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
8328 similar use of the same notation in C@t{++}. When they are in
8329 conflict, the C@t{++} meaning takes precedence; however, this can be
8330 overridden by quoting the file or function name with single quotes.
8332 For example, suppose the program is stopped in a method of a class
8333 that has a field named @code{includefile}, and there is also an
8334 include file named @file{includefile} that defines a variable,
8338 (@value{GDBP}) p includefile
8340 (@value{GDBP}) p includefile::some_global
8341 A syntax error in expression, near `'.
8342 (@value{GDBP}) p 'includefile'::some_global
8346 @cindex wrong values
8347 @cindex variable values, wrong
8348 @cindex function entry/exit, wrong values of variables
8349 @cindex optimized code, wrong values of variables
8351 @emph{Warning:} Occasionally, a local variable may appear to have the
8352 wrong value at certain points in a function---just after entry to a new
8353 scope, and just before exit.
8355 You may see this problem when you are stepping by machine instructions.
8356 This is because, on most machines, it takes more than one instruction to
8357 set up a stack frame (including local variable definitions); if you are
8358 stepping by machine instructions, variables may appear to have the wrong
8359 values until the stack frame is completely built. On exit, it usually
8360 also takes more than one machine instruction to destroy a stack frame;
8361 after you begin stepping through that group of instructions, local
8362 variable definitions may be gone.
8364 This may also happen when the compiler does significant optimizations.
8365 To be sure of always seeing accurate values, turn off all optimization
8368 @cindex ``No symbol "foo" in current context''
8369 Another possible effect of compiler optimizations is to optimize
8370 unused variables out of existence, or assign variables to registers (as
8371 opposed to memory addresses). Depending on the support for such cases
8372 offered by the debug info format used by the compiler, @value{GDBN}
8373 might not be able to display values for such local variables. If that
8374 happens, @value{GDBN} will print a message like this:
8377 No symbol "foo" in current context.
8380 To solve such problems, either recompile without optimizations, or use a
8381 different debug info format, if the compiler supports several such
8382 formats. @xref{Compilation}, for more information on choosing compiler
8383 options. @xref{C, ,C and C@t{++}}, for more information about debug
8384 info formats that are best suited to C@t{++} programs.
8386 If you ask to print an object whose contents are unknown to
8387 @value{GDBN}, e.g., because its data type is not completely specified
8388 by the debug information, @value{GDBN} will say @samp{<incomplete
8389 type>}. @xref{Symbols, incomplete type}, for more about this.
8391 If you append @kbd{@@entry} string to a function parameter name you get its
8392 value at the time the function got called. If the value is not available an
8393 error message is printed. Entry values are available only with some compilers.
8394 Entry values are normally also printed at the function parameter list according
8395 to @ref{set print entry-values}.
8398 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8404 (gdb) print i@@entry
8408 Strings are identified as arrays of @code{char} values without specified
8409 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8410 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8411 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8412 defines literal string type @code{"char"} as @code{char} without a sign.
8417 signed char var1[] = "A";
8420 You get during debugging
8425 $2 = @{65 'A', 0 '\0'@}
8429 @section Artificial Arrays
8431 @cindex artificial array
8433 @kindex @@@r{, referencing memory as an array}
8434 It is often useful to print out several successive objects of the
8435 same type in memory; a section of an array, or an array of
8436 dynamically determined size for which only a pointer exists in the
8439 You can do this by referring to a contiguous span of memory as an
8440 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8441 operand of @samp{@@} should be the first element of the desired array
8442 and be an individual object. The right operand should be the desired length
8443 of the array. The result is an array value whose elements are all of
8444 the type of the left argument. The first element is actually the left
8445 argument; the second element comes from bytes of memory immediately
8446 following those that hold the first element, and so on. Here is an
8447 example. If a program says
8450 int *array = (int *) malloc (len * sizeof (int));
8454 you can print the contents of @code{array} with
8460 The left operand of @samp{@@} must reside in memory. Array values made
8461 with @samp{@@} in this way behave just like other arrays in terms of
8462 subscripting, and are coerced to pointers when used in expressions.
8463 Artificial arrays most often appear in expressions via the value history
8464 (@pxref{Value History, ,Value History}), after printing one out.
8466 Another way to create an artificial array is to use a cast.
8467 This re-interprets a value as if it were an array.
8468 The value need not be in memory:
8470 (@value{GDBP}) p/x (short[2])0x12345678
8471 $1 = @{0x1234, 0x5678@}
8474 As a convenience, if you leave the array length out (as in
8475 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8476 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8478 (@value{GDBP}) p/x (short[])0x12345678
8479 $2 = @{0x1234, 0x5678@}
8482 Sometimes the artificial array mechanism is not quite enough; in
8483 moderately complex data structures, the elements of interest may not
8484 actually be adjacent---for example, if you are interested in the values
8485 of pointers in an array. One useful work-around in this situation is
8486 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8487 Variables}) as a counter in an expression that prints the first
8488 interesting value, and then repeat that expression via @key{RET}. For
8489 instance, suppose you have an array @code{dtab} of pointers to
8490 structures, and you are interested in the values of a field @code{fv}
8491 in each structure. Here is an example of what you might type:
8501 @node Output Formats
8502 @section Output Formats
8504 @cindex formatted output
8505 @cindex output formats
8506 By default, @value{GDBN} prints a value according to its data type. Sometimes
8507 this is not what you want. For example, you might want to print a number
8508 in hex, or a pointer in decimal. Or you might want to view data in memory
8509 at a certain address as a character string or as an instruction. To do
8510 these things, specify an @dfn{output format} when you print a value.
8512 The simplest use of output formats is to say how to print a value
8513 already computed. This is done by starting the arguments of the
8514 @code{print} command with a slash and a format letter. The format
8515 letters supported are:
8519 Regard the bits of the value as an integer, and print the integer in
8523 Print as integer in signed decimal.
8526 Print as integer in unsigned decimal.
8529 Print as integer in octal.
8532 Print as integer in binary. The letter @samp{t} stands for ``two''.
8533 @footnote{@samp{b} cannot be used because these format letters are also
8534 used with the @code{x} command, where @samp{b} stands for ``byte'';
8535 see @ref{Memory,,Examining Memory}.}
8538 @cindex unknown address, locating
8539 @cindex locate address
8540 Print as an address, both absolute in hexadecimal and as an offset from
8541 the nearest preceding symbol. You can use this format used to discover
8542 where (in what function) an unknown address is located:
8545 (@value{GDBP}) p/a 0x54320
8546 $3 = 0x54320 <_initialize_vx+396>
8550 The command @code{info symbol 0x54320} yields similar results.
8551 @xref{Symbols, info symbol}.
8554 Regard as an integer and print it as a character constant. This
8555 prints both the numerical value and its character representation. The
8556 character representation is replaced with the octal escape @samp{\nnn}
8557 for characters outside the 7-bit @sc{ascii} range.
8559 Without this format, @value{GDBN} displays @code{char},
8560 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8561 constants. Single-byte members of vectors are displayed as integer
8565 Regard the bits of the value as a floating point number and print
8566 using typical floating point syntax.
8569 @cindex printing strings
8570 @cindex printing byte arrays
8571 Regard as a string, if possible. With this format, pointers to single-byte
8572 data are displayed as null-terminated strings and arrays of single-byte data
8573 are displayed as fixed-length strings. Other values are displayed in their
8576 Without this format, @value{GDBN} displays pointers to and arrays of
8577 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8578 strings. Single-byte members of a vector are displayed as an integer
8582 Like @samp{x} formatting, the value is treated as an integer and
8583 printed as hexadecimal, but leading zeros are printed to pad the value
8584 to the size of the integer type.
8587 @cindex raw printing
8588 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8589 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8590 Printing}). This typically results in a higher-level display of the
8591 value's contents. The @samp{r} format bypasses any Python
8592 pretty-printer which might exist.
8595 For example, to print the program counter in hex (@pxref{Registers}), type
8602 Note that no space is required before the slash; this is because command
8603 names in @value{GDBN} cannot contain a slash.
8605 To reprint the last value in the value history with a different format,
8606 you can use the @code{print} command with just a format and no
8607 expression. For example, @samp{p/x} reprints the last value in hex.
8610 @section Examining Memory
8612 You can use the command @code{x} (for ``examine'') to examine memory in
8613 any of several formats, independently of your program's data types.
8615 @cindex examining memory
8617 @kindex x @r{(examine memory)}
8618 @item x/@var{nfu} @var{addr}
8621 Use the @code{x} command to examine memory.
8624 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8625 much memory to display and how to format it; @var{addr} is an
8626 expression giving the address where you want to start displaying memory.
8627 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8628 Several commands set convenient defaults for @var{addr}.
8631 @item @var{n}, the repeat count
8632 The repeat count is a decimal integer; the default is 1. It specifies
8633 how much memory (counting by units @var{u}) to display.
8634 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8637 @item @var{f}, the display format
8638 The display format is one of the formats used by @code{print}
8639 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8640 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8641 The default is @samp{x} (hexadecimal) initially. The default changes
8642 each time you use either @code{x} or @code{print}.
8644 @item @var{u}, the unit size
8645 The unit size is any of
8651 Halfwords (two bytes).
8653 Words (four bytes). This is the initial default.
8655 Giant words (eight bytes).
8658 Each time you specify a unit size with @code{x}, that size becomes the
8659 default unit the next time you use @code{x}. For the @samp{i} format,
8660 the unit size is ignored and is normally not written. For the @samp{s} format,
8661 the unit size defaults to @samp{b}, unless it is explicitly given.
8662 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8663 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8664 Note that the results depend on the programming language of the
8665 current compilation unit. If the language is C, the @samp{s}
8666 modifier will use the UTF-16 encoding while @samp{w} will use
8667 UTF-32. The encoding is set by the programming language and cannot
8670 @item @var{addr}, starting display address
8671 @var{addr} is the address where you want @value{GDBN} to begin displaying
8672 memory. The expression need not have a pointer value (though it may);
8673 it is always interpreted as an integer address of a byte of memory.
8674 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8675 @var{addr} is usually just after the last address examined---but several
8676 other commands also set the default address: @code{info breakpoints} (to
8677 the address of the last breakpoint listed), @code{info line} (to the
8678 starting address of a line), and @code{print} (if you use it to display
8679 a value from memory).
8682 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8683 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8684 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8685 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8686 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8688 Since the letters indicating unit sizes are all distinct from the
8689 letters specifying output formats, you do not have to remember whether
8690 unit size or format comes first; either order works. The output
8691 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8692 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8694 Even though the unit size @var{u} is ignored for the formats @samp{s}
8695 and @samp{i}, you might still want to use a count @var{n}; for example,
8696 @samp{3i} specifies that you want to see three machine instructions,
8697 including any operands. For convenience, especially when used with
8698 the @code{display} command, the @samp{i} format also prints branch delay
8699 slot instructions, if any, beyond the count specified, which immediately
8700 follow the last instruction that is within the count. The command
8701 @code{disassemble} gives an alternative way of inspecting machine
8702 instructions; see @ref{Machine Code,,Source and Machine Code}.
8704 All the defaults for the arguments to @code{x} are designed to make it
8705 easy to continue scanning memory with minimal specifications each time
8706 you use @code{x}. For example, after you have inspected three machine
8707 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8708 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8709 the repeat count @var{n} is used again; the other arguments default as
8710 for successive uses of @code{x}.
8712 When examining machine instructions, the instruction at current program
8713 counter is shown with a @code{=>} marker. For example:
8716 (@value{GDBP}) x/5i $pc-6
8717 0x804837f <main+11>: mov %esp,%ebp
8718 0x8048381 <main+13>: push %ecx
8719 0x8048382 <main+14>: sub $0x4,%esp
8720 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8721 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8724 @cindex @code{$_}, @code{$__}, and value history
8725 The addresses and contents printed by the @code{x} command are not saved
8726 in the value history because there is often too much of them and they
8727 would get in the way. Instead, @value{GDBN} makes these values available for
8728 subsequent use in expressions as values of the convenience variables
8729 @code{$_} and @code{$__}. After an @code{x} command, the last address
8730 examined is available for use in expressions in the convenience variable
8731 @code{$_}. The contents of that address, as examined, are available in
8732 the convenience variable @code{$__}.
8734 If the @code{x} command has a repeat count, the address and contents saved
8735 are from the last memory unit printed; this is not the same as the last
8736 address printed if several units were printed on the last line of output.
8738 @cindex remote memory comparison
8739 @cindex verify remote memory image
8740 When you are debugging a program running on a remote target machine
8741 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8742 remote machine's memory against the executable file you downloaded to
8743 the target. The @code{compare-sections} command is provided for such
8747 @kindex compare-sections
8748 @item compare-sections @r{[}@var{section-name}@r{]}
8749 Compare the data of a loadable section @var{section-name} in the
8750 executable file of the program being debugged with the same section in
8751 the remote machine's memory, and report any mismatches. With no
8752 arguments, compares all loadable sections. This command's
8753 availability depends on the target's support for the @code{"qCRC"}
8758 @section Automatic Display
8759 @cindex automatic display
8760 @cindex display of expressions
8762 If you find that you want to print the value of an expression frequently
8763 (to see how it changes), you might want to add it to the @dfn{automatic
8764 display list} so that @value{GDBN} prints its value each time your program stops.
8765 Each expression added to the list is given a number to identify it;
8766 to remove an expression from the list, you specify that number.
8767 The automatic display looks like this:
8771 3: bar[5] = (struct hack *) 0x3804
8775 This display shows item numbers, expressions and their current values. As with
8776 displays you request manually using @code{x} or @code{print}, you can
8777 specify the output format you prefer; in fact, @code{display} decides
8778 whether to use @code{print} or @code{x} depending your format
8779 specification---it uses @code{x} if you specify either the @samp{i}
8780 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8784 @item display @var{expr}
8785 Add the expression @var{expr} to the list of expressions to display
8786 each time your program stops. @xref{Expressions, ,Expressions}.
8788 @code{display} does not repeat if you press @key{RET} again after using it.
8790 @item display/@var{fmt} @var{expr}
8791 For @var{fmt} specifying only a display format and not a size or
8792 count, add the expression @var{expr} to the auto-display list but
8793 arrange to display it each time in the specified format @var{fmt}.
8794 @xref{Output Formats,,Output Formats}.
8796 @item display/@var{fmt} @var{addr}
8797 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8798 number of units, add the expression @var{addr} as a memory address to
8799 be examined each time your program stops. Examining means in effect
8800 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8803 For example, @samp{display/i $pc} can be helpful, to see the machine
8804 instruction about to be executed each time execution stops (@samp{$pc}
8805 is a common name for the program counter; @pxref{Registers, ,Registers}).
8808 @kindex delete display
8810 @item undisplay @var{dnums}@dots{}
8811 @itemx delete display @var{dnums}@dots{}
8812 Remove items from the list of expressions to display. Specify the
8813 numbers of the displays that you want affected with the command
8814 argument @var{dnums}. It can be a single display number, one of the
8815 numbers shown in the first field of the @samp{info display} display;
8816 or it could be a range of display numbers, as in @code{2-4}.
8818 @code{undisplay} does not repeat if you press @key{RET} after using it.
8819 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8821 @kindex disable display
8822 @item disable display @var{dnums}@dots{}
8823 Disable the display of item numbers @var{dnums}. A disabled display
8824 item is not printed automatically, but is not forgotten. It may be
8825 enabled again later. Specify the numbers of the displays that you
8826 want affected with the command argument @var{dnums}. It can be a
8827 single display number, one of the numbers shown in the first field of
8828 the @samp{info display} display; or it could be a range of display
8829 numbers, as in @code{2-4}.
8831 @kindex enable display
8832 @item enable display @var{dnums}@dots{}
8833 Enable display of item numbers @var{dnums}. It becomes effective once
8834 again in auto display of its expression, until you specify otherwise.
8835 Specify the numbers of the displays that you want affected with the
8836 command argument @var{dnums}. It can be a single display number, one
8837 of the numbers shown in the first field of the @samp{info display}
8838 display; or it could be a range of display numbers, as in @code{2-4}.
8841 Display the current values of the expressions on the list, just as is
8842 done when your program stops.
8844 @kindex info display
8846 Print the list of expressions previously set up to display
8847 automatically, each one with its item number, but without showing the
8848 values. This includes disabled expressions, which are marked as such.
8849 It also includes expressions which would not be displayed right now
8850 because they refer to automatic variables not currently available.
8853 @cindex display disabled out of scope
8854 If a display expression refers to local variables, then it does not make
8855 sense outside the lexical context for which it was set up. Such an
8856 expression is disabled when execution enters a context where one of its
8857 variables is not defined. For example, if you give the command
8858 @code{display last_char} while inside a function with an argument
8859 @code{last_char}, @value{GDBN} displays this argument while your program
8860 continues to stop inside that function. When it stops elsewhere---where
8861 there is no variable @code{last_char}---the display is disabled
8862 automatically. The next time your program stops where @code{last_char}
8863 is meaningful, you can enable the display expression once again.
8865 @node Print Settings
8866 @section Print Settings
8868 @cindex format options
8869 @cindex print settings
8870 @value{GDBN} provides the following ways to control how arrays, structures,
8871 and symbols are printed.
8874 These settings are useful for debugging programs in any language:
8878 @item set print address
8879 @itemx set print address on
8880 @cindex print/don't print memory addresses
8881 @value{GDBN} prints memory addresses showing the location of stack
8882 traces, structure values, pointer values, breakpoints, and so forth,
8883 even when it also displays the contents of those addresses. The default
8884 is @code{on}. For example, this is what a stack frame display looks like with
8885 @code{set print address on}:
8890 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8892 530 if (lquote != def_lquote)
8896 @item set print address off
8897 Do not print addresses when displaying their contents. For example,
8898 this is the same stack frame displayed with @code{set print address off}:
8902 (@value{GDBP}) set print addr off
8904 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8905 530 if (lquote != def_lquote)
8909 You can use @samp{set print address off} to eliminate all machine
8910 dependent displays from the @value{GDBN} interface. For example, with
8911 @code{print address off}, you should get the same text for backtraces on
8912 all machines---whether or not they involve pointer arguments.
8915 @item show print address
8916 Show whether or not addresses are to be printed.
8919 When @value{GDBN} prints a symbolic address, it normally prints the
8920 closest earlier symbol plus an offset. If that symbol does not uniquely
8921 identify the address (for example, it is a name whose scope is a single
8922 source file), you may need to clarify. One way to do this is with
8923 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8924 you can set @value{GDBN} to print the source file and line number when
8925 it prints a symbolic address:
8928 @item set print symbol-filename on
8929 @cindex source file and line of a symbol
8930 @cindex symbol, source file and line
8931 Tell @value{GDBN} to print the source file name and line number of a
8932 symbol in the symbolic form of an address.
8934 @item set print symbol-filename off
8935 Do not print source file name and line number of a symbol. This is the
8938 @item show print symbol-filename
8939 Show whether or not @value{GDBN} will print the source file name and
8940 line number of a symbol in the symbolic form of an address.
8943 Another situation where it is helpful to show symbol filenames and line
8944 numbers is when disassembling code; @value{GDBN} shows you the line
8945 number and source file that corresponds to each instruction.
8947 Also, you may wish to see the symbolic form only if the address being
8948 printed is reasonably close to the closest earlier symbol:
8951 @item set print max-symbolic-offset @var{max-offset}
8952 @itemx set print max-symbolic-offset unlimited
8953 @cindex maximum value for offset of closest symbol
8954 Tell @value{GDBN} to only display the symbolic form of an address if the
8955 offset between the closest earlier symbol and the address is less than
8956 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8957 to always print the symbolic form of an address if any symbol precedes
8958 it. Zero is equivalent to @code{unlimited}.
8960 @item show print max-symbolic-offset
8961 Ask how large the maximum offset is that @value{GDBN} prints in a
8965 @cindex wild pointer, interpreting
8966 @cindex pointer, finding referent
8967 If you have a pointer and you are not sure where it points, try
8968 @samp{set print symbol-filename on}. Then you can determine the name
8969 and source file location of the variable where it points, using
8970 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8971 For example, here @value{GDBN} shows that a variable @code{ptt} points
8972 at another variable @code{t}, defined in @file{hi2.c}:
8975 (@value{GDBP}) set print symbol-filename on
8976 (@value{GDBP}) p/a ptt
8977 $4 = 0xe008 <t in hi2.c>
8981 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8982 does not show the symbol name and filename of the referent, even with
8983 the appropriate @code{set print} options turned on.
8986 You can also enable @samp{/a}-like formatting all the time using
8987 @samp{set print symbol on}:
8990 @item set print symbol on
8991 Tell @value{GDBN} to print the symbol corresponding to an address, if
8994 @item set print symbol off
8995 Tell @value{GDBN} not to print the symbol corresponding to an
8996 address. In this mode, @value{GDBN} will still print the symbol
8997 corresponding to pointers to functions. This is the default.
8999 @item show print symbol
9000 Show whether @value{GDBN} will display the symbol corresponding to an
9004 Other settings control how different kinds of objects are printed:
9007 @item set print array
9008 @itemx set print array on
9009 @cindex pretty print arrays
9010 Pretty print arrays. This format is more convenient to read,
9011 but uses more space. The default is off.
9013 @item set print array off
9014 Return to compressed format for arrays.
9016 @item show print array
9017 Show whether compressed or pretty format is selected for displaying
9020 @cindex print array indexes
9021 @item set print array-indexes
9022 @itemx set print array-indexes on
9023 Print the index of each element when displaying arrays. May be more
9024 convenient to locate a given element in the array or quickly find the
9025 index of a given element in that printed array. The default is off.
9027 @item set print array-indexes off
9028 Stop printing element indexes when displaying arrays.
9030 @item show print array-indexes
9031 Show whether the index of each element is printed when displaying
9034 @item set print elements @var{number-of-elements}
9035 @itemx set print elements unlimited
9036 @cindex number of array elements to print
9037 @cindex limit on number of printed array elements
9038 Set a limit on how many elements of an array @value{GDBN} will print.
9039 If @value{GDBN} is printing a large array, it stops printing after it has
9040 printed the number of elements set by the @code{set print elements} command.
9041 This limit also applies to the display of strings.
9042 When @value{GDBN} starts, this limit is set to 200.
9043 Setting @var{number-of-elements} to @code{unlimited} or zero means
9044 that the number of elements to print is unlimited.
9046 @item show print elements
9047 Display the number of elements of a large array that @value{GDBN} will print.
9048 If the number is 0, then the printing is unlimited.
9050 @item set print frame-arguments @var{value}
9051 @kindex set print frame-arguments
9052 @cindex printing frame argument values
9053 @cindex print all frame argument values
9054 @cindex print frame argument values for scalars only
9055 @cindex do not print frame argument values
9056 This command allows to control how the values of arguments are printed
9057 when the debugger prints a frame (@pxref{Frames}). The possible
9062 The values of all arguments are printed.
9065 Print the value of an argument only if it is a scalar. The value of more
9066 complex arguments such as arrays, structures, unions, etc, is replaced
9067 by @code{@dots{}}. This is the default. Here is an example where
9068 only scalar arguments are shown:
9071 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9076 None of the argument values are printed. Instead, the value of each argument
9077 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9080 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9085 By default, only scalar arguments are printed. This command can be used
9086 to configure the debugger to print the value of all arguments, regardless
9087 of their type. However, it is often advantageous to not print the value
9088 of more complex parameters. For instance, it reduces the amount of
9089 information printed in each frame, making the backtrace more readable.
9090 Also, it improves performance when displaying Ada frames, because
9091 the computation of large arguments can sometimes be CPU-intensive,
9092 especially in large applications. Setting @code{print frame-arguments}
9093 to @code{scalars} (the default) or @code{none} avoids this computation,
9094 thus speeding up the display of each Ada frame.
9096 @item show print frame-arguments
9097 Show how the value of arguments should be displayed when printing a frame.
9099 @item set print raw frame-arguments on
9100 Print frame arguments in raw, non pretty-printed, form.
9102 @item set print raw frame-arguments off
9103 Print frame arguments in pretty-printed form, if there is a pretty-printer
9104 for the value (@pxref{Pretty Printing}),
9105 otherwise print the value in raw form.
9106 This is the default.
9108 @item show print raw frame-arguments
9109 Show whether to print frame arguments in raw form.
9111 @anchor{set print entry-values}
9112 @item set print entry-values @var{value}
9113 @kindex set print entry-values
9114 Set printing of frame argument values at function entry. In some cases
9115 @value{GDBN} can determine the value of function argument which was passed by
9116 the function caller, even if the value was modified inside the called function
9117 and therefore is different. With optimized code, the current value could be
9118 unavailable, but the entry value may still be known.
9120 The default value is @code{default} (see below for its description). Older
9121 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9122 this feature will behave in the @code{default} setting the same way as with the
9125 This functionality is currently supported only by DWARF 2 debugging format and
9126 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9127 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9130 The @var{value} parameter can be one of the following:
9134 Print only actual parameter values, never print values from function entry
9138 #0 different (val=6)
9139 #0 lost (val=<optimized out>)
9141 #0 invalid (val=<optimized out>)
9145 Print only parameter values from function entry point. The actual parameter
9146 values are never printed.
9148 #0 equal (val@@entry=5)
9149 #0 different (val@@entry=5)
9150 #0 lost (val@@entry=5)
9151 #0 born (val@@entry=<optimized out>)
9152 #0 invalid (val@@entry=<optimized out>)
9156 Print only parameter values from function entry point. If value from function
9157 entry point is not known while the actual value is known, print the actual
9158 value for such parameter.
9160 #0 equal (val@@entry=5)
9161 #0 different (val@@entry=5)
9162 #0 lost (val@@entry=5)
9164 #0 invalid (val@@entry=<optimized out>)
9168 Print actual parameter values. If actual parameter value is not known while
9169 value from function entry point is known, print the entry point value for such
9173 #0 different (val=6)
9174 #0 lost (val@@entry=5)
9176 #0 invalid (val=<optimized out>)
9180 Always print both the actual parameter value and its value from function entry
9181 point, even if values of one or both are not available due to compiler
9184 #0 equal (val=5, val@@entry=5)
9185 #0 different (val=6, val@@entry=5)
9186 #0 lost (val=<optimized out>, val@@entry=5)
9187 #0 born (val=10, val@@entry=<optimized out>)
9188 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9192 Print the actual parameter value if it is known and also its value from
9193 function entry point if it is known. If neither is known, print for the actual
9194 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9195 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@@entry=5)
9202 #0 invalid (val=<optimized out>)
9206 Always print the actual parameter value. Print also its value from function
9207 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9208 if both values are known and identical, print the shortened
9209 @code{param=param@@entry=VALUE} notation.
9211 #0 equal (val=val@@entry=5)
9212 #0 different (val=6, val@@entry=5)
9213 #0 lost (val=<optimized out>, val@@entry=5)
9215 #0 invalid (val=<optimized out>)
9219 For analysis messages on possible failures of frame argument values at function
9220 entry resolution see @ref{set debug entry-values}.
9222 @item show print entry-values
9223 Show the method being used for printing of frame argument values at function
9226 @item set print repeats @var{number-of-repeats}
9227 @itemx set print repeats unlimited
9228 @cindex repeated array elements
9229 Set the threshold for suppressing display of repeated array
9230 elements. When the number of consecutive identical elements of an
9231 array exceeds the threshold, @value{GDBN} prints the string
9232 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9233 identical repetitions, instead of displaying the identical elements
9234 themselves. Setting the threshold to @code{unlimited} or zero will
9235 cause all elements to be individually printed. The default threshold
9238 @item show print repeats
9239 Display the current threshold for printing repeated identical
9242 @item set print null-stop
9243 @cindex @sc{null} elements in arrays
9244 Cause @value{GDBN} to stop printing the characters of an array when the first
9245 @sc{null} is encountered. This is useful when large arrays actually
9246 contain only short strings.
9249 @item show print null-stop
9250 Show whether @value{GDBN} stops printing an array on the first
9251 @sc{null} character.
9253 @item set print pretty on
9254 @cindex print structures in indented form
9255 @cindex indentation in structure display
9256 Cause @value{GDBN} to print structures in an indented format with one member
9257 per line, like this:
9272 @item set print pretty off
9273 Cause @value{GDBN} to print structures in a compact format, like this:
9277 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9278 meat = 0x54 "Pork"@}
9283 This is the default format.
9285 @item show print pretty
9286 Show which format @value{GDBN} is using to print structures.
9288 @item set print sevenbit-strings on
9289 @cindex eight-bit characters in strings
9290 @cindex octal escapes in strings
9291 Print using only seven-bit characters; if this option is set,
9292 @value{GDBN} displays any eight-bit characters (in strings or
9293 character values) using the notation @code{\}@var{nnn}. This setting is
9294 best if you are working in English (@sc{ascii}) and you use the
9295 high-order bit of characters as a marker or ``meta'' bit.
9297 @item set print sevenbit-strings off
9298 Print full eight-bit characters. This allows the use of more
9299 international character sets, and is the default.
9301 @item show print sevenbit-strings
9302 Show whether or not @value{GDBN} is printing only seven-bit characters.
9304 @item set print union on
9305 @cindex unions in structures, printing
9306 Tell @value{GDBN} to print unions which are contained in structures
9307 and other unions. This is the default setting.
9309 @item set print union off
9310 Tell @value{GDBN} not to print unions which are contained in
9311 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9314 @item show print union
9315 Ask @value{GDBN} whether or not it will print unions which are contained in
9316 structures and other unions.
9318 For example, given the declarations
9321 typedef enum @{Tree, Bug@} Species;
9322 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9323 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9334 struct thing foo = @{Tree, @{Acorn@}@};
9338 with @code{set print union on} in effect @samp{p foo} would print
9341 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9345 and with @code{set print union off} in effect it would print
9348 $1 = @{it = Tree, form = @{...@}@}
9352 @code{set print union} affects programs written in C-like languages
9358 These settings are of interest when debugging C@t{++} programs:
9361 @cindex demangling C@t{++} names
9362 @item set print demangle
9363 @itemx set print demangle on
9364 Print C@t{++} names in their source form rather than in the encoded
9365 (``mangled'') form passed to the assembler and linker for type-safe
9366 linkage. The default is on.
9368 @item show print demangle
9369 Show whether C@t{++} names are printed in mangled or demangled form.
9371 @item set print asm-demangle
9372 @itemx set print asm-demangle on
9373 Print C@t{++} names in their source form rather than their mangled form, even
9374 in assembler code printouts such as instruction disassemblies.
9377 @item show print asm-demangle
9378 Show whether C@t{++} names in assembly listings are printed in mangled
9381 @cindex C@t{++} symbol decoding style
9382 @cindex symbol decoding style, C@t{++}
9383 @kindex set demangle-style
9384 @item set demangle-style @var{style}
9385 Choose among several encoding schemes used by different compilers to
9386 represent C@t{++} names. The choices for @var{style} are currently:
9390 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9391 This is the default.
9394 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9397 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9400 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9403 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9404 @strong{Warning:} this setting alone is not sufficient to allow
9405 debugging @code{cfront}-generated executables. @value{GDBN} would
9406 require further enhancement to permit that.
9409 If you omit @var{style}, you will see a list of possible formats.
9411 @item show demangle-style
9412 Display the encoding style currently in use for decoding C@t{++} symbols.
9414 @item set print object
9415 @itemx set print object on
9416 @cindex derived type of an object, printing
9417 @cindex display derived types
9418 When displaying a pointer to an object, identify the @emph{actual}
9419 (derived) type of the object rather than the @emph{declared} type, using
9420 the virtual function table. Note that the virtual function table is
9421 required---this feature can only work for objects that have run-time
9422 type identification; a single virtual method in the object's declared
9423 type is sufficient. Note that this setting is also taken into account when
9424 working with variable objects via MI (@pxref{GDB/MI}).
9426 @item set print object off
9427 Display only the declared type of objects, without reference to the
9428 virtual function table. This is the default setting.
9430 @item show print object
9431 Show whether actual, or declared, object types are displayed.
9433 @item set print static-members
9434 @itemx set print static-members on
9435 @cindex static members of C@t{++} objects
9436 Print static members when displaying a C@t{++} object. The default is on.
9438 @item set print static-members off
9439 Do not print static members when displaying a C@t{++} object.
9441 @item show print static-members
9442 Show whether C@t{++} static members are printed or not.
9444 @item set print pascal_static-members
9445 @itemx set print pascal_static-members on
9446 @cindex static members of Pascal objects
9447 @cindex Pascal objects, static members display
9448 Print static members when displaying a Pascal object. The default is on.
9450 @item set print pascal_static-members off
9451 Do not print static members when displaying a Pascal object.
9453 @item show print pascal_static-members
9454 Show whether Pascal static members are printed or not.
9456 @c These don't work with HP ANSI C++ yet.
9457 @item set print vtbl
9458 @itemx set print vtbl on
9459 @cindex pretty print C@t{++} virtual function tables
9460 @cindex virtual functions (C@t{++}) display
9461 @cindex VTBL display
9462 Pretty print C@t{++} virtual function tables. The default is off.
9463 (The @code{vtbl} commands do not work on programs compiled with the HP
9464 ANSI C@t{++} compiler (@code{aCC}).)
9466 @item set print vtbl off
9467 Do not pretty print C@t{++} virtual function tables.
9469 @item show print vtbl
9470 Show whether C@t{++} virtual function tables are pretty printed, or not.
9473 @node Pretty Printing
9474 @section Pretty Printing
9476 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9477 Python code. It greatly simplifies the display of complex objects. This
9478 mechanism works for both MI and the CLI.
9481 * Pretty-Printer Introduction:: Introduction to pretty-printers
9482 * Pretty-Printer Example:: An example pretty-printer
9483 * Pretty-Printer Commands:: Pretty-printer commands
9486 @node Pretty-Printer Introduction
9487 @subsection Pretty-Printer Introduction
9489 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9490 registered for the value. If there is then @value{GDBN} invokes the
9491 pretty-printer to print the value. Otherwise the value is printed normally.
9493 Pretty-printers are normally named. This makes them easy to manage.
9494 The @samp{info pretty-printer} command will list all the installed
9495 pretty-printers with their names.
9496 If a pretty-printer can handle multiple data types, then its
9497 @dfn{subprinters} are the printers for the individual data types.
9498 Each such subprinter has its own name.
9499 The format of the name is @var{printer-name};@var{subprinter-name}.
9501 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9502 Typically they are automatically loaded and registered when the corresponding
9503 debug information is loaded, thus making them available without having to
9504 do anything special.
9506 There are three places where a pretty-printer can be registered.
9510 Pretty-printers registered globally are available when debugging
9514 Pretty-printers registered with a program space are available only
9515 when debugging that program.
9516 @xref{Progspaces In Python}, for more details on program spaces in Python.
9519 Pretty-printers registered with an objfile are loaded and unloaded
9520 with the corresponding objfile (e.g., shared library).
9521 @xref{Objfiles In Python}, for more details on objfiles in Python.
9524 @xref{Selecting Pretty-Printers}, for further information on how
9525 pretty-printers are selected,
9527 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9530 @node Pretty-Printer Example
9531 @subsection Pretty-Printer Example
9533 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9536 (@value{GDBP}) print s
9538 static npos = 4294967295,
9540 <std::allocator<char>> = @{
9541 <__gnu_cxx::new_allocator<char>> = @{
9542 <No data fields>@}, <No data fields>
9544 members of std::basic_string<char, std::char_traits<char>,
9545 std::allocator<char> >::_Alloc_hider:
9546 _M_p = 0x804a014 "abcd"
9551 With a pretty-printer for @code{std::string} only the contents are printed:
9554 (@value{GDBP}) print s
9558 @node Pretty-Printer Commands
9559 @subsection Pretty-Printer Commands
9560 @cindex pretty-printer commands
9563 @kindex info pretty-printer
9564 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9565 Print the list of installed pretty-printers.
9566 This includes disabled pretty-printers, which are marked as such.
9568 @var{object-regexp} is a regular expression matching the objects
9569 whose pretty-printers to list.
9570 Objects can be @code{global}, the program space's file
9571 (@pxref{Progspaces In Python}),
9572 and the object files within that program space (@pxref{Objfiles In Python}).
9573 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9574 looks up a printer from these three objects.
9576 @var{name-regexp} is a regular expression matching the name of the printers
9579 @kindex disable pretty-printer
9580 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9581 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9582 A disabled pretty-printer is not forgotten, it may be enabled again later.
9584 @kindex enable pretty-printer
9585 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9586 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9591 Suppose we have three pretty-printers installed: one from library1.so
9592 named @code{foo} that prints objects of type @code{foo}, and
9593 another from library2.so named @code{bar} that prints two types of objects,
9594 @code{bar1} and @code{bar2}.
9597 (gdb) info pretty-printer
9604 (gdb) info pretty-printer library2
9609 (gdb) disable pretty-printer library1
9611 2 of 3 printers enabled
9612 (gdb) info pretty-printer
9619 (gdb) disable pretty-printer library2 bar:bar1
9621 1 of 3 printers enabled
9622 (gdb) info pretty-printer library2
9629 (gdb) disable pretty-printer library2 bar
9631 0 of 3 printers enabled
9632 (gdb) info pretty-printer library2
9641 Note that for @code{bar} the entire printer can be disabled,
9642 as can each individual subprinter.
9645 @section Value History
9647 @cindex value history
9648 @cindex history of values printed by @value{GDBN}
9649 Values printed by the @code{print} command are saved in the @value{GDBN}
9650 @dfn{value history}. This allows you to refer to them in other expressions.
9651 Values are kept until the symbol table is re-read or discarded
9652 (for example with the @code{file} or @code{symbol-file} commands).
9653 When the symbol table changes, the value history is discarded,
9654 since the values may contain pointers back to the types defined in the
9659 @cindex history number
9660 The values printed are given @dfn{history numbers} by which you can
9661 refer to them. These are successive integers starting with one.
9662 @code{print} shows you the history number assigned to a value by
9663 printing @samp{$@var{num} = } before the value; here @var{num} is the
9666 To refer to any previous value, use @samp{$} followed by the value's
9667 history number. The way @code{print} labels its output is designed to
9668 remind you of this. Just @code{$} refers to the most recent value in
9669 the history, and @code{$$} refers to the value before that.
9670 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9671 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9672 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9674 For example, suppose you have just printed a pointer to a structure and
9675 want to see the contents of the structure. It suffices to type
9681 If you have a chain of structures where the component @code{next} points
9682 to the next one, you can print the contents of the next one with this:
9689 You can print successive links in the chain by repeating this
9690 command---which you can do by just typing @key{RET}.
9692 Note that the history records values, not expressions. If the value of
9693 @code{x} is 4 and you type these commands:
9701 then the value recorded in the value history by the @code{print} command
9702 remains 4 even though the value of @code{x} has changed.
9707 Print the last ten values in the value history, with their item numbers.
9708 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9709 values} does not change the history.
9711 @item show values @var{n}
9712 Print ten history values centered on history item number @var{n}.
9715 Print ten history values just after the values last printed. If no more
9716 values are available, @code{show values +} produces no display.
9719 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9720 same effect as @samp{show values +}.
9722 @node Convenience Vars
9723 @section Convenience Variables
9725 @cindex convenience variables
9726 @cindex user-defined variables
9727 @value{GDBN} provides @dfn{convenience variables} that you can use within
9728 @value{GDBN} to hold on to a value and refer to it later. These variables
9729 exist entirely within @value{GDBN}; they are not part of your program, and
9730 setting a convenience variable has no direct effect on further execution
9731 of your program. That is why you can use them freely.
9733 Convenience variables are prefixed with @samp{$}. Any name preceded by
9734 @samp{$} can be used for a convenience variable, unless it is one of
9735 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9736 (Value history references, in contrast, are @emph{numbers} preceded
9737 by @samp{$}. @xref{Value History, ,Value History}.)
9739 You can save a value in a convenience variable with an assignment
9740 expression, just as you would set a variable in your program.
9744 set $foo = *object_ptr
9748 would save in @code{$foo} the value contained in the object pointed to by
9751 Using a convenience variable for the first time creates it, but its
9752 value is @code{void} until you assign a new value. You can alter the
9753 value with another assignment at any time.
9755 Convenience variables have no fixed types. You can assign a convenience
9756 variable any type of value, including structures and arrays, even if
9757 that variable already has a value of a different type. The convenience
9758 variable, when used as an expression, has the type of its current value.
9761 @kindex show convenience
9762 @cindex show all user variables and functions
9763 @item show convenience
9764 Print a list of convenience variables used so far, and their values,
9765 as well as a list of the convenience functions.
9766 Abbreviated @code{show conv}.
9768 @kindex init-if-undefined
9769 @cindex convenience variables, initializing
9770 @item init-if-undefined $@var{variable} = @var{expression}
9771 Set a convenience variable if it has not already been set. This is useful
9772 for user-defined commands that keep some state. It is similar, in concept,
9773 to using local static variables with initializers in C (except that
9774 convenience variables are global). It can also be used to allow users to
9775 override default values used in a command script.
9777 If the variable is already defined then the expression is not evaluated so
9778 any side-effects do not occur.
9781 One of the ways to use a convenience variable is as a counter to be
9782 incremented or a pointer to be advanced. For example, to print
9783 a field from successive elements of an array of structures:
9787 print bar[$i++]->contents
9791 Repeat that command by typing @key{RET}.
9793 Some convenience variables are created automatically by @value{GDBN} and given
9794 values likely to be useful.
9797 @vindex $_@r{, convenience variable}
9799 The variable @code{$_} is automatically set by the @code{x} command to
9800 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9801 commands which provide a default address for @code{x} to examine also
9802 set @code{$_} to that address; these commands include @code{info line}
9803 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9804 except when set by the @code{x} command, in which case it is a pointer
9805 to the type of @code{$__}.
9807 @vindex $__@r{, convenience variable}
9809 The variable @code{$__} is automatically set by the @code{x} command
9810 to the value found in the last address examined. Its type is chosen
9811 to match the format in which the data was printed.
9814 @vindex $_exitcode@r{, convenience variable}
9815 When the program being debugged terminates normally, @value{GDBN}
9816 automatically sets this variable to the exit code of the program, and
9817 resets @code{$_exitsignal} to @code{void}.
9820 @vindex $_exitsignal@r{, convenience variable}
9821 When the program being debugged dies due to an uncaught signal,
9822 @value{GDBN} automatically sets this variable to that signal's number,
9823 and resets @code{$_exitcode} to @code{void}.
9825 To distinguish between whether the program being debugged has exited
9826 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9827 @code{$_exitsignal} is not @code{void}), the convenience function
9828 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9829 Functions}). For example, considering the following source code:
9835 main (int argc, char *argv[])
9842 A valid way of telling whether the program being debugged has exited
9843 or signalled would be:
9846 (@value{GDBP}) define has_exited_or_signalled
9847 Type commands for definition of ``has_exited_or_signalled''.
9848 End with a line saying just ``end''.
9849 >if $_isvoid ($_exitsignal)
9850 >echo The program has exited\n
9852 >echo The program has signalled\n
9858 Program terminated with signal SIGALRM, Alarm clock.
9859 The program no longer exists.
9860 (@value{GDBP}) has_exited_or_signalled
9861 The program has signalled
9864 As can be seen, @value{GDBN} correctly informs that the program being
9865 debugged has signalled, since it calls @code{raise} and raises a
9866 @code{SIGALRM} signal. If the program being debugged had not called
9867 @code{raise}, then @value{GDBN} would report a normal exit:
9870 (@value{GDBP}) has_exited_or_signalled
9871 The program has exited
9875 The variable @code{$_exception} is set to the exception object being
9876 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9879 @itemx $_probe_arg0@dots{}$_probe_arg11
9880 Arguments to a static probe. @xref{Static Probe Points}.
9883 @vindex $_sdata@r{, inspect, convenience variable}
9884 The variable @code{$_sdata} contains extra collected static tracepoint
9885 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9886 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9887 if extra static tracepoint data has not been collected.
