating Point}) types using the following length modifiers
23349 together with a floating point specifier.
23354 @samp{H} for printing @code{Decimal32} types.
23357 @samp{D} for printing @code{Decimal64} types.
23360 @samp{DD} for printing @code{Decimal128} types.
23363 If the underlying @code{C} implementation used to build @value{GDBN} has
23364 support for the three length modifiers for DFP types, other modifiers
23365 such as width and precision will also be available for @value{GDBN} to use.
23367 In case there is no such @code{C} support, no additional modifiers will be
23368 available and the value will be printed in the standard way.
23370 Here's an example of printing DFP types using the above conversion letters:
23372 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23376 @item eval @var{template}, @var{expressions}@dots{}
23377 Convert the values of one or more @var{expressions} under the control of
23378 the string @var{template} to a command line, and call it.
23383 @section Scripting @value{GDBN} using Python
23384 @cindex python scripting
23385 @cindex scripting with python
23387 You can script @value{GDBN} using the @uref{http://www.python.org/,
23388 Python programming language}. This feature is available only if
23389 @value{GDBN} was configured using @option{--with-python}.
23391 @cindex python directory
23392 Python scripts used by @value{GDBN} should be installed in
23393 @file{@var{data-directory}/python}, where @var{data-directory} is
23394 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23395 This directory, known as the @dfn{python directory},
23396 is automatically added to the Python Search Path in order to allow
23397 the Python interpreter to locate all scripts installed at this location.
23399 Additionally, @value{GDBN} commands and convenience functions which
23400 are written in Python and are located in the
23401 @file{@var{data-directory}/python/gdb/command} or
23402 @file{@var{data-directory}/python/gdb/function} directories are
23403 automatically imported when @value{GDBN} starts.
23406 * Python Commands:: Accessing Python from @value{GDBN}.
23407 * Python API:: Accessing @value{GDBN} from Python.
23408 * Python Auto-loading:: Automatically loading Python code.
23409 * Python modules:: Python modules provided by @value{GDBN}.
23412 @node Python Commands
23413 @subsection Python Commands
23414 @cindex python commands
23415 @cindex commands to access python
23417 @value{GDBN} provides two commands for accessing the Python interpreter,
23418 and one related setting:
23421 @kindex python-interactive
23423 @item python-interactive @r{[}@var{command}@r{]}
23424 @itemx pi @r{[}@var{command}@r{]}
23425 Without an argument, the @code{python-interactive} command can be used
23426 to start an interactive Python prompt. To return to @value{GDBN},
23427 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23429 Alternatively, a single-line Python command can be given as an
23430 argument and evaluated. If the command is an expression, the result
23431 will be printed; otherwise, nothing will be printed. For example:
23434 (@value{GDBP}) python-interactive 2 + 3
23440 @item python @r{[}@var{command}@r{]}
23441 @itemx py @r{[}@var{command}@r{]}
23442 The @code{python} command can be used to evaluate Python code.
23444 If given an argument, the @code{python} command will evaluate the
23445 argument as a Python command. For example:
23448 (@value{GDBP}) python print 23
23452 If you do not provide an argument to @code{python}, it will act as a
23453 multi-line command, like @code{define}. In this case, the Python
23454 script is made up of subsequent command lines, given after the
23455 @code{python} command. This command list is terminated using a line
23456 containing @code{end}. For example:
23459 (@value{GDBP}) python
23461 End with a line saying just "end".
23467 @kindex set python print-stack
23468 @item set python print-stack
23469 By default, @value{GDBN} will print only the message component of a
23470 Python exception when an error occurs in a Python script. This can be
23471 controlled using @code{set python print-stack}: if @code{full}, then
23472 full Python stack printing is enabled; if @code{none}, then Python stack
23473 and message printing is disabled; if @code{message}, the default, only
23474 the message component of the error is printed.
23477 It is also possible to execute a Python script from the @value{GDBN}
23481 @item source @file{script-name}
23482 The script name must end with @samp{.py} and @value{GDBN} must be configured
23483 to recognize the script language based on filename extension using
23484 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23486 @item python execfile ("script-name")
23487 This method is based on the @code{execfile} Python built-in function,
23488 and thus is always available.
23492 @subsection Python API
23494 @cindex programming in python
23496 You can get quick online help for @value{GDBN}'s Python API by issuing
23497 the command @w{@kbd{python help (gdb)}}.
23499 Functions and methods which have two or more optional arguments allow
23500 them to be specified using keyword syntax. This allows passing some
23501 optional arguments while skipping others. Example:
23502 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23505 * Basic Python:: Basic Python Functions.
23506 * Exception Handling:: How Python exceptions are translated.
23507 * Values From Inferior:: Python representation of values.
23508 * Types In Python:: Python representation of types.
23509 * Pretty Printing API:: Pretty-printing values.
23510 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23511 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23512 * Type Printing API:: Pretty-printing types.
23513 * Frame Filter API:: Filtering Frames.
23514 * Frame Decorator API:: Decorating Frames.
23515 * Writing a Frame Filter:: Writing a Frame Filter.
23516 * Inferiors In Python:: Python representation of inferiors (processes)
23517 * Events In Python:: Listening for events from @value{GDBN}.
23518 * Threads In Python:: Accessing inferior threads from Python.
23519 * Commands In Python:: Implementing new commands in Python.
23520 * Parameters In Python:: Adding new @value{GDBN} parameters.
23521 * Functions In Python:: Writing new convenience functions.
23522 * Progspaces In Python:: Program spaces.
23523 * Objfiles In Python:: Object files.
23524 * Frames In Python:: Accessing inferior stack frames from Python.
23525 * Blocks In Python:: Accessing blocks from Python.
23526 * Symbols In Python:: Python representation of symbols.
23527 * Symbol Tables In Python:: Python representation of symbol tables.
23528 * Line Tables In Python:: Python representation of line tables.
23529 * Breakpoints In Python:: Manipulating breakpoints using Python.
23530 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23532 * Lazy Strings In Python:: Python representation of lazy strings.
23533 * Architectures In Python:: Python representation of architectures.
23537 @subsubsection Basic Python
23539 @cindex python stdout
23540 @cindex python pagination
23541 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23542 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23543 A Python program which outputs to one of these streams may have its
23544 output interrupted by the user (@pxref{Screen Size}). In this
23545 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23547 Some care must be taken when writing Python code to run in
23548 @value{GDBN}. Two things worth noting in particular:
23552 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23553 Python code must not override these, or even change the options using
23554 @code{sigaction}. If your program changes the handling of these
23555 signals, @value{GDBN} will most likely stop working correctly. Note
23556 that it is unfortunately common for GUI toolkits to install a
23557 @code{SIGCHLD} handler.
23560 @value{GDBN} takes care to mark its internal file descriptors as
23561 close-on-exec. However, this cannot be done in a thread-safe way on
23562 all platforms. Your Python programs should be aware of this and
23563 should both create new file descriptors with the close-on-exec flag
23564 set and arrange to close unneeded file descriptors before starting a
23568 @cindex python functions
23569 @cindex python module
23571 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23572 methods and classes added by @value{GDBN} are placed in this module.
23573 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23574 use in all scripts evaluated by the @code{python} command.
23576 @findex gdb.PYTHONDIR
23577 @defvar gdb.PYTHONDIR
23578 A string containing the python directory (@pxref{Python}).
23581 @findex gdb.execute
23582 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23583 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23584 If a GDB exception happens while @var{command} runs, it is
23585 translated as described in @ref{Exception Handling,,Exception Handling}.
23587 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23588 command as having originated from the user invoking it interactively.
23589 It must be a boolean value. If omitted, it defaults to @code{False}.
23591 By default, any output produced by @var{command} is sent to
23592 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23593 @code{True}, then output will be collected by @code{gdb.execute} and
23594 returned as a string. The default is @code{False}, in which case the
23595 return value is @code{None}. If @var{to_string} is @code{True}, the
23596 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23597 and height, and its pagination will be disabled; @pxref{Screen Size}.
23600 @findex gdb.breakpoints
23601 @defun gdb.breakpoints ()
23602 Return a sequence holding all of @value{GDBN}'s breakpoints.
23603 @xref{Breakpoints In Python}, for more information.
23606 @findex gdb.parameter
23607 @defun gdb.parameter (parameter)
23608 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23609 string naming the parameter to look up; @var{parameter} may contain
23610 spaces if the parameter has a multi-part name. For example,
23611 @samp{print object} is a valid parameter name.
23613 If the named parameter does not exist, this function throws a
23614 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23615 parameter's value is converted to a Python value of the appropriate
23616 type, and returned.
23619 @findex gdb.history
23620 @defun gdb.history (number)
23621 Return a value from @value{GDBN}'s value history (@pxref{Value
23622 History}). @var{number} indicates which history element to return.
23623 If @var{number} is negative, then @value{GDBN} will take its absolute value
23624 and count backward from the last element (i.e., the most recent element) to
23625 find the value to return. If @var{number} is zero, then @value{GDBN} will
23626 return the most recent element. If the element specified by @var{number}
23627 doesn't exist in the value history, a @code{gdb.error} exception will be
23630 If no exception is raised, the return value is always an instance of
23631 @code{gdb.Value} (@pxref{Values From Inferior}).
23634 @findex gdb.parse_and_eval
23635 @defun gdb.parse_and_eval (expression)
23636 Parse @var{expression} as an expression in the current language,
23637 evaluate it, and return the result as a @code{gdb.Value}.
23638 @var{expression} must be a string.
23640 This function can be useful when implementing a new command
23641 (@pxref{Commands In Python}), as it provides a way to parse the
23642 command's argument as an expression. It is also useful simply to
23643 compute values, for example, it is the only way to get the value of a
23644 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23647 @findex gdb.find_pc_line
23648 @defun gdb.find_pc_line (pc)
23649 Return the @code{gdb.Symtab_and_line} object corresponding to the
23650 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23651 value of @var{pc} is passed as an argument, then the @code{symtab} and
23652 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23653 will be @code{None} and 0 respectively.
23656 @findex gdb.post_event
23657 @defun gdb.post_event (event)
23658 Put @var{event}, a callable object taking no arguments, into
23659 @value{GDBN}'s internal event queue. This callable will be invoked at
23660 some later point, during @value{GDBN}'s event processing. Events
23661 posted using @code{post_event} will be run in the order in which they
23662 were posted; however, there is no way to know when they will be
23663 processed relative to other events inside @value{GDBN}.
23665 @value{GDBN} is not thread-safe. If your Python program uses multiple
23666 threads, you must be careful to only call @value{GDBN}-specific
23667 functions in the main @value{GDBN} thread. @code{post_event} ensures
23671 (@value{GDBP}) python
23675 > def __init__(self, message):
23676 > self.message = message;
23677 > def __call__(self):
23678 > gdb.write(self.message)
23680 >class MyThread1 (threading.Thread):
23682 > gdb.post_event(Writer("Hello "))
23684 >class MyThread2 (threading.Thread):
23686 > gdb.post_event(Writer("World\n"))
23688 >MyThread1().start()
23689 >MyThread2().start()
23691 (@value{GDBP}) Hello World
23696 @defun gdb.write (string @r{[}, stream{]})
23697 Print a string to @value{GDBN}'s paginated output stream. The
23698 optional @var{stream} determines the stream to print to. The default
23699 stream is @value{GDBN}'s standard output stream. Possible stream
23706 @value{GDBN}'s standard output stream.
23711 @value{GDBN}'s standard error stream.
23716 @value{GDBN}'s log stream (@pxref{Logging Output}).
23719 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23720 call this function and will automatically direct the output to the
23725 @defun gdb.flush ()
23726 Flush the buffer of a @value{GDBN} paginated stream so that the
23727 contents are displayed immediately. @value{GDBN} will flush the
23728 contents of a stream automatically when it encounters a newline in the
23729 buffer. The optional @var{stream} determines the stream to flush. The
23730 default stream is @value{GDBN}'s standard output stream. Possible
23737 @value{GDBN}'s standard output stream.
23742 @value{GDBN}'s standard error stream.
23747 @value{GDBN}'s log stream (@pxref{Logging Output}).
23751 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23752 call this function for the relevant stream.
23755 @findex gdb.target_charset
23756 @defun gdb.target_charset ()
23757 Return the name of the current target character set (@pxref{Character
23758 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23759 that @samp{auto} is never returned.
23762 @findex gdb.target_wide_charset
23763 @defun gdb.target_wide_charset ()
23764 Return the name of the current target wide character set
23765 (@pxref{Character Sets}). This differs from
23766 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23770 @findex gdb.solib_name
23771 @defun gdb.solib_name (address)
23772 Return the name of the shared library holding the given @var{address}
23773 as a string, or @code{None}.
23776 @findex gdb.decode_line
23777 @defun gdb.decode_line @r{[}expression@r{]}
23778 Return locations of the line specified by @var{expression}, or of the
23779 current line if no argument was given. This function returns a Python
23780 tuple containing two elements. The first element contains a string
23781 holding any unparsed section of @var{expression} (or @code{None} if
23782 the expression has been fully parsed). The second element contains
23783 either @code{None} or another tuple that contains all the locations
23784 that match the expression represented as @code{gdb.Symtab_and_line}
23785 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23786 provided, it is decoded the way that @value{GDBN}'s inbuilt
23787 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23790 @defun gdb.prompt_hook (current_prompt)
23791 @anchor{prompt_hook}
23793 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23794 assigned to this operation before a prompt is displayed by
23797 The parameter @code{current_prompt} contains the current @value{GDBN}
23798 prompt. This method must return a Python string, or @code{None}. If
23799 a string is returned, the @value{GDBN} prompt will be set to that
23800 string. If @code{None} is returned, @value{GDBN} will continue to use
23801 the current prompt.
23803 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23804 such as those used by readline for command input, and annotation
23805 related prompts are prohibited from being changed.
23808 @node Exception Handling
23809 @subsubsection Exception Handling
23810 @cindex python exceptions
23811 @cindex exceptions, python
23813 When executing the @code{python} command, Python exceptions
23814 uncaught within the Python code are translated to calls to
23815 @value{GDBN} error-reporting mechanism. If the command that called
23816 @code{python} does not handle the error, @value{GDBN} will
23817 terminate it and print an error message containing the Python
23818 exception name, the associated value, and the Python call stack
23819 backtrace at the point where the exception was raised. Example:
23822 (@value{GDBP}) python print foo
23823 Traceback (most recent call last):
23824 File "<string>", line 1, in <module>
23825 NameError: name 'foo' is not defined
23828 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23829 Python code are converted to Python exceptions. The type of the
23830 Python exception depends on the error.
23834 This is the base class for most exceptions generated by @value{GDBN}.
23835 It is derived from @code{RuntimeError}, for compatibility with earlier
23836 versions of @value{GDBN}.
23838 If an error occurring in @value{GDBN} does not fit into some more
23839 specific category, then the generated exception will have this type.
23841 @item gdb.MemoryError
23842 This is a subclass of @code{gdb.error} which is thrown when an
23843 operation tried to access invalid memory in the inferior.
23845 @item KeyboardInterrupt
23846 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23847 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23850 In all cases, your exception handler will see the @value{GDBN} error
23851 message as its value and the Python call stack backtrace at the Python
23852 statement closest to where the @value{GDBN} error occured as the
23855 @findex gdb.GdbError
23856 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23857 it is useful to be able to throw an exception that doesn't cause a
23858 traceback to be printed. For example, the user may have invoked the
23859 command incorrectly. Use the @code{gdb.GdbError} exception
23860 to handle this case. Example:
23864 >class HelloWorld (gdb.Command):
23865 > """Greet the whole world."""
23866 > def __init__ (self):
23867 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23868 > def invoke (self, args, from_tty):
23869 > argv = gdb.string_to_argv (args)
23870 > if len (argv) != 0:
23871 > raise gdb.GdbError ("hello-world takes no arguments")
23872 > print "Hello, World!"
23875 (gdb) hello-world 42
23876 hello-world takes no arguments
23879 @node Values From Inferior
23880 @subsubsection Values From Inferior
23881 @cindex values from inferior, with Python
23882 @cindex python, working with values from inferior
23884 @cindex @code{gdb.Value}
23885 @value{GDBN} provides values it obtains from the inferior program in
23886 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23887 for its internal bookkeeping of the inferior's values, and for
23888 fetching values when necessary.
23890 Inferior values that are simple scalars can be used directly in
23891 Python expressions that are valid for the value's data type. Here's
23892 an example for an integer or floating-point value @code{some_val}:
23899 As result of this, @code{bar} will also be a @code{gdb.Value} object
23900 whose values are of the same type as those of @code{some_val}.
23902 Inferior values that are structures or instances of some class can
23903 be accessed using the Python @dfn{dictionary syntax}. For example, if
23904 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23905 can access its @code{foo} element with:
23908 bar = some_val['foo']
23911 Again, @code{bar} will also be a @code{gdb.Value} object.
23913 A @code{gdb.Value} that represents a function can be executed via
23914 inferior function call. Any arguments provided to the call must match
23915 the function's prototype, and must be provided in the order specified
23918 For example, @code{some_val} is a @code{gdb.Value} instance
23919 representing a function that takes two integers as arguments. To
23920 execute this function, call it like so:
23923 result = some_val (10,20)
23926 Any values returned from a function call will be stored as a
23929 The following attributes are provided:
23931 @defvar Value.address
23932 If this object is addressable, this read-only attribute holds a
23933 @code{gdb.Value} object representing the address. Otherwise,
23934 this attribute holds @code{None}.
23937 @cindex optimized out value in Python
23938 @defvar Value.is_optimized_out
23939 This read-only boolean attribute is true if the compiler optimized out
23940 this value, thus it is not available for fetching from the inferior.
23944 The type of this @code{gdb.Value}. The value of this attribute is a
23945 @code{gdb.Type} object (@pxref{Types In Python}).
23948 @defvar Value.dynamic_type
23949 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23950 type information (@acronym{RTTI}) to determine the dynamic type of the
23951 value. If this value is of class type, it will return the class in
23952 which the value is embedded, if any. If this value is of pointer or
23953 reference to a class type, it will compute the dynamic type of the
23954 referenced object, and return a pointer or reference to that type,
23955 respectively. In all other cases, it will return the value's static
23958 Note that this feature will only work when debugging a C@t{++} program
23959 that includes @acronym{RTTI} for the object in question. Otherwise,
23960 it will just return the static type of the value as in @kbd{ptype foo}
23961 (@pxref{Symbols, ptype}).
23964 @defvar Value.is_lazy
23965 The value of this read-only boolean attribute is @code{True} if this
23966 @code{gdb.Value} has not yet been fetched from the inferior.
23967 @value{GDBN} does not fetch values until necessary, for efficiency.
23971 myval = gdb.parse_and_eval ('somevar')
23974 The value of @code{somevar} is not fetched at this time. It will be
23975 fetched when the value is needed, or when the @code{fetch_lazy}
23979 The following methods are provided:
23981 @defun Value.__init__ (@var{val})
23982 Many Python values can be converted directly to a @code{gdb.Value} via
23983 this object initializer. Specifically:
23986 @item Python boolean
23987 A Python boolean is converted to the boolean type from the current
23990 @item Python integer
23991 A Python integer is converted to the C @code{long} type for the
23992 current architecture.
23995 A Python long is converted to the C @code{long long} type for the
23996 current architecture.
23999 A Python float is converted to the C @code{double} type for the
24000 current architecture.
24002 @item Python string
24003 A Python string is converted to a target string, using the current
24006 @item @code{gdb.Value}
24007 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24009 @item @code{gdb.LazyString}
24010 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24011 Python}), then the lazy string's @code{value} method is called, and
24012 its result is used.
24016 @defun Value.cast (type)
24017 Return a new instance of @code{gdb.Value} that is the result of
24018 casting this instance to the type described by @var{type}, which must
24019 be a @code{gdb.Type} object. If the cast cannot be performed for some
24020 reason, this method throws an exception.
24023 @defun Value.dereference ()
24024 For pointer data types, this method returns a new @code{gdb.Value} object
24025 whose contents is the object pointed to by the pointer. For example, if
24026 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24033 then you can use the corresponding @code{gdb.Value} to access what
24034 @code{foo} points to like this:
24037 bar = foo.dereference ()
24040 The result @code{bar} will be a @code{gdb.Value} object holding the
24041 value pointed to by @code{foo}.
24043 A similar function @code{Value.referenced_value} exists which also
24044 returns @code{gdb.Value} objects corresonding to the values pointed to
24045 by pointer values (and additionally, values referenced by reference
24046 values). However, the behavior of @code{Value.dereference}
24047 differs from @code{Value.referenced_value} by the fact that the
24048 behavior of @code{Value.dereference} is identical to applying the C
24049 unary operator @code{*} on a given value. For example, consider a
24050 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24054 typedef int *intptr;
24058 intptr &ptrref = ptr;
24061 Though @code{ptrref} is a reference value, one can apply the method
24062 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24063 to it and obtain a @code{gdb.Value} which is identical to that
24064 corresponding to @code{val}. However, if you apply the method
24065 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24066 object identical to that corresponding to @code{ptr}.
24069 py_ptrref = gdb.parse_and_eval ("ptrref")
24070 py_val = py_ptrref.dereference ()
24071 py_ptr = py_ptrref.referenced_value ()
24074 The @code{gdb.Value} object @code{py_val} is identical to that
24075 corresponding to @code{val}, and @code{py_ptr} is identical to that
24076 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24077 be applied whenever the C unary operator @code{*} can be applied
24078 to the corresponding C value. For those cases where applying both
24079 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24080 the results obtained need not be identical (as we have seen in the above
24081 example). The results are however identical when applied on
24082 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24083 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24086 @defun Value.referenced_value ()
24087 For pointer or reference data types, this method returns a new
24088 @code{gdb.Value} object corresponding to the value referenced by the
24089 pointer/reference value. For pointer data types,
24090 @code{Value.dereference} and @code{Value.referenced_value} produce
24091 identical results. The difference between these methods is that
24092 @code{Value.dereference} cannot get the values referenced by reference
24093 values. For example, consider a reference to an @code{int}, declared
24094 in your C@t{++} program as
24102 then applying @code{Value.dereference} to the @code{gdb.Value} object
24103 corresponding to @code{ref} will result in an error, while applying
24104 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24105 identical to that corresponding to @code{val}.
24108 py_ref = gdb.parse_and_eval ("ref")
24109 er_ref = py_ref.dereference () # Results in error
24110 py_val = py_ref.referenced_value () # Returns the referenced value
24113 The @code{gdb.Value} object @code{py_val} is identical to that
24114 corresponding to @code{val}.
24117 @defun Value.dynamic_cast (type)
24118 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24119 operator were used. Consult a C@t{++} reference for details.
24122 @defun Value.reinterpret_cast (type)
24123 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24124 operator were used. Consult a C@t{++} reference for details.
24127 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24128 If this @code{gdb.Value} represents a string, then this method
24129 converts the contents to a Python string. Otherwise, this method will
24130 throw an exception.
24132 Strings are recognized in a language-specific way; whether a given
24133 @code{gdb.Value} represents a string is determined by the current
24136 For C-like languages, a value is a string if it is a pointer to or an
24137 array of characters or ints. The string is assumed to be terminated
24138 by a zero of the appropriate width. However if the optional length
24139 argument is given, the string will be converted to that given length,
24140 ignoring any embedded zeros that the string may contain.
24142 If the optional @var{encoding} argument is given, it must be a string
24143 naming the encoding of the string in the @code{gdb.Value}, such as
24144 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24145 the same encodings as the corresponding argument to Python's
24146 @code{string.decode} method, and the Python codec machinery will be used
24147 to convert the string. If @var{encoding} is not given, or if
24148 @var{encoding} is the empty string, then either the @code{target-charset}
24149 (@pxref{Character Sets}) will be used, or a language-specific encoding
24150 will be used, if the current language is able to supply one.
24152 The optional @var{errors} argument is the same as the corresponding
24153 argument to Python's @code{string.decode} method.
24155 If the optional @var{length} argument is given, the string will be
24156 fetched and converted to the given length.
24159 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24160 If this @code{gdb.Value} represents a string, then this method
24161 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24162 In Python}). Otherwise, this method will throw an exception.
24164 If the optional @var{encoding} argument is given, it must be a string
24165 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24166 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24167 @var{encoding} argument is an encoding that @value{GDBN} does
24168 recognize, @value{GDBN} will raise an error.
24170 When a lazy string is printed, the @value{GDBN} encoding machinery is
24171 used to convert the string during printing. If the optional
24172 @var{encoding} argument is not provided, or is an empty string,
24173 @value{GDBN} will automatically select the encoding most suitable for
24174 the string type. For further information on encoding in @value{GDBN}
24175 please see @ref{Character Sets}.
24177 If the optional @var{length} argument is given, the string will be
24178 fetched and encoded to the length of characters specified. If
24179 the @var{length} argument is not provided, the string will be fetched
24180 and encoded until a null of appropriate width is found.
24183 @defun Value.fetch_lazy ()
24184 If the @code{gdb.Value} object is currently a lazy value
24185 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24186 fetched from the inferior. Any errors that occur in the process
24187 will produce a Python exception.
24189 If the @code{gdb.Value} object is not a lazy value, this method
24192 This method does not return a value.
24196 @node Types In Python
24197 @subsubsection Types In Python
24198 @cindex types in Python
24199 @cindex Python, working with types
24202 @value{GDBN} represents types from the inferior using the class
24205 The following type-related functions are available in the @code{gdb}
24208 @findex gdb.lookup_type
24209 @defun gdb.lookup_type (name @r{[}, block@r{]})
24210 This function looks up a type by name. @var{name} is the name of the
24211 type to look up. It must be a string.
24213 If @var{block} is given, then @var{name} is looked up in that scope.
24214 Otherwise, it is searched for globally.
24216 Ordinarily, this function will return an instance of @code{gdb.Type}.
24217 If the named type cannot be found, it will throw an exception.
24220 If the type is a structure or class type, or an enum type, the fields
24221 of that type can be accessed using the Python @dfn{dictionary syntax}.
24222 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24223 a structure type, you can access its @code{foo} field with:
24226 bar = some_type['foo']
24229 @code{bar} will be a @code{gdb.Field} object; see below under the
24230 description of the @code{Type.fields} method for a description of the
24231 @code{gdb.Field} class.
24233 An instance of @code{Type} has the following attributes:
24236 The type code for this type. The type code will be one of the
24237 @code{TYPE_CODE_} constants defined below.
24240 @defvar Type.sizeof
24241 The size of this type, in target @code{char} units. Usually, a
24242 target's @code{char} type will be an 8-bit byte. However, on some
24243 unusual platforms, this type may have a different size.
24247 The tag name for this type. The tag name is the name after
24248 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24249 languages have this concept. If this type has no tag name, then
24250 @code{None} is returned.
24253 The following methods are provided:
24255 @defun Type.fields ()
24256 For structure and union types, this method returns the fields. Range
24257 types have two fields, the minimum and maximum values. Enum types
24258 have one field per enum constant. Function and method types have one
24259 field per parameter. The base types of C@t{++} classes are also
24260 represented as fields. If the type has no fields, or does not fit
24261 into one of these categories, an empty sequence will be returned.
24263 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24266 This attribute is not available for @code{static} fields (as in
24267 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24268 position of the field. For @code{enum} fields, the value is the
24269 enumeration member's integer representation.
24272 The name of the field, or @code{None} for anonymous fields.
24275 This is @code{True} if the field is artificial, usually meaning that
24276 it was provided by the compiler and not the user. This attribute is
24277 always provided, and is @code{False} if the field is not artificial.
24279 @item is_base_class
24280 This is @code{True} if the field represents a base class of a C@t{++}
24281 structure. This attribute is always provided, and is @code{False}
24282 if the field is not a base class of the type that is the argument of
24283 @code{fields}, or if that type was not a C@t{++} class.
24286 If the field is packed, or is a bitfield, then this will have a
24287 non-zero value, which is the size of the field in bits. Otherwise,
24288 this will be zero; in this case the field's size is given by its type.
24291 The type of the field. This is usually an instance of @code{Type},
24292 but it can be @code{None} in some situations.
24296 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24297 Return a new @code{gdb.Type} object which represents an array of this
24298 type. If one argument is given, it is the inclusive upper bound of
24299 the array; in this case the lower bound is zero. If two arguments are
24300 given, the first argument is the lower bound of the array, and the
24301 second argument is the upper bound of the array. An array's length
24302 must not be negative, but the bounds can be.
24305 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24306 Return a new @code{gdb.Type} object which represents a vector of this
24307 type. If one argument is given, it is the inclusive upper bound of
24308 the vector; in this case the lower bound is zero. If two arguments are
24309 given, the first argument is the lower bound of the vector, and the
24310 second argument is the upper bound of the vector. A vector's length
24311 must not be negative, but the bounds can be.
24313 The difference between an @code{array} and a @code{vector} is that
24314 arrays behave like in C: when used in expressions they decay to a pointer
24315 to the first element whereas vectors are treated as first class values.
24318 @defun Type.const ()
24319 Return a new @code{gdb.Type} object which represents a
24320 @code{const}-qualified variant of this type.
24323 @defun Type.volatile ()
24324 Return a new @code{gdb.Type} object which represents a
24325 @code{volatile}-qualified variant of this type.
24328 @defun Type.unqualified ()
24329 Return a new @code{gdb.Type} object which represents an unqualified
24330 variant of this type. That is, the result is neither @code{const} nor
24334 @defun Type.range ()
24335 Return a Python @code{Tuple} object that contains two elements: the
24336 low bound of the argument type and the high bound of that type. If
24337 the type does not have a range, @value{GDBN} will raise a
24338 @code{gdb.error} exception (@pxref{Exception Handling}).
24341 @defun Type.reference ()
24342 Return a new @code{gdb.Type} object which represents a reference to this
24346 @defun Type.pointer ()
24347 Return a new @code{gdb.Type} object which represents a pointer to this
24351 @defun Type.strip_typedefs ()
24352 Return a new @code{gdb.Type} that represents the real type,
24353 after removing all layers of typedefs.
24356 @defun Type.target ()
24357 Return a new @code{gdb.Type} object which represents the target type
24360 For a pointer type, the target type is the type of the pointed-to
24361 object. For an array type (meaning C-like arrays), the target type is
24362 the type of the elements of the array. For a function or method type,
24363 the target type is the type of the return value. For a complex type,
24364 the target type is the type of the elements. For a typedef, the
24365 target type is the aliased type.
24367 If the type does not have a target, this method will throw an
24371 @defun Type.template_argument (n @r{[}, block@r{]})
24372 If this @code{gdb.Type} is an instantiation of a template, this will
24373 return a new @code{gdb.Type} which represents the type of the
24374 @var{n}th template argument.
24376 If this @code{gdb.Type} is not a template type, this will throw an
24377 exception. Ordinarily, only C@t{++} code will have template types.
24379 If @var{block} is given, then @var{name} is looked up in that scope.
24380 Otherwise, it is searched for globally.
24384 Each type has a code, which indicates what category this type falls
24385 into. The available type categories are represented by constants
24386 defined in the @code{gdb} module:
24389 @findex TYPE_CODE_PTR
24390 @findex gdb.TYPE_CODE_PTR
24391 @item gdb.TYPE_CODE_PTR
24392 The type is a pointer.
24394 @findex TYPE_CODE_ARRAY
24395 @findex gdb.TYPE_CODE_ARRAY
24396 @item gdb.TYPE_CODE_ARRAY
24397 The type is an array.
24399 @findex TYPE_CODE_STRUCT
24400 @findex gdb.TYPE_CODE_STRUCT
24401 @item gdb.TYPE_CODE_STRUCT
24402 The type is a structure.
24404 @findex TYPE_CODE_UNION
24405 @findex gdb.TYPE_CODE_UNION
24406 @item gdb.TYPE_CODE_UNION
24407 The type is a union.
24409 @findex TYPE_CODE_ENUM
24410 @findex gdb.TYPE_CODE_ENUM
24411 @item gdb.TYPE_CODE_ENUM
24412 The type is an enum.
24414 @findex TYPE_CODE_FLAGS
24415 @findex gdb.TYPE_CODE_FLAGS
24416 @item gdb.TYPE_CODE_FLAGS
24417 A bit flags type, used for things such as status registers.
24419 @findex TYPE_CODE_FUNC
24420 @findex gdb.TYPE_CODE_FUNC
24421 @item gdb.TYPE_CODE_FUNC
24422 The type is a function.
24424 @findex TYPE_CODE_INT
24425 @findex gdb.TYPE_CODE_INT
24426 @item gdb.TYPE_CODE_INT
24427 The type is an integer type.
24429 @findex TYPE_CODE_FLT
24430 @findex gdb.TYPE_CODE_FLT
24431 @item gdb.TYPE_CODE_FLT
24432 A floating point type.
24434 @findex TYPE_CODE_VOID
24435 @findex gdb.TYPE_CODE_VOID
24436 @item gdb.TYPE_CODE_VOID
24437 The special type @code{void}.
24439 @findex TYPE_CODE_SET
24440 @findex gdb.TYPE_CODE_SET
24441 @item gdb.TYPE_CODE_SET
24444 @findex TYPE_CODE_RANGE
24445 @findex gdb.TYPE_CODE_RANGE
24446 @item gdb.TYPE_CODE_RANGE
24447 A range type, that is, an integer type with bounds.
24449 @findex TYPE_CODE_STRING
24450 @findex gdb.TYPE_CODE_STRING
24451 @item gdb.TYPE_CODE_STRING
24452 A string type. Note that this is only used for certain languages with
24453 language-defined string types; C strings are not represented this way.
24455 @findex TYPE_CODE_BITSTRING
24456 @findex gdb.TYPE_CODE_BITSTRING
24457 @item gdb.TYPE_CODE_BITSTRING
24458 A string of bits. It is deprecated.
24460 @findex TYPE_CODE_ERROR
24461 @findex gdb.TYPE_CODE_ERROR
24462 @item gdb.TYPE_CODE_ERROR
24463 An unknown or erroneous type.
24465 @findex TYPE_CODE_METHOD
24466 @findex gdb.TYPE_CODE_METHOD
24467 @item gdb.TYPE_CODE_METHOD
24468 A method type, as found in C@t{++} or Java.
24470 @findex TYPE_CODE_METHODPTR
24471 @findex gdb.TYPE_CODE_METHODPTR
24472 @item gdb.TYPE_CODE_METHODPTR
24473 A pointer-to-member-function.
24475 @findex TYPE_CODE_MEMBERPTR
24476 @findex gdb.TYPE_CODE_MEMBERPTR
24477 @item gdb.TYPE_CODE_MEMBERPTR
24478 A pointer-to-member.
24480 @findex TYPE_CODE_REF
24481 @findex gdb.TYPE_CODE_REF
24482 @item gdb.TYPE_CODE_REF
24485 @findex TYPE_CODE_CHAR
24486 @findex gdb.TYPE_CODE_CHAR
24487 @item gdb.TYPE_CODE_CHAR
24490 @findex TYPE_CODE_BOOL
24491 @findex gdb.TYPE_CODE_BOOL
24492 @item gdb.TYPE_CODE_BOOL
24495 @findex TYPE_CODE_COMPLEX
24496 @findex gdb.TYPE_CODE_COMPLEX
24497 @item gdb.TYPE_CODE_COMPLEX
24498 A complex float type.
24500 @findex TYPE_CODE_TYPEDEF
24501 @findex gdb.TYPE_CODE_TYPEDEF
24502 @item gdb.TYPE_CODE_TYPEDEF
24503 A typedef to some other type.
24505 @findex TYPE_CODE_NAMESPACE
24506 @findex gdb.TYPE_CODE_NAMESPACE
24507 @item gdb.TYPE_CODE_NAMESPACE
24508 A C@t{++} namespace.
24510 @findex TYPE_CODE_DECFLOAT
24511 @findex gdb.TYPE_CODE_DECFLOAT
24512 @item gdb.TYPE_CODE_DECFLOAT
24513 A decimal floating point type.
24515 @findex TYPE_CODE_INTERNAL_FUNCTION
24516 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24517 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24518 A function internal to @value{GDBN}. This is the type used to represent
24519 convenience functions.
24522 Further support for types is provided in the @code{gdb.types}
24523 Python module (@pxref{gdb.types}).
24525 @node Pretty Printing API
24526 @subsubsection Pretty Printing API
24528 An example output is provided (@pxref{Pretty Printing}).
24530 A pretty-printer is just an object that holds a value and implements a
24531 specific interface, defined here.
24533 @defun pretty_printer.children (self)
24534 @value{GDBN} will call this method on a pretty-printer to compute the
24535 children of the pretty-printer's value.
24537 This method must return an object conforming to the Python iterator
24538 protocol. Each item returned by the iterator must be a tuple holding
24539 two elements. The first element is the ``name'' of the child; the
24540 second element is the child's value. The value can be any Python
24541 object which is convertible to a @value{GDBN} value.
24543 This method is optional. If it does not exist, @value{GDBN} will act
24544 as though the value has no children.
24547 @defun pretty_printer.display_hint (self)
24548 The CLI may call this method and use its result to change the
24549 formatting of a value. The result will also be supplied to an MI
24550 consumer as a @samp{displayhint} attribute of the variable being
24553 This method is optional. If it does exist, this method must return a
24556 Some display hints are predefined by @value{GDBN}:
24560 Indicate that the object being printed is ``array-like''. The CLI
24561 uses this to respect parameters such as @code{set print elements} and
24562 @code{set print array}.
24565 Indicate that the object being printed is ``map-like'', and that the
24566 children of this value can be assumed to alternate between keys and
24570 Indicate that the object being printed is ``string-like''. If the
24571 printer's @code{to_string} method returns a Python string of some
24572 kind, then @value{GDBN} will call its internal language-specific
24573 string-printing function to format the string. For the CLI this means
24574 adding quotation marks, possibly escaping some characters, respecting
24575 @code{set print elements}, and the like.
24579 @defun pretty_printer.to_string (self)
24580 @value{GDBN} will call this method to display the string
24581 representation of the value passed to the object's constructor.
24583 When printing from the CLI, if the @code{to_string} method exists,
24584 then @value{GDBN} will prepend its result to the values returned by
24585 @code{children}. Exactly how this formatting is done is dependent on
24586 the display hint, and may change as more hints are added. Also,
24587 depending on the print settings (@pxref{Print Settings}), the CLI may
24588 print just the result of @code{to_string} in a stack trace, omitting
24589 the result of @code{children}.
24591 If this method returns a string, it is printed verbatim.
24593 Otherwise, if this method returns an instance of @code{gdb.Value},
24594 then @value{GDBN} prints this value. This may result in a call to
24595 another pretty-printer.
24597 If instead the method returns a Python value which is convertible to a
24598 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24599 the resulting value. Again, this may result in a call to another
24600 pretty-printer. Python scalars (integers, floats, and booleans) and
24601 strings are convertible to @code{gdb.Value}; other types are not.
24603 Finally, if this method returns @code{None} then no further operations
24604 are peformed in this method and nothing is printed.
24606 If the result is not one of these types, an exception is raised.
24609 @value{GDBN} provides a function which can be used to look up the
24610 default pretty-printer for a @code{gdb.Value}:
24612 @findex gdb.default_visualizer
24613 @defun gdb.default_visualizer (value)
24614 This function takes a @code{gdb.Value} object as an argument. If a
24615 pretty-printer for this value exists, then it is returned. If no such
24616 printer exists, then this returns @code{None}.
24619 @node Selecting Pretty-Printers
24620 @subsubsection Selecting Pretty-Printers
24622 The Python list @code{gdb.pretty_printers} contains an array of
24623 functions or callable objects that have been registered via addition
24624 as a pretty-printer. Printers in this list are called @code{global}
24625 printers, they're available when debugging all inferiors.
24626 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24627 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24630 Each function on these lists is passed a single @code{gdb.Value}
24631 argument and should return a pretty-printer object conforming to the
24632 interface definition above (@pxref{Pretty Printing API}). If a function
24633 cannot create a pretty-printer for the value, it should return
24636 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24637 @code{gdb.Objfile} in the current program space and iteratively calls
24638 each enabled lookup routine in the list for that @code{gdb.Objfile}
24639 until it receives a pretty-printer object.
24640 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24641 searches the pretty-printer list of the current program space,
24642 calling each enabled function until an object is returned.
24643 After these lists have been exhausted, it tries the global
24644 @code{gdb.pretty_printers} list, again calling each enabled function until an
24645 object is returned.
24647 The order in which the objfiles are searched is not specified. For a
24648 given list, functions are always invoked from the head of the list,
24649 and iterated over sequentially until the end of the list, or a printer
24650 object is returned.
24652 For various reasons a pretty-printer may not work.
24653 For example, the underlying data structure may have changed and
24654 the pretty-printer is out of date.
24656 The consequences of a broken pretty-printer are severe enough that
24657 @value{GDBN} provides support for enabling and disabling individual
24658 printers. For example, if @code{print frame-arguments} is on,
24659 a backtrace can become highly illegible if any argument is printed
24660 with a broken printer.
24662 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24663 attribute to the registered function or callable object. If this attribute
24664 is present and its value is @code{False}, the printer is disabled, otherwise
24665 the printer is enabled.
24667 @node Writing a Pretty-Printer
24668 @subsubsection Writing a Pretty-Printer
24669 @cindex writing a pretty-printer
24671 A pretty-printer consists of two parts: a lookup function to detect
24672 if the type is supported, and the printer itself.
24674 Here is an example showing how a @code{std::string} printer might be
24675 written. @xref{Pretty Printing API}, for details on the API this class
24679 class StdStringPrinter(object):
24680 "Print a std::string"
24682 def __init__(self, val):
24685 def to_string(self):
24686 return self.val['_M_dataplus']['_M_p']
24688 def display_hint(self):
24692 And here is an example showing how a lookup function for the printer
24693 example above might be written.
24696 def str_lookup_function(val):
24697 lookup_tag = val.type.tag
24698 if lookup_tag == None:
24700 regex = re.compile("^std::basic_string<char,.*>$")
24701 if regex.match(lookup_tag):
24702 return StdStringPrinter(val)
24706 The example lookup function extracts the value's type, and attempts to
24707 match it to a type that it can pretty-print. If it is a type the
24708 printer can pretty-print, it will return a printer object. If not, it
24709 returns @code{None}.
24711 We recommend that you put your core pretty-printers into a Python
24712 package. If your pretty-printers are for use with a library, we
24713 further recommend embedding a version number into the package name.
24714 This practice will enable @value{GDBN} to load multiple versions of
24715 your pretty-printers at the same time, because they will have
24718 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24719 can be evaluated multiple times without changing its meaning. An
24720 ideal auto-load file will consist solely of @code{import}s of your
24721 printer modules, followed by a call to a register pretty-printers with
24722 the current objfile.
24724 Taken as a whole, this approach will scale nicely to multiple
24725 inferiors, each potentially using a different library version.
24726 Embedding a version number in the Python package name will ensure that
24727 @value{GDBN} is able to load both sets of printers simultaneously.
24728 Then, because the search for pretty-printers is done by objfile, and
24729 because your auto-loaded code took care to register your library's
24730 printers with a specific objfile, @value{GDBN} will find the correct
24731 printers for the specific version of the library used by each
24734 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24735 this code might appear in @code{gdb.libstdcxx.v6}:
24738 def register_printers(objfile):
24739 objfile.pretty_printers.append(str_lookup_function)
24743 And then the corresponding contents of the auto-load file would be:
24746 import gdb.libstdcxx.v6
24747 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24750 The previous example illustrates a basic pretty-printer.
24751 There are a few things that can be improved on.
24752 The printer doesn't have a name, making it hard to identify in a
24753 list of installed printers. The lookup function has a name, but
24754 lookup functions can have arbitrary, even identical, names.
24756 Second, the printer only handles one type, whereas a library typically has
24757 several types. One could install a lookup function for each desired type
24758 in the library, but one could also have a single lookup function recognize
24759 several types. The latter is the conventional way this is handled.
24760 If a pretty-printer can handle multiple data types, then its
24761 @dfn{subprinters} are the printers for the individual data types.
24763 The @code{gdb.printing} module provides a formal way of solving these
24764 problems (@pxref{gdb.printing}).
24765 Here is another example that handles multiple types.
24767 These are the types we are going to pretty-print:
24770 struct foo @{ int a, b; @};
24771 struct bar @{ struct foo x, y; @};
24774 Here are the printers:
24778 """Print a foo object."""
24780 def __init__(self, val):
24783 def to_string(self):
24784 return ("a=<" + str(self.val["a"]) +
24785 "> b=<" + str(self.val["b"]) + ">")
24788 """Print a bar object."""
24790 def __init__(self, val):
24793 def to_string(self):
24794 return ("x=<" + str(self.val["x"]) +
24795 "> y=<" + str(self.val["y"]) + ">")
24798 This example doesn't need a lookup function, that is handled by the
24799 @code{gdb.printing} module. Instead a function is provided to build up
24800 the object that handles the lookup.
24803 import gdb.printing
24805 def build_pretty_printer():
24806 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24808 pp.add_printer('foo', '^foo$', fooPrinter)
24809 pp.add_printer('bar', '^bar$', barPrinter)
24813 And here is the autoload support:
24816 import gdb.printing
24818 gdb.printing.register_pretty_printer(
24819 gdb.current_objfile(),
24820 my_library.build_pretty_printer())
24823 Finally, when this printer is loaded into @value{GDBN}, here is the
24824 corresponding output of @samp{info pretty-printer}:
24827 (gdb) info pretty-printer
24834 @node Type Printing API
24835 @subsubsection Type Printing API
24836 @cindex type printing API for Python
24838 @value{GDBN} provides a way for Python code to customize type display.
24839 This is mainly useful for substituting canonical typedef names for
24842 @cindex type printer
24843 A @dfn{type printer} is just a Python object conforming to a certain
24844 protocol. A simple base class implementing the protocol is provided;
24845 see @ref{gdb.types}. A type printer must supply at least:
24847 @defivar type_printer enabled
24848 A boolean which is True if the printer is enabled, and False
24849 otherwise. This is manipulated by the @code{enable type-printer}
24850 and @code{disable type-printer} commands.
24853 @defivar type_printer name
24854 The name of the type printer. This must be a string. This is used by
24855 the @code{enable type-printer} and @code{disable type-printer}
24859 @defmethod type_printer instantiate (self)
24860 This is called by @value{GDBN} at the start of type-printing. It is
24861 only called if the type printer is enabled. This method must return a
24862 new object that supplies a @code{recognize} method, as described below.
24866 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24867 will compute a list of type recognizers. This is done by iterating
24868 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24869 followed by the per-progspace type printers (@pxref{Progspaces In
24870 Python}), and finally the global type printers.
24872 @value{GDBN} will call the @code{instantiate} method of each enabled
24873 type printer. If this method returns @code{None}, then the result is
24874 ignored; otherwise, it is appended to the list of recognizers.
24876 Then, when @value{GDBN} is going to display a type name, it iterates
24877 over the list of recognizers. For each one, it calls the recognition
24878 function, stopping if the function returns a non-@code{None} value.
24879 The recognition function is defined as:
24881 @defmethod type_recognizer recognize (self, type)
24882 If @var{type} is not recognized, return @code{None}. Otherwise,
24883 return a string which is to be printed as the name of @var{type}.
24884 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24888 @value{GDBN} uses this two-pass approach so that type printers can
24889 efficiently cache information without holding on to it too long. For
24890 example, it can be convenient to look up type information in a type
24891 printer and hold it for a recognizer's lifetime; if a single pass were
24892 done then type printers would have to make use of the event system in
24893 order to avoid holding information that could become stale as the
24896 @node Frame Filter API
24897 @subsubsection Filtering Frames.
24898 @cindex frame filters api
24900 Frame filters are Python objects that manipulate the visibility of a
24901 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24904 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24905 commands (@pxref{GDB/MI}), those that return a collection of frames
24906 are affected. The commands that work with frame filters are:
24908 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24909 @code{-stack-list-frames}
24910 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24911 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24912 -stack-list-variables command}), @code{-stack-list-arguments}
24913 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24914 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24915 -stack-list-locals command}).
24917 A frame filter works by taking an iterator as an argument, applying
24918 actions to the contents of that iterator, and returning another
24919 iterator (or, possibly, the same iterator it was provided in the case
24920 where the filter does not perform any operations). Typically, frame
24921 filters utilize tools such as the Python's @code{itertools} module to
24922 work with and create new iterators from the source iterator.
24923 Regardless of how a filter chooses to apply actions, it must not alter
24924 the underlying @value{GDBN} frame or frames, or attempt to alter the
24925 call-stack within @value{GDBN}. This preserves data integrity within
24926 @value{GDBN}. Frame filters are executed on a priority basis and care
24927 should be taken that some frame filters may have been executed before,
24928 and that some frame filters will be executed after.
24930 An important consideration when designing frame filters, and well
24931 worth reflecting upon, is that frame filters should avoid unwinding
24932 the call stack if possible. Some stacks can run very deep, into the
24933 tens of thousands in some cases. To search every frame when a frame
24934 filter executes may be too expensive at that step. The frame filter
24935 cannot know how many frames it has to iterate over, and it may have to
24936 iterate through them all. This ends up duplicating effort as
24937 @value{GDBN} performs this iteration when it prints the frames. If
24938 the filter can defer unwinding frames until frame decorators are
24939 executed, after the last filter has executed, it should. @xref{Frame
24940 Decorator API}, for more information on decorators. Also, there are
24941 examples for both frame decorators and filters in later chapters.
24942 @xref{Writing a Frame Filter}, for more information.
24944 The Python dictionary @code{gdb.frame_filters} contains key/object
24945 pairings that comprise a frame filter. Frame filters in this
24946 dictionary are called @code{global} frame filters, and they are
24947 available when debugging all inferiors. These frame filters must
24948 register with the dictionary directly. In addition to the
24949 @code{global} dictionary, there are other dictionaries that are loaded
24950 with different inferiors via auto-loading (@pxref{Python
24951 Auto-loading}). The two other areas where frame filter dictionaries
24952 can be found are: @code{gdb.Progspace} which contains a
24953 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24954 object which also contains a @code{frame_filters} dictionary
24957 When a command is executed from @value{GDBN} that is compatible with
24958 frame filters, @value{GDBN} combines the @code{global},
24959 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24960 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24961 several frames, and thus several object files, might be in use.
24962 @value{GDBN} then prunes any frame filter whose @code{enabled}
24963 attribute is @code{False}. This pruned list is then sorted according
24964 to the @code{priority} attribute in each filter.
24966 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24967 creates an iterator which wraps each frame in the call stack in a
24968 @code{FrameDecorator} object, and calls each filter in order. The
24969 output from the previous filter will always be the input to the next
24972 Frame filters have a mandatory interface which each frame filter must
24973 implement, defined here:
24975 @defun FrameFilter.filter (iterator)
24976 @value{GDBN} will call this method on a frame filter when it has
24977 reached the order in the priority list for that filter.
24979 For example, if there are four frame filters:
24990 The order that the frame filters will be called is:
24993 Filter3 -> Filter2 -> Filter1 -> Filter4
24996 Note that the output from @code{Filter3} is passed to the input of
24997 @code{Filter2}, and so on.
24999 This @code{filter} method is passed a Python iterator. This iterator
25000 contains a sequence of frame decorators that wrap each
25001 @code{gdb.Frame}, or a frame decorator that wraps another frame
25002 decorator. The first filter that is executed in the sequence of frame
25003 filters will receive an iterator entirely comprised of default
25004 @code{FrameDecorator} objects. However, after each frame filter is
25005 executed, the previous frame filter may have wrapped some or all of
25006 the frame decorators with their own frame decorator. As frame
25007 decorators must also conform to a mandatory interface, these
25008 decorators can be assumed to act in a uniform manner (@pxref{Frame
25011 This method must return an object conforming to the Python iterator
25012 protocol. Each item in the iterator must be an object conforming to
25013 the frame decorator interface. If a frame filter does not wish to
25014 perform any operations on this iterator, it should return that
25015 iterator untouched.
25017 This method is not optional. If it does not exist, @value{GDBN} will
25018 raise and print an error.
25021 @defvar FrameFilter.name
25022 The @code{name} attribute must be Python string which contains the
25023 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25024 Management}). This attribute may contain any combination of letters
25025 or numbers. Care should be taken to ensure that it is unique. This
25026 attribute is mandatory.
25029 @defvar FrameFilter.enabled
25030 The @code{enabled} attribute must be Python boolean. This attribute
25031 indicates to @value{GDBN} whether the frame filter is enabled, and
25032 should be considered when frame filters are executed. If
25033 @code{enabled} is @code{True}, then the frame filter will be executed
25034 when any of the backtrace commands detailed earlier in this chapter
25035 are executed. If @code{enabled} is @code{False}, then the frame
25036 filter will not be executed. This attribute is mandatory.
25039 @defvar FrameFilter.priority
25040 The @code{priority} attribute must be Python integer. This attribute
25041 controls the order of execution in relation to other frame filters.
25042 There are no imposed limits on the range of @code{priority} other than
25043 it must be a valid integer. The higher the @code{priority} attribute,
25044 the sooner the frame filter will be executed in relation to other
25045 frame filters. Although @code{priority} can be negative, it is
25046 recommended practice to assume zero is the lowest priority that a
25047 frame filter can be assigned. Frame filters that have the same
25048 priority are executed in unsorted order in that priority slot. This
25049 attribute is mandatory.
25052 @node Frame Decorator API
25053 @subsubsection Decorating Frames.
25054 @cindex frame decorator api
25056 Frame decorators are sister objects to frame filters (@pxref{Frame
25057 Filter API}). Frame decorators are applied by a frame filter and can
25058 only be used in conjunction with frame filters.
25060 The purpose of a frame decorator is to customize the printed content
25061 of each @code{gdb.Frame} in commands where frame filters are executed.
25062 This concept is called decorating a frame. Frame decorators decorate
25063 a @code{gdb.Frame} with Python code contained within each API call.
25064 This separates the actual data contained in a @code{gdb.Frame} from
25065 the decorated data produced by a frame decorator. This abstraction is
25066 necessary to maintain integrity of the data contained in each
25069 Frame decorators have a mandatory interface, defined below.
25071 @value{GDBN} already contains a frame decorator called
25072 @code{FrameDecorator}. This contains substantial amounts of
25073 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25074 recommended that other frame decorators inherit and extend this
25075 object, and only to override the methods needed.
25077 @defun FrameDecorator.elided (self)
25079 The @code{elided} method groups frames together in a hierarchical
25080 system. An example would be an interpreter, where multiple low-level
25081 frames make up a single call in the interpreted language. In this
25082 example, the frame filter would elide the low-level frames and present
25083 a single high-level frame, representing the call in the interpreted
25084 language, to the user.
25086 The @code{elided} function must return an iterable and this iterable
25087 must contain the frames that are being elided wrapped in a suitable
25088 frame decorator. If no frames are being elided this function may
25089 return an empty iterable, or @code{None}. Elided frames are indented
25090 from normal frames in a @code{CLI} backtrace, or in the case of
25091 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25094 It is the frame filter's task to also filter out the elided frames from
25095 the source iterator. This will avoid printing the frame twice.
25098 @defun FrameDecorator.function (self)
25100 This method returns the name of the function in the frame that is to
25103 This method must return a Python string describing the function, or
25106 If this function returns @code{None}, @value{GDBN} will not print any
25107 data for this field.
25110 @defun FrameDecorator.address (self)
25112 This method returns the address of the frame that is to be printed.
25114 This method must return a Python numeric integer type of sufficient
25115 size to describe the address of the frame, or @code{None}.
25117 If this function returns a @code{None}, @value{GDBN} will not print
25118 any data for this field.
25121 @defun FrameDecorator.filename (self)
25123 This method returns the filename and path associated with this frame.
25125 This method must return a Python string containing the filename and
25126 the path to the object file backing the frame, or @code{None}.
25128 If this function returns a @code{None}, @value{GDBN} will not print
25129 any data for this field.
25132 @defun FrameDecorator.line (self):
25134 This method returns the line number associated with the current
25135 position within the function addressed by this frame.
25137 This method must return a Python integer type, or @code{None}.
25139 If this function returns a @code{None}, @value{GDBN} will not print
25140 any data for this field.
25143 @defun FrameDecorator.frame_args (self)
25144 @anchor{frame_args}
25146 This method must return an iterable, or @code{None}. Returning an
25147 empty iterable, or @code{None} means frame arguments will not be
25148 printed for this frame. This iterable must contain objects that
25149 implement two methods, described here.
25151 This object must implement a @code{argument} method which takes a
25152 single @code{self} parameter and must return a @code{gdb.Symbol}
25153 (@pxref{Symbols In Python}), or a Python string. The object must also
25154 implement a @code{value} method which takes a single @code{self}
25155 parameter and must return a @code{gdb.Value} (@pxref{Values From
25156 Inferior}), a Python value, or @code{None}. If the @code{value}
25157 method returns @code{None}, and the @code{argument} method returns a
25158 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25159 the @code{gdb.Symbol} automatically.
25164 class SymValueWrapper():
25166 def __init__(self, symbol, value):
25176 class SomeFrameDecorator()
25179 def frame_args(self):
25182 block = self.inferior_frame.block()
25186 # Iterate over all symbols in a block. Only add
25187 # symbols that are arguments.
25189 if not sym.is_argument:
25191 args.append(SymValueWrapper(sym,None))
25193 # Add example synthetic argument.
25194 args.append(SymValueWrapper(``foo'', 42))
25200 @defun FrameDecorator.frame_locals (self)
25202 This method must return an iterable or @code{None}. Returning an
25203 empty iterable, or @code{None} means frame local arguments will not be
25204 printed for this frame.
25206 The object interface, the description of the various strategies for
25207 reading frame locals, and the example are largely similar to those
25208 described in the @code{frame_args} function, (@pxref{frame_args,,The
25209 frame filter frame_args function}). Below is a modified example:
25212 class SomeFrameDecorator()
25215 def frame_locals(self):
25218 block = self.inferior_frame.block()
25222 # Iterate over all symbols in a block. Add all
25223 # symbols, except arguments.
25225 if sym.is_argument:
25227 vars.append(SymValueWrapper(sym,None))
25229 # Add an example of a synthetic local variable.
25230 vars.append(SymValueWrapper(``bar'', 99))
25236 @defun FrameDecorator.inferior_frame (self):
25238 This method must return the underlying @code{gdb.Frame} that this
25239 frame decorator is decorating. @value{GDBN} requires the underlying
25240 frame for internal frame information to determine how to print certain
25241 values when printing a frame.
25244 @node Writing a Frame Filter
25245 @subsubsection Writing a Frame Filter
25246 @cindex writing a frame filter
25248 There are three basic elements that a frame filter must implement: it
25249 must correctly implement the documented interface (@pxref{Frame Filter
25250 API}), it must register itself with @value{GDBN}, and finally, it must
25251 decide if it is to work on the data provided by @value{GDBN}. In all
25252 cases, whether it works on the iterator or not, each frame filter must
25253 return an iterator. A bare-bones frame filter follows the pattern in
25254 the following example.
25259 class FrameFilter():
25261 def __init__(self):
25262 # Frame filter attribute creation.
25264 # 'name' is the name of the filter that GDB will display.
25266 # 'priority' is the priority of the filter relative to other
25269 # 'enabled' is a boolean that indicates whether this filter is
25270 # enabled and should be executed.
25273 self.priority = 100
25274 self.enabled = True
25276 # Register this frame filter with the global frame_filters
25278 gdb.frame_filters[self.name] = self
25280 def filter(self, frame_iter):
25281 # Just return the iterator.
25285 The frame filter in the example above implements the three
25286 requirements for all frame filters. It implements the API, self
25287 registers, and makes a decision on the iterator (in this case, it just
25288 returns the iterator untouched).
25290 The first step is attribute creation and assignment, and as shown in
25291 the comments the filter assigns the following attributes: @code{name},
25292 @code{priority} and whether the filter should be enabled with the
25293 @code{enabled} attribute.
25295 The second step is registering the frame filter with the dictionary or
25296 dictionaries that the frame filter has interest in. As shown in the
25297 comments, this filter just registers itself with the global dictionary
25298 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25299 is a dictionary that is initialized in the @code{gdb} module when
25300 @value{GDBN} starts. What dictionary a filter registers with is an
25301 important consideration. Generally, if a filter is specific to a set
25302 of code, it should be registered either in the @code{objfile} or
25303 @code{progspace} dictionaries as they are specific to the program
25304 currently loaded in @value{GDBN}. The global dictionary is always
25305 present in @value{GDBN} and is never unloaded. Any filters registered
25306 with the global dictionary will exist until @value{GDBN} exits. To
25307 avoid filters that may conflict, it is generally better to register
25308 frame filters against the dictionaries that more closely align with
25309 the usage of the filter currently in question. @xref{Python
25310 Auto-loading}, for further information on auto-loading Python scripts.
25312 @value{GDBN} takes a hands-off approach to frame filter registration,
25313 therefore it is the frame filter's responsibility to ensure
25314 registration has occurred, and that any exceptions are handled
25315 appropriately. In particular, you may wish to handle exceptions
25316 relating to Python dictionary key uniqueness. It is mandatory that
25317 the dictionary key is the same as frame filter's @code{name}
25318 attribute. When a user manages frame filters (@pxref{Frame Filter
25319 Management}), the names @value{GDBN} will display are those contained
25320 in the @code{name} attribute.
25322 The final step of this example is the implementation of the
25323 @code{filter} method. As shown in the example comments, we define the
25324 @code{filter} method and note that the method must take an iterator,
25325 and also must return an iterator. In this bare-bones example, the
25326 frame filter is not very useful as it just returns the iterator
25327 untouched. However this is a valid operation for frame filters that
25328 have the @code{enabled} attribute set, but decide not to operate on
25331 In the next example, the frame filter operates on all frames and
25332 utilizes a frame decorator to perform some work on the frames.
25333 @xref{Frame Decorator API}, for further information on the frame
25334 decorator interface.
25336 This example works on inlined frames. It highlights frames which are
25337 inlined by tagging them with an ``[inlined]'' tag. By applying a
25338 frame decorator to all frames with the Python @code{itertools imap}
25339 method, the example defers actions to the frame decorator. Frame
25340 decorators are only processed when @value{GDBN} prints the backtrace.
25342 This introduces a new decision making topic: whether to perform
25343 decision making operations at the filtering step, or at the printing
25344 step. In this example's approach, it does not perform any filtering
25345 decisions at the filtering step beyond mapping a frame decorator to
25346 each frame. This allows the actual decision making to be performed
25347 when each frame is printed. This is an important consideration, and
25348 well worth reflecting upon when designing a frame filter. An issue
25349 that frame filters should avoid is unwinding the stack if possible.
25350 Some stacks can run very deep, into the tens of thousands in some
25351 cases. To search every frame to determine if it is inlined ahead of
25352 time may be too expensive at the filtering step. The frame filter
25353 cannot know how many frames it has to iterate over, and it would have
25354 to iterate through them all. This ends up duplicating effort as
25355 @value{GDBN} performs this iteration when it prints the frames.
25357 In this example decision making can be deferred to the printing step.
25358 As each frame is printed, the frame decorator can examine each frame
25359 in turn when @value{GDBN} iterates. From a performance viewpoint,
25360 this is the most appropriate decision to make as it avoids duplicating
25361 the effort that the printing step would undertake anyway. Also, if
25362 there are many frame filters unwinding the stack during filtering, it
25363 can substantially delay the printing of the backtrace which will
25364 result in large memory usage, and a poor user experience.
25367 class InlineFilter():
25369 def __init__(self):
25370 self.name = "InlinedFrameFilter"
25371 self.priority = 100
25372 self.enabled = True
25373 gdb.frame_filters[self.name] = self
25375 def filter(self, frame_iter):
25376 frame_iter = itertools.imap(InlinedFrameDecorator,
25381 This frame filter is somewhat similar to the earlier example, except
25382 that the @code{filter} method applies a frame decorator object called
25383 @code{InlinedFrameDecorator} to each element in the iterator. The
25384 @code{imap} Python method is light-weight. It does not proactively
25385 iterate over the iterator, but rather creates a new iterator which
25386 wraps the existing one.
25388 Below is the frame decorator for this example.
25391 class InlinedFrameDecorator(FrameDecorator):
25393 def __init__(self, fobj):
25394 super(InlinedFrameDecorator, self).__init__(fobj)
25396 def function(self):
25397 frame = fobj.inferior_frame()
25398 name = str(frame.name())
25400 if frame.type() == gdb.INLINE_FRAME:
25401 name = name + " [inlined]"
25406 This frame decorator only defines and overrides the @code{function}
25407 method. It lets the supplied @code{FrameDecorator}, which is shipped
25408 with @value{GDBN}, perform the other work associated with printing
25411 The combination of these two objects create this output from a
25415 #0 0x004004e0 in bar () at inline.c:11
25416 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25417 #2 0x00400566 in main () at inline.c:31
25420 So in the case of this example, a frame decorator is applied to all
25421 frames, regardless of whether they may be inlined or not. As
25422 @value{GDBN} iterates over the iterator produced by the frame filters,
25423 @value{GDBN} executes each frame decorator which then makes a decision
25424 on what to print in the @code{function} callback. Using a strategy
25425 like this is a way to defer decisions on the frame content to printing
25428 @subheading Eliding Frames
25430 It might be that the above example is not desirable for representing
25431 inlined frames, and a hierarchical approach may be preferred. If we
25432 want to hierarchically represent frames, the @code{elided} frame
25433 decorator interface might be preferable.
25435 This example approaches the issue with the @code{elided} method. This
25436 example is quite long, but very simplistic. It is out-of-scope for
25437 this section to write a complete example that comprehensively covers
25438 all approaches of finding and printing inlined frames. However, this
25439 example illustrates the approach an author might use.
25441 This example comprises of three sections.
25444 class InlineFrameFilter():
25446 def __init__(self):
25447 self.name = "InlinedFrameFilter"
25448 self.priority = 100
25449 self.enabled = True
25450 gdb.frame_filters[self.name] = self
25452 def filter(self, frame_iter):
25453 return ElidingInlineIterator(frame_iter)
25456 This frame filter is very similar to the other examples. The only
25457 difference is this frame filter is wrapping the iterator provided to
25458 it (@code{frame_iter}) with a custom iterator called
25459 @code{ElidingInlineIterator}. This again defers actions to when
25460 @value{GDBN} prints the backtrace, as the iterator is not traversed
25463 The iterator for this example is as follows. It is in this section of
25464 the example where decisions are made on the content of the backtrace.
25467 class ElidingInlineIterator:
25468 def __init__(self, ii):
25469 self.input_iterator = ii
25471 def __iter__(self):
25475 frame = next(self.input_iterator)
25477 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25481 eliding_frame = next(self.input_iterator)
25482 except StopIteration:
25484 return ElidingFrameDecorator(eliding_frame, [frame])
25487 This iterator implements the Python iterator protocol. When the
25488 @code{next} function is called (when @value{GDBN} prints each frame),
25489 the iterator checks if this frame decorator, @code{frame}, is wrapping
25490 an inlined frame. If it is not, it returns the existing frame decorator
25491 untouched. If it is wrapping an inlined frame, it assumes that the
25492 inlined frame was contained within the next oldest frame,
25493 @code{eliding_frame}, which it fetches. It then creates and returns a
25494 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25495 elided frame, and the eliding frame.
25498 class ElidingInlineDecorator(FrameDecorator):
25500 def __init__(self, frame, elided_frames):
25501 super(ElidingInlineDecorator, self).__init__(frame)
25503 self.elided_frames = elided_frames
25506 return iter(self.elided_frames)
25509 This frame decorator overrides one function and returns the inlined
25510 frame in the @code{elided} method. As before it lets
25511 @code{FrameDecorator} do the rest of the work involved in printing
25512 this frame. This produces the following output.
25515 #0 0x004004e0 in bar () at inline.c:11
25516 #2 0x00400529 in main () at inline.c:25
25517 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25520 In that output, @code{max} which has been inlined into @code{main} is
25521 printed hierarchically. Another approach would be to combine the
25522 @code{function} method, and the @code{elided} method to both print a
25523 marker in the inlined frame, and also show the hierarchical
25526 @node Inferiors In Python
25527 @subsubsection Inferiors In Python
25528 @cindex inferiors in Python
25530 @findex gdb.Inferior
25531 Programs which are being run under @value{GDBN} are called inferiors
25532 (@pxref{Inferiors and Programs}). Python scripts can access
25533 information about and manipulate inferiors controlled by @value{GDBN}
25534 via objects of the @code{gdb.Inferior} class.
25536 The following inferior-related functions are available in the @code{gdb}
25539 @defun gdb.inferiors ()
25540 Return a tuple containing all inferior objects.
25543 @defun gdb.selected_inferior ()
25544 Return an object representing the current inferior.
25547 A @code{gdb.Inferior} object has the following attributes:
25549 @defvar Inferior.num
25550 ID of inferior, as assigned by GDB.
25553 @defvar Inferior.pid
25554 Process ID of the inferior, as assigned by the underlying operating
25558 @defvar Inferior.was_attached
25559 Boolean signaling whether the inferior was created using `attach', or
25560 started by @value{GDBN} itself.