9890 @vindex $_siginfo@r{, convenience variable}
9891 The variable @code{$_siginfo} contains extra signal information
9892 (@pxref{extra signal information}). Note that @code{$_siginfo}
9893 could be empty, if the application has not yet received any signals.
9894 For example, it will be empty before you execute the @code{run} command.
9897 @vindex $_tlb@r{, convenience variable}
9898 The variable @code{$_tlb} is automatically set when debugging
9899 applications running on MS-Windows in native mode or connected to
9900 gdbserver that supports the @code{qGetTIBAddr} request.
9901 @xref{General Query Packets}.
9902 This variable contains the address of the thread information block.
9906 On HP-UX systems, if you refer to a function or variable name that
9907 begins with a dollar sign, @value{GDBN} searches for a user or system
9908 name first, before it searches for a convenience variable.
9910 @node Convenience Funs
9911 @section Convenience Functions
9913 @cindex convenience functions
9914 @value{GDBN} also supplies some @dfn{convenience functions}. These
9915 have a syntax similar to convenience variables. A convenience
9916 function can be used in an expression just like an ordinary function;
9917 however, a convenience function is implemented internally to
9920 These functions do not require @value{GDBN} to be configured with
9921 @code{Python} support, which means that they are always available.
9925 @item $_isvoid (@var{expr})
9926 @findex $_isvoid@r{, convenience function}
9927 Return one if the expression @var{expr} is @code{void}. Otherwise it
9930 A @code{void} expression is an expression where the type of the result
9931 is @code{void}. For example, you can examine a convenience variable
9932 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9936 (@value{GDBP}) print $_exitcode
9938 (@value{GDBP}) print $_isvoid ($_exitcode)
9941 Starting program: ./a.out
9942 [Inferior 1 (process 29572) exited normally]
9943 (@value{GDBP}) print $_exitcode
9945 (@value{GDBP}) print $_isvoid ($_exitcode)
9949 In the example above, we used @code{$_isvoid} to check whether
9950 @code{$_exitcode} is @code{void} before and after the execution of the
9951 program being debugged. Before the execution there is no exit code to
9952 be examined, therefore @code{$_exitcode} is @code{void}. After the
9953 execution the program being debugged returned zero, therefore
9954 @code{$_exitcode} is zero, which means that it is not @code{void}
9957 The @code{void} expression can also be a call of a function from the
9958 program being debugged. For example, given the following function:
9967 The result of calling it inside @value{GDBN} is @code{void}:
9970 (@value{GDBP}) print foo ()
9972 (@value{GDBP}) print $_isvoid (foo ())
9974 (@value{GDBP}) set $v = foo ()
9975 (@value{GDBP}) print $v
9977 (@value{GDBP}) print $_isvoid ($v)
9983 These functions require @value{GDBN} to be configured with
9984 @code{Python} support.
9988 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9989 @findex $_memeq@r{, convenience function}
9990 Returns one if the @var{length} bytes at the addresses given by
9991 @var{buf1} and @var{buf2} are equal.
9992 Otherwise it returns zero.
9994 @item $_regex(@var{str}, @var{regex})
9995 @findex $_regex@r{, convenience function}
9996 Returns one if the string @var{str} matches the regular expression
9997 @var{regex}. Otherwise it returns zero.
9998 The syntax of the regular expression is that specified by @code{Python}'s
9999 regular expression support.
10001 @item $_streq(@var{str1}, @var{str2})
10002 @findex $_streq@r{, convenience function}
10003 Returns one if the strings @var{str1} and @var{str2} are equal.
10004 Otherwise it returns zero.
10006 @item $_strlen(@var{str})
10007 @findex $_strlen@r{, convenience function}
10008 Returns the length of string @var{str}.
10012 @value{GDBN} provides the ability to list and get help on
10013 convenience functions.
10016 @item help function
10017 @kindex help function
10018 @cindex show all convenience functions
10019 Print a list of all convenience functions.
10026 You can refer to machine register contents, in expressions, as variables
10027 with names starting with @samp{$}. The names of registers are different
10028 for each machine; use @code{info registers} to see the names used on
10032 @kindex info registers
10033 @item info registers
10034 Print the names and values of all registers except floating-point
10035 and vector registers (in the selected stack frame).
10037 @kindex info all-registers
10038 @cindex floating point registers
10039 @item info all-registers
10040 Print the names and values of all registers, including floating-point
10041 and vector registers (in the selected stack frame).
10043 @item info registers @var{regname} @dots{}
10044 Print the @dfn{relativized} value of each specified register @var{regname}.
10045 As discussed in detail below, register values are normally relative to
10046 the selected stack frame. @var{regname} may be any register name valid on
10047 the machine you are using, with or without the initial @samp{$}.
10050 @cindex stack pointer register
10051 @cindex program counter register
10052 @cindex process status register
10053 @cindex frame pointer register
10054 @cindex standard registers
10055 @value{GDBN} has four ``standard'' register names that are available (in
10056 expressions) on most machines---whenever they do not conflict with an
10057 architecture's canonical mnemonics for registers. The register names
10058 @code{$pc} and @code{$sp} are used for the program counter register and
10059 the stack pointer. @code{$fp} is used for a register that contains a
10060 pointer to the current stack frame, and @code{$ps} is used for a
10061 register that contains the processor status. For example,
10062 you could print the program counter in hex with
10069 or print the instruction to be executed next with
10076 or add four to the stack pointer@footnote{This is a way of removing
10077 one word from the stack, on machines where stacks grow downward in
10078 memory (most machines, nowadays). This assumes that the innermost
10079 stack frame is selected; setting @code{$sp} is not allowed when other
10080 stack frames are selected. To pop entire frames off the stack,
10081 regardless of machine architecture, use @code{return};
10082 see @ref{Returning, ,Returning from a Function}.} with
10088 Whenever possible, these four standard register names are available on
10089 your machine even though the machine has different canonical mnemonics,
10090 so long as there is no conflict. The @code{info registers} command
10091 shows the canonical names. For example, on the SPARC, @code{info
10092 registers} displays the processor status register as @code{$psr} but you
10093 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10094 is an alias for the @sc{eflags} register.
10096 @value{GDBN} always considers the contents of an ordinary register as an
10097 integer when the register is examined in this way. Some machines have
10098 special registers which can hold nothing but floating point; these
10099 registers are considered to have floating point values. There is no way
10100 to refer to the contents of an ordinary register as floating point value
10101 (although you can @emph{print} it as a floating point value with
10102 @samp{print/f $@var{regname}}).
10104 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10105 means that the data format in which the register contents are saved by
10106 the operating system is not the same one that your program normally
10107 sees. For example, the registers of the 68881 floating point
10108 coprocessor are always saved in ``extended'' (raw) format, but all C
10109 programs expect to work with ``double'' (virtual) format. In such
10110 cases, @value{GDBN} normally works with the virtual format only (the format
10111 that makes sense for your program), but the @code{info registers} command
10112 prints the data in both formats.
10114 @cindex SSE registers (x86)
10115 @cindex MMX registers (x86)
10116 Some machines have special registers whose contents can be interpreted
10117 in several different ways. For example, modern x86-based machines
10118 have SSE and MMX registers that can hold several values packed
10119 together in several different formats. @value{GDBN} refers to such
10120 registers in @code{struct} notation:
10123 (@value{GDBP}) print $xmm1
10125 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10126 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10127 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10128 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10129 v4_int32 = @{0, 20657912, 11, 13@},
10130 v2_int64 = @{88725056443645952, 55834574859@},
10131 uint128 = 0x0000000d0000000b013b36f800000000
10136 To set values of such registers, you need to tell @value{GDBN} which
10137 view of the register you wish to change, as if you were assigning
10138 value to a @code{struct} member:
10141 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10144 Normally, register values are relative to the selected stack frame
10145 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10146 value that the register would contain if all stack frames farther in
10147 were exited and their saved registers restored. In order to see the
10148 true contents of hardware registers, you must select the innermost
10149 frame (with @samp{frame 0}).
10151 @cindex caller-saved registers
10152 @cindex call-clobbered registers
10153 @cindex volatile registers
10154 @cindex <not saved> values
10155 Usually ABIs reserve some registers as not needed to be saved by the
10156 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10157 registers). It may therefore not be possible for @value{GDBN} to know
10158 the value a register had before the call (in other words, in the outer
10159 frame), if the register value has since been changed by the callee.
10160 @value{GDBN} tries to deduce where the inner frame saved
10161 (``callee-saved'') registers, from the debug info, unwind info, or the
10162 machine code generated by your compiler. If some register is not
10163 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10164 its own knowledge of the ABI, or because the debug/unwind info
10165 explicitly says the register's value is undefined), @value{GDBN}
10166 displays @w{@samp{<not saved>}} as the register's value. With targets
10167 that @value{GDBN} has no knowledge of the register saving convention,
10168 if a register was not saved by the callee, then its value and location
10169 in the outer frame are assumed to be the same of the inner frame.
10170 This is usually harmless, because if the register is call-clobbered,
10171 the caller either does not care what is in the register after the
10172 call, or has code to restore the value that it does care about. Note,
10173 however, that if you change such a register in the outer frame, you
10174 may also be affecting the inner frame. Also, the more ``outer'' the
10175 frame is you're looking at, the more likely a call-clobbered
10176 register's value is to be wrong, in the sense that it doesn't actually
10177 represent the value the register had just before the call.
10179 @node Floating Point Hardware
10180 @section Floating Point Hardware
10181 @cindex floating point
10183 Depending on the configuration, @value{GDBN} may be able to give
10184 you more information about the status of the floating point hardware.
10189 Display hardware-dependent information about the floating
10190 point unit. The exact contents and layout vary depending on the
10191 floating point chip. Currently, @samp{info float} is supported on
10192 the ARM and x86 machines.
10196 @section Vector Unit
10197 @cindex vector unit
10199 Depending on the configuration, @value{GDBN} may be able to give you
10200 more information about the status of the vector unit.
10203 @kindex info vector
10205 Display information about the vector unit. The exact contents and
10206 layout vary depending on the hardware.
10209 @node OS Information
10210 @section Operating System Auxiliary Information
10211 @cindex OS information
10213 @value{GDBN} provides interfaces to useful OS facilities that can help
10214 you debug your program.
10216 @cindex auxiliary vector
10217 @cindex vector, auxiliary
10218 Some operating systems supply an @dfn{auxiliary vector} to programs at
10219 startup. This is akin to the arguments and environment that you
10220 specify for a program, but contains a system-dependent variety of
10221 binary values that tell system libraries important details about the
10222 hardware, operating system, and process. Each value's purpose is
10223 identified by an integer tag; the meanings are well-known but system-specific.
10224 Depending on the configuration and operating system facilities,
10225 @value{GDBN} may be able to show you this information. For remote
10226 targets, this functionality may further depend on the remote stub's
10227 support of the @samp{qXfer:auxv:read} packet, see
10228 @ref{qXfer auxiliary vector read}.
10233 Display the auxiliary vector of the inferior, which can be either a
10234 live process or a core dump file. @value{GDBN} prints each tag value
10235 numerically, and also shows names and text descriptions for recognized
10236 tags. Some values in the vector are numbers, some bit masks, and some
10237 pointers to strings or other data. @value{GDBN} displays each value in the
10238 most appropriate form for a recognized tag, and in hexadecimal for
10239 an unrecognized tag.
10242 On some targets, @value{GDBN} can access operating system-specific
10243 information and show it to you. The types of information available
10244 will differ depending on the type of operating system running on the
10245 target. The mechanism used to fetch the data is described in
10246 @ref{Operating System Information}. For remote targets, this
10247 functionality depends on the remote stub's support of the
10248 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10252 @item info os @var{infotype}
10254 Display OS information of the requested type.
10256 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10258 @anchor{linux info os infotypes}
10260 @kindex info os processes
10262 Display the list of processes on the target. For each process,
10263 @value{GDBN} prints the process identifier, the name of the user, the
10264 command corresponding to the process, and the list of processor cores
10265 that the process is currently running on. (To understand what these
10266 properties mean, for this and the following info types, please consult
10267 the general @sc{gnu}/Linux documentation.)
10269 @kindex info os procgroups
10271 Display the list of process groups on the target. For each process,
10272 @value{GDBN} prints the identifier of the process group that it belongs
10273 to, the command corresponding to the process group leader, the process
10274 identifier, and the command line of the process. The list is sorted
10275 first by the process group identifier, then by the process identifier,
10276 so that processes belonging to the same process group are grouped together
10277 and the process group leader is listed first.
10279 @kindex info os threads
10281 Display the list of threads running on the target. For each thread,
10282 @value{GDBN} prints the identifier of the process that the thread
10283 belongs to, the command of the process, the thread identifier, and the
10284 processor core that it is currently running on. The main thread of a
10285 process is not listed.
10287 @kindex info os files
10289 Display the list of open file descriptors on the target. For each
10290 file descriptor, @value{GDBN} prints the identifier of the process
10291 owning the descriptor, the command of the owning process, the value
10292 of the descriptor, and the target of the descriptor.
10294 @kindex info os sockets
10296 Display the list of Internet-domain sockets on the target. For each
10297 socket, @value{GDBN} prints the address and port of the local and
10298 remote endpoints, the current state of the connection, the creator of
10299 the socket, the IP address family of the socket, and the type of the
10302 @kindex info os shm
10304 Display the list of all System V shared-memory regions on the target.
10305 For each shared-memory region, @value{GDBN} prints the region key,
10306 the shared-memory identifier, the access permissions, the size of the
10307 region, the process that created the region, the process that last
10308 attached to or detached from the region, the current number of live
10309 attaches to the region, and the times at which the region was last
10310 attached to, detach from, and changed.
10312 @kindex info os semaphores
10314 Display the list of all System V semaphore sets on the target. For each
10315 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10316 set identifier, the access permissions, the number of semaphores in the
10317 set, the user and group of the owner and creator of the semaphore set,
10318 and the times at which the semaphore set was operated upon and changed.
10320 @kindex info os msg
10322 Display the list of all System V message queues on the target. For each
10323 message queue, @value{GDBN} prints the message queue key, the message
10324 queue identifier, the access permissions, the current number of bytes
10325 on the queue, the current number of messages on the queue, the processes
10326 that last sent and received a message on the queue, the user and group
10327 of the owner and creator of the message queue, the times at which a
10328 message was last sent and received on the queue, and the time at which
10329 the message queue was last changed.
10331 @kindex info os modules
10333 Display the list of all loaded kernel modules on the target. For each
10334 module, @value{GDBN} prints the module name, the size of the module in
10335 bytes, the number of times the module is used, the dependencies of the
10336 module, the status of the module, and the address of the loaded module
10341 If @var{infotype} is omitted, then list the possible values for
10342 @var{infotype} and the kind of OS information available for each
10343 @var{infotype}. If the target does not return a list of possible
10344 types, this command will report an error.
10347 @node Memory Region Attributes
10348 @section Memory Region Attributes
10349 @cindex memory region attributes
10351 @dfn{Memory region attributes} allow you to describe special handling
10352 required by regions of your target's memory. @value{GDBN} uses
10353 attributes to determine whether to allow certain types of memory
10354 accesses; whether to use specific width accesses; and whether to cache
10355 target memory. By default the description of memory regions is
10356 fetched from the target (if the current target supports this), but the
10357 user can override the fetched regions.
10359 Defined memory regions can be individually enabled and disabled. When a
10360 memory region is disabled, @value{GDBN} uses the default attributes when
10361 accessing memory in that region. Similarly, if no memory regions have
10362 been defined, @value{GDBN} uses the default attributes when accessing
10365 When a memory region is defined, it is given a number to identify it;
10366 to enable, disable, or remove a memory region, you specify that number.
10370 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10371 Define a memory region bounded by @var{lower} and @var{upper} with
10372 attributes @var{attributes}@dots{}, and add it to the list of regions
10373 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10374 case: it is treated as the target's maximum memory address.
10375 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10378 Discard any user changes to the memory regions and use target-supplied
10379 regions, if available, or no regions if the target does not support.
10382 @item delete mem @var{nums}@dots{}
10383 Remove memory regions @var{nums}@dots{} from the list of regions
10384 monitored by @value{GDBN}.
10386 @kindex disable mem
10387 @item disable mem @var{nums}@dots{}
10388 Disable monitoring of memory regions @var{nums}@dots{}.
10389 A disabled memory region is not forgotten.
10390 It may be enabled again later.
10393 @item enable mem @var{nums}@dots{}
10394 Enable monitoring of memory regions @var{nums}@dots{}.
10398 Print a table of all defined memory regions, with the following columns
10402 @item Memory Region Number
10403 @item Enabled or Disabled.
10404 Enabled memory regions are marked with @samp{y}.
10405 Disabled memory regions are marked with @samp{n}.
10408 The address defining the inclusive lower bound of the memory region.
10411 The address defining the exclusive upper bound of the memory region.
10414 The list of attributes set for this memory region.
10419 @subsection Attributes
10421 @subsubsection Memory Access Mode
10422 The access mode attributes set whether @value{GDBN} may make read or
10423 write accesses to a memory region.
10425 While these attributes prevent @value{GDBN} from performing invalid
10426 memory accesses, they do nothing to prevent the target system, I/O DMA,
10427 etc.@: from accessing memory.
10431 Memory is read only.
10433 Memory is write only.
10435 Memory is read/write. This is the default.
10438 @subsubsection Memory Access Size
10439 The access size attribute tells @value{GDBN} to use specific sized
10440 accesses in the memory region. Often memory mapped device registers
10441 require specific sized accesses. If no access size attribute is
10442 specified, @value{GDBN} may use accesses of any size.
10446 Use 8 bit memory accesses.
10448 Use 16 bit memory accesses.
10450 Use 32 bit memory accesses.
10452 Use 64 bit memory accesses.
10455 @c @subsubsection Hardware/Software Breakpoints
10456 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10457 @c will use hardware or software breakpoints for the internal breakpoints
10458 @c used by the step, next, finish, until, etc. commands.
10462 @c Always use hardware breakpoints
10463 @c @item swbreak (default)
10466 @subsubsection Data Cache
10467 The data cache attributes set whether @value{GDBN} will cache target
10468 memory. While this generally improves performance by reducing debug
10469 protocol overhead, it can lead to incorrect results because @value{GDBN}
10470 does not know about volatile variables or memory mapped device
10475 Enable @value{GDBN} to cache target memory.
10477 Disable @value{GDBN} from caching target memory. This is the default.
10480 @subsection Memory Access Checking
10481 @value{GDBN} can be instructed to refuse accesses to memory that is
10482 not explicitly described. This can be useful if accessing such
10483 regions has undesired effects for a specific target, or to provide
10484 better error checking. The following commands control this behaviour.
10487 @kindex set mem inaccessible-by-default
10488 @item set mem inaccessible-by-default [on|off]
10489 If @code{on} is specified, make @value{GDBN} treat memory not
10490 explicitly described by the memory ranges as non-existent and refuse accesses
10491 to such memory. The checks are only performed if there's at least one
10492 memory range defined. If @code{off} is specified, make @value{GDBN}
10493 treat the memory not explicitly described by the memory ranges as RAM.
10494 The default value is @code{on}.
10495 @kindex show mem inaccessible-by-default
10496 @item show mem inaccessible-by-default
10497 Show the current handling of accesses to unknown memory.
10501 @c @subsubsection Memory Write Verification
10502 @c The memory write verification attributes set whether @value{GDBN}
10503 @c will re-reads data after each write to verify the write was successful.
10507 @c @item noverify (default)
10510 @node Dump/Restore Files
10511 @section Copy Between Memory and a File
10512 @cindex dump/restore files
10513 @cindex append data to a file
10514 @cindex dump data to a file
10515 @cindex restore data from a file
10517 You can use the commands @code{dump}, @code{append}, and
10518 @code{restore} to copy data between target memory and a file. The
10519 @code{dump} and @code{append} commands write data to a file, and the
10520 @code{restore} command reads data from a file back into the inferior's
10521 memory. Files may be in binary, Motorola S-record, Intel hex, or
10522 Tektronix Hex format; however, @value{GDBN} can only append to binary
10528 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10529 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10530 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10531 or the value of @var{expr}, to @var{filename} in the given format.
10533 The @var{format} parameter may be any one of:
10540 Motorola S-record format.
10542 Tektronix Hex format.
10545 @value{GDBN} uses the same definitions of these formats as the
10546 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10547 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10551 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10552 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10553 Append the contents of memory from @var{start_addr} to @var{end_addr},
10554 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10555 (@value{GDBN} can only append data to files in raw binary form.)
10558 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10559 Restore the contents of file @var{filename} into memory. The
10560 @code{restore} command can automatically recognize any known @sc{bfd}
10561 file format, except for raw binary. To restore a raw binary file you
10562 must specify the optional keyword @code{binary} after the filename.
10564 If @var{bias} is non-zero, its value will be added to the addresses
10565 contained in the file. Binary files always start at address zero, so
10566 they will be restored at address @var{bias}. Other bfd files have
10567 a built-in location; they will be restored at offset @var{bias}
10568 from that location.
10570 If @var{start} and/or @var{end} are non-zero, then only data between
10571 file offset @var{start} and file offset @var{end} will be restored.
10572 These offsets are relative to the addresses in the file, before
10573 the @var{bias} argument is applied.
10577 @node Core File Generation
10578 @section How to Produce a Core File from Your Program
10579 @cindex dump core from inferior
10581 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10582 image of a running process and its process status (register values
10583 etc.). Its primary use is post-mortem debugging of a program that
10584 crashed while it ran outside a debugger. A program that crashes
10585 automatically produces a core file, unless this feature is disabled by
10586 the user. @xref{Files}, for information on invoking @value{GDBN} in
10587 the post-mortem debugging mode.
10589 Occasionally, you may wish to produce a core file of the program you
10590 are debugging in order to preserve a snapshot of its state.
10591 @value{GDBN} has a special command for that.
10595 @kindex generate-core-file
10596 @item generate-core-file [@var{file}]
10597 @itemx gcore [@var{file}]
10598 Produce a core dump of the inferior process. The optional argument
10599 @var{file} specifies the file name where to put the core dump. If not
10600 specified, the file name defaults to @file{core.@var{pid}}, where
10601 @var{pid} is the inferior process ID.
10603 Note that this command is implemented only for some systems (as of
10604 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10607 @node Character Sets
10608 @section Character Sets
10609 @cindex character sets
10611 @cindex translating between character sets
10612 @cindex host character set
10613 @cindex target character set
10615 If the program you are debugging uses a different character set to
10616 represent characters and strings than the one @value{GDBN} uses itself,
10617 @value{GDBN} can automatically translate between the character sets for
10618 you. The character set @value{GDBN} uses we call the @dfn{host
10619 character set}; the one the inferior program uses we call the
10620 @dfn{target character set}.
10622 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10623 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10624 remote protocol (@pxref{Remote Debugging}) to debug a program
10625 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10626 then the host character set is Latin-1, and the target character set is
10627 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10628 target-charset EBCDIC-US}, then @value{GDBN} translates between
10629 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10630 character and string literals in expressions.
10632 @value{GDBN} has no way to automatically recognize which character set
10633 the inferior program uses; you must tell it, using the @code{set
10634 target-charset} command, described below.
10636 Here are the commands for controlling @value{GDBN}'s character set
10640 @item set target-charset @var{charset}
10641 @kindex set target-charset
10642 Set the current target character set to @var{charset}. To display the
10643 list of supported target character sets, type
10644 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10646 @item set host-charset @var{charset}
10647 @kindex set host-charset
10648 Set the current host character set to @var{charset}.
10650 By default, @value{GDBN} uses a host character set appropriate to the
10651 system it is running on; you can override that default using the
10652 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10653 automatically determine the appropriate host character set. In this
10654 case, @value{GDBN} uses @samp{UTF-8}.
10656 @value{GDBN} can only use certain character sets as its host character
10657 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10658 @value{GDBN} will list the host character sets it supports.
10660 @item set charset @var{charset}
10661 @kindex set charset
10662 Set the current host and target character sets to @var{charset}. As
10663 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10664 @value{GDBN} will list the names of the character sets that can be used
10665 for both host and target.
10668 @kindex show charset
10669 Show the names of the current host and target character sets.
10671 @item show host-charset
10672 @kindex show host-charset
10673 Show the name of the current host character set.
10675 @item show target-charset
10676 @kindex show target-charset
10677 Show the name of the current target character set.
10679 @item set target-wide-charset @var{charset}
10680 @kindex set target-wide-charset
10681 Set the current target's wide character set to @var{charset}. This is
10682 the character set used by the target's @code{wchar_t} type. To
10683 display the list of supported wide character sets, type
10684 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10686 @item show target-wide-charset
10687 @kindex show target-wide-charset
10688 Show the name of the current target's wide character set.
10691 Here is an example of @value{GDBN}'s character set support in action.
10692 Assume that the following source code has been placed in the file
10693 @file{charset-test.c}:
10699 = @{72, 101, 108, 108, 111, 44, 32, 119,
10700 111, 114, 108, 100, 33, 10, 0@};
10701 char ibm1047_hello[]
10702 = @{200, 133, 147, 147, 150, 107, 64, 166,
10703 150, 153, 147, 132, 90, 37, 0@};
10707 printf ("Hello, world!\n");
10711 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10712 containing the string @samp{Hello, world!} followed by a newline,
10713 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10715 We compile the program, and invoke the debugger on it:
10718 $ gcc -g charset-test.c -o charset-test
10719 $ gdb -nw charset-test
10720 GNU gdb 2001-12-19-cvs
10721 Copyright 2001 Free Software Foundation, Inc.
10726 We can use the @code{show charset} command to see what character sets
10727 @value{GDBN} is currently using to interpret and display characters and
10731 (@value{GDBP}) show charset
10732 The current host and target character set is `ISO-8859-1'.
10736 For the sake of printing this manual, let's use @sc{ascii} as our
10737 initial character set:
10739 (@value{GDBP}) set charset ASCII
10740 (@value{GDBP}) show charset
10741 The current host and target character set is `ASCII'.
10745 Let's assume that @sc{ascii} is indeed the correct character set for our
10746 host system --- in other words, let's assume that if @value{GDBN} prints
10747 characters using the @sc{ascii} character set, our terminal will display
10748 them properly. Since our current target character set is also
10749 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10752 (@value{GDBP}) print ascii_hello
10753 $1 = 0x401698 "Hello, world!\n"
10754 (@value{GDBP}) print ascii_hello[0]
10759 @value{GDBN} uses the target character set for character and string
10760 literals you use in expressions:
10763 (@value{GDBP}) print '+'
10768 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10771 @value{GDBN} relies on the user to tell it which character set the
10772 target program uses. If we print @code{ibm1047_hello} while our target
10773 character set is still @sc{ascii}, we get jibberish:
10776 (@value{GDBP}) print ibm1047_hello
10777 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10778 (@value{GDBP}) print ibm1047_hello[0]
10783 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10784 @value{GDBN} tells us the character sets it supports:
10787 (@value{GDBP}) set target-charset
10788 ASCII EBCDIC-US IBM1047 ISO-8859-1
10789 (@value{GDBP}) set target-charset
10792 We can select @sc{ibm1047} as our target character set, and examine the
10793 program's strings again. Now the @sc{ascii} string is wrong, but
10794 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10795 target character set, @sc{ibm1047}, to the host character set,
10796 @sc{ascii}, and they display correctly:
10799 (@value{GDBP}) set target-charset IBM1047
10800 (@value{GDBP}) show charset
10801 The current host character set is `ASCII'.
10802 The current target character set is `IBM1047'.
10803 (@value{GDBP}) print ascii_hello
10804 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10805 (@value{GDBP}) print ascii_hello[0]
10807 (@value{GDBP}) print ibm1047_hello
10808 $8 = 0x4016a8 "Hello, world!\n"
10809 (@value{GDBP}) print ibm1047_hello[0]
10814 As above, @value{GDBN} uses the target character set for character and
10815 string literals you use in expressions:
10818 (@value{GDBP}) print '+'
10823 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10826 @node Caching Remote Data
10827 @section Caching Data of Remote Targets
10828 @cindex caching data of remote targets
10830 @value{GDBN} caches data exchanged between the debugger and a
10831 remote target (@pxref{Remote Debugging}). Such caching generally improves
10832 performance, because it reduces the overhead of the remote protocol by
10833 bundling memory reads and writes into large chunks. Unfortunately, simply
10834 caching everything would lead to incorrect results, since @value{GDBN}
10835 does not necessarily know anything about volatile values, memory-mapped I/O
10836 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10837 memory can be changed @emph{while} a gdb command is executing.
10838 Therefore, by default, @value{GDBN} only caches data
10839 known to be on the stack@footnote{In non-stop mode, it is moderately
10840 rare for a running thread to modify the stack of a stopped thread
10841 in a way that would interfere with a backtrace, and caching of
10842 stack reads provides a significant speed up of remote backtraces.}.
10843 Other regions of memory can be explicitly marked as
10844 cacheable; see @pxref{Memory Region Attributes}.
10847 @kindex set remotecache
10848 @item set remotecache on
10849 @itemx set remotecache off
10850 This option no longer does anything; it exists for compatibility
10853 @kindex show remotecache
10854 @item show remotecache
10855 Show the current state of the obsolete remotecache flag.
10857 @kindex set stack-cache
10858 @item set stack-cache on
10859 @itemx set stack-cache off
10860 Enable or disable caching of stack accesses. When @code{ON}, use
10861 caching. By default, this option is @code{ON}.
10863 @kindex show stack-cache
10864 @item show stack-cache
10865 Show the current state of data caching for memory accesses.
10867 @kindex info dcache
10868 @item info dcache @r{[}line@r{]}
10869 Print the information about the data cache performance. The
10870 information displayed includes the dcache width and depth, and for
10871 each cache line, its number, address, and how many times it was
10872 referenced. This command is useful for debugging the data cache
10875 If a line number is specified, the contents of that line will be
10878 @item set dcache size @var{size}
10879 @cindex dcache size
10880 @kindex set dcache size
10881 Set maximum number of entries in dcache (dcache depth above).
10883 @item set dcache line-size @var{line-size}
10884 @cindex dcache line-size
10885 @kindex set dcache line-size
10886 Set number of bytes each dcache entry caches (dcache width above).
10887 Must be a power of 2.
10889 @item show dcache size
10890 @kindex show dcache size
10891 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10893 @item show dcache line-size
10894 @kindex show dcache line-size
10895 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10899 @node Searching Memory
10900 @section Search Memory
10901 @cindex searching memory
10903 Memory can be searched for a particular sequence of bytes with the
10904 @code{find} command.
10908 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10909 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10910 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10911 etc. The search begins at address @var{start_addr} and continues for either
10912 @var{len} bytes or through to @var{end_addr} inclusive.
10915 @var{s} and @var{n} are optional parameters.
10916 They may be specified in either order, apart or together.
10919 @item @var{s}, search query size
10920 The size of each search query value.
10926 halfwords (two bytes)
10930 giant words (eight bytes)
10933 All values are interpreted in the current language.
10934 This means, for example, that if the current source language is C/C@t{++}
10935 then searching for the string ``hello'' includes the trailing '\0'.
10937 If the value size is not specified, it is taken from the
10938 value's type in the current language.
10939 This is useful when one wants to specify the search
10940 pattern as a mixture of types.
10941 Note that this means, for example, that in the case of C-like languages
10942 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10943 which is typically four bytes.
10945 @item @var{n}, maximum number of finds
10946 The maximum number of matches to print. The default is to print all finds.
10949 You can use strings as search values. Quote them with double-quotes
10951 The string value is copied into the search pattern byte by byte,
10952 regardless of the endianness of the target and the size specification.
10954 The address of each match found is printed as well as a count of the
10955 number of matches found.
10957 The address of the last value found is stored in convenience variable
10959 A count of the number of matches is stored in @samp{$numfound}.
10961 For example, if stopped at the @code{printf} in this function:
10967 static char hello[] = "hello-hello";
10968 static struct @{ char c; short s; int i; @}
10969 __attribute__ ((packed)) mixed
10970 = @{ 'c', 0x1234, 0x87654321 @};
10971 printf ("%s\n", hello);
10976 you get during debugging:
10979 (gdb) find &hello[0], +sizeof(hello), "hello"
10980 0x804956d <hello.1620+6>
10982 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10983 0x8049567 <hello.1620>
10984 0x804956d <hello.1620+6>
10986 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10987 0x8049567 <hello.1620>
10989 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10990 0x8049560 <mixed.1625>
10992 (gdb) print $numfound
10995 $2 = (void *) 0x8049560
10998 @node Optimized Code
10999 @chapter Debugging Optimized Code
11000 @cindex optimized code, debugging
11001 @cindex debugging optimized code
11003 Almost all compilers support optimization. With optimization
11004 disabled, the compiler generates assembly code that corresponds
11005 directly to your source code, in a simplistic way. As the compiler
11006 applies more powerful optimizations, the generated assembly code
11007 diverges from your original source code. With help from debugging
11008 information generated by the compiler, @value{GDBN} can map from
11009 the running program back to constructs from your original source.
11011 @value{GDBN} is more accurate with optimization disabled. If you
11012 can recompile without optimization, it is easier to follow the
11013 progress of your program during debugging. But, there are many cases
11014 where you may need to debug an optimized version.
11016 When you debug a program compiled with @samp{-g -O}, remember that the
11017 optimizer has rearranged your code; the debugger shows you what is
11018 really there. Do not be too surprised when the execution path does not
11019 exactly match your source file! An extreme example: if you define a
11020 variable, but never use it, @value{GDBN} never sees that
11021 variable---because the compiler optimizes it out of existence.
11023 Some things do not work as well with @samp{-g -O} as with just
11024 @samp{-g}, particularly on machines with instruction scheduling. If in
11025 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11026 please report it to us as a bug (including a test case!).
11027 @xref{Variables}, for more information about debugging optimized code.
11030 * Inline Functions:: How @value{GDBN} presents inlining
11031 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11034 @node Inline Functions
11035 @section Inline Functions
11036 @cindex inline functions, debugging
11038 @dfn{Inlining} is an optimization that inserts a copy of the function
11039 body directly at each call site, instead of jumping to a shared
11040 routine. @value{GDBN} displays inlined functions just like
11041 non-inlined functions. They appear in backtraces. You can view their
11042 arguments and local variables, step into them with @code{step}, skip
11043 them with @code{next}, and escape from them with @code{finish}.
11044 You can check whether a function was inlined by using the
11045 @code{info frame} command.
11047 For @value{GDBN} to support inlined functions, the compiler must
11048 record information about inlining in the debug information ---
11049 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11050 other compilers do also. @value{GDBN} only supports inlined functions
11051 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11052 do not emit two required attributes (@samp{DW_AT_call_file} and
11053 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11054 function calls with earlier versions of @value{NGCC}. It instead
11055 displays the arguments and local variables of inlined functions as
11056 local variables in the caller.
11058 The body of an inlined function is directly included at its call site;
11059 unlike a non-inlined function, there are no instructions devoted to
11060 the call. @value{GDBN} still pretends that the call site and the
11061 start of the inlined function are different instructions. Stepping to
11062 the call site shows the call site, and then stepping again shows
11063 the first line of the inlined function, even though no additional
11064 instructions are executed.
11066 This makes source-level debugging much clearer; you can see both the
11067 context of the call and then the effect of the call. Only stepping by
11068 a single instruction using @code{stepi} or @code{nexti} does not do
11069 this; single instruction steps always show the inlined body.
11071 There are some ways that @value{GDBN} does not pretend that inlined
11072 function calls are the same as normal calls:
11076 Setting breakpoints at the call site of an inlined function may not
11077 work, because the call site does not contain any code. @value{GDBN}
11078 may incorrectly move the breakpoint to the next line of the enclosing
11079 function, after the call. This limitation will be removed in a future
11080 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11081 or inside the inlined function instead.
11084 @value{GDBN} cannot locate the return value of inlined calls after
11085 using the @code{finish} command. This is a limitation of compiler-generated
11086 debugging information; after @code{finish}, you can step to the next line
11087 and print a variable where your program stored the return value.
11091 @node Tail Call Frames
11092 @section Tail Call Frames
11093 @cindex tail call frames, debugging
11095 Function @code{B} can call function @code{C} in its very last statement. In
11096 unoptimized compilation the call of @code{C} is immediately followed by return
11097 instruction at the end of @code{B} code. Optimizing compiler may replace the
11098 call and return in function @code{B} into one jump to function @code{C}
11099 instead. Such use of a jump instruction is called @dfn{tail call}.
11101 During execution of function @code{C}, there will be no indication in the
11102 function call stack frames that it was tail-called from @code{B}. If function
11103 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11104 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11105 some cases @value{GDBN} can determine that @code{C} was tail-called from
11106 @code{B}, and it will then create fictitious call frame for that, with the
11107 return address set up as if @code{B} called @code{C} normally.
11109 This functionality is currently supported only by DWARF 2 debugging format and
11110 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11111 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11114 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11115 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11119 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11121 Stack level 1, frame at 0x7fffffffda30:
11122 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11123 tail call frame, caller of frame at 0x7fffffffda30
11124 source language c++.
11125 Arglist at unknown address.
11126 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11129 The detection of all the possible code path executions can find them ambiguous.
11130 There is no execution history stored (possible @ref{Reverse Execution} is never
11131 used for this purpose) and the last known caller could have reached the known
11132 callee by multiple different jump sequences. In such case @value{GDBN} still
11133 tries to show at least all the unambiguous top tail callers and all the
11134 unambiguous bottom tail calees, if any.
11137 @anchor{set debug entry-values}
11138 @item set debug entry-values
11139 @kindex set debug entry-values
11140 When set to on, enables printing of analysis messages for both frame argument
11141 values at function entry and tail calls. It will show all the possible valid
11142 tail calls code paths it has considered. It will also print the intersection
11143 of them with the final unambiguous (possibly partial or even empty) code path
11146 @item show debug entry-values
11147 @kindex show debug entry-values
11148 Show the current state of analysis messages printing for both frame argument
11149 values at function entry and tail calls.
11152 The analysis messages for tail calls can for example show why the virtual tail
11153 call frame for function @code{c} has not been recognized (due to the indirect
11154 reference by variable @code{x}):
11157 static void __attribute__((noinline, noclone)) c (void);
11158 void (*x) (void) = c;
11159 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11160 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11161 int main (void) @{ x (); return 0; @}
11163 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11164 DW_TAG_GNU_call_site 0x40039a in main
11166 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11169 #1 0x000000000040039a in main () at t.c:5
11172 Another possibility is an ambiguous virtual tail call frames resolution:
11176 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11177 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11178 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11179 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11180 static void __attribute__((noinline, noclone)) b (void)
11181 @{ if (i) c (); else e (); @}
11182 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11183 int main (void) @{ a (); return 0; @}
11185 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11186 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11187 tailcall: reduced: 0x4004d2(a) |
11190 #1 0x00000000004004d2 in a () at t.c:8
11191 #2 0x0000000000400395 in main () at t.c:9
11194 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11195 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11197 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11198 @ifset HAVE_MAKEINFO_CLICK
11199 @set ARROW @click{}
11200 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11201 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11203 @ifclear HAVE_MAKEINFO_CLICK
11205 @set CALLSEQ1B @value{CALLSEQ1A}
11206 @set CALLSEQ2B @value{CALLSEQ2A}
11209 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11210 The code can have possible execution paths @value{CALLSEQ1B} or
11211 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11213 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11214 has found. It then finds another possible calling sequcen - that one is
11215 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11216 printed as the @code{reduced:} calling sequence. That one could have many
11217 futher @code{compare:} and @code{reduced:} statements as long as there remain
11218 any non-ambiguous sequence entries.
11220 For the frame of function @code{b} in both cases there are different possible
11221 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11222 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11223 therefore this one is displayed to the user while the ambiguous frames are
11226 There can be also reasons why printing of frame argument values at function
11231 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11232 static void __attribute__((noinline, noclone)) a (int i);
11233 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11234 static void __attribute__((noinline, noclone)) a (int i)
11235 @{ if (i) b (i - 1); else c (0); @}
11236 int main (void) @{ a (5); return 0; @}
11239 #0 c (i=i@@entry=0) at t.c:2
11240 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11241 function "a" at 0x400420 can call itself via tail calls
11242 i=<optimized out>) at t.c:6
11243 #2 0x000000000040036e in main () at t.c:7
11246 @value{GDBN} cannot find out from the inferior state if and how many times did
11247 function @code{a} call itself (via function @code{b}) as these calls would be
11248 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11249 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11250 prints @code{<optimized out>} instead.
11253 @chapter C Preprocessor Macros
11255 Some languages, such as C and C@t{++}, provide a way to define and invoke
11256 ``preprocessor macros'' which expand into strings of tokens.
11257 @value{GDBN} can evaluate expressions containing macro invocations, show
11258 the result of macro expansion, and show a macro's definition, including
11259 where it was defined.
11261 You may need to compile your program specially to provide @value{GDBN}
11262 with information about preprocessor macros. Most compilers do not
11263 include macros in their debugging information, even when you compile
11264 with the @option{-g} flag. @xref{Compilation}.
11266 A program may define a macro at one point, remove that definition later,
11267 and then provide a different definition after that. Thus, at different
11268 points in the program, a macro may have different definitions, or have
11269 no definition at all. If there is a current stack frame, @value{GDBN}
11270 uses the macros in scope at that frame's source code line. Otherwise,
11271 @value{GDBN} uses the macros in scope at the current listing location;
11274 Whenever @value{GDBN} evaluates an expression, it always expands any
11275 macro invocations present in the expression. @value{GDBN} also provides
11276 the following commands for working with macros explicitly.
11280 @kindex macro expand
11281 @cindex macro expansion, showing the results of preprocessor
11282 @cindex preprocessor macro expansion, showing the results of
11283 @cindex expanding preprocessor macros
11284 @item macro expand @var{expression}
11285 @itemx macro exp @var{expression}
11286 Show the results of expanding all preprocessor macro invocations in
11287 @var{expression}. Since @value{GDBN} simply expands macros, but does
11288 not parse the result, @var{expression} need not be a valid expression;
11289 it can be any string of tokens.
11292 @item macro expand-once @var{expression}
11293 @itemx macro exp1 @var{expression}
11294 @cindex expand macro once
11295 @i{(This command is not yet implemented.)} Show the results of
11296 expanding those preprocessor macro invocations that appear explicitly in
11297 @var{expression}. Macro invocations appearing in that expansion are
11298 left unchanged. This command allows you to see the effect of a
11299 particular macro more clearly, without being confused by further
11300 expansions. Since @value{GDBN} simply expands macros, but does not
11301 parse the result, @var{expression} need not be a valid expression; it
11302 can be any string of tokens.