25563 A @code{gdb.Inferior} object has the following methods:
25565 @defun Inferior.is_valid ()
25566 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25567 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25568 if the inferior no longer exists within @value{GDBN}. All other
25569 @code{gdb.Inferior} methods will throw an exception if it is invalid
25570 at the time the method is called.
25573 @defun Inferior.threads ()
25574 This method returns a tuple holding all the threads which are valid
25575 when it is called. If there are no valid threads, the method will
25576 return an empty tuple.
25579 @findex Inferior.read_memory
25580 @defun Inferior.read_memory (address, length)
25581 Read @var{length} bytes of memory from the inferior, starting at
25582 @var{address}. Returns a buffer object, which behaves much like an array
25583 or a string. It can be modified and given to the
25584 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25585 value is a @code{memoryview} object.
25588 @findex Inferior.write_memory
25589 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25590 Write the contents of @var{buffer} to the inferior, starting at
25591 @var{address}. The @var{buffer} parameter must be a Python object
25592 which supports the buffer protocol, i.e., a string, an array or the
25593 object returned from @code{Inferior.read_memory}. If given, @var{length}
25594 determines the number of bytes from @var{buffer} to be written.
25597 @findex gdb.search_memory
25598 @defun Inferior.search_memory (address, length, pattern)
25599 Search a region of the inferior memory starting at @var{address} with
25600 the given @var{length} using the search pattern supplied in
25601 @var{pattern}. The @var{pattern} parameter must be a Python object
25602 which supports the buffer protocol, i.e., a string, an array or the
25603 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25604 containing the address where the pattern was found, or @code{None} if
25605 the pattern could not be found.
25608 @node Events In Python
25609 @subsubsection Events In Python
25610 @cindex inferior events in Python
25612 @value{GDBN} provides a general event facility so that Python code can be
25613 notified of various state changes, particularly changes that occur in
25616 An @dfn{event} is just an object that describes some state change. The
25617 type of the object and its attributes will vary depending on the details
25618 of the change. All the existing events are described below.
25620 In order to be notified of an event, you must register an event handler
25621 with an @dfn{event registry}. An event registry is an object in the
25622 @code{gdb.events} module which dispatches particular events. A registry
25623 provides methods to register and unregister event handlers:
25625 @defun EventRegistry.connect (object)
25626 Add the given callable @var{object} to the registry. This object will be
25627 called when an event corresponding to this registry occurs.
25630 @defun EventRegistry.disconnect (object)
25631 Remove the given @var{object} from the registry. Once removed, the object
25632 will no longer receive notifications of events.
25635 Here is an example:
25638 def exit_handler (event):
25639 print "event type: exit"
25640 print "exit code: %d" % (event.exit_code)
25642 gdb.events.exited.connect (exit_handler)
25645 In the above example we connect our handler @code{exit_handler} to the
25646 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25647 called when the inferior exits. The argument @dfn{event} in this example is
25648 of type @code{gdb.ExitedEvent}. As you can see in the example the
25649 @code{ExitedEvent} object has an attribute which indicates the exit code of
25652 The following is a listing of the event registries that are available and
25653 details of the events they emit:
25658 Emits @code{gdb.ThreadEvent}.
25660 Some events can be thread specific when @value{GDBN} is running in non-stop
25661 mode. When represented in Python, these events all extend
25662 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25663 events which are emitted by this or other modules might extend this event.
25664 Examples of these events are @code{gdb.BreakpointEvent} and
25665 @code{gdb.ContinueEvent}.
25667 @defvar ThreadEvent.inferior_thread
25668 In non-stop mode this attribute will be set to the specific thread which was
25669 involved in the emitted event. Otherwise, it will be set to @code{None}.
25672 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25674 This event indicates that the inferior has been continued after a stop. For
25675 inherited attribute refer to @code{gdb.ThreadEvent} above.
25677 @item events.exited
25678 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25679 @code{events.ExitedEvent} has two attributes:
25680 @defvar ExitedEvent.exit_code
25681 An integer representing the exit code, if available, which the inferior
25682 has returned. (The exit code could be unavailable if, for example,
25683 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25684 the attribute does not exist.
25686 @defvar ExitedEvent inferior
25687 A reference to the inferior which triggered the @code{exited} event.
25691 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25693 Indicates that the inferior has stopped. All events emitted by this registry
25694 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25695 will indicate the stopped thread when @value{GDBN} is running in non-stop
25696 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25698 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25700 This event indicates that the inferior or one of its threads has received as
25701 signal. @code{gdb.SignalEvent} has the following attributes:
25703 @defvar SignalEvent.stop_signal
25704 A string representing the signal received by the inferior. A list of possible
25705 signal values can be obtained by running the command @code{info signals} in
25706 the @value{GDBN} command prompt.
25709 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25711 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25712 been hit, and has the following attributes:
25714 @defvar BreakpointEvent.breakpoints
25715 A sequence containing references to all the breakpoints (type
25716 @code{gdb.Breakpoint}) that were hit.
25717 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25719 @defvar BreakpointEvent.breakpoint
25720 A reference to the first breakpoint that was hit.
25721 This function is maintained for backward compatibility and is now deprecated
25722 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25725 @item events.new_objfile
25726 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25727 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25729 @defvar NewObjFileEvent.new_objfile
25730 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25731 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25736 @node Threads In Python
25737 @subsubsection Threads In Python
25738 @cindex threads in python
25740 @findex gdb.InferiorThread
25741 Python scripts can access information about, and manipulate inferior threads
25742 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25744 The following thread-related functions are available in the @code{gdb}
25747 @findex gdb.selected_thread
25748 @defun gdb.selected_thread ()
25749 This function returns the thread object for the selected thread. If there
25750 is no selected thread, this will return @code{None}.
25753 A @code{gdb.InferiorThread} object has the following attributes:
25755 @defvar InferiorThread.name
25756 The name of the thread. If the user specified a name using
25757 @code{thread name}, then this returns that name. Otherwise, if an
25758 OS-supplied name is available, then it is returned. Otherwise, this
25759 returns @code{None}.
25761 This attribute can be assigned to. The new value must be a string
25762 object, which sets the new name, or @code{None}, which removes any
25763 user-specified thread name.
25766 @defvar InferiorThread.num
25767 ID of the thread, as assigned by GDB.
25770 @defvar InferiorThread.ptid
25771 ID of the thread, as assigned by the operating system. This attribute is a
25772 tuple containing three integers. The first is the Process ID (PID); the second
25773 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25774 Either the LWPID or TID may be 0, which indicates that the operating system
25775 does not use that identifier.
25778 A @code{gdb.InferiorThread} object has the following methods:
25780 @defun InferiorThread.is_valid ()
25781 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25782 @code{False} if not. A @code{gdb.InferiorThread} object will become
25783 invalid if the thread exits, or the inferior that the thread belongs
25784 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25785 exception if it is invalid at the time the method is called.
25788 @defun InferiorThread.switch ()
25789 This changes @value{GDBN}'s currently selected thread to the one represented
25793 @defun InferiorThread.is_stopped ()
25794 Return a Boolean indicating whether the thread is stopped.
25797 @defun InferiorThread.is_running ()
25798 Return a Boolean indicating whether the thread is running.
25801 @defun InferiorThread.is_exited ()
25802 Return a Boolean indicating whether the thread is exited.
25805 @node Commands In Python
25806 @subsubsection Commands In Python
25808 @cindex commands in python
25809 @cindex python commands
25810 You can implement new @value{GDBN} CLI commands in Python. A CLI
25811 command is implemented using an instance of the @code{gdb.Command}
25812 class, most commonly using a subclass.
25814 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25815 The object initializer for @code{Command} registers the new command
25816 with @value{GDBN}. This initializer is normally invoked from the
25817 subclass' own @code{__init__} method.
25819 @var{name} is the name of the command. If @var{name} consists of
25820 multiple words, then the initial words are looked for as prefix
25821 commands. In this case, if one of the prefix commands does not exist,
25822 an exception is raised.
25824 There is no support for multi-line commands.
25826 @var{command_class} should be one of the @samp{COMMAND_} constants
25827 defined below. This argument tells @value{GDBN} how to categorize the
25828 new command in the help system.
25830 @var{completer_class} is an optional argument. If given, it should be
25831 one of the @samp{COMPLETE_} constants defined below. This argument
25832 tells @value{GDBN} how to perform completion for this command. If not
25833 given, @value{GDBN} will attempt to complete using the object's
25834 @code{complete} method (see below); if no such method is found, an
25835 error will occur when completion is attempted.
25837 @var{prefix} is an optional argument. If @code{True}, then the new
25838 command is a prefix command; sub-commands of this command may be
25841 The help text for the new command is taken from the Python
25842 documentation string for the command's class, if there is one. If no
25843 documentation string is provided, the default value ``This command is
25844 not documented.'' is used.
25847 @cindex don't repeat Python command
25848 @defun Command.dont_repeat ()
25849 By default, a @value{GDBN} command is repeated when the user enters a
25850 blank line at the command prompt. A command can suppress this
25851 behavior by invoking the @code{dont_repeat} method. This is similar
25852 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25855 @defun Command.invoke (argument, from_tty)
25856 This method is called by @value{GDBN} when this command is invoked.
25858 @var{argument} is a string. It is the argument to the command, after
25859 leading and trailing whitespace has been stripped.
25861 @var{from_tty} is a boolean argument. When true, this means that the
25862 command was entered by the user at the terminal; when false it means
25863 that the command came from elsewhere.
25865 If this method throws an exception, it is turned into a @value{GDBN}
25866 @code{error} call. Otherwise, the return value is ignored.
25868 @findex gdb.string_to_argv
25869 To break @var{argument} up into an argv-like string use
25870 @code{gdb.string_to_argv}. This function behaves identically to
25871 @value{GDBN}'s internal argument lexer @code{buildargv}.
25872 It is recommended to use this for consistency.
25873 Arguments are separated by spaces and may be quoted.
25877 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25878 ['1', '2 "3', '4 "5', "6 '7"]
25883 @cindex completion of Python commands
25884 @defun Command.complete (text, word)
25885 This method is called by @value{GDBN} when the user attempts
25886 completion on this command. All forms of completion are handled by
25887 this method, that is, the @key{TAB} and @key{M-?} key bindings
25888 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25891 The arguments @var{text} and @var{word} are both strings. @var{text}
25892 holds the complete command line up to the cursor's location.
25893 @var{word} holds the last word of the command line; this is computed
25894 using a word-breaking heuristic.
25896 The @code{complete} method can return several values:
25899 If the return value is a sequence, the contents of the sequence are
25900 used as the completions. It is up to @code{complete} to ensure that the
25901 contents actually do complete the word. A zero-length sequence is
25902 allowed, it means that there were no completions available. Only
25903 string elements of the sequence are used; other elements in the
25904 sequence are ignored.
25907 If the return value is one of the @samp{COMPLETE_} constants defined
25908 below, then the corresponding @value{GDBN}-internal completion
25909 function is invoked, and its result is used.
25912 All other results are treated as though there were no available
25917 When a new command is registered, it must be declared as a member of
25918 some general class of commands. This is used to classify top-level
25919 commands in the on-line help system; note that prefix commands are not
25920 listed under their own category but rather that of their top-level
25921 command. The available classifications are represented by constants
25922 defined in the @code{gdb} module:
25925 @findex COMMAND_NONE
25926 @findex gdb.COMMAND_NONE
25927 @item gdb.COMMAND_NONE
25928 The command does not belong to any particular class. A command in
25929 this category will not be displayed in any of the help categories.
25931 @findex COMMAND_RUNNING
25932 @findex gdb.COMMAND_RUNNING
25933 @item gdb.COMMAND_RUNNING
25934 The command is related to running the inferior. For example,
25935 @code{start}, @code{step}, and @code{continue} are in this category.
25936 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25937 commands in this category.
25939 @findex COMMAND_DATA
25940 @findex gdb.COMMAND_DATA
25941 @item gdb.COMMAND_DATA
25942 The command is related to data or variables. For example,
25943 @code{call}, @code{find}, and @code{print} are in this category. Type
25944 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25947 @findex COMMAND_STACK
25948 @findex gdb.COMMAND_STACK
25949 @item gdb.COMMAND_STACK
25950 The command has to do with manipulation of the stack. For example,
25951 @code{backtrace}, @code{frame}, and @code{return} are in this
25952 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25953 list of commands in this category.
25955 @findex COMMAND_FILES
25956 @findex gdb.COMMAND_FILES
25957 @item gdb.COMMAND_FILES
25958 This class is used for file-related commands. For example,
25959 @code{file}, @code{list} and @code{section} are in this category.
25960 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25961 commands in this category.
25963 @findex COMMAND_SUPPORT
25964 @findex gdb.COMMAND_SUPPORT
25965 @item gdb.COMMAND_SUPPORT
25966 This should be used for ``support facilities'', generally meaning
25967 things that are useful to the user when interacting with @value{GDBN},
25968 but not related to the state of the inferior. For example,
25969 @code{help}, @code{make}, and @code{shell} are in this category. Type
25970 @kbd{help support} at the @value{GDBN} prompt to see a list of
25971 commands in this category.
25973 @findex COMMAND_STATUS
25974 @findex gdb.COMMAND_STATUS
25975 @item gdb.COMMAND_STATUS
25976 The command is an @samp{info}-related command, that is, related to the
25977 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25978 and @code{show} are in this category. Type @kbd{help status} at the
25979 @value{GDBN} prompt to see a list of commands in this category.
25981 @findex COMMAND_BREAKPOINTS
25982 @findex gdb.COMMAND_BREAKPOINTS
25983 @item gdb.COMMAND_BREAKPOINTS
25984 The command has to do with breakpoints. For example, @code{break},
25985 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25986 breakpoints} at the @value{GDBN} prompt to see a list of commands in
25989 @findex COMMAND_TRACEPOINTS
25990 @findex gdb.COMMAND_TRACEPOINTS
25991 @item gdb.COMMAND_TRACEPOINTS
25992 The command has to do with tracepoints. For example, @code{trace},
25993 @code{actions}, and @code{tfind} are in this category. Type
25994 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
25995 commands in this category.
25997 @findex COMMAND_USER
25998 @findex gdb.COMMAND_USER
25999 @item gdb.COMMAND_USER
26000 The command is a general purpose command for the user, and typically
26001 does not fit in one of the other categories.
26002 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26003 a list of commands in this category, as well as the list of gdb macros
26004 (@pxref{Sequences}).
26006 @findex COMMAND_OBSCURE
26007 @findex gdb.COMMAND_OBSCURE
26008 @item gdb.COMMAND_OBSCURE
26009 The command is only used in unusual circumstances, or is not of
26010 general interest to users. For example, @code{checkpoint},
26011 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26012 obscure} at the @value{GDBN} prompt to see a list of commands in this
26015 @findex COMMAND_MAINTENANCE
26016 @findex gdb.COMMAND_MAINTENANCE
26017 @item gdb.COMMAND_MAINTENANCE
26018 The command is only useful to @value{GDBN} maintainers. The
26019 @code{maintenance} and @code{flushregs} commands are in this category.
26020 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26021 commands in this category.
26024 A new command can use a predefined completion function, either by
26025 specifying it via an argument at initialization, or by returning it
26026 from the @code{complete} method. These predefined completion
26027 constants are all defined in the @code{gdb} module:
26030 @findex COMPLETE_NONE
26031 @findex gdb.COMPLETE_NONE
26032 @item gdb.COMPLETE_NONE
26033 This constant means that no completion should be done.
26035 @findex COMPLETE_FILENAME
26036 @findex gdb.COMPLETE_FILENAME
26037 @item gdb.COMPLETE_FILENAME
26038 This constant means that filename completion should be performed.
26040 @findex COMPLETE_LOCATION
26041 @findex gdb.COMPLETE_LOCATION
26042 @item gdb.COMPLETE_LOCATION
26043 This constant means that location completion should be done.
26044 @xref{Specify Location}.
26046 @findex COMPLETE_COMMAND
26047 @findex gdb.COMPLETE_COMMAND
26048 @item gdb.COMPLETE_COMMAND
26049 This constant means that completion should examine @value{GDBN}
26052 @findex COMPLETE_SYMBOL
26053 @findex gdb.COMPLETE_SYMBOL
26054 @item gdb.COMPLETE_SYMBOL
26055 This constant means that completion should be done using symbol names
26058 @findex COMPLETE_EXPRESSION
26059 @findex gdb.COMPLETE_EXPRESSION
26060 @item gdb.COMPLETE_EXPRESSION
26061 This constant means that completion should be done on expressions.
26062 Often this means completing on symbol names, but some language
26063 parsers also have support for completing on field names.
26066 The following code snippet shows how a trivial CLI command can be
26067 implemented in Python:
26070 class HelloWorld (gdb.Command):
26071 """Greet the whole world."""
26073 def __init__ (self):
26074 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26076 def invoke (self, arg, from_tty):
26077 print "Hello, World!"
26082 The last line instantiates the class, and is necessary to trigger the
26083 registration of the command with @value{GDBN}. Depending on how the
26084 Python code is read into @value{GDBN}, you may need to import the
26085 @code{gdb} module explicitly.
26087 @node Parameters In Python
26088 @subsubsection Parameters In Python
26090 @cindex parameters in python
26091 @cindex python parameters
26092 @tindex gdb.Parameter
26094 You can implement new @value{GDBN} parameters using Python. A new
26095 parameter is implemented as an instance of the @code{gdb.Parameter}
26098 Parameters are exposed to the user via the @code{set} and
26099 @code{show} commands. @xref{Help}.
26101 There are many parameters that already exist and can be set in
26102 @value{GDBN}. Two examples are: @code{set follow fork} and
26103 @code{set charset}. Setting these parameters influences certain
26104 behavior in @value{GDBN}. Similarly, you can define parameters that
26105 can be used to influence behavior in custom Python scripts and commands.
26107 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26108 The object initializer for @code{Parameter} registers the new
26109 parameter with @value{GDBN}. This initializer is normally invoked
26110 from the subclass' own @code{__init__} method.
26112 @var{name} is the name of the new parameter. If @var{name} consists
26113 of multiple words, then the initial words are looked for as prefix
26114 parameters. An example of this can be illustrated with the
26115 @code{set print} set of parameters. If @var{name} is
26116 @code{print foo}, then @code{print} will be searched as the prefix
26117 parameter. In this case the parameter can subsequently be accessed in
26118 @value{GDBN} as @code{set print foo}.
26120 If @var{name} consists of multiple words, and no prefix parameter group
26121 can be found, an exception is raised.
26123 @var{command-class} should be one of the @samp{COMMAND_} constants
26124 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26125 categorize the new parameter in the help system.
26127 @var{parameter-class} should be one of the @samp{PARAM_} constants
26128 defined below. This argument tells @value{GDBN} the type of the new
26129 parameter; this information is used for input validation and
26132 If @var{parameter-class} is @code{PARAM_ENUM}, then
26133 @var{enum-sequence} must be a sequence of strings. These strings
26134 represent the possible values for the parameter.
26136 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26137 of a fourth argument will cause an exception to be thrown.
26139 The help text for the new parameter is taken from the Python
26140 documentation string for the parameter's class, if there is one. If
26141 there is no documentation string, a default value is used.
26144 @defvar Parameter.set_doc
26145 If this attribute exists, and is a string, then its value is used as
26146 the help text for this parameter's @code{set} command. The value is
26147 examined when @code{Parameter.__init__} is invoked; subsequent changes
26151 @defvar Parameter.show_doc
26152 If this attribute exists, and is a string, then its value is used as
26153 the help text for this parameter's @code{show} command. The value is
26154 examined when @code{Parameter.__init__} is invoked; subsequent changes
26158 @defvar Parameter.value
26159 The @code{value} attribute holds the underlying value of the
26160 parameter. It can be read and assigned to just as any other
26161 attribute. @value{GDBN} does validation when assignments are made.
26164 There are two methods that should be implemented in any
26165 @code{Parameter} class. These are:
26167 @defun Parameter.get_set_string (self)
26168 @value{GDBN} will call this method when a @var{parameter}'s value has
26169 been changed via the @code{set} API (for example, @kbd{set foo off}).
26170 The @code{value} attribute has already been populated with the new
26171 value and may be used in output. This method must return a string.
26174 @defun Parameter.get_show_string (self, svalue)
26175 @value{GDBN} will call this method when a @var{parameter}'s
26176 @code{show} API has been invoked (for example, @kbd{show foo}). The
26177 argument @code{svalue} receives the string representation of the
26178 current value. This method must return a string.
26181 When a new parameter is defined, its type must be specified. The
26182 available types are represented by constants defined in the @code{gdb}
26186 @findex PARAM_BOOLEAN
26187 @findex gdb.PARAM_BOOLEAN
26188 @item gdb.PARAM_BOOLEAN
26189 The value is a plain boolean. The Python boolean values, @code{True}
26190 and @code{False} are the only valid values.
26192 @findex PARAM_AUTO_BOOLEAN
26193 @findex gdb.PARAM_AUTO_BOOLEAN
26194 @item gdb.PARAM_AUTO_BOOLEAN
26195 The value has three possible states: true, false, and @samp{auto}. In
26196 Python, true and false are represented using boolean constants, and
26197 @samp{auto} is represented using @code{None}.
26199 @findex PARAM_UINTEGER
26200 @findex gdb.PARAM_UINTEGER
26201 @item gdb.PARAM_UINTEGER
26202 The value is an unsigned integer. The value of 0 should be
26203 interpreted to mean ``unlimited''.
26205 @findex PARAM_INTEGER
26206 @findex gdb.PARAM_INTEGER
26207 @item gdb.PARAM_INTEGER
26208 The value is a signed integer. The value of 0 should be interpreted
26209 to mean ``unlimited''.
26211 @findex PARAM_STRING
26212 @findex gdb.PARAM_STRING
26213 @item gdb.PARAM_STRING
26214 The value is a string. When the user modifies the string, any escape
26215 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26216 translated into corresponding characters and encoded into the current
26219 @findex PARAM_STRING_NOESCAPE
26220 @findex gdb.PARAM_STRING_NOESCAPE
26221 @item gdb.PARAM_STRING_NOESCAPE
26222 The value is a string. When the user modifies the string, escapes are
26223 passed through untranslated.
26225 @findex PARAM_OPTIONAL_FILENAME
26226 @findex gdb.PARAM_OPTIONAL_FILENAME
26227 @item gdb.PARAM_OPTIONAL_FILENAME
26228 The value is a either a filename (a string), or @code{None}.
26230 @findex PARAM_FILENAME
26231 @findex gdb.PARAM_FILENAME
26232 @item gdb.PARAM_FILENAME
26233 The value is a filename. This is just like
26234 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26236 @findex PARAM_ZINTEGER
26237 @findex gdb.PARAM_ZINTEGER
26238 @item gdb.PARAM_ZINTEGER
26239 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26240 is interpreted as itself.
26243 @findex gdb.PARAM_ENUM
26244 @item gdb.PARAM_ENUM
26245 The value is a string, which must be one of a collection string
26246 constants provided when the parameter is created.
26249 @node Functions In Python
26250 @subsubsection Writing new convenience functions
26252 @cindex writing convenience functions
26253 @cindex convenience functions in python
26254 @cindex python convenience functions
26255 @tindex gdb.Function
26257 You can implement new convenience functions (@pxref{Convenience Vars})
26258 in Python. A convenience function is an instance of a subclass of the
26259 class @code{gdb.Function}.
26261 @defun Function.__init__ (name)
26262 The initializer for @code{Function} registers the new function with
26263 @value{GDBN}. The argument @var{name} is the name of the function,
26264 a string. The function will be visible to the user as a convenience
26265 variable of type @code{internal function}, whose name is the same as
26266 the given @var{name}.
26268 The documentation for the new function is taken from the documentation
26269 string for the new class.
26272 @defun Function.invoke (@var{*args})
26273 When a convenience function is evaluated, its arguments are converted
26274 to instances of @code{gdb.Value}, and then the function's
26275 @code{invoke} method is called. Note that @value{GDBN} does not
26276 predetermine the arity of convenience functions. Instead, all
26277 available arguments are passed to @code{invoke}, following the
26278 standard Python calling convention. In particular, a convenience
26279 function can have default values for parameters without ill effect.
26281 The return value of this method is used as its value in the enclosing
26282 expression. If an ordinary Python value is returned, it is converted
26283 to a @code{gdb.Value} following the usual rules.
26286 The following code snippet shows how a trivial convenience function can
26287 be implemented in Python:
26290 class Greet (gdb.Function):
26291 """Return string to greet someone.
26292 Takes a name as argument."""
26294 def __init__ (self):
26295 super (Greet, self).__init__ ("greet")
26297 def invoke (self, name):
26298 return "Hello, %s!" % name.string ()
26303 The last line instantiates the class, and is necessary to trigger the
26304 registration of the function with @value{GDBN}. Depending on how the
26305 Python code is read into @value{GDBN}, you may need to import the
26306 @code{gdb} module explicitly.
26308 Now you can use the function in an expression:
26311 (gdb) print $greet("Bob")
26315 @node Progspaces In Python
26316 @subsubsection Program Spaces In Python
26318 @cindex progspaces in python
26319 @tindex gdb.Progspace
26321 A program space, or @dfn{progspace}, represents a symbolic view
26322 of an address space.
26323 It consists of all of the objfiles of the program.
26324 @xref{Objfiles In Python}.
26325 @xref{Inferiors and Programs, program spaces}, for more details
26326 about program spaces.
26328 The following progspace-related functions are available in the
26331 @findex gdb.current_progspace
26332 @defun gdb.current_progspace ()
26333 This function returns the program space of the currently selected inferior.
26334 @xref{Inferiors and Programs}.
26337 @findex gdb.progspaces
26338 @defun gdb.progspaces ()
26339 Return a sequence of all the progspaces currently known to @value{GDBN}.
26342 Each progspace is represented by an instance of the @code{gdb.Progspace}
26345 @defvar Progspace.filename
26346 The file name of the progspace as a string.
26349 @defvar Progspace.pretty_printers
26350 The @code{pretty_printers} attribute is a list of functions. It is
26351 used to look up pretty-printers. A @code{Value} is passed to each
26352 function in order; if the function returns @code{None}, then the
26353 search continues. Otherwise, the return value should be an object
26354 which is used to format the value. @xref{Pretty Printing API}, for more
26358 @defvar Progspace.type_printers
26359 The @code{type_printers} attribute is a list of type printer objects.
26360 @xref{Type Printing API}, for more information.
26363 @defvar Progspace.frame_filters
26364 The @code{frame_filters} attribute is a dictionary of frame filter
26365 objects. @xref{Frame Filter API}, for more information.
26368 @node Objfiles In Python
26369 @subsubsection Objfiles In Python
26371 @cindex objfiles in python
26372 @tindex gdb.Objfile
26374 @value{GDBN} loads symbols for an inferior from various
26375 symbol-containing files (@pxref{Files}). These include the primary
26376 executable file, any shared libraries used by the inferior, and any
26377 separate debug info files (@pxref{Separate Debug Files}).
26378 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26380 The following objfile-related functions are available in the
26383 @findex gdb.current_objfile
26384 @defun gdb.current_objfile ()
26385 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26386 sets the ``current objfile'' to the corresponding objfile. This
26387 function returns the current objfile. If there is no current objfile,
26388 this function returns @code{None}.
26391 @findex gdb.objfiles
26392 @defun gdb.objfiles ()
26393 Return a sequence of all the objfiles current known to @value{GDBN}.
26394 @xref{Objfiles In Python}.
26397 Each objfile is represented by an instance of the @code{gdb.Objfile}
26400 @defvar Objfile.filename
26401 The file name of the objfile as a string.
26404 @defvar Objfile.pretty_printers
26405 The @code{pretty_printers} attribute is a list of functions. It is
26406 used to look up pretty-printers. A @code{Value} is passed to each
26407 function in order; if the function returns @code{None}, then the
26408 search continues. Otherwise, the return value should be an object
26409 which is used to format the value. @xref{Pretty Printing API}, for more
26413 @defvar Objfile.type_printers
26414 The @code{type_printers} attribute is a list of type printer objects.
26415 @xref{Type Printing API}, for more information.
26418 @defvar Objfile.frame_filters
26419 The @code{frame_filters} attribute is a dictionary of frame filter
26420 objects. @xref{Frame Filter API}, for more information.
26423 A @code{gdb.Objfile} object has the following methods:
26425 @defun Objfile.is_valid ()
26426 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26427 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26428 if the object file it refers to is not loaded in @value{GDBN} any
26429 longer. All other @code{gdb.Objfile} methods will throw an exception
26430 if it is invalid at the time the method is called.
26433 @node Frames In Python
26434 @subsubsection Accessing inferior stack frames from Python.
26436 @cindex frames in python
26437 When the debugged program stops, @value{GDBN} is able to analyze its call
26438 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26439 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26440 while its corresponding frame exists in the inferior's stack. If you try
26441 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26442 exception (@pxref{Exception Handling}).
26444 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26448 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26452 The following frame-related functions are available in the @code{gdb} module:
26454 @findex gdb.selected_frame
26455 @defun gdb.selected_frame ()
26456 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26459 @findex gdb.newest_frame
26460 @defun gdb.newest_frame ()
26461 Return the newest frame object for the selected thread.
26464 @defun gdb.frame_stop_reason_string (reason)
26465 Return a string explaining the reason why @value{GDBN} stopped unwinding
26466 frames, as expressed by the given @var{reason} code (an integer, see the
26467 @code{unwind_stop_reason} method further down in this section).
26470 A @code{gdb.Frame} object has the following methods:
26472 @defun Frame.is_valid ()
26473 Returns true if the @code{gdb.Frame} object is valid, false if not.
26474 A frame object can become invalid if the frame it refers to doesn't
26475 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26476 an exception if it is invalid at the time the method is called.
26479 @defun Frame.name ()
26480 Returns the function name of the frame, or @code{None} if it can't be
26484 @defun Frame.architecture ()
26485 Returns the @code{gdb.Architecture} object corresponding to the frame's
26486 architecture. @xref{Architectures In Python}.
26489 @defun Frame.type ()
26490 Returns the type of the frame. The value can be one of:
26492 @item gdb.NORMAL_FRAME
26493 An ordinary stack frame.
26495 @item gdb.DUMMY_FRAME
26496 A fake stack frame that was created by @value{GDBN} when performing an
26497 inferior function call.
26499 @item gdb.INLINE_FRAME
26500 A frame representing an inlined function. The function was inlined
26501 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26503 @item gdb.TAILCALL_FRAME
26504 A frame representing a tail call. @xref{Tail Call Frames}.
26506 @item gdb.SIGTRAMP_FRAME
26507 A signal trampoline frame. This is the frame created by the OS when
26508 it calls into a signal handler.
26510 @item gdb.ARCH_FRAME
26511 A fake stack frame representing a cross-architecture call.
26513 @item gdb.SENTINEL_FRAME
26514 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26519 @defun Frame.unwind_stop_reason ()
26520 Return an integer representing the reason why it's not possible to find
26521 more frames toward the outermost frame. Use
26522 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26523 function to a string. The value can be one of:
26526 @item gdb.FRAME_UNWIND_NO_REASON
26527 No particular reason (older frames should be available).
26529 @item gdb.FRAME_UNWIND_NULL_ID
26530 The previous frame's analyzer returns an invalid result.
26532 @item gdb.FRAME_UNWIND_OUTERMOST
26533 This frame is the outermost.
26535 @item gdb.FRAME_UNWIND_UNAVAILABLE
26536 Cannot unwind further, because that would require knowing the
26537 values of registers or memory that have not been collected.
26539 @item gdb.FRAME_UNWIND_INNER_ID
26540 This frame ID looks like it ought to belong to a NEXT frame,
26541 but we got it for a PREV frame. Normally, this is a sign of
26542 unwinder failure. It could also indicate stack corruption.
26544 @item gdb.FRAME_UNWIND_SAME_ID
26545 This frame has the same ID as the previous one. That means
26546 that unwinding further would almost certainly give us another
26547 frame with exactly the same ID, so break the chain. Normally,
26548 this is a sign of unwinder failure. It could also indicate
26551 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26552 The frame unwinder did not find any saved PC, but we needed
26553 one to unwind further.
26555 @item gdb.FRAME_UNWIND_FIRST_ERROR
26556 Any stop reason greater or equal to this value indicates some kind
26557 of error. This special value facilitates writing code that tests
26558 for errors in unwinding in a way that will work correctly even if
26559 the list of the other values is modified in future @value{GDBN}
26560 versions. Using it, you could write:
26562 reason = gdb.selected_frame().unwind_stop_reason ()
26563 reason_str = gdb.frame_stop_reason_string (reason)
26564 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26565 print "An error occured: %s" % reason_str
26572 Returns the frame's resume address.
26575 @defun Frame.block ()
26576 Return the frame's code block. @xref{Blocks In Python}.
26579 @defun Frame.function ()
26580 Return the symbol for the function corresponding to this frame.
26581 @xref{Symbols In Python}.
26584 @defun Frame.older ()
26585 Return the frame that called this frame.
26588 @defun Frame.newer ()
26589 Return the frame called by this frame.
26592 @defun Frame.find_sal ()
26593 Return the frame's symtab and line object.
26594 @xref{Symbol Tables In Python}.
26597 @defun Frame.read_var (variable @r{[}, block@r{]})
26598 Return the value of @var{variable} in this frame. If the optional
26599 argument @var{block} is provided, search for the variable from that
26600 block; otherwise start at the frame's current block (which is
26601 determined by the frame's current program counter). @var{variable}
26602 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26603 @code{gdb.Block} object.
26606 @defun Frame.select ()
26607 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26611 @node Blocks In Python
26612 @subsubsection Accessing blocks from Python.
26614 @cindex blocks in python
26617 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26618 roughly to a scope in the source code. Blocks are organized
26619 hierarchically, and are represented individually in Python as a
26620 @code{gdb.Block}. Blocks rely on debugging information being
26623 A frame has a block. Please see @ref{Frames In Python}, for a more
26624 in-depth discussion of frames.
26626 The outermost block is known as the @dfn{global block}. The global
26627 block typically holds public global variables and functions.
26629 The block nested just inside the global block is the @dfn{static
26630 block}. The static block typically holds file-scoped variables and
26633 @value{GDBN} provides a method to get a block's superblock, but there
26634 is currently no way to examine the sub-blocks of a block, or to
26635 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26638 Here is a short example that should help explain blocks:
26641 /* This is in the global block. */
26644 /* This is in the static block. */
26645 static int file_scope;
26647 /* 'function' is in the global block, and 'argument' is
26648 in a block nested inside of 'function'. */
26649 int function (int argument)
26651 /* 'local' is in a block inside 'function'. It may or may
26652 not be in the same block as 'argument'. */
26656 /* 'inner' is in a block whose superblock is the one holding
26660 /* If this call is expanded by the compiler, you may see
26661 a nested block here whose function is 'inline_function'
26662 and whose superblock is the one holding 'inner'. */
26663 inline_function ();
26668 A @code{gdb.Block} is iterable. The iterator returns the symbols
26669 (@pxref{Symbols In Python}) local to the block. Python programs
26670 should not assume that a specific block object will always contain a
26671 given symbol, since changes in @value{GDBN} features and
26672 infrastructure may cause symbols move across blocks in a symbol
26675 The following block-related functions are available in the @code{gdb}
26678 @findex gdb.block_for_pc
26679 @defun gdb.block_for_pc (pc)
26680 Return the innermost @code{gdb.Block} containing the given @var{pc}
26681 value. If the block cannot be found for the @var{pc} value specified,
26682 the function will return @code{None}.
26685 A @code{gdb.Block} object has the following methods:
26687 @defun Block.is_valid ()
26688 Returns @code{True} if the @code{gdb.Block} object is valid,
26689 @code{False} if not. A block object can become invalid if the block it
26690 refers to doesn't exist anymore in the inferior. All other
26691 @code{gdb.Block} methods will throw an exception if it is invalid at
26692 the time the method is called. The block's validity is also checked
26693 during iteration over symbols of the block.
26696 A @code{gdb.Block} object has the following attributes:
26698 @defvar Block.start
26699 The start address of the block. This attribute is not writable.
26703 The end address of the block. This attribute is not writable.
26706 @defvar Block.function
26707 The name of the block represented as a @code{gdb.Symbol}. If the
26708 block is not named, then this attribute holds @code{None}. This
26709 attribute is not writable.
26711 For ordinary function blocks, the superblock is the static block.
26712 However, you should note that it is possible for a function block to
26713 have a superblock that is not the static block -- for instance this
26714 happens for an inlined function.
26717 @defvar Block.superblock
26718 The block containing this block. If this parent block does not exist,
26719 this attribute holds @code{None}. This attribute is not writable.
26722 @defvar Block.global_block
26723 The global block associated with this block. This attribute is not
26727 @defvar Block.static_block
26728 The static block associated with this block. This attribute is not
26732 @defvar Block.is_global
26733 @code{True} if the @code{gdb.Block} object is a global block,
26734 @code{False} if not. This attribute is not
26738 @defvar Block.is_static
26739 @code{True} if the @code{gdb.Block} object is a static block,
26740 @code{False} if not. This attribute is not writable.
26743 @node Symbols In Python
26744 @subsubsection Python representation of Symbols.
26746 @cindex symbols in python
26749 @value{GDBN} represents every variable, function and type as an
26750 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26751 Similarly, Python represents these symbols in @value{GDBN} with the
26752 @code{gdb.Symbol} object.
26754 The following symbol-related functions are available in the @code{gdb}
26757 @findex gdb.lookup_symbol
26758 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26759 This function searches for a symbol by name. The search scope can be
26760 restricted to the parameters defined in the optional domain and block
26763 @var{name} is the name of the symbol. It must be a string. The
26764 optional @var{block} argument restricts the search to symbols visible
26765 in that @var{block}. The @var{block} argument must be a
26766 @code{gdb.Block} object. If omitted, the block for the current frame
26767 is used. The optional @var{domain} argument restricts
26768 the search to the domain type. The @var{domain} argument must be a
26769 domain constant defined in the @code{gdb} module and described later
26772 The result is a tuple of two elements.
26773 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26775 If the symbol is found, the second element is @code{True} if the symbol
26776 is a field of a method's object (e.g., @code{this} in C@t{++}),
26777 otherwise it is @code{False}.
26778 If the symbol is not found, the second element is @code{False}.
26781 @findex gdb.lookup_global_symbol
26782 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26783 This function searches for a global symbol by name.
26784 The search scope can be restricted to by the domain argument.
26786 @var{name} is the name of the symbol. It must be a string.
26787 The optional @var{domain} argument restricts the search to the domain type.
26788 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26789 module and described later in this chapter.
26791 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26795 A @code{gdb.Symbol} object has the following attributes:
26797 @defvar Symbol.type
26798 The type of the symbol or @code{None} if no type is recorded.
26799 This attribute is represented as a @code{gdb.Type} object.
26800 @xref{Types In Python}. This attribute is not writable.
26803 @defvar Symbol.symtab
26804 The symbol table in which the symbol appears. This attribute is
26805 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26806 Python}. This attribute is not writable.
26809 @defvar Symbol.line
26810 The line number in the source code at which the symbol was defined.
26811 This is an integer.
26814 @defvar Symbol.name
26815 The name of the symbol as a string. This attribute is not writable.
26818 @defvar Symbol.linkage_name
26819 The name of the symbol, as used by the linker (i.e., may be mangled).
26820 This attribute is not writable.
26823 @defvar Symbol.print_name
26824 The name of the symbol in a form suitable for output. This is either
26825 @code{name} or @code{linkage_name}, depending on whether the user
26826 asked @value{GDBN} to display demangled or mangled names.
26829 @defvar Symbol.addr_class
26830 The address class of the symbol. This classifies how to find the value
26831 of a symbol. Each address class is a constant defined in the
26832 @code{gdb} module and described later in this chapter.
26835 @defvar Symbol.needs_frame
26836 This is @code{True} if evaluating this symbol's value requires a frame
26837 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26838 local variables will require a frame, but other symbols will not.
26841 @defvar Symbol.is_argument
26842 @code{True} if the symbol is an argument of a function.
26845 @defvar Symbol.is_constant
26846 @code{True} if the symbol is a constant.
26849 @defvar Symbol.is_function
26850 @code{True} if the symbol is a function or a method.
26853 @defvar Symbol.is_variable
26854 @code{True} if the symbol is a variable.
26857 A @code{gdb.Symbol} object has the following methods:
26859 @defun Symbol.is_valid ()
26860 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26861 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26862 the symbol it refers to does not exist in @value{GDBN} any longer.
26863 All other @code{gdb.Symbol} methods will throw an exception if it is
26864 invalid at the time the method is called.
26867 @defun Symbol.value (@r{[}frame@r{]})
26868 Compute the value of the symbol, as a @code{gdb.Value}. For
26869 functions, this computes the address of the function, cast to the
26870 appropriate type. If the symbol requires a frame in order to compute
26871 its value, then @var{frame} must be given. If @var{frame} is not
26872 given, or if @var{frame} is invalid, then this method will throw an
26876 The available domain categories in @code{gdb.Symbol} are represented
26877 as constants in the @code{gdb} module:
26880 @findex SYMBOL_UNDEF_DOMAIN
26881 @findex gdb.SYMBOL_UNDEF_DOMAIN
26882 @item gdb.SYMBOL_UNDEF_DOMAIN
26883 This is used when a domain has not been discovered or none of the
26884 following domains apply. This usually indicates an error either
26885 in the symbol information or in @value{GDBN}'s handling of symbols.
26886 @findex SYMBOL_VAR_DOMAIN
26887 @findex gdb.SYMBOL_VAR_DOMAIN
26888 @item gdb.SYMBOL_VAR_DOMAIN
26889 This domain contains variables, function names, typedef names and enum
26891 @findex SYMBOL_STRUCT_DOMAIN
26892 @findex gdb.SYMBOL_STRUCT_DOMAIN
26893 @item gdb.SYMBOL_STRUCT_DOMAIN
26894 This domain holds struct, union and enum type names.
26895 @findex SYMBOL_LABEL_DOMAIN
26896 @findex gdb.SYMBOL_LABEL_DOMAIN
26897 @item gdb.SYMBOL_LABEL_DOMAIN
26898 This domain contains names of labels (for gotos).
26899 @findex SYMBOL_VARIABLES_DOMAIN
26900 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26901 @item gdb.SYMBOL_VARIABLES_DOMAIN
26902 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26903 contains everything minus functions and types.
26904 @findex SYMBOL_FUNCTIONS_DOMAIN
26905 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26906 @item gdb.SYMBOL_FUNCTION_DOMAIN
26907 This domain contains all functions.
26908 @findex SYMBOL_TYPES_DOMAIN
26909 @findex gdb.SYMBOL_TYPES_DOMAIN
26910 @item gdb.SYMBOL_TYPES_DOMAIN
26911 This domain contains all types.
26914 The available address class categories in @code{gdb.Symbol} are represented
26915 as constants in the @code{gdb} module:
26918 @findex SYMBOL_LOC_UNDEF
26919 @findex gdb.SYMBOL_LOC_UNDEF
26920 @item gdb.SYMBOL_LOC_UNDEF
26921 If this is returned by address class, it indicates an error either in
26922 the symbol information or in @value{GDBN}'s handling of symbols.
26923 @findex SYMBOL_LOC_CONST
26924 @findex gdb.SYMBOL_LOC_CONST
26925 @item gdb.SYMBOL_LOC_CONST
26926 Value is constant int.
26927 @findex SYMBOL_LOC_STATIC
26928 @findex gdb.SYMBOL_LOC_STATIC
26929 @item gdb.SYMBOL_LOC_STATIC
26930 Value is at a fixed address.
26931 @findex SYMBOL_LOC_REGISTER
26932 @findex gdb.SYMBOL_LOC_REGISTER
26933 @item gdb.SYMBOL_LOC_REGISTER
26934 Value is in a register.
26935 @findex SYMBOL_LOC_ARG
26936 @findex gdb.SYMBOL_LOC_ARG
26937 @item gdb.SYMBOL_LOC_ARG
26938 Value is an argument. This value is at the offset stored within the
26939 symbol inside the frame's argument list.
26940 @findex SYMBOL_LOC_REF_ARG
26941 @findex gdb.SYMBOL_LOC_REF_ARG
26942 @item gdb.SYMBOL_LOC_REF_ARG
26943 Value address is stored in the frame's argument list. Just like
26944 @code{LOC_ARG} except that the value's address is stored at the
26945 offset, not the value itself.
26946 @findex SYMBOL_LOC_REGPARM_ADDR
26947 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26948 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26949 Value is a specified register. Just like @code{LOC_REGISTER} except
26950 the register holds the address of the argument instead of the argument
26952 @findex SYMBOL_LOC_LOCAL
26953 @findex gdb.SYMBOL_LOC_LOCAL
26954 @item gdb.SYMBOL_LOC_LOCAL
26955 Value is a local variable.
26956 @findex SYMBOL_LOC_TYPEDEF
26957 @findex gdb.SYMBOL_LOC_TYPEDEF
26958 @item gdb.SYMBOL_LOC_TYPEDEF
26959 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26961 @findex SYMBOL_LOC_BLOCK
26962 @findex gdb.SYMBOL_LOC_BLOCK
26963 @item gdb.SYMBOL_LOC_BLOCK
26965 @findex SYMBOL_LOC_CONST_BYTES
26966 @findex gdb.SYMBOL_LOC_CONST_BYTES
26967 @item gdb.SYMBOL_LOC_CONST_BYTES
26968 Value is a byte-sequence.
26969 @findex SYMBOL_LOC_UNRESOLVED
26970 @findex gdb.SYMBOL_LOC_UNRESOLVED
26971 @item gdb.SYMBOL_LOC_UNRESOLVED
26972 Value is at a fixed address, but the address of the variable has to be
26973 determined from the minimal symbol table whenever the variable is
26975 @findex SYMBOL_LOC_OPTIMIZED_OUT
26976 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26977 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26978 The value does not actually exist in the program.
26979 @findex SYMBOL_LOC_COMPUTED
26980 @findex gdb.SYMBOL_LOC_COMPUTED
26981 @item gdb.SYMBOL_LOC_COMPUTED
26982 The value's address is a computed location.
26985 @node Symbol Tables In Python
26986 @subsubsection Symbol table representation in Python.
26988 @cindex symbol tables in python
26990 @tindex gdb.Symtab_and_line
26992 Access to symbol table data maintained by @value{GDBN} on the inferior
26993 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
26994 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
26995 from the @code{find_sal} method in @code{gdb.Frame} object.
26996 @xref{Frames In Python}.
26998 For more information on @value{GDBN}'s symbol table management, see
26999 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27001 A @code{gdb.Symtab_and_line} object has the following attributes:
27003 @defvar Symtab_and_line.symtab
27004 The symbol table object (@code{gdb.Symtab}) for this frame.
27005 This attribute is not writable.
27008 @defvar Symtab_and_line.pc
27009 Indicates the start of the address range occupied by code for the
27010 current source line. This attribute is not writable.
27013 @defvar Symtab_and_line.last
27014 Indicates the end of the address range occupied by code for the current
27015 source line. This attribute is not writable.
27018 @defvar Symtab_and_line.line
27019 Indicates the current line number for this object. This
27020 attribute is not writable.
27023 A @code{gdb.Symtab_and_line} object has the following methods:
27025 @defun Symtab_and_line.is_valid ()
27026 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27027 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27028 invalid if the Symbol table and line object it refers to does not
27029 exist in @value{GDBN} any longer. All other
27030 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27031 invalid at the time the method is called.
27034 A @code{gdb.Symtab} object has the following attributes:
27036 @defvar Symtab.filename
27037 The symbol table's source filename. This attribute is not writable.
27040 @defvar Symtab.objfile
27041 The symbol table's backing object file. @xref{Objfiles In Python}.
27042 This attribute is not writable.
27045 A @code{gdb.Symtab} object has the following methods:
27047 @defun Symtab.is_valid ()
27048 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27049 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27050 the symbol table it refers to does not exist in @value{GDBN} any
27051 longer. All other @code{gdb.Symtab} methods will throw an exception
27052 if it is invalid at the time the method is called.
27055 @defun Symtab.fullname ()
27056 Return the symbol table's source absolute file name.
27059 @defun Symtab.global_block ()
27060 Return the global block of the underlying symbol table.
27061 @xref{Blocks In Python}.
27064 @defun Symtab.static_block ()
27065 Return the static block of the underlying symbol table.
27066 @xref{Blocks In Python}.
27069 @defun Symtab.linetable ()
27070 Return the line table associated with the symbol table.
27071 @xref{Line Tables In Python}.
27074 @node Line Tables In Python
27075 @subsubsection Manipulating line tables using Python
27077 @cindex line tables in python
27078 @tindex gdb.LineTable
27080 Python code can request and inspect line table information from a
27081 symbol table that is loaded in @value{GDBN}. A line table is a
27082 mapping of source lines to their executable locations in memory. To
27083 acquire the line table information for a particular symbol table, use
27084 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27086 A @code{gdb.LineTable} is iterable. The iterator returns
27087 @code{LineTableEntry} objects that correspond to the source line and
27088 address for each line table entry. @code{LineTableEntry} objects have
27089 the following attributes:
27091 @defvar LineTableEntry.line
27092 The source line number for this line table entry. This number
27093 corresponds to the actual line of source. This attribute is not
27097 @defvar LineTableEntry.pc
27098 The address that is associated with the line table entry where the
27099 executable code for that source line resides in memory. This
27100 attribute is not writable.
27103 As there can be multiple addresses for a single source line, you may
27104 receive multiple @code{LineTableEntry} objects with matching
27105 @code{line} attributes, but with different @code{pc} attributes. The
27106 iterator is sorted in ascending @code{pc} order. Here is a small
27107 example illustrating iterating over a line table.
27110 symtab = gdb.selected_frame().find_sal().symtab
27111 linetable = symtab.linetable()
27112 for line in linetable:
27113 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27116 This will have the following output:
27119 Line: 33 Address: 0x4005c8L
27120 Line: 37 Address: 0x4005caL
27121 Line: 39 Address: 0x4005d2L
27122 Line: 40 Address: 0x4005f8L
27123 Line: 42 Address: 0x4005ffL
27124 Line: 44 Address: 0x400608L
27125 Line: 42 Address: 0x40060cL
27126 Line: 45 Address: 0x400615L
27129 In addition to being able to iterate over a @code{LineTable}, it also
27130 has the following direct access methods:
27132 @defun LineTable.line (line)
27133 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27134 entries in the line table for the given @var{line}. @var{line} refers
27135 to the source code line. If there are no entries for that source code
27136 @var{line}, the Python @code{None} is returned.
27139 @defun LineTable.has_line (line)
27140 Return a Python @code{Boolean} indicating whether there is an entry in
27141 the line table for this source line. Return @code{True} if an entry
27142 is found, or @code{False} if not.
27145 @defun LineTable.source_lines ()
27146 Return a Python @code{List} of the source line numbers in the symbol
27147 table. Only lines with executable code locations are returned. The
27148 contents of the @code{List} will just be the source line entries
27149 represented as Python @code{Long} values.
27152 @node Breakpoints In Python
27153 @subsubsection Manipulating breakpoints using Python
27155 @cindex breakpoints in python
27156 @tindex gdb.Breakpoint
27158 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27161 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27162 Create a new breakpoint. @var{spec} is a string naming the location
27163 of the breakpoint, or an expression that defines a watchpoint. The
27164 contents can be any location recognized by the @code{break} command,
27165 or in the case of a watchpoint, by the @code{watch} command. The
27166 optional @var{type} denotes the breakpoint to create from the types
27167 defined later in this chapter. This argument can be either:
27168 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27169 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27170 argument allows the breakpoint to become invisible to the user. The
27171 breakpoint will neither be reported when created, nor will it be
27172 listed in the output from @code{info breakpoints} (but will be listed
27173 with the @code{maint info breakpoints} command). The optional
27174 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27175 Temporary breakpoints are deleted after they have been hit. Any
27176 further access to the Python breakpoint after it has been hit will
27177 result in a runtime error (as that breakpoint has now been
27178 automatically deleted). The optional @var{wp_class} argument defines
27179 the class of watchpoint to create, if @var{type} is
27180 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27181 is assumed to be a @code{gdb.WP_WRITE} class.
27184 @defun Breakpoint.stop (self)
27185 The @code{gdb.Breakpoint} class can be sub-classed and, in
27186 particular, you may choose to implement the @code{stop} method.
27187 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27188 it will be called when the inferior reaches any location of a
27189 breakpoint which instantiates that sub-class. If the method returns
27190 @code{True}, the inferior will be stopped at the location of the
27191 breakpoint, otherwise the inferior will continue.
27193 If there are multiple breakpoints at the same location with a
27194 @code{stop} method, each one will be called regardless of the
27195 return status of the previous. This ensures that all @code{stop}
27196 methods have a chance to execute at that location. In this scenario
27197 if one of the methods returns @code{True} but the others return
27198 @code{False}, the inferior will still be stopped.
27200 You should not alter the execution state of the inferior (i.e.@:, step,
27201 next, etc.), alter the current frame context (i.e.@:, change the current
27202 active frame), or alter, add or delete any breakpoint. As a general
27203 rule, you should not alter any data within @value{GDBN} or the inferior
27206 Example @code{stop} implementation:
27209 class MyBreakpoint (gdb.Breakpoint):
27211 inf_val = gdb.parse_and_eval("foo")
27218 The available watchpoint types represented by constants are defined in the
27223 @findex gdb.WP_READ
27225 Read only watchpoint.
27228 @findex gdb.WP_WRITE
27230 Write only watchpoint.
27233 @findex gdb.WP_ACCESS
27234 @item gdb.WP_ACCESS
27235 Read/Write watchpoint.
27238 @defun Breakpoint.is_valid ()
27239 Return @code{True} if this @code{Breakpoint} object is valid,
27240 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27241 if the user deletes the breakpoint. In this case, the object still
27242 exists, but the underlying breakpoint does not. In the cases of
27243 watchpoint scope, the watchpoint remains valid even if execution of the
27244 inferior leaves the scope of that watchpoint.
27247 @defun Breakpoint.delete
27248 Permanently deletes the @value{GDBN} breakpoint. This also
27249 invalidates the Python @code{Breakpoint} object. Any further access
27250 to this object's attributes or methods will raise an error.
27253 @defvar Breakpoint.enabled
27254 This attribute is @code{True} if the breakpoint is enabled, and
27255 @code{False} otherwise. This attribute is writable.
27258 @defvar Breakpoint.silent
27259 This attribute is @code{True} if the breakpoint is silent, and
27260 @code{False} otherwise. This attribute is writable.
27262 Note that a breakpoint can also be silent if it has commands and the
27263 first command is @code{silent}. This is not reported by the
27264 @code{silent} attribute.
27267 @defvar Breakpoint.thread
27268 If the breakpoint is thread-specific, this attribute holds the thread
27269 id. If the breakpoint is not thread-specific, this attribute is
27270 @code{None}. This attribute is writable.
27273 @defvar Breakpoint.task
27274 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27275 id. If the breakpoint is not task-specific (or the underlying
27276 language is not Ada), this attribute is @code{None}. This attribute
27280 @defvar Breakpoint.ignore_count
27281 This attribute holds the ignore count for the breakpoint, an integer.
27282 This attribute is writable.
27285 @defvar Breakpoint.number
27286 This attribute holds the breakpoint's number --- the identifier used by
27287 the user to manipulate the breakpoint. This attribute is not writable.
27290 @defvar Breakpoint.type
27291 This attribute holds the breakpoint's type --- the identifier used to
27292 determine the actual breakpoint type or use-case. This attribute is not
27296 @defvar Breakpoint.visible
27297 This attribute tells whether the breakpoint is visible to the user
27298 when set, or when the @samp{info breakpoints} command is run. This
27299 attribute is not writable.
27302 @defvar Breakpoint.temporary
27303 This attribute indicates whether the breakpoint was created as a
27304 temporary breakpoint. Temporary breakpoints are automatically deleted
27305 after that breakpoint has been hit. Access to this attribute, and all
27306 other attributes and functions other than the @code{is_valid}
27307 function, will result in an error after the breakpoint has been hit
27308 (as it has been automatically deleted). This attribute is not
27312 The available types are represented by constants defined in the @code{gdb}
27316 @findex BP_BREAKPOINT
27317 @findex gdb.BP_BREAKPOINT
27318 @item gdb.BP_BREAKPOINT
27319 Normal code breakpoint.
27321 @findex BP_WATCHPOINT
27322 @findex gdb.BP_WATCHPOINT
27323 @item gdb.BP_WATCHPOINT
27324 Watchpoint breakpoint.
27326 @findex BP_HARDWARE_WATCHPOINT
27327 @findex gdb.BP_HARDWARE_WATCHPOINT
27328 @item gdb.BP_HARDWARE_WATCHPOINT
27329 Hardware assisted watchpoint.
27331 @findex BP_READ_WATCHPOINT
27332 @findex gdb.BP_READ_WATCHPOINT
27333 @item gdb.BP_READ_WATCHPOINT
27334 Hardware assisted read watchpoint.
27336 @findex BP_ACCESS_WATCHPOINT
27337 @findex gdb.BP_ACCESS_WATCHPOINT
27338 @item gdb.BP_ACCESS_WATCHPOINT
27339 Hardware assisted access watchpoint.
27342 @defvar Breakpoint.hit_count
27343 This attribute holds the hit count for the breakpoint, an integer.
27344 This attribute is writable, but currently it can only be set to zero.
27347 @defvar Breakpoint.location
27348 This attribute holds the location of the breakpoint, as specified by
27349 the user. It is a string. If the breakpoint does not have a location
27350 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27351 attribute is not writable.
27354 @defvar Breakpoint.expression
27355 This attribute holds a breakpoint expression, as specified by
27356 the user. It is a string. If the breakpoint does not have an
27357 expression (the breakpoint is not a watchpoint) the attribute's value
27358 is @code{None}. This attribute is not writable.
27361 @defvar Breakpoint.condition
27362 This attribute holds the condition of the breakpoint, as specified by
27363 the user. It is a string. If there is no condition, this attribute's
27364 value is @code{None}. This attribute is writable.
27367 @defvar Breakpoint.commands
27368 This attribute holds the commands attached to the breakpoint. If
27369 there are commands, this attribute's value is a string holding all the
27370 commands, separated by newlines. If there are no commands, this
27371 attribute is @code{None}. This attribute is not writable.
27374 @node Finish Breakpoints in Python
27375 @subsubsection Finish Breakpoints
27377 @cindex python finish breakpoints
27378 @tindex gdb.FinishBreakpoint
27380 A finish breakpoint is a temporary breakpoint set at the return address of
27381 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27382 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27383 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27384 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27385 Finish breakpoints are thread specific and must be create with the right
27388 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27389 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27390 object @var{frame}. If @var{frame} is not provided, this defaults to the
27391 newest frame. The optional @var{internal} argument allows the breakpoint to
27392 become invisible to the user. @xref{Breakpoints In Python}, for further
27393 details about this argument.
27396 @defun FinishBreakpoint.out_of_scope (self)
27397 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27398 @code{return} command, @dots{}), a function may not properly terminate, and
27399 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27400 situation, the @code{out_of_scope} callback will be triggered.
27402 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27406 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27408 print "normal finish"
27411 def out_of_scope ():
27412 print "abnormal finish"
27416 @defvar FinishBreakpoint.return_value
27417 When @value{GDBN} is stopped at a finish breakpoint and the frame
27418 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27419 attribute will contain a @code{gdb.Value} object corresponding to the return
27420 value of the function. The value will be @code{None} if the function return
27421 type is @code{void} or if the return value was not computable. This attribute
27425 @node Lazy Strings In Python
27426 @subsubsection Python representation of lazy strings.
27428 @cindex lazy strings in python
27429 @tindex gdb.LazyString
27431 A @dfn{lazy string} is a string whose contents is not retrieved or
27432 encoded until it is needed.
27434 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27435 @code{address} that points to a region of memory, an @code{encoding}
27436 that will be used to encode that region of memory, and a @code{length}
27437 to delimit the region of memory that represents the string. The
27438 difference between a @code{gdb.LazyString} and a string wrapped within
27439 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27440 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27441 retrieved and encoded during printing, while a @code{gdb.Value}
27442 wrapping a string is immediately retrieved and encoded on creation.
27444 A @code{gdb.LazyString} object has the following functions:
27446 @defun LazyString.value ()
27447 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27448 will point to the string in memory, but will lose all the delayed
27449 retrieval, encoding and handling that @value{GDBN} applies to a
27450 @code{gdb.LazyString}.
27453 @defvar LazyString.address
27454 This attribute holds the address of the string. This attribute is not
27458 @defvar LazyString.length
27459 This attribute holds the length of the string in characters. If the
27460 length is -1, then the string will be fetched and encoded up to the
27461 first null of appropriate width. This attribute is not writable.
27464 @defvar LazyString.encoding
27465 This attribute holds the encoding that will be applied to the string
27466 when the string is printed by @value{GDBN}. If the encoding is not
27467 set, or contains an empty string, then @value{GDBN} will select the
27468 most appropriate encoding when the string is printed. This attribute
27472 @defvar LazyString.type
27473 This attribute holds the type that is represented by the lazy string's
27474 type. For a lazy string this will always be a pointer type. To
27475 resolve this to the lazy string's character type, use the type's
27476 @code{target} method. @xref{Types In Python}. This attribute is not
27480 @node Architectures In Python
27481 @subsubsection Python representation of architectures
27482 @cindex Python architectures
27484 @value{GDBN} uses architecture specific parameters and artifacts in a
27485 number of its various computations. An architecture is represented
27486 by an instance of the @code{gdb.Architecture} class.
27488 A @code{gdb.Architecture} class has the following methods:
27490 @defun Architecture.name ()
27491 Return the name (string value) of the architecture.
27494 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27495 Return a list of disassembled instructions starting from the memory
27496 address @var{start_pc}. The optional arguments @var{end_pc} and
27497 @var{count} determine the number of instructions in the returned list.
27498 If both the optional arguments @var{end_pc} and @var{count} are
27499 specified, then a list of at most @var{count} disassembled instructions
27500 whose start address falls in the closed memory address interval from
27501 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27502 specified, but @var{count} is specified, then @var{count} number of
27503 instructions starting from the address @var{start_pc} are returned. If
27504 @var{count} is not specified but @var{end_pc} is specified, then all
27505 instructions whose start address falls in the closed memory address
27506 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27507 @var{end_pc} nor @var{count} are specified, then a single instruction at
27508 @var{start_pc} is returned. For all of these cases, each element of the
27509 returned list is a Python @code{dict} with the following string keys:
27514 The value corresponding to this key is a Python long integer capturing
27515 the memory address of the instruction.
27518 The value corresponding to this key is a string value which represents
27519 the instruction with assembly language mnemonics. The assembly
27520 language flavor used is the same as that specified by the current CLI
27521 variable @code{disassembly-flavor}. @xref{Machine Code}.
27524 The value corresponding to this key is the length (integer value) of the
27525 instruction in bytes.
27530 @node Python Auto-loading
27531 @subsection Python Auto-loading
27532 @cindex Python auto-loading
27534 When a new object file is read (for example, due to the @code{file}
27535 command, or because the inferior has loaded a shared library),
27536 @value{GDBN} will look for Python support scripts in several ways:
27537 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27538 and @code{.debug_gdb_scripts} section
27539 (@pxref{dotdebug_gdb_scripts section}).
27541 The auto-loading feature is useful for supplying application-specific
27542 debugging commands and scripts.
27544 Auto-loading can be enabled or disabled,
27545 and the list of auto-loaded scripts can be printed.
27548 @anchor{set auto-load python-scripts}
27549 @kindex set auto-load python-scripts
27550 @item set auto-load python-scripts [on|off]
27551 Enable or disable the auto-loading of Python scripts.
27553 @anchor{show auto-load python-scripts}
27554 @kindex show auto-load python-scripts
27555 @item show auto-load python-scripts
27556 Show whether auto-loading of Python scripts is enabled or disabled.
27558 @anchor{info auto-load python-scripts}
27559 @kindex info auto-load python-scripts
27560 @cindex print list of auto-loaded Python scripts
27561 @item info auto-load python-scripts [@var{regexp}]
27562 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27564 Also printed is the list of Python scripts that were mentioned in
27565 the @code{.debug_gdb_scripts} section and were not found
27566 (@pxref{dotdebug_gdb_scripts section}).
27567 This is useful because their names are not printed when @value{GDBN}
27568 tries to load them and fails. There may be many of them, and printing
27569 an error message for each one is problematic.
27571 If @var{regexp} is supplied only Python scripts with matching names are printed.
27576 (gdb) info auto-load python-scripts
27578 Yes py-section-script.py
27579 full name: /tmp/py-section-script.py
27580 No my-foo-pretty-printers.py
27584 When reading an auto-loaded file, @value{GDBN} sets the
27585 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27586 function (@pxref{Objfiles In Python}). This can be useful for
27587 registering objfile-specific pretty-printers and frame-filters.
27590 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27591 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27592 * Which flavor to choose?::
27595 @node objfile-gdb.py file
27596 @subsubsection The @file{@var{objfile}-gdb.py} file
27597 @cindex @file{@var{objfile}-gdb.py}
27599 When a new object file is read, @value{GDBN} looks for
27600 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27601 where @var{objfile} is the object file's real name, formed by ensuring
27602 that the file name is absolute, following all symlinks, and resolving
27603 @code{.} and @code{..} components. If this file exists and is
27604 readable, @value{GDBN} will evaluate it as a Python script.
27606 If this file does not exist, then @value{GDBN} will look for
27607 @var{script-name} file in all of the directories as specified below.
27609 Note that loading of this script file also requires accordingly configured
27610 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27612 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27613 scripts normally according to its @file{.exe} filename. But if no scripts are
27614 found @value{GDBN} also tries script filenames matching the object file without
27615 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27616 is attempted on any platform. This makes the script filenames compatible
27617 between Unix and MS-Windows hosts.
27620 @anchor{set auto-load scripts-directory}
27621 @kindex set auto-load scripts-directory
27622 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27623 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27624 may be delimited by the host platform path separator in use
27625 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27627 Each entry here needs to be covered also by the security setting
27628 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27630 @anchor{with-auto-load-dir}
27631 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27632 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27633 configuration option @option{--with-auto-load-dir}.
27635 Any reference to @file{$debugdir} will get replaced by
27636 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27637 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27638 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27639 @file{$datadir} must be placed as a directory component --- either alone or
27640 delimited by @file{/} or @file{\} directory separators, depending on the host
27643 The list of directories uses path separator (@samp{:} on GNU and Unix
27644 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27645 to the @env{PATH} environment variable.
27647 @anchor{show auto-load scripts-directory}
27648 @kindex show auto-load scripts-directory
27649 @item show auto-load scripts-directory
27650 Show @value{GDBN} auto-loaded scripts location.
27653 @value{GDBN} does not track which files it has already auto-loaded this way.
27654 @value{GDBN} will load the associated script every time the corresponding
27655 @var{objfile} is opened.
27656 So your @file{-gdb.py} file should be careful to avoid errors if it
27657 is evaluated more than once.
27659 @node dotdebug_gdb_scripts section
27660 @subsubsection The @code{.debug_gdb_scripts} section
27661 @cindex @code{.debug_gdb_scripts} section
27663 For systems using file formats like ELF and COFF,
27664 when @value{GDBN} loads a new object file
27665 it will look for a special section named @samp{.debug_gdb_scripts}.
27666 If this section exists, its contents is a list of names of scripts to load.
27668 @value{GDBN} will look for each specified script file first in the
27669 current directory and then along the source search path
27670 (@pxref{Source Path, ,Specifying Source Directories}),
27671 except that @file{$cdir} is not searched, since the compilation
27672 directory is not relevant to scripts.
27674 Entries can be placed in section @code{.debug_gdb_scripts} with,
27675 for example, this GCC macro:
27678 /* Note: The "MS" section flags are to remove duplicates. */
27679 #define DEFINE_GDB_SCRIPT(script_name) \
27681 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27683 .asciz \"" script_name "\"\n\
27689 Then one can reference the macro in a header or source file like this:
27692 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27695 The script name may include directories if desired.
27697 Note that loading of this script file also requires accordingly configured
27698 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27700 If the macro is put in a header, any application or library
27701 using this header will get a reference to the specified script.
27703 @node Which flavor to choose?
27704 @subsubsection Which flavor to choose?
27706 Given the multiple ways of auto-loading Python scripts, it might not always
27707 be clear which one to choose. This section provides some guidance.
27709 Benefits of the @file{-gdb.py} way:
27713 Can be used with file formats that don't support multiple sections.
27716 Ease of finding scripts for public libraries.
27718 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27719 in the source search path.
27720 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27721 isn't a source directory in which to find the script.
27724 Doesn't require source code additions.
27727 Benefits of the @code{.debug_gdb_scripts} way:
27731 Works with static linking.
27733 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27734 trigger their loading. When an application is statically linked the only
27735 objfile available is the executable, and it is cumbersome to attach all the
27736 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27739 Works with classes that are entirely inlined.
27741 Some classes can be entirely inlined, and thus there may not be an associated
27742 shared library to attach a @file{-gdb.py} script to.
27745 Scripts needn't be copied out of the source tree.
27747 In some circumstances, apps can be built out of large collections of internal
27748 libraries, and the build infrastructure necessary to install the
27749 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27750 cumbersome. It may be easier to specify the scripts in the
27751 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27752 top of the source tree to the source search path.