11305 @cindex macro definition, showing
11306 @cindex definition of a macro, showing
11307 @cindex macros, from debug info
11308 @item info macro [-a|-all] [--] @var{macro}
11309 Show the current definition or all definitions of the named @var{macro},
11310 and describe the source location or compiler command-line where that
11311 definition was established. The optional double dash is to signify the end of
11312 argument processing and the beginning of @var{macro} for non C-like macros where
11313 the macro may begin with a hyphen.
11315 @kindex info macros
11316 @item info macros @var{linespec}
11317 Show all macro definitions that are in effect at the location specified
11318 by @var{linespec}, and describe the source location or compiler
11319 command-line where those definitions were established.
11321 @kindex macro define
11322 @cindex user-defined macros
11323 @cindex defining macros interactively
11324 @cindex macros, user-defined
11325 @item macro define @var{macro} @var{replacement-list}
11326 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11327 Introduce a definition for a preprocessor macro named @var{macro},
11328 invocations of which are replaced by the tokens given in
11329 @var{replacement-list}. The first form of this command defines an
11330 ``object-like'' macro, which takes no arguments; the second form
11331 defines a ``function-like'' macro, which takes the arguments given in
11334 A definition introduced by this command is in scope in every
11335 expression evaluated in @value{GDBN}, until it is removed with the
11336 @code{macro undef} command, described below. The definition overrides
11337 all definitions for @var{macro} present in the program being debugged,
11338 as well as any previous user-supplied definition.
11340 @kindex macro undef
11341 @item macro undef @var{macro}
11342 Remove any user-supplied definition for the macro named @var{macro}.
11343 This command only affects definitions provided with the @code{macro
11344 define} command, described above; it cannot remove definitions present
11345 in the program being debugged.
11349 List all the macros defined using the @code{macro define} command.
11352 @cindex macros, example of debugging with
11353 Here is a transcript showing the above commands in action. First, we
11354 show our source files:
11359 #include "sample.h"
11362 #define ADD(x) (M + x)
11367 printf ("Hello, world!\n");
11369 printf ("We're so creative.\n");
11371 printf ("Goodbye, world!\n");
11378 Now, we compile the program using the @sc{gnu} C compiler,
11379 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11380 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11381 and @option{-gdwarf-4}; we recommend always choosing the most recent
11382 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11383 includes information about preprocessor macros in the debugging
11387 $ gcc -gdwarf-2 -g3 sample.c -o sample
11391 Now, we start @value{GDBN} on our sample program:
11395 GNU gdb 2002-05-06-cvs
11396 Copyright 2002 Free Software Foundation, Inc.
11397 GDB is free software, @dots{}
11401 We can expand macros and examine their definitions, even when the
11402 program is not running. @value{GDBN} uses the current listing position
11403 to decide which macro definitions are in scope:
11406 (@value{GDBP}) list main
11409 5 #define ADD(x) (M + x)
11414 10 printf ("Hello, world!\n");
11416 12 printf ("We're so creative.\n");
11417 (@value{GDBP}) info macro ADD
11418 Defined at /home/jimb/gdb/macros/play/sample.c:5
11419 #define ADD(x) (M + x)
11420 (@value{GDBP}) info macro Q
11421 Defined at /home/jimb/gdb/macros/play/sample.h:1
11422 included at /home/jimb/gdb/macros/play/sample.c:2
11424 (@value{GDBP}) macro expand ADD(1)
11425 expands to: (42 + 1)
11426 (@value{GDBP}) macro expand-once ADD(1)
11427 expands to: once (M + 1)
11431 In the example above, note that @code{macro expand-once} expands only
11432 the macro invocation explicit in the original text --- the invocation of
11433 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11434 which was introduced by @code{ADD}.
11436 Once the program is running, @value{GDBN} uses the macro definitions in
11437 force at the source line of the current stack frame:
11440 (@value{GDBP}) break main
11441 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11443 Starting program: /home/jimb/gdb/macros/play/sample
11445 Breakpoint 1, main () at sample.c:10
11446 10 printf ("Hello, world!\n");
11450 At line 10, the definition of the macro @code{N} at line 9 is in force:
11453 (@value{GDBP}) info macro N
11454 Defined at /home/jimb/gdb/macros/play/sample.c:9
11456 (@value{GDBP}) macro expand N Q M
11457 expands to: 28 < 42
11458 (@value{GDBP}) print N Q M
11463 As we step over directives that remove @code{N}'s definition, and then
11464 give it a new definition, @value{GDBN} finds the definition (or lack
11465 thereof) in force at each point:
11468 (@value{GDBP}) next
11470 12 printf ("We're so creative.\n");
11471 (@value{GDBP}) info macro N
11472 The symbol `N' has no definition as a C/C++ preprocessor macro
11473 at /home/jimb/gdb/macros/play/sample.c:12
11474 (@value{GDBP}) next
11476 14 printf ("Goodbye, world!\n");
11477 (@value{GDBP}) info macro N
11478 Defined at /home/jimb/gdb/macros/play/sample.c:13
11480 (@value{GDBP}) macro expand N Q M
11481 expands to: 1729 < 42
11482 (@value{GDBP}) print N Q M
11487 In addition to source files, macros can be defined on the compilation command
11488 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11489 such a way, @value{GDBN} displays the location of their definition as line zero
11490 of the source file submitted to the compiler.
11493 (@value{GDBP}) info macro __STDC__
11494 Defined at /home/jimb/gdb/macros/play/sample.c:0
11501 @chapter Tracepoints
11502 @c This chapter is based on the documentation written by Michael
11503 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11505 @cindex tracepoints
11506 In some applications, it is not feasible for the debugger to interrupt
11507 the program's execution long enough for the developer to learn
11508 anything helpful about its behavior. If the program's correctness
11509 depends on its real-time behavior, delays introduced by a debugger
11510 might cause the program to change its behavior drastically, or perhaps
11511 fail, even when the code itself is correct. It is useful to be able
11512 to observe the program's behavior without interrupting it.
11514 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11515 specify locations in the program, called @dfn{tracepoints}, and
11516 arbitrary expressions to evaluate when those tracepoints are reached.
11517 Later, using the @code{tfind} command, you can examine the values
11518 those expressions had when the program hit the tracepoints. The
11519 expressions may also denote objects in memory---structures or arrays,
11520 for example---whose values @value{GDBN} should record; while visiting
11521 a particular tracepoint, you may inspect those objects as if they were
11522 in memory at that moment. However, because @value{GDBN} records these
11523 values without interacting with you, it can do so quickly and
11524 unobtrusively, hopefully not disturbing the program's behavior.
11526 The tracepoint facility is currently available only for remote
11527 targets. @xref{Targets}. In addition, your remote target must know
11528 how to collect trace data. This functionality is implemented in the
11529 remote stub; however, none of the stubs distributed with @value{GDBN}
11530 support tracepoints as of this writing. The format of the remote
11531 packets used to implement tracepoints are described in @ref{Tracepoint
11534 It is also possible to get trace data from a file, in a manner reminiscent
11535 of corefiles; you specify the filename, and use @code{tfind} to search
11536 through the file. @xref{Trace Files}, for more details.
11538 This chapter describes the tracepoint commands and features.
11541 * Set Tracepoints::
11542 * Analyze Collected Data::
11543 * Tracepoint Variables::
11547 @node Set Tracepoints
11548 @section Commands to Set Tracepoints
11550 Before running such a @dfn{trace experiment}, an arbitrary number of
11551 tracepoints can be set. A tracepoint is actually a special type of
11552 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11553 standard breakpoint commands. For instance, as with breakpoints,
11554 tracepoint numbers are successive integers starting from one, and many
11555 of the commands associated with tracepoints take the tracepoint number
11556 as their argument, to identify which tracepoint to work on.
11558 For each tracepoint, you can specify, in advance, some arbitrary set
11559 of data that you want the target to collect in the trace buffer when
11560 it hits that tracepoint. The collected data can include registers,
11561 local variables, or global data. Later, you can use @value{GDBN}
11562 commands to examine the values these data had at the time the
11563 tracepoint was hit.
11565 Tracepoints do not support every breakpoint feature. Ignore counts on
11566 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11567 commands when they are hit. Tracepoints may not be thread-specific
11570 @cindex fast tracepoints
11571 Some targets may support @dfn{fast tracepoints}, which are inserted in
11572 a different way (such as with a jump instead of a trap), that is
11573 faster but possibly restricted in where they may be installed.
11575 @cindex static tracepoints
11576 @cindex markers, static tracepoints
11577 @cindex probing markers, static tracepoints
11578 Regular and fast tracepoints are dynamic tracing facilities, meaning
11579 that they can be used to insert tracepoints at (almost) any location
11580 in the target. Some targets may also support controlling @dfn{static
11581 tracepoints} from @value{GDBN}. With static tracing, a set of
11582 instrumentation points, also known as @dfn{markers}, are embedded in
11583 the target program, and can be activated or deactivated by name or
11584 address. These are usually placed at locations which facilitate
11585 investigating what the target is actually doing. @value{GDBN}'s
11586 support for static tracing includes being able to list instrumentation
11587 points, and attach them with @value{GDBN} defined high level
11588 tracepoints that expose the whole range of convenience of
11589 @value{GDBN}'s tracepoints support. Namely, support for collecting
11590 registers values and values of global or local (to the instrumentation
11591 point) variables; tracepoint conditions and trace state variables.
11592 The act of installing a @value{GDBN} static tracepoint on an
11593 instrumentation point, or marker, is referred to as @dfn{probing} a
11594 static tracepoint marker.
11596 @code{gdbserver} supports tracepoints on some target systems.
11597 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11599 This section describes commands to set tracepoints and associated
11600 conditions and actions.
11603 * Create and Delete Tracepoints::
11604 * Enable and Disable Tracepoints::
11605 * Tracepoint Passcounts::
11606 * Tracepoint Conditions::
11607 * Trace State Variables::
11608 * Tracepoint Actions::
11609 * Listing Tracepoints::
11610 * Listing Static Tracepoint Markers::
11611 * Starting and Stopping Trace Experiments::
11612 * Tracepoint Restrictions::
11615 @node Create and Delete Tracepoints
11616 @subsection Create and Delete Tracepoints
11619 @cindex set tracepoint
11621 @item trace @var{location}
11622 The @code{trace} command is very similar to the @code{break} command.
11623 Its argument @var{location} can be a source line, a function name, or
11624 an address in the target program. @xref{Specify Location}. The
11625 @code{trace} command defines a tracepoint, which is a point in the
11626 target program where the debugger will briefly stop, collect some
11627 data, and then allow the program to continue. Setting a tracepoint or
11628 changing its actions takes effect immediately if the remote stub
11629 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11631 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11632 these changes don't take effect until the next @code{tstart}
11633 command, and once a trace experiment is running, further changes will
11634 not have any effect until the next trace experiment starts. In addition,
11635 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11636 address is not yet resolved. (This is similar to pending breakpoints.)
11637 Pending tracepoints are not downloaded to the target and not installed
11638 until they are resolved. The resolution of pending tracepoints requires
11639 @value{GDBN} support---when debugging with the remote target, and
11640 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11641 tracing}), pending tracepoints can not be resolved (and downloaded to
11642 the remote stub) while @value{GDBN} is disconnected.
11644 Here are some examples of using the @code{trace} command:
11647 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11649 (@value{GDBP}) @b{trace +2} // 2 lines forward
11651 (@value{GDBP}) @b{trace my_function} // first source line of function
11653 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11655 (@value{GDBP}) @b{trace *0x2117c4} // an address
11659 You can abbreviate @code{trace} as @code{tr}.
11661 @item trace @var{location} if @var{cond}
11662 Set a tracepoint with condition @var{cond}; evaluate the expression
11663 @var{cond} each time the tracepoint is reached, and collect data only
11664 if the value is nonzero---that is, if @var{cond} evaluates as true.
11665 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11666 information on tracepoint conditions.
11668 @item ftrace @var{location} [ if @var{cond} ]
11669 @cindex set fast tracepoint
11670 @cindex fast tracepoints, setting
11672 The @code{ftrace} command sets a fast tracepoint. For targets that
11673 support them, fast tracepoints will use a more efficient but possibly
11674 less general technique to trigger data collection, such as a jump
11675 instruction instead of a trap, or some sort of hardware support. It
11676 may not be possible to create a fast tracepoint at the desired
11677 location, in which case the command will exit with an explanatory
11680 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11683 On 32-bit x86-architecture systems, fast tracepoints normally need to
11684 be placed at an instruction that is 5 bytes or longer, but can be
11685 placed at 4-byte instructions if the low 64K of memory of the target
11686 program is available to install trampolines. Some Unix-type systems,
11687 such as @sc{gnu}/Linux, exclude low addresses from the program's
11688 address space; but for instance with the Linux kernel it is possible
11689 to let @value{GDBN} use this area by doing a @command{sysctl} command
11690 to set the @code{mmap_min_addr} kernel parameter, as in
11693 sudo sysctl -w vm.mmap_min_addr=32768
11697 which sets the low address to 32K, which leaves plenty of room for
11698 trampolines. The minimum address should be set to a page boundary.
11700 @item strace @var{location} [ if @var{cond} ]
11701 @cindex set static tracepoint
11702 @cindex static tracepoints, setting
11703 @cindex probe static tracepoint marker
11705 The @code{strace} command sets a static tracepoint. For targets that
11706 support it, setting a static tracepoint probes a static
11707 instrumentation point, or marker, found at @var{location}. It may not
11708 be possible to set a static tracepoint at the desired location, in
11709 which case the command will exit with an explanatory message.
11711 @value{GDBN} handles arguments to @code{strace} exactly as for
11712 @code{trace}, with the addition that the user can also specify
11713 @code{-m @var{marker}} as @var{location}. This probes the marker
11714 identified by the @var{marker} string identifier. This identifier
11715 depends on the static tracepoint backend library your program is
11716 using. You can find all the marker identifiers in the @samp{ID} field
11717 of the @code{info static-tracepoint-markers} command output.
11718 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11719 Markers}. For example, in the following small program using the UST
11725 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11730 the marker id is composed of joining the first two arguments to the
11731 @code{trace_mark} call with a slash, which translates to:
11734 (@value{GDBP}) info static-tracepoint-markers
11735 Cnt Enb ID Address What
11736 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11742 so you may probe the marker above with:
11745 (@value{GDBP}) strace -m ust/bar33
11748 Static tracepoints accept an extra collect action --- @code{collect
11749 $_sdata}. This collects arbitrary user data passed in the probe point
11750 call to the tracing library. In the UST example above, you'll see
11751 that the third argument to @code{trace_mark} is a printf-like format
11752 string. The user data is then the result of running that formating
11753 string against the following arguments. Note that @code{info
11754 static-tracepoint-markers} command output lists that format string in
11755 the @samp{Data:} field.
11757 You can inspect this data when analyzing the trace buffer, by printing
11758 the $_sdata variable like any other variable available to
11759 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11762 @cindex last tracepoint number
11763 @cindex recent tracepoint number
11764 @cindex tracepoint number
11765 The convenience variable @code{$tpnum} records the tracepoint number
11766 of the most recently set tracepoint.
11768 @kindex delete tracepoint
11769 @cindex tracepoint deletion
11770 @item delete tracepoint @r{[}@var{num}@r{]}
11771 Permanently delete one or more tracepoints. With no argument, the
11772 default is to delete all tracepoints. Note that the regular
11773 @code{delete} command can remove tracepoints also.
11778 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11780 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11784 You can abbreviate this command as @code{del tr}.
11787 @node Enable and Disable Tracepoints
11788 @subsection Enable and Disable Tracepoints
11790 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11793 @kindex disable tracepoint
11794 @item disable tracepoint @r{[}@var{num}@r{]}
11795 Disable tracepoint @var{num}, or all tracepoints if no argument
11796 @var{num} is given. A disabled tracepoint will have no effect during
11797 a trace experiment, but it is not forgotten. You can re-enable
11798 a disabled tracepoint using the @code{enable tracepoint} command.
11799 If the command is issued during a trace experiment and the debug target
11800 has support for disabling tracepoints during a trace experiment, then the
11801 change will be effective immediately. Otherwise, it will be applied to the
11802 next trace experiment.
11804 @kindex enable tracepoint
11805 @item enable tracepoint @r{[}@var{num}@r{]}
11806 Enable tracepoint @var{num}, or all tracepoints. If this command is
11807 issued during a trace experiment and the debug target supports enabling
11808 tracepoints during a trace experiment, then the enabled tracepoints will
11809 become effective immediately. Otherwise, they will become effective the
11810 next time a trace experiment is run.
11813 @node Tracepoint Passcounts
11814 @subsection Tracepoint Passcounts
11818 @cindex tracepoint pass count
11819 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11820 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11821 automatically stop a trace experiment. If a tracepoint's passcount is
11822 @var{n}, then the trace experiment will be automatically stopped on
11823 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11824 @var{num} is not specified, the @code{passcount} command sets the
11825 passcount of the most recently defined tracepoint. If no passcount is
11826 given, the trace experiment will run until stopped explicitly by the
11832 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11833 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11835 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11836 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11837 (@value{GDBP}) @b{trace foo}
11838 (@value{GDBP}) @b{pass 3}
11839 (@value{GDBP}) @b{trace bar}
11840 (@value{GDBP}) @b{pass 2}
11841 (@value{GDBP}) @b{trace baz}
11842 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11843 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11844 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11845 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11849 @node Tracepoint Conditions
11850 @subsection Tracepoint Conditions
11851 @cindex conditional tracepoints
11852 @cindex tracepoint conditions
11854 The simplest sort of tracepoint collects data every time your program
11855 reaches a specified place. You can also specify a @dfn{condition} for
11856 a tracepoint. A condition is just a Boolean expression in your
11857 programming language (@pxref{Expressions, ,Expressions}). A
11858 tracepoint with a condition evaluates the expression each time your
11859 program reaches it, and data collection happens only if the condition
11862 Tracepoint conditions can be specified when a tracepoint is set, by
11863 using @samp{if} in the arguments to the @code{trace} command.
11864 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11865 also be set or changed at any time with the @code{condition} command,
11866 just as with breakpoints.
11868 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11869 the conditional expression itself. Instead, @value{GDBN} encodes the
11870 expression into an agent expression (@pxref{Agent Expressions})
11871 suitable for execution on the target, independently of @value{GDBN}.
11872 Global variables become raw memory locations, locals become stack
11873 accesses, and so forth.
11875 For instance, suppose you have a function that is usually called
11876 frequently, but should not be called after an error has occurred. You
11877 could use the following tracepoint command to collect data about calls
11878 of that function that happen while the error code is propagating
11879 through the program; an unconditional tracepoint could end up
11880 collecting thousands of useless trace frames that you would have to
11884 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11887 @node Trace State Variables
11888 @subsection Trace State Variables
11889 @cindex trace state variables
11891 A @dfn{trace state variable} is a special type of variable that is
11892 created and managed by target-side code. The syntax is the same as
11893 that for GDB's convenience variables (a string prefixed with ``$''),
11894 but they are stored on the target. They must be created explicitly,
11895 using a @code{tvariable} command. They are always 64-bit signed
11898 Trace state variables are remembered by @value{GDBN}, and downloaded
11899 to the target along with tracepoint information when the trace
11900 experiment starts. There are no intrinsic limits on the number of
11901 trace state variables, beyond memory limitations of the target.
11903 @cindex convenience variables, and trace state variables
11904 Although trace state variables are managed by the target, you can use
11905 them in print commands and expressions as if they were convenience
11906 variables; @value{GDBN} will get the current value from the target
11907 while the trace experiment is running. Trace state variables share
11908 the same namespace as other ``$'' variables, which means that you
11909 cannot have trace state variables with names like @code{$23} or
11910 @code{$pc}, nor can you have a trace state variable and a convenience
11911 variable with the same name.
11915 @item tvariable $@var{name} [ = @var{expression} ]
11917 The @code{tvariable} command creates a new trace state variable named
11918 @code{$@var{name}}, and optionally gives it an initial value of
11919 @var{expression}. @var{expression} is evaluated when this command is
11920 entered; the result will be converted to an integer if possible,
11921 otherwise @value{GDBN} will report an error. A subsequent
11922 @code{tvariable} command specifying the same name does not create a
11923 variable, but instead assigns the supplied initial value to the
11924 existing variable of that name, overwriting any previous initial
11925 value. The default initial value is 0.
11927 @item info tvariables
11928 @kindex info tvariables
11929 List all the trace state variables along with their initial values.
11930 Their current values may also be displayed, if the trace experiment is
11933 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11934 @kindex delete tvariable
11935 Delete the given trace state variables, or all of them if no arguments
11940 @node Tracepoint Actions
11941 @subsection Tracepoint Action Lists
11945 @cindex tracepoint actions
11946 @item actions @r{[}@var{num}@r{]}
11947 This command will prompt for a list of actions to be taken when the
11948 tracepoint is hit. If the tracepoint number @var{num} is not
11949 specified, this command sets the actions for the one that was most
11950 recently defined (so that you can define a tracepoint and then say
11951 @code{actions} without bothering about its number). You specify the
11952 actions themselves on the following lines, one action at a time, and
11953 terminate the actions list with a line containing just @code{end}. So
11954 far, the only defined actions are @code{collect}, @code{teval}, and
11955 @code{while-stepping}.
11957 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11958 Commands, ,Breakpoint Command Lists}), except that only the defined
11959 actions are allowed; any other @value{GDBN} command is rejected.
11961 @cindex remove actions from a tracepoint
11962 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11963 and follow it immediately with @samp{end}.
11966 (@value{GDBP}) @b{collect @var{data}} // collect some data
11968 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11970 (@value{GDBP}) @b{end} // signals the end of actions.
11973 In the following example, the action list begins with @code{collect}
11974 commands indicating the things to be collected when the tracepoint is
11975 hit. Then, in order to single-step and collect additional data
11976 following the tracepoint, a @code{while-stepping} command is used,
11977 followed by the list of things to be collected after each step in a
11978 sequence of single steps. The @code{while-stepping} command is
11979 terminated by its own separate @code{end} command. Lastly, the action
11980 list is terminated by an @code{end} command.
11983 (@value{GDBP}) @b{trace foo}
11984 (@value{GDBP}) @b{actions}
11985 Enter actions for tracepoint 1, one per line:
11988 > while-stepping 12
11989 > collect $pc, arr[i]
11994 @kindex collect @r{(tracepoints)}
11995 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11996 Collect values of the given expressions when the tracepoint is hit.
11997 This command accepts a comma-separated list of any valid expressions.
11998 In addition to global, static, or local variables, the following
11999 special arguments are supported:
12003 Collect all registers.
12006 Collect all function arguments.
12009 Collect all local variables.
12012 Collect the return address. This is helpful if you want to see more
12016 Collects the number of arguments from the static probe at which the
12017 tracepoint is located.
12018 @xref{Static Probe Points}.
12020 @item $_probe_arg@var{n}
12021 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12022 from the static probe at which the tracepoint is located.
12023 @xref{Static Probe Points}.
12026 @vindex $_sdata@r{, collect}
12027 Collect static tracepoint marker specific data. Only available for
12028 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12029 Lists}. On the UST static tracepoints library backend, an
12030 instrumentation point resembles a @code{printf} function call. The
12031 tracing library is able to collect user specified data formatted to a
12032 character string using the format provided by the programmer that
12033 instrumented the program. Other backends have similar mechanisms.
12034 Here's an example of a UST marker call:
12037 const char master_name[] = "$your_name";
12038 trace_mark(channel1, marker1, "hello %s", master_name)
12041 In this case, collecting @code{$_sdata} collects the string
12042 @samp{hello $yourname}. When analyzing the trace buffer, you can
12043 inspect @samp{$_sdata} like any other variable available to
12047 You can give several consecutive @code{collect} commands, each one
12048 with a single argument, or one @code{collect} command with several
12049 arguments separated by commas; the effect is the same.
12051 The optional @var{mods} changes the usual handling of the arguments.
12052 @code{s} requests that pointers to chars be handled as strings, in
12053 particular collecting the contents of the memory being pointed at, up
12054 to the first zero. The upper bound is by default the value of the
12055 @code{print elements} variable; if @code{s} is followed by a decimal
12056 number, that is the upper bound instead. So for instance
12057 @samp{collect/s25 mystr} collects as many as 25 characters at
12060 The command @code{info scope} (@pxref{Symbols, info scope}) is
12061 particularly useful for figuring out what data to collect.
12063 @kindex teval @r{(tracepoints)}
12064 @item teval @var{expr1}, @var{expr2}, @dots{}
12065 Evaluate the given expressions when the tracepoint is hit. This
12066 command accepts a comma-separated list of expressions. The results
12067 are discarded, so this is mainly useful for assigning values to trace
12068 state variables (@pxref{Trace State Variables}) without adding those
12069 values to the trace buffer, as would be the case if the @code{collect}
12072 @kindex while-stepping @r{(tracepoints)}
12073 @item while-stepping @var{n}
12074 Perform @var{n} single-step instruction traces after the tracepoint,
12075 collecting new data after each step. The @code{while-stepping}
12076 command is followed by the list of what to collect while stepping
12077 (followed by its own @code{end} command):
12080 > while-stepping 12
12081 > collect $regs, myglobal
12087 Note that @code{$pc} is not automatically collected by
12088 @code{while-stepping}; you need to explicitly collect that register if
12089 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12092 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12093 @kindex set default-collect
12094 @cindex default collection action
12095 This variable is a list of expressions to collect at each tracepoint
12096 hit. It is effectively an additional @code{collect} action prepended
12097 to every tracepoint action list. The expressions are parsed
12098 individually for each tracepoint, so for instance a variable named
12099 @code{xyz} may be interpreted as a global for one tracepoint, and a
12100 local for another, as appropriate to the tracepoint's location.
12102 @item show default-collect
12103 @kindex show default-collect
12104 Show the list of expressions that are collected by default at each
12109 @node Listing Tracepoints
12110 @subsection Listing Tracepoints
12113 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12114 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12115 @cindex information about tracepoints
12116 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12117 Display information about the tracepoint @var{num}. If you don't
12118 specify a tracepoint number, displays information about all the
12119 tracepoints defined so far. The format is similar to that used for
12120 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12121 command, simply restricting itself to tracepoints.
12123 A tracepoint's listing may include additional information specific to
12128 its passcount as given by the @code{passcount @var{n}} command
12131 the state about installed on target of each location
12135 (@value{GDBP}) @b{info trace}
12136 Num Type Disp Enb Address What
12137 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12139 collect globfoo, $regs
12144 2 tracepoint keep y <MULTIPLE>
12146 2.1 y 0x0804859c in func4 at change-loc.h:35
12147 installed on target
12148 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12149 installed on target
12150 2.3 y <PENDING> set_tracepoint
12151 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12152 not installed on target
12157 This command can be abbreviated @code{info tp}.
12160 @node Listing Static Tracepoint Markers
12161 @subsection Listing Static Tracepoint Markers
12164 @kindex info static-tracepoint-markers
12165 @cindex information about static tracepoint markers
12166 @item info static-tracepoint-markers
12167 Display information about all static tracepoint markers defined in the
12170 For each marker, the following columns are printed:
12174 An incrementing counter, output to help readability. This is not a
12177 The marker ID, as reported by the target.
12178 @item Enabled or Disabled
12179 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12180 that are not enabled.
12182 Where the marker is in your program, as a memory address.
12184 Where the marker is in the source for your program, as a file and line
12185 number. If the debug information included in the program does not
12186 allow @value{GDBN} to locate the source of the marker, this column
12187 will be left blank.
12191 In addition, the following information may be printed for each marker:
12195 User data passed to the tracing library by the marker call. In the
12196 UST backend, this is the format string passed as argument to the
12198 @item Static tracepoints probing the marker
12199 The list of static tracepoints attached to the marker.
12203 (@value{GDBP}) info static-tracepoint-markers
12204 Cnt ID Enb Address What
12205 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12206 Data: number1 %d number2 %d
12207 Probed by static tracepoints: #2
12208 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12214 @node Starting and Stopping Trace Experiments
12215 @subsection Starting and Stopping Trace Experiments
12218 @kindex tstart [ @var{notes} ]
12219 @cindex start a new trace experiment
12220 @cindex collected data discarded
12222 This command starts the trace experiment, and begins collecting data.
12223 It has the side effect of discarding all the data collected in the
12224 trace buffer during the previous trace experiment. If any arguments
12225 are supplied, they are taken as a note and stored with the trace
12226 experiment's state. The notes may be arbitrary text, and are
12227 especially useful with disconnected tracing in a multi-user context;
12228 the notes can explain what the trace is doing, supply user contact
12229 information, and so forth.
12231 @kindex tstop [ @var{notes} ]
12232 @cindex stop a running trace experiment
12234 This command stops the trace experiment. If any arguments are
12235 supplied, they are recorded with the experiment as a note. This is
12236 useful if you are stopping a trace started by someone else, for
12237 instance if the trace is interfering with the system's behavior and
12238 needs to be stopped quickly.
12240 @strong{Note}: a trace experiment and data collection may stop
12241 automatically if any tracepoint's passcount is reached
12242 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12245 @cindex status of trace data collection
12246 @cindex trace experiment, status of
12248 This command displays the status of the current trace data
12252 Here is an example of the commands we described so far:
12255 (@value{GDBP}) @b{trace gdb_c_test}
12256 (@value{GDBP}) @b{actions}
12257 Enter actions for tracepoint #1, one per line.
12258 > collect $regs,$locals,$args
12259 > while-stepping 11
12263 (@value{GDBP}) @b{tstart}
12264 [time passes @dots{}]
12265 (@value{GDBP}) @b{tstop}
12268 @anchor{disconnected tracing}
12269 @cindex disconnected tracing
12270 You can choose to continue running the trace experiment even if
12271 @value{GDBN} disconnects from the target, voluntarily or
12272 involuntarily. For commands such as @code{detach}, the debugger will
12273 ask what you want to do with the trace. But for unexpected
12274 terminations (@value{GDBN} crash, network outage), it would be
12275 unfortunate to lose hard-won trace data, so the variable
12276 @code{disconnected-tracing} lets you decide whether the trace should
12277 continue running without @value{GDBN}.
12280 @item set disconnected-tracing on
12281 @itemx set disconnected-tracing off
12282 @kindex set disconnected-tracing
12283 Choose whether a tracing run should continue to run if @value{GDBN}
12284 has disconnected from the target. Note that @code{detach} or
12285 @code{quit} will ask you directly what to do about a running trace no
12286 matter what this variable's setting, so the variable is mainly useful
12287 for handling unexpected situations, such as loss of the network.
12289 @item show disconnected-tracing
12290 @kindex show disconnected-tracing
12291 Show the current choice for disconnected tracing.
12295 When you reconnect to the target, the trace experiment may or may not
12296 still be running; it might have filled the trace buffer in the
12297 meantime, or stopped for one of the other reasons. If it is running,
12298 it will continue after reconnection.
12300 Upon reconnection, the target will upload information about the
12301 tracepoints in effect. @value{GDBN} will then compare that
12302 information to the set of tracepoints currently defined, and attempt
12303 to match them up, allowing for the possibility that the numbers may
12304 have changed due to creation and deletion in the meantime. If one of
12305 the target's tracepoints does not match any in @value{GDBN}, the
12306 debugger will create a new tracepoint, so that you have a number with
12307 which to specify that tracepoint. This matching-up process is
12308 necessarily heuristic, and it may result in useless tracepoints being
12309 created; you may simply delete them if they are of no use.
12311 @cindex circular trace buffer
12312 If your target agent supports a @dfn{circular trace buffer}, then you
12313 can run a trace experiment indefinitely without filling the trace
12314 buffer; when space runs out, the agent deletes already-collected trace
12315 frames, oldest first, until there is enough room to continue
12316 collecting. This is especially useful if your tracepoints are being
12317 hit too often, and your trace gets terminated prematurely because the
12318 buffer is full. To ask for a circular trace buffer, simply set
12319 @samp{circular-trace-buffer} to on. You can set this at any time,
12320 including during tracing; if the agent can do it, it will change
12321 buffer handling on the fly, otherwise it will not take effect until
12325 @item set circular-trace-buffer on
12326 @itemx set circular-trace-buffer off
12327 @kindex set circular-trace-buffer
12328 Choose whether a tracing run should use a linear or circular buffer
12329 for trace data. A linear buffer will not lose any trace data, but may
12330 fill up prematurely, while a circular buffer will discard old trace
12331 data, but it will have always room for the latest tracepoint hits.
12333 @item show circular-trace-buffer
12334 @kindex show circular-trace-buffer
12335 Show the current choice for the trace buffer. Note that this may not
12336 match the agent's current buffer handling, nor is it guaranteed to
12337 match the setting that might have been in effect during a past run,
12338 for instance if you are looking at frames from a trace file.
12343 @item set trace-buffer-size @var{n}
12344 @itemx set trace-buffer-size unlimited
12345 @kindex set trace-buffer-size
12346 Request that the target use a trace buffer of @var{n} bytes. Not all
12347 targets will honor the request; they may have a compiled-in size for
12348 the trace buffer, or some other limitation. Set to a value of
12349 @code{unlimited} or @code{-1} to let the target use whatever size it
12350 likes. This is also the default.
12352 @item show trace-buffer-size
12353 @kindex show trace-buffer-size
12354 Show the current requested size for the trace buffer. Note that this
12355 will only match the actual size if the target supports size-setting,
12356 and was able to handle the requested size. For instance, if the
12357 target can only change buffer size between runs, this variable will
12358 not reflect the change until the next run starts. Use @code{tstatus}
12359 to get a report of the actual buffer size.
12363 @item set trace-user @var{text}
12364 @kindex set trace-user
12366 @item show trace-user
12367 @kindex show trace-user
12369 @item set trace-notes @var{text}
12370 @kindex set trace-notes
12371 Set the trace run's notes.
12373 @item show trace-notes
12374 @kindex show trace-notes
12375 Show the trace run's notes.
12377 @item set trace-stop-notes @var{text}
12378 @kindex set trace-stop-notes
12379 Set the trace run's stop notes. The handling of the note is as for
12380 @code{tstop} arguments; the set command is convenient way to fix a
12381 stop note that is mistaken or incomplete.
12383 @item show trace-stop-notes
12384 @kindex show trace-stop-notes
12385 Show the trace run's stop notes.
12389 @node Tracepoint Restrictions
12390 @subsection Tracepoint Restrictions
12392 @cindex tracepoint restrictions
12393 There are a number of restrictions on the use of tracepoints. As
12394 described above, tracepoint data gathering occurs on the target
12395 without interaction from @value{GDBN}. Thus the full capabilities of
12396 the debugger are not available during data gathering, and then at data
12397 examination time, you will be limited by only having what was
12398 collected. The following items describe some common problems, but it
12399 is not exhaustive, and you may run into additional difficulties not
12405 Tracepoint expressions are intended to gather objects (lvalues). Thus
12406 the full flexibility of GDB's expression evaluator is not available.
12407 You cannot call functions, cast objects to aggregate types, access
12408 convenience variables or modify values (except by assignment to trace
12409 state variables). Some language features may implicitly call
12410 functions (for instance Objective-C fields with accessors), and therefore
12411 cannot be collected either.
12414 Collection of local variables, either individually or in bulk with
12415 @code{$locals} or @code{$args}, during @code{while-stepping} may
12416 behave erratically. The stepping action may enter a new scope (for
12417 instance by stepping into a function), or the location of the variable
12418 may change (for instance it is loaded into a register). The
12419 tracepoint data recorded uses the location information for the
12420 variables that is correct for the tracepoint location. When the
12421 tracepoint is created, it is not possible, in general, to determine
12422 where the steps of a @code{while-stepping} sequence will advance the
12423 program---particularly if a conditional branch is stepped.
12426 Collection of an incompletely-initialized or partially-destroyed object
12427 may result in something that @value{GDBN} cannot display, or displays
12428 in a misleading way.
12431 When @value{GDBN} displays a pointer to character it automatically
12432 dereferences the pointer to also display characters of the string
12433 being pointed to. However, collecting the pointer during tracing does
12434 not automatically collect the string. You need to explicitly
12435 dereference the pointer and provide size information if you want to
12436 collect not only the pointer, but the memory pointed to. For example,
12437 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12441 It is not possible to collect a complete stack backtrace at a
12442 tracepoint. Instead, you may collect the registers and a few hundred
12443 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12444 (adjust to use the name of the actual stack pointer register on your
12445 target architecture, and the amount of stack you wish to capture).
12446 Then the @code{backtrace} command will show a partial backtrace when
12447 using a trace frame. The number of stack frames that can be examined
12448 depends on the sizes of the frames in the collected stack. Note that
12449 if you ask for a block so large that it goes past the bottom of the
12450 stack, the target agent may report an error trying to read from an
12454 If you do not collect registers at a tracepoint, @value{GDBN} can
12455 infer that the value of @code{$pc} must be the same as the address of
12456 the tracepoint and use that when you are looking at a trace frame
12457 for that tracepoint. However, this cannot work if the tracepoint has
12458 multiple locations (for instance if it was set in a function that was
12459 inlined), or if it has a @code{while-stepping} loop. In those cases
12460 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12465 @node Analyze Collected Data
12466 @section Using the Collected Data
12468 After the tracepoint experiment ends, you use @value{GDBN} commands
12469 for examining the trace data. The basic idea is that each tracepoint
12470 collects a trace @dfn{snapshot} every time it is hit and another
12471 snapshot every time it single-steps. All these snapshots are
12472 consecutively numbered from zero and go into a buffer, and you can
12473 examine them later. The way you examine them is to @dfn{focus} on a
12474 specific trace snapshot. When the remote stub is focused on a trace
12475 snapshot, it will respond to all @value{GDBN} requests for memory and
12476 registers by reading from the buffer which belongs to that snapshot,
12477 rather than from @emph{real} memory or registers of the program being
12478 debugged. This means that @strong{all} @value{GDBN} commands
12479 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12480 behave as if we were currently debugging the program state as it was
12481 when the tracepoint occurred. Any requests for data that are not in
12482 the buffer will fail.
12485 * tfind:: How to select a trace snapshot
12486 * tdump:: How to display all data for a snapshot
12487 * save tracepoints:: How to save tracepoints for a future run
12491 @subsection @code{tfind @var{n}}
12494 @cindex select trace snapshot
12495 @cindex find trace snapshot
12496 The basic command for selecting a trace snapshot from the buffer is
12497 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12498 counting from zero. If no argument @var{n} is given, the next
12499 snapshot is selected.
12501 Here are the various forms of using the @code{tfind} command.
12505 Find the first snapshot in the buffer. This is a synonym for
12506 @code{tfind 0} (since 0 is the number of the first snapshot).
12509 Stop debugging trace snapshots, resume @emph{live} debugging.
12512 Same as @samp{tfind none}.
12515 No argument means find the next trace snapshot.
12518 Find the previous trace snapshot before the current one. This permits
12519 retracing earlier steps.
12521 @item tfind tracepoint @var{num}
12522 Find the next snapshot associated with tracepoint @var{num}. Search
12523 proceeds forward from the last examined trace snapshot. If no
12524 argument @var{num} is given, it means find the next snapshot collected
12525 for the same tracepoint as the current snapshot.
12527 @item tfind pc @var{addr}
12528 Find the next snapshot associated with the value @var{addr} of the
12529 program counter. Search proceeds forward from the last examined trace
12530 snapshot. If no argument @var{addr} is given, it means find the next
12531 snapshot with the same value of PC as the current snapshot.
12533 @item tfind outside @var{addr1}, @var{addr2}
12534 Find the next snapshot whose PC is outside the given range of
12535 addresses (exclusive).
12537 @item tfind range @var{addr1}, @var{addr2}
12538 Find the next snapshot whose PC is between @var{addr1} and
12539 @var{addr2} (inclusive).
12541 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12542 Find the next snapshot associated with the source line @var{n}. If
12543 the optional argument @var{file} is given, refer to line @var{n} in
12544 that source file. Search proceeds forward from the last examined
12545 trace snapshot. If no argument @var{n} is given, it means find the
12546 next line other than the one currently being examined; thus saying
12547 @code{tfind line} repeatedly can appear to have the same effect as
12548 stepping from line to line in a @emph{live} debugging session.
12551 The default arguments for the @code{tfind} commands are specifically
12552 designed to make it easy to scan through the trace buffer. For
12553 instance, @code{tfind} with no argument selects the next trace
12554 snapshot, and @code{tfind -} with no argument selects the previous
12555 trace snapshot. So, by giving one @code{tfind} command, and then
12556 simply hitting @key{RET} repeatedly you can examine all the trace
12557 snapshots in order. Or, by saying @code{tfind -} and then hitting
12558 @key{RET} repeatedly you can examine the snapshots in reverse order.
12559 The @code{tfind line} command with no argument selects the snapshot
12560 for the next source line executed. The @code{tfind pc} command with
12561 no argument selects the next snapshot with the same program counter
12562 (PC) as the current frame. The @code{tfind tracepoint} command with
12563 no argument selects the next trace snapshot collected by the same
12564 tracepoint as the current one.
12566 In addition to letting you scan through the trace buffer manually,
12567 these commands make it easy to construct @value{GDBN} scripts that
12568 scan through the trace buffer and print out whatever collected data
12569 you are interested in. Thus, if we want to examine the PC, FP, and SP
12570 registers from each trace frame in the buffer, we can say this:
12573 (@value{GDBP}) @b{tfind start}
12574 (@value{GDBP}) @b{while ($trace_frame != -1)}
12575 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12576 $trace_frame, $pc, $sp, $fp
12580 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12581 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12582 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12583 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12584 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12585 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12586 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12587 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12588 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12589 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12590 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12593 Or, if we want to examine the variable @code{X} at each source line in
12597 (@value{GDBP}) @b{tfind start}
12598 (@value{GDBP}) @b{while ($trace_frame != -1)}
12599 > printf "Frame %d, X == %d\n", $trace_frame, X
12609 @subsection @code{tdump}
12611 @cindex dump all data collected at tracepoint
12612 @cindex tracepoint data, display
12614 This command takes no arguments. It prints all the data collected at
12615 the current trace snapshot.
12618 (@value{GDBP}) @b{trace 444}
12619 (@value{GDBP}) @b{actions}
12620 Enter actions for tracepoint #2, one per line:
12621 > collect $regs, $locals, $args, gdb_long_test
12624 (@value{GDBP}) @b{tstart}
12626 (@value{GDBP}) @b{tfind line 444}
12627 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12629 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12631 (@value{GDBP}) @b{tdump}
12632 Data collected at tracepoint 2, trace frame 1:
12633 d0 0xc4aa0085 -995491707
12637 d4 0x71aea3d 119204413
12640 d7 0x380035 3670069
12641 a0 0x19e24a 1696330
12642 a1 0x3000668 50333288
12644 a3 0x322000 3284992
12645 a4 0x3000698 50333336
12646 a5 0x1ad3cc 1758156
12647 fp 0x30bf3c 0x30bf3c
12648 sp 0x30bf34 0x30bf34
12650 pc 0x20b2c8 0x20b2c8
12654 p = 0x20e5b4 "gdb-test"
12661 gdb_long_test = 17 '\021'
12666 @code{tdump} works by scanning the tracepoint's current collection
12667 actions and printing the value of each expression listed. So
12668 @code{tdump} can fail, if after a run, you change the tracepoint's
12669 actions to mention variables that were not collected during the run.
12671 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12672 uses the collected value of @code{$pc} to distinguish between trace
12673 frames that were collected at the tracepoint hit, and frames that were
12674 collected while stepping. This allows it to correctly choose whether
12675 to display the basic list of collections, or the collections from the
12676 body of the while-stepping loop. However, if @code{$pc} was not collected,
12677 then @code{tdump} will always attempt to dump using the basic collection
12678 list, and may fail if a while-stepping frame does not include all the
12679 same data that is collected at the tracepoint hit.
12680 @c This is getting pretty arcane, example would be good.
12682 @node save tracepoints
12683 @subsection @code{save tracepoints @var{filename}}
12684 @kindex save tracepoints
12685 @kindex save-tracepoints
12686 @cindex save tracepoints for future sessions
12688 This command saves all current tracepoint definitions together with
12689 their actions and passcounts, into a file @file{@var{filename}}
12690 suitable for use in a later debugging session. To read the saved
12691 tracepoint definitions, use the @code{source} command (@pxref{Command
12692 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12693 alias for @w{@code{save tracepoints}}
12695 @node Tracepoint Variables
12696 @section Convenience Variables for Tracepoints
12697 @cindex tracepoint variables
12698 @cindex convenience variables for tracepoints
12701 @vindex $trace_frame
12702 @item (int) $trace_frame
12703 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12704 snapshot is selected.
12706 @vindex $tracepoint
12707 @item (int) $tracepoint
12708 The tracepoint for the current trace snapshot.
12710 @vindex $trace_line
12711 @item (int) $trace_line
12712 The line number for the current trace snapshot.
12714 @vindex $trace_file
12715 @item (char []) $trace_file
12716 The source file for the current trace snapshot.
12718 @vindex $trace_func
12719 @item (char []) $trace_func
12720 The name of the function containing @code{$tracepoint}.
12723 Note: @code{$trace_file} is not suitable for use in @code{printf},
12724 use @code{output} instead.
12726 Here's a simple example of using these convenience variables for
12727 stepping through all the trace snapshots and printing some of their
12728 data. Note that these are not the same as trace state variables,
12729 which are managed by the target.
12732 (@value{GDBP}) @b{tfind start}
12734 (@value{GDBP}) @b{while $trace_frame != -1}
12735 > output $trace_file
12736 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12742 @section Using Trace Files
12743 @cindex trace files
12745 In some situations, the target running a trace experiment may no
12746 longer be available; perhaps it crashed, or the hardware was needed
12747 for a different activity. To handle these cases, you can arrange to
12748 dump the trace data into a file, and later use that file as a source
12749 of trace data, via the @code{target tfile} command.
12754 @item tsave [ -r ] @var{filename}
12755 @itemx tsave [-ctf] @var{dirname}
12756 Save the trace data to @var{filename}. By default, this command
12757 assumes that @var{filename} refers to the host filesystem, so if
12758 necessary @value{GDBN} will copy raw trace data up from the target and
12759 then save it. If the target supports it, you can also supply the
12760 optional argument @code{-r} (``remote'') to direct the target to save
12761 the data directly into @var{filename} in its own filesystem, which may be
12762 more efficient if the trace buffer is very large. (Note, however, that
12763 @code{target tfile} can only read from files accessible to the host.)
12764 By default, this command will save trace frame in tfile format.
12765 You can supply the optional argument @code{-ctf} to save date in CTF
12766 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12767 that can be shared by multiple debugging and tracing tools. Please go to
12768 @indicateurl{http://www.efficios.com/ctf} to get more information.
12770 @kindex target tfile
12774 @item target tfile @var{filename}
12775 @itemx target ctf @var{dirname}
12776 Use the file named @var{filename} or directory named @var{dirname} as
12777 a source of trace data. Commands that examine data work as they do with
12778 a live target, but it is not possible to run any new trace experiments.
12779 @code{tstatus} will report the state of the trace run at the moment
12780 the data was saved, as well as the current trace frame you are examining.
12781 @var{filename} or @var{dirname} must be on a filesystem accessible to
12785 (@value{GDBP}) target ctf ctf.ctf
12786 (@value{GDBP}) tfind
12787 Found trace frame 0, tracepoint 2
12788 39 ++a; /* set tracepoint 1 here */
12789 (@value{GDBP}) tdump
12790 Data collected at tracepoint 2, trace frame 0:
12794 c = @{"123", "456", "789", "123", "456", "789"@}
12795 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12803 @chapter Debugging Programs That Use Overlays
12806 If your program is too large to fit completely in your target system's
12807 memory, you can sometimes use @dfn{overlays} to work around this
12808 problem. @value{GDBN} provides some support for debugging programs that
12812 * How Overlays Work:: A general explanation of overlays.
12813 * Overlay Commands:: Managing overlays in @value{GDBN}.
12814 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12815 mapped by asking the inferior.
12816 * Overlay Sample Program:: A sample program using overlays.
12819 @node How Overlays Work
12820 @section How Overlays Work
12821 @cindex mapped overlays
12822 @cindex unmapped overlays
12823 @cindex load address, overlay's
12824 @cindex mapped address
12825 @cindex overlay area
12827 Suppose you have a computer whose instruction address space is only 64
12828 kilobytes long, but which has much more memory which can be accessed by
12829 other means: special instructions, segment registers, or memory
12830 management hardware, for example. Suppose further that you want to
12831 adapt a program which is larger than 64 kilobytes to run on this system.
12833 One solution is to identify modules of your program which are relatively
12834 independent, and need not call each other directly; call these modules
12835 @dfn{overlays}. Separate the overlays from the main program, and place
12836 their machine code in the larger memory. Place your main program in
12837 instruction memory, but leave at least enough space there to hold the
12838 largest overlay as well.
12840 Now, to call a function located in an overlay, you must first copy that
12841 overlay's machine code from the large memory into the space set aside
12842 for it in the instruction memory, and then jump to its entry point
12845 @c NB: In the below the mapped area's size is greater or equal to the
12846 @c size of all overlays. This is intentional to remind the developer
12847 @c that overlays don't necessarily need to be the same size.
12851 Data Instruction Larger
12852 Address Space Address Space Address Space
12853 +-----------+ +-----------+ +-----------+
12855 +-----------+ +-----------+ +-----------+<-- overlay 1
12856 | program | | main | .----| overlay 1 | load address
12857 | variables | | program | | +-----------+
12858 | and heap | | | | | |
12859 +-----------+ | | | +-----------+<-- overlay 2
12860 | | +-----------+ | | | load address
12861 +-----------+ | | | .-| overlay 2 |
12863 mapped --->+-----------+ | | +-----------+
12864 address | | | | | |
12865 | overlay | <-' | | |
12866 | area | <---' +-----------+<-- overlay 3
12867 | | <---. | | load address
12868 +-----------+ `--| overlay 3 |
12875 @anchor{A code overlay}A code overlay
12879 The diagram (@pxref{A code overlay}) shows a system with separate data
12880 and instruction address spaces. To map an overlay, the program copies
12881 its code from the larger address space to the instruction address space.
12882 Since the overlays shown here all use the same mapped address, only one
12883 may be mapped at a time. For a system with a single address space for
12884 data and instructions, the diagram would be similar, except that the
12885 program variables and heap would share an address space with the main
12886 program and the overlay area.
12888 An overlay loaded into instruction memory and ready for use is called a
12889 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12890 instruction memory. An overlay not present (or only partially present)
12891 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12892 is its address in the larger memory. The mapped address is also called
12893 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12894 called the @dfn{load memory address}, or @dfn{LMA}.
12896 Unfortunately, overlays are not a completely transparent way to adapt a
12897 program to limited instruction memory. They introduce a new set of
12898 global constraints you must keep in mind as you design your program:
12903 Before calling or returning to a function in an overlay, your program
12904 must make sure that overlay is actually mapped. Otherwise, the call or
12905 return will transfer control to the right address, but in the wrong
12906 overlay, and your program will probably crash.
12909 If the process of mapping an overlay is expensive on your system, you
12910 will need to choose your overlays carefully to minimize their effect on
12911 your program's performance.
12914 The executable file you load onto your system must contain each
12915 overlay's instructions, appearing at the overlay's load address, not its
12916 mapped address. However, each overlay's instructions must be relocated
12917 and its symbols defined as if the overlay were at its mapped address.
12918 You can use GNU linker scripts to specify different load and relocation
12919 addresses for pieces of your program; see @ref{Overlay Description,,,
12920 ld.info, Using ld: the GNU linker}.
12923 The procedure for loading executable files onto your system must be able
12924 to load their contents into the larger address space as well as the
12925 instruction and data spaces.
12929 The overlay system described above is rather simple, and could be
12930 improved in many ways:
12935 If your system has suitable bank switch registers or memory management
12936 hardware, you could use those facilities to make an overlay's load area
12937 contents simply appear at their mapped address in instruction space.
12938 This would probably be faster than copying the overlay to its mapped
12939 area in the usual way.
12942 If your overlays are small enough, you could set aside more than one
12943 overlay area, and have more than one overlay mapped at a time.
12946 You can use overlays to manage data, as well as instructions. In
12947 general, data overlays are even less transparent to your design than
12948 code overlays: whereas code overlays only require care when you call or
12949 return to functions, data overlays require care every time you access
12950 the data. Also, if you change the contents of a data overlay, you
12951 must copy its contents back out to its load address before you can copy a
12952 different data overlay into the same mapped area.
12957 @node Overlay Commands
12958 @section Overlay Commands
12960 To use @value{GDBN}'s overlay support, each overlay in your program must
12961 correspond to a separate section of the executable file. The section's
12962 virtual memory address and load memory address must be the overlay's
12963 mapped and load addresses. Identifying overlays with sections allows
12964 @value{GDBN} to determine the appropriate address of a function or
12965 variable, depending on whether the overlay is mapped or not.
12967 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12968 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12973 Disable @value{GDBN}'s overlay support. When overlay support is
12974 disabled, @value{GDBN} assumes that all functions and variables are
12975 always present at their mapped addresses. By default, @value{GDBN}'s
12976 overlay support is disabled.
12978 @item overlay manual
12979 @cindex manual overlay debugging
12980 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12981 relies on you to tell it which overlays are mapped, and which are not,
12982 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12983 commands described below.
12985 @item overlay map-overlay @var{overlay}
12986 @itemx overlay map @var{overlay}
12987 @cindex map an overlay
12988 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12989 be the name of the object file section containing the overlay. When an
12990 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12991 functions and variables at their mapped addresses. @value{GDBN} assumes
12992 that any other overlays whose mapped ranges overlap that of
12993 @var{overlay} are now unmapped.
12995 @item overlay unmap-overlay @var{overlay}
12996 @itemx overlay unmap @var{overlay}
12997 @cindex unmap an overlay
12998 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12999 must be the name of the object file section containing the overlay.
13000 When an overlay is unmapped, @value{GDBN} assumes it can find the
13001 overlay's functions and variables at their load addresses.
13004 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13005 consults a data structure the overlay manager maintains in the inferior
13006 to see which overlays are mapped. For details, see @ref{Automatic
13007 Overlay Debugging}.
13009 @item overlay load-target
13010 @itemx overlay load
13011 @cindex reloading the overlay table
13012 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13013 re-reads the table @value{GDBN} automatically each time the inferior
13014 stops, so this command should only be necessary if you have changed the
13015 overlay mapping yourself using @value{GDBN}. This command is only
13016 useful when using automatic overlay debugging.
13018 @item overlay list-overlays
13019 @itemx overlay list
13020 @cindex listing mapped overlays
13021 Display a list of the overlays currently mapped, along with their mapped
13022 addresses, load addresses, and sizes.
13026 Normally, when @value{GDBN} prints a code address, it includes the name
13027 of the function the address falls in:
13030 (@value{GDBP}) print main
13031 $3 = @{int ()@} 0x11a0 <main>
13034 When overlay debugging is enabled, @value{GDBN} recognizes code in
13035 unmapped overlays, and prints the names of unmapped functions with
13036 asterisks around them. For example, if @code{foo} is a function in an
13037 unmapped overlay, @value{GDBN} prints it this way:
13040 (@value{GDBP}) overlay list
13041 No sections are mapped.
13042 (@value{GDBP}) print foo
13043 $5 = @{int (int)@} 0x100000 <*foo*>
13046 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13050 (@value{GDBP}) overlay list
13051 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13052 mapped at 0x1016 - 0x104a
13053 (@value{GDBP}) print foo
13054 $6 = @{int (int)@} 0x1016 <foo>
13057 When overlay debugging is enabled, @value{GDBN} can find the correct
13058 address for functions and variables in an overlay, whether or not the
13059 overlay is mapped. This allows most @value{GDBN} commands, like
13060 @code{break} and @code{disassemble}, to work normally, even on unmapped
13061 code. However, @value{GDBN}'s breakpoint support has some limitations:
13065 @cindex breakpoints in overlays
13066 @cindex overlays, setting breakpoints in
13067 You can set breakpoints in functions in unmapped overlays, as long as
13068 @value{GDBN} can write to the overlay at its load address.
13070 @value{GDBN} can not set hardware or simulator-based breakpoints in
13071 unmapped overlays. However, if you set a breakpoint at the end of your
13072 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13073 you are using manual overlay management), @value{GDBN} will re-set its
13074 breakpoints properly.
13078 @node Automatic Overlay Debugging
13079 @section Automatic Overlay Debugging
13080 @cindex automatic overlay debugging
13082 @value{GDBN} can automatically track which overlays are mapped and which
13083 are not, given some simple co-operation from the overlay manager in the
13084 inferior. If you enable automatic overlay debugging with the
13085 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13086 looks in the inferior's memory for certain variables describing the
13087 current state of the overlays.
13089 Here are the variables your overlay manager must define to support
13090 @value{GDBN}'s automatic overlay debugging:
13094 @item @code{_ovly_table}:
13095 This variable must be an array of the following structures:
13100 /* The overlay's mapped address. */
13103 /* The size of the overlay, in bytes. */
13104 unsigned long size;
13106 /* The overlay's load address. */
13109 /* Non-zero if the overlay is currently mapped;
13111 unsigned long mapped;
13115 @item @code{_novlys}:
13116 This variable must be a four-byte signed integer, holding the total
13117 number of elements in @code{_ovly_table}.
13121 To decide whether a particular overlay is mapped or not, @value{GDBN}
13122 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13123 @code{lma} members equal the VMA and LMA of the overlay's section in the
13124 executable file. When @value{GDBN} finds a matching entry, it consults
13125 the entry's @code{mapped} member to determine whether the overlay is
13128 In addition, your overlay manager may define a function called
13129 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13130 will silently set a breakpoint there. If the overlay manager then
13131 calls this function whenever it has changed the overlay table, this
13132 will enable @value{GDBN} to accurately keep track of which overlays
13133 are in program memory, and update any breakpoints that may be set
13134 in overlays. This will allow breakpoints to work even if the
13135 overlays are kept in ROM or other non-writable memory while they
13136 are not being executed.
13138 @node Overlay Sample Program
13139 @section Overlay Sample Program
13140 @cindex overlay example program
13142 When linking a program which uses overlays, you must place the overlays
13143 at their load addresses, while relocating them to run at their mapped
13144 addresses. To do this, you must write a linker script (@pxref{Overlay
13145 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13146 since linker scripts are specific to a particular host system, target
13147 architecture, and target memory layout, this manual cannot provide
13148 portable sample code demonstrating @value{GDBN}'s overlay support.
13150 However, the @value{GDBN} source distribution does contain an overlaid
13151 program, with linker scripts for a few systems, as part of its test
13152 suite. The program consists of the following files from
13153 @file{gdb/testsuite/gdb.base}:
13157 The main program file.
13159 A simple overlay manager, used by @file{overlays.c}.
13164 Overlay modules, loaded and used by @file{overlays.c}.
13167 Linker scripts for linking the test program on the @code{d10v-elf}
13168 and @code{m32r-elf} targets.
13171 You can build the test program using the @code{d10v-elf} GCC
13172 cross-compiler like this:
13175 $ d10v-elf-gcc -g -c overlays.c
13176 $ d10v-elf-gcc -g -c ovlymgr.c
13177 $ d10v-elf-gcc -g -c foo.c
13178 $ d10v-elf-gcc -g -c bar.c
13179 $ d10v-elf-gcc -g -c baz.c
13180 $ d10v-elf-gcc -g -c grbx.c
13181 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13182 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13185 The build process is identical for any other architecture, except that
13186 you must substitute the appropriate compiler and linker script for the
13187 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13191 @chapter Using @value{GDBN} with Different Languages
13194 Although programming languages generally have common aspects, they are
13195 rarely expressed in the same manner. For instance, in ANSI C,
13196 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13197 Modula-2, it is accomplished by @code{p^}. Values can also be
13198 represented (and displayed) differently. Hex numbers in C appear as
13199 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13201 @cindex working language
13202 Language-specific information is built into @value{GDBN} for some languages,
13203 allowing you to express operations like the above in your program's
13204 native language, and allowing @value{GDBN} to output values in a manner
13205 consistent with the syntax of your program's native language. The
13206 language you use to build expressions is called the @dfn{working
13210 * Setting:: Switching between source languages
13211 * Show:: Displaying the language
13212 * Checks:: Type and range checks
13213 * Supported Languages:: Supported languages
13214 * Unsupported Languages:: Unsupported languages
13218 @section Switching Between Source Languages
13220 There are two ways to control the working language---either have @value{GDBN}
13221 set it automatically, or select it manually yourself. You can use the
13222 @code{set language} command for either purpose. On startup, @value{GDBN}
13223 defaults to setting the language automatically. The working language is
13224 used to determine how expressions you type are interpreted, how values
13227 In addition to the working language, every source file that
13228 @value{GDBN} knows about has its own working language. For some object
13229 file formats, the compiler might indicate which language a particular
13230 source file is in. However, most of the time @value{GDBN} infers the
13231 language from the name of the file. The language of a source file
13232 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13233 show each frame appropriately for its own language. There is no way to
13234 set the language of a source file from within @value{GDBN}, but you can
13235 set the language associated with a filename extension. @xref{Show, ,
13236 Displaying the Language}.
13238 This is most commonly a problem when you use a program, such
13239 as @code{cfront} or @code{f2c}, that generates C but is written in
13240 another language. In that case, make the
13241 program use @code{#line} directives in its C output; that way
13242 @value{GDBN} will know the correct language of the source code of the original
13243 program, and will display that source code, not the generated C code.
13246 * Filenames:: Filename extensions and languages.
13247 * Manually:: Setting the working language manually
13248 * Automatically:: Having @value{GDBN} infer the source language
13252 @subsection List of Filename Extensions and Languages
13254 If a source file name ends in one of the following extensions, then
13255 @value{GDBN} infers that its language is the one indicated.
13273 C@t{++} source file
13279 Objective-C source file
13283 Fortran source file
13286 Modula-2 source file
13290 Assembler source file. This actually behaves almost like C, but
13291 @value{GDBN} does not skip over function prologues when stepping.
13294 In addition, you may set the language associated with a filename
13295 extension. @xref{Show, , Displaying the Language}.
13298 @subsection Setting the Working Language
13300 If you allow @value{GDBN} to set the language automatically,
13301 expressions are interpreted the same way in your debugging session and
13304 @kindex set language
13305 If you wish, you may set the language manually. To do this, issue the
13306 command @samp{set language @var{lang}}, where @var{lang} is the name of
13307 a language, such as
13308 @code{c} or @code{modula-2}.
13309 For a list of the supported languages, type @samp{set language}.
13311 Setting the language manually prevents @value{GDBN} from updating the working
13312 language automatically. This can lead to confusion if you try
13313 to debug a program when the working language is not the same as the
13314 source language, when an expression is acceptable to both
13315 languages---but means different things. For instance, if the current
13316 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13324 might not have the effect you intended. In C, this means to add
13325 @code{b} and @code{c} and place the result in @code{a}. The result
13326 printed would be the value of @code{a}. In Modula-2, this means to compare
13327 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13329 @node Automatically
13330 @subsection Having @value{GDBN} Infer the Source Language
13332 To have @value{GDBN} set the working language automatically, use
13333 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13334 then infers the working language. That is, when your program stops in a
13335 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13336 working language to the language recorded for the function in that
13337 frame. If the language for a frame is unknown (that is, if the function
13338 or block corresponding to the frame was defined in a source file that
13339 does not have a recognized extension), the current working language is
13340 not changed, and @value{GDBN} issues a warning.
13342 This may not seem necessary for most programs, which are written
13343 entirely in one source language. However, program modules and libraries
13344 written in one source language can be used by a main program written in
13345 a different source language. Using @samp{set language auto} in this
13346 case frees you from having to set the working language manually.
13349 @section Displaying the Language
13351 The following commands help you find out which language is the
13352 working language, and also what language source files were written in.
13355 @item show language
13356 @anchor{show language}
13357 @kindex show language
13358 Display the current working language. This is the
13359 language you can use with commands such as @code{print} to
13360 build and compute expressions that may involve variables in your program.
13363 @kindex info frame@r{, show the source language}
13364 Display the source language for this frame. This language becomes the
13365 working language if you use an identifier from this frame.
13366 @xref{Frame Info, ,Information about a Frame}, to identify the other
13367 information listed here.
13370 @kindex info source@r{, show the source language}
13371 Display the source language of this source file.
13372 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13373 information listed here.
13376 In unusual circumstances, you may have source files with extensions
13377 not in the standard list. You can then set the extension associated
13378 with a language explicitly:
13381 @item set extension-language @var{ext} @var{language}
13382 @kindex set extension-language
13383 Tell @value{GDBN} that source files with extension @var{ext} are to be
13384 assumed as written in the source language @var{language}.
13386 @item info extensions
13387 @kindex info extensions
13388 List all the filename extensions and the associated languages.
13392 @section Type and Range Checking
13394 Some languages are designed to guard you against making seemingly common
13395 errors through a series of compile- and run-time checks. These include
13396 checking the type of arguments to functions and operators and making
13397 sure mathematical overflows are caught at run time. Checks such as
13398 these help to ensure a program's correctness once it has been compiled
13399 by eliminating type mismatches and providing active checks for range
13400 errors when your program is running.
13402 By default @value{GDBN} checks for these errors according to the
13403 rules of the current source language. Although @value{GDBN} does not check
13404 the statements in your program, it can check expressions entered directly
13405 into @value{GDBN} for evaluation via the @code{print} command, for example.
13408 * Type Checking:: An overview of type checking
13409 * Range Checking:: An overview of range checking
13412 @cindex type checking
13413 @cindex checks, type
13414 @node Type Checking
13415 @subsection An Overview of Type Checking
13417 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13418 arguments to operators and functions have to be of the correct type,
13419 otherwise an error occurs. These checks prevent type mismatch
13420 errors from ever causing any run-time problems. For example,
13423 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13425 (@value{GDBP}) print obj.my_method (0)
13428 (@value{GDBP}) print obj.my_method (0x1234)
13429 Cannot resolve method klass::my_method to any overloaded instance
13432 The second example fails because in C@t{++} the integer constant
13433 @samp{0x1234} is not type-compatible with the pointer parameter type.
13435 For the expressions you use in @value{GDBN} commands, you can tell
13436 @value{GDBN} to not enforce strict type checking or
13437 to treat any mismatches as errors and abandon the expression;
13438 When type checking is disabled, @value{GDBN} successfully evaluates
13439 expressions like the second example above.
13441 Even if type checking is off, there may be other reasons
13442 related to type that prevent @value{GDBN} from evaluating an expression.
13443 For instance, @value{GDBN} does not know how to add an @code{int} and
13444 a @code{struct foo}. These particular type errors have nothing to do
13445 with the language in use and usually arise from expressions which make
13446 little sense to evaluate anyway.
13448 @value{GDBN} provides some additional commands for controlling type checking:
13450 @kindex set check type
13451 @kindex show check type
13453 @item set check type on
13454 @itemx set check type off
13455 Set strict type checking on or off. If any type mismatches occur in
13456 evaluating an expression while type checking is on, @value{GDBN} prints a
13457 message and aborts evaluation of the expression.
13459 @item show check type
13460 Show the current setting of type checking and whether @value{GDBN}
13461 is enforcing strict type checking rules.
13464 @cindex range checking
13465 @cindex checks, range
13466 @node Range Checking
13467 @subsection An Overview of Range Checking
13469 In some languages (such as Modula-2), it is an error to exceed the
13470 bounds of a type; this is enforced with run-time checks. Such range
13471 checking is meant to ensure program correctness by making sure
13472 computations do not overflow, or indices on an array element access do
13473 not exceed the bounds of the array.
13475 For expressions you use in @value{GDBN} commands, you can tell
13476 @value{GDBN} to treat range errors in one of three ways: ignore them,
13477 always treat them as errors and abandon the expression, or issue
13478 warnings but evaluate the expression anyway.
13480 A range error can result from numerical overflow, from exceeding an
13481 array index bound, or when you type a constant that is not a member
13482 of any type. Some languages, however, do not treat overflows as an
13483 error. In many implementations of C, mathematical overflow causes the
13484 result to ``wrap around'' to lower values---for example, if @var{m} is
13485 the largest integer value, and @var{s} is the smallest, then
13488 @var{m} + 1 @result{} @var{s}
13491 This, too, is specific to individual languages, and in some cases
13492 specific to individual compilers or machines. @xref{Supported Languages, ,
13493 Supported Languages}, for further details on specific languages.
13495 @value{GDBN} provides some additional commands for controlling the range checker:
13497 @kindex set check range
13498 @kindex show check range
13500 @item set check range auto
13501 Set range checking on or off based on the current working language.
13502 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13505 @item set check range on
13506 @itemx set check range off
13507 Set range checking on or off, overriding the default setting for the
13508 current working language. A warning is issued if the setting does not
13509 match the language default. If a range error occurs and range checking is on,
13510 then a message is printed and evaluation of the expression is aborted.
13512 @item set check range warn
13513 Output messages when the @value{GDBN} range checker detects a range error,
13514 but attempt to evaluate the expression anyway. Evaluating the
13515 expression may still be impossible for other reasons, such as accessing
13516 memory that the process does not own (a typical example from many Unix
13520 Show the current setting of the range checker, and whether or not it is
13521 being set automatically by @value{GDBN}.
13524 @node Supported Languages
13525 @section Supported Languages
13527 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13528 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13529 @c This is false ...
13530 Some @value{GDBN} features may be used in expressions regardless of the
13531 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13532 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13533 ,Expressions}) can be used with the constructs of any supported
13536 The following sections detail to what degree each source language is
13537 supported by @value{GDBN}. These sections are not meant to be language
13538 tutorials or references, but serve only as a reference guide to what the
13539 @value{GDBN} expression parser accepts, and what input and output
13540 formats should look like for different languages. There are many good
13541 books written on each of these languages; please look to these for a
13542 language reference or tutorial.
13545 * C:: C and C@t{++}
13548 * Objective-C:: Objective-C
13549 * OpenCL C:: OpenCL C
13550 * Fortran:: Fortran
13552 * Modula-2:: Modula-2
13557 @subsection C and C@t{++}
13559 @cindex C and C@t{++}
13560 @cindex expressions in C or C@t{++}
13562 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13563 to both languages. Whenever this is the case, we discuss those languages
13567 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13568 @cindex @sc{gnu} C@t{++}
13569 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13570 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13571 effectively, you must compile your C@t{++} programs with a supported
13572 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13573 compiler (@code{aCC}).
13576 * C Operators:: C and C@t{++} operators
13577 * C Constants:: C and C@t{++} constants
13578 * C Plus Plus Expressions:: C@t{++} expressions
13579 * C Defaults:: Default settings for C and C@t{++}
13580 * C Checks:: C and C@t{++} type and range checks
13581 * Debugging C:: @value{GDBN} and C
13582 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13583 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13587 @subsubsection C and C@t{++} Operators
13589 @cindex C and C@t{++} operators
13591 Operators must be defined on values of specific types. For instance,
13592 @code{+} is defined on numbers, but not on structures. Operators are
13593 often defined on groups of types.
13595 For the purposes of C and C@t{++}, the following definitions hold:
13600 @emph{Integral types} include @code{int} with any of its storage-class
13601 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13604 @emph{Floating-point types} include @code{float}, @code{double}, and
13605 @code{long double} (if supported by the target platform).
13608 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13611 @emph{Scalar types} include all of the above.
13616 The following operators are supported. They are listed here
13617 in order of increasing precedence:
13621 The comma or sequencing operator. Expressions in a comma-separated list
13622 are evaluated from left to right, with the result of the entire
13623 expression being the last expression evaluated.
13626 Assignment. The value of an assignment expression is the value
13627 assigned. Defined on scalar types.
13630 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13631 and translated to @w{@code{@var{a} = @var{a op b}}}.
13632 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13633 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13634 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13637 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13638 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13642 Logical @sc{or}. Defined on integral types.
13645 Logical @sc{and}. Defined on integral types.
13648 Bitwise @sc{or}. Defined on integral types.
13651 Bitwise exclusive-@sc{or}. Defined on integral types.
13654 Bitwise @sc{and}. Defined on integral types.
13657 Equality and inequality. Defined on scalar types. The value of these
13658 expressions is 0 for false and non-zero for true.
13660 @item <@r{, }>@r{, }<=@r{, }>=
13661 Less than, greater than, less than or equal, greater than or equal.
13662 Defined on scalar types. The value of these expressions is 0 for false
13663 and non-zero for true.
13666 left shift, and right shift. Defined on integral types.
13669 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13672 Addition and subtraction. Defined on integral types, floating-point types and
13675 @item *@r{, }/@r{, }%
13676 Multiplication, division, and modulus. Multiplication and division are
13677 defined on integral and floating-point types. Modulus is defined on
13681 Increment and decrement. When appearing before a variable, the
13682 operation is performed before the variable is used in an expression;
13683 when appearing after it, the variable's value is used before the
13684 operation takes place.
13687 Pointer dereferencing. Defined on pointer types. Same precedence as
13691 Address operator. Defined on variables. Same precedence as @code{++}.
13693 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13694 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13695 to examine the address
13696 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13700 Negative. Defined on integral and floating-point types. Same
13701 precedence as @code{++}.
13704 Logical negation. Defined on integral types. Same precedence as
13708 Bitwise complement operator. Defined on integral types. Same precedence as
13713 Structure member, and pointer-to-structure member. For convenience,
13714 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13715 pointer based on the stored type information.
13716 Defined on @code{struct} and @code{union} data.
13719 Dereferences of pointers to members.
13722 Array indexing. @code{@var{a}[@var{i}]} is defined as
13723 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13726 Function parameter list. Same precedence as @code{->}.
13729 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13730 and @code{class} types.
13733 Doubled colons also represent the @value{GDBN} scope operator
13734 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13738 If an operator is redefined in the user code, @value{GDBN} usually
13739 attempts to invoke the redefined version instead of using the operator's
13740 predefined meaning.
13743 @subsubsection C and C@t{++} Constants
13745 @cindex C and C@t{++} constants
13747 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13752 Integer constants are a sequence of digits. Octal constants are
13753 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13754 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13755 @samp{l}, specifying that the constant should be treated as a
13759 Floating point constants are a sequence of digits, followed by a decimal
13760 point, followed by a sequence of digits, and optionally followed by an
13761 exponent. An exponent is of the form:
13762 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13763 sequence of digits. The @samp{+} is optional for positive exponents.
13764 A floating-point constant may also end with a letter @samp{f} or
13765 @samp{F}, specifying that the constant should be treated as being of
13766 the @code{float} (as opposed to the default @code{double}) type; or with
13767 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13771 Enumerated constants consist of enumerated identifiers, or their
13772 integral equivalents.
13775 Character constants are a single character surrounded by single quotes
13776 (@code{'}), or a number---the ordinal value of the corresponding character
13777 (usually its @sc{ascii} value). Within quotes, the single character may
13778 be represented by a letter or by @dfn{escape sequences}, which are of
13779 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13780 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13781 @samp{@var{x}} is a predefined special character---for example,
13782 @samp{\n} for newline.
13784 Wide character constants can be written by prefixing a character
13785 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13786 form of @samp{x}. The target wide character set is used when
13787 computing the value of this constant (@pxref{Character Sets}).
13790 String constants are a sequence of character constants surrounded by
13791 double quotes (@code{"}). Any valid character constant (as described
13792 above) may appear. Double quotes within the string must be preceded by
13793 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13796 Wide string constants can be written by prefixing a string constant
13797 with @samp{L}, as in C. The target wide character set is used when
13798 computing the value of this constant (@pxref{Character Sets}).
13801 Pointer constants are an integral value. You can also write pointers
13802 to constants using the C operator @samp{&}.
13805 Array constants are comma-separated lists surrounded by braces @samp{@{}
13806 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13807 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13808 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13811 @node C Plus Plus Expressions
13812 @subsubsection C@t{++} Expressions
13814 @cindex expressions in C@t{++}
13815 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13817 @cindex debugging C@t{++} programs
13818 @cindex C@t{++} compilers
13819 @cindex debug formats and C@t{++}
13820 @cindex @value{NGCC} and C@t{++}
13822 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13823 the proper compiler and the proper debug format. Currently,
13824 @value{GDBN} works best when debugging C@t{++} code that is compiled
13825 with the most recent version of @value{NGCC} possible. The DWARF
13826 debugging format is preferred; @value{NGCC} defaults to this on most
13827 popular platforms. Other compilers and/or debug formats are likely to
13828 work badly or not at all when using @value{GDBN} to debug C@t{++}
13829 code. @xref{Compilation}.
13834 @cindex member functions
13836 Member function calls are allowed; you can use expressions like
13839 count = aml->GetOriginal(x, y)
13842 @vindex this@r{, inside C@t{++} member functions}
13843 @cindex namespace in C@t{++}
13845 While a member function is active (in the selected stack frame), your
13846 expressions have the same namespace available as the member function;
13847 that is, @value{GDBN} allows implicit references to the class instance
13848 pointer @code{this} following the same rules as C@t{++}. @code{using}
13849 declarations in the current scope are also respected by @value{GDBN}.
13851 @cindex call overloaded functions
13852 @cindex overloaded functions, calling
13853 @cindex type conversions in C@t{++}
13855 You can call overloaded functions; @value{GDBN} resolves the function
13856 call to the right definition, with some restrictions. @value{GDBN} does not
13857 perform overload resolution involving user-defined type conversions,
13858 calls to constructors, or instantiations of templates that do not exist
13859 in the program. It also cannot handle ellipsis argument lists or
13862 It does perform integral conversions and promotions, floating-point
13863 promotions, arithmetic conversions, pointer conversions, conversions of
13864 class objects to base classes, and standard conversions such as those of
13865 functions or arrays to pointers; it requires an exact match on the
13866 number of function arguments.
13868 Overload resolution is always performed, unless you have specified
13869 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13870 ,@value{GDBN} Features for C@t{++}}.
13872 You must specify @code{set overload-resolution off} in order to use an
13873 explicit function signature to call an overloaded function, as in
13875 p 'foo(char,int)'('x', 13)
13878 The @value{GDBN} command-completion facility can simplify this;
13879 see @ref{Completion, ,Command Completion}.
13881 @cindex reference declarations
13883 @value{GDBN} understands variables declared as C@t{++} references; you can use
13884 them in expressions just as you do in C@t{++} source---they are automatically
13887 In the parameter list shown when @value{GDBN} displays a frame, the values of
13888 reference variables are not displayed (unlike other variables); this
13889 avoids clutter, since references are often used for large structures.
13890 The @emph{address} of a reference variable is always shown, unless
13891 you have specified @samp{set print address off}.
13894 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13895 expressions can use it just as expressions in your program do. Since
13896 one scope may be defined in another, you can use @code{::} repeatedly if
13897 necessary, for example in an expression like
13898 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13899 resolving name scope by reference to source files, in both C and C@t{++}
13900 debugging (@pxref{Variables, ,Program Variables}).
13903 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13908 @subsubsection C and C@t{++} Defaults
13910 @cindex C and C@t{++} defaults
13912 If you allow @value{GDBN} to set range checking automatically, it
13913 defaults to @code{off} whenever the working language changes to
13914 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13915 selects the working language.
13917 If you allow @value{GDBN} to set the language automatically, it
13918 recognizes source files whose names end with @file{.c}, @file{.C}, or
13919 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13920 these files, it sets the working language to C or C@t{++}.
13921 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13922 for further details.
13925 @subsubsection C and C@t{++} Type and Range Checks
13927 @cindex C and C@t{++} checks
13929 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13930 checking is used. However, if you turn type checking off, @value{GDBN}
13931 will allow certain non-standard conversions, such as promoting integer
13932 constants to pointers.
13934 Range checking, if turned on, is done on mathematical operations. Array
13935 indices are not checked, since they are often used to index a pointer
13936 that is not itself an array.
13939 @subsubsection @value{GDBN} and C
13941 The @code{set print union} and @code{show print union} commands apply to
13942 the @code{union} type. When set to @samp{on}, any @code{union} that is
13943 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13944 appears as @samp{@{...@}}.
13946 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13947 with pointers and a memory allocation function. @xref{Expressions,
13950 @node Debugging C Plus Plus
13951 @subsubsection @value{GDBN} Features for C@t{++}
13953 @cindex commands for C@t{++}
13955 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13956 designed specifically for use with C@t{++}. Here is a summary:
13959 @cindex break in overloaded functions
13960 @item @r{breakpoint menus}
13961 When you want a breakpoint in a function whose name is overloaded,
13962 @value{GDBN} has the capability to display a menu of possible breakpoint
13963 locations to help you specify which function definition you want.
13964 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13966 @cindex overloading in C@t{++}
13967 @item rbreak @var{regex}
13968 Setting breakpoints using regular expressions is helpful for setting
13969 breakpoints on overloaded functions that are not members of any special
13971 @xref{Set Breaks, ,Setting Breakpoints}.
13973 @cindex C@t{++} exception handling
13975 @itemx catch rethrow
13977 Debug C@t{++} exception handling using these commands. @xref{Set
13978 Catchpoints, , Setting Catchpoints}.
13980 @cindex inheritance
13981 @item ptype @var{typename}
13982 Print inheritance relationships as well as other information for type
13984 @xref{Symbols, ,Examining the Symbol Table}.
13986 @item info vtbl @var{expression}.
13987 The @code{info vtbl} command can be used to display the virtual
13988 method tables of the object computed by @var{expression}. This shows
13989 one entry per virtual table; there may be multiple virtual tables when
13990 multiple inheritance is in use.
13992 @cindex C@t{++} symbol display
13993 @item set print demangle
13994 @itemx show print demangle
13995 @itemx set print asm-demangle
13996 @itemx show print asm-demangle
13997 Control whether C@t{++} symbols display in their source form, both when
13998 displaying code as C@t{++} source and when displaying disassemblies.
13999 @xref{Print Settings, ,Print Settings}.
14001 @item set print object
14002 @itemx show print object
14003 Choose whether to print derived (actual) or declared types of objects.
14004 @xref{Print Settings, ,Print Settings}.
14006 @item set print vtbl
14007 @itemx show print vtbl
14008 Control the format for printing virtual function tables.
14009 @xref{Print Settings, ,Print Settings}.
14010 (The @code{vtbl} commands do not work on programs compiled with the HP
14011 ANSI C@t{++} compiler (@code{aCC}).)
14013 @kindex set overload-resolution
14014 @cindex overloaded functions, overload resolution
14015 @item set overload-resolution on
14016 Enable overload resolution for C@t{++} expression evaluation. The default
14017 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14018 and searches for a function whose signature matches the argument types,
14019 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14020 Expressions, ,C@t{++} Expressions}, for details).
14021 If it cannot find a match, it emits a message.
14023 @item set overload-resolution off
14024 Disable overload resolution for C@t{++} expression evaluation. For
14025 overloaded functions that are not class member functions, @value{GDBN}
14026 chooses the first function of the specified name that it finds in the
14027 symbol table, whether or not its arguments are of the correct type. For
14028 overloaded functions that are class member functions, @value{GDBN}
14029 searches for a function whose signature @emph{exactly} matches the
14032 @kindex show overload-resolution
14033 @item show overload-resolution
14034 Show the current setting of overload resolution.
14036 @item @r{Overloaded symbol names}
14037 You can specify a particular definition of an overloaded symbol, using
14038 the same notation that is used to declare such symbols in C@t{++}: type
14039 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14040 also use the @value{GDBN} command-line word completion facilities to list the
14041 available choices, or to finish the type list for you.
14042 @xref{Completion,, Command Completion}, for details on how to do this.
14045 @node Decimal Floating Point
14046 @subsubsection Decimal Floating Point format
14047 @cindex decimal floating point format
14049 @value{GDBN} can examine, set and perform computations with numbers in
14050 decimal floating point format, which in the C language correspond to the
14051 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14052 specified by the extension to support decimal floating-point arithmetic.
14054 There are two encodings in use, depending on the architecture: BID (Binary
14055 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14056 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14059 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14060 to manipulate decimal floating point numbers, it is not possible to convert
14061 (using a cast, for example) integers wider than 32-bit to decimal float.
14063 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14064 point computations, error checking in decimal float operations ignores
14065 underflow, overflow and divide by zero exceptions.
14067 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14068 to inspect @code{_Decimal128} values stored in floating point registers.
14069 See @ref{PowerPC,,PowerPC} for more details.
14075 @value{GDBN} can be used to debug programs written in D and compiled with
14076 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14077 specific feature --- dynamic arrays.
14082 @cindex Go (programming language)
14083 @value{GDBN} can be used to debug programs written in Go and compiled with
14084 @file{gccgo} or @file{6g} compilers.
14086 Here is a summary of the Go-specific features and restrictions:
14089 @cindex current Go package
14090 @item The current Go package
14091 The name of the current package does not need to be specified when
14092 specifying global variables and functions.
14094 For example, given the program:
14098 var myglob = "Shall we?"
14104 When stopped inside @code{main} either of these work:
14108 (gdb) p main.myglob
14111 @cindex builtin Go types
14112 @item Builtin Go types
14113 The @code{string} type is recognized by @value{GDBN} and is printed
14116 @cindex builtin Go functions
14117 @item Builtin Go functions
14118 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14119 function and handles it internally.
14121 @cindex restrictions on Go expressions
14122 @item Restrictions on Go expressions
14123 All Go operators are supported except @code{&^}.
14124 The Go @code{_} ``blank identifier'' is not supported.
14125 Automatic dereferencing of pointers is not supported.
14129 @subsection Objective-C
14131 @cindex Objective-C
14132 This section provides information about some commands and command
14133 options that are useful for debugging Objective-C code. See also
14134 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14135 few more commands specific to Objective-C support.