27755 @node Python modules
27756 @subsection Python modules
27757 @cindex python modules
27759 @value{GDBN} comes with several modules to assist writing Python code.
27762 * gdb.printing:: Building and registering pretty-printers.
27763 * gdb.types:: Utilities for working with types.
27764 * gdb.prompt:: Utilities for prompt value substitution.
27768 @subsubsection gdb.printing
27769 @cindex gdb.printing
27771 This module provides a collection of utilities for working with
27775 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27776 This class specifies the API that makes @samp{info pretty-printer},
27777 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27778 Pretty-printers should generally inherit from this class.
27780 @item SubPrettyPrinter (@var{name})
27781 For printers that handle multiple types, this class specifies the
27782 corresponding API for the subprinters.
27784 @item RegexpCollectionPrettyPrinter (@var{name})
27785 Utility class for handling multiple printers, all recognized via
27786 regular expressions.
27787 @xref{Writing a Pretty-Printer}, for an example.
27789 @item FlagEnumerationPrinter (@var{name})
27790 A pretty-printer which handles printing of @code{enum} values. Unlike
27791 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27792 work properly when there is some overlap between the enumeration
27793 constants. @var{name} is the name of the printer and also the name of
27794 the @code{enum} type to look up.
27796 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27797 Register @var{printer} with the pretty-printer list of @var{obj}.
27798 If @var{replace} is @code{True} then any existing copy of the printer
27799 is replaced. Otherwise a @code{RuntimeError} exception is raised
27800 if a printer with the same name already exists.
27804 @subsubsection gdb.types
27807 This module provides a collection of utilities for working with
27808 @code{gdb.Type} objects.
27811 @item get_basic_type (@var{type})
27812 Return @var{type} with const and volatile qualifiers stripped,
27813 and with typedefs and C@t{++} references converted to the underlying type.
27818 typedef const int const_int;
27820 const_int& foo_ref (foo);
27821 int main () @{ return 0; @}
27828 (gdb) python import gdb.types
27829 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27830 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27834 @item has_field (@var{type}, @var{field})
27835 Return @code{True} if @var{type}, assumed to be a type with fields
27836 (e.g., a structure or union), has field @var{field}.
27838 @item make_enum_dict (@var{enum_type})
27839 Return a Python @code{dictionary} type produced from @var{enum_type}.
27841 @item deep_items (@var{type})
27842 Returns a Python iterator similar to the standard
27843 @code{gdb.Type.iteritems} method, except that the iterator returned
27844 by @code{deep_items} will recursively traverse anonymous struct or
27845 union fields. For example:
27859 Then in @value{GDBN}:
27861 (@value{GDBP}) python import gdb.types
27862 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27863 (@value{GDBP}) python print struct_a.keys ()
27865 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27866 @{['a', 'b0', 'b1']@}
27869 @item get_type_recognizers ()
27870 Return a list of the enabled type recognizers for the current context.
27871 This is called by @value{GDBN} during the type-printing process
27872 (@pxref{Type Printing API}).
27874 @item apply_type_recognizers (recognizers, type_obj)
27875 Apply the type recognizers, @var{recognizers}, to the type object
27876 @var{type_obj}. If any recognizer returns a string, return that
27877 string. Otherwise, return @code{None}. This is called by
27878 @value{GDBN} during the type-printing process (@pxref{Type Printing
27881 @item register_type_printer (locus, printer)
27882 This is a convenience function to register a type printer.
27883 @var{printer} is the type printer to register. It must implement the
27884 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27885 which case the printer is registered with that objfile; a
27886 @code{gdb.Progspace}, in which case the printer is registered with
27887 that progspace; or @code{None}, in which case the printer is
27888 registered globally.
27891 This is a base class that implements the type printer protocol. Type
27892 printers are encouraged, but not required, to derive from this class.
27893 It defines a constructor:
27895 @defmethod TypePrinter __init__ (self, name)
27896 Initialize the type printer with the given name. The new printer
27897 starts in the enabled state.
27903 @subsubsection gdb.prompt
27906 This module provides a method for prompt value-substitution.
27909 @item substitute_prompt (@var{string})
27910 Return @var{string} with escape sequences substituted by values. Some
27911 escape sequences take arguments. You can specify arguments inside
27912 ``@{@}'' immediately following the escape sequence.
27914 The escape sequences you can pass to this function are:
27918 Substitute a backslash.
27920 Substitute an ESC character.
27922 Substitute the selected frame; an argument names a frame parameter.
27924 Substitute a newline.
27926 Substitute a parameter's value; the argument names the parameter.
27928 Substitute a carriage return.
27930 Substitute the selected thread; an argument names a thread parameter.
27932 Substitute the version of GDB.
27934 Substitute the current working directory.
27936 Begin a sequence of non-printing characters. These sequences are
27937 typically used with the ESC character, and are not counted in the string
27938 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27939 blue-colored ``(gdb)'' prompt where the length is five.
27941 End a sequence of non-printing characters.
27947 substitute_prompt (``frame: \f,
27948 print arguments: \p@{print frame-arguments@}'')
27951 @exdent will return the string:
27954 "frame: main, print arguments: scalars"
27959 @section Creating new spellings of existing commands
27960 @cindex aliases for commands
27962 It is often useful to define alternate spellings of existing commands.
27963 For example, if a new @value{GDBN} command defined in Python has
27964 a long name to type, it is handy to have an abbreviated version of it
27965 that involves less typing.
27967 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27968 of the @samp{step} command even though it is otherwise an ambiguous
27969 abbreviation of other commands like @samp{set} and @samp{show}.
27971 Aliases are also used to provide shortened or more common versions
27972 of multi-word commands. For example, @value{GDBN} provides the
27973 @samp{tty} alias of the @samp{set inferior-tty} command.
27975 You can define a new alias with the @samp{alias} command.
27980 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27984 @var{ALIAS} specifies the name of the new alias.
27985 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27988 @var{COMMAND} specifies the name of an existing command
27989 that is being aliased.
27991 The @samp{-a} option specifies that the new alias is an abbreviation
27992 of the command. Abbreviations are not shown in command
27993 lists displayed by the @samp{help} command.
27995 The @samp{--} option specifies the end of options,
27996 and is useful when @var{ALIAS} begins with a dash.
27998 Here is a simple example showing how to make an abbreviation
27999 of a command so that there is less to type.
28000 Suppose you were tired of typing @samp{disas}, the current
28001 shortest unambiguous abbreviation of the @samp{disassemble} command
28002 and you wanted an even shorter version named @samp{di}.
28003 The following will accomplish this.
28006 (gdb) alias -a di = disas
28009 Note that aliases are different from user-defined commands.
28010 With a user-defined command, you also need to write documentation
28011 for it with the @samp{document} command.
28012 An alias automatically picks up the documentation of the existing command.
28014 Here is an example where we make @samp{elms} an abbreviation of
28015 @samp{elements} in the @samp{set print elements} command.
28016 This is to show that you can make an abbreviation of any part
28020 (gdb) alias -a set print elms = set print elements
28021 (gdb) alias -a show print elms = show print elements
28022 (gdb) set p elms 20
28024 Limit on string chars or array elements to print is 200.
28027 Note that if you are defining an alias of a @samp{set} command,
28028 and you want to have an alias for the corresponding @samp{show}
28029 command, then you need to define the latter separately.
28031 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28032 @var{ALIAS}, just as they are normally.
28035 (gdb) alias -a set pr elms = set p ele
28038 Finally, here is an example showing the creation of a one word
28039 alias for a more complex command.
28040 This creates alias @samp{spe} of the command @samp{set print elements}.
28043 (gdb) alias spe = set print elements
28048 @chapter Command Interpreters
28049 @cindex command interpreters
28051 @value{GDBN} supports multiple command interpreters, and some command
28052 infrastructure to allow users or user interface writers to switch
28053 between interpreters or run commands in other interpreters.
28055 @value{GDBN} currently supports two command interpreters, the console
28056 interpreter (sometimes called the command-line interpreter or @sc{cli})
28057 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28058 describes both of these interfaces in great detail.
28060 By default, @value{GDBN} will start with the console interpreter.
28061 However, the user may choose to start @value{GDBN} with another
28062 interpreter by specifying the @option{-i} or @option{--interpreter}
28063 startup options. Defined interpreters include:
28067 @cindex console interpreter
28068 The traditional console or command-line interpreter. This is the most often
28069 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28070 @value{GDBN} will use this interpreter.
28073 @cindex mi interpreter
28074 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28075 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28076 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28080 @cindex mi2 interpreter
28081 The current @sc{gdb/mi} interface.
28084 @cindex mi1 interpreter
28085 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28089 @cindex invoke another interpreter
28090 The interpreter being used by @value{GDBN} may not be dynamically
28091 switched at runtime. Although possible, this could lead to a very
28092 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28093 enters the command "interpreter-set console" in a console view,
28094 @value{GDBN} would switch to using the console interpreter, rendering
28095 the IDE inoperable!
28097 @kindex interpreter-exec
28098 Although you may only choose a single interpreter at startup, you may execute
28099 commands in any interpreter from the current interpreter using the appropriate
28100 command. If you are running the console interpreter, simply use the
28101 @code{interpreter-exec} command:
28104 interpreter-exec mi "-data-list-register-names"
28107 @sc{gdb/mi} has a similar command, although it is only available in versions of
28108 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28111 @chapter @value{GDBN} Text User Interface
28113 @cindex Text User Interface
28116 * TUI Overview:: TUI overview
28117 * TUI Keys:: TUI key bindings
28118 * TUI Single Key Mode:: TUI single key mode
28119 * TUI Commands:: TUI-specific commands
28120 * TUI Configuration:: TUI configuration variables
28123 The @value{GDBN} Text User Interface (TUI) is a terminal
28124 interface which uses the @code{curses} library to show the source
28125 file, the assembly output, the program registers and @value{GDBN}
28126 commands in separate text windows. The TUI mode is supported only
28127 on platforms where a suitable version of the @code{curses} library
28130 The TUI mode is enabled by default when you invoke @value{GDBN} as
28131 @samp{@value{GDBP} -tui}.
28132 You can also switch in and out of TUI mode while @value{GDBN} runs by
28133 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28134 @xref{TUI Keys, ,TUI Key Bindings}.
28137 @section TUI Overview
28139 In TUI mode, @value{GDBN} can display several text windows:
28143 This window is the @value{GDBN} command window with the @value{GDBN}
28144 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28145 managed using readline.
28148 The source window shows the source file of the program. The current
28149 line and active breakpoints are displayed in this window.
28152 The assembly window shows the disassembly output of the program.
28155 This window shows the processor registers. Registers are highlighted
28156 when their values change.
28159 The source and assembly windows show the current program position
28160 by highlighting the current line and marking it with a @samp{>} marker.
28161 Breakpoints are indicated with two markers. The first marker
28162 indicates the breakpoint type:
28166 Breakpoint which was hit at least once.
28169 Breakpoint which was never hit.
28172 Hardware breakpoint which was hit at least once.
28175 Hardware breakpoint which was never hit.
28178 The second marker indicates whether the breakpoint is enabled or not:
28182 Breakpoint is enabled.
28185 Breakpoint is disabled.
28188 The source, assembly and register windows are updated when the current
28189 thread changes, when the frame changes, or when the program counter
28192 These windows are not all visible at the same time. The command
28193 window is always visible. The others can be arranged in several
28204 source and assembly,
28207 source and registers, or
28210 assembly and registers.
28213 A status line above the command window shows the following information:
28217 Indicates the current @value{GDBN} target.
28218 (@pxref{Targets, ,Specifying a Debugging Target}).
28221 Gives the current process or thread number.
28222 When no process is being debugged, this field is set to @code{No process}.
28225 Gives the current function name for the selected frame.
28226 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28227 When there is no symbol corresponding to the current program counter,
28228 the string @code{??} is displayed.
28231 Indicates the current line number for the selected frame.
28232 When the current line number is not known, the string @code{??} is displayed.
28235 Indicates the current program counter address.
28239 @section TUI Key Bindings
28240 @cindex TUI key bindings
28242 The TUI installs several key bindings in the readline keymaps
28243 @ifset SYSTEM_READLINE
28244 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28246 @ifclear SYSTEM_READLINE
28247 (@pxref{Command Line Editing}).
28249 The following key bindings are installed for both TUI mode and the
28250 @value{GDBN} standard mode.
28259 Enter or leave the TUI mode. When leaving the TUI mode,
28260 the curses window management stops and @value{GDBN} operates using
28261 its standard mode, writing on the terminal directly. When reentering
28262 the TUI mode, control is given back to the curses windows.
28263 The screen is then refreshed.
28267 Use a TUI layout with only one window. The layout will
28268 either be @samp{source} or @samp{assembly}. When the TUI mode
28269 is not active, it will switch to the TUI mode.
28271 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28275 Use a TUI layout with at least two windows. When the current
28276 layout already has two windows, the next layout with two windows is used.
28277 When a new layout is chosen, one window will always be common to the
28278 previous layout and the new one.
28280 Think of it as the Emacs @kbd{C-x 2} binding.
28284 Change the active window. The TUI associates several key bindings
28285 (like scrolling and arrow keys) with the active window. This command
28286 gives the focus to the next TUI window.
28288 Think of it as the Emacs @kbd{C-x o} binding.
28292 Switch in and out of the TUI SingleKey mode that binds single
28293 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28296 The following key bindings only work in the TUI mode:
28301 Scroll the active window one page up.
28305 Scroll the active window one page down.
28309 Scroll the active window one line up.
28313 Scroll the active window one line down.
28317 Scroll the active window one column left.
28321 Scroll the active window one column right.
28325 Refresh the screen.
28328 Because the arrow keys scroll the active window in the TUI mode, they
28329 are not available for their normal use by readline unless the command
28330 window has the focus. When another window is active, you must use
28331 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28332 and @kbd{C-f} to control the command window.
28334 @node TUI Single Key Mode
28335 @section TUI Single Key Mode
28336 @cindex TUI single key mode
28338 The TUI also provides a @dfn{SingleKey} mode, which binds several
28339 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28340 switch into this mode, where the following key bindings are used:
28343 @kindex c @r{(SingleKey TUI key)}
28347 @kindex d @r{(SingleKey TUI key)}
28351 @kindex f @r{(SingleKey TUI key)}
28355 @kindex n @r{(SingleKey TUI key)}
28359 @kindex q @r{(SingleKey TUI key)}
28361 exit the SingleKey mode.
28363 @kindex r @r{(SingleKey TUI key)}
28367 @kindex s @r{(SingleKey TUI key)}
28371 @kindex u @r{(SingleKey TUI key)}
28375 @kindex v @r{(SingleKey TUI key)}
28379 @kindex w @r{(SingleKey TUI key)}
28384 Other keys temporarily switch to the @value{GDBN} command prompt.
28385 The key that was pressed is inserted in the editing buffer so that
28386 it is possible to type most @value{GDBN} commands without interaction
28387 with the TUI SingleKey mode. Once the command is entered the TUI
28388 SingleKey mode is restored. The only way to permanently leave
28389 this mode is by typing @kbd{q} or @kbd{C-x s}.
28393 @section TUI-specific Commands
28394 @cindex TUI commands
28396 The TUI has specific commands to control the text windows.
28397 These commands are always available, even when @value{GDBN} is not in
28398 the TUI mode. When @value{GDBN} is in the standard mode, most
28399 of these commands will automatically switch to the TUI mode.
28401 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28402 terminal, or @value{GDBN} has been started with the machine interface
28403 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28404 these commands will fail with an error, because it would not be
28405 possible or desirable to enable curses window management.
28410 List and give the size of all displayed windows.
28414 Display the next layout.
28417 Display the previous layout.
28420 Display the source window only.
28423 Display the assembly window only.
28426 Display the source and assembly window.
28429 Display the register window together with the source or assembly window.
28433 Make the next window active for scrolling.
28436 Make the previous window active for scrolling.
28439 Make the source window active for scrolling.
28442 Make the assembly window active for scrolling.
28445 Make the register window active for scrolling.
28448 Make the command window active for scrolling.
28452 Refresh the screen. This is similar to typing @kbd{C-L}.
28454 @item tui reg float
28456 Show the floating point registers in the register window.
28458 @item tui reg general
28459 Show the general registers in the register window.
28462 Show the next register group. The list of register groups as well as
28463 their order is target specific. The predefined register groups are the
28464 following: @code{general}, @code{float}, @code{system}, @code{vector},
28465 @code{all}, @code{save}, @code{restore}.
28467 @item tui reg system
28468 Show the system registers in the register window.
28472 Update the source window and the current execution point.
28474 @item winheight @var{name} +@var{count}
28475 @itemx winheight @var{name} -@var{count}
28477 Change the height of the window @var{name} by @var{count}
28478 lines. Positive counts increase the height, while negative counts
28481 @item tabset @var{nchars}
28483 Set the width of tab stops to be @var{nchars} characters.
28486 @node TUI Configuration
28487 @section TUI Configuration Variables
28488 @cindex TUI configuration variables
28490 Several configuration variables control the appearance of TUI windows.
28493 @item set tui border-kind @var{kind}
28494 @kindex set tui border-kind
28495 Select the border appearance for the source, assembly and register windows.
28496 The possible values are the following:
28499 Use a space character to draw the border.
28502 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28505 Use the Alternate Character Set to draw the border. The border is
28506 drawn using character line graphics if the terminal supports them.
28509 @item set tui border-mode @var{mode}
28510 @kindex set tui border-mode
28511 @itemx set tui active-border-mode @var{mode}
28512 @kindex set tui active-border-mode
28513 Select the display attributes for the borders of the inactive windows
28514 or the active window. The @var{mode} can be one of the following:
28517 Use normal attributes to display the border.
28523 Use reverse video mode.
28526 Use half bright mode.
28528 @item half-standout
28529 Use half bright and standout mode.
28532 Use extra bright or bold mode.
28534 @item bold-standout
28535 Use extra bright or bold and standout mode.
28540 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28543 @cindex @sc{gnu} Emacs
28544 A special interface allows you to use @sc{gnu} Emacs to view (and
28545 edit) the source files for the program you are debugging with
28548 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28549 executable file you want to debug as an argument. This command starts
28550 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28551 created Emacs buffer.
28552 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28554 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28559 All ``terminal'' input and output goes through an Emacs buffer, called
28562 This applies both to @value{GDBN} commands and their output, and to the input
28563 and output done by the program you are debugging.
28565 This is useful because it means that you can copy the text of previous
28566 commands and input them again; you can even use parts of the output
28569 All the facilities of Emacs' Shell mode are available for interacting
28570 with your program. In particular, you can send signals the usual
28571 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28575 @value{GDBN} displays source code through Emacs.
28577 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28578 source file for that frame and puts an arrow (@samp{=>}) at the
28579 left margin of the current line. Emacs uses a separate buffer for
28580 source display, and splits the screen to show both your @value{GDBN} session
28583 Explicit @value{GDBN} @code{list} or search commands still produce output as
28584 usual, but you probably have no reason to use them from Emacs.
28587 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28588 a graphical mode, enabled by default, which provides further buffers
28589 that can control the execution and describe the state of your program.
28590 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28592 If you specify an absolute file name when prompted for the @kbd{M-x
28593 gdb} argument, then Emacs sets your current working directory to where
28594 your program resides. If you only specify the file name, then Emacs
28595 sets your current working directory to the directory associated
28596 with the previous buffer. In this case, @value{GDBN} may find your
28597 program by searching your environment's @code{PATH} variable, but on
28598 some operating systems it might not find the source. So, although the
28599 @value{GDBN} input and output session proceeds normally, the auxiliary
28600 buffer does not display the current source and line of execution.
28602 The initial working directory of @value{GDBN} is printed on the top
28603 line of the GUD buffer and this serves as a default for the commands
28604 that specify files for @value{GDBN} to operate on. @xref{Files,
28605 ,Commands to Specify Files}.
28607 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28608 need to call @value{GDBN} by a different name (for example, if you
28609 keep several configurations around, with different names) you can
28610 customize the Emacs variable @code{gud-gdb-command-name} to run the
28613 In the GUD buffer, you can use these special Emacs commands in
28614 addition to the standard Shell mode commands:
28618 Describe the features of Emacs' GUD Mode.
28621 Execute to another source line, like the @value{GDBN} @code{step} command; also
28622 update the display window to show the current file and location.
28625 Execute to next source line in this function, skipping all function
28626 calls, like the @value{GDBN} @code{next} command. Then update the display window
28627 to show the current file and location.
28630 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28631 display window accordingly.
28634 Execute until exit from the selected stack frame, like the @value{GDBN}
28635 @code{finish} command.
28638 Continue execution of your program, like the @value{GDBN} @code{continue}
28642 Go up the number of frames indicated by the numeric argument
28643 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28644 like the @value{GDBN} @code{up} command.
28647 Go down the number of frames indicated by the numeric argument, like the
28648 @value{GDBN} @code{down} command.
28651 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28652 tells @value{GDBN} to set a breakpoint on the source line point is on.
28654 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28655 separate frame which shows a backtrace when the GUD buffer is current.
28656 Move point to any frame in the stack and type @key{RET} to make it
28657 become the current frame and display the associated source in the
28658 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28659 selected frame become the current one. In graphical mode, the
28660 speedbar displays watch expressions.
28662 If you accidentally delete the source-display buffer, an easy way to get
28663 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28664 request a frame display; when you run under Emacs, this recreates
28665 the source buffer if necessary to show you the context of the current
28668 The source files displayed in Emacs are in ordinary Emacs buffers
28669 which are visiting the source files in the usual way. You can edit
28670 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28671 communicates with Emacs in terms of line numbers. If you add or
28672 delete lines from the text, the line numbers that @value{GDBN} knows cease
28673 to correspond properly with the code.
28675 A more detailed description of Emacs' interaction with @value{GDBN} is
28676 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28680 @chapter The @sc{gdb/mi} Interface
28682 @unnumberedsec Function and Purpose
28684 @cindex @sc{gdb/mi}, its purpose
28685 @sc{gdb/mi} is a line based machine oriented text interface to
28686 @value{GDBN} and is activated by specifying using the
28687 @option{--interpreter} command line option (@pxref{Mode Options}). It
28688 is specifically intended to support the development of systems which
28689 use the debugger as just one small component of a larger system.
28691 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28692 in the form of a reference manual.
28694 Note that @sc{gdb/mi} is still under construction, so some of the
28695 features described below are incomplete and subject to change
28696 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28698 @unnumberedsec Notation and Terminology
28700 @cindex notational conventions, for @sc{gdb/mi}
28701 This chapter uses the following notation:
28705 @code{|} separates two alternatives.
28708 @code{[ @var{something} ]} indicates that @var{something} is optional:
28709 it may or may not be given.
28712 @code{( @var{group} )*} means that @var{group} inside the parentheses
28713 may repeat zero or more times.
28716 @code{( @var{group} )+} means that @var{group} inside the parentheses
28717 may repeat one or more times.
28720 @code{"@var{string}"} means a literal @var{string}.
28724 @heading Dependencies
28728 * GDB/MI General Design::
28729 * GDB/MI Command Syntax::
28730 * GDB/MI Compatibility with CLI::
28731 * GDB/MI Development and Front Ends::
28732 * GDB/MI Output Records::
28733 * GDB/MI Simple Examples::
28734 * GDB/MI Command Description Format::
28735 * GDB/MI Breakpoint Commands::
28736 * GDB/MI Catchpoint Commands::
28737 * GDB/MI Program Context::
28738 * GDB/MI Thread Commands::
28739 * GDB/MI Ada Tasking Commands::
28740 * GDB/MI Program Execution::
28741 * GDB/MI Stack Manipulation::
28742 * GDB/MI Variable Objects::
28743 * GDB/MI Data Manipulation::
28744 * GDB/MI Tracepoint Commands::
28745 * GDB/MI Symbol Query::
28746 * GDB/MI File Commands::
28748 * GDB/MI Kod Commands::
28749 * GDB/MI Memory Overlay Commands::
28750 * GDB/MI Signal Handling Commands::
28752 * GDB/MI Target Manipulation::
28753 * GDB/MI File Transfer Commands::
28754 * GDB/MI Ada Exceptions Commands::
28755 * GDB/MI Miscellaneous Commands::
28758 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28759 @node GDB/MI General Design
28760 @section @sc{gdb/mi} General Design
28761 @cindex GDB/MI General Design
28763 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28764 parts---commands sent to @value{GDBN}, responses to those commands
28765 and notifications. Each command results in exactly one response,
28766 indicating either successful completion of the command, or an error.
28767 For the commands that do not resume the target, the response contains the
28768 requested information. For the commands that resume the target, the
28769 response only indicates whether the target was successfully resumed.
28770 Notifications is the mechanism for reporting changes in the state of the
28771 target, or in @value{GDBN} state, that cannot conveniently be associated with
28772 a command and reported as part of that command response.
28774 The important examples of notifications are:
28778 Exec notifications. These are used to report changes in
28779 target state---when a target is resumed, or stopped. It would not
28780 be feasible to include this information in response of resuming
28781 commands, because one resume commands can result in multiple events in
28782 different threads. Also, quite some time may pass before any event
28783 happens in the target, while a frontend needs to know whether the resuming
28784 command itself was successfully executed.
28787 Console output, and status notifications. Console output
28788 notifications are used to report output of CLI commands, as well as
28789 diagnostics for other commands. Status notifications are used to
28790 report the progress of a long-running operation. Naturally, including
28791 this information in command response would mean no output is produced
28792 until the command is finished, which is undesirable.
28795 General notifications. Commands may have various side effects on
28796 the @value{GDBN} or target state beyond their official purpose. For example,
28797 a command may change the selected thread. Although such changes can
28798 be included in command response, using notification allows for more
28799 orthogonal frontend design.
28803 There's no guarantee that whenever an MI command reports an error,
28804 @value{GDBN} or the target are in any specific state, and especially,
28805 the state is not reverted to the state before the MI command was
28806 processed. Therefore, whenever an MI command results in an error,
28807 we recommend that the frontend refreshes all the information shown in
28808 the user interface.
28812 * Context management::
28813 * Asynchronous and non-stop modes::
28817 @node Context management
28818 @subsection Context management
28820 @subsubsection Threads and Frames
28822 In most cases when @value{GDBN} accesses the target, this access is
28823 done in context of a specific thread and frame (@pxref{Frames}).
28824 Often, even when accessing global data, the target requires that a thread
28825 be specified. The CLI interface maintains the selected thread and frame,
28826 and supplies them to target on each command. This is convenient,
28827 because a command line user would not want to specify that information
28828 explicitly on each command, and because user interacts with
28829 @value{GDBN} via a single terminal, so no confusion is possible as
28830 to what thread and frame are the current ones.
28832 In the case of MI, the concept of selected thread and frame is less
28833 useful. First, a frontend can easily remember this information
28834 itself. Second, a graphical frontend can have more than one window,
28835 each one used for debugging a different thread, and the frontend might
28836 want to access additional threads for internal purposes. This
28837 increases the risk that by relying on implicitly selected thread, the
28838 frontend may be operating on a wrong one. Therefore, each MI command
28839 should explicitly specify which thread and frame to operate on. To
28840 make it possible, each MI command accepts the @samp{--thread} and
28841 @samp{--frame} options, the value to each is @value{GDBN} identifier
28842 for thread and frame to operate on.
28844 Usually, each top-level window in a frontend allows the user to select
28845 a thread and a frame, and remembers the user selection for further
28846 operations. However, in some cases @value{GDBN} may suggest that the
28847 current thread be changed. For example, when stopping on a breakpoint
28848 it is reasonable to switch to the thread where breakpoint is hit. For
28849 another example, if the user issues the CLI @samp{thread} command via
28850 the frontend, it is desirable to change the frontend's selected thread to the
28851 one specified by user. @value{GDBN} communicates the suggestion to
28852 change current thread using the @samp{=thread-selected} notification.
28853 No such notification is available for the selected frame at the moment.
28855 Note that historically, MI shares the selected thread with CLI, so
28856 frontends used the @code{-thread-select} to execute commands in the
28857 right context. However, getting this to work right is cumbersome. The
28858 simplest way is for frontend to emit @code{-thread-select} command
28859 before every command. This doubles the number of commands that need
28860 to be sent. The alternative approach is to suppress @code{-thread-select}
28861 if the selected thread in @value{GDBN} is supposed to be identical to the
28862 thread the frontend wants to operate on. However, getting this
28863 optimization right can be tricky. In particular, if the frontend
28864 sends several commands to @value{GDBN}, and one of the commands changes the
28865 selected thread, then the behaviour of subsequent commands will
28866 change. So, a frontend should either wait for response from such
28867 problematic commands, or explicitly add @code{-thread-select} for
28868 all subsequent commands. No frontend is known to do this exactly
28869 right, so it is suggested to just always pass the @samp{--thread} and
28870 @samp{--frame} options.
28872 @subsubsection Language
28874 The execution of several commands depends on which language is selected.
28875 By default, the current language (@pxref{show language}) is used.
28876 But for commands known to be language-sensitive, it is recommended
28877 to use the @samp{--language} option. This option takes one argument,
28878 which is the name of the language to use while executing the command.
28882 -data-evaluate-expression --language c "sizeof (void*)"
28887 The valid language names are the same names accepted by the
28888 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28889 @samp{local} or @samp{unknown}.
28891 @node Asynchronous and non-stop modes
28892 @subsection Asynchronous command execution and non-stop mode
28894 On some targets, @value{GDBN} is capable of processing MI commands
28895 even while the target is running. This is called @dfn{asynchronous
28896 command execution} (@pxref{Background Execution}). The frontend may
28897 specify a preferrence for asynchronous execution using the
28898 @code{-gdb-set target-async 1} command, which should be emitted before
28899 either running the executable or attaching to the target. After the
28900 frontend has started the executable or attached to the target, it can
28901 find if asynchronous execution is enabled using the
28902 @code{-list-target-features} command.
28904 Even if @value{GDBN} can accept a command while target is running,
28905 many commands that access the target do not work when the target is
28906 running. Therefore, asynchronous command execution is most useful
28907 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28908 it is possible to examine the state of one thread, while other threads
28911 When a given thread is running, MI commands that try to access the
28912 target in the context of that thread may not work, or may work only on
28913 some targets. In particular, commands that try to operate on thread's
28914 stack will not work, on any target. Commands that read memory, or
28915 modify breakpoints, may work or not work, depending on the target. Note
28916 that even commands that operate on global state, such as @code{print},
28917 @code{set}, and breakpoint commands, still access the target in the
28918 context of a specific thread, so frontend should try to find a
28919 stopped thread and perform the operation on that thread (using the
28920 @samp{--thread} option).
28922 Which commands will work in the context of a running thread is
28923 highly target dependent. However, the two commands
28924 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28925 to find the state of a thread, will always work.
28927 @node Thread groups
28928 @subsection Thread groups
28929 @value{GDBN} may be used to debug several processes at the same time.
28930 On some platfroms, @value{GDBN} may support debugging of several
28931 hardware systems, each one having several cores with several different
28932 processes running on each core. This section describes the MI
28933 mechanism to support such debugging scenarios.
28935 The key observation is that regardless of the structure of the
28936 target, MI can have a global list of threads, because most commands that
28937 accept the @samp{--thread} option do not need to know what process that
28938 thread belongs to. Therefore, it is not necessary to introduce
28939 neither additional @samp{--process} option, nor an notion of the
28940 current process in the MI interface. The only strictly new feature
28941 that is required is the ability to find how the threads are grouped
28944 To allow the user to discover such grouping, and to support arbitrary
28945 hierarchy of machines/cores/processes, MI introduces the concept of a
28946 @dfn{thread group}. Thread group is a collection of threads and other
28947 thread groups. A thread group always has a string identifier, a type,
28948 and may have additional attributes specific to the type. A new
28949 command, @code{-list-thread-groups}, returns the list of top-level
28950 thread groups, which correspond to processes that @value{GDBN} is
28951 debugging at the moment. By passing an identifier of a thread group
28952 to the @code{-list-thread-groups} command, it is possible to obtain
28953 the members of specific thread group.
28955 To allow the user to easily discover processes, and other objects, he
28956 wishes to debug, a concept of @dfn{available thread group} is
28957 introduced. Available thread group is an thread group that
28958 @value{GDBN} is not debugging, but that can be attached to, using the
28959 @code{-target-attach} command. The list of available top-level thread
28960 groups can be obtained using @samp{-list-thread-groups --available}.
28961 In general, the content of a thread group may be only retrieved only
28962 after attaching to that thread group.
28964 Thread groups are related to inferiors (@pxref{Inferiors and
28965 Programs}). Each inferior corresponds to a thread group of a special
28966 type @samp{process}, and some additional operations are permitted on
28967 such thread groups.
28969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28970 @node GDB/MI Command Syntax
28971 @section @sc{gdb/mi} Command Syntax
28974 * GDB/MI Input Syntax::
28975 * GDB/MI Output Syntax::
28978 @node GDB/MI Input Syntax
28979 @subsection @sc{gdb/mi} Input Syntax
28981 @cindex input syntax for @sc{gdb/mi}
28982 @cindex @sc{gdb/mi}, input syntax
28984 @item @var{command} @expansion{}
28985 @code{@var{cli-command} | @var{mi-command}}
28987 @item @var{cli-command} @expansion{}
28988 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28989 @var{cli-command} is any existing @value{GDBN} CLI command.
28991 @item @var{mi-command} @expansion{}
28992 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28993 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28995 @item @var{token} @expansion{}
28996 "any sequence of digits"
28998 @item @var{option} @expansion{}
28999 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29001 @item @var{parameter} @expansion{}
29002 @code{@var{non-blank-sequence} | @var{c-string}}
29004 @item @var{operation} @expansion{}
29005 @emph{any of the operations described in this chapter}
29007 @item @var{non-blank-sequence} @expansion{}
29008 @emph{anything, provided it doesn't contain special characters such as
29009 "-", @var{nl}, """ and of course " "}
29011 @item @var{c-string} @expansion{}
29012 @code{""" @var{seven-bit-iso-c-string-content} """}
29014 @item @var{nl} @expansion{}
29023 The CLI commands are still handled by the @sc{mi} interpreter; their
29024 output is described below.
29027 The @code{@var{token}}, when present, is passed back when the command
29031 Some @sc{mi} commands accept optional arguments as part of the parameter
29032 list. Each option is identified by a leading @samp{-} (dash) and may be
29033 followed by an optional argument parameter. Options occur first in the
29034 parameter list and can be delimited from normal parameters using
29035 @samp{--} (this is useful when some parameters begin with a dash).
29042 We want easy access to the existing CLI syntax (for debugging).
29045 We want it to be easy to spot a @sc{mi} operation.
29048 @node GDB/MI Output Syntax
29049 @subsection @sc{gdb/mi} Output Syntax
29051 @cindex output syntax of @sc{gdb/mi}
29052 @cindex @sc{gdb/mi}, output syntax
29053 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29054 followed, optionally, by a single result record. This result record
29055 is for the most recent command. The sequence of output records is
29056 terminated by @samp{(gdb)}.
29058 If an input command was prefixed with a @code{@var{token}} then the
29059 corresponding output for that command will also be prefixed by that same
29063 @item @var{output} @expansion{}
29064 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29066 @item @var{result-record} @expansion{}
29067 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29069 @item @var{out-of-band-record} @expansion{}
29070 @code{@var{async-record} | @var{stream-record}}
29072 @item @var{async-record} @expansion{}
29073 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29075 @item @var{exec-async-output} @expansion{}
29076 @code{[ @var{token} ] "*" @var{async-output}}
29078 @item @var{status-async-output} @expansion{}
29079 @code{[ @var{token} ] "+" @var{async-output}}
29081 @item @var{notify-async-output} @expansion{}
29082 @code{[ @var{token} ] "=" @var{async-output}}
29084 @item @var{async-output} @expansion{}
29085 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29087 @item @var{result-class} @expansion{}
29088 @code{"done" | "running" | "connected" | "error" | "exit"}
29090 @item @var{async-class} @expansion{}
29091 @code{"stopped" | @var{others}} (where @var{others} will be added
29092 depending on the needs---this is still in development).
29094 @item @var{result} @expansion{}
29095 @code{ @var{variable} "=" @var{value}}
29097 @item @var{variable} @expansion{}
29098 @code{ @var{string} }
29100 @item @var{value} @expansion{}
29101 @code{ @var{const} | @var{tuple} | @var{list} }
29103 @item @var{const} @expansion{}
29104 @code{@var{c-string}}
29106 @item @var{tuple} @expansion{}
29107 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29109 @item @var{list} @expansion{}
29110 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29111 @var{result} ( "," @var{result} )* "]" }
29113 @item @var{stream-record} @expansion{}
29114 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29116 @item @var{console-stream-output} @expansion{}
29117 @code{"~" @var{c-string}}
29119 @item @var{target-stream-output} @expansion{}
29120 @code{"@@" @var{c-string}}
29122 @item @var{log-stream-output} @expansion{}
29123 @code{"&" @var{c-string}}
29125 @item @var{nl} @expansion{}
29128 @item @var{token} @expansion{}
29129 @emph{any sequence of digits}.
29137 All output sequences end in a single line containing a period.
29140 The @code{@var{token}} is from the corresponding request. Note that
29141 for all async output, while the token is allowed by the grammar and
29142 may be output by future versions of @value{GDBN} for select async
29143 output messages, it is generally omitted. Frontends should treat
29144 all async output as reporting general changes in the state of the
29145 target and there should be no need to associate async output to any
29149 @cindex status output in @sc{gdb/mi}
29150 @var{status-async-output} contains on-going status information about the
29151 progress of a slow operation. It can be discarded. All status output is
29152 prefixed by @samp{+}.
29155 @cindex async output in @sc{gdb/mi}
29156 @var{exec-async-output} contains asynchronous state change on the target
29157 (stopped, started, disappeared). All async output is prefixed by
29161 @cindex notify output in @sc{gdb/mi}
29162 @var{notify-async-output} contains supplementary information that the
29163 client should handle (e.g., a new breakpoint information). All notify
29164 output is prefixed by @samp{=}.
29167 @cindex console output in @sc{gdb/mi}
29168 @var{console-stream-output} is output that should be displayed as is in the
29169 console. It is the textual response to a CLI command. All the console
29170 output is prefixed by @samp{~}.
29173 @cindex target output in @sc{gdb/mi}
29174 @var{target-stream-output} is the output produced by the target program.
29175 All the target output is prefixed by @samp{@@}.
29178 @cindex log output in @sc{gdb/mi}
29179 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29180 instance messages that should be displayed as part of an error log. All
29181 the log output is prefixed by @samp{&}.
29184 @cindex list output in @sc{gdb/mi}
29185 New @sc{gdb/mi} commands should only output @var{lists} containing
29191 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29192 details about the various output records.
29194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29195 @node GDB/MI Compatibility with CLI
29196 @section @sc{gdb/mi} Compatibility with CLI
29198 @cindex compatibility, @sc{gdb/mi} and CLI
29199 @cindex @sc{gdb/mi}, compatibility with CLI
29201 For the developers convenience CLI commands can be entered directly,
29202 but there may be some unexpected behaviour. For example, commands
29203 that query the user will behave as if the user replied yes, breakpoint
29204 command lists are not executed and some CLI commands, such as
29205 @code{if}, @code{when} and @code{define}, prompt for further input with
29206 @samp{>}, which is not valid MI output.
29208 This feature may be removed at some stage in the future and it is
29209 recommended that front ends use the @code{-interpreter-exec} command
29210 (@pxref{-interpreter-exec}).
29212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29213 @node GDB/MI Development and Front Ends
29214 @section @sc{gdb/mi} Development and Front Ends
29215 @cindex @sc{gdb/mi} development
29217 The application which takes the MI output and presents the state of the
29218 program being debugged to the user is called a @dfn{front end}.
29220 Although @sc{gdb/mi} is still incomplete, it is currently being used
29221 by a variety of front ends to @value{GDBN}. This makes it difficult
29222 to introduce new functionality without breaking existing usage. This
29223 section tries to minimize the problems by describing how the protocol
29226 Some changes in MI need not break a carefully designed front end, and
29227 for these the MI version will remain unchanged. The following is a
29228 list of changes that may occur within one level, so front ends should
29229 parse MI output in a way that can handle them:
29233 New MI commands may be added.
29236 New fields may be added to the output of any MI command.
29239 The range of values for fields with specified values, e.g.,
29240 @code{in_scope} (@pxref{-var-update}) may be extended.
29242 @c The format of field's content e.g type prefix, may change so parse it
29243 @c at your own risk. Yes, in general?
29245 @c The order of fields may change? Shouldn't really matter but it might
29246 @c resolve inconsistencies.
29249 If the changes are likely to break front ends, the MI version level
29250 will be increased by one. This will allow the front end to parse the
29251 output according to the MI version. Apart from mi0, new versions of
29252 @value{GDBN} will not support old versions of MI and it will be the
29253 responsibility of the front end to work with the new one.
29255 @c Starting with mi3, add a new command -mi-version that prints the MI
29258 The best way to avoid unexpected changes in MI that might break your front
29259 end is to make your project known to @value{GDBN} developers and
29260 follow development on @email{gdb@@sourceware.org} and
29261 @email{gdb-patches@@sourceware.org}.
29262 @cindex mailing lists
29264 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29265 @node GDB/MI Output Records
29266 @section @sc{gdb/mi} Output Records
29269 * GDB/MI Result Records::
29270 * GDB/MI Stream Records::
29271 * GDB/MI Async Records::
29272 * GDB/MI Breakpoint Information::
29273 * GDB/MI Frame Information::
29274 * GDB/MI Thread Information::
29275 * GDB/MI Ada Exception Information::
29278 @node GDB/MI Result Records
29279 @subsection @sc{gdb/mi} Result Records
29281 @cindex result records in @sc{gdb/mi}
29282 @cindex @sc{gdb/mi}, result records
29283 In addition to a number of out-of-band notifications, the response to a
29284 @sc{gdb/mi} command includes one of the following result indications:
29288 @item "^done" [ "," @var{results} ]
29289 The synchronous operation was successful, @code{@var{results}} are the return
29294 This result record is equivalent to @samp{^done}. Historically, it
29295 was output instead of @samp{^done} if the command has resumed the
29296 target. This behaviour is maintained for backward compatibility, but
29297 all frontends should treat @samp{^done} and @samp{^running}
29298 identically and rely on the @samp{*running} output record to determine
29299 which threads are resumed.
29303 @value{GDBN} has connected to a remote target.
29305 @item "^error" "," @var{c-string}
29307 The operation failed. The @code{@var{c-string}} contains the corresponding
29312 @value{GDBN} has terminated.
29316 @node GDB/MI Stream Records
29317 @subsection @sc{gdb/mi} Stream Records
29319 @cindex @sc{gdb/mi}, stream records
29320 @cindex stream records in @sc{gdb/mi}
29321 @value{GDBN} internally maintains a number of output streams: the console, the
29322 target, and the log. The output intended for each of these streams is
29323 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29325 Each stream record begins with a unique @dfn{prefix character} which
29326 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29327 Syntax}). In addition to the prefix, each stream record contains a
29328 @code{@var{string-output}}. This is either raw text (with an implicit new
29329 line) or a quoted C string (which does not contain an implicit newline).
29332 @item "~" @var{string-output}
29333 The console output stream contains text that should be displayed in the
29334 CLI console window. It contains the textual responses to CLI commands.
29336 @item "@@" @var{string-output}
29337 The target output stream contains any textual output from the running
29338 target. This is only present when GDB's event loop is truly
29339 asynchronous, which is currently only the case for remote targets.
29341 @item "&" @var{string-output}
29342 The log stream contains debugging messages being produced by @value{GDBN}'s
29346 @node GDB/MI Async Records
29347 @subsection @sc{gdb/mi} Async Records
29349 @cindex async records in @sc{gdb/mi}
29350 @cindex @sc{gdb/mi}, async records
29351 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29352 additional changes that have occurred. Those changes can either be a
29353 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29354 target activity (e.g., target stopped).
29356 The following is the list of possible async records:
29360 @item *running,thread-id="@var{thread}"
29361 The target is now running. The @var{thread} field tells which
29362 specific thread is now running, and can be @samp{all} if all threads
29363 are running. The frontend should assume that no interaction with a
29364 running thread is possible after this notification is produced.
29365 The frontend should not assume that this notification is output
29366 only once for any command. @value{GDBN} may emit this notification
29367 several times, either for different threads, because it cannot resume
29368 all threads together, or even for a single thread, if the thread must
29369 be stepped though some code before letting it run freely.
29371 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29372 The target has stopped. The @var{reason} field can have one of the
29376 @item breakpoint-hit
29377 A breakpoint was reached.
29378 @item watchpoint-trigger
29379 A watchpoint was triggered.
29380 @item read-watchpoint-trigger
29381 A read watchpoint was triggered.
29382 @item access-watchpoint-trigger
29383 An access watchpoint was triggered.
29384 @item function-finished
29385 An -exec-finish or similar CLI command was accomplished.
29386 @item location-reached
29387 An -exec-until or similar CLI command was accomplished.
29388 @item watchpoint-scope
29389 A watchpoint has gone out of scope.
29390 @item end-stepping-range
29391 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29392 similar CLI command was accomplished.
29393 @item exited-signalled
29394 The inferior exited because of a signal.
29396 The inferior exited.
29397 @item exited-normally
29398 The inferior exited normally.
29399 @item signal-received
29400 A signal was received by the inferior.
29402 The inferior has stopped due to a library being loaded or unloaded.
29403 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29404 set or when a @code{catch load} or @code{catch unload} catchpoint is
29405 in use (@pxref{Set Catchpoints}).
29407 The inferior has forked. This is reported when @code{catch fork}
29408 (@pxref{Set Catchpoints}) has been used.
29410 The inferior has vforked. This is reported in when @code{catch vfork}
29411 (@pxref{Set Catchpoints}) has been used.
29412 @item syscall-entry
29413 The inferior entered a system call. This is reported when @code{catch
29414 syscall} (@pxref{Set Catchpoints}) has been used.
29415 @item syscall-entry
29416 The inferior returned from a system call. This is reported when
29417 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29419 The inferior called @code{exec}. This is reported when @code{catch exec}
29420 (@pxref{Set Catchpoints}) has been used.
29423 The @var{id} field identifies the thread that directly caused the stop
29424 -- for example by hitting a breakpoint. Depending on whether all-stop
29425 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29426 stop all threads, or only the thread that directly triggered the stop.
29427 If all threads are stopped, the @var{stopped} field will have the
29428 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29429 field will be a list of thread identifiers. Presently, this list will
29430 always include a single thread, but frontend should be prepared to see
29431 several threads in the list. The @var{core} field reports the
29432 processor core on which the stop event has happened. This field may be absent
29433 if such information is not available.
29435 @item =thread-group-added,id="@var{id}"
29436 @itemx =thread-group-removed,id="@var{id}"
29437 A thread group was either added or removed. The @var{id} field
29438 contains the @value{GDBN} identifier of the thread group. When a thread
29439 group is added, it generally might not be associated with a running
29440 process. When a thread group is removed, its id becomes invalid and
29441 cannot be used in any way.
29443 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29444 A thread group became associated with a running program,
29445 either because the program was just started or the thread group
29446 was attached to a program. The @var{id} field contains the
29447 @value{GDBN} identifier of the thread group. The @var{pid} field
29448 contains process identifier, specific to the operating system.
29450 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29451 A thread group is no longer associated with a running program,
29452 either because the program has exited, or because it was detached
29453 from. The @var{id} field contains the @value{GDBN} identifier of the
29454 thread group. @var{code} is the exit code of the inferior; it exists
29455 only when the inferior exited with some code.
29457 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29458 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29459 A thread either was created, or has exited. The @var{id} field
29460 contains the @value{GDBN} identifier of the thread. The @var{gid}
29461 field identifies the thread group this thread belongs to.
29463 @item =thread-selected,id="@var{id}"
29464 Informs that the selected thread was changed as result of the last
29465 command. This notification is not emitted as result of @code{-thread-select}
29466 command but is emitted whenever an MI command that is not documented
29467 to change the selected thread actually changes it. In particular,
29468 invoking, directly or indirectly (via user-defined command), the CLI
29469 @code{thread} command, will generate this notification.
29471 We suggest that in response to this notification, front ends
29472 highlight the selected thread and cause subsequent commands to apply to
29475 @item =library-loaded,...
29476 Reports that a new library file was loaded by the program. This
29477 notification has 4 fields---@var{id}, @var{target-name},
29478 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29479 opaque identifier of the library. For remote debugging case,
29480 @var{target-name} and @var{host-name} fields give the name of the
29481 library file on the target, and on the host respectively. For native
29482 debugging, both those fields have the same value. The
29483 @var{symbols-loaded} field is emitted only for backward compatibility
29484 and should not be relied on to convey any useful information. The
29485 @var{thread-group} field, if present, specifies the id of the thread
29486 group in whose context the library was loaded. If the field is
29487 absent, it means the library was loaded in the context of all present
29490 @item =library-unloaded,...
29491 Reports that a library was unloaded by the program. This notification
29492 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29493 the same meaning as for the @code{=library-loaded} notification.
29494 The @var{thread-group} field, if present, specifies the id of the
29495 thread group in whose context the library was unloaded. If the field is
29496 absent, it means the library was unloaded in the context of all present
29499 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29500 @itemx =traceframe-changed,end
29501 Reports that the trace frame was changed and its new number is
29502 @var{tfnum}. The number of the tracepoint associated with this trace
29503 frame is @var{tpnum}.
29505 @item =tsv-created,name=@var{name},initial=@var{initial}
29506 Reports that the new trace state variable @var{name} is created with
29507 initial value @var{initial}.
29509 @item =tsv-deleted,name=@var{name}
29510 @itemx =tsv-deleted
29511 Reports that the trace state variable @var{name} is deleted or all
29512 trace state variables are deleted.
29514 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29515 Reports that the trace state variable @var{name} is modified with
29516 the initial value @var{initial}. The current value @var{current} of
29517 trace state variable is optional and is reported if the current
29518 value of trace state variable is known.
29520 @item =breakpoint-created,bkpt=@{...@}
29521 @itemx =breakpoint-modified,bkpt=@{...@}
29522 @itemx =breakpoint-deleted,id=@var{number}
29523 Reports that a breakpoint was created, modified, or deleted,
29524 respectively. Only user-visible breakpoints are reported to the MI
29527 The @var{bkpt} argument is of the same form as returned by the various
29528 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29529 @var{number} is the ordinal number of the breakpoint.
29531 Note that if a breakpoint is emitted in the result record of a
29532 command, then it will not also be emitted in an async record.
29534 @item =record-started,thread-group="@var{id}"
29535 @itemx =record-stopped,thread-group="@var{id}"
29536 Execution log recording was either started or stopped on an
29537 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29538 group corresponding to the affected inferior.
29540 @item =cmd-param-changed,param=@var{param},value=@var{value}
29541 Reports that a parameter of the command @code{set @var{param}} is
29542 changed to @var{value}. In the multi-word @code{set} command,
29543 the @var{param} is the whole parameter list to @code{set} command.
29544 For example, In command @code{set check type on}, @var{param}
29545 is @code{check type} and @var{value} is @code{on}.
29547 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29548 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29549 written in an inferior. The @var{id} is the identifier of the
29550 thread group corresponding to the affected inferior. The optional
29551 @code{type="code"} part is reported if the memory written to holds
29555 @node GDB/MI Breakpoint Information
29556 @subsection @sc{gdb/mi} Breakpoint Information
29558 When @value{GDBN} reports information about a breakpoint, a
29559 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29564 The breakpoint number. For a breakpoint that represents one location
29565 of a multi-location breakpoint, this will be a dotted pair, like
29569 The type of the breakpoint. For ordinary breakpoints this will be
29570 @samp{breakpoint}, but many values are possible.
29573 If the type of the breakpoint is @samp{catchpoint}, then this
29574 indicates the exact type of catchpoint.
29577 This is the breakpoint disposition---either @samp{del}, meaning that
29578 the breakpoint will be deleted at the next stop, or @samp{keep},
29579 meaning that the breakpoint will not be deleted.
29582 This indicates whether the breakpoint is enabled, in which case the
29583 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29584 Note that this is not the same as the field @code{enable}.
29587 The address of the breakpoint. This may be a hexidecimal number,
29588 giving the address; or the string @samp{<PENDING>}, for a pending
29589 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29590 multiple locations. This field will not be present if no address can
29591 be determined. For example, a watchpoint does not have an address.
29594 If known, the function in which the breakpoint appears.
29595 If not known, this field is not present.
29598 The name of the source file which contains this function, if known.
29599 If not known, this field is not present.
29602 The full file name of the source file which contains this function, if
29603 known. If not known, this field is not present.
29606 The line number at which this breakpoint appears, if known.
29607 If not known, this field is not present.
29610 If the source file is not known, this field may be provided. If
29611 provided, this holds the address of the breakpoint, possibly followed
29615 If this breakpoint is pending, this field is present and holds the
29616 text used to set the breakpoint, as entered by the user.
29619 Where this breakpoint's condition is evaluated, either @samp{host} or
29623 If this is a thread-specific breakpoint, then this identifies the
29624 thread in which the breakpoint can trigger.
29627 If this breakpoint is restricted to a particular Ada task, then this
29628 field will hold the task identifier.
29631 If the breakpoint is conditional, this is the condition expression.
29634 The ignore count of the breakpoint.
29637 The enable count of the breakpoint.
29639 @item traceframe-usage
29642 @item static-tracepoint-marker-string-id
29643 For a static tracepoint, the name of the static tracepoint marker.
29646 For a masked watchpoint, this is the mask.
29649 A tracepoint's pass count.
29651 @item original-location
29652 The location of the breakpoint as originally specified by the user.
29653 This field is optional.
29656 The number of times the breakpoint has been hit.
29659 This field is only given for tracepoints. This is either @samp{y},
29660 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29664 Some extra data, the exact contents of which are type-dependent.
29668 For example, here is what the output of @code{-break-insert}
29669 (@pxref{GDB/MI Breakpoint Commands}) might be:
29672 -> -break-insert main
29673 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29674 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29675 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29680 @node GDB/MI Frame Information
29681 @subsection @sc{gdb/mi} Frame Information
29683 Response from many MI commands includes an information about stack
29684 frame. This information is a tuple that may have the following
29689 The level of the stack frame. The innermost frame has the level of
29690 zero. This field is always present.
29693 The name of the function corresponding to the frame. This field may
29694 be absent if @value{GDBN} is unable to determine the function name.
29697 The code address for the frame. This field is always present.
29700 The name of the source files that correspond to the frame's code
29701 address. This field may be absent.
29704 The source line corresponding to the frames' code address. This field
29708 The name of the binary file (either executable or shared library) the
29709 corresponds to the frame's code address. This field may be absent.
29713 @node GDB/MI Thread Information
29714 @subsection @sc{gdb/mi} Thread Information
29716 Whenever @value{GDBN} has to report an information about a thread, it
29717 uses a tuple with the following fields:
29721 The numeric id assigned to the thread by @value{GDBN}. This field is
29725 Target-specific string identifying the thread. This field is always present.
29728 Additional information about the thread provided by the target.
29729 It is supposed to be human-readable and not interpreted by the
29730 frontend. This field is optional.
29733 Either @samp{stopped} or @samp{running}, depending on whether the
29734 thread is presently running. This field is always present.
29737 The value of this field is an integer number of the processor core the
29738 thread was last seen on. This field is optional.
29741 @node GDB/MI Ada Exception Information
29742 @subsection @sc{gdb/mi} Ada Exception Information
29744 Whenever a @code{*stopped} record is emitted because the program
29745 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29746 @value{GDBN} provides the name of the exception that was raised via
29747 the @code{exception-name} field.
29749 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29750 @node GDB/MI Simple Examples
29751 @section Simple Examples of @sc{gdb/mi} Interaction
29752 @cindex @sc{gdb/mi}, simple examples
29754 This subsection presents several simple examples of interaction using
29755 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29756 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29757 the output received from @sc{gdb/mi}.
29759 Note the line breaks shown in the examples are here only for
29760 readability, they don't appear in the real output.
29762 @subheading Setting a Breakpoint
29764 Setting a breakpoint generates synchronous output which contains detailed
29765 information of the breakpoint.
29768 -> -break-insert main
29769 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29770 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29771 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29776 @subheading Program Execution
29778 Program execution generates asynchronous records and MI gives the
29779 reason that execution stopped.
29785 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29786 frame=@{addr="0x08048564",func="main",
29787 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29788 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29793 <- *stopped,reason="exited-normally"
29797 @subheading Quitting @value{GDBN}
29799 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29807 Please note that @samp{^exit} is printed immediately, but it might
29808 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29809 performs necessary cleanups, including killing programs being debugged
29810 or disconnecting from debug hardware, so the frontend should wait till
29811 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29812 fails to exit in reasonable time.
29814 @subheading A Bad Command
29816 Here's what happens if you pass a non-existent command:
29820 <- ^error,msg="Undefined MI command: rubbish"
29825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29826 @node GDB/MI Command Description Format
29827 @section @sc{gdb/mi} Command Description Format
29829 The remaining sections describe blocks of commands. Each block of
29830 commands is laid out in a fashion similar to this section.
29832 @subheading Motivation
29834 The motivation for this collection of commands.
29836 @subheading Introduction
29838 A brief introduction to this collection of commands as a whole.
29840 @subheading Commands
29842 For each command in the block, the following is described:
29844 @subsubheading Synopsis
29847 -command @var{args}@dots{}
29850 @subsubheading Result
29852 @subsubheading @value{GDBN} Command
29854 The corresponding @value{GDBN} CLI command(s), if any.
29856 @subsubheading Example
29858 Example(s) formatted for readability. Some of the described commands have
29859 not been implemented yet and these are labeled N.A.@: (not available).
29862 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29863 @node GDB/MI Breakpoint Commands
29864 @section @sc{gdb/mi} Breakpoint Commands
29866 @cindex breakpoint commands for @sc{gdb/mi}
29867 @cindex @sc{gdb/mi}, breakpoint commands
29868 This section documents @sc{gdb/mi} commands for manipulating
29871 @subheading The @code{-break-after} Command
29872 @findex -break-after
29874 @subsubheading Synopsis
29877 -break-after @var{number} @var{count}
29880 The breakpoint number @var{number} is not in effect until it has been
29881 hit @var{count} times. To see how this is reflected in the output of
29882 the @samp{-break-list} command, see the description of the
29883 @samp{-break-list} command below.
29885 @subsubheading @value{GDBN} Command
29887 The corresponding @value{GDBN} command is @samp{ignore}.
29889 @subsubheading Example
29894 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29895 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29896 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29904 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29905 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29906 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29907 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29908 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29909 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29910 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29911 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29912 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29913 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29918 @subheading The @code{-break-catch} Command
29919 @findex -break-catch
29922 @subheading The @code{-break-commands} Command
29923 @findex -break-commands
29925 @subsubheading Synopsis
29928 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29931 Specifies the CLI commands that should be executed when breakpoint
29932 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29933 are the commands. If no command is specified, any previously-set
29934 commands are cleared. @xref{Break Commands}. Typical use of this
29935 functionality is tracing a program, that is, printing of values of
29936 some variables whenever breakpoint is hit and then continuing.
29938 @subsubheading @value{GDBN} Command
29940 The corresponding @value{GDBN} command is @samp{commands}.
29942 @subsubheading Example
29947 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29948 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29949 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29952 -break-commands 1 "print v" "continue"
29957 @subheading The @code{-break-condition} Command
29958 @findex -break-condition
29960 @subsubheading Synopsis
29963 -break-condition @var{number} @var{expr}
29966 Breakpoint @var{number} will stop the program only if the condition in
29967 @var{expr} is true. The condition becomes part of the
29968 @samp{-break-list} output (see the description of the @samp{-break-list}
29971 @subsubheading @value{GDBN} Command
29973 The corresponding @value{GDBN} command is @samp{condition}.
29975 @subsubheading Example
29979 -break-condition 1 1
29983 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29984 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29985 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29986 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29987 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29988 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29989 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29990 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29991 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29992 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29996 @subheading The @code{-break-delete} Command
29997 @findex -break-delete
29999 @subsubheading Synopsis
30002 -break-delete ( @var{breakpoint} )+
30005 Delete the breakpoint(s) whose number(s) are specified in the argument
30006 list. This is obviously reflected in the breakpoint list.
30008 @subsubheading @value{GDBN} Command
30010 The corresponding @value{GDBN} command is @samp{delete}.
30012 @subsubheading Example
30020 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30021 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30022 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30023 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30024 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30025 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30026 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30031 @subheading The @code{-break-disable} Command
30032 @findex -break-disable
30034 @subsubheading Synopsis
30037 -break-disable ( @var{breakpoint} )+
30040 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30041 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30043 @subsubheading @value{GDBN} Command
30045 The corresponding @value{GDBN} command is @samp{disable}.
30047 @subsubheading Example
30055 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30056 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30057 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30058 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30059 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30060 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30061 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30062 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30063 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30064 line="5",thread-groups=["i1"],times="0"@}]@}
30068 @subheading The @code{-break-enable} Command
30069 @findex -break-enable
30071 @subsubheading Synopsis
30074 -break-enable ( @var{breakpoint} )+
30077 Enable (previously disabled) @var{breakpoint}(s).
30079 @subsubheading @value{GDBN} Command
30081 The corresponding @value{GDBN} command is @samp{enable}.
30083 @subsubheading Example
30091 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30098 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30099 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30100 line="5",thread-groups=["i1"],times="0"@}]@}
30104 @subheading The @code{-break-info} Command
30105 @findex -break-info
30107 @subsubheading Synopsis
30110 -break-info @var{breakpoint}
30114 Get information about a single breakpoint.
30116 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30117 Information}, for details on the format of each breakpoint in the
30120 @subsubheading @value{GDBN} Command
30122 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30124 @subsubheading Example
30127 @subheading The @code{-break-insert} Command
30128 @findex -break-insert
30130 @subsubheading Synopsis
30133 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30134 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30135 [ -p @var{thread-id} ] [ @var{location} ]
30139 If specified, @var{location}, can be one of:
30146 @item filename:linenum
30147 @item filename:function
30151 The possible optional parameters of this command are:
30155 Insert a temporary breakpoint.
30157 Insert a hardware breakpoint.
30159 If @var{location} cannot be parsed (for example if it
30160 refers to unknown files or functions), create a pending
30161 breakpoint. Without this flag, @value{GDBN} will report
30162 an error, and won't create a breakpoint, if @var{location}
30165 Create a disabled breakpoint.
30167 Create a tracepoint. @xref{Tracepoints}. When this parameter
30168 is used together with @samp{-h}, a fast tracepoint is created.
30169 @item -c @var{condition}
30170 Make the breakpoint conditional on @var{condition}.
30171 @item -i @var{ignore-count}
30172 Initialize the @var{ignore-count}.
30173 @item -p @var{thread-id}
30174 Restrict the breakpoint to the specified @var{thread-id}.
30177 @subsubheading Result
30179 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30180 resulting breakpoint.
30182 Note: this format is open to change.
30183 @c An out-of-band breakpoint instead of part of the result?
30185 @subsubheading @value{GDBN} Command
30187 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30188 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30190 @subsubheading Example
30195 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30196 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30199 -break-insert -t foo
30200 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30201 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30205 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30206 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30207 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30208 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30209 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30210 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30211 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30212 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30213 addr="0x0001072c", func="main",file="recursive2.c",
30214 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30216 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30217 addr="0x00010774",func="foo",file="recursive2.c",
30218 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30221 @c -break-insert -r foo.*
30222 @c ~int foo(int, int);
30223 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30224 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30229 @subheading The @code{-dprintf-insert} Command
30230 @findex -dprintf-insert
30232 @subsubheading Synopsis
30235 -dprintf-insert [ -t ] [ -f ] [ -d ]
30236 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30237 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30242 If specified, @var{location}, can be one of:
30245 @item @var{function}
30248 @c @item @var{linenum}
30249 @item @var{filename}:@var{linenum}
30250 @item @var{filename}:function
30251 @item *@var{address}
30254 The possible optional parameters of this command are:
30258 Insert a temporary breakpoint.
30260 If @var{location} cannot be parsed (for example, if it
30261 refers to unknown files or functions), create a pending
30262 breakpoint. Without this flag, @value{GDBN} will report
30263 an error, and won't create a breakpoint, if @var{location}
30266 Create a disabled breakpoint.
30267 @item -c @var{condition}
30268 Make the breakpoint conditional on @var{condition}.
30269 @item -i @var{ignore-count}
30270 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30271 to @var{ignore-count}.
30272 @item -p @var{thread-id}
30273 Restrict the breakpoint to the specified @var{thread-id}.
30276 @subsubheading Result
30278 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30279 resulting breakpoint.
30281 @c An out-of-band breakpoint instead of part of the result?
30283 @subsubheading @value{GDBN} Command
30285 The corresponding @value{GDBN} command is @samp{dprintf}.
30287 @subsubheading Example
30291 4-dprintf-insert foo "At foo entry\n"
30292 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30293 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30294 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30295 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30296 original-location="foo"@}
30298 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30299 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30300 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30301 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30302 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30303 original-location="mi-dprintf.c:26"@}
30307 @subheading The @code{-break-list} Command
30308 @findex -break-list
30310 @subsubheading Synopsis
30316 Displays the list of inserted breakpoints, showing the following fields:
30320 number of the breakpoint
30322 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30324 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30327 is the breakpoint enabled or no: @samp{y} or @samp{n}
30329 memory location at which the breakpoint is set
30331 logical location of the breakpoint, expressed by function name, file
30333 @item Thread-groups
30334 list of thread groups to which this breakpoint applies
30336 number of times the breakpoint has been hit
30339 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30340 @code{body} field is an empty list.
30342 @subsubheading @value{GDBN} Command
30344 The corresponding @value{GDBN} command is @samp{info break}.
30346 @subsubheading Example
30351 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30352 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30353 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30354 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30355 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30356 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30357 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30358 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30359 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30361 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30362 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30363 line="13",thread-groups=["i1"],times="0"@}]@}
30367 Here's an example of the result when there are no breakpoints:
30372 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30373 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30374 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30375 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30376 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30377 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30378 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30383 @subheading The @code{-break-passcount} Command
30384 @findex -break-passcount
30386 @subsubheading Synopsis
30389 -break-passcount @var{tracepoint-number} @var{passcount}
30392 Set the passcount for tracepoint @var{tracepoint-number} to
30393 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30394 is not a tracepoint, error is emitted. This corresponds to CLI
30395 command @samp{passcount}.
30397 @subheading The @code{-break-watch} Command
30398 @findex -break-watch
30400 @subsubheading Synopsis
30403 -break-watch [ -a | -r ]
30406 Create a watchpoint. With the @samp{-a} option it will create an
30407 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30408 read from or on a write to the memory location. With the @samp{-r}
30409 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30410 trigger only when the memory location is accessed for reading. Without
30411 either of the options, the watchpoint created is a regular watchpoint,
30412 i.e., it will trigger when the memory location is accessed for writing.
30413 @xref{Set Watchpoints, , Setting Watchpoints}.
30415 Note that @samp{-break-list} will report a single list of watchpoints and
30416 breakpoints inserted.
30418 @subsubheading @value{GDBN} Command
30420 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30423 @subsubheading Example
30425 Setting a watchpoint on a variable in the @code{main} function:
30430 ^done,wpt=@{number="2",exp="x"@}
30435 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30436 value=@{old="-268439212",new="55"@},
30437 frame=@{func="main",args=[],file="recursive2.c",
30438 fullname="/home/foo/bar/recursive2.c",line="5"@}
30442 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30443 the program execution twice: first for the variable changing value, then
30444 for the watchpoint going out of scope.
30449 ^done,wpt=@{number="5",exp="C"@}
30454 *stopped,reason="watchpoint-trigger",
30455 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30456 frame=@{func="callee4",args=[],
30457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30463 *stopped,reason="watchpoint-scope",wpnum="5",
30464 frame=@{func="callee3",args=[@{name="strarg",
30465 value="0x11940 \"A string argument.\""@}],
30466 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30467 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30471 Listing breakpoints and watchpoints, at different points in the program
30472 execution. Note that once the watchpoint goes out of scope, it is
30478 ^done,wpt=@{number="2",exp="C"@}
30481 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30482 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30483 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30484 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30485 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30486 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30487 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30488 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30489 addr="0x00010734",func="callee4",
30490 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30491 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30493 bkpt=@{number="2",type="watchpoint",disp="keep",
30494 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30499 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30500 value=@{old="-276895068",new="3"@},
30501 frame=@{func="callee4",args=[],
30502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30503 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30506 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30513 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30514 addr="0x00010734",func="callee4",
30515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30516 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30518 bkpt=@{number="2",type="watchpoint",disp="keep",
30519 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30523 ^done,reason="watchpoint-scope",wpnum="2",
30524 frame=@{func="callee3",args=[@{name="strarg",
30525 value="0x11940 \"A string argument.\""@}],
30526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30530 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30531 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30532 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30533 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30534 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30535 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30536 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30537 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30538 addr="0x00010734",func="callee4",
30539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30540 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30541 thread-groups=["i1"],times="1"@}]@}
30546 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30547 @node GDB/MI Catchpoint Commands
30548 @section @sc{gdb/mi} Catchpoint Commands
30550 This section documents @sc{gdb/mi} commands for manipulating
30554 * Shared Library GDB/MI Catchpoint Commands::
30555 * Ada Exception GDB/MI Catchpoint Commands::
30558 @node Shared Library GDB/MI Catchpoint Commands
30559 @subsection Shared Library @sc{gdb/mi} Catchpoints
30561 @subheading The @code{-catch-load} Command
30562 @findex -catch-load
30564 @subsubheading Synopsis
30567 -catch-load [ -t ] [ -d ] @var{regexp}
30570 Add a catchpoint for library load events. If the @samp{-t} option is used,
30571 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30572 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30573 in a disabled state. The @samp{regexp} argument is a regular
30574 expression used to match the name of the loaded library.