14138 * Method Names in Commands::
14139 * The Print Command with Objective-C::
14142 @node Method Names in Commands
14143 @subsubsection Method Names in Commands
14145 The following commands have been extended to accept Objective-C method
14146 names as line specifications:
14148 @kindex clear@r{, and Objective-C}
14149 @kindex break@r{, and Objective-C}
14150 @kindex info line@r{, and Objective-C}
14151 @kindex jump@r{, and Objective-C}
14152 @kindex list@r{, and Objective-C}
14156 @item @code{info line}
14161 A fully qualified Objective-C method name is specified as
14164 -[@var{Class} @var{methodName}]
14167 where the minus sign is used to indicate an instance method and a
14168 plus sign (not shown) is used to indicate a class method. The class
14169 name @var{Class} and method name @var{methodName} are enclosed in
14170 brackets, similar to the way messages are specified in Objective-C
14171 source code. For example, to set a breakpoint at the @code{create}
14172 instance method of class @code{Fruit} in the program currently being
14176 break -[Fruit create]
14179 To list ten program lines around the @code{initialize} class method,
14183 list +[NSText initialize]
14186 In the current version of @value{GDBN}, the plus or minus sign is
14187 required. In future versions of @value{GDBN}, the plus or minus
14188 sign will be optional, but you can use it to narrow the search. It
14189 is also possible to specify just a method name:
14195 You must specify the complete method name, including any colons. If
14196 your program's source files contain more than one @code{create} method,
14197 you'll be presented with a numbered list of classes that implement that
14198 method. Indicate your choice by number, or type @samp{0} to exit if
14201 As another example, to clear a breakpoint established at the
14202 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14205 clear -[NSWindow makeKeyAndOrderFront:]
14208 @node The Print Command with Objective-C
14209 @subsubsection The Print Command With Objective-C
14210 @cindex Objective-C, print objects
14211 @kindex print-object
14212 @kindex po @r{(@code{print-object})}
14214 The print command has also been extended to accept methods. For example:
14217 print -[@var{object} hash]
14220 @cindex print an Objective-C object description
14221 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14223 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14224 and print the result. Also, an additional command has been added,
14225 @code{print-object} or @code{po} for short, which is meant to print
14226 the description of an object. However, this command may only work
14227 with certain Objective-C libraries that have a particular hook
14228 function, @code{_NSPrintForDebugger}, defined.
14231 @subsection OpenCL C
14234 This section provides information about @value{GDBN}s OpenCL C support.
14237 * OpenCL C Datatypes::
14238 * OpenCL C Expressions::
14239 * OpenCL C Operators::
14242 @node OpenCL C Datatypes
14243 @subsubsection OpenCL C Datatypes
14245 @cindex OpenCL C Datatypes
14246 @value{GDBN} supports the builtin scalar and vector datatypes specified
14247 by OpenCL 1.1. In addition the half- and double-precision floating point
14248 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14249 extensions are also known to @value{GDBN}.
14251 @node OpenCL C Expressions
14252 @subsubsection OpenCL C Expressions
14254 @cindex OpenCL C Expressions
14255 @value{GDBN} supports accesses to vector components including the access as
14256 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14257 supported by @value{GDBN} can be used as well.
14259 @node OpenCL C Operators
14260 @subsubsection OpenCL C Operators
14262 @cindex OpenCL C Operators
14263 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14267 @subsection Fortran
14268 @cindex Fortran-specific support in @value{GDBN}
14270 @value{GDBN} can be used to debug programs written in Fortran, but it
14271 currently supports only the features of Fortran 77 language.
14273 @cindex trailing underscore, in Fortran symbols
14274 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14275 among them) append an underscore to the names of variables and
14276 functions. When you debug programs compiled by those compilers, you
14277 will need to refer to variables and functions with a trailing
14281 * Fortran Operators:: Fortran operators and expressions
14282 * Fortran Defaults:: Default settings for Fortran
14283 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14286 @node Fortran Operators
14287 @subsubsection Fortran Operators and Expressions
14289 @cindex Fortran operators and expressions
14291 Operators must be defined on values of specific types. For instance,
14292 @code{+} is defined on numbers, but not on characters or other non-
14293 arithmetic types. Operators are often defined on groups of types.
14297 The exponentiation operator. It raises the first operand to the power
14301 The range operator. Normally used in the form of array(low:high) to
14302 represent a section of array.
14305 The access component operator. Normally used to access elements in derived
14306 types. Also suitable for unions. As unions aren't part of regular Fortran,
14307 this can only happen when accessing a register that uses a gdbarch-defined
14311 @node Fortran Defaults
14312 @subsubsection Fortran Defaults
14314 @cindex Fortran Defaults
14316 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14317 default uses case-insensitive matches for Fortran symbols. You can
14318 change that with the @samp{set case-insensitive} command, see
14319 @ref{Symbols}, for the details.
14321 @node Special Fortran Commands
14322 @subsubsection Special Fortran Commands
14324 @cindex Special Fortran commands
14326 @value{GDBN} has some commands to support Fortran-specific features,
14327 such as displaying common blocks.
14330 @cindex @code{COMMON} blocks, Fortran
14331 @kindex info common
14332 @item info common @r{[}@var{common-name}@r{]}
14333 This command prints the values contained in the Fortran @code{COMMON}
14334 block whose name is @var{common-name}. With no argument, the names of
14335 all @code{COMMON} blocks visible at the current program location are
14342 @cindex Pascal support in @value{GDBN}, limitations
14343 Debugging Pascal programs which use sets, subranges, file variables, or
14344 nested functions does not currently work. @value{GDBN} does not support
14345 entering expressions, printing values, or similar features using Pascal
14348 The Pascal-specific command @code{set print pascal_static-members}
14349 controls whether static members of Pascal objects are displayed.
14350 @xref{Print Settings, pascal_static-members}.
14353 @subsection Modula-2
14355 @cindex Modula-2, @value{GDBN} support
14357 The extensions made to @value{GDBN} to support Modula-2 only support
14358 output from the @sc{gnu} Modula-2 compiler (which is currently being
14359 developed). Other Modula-2 compilers are not currently supported, and
14360 attempting to debug executables produced by them is most likely
14361 to give an error as @value{GDBN} reads in the executable's symbol
14364 @cindex expressions in Modula-2
14366 * M2 Operators:: Built-in operators
14367 * Built-In Func/Proc:: Built-in functions and procedures
14368 * M2 Constants:: Modula-2 constants
14369 * M2 Types:: Modula-2 types
14370 * M2 Defaults:: Default settings for Modula-2
14371 * Deviations:: Deviations from standard Modula-2
14372 * M2 Checks:: Modula-2 type and range checks
14373 * M2 Scope:: The scope operators @code{::} and @code{.}
14374 * GDB/M2:: @value{GDBN} and Modula-2
14378 @subsubsection Operators
14379 @cindex Modula-2 operators
14381 Operators must be defined on values of specific types. For instance,
14382 @code{+} is defined on numbers, but not on structures. Operators are
14383 often defined on groups of types. For the purposes of Modula-2, the
14384 following definitions hold:
14389 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14393 @emph{Character types} consist of @code{CHAR} and its subranges.
14396 @emph{Floating-point types} consist of @code{REAL}.
14399 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14403 @emph{Scalar types} consist of all of the above.
14406 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14409 @emph{Boolean types} consist of @code{BOOLEAN}.
14413 The following operators are supported, and appear in order of
14414 increasing precedence:
14418 Function argument or array index separator.
14421 Assignment. The value of @var{var} @code{:=} @var{value} is
14425 Less than, greater than on integral, floating-point, or enumerated
14429 Less than or equal to, greater than or equal to
14430 on integral, floating-point and enumerated types, or set inclusion on
14431 set types. Same precedence as @code{<}.
14433 @item =@r{, }<>@r{, }#
14434 Equality and two ways of expressing inequality, valid on scalar types.
14435 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14436 available for inequality, since @code{#} conflicts with the script
14440 Set membership. Defined on set types and the types of their members.
14441 Same precedence as @code{<}.
14444 Boolean disjunction. Defined on boolean types.
14447 Boolean conjunction. Defined on boolean types.
14450 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14453 Addition and subtraction on integral and floating-point types, or union
14454 and difference on set types.
14457 Multiplication on integral and floating-point types, or set intersection
14461 Division on floating-point types, or symmetric set difference on set
14462 types. Same precedence as @code{*}.
14465 Integer division and remainder. Defined on integral types. Same
14466 precedence as @code{*}.
14469 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14472 Pointer dereferencing. Defined on pointer types.
14475 Boolean negation. Defined on boolean types. Same precedence as
14479 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14480 precedence as @code{^}.
14483 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14486 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14490 @value{GDBN} and Modula-2 scope operators.
14494 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14495 treats the use of the operator @code{IN}, or the use of operators
14496 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14497 @code{<=}, and @code{>=} on sets as an error.
14501 @node Built-In Func/Proc
14502 @subsubsection Built-in Functions and Procedures
14503 @cindex Modula-2 built-ins
14505 Modula-2 also makes available several built-in procedures and functions.
14506 In describing these, the following metavariables are used:
14511 represents an @code{ARRAY} variable.
14514 represents a @code{CHAR} constant or variable.
14517 represents a variable or constant of integral type.
14520 represents an identifier that belongs to a set. Generally used in the
14521 same function with the metavariable @var{s}. The type of @var{s} should
14522 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14525 represents a variable or constant of integral or floating-point type.
14528 represents a variable or constant of floating-point type.
14534 represents a variable.
14537 represents a variable or constant of one of many types. See the
14538 explanation of the function for details.
14541 All Modula-2 built-in procedures also return a result, described below.
14545 Returns the absolute value of @var{n}.
14548 If @var{c} is a lower case letter, it returns its upper case
14549 equivalent, otherwise it returns its argument.
14552 Returns the character whose ordinal value is @var{i}.
14555 Decrements the value in the variable @var{v} by one. Returns the new value.
14557 @item DEC(@var{v},@var{i})
14558 Decrements the value in the variable @var{v} by @var{i}. Returns the
14561 @item EXCL(@var{m},@var{s})
14562 Removes the element @var{m} from the set @var{s}. Returns the new
14565 @item FLOAT(@var{i})
14566 Returns the floating point equivalent of the integer @var{i}.
14568 @item HIGH(@var{a})
14569 Returns the index of the last member of @var{a}.
14572 Increments the value in the variable @var{v} by one. Returns the new value.
14574 @item INC(@var{v},@var{i})
14575 Increments the value in the variable @var{v} by @var{i}. Returns the
14578 @item INCL(@var{m},@var{s})
14579 Adds the element @var{m} to the set @var{s} if it is not already
14580 there. Returns the new set.
14583 Returns the maximum value of the type @var{t}.
14586 Returns the minimum value of the type @var{t}.
14589 Returns boolean TRUE if @var{i} is an odd number.
14592 Returns the ordinal value of its argument. For example, the ordinal
14593 value of a character is its @sc{ascii} value (on machines supporting the
14594 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14595 integral, character and enumerated types.
14597 @item SIZE(@var{x})
14598 Returns the size of its argument. @var{x} can be a variable or a type.
14600 @item TRUNC(@var{r})
14601 Returns the integral part of @var{r}.
14603 @item TSIZE(@var{x})
14604 Returns the size of its argument. @var{x} can be a variable or a type.
14606 @item VAL(@var{t},@var{i})
14607 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14611 @emph{Warning:} Sets and their operations are not yet supported, so
14612 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14616 @cindex Modula-2 constants
14618 @subsubsection Constants
14620 @value{GDBN} allows you to express the constants of Modula-2 in the following
14626 Integer constants are simply a sequence of digits. When used in an
14627 expression, a constant is interpreted to be type-compatible with the
14628 rest of the expression. Hexadecimal integers are specified by a
14629 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14632 Floating point constants appear as a sequence of digits, followed by a
14633 decimal point and another sequence of digits. An optional exponent can
14634 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14635 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14636 digits of the floating point constant must be valid decimal (base 10)
14640 Character constants consist of a single character enclosed by a pair of
14641 like quotes, either single (@code{'}) or double (@code{"}). They may
14642 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14643 followed by a @samp{C}.
14646 String constants consist of a sequence of characters enclosed by a
14647 pair of like quotes, either single (@code{'}) or double (@code{"}).
14648 Escape sequences in the style of C are also allowed. @xref{C
14649 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14653 Enumerated constants consist of an enumerated identifier.
14656 Boolean constants consist of the identifiers @code{TRUE} and
14660 Pointer constants consist of integral values only.
14663 Set constants are not yet supported.
14667 @subsubsection Modula-2 Types
14668 @cindex Modula-2 types
14670 Currently @value{GDBN} can print the following data types in Modula-2
14671 syntax: array types, record types, set types, pointer types, procedure
14672 types, enumerated types, subrange types and base types. You can also
14673 print the contents of variables declared using these type.
14674 This section gives a number of simple source code examples together with
14675 sample @value{GDBN} sessions.
14677 The first example contains the following section of code:
14686 and you can request @value{GDBN} to interrogate the type and value of
14687 @code{r} and @code{s}.
14690 (@value{GDBP}) print s
14692 (@value{GDBP}) ptype s
14694 (@value{GDBP}) print r
14696 (@value{GDBP}) ptype r
14701 Likewise if your source code declares @code{s} as:
14705 s: SET ['A'..'Z'] ;
14709 then you may query the type of @code{s} by:
14712 (@value{GDBP}) ptype s
14713 type = SET ['A'..'Z']
14717 Note that at present you cannot interactively manipulate set
14718 expressions using the debugger.
14720 The following example shows how you might declare an array in Modula-2
14721 and how you can interact with @value{GDBN} to print its type and contents:
14725 s: ARRAY [-10..10] OF CHAR ;
14729 (@value{GDBP}) ptype s
14730 ARRAY [-10..10] OF CHAR
14733 Note that the array handling is not yet complete and although the type
14734 is printed correctly, expression handling still assumes that all
14735 arrays have a lower bound of zero and not @code{-10} as in the example
14738 Here are some more type related Modula-2 examples:
14742 colour = (blue, red, yellow, green) ;
14743 t = [blue..yellow] ;
14751 The @value{GDBN} interaction shows how you can query the data type
14752 and value of a variable.
14755 (@value{GDBP}) print s
14757 (@value{GDBP}) ptype t
14758 type = [blue..yellow]
14762 In this example a Modula-2 array is declared and its contents
14763 displayed. Observe that the contents are written in the same way as
14764 their @code{C} counterparts.
14768 s: ARRAY [1..5] OF CARDINAL ;
14774 (@value{GDBP}) print s
14775 $1 = @{1, 0, 0, 0, 0@}
14776 (@value{GDBP}) ptype s
14777 type = ARRAY [1..5] OF CARDINAL
14780 The Modula-2 language interface to @value{GDBN} also understands
14781 pointer types as shown in this example:
14785 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14792 and you can request that @value{GDBN} describes the type of @code{s}.
14795 (@value{GDBP}) ptype s
14796 type = POINTER TO ARRAY [1..5] OF CARDINAL
14799 @value{GDBN} handles compound types as we can see in this example.
14800 Here we combine array types, record types, pointer types and subrange
14811 myarray = ARRAY myrange OF CARDINAL ;
14812 myrange = [-2..2] ;
14814 s: POINTER TO ARRAY myrange OF foo ;
14818 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14822 (@value{GDBP}) ptype s
14823 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14826 f3 : ARRAY [-2..2] OF CARDINAL;
14831 @subsubsection Modula-2 Defaults
14832 @cindex Modula-2 defaults
14834 If type and range checking are set automatically by @value{GDBN}, they
14835 both default to @code{on} whenever the working language changes to
14836 Modula-2. This happens regardless of whether you or @value{GDBN}
14837 selected the working language.
14839 If you allow @value{GDBN} to set the language automatically, then entering
14840 code compiled from a file whose name ends with @file{.mod} sets the
14841 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14842 Infer the Source Language}, for further details.
14845 @subsubsection Deviations from Standard Modula-2
14846 @cindex Modula-2, deviations from
14848 A few changes have been made to make Modula-2 programs easier to debug.
14849 This is done primarily via loosening its type strictness:
14853 Unlike in standard Modula-2, pointer constants can be formed by
14854 integers. This allows you to modify pointer variables during
14855 debugging. (In standard Modula-2, the actual address contained in a
14856 pointer variable is hidden from you; it can only be modified
14857 through direct assignment to another pointer variable or expression that
14858 returned a pointer.)
14861 C escape sequences can be used in strings and characters to represent
14862 non-printable characters. @value{GDBN} prints out strings with these
14863 escape sequences embedded. Single non-printable characters are
14864 printed using the @samp{CHR(@var{nnn})} format.
14867 The assignment operator (@code{:=}) returns the value of its right-hand
14871 All built-in procedures both modify @emph{and} return their argument.
14875 @subsubsection Modula-2 Type and Range Checks
14876 @cindex Modula-2 checks
14879 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14882 @c FIXME remove warning when type/range checks added
14884 @value{GDBN} considers two Modula-2 variables type equivalent if:
14888 They are of types that have been declared equivalent via a @code{TYPE
14889 @var{t1} = @var{t2}} statement
14892 They have been declared on the same line. (Note: This is true of the
14893 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14896 As long as type checking is enabled, any attempt to combine variables
14897 whose types are not equivalent is an error.
14899 Range checking is done on all mathematical operations, assignment, array
14900 index bounds, and all built-in functions and procedures.
14903 @subsubsection The Scope Operators @code{::} and @code{.}
14905 @cindex @code{.}, Modula-2 scope operator
14906 @cindex colon, doubled as scope operator
14908 @vindex colon-colon@r{, in Modula-2}
14909 @c Info cannot handle :: but TeX can.
14912 @vindex ::@r{, in Modula-2}
14915 There are a few subtle differences between the Modula-2 scope operator
14916 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14921 @var{module} . @var{id}
14922 @var{scope} :: @var{id}
14926 where @var{scope} is the name of a module or a procedure,
14927 @var{module} the name of a module, and @var{id} is any declared
14928 identifier within your program, except another module.
14930 Using the @code{::} operator makes @value{GDBN} search the scope
14931 specified by @var{scope} for the identifier @var{id}. If it is not
14932 found in the specified scope, then @value{GDBN} searches all scopes
14933 enclosing the one specified by @var{scope}.
14935 Using the @code{.} operator makes @value{GDBN} search the current scope for
14936 the identifier specified by @var{id} that was imported from the
14937 definition module specified by @var{module}. With this operator, it is
14938 an error if the identifier @var{id} was not imported from definition
14939 module @var{module}, or if @var{id} is not an identifier in
14943 @subsubsection @value{GDBN} and Modula-2
14945 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14946 Five subcommands of @code{set print} and @code{show print} apply
14947 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14948 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14949 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14950 analogue in Modula-2.
14952 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14953 with any language, is not useful with Modula-2. Its
14954 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14955 created in Modula-2 as they can in C or C@t{++}. However, because an
14956 address can be specified by an integral constant, the construct
14957 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14959 @cindex @code{#} in Modula-2
14960 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14961 interpreted as the beginning of a comment. Use @code{<>} instead.
14967 The extensions made to @value{GDBN} for Ada only support
14968 output from the @sc{gnu} Ada (GNAT) compiler.
14969 Other Ada compilers are not currently supported, and
14970 attempting to debug executables produced by them is most likely
14974 @cindex expressions in Ada
14976 * Ada Mode Intro:: General remarks on the Ada syntax
14977 and semantics supported by Ada mode
14979 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14980 * Additions to Ada:: Extensions of the Ada expression syntax.
14981 * Stopping Before Main Program:: Debugging the program during elaboration.
14982 * Ada Exceptions:: Ada Exceptions
14983 * Ada Tasks:: Listing and setting breakpoints in tasks.
14984 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14985 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14987 * Ada Glitches:: Known peculiarities of Ada mode.
14990 @node Ada Mode Intro
14991 @subsubsection Introduction
14992 @cindex Ada mode, general
14994 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14995 syntax, with some extensions.
14996 The philosophy behind the design of this subset is
15000 That @value{GDBN} should provide basic literals and access to operations for
15001 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15002 leaving more sophisticated computations to subprograms written into the
15003 program (which therefore may be called from @value{GDBN}).
15006 That type safety and strict adherence to Ada language restrictions
15007 are not particularly important to the @value{GDBN} user.
15010 That brevity is important to the @value{GDBN} user.
15013 Thus, for brevity, the debugger acts as if all names declared in
15014 user-written packages are directly visible, even if they are not visible
15015 according to Ada rules, thus making it unnecessary to fully qualify most
15016 names with their packages, regardless of context. Where this causes
15017 ambiguity, @value{GDBN} asks the user's intent.
15019 The debugger will start in Ada mode if it detects an Ada main program.
15020 As for other languages, it will enter Ada mode when stopped in a program that
15021 was translated from an Ada source file.
15023 While in Ada mode, you may use `@t{--}' for comments. This is useful
15024 mostly for documenting command files. The standard @value{GDBN} comment
15025 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15026 middle (to allow based literals).
15028 The debugger supports limited overloading. Given a subprogram call in which
15029 the function symbol has multiple definitions, it will use the number of
15030 actual parameters and some information about their types to attempt to narrow
15031 the set of definitions. It also makes very limited use of context, preferring
15032 procedures to functions in the context of the @code{call} command, and
15033 functions to procedures elsewhere.
15035 @node Omissions from Ada
15036 @subsubsection Omissions from Ada
15037 @cindex Ada, omissions from
15039 Here are the notable omissions from the subset:
15043 Only a subset of the attributes are supported:
15047 @t{'First}, @t{'Last}, and @t{'Length}
15048 on array objects (not on types and subtypes).
15051 @t{'Min} and @t{'Max}.
15054 @t{'Pos} and @t{'Val}.
15060 @t{'Range} on array objects (not subtypes), but only as the right
15061 operand of the membership (@code{in}) operator.
15064 @t{'Access}, @t{'Unchecked_Access}, and
15065 @t{'Unrestricted_Access} (a GNAT extension).
15073 @code{Characters.Latin_1} are not available and
15074 concatenation is not implemented. Thus, escape characters in strings are
15075 not currently available.
15078 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15079 equality of representations. They will generally work correctly
15080 for strings and arrays whose elements have integer or enumeration types.
15081 They may not work correctly for arrays whose element
15082 types have user-defined equality, for arrays of real values
15083 (in particular, IEEE-conformant floating point, because of negative
15084 zeroes and NaNs), and for arrays whose elements contain unused bits with
15085 indeterminate values.
15088 The other component-by-component array operations (@code{and}, @code{or},
15089 @code{xor}, @code{not}, and relational tests other than equality)
15090 are not implemented.
15093 @cindex array aggregates (Ada)
15094 @cindex record aggregates (Ada)
15095 @cindex aggregates (Ada)
15096 There is limited support for array and record aggregates. They are
15097 permitted only on the right sides of assignments, as in these examples:
15100 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15101 (@value{GDBP}) set An_Array := (1, others => 0)
15102 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15103 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15104 (@value{GDBP}) set A_Record := (1, "Peter", True);
15105 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15109 discriminant's value by assigning an aggregate has an
15110 undefined effect if that discriminant is used within the record.
15111 However, you can first modify discriminants by directly assigning to
15112 them (which normally would not be allowed in Ada), and then performing an
15113 aggregate assignment. For example, given a variable @code{A_Rec}
15114 declared to have a type such as:
15117 type Rec (Len : Small_Integer := 0) is record
15119 Vals : IntArray (1 .. Len);
15123 you can assign a value with a different size of @code{Vals} with two
15127 (@value{GDBP}) set A_Rec.Len := 4
15128 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15131 As this example also illustrates, @value{GDBN} is very loose about the usual
15132 rules concerning aggregates. You may leave out some of the
15133 components of an array or record aggregate (such as the @code{Len}
15134 component in the assignment to @code{A_Rec} above); they will retain their
15135 original values upon assignment. You may freely use dynamic values as
15136 indices in component associations. You may even use overlapping or
15137 redundant component associations, although which component values are
15138 assigned in such cases is not defined.
15141 Calls to dispatching subprograms are not implemented.
15144 The overloading algorithm is much more limited (i.e., less selective)
15145 than that of real Ada. It makes only limited use of the context in
15146 which a subexpression appears to resolve its meaning, and it is much
15147 looser in its rules for allowing type matches. As a result, some
15148 function calls will be ambiguous, and the user will be asked to choose
15149 the proper resolution.
15152 The @code{new} operator is not implemented.
15155 Entry calls are not implemented.
15158 Aside from printing, arithmetic operations on the native VAX floating-point
15159 formats are not supported.
15162 It is not possible to slice a packed array.
15165 The names @code{True} and @code{False}, when not part of a qualified name,
15166 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15168 Should your program
15169 redefine these names in a package or procedure (at best a dubious practice),
15170 you will have to use fully qualified names to access their new definitions.
15173 @node Additions to Ada
15174 @subsubsection Additions to Ada
15175 @cindex Ada, deviations from
15177 As it does for other languages, @value{GDBN} makes certain generic
15178 extensions to Ada (@pxref{Expressions}):
15182 If the expression @var{E} is a variable residing in memory (typically
15183 a local variable or array element) and @var{N} is a positive integer,
15184 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15185 @var{N}-1 adjacent variables following it in memory as an array. In
15186 Ada, this operator is generally not necessary, since its prime use is
15187 in displaying parts of an array, and slicing will usually do this in
15188 Ada. However, there are occasional uses when debugging programs in
15189 which certain debugging information has been optimized away.
15192 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15193 appears in function or file @var{B}.'' When @var{B} is a file name,
15194 you must typically surround it in single quotes.
15197 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15198 @var{type} that appears at address @var{addr}.''
15201 A name starting with @samp{$} is a convenience variable
15202 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15205 In addition, @value{GDBN} provides a few other shortcuts and outright
15206 additions specific to Ada:
15210 The assignment statement is allowed as an expression, returning
15211 its right-hand operand as its value. Thus, you may enter
15214 (@value{GDBP}) set x := y + 3
15215 (@value{GDBP}) print A(tmp := y + 1)
15219 The semicolon is allowed as an ``operator,'' returning as its value
15220 the value of its right-hand operand.
15221 This allows, for example,
15222 complex conditional breaks:
15225 (@value{GDBP}) break f
15226 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15230 Rather than use catenation and symbolic character names to introduce special
15231 characters into strings, one may instead use a special bracket notation,
15232 which is also used to print strings. A sequence of characters of the form
15233 @samp{["@var{XX}"]} within a string or character literal denotes the
15234 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15235 sequence of characters @samp{["""]} also denotes a single quotation mark
15236 in strings. For example,
15238 "One line.["0a"]Next line.["0a"]"
15241 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15245 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15246 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15250 (@value{GDBP}) print 'max(x, y)
15254 When printing arrays, @value{GDBN} uses positional notation when the
15255 array has a lower bound of 1, and uses a modified named notation otherwise.
15256 For example, a one-dimensional array of three integers with a lower bound
15257 of 3 might print as
15264 That is, in contrast to valid Ada, only the first component has a @code{=>}
15268 You may abbreviate attributes in expressions with any unique,
15269 multi-character subsequence of
15270 their names (an exact match gets preference).
15271 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15272 in place of @t{a'length}.
15275 @cindex quoting Ada internal identifiers
15276 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15277 to lower case. The GNAT compiler uses upper-case characters for
15278 some of its internal identifiers, which are normally of no interest to users.
15279 For the rare occasions when you actually have to look at them,
15280 enclose them in angle brackets to avoid the lower-case mapping.
15283 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15287 Printing an object of class-wide type or dereferencing an
15288 access-to-class-wide value will display all the components of the object's
15289 specific type (as indicated by its run-time tag). Likewise, component
15290 selection on such a value will operate on the specific type of the
15295 @node Stopping Before Main Program
15296 @subsubsection Stopping at the Very Beginning
15298 @cindex breakpointing Ada elaboration code
15299 It is sometimes necessary to debug the program during elaboration, and
15300 before reaching the main procedure.
15301 As defined in the Ada Reference
15302 Manual, the elaboration code is invoked from a procedure called
15303 @code{adainit}. To run your program up to the beginning of
15304 elaboration, simply use the following two commands:
15305 @code{tbreak adainit} and @code{run}.
15307 @node Ada Exceptions
15308 @subsubsection Ada Exceptions
15310 A command is provided to list all Ada exceptions:
15313 @kindex info exceptions
15314 @item info exceptions
15315 @itemx info exceptions @var{regexp}
15316 The @code{info exceptions} command allows you to list all Ada exceptions
15317 defined within the program being debugged, as well as their addresses.
15318 With a regular expression, @var{regexp}, as argument, only those exceptions
15319 whose names match @var{regexp} are listed.
15322 Below is a small example, showing how the command can be used, first
15323 without argument, and next with a regular expression passed as an
15327 (@value{GDBP}) info exceptions
15328 All defined Ada exceptions:
15329 constraint_error: 0x613da0
15330 program_error: 0x613d20
15331 storage_error: 0x613ce0
15332 tasking_error: 0x613ca0
15333 const.aint_global_e: 0x613b00
15334 (@value{GDBP}) info exceptions const.aint
15335 All Ada exceptions matching regular expression "const.aint":
15336 constraint_error: 0x613da0
15337 const.aint_global_e: 0x613b00
15340 It is also possible to ask @value{GDBN} to stop your program's execution
15341 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15344 @subsubsection Extensions for Ada Tasks
15345 @cindex Ada, tasking
15347 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15348 @value{GDBN} provides the following task-related commands:
15353 This command shows a list of current Ada tasks, as in the following example:
15360 (@value{GDBP}) info tasks
15361 ID TID P-ID Pri State Name
15362 1 8088000 0 15 Child Activation Wait main_task
15363 2 80a4000 1 15 Accept Statement b
15364 3 809a800 1 15 Child Activation Wait a
15365 * 4 80ae800 3 15 Runnable c
15370 In this listing, the asterisk before the last task indicates it to be the
15371 task currently being inspected.
15375 Represents @value{GDBN}'s internal task number.
15381 The parent's task ID (@value{GDBN}'s internal task number).
15384 The base priority of the task.
15387 Current state of the task.
15391 The task has been created but has not been activated. It cannot be
15395 The task is not blocked for any reason known to Ada. (It may be waiting
15396 for a mutex, though.) It is conceptually "executing" in normal mode.
15399 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15400 that were waiting on terminate alternatives have been awakened and have
15401 terminated themselves.
15403 @item Child Activation Wait
15404 The task is waiting for created tasks to complete activation.
15406 @item Accept Statement
15407 The task is waiting on an accept or selective wait statement.
15409 @item Waiting on entry call
15410 The task is waiting on an entry call.
15412 @item Async Select Wait
15413 The task is waiting to start the abortable part of an asynchronous
15417 The task is waiting on a select statement with only a delay
15420 @item Child Termination Wait
15421 The task is sleeping having completed a master within itself, and is
15422 waiting for the tasks dependent on that master to become terminated or
15423 waiting on a terminate Phase.
15425 @item Wait Child in Term Alt
15426 The task is sleeping waiting for tasks on terminate alternatives to
15427 finish terminating.
15429 @item Accepting RV with @var{taskno}
15430 The task is accepting a rendez-vous with the task @var{taskno}.
15434 Name of the task in the program.
15438 @kindex info task @var{taskno}
15439 @item info task @var{taskno}
15440 This command shows detailled informations on the specified task, as in
15441 the following example:
15446 (@value{GDBP}) info tasks
15447 ID TID P-ID Pri State Name
15448 1 8077880 0 15 Child Activation Wait main_task
15449 * 2 807c468 1 15 Runnable task_1
15450 (@value{GDBP}) info task 2
15451 Ada Task: 0x807c468
15454 Parent: 1 (main_task)
15460 @kindex task@r{ (Ada)}
15461 @cindex current Ada task ID
15462 This command prints the ID of the current task.
15468 (@value{GDBP}) info tasks
15469 ID TID P-ID Pri State Name
15470 1 8077870 0 15 Child Activation Wait main_task
15471 * 2 807c458 1 15 Runnable t
15472 (@value{GDBP}) task
15473 [Current task is 2]
15476 @item task @var{taskno}
15477 @cindex Ada task switching
15478 This command is like the @code{thread @var{threadno}}
15479 command (@pxref{Threads}). It switches the context of debugging
15480 from the current task to the given task.
15486 (@value{GDBP}) info tasks
15487 ID TID P-ID Pri State Name
15488 1 8077870 0 15 Child Activation Wait main_task
15489 * 2 807c458 1 15 Runnable t
15490 (@value{GDBP}) task 1
15491 [Switching to task 1]
15492 #0 0x8067726 in pthread_cond_wait ()
15494 #0 0x8067726 in pthread_cond_wait ()
15495 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15496 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15497 #3 0x806153e in system.tasking.stages.activate_tasks ()
15498 #4 0x804aacc in un () at un.adb:5
15501 @item break @var{linespec} task @var{taskno}
15502 @itemx break @var{linespec} task @var{taskno} if @dots{}
15503 @cindex breakpoints and tasks, in Ada
15504 @cindex task breakpoints, in Ada
15505 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15506 These commands are like the @code{break @dots{} thread @dots{}}
15507 command (@pxref{Thread Stops}).
15508 @var{linespec} specifies source lines, as described
15509 in @ref{Specify Location}.
15511 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15512 to specify that you only want @value{GDBN} to stop the program when a
15513 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15514 numeric task identifiers assigned by @value{GDBN}, shown in the first
15515 column of the @samp{info tasks} display.
15517 If you do not specify @samp{task @var{taskno}} when you set a
15518 breakpoint, the breakpoint applies to @emph{all} tasks of your
15521 You can use the @code{task} qualifier on conditional breakpoints as
15522 well; in this case, place @samp{task @var{taskno}} before the
15523 breakpoint condition (before the @code{if}).
15531 (@value{GDBP}) info tasks
15532 ID TID P-ID Pri State Name
15533 1 140022020 0 15 Child Activation Wait main_task
15534 2 140045060 1 15 Accept/Select Wait t2
15535 3 140044840 1 15 Runnable t1
15536 * 4 140056040 1 15 Runnable t3
15537 (@value{GDBP}) b 15 task 2
15538 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15539 (@value{GDBP}) cont
15544 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15546 (@value{GDBP}) info tasks
15547 ID TID P-ID Pri State Name
15548 1 140022020 0 15 Child Activation Wait main_task
15549 * 2 140045060 1 15 Runnable t2
15550 3 140044840 1 15 Runnable t1
15551 4 140056040 1 15 Delay Sleep t3
15555 @node Ada Tasks and Core Files
15556 @subsubsection Tasking Support when Debugging Core Files
15557 @cindex Ada tasking and core file debugging
15559 When inspecting a core file, as opposed to debugging a live program,
15560 tasking support may be limited or even unavailable, depending on
15561 the platform being used.
15562 For instance, on x86-linux, the list of tasks is available, but task
15563 switching is not supported. On Tru64, however, task switching will work
15566 On certain platforms, including Tru64, the debugger needs to perform some
15567 memory writes in order to provide Ada tasking support. When inspecting
15568 a core file, this means that the core file must be opened with read-write
15569 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15570 Under these circumstances, you should make a backup copy of the core
15571 file before inspecting it with @value{GDBN}.
15573 @node Ravenscar Profile
15574 @subsubsection Tasking Support when using the Ravenscar Profile
15575 @cindex Ravenscar Profile
15577 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15578 specifically designed for systems with safety-critical real-time
15582 @kindex set ravenscar task-switching on
15583 @cindex task switching with program using Ravenscar Profile
15584 @item set ravenscar task-switching on
15585 Allows task switching when debugging a program that uses the Ravenscar
15586 Profile. This is the default.
15588 @kindex set ravenscar task-switching off
15589 @item set ravenscar task-switching off
15590 Turn off task switching when debugging a program that uses the Ravenscar
15591 Profile. This is mostly intended to disable the code that adds support
15592 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15593 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15594 To be effective, this command should be run before the program is started.
15596 @kindex show ravenscar task-switching
15597 @item show ravenscar task-switching
15598 Show whether it is possible to switch from task to task in a program
15599 using the Ravenscar Profile.
15604 @subsubsection Known Peculiarities of Ada Mode
15605 @cindex Ada, problems
15607 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15608 we know of several problems with and limitations of Ada mode in
15610 some of which will be fixed with planned future releases of the debugger
15611 and the GNU Ada compiler.
15615 Static constants that the compiler chooses not to materialize as objects in
15616 storage are invisible to the debugger.
15619 Named parameter associations in function argument lists are ignored (the
15620 argument lists are treated as positional).
15623 Many useful library packages are currently invisible to the debugger.
15626 Fixed-point arithmetic, conversions, input, and output is carried out using
15627 floating-point arithmetic, and may give results that only approximate those on
15631 The GNAT compiler never generates the prefix @code{Standard} for any of
15632 the standard symbols defined by the Ada language. @value{GDBN} knows about
15633 this: it will strip the prefix from names when you use it, and will never
15634 look for a name you have so qualified among local symbols, nor match against
15635 symbols in other packages or subprograms. If you have
15636 defined entities anywhere in your program other than parameters and
15637 local variables whose simple names match names in @code{Standard},
15638 GNAT's lack of qualification here can cause confusion. When this happens,
15639 you can usually resolve the confusion
15640 by qualifying the problematic names with package
15641 @code{Standard} explicitly.
15644 Older versions of the compiler sometimes generate erroneous debugging
15645 information, resulting in the debugger incorrectly printing the value
15646 of affected entities. In some cases, the debugger is able to work
15647 around an issue automatically. In other cases, the debugger is able
15648 to work around the issue, but the work-around has to be specifically
15651 @kindex set ada trust-PAD-over-XVS
15652 @kindex show ada trust-PAD-over-XVS
15655 @item set ada trust-PAD-over-XVS on
15656 Configure GDB to strictly follow the GNAT encoding when computing the
15657 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15658 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15659 a complete description of the encoding used by the GNAT compiler).
15660 This is the default.
15662 @item set ada trust-PAD-over-XVS off
15663 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15664 sometimes prints the wrong value for certain entities, changing @code{ada
15665 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15666 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15667 @code{off}, but this incurs a slight performance penalty, so it is
15668 recommended to leave this setting to @code{on} unless necessary.
15672 @node Unsupported Languages
15673 @section Unsupported Languages
15675 @cindex unsupported languages
15676 @cindex minimal language
15677 In addition to the other fully-supported programming languages,
15678 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15679 It does not represent a real programming language, but provides a set
15680 of capabilities close to what the C or assembly languages provide.
15681 This should allow most simple operations to be performed while debugging
15682 an application that uses a language currently not supported by @value{GDBN}.
15684 If the language is set to @code{auto}, @value{GDBN} will automatically
15685 select this language if the current frame corresponds to an unsupported
15689 @chapter Examining the Symbol Table
15691 The commands described in this chapter allow you to inquire about the
15692 symbols (names of variables, functions and types) defined in your
15693 program. This information is inherent in the text of your program and
15694 does not change as your program executes. @value{GDBN} finds it in your
15695 program's symbol table, in the file indicated when you started @value{GDBN}
15696 (@pxref{File Options, ,Choosing Files}), or by one of the
15697 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15699 @cindex symbol names
15700 @cindex names of symbols
15701 @cindex quoting names
15702 Occasionally, you may need to refer to symbols that contain unusual
15703 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15704 most frequent case is in referring to static variables in other
15705 source files (@pxref{Variables,,Program Variables}). File names
15706 are recorded in object files as debugging symbols, but @value{GDBN} would
15707 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15708 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15709 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15716 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15719 @cindex case-insensitive symbol names
15720 @cindex case sensitivity in symbol names
15721 @kindex set case-sensitive
15722 @item set case-sensitive on
15723 @itemx set case-sensitive off
15724 @itemx set case-sensitive auto
15725 Normally, when @value{GDBN} looks up symbols, it matches their names
15726 with case sensitivity determined by the current source language.
15727 Occasionally, you may wish to control that. The command @code{set
15728 case-sensitive} lets you do that by specifying @code{on} for
15729 case-sensitive matches or @code{off} for case-insensitive ones. If
15730 you specify @code{auto}, case sensitivity is reset to the default
15731 suitable for the source language. The default is case-sensitive
15732 matches for all languages except for Fortran, for which the default is
15733 case-insensitive matches.
15735 @kindex show case-sensitive
15736 @item show case-sensitive
15737 This command shows the current setting of case sensitivity for symbols
15740 @kindex set print type methods
15741 @item set print type methods
15742 @itemx set print type methods on
15743 @itemx set print type methods off
15744 Normally, when @value{GDBN} prints a class, it displays any methods
15745 declared in that class. You can control this behavior either by
15746 passing the appropriate flag to @code{ptype}, or using @command{set
15747 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15748 display the methods; this is the default. Specifying @code{off} will
15749 cause @value{GDBN} to omit the methods.
15751 @kindex show print type methods
15752 @item show print type methods
15753 This command shows the current setting of method display when printing
15756 @kindex set print type typedefs
15757 @item set print type typedefs
15758 @itemx set print type typedefs on
15759 @itemx set print type typedefs off
15761 Normally, when @value{GDBN} prints a class, it displays any typedefs
15762 defined in that class. You can control this behavior either by
15763 passing the appropriate flag to @code{ptype}, or using @command{set
15764 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15765 display the typedef definitions; this is the default. Specifying
15766 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15767 Note that this controls whether the typedef definition itself is
15768 printed, not whether typedef names are substituted when printing other
15771 @kindex show print type typedefs
15772 @item show print type typedefs
15773 This command shows the current setting of typedef display when
15776 @kindex info address
15777 @cindex address of a symbol
15778 @item info address @var{symbol}
15779 Describe where the data for @var{symbol} is stored. For a register
15780 variable, this says which register it is kept in. For a non-register
15781 local variable, this prints the stack-frame offset at which the variable
15784 Note the contrast with @samp{print &@var{symbol}}, which does not work
15785 at all for a register variable, and for a stack local variable prints
15786 the exact address of the current instantiation of the variable.
15788 @kindex info symbol
15789 @cindex symbol from address
15790 @cindex closest symbol and offset for an address
15791 @item info symbol @var{addr}
15792 Print the name of a symbol which is stored at the address @var{addr}.
15793 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15794 nearest symbol and an offset from it:
15797 (@value{GDBP}) info symbol 0x54320
15798 _initialize_vx + 396 in section .text
15802 This is the opposite of the @code{info address} command. You can use
15803 it to find out the name of a variable or a function given its address.
15805 For dynamically linked executables, the name of executable or shared
15806 library containing the symbol is also printed:
15809 (@value{GDBP}) info symbol 0x400225
15810 _start + 5 in section .text of /tmp/a.out
15811 (@value{GDBP}) info symbol 0x2aaaac2811cf
15812 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15816 @item whatis[/@var{flags}] [@var{arg}]
15817 Print the data type of @var{arg}, which can be either an expression
15818 or a name of a data type. With no argument, print the data type of
15819 @code{$}, the last value in the value history.
15821 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15822 is not actually evaluated, and any side-effecting operations (such as
15823 assignments or function calls) inside it do not take place.
15825 If @var{arg} is a variable or an expression, @code{whatis} prints its
15826 literal type as it is used in the source code. If the type was
15827 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15828 the data type underlying the @code{typedef}. If the type of the
15829 variable or the expression is a compound data type, such as
15830 @code{struct} or @code{class}, @code{whatis} never prints their
15831 fields or methods. It just prints the @code{struct}/@code{class}
15832 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15833 such a compound data type, use @code{ptype}.
15835 If @var{arg} is a type name that was defined using @code{typedef},
15836 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15837 Unrolling means that @code{whatis} will show the underlying type used
15838 in the @code{typedef} declaration of @var{arg}. However, if that
15839 underlying type is also a @code{typedef}, @code{whatis} will not
15842 For C code, the type names may also have the form @samp{class
15843 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15844 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15846 @var{flags} can be used to modify how the type is displayed.