30577 @subsubheading @value{GDBN} Command
30579 The corresponding @value{GDBN} command is @samp{catch load}.
30581 @subsubheading Example
30584 -catch-load -t foo.so
30585 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30586 what="load of library matching foo.so",catch-type="load",times="0"@}
30591 @subheading The @code{-catch-unload} Command
30592 @findex -catch-unload
30594 @subsubheading Synopsis
30597 -catch-unload [ -t ] [ -d ] @var{regexp}
30600 Add a catchpoint for library unload events. If the @samp{-t} option is
30601 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30602 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30603 created in a disabled state. The @samp{regexp} argument is a regular
30604 expression used to match the name of the unloaded library.
30606 @subsubheading @value{GDBN} Command
30608 The corresponding @value{GDBN} command is @samp{catch unload}.
30610 @subsubheading Example
30613 -catch-unload -d bar.so
30614 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30615 what="load of library matching bar.so",catch-type="unload",times="0"@}
30619 @node Ada Exception GDB/MI Catchpoint Commands
30620 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30622 The following @sc{gdb/mi} commands can be used to create catchpoints
30623 that stop the execution when Ada exceptions are being raised.
30625 @subheading The @code{-catch-assert} Command
30626 @findex -catch-assert
30628 @subsubheading Synopsis
30631 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30634 Add a catchpoint for failed Ada assertions.
30636 The possible optional parameters for this command are:
30639 @item -c @var{condition}
30640 Make the catchpoint conditional on @var{condition}.
30642 Create a disabled catchpoint.
30644 Create a temporary catchpoint.
30647 @subsubheading @value{GDBN} Command
30649 The corresponding @value{GDBN} command is @samp{catch assert}.
30651 @subsubheading Example
30655 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30656 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30657 thread-groups=["i1"],times="0",
30658 original-location="__gnat_debug_raise_assert_failure"@}
30662 @subheading The @code{-catch-exception} Command
30663 @findex -catch-exception
30665 @subsubheading Synopsis
30668 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30672 Add a catchpoint stopping when Ada exceptions are raised.
30673 By default, the command stops the program when any Ada exception
30674 gets raised. But it is also possible, by using some of the
30675 optional parameters described below, to create more selective
30678 The possible optional parameters for this command are:
30681 @item -c @var{condition}
30682 Make the catchpoint conditional on @var{condition}.
30684 Create a disabled catchpoint.
30685 @item -e @var{exception-name}
30686 Only stop when @var{exception-name} is raised. This option cannot
30687 be used combined with @samp{-u}.
30689 Create a temporary catchpoint.
30691 Stop only when an unhandled exception gets raised. This option
30692 cannot be used combined with @samp{-e}.
30695 @subsubheading @value{GDBN} Command
30697 The corresponding @value{GDBN} commands are @samp{catch exception}
30698 and @samp{catch exception unhandled}.
30700 @subsubheading Example
30703 -catch-exception -e Program_Error
30704 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30705 enabled="y",addr="0x0000000000404874",
30706 what="`Program_Error' Ada exception", thread-groups=["i1"],
30707 times="0",original-location="__gnat_debug_raise_exception"@}
30711 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30712 @node GDB/MI Program Context
30713 @section @sc{gdb/mi} Program Context
30715 @subheading The @code{-exec-arguments} Command
30716 @findex -exec-arguments
30719 @subsubheading Synopsis
30722 -exec-arguments @var{args}
30725 Set the inferior program arguments, to be used in the next
30728 @subsubheading @value{GDBN} Command
30730 The corresponding @value{GDBN} command is @samp{set args}.
30732 @subsubheading Example
30736 -exec-arguments -v word
30743 @subheading The @code{-exec-show-arguments} Command
30744 @findex -exec-show-arguments
30746 @subsubheading Synopsis
30749 -exec-show-arguments
30752 Print the arguments of the program.
30754 @subsubheading @value{GDBN} Command
30756 The corresponding @value{GDBN} command is @samp{show args}.
30758 @subsubheading Example
30763 @subheading The @code{-environment-cd} Command
30764 @findex -environment-cd
30766 @subsubheading Synopsis
30769 -environment-cd @var{pathdir}
30772 Set @value{GDBN}'s working directory.
30774 @subsubheading @value{GDBN} Command
30776 The corresponding @value{GDBN} command is @samp{cd}.
30778 @subsubheading Example
30782 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30788 @subheading The @code{-environment-directory} Command
30789 @findex -environment-directory
30791 @subsubheading Synopsis
30794 -environment-directory [ -r ] [ @var{pathdir} ]+
30797 Add directories @var{pathdir} to beginning of search path for source files.
30798 If the @samp{-r} option is used, the search path is reset to the default
30799 search path. If directories @var{pathdir} are supplied in addition to the
30800 @samp{-r} option, the search path is first reset and then addition
30802 Multiple directories may be specified, separated by blanks. Specifying
30803 multiple directories in a single command
30804 results in the directories added to the beginning of the
30805 search path in the same order they were presented in the command.
30806 If blanks are needed as
30807 part of a directory name, double-quotes should be used around
30808 the name. In the command output, the path will show up separated
30809 by the system directory-separator character. The directory-separator
30810 character must not be used
30811 in any directory name.
30812 If no directories are specified, the current search path is displayed.
30814 @subsubheading @value{GDBN} Command
30816 The corresponding @value{GDBN} command is @samp{dir}.
30818 @subsubheading Example
30822 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30823 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30825 -environment-directory ""
30826 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30828 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30829 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30831 -environment-directory -r
30832 ^done,source-path="$cdir:$cwd"
30837 @subheading The @code{-environment-path} Command
30838 @findex -environment-path
30840 @subsubheading Synopsis
30843 -environment-path [ -r ] [ @var{pathdir} ]+
30846 Add directories @var{pathdir} to beginning of search path for object files.
30847 If the @samp{-r} option is used, the search path is reset to the original
30848 search path that existed at gdb start-up. If directories @var{pathdir} are
30849 supplied in addition to the
30850 @samp{-r} option, the search path is first reset and then addition
30852 Multiple directories may be specified, separated by blanks. Specifying
30853 multiple directories in a single command
30854 results in the directories added to the beginning of the
30855 search path in the same order they were presented in the command.
30856 If blanks are needed as
30857 part of a directory name, double-quotes should be used around
30858 the name. In the command output, the path will show up separated
30859 by the system directory-separator character. The directory-separator
30860 character must not be used
30861 in any directory name.
30862 If no directories are specified, the current path is displayed.
30865 @subsubheading @value{GDBN} Command
30867 The corresponding @value{GDBN} command is @samp{path}.
30869 @subsubheading Example
30874 ^done,path="/usr/bin"
30876 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30877 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30879 -environment-path -r /usr/local/bin
30880 ^done,path="/usr/local/bin:/usr/bin"
30885 @subheading The @code{-environment-pwd} Command
30886 @findex -environment-pwd
30888 @subsubheading Synopsis
30894 Show the current working directory.
30896 @subsubheading @value{GDBN} Command
30898 The corresponding @value{GDBN} command is @samp{pwd}.
30900 @subsubheading Example
30905 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30910 @node GDB/MI Thread Commands
30911 @section @sc{gdb/mi} Thread Commands
30914 @subheading The @code{-thread-info} Command
30915 @findex -thread-info
30917 @subsubheading Synopsis
30920 -thread-info [ @var{thread-id} ]
30923 Reports information about either a specific thread, if
30924 the @var{thread-id} parameter is present, or about all
30925 threads. When printing information about all threads,
30926 also reports the current thread.
30928 @subsubheading @value{GDBN} Command
30930 The @samp{info thread} command prints the same information
30933 @subsubheading Result
30935 The result is a list of threads. The following attributes are
30936 defined for a given thread:
30940 This field exists only for the current thread. It has the value @samp{*}.
30943 The identifier that @value{GDBN} uses to refer to the thread.
30946 The identifier that the target uses to refer to the thread.
30949 Extra information about the thread, in a target-specific format. This
30953 The name of the thread. If the user specified a name using the
30954 @code{thread name} command, then this name is given. Otherwise, if
30955 @value{GDBN} can extract the thread name from the target, then that
30956 name is given. If @value{GDBN} cannot find the thread name, then this
30960 The stack frame currently executing in the thread.
30963 The thread's state. The @samp{state} field may have the following
30968 The thread is stopped. Frame information is available for stopped
30972 The thread is running. There's no frame information for running
30978 If @value{GDBN} can find the CPU core on which this thread is running,
30979 then this field is the core identifier. This field is optional.
30983 @subsubheading Example
30988 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30989 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30990 args=[]@},state="running"@},
30991 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30992 frame=@{level="0",addr="0x0804891f",func="foo",
30993 args=[@{name="i",value="10"@}],
30994 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
30995 state="running"@}],
30996 current-thread-id="1"
31000 @subheading The @code{-thread-list-ids} Command
31001 @findex -thread-list-ids
31003 @subsubheading Synopsis
31009 Produces a list of the currently known @value{GDBN} thread ids. At the
31010 end of the list it also prints the total number of such threads.
31012 This command is retained for historical reasons, the
31013 @code{-thread-info} command should be used instead.
31015 @subsubheading @value{GDBN} Command
31017 Part of @samp{info threads} supplies the same information.
31019 @subsubheading Example
31024 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31025 current-thread-id="1",number-of-threads="3"
31030 @subheading The @code{-thread-select} Command
31031 @findex -thread-select
31033 @subsubheading Synopsis
31036 -thread-select @var{threadnum}
31039 Make @var{threadnum} the current thread. It prints the number of the new
31040 current thread, and the topmost frame for that thread.
31042 This command is deprecated in favor of explicitly using the
31043 @samp{--thread} option to each command.
31045 @subsubheading @value{GDBN} Command
31047 The corresponding @value{GDBN} command is @samp{thread}.
31049 @subsubheading Example
31056 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31057 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31061 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31062 number-of-threads="3"
31065 ^done,new-thread-id="3",
31066 frame=@{level="0",func="vprintf",
31067 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31068 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31073 @node GDB/MI Ada Tasking Commands
31074 @section @sc{gdb/mi} Ada Tasking Commands
31076 @subheading The @code{-ada-task-info} Command
31077 @findex -ada-task-info
31079 @subsubheading Synopsis
31082 -ada-task-info [ @var{task-id} ]
31085 Reports information about either a specific Ada task, if the
31086 @var{task-id} parameter is present, or about all Ada tasks.
31088 @subsubheading @value{GDBN} Command
31090 The @samp{info tasks} command prints the same information
31091 about all Ada tasks (@pxref{Ada Tasks}).
31093 @subsubheading Result
31095 The result is a table of Ada tasks. The following columns are
31096 defined for each Ada task:
31100 This field exists only for the current thread. It has the value @samp{*}.
31103 The identifier that @value{GDBN} uses to refer to the Ada task.
31106 The identifier that the target uses to refer to the Ada task.
31109 The identifier of the thread corresponding to the Ada task.
31111 This field should always exist, as Ada tasks are always implemented
31112 on top of a thread. But if @value{GDBN} cannot find this corresponding
31113 thread for any reason, the field is omitted.
31116 This field exists only when the task was created by another task.
31117 In this case, it provides the ID of the parent task.
31120 The base priority of the task.
31123 The current state of the task. For a detailed description of the
31124 possible states, see @ref{Ada Tasks}.
31127 The name of the task.
31131 @subsubheading Example
31135 ^done,tasks=@{nr_rows="3",nr_cols="8",
31136 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31137 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31138 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31139 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31140 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31141 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31142 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31143 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31144 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31145 state="Child Termination Wait",name="main_task"@}]@}
31149 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31150 @node GDB/MI Program Execution
31151 @section @sc{gdb/mi} Program Execution
31153 These are the asynchronous commands which generate the out-of-band
31154 record @samp{*stopped}. Currently @value{GDBN} only really executes
31155 asynchronously with remote targets and this interaction is mimicked in
31158 @subheading The @code{-exec-continue} Command
31159 @findex -exec-continue
31161 @subsubheading Synopsis
31164 -exec-continue [--reverse] [--all|--thread-group N]
31167 Resumes the execution of the inferior program, which will continue
31168 to execute until it reaches a debugger stop event. If the
31169 @samp{--reverse} option is specified, execution resumes in reverse until
31170 it reaches a stop event. Stop events may include
31173 breakpoints or watchpoints
31175 signals or exceptions
31177 the end of the process (or its beginning under @samp{--reverse})
31179 the end or beginning of a replay log if one is being used.
31181 In all-stop mode (@pxref{All-Stop
31182 Mode}), may resume only one thread, or all threads, depending on the
31183 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31184 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31185 ignored in all-stop mode. If the @samp{--thread-group} options is
31186 specified, then all threads in that thread group are resumed.
31188 @subsubheading @value{GDBN} Command
31190 The corresponding @value{GDBN} corresponding is @samp{continue}.
31192 @subsubheading Example
31199 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31200 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31206 @subheading The @code{-exec-finish} Command
31207 @findex -exec-finish
31209 @subsubheading Synopsis
31212 -exec-finish [--reverse]
31215 Resumes the execution of the inferior program until the current
31216 function is exited. Displays the results returned by the function.
31217 If the @samp{--reverse} option is specified, resumes the reverse
31218 execution of the inferior program until the point where current
31219 function was called.
31221 @subsubheading @value{GDBN} Command
31223 The corresponding @value{GDBN} command is @samp{finish}.
31225 @subsubheading Example
31227 Function returning @code{void}.
31234 *stopped,reason="function-finished",frame=@{func="main",args=[],
31235 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31239 Function returning other than @code{void}. The name of the internal
31240 @value{GDBN} variable storing the result is printed, together with the
31247 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31248 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31249 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31250 gdb-result-var="$1",return-value="0"
31255 @subheading The @code{-exec-interrupt} Command
31256 @findex -exec-interrupt
31258 @subsubheading Synopsis
31261 -exec-interrupt [--all|--thread-group N]
31264 Interrupts the background execution of the target. Note how the token
31265 associated with the stop message is the one for the execution command
31266 that has been interrupted. The token for the interrupt itself only
31267 appears in the @samp{^done} output. If the user is trying to
31268 interrupt a non-running program, an error message will be printed.
31270 Note that when asynchronous execution is enabled, this command is
31271 asynchronous just like other execution commands. That is, first the
31272 @samp{^done} response will be printed, and the target stop will be
31273 reported after that using the @samp{*stopped} notification.
31275 In non-stop mode, only the context thread is interrupted by default.
31276 All threads (in all inferiors) will be interrupted if the
31277 @samp{--all} option is specified. If the @samp{--thread-group}
31278 option is specified, all threads in that group will be interrupted.
31280 @subsubheading @value{GDBN} Command
31282 The corresponding @value{GDBN} command is @samp{interrupt}.
31284 @subsubheading Example
31295 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31296 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31297 fullname="/home/foo/bar/try.c",line="13"@}
31302 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31306 @subheading The @code{-exec-jump} Command
31309 @subsubheading Synopsis
31312 -exec-jump @var{location}
31315 Resumes execution of the inferior program at the location specified by
31316 parameter. @xref{Specify Location}, for a description of the
31317 different forms of @var{location}.
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} command is @samp{jump}.
31323 @subsubheading Example
31326 -exec-jump foo.c:10
31327 *running,thread-id="all"
31332 @subheading The @code{-exec-next} Command
31335 @subsubheading Synopsis
31338 -exec-next [--reverse]
31341 Resumes execution of the inferior program, stopping when the beginning
31342 of the next source line is reached.
31344 If the @samp{--reverse} option is specified, resumes reverse execution
31345 of the inferior program, stopping at the beginning of the previous
31346 source line. If you issue this command on the first line of a
31347 function, it will take you back to the caller of that function, to the
31348 source line where the function was called.
31351 @subsubheading @value{GDBN} Command
31353 The corresponding @value{GDBN} command is @samp{next}.
31355 @subsubheading Example
31361 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31366 @subheading The @code{-exec-next-instruction} Command
31367 @findex -exec-next-instruction
31369 @subsubheading Synopsis
31372 -exec-next-instruction [--reverse]
31375 Executes one machine instruction. If the instruction is a function
31376 call, continues until the function returns. If the program stops at an
31377 instruction in the middle of a source line, the address will be
31380 If the @samp{--reverse} option is specified, resumes reverse execution
31381 of the inferior program, stopping at the previous instruction. If the
31382 previously executed instruction was a return from another function,
31383 it will continue to execute in reverse until the call to that function
31384 (from the current stack frame) is reached.
31386 @subsubheading @value{GDBN} Command
31388 The corresponding @value{GDBN} command is @samp{nexti}.
31390 @subsubheading Example
31394 -exec-next-instruction
31398 *stopped,reason="end-stepping-range",
31399 addr="0x000100d4",line="5",file="hello.c"
31404 @subheading The @code{-exec-return} Command
31405 @findex -exec-return
31407 @subsubheading Synopsis
31413 Makes current function return immediately. Doesn't execute the inferior.
31414 Displays the new current frame.
31416 @subsubheading @value{GDBN} Command
31418 The corresponding @value{GDBN} command is @samp{return}.
31420 @subsubheading Example
31424 200-break-insert callee4
31425 200^done,bkpt=@{number="1",addr="0x00010734",
31426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31431 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31432 frame=@{func="callee4",args=[],
31433 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31434 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31440 111^done,frame=@{level="0",func="callee3",
31441 args=[@{name="strarg",
31442 value="0x11940 \"A string argument.\""@}],
31443 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31444 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31449 @subheading The @code{-exec-run} Command
31452 @subsubheading Synopsis
31455 -exec-run [ --all | --thread-group N ] [ --start ]
31458 Starts execution of the inferior from the beginning. The inferior
31459 executes until either a breakpoint is encountered or the program
31460 exits. In the latter case the output will include an exit code, if
31461 the program has exited exceptionally.
31463 When neither the @samp{--all} nor the @samp{--thread-group} option
31464 is specified, the current inferior is started. If the
31465 @samp{--thread-group} option is specified, it should refer to a thread
31466 group of type @samp{process}, and that thread group will be started.
31467 If the @samp{--all} option is specified, then all inferiors will be started.
31469 Using the @samp{--start} option instructs the debugger to stop
31470 the execution at the start of the inferior's main subprogram,
31471 following the same behavior as the @code{start} command
31472 (@pxref{Starting}).
31474 @subsubheading @value{GDBN} Command
31476 The corresponding @value{GDBN} command is @samp{run}.
31478 @subsubheading Examples
31483 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31488 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31489 frame=@{func="main",args=[],file="recursive2.c",
31490 fullname="/home/foo/bar/recursive2.c",line="4"@}
31495 Program exited normally:
31503 *stopped,reason="exited-normally"
31508 Program exited exceptionally:
31516 *stopped,reason="exited",exit-code="01"
31520 Another way the program can terminate is if it receives a signal such as
31521 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31525 *stopped,reason="exited-signalled",signal-name="SIGINT",
31526 signal-meaning="Interrupt"
31530 @c @subheading -exec-signal
31533 @subheading The @code{-exec-step} Command
31536 @subsubheading Synopsis
31539 -exec-step [--reverse]
31542 Resumes execution of the inferior program, stopping when the beginning
31543 of the next source line is reached, if the next source line is not a
31544 function call. If it is, stop at the first instruction of the called
31545 function. If the @samp{--reverse} option is specified, resumes reverse
31546 execution of the inferior program, stopping at the beginning of the
31547 previously executed source line.
31549 @subsubheading @value{GDBN} Command
31551 The corresponding @value{GDBN} command is @samp{step}.
31553 @subsubheading Example
31555 Stepping into a function:
31561 *stopped,reason="end-stepping-range",
31562 frame=@{func="foo",args=[@{name="a",value="10"@},
31563 @{name="b",value="0"@}],file="recursive2.c",
31564 fullname="/home/foo/bar/recursive2.c",line="11"@}
31574 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31579 @subheading The @code{-exec-step-instruction} Command
31580 @findex -exec-step-instruction
31582 @subsubheading Synopsis
31585 -exec-step-instruction [--reverse]
31588 Resumes the inferior which executes one machine instruction. If the
31589 @samp{--reverse} option is specified, resumes reverse execution of the
31590 inferior program, stopping at the previously executed instruction.
31591 The output, once @value{GDBN} has stopped, will vary depending on
31592 whether we have stopped in the middle of a source line or not. In the
31593 former case, the address at which the program stopped will be printed
31596 @subsubheading @value{GDBN} Command
31598 The corresponding @value{GDBN} command is @samp{stepi}.
31600 @subsubheading Example
31604 -exec-step-instruction
31608 *stopped,reason="end-stepping-range",
31609 frame=@{func="foo",args=[],file="try.c",
31610 fullname="/home/foo/bar/try.c",line="10"@}
31612 -exec-step-instruction
31616 *stopped,reason="end-stepping-range",
31617 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31618 fullname="/home/foo/bar/try.c",line="10"@}
31623 @subheading The @code{-exec-until} Command
31624 @findex -exec-until
31626 @subsubheading Synopsis
31629 -exec-until [ @var{location} ]
31632 Executes the inferior until the @var{location} specified in the
31633 argument is reached. If there is no argument, the inferior executes
31634 until a source line greater than the current one is reached. The
31635 reason for stopping in this case will be @samp{location-reached}.
31637 @subsubheading @value{GDBN} Command
31639 The corresponding @value{GDBN} command is @samp{until}.
31641 @subsubheading Example
31645 -exec-until recursive2.c:6
31649 *stopped,reason="location-reached",frame=@{func="main",args=[],
31650 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31655 @subheading -file-clear
31656 Is this going away????
31659 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31660 @node GDB/MI Stack Manipulation
31661 @section @sc{gdb/mi} Stack Manipulation Commands
31663 @subheading The @code{-enable-frame-filters} Command
31664 @findex -enable-frame-filters
31667 -enable-frame-filters
31670 @value{GDBN} allows Python-based frame filters to affect the output of
31671 the MI commands relating to stack traces. As there is no way to
31672 implement this in a fully backward-compatible way, a front end must
31673 request that this functionality be enabled.
31675 Once enabled, this feature cannot be disabled.
31677 Note that if Python support has not been compiled into @value{GDBN},
31678 this command will still succeed (and do nothing).
31680 @subheading The @code{-stack-info-frame} Command
31681 @findex -stack-info-frame
31683 @subsubheading Synopsis
31689 Get info on the selected frame.
31691 @subsubheading @value{GDBN} Command
31693 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31694 (without arguments).
31696 @subsubheading Example
31701 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31702 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31703 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31707 @subheading The @code{-stack-info-depth} Command
31708 @findex -stack-info-depth
31710 @subsubheading Synopsis
31713 -stack-info-depth [ @var{max-depth} ]
31716 Return the depth of the stack. If the integer argument @var{max-depth}
31717 is specified, do not count beyond @var{max-depth} frames.
31719 @subsubheading @value{GDBN} Command
31721 There's no equivalent @value{GDBN} command.
31723 @subsubheading Example
31725 For a stack with frame levels 0 through 11:
31732 -stack-info-depth 4
31735 -stack-info-depth 12
31738 -stack-info-depth 11
31741 -stack-info-depth 13
31746 @anchor{-stack-list-arguments}
31747 @subheading The @code{-stack-list-arguments} Command
31748 @findex -stack-list-arguments
31750 @subsubheading Synopsis
31753 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31754 [ @var{low-frame} @var{high-frame} ]
31757 Display a list of the arguments for the frames between @var{low-frame}
31758 and @var{high-frame} (inclusive). If @var{low-frame} and
31759 @var{high-frame} are not provided, list the arguments for the whole
31760 call stack. If the two arguments are equal, show the single frame
31761 at the corresponding level. It is an error if @var{low-frame} is
31762 larger than the actual number of frames. On the other hand,
31763 @var{high-frame} may be larger than the actual number of frames, in
31764 which case only existing frames will be returned.
31766 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31767 the variables; if it is 1 or @code{--all-values}, print also their
31768 values; and if it is 2 or @code{--simple-values}, print the name,
31769 type and value for simple data types, and the name and type for arrays,
31770 structures and unions. If the option @code{--no-frame-filters} is
31771 supplied, then Python frame filters will not be executed.
31773 If the @code{--skip-unavailable} option is specified, arguments that
31774 are not available are not listed. Partially available arguments
31775 are still displayed, however.
31777 Use of this command to obtain arguments in a single frame is
31778 deprecated in favor of the @samp{-stack-list-variables} command.
31780 @subsubheading @value{GDBN} Command
31782 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31783 @samp{gdb_get_args} command which partially overlaps with the
31784 functionality of @samp{-stack-list-arguments}.
31786 @subsubheading Example
31793 frame=@{level="0",addr="0x00010734",func="callee4",
31794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31795 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31796 frame=@{level="1",addr="0x0001076c",func="callee3",
31797 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31798 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31799 frame=@{level="2",addr="0x0001078c",func="callee2",
31800 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31801 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31802 frame=@{level="3",addr="0x000107b4",func="callee1",
31803 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31804 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31805 frame=@{level="4",addr="0x000107e0",func="main",
31806 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31807 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31809 -stack-list-arguments 0
31812 frame=@{level="0",args=[]@},
31813 frame=@{level="1",args=[name="strarg"]@},
31814 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31815 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31816 frame=@{level="4",args=[]@}]
31818 -stack-list-arguments 1
31821 frame=@{level="0",args=[]@},
31823 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31824 frame=@{level="2",args=[
31825 @{name="intarg",value="2"@},
31826 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31827 @{frame=@{level="3",args=[
31828 @{name="intarg",value="2"@},
31829 @{name="strarg",value="0x11940 \"A string argument.\""@},
31830 @{name="fltarg",value="3.5"@}]@},
31831 frame=@{level="4",args=[]@}]
31833 -stack-list-arguments 0 2 2
31834 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31836 -stack-list-arguments 1 2 2
31837 ^done,stack-args=[frame=@{level="2",
31838 args=[@{name="intarg",value="2"@},
31839 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31843 @c @subheading -stack-list-exception-handlers
31846 @anchor{-stack-list-frames}
31847 @subheading The @code{-stack-list-frames} Command
31848 @findex -stack-list-frames
31850 @subsubheading Synopsis
31853 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31856 List the frames currently on the stack. For each frame it displays the
31861 The frame number, 0 being the topmost frame, i.e., the innermost function.
31863 The @code{$pc} value for that frame.
31867 File name of the source file where the function lives.
31868 @item @var{fullname}
31869 The full file name of the source file where the function lives.
31871 Line number corresponding to the @code{$pc}.
31873 The shared library where this function is defined. This is only given
31874 if the frame's function is not known.
31877 If invoked without arguments, this command prints a backtrace for the
31878 whole stack. If given two integer arguments, it shows the frames whose
31879 levels are between the two arguments (inclusive). If the two arguments
31880 are equal, it shows the single frame at the corresponding level. It is
31881 an error if @var{low-frame} is larger than the actual number of
31882 frames. On the other hand, @var{high-frame} may be larger than the
31883 actual number of frames, in which case only existing frames will be
31884 returned. If the option @code{--no-frame-filters} is supplied, then
31885 Python frame filters will not be executed.
31887 @subsubheading @value{GDBN} Command
31889 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31891 @subsubheading Example
31893 Full stack backtrace:
31899 [frame=@{level="0",addr="0x0001076c",func="foo",
31900 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31901 frame=@{level="1",addr="0x000107a4",func="foo",
31902 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31903 frame=@{level="2",addr="0x000107a4",func="foo",
31904 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31905 frame=@{level="3",addr="0x000107a4",func="foo",
31906 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31907 frame=@{level="4",addr="0x000107a4",func="foo",
31908 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31909 frame=@{level="5",addr="0x000107a4",func="foo",
31910 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31911 frame=@{level="6",addr="0x000107a4",func="foo",
31912 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31913 frame=@{level="7",addr="0x000107a4",func="foo",
31914 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31915 frame=@{level="8",addr="0x000107a4",func="foo",
31916 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31917 frame=@{level="9",addr="0x000107a4",func="foo",
31918 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31919 frame=@{level="10",addr="0x000107a4",func="foo",
31920 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31921 frame=@{level="11",addr="0x00010738",func="main",
31922 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31926 Show frames between @var{low_frame} and @var{high_frame}:
31930 -stack-list-frames 3 5
31932 [frame=@{level="3",addr="0x000107a4",func="foo",
31933 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31934 frame=@{level="4",addr="0x000107a4",func="foo",
31935 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31936 frame=@{level="5",addr="0x000107a4",func="foo",
31937 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31941 Show a single frame:
31945 -stack-list-frames 3 3
31947 [frame=@{level="3",addr="0x000107a4",func="foo",
31948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31953 @subheading The @code{-stack-list-locals} Command
31954 @findex -stack-list-locals
31955 @anchor{-stack-list-locals}
31957 @subsubheading Synopsis
31960 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31963 Display the local variable names for the selected frame. If
31964 @var{print-values} is 0 or @code{--no-values}, print only the names of
31965 the variables; if it is 1 or @code{--all-values}, print also their
31966 values; and if it is 2 or @code{--simple-values}, print the name,
31967 type and value for simple data types, and the name and type for arrays,
31968 structures and unions. In this last case, a frontend can immediately
31969 display the value of simple data types and create variable objects for
31970 other data types when the user wishes to explore their values in
31971 more detail. If the option @code{--no-frame-filters} is supplied, then
31972 Python frame filters will not be executed.
31974 If the @code{--skip-unavailable} option is specified, local variables
31975 that are not available are not listed. Partially available local
31976 variables are still displayed, however.
31978 This command is deprecated in favor of the
31979 @samp{-stack-list-variables} command.
31981 @subsubheading @value{GDBN} Command
31983 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31985 @subsubheading Example
31989 -stack-list-locals 0
31990 ^done,locals=[name="A",name="B",name="C"]
31992 -stack-list-locals --all-values
31993 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31994 @{name="C",value="@{1, 2, 3@}"@}]
31995 -stack-list-locals --simple-values
31996 ^done,locals=[@{name="A",type="int",value="1"@},
31997 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32001 @anchor{-stack-list-variables}
32002 @subheading The @code{-stack-list-variables} Command
32003 @findex -stack-list-variables
32005 @subsubheading Synopsis
32008 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32011 Display the names of local variables and function arguments for the selected frame. If
32012 @var{print-values} is 0 or @code{--no-values}, print only the names of
32013 the variables; if it is 1 or @code{--all-values}, print also their
32014 values; and if it is 2 or @code{--simple-values}, print the name,
32015 type and value for simple data types, and the name and type for arrays,
32016 structures and unions. If the option @code{--no-frame-filters} is
32017 supplied, then Python frame filters will not be executed.
32019 If the @code{--skip-unavailable} option is specified, local variables
32020 and arguments that are not available are not listed. Partially
32021 available arguments and local variables are still displayed, however.
32023 @subsubheading Example
32027 -stack-list-variables --thread 1 --frame 0 --all-values
32028 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32033 @subheading The @code{-stack-select-frame} Command
32034 @findex -stack-select-frame
32036 @subsubheading Synopsis
32039 -stack-select-frame @var{framenum}
32042 Change the selected frame. Select a different frame @var{framenum} on
32045 This command in deprecated in favor of passing the @samp{--frame}
32046 option to every command.
32048 @subsubheading @value{GDBN} Command
32050 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32051 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32053 @subsubheading Example
32057 -stack-select-frame 2
32062 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32063 @node GDB/MI Variable Objects
32064 @section @sc{gdb/mi} Variable Objects
32068 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32070 For the implementation of a variable debugger window (locals, watched
32071 expressions, etc.), we are proposing the adaptation of the existing code
32072 used by @code{Insight}.
32074 The two main reasons for that are:
32078 It has been proven in practice (it is already on its second generation).
32081 It will shorten development time (needless to say how important it is
32085 The original interface was designed to be used by Tcl code, so it was
32086 slightly changed so it could be used through @sc{gdb/mi}. This section
32087 describes the @sc{gdb/mi} operations that will be available and gives some
32088 hints about their use.
32090 @emph{Note}: In addition to the set of operations described here, we
32091 expect the @sc{gui} implementation of a variable window to require, at
32092 least, the following operations:
32095 @item @code{-gdb-show} @code{output-radix}
32096 @item @code{-stack-list-arguments}
32097 @item @code{-stack-list-locals}
32098 @item @code{-stack-select-frame}
32103 @subheading Introduction to Variable Objects
32105 @cindex variable objects in @sc{gdb/mi}
32107 Variable objects are "object-oriented" MI interface for examining and
32108 changing values of expressions. Unlike some other MI interfaces that
32109 work with expressions, variable objects are specifically designed for
32110 simple and efficient presentation in the frontend. A variable object
32111 is identified by string name. When a variable object is created, the
32112 frontend specifies the expression for that variable object. The
32113 expression can be a simple variable, or it can be an arbitrary complex
32114 expression, and can even involve CPU registers. After creating a
32115 variable object, the frontend can invoke other variable object
32116 operations---for example to obtain or change the value of a variable
32117 object, or to change display format.
32119 Variable objects have hierarchical tree structure. Any variable object
32120 that corresponds to a composite type, such as structure in C, has
32121 a number of child variable objects, for example corresponding to each
32122 element of a structure. A child variable object can itself have
32123 children, recursively. Recursion ends when we reach
32124 leaf variable objects, which always have built-in types. Child variable
32125 objects are created only by explicit request, so if a frontend
32126 is not interested in the children of a particular variable object, no
32127 child will be created.
32129 For a leaf variable object it is possible to obtain its value as a
32130 string, or set the value from a string. String value can be also
32131 obtained for a non-leaf variable object, but it's generally a string
32132 that only indicates the type of the object, and does not list its
32133 contents. Assignment to a non-leaf variable object is not allowed.
32135 A frontend does not need to read the values of all variable objects each time
32136 the program stops. Instead, MI provides an update command that lists all
32137 variable objects whose values has changed since the last update
32138 operation. This considerably reduces the amount of data that must
32139 be transferred to the frontend. As noted above, children variable
32140 objects are created on demand, and only leaf variable objects have a
32141 real value. As result, gdb will read target memory only for leaf
32142 variables that frontend has created.
32144 The automatic update is not always desirable. For example, a frontend
32145 might want to keep a value of some expression for future reference,
32146 and never update it. For another example, fetching memory is
32147 relatively slow for embedded targets, so a frontend might want
32148 to disable automatic update for the variables that are either not
32149 visible on the screen, or ``closed''. This is possible using so
32150 called ``frozen variable objects''. Such variable objects are never
32151 implicitly updated.
32153 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32154 fixed variable object, the expression is parsed when the variable
32155 object is created, including associating identifiers to specific
32156 variables. The meaning of expression never changes. For a floating
32157 variable object the values of variables whose names appear in the
32158 expressions are re-evaluated every time in the context of the current
32159 frame. Consider this example:
32164 struct work_state state;
32171 If a fixed variable object for the @code{state} variable is created in
32172 this function, and we enter the recursive call, the variable
32173 object will report the value of @code{state} in the top-level
32174 @code{do_work} invocation. On the other hand, a floating variable
32175 object will report the value of @code{state} in the current frame.
32177 If an expression specified when creating a fixed variable object
32178 refers to a local variable, the variable object becomes bound to the
32179 thread and frame in which the variable object is created. When such
32180 variable object is updated, @value{GDBN} makes sure that the
32181 thread/frame combination the variable object is bound to still exists,
32182 and re-evaluates the variable object in context of that thread/frame.
32184 The following is the complete set of @sc{gdb/mi} operations defined to
32185 access this functionality:
32187 @multitable @columnfractions .4 .6
32188 @item @strong{Operation}
32189 @tab @strong{Description}
32191 @item @code{-enable-pretty-printing}
32192 @tab enable Python-based pretty-printing
32193 @item @code{-var-create}
32194 @tab create a variable object
32195 @item @code{-var-delete}
32196 @tab delete the variable object and/or its children
32197 @item @code{-var-set-format}
32198 @tab set the display format of this variable
32199 @item @code{-var-show-format}
32200 @tab show the display format of this variable
32201 @item @code{-var-info-num-children}
32202 @tab tells how many children this object has
32203 @item @code{-var-list-children}
32204 @tab return a list of the object's children
32205 @item @code{-var-info-type}
32206 @tab show the type of this variable object
32207 @item @code{-var-info-expression}
32208 @tab print parent-relative expression that this variable object represents
32209 @item @code{-var-info-path-expression}
32210 @tab print full expression that this variable object represents
32211 @item @code{-var-show-attributes}
32212 @tab is this variable editable? does it exist here?
32213 @item @code{-var-evaluate-expression}
32214 @tab get the value of this variable
32215 @item @code{-var-assign}
32216 @tab set the value of this variable
32217 @item @code{-var-update}
32218 @tab update the variable and its children
32219 @item @code{-var-set-frozen}
32220 @tab set frozeness attribute
32221 @item @code{-var-set-update-range}
32222 @tab set range of children to display on update
32225 In the next subsection we describe each operation in detail and suggest
32226 how it can be used.
32228 @subheading Description And Use of Operations on Variable Objects
32230 @subheading The @code{-enable-pretty-printing} Command
32231 @findex -enable-pretty-printing
32234 -enable-pretty-printing
32237 @value{GDBN} allows Python-based visualizers to affect the output of the
32238 MI variable object commands. However, because there was no way to
32239 implement this in a fully backward-compatible way, a front end must
32240 request that this functionality be enabled.
32242 Once enabled, this feature cannot be disabled.
32244 Note that if Python support has not been compiled into @value{GDBN},
32245 this command will still succeed (and do nothing).
32247 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32248 may work differently in future versions of @value{GDBN}.
32250 @subheading The @code{-var-create} Command
32251 @findex -var-create
32253 @subsubheading Synopsis
32256 -var-create @{@var{name} | "-"@}
32257 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32260 This operation creates a variable object, which allows the monitoring of
32261 a variable, the result of an expression, a memory cell or a CPU
32264 The @var{name} parameter is the string by which the object can be
32265 referenced. It must be unique. If @samp{-} is specified, the varobj
32266 system will generate a string ``varNNNNNN'' automatically. It will be
32267 unique provided that one does not specify @var{name} of that format.
32268 The command fails if a duplicate name is found.
32270 The frame under which the expression should be evaluated can be
32271 specified by @var{frame-addr}. A @samp{*} indicates that the current
32272 frame should be used. A @samp{@@} indicates that a floating variable
32273 object must be created.
32275 @var{expression} is any expression valid on the current language set (must not
32276 begin with a @samp{*}), or one of the following:
32280 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32283 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32286 @samp{$@var{regname}} --- a CPU register name
32289 @cindex dynamic varobj
32290 A varobj's contents may be provided by a Python-based pretty-printer. In this
32291 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32292 have slightly different semantics in some cases. If the
32293 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32294 will never create a dynamic varobj. This ensures backward
32295 compatibility for existing clients.
32297 @subsubheading Result
32299 This operation returns attributes of the newly-created varobj. These
32304 The name of the varobj.
32307 The number of children of the varobj. This number is not necessarily
32308 reliable for a dynamic varobj. Instead, you must examine the
32309 @samp{has_more} attribute.
32312 The varobj's scalar value. For a varobj whose type is some sort of
32313 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32314 will not be interesting.
32317 The varobj's type. This is a string representation of the type, as
32318 would be printed by the @value{GDBN} CLI. If @samp{print object}
32319 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32320 @emph{actual} (derived) type of the object is shown rather than the
32321 @emph{declared} one.
32324 If a variable object is bound to a specific thread, then this is the
32325 thread's identifier.
32328 For a dynamic varobj, this indicates whether there appear to be any
32329 children available. For a non-dynamic varobj, this will be 0.
32332 This attribute will be present and have the value @samp{1} if the
32333 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32334 then this attribute will not be present.
32337 A dynamic varobj can supply a display hint to the front end. The
32338 value comes directly from the Python pretty-printer object's
32339 @code{display_hint} method. @xref{Pretty Printing API}.
32342 Typical output will look like this:
32345 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32346 has_more="@var{has_more}"
32350 @subheading The @code{-var-delete} Command
32351 @findex -var-delete
32353 @subsubheading Synopsis
32356 -var-delete [ -c ] @var{name}
32359 Deletes a previously created variable object and all of its children.
32360 With the @samp{-c} option, just deletes the children.
32362 Returns an error if the object @var{name} is not found.
32365 @subheading The @code{-var-set-format} Command
32366 @findex -var-set-format
32368 @subsubheading Synopsis
32371 -var-set-format @var{name} @var{format-spec}
32374 Sets the output format for the value of the object @var{name} to be
32377 @anchor{-var-set-format}
32378 The syntax for the @var{format-spec} is as follows:
32381 @var{format-spec} @expansion{}
32382 @{binary | decimal | hexadecimal | octal | natural@}
32385 The natural format is the default format choosen automatically
32386 based on the variable type (like decimal for an @code{int}, hex
32387 for pointers, etc.).
32389 For a variable with children, the format is set only on the
32390 variable itself, and the children are not affected.
32392 @subheading The @code{-var-show-format} Command
32393 @findex -var-show-format
32395 @subsubheading Synopsis
32398 -var-show-format @var{name}
32401 Returns the format used to display the value of the object @var{name}.
32404 @var{format} @expansion{}
32409 @subheading The @code{-var-info-num-children} Command
32410 @findex -var-info-num-children
32412 @subsubheading Synopsis
32415 -var-info-num-children @var{name}
32418 Returns the number of children of a variable object @var{name}:
32424 Note that this number is not completely reliable for a dynamic varobj.
32425 It will return the current number of children, but more children may
32429 @subheading The @code{-var-list-children} Command
32430 @findex -var-list-children
32432 @subsubheading Synopsis
32435 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32437 @anchor{-var-list-children}
32439 Return a list of the children of the specified variable object and
32440 create variable objects for them, if they do not already exist. With
32441 a single argument or if @var{print-values} has a value of 0 or
32442 @code{--no-values}, print only the names of the variables; if
32443 @var{print-values} is 1 or @code{--all-values}, also print their
32444 values; and if it is 2 or @code{--simple-values} print the name and
32445 value for simple data types and just the name for arrays, structures
32448 @var{from} and @var{to}, if specified, indicate the range of children
32449 to report. If @var{from} or @var{to} is less than zero, the range is
32450 reset and all children will be reported. Otherwise, children starting
32451 at @var{from} (zero-based) and up to and excluding @var{to} will be
32454 If a child range is requested, it will only affect the current call to
32455 @code{-var-list-children}, but not future calls to @code{-var-update}.
32456 For this, you must instead use @code{-var-set-update-range}. The
32457 intent of this approach is to enable a front end to implement any
32458 update approach it likes; for example, scrolling a view may cause the
32459 front end to request more children with @code{-var-list-children}, and
32460 then the front end could call @code{-var-set-update-range} with a
32461 different range to ensure that future updates are restricted to just
32464 For each child the following results are returned:
32469 Name of the variable object created for this child.
32472 The expression to be shown to the user by the front end to designate this child.
32473 For example this may be the name of a structure member.
32475 For a dynamic varobj, this value cannot be used to form an
32476 expression. There is no way to do this at all with a dynamic varobj.
32478 For C/C@t{++} structures there are several pseudo children returned to
32479 designate access qualifiers. For these pseudo children @var{exp} is
32480 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32481 type and value are not present.
32483 A dynamic varobj will not report the access qualifying
32484 pseudo-children, regardless of the language. This information is not
32485 available at all with a dynamic varobj.
32488 Number of children this child has. For a dynamic varobj, this will be
32492 The type of the child. If @samp{print object}
32493 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32494 @emph{actual} (derived) type of the object is shown rather than the
32495 @emph{declared} one.
32498 If values were requested, this is the value.
32501 If this variable object is associated with a thread, this is the thread id.
32502 Otherwise this result is not present.
32505 If the variable object is frozen, this variable will be present with a value of 1.
32508 The result may have its own attributes:
32512 A dynamic varobj can supply a display hint to the front end. The
32513 value comes directly from the Python pretty-printer object's
32514 @code{display_hint} method. @xref{Pretty Printing API}.
32517 This is an integer attribute which is nonzero if there are children
32518 remaining after the end of the selected range.
32521 @subsubheading Example
32525 -var-list-children n
32526 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32527 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32529 -var-list-children --all-values n
32530 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32531 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32535 @subheading The @code{-var-info-type} Command
32536 @findex -var-info-type
32538 @subsubheading Synopsis
32541 -var-info-type @var{name}
32544 Returns the type of the specified variable @var{name}. The type is
32545 returned as a string in the same format as it is output by the
32549 type=@var{typename}
32553 @subheading The @code{-var-info-expression} Command
32554 @findex -var-info-expression
32556 @subsubheading Synopsis
32559 -var-info-expression @var{name}
32562 Returns a string that is suitable for presenting this
32563 variable object in user interface. The string is generally
32564 not valid expression in the current language, and cannot be evaluated.
32566 For example, if @code{a} is an array, and variable object
32567 @code{A} was created for @code{a}, then we'll get this output:
32570 (gdb) -var-info-expression A.1
32571 ^done,lang="C",exp="1"
32575 Here, the value of @code{lang} is the language name, which can be
32576 found in @ref{Supported Languages}.
32578 Note that the output of the @code{-var-list-children} command also
32579 includes those expressions, so the @code{-var-info-expression} command
32582 @subheading The @code{-var-info-path-expression} Command
32583 @findex -var-info-path-expression
32585 @subsubheading Synopsis
32588 -var-info-path-expression @var{name}
32591 Returns an expression that can be evaluated in the current
32592 context and will yield the same value that a variable object has.
32593 Compare this with the @code{-var-info-expression} command, which
32594 result can be used only for UI presentation. Typical use of
32595 the @code{-var-info-path-expression} command is creating a
32596 watchpoint from a variable object.
32598 This command is currently not valid for children of a dynamic varobj,
32599 and will give an error when invoked on one.
32601 For example, suppose @code{C} is a C@t{++} class, derived from class
32602 @code{Base}, and that the @code{Base} class has a member called
32603 @code{m_size}. Assume a variable @code{c} is has the type of
32604 @code{C} and a variable object @code{C} was created for variable
32605 @code{c}. Then, we'll get this output:
32607 (gdb) -var-info-path-expression C.Base.public.m_size
32608 ^done,path_expr=((Base)c).m_size)
32611 @subheading The @code{-var-show-attributes} Command
32612 @findex -var-show-attributes
32614 @subsubheading Synopsis
32617 -var-show-attributes @var{name}
32620 List attributes of the specified variable object @var{name}:
32623 status=@var{attr} [ ( ,@var{attr} )* ]
32627 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32629 @subheading The @code{-var-evaluate-expression} Command
32630 @findex -var-evaluate-expression
32632 @subsubheading Synopsis
32635 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32638 Evaluates the expression that is represented by the specified variable
32639 object and returns its value as a string. The format of the string
32640 can be specified with the @samp{-f} option. The possible values of
32641 this option are the same as for @code{-var-set-format}
32642 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32643 the current display format will be used. The current display format
32644 can be changed using the @code{-var-set-format} command.
32650 Note that one must invoke @code{-var-list-children} for a variable
32651 before the value of a child variable can be evaluated.
32653 @subheading The @code{-var-assign} Command
32654 @findex -var-assign
32656 @subsubheading Synopsis
32659 -var-assign @var{name} @var{expression}
32662 Assigns the value of @var{expression} to the variable object specified
32663 by @var{name}. The object must be @samp{editable}. If the variable's
32664 value is altered by the assign, the variable will show up in any
32665 subsequent @code{-var-update} list.
32667 @subsubheading Example
32675 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32679 @subheading The @code{-var-update} Command
32680 @findex -var-update
32682 @subsubheading Synopsis
32685 -var-update [@var{print-values}] @{@var{name} | "*"@}
32688 Reevaluate the expressions corresponding to the variable object
32689 @var{name} and all its direct and indirect children, and return the
32690 list of variable objects whose values have changed; @var{name} must
32691 be a root variable object. Here, ``changed'' means that the result of
32692 @code{-var-evaluate-expression} before and after the
32693 @code{-var-update} is different. If @samp{*} is used as the variable
32694 object names, all existing variable objects are updated, except
32695 for frozen ones (@pxref{-var-set-frozen}). The option
32696 @var{print-values} determines whether both names and values, or just
32697 names are printed. The possible values of this option are the same
32698 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32699 recommended to use the @samp{--all-values} option, to reduce the
32700 number of MI commands needed on each program stop.
32702 With the @samp{*} parameter, if a variable object is bound to a
32703 currently running thread, it will not be updated, without any
32706 If @code{-var-set-update-range} was previously used on a varobj, then
32707 only the selected range of children will be reported.
32709 @code{-var-update} reports all the changed varobjs in a tuple named
32712 Each item in the change list is itself a tuple holding:
32716 The name of the varobj.
32719 If values were requested for this update, then this field will be
32720 present and will hold the value of the varobj.
32723 @anchor{-var-update}
32724 This field is a string which may take one of three values:
32728 The variable object's current value is valid.
32731 The variable object does not currently hold a valid value but it may
32732 hold one in the future if its associated expression comes back into
32736 The variable object no longer holds a valid value.
32737 This can occur when the executable file being debugged has changed,
32738 either through recompilation or by using the @value{GDBN} @code{file}
32739 command. The front end should normally choose to delete these variable
32743 In the future new values may be added to this list so the front should
32744 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32747 This is only present if the varobj is still valid. If the type
32748 changed, then this will be the string @samp{true}; otherwise it will
32751 When a varobj's type changes, its children are also likely to have
32752 become incorrect. Therefore, the varobj's children are automatically
32753 deleted when this attribute is @samp{true}. Also, the varobj's update
32754 range, when set using the @code{-var-set-update-range} command, is
32758 If the varobj's type changed, then this field will be present and will
32761 @item new_num_children
32762 For a dynamic varobj, if the number of children changed, or if the
32763 type changed, this will be the new number of children.
32765 The @samp{numchild} field in other varobj responses is generally not
32766 valid for a dynamic varobj -- it will show the number of children that
32767 @value{GDBN} knows about, but because dynamic varobjs lazily
32768 instantiate their children, this will not reflect the number of
32769 children which may be available.
32771 The @samp{new_num_children} attribute only reports changes to the
32772 number of children known by @value{GDBN}. This is the only way to
32773 detect whether an update has removed children (which necessarily can
32774 only happen at the end of the update range).
32777 The display hint, if any.
32780 This is an integer value, which will be 1 if there are more children
32781 available outside the varobj's update range.
32784 This attribute will be present and have the value @samp{1} if the
32785 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32786 then this attribute will not be present.
32789 If new children were added to a dynamic varobj within the selected
32790 update range (as set by @code{-var-set-update-range}), then they will
32791 be listed in this attribute.
32794 @subsubheading Example
32801 -var-update --all-values var1
32802 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32803 type_changed="false"@}]
32807 @subheading The @code{-var-set-frozen} Command
32808 @findex -var-set-frozen
32809 @anchor{-var-set-frozen}
32811 @subsubheading Synopsis
32814 -var-set-frozen @var{name} @var{flag}
32817 Set the frozenness flag on the variable object @var{name}. The
32818 @var{flag} parameter should be either @samp{1} to make the variable
32819 frozen or @samp{0} to make it unfrozen. If a variable object is
32820 frozen, then neither itself, nor any of its children, are
32821 implicitly updated by @code{-var-update} of
32822 a parent variable or by @code{-var-update *}. Only
32823 @code{-var-update} of the variable itself will update its value and
32824 values of its children. After a variable object is unfrozen, it is
32825 implicitly updated by all subsequent @code{-var-update} operations.
32826 Unfreezing a variable does not update it, only subsequent
32827 @code{-var-update} does.
32829 @subsubheading Example
32833 -var-set-frozen V 1
32838 @subheading The @code{-var-set-update-range} command
32839 @findex -var-set-update-range
32840 @anchor{-var-set-update-range}
32842 @subsubheading Synopsis
32845 -var-set-update-range @var{name} @var{from} @var{to}
32848 Set the range of children to be returned by future invocations of
32849 @code{-var-update}.
32851 @var{from} and @var{to} indicate the range of children to report. If
32852 @var{from} or @var{to} is less than zero, the range is reset and all
32853 children will be reported. Otherwise, children starting at @var{from}
32854 (zero-based) and up to and excluding @var{to} will be reported.
32856 @subsubheading Example
32860 -var-set-update-range V 1 2
32864 @subheading The @code{-var-set-visualizer} command
32865 @findex -var-set-visualizer
32866 @anchor{-var-set-visualizer}
32868 @subsubheading Synopsis
32871 -var-set-visualizer @var{name} @var{visualizer}
32874 Set a visualizer for the variable object @var{name}.
32876 @var{visualizer} is the visualizer to use. The special value
32877 @samp{None} means to disable any visualizer in use.
32879 If not @samp{None}, @var{visualizer} must be a Python expression.
32880 This expression must evaluate to a callable object which accepts a
32881 single argument. @value{GDBN} will call this object with the value of
32882 the varobj @var{name} as an argument (this is done so that the same
32883 Python pretty-printing code can be used for both the CLI and MI).
32884 When called, this object must return an object which conforms to the
32885 pretty-printing interface (@pxref{Pretty Printing API}).
32887 The pre-defined function @code{gdb.default_visualizer} may be used to
32888 select a visualizer by following the built-in process
32889 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32890 a varobj is created, and so ordinarily is not needed.
32892 This feature is only available if Python support is enabled. The MI
32893 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32894 can be used to check this.
32896 @subsubheading Example
32898 Resetting the visualizer:
32902 -var-set-visualizer V None
32906 Reselecting the default (type-based) visualizer:
32910 -var-set-visualizer V gdb.default_visualizer
32914 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32915 can be used to instantiate this class for a varobj:
32919 -var-set-visualizer V "lambda val: SomeClass()"
32923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32924 @node GDB/MI Data Manipulation
32925 @section @sc{gdb/mi} Data Manipulation
32927 @cindex data manipulation, in @sc{gdb/mi}
32928 @cindex @sc{gdb/mi}, data manipulation
32929 This section describes the @sc{gdb/mi} commands that manipulate data:
32930 examine memory and registers, evaluate expressions, etc.
32932 @c REMOVED FROM THE INTERFACE.
32933 @c @subheading -data-assign
32934 @c Change the value of a program variable. Plenty of side effects.
32935 @c @subsubheading GDB Command
32937 @c @subsubheading Example
32940 @subheading The @code{-data-disassemble} Command
32941 @findex -data-disassemble
32943 @subsubheading Synopsis
32947 [ -s @var{start-addr} -e @var{end-addr} ]
32948 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32956 @item @var{start-addr}
32957 is the beginning address (or @code{$pc})
32958 @item @var{end-addr}
32960 @item @var{filename}
32961 is the name of the file to disassemble
32962 @item @var{linenum}
32963 is the line number to disassemble around
32965 is the number of disassembly lines to be produced. If it is -1,
32966 the whole function will be disassembled, in case no @var{end-addr} is
32967 specified. If @var{end-addr} is specified as a non-zero value, and
32968 @var{lines} is lower than the number of disassembly lines between
32969 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32970 displayed; if @var{lines} is higher than the number of lines between
32971 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32974 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32975 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32976 mixed source and disassembly with raw opcodes).
32979 @subsubheading Result
32981 The result of the @code{-data-disassemble} command will be a list named
32982 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32983 used with the @code{-data-disassemble} command.
32985 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32990 The address at which this instruction was disassembled.
32993 The name of the function this instruction is within.
32996 The decimal offset in bytes from the start of @samp{func-name}.
32999 The text disassembly for this @samp{address}.
33002 This field is only present for mode 2. This contains the raw opcode
33003 bytes for the @samp{inst} field.
33007 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33008 @samp{src_and_asm_line}, each of which has the following fields:
33012 The line number within @samp{file}.
33015 The file name from the compilation unit. This might be an absolute
33016 file name or a relative file name depending on the compile command
33020 Absolute file name of @samp{file}. It is converted to a canonical form
33021 using the source file search path
33022 (@pxref{Source Path, ,Specifying Source Directories})
33023 and after resolving all the symbolic links.
33025 If the source file is not found this field will contain the path as
33026 present in the debug information.
33028 @item line_asm_insn
33029 This is a list of tuples containing the disassembly for @samp{line} in
33030 @samp{file}. The fields of each tuple are the same as for
33031 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33032 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33037 Note that whatever included in the @samp{inst} field, is not
33038 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33041 @subsubheading @value{GDBN} Command
33043 The corresponding @value{GDBN} command is @samp{disassemble}.
33045 @subsubheading Example
33047 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33051 -data-disassemble -s $pc -e "$pc + 20" -- 0
33054 @{address="0x000107c0",func-name="main",offset="4",
33055 inst="mov 2, %o0"@},
33056 @{address="0x000107c4",func-name="main",offset="8",
33057 inst="sethi %hi(0x11800), %o2"@},
33058 @{address="0x000107c8",func-name="main",offset="12",
33059 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33060 @{address="0x000107cc",func-name="main",offset="16",
33061 inst="sethi %hi(0x11800), %o2"@},
33062 @{address="0x000107d0",func-name="main",offset="20",
33063 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33067 Disassemble the whole @code{main} function. Line 32 is part of
33071 -data-disassemble -f basics.c -l 32 -- 0
33073 @{address="0x000107bc",func-name="main",offset="0",
33074 inst="save %sp, -112, %sp"@},
33075 @{address="0x000107c0",func-name="main",offset="4",
33076 inst="mov 2, %o0"@},
33077 @{address="0x000107c4",func-name="main",offset="8",
33078 inst="sethi %hi(0x11800), %o2"@},
33080 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33081 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33085 Disassemble 3 instructions from the start of @code{main}:
33089 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33091 @{address="0x000107bc",func-name="main",offset="0",
33092 inst="save %sp, -112, %sp"@},
33093 @{address="0x000107c0",func-name="main",offset="4",
33094 inst="mov 2, %o0"@},
33095 @{address="0x000107c4",func-name="main",offset="8",
33096 inst="sethi %hi(0x11800), %o2"@}]
33100 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33104 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33106 src_and_asm_line=@{line="31",
33107 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33108 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33109 line_asm_insn=[@{address="0x000107bc",
33110 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33111 src_and_asm_line=@{line="32",
33112 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33113 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33114 line_asm_insn=[@{address="0x000107c0",
33115 func-name="main",offset="4",inst="mov 2, %o0"@},
33116 @{address="0x000107c4",func-name="main",offset="8",
33117 inst="sethi %hi(0x11800), %o2"@}]@}]
33122 @subheading The @code{-data-evaluate-expression} Command
33123 @findex -data-evaluate-expression
33125 @subsubheading Synopsis
33128 -data-evaluate-expression @var{expr}
33131 Evaluate @var{expr} as an expression. The expression could contain an
33132 inferior function call. The function call will execute synchronously.
33133 If the expression contains spaces, it must be enclosed in double quotes.
33135 @subsubheading @value{GDBN} Command
33137 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33138 @samp{call}. In @code{gdbtk} only, there's a corresponding
33139 @samp{gdb_eval} command.
33141 @subsubheading Example
33143 In the following example, the numbers that precede the commands are the
33144 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33145 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33149 211-data-evaluate-expression A
33152 311-data-evaluate-expression &A
33153 311^done,value="0xefffeb7c"
33155 411-data-evaluate-expression A+3
33158 511-data-evaluate-expression "A + 3"
33164 @subheading The @code{-data-list-changed-registers} Command
33165 @findex -data-list-changed-registers
33167 @subsubheading Synopsis
33170 -data-list-changed-registers
33173 Display a list of the registers that have changed.
33175 @subsubheading @value{GDBN} Command
33177 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33178 has the corresponding command @samp{gdb_changed_register_list}.
33180 @subsubheading Example
33182 On a PPC MBX board:
33190 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33191 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33194 -data-list-changed-registers
33195 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33196 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33197 "24","25","26","27","28","30","31","64","65","66","67","69"]
33202 @subheading The @code{-data-list-register-names} Command
33203 @findex -data-list-register-names
33205 @subsubheading Synopsis
33208 -data-list-register-names [ ( @var{regno} )+ ]
33211 Show a list of register names for the current target. If no arguments
33212 are given, it shows a list of the names of all the registers. If
33213 integer numbers are given as arguments, it will print a list of the
33214 names of the registers corresponding to the arguments. To ensure
33215 consistency between a register name and its number, the output list may
33216 include empty register names.
33218 @subsubheading @value{GDBN} Command
33220 @value{GDBN} does not have a command which corresponds to
33221 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33222 corresponding command @samp{gdb_regnames}.
33224 @subsubheading Example
33226 For the PPC MBX board:
33229 -data-list-register-names
33230 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33231 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33232 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33233 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33234 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33235 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33236 "", "pc","ps","cr","lr","ctr","xer"]
33238 -data-list-register-names 1 2 3
33239 ^done,register-names=["r1","r2","r3"]
33243 @subheading The @code{-data-list-register-values} Command
33244 @findex -data-list-register-values
33246 @subsubheading Synopsis
33249 -data-list-register-values
33250 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33253 Display the registers' contents. @var{fmt} is the format according to
33254 which the registers' contents are to be returned, followed by an optional
33255 list of numbers specifying the registers to display. A missing list of
33256 numbers indicates that the contents of all the registers must be
33257 returned. The @code{--skip-unavailable} option indicates that only
33258 the available registers are to be returned.
33260 Allowed formats for @var{fmt} are:
33277 @subsubheading @value{GDBN} Command
33279 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33280 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33282 @subsubheading Example
33284 For a PPC MBX board (note: line breaks are for readability only, they
33285 don't appear in the actual output):
33289 -data-list-register-values r 64 65
33290 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33291 @{number="65",value="0x00029002"@}]
33293 -data-list-register-values x
33294 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33295 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33296 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33297 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33298 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33299 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33300 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33301 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33302 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33303 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33304 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33305 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33306 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33307 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33308 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33309 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33310 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33311 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33312 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33313 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33314 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33315 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33316 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33317 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33318 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33319 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33320 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33321 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33322 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33323 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33324 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33325 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33326 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33327 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33328 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33329 @{number="69",value="0x20002b03"@}]
33334 @subheading The @code{-data-read-memory} Command
33335 @findex -data-read-memory
33337 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33339 @subsubheading Synopsis
33342 -data-read-memory [ -o @var{byte-offset} ]
33343 @var{address} @var{word-format} @var{word-size}
33344 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33351 @item @var{address}
33352 An expression specifying the address of the first memory word to be
33353 read. Complex expressions containing embedded white space should be
33354 quoted using the C convention.
33356 @item @var{word-format}
33357 The format to be used to print the memory words. The notation is the
33358 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33361 @item @var{word-size}
33362 The size of each memory word in bytes.
33364 @item @var{nr-rows}
33365 The number of rows in the output table.
33367 @item @var{nr-cols}
33368 The number of columns in the output table.
33371 If present, indicates that each row should include an @sc{ascii} dump. The
33372 value of @var{aschar} is used as a padding character when a byte is not a
33373 member of the printable @sc{ascii} character set (printable @sc{ascii}
33374 characters are those whose code is between 32 and 126, inclusively).
33376 @item @var{byte-offset}
33377 An offset to add to the @var{address} before fetching memory.
33380 This command displays memory contents as a table of @var{nr-rows} by
33381 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33382 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33383 (returned as @samp{total-bytes}). Should less than the requested number
33384 of bytes be returned by the target, the missing words are identified
33385 using @samp{N/A}. The number of bytes read from the target is returned
33386 in @samp{nr-bytes} and the starting address used to read memory in
33389 The address of the next/previous row or page is available in
33390 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33393 @subsubheading @value{GDBN} Command
33395 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33396 @samp{gdb_get_mem} memory read command.
33398 @subsubheading Example
33400 Read six bytes of memory starting at @code{bytes+6} but then offset by
33401 @code{-6} bytes. Format as three rows of two columns. One byte per
33402 word. Display each word in hex.
33406 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33407 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33408 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33409 prev-page="0x0000138a",memory=[
33410 @{addr="0x00001390",data=["0x00","0x01"]@},
33411 @{addr="0x00001392",data=["0x02","0x03"]@},
33412 @{addr="0x00001394",data=["0x04","0x05"]@}]
33416 Read two bytes of memory starting at address @code{shorts + 64} and
33417 display as a single word formatted in decimal.
33421 5-data-read-memory shorts+64 d 2 1 1
33422 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33423 next-row="0x00001512",prev-row="0x0000150e",
33424 next-page="0x00001512",prev-page="0x0000150e",memory=[
33425 @{addr="0x00001510",data=["128"]@}]
33429 Read thirty two bytes of memory starting at @code{bytes+16} and format
33430 as eight rows of four columns. Include a string encoding with @samp{x}
33431 used as the non-printable character.
33435 4-data-read-memory bytes+16 x 1 8 4 x
33436 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33437 next-row="0x000013c0",prev-row="0x0000139c",
33438 next-page="0x000013c0",prev-page="0x00001380",memory=[
33439 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33440 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33441 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33442 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33443 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33444 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33445 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33446 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33450 @subheading The @code{-data-read-memory-bytes} Command
33451 @findex -data-read-memory-bytes
33453 @subsubheading Synopsis
33456 -data-read-memory-bytes [ -o @var{byte-offset} ]
33457 @var{address} @var{count}
33464 @item @var{address}
33465 An expression specifying the address of the first memory word to be
33466 read. Complex expressions containing embedded white space should be
33467 quoted using the C convention.
33470 The number of bytes to read. This should be an integer literal.
33472 @item @var{byte-offset}
33473 The offsets in bytes relative to @var{address} at which to start
33474 reading. This should be an integer literal. This option is provided
33475 so that a frontend is not required to first evaluate address and then
33476 perform address arithmetics itself.
33480 This command attempts to read all accessible memory regions in the
33481 specified range. First, all regions marked as unreadable in the memory
33482 map (if one is defined) will be skipped. @xref{Memory Region
33483 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33484 regions. For each one, if reading full region results in an errors,
33485 @value{GDBN} will try to read a subset of the region.
33487 In general, every single byte in the region may be readable or not,
33488 and the only way to read every readable byte is to try a read at
33489 every address, which is not practical. Therefore, @value{GDBN} will
33490 attempt to read all accessible bytes at either beginning or the end
33491 of the region, using a binary division scheme. This heuristic works
33492 well for reading accross a memory map boundary. Note that if a region
33493 has a readable range that is neither at the beginning or the end,
33494 @value{GDBN} will not read it.
33496 The result record (@pxref{GDB/MI Result Records}) that is output of
33497 the command includes a field named @samp{memory} whose content is a
33498 list of tuples. Each tuple represent a successfully read memory block
33499 and has the following fields:
33503 The start address of the memory block, as hexadecimal literal.
33506 The end address of the memory block, as hexadecimal literal.
33509 The offset of the memory block, as hexadecimal literal, relative to
33510 the start address passed to @code{-data-read-memory-bytes}.
33513 The contents of the memory block, in hex.
33519 @subsubheading @value{GDBN} Command
33521 The corresponding @value{GDBN} command is @samp{x}.
33523 @subsubheading Example
33527 -data-read-memory-bytes &a 10
33528 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33530 contents="01000000020000000300"@}]
33535 @subheading The @code{-data-write-memory-bytes} Command
33536 @findex -data-write-memory-bytes
33538 @subsubheading Synopsis
33541 -data-write-memory-bytes @var{address} @var{contents}
33542 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33549 @item @var{address}
33550 An expression specifying the address of the first memory word to be
33551 read. Complex expressions containing embedded white space should be
33552 quoted using the C convention.
33554 @item @var{contents}
33555 The hex-encoded bytes to write.
33558 Optional argument indicating the number of bytes to be written. If @var{count}
33559 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33560 write @var{contents} until it fills @var{count} bytes.
33564 @subsubheading @value{GDBN} Command
33566 There's no corresponding @value{GDBN} command.
33568 @subsubheading Example
33572 -data-write-memory-bytes &a "aabbccdd"
33579 -data-write-memory-bytes &a "aabbccdd" 16e
33584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33585 @node GDB/MI Tracepoint Commands
33586 @section @sc{gdb/mi} Tracepoint Commands
33588 The commands defined in this section implement MI support for
33589 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33591 @subheading The @code{-trace-find} Command
33592 @findex -trace-find
33594 @subsubheading Synopsis
33597 -trace-find @var{mode} [@var{parameters}@dots{}]
33600 Find a trace frame using criteria defined by @var{mode} and
33601 @var{parameters}. The following table lists permissible
33602 modes and their parameters. For details of operation, see @ref{tfind}.
33607 No parameters are required. Stops examining trace frames.
33610 An integer is required as parameter. Selects tracepoint frame with
33613 @item tracepoint-number
33614 An integer is required as parameter. Finds next
33615 trace frame that corresponds to tracepoint with the specified number.
33618 An address is required as parameter. Finds
33619 next trace frame that corresponds to any tracepoint at the specified
33622 @item pc-inside-range
33623 Two addresses are required as parameters. Finds next trace
33624 frame that corresponds to a tracepoint at an address inside the
33625 specified range. Both bounds are considered to be inside the range.
33627 @item pc-outside-range
33628 Two addresses are required as parameters. Finds
33629 next trace frame that corresponds to a tracepoint at an address outside
33630 the specified range. Both bounds are considered to be inside the range.
33633 Line specification is required as parameter. @xref{Specify Location}.
33634 Finds next trace frame that corresponds to a tracepoint at
33635 the specified location.
33639 If @samp{none} was passed as @var{mode}, the response does not
33640 have fields. Otherwise, the response may have the following fields:
33644 This field has either @samp{0} or @samp{1} as the value, depending
33645 on whether a matching tracepoint was found.
33648 The index of the found traceframe. This field is present iff
33649 the @samp{found} field has value of @samp{1}.
33652 The index of the found tracepoint. This field is present iff
33653 the @samp{found} field has value of @samp{1}.
33656 The information about the frame corresponding to the found trace
33657 frame. This field is present only if a trace frame was found.
33658 @xref{GDB/MI Frame Information}, for description of this field.
33662 @subsubheading @value{GDBN} Command
33664 The corresponding @value{GDBN} command is @samp{tfind}.
33666 @subheading -trace-define-variable
33667 @findex -trace-define-variable
33669 @subsubheading Synopsis
33672 -trace-define-variable @var{name} [ @var{value} ]
33675 Create trace variable @var{name} if it does not exist. If
33676 @var{value} is specified, sets the initial value of the specified
33677 trace variable to that value. Note that the @var{name} should start
33678 with the @samp{$} character.
33680 @subsubheading @value{GDBN} Command
33682 The corresponding @value{GDBN} command is @samp{tvariable}.
33684 @subheading The @code{-trace-frame-collected} Command
33685 @findex -trace-frame-collected
33687 @subsubheading Synopsis
33690 -trace-frame-collected
33691 [--var-print-values @var{var_pval}]
33692 [--comp-print-values @var{comp_pval}]
33693 [--registers-format @var{regformat}]
33694 [--memory-contents]
33697 This command returns the set of collected objects, register names,
33698 trace state variable names, memory ranges and computed expressions
33699 that have been collected at a particular trace frame. The optional
33700 parameters to the command affect the output format in different ways.
33701 See the output description table below for more details.
33703 The reported names can be used in the normal manner to create
33704 varobjs and inspect the objects themselves. The items returned by
33705 this command are categorized so that it is clear which is a variable,
33706 which is a register, which is a trace state variable, which is a
33707 memory range and which is a computed expression.
33709 For instance, if the actions were
33711 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33712 collect *(int*)0xaf02bef0@@40
33716 the object collected in its entirety would be @code{myVar}. The
33717 object @code{myArray} would be partially collected, because only the
33718 element at index @code{myIndex} would be collected. The remaining
33719 objects would be computed expressions.
33721 An example output would be:
33725 -trace-frame-collected
33727 explicit-variables=[@{name="myVar",value="1"@}],
33728 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33729 @{name="myObj.field",value="0"@},
33730 @{name="myPtr->field",value="1"@},
33731 @{name="myCount + 2",value="3"@},
33732 @{name="$tvar1 + 1",value="43970027"@}],
33733 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33734 @{number="1",value="0x0"@},
33735 @{number="2",value="0x4"@},
33737 @{number="125",value="0x0"@}],
33738 tvars=[@{name="$tvar1",current="43970026"@}],
33739 memory=[@{address="0x0000000000602264",length="4"@},
33740 @{address="0x0000000000615bc0",length="4"@}]
33747 @item explicit-variables
33748 The set of objects that have been collected in their entirety (as
33749 opposed to collecting just a few elements of an array or a few struct
33750 members). For each object, its name and value are printed.
33751 The @code{--var-print-values} option affects how or whether the value
33752 field is output. If @var{var_pval} is 0, then print only the names;
33753 if it is 1, print also their values; and if it is 2, print the name,
33754 type and value for simple data types, and the name and type for
33755 arrays, structures and unions.
33757 @item computed-expressions
33758 The set of computed expressions that have been collected at the
33759 current trace frame. The @code{--comp-print-values} option affects
33760 this set like the @code{--var-print-values} option affects the
33761 @code{explicit-variables} set. See above.
33764 The registers that have been collected at the current trace frame.
33765 For each register collected, the name and current value are returned.
33766 The value is formatted according to the @code{--registers-format}
33767 option. See the @command{-data-list-register-values} command for a
33768 list of the allowed formats. The default is @samp{x}.
33771 The trace state variables that have been collected at the current
33772 trace frame. For each trace state variable collected, the name and
33773 current value are returned.
33776 The set of memory ranges that have been collected at the current trace
33777 frame. Its content is a list of tuples. Each tuple represents a
33778 collected memory range and has the following fields:
33782 The start address of the memory range, as hexadecimal literal.
33785 The length of the memory range, as decimal literal.
33788 The contents of the memory block, in hex. This field is only present
33789 if the @code{--memory-contents} option is specified.
33795 @subsubheading @value{GDBN} Command
33797 There is no corresponding @value{GDBN} command.
33799 @subsubheading Example
33801 @subheading -trace-list-variables
33802 @findex -trace-list-variables
33804 @subsubheading Synopsis
33807 -trace-list-variables
33810 Return a table of all defined trace variables. Each element of the
33811 table has the following fields:
33815 The name of the trace variable. This field is always present.
33818 The initial value. This is a 64-bit signed integer. This
33819 field is always present.
33822 The value the trace variable has at the moment. This is a 64-bit
33823 signed integer. This field is absent iff current value is
33824 not defined, for example if the trace was never run, or is
33829 @subsubheading @value{GDBN} Command
33831 The corresponding @value{GDBN} command is @samp{tvariables}.
33833 @subsubheading Example
33837 -trace-list-variables
33838 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33839 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33840 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33841 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33842 body=[variable=@{name="$trace_timestamp",initial="0"@}
33843 variable=@{name="$foo",initial="10",current="15"@}]@}
33847 @subheading -trace-save
33848 @findex -trace-save
33850 @subsubheading Synopsis
33853 -trace-save [-r ] @var{filename}
33856 Saves the collected trace data to @var{filename}. Without the
33857 @samp{-r} option, the data is downloaded from the target and saved
33858 in a local file. With the @samp{-r} option the target is asked
33859 to perform the save.
33861 @subsubheading @value{GDBN} Command
33863 The corresponding @value{GDBN} command is @samp{tsave}.
33866 @subheading -trace-start
33867 @findex -trace-start
33869 @subsubheading Synopsis
33875 Starts a tracing experiments. The result of this command does not
33878 @subsubheading @value{GDBN} Command
33880 The corresponding @value{GDBN} command is @samp{tstart}.
33882 @subheading -trace-status
33883 @findex -trace-status
33885 @subsubheading Synopsis
33891 Obtains the status of a tracing experiment. The result may include
33892 the following fields:
33897 May have a value of either @samp{0}, when no tracing operations are
33898 supported, @samp{1}, when all tracing operations are supported, or
33899 @samp{file} when examining trace file. In the latter case, examining
33900 of trace frame is possible but new tracing experiement cannot be
33901 started. This field is always present.
33904 May have a value of either @samp{0} or @samp{1} depending on whether
33905 tracing experiement is in progress on target. This field is present
33906 if @samp{supported} field is not @samp{0}.
33909 Report the reason why the tracing was stopped last time. This field
33910 may be absent iff tracing was never stopped on target yet. The
33911 value of @samp{request} means the tracing was stopped as result of
33912 the @code{-trace-stop} command. The value of @samp{overflow} means
33913 the tracing buffer is full. The value of @samp{disconnection} means
33914 tracing was automatically stopped when @value{GDBN} has disconnected.
33915 The value of @samp{passcount} means tracing was stopped when a
33916 tracepoint was passed a maximal number of times for that tracepoint.
33917 This field is present if @samp{supported} field is not @samp{0}.
33919 @item stopping-tracepoint
33920 The number of tracepoint whose passcount as exceeded. This field is
33921 present iff the @samp{stop-reason} field has the value of
33925 @itemx frames-created
33926 The @samp{frames} field is a count of the total number of trace frames
33927 in the trace buffer, while @samp{frames-created} is the total created
33928 during the run, including ones that were discarded, such as when a
33929 circular trace buffer filled up. Both fields are optional.
33933 These fields tell the current size of the tracing buffer and the
33934 remaining space. These fields are optional.
33937 The value of the circular trace buffer flag. @code{1} means that the
33938 trace buffer is circular and old trace frames will be discarded if
33939 necessary to make room, @code{0} means that the trace buffer is linear
33943 The value of the disconnected tracing flag. @code{1} means that
33944 tracing will continue after @value{GDBN} disconnects, @code{0} means
33945 that the trace run will stop.
33948 The filename of the trace file being examined. This field is
33949 optional, and only present when examining a trace file.
33953 @subsubheading @value{GDBN} Command
33955 The corresponding @value{GDBN} command is @samp{tstatus}.
33957 @subheading -trace-stop
33958 @findex -trace-stop
33960 @subsubheading Synopsis
33966 Stops a tracing experiment. The result of this command has the same
33967 fields as @code{-trace-status}, except that the @samp{supported} and
33968 @samp{running} fields are not output.
33970 @subsubheading @value{GDBN} Command
33972 The corresponding @value{GDBN} command is @samp{tstop}.
33975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33976 @node GDB/MI Symbol Query
33977 @section @sc{gdb/mi} Symbol Query Commands
33981 @subheading The @code{-symbol-info-address} Command
33982 @findex -symbol-info-address
33984 @subsubheading Synopsis
33987 -symbol-info-address @var{symbol}
33990 Describe where @var{symbol} is stored.
33992 @subsubheading @value{GDBN} Command
33994 The corresponding @value{GDBN} command is @samp{info address}.
33996 @subsubheading Example
34000 @subheading The @code{-symbol-info-file} Command
34001 @findex -symbol-info-file
34003 @subsubheading Synopsis
34009 Show the file for the symbol.
34011 @subsubheading @value{GDBN} Command
34013 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34014 @samp{gdb_find_file}.
34016 @subsubheading Example
34020 @subheading The @code{-symbol-info-function} Command
34021 @findex -symbol-info-function
34023 @subsubheading Synopsis
34026 -symbol-info-function
34029 Show which function the symbol lives in.
34031 @subsubheading @value{GDBN} Command
34033 @samp{gdb_get_function} in @code{gdbtk}.
34035 @subsubheading Example
34039 @subheading The @code{-symbol-info-line} Command
34040 @findex -symbol-info-line
34042 @subsubheading Synopsis
34048 Show the core addresses of the code for a source line.
34050 @subsubheading @value{GDBN} Command
34052 The corresponding @value{GDBN} command is @samp{info line}.
34053 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34055 @subsubheading Example
34059 @subheading The @code{-symbol-info-symbol} Command
34060 @findex -symbol-info-symbol
34062 @subsubheading Synopsis
34065 -symbol-info-symbol @var{addr}
34068 Describe what symbol is at location @var{addr}.
34070 @subsubheading @value{GDBN} Command
34072 The corresponding @value{GDBN} command is @samp{info symbol}.
34074 @subsubheading Example
34078 @subheading The @code{-symbol-list-functions} Command
34079 @findex -symbol-list-functions
34081 @subsubheading Synopsis
34084 -symbol-list-functions
34087 List the functions in the executable.
34089 @subsubheading @value{GDBN} Command
34091 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34092 @samp{gdb_search} in @code{gdbtk}.
34094 @subsubheading Example
34099 @subheading The @code{-symbol-list-lines} Command
34100 @findex -symbol-list-lines
34102 @subsubheading Synopsis
34105 -symbol-list-lines @var{filename}
34108 Print the list of lines that contain code and their associated program
34109 addresses for the given source filename. The entries are sorted in
34110 ascending PC order.
34112 @subsubheading @value{GDBN} Command
34114 There is no corresponding @value{GDBN} command.
34116 @subsubheading Example
34119 -symbol-list-lines basics.c
34120 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34126 @subheading The @code{-symbol-list-types} Command
34127 @findex -symbol-list-types
34129 @subsubheading Synopsis
34135 List all the type names.
34137 @subsubheading @value{GDBN} Command
34139 The corresponding commands are @samp{info types} in @value{GDBN},
34140 @samp{gdb_search} in @code{gdbtk}.
34142 @subsubheading Example
34146 @subheading The @code{-symbol-list-variables} Command
34147 @findex -symbol-list-variables
34149 @subsubheading Synopsis
34152 -symbol-list-variables
34155 List all the global and static variable names.
34157 @subsubheading @value{GDBN} Command
34159 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34161 @subsubheading Example
34165 @subheading The @code{-symbol-locate} Command
34166 @findex -symbol-locate
34168 @subsubheading Synopsis
34174 @subsubheading @value{GDBN} Command
34176 @samp{gdb_loc} in @code{gdbtk}.
34178 @subsubheading Example
34182 @subheading The @code{-symbol-type} Command
34183 @findex -symbol-type
34185 @subsubheading Synopsis
34188 -symbol-type @var{variable}
34191 Show type of @var{variable}.
34193 @subsubheading @value{GDBN} Command
34195 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34196 @samp{gdb_obj_variable}.
34198 @subsubheading Example
34203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34204 @node GDB/MI File Commands
34205 @section @sc{gdb/mi} File Commands
34207 This section describes the GDB/MI commands to specify executable file names
34208 and to read in and obtain symbol table information.
34210 @subheading The @code{-file-exec-and-symbols} Command
34211 @findex -file-exec-and-symbols
34213 @subsubheading Synopsis
34216 -file-exec-and-symbols @var{file}
34219 Specify the executable file to be debugged. This file is the one from
34220 which the symbol table is also read. If no file is specified, the
34221 command clears the executable and symbol information. If breakpoints
34222 are set when using this command with no arguments, @value{GDBN} will produce
34223 error messages. Otherwise, no output is produced, except a completion
34226 @subsubheading @value{GDBN} Command
34228 The corresponding @value{GDBN} command is @samp{file}.
34230 @subsubheading Example
34234 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34240 @subheading The @code{-file-exec-file} Command
34241 @findex -file-exec-file
34243 @subsubheading Synopsis
34246 -file-exec-file @var{file}
34249 Specify the executable file to be debugged. Unlike
34250 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34251 from this file. If used without argument, @value{GDBN} clears the information
34252 about the executable file. No output is produced, except a completion
34255 @subsubheading @value{GDBN} Command
34257 The corresponding @value{GDBN} command is @samp{exec-file}.
34259 @subsubheading Example
34263 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34270 @subheading The @code{-file-list-exec-sections} Command
34271 @findex -file-list-exec-sections
34273 @subsubheading Synopsis
34276 -file-list-exec-sections
34279 List the sections of the current executable file.
34281 @subsubheading @value{GDBN} Command
34283 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34284 information as this command. @code{gdbtk} has a corresponding command
34285 @samp{gdb_load_info}.
34287 @subsubheading Example
34292 @subheading The @code{-file-list-exec-source-file} Command
34293 @findex -file-list-exec-source-file
34295 @subsubheading Synopsis
34298 -file-list-exec-source-file
34301 List the line number, the current source file, and the absolute path
34302 to the current source file for the current executable. The macro
34303 information field has a value of @samp{1} or @samp{0} depending on
34304 whether or not the file includes preprocessor macro information.
34306 @subsubheading @value{GDBN} Command
34308 The @value{GDBN} equivalent is @samp{info source}
34310 @subsubheading Example
34314 123-file-list-exec-source-file
34315 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34320 @subheading The @code{-file-list-exec-source-files} Command
34321 @findex -file-list-exec-source-files
34323 @subsubheading Synopsis
34326 -file-list-exec-source-files
34329 List the source files for the current executable.
34331 It will always output both the filename and fullname (absolute file
34332 name) of a source file.
34334 @subsubheading @value{GDBN} Command
34336 The @value{GDBN} equivalent is @samp{info sources}.
34337 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34339 @subsubheading Example
34342 -file-list-exec-source-files
34344 @{file=foo.c,fullname=/home/foo.c@},
34345 @{file=/home/bar.c,fullname=/home/bar.c@},
34346 @{file=gdb_could_not_find_fullpath.c@}]
34351 @subheading The @code{-file-list-shared-libraries} Command
34352 @findex -file-list-shared-libraries
34354 @subsubheading Synopsis
34357 -file-list-shared-libraries
34360 List the shared libraries in the program.
34362 @subsubheading @value{GDBN} Command
34364 The corresponding @value{GDBN} command is @samp{info shared}.
34366 @subsubheading Example
34370 @subheading The @code{-file-list-symbol-files} Command
34371 @findex -file-list-symbol-files
34373 @subsubheading Synopsis
34376 -file-list-symbol-files
34381 @subsubheading @value{GDBN} Command
34383 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34385 @subsubheading Example
34390 @subheading The @code{-file-symbol-file} Command
34391 @findex -file-symbol-file
34393 @subsubheading Synopsis
34396 -file-symbol-file @var{file}
34399 Read symbol table info from the specified @var{file} argument. When
34400 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34401 produced, except for a completion notification.
34403 @subsubheading @value{GDBN} Command
34405 The corresponding @value{GDBN} command is @samp{symbol-file}.
34407 @subsubheading Example
34411 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34418 @node GDB/MI Memory Overlay Commands
34419 @section @sc{gdb/mi} Memory Overlay Commands
34421 The memory overlay commands are not implemented.
34423 @c @subheading -overlay-auto
34425 @c @subheading -overlay-list-mapping-state
34427 @c @subheading -overlay-list-overlays
34429 @c @subheading -overlay-map
34431 @c @subheading -overlay-off
34433 @c @subheading -overlay-on
34435 @c @subheading -overlay-unmap
34437 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34438 @node GDB/MI Signal Handling Commands
34439 @section @sc{gdb/mi} Signal Handling Commands
34441 Signal handling commands are not implemented.
34443 @c @subheading -signal-handle
34445 @c @subheading -signal-list-handle-actions
34447 @c @subheading -signal-list-signal-types
34451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34452 @node GDB/MI Target Manipulation
34453 @section @sc{gdb/mi} Target Manipulation Commands
34456 @subheading The @code{-target-attach} Command
34457 @findex -target-attach
34459 @subsubheading Synopsis
34462 -target-attach @var{pid} | @var{gid} | @var{file}
34465 Attach to a process @var{pid} or a file @var{file} outside of
34466 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34467 group, the id previously returned by
34468 @samp{-list-thread-groups --available} must be used.
34470 @subsubheading @value{GDBN} Command
34472 The corresponding @value{GDBN} command is @samp{attach}.
34474 @subsubheading Example
34478 =thread-created,id="1"
34479 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34485 @subheading The @code{-target-compare-sections} Command
34486 @findex -target-compare-sections
34488 @subsubheading Synopsis
34491 -target-compare-sections [ @var{section} ]
34494 Compare data of section @var{section} on target to the exec file.
34495 Without the argument, all sections are compared.
34497 @subsubheading @value{GDBN} Command
34499 The @value{GDBN} equivalent is @samp{compare-sections}.
34501 @subsubheading Example
34506 @subheading The @code{-target-detach} Command
34507 @findex -target-detach
34509 @subsubheading Synopsis
34512 -target-detach [ @var{pid} | @var{gid} ]
34515 Detach from the remote target which normally resumes its execution.
34516 If either @var{pid} or @var{gid} is specified, detaches from either
34517 the specified process, or specified thread group. There's no output.
34519 @subsubheading @value{GDBN} Command
34521 The corresponding @value{GDBN} command is @samp{detach}.
34523 @subsubheading Example
34533 @subheading The @code{-target-disconnect} Command
34534 @findex -target-disconnect
34536 @subsubheading Synopsis
34542 Disconnect from the remote target. There's no output and the target is
34543 generally not resumed.
34545 @subsubheading @value{GDBN} Command
34547 The corresponding @value{GDBN} command is @samp{disconnect}.
34549 @subsubheading Example
34559 @subheading The @code{-target-download} Command
34560 @findex -target-download
34562 @subsubheading Synopsis
34568 Loads the executable onto the remote target.
34569 It prints out an update message every half second, which includes the fields:
34573 The name of the section.
34575 The size of what has been sent so far for that section.
34577 The size of the section.
34579 The total size of what was sent so far (the current and the previous sections).
34581 The size of the overall executable to download.
34585 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34586 @sc{gdb/mi} Output Syntax}).
34588 In addition, it prints the name and size of the sections, as they are
34589 downloaded. These messages include the following fields:
34593 The name of the section.
34595 The size of the section.
34597 The size of the overall executable to download.
34601 At the end, a summary is printed.
34603 @subsubheading @value{GDBN} Command
34605 The corresponding @value{GDBN} command is @samp{load}.
34607 @subsubheading Example
34609 Note: each status message appears on a single line. Here the messages
34610 have been broken down so that they can fit onto a page.
34615 +download,@{section=".text",section-size="6668",total-size="9880"@}
34616 +download,@{section=".text",section-sent="512",section-size="6668",
34617 total-sent="512",total-size="9880"@}
34618 +download,@{section=".text",section-sent="1024",section-size="6668",
34619 total-sent="1024",total-size="9880"@}
34620 +download,@{section=".text",section-sent="1536",section-size="6668",
34621 total-sent="1536",total-size="9880"@}
34622 +download,@{section=".text",section-sent="2048",section-size="6668",
34623 total-sent="2048",total-size="9880"@}
34624 +download,@{section=".text",section-sent="2560",section-size="6668",
34625 total-sent="2560",total-size="9880"@}
34626 +download,@{section=".text",section-sent="3072",section-size="6668",
34627 total-sent="3072",total-size="9880"@}
34628 +download,@{section=".text",section-sent="3584",section-size="6668",
34629 total-sent="3584",total-size="9880"@}
34630 +download,@{section=".text",section-sent="4096",section-size="6668",
34631 total-sent="4096",total-size="9880"@}
34632 +download,@{section=".text",section-sent="4608",section-size="6668",
34633 total-sent="4608",total-size="9880"@}
34634 +download,@{section=".text",section-sent="5120",section-size="6668",
34635 total-sent="5120",total-size="9880"@}
34636 +download,@{section=".text",section-sent="5632",section-size="6668",
34637 total-sent="5632",total-size="9880"@}
34638 +download,@{section=".text",section-sent="6144",section-size="6668",
34639 total-sent="6144",total-size="9880"@}
34640 +download,@{section=".text",section-sent="6656",section-size="6668",
34641 total-sent="6656",total-size="9880"@}
34642 +download,@{section=".init",section-size="28",total-size="9880"@}
34643 +download,@{section=".fini",section-size="28",total-size="9880"@}
34644 +download,@{section=".data",section-size="3156",total-size="9880"@}
34645 +download,@{section=".data",section-sent="512",section-size="3156",
34646 total-sent="7236",total-size="9880"@}
34647 +download,@{section=".data",section-sent="1024",section-size="3156",
34648 total-sent="7748",total-size="9880"@}
34649 +download,@{section=".data",section-sent="1536",section-size="3156",
34650 total-sent="8260",total-size="9880"@}
34651 +download,@{section=".data",section-sent="2048",section-size="3156",
34652 total-sent="8772",total-size="9880"@}
34653 +download,@{section=".data",section-sent="2560",section-size="3156",
34654 total-sent="9284",total-size="9880"@}
34655 +download,@{section=".data",section-sent="3072",section-size="3156",
34656 total-sent="9796",total-size="9880"@}
34657 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34664 @subheading The @code{-target-exec-status} Command
34665 @findex -target-exec-status
34667 @subsubheading Synopsis
34670 -target-exec-status
34673 Provide information on the state of the target (whether it is running or
34674 not, for instance).
34676 @subsubheading @value{GDBN} Command
34678 There's no equivalent @value{GDBN} command.
34680 @subsubheading Example
34684 @subheading The @code{-target-list-available-targets} Command
34685 @findex -target-list-available-targets
34687 @subsubheading Synopsis
34690 -target-list-available-targets
34693 List the possible targets to connect to.
34695 @subsubheading @value{GDBN} Command
34697 The corresponding @value{GDBN} command is @samp{help target}.
34699 @subsubheading Example
34703 @subheading The @code{-target-list-current-targets} Command
34704 @findex -target-list-current-targets
34706 @subsubheading Synopsis
34709 -target-list-current-targets
34712 Describe the current target.
34714 @subsubheading @value{GDBN} Command
34716 The corresponding information is printed by @samp{info file} (among
34719 @subsubheading Example
34723 @subheading The @code{-target-list-parameters} Command
34724 @findex -target-list-parameters
34726 @subsubheading Synopsis
34729 -target-list-parameters
34735 @subsubheading @value{GDBN} Command
34739 @subsubheading Example
34743 @subheading The @code{-target-select} Command
34744 @findex -target-select
34746 @subsubheading Synopsis
34749 -target-select @var{type} @var{parameters @dots{}}
34752 Connect @value{GDBN} to the remote target. This command takes two args:
34756 The type of target, for instance @samp{remote}, etc.
34757 @item @var{parameters}
34758 Device names, host names and the like. @xref{Target Commands, ,
34759 Commands for Managing Targets}, for more details.
34762 The output is a connection notification, followed by the address at
34763 which the target program is, in the following form:
34766 ^connected,addr="@var{address}",func="@var{function name}",
34767 args=[@var{arg list}]
34770 @subsubheading @value{GDBN} Command
34772 The corresponding @value{GDBN} command is @samp{target}.
34774 @subsubheading Example
34778 -target-select remote /dev/ttya
34779 ^connected,addr="0xfe00a300",func="??",args=[]
34783 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34784 @node GDB/MI File Transfer Commands
34785 @section @sc{gdb/mi} File Transfer Commands
34788 @subheading The @code{-target-file-put} Command
34789 @findex -target-file-put
34791 @subsubheading Synopsis
34794 -target-file-put @var{hostfile} @var{targetfile}
34797 Copy file @var{hostfile} from the host system (the machine running
34798 @value{GDBN}) to @var{targetfile} on the target system.
34800 @subsubheading @value{GDBN} Command
34802 The corresponding @value{GDBN} command is @samp{remote put}.
34804 @subsubheading Example
34808 -target-file-put localfile remotefile
34814 @subheading The @code{-target-file-get} Command
34815 @findex -target-file-get
34817 @subsubheading Synopsis
34820 -target-file-get @var{targetfile} @var{hostfile}
34823 Copy file @var{targetfile} from the target system to @var{hostfile}
34824 on the host system.
34826 @subsubheading @value{GDBN} Command
34828 The corresponding @value{GDBN} command is @samp{remote get}.
34830 @subsubheading Example
34834 -target-file-get remotefile localfile
34840 @subheading The @code{-target-file-delete} Command
34841 @findex -target-file-delete
34843 @subsubheading Synopsis
34846 -target-file-delete @var{targetfile}
34849 Delete @var{targetfile} from the target system.
34851 @subsubheading @value{GDBN} Command
34853 The corresponding @value{GDBN} command is @samp{remote delete}.
34855 @subsubheading Example
34859 -target-file-delete remotefile
34865 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34866 @node GDB/MI Ada Exceptions Commands
34867 @section Ada Exceptions @sc{gdb/mi} Commands
34869 @subheading The @code{-info-ada-exceptions} Command
34870 @findex -info-ada-exceptions
34872 @subsubheading Synopsis
34875 -info-ada-exceptions [ @var{regexp}]
34878 List all Ada exceptions defined within the program being debugged.
34879 With a regular expression @var{regexp}, only those exceptions whose
34880 names match @var{regexp} are listed.
34882 @subsubheading @value{GDBN} Command
34884 The corresponding @value{GDBN} command is @samp{info exceptions}.
34886 @subsubheading Result
34888 The result is a table of Ada exceptions. The following columns are
34889 defined for each exception:
34893 The name of the exception.
34896 The address of the exception.
34900 @subsubheading Example
34903 -info-ada-exceptions aint
34904 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34905 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34906 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34907 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34908 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34911 @subheading Catching Ada Exceptions
34913 The commands describing how to ask @value{GDBN} to stop when a program
34914 raises an exception are described at @ref{Ada Exception GDB/MI
34915 Catchpoint Commands}.
34918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34919 @node GDB/MI Miscellaneous Commands
34920 @section Miscellaneous @sc{gdb/mi} Commands
34922 @c @subheading -gdb-complete
34924 @subheading The @code{-gdb-exit} Command
34927 @subsubheading Synopsis
34933 Exit @value{GDBN} immediately.
34935 @subsubheading @value{GDBN} Command
34937 Approximately corresponds to @samp{quit}.
34939 @subsubheading Example
34949 @subheading The @code{-exec-abort} Command
34950 @findex -exec-abort
34952 @subsubheading Synopsis
34958 Kill the inferior running program.
34960 @subsubheading @value{GDBN} Command
34962 The corresponding @value{GDBN} command is @samp{kill}.
34964 @subsubheading Example
34969 @subheading The @code{-gdb-set} Command
34972 @subsubheading Synopsis
34978 Set an internal @value{GDBN} variable.
34979 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34981 @subsubheading @value{GDBN} Command
34983 The corresponding @value{GDBN} command is @samp{set}.
34985 @subsubheading Example
34995 @subheading The @code{-gdb-show} Command
34998 @subsubheading Synopsis
35004 Show the current value of a @value{GDBN} variable.
35006 @subsubheading @value{GDBN} Command
35008 The corresponding @value{GDBN} command is @samp{show}.
35010 @subsubheading Example
35019 @c @subheading -gdb-source
35022 @subheading The @code{-gdb-version} Command
35023 @findex -gdb-version
35025 @subsubheading Synopsis
35031 Show version information for @value{GDBN}. Used mostly in testing.
35033 @subsubheading @value{GDBN} Command
35035 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35036 default shows this information when you start an interactive session.
35038 @subsubheading Example
35040 @c This example modifies the actual output from GDB to avoid overfull
35046 ~Copyright 2000 Free Software Foundation, Inc.
35047 ~GDB is free software, covered by the GNU General Public License, and
35048 ~you are welcome to change it and/or distribute copies of it under
35049 ~ certain conditions.
35050 ~Type "show copying" to see the conditions.
35051 ~There is absolutely no warranty for GDB. Type "show warranty" for
35053 ~This GDB was configured as
35054 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35059 @subheading The @code{-list-features} Command
35060 @findex -list-features
35062 Returns a list of particular features of the MI protocol that
35063 this version of gdb implements. A feature can be a command,
35064 or a new field in an output of some command, or even an
35065 important bugfix. While a frontend can sometimes detect presence
35066 of a feature at runtime, it is easier to perform detection at debugger
35069 The command returns a list of strings, with each string naming an
35070 available feature. Each returned string is just a name, it does not
35071 have any internal structure. The list of possible feature names
35077 (gdb) -list-features
35078 ^done,result=["feature1","feature2"]
35081 The current list of features is:
35084 @item frozen-varobjs
35085 Indicates support for the @code{-var-set-frozen} command, as well
35086 as possible presense of the @code{frozen} field in the output
35087 of @code{-varobj-create}.
35088 @item pending-breakpoints
35089 Indicates support for the @option{-f} option to the @code{-break-insert}
35092 Indicates Python scripting support, Python-based
35093 pretty-printing commands, and possible presence of the
35094 @samp{display_hint} field in the output of @code{-var-list-children}
35096 Indicates support for the @code{-thread-info} command.
35097 @item data-read-memory-bytes
35098 Indicates support for the @code{-data-read-memory-bytes} and the
35099 @code{-data-write-memory-bytes} commands.
35100 @item breakpoint-notifications
35101 Indicates that changes to breakpoints and breakpoints created via the
35102 CLI will be announced via async records.
35103 @item ada-task-info
35104 Indicates support for the @code{-ada-task-info} command.
35105 @item ada-exceptions
35106 Indicates support for the following commands, all of them related to Ada
35107 exceptions: @code{-info-ada-exceptions}, @code{-catch-assert} and
35108 @code{-catch-exception}.
35111 @subheading The @code{-list-target-features} Command
35112 @findex -list-target-features
35114 Returns a list of particular features that are supported by the
35115 target. Those features affect the permitted MI commands, but
35116 unlike the features reported by the @code{-list-features} command, the
35117 features depend on which target GDB is using at the moment. Whenever
35118 a target can change, due to commands such as @code{-target-select},
35119 @code{-target-attach} or @code{-exec-run}, the list of target features
35120 may change, and the frontend should obtain it again.
35124 (gdb) -list-target-features
35125 ^done,result=["async"]
35128 The current list of features is:
35132 Indicates that the target is capable of asynchronous command
35133 execution, which means that @value{GDBN} will accept further commands
35134 while the target is running.
35137 Indicates that the target is capable of reverse execution.
35138 @xref{Reverse Execution}, for more information.
35142 @subheading The @code{-list-thread-groups} Command
35143 @findex -list-thread-groups
35145 @subheading Synopsis
35148 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35151 Lists thread groups (@pxref{Thread groups}). When a single thread
35152 group is passed as the argument, lists the children of that group.
35153 When several thread group are passed, lists information about those
35154 thread groups. Without any parameters, lists information about all
35155 top-level thread groups.
35157 Normally, thread groups that are being debugged are reported.
35158 With the @samp{--available} option, @value{GDBN} reports thread groups
35159 available on the target.
35161 The output of this command may have either a @samp{threads} result or
35162 a @samp{groups} result. The @samp{thread} result has a list of tuples
35163 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35164 Information}). The @samp{groups} result has a list of tuples as value,
35165 each tuple describing a thread group. If top-level groups are
35166 requested (that is, no parameter is passed), or when several groups
35167 are passed, the output always has a @samp{groups} result. The format
35168 of the @samp{group} result is described below.
35170 To reduce the number of roundtrips it's possible to list thread groups
35171 together with their children, by passing the @samp{--recurse} option
35172 and the recursion depth. Presently, only recursion depth of 1 is
35173 permitted. If this option is present, then every reported thread group
35174 will also include its children, either as @samp{group} or
35175 @samp{threads} field.
35177 In general, any combination of option and parameters is permitted, with
35178 the following caveats:
35182 When a single thread group is passed, the output will typically
35183 be the @samp{threads} result. Because threads may not contain
35184 anything, the @samp{recurse} option will be ignored.
35187 When the @samp{--available} option is passed, limited information may
35188 be available. In particular, the list of threads of a process might
35189 be inaccessible. Further, specifying specific thread groups might
35190 not give any performance advantage over listing all thread groups.
35191 The frontend should assume that @samp{-list-thread-groups --available}
35192 is always an expensive operation and cache the results.
35196 The @samp{groups} result is a list of tuples, where each tuple may
35197 have the following fields:
35201 Identifier of the thread group. This field is always present.
35202 The identifier is an opaque string; frontends should not try to
35203 convert it to an integer, even though it might look like one.
35206 The type of the thread group. At present, only @samp{process} is a
35210 The target-specific process identifier. This field is only present
35211 for thread groups of type @samp{process} and only if the process exists.
35214 The number of children this thread group has. This field may be
35215 absent for an available thread group.
35218 This field has a list of tuples as value, each tuple describing a
35219 thread. It may be present if the @samp{--recurse} option is
35220 specified, and it's actually possible to obtain the threads.
35223 This field is a list of integers, each identifying a core that one
35224 thread of the group is running on. This field may be absent if
35225 such information is not available.
35228 The name of the executable file that corresponds to this thread group.
35229 The field is only present for thread groups of type @samp{process},
35230 and only if there is a corresponding executable file.
35234 @subheading Example
35238 -list-thread-groups
35239 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35240 -list-thread-groups 17
35241 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35242 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35243 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35244 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35245 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35246 -list-thread-groups --available
35247 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35248 -list-thread-groups --available --recurse 1
35249 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35250 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35251 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35252 -list-thread-groups --available --recurse 1 17 18
35253 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35254 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35255 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35258 @subheading The @code{-info-os} Command
35261 @subsubheading Synopsis
35264 -info-os [ @var{type} ]
35267 If no argument is supplied, the command returns a table of available
35268 operating-system-specific information types. If one of these types is
35269 supplied as an argument @var{type}, then the command returns a table
35270 of data of that type.
35272 The types of information available depend on the target operating
35275 @subsubheading @value{GDBN} Command
35277 The corresponding @value{GDBN} command is @samp{info os}.
35279 @subsubheading Example
35281 When run on a @sc{gnu}/Linux system, the output will look something
35287 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35288 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35289 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35290 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35291 body=[item=@{col0="processes",col1="Listing of all processes",
35292 col2="Processes"@},
35293 item=@{col0="procgroups",col1="Listing of all process groups",
35294 col2="Process groups"@},
35295 item=@{col0="threads",col1="Listing of all threads",
35297 item=@{col0="files",col1="Listing of all file descriptors",
35298 col2="File descriptors"@},
35299 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35301 item=@{col0="shm",col1="Listing of all shared-memory regions",
35302 col2="Shared-memory regions"@},
35303 item=@{col0="semaphores",col1="Listing of all semaphores",
35304 col2="Semaphores"@},
35305 item=@{col0="msg",col1="Listing of all message queues",
35306 col2="Message queues"@},
35307 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35308 col2="Kernel modules"@}]@}
35311 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35312 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35313 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35314 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35315 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35316 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35317 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35318 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35320 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35321 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35325 (Note that the MI output here includes a @code{"Title"} column that
35326 does not appear in command-line @code{info os}; this column is useful
35327 for MI clients that want to enumerate the types of data, such as in a
35328 popup menu, but is needless clutter on the command line, and
35329 @code{info os} omits it.)
35331 @subheading The @code{-add-inferior} Command
35332 @findex -add-inferior
35334 @subheading Synopsis
35340 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35341 inferior is not associated with any executable. Such association may
35342 be established with the @samp{-file-exec-and-symbols} command
35343 (@pxref{GDB/MI File Commands}). The command response has a single
35344 field, @samp{inferior}, whose value is the identifier of the
35345 thread group corresponding to the new inferior.
35347 @subheading Example
35352 ^done,inferior="i3"
35355 @subheading The @code{-interpreter-exec} Command
35356 @findex -interpreter-exec
35358 @subheading Synopsis
35361 -interpreter-exec @var{interpreter} @var{command}
35363 @anchor{-interpreter-exec}
35365 Execute the specified @var{command} in the given @var{interpreter}.
35367 @subheading @value{GDBN} Command
35369 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35371 @subheading Example
35375 -interpreter-exec console "break main"
35376 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35377 &"During symbol reading, bad structure-type format.\n"
35378 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35383 @subheading The @code{-inferior-tty-set} Command
35384 @findex -inferior-tty-set
35386 @subheading Synopsis
35389 -inferior-tty-set /dev/pts/1
35392 Set terminal for future runs of the program being debugged.
35394 @subheading @value{GDBN} Command
35396 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35398 @subheading Example
35402 -inferior-tty-set /dev/pts/1
35407 @subheading The @code{-inferior-tty-show} Command
35408 @findex -inferior-tty-show
35410 @subheading Synopsis
35416 Show terminal for future runs of program being debugged.
35418 @subheading @value{GDBN} Command
35420 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35422 @subheading Example
35426 -inferior-tty-set /dev/pts/1
35430 ^done,inferior_tty_terminal="/dev/pts/1"
35434 @subheading The @code{-enable-timings} Command
35435 @findex -enable-timings
35437 @subheading Synopsis
35440 -enable-timings [yes | no]
35443 Toggle the printing of the wallclock, user and system times for an MI
35444 command as a field in its output. This command is to help frontend
35445 developers optimize the performance of their code. No argument is
35446 equivalent to @samp{yes}.
35448 @subheading @value{GDBN} Command
35452 @subheading Example
35460 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35461 addr="0x080484ed",func="main",file="myprog.c",
35462 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35464 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35472 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35473 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35474 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35475 fullname="/home/nickrob/myprog.c",line="73"@}
35480 @chapter @value{GDBN} Annotations
35482 This chapter describes annotations in @value{GDBN}. Annotations were
35483 designed to interface @value{GDBN} to graphical user interfaces or other
35484 similar programs which want to interact with @value{GDBN} at a
35485 relatively high level.
35487 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35491 This is Edition @value{EDITION}, @value{DATE}.
35495 * Annotations Overview:: What annotations are; the general syntax.
35496 * Server Prefix:: Issuing a command without affecting user state.
35497 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35498 * Errors:: Annotations for error messages.
35499 * Invalidation:: Some annotations describe things now invalid.
35500 * Annotations for Running::
35501 Whether the program is running, how it stopped, etc.
35502 * Source Annotations:: Annotations describing source code.
35505 @node Annotations Overview
35506 @section What is an Annotation?
35507 @cindex annotations
35509 Annotations start with a newline character, two @samp{control-z}
35510 characters, and the name of the annotation. If there is no additional
35511 information associated with this annotation, the name of the annotation
35512 is followed immediately by a newline. If there is additional
35513 information, the name of the annotation is followed by a space, the
35514 additional information, and a newline. The additional information
35515 cannot contain newline characters.
35517 Any output not beginning with a newline and two @samp{control-z}
35518 characters denotes literal output from @value{GDBN}. Currently there is
35519 no need for @value{GDBN} to output a newline followed by two
35520 @samp{control-z} characters, but if there was such a need, the
35521 annotations could be extended with an @samp{escape} annotation which
35522 means those three characters as output.
35524 The annotation @var{level}, which is specified using the
35525 @option{--annotate} command line option (@pxref{Mode Options}), controls
35526 how much information @value{GDBN} prints together with its prompt,
35527 values of expressions, source lines, and other types of output. Level 0
35528 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35529 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35530 for programs that control @value{GDBN}, and level 2 annotations have
35531 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35532 Interface, annotate, GDB's Obsolete Annotations}).
35535 @kindex set annotate
35536 @item set annotate @var{level}
35537 The @value{GDBN} command @code{set annotate} sets the level of
35538 annotations to the specified @var{level}.
35540 @item show annotate
35541 @kindex show annotate
35542 Show the current annotation level.
35545 This chapter describes level 3 annotations.
35547 A simple example of starting up @value{GDBN} with annotations is:
35550 $ @kbd{gdb --annotate=3}
35552 Copyright 2003 Free Software Foundation, Inc.
35553 GDB is free software, covered by the GNU General Public License,
35554 and you are welcome to change it and/or distribute copies of it
35555 under certain conditions.
35556 Type "show copying" to see the conditions.
35557 There is absolutely no warranty for GDB. Type "show warranty"
35559 This GDB was configured as "i386-pc-linux-gnu"
35570 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35571 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35572 denotes a @samp{control-z} character) are annotations; the rest is
35573 output from @value{GDBN}.
35575 @node Server Prefix
35576 @section The Server Prefix
35577 @cindex server prefix
35579 If you prefix a command with @samp{server } then it will not affect
35580 the command history, nor will it affect @value{GDBN}'s notion of which
35581 command to repeat if @key{RET} is pressed on a line by itself. This
35582 means that commands can be run behind a user's back by a front-end in
35583 a transparent manner.
35585 The @code{server } prefix does not affect the recording of values into
35586 the value history; to print a value without recording it into the
35587 value history, use the @code{output} command instead of the
35588 @code{print} command.
35590 Using this prefix also disables confirmation requests
35591 (@pxref{confirmation requests}).
35594 @section Annotation for @value{GDBN} Input
35596 @cindex annotations for prompts
35597 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35598 to know when to send output, when the output from a given command is
35601 Different kinds of input each have a different @dfn{input type}. Each
35602 input type has three annotations: a @code{pre-} annotation, which
35603 denotes the beginning of any prompt which is being output, a plain
35604 annotation, which denotes the end of the prompt, and then a @code{post-}
35605 annotation which denotes the end of any echo which may (or may not) be
35606 associated with the input. For example, the @code{prompt} input type
35607 features the following annotations:
35615 The input types are
35618 @findex pre-prompt annotation
35619 @findex prompt annotation
35620 @findex post-prompt annotation
35622 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35624 @findex pre-commands annotation
35625 @findex commands annotation
35626 @findex post-commands annotation
35628 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35629 command. The annotations are repeated for each command which is input.
35631 @findex pre-overload-choice annotation
35632 @findex overload-choice annotation
35633 @findex post-overload-choice annotation
35634 @item overload-choice
35635 When @value{GDBN} wants the user to select between various overloaded functions.
35637 @findex pre-query annotation
35638 @findex query annotation
35639 @findex post-query annotation
35641 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35643 @findex pre-prompt-for-continue annotation
35644 @findex prompt-for-continue annotation
35645 @findex post-prompt-for-continue annotation
35646 @item prompt-for-continue
35647 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35648 expect this to work well; instead use @code{set height 0} to disable
35649 prompting. This is because the counting of lines is buggy in the
35650 presence of annotations.
35655 @cindex annotations for errors, warnings and interrupts
35657 @findex quit annotation
35662 This annotation occurs right before @value{GDBN} responds to an interrupt.
35664 @findex error annotation
35669 This annotation occurs right before @value{GDBN} responds to an error.
35671 Quit and error annotations indicate that any annotations which @value{GDBN} was
35672 in the middle of may end abruptly. For example, if a
35673 @code{value-history-begin} annotation is followed by a @code{error}, one
35674 cannot expect to receive the matching @code{value-history-end}. One
35675 cannot expect not to receive it either, however; an error annotation
35676 does not necessarily mean that @value{GDBN} is immediately returning all the way
35679 @findex error-begin annotation
35680 A quit or error annotation may be preceded by
35686 Any output between that and the quit or error annotation is the error
35689 Warning messages are not yet annotated.
35690 @c If we want to change that, need to fix warning(), type_error(),
35691 @c range_error(), and possibly other places.
35694 @section Invalidation Notices
35696 @cindex annotations for invalidation messages
35697 The following annotations say that certain pieces of state may have
35701 @findex frames-invalid annotation
35702 @item ^Z^Zframes-invalid
35704 The frames (for example, output from the @code{backtrace} command) may
35707 @findex breakpoints-invalid annotation
35708 @item ^Z^Zbreakpoints-invalid
35710 The breakpoints may have changed. For example, the user just added or
35711 deleted a breakpoint.
35714 @node Annotations for Running
35715 @section Running the Program
35716 @cindex annotations for running programs
35718 @findex starting annotation
35719 @findex stopping annotation
35720 When the program starts executing due to a @value{GDBN} command such as
35721 @code{step} or @code{continue},
35727 is output. When the program stops,
35733 is output. Before the @code{stopped} annotation, a variety of
35734 annotations describe how the program stopped.
35737 @findex exited annotation
35738 @item ^Z^Zexited @var{exit-status}
35739 The program exited, and @var{exit-status} is the exit status (zero for
35740 successful exit, otherwise nonzero).
35742 @findex signalled annotation
35743 @findex signal-name annotation
35744 @findex signal-name-end annotation
35745 @findex signal-string annotation
35746 @findex signal-string-end annotation
35747 @item ^Z^Zsignalled
35748 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35749 annotation continues:
35755 ^Z^Zsignal-name-end
35759 ^Z^Zsignal-string-end
35764 where @var{name} is the name of the signal, such as @code{SIGILL} or
35765 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35766 as @code{Illegal Instruction} or @code{Segmentation fault}.
35767 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35768 user's benefit and have no particular format.
35770 @findex signal annotation
35772 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35773 just saying that the program received the signal, not that it was
35774 terminated with it.
35776 @findex breakpoint annotation
35777 @item ^Z^Zbreakpoint @var{number}
35778 The program hit breakpoint number @var{number}.
35780 @findex watchpoint annotation
35781 @item ^Z^Zwatchpoint @var{number}
35782 The program hit watchpoint number @var{number}.
35785 @node Source Annotations
35786 @section Displaying Source
35787 @cindex annotations for source display
35789 @findex source annotation
35790 The following annotation is used instead of displaying source code:
35793 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35796 where @var{filename} is an absolute file name indicating which source
35797 file, @var{line} is the line number within that file (where 1 is the
35798 first line in the file), @var{character} is the character position
35799 within the file (where 0 is the first character in the file) (for most
35800 debug formats this will necessarily point to the beginning of a line),
35801 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35802 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35803 @var{addr} is the address in the target program associated with the
35804 source which is being displayed. @var{addr} is in the form @samp{0x}
35805 followed by one or more lowercase hex digits (note that this does not
35806 depend on the language).
35808 @node JIT Interface
35809 @chapter JIT Compilation Interface
35810 @cindex just-in-time compilation
35811 @cindex JIT compilation interface
35813 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35814 interface. A JIT compiler is a program or library that generates native
35815 executable code at runtime and executes it, usually in order to achieve good
35816 performance while maintaining platform independence.
35818 Programs that use JIT compilation are normally difficult to debug because
35819 portions of their code are generated at runtime, instead of being loaded from
35820 object files, which is where @value{GDBN} normally finds the program's symbols
35821 and debug information. In order to debug programs that use JIT compilation,
35822 @value{GDBN} has an interface that allows the program to register in-memory
35823 symbol files with @value{GDBN} at runtime.
35825 If you are using @value{GDBN} to debug a program that uses this interface, then
35826 it should work transparently so long as you have not stripped the binary. If
35827 you are developing a JIT compiler, then the interface is documented in the rest
35828 of this chapter. At this time, the only known client of this interface is the
35831 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35832 JIT compiler communicates with @value{GDBN} by writing data into a global
35833 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35834 attaches, it reads a linked list of symbol files from the global variable to
35835 find existing code, and puts a breakpoint in the function so that it can find
35836 out about additional code.
35839 * Declarations:: Relevant C struct declarations
35840 * Registering Code:: Steps to register code
35841 * Unregistering Code:: Steps to unregister code
35842 * Custom Debug Info:: Emit debug information in a custom format
35846 @section JIT Declarations
35848 These are the relevant struct declarations that a C program should include to
35849 implement the interface:
35859 struct jit_code_entry
35861 struct jit_code_entry *next_entry;
35862 struct jit_code_entry *prev_entry;
35863 const char *symfile_addr;
35864 uint64_t symfile_size;
35867 struct jit_descriptor
35870 /* This type should be jit_actions_t, but we use uint32_t
35871 to be explicit about the bitwidth. */
35872 uint32_t action_flag;
35873 struct jit_code_entry *relevant_entry;
35874 struct jit_code_entry *first_entry;
35877 /* GDB puts a breakpoint in this function. */
35878 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35880 /* Make sure to specify the version statically, because the
35881 debugger may check the version before we can set it. */
35882 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35885 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35886 modifications to this global data properly, which can easily be done by putting
35887 a global mutex around modifications to these structures.
35889 @node Registering Code
35890 @section Registering Code
35892 To register code with @value{GDBN}, the JIT should follow this protocol:
35896 Generate an object file in memory with symbols and other desired debug
35897 information. The file must include the virtual addresses of the sections.
35900 Create a code entry for the file, which gives the start and size of the symbol
35904 Add it to the linked list in the JIT descriptor.
35907 Point the relevant_entry field of the descriptor at the entry.
35910 Set @code{action_flag} to @code{JIT_REGISTER} and call
35911 @code{__jit_debug_register_code}.
35914 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35915 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35916 new code. However, the linked list must still be maintained in order to allow
35917 @value{GDBN} to attach to a running process and still find the symbol files.
35919 @node Unregistering Code
35920 @section Unregistering Code
35922 If code is freed, then the JIT should use the following protocol:
35926 Remove the code entry corresponding to the code from the linked list.
35929 Point the @code{relevant_entry} field of the descriptor at the code entry.
35932 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35933 @code{__jit_debug_register_code}.
35936 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35937 and the JIT will leak the memory used for the associated symbol files.
35939 @node Custom Debug Info
35940 @section Custom Debug Info
35941 @cindex custom JIT debug info
35942 @cindex JIT debug info reader
35944 Generating debug information in platform-native file formats (like ELF
35945 or COFF) may be an overkill for JIT compilers; especially if all the
35946 debug info is used for is displaying a meaningful backtrace. The
35947 issue can be resolved by having the JIT writers decide on a debug info
35948 format and also provide a reader that parses the debug info generated
35949 by the JIT compiler. This section gives a brief overview on writing
35950 such a parser. More specific details can be found in the source file
35951 @file{gdb/jit-reader.in}, which is also installed as a header at
35952 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35954 The reader is implemented as a shared object (so this functionality is
35955 not available on platforms which don't allow loading shared objects at
35956 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35957 @code{jit-reader-unload} are provided, to be used to load and unload
35958 the readers from a preconfigured directory. Once loaded, the shared
35959 object is used the parse the debug information emitted by the JIT
35963 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35964 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35967 @node Using JIT Debug Info Readers
35968 @subsection Using JIT Debug Info Readers
35969 @kindex jit-reader-load
35970 @kindex jit-reader-unload
35972 Readers can be loaded and unloaded using the @code{jit-reader-load}
35973 and @code{jit-reader-unload} commands.
35976 @item jit-reader-load @var{reader}
35977 Load the JIT reader named @var{reader}. @var{reader} is a shared
35978 object specified as either an absolute or a relative file name. In
35979 the latter case, @value{GDBN} will try to load the reader from a
35980 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35981 system (here @var{libdir} is the system library directory, often
35982 @file{/usr/local/lib}).
35984 Only one reader can be active at a time; trying to load a second
35985 reader when one is already loaded will result in @value{GDBN}
35986 reporting an error. A new JIT reader can be loaded by first unloading
35987 the current one using @code{jit-reader-unload} and then invoking
35988 @code{jit-reader-load}.
35990 @item jit-reader-unload
35991 Unload the currently loaded JIT reader.
35995 @node Writing JIT Debug Info Readers
35996 @subsection Writing JIT Debug Info Readers
35997 @cindex writing JIT debug info readers
35999 As mentioned, a reader is essentially a shared object conforming to a
36000 certain ABI. This ABI is described in @file{jit-reader.h}.
36002 @file{jit-reader.h} defines the structures, macros and functions
36003 required to write a reader. It is installed (along with
36004 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36005 the system include directory.
36007 Readers need to be released under a GPL compatible license. A reader
36008 can be declared as released under such a license by placing the macro
36009 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36011 The entry point for readers is the symbol @code{gdb_init_reader},
36012 which is expected to be a function with the prototype
36014 @findex gdb_init_reader
36016 extern struct gdb_reader_funcs *gdb_init_reader (void);
36019 @cindex @code{struct gdb_reader_funcs}
36021 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36022 functions. These functions are executed to read the debug info
36023 generated by the JIT compiler (@code{read}), to unwind stack frames
36024 (@code{unwind}) and to create canonical frame IDs
36025 (@code{get_Frame_id}). It also has a callback that is called when the
36026 reader is being unloaded (@code{destroy}). The struct looks like this
36029 struct gdb_reader_funcs
36031 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36032 int reader_version;
36034 /* For use by the reader. */
36037 gdb_read_debug_info *read;
36038 gdb_unwind_frame *unwind;
36039 gdb_get_frame_id *get_frame_id;
36040 gdb_destroy_reader *destroy;
36044 @cindex @code{struct gdb_symbol_callbacks}
36045 @cindex @code{struct gdb_unwind_callbacks}
36047 The callbacks are provided with another set of callbacks by
36048 @value{GDBN} to do their job. For @code{read}, these callbacks are
36049 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36050 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36051 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36052 files and new symbol tables inside those object files. @code{struct
36053 gdb_unwind_callbacks} has callbacks to read registers off the current
36054 frame and to write out the values of the registers in the previous
36055 frame. Both have a callback (@code{target_read}) to read bytes off the
36056 target's address space.
36058 @node In-Process Agent
36059 @chapter In-Process Agent
36060 @cindex debugging agent
36061 The traditional debugging model is conceptually low-speed, but works fine,
36062 because most bugs can be reproduced in debugging-mode execution. However,
36063 as multi-core or many-core processors are becoming mainstream, and
36064 multi-threaded programs become more and more popular, there should be more
36065 and more bugs that only manifest themselves at normal-mode execution, for
36066 example, thread races, because debugger's interference with the program's
36067 timing may conceal the bugs. On the other hand, in some applications,
36068 it is not feasible for the debugger to interrupt the program's execution
36069 long enough for the developer to learn anything helpful about its behavior.
36070 If the program's correctness depends on its real-time behavior, delays
36071 introduced by a debugger might cause the program to fail, even when the
36072 code itself is correct. It is useful to be able to observe the program's
36073 behavior without interrupting it.
36075 Therefore, traditional debugging model is too intrusive to reproduce
36076 some bugs. In order to reduce the interference with the program, we can
36077 reduce the number of operations performed by debugger. The
36078 @dfn{In-Process Agent}, a shared library, is running within the same
36079 process with inferior, and is able to perform some debugging operations
36080 itself. As a result, debugger is only involved when necessary, and
36081 performance of debugging can be improved accordingly. Note that
36082 interference with program can be reduced but can't be removed completely,
36083 because the in-process agent will still stop or slow down the program.
36085 The in-process agent can interpret and execute Agent Expressions
36086 (@pxref{Agent Expressions}) during performing debugging operations. The
36087 agent expressions can be used for different purposes, such as collecting
36088 data in tracepoints, and condition evaluation in breakpoints.
36090 @anchor{Control Agent}
36091 You can control whether the in-process agent is used as an aid for
36092 debugging with the following commands:
36095 @kindex set agent on
36097 Causes the in-process agent to perform some operations on behalf of the
36098 debugger. Just which operations requested by the user will be done
36099 by the in-process agent depends on the its capabilities. For example,
36100 if you request to evaluate breakpoint conditions in the in-process agent,
36101 and the in-process agent has such capability as well, then breakpoint
36102 conditions will be evaluated in the in-process agent.
36104 @kindex set agent off
36105 @item set agent off
36106 Disables execution of debugging operations by the in-process agent. All
36107 of the operations will be performed by @value{GDBN}.
36111 Display the current setting of execution of debugging operations by
36112 the in-process agent.
36116 * In-Process Agent Protocol::
36119 @node In-Process Agent Protocol
36120 @section In-Process Agent Protocol
36121 @cindex in-process agent protocol
36123 The in-process agent is able to communicate with both @value{GDBN} and
36124 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36125 used for communications between @value{GDBN} or GDBserver and the IPA.
36126 In general, @value{GDBN} or GDBserver sends commands
36127 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36128 in-process agent replies back with the return result of the command, or
36129 some other information. The data sent to in-process agent is composed
36130 of primitive data types, such as 4-byte or 8-byte type, and composite
36131 types, which are called objects (@pxref{IPA Protocol Objects}).
36134 * IPA Protocol Objects::
36135 * IPA Protocol Commands::
36138 @node IPA Protocol Objects
36139 @subsection IPA Protocol Objects
36140 @cindex ipa protocol objects
36142 The commands sent to and results received from agent may contain some
36143 complex data types called @dfn{objects}.
36145 The in-process agent is running on the same machine with @value{GDBN}
36146 or GDBserver, so it doesn't have to handle as much differences between
36147 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36148 However, there are still some differences of two ends in two processes:
36152 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36153 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36155 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36156 GDBserver is compiled with one, and in-process agent is compiled with
36160 Here are the IPA Protocol Objects:
36164 agent expression object. It represents an agent expression
36165 (@pxref{Agent Expressions}).
36166 @anchor{agent expression object}
36168 tracepoint action object. It represents a tracepoint action
36169 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36170 memory, static trace data and to evaluate expression.
36171 @anchor{tracepoint action object}
36173 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36174 @anchor{tracepoint object}
36178 The following table describes important attributes of each IPA protocol
36181 @multitable @columnfractions .30 .20 .50
36182 @headitem Name @tab Size @tab Description
36183 @item @emph{agent expression object} @tab @tab
36184 @item length @tab 4 @tab length of bytes code
36185 @item byte code @tab @var{length} @tab contents of byte code
36186 @item @emph{tracepoint action for collecting memory} @tab @tab
36187 @item 'M' @tab 1 @tab type of tracepoint action
36188 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36189 address of the lowest byte to collect, otherwise @var{addr} is the offset
36190 of @var{basereg} for memory collecting.
36191 @item len @tab 8 @tab length of memory for collecting
36192 @item basereg @tab 4 @tab the register number containing the starting
36193 memory address for collecting.
36194 @item @emph{tracepoint action for collecting registers} @tab @tab
36195 @item 'R' @tab 1 @tab type of tracepoint action
36196 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36197 @item 'L' @tab 1 @tab type of tracepoint action
36198 @item @emph{tracepoint action for expression evaluation} @tab @tab
36199 @item 'X' @tab 1 @tab type of tracepoint action
36200 @item agent expression @tab length of @tab @ref{agent expression object}
36201 @item @emph{tracepoint object} @tab @tab
36202 @item number @tab 4 @tab number of tracepoint
36203 @item address @tab 8 @tab address of tracepoint inserted on
36204 @item type @tab 4 @tab type of tracepoint
36205 @item enabled @tab 1 @tab enable or disable of tracepoint
36206 @item step_count @tab 8 @tab step
36207 @item pass_count @tab 8 @tab pass
36208 @item numactions @tab 4 @tab number of tracepoint actions
36209 @item hit count @tab 8 @tab hit count
36210 @item trace frame usage @tab 8 @tab trace frame usage
36211 @item compiled_cond @tab 8 @tab compiled condition
36212 @item orig_size @tab 8 @tab orig size
36213 @item condition @tab 4 if condition is NULL otherwise length of
36214 @ref{agent expression object}
36215 @tab zero if condition is NULL, otherwise is
36216 @ref{agent expression object}
36217 @item actions @tab variable
36218 @tab numactions number of @ref{tracepoint action object}
36221 @node IPA Protocol Commands
36222 @subsection IPA Protocol Commands
36223 @cindex ipa protocol commands
36225 The spaces in each command are delimiters to ease reading this commands
36226 specification. They don't exist in real commands.
36230 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36231 Installs a new fast tracepoint described by @var{tracepoint_object}
36232 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36233 head of @dfn{jumppad}, which is used to jump to data collection routine
36238 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36239 @var{target_address} is address of tracepoint in the inferior.
36240 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36241 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36242 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36243 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36250 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36251 is about to kill inferiors.
36259 @item probe_marker_at:@var{address}
36260 Asks in-process agent to probe the marker at @var{address}.
36267 @item unprobe_marker_at:@var{address}
36268 Asks in-process agent to unprobe the marker at @var{address}.
36272 @chapter Reporting Bugs in @value{GDBN}
36273 @cindex bugs in @value{GDBN}
36274 @cindex reporting bugs in @value{GDBN}
36276 Your bug reports play an essential role in making @value{GDBN} reliable.
36278 Reporting a bug may help you by bringing a solution to your problem, or it
36279 may not. But in any case the principal function of a bug report is to help
36280 the entire community by making the next version of @value{GDBN} work better. Bug
36281 reports are your contribution to the maintenance of @value{GDBN}.
36283 In order for a bug report to serve its purpose, you must include the
36284 information that enables us to fix the bug.
36287 * Bug Criteria:: Have you found a bug?
36288 * Bug Reporting:: How to report bugs
36292 @section Have You Found a Bug?
36293 @cindex bug criteria
36295 If you are not sure whether you have found a bug, here are some guidelines:
36298 @cindex fatal signal
36299 @cindex debugger crash
36300 @cindex crash of debugger
36302 If the debugger gets a fatal signal, for any input whatever, that is a
36303 @value{GDBN} bug. Reliable debuggers never crash.
36305 @cindex error on valid input
36307 If @value{GDBN} produces an error message for valid input, that is a
36308 bug. (Note that if you're cross debugging, the problem may also be
36309 somewhere in the connection to the target.)
36311 @cindex invalid input
36313 If @value{GDBN} does not produce an error message for invalid input,
36314 that is a bug. However, you should note that your idea of
36315 ``invalid input'' might be our idea of ``an extension'' or ``support
36316 for traditional practice''.
36319 If you are an experienced user of debugging tools, your suggestions
36320 for improvement of @value{GDBN} are welcome in any case.
36323 @node Bug Reporting
36324 @section How to Report Bugs
36325 @cindex bug reports
36326 @cindex @value{GDBN} bugs, reporting
36328 A number of companies and individuals offer support for @sc{gnu} products.
36329 If you obtained @value{GDBN} from a support organization, we recommend you
36330 contact that organization first.
36332 You can find contact information for many support companies and
36333 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36335 @c should add a web page ref...
36338 @ifset BUGURL_DEFAULT
36339 In any event, we also recommend that you submit bug reports for
36340 @value{GDBN}. The preferred method is to submit them directly using
36341 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36342 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36345 @strong{Do not send bug reports to @samp{info-gdb}, or to
36346 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36347 not want to receive bug reports. Those that do have arranged to receive
36350 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36351 serves as a repeater. The mailing list and the newsgroup carry exactly
36352 the same messages. Often people think of posting bug reports to the
36353 newsgroup instead of mailing them. This appears to work, but it has one
36354 problem which can be crucial: a newsgroup posting often lacks a mail
36355 path back to the sender. Thus, if we need to ask for more information,
36356 we may be unable to reach you. For this reason, it is better to send
36357 bug reports to the mailing list.
36359 @ifclear BUGURL_DEFAULT
36360 In any event, we also recommend that you submit bug reports for
36361 @value{GDBN} to @value{BUGURL}.
36365 The fundamental principle of reporting bugs usefully is this:
36366 @strong{report all the facts}. If you are not sure whether to state a
36367 fact or leave it out, state it!
36369 Often people omit facts because they think they know what causes the
36370 problem and assume that some details do not matter. Thus, you might
36371 assume that the name of the variable you use in an example does not matter.
36372 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36373 stray memory reference which happens to fetch from the location where that
36374 name is stored in memory; perhaps, if the name were different, the contents
36375 of that location would fool the debugger into doing the right thing despite
36376 the bug. Play it safe and give a specific, complete example. That is the
36377 easiest thing for you to do, and the most helpful.
36379 Keep in mind that the purpose of a bug report is to enable us to fix the
36380 bug. It may be that the bug has been reported previously, but neither
36381 you nor we can know that unless your bug report is complete and
36384 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36385 bell?'' Those bug reports are useless, and we urge everyone to
36386 @emph{refuse to respond to them} except to chide the sender to report
36389 To enable us to fix the bug, you should include all these things:
36393 The version of @value{GDBN}. @value{GDBN} announces it if you start
36394 with no arguments; you can also print it at any time using @code{show
36397 Without this, we will not know whether there is any point in looking for
36398 the bug in the current version of @value{GDBN}.
36401 The type of machine you are using, and the operating system name and
36405 The details of the @value{GDBN} build-time configuration.
36406 @value{GDBN} shows these details if you invoke it with the
36407 @option{--configuration} command-line option, or if you type
36408 @code{show configuration} at @value{GDBN}'s prompt.
36411 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36412 ``@value{GCC}--2.8.1''.
36415 What compiler (and its version) was used to compile the program you are
36416 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36417 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36418 to get this information; for other compilers, see the documentation for
36422 The command arguments you gave the compiler to compile your example and
36423 observe the bug. For example, did you use @samp{-O}? To guarantee
36424 you will not omit something important, list them all. A copy of the
36425 Makefile (or the output from make) is sufficient.
36427 If we were to try to guess the arguments, we would probably guess wrong
36428 and then we might not encounter the bug.
36431 A complete input script, and all necessary source files, that will
36435 A description of what behavior you observe that you believe is
36436 incorrect. For example, ``It gets a fatal signal.''
36438 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36439 will certainly notice it. But if the bug is incorrect output, we might
36440 not notice unless it is glaringly wrong. You might as well not give us
36441 a chance to make a mistake.
36443 Even if the problem you experience is a fatal signal, you should still
36444 say so explicitly. Suppose something strange is going on, such as, your
36445 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36446 the C library on your system. (This has happened!) Your copy might
36447 crash and ours would not. If you told us to expect a crash, then when
36448 ours fails to crash, we would know that the bug was not happening for
36449 us. If you had not told us to expect a crash, then we would not be able
36450 to draw any conclusion from our observations.
36453 @cindex recording a session script
36454 To collect all this information, you can use a session recording program
36455 such as @command{script}, which is available on many Unix systems.
36456 Just run your @value{GDBN} session inside @command{script} and then
36457 include the @file{typescript} file with your bug report.
36459 Another way to record a @value{GDBN} session is to run @value{GDBN}
36460 inside Emacs and then save the entire buffer to a file.
36463 If you wish to suggest changes to the @value{GDBN} source, send us context
36464 diffs. If you even discuss something in the @value{GDBN} source, refer to
36465 it by context, not by line number.
36467 The line numbers in our development sources will not match those in your
36468 sources. Your line numbers would convey no useful information to us.
36472 Here are some things that are not necessary:
36476 A description of the envelope of the bug.
36478 Often people who encounter a bug spend a lot of time investigating
36479 which changes to the input file will make the bug go away and which
36480 changes will not affect it.
36482 This is often time consuming and not very useful, because the way we
36483 will find the bug is by running a single example under the debugger
36484 with breakpoints, not by pure deduction from a series of examples.