15847 Available flags are:
15851 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15852 parameters and typedefs defined in a class when printing the class'
15853 members. The @code{/r} flag disables this.
15856 Do not print methods defined in the class.
15859 Print methods defined in the class. This is the default, but the flag
15860 exists in case you change the default with @command{set print type methods}.
15863 Do not print typedefs defined in the class. Note that this controls
15864 whether the typedef definition itself is printed, not whether typedef
15865 names are substituted when printing other types.
15868 Print typedefs defined in the class. This is the default, but the flag
15869 exists in case you change the default with @command{set print type typedefs}.
15873 @item ptype[/@var{flags}] [@var{arg}]
15874 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15875 detailed description of the type, instead of just the name of the type.
15876 @xref{Expressions, ,Expressions}.
15878 Contrary to @code{whatis}, @code{ptype} always unrolls any
15879 @code{typedef}s in its argument declaration, whether the argument is
15880 a variable, expression, or a data type. This means that @code{ptype}
15881 of a variable or an expression will not print literally its type as
15882 present in the source code---use @code{whatis} for that. @code{typedef}s at
15883 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15884 fields, methods and inner @code{class typedef}s of @code{struct}s,
15885 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15887 For example, for this variable declaration:
15890 typedef double real_t;
15891 struct complex @{ real_t real; double imag; @};
15892 typedef struct complex complex_t;
15894 real_t *real_pointer_var;
15898 the two commands give this output:
15902 (@value{GDBP}) whatis var
15904 (@value{GDBP}) ptype var
15905 type = struct complex @{
15909 (@value{GDBP}) whatis complex_t
15910 type = struct complex
15911 (@value{GDBP}) whatis struct complex
15912 type = struct complex
15913 (@value{GDBP}) ptype struct complex
15914 type = struct complex @{
15918 (@value{GDBP}) whatis real_pointer_var
15920 (@value{GDBP}) ptype real_pointer_var
15926 As with @code{whatis}, using @code{ptype} without an argument refers to
15927 the type of @code{$}, the last value in the value history.
15929 @cindex incomplete type
15930 Sometimes, programs use opaque data types or incomplete specifications
15931 of complex data structure. If the debug information included in the
15932 program does not allow @value{GDBN} to display a full declaration of
15933 the data type, it will say @samp{<incomplete type>}. For example,
15934 given these declarations:
15938 struct foo *fooptr;
15942 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15945 (@value{GDBP}) ptype foo
15946 $1 = <incomplete type>
15950 ``Incomplete type'' is C terminology for data types that are not
15951 completely specified.
15954 @item info types @var{regexp}
15956 Print a brief description of all types whose names match the regular
15957 expression @var{regexp} (or all types in your program, if you supply
15958 no argument). Each complete typename is matched as though it were a
15959 complete line; thus, @samp{i type value} gives information on all
15960 types in your program whose names include the string @code{value}, but
15961 @samp{i type ^value$} gives information only on types whose complete
15962 name is @code{value}.
15964 This command differs from @code{ptype} in two ways: first, like
15965 @code{whatis}, it does not print a detailed description; second, it
15966 lists all source files where a type is defined.
15968 @kindex info type-printers
15969 @item info type-printers
15970 Versions of @value{GDBN} that ship with Python scripting enabled may
15971 have ``type printers'' available. When using @command{ptype} or
15972 @command{whatis}, these printers are consulted when the name of a type
15973 is needed. @xref{Type Printing API}, for more information on writing
15976 @code{info type-printers} displays all the available type printers.
15978 @kindex enable type-printer
15979 @kindex disable type-printer
15980 @item enable type-printer @var{name}@dots{}
15981 @item disable type-printer @var{name}@dots{}
15982 These commands can be used to enable or disable type printers.
15985 @cindex local variables
15986 @item info scope @var{location}
15987 List all the variables local to a particular scope. This command
15988 accepts a @var{location} argument---a function name, a source line, or
15989 an address preceded by a @samp{*}, and prints all the variables local
15990 to the scope defined by that location. (@xref{Specify Location}, for
15991 details about supported forms of @var{location}.) For example:
15994 (@value{GDBP}) @b{info scope command_line_handler}
15995 Scope for command_line_handler:
15996 Symbol rl is an argument at stack/frame offset 8, length 4.
15997 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15998 Symbol linelength is in static storage at address 0x150a1c, length 4.
15999 Symbol p is a local variable in register $esi, length 4.
16000 Symbol p1 is a local variable in register $ebx, length 4.
16001 Symbol nline is a local variable in register $edx, length 4.
16002 Symbol repeat is a local variable at frame offset -8, length 4.
16006 This command is especially useful for determining what data to collect
16007 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16010 @kindex info source
16012 Show information about the current source file---that is, the source file for
16013 the function containing the current point of execution:
16016 the name of the source file, and the directory containing it,
16018 the directory it was compiled in,
16020 its length, in lines,
16022 which programming language it is written in,
16024 whether the executable includes debugging information for that file, and
16025 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16027 whether the debugging information includes information about
16028 preprocessor macros.
16032 @kindex info sources
16034 Print the names of all source files in your program for which there is
16035 debugging information, organized into two lists: files whose symbols
16036 have already been read, and files whose symbols will be read when needed.
16038 @kindex info functions
16039 @item info functions
16040 Print the names and data types of all defined functions.
16042 @item info functions @var{regexp}
16043 Print the names and data types of all defined functions
16044 whose names contain a match for regular expression @var{regexp}.
16045 Thus, @samp{info fun step} finds all functions whose names
16046 include @code{step}; @samp{info fun ^step} finds those whose names
16047 start with @code{step}. If a function name contains characters
16048 that conflict with the regular expression language (e.g.@:
16049 @samp{operator*()}), they may be quoted with a backslash.
16051 @kindex info variables
16052 @item info variables
16053 Print the names and data types of all variables that are defined
16054 outside of functions (i.e.@: excluding local variables).
16056 @item info variables @var{regexp}
16057 Print the names and data types of all variables (except for local
16058 variables) whose names contain a match for regular expression
16061 @kindex info classes
16062 @cindex Objective-C, classes and selectors
16064 @itemx info classes @var{regexp}
16065 Display all Objective-C classes in your program, or
16066 (with the @var{regexp} argument) all those matching a particular regular
16069 @kindex info selectors
16070 @item info selectors
16071 @itemx info selectors @var{regexp}
16072 Display all Objective-C selectors in your program, or
16073 (with the @var{regexp} argument) all those matching a particular regular
16077 This was never implemented.
16078 @kindex info methods
16080 @itemx info methods @var{regexp}
16081 The @code{info methods} command permits the user to examine all defined
16082 methods within C@t{++} program, or (with the @var{regexp} argument) a
16083 specific set of methods found in the various C@t{++} classes. Many
16084 C@t{++} classes provide a large number of methods. Thus, the output
16085 from the @code{ptype} command can be overwhelming and hard to use. The
16086 @code{info-methods} command filters the methods, printing only those
16087 which match the regular-expression @var{regexp}.
16090 @cindex opaque data types
16091 @kindex set opaque-type-resolution
16092 @item set opaque-type-resolution on
16093 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16094 declared as a pointer to a @code{struct}, @code{class}, or
16095 @code{union}---for example, @code{struct MyType *}---that is used in one
16096 source file although the full declaration of @code{struct MyType} is in
16097 another source file. The default is on.
16099 A change in the setting of this subcommand will not take effect until
16100 the next time symbols for a file are loaded.
16102 @item set opaque-type-resolution off
16103 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16104 is printed as follows:
16106 @{<no data fields>@}
16109 @kindex show opaque-type-resolution
16110 @item show opaque-type-resolution
16111 Show whether opaque types are resolved or not.
16113 @kindex maint print symbols
16114 @cindex symbol dump
16115 @kindex maint print psymbols
16116 @cindex partial symbol dump
16117 @kindex maint print msymbols
16118 @cindex minimal symbol dump
16119 @item maint print symbols @var{filename}
16120 @itemx maint print psymbols @var{filename}
16121 @itemx maint print msymbols @var{filename}
16122 Write a dump of debugging symbol data into the file @var{filename}.
16123 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16124 symbols with debugging data are included. If you use @samp{maint print
16125 symbols}, @value{GDBN} includes all the symbols for which it has already
16126 collected full details: that is, @var{filename} reflects symbols for
16127 only those files whose symbols @value{GDBN} has read. You can use the
16128 command @code{info sources} to find out which files these are. If you
16129 use @samp{maint print psymbols} instead, the dump shows information about
16130 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16131 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16132 @samp{maint print msymbols} dumps just the minimal symbol information
16133 required for each object file from which @value{GDBN} has read some symbols.
16134 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16135 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16137 @kindex maint info symtabs
16138 @kindex maint info psymtabs
16139 @cindex listing @value{GDBN}'s internal symbol tables
16140 @cindex symbol tables, listing @value{GDBN}'s internal
16141 @cindex full symbol tables, listing @value{GDBN}'s internal
16142 @cindex partial symbol tables, listing @value{GDBN}'s internal
16143 @item maint info symtabs @r{[} @var{regexp} @r{]}
16144 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16146 List the @code{struct symtab} or @code{struct partial_symtab}
16147 structures whose names match @var{regexp}. If @var{regexp} is not
16148 given, list them all. The output includes expressions which you can
16149 copy into a @value{GDBN} debugging this one to examine a particular
16150 structure in more detail. For example:
16153 (@value{GDBP}) maint info psymtabs dwarf2read
16154 @{ objfile /home/gnu/build/gdb/gdb
16155 ((struct objfile *) 0x82e69d0)
16156 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16157 ((struct partial_symtab *) 0x8474b10)
16160 text addresses 0x814d3c8 -- 0x8158074
16161 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16162 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16163 dependencies (none)
16166 (@value{GDBP}) maint info symtabs
16170 We see that there is one partial symbol table whose filename contains
16171 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16172 and we see that @value{GDBN} has not read in any symtabs yet at all.
16173 If we set a breakpoint on a function, that will cause @value{GDBN} to
16174 read the symtab for the compilation unit containing that function:
16177 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16178 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16180 (@value{GDBP}) maint info symtabs
16181 @{ objfile /home/gnu/build/gdb/gdb
16182 ((struct objfile *) 0x82e69d0)
16183 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16184 ((struct symtab *) 0x86c1f38)
16187 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16188 linetable ((struct linetable *) 0x8370fa0)
16189 debugformat DWARF 2
16198 @chapter Altering Execution
16200 Once you think you have found an error in your program, you might want to
16201 find out for certain whether correcting the apparent error would lead to
16202 correct results in the rest of the run. You can find the answer by
16203 experiment, using the @value{GDBN} features for altering execution of the
16206 For example, you can store new values into variables or memory
16207 locations, give your program a signal, restart it at a different
16208 address, or even return prematurely from a function.
16211 * Assignment:: Assignment to variables
16212 * Jumping:: Continuing at a different address
16213 * Signaling:: Giving your program a signal
16214 * Returning:: Returning from a function
16215 * Calling:: Calling your program's functions
16216 * Patching:: Patching your program
16220 @section Assignment to Variables
16223 @cindex setting variables
16224 To alter the value of a variable, evaluate an assignment expression.
16225 @xref{Expressions, ,Expressions}. For example,
16232 stores the value 4 into the variable @code{x}, and then prints the
16233 value of the assignment expression (which is 4).
16234 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16235 information on operators in supported languages.
16237 @kindex set variable
16238 @cindex variables, setting
16239 If you are not interested in seeing the value of the assignment, use the
16240 @code{set} command instead of the @code{print} command. @code{set} is
16241 really the same as @code{print} except that the expression's value is
16242 not printed and is not put in the value history (@pxref{Value History,
16243 ,Value History}). The expression is evaluated only for its effects.
16245 If the beginning of the argument string of the @code{set} command
16246 appears identical to a @code{set} subcommand, use the @code{set
16247 variable} command instead of just @code{set}. This command is identical
16248 to @code{set} except for its lack of subcommands. For example, if your
16249 program has a variable @code{width}, you get an error if you try to set
16250 a new value with just @samp{set width=13}, because @value{GDBN} has the
16251 command @code{set width}:
16254 (@value{GDBP}) whatis width
16256 (@value{GDBP}) p width
16258 (@value{GDBP}) set width=47
16259 Invalid syntax in expression.
16263 The invalid expression, of course, is @samp{=47}. In
16264 order to actually set the program's variable @code{width}, use
16267 (@value{GDBP}) set var width=47
16270 Because the @code{set} command has many subcommands that can conflict
16271 with the names of program variables, it is a good idea to use the
16272 @code{set variable} command instead of just @code{set}. For example, if
16273 your program has a variable @code{g}, you run into problems if you try
16274 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16275 the command @code{set gnutarget}, abbreviated @code{set g}:
16279 (@value{GDBP}) whatis g
16283 (@value{GDBP}) set g=4
16287 The program being debugged has been started already.
16288 Start it from the beginning? (y or n) y
16289 Starting program: /home/smith/cc_progs/a.out
16290 "/home/smith/cc_progs/a.out": can't open to read symbols:
16291 Invalid bfd target.
16292 (@value{GDBP}) show g
16293 The current BFD target is "=4".
16298 The program variable @code{g} did not change, and you silently set the
16299 @code{gnutarget} to an invalid value. In order to set the variable
16303 (@value{GDBP}) set var g=4
16306 @value{GDBN} allows more implicit conversions in assignments than C; you can
16307 freely store an integer value into a pointer variable or vice versa,
16308 and you can convert any structure to any other structure that is the
16309 same length or shorter.
16310 @comment FIXME: how do structs align/pad in these conversions?
16311 @comment /doc@cygnus.com 18dec1990
16313 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16314 construct to generate a value of specified type at a specified address
16315 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16316 to memory location @code{0x83040} as an integer (which implies a certain size
16317 and representation in memory), and
16320 set @{int@}0x83040 = 4
16324 stores the value 4 into that memory location.
16327 @section Continuing at a Different Address
16329 Ordinarily, when you continue your program, you do so at the place where
16330 it stopped, with the @code{continue} command. You can instead continue at
16331 an address of your own choosing, with the following commands:
16335 @kindex j @r{(@code{jump})}
16336 @item jump @var{linespec}
16337 @itemx j @var{linespec}
16338 @itemx jump @var{location}
16339 @itemx j @var{location}
16340 Resume execution at line @var{linespec} or at address given by
16341 @var{location}. Execution stops again immediately if there is a
16342 breakpoint there. @xref{Specify Location}, for a description of the
16343 different forms of @var{linespec} and @var{location}. It is common
16344 practice to use the @code{tbreak} command in conjunction with
16345 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16347 The @code{jump} command does not change the current stack frame, or
16348 the stack pointer, or the contents of any memory location or any
16349 register other than the program counter. If line @var{linespec} is in
16350 a different function from the one currently executing, the results may
16351 be bizarre if the two functions expect different patterns of arguments or
16352 of local variables. For this reason, the @code{jump} command requests
16353 confirmation if the specified line is not in the function currently
16354 executing. However, even bizarre results are predictable if you are
16355 well acquainted with the machine-language code of your program.
16358 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16359 On many systems, you can get much the same effect as the @code{jump}
16360 command by storing a new value into the register @code{$pc}. The
16361 difference is that this does not start your program running; it only
16362 changes the address of where it @emph{will} run when you continue. For
16370 makes the next @code{continue} command or stepping command execute at
16371 address @code{0x485}, rather than at the address where your program stopped.
16372 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16374 The most common occasion to use the @code{jump} command is to back
16375 up---perhaps with more breakpoints set---over a portion of a program
16376 that has already executed, in order to examine its execution in more
16381 @section Giving your Program a Signal
16382 @cindex deliver a signal to a program
16386 @item signal @var{signal}
16387 Resume execution where your program stopped, but immediately give it the
16388 signal @var{signal}. @var{signal} can be the name or the number of a
16389 signal. For example, on many systems @code{signal 2} and @code{signal
16390 SIGINT} are both ways of sending an interrupt signal.
16392 Alternatively, if @var{signal} is zero, continue execution without
16393 giving a signal. This is useful when your program stopped on account of
16394 a signal and would ordinarily see the signal when resumed with the
16395 @code{continue} command; @samp{signal 0} causes it to resume without a
16398 @code{signal} does not repeat when you press @key{RET} a second time
16399 after executing the command.
16403 Invoking the @code{signal} command is not the same as invoking the
16404 @code{kill} utility from the shell. Sending a signal with @code{kill}
16405 causes @value{GDBN} to decide what to do with the signal depending on
16406 the signal handling tables (@pxref{Signals}). The @code{signal} command
16407 passes the signal directly to your program.
16411 @section Returning from a Function
16414 @cindex returning from a function
16417 @itemx return @var{expression}
16418 You can cancel execution of a function call with the @code{return}
16419 command. If you give an
16420 @var{expression} argument, its value is used as the function's return
16424 When you use @code{return}, @value{GDBN} discards the selected stack frame
16425 (and all frames within it). You can think of this as making the
16426 discarded frame return prematurely. If you wish to specify a value to
16427 be returned, give that value as the argument to @code{return}.
16429 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16430 Frame}), and any other frames inside of it, leaving its caller as the
16431 innermost remaining frame. That frame becomes selected. The
16432 specified value is stored in the registers used for returning values
16435 The @code{return} command does not resume execution; it leaves the
16436 program stopped in the state that would exist if the function had just
16437 returned. In contrast, the @code{finish} command (@pxref{Continuing
16438 and Stepping, ,Continuing and Stepping}) resumes execution until the
16439 selected stack frame returns naturally.
16441 @value{GDBN} needs to know how the @var{expression} argument should be set for
16442 the inferior. The concrete registers assignment depends on the OS ABI and the
16443 type being returned by the selected stack frame. For example it is common for
16444 OS ABI to return floating point values in FPU registers while integer values in
16445 CPU registers. Still some ABIs return even floating point values in CPU
16446 registers. Larger integer widths (such as @code{long long int}) also have
16447 specific placement rules. @value{GDBN} already knows the OS ABI from its
16448 current target so it needs to find out also the type being returned to make the
16449 assignment into the right register(s).
16451 Normally, the selected stack frame has debug info. @value{GDBN} will always
16452 use the debug info instead of the implicit type of @var{expression} when the
16453 debug info is available. For example, if you type @kbd{return -1}, and the
16454 function in the current stack frame is declared to return a @code{long long
16455 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16456 into a @code{long long int}:
16459 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16461 (@value{GDBP}) return -1
16462 Make func return now? (y or n) y
16463 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16464 43 printf ("result=%lld\n", func ());
16468 However, if the selected stack frame does not have a debug info, e.g., if the
16469 function was compiled without debug info, @value{GDBN} has to find out the type
16470 to return from user. Specifying a different type by mistake may set the value
16471 in different inferior registers than the caller code expects. For example,
16472 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16473 of a @code{long long int} result for a debug info less function (on 32-bit
16474 architectures). Therefore the user is required to specify the return type by
16475 an appropriate cast explicitly:
16478 Breakpoint 2, 0x0040050b in func ()
16479 (@value{GDBP}) return -1
16480 Return value type not available for selected stack frame.
16481 Please use an explicit cast of the value to return.
16482 (@value{GDBP}) return (long long int) -1
16483 Make selected stack frame return now? (y or n) y
16484 #0 0x00400526 in main ()
16489 @section Calling Program Functions
16492 @cindex calling functions
16493 @cindex inferior functions, calling
16494 @item print @var{expr}
16495 Evaluate the expression @var{expr} and display the resulting value.
16496 @var{expr} may include calls to functions in the program being
16500 @item call @var{expr}
16501 Evaluate the expression @var{expr} without displaying @code{void}
16504 You can use this variant of the @code{print} command if you want to
16505 execute a function from your program that does not return anything
16506 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16507 with @code{void} returned values that @value{GDBN} will otherwise
16508 print. If the result is not void, it is printed and saved in the
16512 It is possible for the function you call via the @code{print} or
16513 @code{call} command to generate a signal (e.g., if there's a bug in
16514 the function, or if you passed it incorrect arguments). What happens
16515 in that case is controlled by the @code{set unwindonsignal} command.
16517 Similarly, with a C@t{++} program it is possible for the function you
16518 call via the @code{print} or @code{call} command to generate an
16519 exception that is not handled due to the constraints of the dummy
16520 frame. In this case, any exception that is raised in the frame, but has
16521 an out-of-frame exception handler will not be found. GDB builds a
16522 dummy-frame for the inferior function call, and the unwinder cannot
16523 seek for exception handlers outside of this dummy-frame. What happens
16524 in that case is controlled by the
16525 @code{set unwind-on-terminating-exception} command.
16528 @item set unwindonsignal
16529 @kindex set unwindonsignal
16530 @cindex unwind stack in called functions
16531 @cindex call dummy stack unwinding
16532 Set unwinding of the stack if a signal is received while in a function
16533 that @value{GDBN} called in the program being debugged. If set to on,
16534 @value{GDBN} unwinds the stack it created for the call and restores
16535 the context to what it was before the call. If set to off (the
16536 default), @value{GDBN} stops in the frame where the signal was
16539 @item show unwindonsignal
16540 @kindex show unwindonsignal
16541 Show the current setting of stack unwinding in the functions called by
16544 @item set unwind-on-terminating-exception
16545 @kindex set unwind-on-terminating-exception
16546 @cindex unwind stack in called functions with unhandled exceptions
16547 @cindex call dummy stack unwinding on unhandled exception.
16548 Set unwinding of the stack if a C@t{++} exception is raised, but left
16549 unhandled while in a function that @value{GDBN} called in the program being
16550 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16551 it created for the call and restores the context to what it was before
16552 the call. If set to off, @value{GDBN} the exception is delivered to
16553 the default C@t{++} exception handler and the inferior terminated.
16555 @item show unwind-on-terminating-exception
16556 @kindex show unwind-on-terminating-exception
16557 Show the current setting of stack unwinding in the functions called by
16562 @cindex weak alias functions
16563 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16564 for another function. In such case, @value{GDBN} might not pick up
16565 the type information, including the types of the function arguments,
16566 which causes @value{GDBN} to call the inferior function incorrectly.
16567 As a result, the called function will function erroneously and may
16568 even crash. A solution to that is to use the name of the aliased
16572 @section Patching Programs
16574 @cindex patching binaries
16575 @cindex writing into executables
16576 @cindex writing into corefiles
16578 By default, @value{GDBN} opens the file containing your program's
16579 executable code (or the corefile) read-only. This prevents accidental
16580 alterations to machine code; but it also prevents you from intentionally
16581 patching your program's binary.
16583 If you'd like to be able to patch the binary, you can specify that
16584 explicitly with the @code{set write} command. For example, you might
16585 want to turn on internal debugging flags, or even to make emergency
16591 @itemx set write off
16592 If you specify @samp{set write on}, @value{GDBN} opens executable and
16593 core files for both reading and writing; if you specify @kbd{set write
16594 off} (the default), @value{GDBN} opens them read-only.
16596 If you have already loaded a file, you must load it again (using the
16597 @code{exec-file} or @code{core-file} command) after changing @code{set
16598 write}, for your new setting to take effect.
16602 Display whether executable files and core files are opened for writing
16603 as well as reading.
16607 @chapter @value{GDBN} Files
16609 @value{GDBN} needs to know the file name of the program to be debugged,
16610 both in order to read its symbol table and in order to start your
16611 program. To debug a core dump of a previous run, you must also tell
16612 @value{GDBN} the name of the core dump file.
16615 * Files:: Commands to specify files
16616 * Separate Debug Files:: Debugging information in separate files
16617 * MiniDebugInfo:: Debugging information in a special section
16618 * Index Files:: Index files speed up GDB
16619 * Symbol Errors:: Errors reading symbol files
16620 * Data Files:: GDB data files
16624 @section Commands to Specify Files
16626 @cindex symbol table
16627 @cindex core dump file
16629 You may want to specify executable and core dump file names. The usual
16630 way to do this is at start-up time, using the arguments to
16631 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16632 Out of @value{GDBN}}).
16634 Occasionally it is necessary to change to a different file during a
16635 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16636 specify a file you want to use. Or you are debugging a remote target
16637 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16638 Program}). In these situations the @value{GDBN} commands to specify
16639 new files are useful.
16642 @cindex executable file
16644 @item file @var{filename}
16645 Use @var{filename} as the program to be debugged. It is read for its
16646 symbols and for the contents of pure memory. It is also the program
16647 executed when you use the @code{run} command. If you do not specify a
16648 directory and the file is not found in the @value{GDBN} working directory,
16649 @value{GDBN} uses the environment variable @code{PATH} as a list of
16650 directories to search, just as the shell does when looking for a program
16651 to run. You can change the value of this variable, for both @value{GDBN}
16652 and your program, using the @code{path} command.
16654 @cindex unlinked object files
16655 @cindex patching object files
16656 You can load unlinked object @file{.o} files into @value{GDBN} using
16657 the @code{file} command. You will not be able to ``run'' an object
16658 file, but you can disassemble functions and inspect variables. Also,
16659 if the underlying BFD functionality supports it, you could use
16660 @kbd{gdb -write} to patch object files using this technique. Note
16661 that @value{GDBN} can neither interpret nor modify relocations in this
16662 case, so branches and some initialized variables will appear to go to
16663 the wrong place. But this feature is still handy from time to time.
16666 @code{file} with no argument makes @value{GDBN} discard any information it
16667 has on both executable file and the symbol table.
16670 @item exec-file @r{[} @var{filename} @r{]}
16671 Specify that the program to be run (but not the symbol table) is found
16672 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16673 if necessary to locate your program. Omitting @var{filename} means to
16674 discard information on the executable file.
16676 @kindex symbol-file
16677 @item symbol-file @r{[} @var{filename} @r{]}
16678 Read symbol table information from file @var{filename}. @code{PATH} is
16679 searched when necessary. Use the @code{file} command to get both symbol
16680 table and program to run from the same file.
16682 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16683 program's symbol table.
16685 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16686 some breakpoints and auto-display expressions. This is because they may
16687 contain pointers to the internal data recording symbols and data types,
16688 which are part of the old symbol table data being discarded inside
16691 @code{symbol-file} does not repeat if you press @key{RET} again after
16694 When @value{GDBN} is configured for a particular environment, it
16695 understands debugging information in whatever format is the standard
16696 generated for that environment; you may use either a @sc{gnu} compiler, or
16697 other compilers that adhere to the local conventions.
16698 Best results are usually obtained from @sc{gnu} compilers; for example,
16699 using @code{@value{NGCC}} you can generate debugging information for
16702 For most kinds of object files, with the exception of old SVR3 systems
16703 using COFF, the @code{symbol-file} command does not normally read the
16704 symbol table in full right away. Instead, it scans the symbol table
16705 quickly to find which source files and which symbols are present. The
16706 details are read later, one source file at a time, as they are needed.
16708 The purpose of this two-stage reading strategy is to make @value{GDBN}
16709 start up faster. For the most part, it is invisible except for
16710 occasional pauses while the symbol table details for a particular source
16711 file are being read. (The @code{set verbose} command can turn these
16712 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16713 Warnings and Messages}.)
16715 We have not implemented the two-stage strategy for COFF yet. When the
16716 symbol table is stored in COFF format, @code{symbol-file} reads the
16717 symbol table data in full right away. Note that ``stabs-in-COFF''
16718 still does the two-stage strategy, since the debug info is actually
16722 @cindex reading symbols immediately
16723 @cindex symbols, reading immediately
16724 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16725 @itemx file @r{[} -readnow @r{]} @var{filename}
16726 You can override the @value{GDBN} two-stage strategy for reading symbol
16727 tables by using the @samp{-readnow} option with any of the commands that
16728 load symbol table information, if you want to be sure @value{GDBN} has the
16729 entire symbol table available.
16731 @c FIXME: for now no mention of directories, since this seems to be in
16732 @c flux. 13mar1992 status is that in theory GDB would look either in
16733 @c current dir or in same dir as myprog; but issues like competing
16734 @c GDB's, or clutter in system dirs, mean that in practice right now
16735 @c only current dir is used. FFish says maybe a special GDB hierarchy
16736 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16740 @item core-file @r{[}@var{filename}@r{]}
16742 Specify the whereabouts of a core dump file to be used as the ``contents
16743 of memory''. Traditionally, core files contain only some parts of the
16744 address space of the process that generated them; @value{GDBN} can access the
16745 executable file itself for other parts.
16747 @code{core-file} with no argument specifies that no core file is
16750 Note that the core file is ignored when your program is actually running
16751 under @value{GDBN}. So, if you have been running your program and you
16752 wish to debug a core file instead, you must kill the subprocess in which
16753 the program is running. To do this, use the @code{kill} command
16754 (@pxref{Kill Process, ,Killing the Child Process}).
16756 @kindex add-symbol-file
16757 @cindex dynamic linking
16758 @item add-symbol-file @var{filename} @var{address}
16759 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16760 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16761 The @code{add-symbol-file} command reads additional symbol table
16762 information from the file @var{filename}. You would use this command
16763 when @var{filename} has been dynamically loaded (by some other means)
16764 into the program that is running. @var{address} should be the memory
16765 address at which the file has been loaded; @value{GDBN} cannot figure
16766 this out for itself. You can additionally specify an arbitrary number
16767 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16768 section name and base address for that section. You can specify any
16769 @var{address} as an expression.
16771 The symbol table of the file @var{filename} is added to the symbol table
16772 originally read with the @code{symbol-file} command. You can use the
16773 @code{add-symbol-file} command any number of times; the new symbol data
16774 thus read is kept in addition to the old.
16776 Changes can be reverted using the command @code{remove-symbol-file}.
16778 @cindex relocatable object files, reading symbols from
16779 @cindex object files, relocatable, reading symbols from
16780 @cindex reading symbols from relocatable object files
16781 @cindex symbols, reading from relocatable object files
16782 @cindex @file{.o} files, reading symbols from
16783 Although @var{filename} is typically a shared library file, an
16784 executable file, or some other object file which has been fully
16785 relocated for loading into a process, you can also load symbolic
16786 information from relocatable @file{.o} files, as long as:
16790 the file's symbolic information refers only to linker symbols defined in
16791 that file, not to symbols defined by other object files,
16793 every section the file's symbolic information refers to has actually
16794 been loaded into the inferior, as it appears in the file, and
16796 you can determine the address at which every section was loaded, and
16797 provide these to the @code{add-symbol-file} command.
16801 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16802 relocatable files into an already running program; such systems
16803 typically make the requirements above easy to meet. However, it's
16804 important to recognize that many native systems use complex link
16805 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16806 assembly, for example) that make the requirements difficult to meet. In
16807 general, one cannot assume that using @code{add-symbol-file} to read a
16808 relocatable object file's symbolic information will have the same effect
16809 as linking the relocatable object file into the program in the normal
16812 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16814 @kindex remove-symbol-file
16815 @item remove-symbol-file @var{filename}
16816 @item remove-symbol-file -a @var{address}
16817 Remove a symbol file added via the @code{add-symbol-file} command. The
16818 file to remove can be identified by its @var{filename} or by an @var{address}
16819 that lies within the boundaries of this symbol file in memory. Example:
16822 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16823 add symbol table from file "/home/user/gdb/mylib.so" at
16824 .text_addr = 0x7ffff7ff9480
16826 Reading symbols from /home/user/gdb/mylib.so...done.
16827 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16828 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16833 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16835 @kindex add-symbol-file-from-memory
16836 @cindex @code{syscall DSO}
16837 @cindex load symbols from memory
16838 @item add-symbol-file-from-memory @var{address}
16839 Load symbols from the given @var{address} in a dynamically loaded
16840 object file whose image is mapped directly into the inferior's memory.
16841 For example, the Linux kernel maps a @code{syscall DSO} into each
16842 process's address space; this DSO provides kernel-specific code for
16843 some system calls. The argument can be any expression whose
16844 evaluation yields the address of the file's shared object file header.
16845 For this command to work, you must have used @code{symbol-file} or
16846 @code{exec-file} commands in advance.
16848 @kindex add-shared-symbol-files
16850 @item add-shared-symbol-files @var{library-file}
16851 @itemx assf @var{library-file}
16852 The @code{add-shared-symbol-files} command can currently be used only
16853 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16854 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16855 @value{GDBN} automatically looks for shared libraries, however if
16856 @value{GDBN} does not find yours, you can invoke
16857 @code{add-shared-symbol-files}. It takes one argument: the shared
16858 library's file name. @code{assf} is a shorthand alias for
16859 @code{add-shared-symbol-files}.
16862 @item section @var{section} @var{addr}
16863 The @code{section} command changes the base address of the named
16864 @var{section} of the exec file to @var{addr}. This can be used if the
16865 exec file does not contain section addresses, (such as in the
16866 @code{a.out} format), or when the addresses specified in the file
16867 itself are wrong. Each section must be changed separately. The
16868 @code{info files} command, described below, lists all the sections and
16872 @kindex info target
16875 @code{info files} and @code{info target} are synonymous; both print the
16876 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16877 including the names of the executable and core dump files currently in
16878 use by @value{GDBN}, and the files from which symbols were loaded. The
16879 command @code{help target} lists all possible targets rather than
16882 @kindex maint info sections
16883 @item maint info sections
16884 Another command that can give you extra information about program sections
16885 is @code{maint info sections}. In addition to the section information
16886 displayed by @code{info files}, this command displays the flags and file
16887 offset of each section in the executable and core dump files. In addition,
16888 @code{maint info sections} provides the following command options (which
16889 may be arbitrarily combined):
16893 Display sections for all loaded object files, including shared libraries.
16894 @item @var{sections}
16895 Display info only for named @var{sections}.
16896 @item @var{section-flags}
16897 Display info only for sections for which @var{section-flags} are true.
16898 The section flags that @value{GDBN} currently knows about are:
16901 Section will have space allocated in the process when loaded.
16902 Set for all sections except those containing debug information.
16904 Section will be loaded from the file into the child process memory.
16905 Set for pre-initialized code and data, clear for @code{.bss} sections.
16907 Section needs to be relocated before loading.
16909 Section cannot be modified by the child process.
16911 Section contains executable code only.
16913 Section contains data only (no executable code).
16915 Section will reside in ROM.
16917 Section contains data for constructor/destructor lists.
16919 Section is not empty.
16921 An instruction to the linker to not output the section.
16922 @item COFF_SHARED_LIBRARY
16923 A notification to the linker that the section contains
16924 COFF shared library information.
16926 Section contains common symbols.
16929 @kindex set trust-readonly-sections
16930 @cindex read-only sections
16931 @item set trust-readonly-sections on
16932 Tell @value{GDBN} that readonly sections in your object file
16933 really are read-only (i.e.@: that their contents will not change).
16934 In that case, @value{GDBN} can fetch values from these sections
16935 out of the object file, rather than from the target program.
16936 For some targets (notably embedded ones), this can be a significant
16937 enhancement to debugging performance.
16939 The default is off.
16941 @item set trust-readonly-sections off
16942 Tell @value{GDBN} not to trust readonly sections. This means that
16943 the contents of the section might change while the program is running,
16944 and must therefore be fetched from the target when needed.
16946 @item show trust-readonly-sections
16947 Show the current setting of trusting readonly sections.
16950 All file-specifying commands allow both absolute and relative file names
16951 as arguments. @value{GDBN} always converts the file name to an absolute file
16952 name and remembers it that way.
16954 @cindex shared libraries
16955 @anchor{Shared Libraries}
16956 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16957 and IBM RS/6000 AIX shared libraries.
16959 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16960 shared libraries. @xref{Expat}.
16962 @value{GDBN} automatically loads symbol definitions from shared libraries
16963 when you use the @code{run} command, or when you examine a core file.
16964 (Before you issue the @code{run} command, @value{GDBN} does not understand
16965 references to a function in a shared library, however---unless you are
16966 debugging a core file).
16968 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16969 automatically loads the symbols at the time of the @code{shl_load} call.
16971 @c FIXME: some @value{GDBN} release may permit some refs to undef
16972 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16973 @c FIXME...lib; check this from time to time when updating manual
16975 There are times, however, when you may wish to not automatically load
16976 symbol definitions from shared libraries, such as when they are
16977 particularly large or there are many of them.
16979 To control the automatic loading of shared library symbols, use the
16983 @kindex set auto-solib-add
16984 @item set auto-solib-add @var{mode}
16985 If @var{mode} is @code{on}, symbols from all shared object libraries
16986 will be loaded automatically when the inferior begins execution, you
16987 attach to an independently started inferior, or when the dynamic linker
16988 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16989 is @code{off}, symbols must be loaded manually, using the
16990 @code{sharedlibrary} command. The default value is @code{on}.
16992 @cindex memory used for symbol tables
16993 If your program uses lots of shared libraries with debug info that
16994 takes large amounts of memory, you can decrease the @value{GDBN}
16995 memory footprint by preventing it from automatically loading the
16996 symbols from shared libraries. To that end, type @kbd{set
16997 auto-solib-add off} before running the inferior, then load each
16998 library whose debug symbols you do need with @kbd{sharedlibrary
16999 @var{regexp}}, where @var{regexp} is a regular expression that matches
17000 the libraries whose symbols you want to be loaded.
17002 @kindex show auto-solib-add
17003 @item show auto-solib-add
17004 Display the current autoloading mode.
17007 @cindex load shared library
17008 To explicitly load shared library symbols, use the @code{sharedlibrary}
17012 @kindex info sharedlibrary
17014 @item info share @var{regex}
17015 @itemx info sharedlibrary @var{regex}
17016 Print the names of the shared libraries which are currently loaded
17017 that match @var{regex}. If @var{regex} is omitted then print
17018 all shared libraries that are loaded.
17020 @kindex sharedlibrary
17022 @item sharedlibrary @var{regex}
17023 @itemx share @var{regex}
17024 Load shared object library symbols for files matching a
17025 Unix regular expression.
17026 As with files loaded automatically, it only loads shared libraries
17027 required by your program for a core file or after typing @code{run}. If
17028 @var{regex} is omitted all shared libraries required by your program are
17031 @item nosharedlibrary
17032 @kindex nosharedlibrary
17033 @cindex unload symbols from shared libraries
17034 Unload all shared object library symbols. This discards all symbols
17035 that have been loaded from all shared libraries. Symbols from shared
17036 libraries that were loaded by explicit user requests are not
17040 Sometimes you may wish that @value{GDBN} stops and gives you control
17041 when any of shared library events happen. The best way to do this is
17042 to use @code{catch load} and @code{catch unload} (@pxref{Set
17045 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17046 command for this. This command exists for historical reasons. It is
17047 less useful than setting a catchpoint, because it does not allow for
17048 conditions or commands as a catchpoint does.
17051 @item set stop-on-solib-events
17052 @kindex set stop-on-solib-events
17053 This command controls whether @value{GDBN} should give you control
17054 when the dynamic linker notifies it about some shared library event.
17055 The most common event of interest is loading or unloading of a new
17058 @item show stop-on-solib-events
17059 @kindex show stop-on-solib-events
17060 Show whether @value{GDBN} stops and gives you control when shared
17061 library events happen.
17064 Shared libraries are also supported in many cross or remote debugging
17065 configurations. @value{GDBN} needs to have access to the target's libraries;
17066 this can be accomplished either by providing copies of the libraries
17067 on the host system, or by asking @value{GDBN} to automatically retrieve the
17068 libraries from the target. If copies of the target libraries are
17069 provided, they need to be the same as the target libraries, although the
17070 copies on the target can be stripped as long as the copies on the host are
17073 @cindex where to look for shared libraries
17074 For remote debugging, you need to tell @value{GDBN} where the target
17075 libraries are, so that it can load the correct copies---otherwise, it
17076 may try to load the host's libraries. @value{GDBN} has two variables
17077 to specify the search directories for target libraries.
17080 @cindex prefix for shared library file names
17081 @cindex system root, alternate
17082 @kindex set solib-absolute-prefix
17083 @kindex set sysroot
17084 @item set sysroot @var{path}
17085 Use @var{path} as the system root for the program being debugged. Any
17086 absolute shared library paths will be prefixed with @var{path}; many
17087 runtime loaders store the absolute paths to the shared library in the
17088 target program's memory. If you use @code{set sysroot} to find shared
17089 libraries, they need to be laid out in the same way that they are on
17090 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17093 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17094 retrieve the target libraries from the remote system. This is only
17095 supported when using a remote target that supports the @code{remote get}
17096 command (@pxref{File Transfer,,Sending files to a remote system}).
17097 The part of @var{path} following the initial @file{remote:}
17098 (if present) is used as system root prefix on the remote file system.
17099 @footnote{If you want to specify a local system root using a directory
17100 that happens to be named @file{remote:}, you need to use some equivalent
17101 variant of the name like @file{./remote:}.}
17103 For targets with an MS-DOS based filesystem, such as MS-Windows and
17104 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17105 absolute file name with @var{path}. But first, on Unix hosts,
17106 @value{GDBN} converts all backslash directory separators into forward
17107 slashes, because the backslash is not a directory separator on Unix:
17110 c:\foo\bar.dll @result{} c:/foo/bar.dll
17113 Then, @value{GDBN} attempts prefixing the target file name with
17114 @var{path}, and looks for the resulting file name in the host file
17118 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17121 If that does not find the shared library, @value{GDBN} tries removing
17122 the @samp{:} character from the drive spec, both for convenience, and,
17123 for the case of the host file system not supporting file names with
17127 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17130 This makes it possible to have a system root that mirrors a target
17131 with more than one drive. E.g., you may want to setup your local
17132 copies of the target system shared libraries like so (note @samp{c} vs
17136 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17137 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17138 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17142 and point the system root at @file{/path/to/sysroot}, so that
17143 @value{GDBN} can find the correct copies of both
17144 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17146 If that still does not find the shared library, @value{GDBN} tries
17147 removing the whole drive spec from the target file name:
17150 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17153 This last lookup makes it possible to not care about the drive name,
17154 if you don't want or need to.
17156 The @code{set solib-absolute-prefix} command is an alias for @code{set
17159 @cindex default system root
17160 @cindex @samp{--with-sysroot}
17161 You can set the default system root by using the configure-time
17162 @samp{--with-sysroot} option. If the system root is inside
17163 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17164 @samp{--exec-prefix}), then the default system root will be updated
17165 automatically if the installed @value{GDBN} is moved to a new
17168 @kindex show sysroot
17170 Display the current shared library prefix.
17172 @kindex set solib-search-path
17173 @item set solib-search-path @var{path}
17174 If this variable is set, @var{path} is a colon-separated list of
17175 directories to search for shared libraries. @samp{solib-search-path}
17176 is used after @samp{sysroot} fails to locate the library, or if the
17177 path to the library is relative instead of absolute. If you want to
17178 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17179 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17180 finding your host's libraries. @samp{sysroot} is preferred; setting
17181 it to a nonexistent directory may interfere with automatic loading
17182 of shared library symbols.
17184 @kindex show solib-search-path
17185 @item show solib-search-path
17186 Display the current shared library search path.
17188 @cindex DOS file-name semantics of file names.