36485 We recommend that you save your time for something else.
36487 Of course, if you can find a simpler example to report @emph{instead}
36488 of the original one, that is a convenience for us. Errors in the
36489 output will be easier to spot, running under the debugger will take
36490 less time, and so on.
36492 However, simplification is not vital; if you do not want to do this,
36493 report the bug anyway and send us the entire test case you used.
36496 A patch for the bug.
36498 A patch for the bug does help us if it is a good one. But do not omit
36499 the necessary information, such as the test case, on the assumption that
36500 a patch is all we need. We might see problems with your patch and decide
36501 to fix the problem another way, or we might not understand it at all.
36503 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36504 construct an example that will make the program follow a certain path
36505 through the code. If you do not send us the example, we will not be able
36506 to construct one, so we will not be able to verify that the bug is fixed.
36508 And if we cannot understand what bug you are trying to fix, or why your
36509 patch should be an improvement, we will not install it. A test case will
36510 help us to understand.
36513 A guess about what the bug is or what it depends on.
36515 Such guesses are usually wrong. Even we cannot guess right about such
36516 things without first using the debugger to find the facts.
36519 @c The readline documentation is distributed with the readline code
36520 @c and consists of the two following files:
36523 @c Use -I with makeinfo to point to the appropriate directory,
36524 @c environment var TEXINPUTS with TeX.
36525 @ifclear SYSTEM_READLINE
36526 @include rluser.texi
36527 @include hsuser.texi
36531 @appendix In Memoriam
36533 The @value{GDBN} project mourns the loss of the following long-time
36538 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36539 to Free Software in general. Outside of @value{GDBN}, he was known in
36540 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36542 @item Michael Snyder
36543 Michael was one of the Global Maintainers of the @value{GDBN} project,
36544 with contributions recorded as early as 1996, until 2011. In addition
36545 to his day to day participation, he was a large driving force behind
36546 adding Reverse Debugging to @value{GDBN}.
36549 Beyond their technical contributions to the project, they were also
36550 enjoyable members of the Free Software Community. We will miss them.
36552 @node Formatting Documentation
36553 @appendix Formatting Documentation
36555 @cindex @value{GDBN} reference card
36556 @cindex reference card
36557 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36558 for printing with PostScript or Ghostscript, in the @file{gdb}
36559 subdirectory of the main source directory@footnote{In
36560 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36561 release.}. If you can use PostScript or Ghostscript with your printer,
36562 you can print the reference card immediately with @file{refcard.ps}.
36564 The release also includes the source for the reference card. You
36565 can format it, using @TeX{}, by typing:
36571 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36572 mode on US ``letter'' size paper;
36573 that is, on a sheet 11 inches wide by 8.5 inches
36574 high. You will need to specify this form of printing as an option to
36575 your @sc{dvi} output program.
36577 @cindex documentation
36579 All the documentation for @value{GDBN} comes as part of the machine-readable
36580 distribution. The documentation is written in Texinfo format, which is
36581 a documentation system that uses a single source file to produce both
36582 on-line information and a printed manual. You can use one of the Info
36583 formatting commands to create the on-line version of the documentation
36584 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36586 @value{GDBN} includes an already formatted copy of the on-line Info
36587 version of this manual in the @file{gdb} subdirectory. The main Info
36588 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36589 subordinate files matching @samp{gdb.info*} in the same directory. If
36590 necessary, you can print out these files, or read them with any editor;
36591 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36592 Emacs or the standalone @code{info} program, available as part of the
36593 @sc{gnu} Texinfo distribution.
36595 If you want to format these Info files yourself, you need one of the
36596 Info formatting programs, such as @code{texinfo-format-buffer} or
36599 If you have @code{makeinfo} installed, and are in the top level
36600 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36601 version @value{GDBVN}), you can make the Info file by typing:
36608 If you want to typeset and print copies of this manual, you need @TeX{},
36609 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36610 Texinfo definitions file.
36612 @TeX{} is a typesetting program; it does not print files directly, but
36613 produces output files called @sc{dvi} files. To print a typeset
36614 document, you need a program to print @sc{dvi} files. If your system
36615 has @TeX{} installed, chances are it has such a program. The precise
36616 command to use depends on your system; @kbd{lpr -d} is common; another
36617 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36618 require a file name without any extension or a @samp{.dvi} extension.
36620 @TeX{} also requires a macro definitions file called
36621 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36622 written in Texinfo format. On its own, @TeX{} cannot either read or
36623 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36624 and is located in the @file{gdb-@var{version-number}/texinfo}
36627 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36628 typeset and print this manual. First switch to the @file{gdb}
36629 subdirectory of the main source directory (for example, to
36630 @file{gdb-@value{GDBVN}/gdb}) and type:
36636 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36638 @node Installing GDB
36639 @appendix Installing @value{GDBN}
36640 @cindex installation
36643 * Requirements:: Requirements for building @value{GDBN}
36644 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36645 * Separate Objdir:: Compiling @value{GDBN} in another directory
36646 * Config Names:: Specifying names for hosts and targets
36647 * Configure Options:: Summary of options for configure
36648 * System-wide configuration:: Having a system-wide init file
36652 @section Requirements for Building @value{GDBN}
36653 @cindex building @value{GDBN}, requirements for
36655 Building @value{GDBN} requires various tools and packages to be available.
36656 Other packages will be used only if they are found.
36658 @heading Tools/Packages Necessary for Building @value{GDBN}
36660 @item ISO C90 compiler
36661 @value{GDBN} is written in ISO C90. It should be buildable with any
36662 working C90 compiler, e.g.@: GCC.
36666 @heading Tools/Packages Optional for Building @value{GDBN}
36670 @value{GDBN} can use the Expat XML parsing library. This library may be
36671 included with your operating system distribution; if it is not, you
36672 can get the latest version from @url{http://expat.sourceforge.net}.
36673 The @file{configure} script will search for this library in several
36674 standard locations; if it is installed in an unusual path, you can
36675 use the @option{--with-libexpat-prefix} option to specify its location.
36681 Remote protocol memory maps (@pxref{Memory Map Format})
36683 Target descriptions (@pxref{Target Descriptions})
36685 Remote shared library lists (@xref{Library List Format},
36686 or alternatively @pxref{Library List Format for SVR4 Targets})
36688 MS-Windows shared libraries (@pxref{Shared Libraries})
36690 Traceframe info (@pxref{Traceframe Info Format})
36692 Branch trace (@pxref{Branch Trace Format})
36696 @cindex compressed debug sections
36697 @value{GDBN} will use the @samp{zlib} library, if available, to read
36698 compressed debug sections. Some linkers, such as GNU gold, are capable
36699 of producing binaries with compressed debug sections. If @value{GDBN}
36700 is compiled with @samp{zlib}, it will be able to read the debug
36701 information in such binaries.
36703 The @samp{zlib} library is likely included with your operating system
36704 distribution; if it is not, you can get the latest version from
36705 @url{http://zlib.net}.
36708 @value{GDBN}'s features related to character sets (@pxref{Character
36709 Sets}) require a functioning @code{iconv} implementation. If you are
36710 on a GNU system, then this is provided by the GNU C Library. Some
36711 other systems also provide a working @code{iconv}.
36713 If @value{GDBN} is using the @code{iconv} program which is installed
36714 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36715 This is done with @option{--with-iconv-bin} which specifies the
36716 directory that contains the @code{iconv} program.
36718 On systems without @code{iconv}, you can install GNU Libiconv. If you
36719 have previously installed Libiconv, you can use the
36720 @option{--with-libiconv-prefix} option to configure.
36722 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36723 arrange to build Libiconv if a directory named @file{libiconv} appears
36724 in the top-most source directory. If Libiconv is built this way, and
36725 if the operating system does not provide a suitable @code{iconv}
36726 implementation, then the just-built library will automatically be used
36727 by @value{GDBN}. One easy way to set this up is to download GNU
36728 Libiconv, unpack it, and then rename the directory holding the
36729 Libiconv source code to @samp{libiconv}.
36732 @node Running Configure
36733 @section Invoking the @value{GDBN} @file{configure} Script
36734 @cindex configuring @value{GDBN}
36735 @value{GDBN} comes with a @file{configure} script that automates the process
36736 of preparing @value{GDBN} for installation; you can then use @code{make} to
36737 build the @code{gdb} program.
36739 @c irrelevant in info file; it's as current as the code it lives with.
36740 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36741 look at the @file{README} file in the sources; we may have improved the
36742 installation procedures since publishing this manual.}
36745 The @value{GDBN} distribution includes all the source code you need for
36746 @value{GDBN} in a single directory, whose name is usually composed by
36747 appending the version number to @samp{gdb}.
36749 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36750 @file{gdb-@value{GDBVN}} directory. That directory contains:
36753 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36754 script for configuring @value{GDBN} and all its supporting libraries
36756 @item gdb-@value{GDBVN}/gdb
36757 the source specific to @value{GDBN} itself
36759 @item gdb-@value{GDBVN}/bfd
36760 source for the Binary File Descriptor library
36762 @item gdb-@value{GDBVN}/include
36763 @sc{gnu} include files
36765 @item gdb-@value{GDBVN}/libiberty
36766 source for the @samp{-liberty} free software library
36768 @item gdb-@value{GDBVN}/opcodes
36769 source for the library of opcode tables and disassemblers
36771 @item gdb-@value{GDBVN}/readline
36772 source for the @sc{gnu} command-line interface
36774 @item gdb-@value{GDBVN}/glob
36775 source for the @sc{gnu} filename pattern-matching subroutine
36777 @item gdb-@value{GDBVN}/mmalloc
36778 source for the @sc{gnu} memory-mapped malloc package
36781 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36782 from the @file{gdb-@var{version-number}} source directory, which in
36783 this example is the @file{gdb-@value{GDBVN}} directory.
36785 First switch to the @file{gdb-@var{version-number}} source directory
36786 if you are not already in it; then run @file{configure}. Pass the
36787 identifier for the platform on which @value{GDBN} will run as an
36793 cd gdb-@value{GDBVN}
36794 ./configure @var{host}
36799 where @var{host} is an identifier such as @samp{sun4} or
36800 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36801 (You can often leave off @var{host}; @file{configure} tries to guess the
36802 correct value by examining your system.)
36804 Running @samp{configure @var{host}} and then running @code{make} builds the
36805 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36806 libraries, then @code{gdb} itself. The configured source files, and the
36807 binaries, are left in the corresponding source directories.
36810 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36811 system does not recognize this automatically when you run a different
36812 shell, you may need to run @code{sh} on it explicitly:
36815 sh configure @var{host}
36818 If you run @file{configure} from a directory that contains source
36819 directories for multiple libraries or programs, such as the
36820 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36822 creates configuration files for every directory level underneath (unless
36823 you tell it not to, with the @samp{--norecursion} option).
36825 You should run the @file{configure} script from the top directory in the
36826 source tree, the @file{gdb-@var{version-number}} directory. If you run
36827 @file{configure} from one of the subdirectories, you will configure only
36828 that subdirectory. That is usually not what you want. In particular,
36829 if you run the first @file{configure} from the @file{gdb} subdirectory
36830 of the @file{gdb-@var{version-number}} directory, you will omit the
36831 configuration of @file{bfd}, @file{readline}, and other sibling
36832 directories of the @file{gdb} subdirectory. This leads to build errors
36833 about missing include files such as @file{bfd/bfd.h}.
36835 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36836 However, you should make sure that the shell on your path (named by
36837 the @samp{SHELL} environment variable) is publicly readable. Remember
36838 that @value{GDBN} uses the shell to start your program---some systems refuse to
36839 let @value{GDBN} debug child processes whose programs are not readable.
36841 @node Separate Objdir
36842 @section Compiling @value{GDBN} in Another Directory
36844 If you want to run @value{GDBN} versions for several host or target machines,
36845 you need a different @code{gdb} compiled for each combination of
36846 host and target. @file{configure} is designed to make this easy by
36847 allowing you to generate each configuration in a separate subdirectory,
36848 rather than in the source directory. If your @code{make} program
36849 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36850 @code{make} in each of these directories builds the @code{gdb}
36851 program specified there.
36853 To build @code{gdb} in a separate directory, run @file{configure}
36854 with the @samp{--srcdir} option to specify where to find the source.
36855 (You also need to specify a path to find @file{configure}
36856 itself from your working directory. If the path to @file{configure}
36857 would be the same as the argument to @samp{--srcdir}, you can leave out
36858 the @samp{--srcdir} option; it is assumed.)
36860 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36861 separate directory for a Sun 4 like this:
36865 cd gdb-@value{GDBVN}
36868 ../gdb-@value{GDBVN}/configure sun4
36873 When @file{configure} builds a configuration using a remote source
36874 directory, it creates a tree for the binaries with the same structure
36875 (and using the same names) as the tree under the source directory. In
36876 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36877 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36878 @file{gdb-sun4/gdb}.
36880 Make sure that your path to the @file{configure} script has just one
36881 instance of @file{gdb} in it. If your path to @file{configure} looks
36882 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36883 one subdirectory of @value{GDBN}, not the whole package. This leads to
36884 build errors about missing include files such as @file{bfd/bfd.h}.
36886 One popular reason to build several @value{GDBN} configurations in separate
36887 directories is to configure @value{GDBN} for cross-compiling (where
36888 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36889 programs that run on another machine---the @dfn{target}).
36890 You specify a cross-debugging target by
36891 giving the @samp{--target=@var{target}} option to @file{configure}.
36893 When you run @code{make} to build a program or library, you must run
36894 it in a configured directory---whatever directory you were in when you
36895 called @file{configure} (or one of its subdirectories).
36897 The @code{Makefile} that @file{configure} generates in each source
36898 directory also runs recursively. If you type @code{make} in a source
36899 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36900 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36901 will build all the required libraries, and then build GDB.
36903 When you have multiple hosts or targets configured in separate
36904 directories, you can run @code{make} on them in parallel (for example,
36905 if they are NFS-mounted on each of the hosts); they will not interfere
36909 @section Specifying Names for Hosts and Targets
36911 The specifications used for hosts and targets in the @file{configure}
36912 script are based on a three-part naming scheme, but some short predefined
36913 aliases are also supported. The full naming scheme encodes three pieces
36914 of information in the following pattern:
36917 @var{architecture}-@var{vendor}-@var{os}
36920 For example, you can use the alias @code{sun4} as a @var{host} argument,
36921 or as the value for @var{target} in a @code{--target=@var{target}}
36922 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36924 The @file{configure} script accompanying @value{GDBN} does not provide
36925 any query facility to list all supported host and target names or
36926 aliases. @file{configure} calls the Bourne shell script
36927 @code{config.sub} to map abbreviations to full names; you can read the
36928 script, if you wish, or you can use it to test your guesses on
36929 abbreviations---for example:
36932 % sh config.sub i386-linux
36934 % sh config.sub alpha-linux
36935 alpha-unknown-linux-gnu
36936 % sh config.sub hp9k700
36938 % sh config.sub sun4
36939 sparc-sun-sunos4.1.1
36940 % sh config.sub sun3
36941 m68k-sun-sunos4.1.1
36942 % sh config.sub i986v
36943 Invalid configuration `i986v': machine `i986v' not recognized
36947 @code{config.sub} is also distributed in the @value{GDBN} source
36948 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36950 @node Configure Options
36951 @section @file{configure} Options
36953 Here is a summary of the @file{configure} options and arguments that
36954 are most often useful for building @value{GDBN}. @file{configure} also has
36955 several other options not listed here. @inforef{What Configure
36956 Does,,configure.info}, for a full explanation of @file{configure}.
36959 configure @r{[}--help@r{]}
36960 @r{[}--prefix=@var{dir}@r{]}
36961 @r{[}--exec-prefix=@var{dir}@r{]}
36962 @r{[}--srcdir=@var{dirname}@r{]}
36963 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36964 @r{[}--target=@var{target}@r{]}
36969 You may introduce options with a single @samp{-} rather than
36970 @samp{--} if you prefer; but you may abbreviate option names if you use
36975 Display a quick summary of how to invoke @file{configure}.
36977 @item --prefix=@var{dir}
36978 Configure the source to install programs and files under directory
36981 @item --exec-prefix=@var{dir}
36982 Configure the source to install programs under directory
36985 @c avoid splitting the warning from the explanation:
36987 @item --srcdir=@var{dirname}
36988 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
36989 @code{make} that implements the @code{VPATH} feature.}@*
36990 Use this option to make configurations in directories separate from the
36991 @value{GDBN} source directories. Among other things, you can use this to
36992 build (or maintain) several configurations simultaneously, in separate
36993 directories. @file{configure} writes configuration-specific files in
36994 the current directory, but arranges for them to use the source in the
36995 directory @var{dirname}. @file{configure} creates directories under
36996 the working directory in parallel to the source directories below
36999 @item --norecursion
37000 Configure only the directory level where @file{configure} is executed; do not
37001 propagate configuration to subdirectories.
37003 @item --target=@var{target}
37004 Configure @value{GDBN} for cross-debugging programs running on the specified
37005 @var{target}. Without this option, @value{GDBN} is configured to debug
37006 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37008 There is no convenient way to generate a list of all available targets.
37010 @item @var{host} @dots{}
37011 Configure @value{GDBN} to run on the specified @var{host}.
37013 There is no convenient way to generate a list of all available hosts.
37016 There are many other options available as well, but they are generally
37017 needed for special purposes only.
37019 @node System-wide configuration
37020 @section System-wide configuration and settings
37021 @cindex system-wide init file
37023 @value{GDBN} can be configured to have a system-wide init file;
37024 this file will be read and executed at startup (@pxref{Startup, , What
37025 @value{GDBN} does during startup}).
37027 Here is the corresponding configure option:
37030 @item --with-system-gdbinit=@var{file}
37031 Specify that the default location of the system-wide init file is
37035 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37036 it may be subject to relocation. Two possible cases:
37040 If the default location of this init file contains @file{$prefix},
37041 it will be subject to relocation. Suppose that the configure options
37042 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37043 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37044 init file is looked for as @file{$install/etc/gdbinit} instead of
37045 @file{$prefix/etc/gdbinit}.
37048 By contrast, if the default location does not contain the prefix,
37049 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37050 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37051 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37052 wherever @value{GDBN} is installed.
37055 If the configured location of the system-wide init file (as given by the
37056 @option{--with-system-gdbinit} option at configure time) is in the
37057 data-directory (as specified by @option{--with-gdb-datadir} at configure
37058 time) or in one of its subdirectories, then @value{GDBN} will look for the
37059 system-wide init file in the directory specified by the
37060 @option{--data-directory} command-line option.
37061 Note that the system-wide init file is only read once, during @value{GDBN}
37062 initialization. If the data-directory is changed after @value{GDBN} has
37063 started with the @code{set data-directory} command, the file will not be
37067 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37070 @node System-wide Configuration Scripts
37071 @subsection Installed System-wide Configuration Scripts
37072 @cindex system-wide configuration scripts
37074 The @file{system-gdbinit} directory, located inside the data-directory
37075 (as specified by @option{--with-gdb-datadir} at configure time) contains
37076 a number of scripts which can be used as system-wide init files. To
37077 automatically source those scripts at startup, @value{GDBN} should be
37078 configured with @option{--with-system-gdbinit}. Otherwise, any user
37079 should be able to source them by hand as needed.
37081 The following scripts are currently available:
37084 @item @file{elinos.py}
37086 @cindex ELinOS system-wide configuration script
37087 This script is useful when debugging a program on an ELinOS target.
37088 It takes advantage of the environment variables defined in a standard
37089 ELinOS environment in order to determine the location of the system
37090 shared libraries, and then sets the @samp{solib-absolute-prefix}
37091 and @samp{solib-search-path} variables appropriately.
37093 @item @file{wrs-linux.py}
37094 @pindex wrs-linux.py
37095 @cindex Wind River Linux system-wide configuration script
37096 This script is useful when debugging a program on a target running
37097 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37098 the host-side sysroot used by the target system.
37102 @node Maintenance Commands
37103 @appendix Maintenance Commands
37104 @cindex maintenance commands
37105 @cindex internal commands
37107 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37108 includes a number of commands intended for @value{GDBN} developers,
37109 that are not documented elsewhere in this manual. These commands are
37110 provided here for reference. (For commands that turn on debugging
37111 messages, see @ref{Debugging Output}.)
37114 @kindex maint agent
37115 @kindex maint agent-eval
37116 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37117 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37118 Translate the given @var{expression} into remote agent bytecodes.
37119 This command is useful for debugging the Agent Expression mechanism
37120 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37121 expression useful for data collection, such as by tracepoints, while
37122 @samp{maint agent-eval} produces an expression that evaluates directly
37123 to a result. For instance, a collection expression for @code{globa +
37124 globb} will include bytecodes to record four bytes of memory at each
37125 of the addresses of @code{globa} and @code{globb}, while discarding
37126 the result of the addition, while an evaluation expression will do the
37127 addition and return the sum.
37128 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37129 If not, generate remote agent bytecode for current frame PC address.
37131 @kindex maint agent-printf
37132 @item maint agent-printf @var{format},@var{expr},...
37133 Translate the given format string and list of argument expressions
37134 into remote agent bytecodes and display them as a disassembled list.
37135 This command is useful for debugging the agent version of dynamic
37136 printf (@pxref{Dynamic Printf}).
37138 @kindex maint info breakpoints
37139 @item @anchor{maint info breakpoints}maint info breakpoints
37140 Using the same format as @samp{info breakpoints}, display both the
37141 breakpoints you've set explicitly, and those @value{GDBN} is using for
37142 internal purposes. Internal breakpoints are shown with negative
37143 breakpoint numbers. The type column identifies what kind of breakpoint
37148 Normal, explicitly set breakpoint.
37151 Normal, explicitly set watchpoint.
37154 Internal breakpoint, used to handle correctly stepping through
37155 @code{longjmp} calls.
37157 @item longjmp resume
37158 Internal breakpoint at the target of a @code{longjmp}.
37161 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37164 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37167 Shared library events.
37171 @kindex maint info bfds
37172 @item maint info bfds
37173 This prints information about each @code{bfd} object that is known to
37174 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37176 @kindex set displaced-stepping
37177 @kindex show displaced-stepping
37178 @cindex displaced stepping support
37179 @cindex out-of-line single-stepping
37180 @item set displaced-stepping
37181 @itemx show displaced-stepping
37182 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37183 if the target supports it. Displaced stepping is a way to single-step
37184 over breakpoints without removing them from the inferior, by executing
37185 an out-of-line copy of the instruction that was originally at the
37186 breakpoint location. It is also known as out-of-line single-stepping.
37189 @item set displaced-stepping on
37190 If the target architecture supports it, @value{GDBN} will use
37191 displaced stepping to step over breakpoints.
37193 @item set displaced-stepping off
37194 @value{GDBN} will not use displaced stepping to step over breakpoints,
37195 even if such is supported by the target architecture.
37197 @cindex non-stop mode, and @samp{set displaced-stepping}
37198 @item set displaced-stepping auto
37199 This is the default mode. @value{GDBN} will use displaced stepping
37200 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37201 architecture supports displaced stepping.
37204 @kindex maint check-psymtabs
37205 @item maint check-psymtabs
37206 Check the consistency of currently expanded psymtabs versus symtabs.
37207 Use this to check, for example, whether a symbol is in one but not the other.
37209 @kindex maint check-symtabs
37210 @item maint check-symtabs
37211 Check the consistency of currently expanded symtabs.
37213 @kindex maint expand-symtabs
37214 @item maint expand-symtabs [@var{regexp}]
37215 Expand symbol tables.
37216 If @var{regexp} is specified, only expand symbol tables for file
37217 names matching @var{regexp}.
37219 @kindex maint cplus first_component
37220 @item maint cplus first_component @var{name}
37221 Print the first C@t{++} class/namespace component of @var{name}.
37223 @kindex maint cplus namespace
37224 @item maint cplus namespace
37225 Print the list of possible C@t{++} namespaces.
37227 @kindex maint demangle
37228 @item maint demangle @var{name}
37229 Demangle a C@t{++} or Objective-C mangled @var{name}.
37231 @kindex maint deprecate
37232 @kindex maint undeprecate
37233 @cindex deprecated commands
37234 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37235 @itemx maint undeprecate @var{command}
37236 Deprecate or undeprecate the named @var{command}. Deprecated commands
37237 cause @value{GDBN} to issue a warning when you use them. The optional
37238 argument @var{replacement} says which newer command should be used in
37239 favor of the deprecated one; if it is given, @value{GDBN} will mention
37240 the replacement as part of the warning.
37242 @kindex maint dump-me
37243 @item maint dump-me
37244 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37245 Cause a fatal signal in the debugger and force it to dump its core.
37246 This is supported only on systems which support aborting a program
37247 with the @code{SIGQUIT} signal.
37249 @kindex maint internal-error
37250 @kindex maint internal-warning
37251 @item maint internal-error @r{[}@var{message-text}@r{]}
37252 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37253 Cause @value{GDBN} to call the internal function @code{internal_error}
37254 or @code{internal_warning} and hence behave as though an internal error
37255 or internal warning has been detected. In addition to reporting the
37256 internal problem, these functions give the user the opportunity to
37257 either quit @value{GDBN} or create a core file of the current
37258 @value{GDBN} session.
37260 These commands take an optional parameter @var{message-text} that is
37261 used as the text of the error or warning message.
37263 Here's an example of using @code{internal-error}:
37266 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37267 @dots{}/maint.c:121: internal-error: testing, 1, 2
37268 A problem internal to GDB has been detected. Further
37269 debugging may prove unreliable.
37270 Quit this debugging session? (y or n) @kbd{n}
37271 Create a core file? (y or n) @kbd{n}
37275 @cindex @value{GDBN} internal error
37276 @cindex internal errors, control of @value{GDBN} behavior
37278 @kindex maint set internal-error
37279 @kindex maint show internal-error
37280 @kindex maint set internal-warning
37281 @kindex maint show internal-warning
37282 @item maint set internal-error @var{action} [ask|yes|no]
37283 @itemx maint show internal-error @var{action}
37284 @itemx maint set internal-warning @var{action} [ask|yes|no]
37285 @itemx maint show internal-warning @var{action}
37286 When @value{GDBN} reports an internal problem (error or warning) it
37287 gives the user the opportunity to both quit @value{GDBN} and create a
37288 core file of the current @value{GDBN} session. These commands let you
37289 override the default behaviour for each particular @var{action},
37290 described in the table below.
37294 You can specify that @value{GDBN} should always (yes) or never (no)
37295 quit. The default is to ask the user what to do.
37298 You can specify that @value{GDBN} should always (yes) or never (no)
37299 create a core file. The default is to ask the user what to do.
37302 @kindex maint packet
37303 @item maint packet @var{text}
37304 If @value{GDBN} is talking to an inferior via the serial protocol,
37305 then this command sends the string @var{text} to the inferior, and
37306 displays the response packet. @value{GDBN} supplies the initial
37307 @samp{$} character, the terminating @samp{#} character, and the
37310 @kindex maint print architecture
37311 @item maint print architecture @r{[}@var{file}@r{]}
37312 Print the entire architecture configuration. The optional argument
37313 @var{file} names the file where the output goes.
37315 @kindex maint print c-tdesc
37316 @item maint print c-tdesc
37317 Print the current target description (@pxref{Target Descriptions}) as
37318 a C source file. The created source file can be used in @value{GDBN}
37319 when an XML parser is not available to parse the description.
37321 @kindex maint print dummy-frames
37322 @item maint print dummy-frames
37323 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37326 (@value{GDBP}) @kbd{b add}
37328 (@value{GDBP}) @kbd{print add(2,3)}
37329 Breakpoint 2, add (a=2, b=3) at @dots{}
37331 The program being debugged stopped while in a function called from GDB.
37333 (@value{GDBP}) @kbd{maint print dummy-frames}
37334 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37335 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37336 call_lo=0x01014000 call_hi=0x01014001
37340 Takes an optional file parameter.
37342 @kindex maint print registers
37343 @kindex maint print raw-registers
37344 @kindex maint print cooked-registers
37345 @kindex maint print register-groups
37346 @kindex maint print remote-registers
37347 @item maint print registers @r{[}@var{file}@r{]}
37348 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37349 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37350 @itemx maint print register-groups @r{[}@var{file}@r{]}
37351 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37352 Print @value{GDBN}'s internal register data structures.
37354 The command @code{maint print raw-registers} includes the contents of
37355 the raw register cache; the command @code{maint print
37356 cooked-registers} includes the (cooked) value of all registers,
37357 including registers which aren't available on the target nor visible
37358 to user; the command @code{maint print register-groups} includes the
37359 groups that each register is a member of; and the command @code{maint
37360 print remote-registers} includes the remote target's register numbers
37361 and offsets in the `G' packets.
37363 These commands take an optional parameter, a file name to which to
37364 write the information.
37366 @kindex maint print reggroups
37367 @item maint print reggroups @r{[}@var{file}@r{]}
37368 Print @value{GDBN}'s internal register group data structures. The
37369 optional argument @var{file} tells to what file to write the
37372 The register groups info looks like this:
37375 (@value{GDBP}) @kbd{maint print reggroups}
37388 This command forces @value{GDBN} to flush its internal register cache.
37390 @kindex maint print objfiles
37391 @cindex info for known object files
37392 @item maint print objfiles @r{[}@var{regexp}@r{]}
37393 Print a dump of all known object files.
37394 If @var{regexp} is specified, only print object files whose names
37395 match @var{regexp}. For each object file, this command prints its name,
37396 address in memory, and all of its psymtabs and symtabs.
37398 @kindex maint print section-scripts
37399 @cindex info for known .debug_gdb_scripts-loaded scripts
37400 @item maint print section-scripts [@var{regexp}]
37401 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37402 If @var{regexp} is specified, only print scripts loaded by object files
37403 matching @var{regexp}.
37404 For each script, this command prints its name as specified in the objfile,
37405 and the full path if known.
37406 @xref{dotdebug_gdb_scripts section}.
37408 @kindex maint print statistics
37409 @cindex bcache statistics
37410 @item maint print statistics
37411 This command prints, for each object file in the program, various data
37412 about that object file followed by the byte cache (@dfn{bcache})
37413 statistics for the object file. The objfile data includes the number
37414 of minimal, partial, full, and stabs symbols, the number of types
37415 defined by the objfile, the number of as yet unexpanded psym tables,
37416 the number of line tables and string tables, and the amount of memory
37417 used by the various tables. The bcache statistics include the counts,
37418 sizes, and counts of duplicates of all and unique objects, max,
37419 average, and median entry size, total memory used and its overhead and
37420 savings, and various measures of the hash table size and chain
37423 @kindex maint print target-stack
37424 @cindex target stack description
37425 @item maint print target-stack
37426 A @dfn{target} is an interface between the debugger and a particular
37427 kind of file or process. Targets can be stacked in @dfn{strata},
37428 so that more than one target can potentially respond to a request.
37429 In particular, memory accesses will walk down the stack of targets
37430 until they find a target that is interested in handling that particular
37433 This command prints a short description of each layer that was pushed on
37434 the @dfn{target stack}, starting from the top layer down to the bottom one.
37436 @kindex maint print type
37437 @cindex type chain of a data type
37438 @item maint print type @var{expr}
37439 Print the type chain for a type specified by @var{expr}. The argument
37440 can be either a type name or a symbol. If it is a symbol, the type of
37441 that symbol is described. The type chain produced by this command is
37442 a recursive definition of the data type as stored in @value{GDBN}'s
37443 data structures, including its flags and contained types.
37445 @kindex maint set dwarf2 always-disassemble
37446 @kindex maint show dwarf2 always-disassemble
37447 @item maint set dwarf2 always-disassemble
37448 @item maint show dwarf2 always-disassemble
37449 Control the behavior of @code{info address} when using DWARF debugging
37452 The default is @code{off}, which means that @value{GDBN} should try to
37453 describe a variable's location in an easily readable format. When
37454 @code{on}, @value{GDBN} will instead display the DWARF location
37455 expression in an assembly-like format. Note that some locations are
37456 too complex for @value{GDBN} to describe simply; in this case you will
37457 always see the disassembly form.
37459 Here is an example of the resulting disassembly:
37462 (gdb) info addr argc
37463 Symbol "argc" is a complex DWARF expression:
37467 For more information on these expressions, see
37468 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37470 @kindex maint set dwarf2 max-cache-age
37471 @kindex maint show dwarf2 max-cache-age
37472 @item maint set dwarf2 max-cache-age
37473 @itemx maint show dwarf2 max-cache-age
37474 Control the DWARF 2 compilation unit cache.
37476 @cindex DWARF 2 compilation units cache
37477 In object files with inter-compilation-unit references, such as those
37478 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37479 reader needs to frequently refer to previously read compilation units.
37480 This setting controls how long a compilation unit will remain in the
37481 cache if it is not referenced. A higher limit means that cached
37482 compilation units will be stored in memory longer, and more total
37483 memory will be used. Setting it to zero disables caching, which will
37484 slow down @value{GDBN} startup, but reduce memory consumption.
37486 @kindex maint set profile
37487 @kindex maint show profile
37488 @cindex profiling GDB
37489 @item maint set profile
37490 @itemx maint show profile
37491 Control profiling of @value{GDBN}.
37493 Profiling will be disabled until you use the @samp{maint set profile}
37494 command to enable it. When you enable profiling, the system will begin
37495 collecting timing and execution count data; when you disable profiling or
37496 exit @value{GDBN}, the results will be written to a log file. Remember that
37497 if you use profiling, @value{GDBN} will overwrite the profiling log file
37498 (often called @file{gmon.out}). If you have a record of important profiling
37499 data in a @file{gmon.out} file, be sure to move it to a safe location.
37501 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37502 compiled with the @samp{-pg} compiler option.
37504 @kindex maint set show-debug-regs
37505 @kindex maint show show-debug-regs
37506 @cindex hardware debug registers
37507 @item maint set show-debug-regs
37508 @itemx maint show show-debug-regs
37509 Control whether to show variables that mirror the hardware debug
37510 registers. Use @code{ON} to enable, @code{OFF} to disable. If
37511 enabled, the debug registers values are shown when @value{GDBN} inserts or
37512 removes a hardware breakpoint or watchpoint, and when the inferior
37513 triggers a hardware-assisted breakpoint or watchpoint.
37515 @kindex maint set show-all-tib
37516 @kindex maint show show-all-tib
37517 @item maint set show-all-tib
37518 @itemx maint show show-all-tib
37519 Control whether to show all non zero areas within a 1k block starting
37520 at thread local base, when using the @samp{info w32 thread-information-block}
37523 @kindex maint set per-command
37524 @kindex maint show per-command
37525 @item maint set per-command
37526 @itemx maint show per-command
37527 @cindex resources used by commands
37529 @value{GDBN} can display the resources used by each command.
37530 This is useful in debugging performance problems.
37533 @item maint set per-command space [on|off]
37534 @itemx maint show per-command space
37535 Enable or disable the printing of the memory used by GDB for each command.
37536 If enabled, @value{GDBN} will display how much memory each command
37537 took, following the command's own output.
37538 This can also be requested by invoking @value{GDBN} with the
37539 @option{--statistics} command-line switch (@pxref{Mode Options}).
37541 @item maint set per-command time [on|off]
37542 @itemx maint show per-command time
37543 Enable or disable the printing of the execution time of @value{GDBN}
37545 If enabled, @value{GDBN} will display how much time it
37546 took to execute each command, following the command's own output.
37547 Both CPU time and wallclock time are printed.
37548 Printing both is useful when trying to determine whether the cost is
37549 CPU or, e.g., disk/network latency.
37550 Note that the CPU time printed is for @value{GDBN} only, it does not include
37551 the execution time of the inferior because there's no mechanism currently
37552 to compute how much time was spent by @value{GDBN} and how much time was
37553 spent by the program been debugged.
37554 This can also be requested by invoking @value{GDBN} with the
37555 @option{--statistics} command-line switch (@pxref{Mode Options}).
37557 @item maint set per-command symtab [on|off]
37558 @itemx maint show per-command symtab
37559 Enable or disable the printing of basic symbol table statistics
37561 If enabled, @value{GDBN} will display the following information:
37565 number of symbol tables
37567 number of primary symbol tables
37569 number of blocks in the blockvector
37573 @kindex maint space
37574 @cindex memory used by commands
37575 @item maint space @var{value}
37576 An alias for @code{maint set per-command space}.
37577 A non-zero value enables it, zero disables it.
37580 @cindex time of command execution
37581 @item maint time @var{value}
37582 An alias for @code{maint set per-command time}.
37583 A non-zero value enables it, zero disables it.
37585 @kindex maint translate-address
37586 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37587 Find the symbol stored at the location specified by the address
37588 @var{addr} and an optional section name @var{section}. If found,
37589 @value{GDBN} prints the name of the closest symbol and an offset from
37590 the symbol's location to the specified address. This is similar to
37591 the @code{info address} command (@pxref{Symbols}), except that this
37592 command also allows to find symbols in other sections.
37594 If section was not specified, the section in which the symbol was found
37595 is also printed. For dynamically linked executables, the name of
37596 executable or shared library containing the symbol is printed as well.
37600 The following command is useful for non-interactive invocations of
37601 @value{GDBN}, such as in the test suite.
37604 @item set watchdog @var{nsec}
37605 @kindex set watchdog
37606 @cindex watchdog timer
37607 @cindex timeout for commands
37608 Set the maximum number of seconds @value{GDBN} will wait for the
37609 target operation to finish. If this time expires, @value{GDBN}
37610 reports and error and the command is aborted.
37612 @item show watchdog
37613 Show the current setting of the target wait timeout.
37616 @node Remote Protocol
37617 @appendix @value{GDBN} Remote Serial Protocol
37622 * Stop Reply Packets::
37623 * General Query Packets::
37624 * Architecture-Specific Protocol Details::
37625 * Tracepoint Packets::
37626 * Host I/O Packets::
37628 * Notification Packets::
37629 * Remote Non-Stop::
37630 * Packet Acknowledgment::
37632 * File-I/O Remote Protocol Extension::
37633 * Library List Format::
37634 * Library List Format for SVR4 Targets::
37635 * Memory Map Format::
37636 * Thread List Format::
37637 * Traceframe Info Format::
37638 * Branch Trace Format::
37644 There may be occasions when you need to know something about the
37645 protocol---for example, if there is only one serial port to your target
37646 machine, you might want your program to do something special if it
37647 recognizes a packet meant for @value{GDBN}.
37649 In the examples below, @samp{->} and @samp{<-} are used to indicate
37650 transmitted and received data, respectively.
37652 @cindex protocol, @value{GDBN} remote serial
37653 @cindex serial protocol, @value{GDBN} remote
37654 @cindex remote serial protocol
37655 All @value{GDBN} commands and responses (other than acknowledgments
37656 and notifications, see @ref{Notification Packets}) are sent as a
37657 @var{packet}. A @var{packet} is introduced with the character
37658 @samp{$}, the actual @var{packet-data}, and the terminating character
37659 @samp{#} followed by a two-digit @var{checksum}:
37662 @code{$}@var{packet-data}@code{#}@var{checksum}
37666 @cindex checksum, for @value{GDBN} remote
37668 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37669 characters between the leading @samp{$} and the trailing @samp{#} (an
37670 eight bit unsigned checksum).
37672 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37673 specification also included an optional two-digit @var{sequence-id}:
37676 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37679 @cindex sequence-id, for @value{GDBN} remote
37681 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37682 has never output @var{sequence-id}s. Stubs that handle packets added
37683 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37685 When either the host or the target machine receives a packet, the first
37686 response expected is an acknowledgment: either @samp{+} (to indicate
37687 the package was received correctly) or @samp{-} (to request
37691 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37696 The @samp{+}/@samp{-} acknowledgments can be disabled
37697 once a connection is established.
37698 @xref{Packet Acknowledgment}, for details.
37700 The host (@value{GDBN}) sends @var{command}s, and the target (the
37701 debugging stub incorporated in your program) sends a @var{response}. In
37702 the case of step and continue @var{command}s, the response is only sent
37703 when the operation has completed, and the target has again stopped all
37704 threads in all attached processes. This is the default all-stop mode
37705 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37706 execution mode; see @ref{Remote Non-Stop}, for details.
37708 @var{packet-data} consists of a sequence of characters with the
37709 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37712 @cindex remote protocol, field separator
37713 Fields within the packet should be separated using @samp{,} @samp{;} or
37714 @samp{:}. Except where otherwise noted all numbers are represented in
37715 @sc{hex} with leading zeros suppressed.
37717 Implementors should note that prior to @value{GDBN} 5.0, the character
37718 @samp{:} could not appear as the third character in a packet (as it
37719 would potentially conflict with the @var{sequence-id}).
37721 @cindex remote protocol, binary data
37722 @anchor{Binary Data}
37723 Binary data in most packets is encoded either as two hexadecimal
37724 digits per byte of binary data. This allowed the traditional remote
37725 protocol to work over connections which were only seven-bit clean.
37726 Some packets designed more recently assume an eight-bit clean
37727 connection, and use a more efficient encoding to send and receive
37730 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37731 as an escape character. Any escaped byte is transmitted as the escape
37732 character followed by the original character XORed with @code{0x20}.
37733 For example, the byte @code{0x7d} would be transmitted as the two
37734 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37735 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37736 @samp{@}}) must always be escaped. Responses sent by the stub
37737 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37738 is not interpreted as the start of a run-length encoded sequence
37741 Response @var{data} can be run-length encoded to save space.
37742 Run-length encoding replaces runs of identical characters with one
37743 instance of the repeated character, followed by a @samp{*} and a
37744 repeat count. The repeat count is itself sent encoded, to avoid
37745 binary characters in @var{data}: a value of @var{n} is sent as
37746 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37747 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37748 code 32) for a repeat count of 3. (This is because run-length
37749 encoding starts to win for counts 3 or more.) Thus, for example,
37750 @samp{0* } is a run-length encoding of ``0000'': the space character
37751 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37754 The printable characters @samp{#} and @samp{$} or with a numeric value
37755 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37756 seven repeats (@samp{$}) can be expanded using a repeat count of only
37757 five (@samp{"}). For example, @samp{00000000} can be encoded as
37760 The error response returned for some packets includes a two character
37761 error number. That number is not well defined.
37763 @cindex empty response, for unsupported packets
37764 For any @var{command} not supported by the stub, an empty response
37765 (@samp{$#00}) should be returned. That way it is possible to extend the
37766 protocol. A newer @value{GDBN} can tell if a packet is supported based
37769 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37770 commands for register access, and the @samp{m} and @samp{M} commands
37771 for memory access. Stubs that only control single-threaded targets
37772 can implement run control with the @samp{c} (continue), and @samp{s}
37773 (step) commands. Stubs that support multi-threading targets should
37774 support the @samp{vCont} command. All other commands are optional.
37779 The following table provides a complete list of all currently defined
37780 @var{command}s and their corresponding response @var{data}.
37781 @xref{File-I/O Remote Protocol Extension}, for details about the File
37782 I/O extension of the remote protocol.
37784 Each packet's description has a template showing the packet's overall
37785 syntax, followed by an explanation of the packet's meaning. We
37786 include spaces in some of the templates for clarity; these are not
37787 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37788 separate its components. For example, a template like @samp{foo
37789 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37790 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37791 @var{baz}. @value{GDBN} does not transmit a space character between the
37792 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37795 @cindex @var{thread-id}, in remote protocol
37796 @anchor{thread-id syntax}
37797 Several packets and replies include a @var{thread-id} field to identify
37798 a thread. Normally these are positive numbers with a target-specific
37799 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37800 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37803 In addition, the remote protocol supports a multiprocess feature in
37804 which the @var{thread-id} syntax is extended to optionally include both
37805 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37806 The @var{pid} (process) and @var{tid} (thread) components each have the
37807 format described above: a positive number with target-specific
37808 interpretation formatted as a big-endian hex string, literal @samp{-1}
37809 to indicate all processes or threads (respectively), or @samp{0} to
37810 indicate an arbitrary process or thread. Specifying just a process, as
37811 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37812 error to specify all processes but a specific thread, such as
37813 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37814 for those packets and replies explicitly documented to include a process
37815 ID, rather than a @var{thread-id}.
37817 The multiprocess @var{thread-id} syntax extensions are only used if both
37818 @value{GDBN} and the stub report support for the @samp{multiprocess}
37819 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37822 Note that all packet forms beginning with an upper- or lower-case
37823 letter, other than those described here, are reserved for future use.
37825 Here are the packet descriptions.
37830 @cindex @samp{!} packet
37831 @anchor{extended mode}
37832 Enable extended mode. In extended mode, the remote server is made
37833 persistent. The @samp{R} packet is used to restart the program being
37839 The remote target both supports and has enabled extended mode.
37843 @cindex @samp{?} packet
37844 Indicate the reason the target halted. The reply is the same as for
37845 step and continue. This packet has a special interpretation when the
37846 target is in non-stop mode; see @ref{Remote Non-Stop}.
37849 @xref{Stop Reply Packets}, for the reply specifications.
37851 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37852 @cindex @samp{A} packet
37853 Initialized @code{argv[]} array passed into program. @var{arglen}
37854 specifies the number of bytes in the hex encoded byte stream
37855 @var{arg}. See @code{gdbserver} for more details.
37860 The arguments were set.
37866 @cindex @samp{b} packet
37867 (Don't use this packet; its behavior is not well-defined.)
37868 Change the serial line speed to @var{baud}.
37870 JTC: @emph{When does the transport layer state change? When it's
37871 received, or after the ACK is transmitted. In either case, there are
37872 problems if the command or the acknowledgment packet is dropped.}
37874 Stan: @emph{If people really wanted to add something like this, and get
37875 it working for the first time, they ought to modify ser-unix.c to send
37876 some kind of out-of-band message to a specially-setup stub and have the
37877 switch happen "in between" packets, so that from remote protocol's point
37878 of view, nothing actually happened.}
37880 @item B @var{addr},@var{mode}
37881 @cindex @samp{B} packet
37882 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37883 breakpoint at @var{addr}.
37885 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37886 (@pxref{insert breakpoint or watchpoint packet}).
37888 @cindex @samp{bc} packet
37891 Backward continue. Execute the target system in reverse. No parameter.
37892 @xref{Reverse Execution}, for more information.
37895 @xref{Stop Reply Packets}, for the reply specifications.
37897 @cindex @samp{bs} packet
37900 Backward single step. Execute one instruction in reverse. No parameter.
37901 @xref{Reverse Execution}, for more information.
37904 @xref{Stop Reply Packets}, for the reply specifications.
37906 @item c @r{[}@var{addr}@r{]}
37907 @cindex @samp{c} packet
37908 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37909 resume at current address.
37911 This packet is deprecated for multi-threading support. @xref{vCont
37915 @xref{Stop Reply Packets}, for the reply specifications.
37917 @item C @var{sig}@r{[};@var{addr}@r{]}
37918 @cindex @samp{C} packet
37919 Continue with signal @var{sig} (hex signal number). If
37920 @samp{;@var{addr}} is omitted, resume at same address.
37922 This packet is deprecated for multi-threading support. @xref{vCont
37926 @xref{Stop Reply Packets}, for the reply specifications.
37929 @cindex @samp{d} packet
37932 Don't use this packet; instead, define a general set packet
37933 (@pxref{General Query Packets}).
37937 @cindex @samp{D} packet
37938 The first form of the packet is used to detach @value{GDBN} from the
37939 remote system. It is sent to the remote target
37940 before @value{GDBN} disconnects via the @code{detach} command.
37942 The second form, including a process ID, is used when multiprocess
37943 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37944 detach only a specific process. The @var{pid} is specified as a
37945 big-endian hex string.
37955 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37956 @cindex @samp{F} packet
37957 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37958 This is part of the File-I/O protocol extension. @xref{File-I/O
37959 Remote Protocol Extension}, for the specification.
37962 @anchor{read registers packet}
37963 @cindex @samp{g} packet
37964 Read general registers.
37968 @item @var{XX@dots{}}
37969 Each byte of register data is described by two hex digits. The bytes
37970 with the register are transmitted in target byte order. The size of
37971 each register and their position within the @samp{g} packet are
37972 determined by the @value{GDBN} internal gdbarch functions
37973 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37974 specification of several standard @samp{g} packets is specified below.
37976 When reading registers from a trace frame (@pxref{Analyze Collected
37977 Data,,Using the Collected Data}), the stub may also return a string of
37978 literal @samp{x}'s in place of the register data digits, to indicate
37979 that the corresponding register has not been collected, thus its value
37980 is unavailable. For example, for an architecture with 4 registers of
37981 4 bytes each, the following reply indicates to @value{GDBN} that
37982 registers 0 and 2 have not been collected, while registers 1 and 3
37983 have been collected, and both have zero value:
37987 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37994 @item G @var{XX@dots{}}
37995 @cindex @samp{G} packet
37996 Write general registers. @xref{read registers packet}, for a
37997 description of the @var{XX@dots{}} data.
38007 @item H @var{op} @var{thread-id}
38008 @cindex @samp{H} packet
38009 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38010 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38011 it should be @samp{c} for step and continue operations (note that this
38012 is deprecated, supporting the @samp{vCont} command is a better
38013 option), @samp{g} for other operations. The thread designator
38014 @var{thread-id} has the format and interpretation described in
38015 @ref{thread-id syntax}.
38026 @c 'H': How restrictive (or permissive) is the thread model. If a
38027 @c thread is selected and stopped, are other threads allowed
38028 @c to continue to execute? As I mentioned above, I think the
38029 @c semantics of each command when a thread is selected must be
38030 @c described. For example:
38032 @c 'g': If the stub supports threads and a specific thread is
38033 @c selected, returns the register block from that thread;
38034 @c otherwise returns current registers.
38036 @c 'G' If the stub supports threads and a specific thread is
38037 @c selected, sets the registers of the register block of
38038 @c that thread; otherwise sets current registers.
38040 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38041 @anchor{cycle step packet}
38042 @cindex @samp{i} packet
38043 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38044 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38045 step starting at that address.
38048 @cindex @samp{I} packet
38049 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38053 @cindex @samp{k} packet
38056 FIXME: @emph{There is no description of how to operate when a specific
38057 thread context has been selected (i.e.@: does 'k' kill only that
38060 @item m @var{addr},@var{length}
38061 @cindex @samp{m} packet
38062 Read @var{length} bytes of memory starting at address @var{addr}.
38063 Note that @var{addr} may not be aligned to any particular boundary.
38065 The stub need not use any particular size or alignment when gathering
38066 data from memory for the response; even if @var{addr} is word-aligned
38067 and @var{length} is a multiple of the word size, the stub is free to
38068 use byte accesses, or not. For this reason, this packet may not be
38069 suitable for accessing memory-mapped I/O devices.
38070 @cindex alignment of remote memory accesses
38071 @cindex size of remote memory accesses
38072 @cindex memory, alignment and size of remote accesses
38076 @item @var{XX@dots{}}
38077 Memory contents; each byte is transmitted as a two-digit hexadecimal
38078 number. The reply may contain fewer bytes than requested if the
38079 server was able to read only part of the region of memory.
38084 @item M @var{addr},@var{length}:@var{XX@dots{}}
38085 @cindex @samp{M} packet
38086 Write @var{length} bytes of memory starting at address @var{addr}.
38087 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38088 hexadecimal number.
38095 for an error (this includes the case where only part of the data was
38100 @cindex @samp{p} packet
38101 Read the value of register @var{n}; @var{n} is in hex.
38102 @xref{read registers packet}, for a description of how the returned
38103 register value is encoded.
38107 @item @var{XX@dots{}}
38108 the register's value
38112 Indicating an unrecognized @var{query}.
38115 @item P @var{n@dots{}}=@var{r@dots{}}
38116 @anchor{write register packet}
38117 @cindex @samp{P} packet
38118 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38119 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38120 digits for each byte in the register (target byte order).
38130 @item q @var{name} @var{params}@dots{}
38131 @itemx Q @var{name} @var{params}@dots{}
38132 @cindex @samp{q} packet
38133 @cindex @samp{Q} packet
38134 General query (@samp{q}) and set (@samp{Q}). These packets are
38135 described fully in @ref{General Query Packets}.
38138 @cindex @samp{r} packet
38139 Reset the entire system.
38141 Don't use this packet; use the @samp{R} packet instead.
38144 @cindex @samp{R} packet
38145 Restart the program being debugged. @var{XX}, while needed, is ignored.
38146 This packet is only available in extended mode (@pxref{extended mode}).
38148 The @samp{R} packet has no reply.
38150 @item s @r{[}@var{addr}@r{]}
38151 @cindex @samp{s} packet
38152 Single step. @var{addr} is the address at which to resume. If
38153 @var{addr} is omitted, resume at same address.
38155 This packet is deprecated for multi-threading support. @xref{vCont
38159 @xref{Stop Reply Packets}, for the reply specifications.
38161 @item S @var{sig}@r{[};@var{addr}@r{]}
38162 @anchor{step with signal packet}
38163 @cindex @samp{S} packet
38164 Step with signal. This is analogous to the @samp{C} packet, but
38165 requests a single-step, rather than a normal resumption of execution.
38167 This packet is deprecated for multi-threading support. @xref{vCont
38171 @xref{Stop Reply Packets}, for the reply specifications.
38173 @item t @var{addr}:@var{PP},@var{MM}
38174 @cindex @samp{t} packet
38175 Search backwards starting at address @var{addr} for a match with pattern
38176 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38177 @var{addr} must be at least 3 digits.
38179 @item T @var{thread-id}
38180 @cindex @samp{T} packet
38181 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38186 thread is still alive
38192 Packets starting with @samp{v} are identified by a multi-letter name,
38193 up to the first @samp{;} or @samp{?} (or the end of the packet).
38195 @item vAttach;@var{pid}
38196 @cindex @samp{vAttach} packet
38197 Attach to a new process with the specified process ID @var{pid}.
38198 The process ID is a
38199 hexadecimal integer identifying the process. In all-stop mode, all
38200 threads in the attached process are stopped; in non-stop mode, it may be
38201 attached without being stopped if that is supported by the target.
38203 @c In non-stop mode, on a successful vAttach, the stub should set the
38204 @c current thread to a thread of the newly-attached process. After
38205 @c attaching, GDB queries for the attached process's thread ID with qC.
38206 @c Also note that, from a user perspective, whether or not the
38207 @c target is stopped on attach in non-stop mode depends on whether you
38208 @c use the foreground or background version of the attach command, not
38209 @c on what vAttach does; GDB does the right thing with respect to either
38210 @c stopping or restarting threads.
38212 This packet is only available in extended mode (@pxref{extended mode}).
38218 @item @r{Any stop packet}
38219 for success in all-stop mode (@pxref{Stop Reply Packets})
38221 for success in non-stop mode (@pxref{Remote Non-Stop})
38224 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38225 @cindex @samp{vCont} packet
38226 @anchor{vCont packet}
38227 Resume the inferior, specifying different actions for each thread.
38228 If an action is specified with no @var{thread-id}, then it is applied to any
38229 threads that don't have a specific action specified; if no default action is
38230 specified then other threads should remain stopped in all-stop mode and
38231 in their current state in non-stop mode.
38232 Specifying multiple
38233 default actions is an error; specifying no actions is also an error.
38234 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38236 Currently supported actions are:
38242 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38246 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38249 @item r @var{start},@var{end}
38250 Step once, and then keep stepping as long as the thread stops at
38251 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38252 The remote stub reports a stop reply when either the thread goes out
38253 of the range or is stopped due to an unrelated reason, such as hitting
38254 a breakpoint. @xref{range stepping}.
38256 If the range is empty (@var{start} == @var{end}), then the action
38257 becomes equivalent to the @samp{s} action. In other words,
38258 single-step once, and report the stop (even if the stepped instruction
38259 jumps to @var{start}).
38261 (A stop reply may be sent at any point even if the PC is still within
38262 the stepping range; for example, it is valid to implement this packet
38263 in a degenerate way as a single instruction step operation.)
38267 The optional argument @var{addr} normally associated with the
38268 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38269 not supported in @samp{vCont}.
38271 The @samp{t} action is only relevant in non-stop mode
38272 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38273 A stop reply should be generated for any affected thread not already stopped.
38274 When a thread is stopped by means of a @samp{t} action,
38275 the corresponding stop reply should indicate that the thread has stopped with
38276 signal @samp{0}, regardless of whether the target uses some other signal
38277 as an implementation detail.
38279 The stub must support @samp{vCont} if it reports support for
38280 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38281 this case @samp{vCont} actions can be specified to apply to all threads
38282 in a process by using the @samp{p@var{pid}.-1} form of the
38286 @xref{Stop Reply Packets}, for the reply specifications.
38289 @cindex @samp{vCont?} packet
38290 Request a list of actions supported by the @samp{vCont} packet.
38294 @item vCont@r{[};@var{action}@dots{}@r{]}
38295 The @samp{vCont} packet is supported. Each @var{action} is a supported
38296 command in the @samp{vCont} packet.
38298 The @samp{vCont} packet is not supported.
38301 @item vFile:@var{operation}:@var{parameter}@dots{}
38302 @cindex @samp{vFile} packet
38303 Perform a file operation on the target system. For details,
38304 see @ref{Host I/O Packets}.
38306 @item vFlashErase:@var{addr},@var{length}
38307 @cindex @samp{vFlashErase} packet
38308 Direct the stub to erase @var{length} bytes of flash starting at
38309 @var{addr}. The region may enclose any number of flash blocks, but
38310 its start and end must fall on block boundaries, as indicated by the
38311 flash block size appearing in the memory map (@pxref{Memory Map
38312 Format}). @value{GDBN} groups flash memory programming operations
38313 together, and sends a @samp{vFlashDone} request after each group; the
38314 stub is allowed to delay erase operation until the @samp{vFlashDone}
38315 packet is received.
38325 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38326 @cindex @samp{vFlashWrite} packet
38327 Direct the stub to write data to flash address @var{addr}. The data
38328 is passed in binary form using the same encoding as for the @samp{X}
38329 packet (@pxref{Binary Data}). The memory ranges specified by
38330 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38331 not overlap, and must appear in order of increasing addresses
38332 (although @samp{vFlashErase} packets for higher addresses may already
38333 have been received; the ordering is guaranteed only between
38334 @samp{vFlashWrite} packets). If a packet writes to an address that was
38335 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38336 target-specific method, the results are unpredictable.
38344 for vFlashWrite addressing non-flash memory
38350 @cindex @samp{vFlashDone} packet
38351 Indicate to the stub that flash programming operation is finished.
38352 The stub is permitted to delay or batch the effects of a group of
38353 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38354 @samp{vFlashDone} packet is received. The contents of the affected
38355 regions of flash memory are unpredictable until the @samp{vFlashDone}
38356 request is completed.
38358 @item vKill;@var{pid}
38359 @cindex @samp{vKill} packet
38360 Kill the process with the specified process ID. @var{pid} is a
38361 hexadecimal integer identifying the process. This packet is used in
38362 preference to @samp{k} when multiprocess protocol extensions are
38363 supported; see @ref{multiprocess extensions}.
38373 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38374 @cindex @samp{vRun} packet
38375 Run the program @var{filename}, passing it each @var{argument} on its
38376 command line. The file and arguments are hex-encoded strings. If
38377 @var{filename} is an empty string, the stub may use a default program
38378 (e.g.@: the last program run). The program is created in the stopped
38381 @c FIXME: What about non-stop mode?
38383 This packet is only available in extended mode (@pxref{extended mode}).
38389 @item @r{Any stop packet}
38390 for success (@pxref{Stop Reply Packets})
38394 @cindex @samp{vStopped} packet
38395 @xref{Notification Packets}.
38397 @item X @var{addr},@var{length}:@var{XX@dots{}}
38399 @cindex @samp{X} packet
38400 Write data to memory, where the data is transmitted in binary.
38401 @var{addr} is address, @var{length} is number of bytes,
38402 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38412 @item z @var{type},@var{addr},@var{kind}
38413 @itemx Z @var{type},@var{addr},@var{kind}
38414 @anchor{insert breakpoint or watchpoint packet}
38415 @cindex @samp{z} packet
38416 @cindex @samp{Z} packets
38417 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38418 watchpoint starting at address @var{address} of kind @var{kind}.
38420 Each breakpoint and watchpoint packet @var{type} is documented
38423 @emph{Implementation notes: A remote target shall return an empty string
38424 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38425 remote target shall support either both or neither of a given
38426 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38427 avoid potential problems with duplicate packets, the operations should
38428 be implemented in an idempotent way.}
38430 @item z0,@var{addr},@var{kind}
38431 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38432 @cindex @samp{z0} packet
38433 @cindex @samp{Z0} packet
38434 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38435 @var{addr} of type @var{kind}.
38437 A memory breakpoint is implemented by replacing the instruction at
38438 @var{addr} with a software breakpoint or trap instruction. The
38439 @var{kind} is target-specific and typically indicates the size of
38440 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38441 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38442 architectures have additional meanings for @var{kind};
38443 @var{cond_list} is an optional list of conditional expressions in bytecode
38444 form that should be evaluated on the target's side. These are the
38445 conditions that should be taken into consideration when deciding if
38446 the breakpoint trigger should be reported back to @var{GDBN}.
38448 The @var{cond_list} parameter is comprised of a series of expressions,
38449 concatenated without separators. Each expression has the following form:
38453 @item X @var{len},@var{expr}
38454 @var{len} is the length of the bytecode expression and @var{expr} is the
38455 actual conditional expression in bytecode form.
38459 The optional @var{cmd_list} parameter introduces commands that may be
38460 run on the target, rather than being reported back to @value{GDBN}.
38461 The parameter starts with a numeric flag @var{persist}; if the flag is
38462 nonzero, then the breakpoint may remain active and the commands
38463 continue to be run even when @value{GDBN} disconnects from the target.
38464 Following this flag is a series of expressions concatenated with no
38465 separators. Each expression has the following form:
38469 @item X @var{len},@var{expr}
38470 @var{len} is the length of the bytecode expression and @var{expr} is the
38471 actual conditional expression in bytecode form.
38475 see @ref{Architecture-Specific Protocol Details}.
38477 @emph{Implementation note: It is possible for a target to copy or move
38478 code that contains memory breakpoints (e.g., when implementing
38479 overlays). The behavior of this packet, in the presence of such a
38480 target, is not defined.}
38492 @item z1,@var{addr},@var{kind}
38493 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38494 @cindex @samp{z1} packet
38495 @cindex @samp{Z1} packet
38496 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38497 address @var{addr}.
38499 A hardware breakpoint is implemented using a mechanism that is not
38500 dependant on being able to modify the target's memory. @var{kind}
38501 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38503 @emph{Implementation note: A hardware breakpoint is not affected by code
38516 @item z2,@var{addr},@var{kind}
38517 @itemx Z2,@var{addr},@var{kind}
38518 @cindex @samp{z2} packet
38519 @cindex @samp{Z2} packet
38520 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38521 @var{kind} is interpreted as the number of bytes to watch.
38533 @item z3,@var{addr},@var{kind}
38534 @itemx Z3,@var{addr},@var{kind}
38535 @cindex @samp{z3} packet
38536 @cindex @samp{Z3} packet
38537 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38538 @var{kind} is interpreted as the number of bytes to watch.
38550 @item z4,@var{addr},@var{kind}
38551 @itemx Z4,@var{addr},@var{kind}
38552 @cindex @samp{z4} packet
38553 @cindex @samp{Z4} packet
38554 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38555 @var{kind} is interpreted as the number of bytes to watch.
38569 @node Stop Reply Packets
38570 @section Stop Reply Packets
38571 @cindex stop reply packets
38573 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38574 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38575 receive any of the below as a reply. Except for @samp{?}
38576 and @samp{vStopped}, that reply is only returned
38577 when the target halts. In the below the exact meaning of @dfn{signal
38578 number} is defined by the header @file{include/gdb/signals.h} in the
38579 @value{GDBN} source code.
38581 As in the description of request packets, we include spaces in the
38582 reply templates for clarity; these are not part of the reply packet's
38583 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38589 The program received signal number @var{AA} (a two-digit hexadecimal
38590 number). This is equivalent to a @samp{T} response with no
38591 @var{n}:@var{r} pairs.
38593 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38594 @cindex @samp{T} packet reply
38595 The program received signal number @var{AA} (a two-digit hexadecimal
38596 number). This is equivalent to an @samp{S} response, except that the
38597 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38598 and other information directly in the stop reply packet, reducing
38599 round-trip latency. Single-step and breakpoint traps are reported
38600 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38604 If @var{n} is a hexadecimal number, it is a register number, and the
38605 corresponding @var{r} gives that register's value. @var{r} is a
38606 series of bytes in target byte order, with each byte given by a
38607 two-digit hex number.
38610 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38611 the stopped thread, as specified in @ref{thread-id syntax}.
38614 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38615 the core on which the stop event was detected.
38618 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38619 specific event that stopped the target. The currently defined stop
38620 reasons are listed below. @var{aa} should be @samp{05}, the trap
38621 signal. At most one stop reason should be present.
38624 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38625 and go on to the next; this allows us to extend the protocol in the
38629 The currently defined stop reasons are:
38635 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38638 @cindex shared library events, remote reply
38640 The packet indicates that the loaded libraries have changed.
38641 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38642 list of loaded libraries. @var{r} is ignored.
38644 @cindex replay log events, remote reply
38646 The packet indicates that the target cannot continue replaying
38647 logged execution events, because it has reached the end (or the
38648 beginning when executing backward) of the log. The value of @var{r}
38649 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38650 for more information.
38654 @itemx W @var{AA} ; process:@var{pid}
38655 The process exited, and @var{AA} is the exit status. This is only
38656 applicable to certain targets.
38658 The second form of the response, including the process ID of the exited
38659 process, can be used only when @value{GDBN} has reported support for
38660 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38661 The @var{pid} is formatted as a big-endian hex string.
38664 @itemx X @var{AA} ; process:@var{pid}
38665 The process terminated with signal @var{AA}.
38667 The second form of the response, including the process ID of the
38668 terminated process, can be used only when @value{GDBN} has reported
38669 support for multiprocess protocol extensions; see @ref{multiprocess
38670 extensions}. The @var{pid} is formatted as a big-endian hex string.
38672 @item O @var{XX}@dots{}
38673 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38674 written as the program's console output. This can happen at any time
38675 while the program is running and the debugger should continue to wait
38676 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38678 @item F @var{call-id},@var{parameter}@dots{}
38679 @var{call-id} is the identifier which says which host system call should
38680 be called. This is just the name of the function. Translation into the
38681 correct system call is only applicable as it's defined in @value{GDBN}.
38682 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38685 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38686 this very system call.
38688 The target replies with this packet when it expects @value{GDBN} to
38689 call a host system call on behalf of the target. @value{GDBN} replies
38690 with an appropriate @samp{F} packet and keeps up waiting for the next
38691 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38692 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38693 Protocol Extension}, for more details.
38697 @node General Query Packets
38698 @section General Query Packets
38699 @cindex remote query requests
38701 Packets starting with @samp{q} are @dfn{general query packets};
38702 packets starting with @samp{Q} are @dfn{general set packets}. General
38703 query and set packets are a semi-unified form for retrieving and
38704 sending information to and from the stub.
38706 The initial letter of a query or set packet is followed by a name
38707 indicating what sort of thing the packet applies to. For example,
38708 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38709 definitions with the stub. These packet names follow some
38714 The name must not contain commas, colons or semicolons.
38716 Most @value{GDBN} query and set packets have a leading upper case
38719 The names of custom vendor packets should use a company prefix, in
38720 lower case, followed by a period. For example, packets designed at
38721 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38722 foos) or @samp{Qacme.bar} (for setting bars).
38725 The name of a query or set packet should be separated from any
38726 parameters by a @samp{:}; the parameters themselves should be
38727 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38728 full packet name, and check for a separator or the end of the packet,
38729 in case two packet names share a common prefix. New packets should not begin
38730 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38731 packets predate these conventions, and have arguments without any terminator
38732 for the packet name; we suspect they are in widespread use in places that
38733 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38734 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38737 Like the descriptions of the other packets, each description here
38738 has a template showing the packet's overall syntax, followed by an
38739 explanation of the packet's meaning. We include spaces in some of the
38740 templates for clarity; these are not part of the packet's syntax. No
38741 @value{GDBN} packet uses spaces to separate its components.
38743 Here are the currently defined query and set packets:
38749 Turn on or off the agent as a helper to perform some debugging operations
38750 delegated from @value{GDBN} (@pxref{Control Agent}).
38752 @item QAllow:@var{op}:@var{val}@dots{}
38753 @cindex @samp{QAllow} packet
38754 Specify which operations @value{GDBN} expects to request of the
38755 target, as a semicolon-separated list of operation name and value
38756 pairs. Possible values for @var{op} include @samp{WriteReg},
38757 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38758 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38759 indicating that @value{GDBN} will not request the operation, or 1,
38760 indicating that it may. (The target can then use this to set up its
38761 own internals optimally, for instance if the debugger never expects to
38762 insert breakpoints, it may not need to install its own trap handler.)
38765 @cindex current thread, remote request
38766 @cindex @samp{qC} packet
38767 Return the current thread ID.
38771 @item QC @var{thread-id}
38772 Where @var{thread-id} is a thread ID as documented in
38773 @ref{thread-id syntax}.
38774 @item @r{(anything else)}
38775 Any other reply implies the old thread ID.
38778 @item qCRC:@var{addr},@var{length}
38779 @cindex CRC of memory block, remote request
38780 @cindex @samp{qCRC} packet
38781 Compute the CRC checksum of a block of memory using CRC-32 defined in
38782 IEEE 802.3. The CRC is computed byte at a time, taking the most
38783 significant bit of each byte first. The initial pattern code
38784 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38786 @emph{Note:} This is the same CRC used in validating separate debug
38787 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38788 Files}). However the algorithm is slightly different. When validating
38789 separate debug files, the CRC is computed taking the @emph{least}
38790 significant bit of each byte first, and the final result is inverted to
38791 detect trailing zeros.
38796 An error (such as memory fault)
38797 @item C @var{crc32}
38798 The specified memory region's checksum is @var{crc32}.
38801 @item QDisableRandomization:@var{value}
38802 @cindex disable address space randomization, remote request
38803 @cindex @samp{QDisableRandomization} packet
38804 Some target operating systems will randomize the virtual address space
38805 of the inferior process as a security feature, but provide a feature
38806 to disable such randomization, e.g.@: to allow for a more deterministic
38807 debugging experience. On such systems, this packet with a @var{value}
38808 of 1 directs the target to disable address space randomization for
38809 processes subsequently started via @samp{vRun} packets, while a packet
38810 with a @var{value} of 0 tells the target to enable address space
38813 This packet is only available in extended mode (@pxref{extended mode}).
38818 The request succeeded.
38821 An error occurred. @var{nn} are hex digits.
38824 An empty reply indicates that @samp{QDisableRandomization} is not supported
38828 This packet is not probed by default; the remote stub must request it,
38829 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38830 This should only be done on targets that actually support disabling
38831 address space randomization.
38834 @itemx qsThreadInfo
38835 @cindex list active threads, remote request
38836 @cindex @samp{qfThreadInfo} packet
38837 @cindex @samp{qsThreadInfo} packet
38838 Obtain a list of all active thread IDs from the target (OS). Since there
38839 may be too many active threads to fit into one reply packet, this query
38840 works iteratively: it may require more than one query/reply sequence to
38841 obtain the entire list of threads. The first query of the sequence will
38842 be the @samp{qfThreadInfo} query; subsequent queries in the
38843 sequence will be the @samp{qsThreadInfo} query.
38845 NOTE: This packet replaces the @samp{qL} query (see below).
38849 @item m @var{thread-id}
38851 @item m @var{thread-id},@var{thread-id}@dots{}
38852 a comma-separated list of thread IDs
38854 (lower case letter @samp{L}) denotes end of list.
38857 In response to each query, the target will reply with a list of one or
38858 more thread IDs, separated by commas.
38859 @value{GDBN} will respond to each reply with a request for more thread
38860 ids (using the @samp{qs} form of the query), until the target responds
38861 with @samp{l} (lower-case ell, for @dfn{last}).
38862 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38865 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38866 @cindex get thread-local storage address, remote request
38867 @cindex @samp{qGetTLSAddr} packet
38868 Fetch the address associated with thread local storage specified
38869 by @var{thread-id}, @var{offset}, and @var{lm}.
38871 @var{thread-id} is the thread ID associated with the
38872 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38874 @var{offset} is the (big endian, hex encoded) offset associated with the
38875 thread local variable. (This offset is obtained from the debug
38876 information associated with the variable.)
38878 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38879 load module associated with the thread local storage. For example,
38880 a @sc{gnu}/Linux system will pass the link map address of the shared
38881 object associated with the thread local storage under consideration.
38882 Other operating environments may choose to represent the load module
38883 differently, so the precise meaning of this parameter will vary.
38887 @item @var{XX}@dots{}
38888 Hex encoded (big endian) bytes representing the address of the thread
38889 local storage requested.
38892 An error occurred. @var{nn} are hex digits.
38895 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38898 @item qGetTIBAddr:@var{thread-id}
38899 @cindex get thread information block address
38900 @cindex @samp{qGetTIBAddr} packet
38901 Fetch address of the Windows OS specific Thread Information Block.
38903 @var{thread-id} is the thread ID associated with the thread.
38907 @item @var{XX}@dots{}
38908 Hex encoded (big endian) bytes representing the linear address of the
38909 thread information block.
38912 An error occured. This means that either the thread was not found, or the
38913 address could not be retrieved.
38916 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38919 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38920 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38921 digit) is one to indicate the first query and zero to indicate a
38922 subsequent query; @var{threadcount} (two hex digits) is the maximum
38923 number of threads the response packet can contain; and @var{nextthread}
38924 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38925 returned in the response as @var{argthread}.
38927 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38931 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38932 Where: @var{count} (two hex digits) is the number of threads being
38933 returned; @var{done} (one hex digit) is zero to indicate more threads
38934 and one indicates no further threads; @var{argthreadid} (eight hex
38935 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38936 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38937 digits). See @code{remote.c:parse_threadlist_response()}.
38941 @cindex section offsets, remote request
38942 @cindex @samp{qOffsets} packet
38943 Get section offsets that the target used when relocating the downloaded
38948 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38949 Relocate the @code{Text} section by @var{xxx} from its original address.
38950 Relocate the @code{Data} section by @var{yyy} from its original address.
38951 If the object file format provides segment information (e.g.@: @sc{elf}
38952 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38953 segments by the supplied offsets.
38955 @emph{Note: while a @code{Bss} offset may be included in the response,
38956 @value{GDBN} ignores this and instead applies the @code{Data} offset
38957 to the @code{Bss} section.}
38959 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38960 Relocate the first segment of the object file, which conventionally
38961 contains program code, to a starting address of @var{xxx}. If
38962 @samp{DataSeg} is specified, relocate the second segment, which
38963 conventionally contains modifiable data, to a starting address of
38964 @var{yyy}. @value{GDBN} will report an error if the object file
38965 does not contain segment information, or does not contain at least
38966 as many segments as mentioned in the reply. Extra segments are
38967 kept at fixed offsets relative to the last relocated segment.
38970 @item qP @var{mode} @var{thread-id}
38971 @cindex thread information, remote request
38972 @cindex @samp{qP} packet
38973 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38974 encoded 32 bit mode; @var{thread-id} is a thread ID
38975 (@pxref{thread-id syntax}).
38977 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38980 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38984 @cindex non-stop mode, remote request
38985 @cindex @samp{QNonStop} packet
38987 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38988 @xref{Remote Non-Stop}, for more information.
38993 The request succeeded.
38996 An error occurred. @var{nn} are hex digits.
38999 An empty reply indicates that @samp{QNonStop} is not supported by
39003 This packet is not probed by default; the remote stub must request it,
39004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39005 Use of this packet is controlled by the @code{set non-stop} command;
39006 @pxref{Non-Stop Mode}.
39008 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39009 @cindex pass signals to inferior, remote request
39010 @cindex @samp{QPassSignals} packet
39011 @anchor{QPassSignals}
39012 Each listed @var{signal} should be passed directly to the inferior process.
39013 Signals are numbered identically to continue packets and stop replies
39014 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39015 strictly greater than the previous item. These signals do not need to stop
39016 the inferior, or be reported to @value{GDBN}. All other signals should be
39017 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39018 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39019 new list. This packet improves performance when using @samp{handle
39020 @var{signal} nostop noprint pass}.
39025 The request succeeded.
39028 An error occurred. @var{nn} are hex digits.
39031 An empty reply indicates that @samp{QPassSignals} is not supported by
39035 Use of this packet is controlled by the @code{set remote pass-signals}
39036 command (@pxref{Remote Configuration, set remote pass-signals}).
39037 This packet is not probed by default; the remote stub must request it,
39038 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39040 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39041 @cindex signals the inferior may see, remote request
39042 @cindex @samp{QProgramSignals} packet
39043 @anchor{QProgramSignals}
39044 Each listed @var{signal} may be delivered to the inferior process.
39045 Others should be silently discarded.
39047 In some cases, the remote stub may need to decide whether to deliver a
39048 signal to the program or not without @value{GDBN} involvement. One
39049 example of that is while detaching --- the program's threads may have
39050 stopped for signals that haven't yet had a chance of being reported to
39051 @value{GDBN}, and so the remote stub can use the signal list specified
39052 by this packet to know whether to deliver or ignore those pending
39055 This does not influence whether to deliver a signal as requested by a
39056 resumption packet (@pxref{vCont packet}).
39058 Signals are numbered identically to continue packets and stop replies
39059 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39060 strictly greater than the previous item. Multiple
39061 @samp{QProgramSignals} packets do not combine; any earlier
39062 @samp{QProgramSignals} list is completely replaced by the new list.
39067 The request succeeded.
39070 An error occurred. @var{nn} are hex digits.
39073 An empty reply indicates that @samp{QProgramSignals} is not supported
39077 Use of this packet is controlled by the @code{set remote program-signals}
39078 command (@pxref{Remote Configuration, set remote program-signals}).
39079 This packet is not probed by default; the remote stub must request it,
39080 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39082 @item qRcmd,@var{command}
39083 @cindex execute remote command, remote request
39084 @cindex @samp{qRcmd} packet
39085 @var{command} (hex encoded) is passed to the local interpreter for
39086 execution. Invalid commands should be reported using the output
39087 string. Before the final result packet, the target may also respond
39088 with a number of intermediate @samp{O@var{output}} console output
39089 packets. @emph{Implementors should note that providing access to a
39090 stubs's interpreter may have security implications}.
39095 A command response with no output.
39097 A command response with the hex encoded output string @var{OUTPUT}.
39099 Indicate a badly formed request.
39101 An empty reply indicates that @samp{qRcmd} is not recognized.
39104 (Note that the @code{qRcmd} packet's name is separated from the
39105 command by a @samp{,}, not a @samp{:}, contrary to the naming
39106 conventions above. Please don't use this packet as a model for new
39109 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39110 @cindex searching memory, in remote debugging
39112 @cindex @samp{qSearch:memory} packet
39114 @cindex @samp{qSearch memory} packet
39115 @anchor{qSearch memory}
39116 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39117 @var{address} and @var{length} are encoded in hex.
39118 @var{search-pattern} is a sequence of bytes, hex encoded.
39123 The pattern was not found.
39125 The pattern was found at @var{address}.
39127 A badly formed request or an error was encountered while searching memory.
39129 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39132 @item QStartNoAckMode
39133 @cindex @samp{QStartNoAckMode} packet
39134 @anchor{QStartNoAckMode}
39135 Request that the remote stub disable the normal @samp{+}/@samp{-}
39136 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39141 The stub has switched to no-acknowledgment mode.
39142 @value{GDBN} acknowledges this reponse,
39143 but neither the stub nor @value{GDBN} shall send or expect further
39144 @samp{+}/@samp{-} acknowledgments in the current connection.
39146 An empty reply indicates that the stub does not support no-acknowledgment mode.
39149 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39150 @cindex supported packets, remote query
39151 @cindex features of the remote protocol
39152 @cindex @samp{qSupported} packet
39153 @anchor{qSupported}
39154 Tell the remote stub about features supported by @value{GDBN}, and
39155 query the stub for features it supports. This packet allows
39156 @value{GDBN} and the remote stub to take advantage of each others'
39157 features. @samp{qSupported} also consolidates multiple feature probes
39158 at startup, to improve @value{GDBN} performance---a single larger
39159 packet performs better than multiple smaller probe packets on
39160 high-latency links. Some features may enable behavior which must not
39161 be on by default, e.g.@: because it would confuse older clients or
39162 stubs. Other features may describe packets which could be
39163 automatically probed for, but are not. These features must be
39164 reported before @value{GDBN} will use them. This ``default
39165 unsupported'' behavior is not appropriate for all packets, but it
39166 helps to keep the initial connection time under control with new
39167 versions of @value{GDBN} which support increasing numbers of packets.
39171 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39172 The stub supports or does not support each returned @var{stubfeature},
39173 depending on the form of each @var{stubfeature} (see below for the
39176 An empty reply indicates that @samp{qSupported} is not recognized,
39177 or that no features needed to be reported to @value{GDBN}.
39180 The allowed forms for each feature (either a @var{gdbfeature} in the
39181 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39185 @item @var{name}=@var{value}
39186 The remote protocol feature @var{name} is supported, and associated
39187 with the specified @var{value}. The format of @var{value} depends
39188 on the feature, but it must not include a semicolon.
39190 The remote protocol feature @var{name} is supported, and does not
39191 need an associated value.
39193 The remote protocol feature @var{name} is not supported.
39195 The remote protocol feature @var{name} may be supported, and
39196 @value{GDBN} should auto-detect support in some other way when it is
39197 needed. This form will not be used for @var{gdbfeature} notifications,
39198 but may be used for @var{stubfeature} responses.
39201 Whenever the stub receives a @samp{qSupported} request, the
39202 supplied set of @value{GDBN} features should override any previous
39203 request. This allows @value{GDBN} to put the stub in a known
39204 state, even if the stub had previously been communicating with
39205 a different version of @value{GDBN}.
39207 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39212 This feature indicates whether @value{GDBN} supports multiprocess
39213 extensions to the remote protocol. @value{GDBN} does not use such
39214 extensions unless the stub also reports that it supports them by
39215 including @samp{multiprocess+} in its @samp{qSupported} reply.
39216 @xref{multiprocess extensions}, for details.
39219 This feature indicates that @value{GDBN} supports the XML target
39220 description. If the stub sees @samp{xmlRegisters=} with target
39221 specific strings separated by a comma, it will report register
39225 This feature indicates whether @value{GDBN} supports the
39226 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39227 instruction reply packet}).
39230 Stubs should ignore any unknown values for
39231 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39232 packet supports receiving packets of unlimited length (earlier
39233 versions of @value{GDBN} may reject overly long responses). Additional values
39234 for @var{gdbfeature} may be defined in the future to let the stub take
39235 advantage of new features in @value{GDBN}, e.g.@: incompatible
39236 improvements in the remote protocol---the @samp{multiprocess} feature is
39237 an example of such a feature. The stub's reply should be independent
39238 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39239 describes all the features it supports, and then the stub replies with
39240 all the features it supports.
39242 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39243 responses, as long as each response uses one of the standard forms.
39245 Some features are flags. A stub which supports a flag feature
39246 should respond with a @samp{+} form response. Other features
39247 require values, and the stub should respond with an @samp{=}
39250 Each feature has a default value, which @value{GDBN} will use if
39251 @samp{qSupported} is not available or if the feature is not mentioned
39252 in the @samp{qSupported} response. The default values are fixed; a
39253 stub is free to omit any feature responses that match the defaults.
39255 Not all features can be probed, but for those which can, the probing
39256 mechanism is useful: in some cases, a stub's internal
39257 architecture may not allow the protocol layer to know some information
39258 about the underlying target in advance. This is especially common in
39259 stubs which may be configured for multiple targets.
39261 These are the currently defined stub features and their properties:
39263 @multitable @columnfractions 0.35 0.2 0.12 0.2
39264 @c NOTE: The first row should be @headitem, but we do not yet require
39265 @c a new enough version of Texinfo (4.7) to use @headitem.
39267 @tab Value Required
39271 @item @samp{PacketSize}
39276 @item @samp{qXfer:auxv:read}
39281 @item @samp{qXfer:btrace:read}
39286 @item @samp{qXfer:features:read}
39291 @item @samp{qXfer:libraries:read}
39296 @item @samp{qXfer:libraries-svr4:read}
39301 @item @samp{augmented-libraries-svr4-read}
39306 @item @samp{qXfer:memory-map:read}
39311 @item @samp{qXfer:sdata:read}
39316 @item @samp{qXfer:spu:read}
39321 @item @samp{qXfer:spu:write}
39326 @item @samp{qXfer:siginfo:read}
39331 @item @samp{qXfer:siginfo:write}
39336 @item @samp{qXfer:threads:read}
39341 @item @samp{qXfer:traceframe-info:read}
39346 @item @samp{qXfer:uib:read}
39351 @item @samp{qXfer:fdpic:read}
39356 @item @samp{Qbtrace:off}
39361 @item @samp{Qbtrace:bts}
39366 @item @samp{QNonStop}
39371 @item @samp{QPassSignals}
39376 @item @samp{QStartNoAckMode}
39381 @item @samp{multiprocess}
39386 @item @samp{ConditionalBreakpoints}
39391 @item @samp{ConditionalTracepoints}
39396 @item @samp{ReverseContinue}
39401 @item @samp{ReverseStep}
39406 @item @samp{TracepointSource}
39411 @item @samp{QAgent}
39416 @item @samp{QAllow}
39421 @item @samp{QDisableRandomization}
39426 @item @samp{EnableDisableTracepoints}
39431 @item @samp{QTBuffer:size}
39436 @item @samp{tracenz}
39441 @item @samp{BreakpointCommands}
39448 These are the currently defined stub features, in more detail:
39451 @cindex packet size, remote protocol
39452 @item PacketSize=@var{bytes}
39453 The remote stub can accept packets up to at least @var{bytes} in
39454 length. @value{GDBN} will send packets up to this size for bulk
39455 transfers, and will never send larger packets. This is a limit on the
39456 data characters in the packet, including the frame and checksum.
39457 There is no trailing NUL byte in a remote protocol packet; if the stub
39458 stores packets in a NUL-terminated format, it should allow an extra
39459 byte in its buffer for the NUL. If this stub feature is not supported,
39460 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39462 @item qXfer:auxv:read
39463 The remote stub understands the @samp{qXfer:auxv:read} packet
39464 (@pxref{qXfer auxiliary vector read}).
39466 @item qXfer:btrace:read
39467 The remote stub understands the @samp{qXfer:btrace:read}
39468 packet (@pxref{qXfer btrace read}).
39470 @item qXfer:features:read
39471 The remote stub understands the @samp{qXfer:features:read} packet
39472 (@pxref{qXfer target description read}).
39474 @item qXfer:libraries:read
39475 The remote stub understands the @samp{qXfer:libraries:read} packet
39476 (@pxref{qXfer library list read}).
39478 @item qXfer:libraries-svr4:read
39479 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39480 (@pxref{qXfer svr4 library list read}).
39482 @item augmented-libraries-svr4-read
39483 The remote stub understands the augmented form of the
39484 @samp{qXfer:libraries-svr4:read} packet
39485 (@pxref{qXfer svr4 library list read}).
39487 @item qXfer:memory-map:read
39488 The remote stub understands the @samp{qXfer:memory-map:read} packet
39489 (@pxref{qXfer memory map read}).
39491 @item qXfer:sdata:read
39492 The remote stub understands the @samp{qXfer:sdata:read} packet
39493 (@pxref{qXfer sdata read}).
39495 @item qXfer:spu:read
39496 The remote stub understands the @samp{qXfer:spu:read} packet
39497 (@pxref{qXfer spu read}).
39499 @item qXfer:spu:write
39500 The remote stub understands the @samp{qXfer:spu:write} packet
39501 (@pxref{qXfer spu write}).
39503 @item qXfer:siginfo:read
39504 The remote stub understands the @samp{qXfer:siginfo:read} packet
39505 (@pxref{qXfer siginfo read}).
39507 @item qXfer:siginfo:write
39508 The remote stub understands the @samp{qXfer:siginfo:write} packet
39509 (@pxref{qXfer siginfo write}).
39511 @item qXfer:threads:read
39512 The remote stub understands the @samp{qXfer:threads:read} packet
39513 (@pxref{qXfer threads read}).
39515 @item qXfer:traceframe-info:read
39516 The remote stub understands the @samp{qXfer:traceframe-info:read}
39517 packet (@pxref{qXfer traceframe info read}).
39519 @item qXfer:uib:read
39520 The remote stub understands the @samp{qXfer:uib:read}
39521 packet (@pxref{qXfer unwind info block}).
39523 @item qXfer:fdpic:read
39524 The remote stub understands the @samp{qXfer:fdpic:read}
39525 packet (@pxref{qXfer fdpic loadmap read}).
39528 The remote stub understands the @samp{QNonStop} packet
39529 (@pxref{QNonStop}).
39532 The remote stub understands the @samp{QPassSignals} packet
39533 (@pxref{QPassSignals}).
39535 @item QStartNoAckMode
39536 The remote stub understands the @samp{QStartNoAckMode} packet and
39537 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39540 @anchor{multiprocess extensions}
39541 @cindex multiprocess extensions, in remote protocol
39542 The remote stub understands the multiprocess extensions to the remote
39543 protocol syntax. The multiprocess extensions affect the syntax of
39544 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39545 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39546 replies. Note that reporting this feature indicates support for the
39547 syntactic extensions only, not that the stub necessarily supports
39548 debugging of more than one process at a time. The stub must not use
39549 multiprocess extensions in packet replies unless @value{GDBN} has also
39550 indicated it supports them in its @samp{qSupported} request.
39552 @item qXfer:osdata:read
39553 The remote stub understands the @samp{qXfer:osdata:read} packet
39554 ((@pxref{qXfer osdata read}).
39556 @item ConditionalBreakpoints
39557 The target accepts and implements evaluation of conditional expressions
39558 defined for breakpoints. The target will only report breakpoint triggers
39559 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39561 @item ConditionalTracepoints
39562 The remote stub accepts and implements conditional expressions defined
39563 for tracepoints (@pxref{Tracepoint Conditions}).
39565 @item ReverseContinue
39566 The remote stub accepts and implements the reverse continue packet
39570 The remote stub accepts and implements the reverse step packet
39573 @item TracepointSource
39574 The remote stub understands the @samp{QTDPsrc} packet that supplies
39575 the source form of tracepoint definitions.
39578 The remote stub understands the @samp{QAgent} packet.
39581 The remote stub understands the @samp{QAllow} packet.
39583 @item QDisableRandomization
39584 The remote stub understands the @samp{QDisableRandomization} packet.
39586 @item StaticTracepoint
39587 @cindex static tracepoints, in remote protocol
39588 The remote stub supports static tracepoints.
39590 @item InstallInTrace
39591 @anchor{install tracepoint in tracing}
39592 The remote stub supports installing tracepoint in tracing.
39594 @item EnableDisableTracepoints
39595 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39596 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39597 to be enabled and disabled while a trace experiment is running.
39599 @item QTBuffer:size
39600 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39601 packet that allows to change the size of the trace buffer.
39604 @cindex string tracing, in remote protocol
39605 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39606 See @ref{Bytecode Descriptions} for details about the bytecode.
39608 @item BreakpointCommands
39609 @cindex breakpoint commands, in remote protocol
39610 The remote stub supports running a breakpoint's command list itself,
39611 rather than reporting the hit to @value{GDBN}.
39614 The remote stub understands the @samp{Qbtrace:off} packet.
39617 The remote stub understands the @samp{Qbtrace:bts} packet.
39622 @cindex symbol lookup, remote request
39623 @cindex @samp{qSymbol} packet
39624 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39625 requests. Accept requests from the target for the values of symbols.
39630 The target does not need to look up any (more) symbols.
39631 @item qSymbol:@var{sym_name}
39632 The target requests the value of symbol @var{sym_name} (hex encoded).
39633 @value{GDBN} may provide the value by using the
39634 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39638 @item qSymbol:@var{sym_value}:@var{sym_name}
39639 Set the value of @var{sym_name} to @var{sym_value}.
39641 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39642 target has previously requested.
39644 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39645 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39651 The target does not need to look up any (more) symbols.
39652 @item qSymbol:@var{sym_name}
39653 The target requests the value of a new symbol @var{sym_name} (hex
39654 encoded). @value{GDBN} will continue to supply the values of symbols
39655 (if available), until the target ceases to request them.
39660 @itemx QTDisconnected
39667 @itemx qTMinFTPILen
39669 @xref{Tracepoint Packets}.
39671 @item qThreadExtraInfo,@var{thread-id}
39672 @cindex thread attributes info, remote request
39673 @cindex @samp{qThreadExtraInfo} packet
39674 Obtain a printable string description of a thread's attributes from
39675 the target OS. @var{thread-id} is a thread ID;
39676 see @ref{thread-id syntax}. This
39677 string may contain anything that the target OS thinks is interesting
39678 for @value{GDBN} to tell the user about the thread. The string is
39679 displayed in @value{GDBN}'s @code{info threads} display. Some
39680 examples of possible thread extra info strings are @samp{Runnable}, or
39681 @samp{Blocked on Mutex}.
39685 @item @var{XX}@dots{}
39686 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39687 comprising the printable string containing the extra information about
39688 the thread's attributes.
39691 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39692 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39693 conventions above. Please don't use this packet as a model for new
39712 @xref{Tracepoint Packets}.
39714 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39715 @cindex read special object, remote request
39716 @cindex @samp{qXfer} packet
39717 @anchor{qXfer read}
39718 Read uninterpreted bytes from the target's special data area
39719 identified by the keyword @var{object}. Request @var{length} bytes
39720 starting at @var{offset} bytes into the data. The content and
39721 encoding of @var{annex} is specific to @var{object}; it can supply
39722 additional details about what data to access.
39724 Here are the specific requests of this form defined so far. All
39725 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39726 formats, listed below.
39729 @item qXfer:auxv:read::@var{offset},@var{length}
39730 @anchor{qXfer auxiliary vector read}
39731 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39732 auxiliary vector}. Note @var{annex} must be empty.
39734 This packet is not probed by default; the remote stub must request it,
39735 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39737 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39738 @anchor{qXfer btrace read}
39740 Return a description of the current branch trace.
39741 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39742 packet may have one of the following values:
39746 Returns all available branch trace.
39749 Returns all available branch trace if the branch trace changed since
39750 the last read request.
39753 This packet is not probed by default; the remote stub must request it
39754 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39756 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39757 @anchor{qXfer target description read}
39758 Access the @dfn{target description}. @xref{Target Descriptions}. The
39759 annex specifies which XML document to access. The main description is
39760 always loaded from the @samp{target.xml} annex.
39762 This packet is not probed by default; the remote stub must request it,
39763 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39765 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39766 @anchor{qXfer library list read}
39767 Access the target's list of loaded libraries. @xref{Library List Format}.
39768 The annex part of the generic @samp{qXfer} packet must be empty
39769 (@pxref{qXfer read}).
39771 Targets which maintain a list of libraries in the program's memory do
39772 not need to implement this packet; it is designed for platforms where
39773 the operating system manages the list of loaded libraries.
39775 This packet is not probed by default; the remote stub must request it,
39776 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39778 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39779 @anchor{qXfer svr4 library list read}
39780 Access the target's list of loaded libraries when the target is an SVR4
39781 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39782 of the generic @samp{qXfer} packet must be empty unless the remote
39783 stub indicated it supports the augmented form of this packet
39784 by supplying an appropriate @samp{qSupported} response
39785 (@pxref{qXfer read}, @ref{qSupported}).
39787 This packet is optional for better performance on SVR4 targets.
39788 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39790 This packet is not probed by default; the remote stub must request it,
39791 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39793 If the remote stub indicates it supports the augmented form of this
39794 packet then the annex part of the generic @samp{qXfer} packet may
39795 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39796 arguments. The currently supported arguments are:
39799 @item start=@var{address}
39800 A hexadecimal number specifying the address of the @samp{struct
39801 link_map} to start reading the library list from. If unset or zero
39802 then the first @samp{struct link_map} in the library list will be
39803 chosen as the starting point.
39805 @item prev=@var{address}
39806 A hexadecimal number specifying the address of the @samp{struct
39807 link_map} immediately preceding the @samp{struct link_map}
39808 specified by the @samp{start} argument. If unset or zero then
39809 the remote stub will expect that no @samp{struct link_map}
39810 exists prior to the starting point.
39814 Arguments that are not understood by the remote stub will be silently
39817 @item qXfer:memory-map:read::@var{offset},@var{length}
39818 @anchor{qXfer memory map read}
39819 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39820 annex part of the generic @samp{qXfer} packet must be empty
39821 (@pxref{qXfer read}).
39823 This packet is not probed by default; the remote stub must request it,
39824 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39826 @item qXfer:sdata:read::@var{offset},@var{length}
39827 @anchor{qXfer sdata read}
39829 Read contents of the extra collected static tracepoint marker
39830 information. The annex part of the generic @samp{qXfer} packet must
39831 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39834 This packet is not probed by default; the remote stub must request it,
39835 by supplying an appropriate @samp{qSupported} response
39836 (@pxref{qSupported}).
39838 @item qXfer:siginfo:read::@var{offset},@var{length}
39839 @anchor{qXfer siginfo read}
39840 Read contents of the extra signal information on the target
39841 system. The annex part of the generic @samp{qXfer} packet must be
39842 empty (@pxref{qXfer read}).
39844 This packet is not probed by default; the remote stub must request it,
39845 by supplying an appropriate @samp{qSupported} response
39846 (@pxref{qSupported}).
39848 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39849 @anchor{qXfer spu read}
39850 Read contents of an @code{spufs} file on the target system. The
39851 annex specifies which file to read; it must be of the form
39852 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39853 in the target process, and @var{name} identifes the @code{spufs} file
39854 in that context to be accessed.
39856 This packet is not probed by default; the remote stub must request it,
39857 by supplying an appropriate @samp{qSupported} response
39858 (@pxref{qSupported}).
39860 @item qXfer:threads:read::@var{offset},@var{length}
39861 @anchor{qXfer threads read}
39862 Access the list of threads on target. @xref{Thread List Format}. The
39863 annex part of the generic @samp{qXfer} packet must be empty
39864 (@pxref{qXfer read}).
39866 This packet is not probed by default; the remote stub must request it,
39867 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39869 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39870 @anchor{qXfer traceframe info read}
39872 Return a description of the current traceframe's contents.
39873 @xref{Traceframe Info Format}. The annex part of the generic
39874 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39876 This packet is not probed by default; the remote stub must request it,
39877 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39879 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39880 @anchor{qXfer unwind info block}
39882 Return the unwind information block for @var{pc}. This packet is used
39883 on OpenVMS/ia64 to ask the kernel unwind information.
39885 This packet is not probed by default.
39887 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39888 @anchor{qXfer fdpic loadmap read}
39889 Read contents of @code{loadmap}s on the target system. The
39890 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39891 executable @code{loadmap} or interpreter @code{loadmap} to read.
39893 This packet is not probed by default; the remote stub must request it,
39894 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39896 @item qXfer:osdata:read::@var{offset},@var{length}
39897 @anchor{qXfer osdata read}
39898 Access the target's @dfn{operating system information}.
39899 @xref{Operating System Information}.
39906 Data @var{data} (@pxref{Binary Data}) has been read from the
39907 target. There may be more data at a higher address (although
39908 it is permitted to return @samp{m} even for the last valid
39909 block of data, as long as at least one byte of data was read).
39910 @var{data} may have fewer bytes than the @var{length} in the
39914 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39915 There is no more data to be read. @var{data} may have fewer bytes
39916 than the @var{length} in the request.
39919 The @var{offset} in the request is at the end of the data.
39920 There is no more data to be read.
39923 The request was malformed, or @var{annex} was invalid.
39926 The offset was invalid, or there was an error encountered reading the data.
39927 @var{nn} is a hex-encoded @code{errno} value.
39930 An empty reply indicates the @var{object} string was not recognized by
39931 the stub, or that the object does not support reading.
39934 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39935 @cindex write data into object, remote request
39936 @anchor{qXfer write}
39937 Write uninterpreted bytes into the target's special data area
39938 identified by the keyword @var{object}, starting at @var{offset} bytes
39939 into the data. @var{data}@dots{} is the binary-encoded data
39940 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39941 is specific to @var{object}; it can supply additional details about what data
39944 Here are the specific requests of this form defined so far. All
39945 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39946 formats, listed below.
39949 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39950 @anchor{qXfer siginfo write}
39951 Write @var{data} to the extra signal information on the target system.
39952 The annex part of the generic @samp{qXfer} packet must be
39953 empty (@pxref{qXfer write}).
39955 This packet is not probed by default; the remote stub must request it,
39956 by supplying an appropriate @samp{qSupported} response
39957 (@pxref{qSupported}).
39959 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39960 @anchor{qXfer spu write}
39961 Write @var{data} to an @code{spufs} file on the target system. The
39962 annex specifies which file to write; it must be of the form
39963 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39964 in the target process, and @var{name} identifes the @code{spufs} file
39965 in that context to be accessed.
39967 This packet is not probed by default; the remote stub must request it,
39968 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39974 @var{nn} (hex encoded) is the number of bytes written.
39975 This may be fewer bytes than supplied in the request.
39978 The request was malformed, or @var{annex} was invalid.
39981 The offset was invalid, or there was an error encountered writing the data.
39982 @var{nn} is a hex-encoded @code{errno} value.
39985 An empty reply indicates the @var{object} string was not
39986 recognized by the stub, or that the object does not support writing.
39989 @item qXfer:@var{object}:@var{operation}:@dots{}
39990 Requests of this form may be added in the future. When a stub does
39991 not recognize the @var{object} keyword, or its support for
39992 @var{object} does not recognize the @var{operation} keyword, the stub
39993 must respond with an empty packet.
39995 @item qAttached:@var{pid}
39996 @cindex query attached, remote request
39997 @cindex @samp{qAttached} packet
39998 Return an indication of whether the remote server attached to an
39999 existing process or created a new process. When the multiprocess
40000 protocol extensions are supported (@pxref{multiprocess extensions}),
40001 @var{pid} is an integer in hexadecimal format identifying the target
40002 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40003 the query packet will be simplified as @samp{qAttached}.
40005 This query is used, for example, to know whether the remote process
40006 should be detached or killed when a @value{GDBN} session is ended with
40007 the @code{quit} command.
40012 The remote server attached to an existing process.
40014 The remote server created a new process.
40016 A badly formed request or an error was encountered.
40020 Enable branch tracing for the current thread using bts tracing.
40025 Branch tracing has been enabled.
40027 A badly formed request or an error was encountered.
40031 Disable branch tracing for the current thread.
40036 Branch tracing has been disabled.
40038 A badly formed request or an error was encountered.
40043 @node Architecture-Specific Protocol Details
40044 @section Architecture-Specific Protocol Details
40046 This section describes how the remote protocol is applied to specific
40047 target architectures. Also see @ref{Standard Target Features}, for
40048 details of XML target descriptions for each architecture.
40051 * ARM-Specific Protocol Details::
40052 * MIPS-Specific Protocol Details::
40055 @node ARM-Specific Protocol Details
40056 @subsection @acronym{ARM}-specific Protocol Details
40059 * ARM Breakpoint Kinds::
40062 @node ARM Breakpoint Kinds
40063 @subsubsection @acronym{ARM} Breakpoint Kinds
40064 @cindex breakpoint kinds, @acronym{ARM}
40066 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40071 16-bit Thumb mode breakpoint.
40074 32-bit Thumb mode (Thumb-2) breakpoint.
40077 32-bit @acronym{ARM} mode breakpoint.
40081 @node MIPS-Specific Protocol Details
40082 @subsection @acronym{MIPS}-specific Protocol Details
40085 * MIPS Register packet Format::
40086 * MIPS Breakpoint Kinds::
40089 @node MIPS Register packet Format
40090 @subsubsection @acronym{MIPS} Register Packet Format
40091 @cindex register packet format, @acronym{MIPS}
40093 The following @code{g}/@code{G} packets have previously been defined.
40094 In the below, some thirty-two bit registers are transferred as
40095 sixty-four bits. Those registers should be zero/sign extended (which?)
40096 to fill the space allocated. Register bytes are transferred in target
40097 byte order. The two nibbles within a register byte are transferred
40098 most-significant -- least-significant.
40103 All registers are transferred as thirty-two bit quantities in the order:
40104 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40105 registers; fsr; fir; fp.
40108 All registers are transferred as sixty-four bit quantities (including
40109 thirty-two bit registers such as @code{sr}). The ordering is the same
40114 @node MIPS Breakpoint Kinds
40115 @subsubsection @acronym{MIPS} Breakpoint Kinds
40116 @cindex breakpoint kinds, @acronym{MIPS}
40118 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40123 16-bit @acronym{MIPS16} mode breakpoint.
40126 16-bit @acronym{microMIPS} mode breakpoint.
40129 32-bit standard @acronym{MIPS} mode breakpoint.
40132 32-bit @acronym{microMIPS} mode breakpoint.
40136 @node Tracepoint Packets
40137 @section Tracepoint Packets
40138 @cindex tracepoint packets
40139 @cindex packets, tracepoint
40141 Here we describe the packets @value{GDBN} uses to implement
40142 tracepoints (@pxref{Tracepoints}).
40146 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40147 @cindex @samp{QTDP} packet
40148 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40149 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40150 the tracepoint is disabled. @var{step} is the tracepoint's step
40151 count, and @var{pass} is its pass count. If an @samp{F} is present,
40152 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40153 the number of bytes that the target should copy elsewhere to make room
40154 for the tracepoint. If an @samp{X} is present, it introduces a
40155 tracepoint condition, which consists of a hexadecimal length, followed
40156 by a comma and hex-encoded bytes, in a manner similar to action
40157 encodings as described below. If the trailing @samp{-} is present,
40158 further @samp{QTDP} packets will follow to specify this tracepoint's
40164 The packet was understood and carried out.
40166 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40168 The packet was not recognized.
40171 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40172 Define actions to be taken when a tracepoint is hit. @var{n} and
40173 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40174 this tracepoint. This packet may only be sent immediately after
40175 another @samp{QTDP} packet that ended with a @samp{-}. If the
40176 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40177 specifying more actions for this tracepoint.
40179 In the series of action packets for a given tracepoint, at most one
40180 can have an @samp{S} before its first @var{action}. If such a packet
40181 is sent, it and the following packets define ``while-stepping''
40182 actions. Any prior packets define ordinary actions --- that is, those
40183 taken when the tracepoint is first hit. If no action packet has an
40184 @samp{S}, then all the packets in the series specify ordinary
40185 tracepoint actions.
40187 The @samp{@var{action}@dots{}} portion of the packet is a series of
40188 actions, concatenated without separators. Each action has one of the
40194 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40195 a hexadecimal number whose @var{i}'th bit is set if register number
40196 @var{i} should be collected. (The least significant bit is numbered
40197 zero.) Note that @var{mask} may be any number of digits long; it may
40198 not fit in a 32-bit word.
40200 @item M @var{basereg},@var{offset},@var{len}
40201 Collect @var{len} bytes of memory starting at the address in register
40202 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40203 @samp{-1}, then the range has a fixed address: @var{offset} is the
40204 address of the lowest byte to collect. The @var{basereg},
40205 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40206 values (the @samp{-1} value for @var{basereg} is a special case).
40208 @item X @var{len},@var{expr}
40209 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40210 it directs. @var{expr} is an agent expression, as described in
40211 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40212 two-digit hex number in the packet; @var{len} is the number of bytes
40213 in the expression (and thus one-half the number of hex digits in the
40218 Any number of actions may be packed together in a single @samp{QTDP}
40219 packet, as long as the packet does not exceed the maximum packet
40220 length (400 bytes, for many stubs). There may be only one @samp{R}
40221 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40222 actions. Any registers referred to by @samp{M} and @samp{X} actions
40223 must be collected by a preceding @samp{R} action. (The
40224 ``while-stepping'' actions are treated as if they were attached to a
40225 separate tracepoint, as far as these restrictions are concerned.)
40230 The packet was understood and carried out.
40232 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40234 The packet was not recognized.
40237 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40238 @cindex @samp{QTDPsrc} packet
40239 Specify a source string of tracepoint @var{n} at address @var{addr}.
40240 This is useful to get accurate reproduction of the tracepoints
40241 originally downloaded at the beginning of the trace run. @var{type}
40242 is the name of the tracepoint part, such as @samp{cond} for the
40243 tracepoint's conditional expression (see below for a list of types), while
40244 @var{bytes} is the string, encoded in hexadecimal.
40246 @var{start} is the offset of the @var{bytes} within the overall source
40247 string, while @var{slen} is the total length of the source string.
40248 This is intended for handling source strings that are longer than will
40249 fit in a single packet.
40250 @c Add detailed example when this info is moved into a dedicated
40251 @c tracepoint descriptions section.
40253 The available string types are @samp{at} for the location,
40254 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40255 @value{GDBN} sends a separate packet for each command in the action
40256 list, in the same order in which the commands are stored in the list.
40258 The target does not need to do anything with source strings except
40259 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40262 Although this packet is optional, and @value{GDBN} will only send it
40263 if the target replies with @samp{TracepointSource} @xref{General
40264 Query Packets}, it makes both disconnected tracing and trace files
40265 much easier to use. Otherwise the user must be careful that the
40266 tracepoints in effect while looking at trace frames are identical to
40267 the ones in effect during the trace run; even a small discrepancy
40268 could cause @samp{tdump} not to work, or a particular trace frame not
40271 @item QTDV:@var{n}:@var{value}
40272 @cindex define trace state variable, remote request
40273 @cindex @samp{QTDV} packet
40274 Create a new trace state variable, number @var{n}, with an initial
40275 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40276 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40277 the option of not using this packet for initial values of zero; the
40278 target should simply create the trace state variables as they are
40279 mentioned in expressions.
40281 @item QTFrame:@var{n}
40282 @cindex @samp{QTFrame} packet
40283 Select the @var{n}'th tracepoint frame from the buffer, and use the
40284 register and memory contents recorded there to answer subsequent
40285 request packets from @value{GDBN}.
40287 A successful reply from the stub indicates that the stub has found the
40288 requested frame. The response is a series of parts, concatenated
40289 without separators, describing the frame we selected. Each part has
40290 one of the following forms:
40294 The selected frame is number @var{n} in the trace frame buffer;
40295 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40296 was no frame matching the criteria in the request packet.
40299 The selected trace frame records a hit of tracepoint number @var{t};
40300 @var{t} is a hexadecimal number.
40304 @item QTFrame:pc:@var{addr}
40305 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40306 currently selected frame whose PC is @var{addr};
40307 @var{addr} is a hexadecimal number.
40309 @item QTFrame:tdp:@var{t}
40310 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40311 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40312 is a hexadecimal number.
40314 @item QTFrame:range:@var{start}:@var{end}
40315 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40316 currently selected frame whose PC is between @var{start} (inclusive)
40317 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40320 @item QTFrame:outside:@var{start}:@var{end}
40321 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40322 frame @emph{outside} the given range of addresses (exclusive).
40325 @cindex @samp{qTMinFTPILen} packet
40326 This packet requests the minimum length of instruction at which a fast
40327 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40328 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40329 it depends on the target system being able to create trampolines in
40330 the first 64K of memory, which might or might not be possible for that
40331 system. So the reply to this packet will be 4 if it is able to
40338 The minimum instruction length is currently unknown.
40340 The minimum instruction length is @var{length}, where @var{length} is greater
40341 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40342 that a fast tracepoint may be placed on any instruction regardless of size.
40344 An error has occurred.
40346 An empty reply indicates that the request is not supported by the stub.
40350 @cindex @samp{QTStart} packet
40351 Begin the tracepoint experiment. Begin collecting data from
40352 tracepoint hits in the trace frame buffer. This packet supports the
40353 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40354 instruction reply packet}).
40357 @cindex @samp{QTStop} packet
40358 End the tracepoint experiment. Stop collecting trace frames.
40360 @item QTEnable:@var{n}:@var{addr}
40362 @cindex @samp{QTEnable} packet
40363 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40364 experiment. If the tracepoint was previously disabled, then collection
40365 of data from it will resume.
40367 @item QTDisable:@var{n}:@var{addr}
40369 @cindex @samp{QTDisable} packet
40370 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40371 experiment. No more data will be collected from the tracepoint unless
40372 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40375 @cindex @samp{QTinit} packet
40376 Clear the table of tracepoints, and empty the trace frame buffer.
40378 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40379 @cindex @samp{QTro} packet
40380 Establish the given ranges of memory as ``transparent''. The stub
40381 will answer requests for these ranges from memory's current contents,
40382 if they were not collected as part of the tracepoint hit.
40384 @value{GDBN} uses this to mark read-only regions of memory, like those
40385 containing program code. Since these areas never change, they should
40386 still have the same contents they did when the tracepoint was hit, so
40387 there's no reason for the stub to refuse to provide their contents.
40389 @item QTDisconnected:@var{value}
40390 @cindex @samp{QTDisconnected} packet
40391 Set the choice to what to do with the tracing run when @value{GDBN}
40392 disconnects from the target. A @var{value} of 1 directs the target to
40393 continue the tracing run, while 0 tells the target to stop tracing if
40394 @value{GDBN} is no longer in the picture.
40397 @cindex @samp{qTStatus} packet
40398 Ask the stub if there is a trace experiment running right now.
40400 The reply has the form:
40404 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40405 @var{running} is a single digit @code{1} if the trace is presently
40406 running, or @code{0} if not. It is followed by semicolon-separated
40407 optional fields that an agent may use to report additional status.
40411 If the trace is not running, the agent may report any of several
40412 explanations as one of the optional fields:
40417 No trace has been run yet.
40419 @item tstop[:@var{text}]:0
40420 The trace was stopped by a user-originated stop command. The optional
40421 @var{text} field is a user-supplied string supplied as part of the
40422 stop command (for instance, an explanation of why the trace was
40423 stopped manually). It is hex-encoded.
40426 The trace stopped because the trace buffer filled up.
40428 @item tdisconnected:0
40429 The trace stopped because @value{GDBN} disconnected from the target.
40431 @item tpasscount:@var{tpnum}
40432 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40434 @item terror:@var{text}:@var{tpnum}
40435 The trace stopped because tracepoint @var{tpnum} had an error. The
40436 string @var{text} is available to describe the nature of the error
40437 (for instance, a divide by zero in the condition expression).
40438 @var{text} is hex encoded.
40441 The trace stopped for some other reason.
40445 Additional optional fields supply statistical and other information.
40446 Although not required, they are extremely useful for users monitoring
40447 the progress of a trace run. If a trace has stopped, and these
40448 numbers are reported, they must reflect the state of the just-stopped
40453 @item tframes:@var{n}
40454 The number of trace frames in the buffer.
40456 @item tcreated:@var{n}
40457 The total number of trace frames created during the run. This may
40458 be larger than the trace frame count, if the buffer is circular.
40460 @item tsize:@var{n}
40461 The total size of the trace buffer, in bytes.
40463 @item tfree:@var{n}
40464 The number of bytes still unused in the buffer.
40466 @item circular:@var{n}
40467 The value of the circular trace buffer flag. @code{1} means that the
40468 trace buffer is circular and old trace frames will be discarded if
40469 necessary to make room, @code{0} means that the trace buffer is linear
40472 @item disconn:@var{n}
40473 The value of the disconnected tracing flag. @code{1} means that
40474 tracing will continue after @value{GDBN} disconnects, @code{0} means
40475 that the trace run will stop.
40479 @item qTP:@var{tp}:@var{addr}
40480 @cindex tracepoint status, remote request
40481 @cindex @samp{qTP} packet
40482 Ask the stub for the current state of tracepoint number @var{tp} at
40483 address @var{addr}.
40487 @item V@var{hits}:@var{usage}
40488 The tracepoint has been hit @var{hits} times so far during the trace
40489 run, and accounts for @var{usage} in the trace buffer. Note that
40490 @code{while-stepping} steps are not counted as separate hits, but the
40491 steps' space consumption is added into the usage number.
40495 @item qTV:@var{var}
40496 @cindex trace state variable value, remote request
40497 @cindex @samp{qTV} packet
40498 Ask the stub for the value of the trace state variable number @var{var}.
40503 The value of the variable is @var{value}. This will be the current
40504 value of the variable if the user is examining a running target, or a
40505 saved value if the variable was collected in the trace frame that the
40506 user is looking at. Note that multiple requests may result in
40507 different reply values, such as when requesting values while the
40508 program is running.
40511 The value of the variable is unknown. This would occur, for example,
40512 if the user is examining a trace frame in which the requested variable
40517 @cindex @samp{qTfP} packet
40519 @cindex @samp{qTsP} packet
40520 These packets request data about tracepoints that are being used by
40521 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40522 of data, and multiple @code{qTsP} to get additional pieces. Replies
40523 to these packets generally take the form of the @code{QTDP} packets
40524 that define tracepoints. (FIXME add detailed syntax)
40527 @cindex @samp{qTfV} packet
40529 @cindex @samp{qTsV} packet
40530 These packets request data about trace state variables that are on the
40531 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40532 and multiple @code{qTsV} to get additional variables. Replies to
40533 these packets follow the syntax of the @code{QTDV} packets that define
40534 trace state variables.
40540 @cindex @samp{qTfSTM} packet
40541 @cindex @samp{qTsSTM} packet
40542 These packets request data about static tracepoint markers that exist
40543 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40544 first piece of data, and multiple @code{qTsSTM} to get additional
40545 pieces. Replies to these packets take the following form:
40549 @item m @var{address}:@var{id}:@var{extra}
40551 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40552 a comma-separated list of markers
40554 (lower case letter @samp{L}) denotes end of list.
40556 An error occurred. @var{nn} are hex digits.
40558 An empty reply indicates that the request is not supported by the
40562 @var{address} is encoded in hex.
40563 @var{id} and @var{extra} are strings encoded in hex.
40565 In response to each query, the target will reply with a list of one or
40566 more markers, separated by commas. @value{GDBN} will respond to each
40567 reply with a request for more markers (using the @samp{qs} form of the
40568 query), until the target responds with @samp{l} (lower-case ell, for
40571 @item qTSTMat:@var{address}
40573 @cindex @samp{qTSTMat} packet
40574 This packets requests data about static tracepoint markers in the
40575 target program at @var{address}. Replies to this packet follow the
40576 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40577 tracepoint markers.
40579 @item QTSave:@var{filename}
40580 @cindex @samp{QTSave} packet
40581 This packet directs the target to save trace data to the file name
40582 @var{filename} in the target's filesystem. @var{filename} is encoded
40583 as a hex string; the interpretation of the file name (relative vs
40584 absolute, wild cards, etc) is up to the target.
40586 @item qTBuffer:@var{offset},@var{len}
40587 @cindex @samp{qTBuffer} packet
40588 Return up to @var{len} bytes of the current contents of trace buffer,
40589 starting at @var{offset}. The trace buffer is treated as if it were
40590 a contiguous collection of traceframes, as per the trace file format.
40591 The reply consists as many hex-encoded bytes as the target can deliver
40592 in a packet; it is not an error to return fewer than were asked for.
40593 A reply consisting of just @code{l} indicates that no bytes are
40596 @item QTBuffer:circular:@var{value}
40597 This packet directs the target to use a circular trace buffer if
40598 @var{value} is 1, or a linear buffer if the value is 0.
40600 @item QTBuffer:size:@var{size}
40601 @anchor{QTBuffer-size}
40602 @cindex @samp{QTBuffer size} packet
40603 This packet directs the target to make the trace buffer be of size
40604 @var{size} if possible. A value of @code{-1} tells the target to
40605 use whatever size it prefers.
40607 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40608 @cindex @samp{QTNotes} packet
40609 This packet adds optional textual notes to the trace run. Allowable
40610 types include @code{user}, @code{notes}, and @code{tstop}, the
40611 @var{text} fields are arbitrary strings, hex-encoded.
40615 @subsection Relocate instruction reply packet
40616 When installing fast tracepoints in memory, the target may need to
40617 relocate the instruction currently at the tracepoint address to a
40618 different address in memory. For most instructions, a simple copy is
40619 enough, but, for example, call instructions that implicitly push the
40620 return address on the stack, and relative branches or other
40621 PC-relative instructions require offset adjustment, so that the effect
40622 of executing the instruction at a different address is the same as if
40623 it had executed in the original location.
40625 In response to several of the tracepoint packets, the target may also
40626 respond with a number of intermediate @samp{qRelocInsn} request
40627 packets before the final result packet, to have @value{GDBN} handle
40628 this relocation operation. If a packet supports this mechanism, its
40629 documentation will explicitly say so. See for example the above
40630 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40631 format of the request is:
40634 @item qRelocInsn:@var{from};@var{to}
40636 This requests @value{GDBN} to copy instruction at address @var{from}
40637 to address @var{to}, possibly adjusted so that executing the
40638 instruction at @var{to} has the same effect as executing it at
40639 @var{from}. @value{GDBN} writes the adjusted instruction to target
40640 memory starting at @var{to}.
40645 @item qRelocInsn:@var{adjusted_size}
40646 Informs the stub the relocation is complete. @var{adjusted_size} is
40647 the length in bytes of resulting relocated instruction sequence.
40649 A badly formed request was detected, or an error was encountered while
40650 relocating the instruction.
40653 @node Host I/O Packets
40654 @section Host I/O Packets
40655 @cindex Host I/O, remote protocol
40656 @cindex file transfer, remote protocol
40658 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40659 operations on the far side of a remote link. For example, Host I/O is
40660 used to upload and download files to a remote target with its own
40661 filesystem. Host I/O uses the same constant values and data structure
40662 layout as the target-initiated File-I/O protocol. However, the
40663 Host I/O packets are structured differently. The target-initiated
40664 protocol relies on target memory to store parameters and buffers.
40665 Host I/O requests are initiated by @value{GDBN}, and the
40666 target's memory is not involved. @xref{File-I/O Remote Protocol
40667 Extension}, for more details on the target-initiated protocol.
40669 The Host I/O request packets all encode a single operation along with
40670 its arguments. They have this format:
40674 @item vFile:@var{operation}: @var{parameter}@dots{}
40675 @var{operation} is the name of the particular request; the target
40676 should compare the entire packet name up to the second colon when checking
40677 for a supported operation. The format of @var{parameter} depends on
40678 the operation. Numbers are always passed in hexadecimal. Negative
40679 numbers have an explicit minus sign (i.e.@: two's complement is not
40680 used). Strings (e.g.@: filenames) are encoded as a series of
40681 hexadecimal bytes. The last argument to a system call may be a
40682 buffer of escaped binary data (@pxref{Binary Data}).
40686 The valid responses to Host I/O packets are:
40690 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40691 @var{result} is the integer value returned by this operation, usually
40692 non-negative for success and -1 for errors. If an error has occured,
40693 @var{errno} will be included in the result. @var{errno} will have a
40694 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40695 operations which return data, @var{attachment} supplies the data as a
40696 binary buffer. Binary buffers in response packets are escaped in the
40697 normal way (@pxref{Binary Data}). See the individual packet
40698 documentation for the interpretation of @var{result} and
40702 An empty response indicates that this operation is not recognized.
40706 These are the supported Host I/O operations:
40709 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40710 Open a file at @var{pathname} and return a file descriptor for it, or
40711 return -1 if an error occurs. @var{pathname} is a string,
40712 @var{flags} is an integer indicating a mask of open flags
40713 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40714 of mode bits to use if the file is created (@pxref{mode_t Values}).
40715 @xref{open}, for details of the open flags and mode values.
40717 @item vFile:close: @var{fd}
40718 Close the open file corresponding to @var{fd} and return 0, or
40719 -1 if an error occurs.
40721 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40722 Read data from the open file corresponding to @var{fd}. Up to
40723 @var{count} bytes will be read from the file, starting at @var{offset}
40724 relative to the start of the file. The target may read fewer bytes;
40725 common reasons include packet size limits and an end-of-file
40726 condition. The number of bytes read is returned. Zero should only be
40727 returned for a successful read at the end of the file, or if
40728 @var{count} was zero.
40730 The data read should be returned as a binary attachment on success.
40731 If zero bytes were read, the response should include an empty binary
40732 attachment (i.e.@: a trailing semicolon). The return value is the
40733 number of target bytes read; the binary attachment may be longer if
40734 some characters were escaped.
40736 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40737 Write @var{data} (a binary buffer) to the open file corresponding
40738 to @var{fd}. Start the write at @var{offset} from the start of the
40739 file. Unlike many @code{write} system calls, there is no
40740 separate @var{count} argument; the length of @var{data} in the
40741 packet is used. @samp{vFile:write} returns the number of bytes written,
40742 which may be shorter than the length of @var{data}, or -1 if an
40745 @item vFile:unlink: @var{pathname}
40746 Delete the file at @var{pathname} on the target. Return 0,
40747 or -1 if an error occurs. @var{pathname} is a string.
40749 @item vFile:readlink: @var{filename}
40750 Read value of symbolic link @var{filename} on the target. Return
40751 the number of bytes read, or -1 if an error occurs.
40753 The data read should be returned as a binary attachment on success.
40754 If zero bytes were read, the response should include an empty binary
40755 attachment (i.e.@: a trailing semicolon). The return value is the
40756 number of target bytes read; the binary attachment may be longer if
40757 some characters were escaped.
40762 @section Interrupts
40763 @cindex interrupts (remote protocol)
40765 When a program on the remote target is running, @value{GDBN} may
40766 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40767 a @code{BREAK} followed by @code{g},
40768 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40770 The precise meaning of @code{BREAK} is defined by the transport
40771 mechanism and may, in fact, be undefined. @value{GDBN} does not
40772 currently define a @code{BREAK} mechanism for any of the network
40773 interfaces except for TCP, in which case @value{GDBN} sends the
40774 @code{telnet} BREAK sequence.
40776 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40777 transport mechanisms. It is represented by sending the single byte
40778 @code{0x03} without any of the usual packet overhead described in
40779 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40780 transmitted as part of a packet, it is considered to be packet data
40781 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40782 (@pxref{X packet}), used for binary downloads, may include an unescaped
40783 @code{0x03} as part of its packet.
40785 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40786 When Linux kernel receives this sequence from serial port,
40787 it stops execution and connects to gdb.
40789 Stubs are not required to recognize these interrupt mechanisms and the
40790 precise meaning associated with receipt of the interrupt is
40791 implementation defined. If the target supports debugging of multiple
40792 threads and/or processes, it should attempt to interrupt all
40793 currently-executing threads and processes.
40794 If the stub is successful at interrupting the
40795 running program, it should send one of the stop
40796 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40797 of successfully stopping the program in all-stop mode, and a stop reply
40798 for each stopped thread in non-stop mode.
40799 Interrupts received while the
40800 program is stopped are discarded.
40802 @node Notification Packets
40803 @section Notification Packets
40804 @cindex notification packets
40805 @cindex packets, notification
40807 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40808 packets that require no acknowledgment. Both the GDB and the stub
40809 may send notifications (although the only notifications defined at
40810 present are sent by the stub). Notifications carry information
40811 without incurring the round-trip latency of an acknowledgment, and so
40812 are useful for low-impact communications where occasional packet loss
40815 A notification packet has the form @samp{% @var{data} #
40816 @var{checksum}}, where @var{data} is the content of the notification,
40817 and @var{checksum} is a checksum of @var{data}, computed and formatted
40818 as for ordinary @value{GDBN} packets. A notification's @var{data}
40819 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40820 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40821 to acknowledge the notification's receipt or to report its corruption.
40823 Every notification's @var{data} begins with a name, which contains no
40824 colon characters, followed by a colon character.
40826 Recipients should silently ignore corrupted notifications and
40827 notifications they do not understand. Recipients should restart
40828 timeout periods on receipt of a well-formed notification, whether or
40829 not they understand it.
40831 Senders should only send the notifications described here when this
40832 protocol description specifies that they are permitted. In the
40833 future, we may extend the protocol to permit existing notifications in
40834 new contexts; this rule helps older senders avoid confusing newer
40837 (Older versions of @value{GDBN} ignore bytes received until they see
40838 the @samp{$} byte that begins an ordinary packet, so new stubs may
40839 transmit notifications without fear of confusing older clients. There
40840 are no notifications defined for @value{GDBN} to send at the moment, but we
40841 assume that most older stubs would ignore them, as well.)
40843 Each notification is comprised of three parts:
40845 @item @var{name}:@var{event}
40846 The notification packet is sent by the side that initiates the
40847 exchange (currently, only the stub does that), with @var{event}
40848 carrying the specific information about the notification.
40849 @var{name} is the name of the notification.
40851 The acknowledge sent by the other side, usually @value{GDBN}, to
40852 acknowledge the exchange and request the event.
40855 The purpose of an asynchronous notification mechanism is to report to
40856 @value{GDBN} that something interesting happened in the remote stub.
40858 The remote stub may send notification @var{name}:@var{event}
40859 at any time, but @value{GDBN} acknowledges the notification when
40860 appropriate. The notification event is pending before @value{GDBN}
40861 acknowledges. Only one notification at a time may be pending; if
40862 additional events occur before @value{GDBN} has acknowledged the
40863 previous notification, they must be queued by the stub for later
40864 synchronous transmission in response to @var{ack} packets from
40865 @value{GDBN}. Because the notification mechanism is unreliable,
40866 the stub is permitted to resend a notification if it believes
40867 @value{GDBN} may not have received it.
40869 Specifically, notifications may appear when @value{GDBN} is not
40870 otherwise reading input from the stub, or when @value{GDBN} is
40871 expecting to read a normal synchronous response or a
40872 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40873 Notification packets are distinct from any other communication from
40874 the stub so there is no ambiguity.
40876 After receiving a notification, @value{GDBN} shall acknowledge it by
40877 sending a @var{ack} packet as a regular, synchronous request to the
40878 stub. Such acknowledgment is not required to happen immediately, as
40879 @value{GDBN} is permitted to send other, unrelated packets to the
40880 stub first, which the stub should process normally.
40882 Upon receiving a @var{ack} packet, if the stub has other queued
40883 events to report to @value{GDBN}, it shall respond by sending a
40884 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40885 packet to solicit further responses; again, it is permitted to send
40886 other, unrelated packets as well which the stub should process
40889 If the stub receives a @var{ack} packet and there are no additional
40890 @var{event} to report, the stub shall return an @samp{OK} response.
40891 At this point, @value{GDBN} has finished processing a notification
40892 and the stub has completed sending any queued events. @value{GDBN}
40893 won't accept any new notifications until the final @samp{OK} is
40894 received . If further notification events occur, the stub shall send
40895 a new notification, @value{GDBN} shall accept the notification, and
40896 the process shall be repeated.
40898 The process of asynchronous notification can be illustrated by the
40901 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40904 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40906 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40911 The following notifications are defined:
40912 @multitable @columnfractions 0.12 0.12 0.38 0.38
40921 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40922 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40923 for information on how these notifications are acknowledged by
40925 @tab Report an asynchronous stop event in non-stop mode.
40929 @node Remote Non-Stop
40930 @section Remote Protocol Support for Non-Stop Mode
40932 @value{GDBN}'s remote protocol supports non-stop debugging of
40933 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40934 supports non-stop mode, it should report that to @value{GDBN} by including
40935 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40937 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40938 establishing a new connection with the stub. Entering non-stop mode
40939 does not alter the state of any currently-running threads, but targets
40940 must stop all threads in any already-attached processes when entering
40941 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40942 probe the target state after a mode change.
40944 In non-stop mode, when an attached process encounters an event that
40945 would otherwise be reported with a stop reply, it uses the
40946 asynchronous notification mechanism (@pxref{Notification Packets}) to
40947 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40948 in all processes are stopped when a stop reply is sent, in non-stop
40949 mode only the thread reporting the stop event is stopped. That is,
40950 when reporting a @samp{S} or @samp{T} response to indicate completion
40951 of a step operation, hitting a breakpoint, or a fault, only the
40952 affected thread is stopped; any other still-running threads continue
40953 to run. When reporting a @samp{W} or @samp{X} response, all running
40954 threads belonging to other attached processes continue to run.
40956 In non-stop mode, the target shall respond to the @samp{?} packet as
40957 follows. First, any incomplete stop reply notification/@samp{vStopped}
40958 sequence in progress is abandoned. The target must begin a new
40959 sequence reporting stop events for all stopped threads, whether or not
40960 it has previously reported those events to @value{GDBN}. The first
40961 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40962 subsequent stop replies are sent as responses to @samp{vStopped} packets
40963 using the mechanism described above. The target must not send
40964 asynchronous stop reply notifications until the sequence is complete.
40965 If all threads are running when the target receives the @samp{?} packet,
40966 or if the target is not attached to any process, it shall respond
40969 @node Packet Acknowledgment
40970 @section Packet Acknowledgment
40972 @cindex acknowledgment, for @value{GDBN} remote
40973 @cindex packet acknowledgment, for @value{GDBN} remote
40974 By default, when either the host or the target machine receives a packet,
40975 the first response expected is an acknowledgment: either @samp{+} (to indicate
40976 the package was received correctly) or @samp{-} (to request retransmission).
40977 This mechanism allows the @value{GDBN} remote protocol to operate over
40978 unreliable transport mechanisms, such as a serial line.
40980 In cases where the transport mechanism is itself reliable (such as a pipe or
40981 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40982 It may be desirable to disable them in that case to reduce communication
40983 overhead, or for other reasons. This can be accomplished by means of the
40984 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40986 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40987 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40988 and response format still includes the normal checksum, as described in
40989 @ref{Overview}, but the checksum may be ignored by the receiver.
40991 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40992 no-acknowledgment mode, it should report that to @value{GDBN}
40993 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40994 @pxref{qSupported}.
40995 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40996 disabled via the @code{set remote noack-packet off} command
40997 (@pxref{Remote Configuration}),
40998 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40999 Only then may the stub actually turn off packet acknowledgments.
41000 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41001 response, which can be safely ignored by the stub.
41003 Note that @code{set remote noack-packet} command only affects negotiation
41004 between @value{GDBN} and the stub when subsequent connections are made;
41005 it does not affect the protocol acknowledgment state for any current
41007 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41008 new connection is established,
41009 there is also no protocol request to re-enable the acknowledgments
41010 for the current connection, once disabled.
41015 Example sequence of a target being re-started. Notice how the restart
41016 does not get any direct output:
41021 @emph{target restarts}
41024 <- @code{T001:1234123412341234}
41028 Example sequence of a target being stepped by a single instruction:
41031 -> @code{G1445@dots{}}
41036 <- @code{T001:1234123412341234}
41040 <- @code{1455@dots{}}
41044 @node File-I/O Remote Protocol Extension
41045 @section File-I/O Remote Protocol Extension
41046 @cindex File-I/O remote protocol extension
41049 * File-I/O Overview::
41050 * Protocol Basics::
41051 * The F Request Packet::
41052 * The F Reply Packet::
41053 * The Ctrl-C Message::
41055 * List of Supported Calls::
41056 * Protocol-specific Representation of Datatypes::
41058 * File-I/O Examples::
41061 @node File-I/O Overview
41062 @subsection File-I/O Overview
41063 @cindex file-i/o overview
41065 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41066 target to use the host's file system and console I/O to perform various
41067 system calls. System calls on the target system are translated into a
41068 remote protocol packet to the host system, which then performs the needed
41069 actions and returns a response packet to the target system.
41070 This simulates file system operations even on targets that lack file systems.
41072 The protocol is defined to be independent of both the host and target systems.
41073 It uses its own internal representation of datatypes and values. Both
41074 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41075 translating the system-dependent value representations into the internal
41076 protocol representations when data is transmitted.
41078 The communication is synchronous. A system call is possible only when
41079 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41080 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41081 the target is stopped to allow deterministic access to the target's
41082 memory. Therefore File-I/O is not interruptible by target signals. On
41083 the other hand, it is possible to interrupt File-I/O by a user interrupt
41084 (@samp{Ctrl-C}) within @value{GDBN}.
41086 The target's request to perform a host system call does not finish
41087 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41088 after finishing the system call, the target returns to continuing the
41089 previous activity (continue, step). No additional continue or step
41090 request from @value{GDBN} is required.
41093 (@value{GDBP}) continue
41094 <- target requests 'system call X'
41095 target is stopped, @value{GDBN} executes system call
41096 -> @value{GDBN} returns result
41097 ... target continues, @value{GDBN} returns to wait for the target
41098 <- target hits breakpoint and sends a Txx packet
41101 The protocol only supports I/O on the console and to regular files on
41102 the host file system. Character or block special devices, pipes,
41103 named pipes, sockets or any other communication method on the host
41104 system are not supported by this protocol.
41106 File I/O is not supported in non-stop mode.
41108 @node Protocol Basics
41109 @subsection Protocol Basics
41110 @cindex protocol basics, file-i/o
41112 The File-I/O protocol uses the @code{F} packet as the request as well
41113 as reply packet. Since a File-I/O system call can only occur when
41114 @value{GDBN} is waiting for a response from the continuing or stepping target,
41115 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41116 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41117 This @code{F} packet contains all information needed to allow @value{GDBN}
41118 to call the appropriate host system call:
41122 A unique identifier for the requested system call.
41125 All parameters to the system call. Pointers are given as addresses
41126 in the target memory address space. Pointers to strings are given as
41127 pointer/length pair. Numerical values are given as they are.
41128 Numerical control flags are given in a protocol-specific representation.
41132 At this point, @value{GDBN} has to perform the following actions.
41136 If the parameters include pointer values to data needed as input to a
41137 system call, @value{GDBN} requests this data from the target with a
41138 standard @code{m} packet request. This additional communication has to be
41139 expected by the target implementation and is handled as any other @code{m}
41143 @value{GDBN} translates all value from protocol representation to host
41144 representation as needed. Datatypes are coerced into the host types.
41147 @value{GDBN} calls the system call.
41150 It then coerces datatypes back to protocol representation.
41153 If the system call is expected to return data in buffer space specified
41154 by pointer parameters to the call, the data is transmitted to the
41155 target using a @code{M} or @code{X} packet. This packet has to be expected
41156 by the target implementation and is handled as any other @code{M} or @code{X}
41161 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41162 necessary information for the target to continue. This at least contains
41169 @code{errno}, if has been changed by the system call.