17189 @kindex set target-file-system-kind (unix|dos-based|auto)
17190 @kindex show target-file-system-kind
17191 @item set target-file-system-kind @var{kind}
17192 Set assumed file system kind for target reported file names.
17194 Shared library file names as reported by the target system may not
17195 make sense as is on the system @value{GDBN} is running on. For
17196 example, when remote debugging a target that has MS-DOS based file
17197 system semantics, from a Unix host, the target may be reporting to
17198 @value{GDBN} a list of loaded shared libraries with file names such as
17199 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17200 drive letters, so the @samp{c:\} prefix is not normally understood as
17201 indicating an absolute file name, and neither is the backslash
17202 normally considered a directory separator character. In that case,
17203 the native file system would interpret this whole absolute file name
17204 as a relative file name with no directory components. This would make
17205 it impossible to point @value{GDBN} at a copy of the remote target's
17206 shared libraries on the host using @code{set sysroot}, and impractical
17207 with @code{set solib-search-path}. Setting
17208 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17209 to interpret such file names similarly to how the target would, and to
17210 map them to file names valid on @value{GDBN}'s native file system
17211 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17212 to one of the supported file system kinds. In that case, @value{GDBN}
17213 tries to determine the appropriate file system variant based on the
17214 current target's operating system (@pxref{ABI, ,Configuring the
17215 Current ABI}). The supported file system settings are:
17219 Instruct @value{GDBN} to assume the target file system is of Unix
17220 kind. Only file names starting the forward slash (@samp{/}) character
17221 are considered absolute, and the directory separator character is also
17225 Instruct @value{GDBN} to assume the target file system is DOS based.
17226 File names starting with either a forward slash, or a drive letter
17227 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17228 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17229 considered directory separators.
17232 Instruct @value{GDBN} to use the file system kind associated with the
17233 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17234 This is the default.
17238 @cindex file name canonicalization
17239 @cindex base name differences
17240 When processing file names provided by the user, @value{GDBN}
17241 frequently needs to compare them to the file names recorded in the
17242 program's debug info. Normally, @value{GDBN} compares just the
17243 @dfn{base names} of the files as strings, which is reasonably fast
17244 even for very large programs. (The base name of a file is the last
17245 portion of its name, after stripping all the leading directories.)
17246 This shortcut in comparison is based upon the assumption that files
17247 cannot have more than one base name. This is usually true, but
17248 references to files that use symlinks or similar filesystem
17249 facilities violate that assumption. If your program records files
17250 using such facilities, or if you provide file names to @value{GDBN}
17251 using symlinks etc., you can set @code{basenames-may-differ} to
17252 @code{true} to instruct @value{GDBN} to completely canonicalize each
17253 pair of file names it needs to compare. This will make file-name
17254 comparisons accurate, but at a price of a significant slowdown.
17257 @item set basenames-may-differ
17258 @kindex set basenames-may-differ
17259 Set whether a source file may have multiple base names.
17261 @item show basenames-may-differ
17262 @kindex show basenames-may-differ
17263 Show whether a source file may have multiple base names.
17266 @node Separate Debug Files
17267 @section Debugging Information in Separate Files
17268 @cindex separate debugging information files
17269 @cindex debugging information in separate files
17270 @cindex @file{.debug} subdirectories
17271 @cindex debugging information directory, global
17272 @cindex global debugging information directories
17273 @cindex build ID, and separate debugging files
17274 @cindex @file{.build-id} directory
17276 @value{GDBN} allows you to put a program's debugging information in a
17277 file separate from the executable itself, in a way that allows
17278 @value{GDBN} to find and load the debugging information automatically.
17279 Since debugging information can be very large---sometimes larger
17280 than the executable code itself---some systems distribute debugging
17281 information for their executables in separate files, which users can
17282 install only when they need to debug a problem.
17284 @value{GDBN} supports two ways of specifying the separate debug info
17289 The executable contains a @dfn{debug link} that specifies the name of
17290 the separate debug info file. The separate debug file's name is
17291 usually @file{@var{executable}.debug}, where @var{executable} is the
17292 name of the corresponding executable file without leading directories
17293 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17294 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17295 checksum for the debug file, which @value{GDBN} uses to validate that
17296 the executable and the debug file came from the same build.
17299 The executable contains a @dfn{build ID}, a unique bit string that is
17300 also present in the corresponding debug info file. (This is supported
17301 only on some operating systems, notably those which use the ELF format
17302 for binary files and the @sc{gnu} Binutils.) For more details about
17303 this feature, see the description of the @option{--build-id}
17304 command-line option in @ref{Options, , Command Line Options, ld.info,
17305 The GNU Linker}. The debug info file's name is not specified
17306 explicitly by the build ID, but can be computed from the build ID, see
17310 Depending on the way the debug info file is specified, @value{GDBN}
17311 uses two different methods of looking for the debug file:
17315 For the ``debug link'' method, @value{GDBN} looks up the named file in
17316 the directory of the executable file, then in a subdirectory of that
17317 directory named @file{.debug}, and finally under each one of the global debug
17318 directories, in a subdirectory whose name is identical to the leading
17319 directories of the executable's absolute file name.
17322 For the ``build ID'' method, @value{GDBN} looks in the
17323 @file{.build-id} subdirectory of each one of the global debug directories for
17324 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17325 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17326 are the rest of the bit string. (Real build ID strings are 32 or more
17327 hex characters, not 10.)
17330 So, for example, suppose you ask @value{GDBN} to debug
17331 @file{/usr/bin/ls}, which has a debug link that specifies the
17332 file @file{ls.debug}, and a build ID whose value in hex is
17333 @code{abcdef1234}. If the list of the global debug directories includes
17334 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17335 debug information files, in the indicated order:
17339 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17341 @file{/usr/bin/ls.debug}
17343 @file{/usr/bin/.debug/ls.debug}
17345 @file{/usr/lib/debug/usr/bin/ls.debug}.
17348 @anchor{debug-file-directory}
17349 Global debugging info directories default to what is set by @value{GDBN}
17350 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17351 you can also set the global debugging info directories, and view the list
17352 @value{GDBN} is currently using.
17356 @kindex set debug-file-directory
17357 @item set debug-file-directory @var{directories}
17358 Set the directories which @value{GDBN} searches for separate debugging
17359 information files to @var{directory}. Multiple path components can be set
17360 concatenating them by a path separator.
17362 @kindex show debug-file-directory
17363 @item show debug-file-directory
17364 Show the directories @value{GDBN} searches for separate debugging
17369 @cindex @code{.gnu_debuglink} sections
17370 @cindex debug link sections
17371 A debug link is a special section of the executable file named
17372 @code{.gnu_debuglink}. The section must contain:
17376 A filename, with any leading directory components removed, followed by
17379 zero to three bytes of padding, as needed to reach the next four-byte
17380 boundary within the section, and
17382 a four-byte CRC checksum, stored in the same endianness used for the
17383 executable file itself. The checksum is computed on the debugging
17384 information file's full contents by the function given below, passing
17385 zero as the @var{crc} argument.
17388 Any executable file format can carry a debug link, as long as it can
17389 contain a section named @code{.gnu_debuglink} with the contents
17392 @cindex @code{.note.gnu.build-id} sections
17393 @cindex build ID sections
17394 The build ID is a special section in the executable file (and in other
17395 ELF binary files that @value{GDBN} may consider). This section is
17396 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17397 It contains unique identification for the built files---the ID remains
17398 the same across multiple builds of the same build tree. The default
17399 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17400 content for the build ID string. The same section with an identical
17401 value is present in the original built binary with symbols, in its
17402 stripped variant, and in the separate debugging information file.
17404 The debugging information file itself should be an ordinary
17405 executable, containing a full set of linker symbols, sections, and
17406 debugging information. The sections of the debugging information file
17407 should have the same names, addresses, and sizes as the original file,
17408 but they need not contain any data---much like a @code{.bss} section
17409 in an ordinary executable.
17411 The @sc{gnu} binary utilities (Binutils) package includes the
17412 @samp{objcopy} utility that can produce
17413 the separated executable / debugging information file pairs using the
17414 following commands:
17417 @kbd{objcopy --only-keep-debug foo foo.debug}
17422 These commands remove the debugging
17423 information from the executable file @file{foo} and place it in the file
17424 @file{foo.debug}. You can use the first, second or both methods to link the
17429 The debug link method needs the following additional command to also leave
17430 behind a debug link in @file{foo}:
17433 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17436 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17437 a version of the @code{strip} command such that the command @kbd{strip foo -f
17438 foo.debug} has the same functionality as the two @code{objcopy} commands and
17439 the @code{ln -s} command above, together.
17442 Build ID gets embedded into the main executable using @code{ld --build-id} or
17443 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17444 compatibility fixes for debug files separation are present in @sc{gnu} binary
17445 utilities (Binutils) package since version 2.18.
17450 @cindex CRC algorithm definition
17451 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17452 IEEE 802.3 using the polynomial:
17454 @c TexInfo requires naked braces for multi-digit exponents for Tex
17455 @c output, but this causes HTML output to barf. HTML has to be set using
17456 @c raw commands. So we end up having to specify this equation in 2
17461 <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>
17462 + <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
17468 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17469 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17473 The function is computed byte at a time, taking the least
17474 significant bit of each byte first. The initial pattern
17475 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17476 the final result is inverted to ensure trailing zeros also affect the
17479 @emph{Note:} This is the same CRC polynomial as used in handling the
17480 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17481 , @value{GDBN} Remote Serial Protocol}). However in the
17482 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17483 significant bit first, and the result is not inverted, so trailing
17484 zeros have no effect on the CRC value.
17486 To complete the description, we show below the code of the function
17487 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17488 initially supplied @code{crc} argument means that an initial call to
17489 this function passing in zero will start computing the CRC using
17492 @kindex gnu_debuglink_crc32
17495 gnu_debuglink_crc32 (unsigned long crc,
17496 unsigned char *buf, size_t len)
17498 static const unsigned long crc32_table[256] =
17500 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17501 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17502 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17503 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17504 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17505 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17506 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17507 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17508 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17509 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17510 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17511 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17512 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17513 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17514 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17515 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17516 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17517 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17518 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17519 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17520 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17521 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17522 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17523 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17524 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17525 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17526 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17527 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17528 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17529 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17530 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17531 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17532 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17533 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17534 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17535 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17536 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17537 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17538 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17539 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17540 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17541 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17542 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17543 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17544 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17545 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17546 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17547 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17548 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17549 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17550 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17553 unsigned char *end;
17555 crc = ~crc & 0xffffffff;
17556 for (end = buf + len; buf < end; ++buf)
17557 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17558 return ~crc & 0xffffffff;
17563 This computation does not apply to the ``build ID'' method.
17565 @node MiniDebugInfo
17566 @section Debugging information in a special section
17567 @cindex separate debug sections
17568 @cindex @samp{.gnu_debugdata} section
17570 Some systems ship pre-built executables and libraries that have a
17571 special @samp{.gnu_debugdata} section. This feature is called
17572 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17573 is used to supply extra symbols for backtraces.
17575 The intent of this section is to provide extra minimal debugging
17576 information for use in simple backtraces. It is not intended to be a
17577 replacement for full separate debugging information (@pxref{Separate
17578 Debug Files}). The example below shows the intended use; however,
17579 @value{GDBN} does not currently put restrictions on what sort of
17580 debugging information might be included in the section.
17582 @value{GDBN} has support for this extension. If the section exists,
17583 then it is used provided that no other source of debugging information
17584 can be found, and that @value{GDBN} was configured with LZMA support.
17586 This section can be easily created using @command{objcopy} and other
17587 standard utilities:
17590 # Extract the dynamic symbols from the main binary, there is no need
17591 # to also have these in the normal symbol table.
17592 nm -D @var{binary} --format=posix --defined-only \
17593 | awk '@{ print $1 @}' | sort > dynsyms
17595 # Extract all the text (i.e. function) symbols from the debuginfo.
17596 # (Note that we actually also accept "D" symbols, for the benefit
17597 # of platforms like PowerPC64 that use function descriptors.)
17598 nm @var{binary} --format=posix --defined-only \
17599 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17602 # Keep all the function symbols not already in the dynamic symbol
17604 comm -13 dynsyms funcsyms > keep_symbols
17606 # Separate full debug info into debug binary.
17607 objcopy --only-keep-debug @var{binary} debug
17609 # Copy the full debuginfo, keeping only a minimal set of symbols and
17610 # removing some unnecessary sections.
17611 objcopy -S --remove-section .gdb_index --remove-section .comment \
17612 --keep-symbols=keep_symbols debug mini_debuginfo
17614 # Drop the full debug info from the original binary.
17615 strip --strip-all -R .comment @var{binary}
17617 # Inject the compressed data into the .gnu_debugdata section of the
17620 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17624 @section Index Files Speed Up @value{GDBN}
17625 @cindex index files
17626 @cindex @samp{.gdb_index} section
17628 When @value{GDBN} finds a symbol file, it scans the symbols in the
17629 file in order to construct an internal symbol table. This lets most
17630 @value{GDBN} operations work quickly---at the cost of a delay early
17631 on. For large programs, this delay can be quite lengthy, so
17632 @value{GDBN} provides a way to build an index, which speeds up
17635 The index is stored as a section in the symbol file. @value{GDBN} can
17636 write the index to a file, then you can put it into the symbol file
17637 using @command{objcopy}.
17639 To create an index file, use the @code{save gdb-index} command:
17642 @item save gdb-index @var{directory}
17643 @kindex save gdb-index
17644 Create an index file for each symbol file currently known by
17645 @value{GDBN}. Each file is named after its corresponding symbol file,
17646 with @samp{.gdb-index} appended, and is written into the given
17650 Once you have created an index file you can merge it into your symbol
17651 file, here named @file{symfile}, using @command{objcopy}:
17654 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17655 --set-section-flags .gdb_index=readonly symfile symfile
17658 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17659 sections that have been deprecated. Usually they are deprecated because
17660 they are missing a new feature or have performance issues.
17661 To tell @value{GDBN} to use a deprecated index section anyway
17662 specify @code{set use-deprecated-index-sections on}.
17663 The default is @code{off}.
17664 This can speed up startup, but may result in some functionality being lost.
17665 @xref{Index Section Format}.
17667 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17668 must be done before gdb reads the file. The following will not work:
17671 $ gdb -ex "set use-deprecated-index-sections on" <program>
17674 Instead you must do, for example,
17677 $ gdb -iex "set use-deprecated-index-sections on" <program>
17680 There are currently some limitation on indices. They only work when
17681 for DWARF debugging information, not stabs. And, they do not
17682 currently work for programs using Ada.
17684 @node Symbol Errors
17685 @section Errors Reading Symbol Files
17687 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17688 such as symbol types it does not recognize, or known bugs in compiler
17689 output. By default, @value{GDBN} does not notify you of such problems, since
17690 they are relatively common and primarily of interest to people
17691 debugging compilers. If you are interested in seeing information
17692 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17693 only one message about each such type of problem, no matter how many
17694 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17695 to see how many times the problems occur, with the @code{set
17696 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17699 The messages currently printed, and their meanings, include:
17702 @item inner block not inside outer block in @var{symbol}
17704 The symbol information shows where symbol scopes begin and end
17705 (such as at the start of a function or a block of statements). This
17706 error indicates that an inner scope block is not fully contained
17707 in its outer scope blocks.
17709 @value{GDBN} circumvents the problem by treating the inner block as if it had
17710 the same scope as the outer block. In the error message, @var{symbol}
17711 may be shown as ``@code{(don't know)}'' if the outer block is not a
17714 @item block at @var{address} out of order
17716 The symbol information for symbol scope blocks should occur in
17717 order of increasing addresses. This error indicates that it does not
17720 @value{GDBN} does not circumvent this problem, and has trouble
17721 locating symbols in the source file whose symbols it is reading. (You
17722 can often determine what source file is affected by specifying
17723 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17726 @item bad block start address patched
17728 The symbol information for a symbol scope block has a start address
17729 smaller than the address of the preceding source line. This is known
17730 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17732 @value{GDBN} circumvents the problem by treating the symbol scope block as
17733 starting on the previous source line.
17735 @item bad string table offset in symbol @var{n}
17738 Symbol number @var{n} contains a pointer into the string table which is
17739 larger than the size of the string table.
17741 @value{GDBN} circumvents the problem by considering the symbol to have the
17742 name @code{foo}, which may cause other problems if many symbols end up
17745 @item unknown symbol type @code{0x@var{nn}}
17747 The symbol information contains new data types that @value{GDBN} does
17748 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17749 uncomprehended information, in hexadecimal.
17751 @value{GDBN} circumvents the error by ignoring this symbol information.
17752 This usually allows you to debug your program, though certain symbols
17753 are not accessible. If you encounter such a problem and feel like
17754 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17755 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17756 and examine @code{*bufp} to see the symbol.
17758 @item stub type has NULL name
17760 @value{GDBN} could not find the full definition for a struct or class.
17762 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17763 The symbol information for a C@t{++} member function is missing some
17764 information that recent versions of the compiler should have output for
17767 @item info mismatch between compiler and debugger
17769 @value{GDBN} could not parse a type specification output by the compiler.
17774 @section GDB Data Files
17776 @cindex prefix for data files
17777 @value{GDBN} will sometimes read an auxiliary data file. These files
17778 are kept in a directory known as the @dfn{data directory}.
17780 You can set the data directory's name, and view the name @value{GDBN}
17781 is currently using.
17784 @kindex set data-directory
17785 @item set data-directory @var{directory}
17786 Set the directory which @value{GDBN} searches for auxiliary data files
17787 to @var{directory}.
17789 @kindex show data-directory
17790 @item show data-directory
17791 Show the directory @value{GDBN} searches for auxiliary data files.
17794 @cindex default data directory
17795 @cindex @samp{--with-gdb-datadir}
17796 You can set the default data directory by using the configure-time
17797 @samp{--with-gdb-datadir} option. If the data directory is inside
17798 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17799 @samp{--exec-prefix}), then the default data directory will be updated
17800 automatically if the installed @value{GDBN} is moved to a new
17803 The data directory may also be specified with the
17804 @code{--data-directory} command line option.
17805 @xref{Mode Options}.
17808 @chapter Specifying a Debugging Target
17810 @cindex debugging target
17811 A @dfn{target} is the execution environment occupied by your program.
17813 Often, @value{GDBN} runs in the same host environment as your program;
17814 in that case, the debugging target is specified as a side effect when
17815 you use the @code{file} or @code{core} commands. When you need more
17816 flexibility---for example, running @value{GDBN} on a physically separate
17817 host, or controlling a standalone system over a serial port or a
17818 realtime system over a TCP/IP connection---you can use the @code{target}
17819 command to specify one of the target types configured for @value{GDBN}
17820 (@pxref{Target Commands, ,Commands for Managing Targets}).
17822 @cindex target architecture
17823 It is possible to build @value{GDBN} for several different @dfn{target
17824 architectures}. When @value{GDBN} is built like that, you can choose
17825 one of the available architectures with the @kbd{set architecture}
17829 @kindex set architecture
17830 @kindex show architecture
17831 @item set architecture @var{arch}
17832 This command sets the current target architecture to @var{arch}. The
17833 value of @var{arch} can be @code{"auto"}, in addition to one of the
17834 supported architectures.
17836 @item show architecture
17837 Show the current target architecture.
17839 @item set processor
17841 @kindex set processor
17842 @kindex show processor
17843 These are alias commands for, respectively, @code{set architecture}
17844 and @code{show architecture}.
17848 * Active Targets:: Active targets
17849 * Target Commands:: Commands for managing targets
17850 * Byte Order:: Choosing target byte order
17853 @node Active Targets
17854 @section Active Targets
17856 @cindex stacking targets
17857 @cindex active targets
17858 @cindex multiple targets
17860 There are multiple classes of targets such as: processes, executable files or
17861 recording sessions. Core files belong to the process class, making core file
17862 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17863 on multiple active targets, one in each class. This allows you to (for
17864 example) start a process and inspect its activity, while still having access to
17865 the executable file after the process finishes. Or if you start process
17866 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17867 presented a virtual layer of the recording target, while the process target
17868 remains stopped at the chronologically last point of the process execution.
17870 Use the @code{core-file} and @code{exec-file} commands to select a new core
17871 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17872 specify as a target a process that is already running, use the @code{attach}
17873 command (@pxref{Attach, ,Debugging an Already-running Process}).
17875 @node Target Commands
17876 @section Commands for Managing Targets
17879 @item target @var{type} @var{parameters}
17880 Connects the @value{GDBN} host environment to a target machine or
17881 process. A target is typically a protocol for talking to debugging
17882 facilities. You use the argument @var{type} to specify the type or
17883 protocol of the target machine.
17885 Further @var{parameters} are interpreted by the target protocol, but
17886 typically include things like device names or host names to connect
17887 with, process numbers, and baud rates.
17889 The @code{target} command does not repeat if you press @key{RET} again
17890 after executing the command.
17892 @kindex help target
17894 Displays the names of all targets available. To display targets
17895 currently selected, use either @code{info target} or @code{info files}
17896 (@pxref{Files, ,Commands to Specify Files}).
17898 @item help target @var{name}
17899 Describe a particular target, including any parameters necessary to
17902 @kindex set gnutarget
17903 @item set gnutarget @var{args}
17904 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17905 knows whether it is reading an @dfn{executable},
17906 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17907 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17908 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17911 @emph{Warning:} To specify a file format with @code{set gnutarget},
17912 you must know the actual BFD name.
17916 @xref{Files, , Commands to Specify Files}.
17918 @kindex show gnutarget
17919 @item show gnutarget
17920 Use the @code{show gnutarget} command to display what file format
17921 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17922 @value{GDBN} will determine the file format for each file automatically,
17923 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17926 @cindex common targets
17927 Here are some common targets (available, or not, depending on the GDB
17932 @item target exec @var{program}
17933 @cindex executable file target
17934 An executable file. @samp{target exec @var{program}} is the same as
17935 @samp{exec-file @var{program}}.
17937 @item target core @var{filename}
17938 @cindex core dump file target
17939 A core dump file. @samp{target core @var{filename}} is the same as
17940 @samp{core-file @var{filename}}.
17942 @item target remote @var{medium}
17943 @cindex remote target
17944 A remote system connected to @value{GDBN} via a serial line or network
17945 connection. This command tells @value{GDBN} to use its own remote
17946 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17948 For example, if you have a board connected to @file{/dev/ttya} on the
17949 machine running @value{GDBN}, you could say:
17952 target remote /dev/ttya
17955 @code{target remote} supports the @code{load} command. This is only
17956 useful if you have some other way of getting the stub to the target
17957 system, and you can put it somewhere in memory where it won't get
17958 clobbered by the download.
17960 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17961 @cindex built-in simulator target
17962 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17970 works; however, you cannot assume that a specific memory map, device
17971 drivers, or even basic I/O is available, although some simulators do
17972 provide these. For info about any processor-specific simulator details,
17973 see the appropriate section in @ref{Embedded Processors, ,Embedded
17978 Different targets are available on different configurations of @value{GDBN};
17979 your configuration may have more or fewer targets.
17981 Many remote targets require you to download the executable's code once
17982 you've successfully established a connection. You may wish to control
17983 various aspects of this process.
17988 @kindex set hash@r{, for remote monitors}
17989 @cindex hash mark while downloading
17990 This command controls whether a hash mark @samp{#} is displayed while
17991 downloading a file to the remote monitor. If on, a hash mark is
17992 displayed after each S-record is successfully downloaded to the
17996 @kindex show hash@r{, for remote monitors}
17997 Show the current status of displaying the hash mark.
17999 @item set debug monitor
18000 @kindex set debug monitor
18001 @cindex display remote monitor communications
18002 Enable or disable display of communications messages between
18003 @value{GDBN} and the remote monitor.
18005 @item show debug monitor
18006 @kindex show debug monitor
18007 Show the current status of displaying communications between
18008 @value{GDBN} and the remote monitor.
18013 @kindex load @var{filename}
18014 @item load @var{filename}
18016 Depending on what remote debugging facilities are configured into
18017 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18018 is meant to make @var{filename} (an executable) available for debugging
18019 on the remote system---by downloading, or dynamic linking, for example.
18020 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18021 the @code{add-symbol-file} command.
18023 If your @value{GDBN} does not have a @code{load} command, attempting to
18024 execute it gets the error message ``@code{You can't do that when your
18025 target is @dots{}}''
18027 The file is loaded at whatever address is specified in the executable.
18028 For some object file formats, you can specify the load address when you
18029 link the program; for other formats, like a.out, the object file format
18030 specifies a fixed address.
18031 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18033 Depending on the remote side capabilities, @value{GDBN} may be able to
18034 load programs into flash memory.
18036 @code{load} does not repeat if you press @key{RET} again after using it.
18040 @section Choosing Target Byte Order
18042 @cindex choosing target byte order
18043 @cindex target byte order
18045 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18046 offer the ability to run either big-endian or little-endian byte
18047 orders. Usually the executable or symbol will include a bit to
18048 designate the endian-ness, and you will not need to worry about
18049 which to use. However, you may still find it useful to adjust
18050 @value{GDBN}'s idea of processor endian-ness manually.
18054 @item set endian big
18055 Instruct @value{GDBN} to assume the target is big-endian.
18057 @item set endian little
18058 Instruct @value{GDBN} to assume the target is little-endian.
18060 @item set endian auto
18061 Instruct @value{GDBN} to use the byte order associated with the
18065 Display @value{GDBN}'s current idea of the target byte order.
18069 Note that these commands merely adjust interpretation of symbolic
18070 data on the host, and that they have absolutely no effect on the
18074 @node Remote Debugging
18075 @chapter Debugging Remote Programs
18076 @cindex remote debugging
18078 If you are trying to debug a program running on a machine that cannot run
18079 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18080 For example, you might use remote debugging on an operating system kernel,
18081 or on a small system which does not have a general purpose operating system
18082 powerful enough to run a full-featured debugger.
18084 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18085 to make this work with particular debugging targets. In addition,
18086 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18087 but not specific to any particular target system) which you can use if you
18088 write the remote stubs---the code that runs on the remote system to
18089 communicate with @value{GDBN}.
18091 Other remote targets may be available in your
18092 configuration of @value{GDBN}; use @code{help target} to list them.
18095 * Connecting:: Connecting to a remote target
18096 * File Transfer:: Sending files to a remote system
18097 * Server:: Using the gdbserver program
18098 * Remote Configuration:: Remote configuration
18099 * Remote Stub:: Implementing a remote stub
18103 @section Connecting to a Remote Target
18105 On the @value{GDBN} host machine, you will need an unstripped copy of
18106 your program, since @value{GDBN} needs symbol and debugging information.
18107 Start up @value{GDBN} as usual, using the name of the local copy of your
18108 program as the first argument.
18110 @cindex @code{target remote}
18111 @value{GDBN} can communicate with the target over a serial line, or
18112 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18113 each case, @value{GDBN} uses the same protocol for debugging your
18114 program; only the medium carrying the debugging packets varies. The
18115 @code{target remote} command establishes a connection to the target.
18116 Its arguments indicate which medium to use:
18120 @item target remote @var{serial-device}
18121 @cindex serial line, @code{target remote}
18122 Use @var{serial-device} to communicate with the target. For example,
18123 to use a serial line connected to the device named @file{/dev/ttyb}:
18126 target remote /dev/ttyb
18129 If you're using a serial line, you may want to give @value{GDBN} the
18130 @samp{--baud} option, or use the @code{set serial baud} command
18131 (@pxref{Remote Configuration, set serial baud}) before the
18132 @code{target} command.
18134 @item target remote @code{@var{host}:@var{port}}
18135 @itemx target remote @code{tcp:@var{host}:@var{port}}
18136 @cindex @acronym{TCP} port, @code{target remote}
18137 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18138 The @var{host} may be either a host name or a numeric @acronym{IP}
18139 address; @var{port} must be a decimal number. The @var{host} could be
18140 the target machine itself, if it is directly connected to the net, or
18141 it might be a terminal server which in turn has a serial line to the
18144 For example, to connect to port 2828 on a terminal server named
18148 target remote manyfarms:2828
18151 If your remote target is actually running on the same machine as your
18152 debugger session (e.g.@: a simulator for your target running on the
18153 same host), you can omit the hostname. For example, to connect to
18154 port 1234 on your local machine:
18157 target remote :1234
18161 Note that the colon is still required here.
18163 @item target remote @code{udp:@var{host}:@var{port}}
18164 @cindex @acronym{UDP} port, @code{target remote}
18165 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18166 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18169 target remote udp:manyfarms:2828
18172 When using a @acronym{UDP} connection for remote debugging, you should
18173 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18174 can silently drop packets on busy or unreliable networks, which will
18175 cause havoc with your debugging session.
18177 @item target remote | @var{command}
18178 @cindex pipe, @code{target remote} to
18179 Run @var{command} in the background and communicate with it using a
18180 pipe. The @var{command} is a shell command, to be parsed and expanded
18181 by the system's command shell, @code{/bin/sh}; it should expect remote
18182 protocol packets on its standard input, and send replies on its
18183 standard output. You could use this to run a stand-alone simulator
18184 that speaks the remote debugging protocol, to make net connections
18185 using programs like @code{ssh}, or for other similar tricks.
18187 If @var{command} closes its standard output (perhaps by exiting),
18188 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18189 program has already exited, this will have no effect.)
18193 Once the connection has been established, you can use all the usual
18194 commands to examine and change data. The remote program is already
18195 running; you can use @kbd{step} and @kbd{continue}, and you do not
18196 need to use @kbd{run}.
18198 @cindex interrupting remote programs
18199 @cindex remote programs, interrupting
18200 Whenever @value{GDBN} is waiting for the remote program, if you type the
18201 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18202 program. This may or may not succeed, depending in part on the hardware
18203 and the serial drivers the remote system uses. If you type the
18204 interrupt character once again, @value{GDBN} displays this prompt:
18207 Interrupted while waiting for the program.
18208 Give up (and stop debugging it)? (y or n)
18211 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18212 (If you decide you want to try again later, you can use @samp{target
18213 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18214 goes back to waiting.
18217 @kindex detach (remote)
18219 When you have finished debugging the remote program, you can use the
18220 @code{detach} command to release it from @value{GDBN} control.
18221 Detaching from the target normally resumes its execution, but the results
18222 will depend on your particular remote stub. After the @code{detach}
18223 command, @value{GDBN} is free to connect to another target.
18227 The @code{disconnect} command behaves like @code{detach}, except that
18228 the target is generally not resumed. It will wait for @value{GDBN}
18229 (this instance or another one) to connect and continue debugging. After
18230 the @code{disconnect} command, @value{GDBN} is again free to connect to
18233 @cindex send command to remote monitor
18234 @cindex extend @value{GDBN} for remote targets
18235 @cindex add new commands for external monitor
18237 @item monitor @var{cmd}
18238 This command allows you to send arbitrary commands directly to the
18239 remote monitor. Since @value{GDBN} doesn't care about the commands it
18240 sends like this, this command is the way to extend @value{GDBN}---you
18241 can add new commands that only the external monitor will understand
18245 @node File Transfer
18246 @section Sending files to a remote system
18247 @cindex remote target, file transfer
18248 @cindex file transfer
18249 @cindex sending files to remote systems
18251 Some remote targets offer the ability to transfer files over the same
18252 connection used to communicate with @value{GDBN}. This is convenient
18253 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18254 running @code{gdbserver} over a network interface. For other targets,
18255 e.g.@: embedded devices with only a single serial port, this may be
18256 the only way to upload or download files.
18258 Not all remote targets support these commands.
18262 @item remote put @var{hostfile} @var{targetfile}
18263 Copy file @var{hostfile} from the host system (the machine running
18264 @value{GDBN}) to @var{targetfile} on the target system.
18267 @item remote get @var{targetfile} @var{hostfile}
18268 Copy file @var{targetfile} from the target system to @var{hostfile}
18269 on the host system.
18271 @kindex remote delete
18272 @item remote delete @var{targetfile}
18273 Delete @var{targetfile} from the target system.
18278 @section Using the @code{gdbserver} Program
18281 @cindex remote connection without stubs
18282 @code{gdbserver} is a control program for Unix-like systems, which
18283 allows you to connect your program with a remote @value{GDBN} via
18284 @code{target remote}---but without linking in the usual debugging stub.
18286 @code{gdbserver} is not a complete replacement for the debugging stubs,
18287 because it requires essentially the same operating-system facilities
18288 that @value{GDBN} itself does. In fact, a system that can run
18289 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18290 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18291 because it is a much smaller program than @value{GDBN} itself. It is
18292 also easier to port than all of @value{GDBN}, so you may be able to get
18293 started more quickly on a new system by using @code{gdbserver}.
18294 Finally, if you develop code for real-time systems, you may find that
18295 the tradeoffs involved in real-time operation make it more convenient to
18296 do as much development work as possible on another system, for example
18297 by cross-compiling. You can use @code{gdbserver} to make a similar
18298 choice for debugging.
18300 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18301 or a TCP connection, using the standard @value{GDBN} remote serial
18305 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18306 Do not run @code{gdbserver} connected to any public network; a
18307 @value{GDBN} connection to @code{gdbserver} provides access to the
18308 target system with the same privileges as the user running
18312 @subsection Running @code{gdbserver}
18313 @cindex arguments, to @code{gdbserver}
18314 @cindex @code{gdbserver}, command-line arguments
18316 Run @code{gdbserver} on the target system. You need a copy of the
18317 program you want to debug, including any libraries it requires.
18318 @code{gdbserver} does not need your program's symbol table, so you can
18319 strip the program if necessary to save space. @value{GDBN} on the host
18320 system does all the symbol handling.
18322 To use the server, you must tell it how to communicate with @value{GDBN};
18323 the name of your program; and the arguments for your program. The usual
18327 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18330 @var{comm} is either a device name (to use a serial line), or a TCP
18331 hostname and portnumber, or @code{-} or @code{stdio} to use
18332 stdin/stdout of @code{gdbserver}.
18333 For example, to debug Emacs with the argument
18334 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18338 target> gdbserver /dev/com1 emacs foo.txt
18341 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18344 To use a TCP connection instead of a serial line:
18347 target> gdbserver host:2345 emacs foo.txt
18350 The only difference from the previous example is the first argument,
18351 specifying that you are communicating with the host @value{GDBN} via
18352 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18353 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18354 (Currently, the @samp{host} part is ignored.) You can choose any number
18355 you want for the port number as long as it does not conflict with any
18356 TCP ports already in use on the target system (for example, @code{23} is
18357 reserved for @code{telnet}).@footnote{If you choose a port number that
18358 conflicts with another service, @code{gdbserver} prints an error message
18359 and exits.} You must use the same port number with the host @value{GDBN}
18360 @code{target remote} command.
18362 The @code{stdio} connection is useful when starting @code{gdbserver}
18366 (gdb) target remote | ssh -T hostname gdbserver - hello
18369 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18370 and we don't want escape-character handling. Ssh does this by default when
18371 a command is provided, the flag is provided to make it explicit.
18372 You could elide it if you want to.
18374 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18375 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18376 display through a pipe connected to gdbserver.
18377 Both @code{stdout} and @code{stderr} use the same pipe.
18379 @subsubsection Attaching to a Running Program
18380 @cindex attach to a program, @code{gdbserver}
18381 @cindex @option{--attach}, @code{gdbserver} option
18383 On some targets, @code{gdbserver} can also attach to running programs.
18384 This is accomplished via the @code{--attach} argument. The syntax is:
18387 target> gdbserver --attach @var{comm} @var{pid}
18390 @var{pid} is the process ID of a currently running process. It isn't necessary
18391 to point @code{gdbserver} at a binary for the running process.
18394 You can debug processes by name instead of process ID if your target has the
18395 @code{pidof} utility:
18398 target> gdbserver --attach @var{comm} `pidof @var{program}`
18401 In case more than one copy of @var{program} is running, or @var{program}
18402 has multiple threads, most versions of @code{pidof} support the
18403 @code{-s} option to only return the first process ID.
18405 @subsubsection Multi-Process Mode for @code{gdbserver}
18406 @cindex @code{gdbserver}, multiple processes
18407 @cindex multiple processes with @code{gdbserver}
18409 When you connect to @code{gdbserver} using @code{target remote},
18410 @code{gdbserver} debugs the specified program only once. When the
18411 program exits, or you detach from it, @value{GDBN} closes the connection
18412 and @code{gdbserver} exits.
18414 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18415 enters multi-process mode. When the debugged program exits, or you
18416 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18417 though no program is running. The @code{run} and @code{attach}
18418 commands instruct @code{gdbserver} to run or attach to a new program.
18419 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18420 remote exec-file}) to select the program to run. Command line
18421 arguments are supported, except for wildcard expansion and I/O
18422 redirection (@pxref{Arguments}).
18424 @cindex @option{--multi}, @code{gdbserver} option
18425 To start @code{gdbserver} without supplying an initial command to run
18426 or process ID to attach, use the @option{--multi} command line option.
18427 Then you can connect using @kbd{target extended-remote} and start
18428 the program you want to debug.
18430 In multi-process mode @code{gdbserver} does not automatically exit unless you
18431 use the option @option{--once}. You can terminate it by using
18432 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18433 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18434 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18435 @option{--multi} option to @code{gdbserver} has no influence on that.
18437 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18439 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18441 @code{gdbserver} normally terminates after all of its debugged processes have
18442 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18443 extended-remote}, @code{gdbserver} stays running even with no processes left.
18444 @value{GDBN} normally terminates the spawned debugged process on its exit,
18445 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18446 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18447 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18448 stays running even in the @kbd{target remote} mode.
18450 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18451 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18452 completeness, at most one @value{GDBN} can be connected at a time.
18454 @cindex @option{--once}, @code{gdbserver} option
18455 By default, @code{gdbserver} keeps the listening TCP port open, so that
18456 subsequent connections are possible. However, if you start @code{gdbserver}
18457 with the @option{--once} option, it will stop listening for any further
18458 connection attempts after connecting to the first @value{GDBN} session. This
18459 means no further connections to @code{gdbserver} will be possible after the
18460 first one. It also means @code{gdbserver} will terminate after the first
18461 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18462 connections and even in the @kbd{target extended-remote} mode. The
18463 @option{--once} option allows reusing the same port number for connecting to
18464 multiple instances of @code{gdbserver} running on the same host, since each
18465 instance closes its port after the first connection.
18467 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18469 @cindex @option{--debug}, @code{gdbserver} option
18470 The @option{--debug} option tells @code{gdbserver} to display extra
18471 status information about the debugging process.
18472 @cindex @option{--remote-debug}, @code{gdbserver} option
18473 The @option{--remote-debug} option tells @code{gdbserver} to display
18474 remote protocol debug output. These options are intended for
18475 @code{gdbserver} development and for bug reports to the developers.
18477 @cindex @option{--wrapper}, @code{gdbserver} option
18478 The @option{--wrapper} option specifies a wrapper to launch programs
18479 for debugging. The option should be followed by the name of the
18480 wrapper, then any command-line arguments to pass to the wrapper, then
18481 @kbd{--} indicating the end of the wrapper arguments.
18483 @code{gdbserver} runs the specified wrapper program with a combined
18484 command line including the wrapper arguments, then the name of the
18485 program to debug, then any arguments to the program. The wrapper
18486 runs until it executes your program, and then @value{GDBN} gains control.
18488 You can use any program that eventually calls @code{execve} with
18489 its arguments as a wrapper. Several standard Unix utilities do
18490 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18491 with @code{exec "$@@"} will also work.
18493 For example, you can use @code{env} to pass an environment variable to
18494 the debugged program, without setting the variable in @code{gdbserver}'s
18498 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18501 @subsection Connecting to @code{gdbserver}
18503 Run @value{GDBN} on the host system.
18505 First make sure you have the necessary symbol files. Load symbols for
18506 your application using the @code{file} command before you connect. Use
18507 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18508 was compiled with the correct sysroot using @code{--with-sysroot}).
18510 The symbol file and target libraries must exactly match the executable
18511 and libraries on the target, with one exception: the files on the host
18512 system should not be stripped, even if the files on the target system
18513 are. Mismatched or missing files will lead to confusing results
18514 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18515 files may also prevent @code{gdbserver} from debugging multi-threaded
18518 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18519 For TCP connections, you must start up @code{gdbserver} prior to using
18520 the @code{target remote} command. Otherwise you may get an error whose
18521 text depends on the host system, but which usually looks something like
18522 @samp{Connection refused}. Don't use the @code{load}
18523 command in @value{GDBN} when using @code{gdbserver}, since the program is
18524 already on the target.
18526 @subsection Monitor Commands for @code{gdbserver}
18527 @cindex monitor commands, for @code{gdbserver}
18528 @anchor{Monitor Commands for gdbserver}
18530 During a @value{GDBN} session using @code{gdbserver}, you can use the
18531 @code{monitor} command to send special requests to @code{gdbserver}.
18532 Here are the available commands.
18536 List the available monitor commands.
18538 @item monitor set debug 0
18539 @itemx monitor set debug 1
18540 Disable or enable general debugging messages.
18542 @item monitor set remote-debug 0
18543 @itemx monitor set remote-debug 1
18544 Disable or enable specific debugging messages associated with the remote
18545 protocol (@pxref{Remote Protocol}).
18547 @item monitor set libthread-db-search-path [PATH]
18548 @cindex gdbserver, search path for @code{libthread_db}
18549 When this command is issued, @var{path} is a colon-separated list of
18550 directories to search for @code{libthread_db} (@pxref{Threads,,set
18551 libthread-db-search-path}). If you omit @var{path},
18552 @samp{libthread-db-search-path} will be reset to its default value.
18554 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18555 not supported in @code{gdbserver}.
18558 Tell gdbserver to exit immediately. This command should be followed by
18559 @code{disconnect} to close the debugging session. @code{gdbserver} will
18560 detach from any attached processes and kill any processes it created.
18561 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18562 of a multi-process mode debug session.
18566 @subsection Tracepoints support in @code{gdbserver}
18567 @cindex tracepoints support in @code{gdbserver}
18569 On some targets, @code{gdbserver} supports tracepoints, fast
18570 tracepoints and static tracepoints.
18572 For fast or static tracepoints to work, a special library called the
18573 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18574 This library is built and distributed as an integral part of
18575 @code{gdbserver}. In addition, support for static tracepoints
18576 requires building the in-process agent library with static tracepoints
18577 support. At present, the UST (LTTng Userspace Tracer,
18578 @url{http://lttng.org/ust}) tracing engine is supported. This support
18579 is automatically available if UST development headers are found in the
18580 standard include path when @code{gdbserver} is built, or if
18581 @code{gdbserver} was explicitly configured using @option{--with-ust}
18582 to point at such headers. You can explicitly disable the support
18583 using @option{--with-ust=no}.
18585 There are several ways to load the in-process agent in your program:
18588 @item Specifying it as dependency at link time
18590 You can link your program dynamically with the in-process agent
18591 library. On most systems, this is accomplished by adding
18592 @code{-linproctrace} to the link command.
18594 @item Using the system's preloading mechanisms
18596 You can force loading the in-process agent at startup time by using
18597 your system's support for preloading shared libraries. Many Unixes
18598 support the concept of preloading user defined libraries. In most
18599 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18600 in the environment. See also the description of @code{gdbserver}'s
18601 @option{--wrapper} command line option.