41176 After having done the needed type and value coercion, the target continues
41177 the latest continue or step action.
41179 @node The F Request Packet
41180 @subsection The @code{F} Request Packet
41181 @cindex file-i/o request packet
41182 @cindex @code{F} request packet
41184 The @code{F} request packet has the following format:
41187 @item F@var{call-id},@var{parameter@dots{}}
41189 @var{call-id} is the identifier to indicate the host system call to be called.
41190 This is just the name of the function.
41192 @var{parameter@dots{}} are the parameters to the system call.
41193 Parameters are hexadecimal integer values, either the actual values in case
41194 of scalar datatypes, pointers to target buffer space in case of compound
41195 datatypes and unspecified memory areas, or pointer/length pairs in case
41196 of string parameters. These are appended to the @var{call-id} as a
41197 comma-delimited list. All values are transmitted in ASCII
41198 string representation, pointer/length pairs separated by a slash.
41204 @node The F Reply Packet
41205 @subsection The @code{F} Reply Packet
41206 @cindex file-i/o reply packet
41207 @cindex @code{F} reply packet
41209 The @code{F} reply packet has the following format:
41213 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41215 @var{retcode} is the return code of the system call as hexadecimal value.
41217 @var{errno} is the @code{errno} set by the call, in protocol-specific
41219 This parameter can be omitted if the call was successful.
41221 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41222 case, @var{errno} must be sent as well, even if the call was successful.
41223 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41230 or, if the call was interrupted before the host call has been performed:
41237 assuming 4 is the protocol-specific representation of @code{EINTR}.
41242 @node The Ctrl-C Message
41243 @subsection The @samp{Ctrl-C} Message
41244 @cindex ctrl-c message, in file-i/o protocol
41246 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41247 reply packet (@pxref{The F Reply Packet}),
41248 the target should behave as if it had
41249 gotten a break message. The meaning for the target is ``system call
41250 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41251 (as with a break message) and return to @value{GDBN} with a @code{T02}
41254 It's important for the target to know in which
41255 state the system call was interrupted. There are two possible cases:
41259 The system call hasn't been performed on the host yet.
41262 The system call on the host has been finished.
41266 These two states can be distinguished by the target by the value of the
41267 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41268 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41269 on POSIX systems. In any other case, the target may presume that the
41270 system call has been finished --- successfully or not --- and should behave
41271 as if the break message arrived right after the system call.
41273 @value{GDBN} must behave reliably. If the system call has not been called
41274 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41275 @code{errno} in the packet. If the system call on the host has been finished
41276 before the user requests a break, the full action must be finished by
41277 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41278 The @code{F} packet may only be sent when either nothing has happened
41279 or the full action has been completed.
41282 @subsection Console I/O
41283 @cindex console i/o as part of file-i/o
41285 By default and if not explicitly closed by the target system, the file
41286 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41287 on the @value{GDBN} console is handled as any other file output operation
41288 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41289 by @value{GDBN} so that after the target read request from file descriptor
41290 0 all following typing is buffered until either one of the following
41295 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41297 system call is treated as finished.
41300 The user presses @key{RET}. This is treated as end of input with a trailing
41304 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41305 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41309 If the user has typed more characters than fit in the buffer given to
41310 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41311 either another @code{read(0, @dots{})} is requested by the target, or debugging
41312 is stopped at the user's request.
41315 @node List of Supported Calls
41316 @subsection List of Supported Calls
41317 @cindex list of supported file-i/o calls
41334 @unnumberedsubsubsec open
41335 @cindex open, file-i/o system call
41340 int open(const char *pathname, int flags);
41341 int open(const char *pathname, int flags, mode_t mode);
41345 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41348 @var{flags} is the bitwise @code{OR} of the following values:
41352 If the file does not exist it will be created. The host
41353 rules apply as far as file ownership and time stamps
41357 When used with @code{O_CREAT}, if the file already exists it is
41358 an error and open() fails.
41361 If the file already exists and the open mode allows
41362 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41363 truncated to zero length.
41366 The file is opened in append mode.
41369 The file is opened for reading only.
41372 The file is opened for writing only.
41375 The file is opened for reading and writing.
41379 Other bits are silently ignored.
41383 @var{mode} is the bitwise @code{OR} of the following values:
41387 User has read permission.
41390 User has write permission.
41393 Group has read permission.
41396 Group has write permission.
41399 Others have read permission.
41402 Others have write permission.
41406 Other bits are silently ignored.
41409 @item Return value:
41410 @code{open} returns the new file descriptor or -1 if an error
41417 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41420 @var{pathname} refers to a directory.
41423 The requested access is not allowed.
41426 @var{pathname} was too long.
41429 A directory component in @var{pathname} does not exist.
41432 @var{pathname} refers to a device, pipe, named pipe or socket.
41435 @var{pathname} refers to a file on a read-only filesystem and
41436 write access was requested.
41439 @var{pathname} is an invalid pointer value.
41442 No space on device to create the file.
41445 The process already has the maximum number of files open.
41448 The limit on the total number of files open on the system
41452 The call was interrupted by the user.
41458 @unnumberedsubsubsec close
41459 @cindex close, file-i/o system call
41468 @samp{Fclose,@var{fd}}
41470 @item Return value:
41471 @code{close} returns zero on success, or -1 if an error occurred.
41477 @var{fd} isn't a valid open file descriptor.
41480 The call was interrupted by the user.
41486 @unnumberedsubsubsec read
41487 @cindex read, file-i/o system call
41492 int read(int fd, void *buf, unsigned int count);
41496 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41498 @item Return value:
41499 On success, the number of bytes read is returned.
41500 Zero indicates end of file. If count is zero, read
41501 returns zero as well. On error, -1 is returned.
41507 @var{fd} is not a valid file descriptor or is not open for
41511 @var{bufptr} is an invalid pointer value.
41514 The call was interrupted by the user.
41520 @unnumberedsubsubsec write
41521 @cindex write, file-i/o system call
41526 int write(int fd, const void *buf, unsigned int count);
41530 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41532 @item Return value:
41533 On success, the number of bytes written are returned.
41534 Zero indicates nothing was written. On error, -1
41541 @var{fd} is not a valid file descriptor or is not open for
41545 @var{bufptr} is an invalid pointer value.
41548 An attempt was made to write a file that exceeds the
41549 host-specific maximum file size allowed.
41552 No space on device to write the data.
41555 The call was interrupted by the user.
41561 @unnumberedsubsubsec lseek
41562 @cindex lseek, file-i/o system call
41567 long lseek (int fd, long offset, int flag);
41571 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41573 @var{flag} is one of:
41577 The offset is set to @var{offset} bytes.
41580 The offset is set to its current location plus @var{offset}
41584 The offset is set to the size of the file plus @var{offset}
41588 @item Return value:
41589 On success, the resulting unsigned offset in bytes from
41590 the beginning of the file is returned. Otherwise, a
41591 value of -1 is returned.
41597 @var{fd} is not a valid open file descriptor.
41600 @var{fd} is associated with the @value{GDBN} console.
41603 @var{flag} is not a proper value.
41606 The call was interrupted by the user.
41612 @unnumberedsubsubsec rename
41613 @cindex rename, file-i/o system call
41618 int rename(const char *oldpath, const char *newpath);
41622 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41624 @item Return value:
41625 On success, zero is returned. On error, -1 is returned.
41631 @var{newpath} is an existing directory, but @var{oldpath} is not a
41635 @var{newpath} is a non-empty directory.
41638 @var{oldpath} or @var{newpath} is a directory that is in use by some
41642 An attempt was made to make a directory a subdirectory
41646 A component used as a directory in @var{oldpath} or new
41647 path is not a directory. Or @var{oldpath} is a directory
41648 and @var{newpath} exists but is not a directory.
41651 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41654 No access to the file or the path of the file.
41658 @var{oldpath} or @var{newpath} was too long.
41661 A directory component in @var{oldpath} or @var{newpath} does not exist.
41664 The file is on a read-only filesystem.
41667 The device containing the file has no room for the new
41671 The call was interrupted by the user.
41677 @unnumberedsubsubsec unlink
41678 @cindex unlink, file-i/o system call
41683 int unlink(const char *pathname);
41687 @samp{Funlink,@var{pathnameptr}/@var{len}}
41689 @item Return value:
41690 On success, zero is returned. On error, -1 is returned.
41696 No access to the file or the path of the file.
41699 The system does not allow unlinking of directories.
41702 The file @var{pathname} cannot be unlinked because it's
41703 being used by another process.
41706 @var{pathnameptr} is an invalid pointer value.
41709 @var{pathname} was too long.
41712 A directory component in @var{pathname} does not exist.
41715 A component of the path is not a directory.
41718 The file is on a read-only filesystem.
41721 The call was interrupted by the user.
41727 @unnumberedsubsubsec stat/fstat
41728 @cindex fstat, file-i/o system call
41729 @cindex stat, file-i/o system call
41734 int stat(const char *pathname, struct stat *buf);
41735 int fstat(int fd, struct stat *buf);
41739 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41740 @samp{Ffstat,@var{fd},@var{bufptr}}
41742 @item Return value:
41743 On success, zero is returned. On error, -1 is returned.
41749 @var{fd} is not a valid open file.
41752 A directory component in @var{pathname} does not exist or the
41753 path is an empty string.
41756 A component of the path is not a directory.
41759 @var{pathnameptr} is an invalid pointer value.
41762 No access to the file or the path of the file.
41765 @var{pathname} was too long.
41768 The call was interrupted by the user.
41774 @unnumberedsubsubsec gettimeofday
41775 @cindex gettimeofday, file-i/o system call
41780 int gettimeofday(struct timeval *tv, void *tz);
41784 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41786 @item Return value:
41787 On success, 0 is returned, -1 otherwise.
41793 @var{tz} is a non-NULL pointer.
41796 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41802 @unnumberedsubsubsec isatty
41803 @cindex isatty, file-i/o system call
41808 int isatty(int fd);
41812 @samp{Fisatty,@var{fd}}
41814 @item Return value:
41815 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41821 The call was interrupted by the user.
41826 Note that the @code{isatty} call is treated as a special case: it returns
41827 1 to the target if the file descriptor is attached
41828 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41829 would require implementing @code{ioctl} and would be more complex than
41834 @unnumberedsubsubsec system
41835 @cindex system, file-i/o system call
41840 int system(const char *command);
41844 @samp{Fsystem,@var{commandptr}/@var{len}}
41846 @item Return value:
41847 If @var{len} is zero, the return value indicates whether a shell is
41848 available. A zero return value indicates a shell is not available.
41849 For non-zero @var{len}, the value returned is -1 on error and the
41850 return status of the command otherwise. Only the exit status of the
41851 command is returned, which is extracted from the host's @code{system}
41852 return value by calling @code{WEXITSTATUS(retval)}. In case
41853 @file{/bin/sh} could not be executed, 127 is returned.
41859 The call was interrupted by the user.
41864 @value{GDBN} takes over the full task of calling the necessary host calls
41865 to perform the @code{system} call. The return value of @code{system} on
41866 the host is simplified before it's returned
41867 to the target. Any termination signal information from the child process
41868 is discarded, and the return value consists
41869 entirely of the exit status of the called command.
41871 Due to security concerns, the @code{system} call is by default refused
41872 by @value{GDBN}. The user has to allow this call explicitly with the
41873 @code{set remote system-call-allowed 1} command.
41876 @item set remote system-call-allowed
41877 @kindex set remote system-call-allowed
41878 Control whether to allow the @code{system} calls in the File I/O
41879 protocol for the remote target. The default is zero (disabled).
41881 @item show remote system-call-allowed
41882 @kindex show remote system-call-allowed
41883 Show whether the @code{system} calls are allowed in the File I/O
41887 @node Protocol-specific Representation of Datatypes
41888 @subsection Protocol-specific Representation of Datatypes
41889 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41892 * Integral Datatypes::
41894 * Memory Transfer::
41899 @node Integral Datatypes
41900 @unnumberedsubsubsec Integral Datatypes
41901 @cindex integral datatypes, in file-i/o protocol
41903 The integral datatypes used in the system calls are @code{int},
41904 @code{unsigned int}, @code{long}, @code{unsigned long},
41905 @code{mode_t}, and @code{time_t}.
41907 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41908 implemented as 32 bit values in this protocol.
41910 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41912 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41913 in @file{limits.h}) to allow range checking on host and target.
41915 @code{time_t} datatypes are defined as seconds since the Epoch.
41917 All integral datatypes transferred as part of a memory read or write of a
41918 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41921 @node Pointer Values
41922 @unnumberedsubsubsec Pointer Values
41923 @cindex pointer values, in file-i/o protocol
41925 Pointers to target data are transmitted as they are. An exception
41926 is made for pointers to buffers for which the length isn't
41927 transmitted as part of the function call, namely strings. Strings
41928 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41935 which is a pointer to data of length 18 bytes at position 0x1aaf.
41936 The length is defined as the full string length in bytes, including
41937 the trailing null byte. For example, the string @code{"hello world"}
41938 at address 0x123456 is transmitted as
41944 @node Memory Transfer
41945 @unnumberedsubsubsec Memory Transfer
41946 @cindex memory transfer, in file-i/o protocol
41948 Structured data which is transferred using a memory read or write (for
41949 example, a @code{struct stat}) is expected to be in a protocol-specific format
41950 with all scalar multibyte datatypes being big endian. Translation to
41951 this representation needs to be done both by the target before the @code{F}
41952 packet is sent, and by @value{GDBN} before
41953 it transfers memory to the target. Transferred pointers to structured
41954 data should point to the already-coerced data at any time.
41958 @unnumberedsubsubsec struct stat
41959 @cindex struct stat, in file-i/o protocol
41961 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41962 is defined as follows:
41966 unsigned int st_dev; /* device */
41967 unsigned int st_ino; /* inode */
41968 mode_t st_mode; /* protection */
41969 unsigned int st_nlink; /* number of hard links */
41970 unsigned int st_uid; /* user ID of owner */
41971 unsigned int st_gid; /* group ID of owner */
41972 unsigned int st_rdev; /* device type (if inode device) */
41973 unsigned long st_size; /* total size, in bytes */
41974 unsigned long st_blksize; /* blocksize for filesystem I/O */
41975 unsigned long st_blocks; /* number of blocks allocated */
41976 time_t st_atime; /* time of last access */
41977 time_t st_mtime; /* time of last modification */
41978 time_t st_ctime; /* time of last change */
41982 The integral datatypes conform to the definitions given in the
41983 appropriate section (see @ref{Integral Datatypes}, for details) so this
41984 structure is of size 64 bytes.
41986 The values of several fields have a restricted meaning and/or
41992 A value of 0 represents a file, 1 the console.
41995 No valid meaning for the target. Transmitted unchanged.
41998 Valid mode bits are described in @ref{Constants}. Any other
41999 bits have currently no meaning for the target.
42004 No valid meaning for the target. Transmitted unchanged.
42009 These values have a host and file system dependent
42010 accuracy. Especially on Windows hosts, the file system may not
42011 support exact timing values.
42014 The target gets a @code{struct stat} of the above representation and is
42015 responsible for coercing it to the target representation before
42018 Note that due to size differences between the host, target, and protocol
42019 representations of @code{struct stat} members, these members could eventually
42020 get truncated on the target.
42022 @node struct timeval
42023 @unnumberedsubsubsec struct timeval
42024 @cindex struct timeval, in file-i/o protocol
42026 The buffer of type @code{struct timeval} used by the File-I/O protocol
42027 is defined as follows:
42031 time_t tv_sec; /* second */
42032 long tv_usec; /* microsecond */
42036 The integral datatypes conform to the definitions given in the
42037 appropriate section (see @ref{Integral Datatypes}, for details) so this
42038 structure is of size 8 bytes.
42041 @subsection Constants
42042 @cindex constants, in file-i/o protocol
42044 The following values are used for the constants inside of the
42045 protocol. @value{GDBN} and target are responsible for translating these
42046 values before and after the call as needed.
42057 @unnumberedsubsubsec Open Flags
42058 @cindex open flags, in file-i/o protocol
42060 All values are given in hexadecimal representation.
42072 @node mode_t Values
42073 @unnumberedsubsubsec mode_t Values
42074 @cindex mode_t values, in file-i/o protocol
42076 All values are given in octal representation.
42093 @unnumberedsubsubsec Errno Values
42094 @cindex errno values, in file-i/o protocol
42096 All values are given in decimal representation.
42121 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42122 any error value not in the list of supported error numbers.
42125 @unnumberedsubsubsec Lseek Flags
42126 @cindex lseek flags, in file-i/o protocol
42135 @unnumberedsubsubsec Limits
42136 @cindex limits, in file-i/o protocol
42138 All values are given in decimal representation.
42141 INT_MIN -2147483648
42143 UINT_MAX 4294967295
42144 LONG_MIN -9223372036854775808
42145 LONG_MAX 9223372036854775807
42146 ULONG_MAX 18446744073709551615
42149 @node File-I/O Examples
42150 @subsection File-I/O Examples
42151 @cindex file-i/o examples
42153 Example sequence of a write call, file descriptor 3, buffer is at target
42154 address 0x1234, 6 bytes should be written:
42157 <- @code{Fwrite,3,1234,6}
42158 @emph{request memory read from target}
42161 @emph{return "6 bytes written"}
42165 Example sequence of a read call, file descriptor 3, buffer is at target
42166 address 0x1234, 6 bytes should be read:
42169 <- @code{Fread,3,1234,6}
42170 @emph{request memory write to target}
42171 -> @code{X1234,6:XXXXXX}
42172 @emph{return "6 bytes read"}
42176 Example sequence of a read call, call fails on the host due to invalid
42177 file descriptor (@code{EBADF}):
42180 <- @code{Fread,3,1234,6}
42184 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42188 <- @code{Fread,3,1234,6}
42193 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42197 <- @code{Fread,3,1234,6}
42198 -> @code{X1234,6:XXXXXX}
42202 @node Library List Format
42203 @section Library List Format
42204 @cindex library list format, remote protocol
42206 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42207 same process as your application to manage libraries. In this case,
42208 @value{GDBN} can use the loader's symbol table and normal memory
42209 operations to maintain a list of shared libraries. On other
42210 platforms, the operating system manages loaded libraries.
42211 @value{GDBN} can not retrieve the list of currently loaded libraries
42212 through memory operations, so it uses the @samp{qXfer:libraries:read}
42213 packet (@pxref{qXfer library list read}) instead. The remote stub
42214 queries the target's operating system and reports which libraries
42217 The @samp{qXfer:libraries:read} packet returns an XML document which
42218 lists loaded libraries and their offsets. Each library has an
42219 associated name and one or more segment or section base addresses,
42220 which report where the library was loaded in memory.
42222 For the common case of libraries that are fully linked binaries, the
42223 library should have a list of segments. If the target supports
42224 dynamic linking of a relocatable object file, its library XML element
42225 should instead include a list of allocated sections. The segment or
42226 section bases are start addresses, not relocation offsets; they do not
42227 depend on the library's link-time base addresses.
42229 @value{GDBN} must be linked with the Expat library to support XML
42230 library lists. @xref{Expat}.
42232 A simple memory map, with one loaded library relocated by a single
42233 offset, looks like this:
42237 <library name="/lib/libc.so.6">
42238 <segment address="0x10000000"/>
42243 Another simple memory map, with one loaded library with three
42244 allocated sections (.text, .data, .bss), looks like this:
42248 <library name="sharedlib.o">
42249 <section address="0x10000000"/>
42250 <section address="0x20000000"/>
42251 <section address="0x30000000"/>
42256 The format of a library list is described by this DTD:
42259 <!-- library-list: Root element with versioning -->
42260 <!ELEMENT library-list (library)*>
42261 <!ATTLIST library-list version CDATA #FIXED "1.0">
42262 <!ELEMENT library (segment*, section*)>
42263 <!ATTLIST library name CDATA #REQUIRED>
42264 <!ELEMENT segment EMPTY>
42265 <!ATTLIST segment address CDATA #REQUIRED>
42266 <!ELEMENT section EMPTY>
42267 <!ATTLIST section address CDATA #REQUIRED>
42270 In addition, segments and section descriptors cannot be mixed within a
42271 single library element, and you must supply at least one segment or
42272 section for each library.
42274 @node Library List Format for SVR4 Targets
42275 @section Library List Format for SVR4 Targets
42276 @cindex library list format, remote protocol
42278 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42279 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42280 shared libraries. Still a special library list provided by this packet is
42281 more efficient for the @value{GDBN} remote protocol.
42283 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42284 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42285 target, the following parameters are reported:
42289 @code{name}, the absolute file name from the @code{l_name} field of
42290 @code{struct link_map}.
42292 @code{lm} with address of @code{struct link_map} used for TLS
42293 (Thread Local Storage) access.
42295 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42296 @code{struct link_map}. For prelinked libraries this is not an absolute
42297 memory address. It is a displacement of absolute memory address against
42298 address the file was prelinked to during the library load.
42300 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42303 Additionally the single @code{main-lm} attribute specifies address of
42304 @code{struct link_map} used for the main executable. This parameter is used
42305 for TLS access and its presence is optional.
42307 @value{GDBN} must be linked with the Expat library to support XML
42308 SVR4 library lists. @xref{Expat}.
42310 A simple memory map, with two loaded libraries (which do not use prelink),
42314 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42315 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42317 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42319 </library-list-svr>
42322 The format of an SVR4 library list is described by this DTD:
42325 <!-- library-list-svr4: Root element with versioning -->
42326 <!ELEMENT library-list-svr4 (library)*>
42327 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42328 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42329 <!ELEMENT library EMPTY>
42330 <!ATTLIST library name CDATA #REQUIRED>
42331 <!ATTLIST library lm CDATA #REQUIRED>
42332 <!ATTLIST library l_addr CDATA #REQUIRED>
42333 <!ATTLIST library l_ld CDATA #REQUIRED>
42336 @node Memory Map Format
42337 @section Memory Map Format
42338 @cindex memory map format
42340 To be able to write into flash memory, @value{GDBN} needs to obtain a
42341 memory map from the target. This section describes the format of the
42344 The memory map is obtained using the @samp{qXfer:memory-map:read}
42345 (@pxref{qXfer memory map read}) packet and is an XML document that
42346 lists memory regions.
42348 @value{GDBN} must be linked with the Expat library to support XML
42349 memory maps. @xref{Expat}.
42351 The top-level structure of the document is shown below:
42354 <?xml version="1.0"?>
42355 <!DOCTYPE memory-map
42356 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42357 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42363 Each region can be either:
42368 A region of RAM starting at @var{addr} and extending for @var{length}
42372 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42377 A region of read-only memory:
42380 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42385 A region of flash memory, with erasure blocks @var{blocksize}
42389 <memory type="flash" start="@var{addr}" length="@var{length}">
42390 <property name="blocksize">@var{blocksize}</property>
42396 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42397 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42398 packets to write to addresses in such ranges.
42400 The formal DTD for memory map format is given below:
42403 <!-- ................................................... -->
42404 <!-- Memory Map XML DTD ................................ -->
42405 <!-- File: memory-map.dtd .............................. -->
42406 <!-- .................................... .............. -->
42407 <!-- memory-map.dtd -->
42408 <!-- memory-map: Root element with versioning -->
42409 <!ELEMENT memory-map (memory | property)>
42410 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42411 <!ELEMENT memory (property)>
42412 <!-- memory: Specifies a memory region,
42413 and its type, or device. -->
42414 <!ATTLIST memory type CDATA #REQUIRED
42415 start CDATA #REQUIRED
42416 length CDATA #REQUIRED
42417 device CDATA #IMPLIED>
42418 <!-- property: Generic attribute tag -->
42419 <!ELEMENT property (#PCDATA | property)*>
42420 <!ATTLIST property name CDATA #REQUIRED>
42423 @node Thread List Format
42424 @section Thread List Format
42425 @cindex thread list format
42427 To efficiently update the list of threads and their attributes,
42428 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42429 (@pxref{qXfer threads read}) and obtains the XML document with
42430 the following structure:
42433 <?xml version="1.0"?>
42435 <thread id="id" core="0">
42436 ... description ...
42441 Each @samp{thread} element must have the @samp{id} attribute that
42442 identifies the thread (@pxref{thread-id syntax}). The
42443 @samp{core} attribute, if present, specifies which processor core
42444 the thread was last executing on. The content of the of @samp{thread}
42445 element is interpreted as human-readable auxilliary information.
42447 @node Traceframe Info Format
42448 @section Traceframe Info Format
42449 @cindex traceframe info format
42451 To be able to know which objects in the inferior can be examined when
42452 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42453 memory ranges, registers and trace state variables that have been
42454 collected in a traceframe.
42456 This list is obtained using the @samp{qXfer:traceframe-info:read}
42457 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42459 @value{GDBN} must be linked with the Expat library to support XML
42460 traceframe info discovery. @xref{Expat}.
42462 The top-level structure of the document is shown below:
42465 <?xml version="1.0"?>
42466 <!DOCTYPE traceframe-info
42467 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42468 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42474 Each traceframe block can be either:
42479 A region of collected memory starting at @var{addr} and extending for
42480 @var{length} bytes from there:
42483 <memory start="@var{addr}" length="@var{length}"/>
42487 A block indicating trace state variable numbered @var{number} has been
42491 <tvar id="@var{number}"/>
42496 The formal DTD for the traceframe info format is given below:
42499 <!ELEMENT traceframe-info (memory | tvar)* >
42500 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42502 <!ELEMENT memory EMPTY>
42503 <!ATTLIST memory start CDATA #REQUIRED
42504 length CDATA #REQUIRED>
42506 <!ATTLIST tvar id CDATA #REQUIRED>
42509 @node Branch Trace Format
42510 @section Branch Trace Format
42511 @cindex branch trace format
42513 In order to display the branch trace of an inferior thread,
42514 @value{GDBN} needs to obtain the list of branches. This list is
42515 represented as list of sequential code blocks that are connected via
42516 branches. The code in each block has been executed sequentially.
42518 This list is obtained using the @samp{qXfer:btrace:read}
42519 (@pxref{qXfer btrace read}) packet and is an XML document.
42521 @value{GDBN} must be linked with the Expat library to support XML
42522 traceframe info discovery. @xref{Expat}.
42524 The top-level structure of the document is shown below:
42527 <?xml version="1.0"?>
42529 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42530 "http://sourceware.org/gdb/gdb-btrace.dtd">
42539 A block of sequentially executed instructions starting at @var{begin}
42540 and ending at @var{end}:
42543 <block begin="@var{begin}" end="@var{end}"/>
42548 The formal DTD for the branch trace format is given below:
42551 <!ELEMENT btrace (block)* >
42552 <!ATTLIST btrace version CDATA #FIXED "1.0">
42554 <!ELEMENT block EMPTY>
42555 <!ATTLIST block begin CDATA #REQUIRED
42556 end CDATA #REQUIRED>
42559 @include agentexpr.texi
42561 @node Target Descriptions
42562 @appendix Target Descriptions
42563 @cindex target descriptions
42565 One of the challenges of using @value{GDBN} to debug embedded systems
42566 is that there are so many minor variants of each processor
42567 architecture in use. It is common practice for vendors to start with
42568 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42569 and then make changes to adapt it to a particular market niche. Some
42570 architectures have hundreds of variants, available from dozens of
42571 vendors. This leads to a number of problems:
42575 With so many different customized processors, it is difficult for
42576 the @value{GDBN} maintainers to keep up with the changes.
42578 Since individual variants may have short lifetimes or limited
42579 audiences, it may not be worthwhile to carry information about every
42580 variant in the @value{GDBN} source tree.
42582 When @value{GDBN} does support the architecture of the embedded system
42583 at hand, the task of finding the correct architecture name to give the
42584 @command{set architecture} command can be error-prone.
42587 To address these problems, the @value{GDBN} remote protocol allows a
42588 target system to not only identify itself to @value{GDBN}, but to
42589 actually describe its own features. This lets @value{GDBN} support
42590 processor variants it has never seen before --- to the extent that the
42591 descriptions are accurate, and that @value{GDBN} understands them.
42593 @value{GDBN} must be linked with the Expat library to support XML
42594 target descriptions. @xref{Expat}.
42597 * Retrieving Descriptions:: How descriptions are fetched from a target.
42598 * Target Description Format:: The contents of a target description.
42599 * Predefined Target Types:: Standard types available for target
42601 * Standard Target Features:: Features @value{GDBN} knows about.
42604 @node Retrieving Descriptions
42605 @section Retrieving Descriptions
42607 Target descriptions can be read from the target automatically, or
42608 specified by the user manually. The default behavior is to read the
42609 description from the target. @value{GDBN} retrieves it via the remote
42610 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42611 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42612 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42613 XML document, of the form described in @ref{Target Description
42616 Alternatively, you can specify a file to read for the target description.
42617 If a file is set, the target will not be queried. The commands to
42618 specify a file are:
42621 @cindex set tdesc filename
42622 @item set tdesc filename @var{path}
42623 Read the target description from @var{path}.
42625 @cindex unset tdesc filename
42626 @item unset tdesc filename
42627 Do not read the XML target description from a file. @value{GDBN}
42628 will use the description supplied by the current target.
42630 @cindex show tdesc filename
42631 @item show tdesc filename
42632 Show the filename to read for a target description, if any.
42636 @node Target Description Format
42637 @section Target Description Format
42638 @cindex target descriptions, XML format
42640 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42641 document which complies with the Document Type Definition provided in
42642 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42643 means you can use generally available tools like @command{xmllint} to
42644 check that your feature descriptions are well-formed and valid.
42645 However, to help people unfamiliar with XML write descriptions for
42646 their targets, we also describe the grammar here.
42648 Target descriptions can identify the architecture of the remote target
42649 and (for some architectures) provide information about custom register
42650 sets. They can also identify the OS ABI of the remote target.
42651 @value{GDBN} can use this information to autoconfigure for your
42652 target, or to warn you if you connect to an unsupported target.
42654 Here is a simple target description:
42657 <target version="1.0">
42658 <architecture>i386:x86-64</architecture>
42663 This minimal description only says that the target uses
42664 the x86-64 architecture.
42666 A target description has the following overall form, with [ ] marking
42667 optional elements and @dots{} marking repeatable elements. The elements
42668 are explained further below.
42671 <?xml version="1.0"?>
42672 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42673 <target version="1.0">
42674 @r{[}@var{architecture}@r{]}
42675 @r{[}@var{osabi}@r{]}
42676 @r{[}@var{compatible}@r{]}
42677 @r{[}@var{feature}@dots{}@r{]}
42682 The description is generally insensitive to whitespace and line
42683 breaks, under the usual common-sense rules. The XML version
42684 declaration and document type declaration can generally be omitted
42685 (@value{GDBN} does not require them), but specifying them may be
42686 useful for XML validation tools. The @samp{version} attribute for
42687 @samp{<target>} may also be omitted, but we recommend
42688 including it; if future versions of @value{GDBN} use an incompatible
42689 revision of @file{gdb-target.dtd}, they will detect and report
42690 the version mismatch.
42692 @subsection Inclusion
42693 @cindex target descriptions, inclusion
42696 @cindex <xi:include>
42699 It can sometimes be valuable to split a target description up into
42700 several different annexes, either for organizational purposes, or to
42701 share files between different possible target descriptions. You can
42702 divide a description into multiple files by replacing any element of
42703 the target description with an inclusion directive of the form:
42706 <xi:include href="@var{document}"/>
42710 When @value{GDBN} encounters an element of this form, it will retrieve
42711 the named XML @var{document}, and replace the inclusion directive with
42712 the contents of that document. If the current description was read
42713 using @samp{qXfer}, then so will be the included document;
42714 @var{document} will be interpreted as the name of an annex. If the
42715 current description was read from a file, @value{GDBN} will look for
42716 @var{document} as a file in the same directory where it found the
42717 original description.
42719 @subsection Architecture
42720 @cindex <architecture>
42722 An @samp{<architecture>} element has this form:
42725 <architecture>@var{arch}</architecture>
42728 @var{arch} is one of the architectures from the set accepted by
42729 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42732 @cindex @code{<osabi>}
42734 This optional field was introduced in @value{GDBN} version 7.0.
42735 Previous versions of @value{GDBN} ignore it.
42737 An @samp{<osabi>} element has this form:
42740 <osabi>@var{abi-name}</osabi>
42743 @var{abi-name} is an OS ABI name from the same selection accepted by
42744 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42746 @subsection Compatible Architecture
42747 @cindex @code{<compatible>}
42749 This optional field was introduced in @value{GDBN} version 7.0.
42750 Previous versions of @value{GDBN} ignore it.
42752 A @samp{<compatible>} element has this form:
42755 <compatible>@var{arch}</compatible>
42758 @var{arch} is one of the architectures from the set accepted by
42759 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42761 A @samp{<compatible>} element is used to specify that the target
42762 is able to run binaries in some other than the main target architecture
42763 given by the @samp{<architecture>} element. For example, on the
42764 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42765 or @code{powerpc:common64}, but the system is able to run binaries
42766 in the @code{spu} architecture as well. The way to describe this
42767 capability with @samp{<compatible>} is as follows:
42770 <architecture>powerpc:common</architecture>
42771 <compatible>spu</compatible>
42774 @subsection Features
42777 Each @samp{<feature>} describes some logical portion of the target
42778 system. Features are currently used to describe available CPU
42779 registers and the types of their contents. A @samp{<feature>} element
42783 <feature name="@var{name}">
42784 @r{[}@var{type}@dots{}@r{]}
42790 Each feature's name should be unique within the description. The name
42791 of a feature does not matter unless @value{GDBN} has some special
42792 knowledge of the contents of that feature; if it does, the feature
42793 should have its standard name. @xref{Standard Target Features}.
42797 Any register's value is a collection of bits which @value{GDBN} must
42798 interpret. The default interpretation is a two's complement integer,
42799 but other types can be requested by name in the register description.
42800 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42801 Target Types}), and the description can define additional composite types.
42803 Each type element must have an @samp{id} attribute, which gives
42804 a unique (within the containing @samp{<feature>}) name to the type.
42805 Types must be defined before they are used.
42808 Some targets offer vector registers, which can be treated as arrays
42809 of scalar elements. These types are written as @samp{<vector>} elements,
42810 specifying the array element type, @var{type}, and the number of elements,
42814 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42818 If a register's value is usefully viewed in multiple ways, define it
42819 with a union type containing the useful representations. The
42820 @samp{<union>} element contains one or more @samp{<field>} elements,
42821 each of which has a @var{name} and a @var{type}:
42824 <union id="@var{id}">
42825 <field name="@var{name}" type="@var{type}"/>
42831 If a register's value is composed from several separate values, define
42832 it with a structure type. There are two forms of the @samp{<struct>}
42833 element; a @samp{<struct>} element must either contain only bitfields
42834 or contain no bitfields. If the structure contains only bitfields,
42835 its total size in bytes must be specified, each bitfield must have an
42836 explicit start and end, and bitfields are automatically assigned an
42837 integer type. The field's @var{start} should be less than or
42838 equal to its @var{end}, and zero represents the least significant bit.
42841 <struct id="@var{id}" size="@var{size}">
42842 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42847 If the structure contains no bitfields, then each field has an
42848 explicit type, and no implicit padding is added.
42851 <struct id="@var{id}">
42852 <field name="@var{name}" type="@var{type}"/>
42858 If a register's value is a series of single-bit flags, define it with
42859 a flags type. The @samp{<flags>} element has an explicit @var{size}
42860 and contains one or more @samp{<field>} elements. Each field has a
42861 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42865 <flags id="@var{id}" size="@var{size}">
42866 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42871 @subsection Registers
42874 Each register is represented as an element with this form:
42877 <reg name="@var{name}"
42878 bitsize="@var{size}"
42879 @r{[}regnum="@var{num}"@r{]}
42880 @r{[}save-restore="@var{save-restore}"@r{]}
42881 @r{[}type="@var{type}"@r{]}
42882 @r{[}group="@var{group}"@r{]}/>
42886 The components are as follows:
42891 The register's name; it must be unique within the target description.
42894 The register's size, in bits.
42897 The register's number. If omitted, a register's number is one greater
42898 than that of the previous register (either in the current feature or in
42899 a preceding feature); the first register in the target description
42900 defaults to zero. This register number is used to read or write
42901 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42902 packets, and registers appear in the @code{g} and @code{G} packets
42903 in order of increasing register number.
42906 Whether the register should be preserved across inferior function
42907 calls; this must be either @code{yes} or @code{no}. The default is
42908 @code{yes}, which is appropriate for most registers except for
42909 some system control registers; this is not related to the target's
42913 The type of the register. @var{type} may be a predefined type, a type
42914 defined in the current feature, or one of the special types @code{int}
42915 and @code{float}. @code{int} is an integer type of the correct size
42916 for @var{bitsize}, and @code{float} is a floating point type (in the
42917 architecture's normal floating point format) of the correct size for
42918 @var{bitsize}. The default is @code{int}.
42921 The register group to which this register belongs. @var{group} must
42922 be either @code{general}, @code{float}, or @code{vector}. If no
42923 @var{group} is specified, @value{GDBN} will not display the register
42924 in @code{info registers}.
42928 @node Predefined Target Types
42929 @section Predefined Target Types
42930 @cindex target descriptions, predefined types
42932 Type definitions in the self-description can build up composite types
42933 from basic building blocks, but can not define fundamental types. Instead,
42934 standard identifiers are provided by @value{GDBN} for the fundamental
42935 types. The currently supported types are:
42944 Signed integer types holding the specified number of bits.
42951 Unsigned integer types holding the specified number of bits.
42955 Pointers to unspecified code and data. The program counter and
42956 any dedicated return address register may be marked as code
42957 pointers; printing a code pointer converts it into a symbolic
42958 address. The stack pointer and any dedicated address registers
42959 may be marked as data pointers.
42962 Single precision IEEE floating point.
42965 Double precision IEEE floating point.
42968 The 12-byte extended precision format used by ARM FPA registers.
42971 The 10-byte extended precision format used by x87 registers.
42974 32bit @sc{eflags} register used by x86.
42977 32bit @sc{mxcsr} register used by x86.
42981 @node Standard Target Features
42982 @section Standard Target Features
42983 @cindex target descriptions, standard features
42985 A target description must contain either no registers or all the
42986 target's registers. If the description contains no registers, then
42987 @value{GDBN} will assume a default register layout, selected based on
42988 the architecture. If the description contains any registers, the
42989 default layout will not be used; the standard registers must be
42990 described in the target description, in such a way that @value{GDBN}
42991 can recognize them.
42993 This is accomplished by giving specific names to feature elements
42994 which contain standard registers. @value{GDBN} will look for features
42995 with those names and verify that they contain the expected registers;
42996 if any known feature is missing required registers, or if any required
42997 feature is missing, @value{GDBN} will reject the target
42998 description. You can add additional registers to any of the
42999 standard features --- @value{GDBN} will display them just as if
43000 they were added to an unrecognized feature.
43002 This section lists the known features and their expected contents.
43003 Sample XML documents for these features are included in the
43004 @value{GDBN} source tree, in the directory @file{gdb/features}.
43006 Names recognized by @value{GDBN} should include the name of the
43007 company or organization which selected the name, and the overall
43008 architecture to which the feature applies; so e.g.@: the feature
43009 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43011 The names of registers are not case sensitive for the purpose
43012 of recognizing standard features, but @value{GDBN} will only display
43013 registers using the capitalization used in the description.
43016 * AArch64 Features::
43021 * Nios II Features::
43022 * PowerPC Features::
43023 * S/390 and System z Features::
43028 @node AArch64 Features
43029 @subsection AArch64 Features
43030 @cindex target descriptions, AArch64 features
43032 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43033 targets. It should contain registers @samp{x0} through @samp{x30},
43034 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43036 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43037 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43041 @subsection ARM Features
43042 @cindex target descriptions, ARM features
43044 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43046 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43047 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43049 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43050 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43051 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43054 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43055 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43057 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43058 it should contain at least registers @samp{wR0} through @samp{wR15} and
43059 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43060 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43062 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43063 should contain at least registers @samp{d0} through @samp{d15}. If
43064 they are present, @samp{d16} through @samp{d31} should also be included.
43065 @value{GDBN} will synthesize the single-precision registers from
43066 halves of the double-precision registers.
43068 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43069 need to contain registers; it instructs @value{GDBN} to display the
43070 VFP double-precision registers as vectors and to synthesize the
43071 quad-precision registers from pairs of double-precision registers.
43072 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43073 be present and include 32 double-precision registers.
43075 @node i386 Features
43076 @subsection i386 Features
43077 @cindex target descriptions, i386 features
43079 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43080 targets. It should describe the following registers:
43084 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43086 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43088 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43089 @samp{fs}, @samp{gs}
43091 @samp{st0} through @samp{st7}
43093 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43094 @samp{foseg}, @samp{fooff} and @samp{fop}
43097 The register sets may be different, depending on the target.
43099 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43100 describe registers:
43104 @samp{xmm0} through @samp{xmm7} for i386
43106 @samp{xmm0} through @samp{xmm15} for amd64
43111 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43112 @samp{org.gnu.gdb.i386.sse} feature. It should
43113 describe the upper 128 bits of @sc{ymm} registers:
43117 @samp{ymm0h} through @samp{ymm7h} for i386
43119 @samp{ymm0h} through @samp{ymm15h} for amd64
43122 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43123 describe a single register, @samp{orig_eax}.
43125 @node MIPS Features
43126 @subsection @acronym{MIPS} Features
43127 @cindex target descriptions, @acronym{MIPS} features
43129 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43130 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43131 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43134 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43135 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43136 registers. They may be 32-bit or 64-bit depending on the target.
43138 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43139 it may be optional in a future version of @value{GDBN}. It should
43140 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43141 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43143 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43144 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43145 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43146 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43148 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43149 contain a single register, @samp{restart}, which is used by the
43150 Linux kernel to control restartable syscalls.
43152 @node M68K Features
43153 @subsection M68K Features
43154 @cindex target descriptions, M68K features
43157 @item @samp{org.gnu.gdb.m68k.core}
43158 @itemx @samp{org.gnu.gdb.coldfire.core}
43159 @itemx @samp{org.gnu.gdb.fido.core}
43160 One of those features must be always present.
43161 The feature that is present determines which flavor of m68k is
43162 used. The feature that is present should contain registers
43163 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43164 @samp{sp}, @samp{ps} and @samp{pc}.
43166 @item @samp{org.gnu.gdb.coldfire.fp}
43167 This feature is optional. If present, it should contain registers
43168 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43172 @node Nios II Features
43173 @subsection Nios II Features
43174 @cindex target descriptions, Nios II features
43176 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43177 targets. It should contain the 32 core registers (@samp{zero},
43178 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43179 @samp{pc}, and the 16 control registers (@samp{status} through
43182 @node PowerPC Features
43183 @subsection PowerPC Features
43184 @cindex target descriptions, PowerPC features
43186 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43187 targets. It should contain registers @samp{r0} through @samp{r31},
43188 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43189 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43191 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43192 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43194 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43195 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43198 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43199 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43200 will combine these registers with the floating point registers
43201 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43202 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43203 through @samp{vs63}, the set of vector registers for POWER7.
43205 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43206 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43207 @samp{spefscr}. SPE targets should provide 32-bit registers in
43208 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43209 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43210 these to present registers @samp{ev0} through @samp{ev31} to the
43213 @node S/390 and System z Features
43214 @subsection S/390 and System z Features
43215 @cindex target descriptions, S/390 features
43216 @cindex target descriptions, System z features
43218 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43219 System z targets. It should contain the PSW and the 16 general
43220 registers. In particular, System z targets should provide the 64-bit
43221 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43222 S/390 targets should provide the 32-bit versions of these registers.
43223 A System z target that runs in 31-bit addressing mode should provide
43224 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43225 register's upper halves @samp{r0h} through @samp{r15h}, and their
43226 lower halves @samp{r0l} through @samp{r15l}.
43228 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43229 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43232 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43233 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43235 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43236 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43237 targets and 32-bit otherwise. In addition, the feature may contain
43238 the @samp{last_break} register, whose width depends on the addressing
43239 mode, as well as the @samp{system_call} register, which is always
43242 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43243 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43244 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43246 @node TIC6x Features
43247 @subsection TMS320C6x Features
43248 @cindex target descriptions, TIC6x features
43249 @cindex target descriptions, TMS320C6x features
43250 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43251 targets. It should contain registers @samp{A0} through @samp{A15},
43252 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43254 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43255 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43256 through @samp{B31}.
43258 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43259 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43261 @node Operating System Information
43262 @appendix Operating System Information
43263 @cindex operating system information
43269 Users of @value{GDBN} often wish to obtain information about the state of
43270 the operating system running on the target---for example the list of
43271 processes, or the list of open files. This section describes the
43272 mechanism that makes it possible. This mechanism is similar to the
43273 target features mechanism (@pxref{Target Descriptions}), but focuses
43274 on a different aspect of target.
43276 Operating system information is retrived from the target via the
43277 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43278 read}). The object name in the request should be @samp{osdata}, and
43279 the @var{annex} identifies the data to be fetched.
43282 @appendixsection Process list
43283 @cindex operating system information, process list
43285 When requesting the process list, the @var{annex} field in the
43286 @samp{qXfer} request should be @samp{processes}. The returned data is
43287 an XML document. The formal syntax of this document is defined in
43288 @file{gdb/features/osdata.dtd}.
43290 An example document is:
43293 <?xml version="1.0"?>
43294 <!DOCTYPE target SYSTEM "osdata.dtd">
43295 <osdata type="processes">
43297 <column name="pid">1</column>
43298 <column name="user">root</column>
43299 <column name="command">/sbin/init</column>
43300 <column name="cores">1,2,3</column>
43305 Each item should include a column whose name is @samp{pid}. The value
43306 of that column should identify the process on the target. The
43307 @samp{user} and @samp{command} columns are optional, and will be
43308 displayed by @value{GDBN}. The @samp{cores} column, if present,
43309 should contain a comma-separated list of cores that this process
43310 is running on. Target may provide additional columns,
43311 which @value{GDBN} currently ignores.
43313 @node Trace File Format
43314 @appendix Trace File Format
43315 @cindex trace file format
43317 The trace file comes in three parts: a header, a textual description
43318 section, and a trace frame section with binary data.
43320 The header has the form @code{\x7fTRACE0\n}. The first byte is
43321 @code{0x7f} so as to indicate that the file contains binary data,
43322 while the @code{0} is a version number that may have different values
43325 The description section consists of multiple lines of @sc{ascii} text
43326 separated by newline characters (@code{0xa}). The lines may include a
43327 variety of optional descriptive or context-setting information, such
43328 as tracepoint definitions or register set size. @value{GDBN} will
43329 ignore any line that it does not recognize. An empty line marks the end
43332 @c FIXME add some specific types of data
43334 The trace frame section consists of a number of consecutive frames.
43335 Each frame begins with a two-byte tracepoint number, followed by a
43336 four-byte size giving the amount of data in the frame. The data in
43337 the frame consists of a number of blocks, each introduced by a
43338 character indicating its type (at least register, memory, and trace
43339 state variable). The data in this section is raw binary, not a
43340 hexadecimal or other encoding; its endianness matches the target's
43343 @c FIXME bi-arch may require endianness/arch info in description section
43346 @item R @var{bytes}
43347 Register block. The number and ordering of bytes matches that of a
43348 @code{g} packet in the remote protocol. Note that these are the
43349 actual bytes, in target order and @value{GDBN} register order, not a
43350 hexadecimal encoding.
43352 @item M @var{address} @var{length} @var{bytes}...
43353 Memory block. This is a contiguous block of memory, at the 8-byte
43354 address @var{address}, with a 2-byte length @var{length}, followed by
43355 @var{length} bytes.
43357 @item V @var{number} @var{value}
43358 Trace state variable block. This records the 8-byte signed value
43359 @var{value} of trace state variable numbered @var{number}.
43363 Future enhancements of the trace file format may include additional types
43366 @node Index Section Format
43367 @appendix @code{.gdb_index} section format
43368 @cindex .gdb_index section format
43369 @cindex index section format
43371 This section documents the index section that is created by @code{save
43372 gdb-index} (@pxref{Index Files}). The index section is
43373 DWARF-specific; some knowledge of DWARF is assumed in this
43376 The mapped index file format is designed to be directly
43377 @code{mmap}able on any architecture. In most cases, a datum is
43378 represented using a little-endian 32-bit integer value, called an
43379 @code{offset_type}. Big endian machines must byte-swap the values
43380 before using them. Exceptions to this rule are noted. The data is
43381 laid out such that alignment is always respected.
43383 A mapped index consists of several areas, laid out in order.
43387 The file header. This is a sequence of values, of @code{offset_type}
43388 unless otherwise noted:
43392 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43393 Version 4 uses a different hashing function from versions 5 and 6.
43394 Version 6 includes symbols for inlined functions, whereas versions 4
43395 and 5 do not. Version 7 adds attributes to the CU indices in the
43396 symbol table. Version 8 specifies that symbols from DWARF type units
43397 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43398 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43400 @value{GDBN} will only read version 4, 5, or 6 indices
43401 by specifying @code{set use-deprecated-index-sections on}.
43402 GDB has a workaround for potentially broken version 7 indices so it is
43403 currently not flagged as deprecated.
43406 The offset, from the start of the file, of the CU list.
43409 The offset, from the start of the file, of the types CU list. Note
43410 that this area can be empty, in which case this offset will be equal
43411 to the next offset.
43414 The offset, from the start of the file, of the address area.
43417 The offset, from the start of the file, of the symbol table.
43420 The offset, from the start of the file, of the constant pool.
43424 The CU list. This is a sequence of pairs of 64-bit little-endian
43425 values, sorted by the CU offset. The first element in each pair is
43426 the offset of a CU in the @code{.debug_info} section. The second
43427 element in each pair is the length of that CU. References to a CU
43428 elsewhere in the map are done using a CU index, which is just the
43429 0-based index into this table. Note that if there are type CUs, then
43430 conceptually CUs and type CUs form a single list for the purposes of
43434 The types CU list. This is a sequence of triplets of 64-bit
43435 little-endian values. In a triplet, the first value is the CU offset,
43436 the second value is the type offset in the CU, and the third value is
43437 the type signature. The types CU list is not sorted.
43440 The address area. The address area consists of a sequence of address
43441 entries. Each address entry has three elements:
43445 The low address. This is a 64-bit little-endian value.
43448 The high address. This is a 64-bit little-endian value. Like
43449 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43452 The CU index. This is an @code{offset_type} value.
43456 The symbol table. This is an open-addressed hash table. The size of
43457 the hash table is always a power of 2.
43459 Each slot in the hash table consists of a pair of @code{offset_type}
43460 values. The first value is the offset of the symbol's name in the
43461 constant pool. The second value is the offset of the CU vector in the
43464 If both values are 0, then this slot in the hash table is empty. This
43465 is ok because while 0 is a valid constant pool index, it cannot be a
43466 valid index for both a string and a CU vector.
43468 The hash value for a table entry is computed by applying an
43469 iterative hash function to the symbol's name. Starting with an
43470 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43471 the string is incorporated into the hash using the formula depending on the
43476 The formula is @code{r = r * 67 + c - 113}.
43478 @item Versions 5 to 7
43479 The formula is @code{r = r * 67 + tolower (c) - 113}.
43482 The terminating @samp{\0} is not incorporated into the hash.
43484 The step size used in the hash table is computed via
43485 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43486 value, and @samp{size} is the size of the hash table. The step size
43487 is used to find the next candidate slot when handling a hash
43490 The names of C@t{++} symbols in the hash table are canonicalized. We
43491 don't currently have a simple description of the canonicalization
43492 algorithm; if you intend to create new index sections, you must read
43496 The constant pool. This is simply a bunch of bytes. It is organized
43497 so that alignment is correct: CU vectors are stored first, followed by
43500 A CU vector in the constant pool is a sequence of @code{offset_type}
43501 values. The first value is the number of CU indices in the vector.
43502 Each subsequent value is the index and symbol attributes of a CU in
43503 the CU list. This element in the hash table is used to indicate which
43504 CUs define the symbol and how the symbol is used.
43505 See below for the format of each CU index+attributes entry.
43507 A string in the constant pool is zero-terminated.
43510 Attributes were added to CU index values in @code{.gdb_index} version 7.
43511 If a symbol has multiple uses within a CU then there is one
43512 CU index+attributes value for each use.
43514 The format of each CU index+attributes entry is as follows
43520 This is the index of the CU in the CU list.
43522 These bits are reserved for future purposes and must be zero.
43524 The kind of the symbol in the CU.
43528 This value is reserved and should not be used.
43529 By reserving zero the full @code{offset_type} value is backwards compatible
43530 with previous versions of the index.
43532 The symbol is a type.
43534 The symbol is a variable or an enum value.
43536 The symbol is a function.
43538 Any other kind of symbol.
43540 These values are reserved.
43544 This bit is zero if the value is global and one if it is static.
43546 The determination of whether a symbol is global or static is complicated.
43547 The authorative reference is the file @file{dwarf2read.c} in
43548 @value{GDBN} sources.
43552 This pseudo-code describes the computation of a symbol's kind and
43553 global/static attributes in the index.
43556 is_external = get_attribute (die, DW_AT_external);
43557 language = get_attribute (cu_die, DW_AT_language);
43560 case DW_TAG_typedef:
43561 case DW_TAG_base_type:
43562 case DW_TAG_subrange_type:
43566 case DW_TAG_enumerator:
43568 is_static = (language != CPLUS && language != JAVA);
43570 case DW_TAG_subprogram:
43572 is_static = ! (is_external || language == ADA);
43574 case DW_TAG_constant:
43576 is_static = ! is_external;
43578 case DW_TAG_variable:
43580 is_static = ! is_external;
43582 case DW_TAG_namespace:
43586 case DW_TAG_class_type:
43587 case DW_TAG_interface_type:
43588 case DW_TAG_structure_type:
43589 case DW_TAG_union_type:
43590 case DW_TAG_enumeration_type:
43592 is_static = (language != CPLUS && language != JAVA);
43600 @appendix Manual pages
43604 * gdb man:: The GNU Debugger man page
43605 * gdbserver man:: Remote Server for the GNU Debugger man page
43606 * gcore man:: Generate a core file of a running program
43607 * gdbinit man:: gdbinit scripts
43613 @c man title gdb The GNU Debugger
43615 @c man begin SYNOPSIS gdb
43616 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43617 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43618 [@option{-b}@w{ }@var{bps}]
43619 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43620 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43621 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43622 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43623 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43626 @c man begin DESCRIPTION gdb
43627 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43628 going on ``inside'' another program while it executes -- or what another
43629 program was doing at the moment it crashed.
43631 @value{GDBN} can do four main kinds of things (plus other things in support of
43632 these) to help you catch bugs in the act:
43636 Start your program, specifying anything that might affect its behavior.
43639 Make your program stop on specified conditions.
43642 Examine what has happened, when your program has stopped.
43645 Change things in your program, so you can experiment with correcting the
43646 effects of one bug and go on to learn about another.
43649 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43652 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43653 commands from the terminal until you tell it to exit with the @value{GDBN}
43654 command @code{quit}. You can get online help from @value{GDBN} itself
43655 by using the command @code{help}.
43657 You can run @code{gdb} with no arguments or options; but the most
43658 usual way to start @value{GDBN} is with one argument or two, specifying an
43659 executable program as the argument:
43665 You can also start with both an executable program and a core file specified:
43671 You can, instead, specify a process ID as a second argument, if you want
43672 to debug a running process:
43680 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43681 named @file{1234}; @value{GDBN} does check for a core file first).
43682 With option @option{-p} you can omit the @var{program} filename.
43684 Here are some of the most frequently needed @value{GDBN} commands:
43686 @c pod2man highlights the right hand side of the @item lines.
43688 @item break [@var{file}:]@var{functiop}
43689 Set a breakpoint at @var{function} (in @var{file}).
43691 @item run [@var{arglist}]
43692 Start your program (with @var{arglist}, if specified).
43695 Backtrace: display the program stack.
43697 @item print @var{expr}
43698 Display the value of an expression.
43701 Continue running your program (after stopping, e.g. at a breakpoint).
43704 Execute next program line (after stopping); step @emph{over} any
43705 function calls in the line.
43707 @item edit [@var{file}:]@var{function}
43708 look at the program line where it is presently stopped.
43710 @item list [@var{file}:]@var{function}
43711 type the text of the program in the vicinity of where it is presently stopped.
43714 Execute next program line (after stopping); step @emph{into} any
43715 function calls in the line.
43717 @item help [@var{name}]
43718 Show information about @value{GDBN} command @var{name}, or general information
43719 about using @value{GDBN}.
43722 Exit from @value{GDBN}.
43726 For full details on @value{GDBN},
43727 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43728 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43729 as the @code{gdb} entry in the @code{info} program.
43733 @c man begin OPTIONS gdb
43734 Any arguments other than options specify an executable
43735 file and core file (or process ID); that is, the first argument
43736 encountered with no
43737 associated option flag is equivalent to a @option{-se} option, and the second,
43738 if any, is equivalent to a @option{-c} option if it's the name of a file.
43740 both long and short forms; both are shown here. The long forms are also
43741 recognized if you truncate them, so long as enough of the option is
43742 present to be unambiguous. (If you prefer, you can flag option
43743 arguments with @option{+} rather than @option{-}, though we illustrate the
43744 more usual convention.)
43746 All the options and command line arguments you give are processed
43747 in sequential order. The order makes a difference when the @option{-x}
43753 List all options, with brief explanations.
43755 @item -symbols=@var{file}
43756 @itemx -s @var{file}
43757 Read symbol table from file @var{file}.
43760 Enable writing into executable and core files.
43762 @item -exec=@var{file}
43763 @itemx -e @var{file}
43764 Use file @var{file} as the executable file to execute when
43765 appropriate, and for examining pure data in conjunction with a core
43768 @item -se=@var{file}
43769 Read symbol table from file @var{file} and use it as the executable
43772 @item -core=@var{file}
43773 @itemx -c @var{file}
43774 Use file @var{file} as a core dump to examine.
43776 @item -command=@var{file}
43777 @itemx -x @var{file}
43778 Execute @value{GDBN} commands from file @var{file}.
43780 @item -ex @var{command}
43781 Execute given @value{GDBN} @var{command}.
43783 @item -directory=@var{directory}
43784 @itemx -d @var{directory}
43785 Add @var{directory} to the path to search for source files.
43788 Do not execute commands from @file{~/.gdbinit}.
43792 Do not execute commands from any @file{.gdbinit} initialization files.
43796 ``Quiet''. Do not print the introductory and copyright messages. These
43797 messages are also suppressed in batch mode.
43800 Run in batch mode. Exit with status @code{0} after processing all the command
43801 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43802 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43803 commands in the command files.
43805 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43806 download and run a program on another computer; in order to make this
43807 more useful, the message
43810 Program exited normally.
43814 (which is ordinarily issued whenever a program running under @value{GDBN} control
43815 terminates) is not issued when running in batch mode.
43817 @item -cd=@var{directory}
43818 Run @value{GDBN} using @var{directory} as its working directory,
43819 instead of the current directory.
43823 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43824 @value{GDBN} to output the full file name and line number in a standard,
43825 recognizable fashion each time a stack frame is displayed (which
43826 includes each time the program stops). This recognizable format looks
43827 like two @samp{\032} characters, followed by the file name, line number
43828 and character position separated by colons, and a newline. The
43829 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43830 characters as a signal to display the source code for the frame.
43833 Set the line speed (baud rate or bits per second) of any serial
43834 interface used by @value{GDBN} for remote debugging.
43836 @item -tty=@var{device}
43837 Run using @var{device} for your program's standard input and output.
43841 @c man begin SEEALSO gdb
43843 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43844 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43845 documentation are properly installed at your site, the command
43852 should give you access to the complete manual.
43854 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43855 Richard M. Stallman and Roland H. Pesch, July 1991.
43859 @node gdbserver man
43860 @heading gdbserver man
43862 @c man title gdbserver Remote Server for the GNU Debugger
43864 @c man begin SYNOPSIS gdbserver
43865 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43867 gdbserver --attach @var{comm} @var{pid}
43869 gdbserver --multi @var{comm}
43873 @c man begin DESCRIPTION gdbserver
43874 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43875 than the one which is running the program being debugged.
43878 @subheading Usage (server (target) side)
43881 Usage (server (target) side):
43884 First, you need to have a copy of the program you want to debug put onto
43885 the target system. The program can be stripped to save space if needed, as
43886 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43887 the @value{GDBN} running on the host system.
43889 To use the server, you log on to the target system, and run the @command{gdbserver}
43890 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43891 your program, and (c) its arguments. The general syntax is:
43894 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43897 For example, using a serial port, you might say:
43901 @c @file would wrap it as F</dev/com1>.
43902 target> gdbserver /dev/com1 emacs foo.txt
43905 target> gdbserver @file{/dev/com1} emacs foo.txt
43909 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43910 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43911 waits patiently for the host @value{GDBN} to communicate with it.
43913 To use a TCP connection, you could say:
43916 target> gdbserver host:2345 emacs foo.txt
43919 This says pretty much the same thing as the last example, except that we are
43920 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43921 that we are expecting to see a TCP connection from @code{host} to local TCP port
43922 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43923 want for the port number as long as it does not conflict with any existing TCP
43924 ports on the target system. This same port number must be used in the host
43925 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43926 you chose a port number that conflicts with another service, @command{gdbserver} will
43927 print an error message and exit.
43929 @command{gdbserver} can also attach to running programs.
43930 This is accomplished via the @option{--attach} argument. The syntax is:
43933 target> gdbserver --attach @var{comm} @var{pid}
43936 @var{pid} is the process ID of a currently running process. It isn't
43937 necessary to point @command{gdbserver} at a binary for the running process.
43939 To start @code{gdbserver} without supplying an initial command to run
43940 or process ID to attach, use the @option{--multi} command line option.
43941 In such case you should connect using @kbd{target extended-remote} to start
43942 the program you want to debug.
43945 target> gdbserver --multi @var{comm}
43949 @subheading Usage (host side)
43955 You need an unstripped copy of the target program on your host system, since
43956 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43957 would, with the target program as the first argument. (You may need to use the
43958 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43959 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43960 new command you need to know about is @code{target remote}
43961 (or @code{target extended-remote}). Its argument is either
43962 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43963 descriptor. For example:
43967 @c @file would wrap it as F</dev/ttyb>.
43968 (gdb) target remote /dev/ttyb
43971 (gdb) target remote @file{/dev/ttyb}
43976 communicates with the server via serial line @file{/dev/ttyb}, and:
43979 (gdb) target remote the-target:2345
43983 communicates via a TCP connection to port 2345 on host `the-target', where
43984 you previously started up @command{gdbserver} with the same port number. Note that for
43985 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43986 command, otherwise you may get an error that looks something like
43987 `Connection refused'.
43989 @command{gdbserver} can also debug multiple inferiors at once,
43992 the @value{GDBN} manual in node @code{Inferiors and Programs}
43993 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43996 @ref{Inferiors and Programs}.
43998 In such case use the @code{extended-remote} @value{GDBN} command variant:
44001 (gdb) target extended-remote the-target:2345
44004 The @command{gdbserver} option @option{--multi} may or may not be used in such
44008 @c man begin OPTIONS gdbserver
44009 There are three different modes for invoking @command{gdbserver}:
44014 Debug a specific program specified by its program name:
44017 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44020 The @var{comm} parameter specifies how should the server communicate
44021 with @value{GDBN}; it is either a device name (to use a serial line),
44022 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44023 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44024 debug in @var{prog}. Any remaining arguments will be passed to the
44025 program verbatim. When the program exits, @value{GDBN} will close the
44026 connection, and @code{gdbserver} will exit.
44029 Debug a specific program by specifying the process ID of a running
44033 gdbserver --attach @var{comm} @var{pid}
44036 The @var{comm} parameter is as described above. Supply the process ID
44037 of a running program in @var{pid}; @value{GDBN} will do everything
44038 else. Like with the previous mode, when the process @var{pid} exits,
44039 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44042 Multi-process mode -- debug more than one program/process:
44045 gdbserver --multi @var{comm}
44048 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44049 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44050 close the connection when a process being debugged exits, so you can
44051 debug several processes in the same session.
44054 In each of the modes you may specify these options:
44059 List all options, with brief explanations.
44062 This option causes @command{gdbserver} to print its version number and exit.
44065 @command{gdbserver} will attach to a running program. The syntax is:
44068 target> gdbserver --attach @var{comm} @var{pid}
44071 @var{pid} is the process ID of a currently running process. It isn't
44072 necessary to point @command{gdbserver} at a binary for the running process.
44075 To start @code{gdbserver} without supplying an initial command to run
44076 or process ID to attach, use this command line option.
44077 Then you can connect using @kbd{target extended-remote} and start
44078 the program you want to debug. The syntax is:
44081 target> gdbserver --multi @var{comm}
44085 Instruct @code{gdbserver} to display extra status information about the debugging
44087 This option is intended for @code{gdbserver} development and for bug reports to
44090 @item --remote-debug
44091 Instruct @code{gdbserver} to display remote protocol debug output.
44092 This option is intended for @code{gdbserver} development and for bug reports to
44096 Specify a wrapper to launch programs
44097 for debugging. The option should be followed by the name of the
44098 wrapper, then any command-line arguments to pass to the wrapper, then
44099 @kbd{--} indicating the end of the wrapper arguments.
44102 By default, @command{gdbserver} keeps the listening TCP port open, so that
44103 additional connections are possible. However, if you start @code{gdbserver}
44104 with the @option{--once} option, it will stop listening for any further
44105 connection attempts after connecting to the first @value{GDBN} session.
44107 @c --disable-packet is not documented for users.
44109 @c --disable-randomization and --no-disable-randomization are superseded by
44110 @c QDisableRandomization.
44115 @c man begin SEEALSO gdbserver
44117 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44118 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44119 documentation are properly installed at your site, the command
44125 should give you access to the complete manual.
44127 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44128 Richard M. Stallman and Roland H. Pesch, July 1991.
44135 @c man title gcore Generate a core file of a running program
44138 @c man begin SYNOPSIS gcore
44139 gcore [-o @var{filename}] @var{pid}
44143 @c man begin DESCRIPTION gcore
44144 Generate a core dump of a running program with process ID @var{pid}.
44145 Produced file is equivalent to a kernel produced core file as if the process
44146 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44147 limit). Unlike after a crash, after @command{gcore} the program remains
44148 running without any change.
44151 @c man begin OPTIONS gcore
44153 @item -o @var{filename}
44154 The optional argument
44155 @var{filename} specifies the file name where to put the core dump.
44156 If not specified, the file name defaults to @file{core.@var{pid}},
44157 where @var{pid} is the running program process ID.
44161 @c man begin SEEALSO gcore
44163 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44164 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44165 documentation are properly installed at your site, the command
44172 should give you access to the complete manual.
44174 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44175 Richard M. Stallman and Roland H. Pesch, July 1991.
44182 @c man title gdbinit GDB initialization scripts
44185 @c man begin SYNOPSIS gdbinit
44186 @ifset SYSTEM_GDBINIT
44187 @value{SYSTEM_GDBINIT}
44196 @c man begin DESCRIPTION gdbinit
44197 These files contain @value{GDBN} commands to automatically execute during
44198 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44201 the @value{GDBN} manual in node @code{Sequences}
44202 -- shell command @code{info -f gdb -n Sequences}.
44208 Please read more in
44210 the @value{GDBN} manual in node @code{Startup}
44211 -- shell command @code{info -f gdb -n Startup}.
44218 @ifset SYSTEM_GDBINIT
44219 @item @value{SYSTEM_GDBINIT}
44221 @ifclear SYSTEM_GDBINIT
44222 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44224 System-wide initialization file. It is executed unless user specified
44225 @value{GDBN} option @code{-nx} or @code{-n}.
44228 the @value{GDBN} manual in node @code{System-wide configuration}
44229 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44232 @ref{System-wide configuration}.
44236 User initialization file. It is executed unless user specified
44237 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44240 Initialization file for current directory. It may need to be enabled with
44241 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44244 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44245 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44248 @ref{Init File in the Current Directory}.
44253 @c man begin SEEALSO gdbinit
44255 gdb(1), @code{info -f gdb -n Startup}
44257 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44258 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44259 documentation are properly installed at your site, the command
44265 should give you access to the complete manual.
44267 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44268 Richard M. Stallman and Roland H. Pesch, July 1991.
44274 @node GNU Free Documentation License
44275 @appendix GNU Free Documentation License
44278 @node Concept Index
44279 @unnumbered Concept Index
44283 @node Command and Variable Index
44284 @unnumbered Command, Variable, and Function Index
44289 % I think something like @@colophon should be in texinfo. In the
44291 \long\def\colophon{\hbox to0pt{}\vfill
44292 \centerline{The body of this manual is set in}
44293 \centerline{\fontname\tenrm,}
44294 \centerline{with headings in {\bf\fontname\tenbf}}
44295 \centerline{and examples in {\tt\fontname\tentt}.}
44296 \centerline{{\it\fontname\tenit\/},}
44297 \centerline{{\bf\fontname\tenbf}, and}
44298 \centerline{{\sl\fontname\tensl\/}}
44299 \centerline{are used for emphasis.}\vfill}
44301 % Blame: doc@@cygnus.com, 1991.