18603 @item Using @value{GDBN} to force loading the agent at run time
18605 On some systems, you can force the inferior to load a shared library,
18606 by calling a dynamic loader function in the inferior that takes care
18607 of dynamically looking up and loading a shared library. On most Unix
18608 systems, the function is @code{dlopen}. You'll use the @code{call}
18609 command for that. For example:
18612 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18615 Note that on most Unix systems, for the @code{dlopen} function to be
18616 available, the program needs to be linked with @code{-ldl}.
18619 On systems that have a userspace dynamic loader, like most Unix
18620 systems, when you connect to @code{gdbserver} using @code{target
18621 remote}, you'll find that the program is stopped at the dynamic
18622 loader's entry point, and no shared library has been loaded in the
18623 program's address space yet, including the in-process agent. In that
18624 case, before being able to use any of the fast or static tracepoints
18625 features, you need to let the loader run and load the shared
18626 libraries. The simplest way to do that is to run the program to the
18627 main procedure. E.g., if debugging a C or C@t{++} program, start
18628 @code{gdbserver} like so:
18631 $ gdbserver :9999 myprogram
18634 Start GDB and connect to @code{gdbserver} like so, and run to main:
18638 (@value{GDBP}) target remote myhost:9999
18639 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18640 (@value{GDBP}) b main
18641 (@value{GDBP}) continue
18644 The in-process tracing agent library should now be loaded into the
18645 process; you can confirm it with the @code{info sharedlibrary}
18646 command, which will list @file{libinproctrace.so} as loaded in the
18647 process. You are now ready to install fast tracepoints, list static
18648 tracepoint markers, probe static tracepoints markers, and start
18651 @node Remote Configuration
18652 @section Remote Configuration
18655 @kindex show remote
18656 This section documents the configuration options available when
18657 debugging remote programs. For the options related to the File I/O
18658 extensions of the remote protocol, see @ref{system,
18659 system-call-allowed}.
18662 @item set remoteaddresssize @var{bits}
18663 @cindex address size for remote targets
18664 @cindex bits in remote address
18665 Set the maximum size of address in a memory packet to the specified
18666 number of bits. @value{GDBN} will mask off the address bits above
18667 that number, when it passes addresses to the remote target. The
18668 default value is the number of bits in the target's address.
18670 @item show remoteaddresssize
18671 Show the current value of remote address size in bits.
18673 @item set serial baud @var{n}
18674 @cindex baud rate for remote targets
18675 Set the baud rate for the remote serial I/O to @var{n} baud. The
18676 value is used to set the speed of the serial port used for debugging
18679 @item show serial baud
18680 Show the current speed of the remote connection.
18682 @item set remotebreak
18683 @cindex interrupt remote programs
18684 @cindex BREAK signal instead of Ctrl-C
18685 @anchor{set remotebreak}
18686 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18687 when you type @kbd{Ctrl-c} to interrupt the program running
18688 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18689 character instead. The default is off, since most remote systems
18690 expect to see @samp{Ctrl-C} as the interrupt signal.
18692 @item show remotebreak
18693 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18694 interrupt the remote program.
18696 @item set remoteflow on
18697 @itemx set remoteflow off
18698 @kindex set remoteflow
18699 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18700 on the serial port used to communicate to the remote target.
18702 @item show remoteflow
18703 @kindex show remoteflow
18704 Show the current setting of hardware flow control.
18706 @item set remotelogbase @var{base}
18707 Set the base (a.k.a.@: radix) of logging serial protocol
18708 communications to @var{base}. Supported values of @var{base} are:
18709 @code{ascii}, @code{octal}, and @code{hex}. The default is
18712 @item show remotelogbase
18713 Show the current setting of the radix for logging remote serial
18716 @item set remotelogfile @var{file}
18717 @cindex record serial communications on file
18718 Record remote serial communications on the named @var{file}. The
18719 default is not to record at all.
18721 @item show remotelogfile.
18722 Show the current setting of the file name on which to record the
18723 serial communications.
18725 @item set remotetimeout @var{num}
18726 @cindex timeout for serial communications
18727 @cindex remote timeout
18728 Set the timeout limit to wait for the remote target to respond to
18729 @var{num} seconds. The default is 2 seconds.
18731 @item show remotetimeout
18732 Show the current number of seconds to wait for the remote target
18735 @cindex limit hardware breakpoints and watchpoints
18736 @cindex remote target, limit break- and watchpoints
18737 @anchor{set remote hardware-watchpoint-limit}
18738 @anchor{set remote hardware-breakpoint-limit}
18739 @item set remote hardware-watchpoint-limit @var{limit}
18740 @itemx set remote hardware-breakpoint-limit @var{limit}
18741 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18742 watchpoints. A limit of -1, the default, is treated as unlimited.
18744 @cindex limit hardware watchpoints length
18745 @cindex remote target, limit watchpoints length
18746 @anchor{set remote hardware-watchpoint-length-limit}
18747 @item set remote hardware-watchpoint-length-limit @var{limit}
18748 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18749 a remote hardware watchpoint. A limit of -1, the default, is treated
18752 @item show remote hardware-watchpoint-length-limit
18753 Show the current limit (in bytes) of the maximum length of
18754 a remote hardware watchpoint.
18756 @item set remote exec-file @var{filename}
18757 @itemx show remote exec-file
18758 @anchor{set remote exec-file}
18759 @cindex executable file, for remote target
18760 Select the file used for @code{run} with @code{target
18761 extended-remote}. This should be set to a filename valid on the
18762 target system. If it is not set, the target will use a default
18763 filename (e.g.@: the last program run).
18765 @item set remote interrupt-sequence
18766 @cindex interrupt remote programs
18767 @cindex select Ctrl-C, BREAK or BREAK-g
18768 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18769 @samp{BREAK-g} as the
18770 sequence to the remote target in order to interrupt the execution.
18771 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18772 is high level of serial line for some certain time.
18773 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18774 It is @code{BREAK} signal followed by character @code{g}.
18776 @item show interrupt-sequence
18777 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18778 is sent by @value{GDBN} to interrupt the remote program.
18779 @code{BREAK-g} is BREAK signal followed by @code{g} and
18780 also known as Magic SysRq g.
18782 @item set remote interrupt-on-connect
18783 @cindex send interrupt-sequence on start
18784 Specify whether interrupt-sequence is sent to remote target when
18785 @value{GDBN} connects to it. This is mostly needed when you debug
18786 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18787 which is known as Magic SysRq g in order to connect @value{GDBN}.
18789 @item show interrupt-on-connect
18790 Show whether interrupt-sequence is sent
18791 to remote target when @value{GDBN} connects to it.
18795 @item set tcp auto-retry on
18796 @cindex auto-retry, for remote TCP target
18797 Enable auto-retry for remote TCP connections. This is useful if the remote
18798 debugging agent is launched in parallel with @value{GDBN}; there is a race
18799 condition because the agent may not become ready to accept the connection
18800 before @value{GDBN} attempts to connect. When auto-retry is
18801 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18802 to establish the connection using the timeout specified by
18803 @code{set tcp connect-timeout}.
18805 @item set tcp auto-retry off
18806 Do not auto-retry failed TCP connections.
18808 @item show tcp auto-retry
18809 Show the current auto-retry setting.
18811 @item set tcp connect-timeout @var{seconds}
18812 @itemx set tcp connect-timeout unlimited
18813 @cindex connection timeout, for remote TCP target
18814 @cindex timeout, for remote target connection
18815 Set the timeout for establishing a TCP connection to the remote target to
18816 @var{seconds}. The timeout affects both polling to retry failed connections
18817 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18818 that are merely slow to complete, and represents an approximate cumulative
18819 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18820 @value{GDBN} will keep attempting to establish a connection forever,
18821 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18823 @item show tcp connect-timeout
18824 Show the current connection timeout setting.
18827 @cindex remote packets, enabling and disabling
18828 The @value{GDBN} remote protocol autodetects the packets supported by
18829 your debugging stub. If you need to override the autodetection, you
18830 can use these commands to enable or disable individual packets. Each
18831 packet can be set to @samp{on} (the remote target supports this
18832 packet), @samp{off} (the remote target does not support this packet),
18833 or @samp{auto} (detect remote target support for this packet). They
18834 all default to @samp{auto}. For more information about each packet,
18835 see @ref{Remote Protocol}.
18837 During normal use, you should not have to use any of these commands.
18838 If you do, that may be a bug in your remote debugging stub, or a bug
18839 in @value{GDBN}. You may want to report the problem to the
18840 @value{GDBN} developers.
18842 For each packet @var{name}, the command to enable or disable the
18843 packet is @code{set remote @var{name}-packet}. The available settings
18846 @multitable @columnfractions 0.28 0.32 0.25
18849 @tab Related Features
18851 @item @code{fetch-register}
18853 @tab @code{info registers}
18855 @item @code{set-register}
18859 @item @code{binary-download}
18861 @tab @code{load}, @code{set}
18863 @item @code{read-aux-vector}
18864 @tab @code{qXfer:auxv:read}
18865 @tab @code{info auxv}
18867 @item @code{symbol-lookup}
18868 @tab @code{qSymbol}
18869 @tab Detecting multiple threads
18871 @item @code{attach}
18872 @tab @code{vAttach}
18875 @item @code{verbose-resume}
18877 @tab Stepping or resuming multiple threads
18883 @item @code{software-breakpoint}
18887 @item @code{hardware-breakpoint}
18891 @item @code{write-watchpoint}
18895 @item @code{read-watchpoint}
18899 @item @code{access-watchpoint}
18903 @item @code{target-features}
18904 @tab @code{qXfer:features:read}
18905 @tab @code{set architecture}
18907 @item @code{library-info}
18908 @tab @code{qXfer:libraries:read}
18909 @tab @code{info sharedlibrary}
18911 @item @code{memory-map}
18912 @tab @code{qXfer:memory-map:read}
18913 @tab @code{info mem}
18915 @item @code{read-sdata-object}
18916 @tab @code{qXfer:sdata:read}
18917 @tab @code{print $_sdata}
18919 @item @code{read-spu-object}
18920 @tab @code{qXfer:spu:read}
18921 @tab @code{info spu}
18923 @item @code{write-spu-object}
18924 @tab @code{qXfer:spu:write}
18925 @tab @code{info spu}
18927 @item @code{read-siginfo-object}
18928 @tab @code{qXfer:siginfo:read}
18929 @tab @code{print $_siginfo}
18931 @item @code{write-siginfo-object}
18932 @tab @code{qXfer:siginfo:write}
18933 @tab @code{set $_siginfo}
18935 @item @code{threads}
18936 @tab @code{qXfer:threads:read}
18937 @tab @code{info threads}
18939 @item @code{get-thread-local-@*storage-address}
18940 @tab @code{qGetTLSAddr}
18941 @tab Displaying @code{__thread} variables
18943 @item @code{get-thread-information-block-address}
18944 @tab @code{qGetTIBAddr}
18945 @tab Display MS-Windows Thread Information Block.
18947 @item @code{search-memory}
18948 @tab @code{qSearch:memory}
18951 @item @code{supported-packets}
18952 @tab @code{qSupported}
18953 @tab Remote communications parameters
18955 @item @code{pass-signals}
18956 @tab @code{QPassSignals}
18957 @tab @code{handle @var{signal}}
18959 @item @code{program-signals}
18960 @tab @code{QProgramSignals}
18961 @tab @code{handle @var{signal}}
18963 @item @code{hostio-close-packet}
18964 @tab @code{vFile:close}
18965 @tab @code{remote get}, @code{remote put}
18967 @item @code{hostio-open-packet}
18968 @tab @code{vFile:open}
18969 @tab @code{remote get}, @code{remote put}
18971 @item @code{hostio-pread-packet}
18972 @tab @code{vFile:pread}
18973 @tab @code{remote get}, @code{remote put}
18975 @item @code{hostio-pwrite-packet}
18976 @tab @code{vFile:pwrite}
18977 @tab @code{remote get}, @code{remote put}
18979 @item @code{hostio-unlink-packet}
18980 @tab @code{vFile:unlink}
18981 @tab @code{remote delete}
18983 @item @code{hostio-readlink-packet}
18984 @tab @code{vFile:readlink}
18987 @item @code{noack-packet}
18988 @tab @code{QStartNoAckMode}
18989 @tab Packet acknowledgment
18991 @item @code{osdata}
18992 @tab @code{qXfer:osdata:read}
18993 @tab @code{info os}
18995 @item @code{query-attached}
18996 @tab @code{qAttached}
18997 @tab Querying remote process attach state.
18999 @item @code{trace-buffer-size}
19000 @tab @code{QTBuffer:size}
19001 @tab @code{set trace-buffer-size}
19003 @item @code{trace-status}
19004 @tab @code{qTStatus}
19005 @tab @code{tstatus}
19007 @item @code{traceframe-info}
19008 @tab @code{qXfer:traceframe-info:read}
19009 @tab Traceframe info
19011 @item @code{install-in-trace}
19012 @tab @code{InstallInTrace}
19013 @tab Install tracepoint in tracing
19015 @item @code{disable-randomization}
19016 @tab @code{QDisableRandomization}
19017 @tab @code{set disable-randomization}
19019 @item @code{conditional-breakpoints-packet}
19020 @tab @code{Z0 and Z1}
19021 @tab @code{Support for target-side breakpoint condition evaluation}
19025 @section Implementing a Remote Stub
19027 @cindex debugging stub, example
19028 @cindex remote stub, example
19029 @cindex stub example, remote debugging
19030 The stub files provided with @value{GDBN} implement the target side of the
19031 communication protocol, and the @value{GDBN} side is implemented in the
19032 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19033 these subroutines to communicate, and ignore the details. (If you're
19034 implementing your own stub file, you can still ignore the details: start
19035 with one of the existing stub files. @file{sparc-stub.c} is the best
19036 organized, and therefore the easiest to read.)
19038 @cindex remote serial debugging, overview
19039 To debug a program running on another machine (the debugging
19040 @dfn{target} machine), you must first arrange for all the usual
19041 prerequisites for the program to run by itself. For example, for a C
19046 A startup routine to set up the C runtime environment; these usually
19047 have a name like @file{crt0}. The startup routine may be supplied by
19048 your hardware supplier, or you may have to write your own.
19051 A C subroutine library to support your program's
19052 subroutine calls, notably managing input and output.
19055 A way of getting your program to the other machine---for example, a
19056 download program. These are often supplied by the hardware
19057 manufacturer, but you may have to write your own from hardware
19061 The next step is to arrange for your program to use a serial port to
19062 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19063 machine). In general terms, the scheme looks like this:
19067 @value{GDBN} already understands how to use this protocol; when everything
19068 else is set up, you can simply use the @samp{target remote} command
19069 (@pxref{Targets,,Specifying a Debugging Target}).
19071 @item On the target,
19072 you must link with your program a few special-purpose subroutines that
19073 implement the @value{GDBN} remote serial protocol. The file containing these
19074 subroutines is called a @dfn{debugging stub}.
19076 On certain remote targets, you can use an auxiliary program
19077 @code{gdbserver} instead of linking a stub into your program.
19078 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19081 The debugging stub is specific to the architecture of the remote
19082 machine; for example, use @file{sparc-stub.c} to debug programs on
19085 @cindex remote serial stub list
19086 These working remote stubs are distributed with @value{GDBN}:
19091 @cindex @file{i386-stub.c}
19094 For Intel 386 and compatible architectures.
19097 @cindex @file{m68k-stub.c}
19098 @cindex Motorola 680x0
19100 For Motorola 680x0 architectures.
19103 @cindex @file{sh-stub.c}
19106 For Renesas SH architectures.
19109 @cindex @file{sparc-stub.c}
19111 For @sc{sparc} architectures.
19113 @item sparcl-stub.c
19114 @cindex @file{sparcl-stub.c}
19117 For Fujitsu @sc{sparclite} architectures.
19121 The @file{README} file in the @value{GDBN} distribution may list other
19122 recently added stubs.
19125 * Stub Contents:: What the stub can do for you
19126 * Bootstrapping:: What you must do for the stub
19127 * Debug Session:: Putting it all together
19130 @node Stub Contents
19131 @subsection What the Stub Can Do for You
19133 @cindex remote serial stub
19134 The debugging stub for your architecture supplies these three
19138 @item set_debug_traps
19139 @findex set_debug_traps
19140 @cindex remote serial stub, initialization
19141 This routine arranges for @code{handle_exception} to run when your
19142 program stops. You must call this subroutine explicitly in your
19143 program's startup code.
19145 @item handle_exception
19146 @findex handle_exception
19147 @cindex remote serial stub, main routine
19148 This is the central workhorse, but your program never calls it
19149 explicitly---the setup code arranges for @code{handle_exception} to
19150 run when a trap is triggered.
19152 @code{handle_exception} takes control when your program stops during
19153 execution (for example, on a breakpoint), and mediates communications
19154 with @value{GDBN} on the host machine. This is where the communications
19155 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19156 representative on the target machine. It begins by sending summary
19157 information on the state of your program, then continues to execute,
19158 retrieving and transmitting any information @value{GDBN} needs, until you
19159 execute a @value{GDBN} command that makes your program resume; at that point,
19160 @code{handle_exception} returns control to your own code on the target
19164 @cindex @code{breakpoint} subroutine, remote
19165 Use this auxiliary subroutine to make your program contain a
19166 breakpoint. Depending on the particular situation, this may be the only
19167 way for @value{GDBN} to get control. For instance, if your target
19168 machine has some sort of interrupt button, you won't need to call this;
19169 pressing the interrupt button transfers control to
19170 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19171 simply receiving characters on the serial port may also trigger a trap;
19172 again, in that situation, you don't need to call @code{breakpoint} from
19173 your own program---simply running @samp{target remote} from the host
19174 @value{GDBN} session gets control.
19176 Call @code{breakpoint} if none of these is true, or if you simply want
19177 to make certain your program stops at a predetermined point for the
19178 start of your debugging session.
19181 @node Bootstrapping
19182 @subsection What You Must Do for the Stub
19184 @cindex remote stub, support routines
19185 The debugging stubs that come with @value{GDBN} are set up for a particular
19186 chip architecture, but they have no information about the rest of your
19187 debugging target machine.
19189 First of all you need to tell the stub how to communicate with the
19193 @item int getDebugChar()
19194 @findex getDebugChar
19195 Write this subroutine to read a single character from the serial port.
19196 It may be identical to @code{getchar} for your target system; a
19197 different name is used to allow you to distinguish the two if you wish.
19199 @item void putDebugChar(int)
19200 @findex putDebugChar
19201 Write this subroutine to write a single character to the serial port.
19202 It may be identical to @code{putchar} for your target system; a
19203 different name is used to allow you to distinguish the two if you wish.
19206 @cindex control C, and remote debugging
19207 @cindex interrupting remote targets
19208 If you want @value{GDBN} to be able to stop your program while it is
19209 running, you need to use an interrupt-driven serial driver, and arrange
19210 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19211 character). That is the character which @value{GDBN} uses to tell the
19212 remote system to stop.
19214 Getting the debugging target to return the proper status to @value{GDBN}
19215 probably requires changes to the standard stub; one quick and dirty way
19216 is to just execute a breakpoint instruction (the ``dirty'' part is that
19217 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19219 Other routines you need to supply are:
19222 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19223 @findex exceptionHandler
19224 Write this function to install @var{exception_address} in the exception
19225 handling tables. You need to do this because the stub does not have any
19226 way of knowing what the exception handling tables on your target system
19227 are like (for example, the processor's table might be in @sc{rom},
19228 containing entries which point to a table in @sc{ram}).
19229 @var{exception_number} is the exception number which should be changed;
19230 its meaning is architecture-dependent (for example, different numbers
19231 might represent divide by zero, misaligned access, etc). When this
19232 exception occurs, control should be transferred directly to
19233 @var{exception_address}, and the processor state (stack, registers,
19234 and so on) should be just as it is when a processor exception occurs. So if
19235 you want to use a jump instruction to reach @var{exception_address}, it
19236 should be a simple jump, not a jump to subroutine.
19238 For the 386, @var{exception_address} should be installed as an interrupt
19239 gate so that interrupts are masked while the handler runs. The gate
19240 should be at privilege level 0 (the most privileged level). The
19241 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19242 help from @code{exceptionHandler}.
19244 @item void flush_i_cache()
19245 @findex flush_i_cache
19246 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19247 instruction cache, if any, on your target machine. If there is no
19248 instruction cache, this subroutine may be a no-op.
19250 On target machines that have instruction caches, @value{GDBN} requires this
19251 function to make certain that the state of your program is stable.
19255 You must also make sure this library routine is available:
19258 @item void *memset(void *, int, int)
19260 This is the standard library function @code{memset} that sets an area of
19261 memory to a known value. If you have one of the free versions of
19262 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19263 either obtain it from your hardware manufacturer, or write your own.
19266 If you do not use the GNU C compiler, you may need other standard
19267 library subroutines as well; this varies from one stub to another,
19268 but in general the stubs are likely to use any of the common library
19269 subroutines which @code{@value{NGCC}} generates as inline code.
19272 @node Debug Session
19273 @subsection Putting it All Together
19275 @cindex remote serial debugging summary
19276 In summary, when your program is ready to debug, you must follow these
19281 Make sure you have defined the supporting low-level routines
19282 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19284 @code{getDebugChar}, @code{putDebugChar},
19285 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19289 Insert these lines in your program's startup code, before the main
19290 procedure is called:
19297 On some machines, when a breakpoint trap is raised, the hardware
19298 automatically makes the PC point to the instruction after the
19299 breakpoint. If your machine doesn't do that, you may need to adjust
19300 @code{handle_exception} to arrange for it to return to the instruction
19301 after the breakpoint on this first invocation, so that your program
19302 doesn't keep hitting the initial breakpoint instead of making
19306 For the 680x0 stub only, you need to provide a variable called
19307 @code{exceptionHook}. Normally you just use:
19310 void (*exceptionHook)() = 0;
19314 but if before calling @code{set_debug_traps}, you set it to point to a
19315 function in your program, that function is called when
19316 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19317 error). The function indicated by @code{exceptionHook} is called with
19318 one parameter: an @code{int} which is the exception number.
19321 Compile and link together: your program, the @value{GDBN} debugging stub for
19322 your target architecture, and the supporting subroutines.
19325 Make sure you have a serial connection between your target machine and
19326 the @value{GDBN} host, and identify the serial port on the host.
19329 @c The "remote" target now provides a `load' command, so we should
19330 @c document that. FIXME.
19331 Download your program to your target machine (or get it there by
19332 whatever means the manufacturer provides), and start it.
19335 Start @value{GDBN} on the host, and connect to the target
19336 (@pxref{Connecting,,Connecting to a Remote Target}).
19340 @node Configurations
19341 @chapter Configuration-Specific Information
19343 While nearly all @value{GDBN} commands are available for all native and
19344 cross versions of the debugger, there are some exceptions. This chapter
19345 describes things that are only available in certain configurations.
19347 There are three major categories of configurations: native
19348 configurations, where the host and target are the same, embedded
19349 operating system configurations, which are usually the same for several
19350 different processor architectures, and bare embedded processors, which
19351 are quite different from each other.
19356 * Embedded Processors::
19363 This section describes details specific to particular native
19368 * BSD libkvm Interface:: Debugging BSD kernel memory images
19369 * SVR4 Process Information:: SVR4 process information
19370 * DJGPP Native:: Features specific to the DJGPP port
19371 * Cygwin Native:: Features specific to the Cygwin port
19372 * Hurd Native:: Features specific to @sc{gnu} Hurd
19373 * Darwin:: Features specific to Darwin
19379 On HP-UX systems, if you refer to a function or variable name that
19380 begins with a dollar sign, @value{GDBN} searches for a user or system
19381 name first, before it searches for a convenience variable.
19384 @node BSD libkvm Interface
19385 @subsection BSD libkvm Interface
19388 @cindex kernel memory image
19389 @cindex kernel crash dump
19391 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19392 interface that provides a uniform interface for accessing kernel virtual
19393 memory images, including live systems and crash dumps. @value{GDBN}
19394 uses this interface to allow you to debug live kernels and kernel crash
19395 dumps on many native BSD configurations. This is implemented as a
19396 special @code{kvm} debugging target. For debugging a live system, load
19397 the currently running kernel into @value{GDBN} and connect to the
19401 (@value{GDBP}) @b{target kvm}
19404 For debugging crash dumps, provide the file name of the crash dump as an
19408 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19411 Once connected to the @code{kvm} target, the following commands are
19417 Set current context from the @dfn{Process Control Block} (PCB) address.
19420 Set current context from proc address. This command isn't available on
19421 modern FreeBSD systems.
19424 @node SVR4 Process Information
19425 @subsection SVR4 Process Information
19427 @cindex examine process image
19428 @cindex process info via @file{/proc}
19430 Many versions of SVR4 and compatible systems provide a facility called
19431 @samp{/proc} that can be used to examine the image of a running
19432 process using file-system subroutines.
19434 If @value{GDBN} is configured for an operating system with this
19435 facility, the command @code{info proc} is available to report
19436 information about the process running your program, or about any
19437 process running on your system. This includes, as of this writing,
19438 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19439 not HP-UX, for example.
19441 This command may also work on core files that were created on a system
19442 that has the @samp{/proc} facility.
19448 @itemx info proc @var{process-id}
19449 Summarize available information about any running process. If a
19450 process ID is specified by @var{process-id}, display information about
19451 that process; otherwise display information about the program being
19452 debugged. The summary includes the debugged process ID, the command
19453 line used to invoke it, its current working directory, and its
19454 executable file's absolute file name.
19456 On some systems, @var{process-id} can be of the form
19457 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19458 within a process. If the optional @var{pid} part is missing, it means
19459 a thread from the process being debugged (the leading @samp{/} still
19460 needs to be present, or else @value{GDBN} will interpret the number as
19461 a process ID rather than a thread ID).
19463 @item info proc cmdline
19464 @cindex info proc cmdline
19465 Show the original command line of the process. This command is
19466 specific to @sc{gnu}/Linux.
19468 @item info proc cwd
19469 @cindex info proc cwd
19470 Show the current working directory of the process. This command is
19471 specific to @sc{gnu}/Linux.
19473 @item info proc exe
19474 @cindex info proc exe
19475 Show the name of executable of the process. This command is specific
19478 @item info proc mappings
19479 @cindex memory address space mappings
19480 Report the memory address space ranges accessible in the program, with
19481 information on whether the process has read, write, or execute access
19482 rights to each range. On @sc{gnu}/Linux systems, each memory range
19483 includes the object file which is mapped to that range, instead of the
19484 memory access rights to that range.
19486 @item info proc stat
19487 @itemx info proc status
19488 @cindex process detailed status information
19489 These subcommands are specific to @sc{gnu}/Linux systems. They show
19490 the process-related information, including the user ID and group ID;
19491 how many threads are there in the process; its virtual memory usage;
19492 the signals that are pending, blocked, and ignored; its TTY; its
19493 consumption of system and user time; its stack size; its @samp{nice}
19494 value; etc. For more information, see the @samp{proc} man page
19495 (type @kbd{man 5 proc} from your shell prompt).
19497 @item info proc all
19498 Show all the information about the process described under all of the
19499 above @code{info proc} subcommands.
19502 @comment These sub-options of 'info proc' were not included when
19503 @comment procfs.c was re-written. Keep their descriptions around
19504 @comment against the day when someone finds the time to put them back in.
19505 @kindex info proc times
19506 @item info proc times
19507 Starting time, user CPU time, and system CPU time for your program and
19510 @kindex info proc id
19512 Report on the process IDs related to your program: its own process ID,
19513 the ID of its parent, the process group ID, and the session ID.
19516 @item set procfs-trace
19517 @kindex set procfs-trace
19518 @cindex @code{procfs} API calls
19519 This command enables and disables tracing of @code{procfs} API calls.
19521 @item show procfs-trace
19522 @kindex show procfs-trace
19523 Show the current state of @code{procfs} API call tracing.
19525 @item set procfs-file @var{file}
19526 @kindex set procfs-file
19527 Tell @value{GDBN} to write @code{procfs} API trace to the named
19528 @var{file}. @value{GDBN} appends the trace info to the previous
19529 contents of the file. The default is to display the trace on the
19532 @item show procfs-file
19533 @kindex show procfs-file
19534 Show the file to which @code{procfs} API trace is written.
19536 @item proc-trace-entry
19537 @itemx proc-trace-exit
19538 @itemx proc-untrace-entry
19539 @itemx proc-untrace-exit
19540 @kindex proc-trace-entry
19541 @kindex proc-trace-exit
19542 @kindex proc-untrace-entry
19543 @kindex proc-untrace-exit
19544 These commands enable and disable tracing of entries into and exits
19545 from the @code{syscall} interface.
19548 @kindex info pidlist
19549 @cindex process list, QNX Neutrino
19550 For QNX Neutrino only, this command displays the list of all the
19551 processes and all the threads within each process.
19554 @kindex info meminfo
19555 @cindex mapinfo list, QNX Neutrino
19556 For QNX Neutrino only, this command displays the list of all mapinfos.
19560 @subsection Features for Debugging @sc{djgpp} Programs
19561 @cindex @sc{djgpp} debugging
19562 @cindex native @sc{djgpp} debugging
19563 @cindex MS-DOS-specific commands
19566 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19567 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19568 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19569 top of real-mode DOS systems and their emulations.
19571 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19572 defines a few commands specific to the @sc{djgpp} port. This
19573 subsection describes those commands.
19578 This is a prefix of @sc{djgpp}-specific commands which print
19579 information about the target system and important OS structures.
19582 @cindex MS-DOS system info
19583 @cindex free memory information (MS-DOS)
19584 @item info dos sysinfo
19585 This command displays assorted information about the underlying
19586 platform: the CPU type and features, the OS version and flavor, the
19587 DPMI version, and the available conventional and DPMI memory.
19592 @cindex segment descriptor tables
19593 @cindex descriptor tables display
19595 @itemx info dos ldt
19596 @itemx info dos idt
19597 These 3 commands display entries from, respectively, Global, Local,
19598 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19599 tables are data structures which store a descriptor for each segment
19600 that is currently in use. The segment's selector is an index into a
19601 descriptor table; the table entry for that index holds the
19602 descriptor's base address and limit, and its attributes and access
19605 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19606 segment (used for both data and the stack), and a DOS segment (which
19607 allows access to DOS/BIOS data structures and absolute addresses in
19608 conventional memory). However, the DPMI host will usually define
19609 additional segments in order to support the DPMI environment.
19611 @cindex garbled pointers
19612 These commands allow to display entries from the descriptor tables.
19613 Without an argument, all entries from the specified table are
19614 displayed. An argument, which should be an integer expression, means
19615 display a single entry whose index is given by the argument. For
19616 example, here's a convenient way to display information about the
19617 debugged program's data segment:
19620 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19621 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19625 This comes in handy when you want to see whether a pointer is outside
19626 the data segment's limit (i.e.@: @dfn{garbled}).
19628 @cindex page tables display (MS-DOS)
19630 @itemx info dos pte
19631 These two commands display entries from, respectively, the Page
19632 Directory and the Page Tables. Page Directories and Page Tables are
19633 data structures which control how virtual memory addresses are mapped
19634 into physical addresses. A Page Table includes an entry for every
19635 page of memory that is mapped into the program's address space; there
19636 may be several Page Tables, each one holding up to 4096 entries. A
19637 Page Directory has up to 4096 entries, one each for every Page Table
19638 that is currently in use.
19640 Without an argument, @kbd{info dos pde} displays the entire Page
19641 Directory, and @kbd{info dos pte} displays all the entries in all of
19642 the Page Tables. An argument, an integer expression, given to the
19643 @kbd{info dos pde} command means display only that entry from the Page
19644 Directory table. An argument given to the @kbd{info dos pte} command
19645 means display entries from a single Page Table, the one pointed to by
19646 the specified entry in the Page Directory.
19648 @cindex direct memory access (DMA) on MS-DOS
19649 These commands are useful when your program uses @dfn{DMA} (Direct
19650 Memory Access), which needs physical addresses to program the DMA
19653 These commands are supported only with some DPMI servers.
19655 @cindex physical address from linear address
19656 @item info dos address-pte @var{addr}
19657 This command displays the Page Table entry for a specified linear
19658 address. The argument @var{addr} is a linear address which should
19659 already have the appropriate segment's base address added to it,
19660 because this command accepts addresses which may belong to @emph{any}
19661 segment. For example, here's how to display the Page Table entry for
19662 the page where a variable @code{i} is stored:
19665 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19666 @exdent @code{Page Table entry for address 0x11a00d30:}
19667 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19671 This says that @code{i} is stored at offset @code{0xd30} from the page
19672 whose physical base address is @code{0x02698000}, and shows all the
19673 attributes of that page.
19675 Note that you must cast the addresses of variables to a @code{char *},
19676 since otherwise the value of @code{__djgpp_base_address}, the base
19677 address of all variables and functions in a @sc{djgpp} program, will
19678 be added using the rules of C pointer arithmetics: if @code{i} is
19679 declared an @code{int}, @value{GDBN} will add 4 times the value of
19680 @code{__djgpp_base_address} to the address of @code{i}.
19682 Here's another example, it displays the Page Table entry for the
19686 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19687 @exdent @code{Page Table entry for address 0x29110:}
19688 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19692 (The @code{+ 3} offset is because the transfer buffer's address is the
19693 3rd member of the @code{_go32_info_block} structure.) The output
19694 clearly shows that this DPMI server maps the addresses in conventional
19695 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19696 linear (@code{0x29110}) addresses are identical.
19698 This command is supported only with some DPMI servers.
19701 @cindex DOS serial data link, remote debugging
19702 In addition to native debugging, the DJGPP port supports remote
19703 debugging via a serial data link. The following commands are specific
19704 to remote serial debugging in the DJGPP port of @value{GDBN}.
19707 @kindex set com1base
19708 @kindex set com1irq
19709 @kindex set com2base
19710 @kindex set com2irq
19711 @kindex set com3base
19712 @kindex set com3irq
19713 @kindex set com4base
19714 @kindex set com4irq
19715 @item set com1base @var{addr}
19716 This command sets the base I/O port address of the @file{COM1} serial
19719 @item set com1irq @var{irq}
19720 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19721 for the @file{COM1} serial port.
19723 There are similar commands @samp{set com2base}, @samp{set com3irq},
19724 etc.@: for setting the port address and the @code{IRQ} lines for the
19727 @kindex show com1base
19728 @kindex show com1irq
19729 @kindex show com2base
19730 @kindex show com2irq
19731 @kindex show com3base
19732 @kindex show com3irq
19733 @kindex show com4base
19734 @kindex show com4irq
19735 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19736 display the current settings of the base address and the @code{IRQ}
19737 lines used by the COM ports.
19740 @kindex info serial
19741 @cindex DOS serial port status
19742 This command prints the status of the 4 DOS serial ports. For each
19743 port, it prints whether it's active or not, its I/O base address and
19744 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19745 counts of various errors encountered so far.
19749 @node Cygwin Native
19750 @subsection Features for Debugging MS Windows PE Executables
19751 @cindex MS Windows debugging
19752 @cindex native Cygwin debugging
19753 @cindex Cygwin-specific commands
19755 @value{GDBN} supports native debugging of MS Windows programs, including
19756 DLLs with and without symbolic debugging information.
19758 @cindex Ctrl-BREAK, MS-Windows
19759 @cindex interrupt debuggee on MS-Windows
19760 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19761 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19762 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19763 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19764 sequence, which can be used to interrupt the debuggee even if it
19767 There are various additional Cygwin-specific commands, described in
19768 this section. Working with DLLs that have no debugging symbols is
19769 described in @ref{Non-debug DLL Symbols}.
19774 This is a prefix of MS Windows-specific commands which print
19775 information about the target system and important OS structures.
19777 @item info w32 selector
19778 This command displays information returned by
19779 the Win32 API @code{GetThreadSelectorEntry} function.
19780 It takes an optional argument that is evaluated to
19781 a long value to give the information about this given selector.
19782 Without argument, this command displays information
19783 about the six segment registers.
19785 @item info w32 thread-information-block
19786 This command displays thread specific information stored in the
19787 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19788 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19792 This is a Cygwin-specific alias of @code{info shared}.
19794 @kindex dll-symbols
19796 This command loads symbols from a dll similarly to
19797 add-sym command but without the need to specify a base address.
19799 @kindex set cygwin-exceptions
19800 @cindex debugging the Cygwin DLL
19801 @cindex Cygwin DLL, debugging
19802 @item set cygwin-exceptions @var{mode}
19803 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19804 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19805 @value{GDBN} will delay recognition of exceptions, and may ignore some
19806 exceptions which seem to be caused by internal Cygwin DLL
19807 ``bookkeeping''. This option is meant primarily for debugging the
19808 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19809 @value{GDBN} users with false @code{SIGSEGV} signals.
19811 @kindex show cygwin-exceptions
19812 @item show cygwin-exceptions
19813 Displays whether @value{GDBN} will break on exceptions that happen
19814 inside the Cygwin DLL itself.
19816 @kindex set new-console
19817 @item set new-console @var{mode}
19818 If @var{mode} is @code{on} the debuggee will
19819 be started in a new console on next start.
19820 If @var{mode} is @code{off}, the debuggee will
19821 be started in the same console as the debugger.
19823 @kindex show new-console
19824 @item show new-console
19825 Displays whether a new console is used
19826 when the debuggee is started.
19828 @kindex set new-group
19829 @item set new-group @var{mode}
19830 This boolean value controls whether the debuggee should
19831 start a new group or stay in the same group as the debugger.
19832 This affects the way the Windows OS handles
19835 @kindex show new-group
19836 @item show new-group
19837 Displays current value of new-group boolean.
19839 @kindex set debugevents
19840 @item set debugevents
19841 This boolean value adds debug output concerning kernel events related
19842 to the debuggee seen by the debugger. This includes events that
19843 signal thread and process creation and exit, DLL loading and
19844 unloading, console interrupts, and debugging messages produced by the
19845 Windows @code{OutputDebugString} API call.
19847 @kindex set debugexec
19848 @item set debugexec
19849 This boolean value adds debug output concerning execute events
19850 (such as resume thread) seen by the debugger.
19852 @kindex set debugexceptions
19853 @item set debugexceptions
19854 This boolean value adds debug output concerning exceptions in the
19855 debuggee seen by the debugger.
19857 @kindex set debugmemory
19858 @item set debugmemory
19859 This boolean value adds debug output concerning debuggee memory reads
19860 and writes by the debugger.
19864 This boolean values specifies whether the debuggee is called
19865 via a shell or directly (default value is on).
19869 Displays if the debuggee will be started with a shell.
19874 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19877 @node Non-debug DLL Symbols
19878 @subsubsection Support for DLLs without Debugging Symbols
19879 @cindex DLLs with no debugging symbols
19880 @cindex Minimal symbols and DLLs
19882 Very often on windows, some of the DLLs that your program relies on do
19883 not include symbolic debugging information (for example,
19884 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19885 symbols in a DLL, it relies on the minimal amount of symbolic
19886 information contained in the DLL's export table. This section
19887 describes working with such symbols, known internally to @value{GDBN} as
19888 ``minimal symbols''.
19890 Note that before the debugged program has started execution, no DLLs
19891 will have been loaded. The easiest way around this problem is simply to
19892 start the program --- either by setting a breakpoint or letting the
19893 program run once to completion. It is also possible to force
19894 @value{GDBN} to load a particular DLL before starting the executable ---
19895 see the shared library information in @ref{Files}, or the
19896 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19897 explicitly loading symbols from a DLL with no debugging information will
19898 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19899 which may adversely affect symbol lookup performance.
19901 @subsubsection DLL Name Prefixes
19903 In keeping with the naming conventions used by the Microsoft debugging
19904 tools, DLL export symbols are made available with a prefix based on the
19905 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19906 also entered into the symbol table, so @code{CreateFileA} is often
19907 sufficient. In some cases there will be name clashes within a program
19908 (particularly if the executable itself includes full debugging symbols)
19909 necessitating the use of the fully qualified name when referring to the
19910 contents of the DLL. Use single-quotes around the name to avoid the
19911 exclamation mark (``!'') being interpreted as a language operator.
19913 Note that the internal name of the DLL may be all upper-case, even
19914 though the file name of the DLL is lower-case, or vice-versa. Since
19915 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19916 some confusion. If in doubt, try the @code{info functions} and
19917 @code{info variables} commands or even @code{maint print msymbols}
19918 (@pxref{Symbols}). Here's an example:
19921 (@value{GDBP}) info function CreateFileA
19922 All functions matching regular expression "CreateFileA":
19924 Non-debugging symbols:
19925 0x77e885f4 CreateFileA
19926 0x77e885f4 KERNEL32!CreateFileA
19930 (@value{GDBP}) info function !
19931 All functions matching regular expression "!":
19933 Non-debugging symbols:
19934 0x6100114c cygwin1!__assert
19935 0x61004034 cygwin1!_dll_crt0@@0
19936 0x61004240 cygwin1!dll_crt0(per_process *)
19940 @subsubsection Working with Minimal Symbols
19942 Symbols extracted from a DLL's export table do not contain very much
19943 type information. All that @value{GDBN} can do is guess whether a symbol
19944 refers to a function or variable depending on the linker section that
19945 contains the symbol. Also note that the actual contents of the memory
19946 contained in a DLL are not available unless the program is running. This
19947 means that you cannot examine the contents of a variable or disassemble
19948 a function within a DLL without a running program.
19950 Variables are generally treated as pointers and dereferenced
19951 automatically. For this reason, it is often necessary to prefix a
19952 variable name with the address-of operator (``&'') and provide explicit
19953 type information in the command. Here's an example of the type of
19957 (@value{GDBP}) print 'cygwin1!__argv'
19962 (@value{GDBP}) x 'cygwin1!__argv'
19963 0x10021610: "\230y\""
19966 And two possible solutions:
19969 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19970 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19974 (@value{GDBP}) x/2x &'cygwin1!__argv'
19975 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19976 (@value{GDBP}) x/x 0x10021608
19977 0x10021608: 0x0022fd98
19978 (@value{GDBP}) x/s 0x0022fd98
19979 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19982 Setting a break point within a DLL is possible even before the program
19983 starts execution. However, under these circumstances, @value{GDBN} can't
19984 examine the initial instructions of the function in order to skip the
19985 function's frame set-up code. You can work around this by using ``*&''
19986 to set the breakpoint at a raw memory address:
19989 (@value{GDBP}) break *&'python22!PyOS_Readline'
19990 Breakpoint 1 at 0x1e04eff0
19993 The author of these extensions is not entirely convinced that setting a
19994 break point within a shared DLL like @file{kernel32.dll} is completely
19998 @subsection Commands Specific to @sc{gnu} Hurd Systems
19999 @cindex @sc{gnu} Hurd debugging
20001 This subsection describes @value{GDBN} commands specific to the
20002 @sc{gnu} Hurd native debugging.
20007 @kindex set signals@r{, Hurd command}
20008 @kindex set sigs@r{, Hurd command}
20009 This command toggles the state of inferior signal interception by
20010 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20011 affected by this command. @code{sigs} is a shorthand alias for
20016 @kindex show signals@r{, Hurd command}
20017 @kindex show sigs@r{, Hurd command}
20018 Show the current state of intercepting inferior's signals.
20020 @item set signal-thread
20021 @itemx set sigthread
20022 @kindex set signal-thread
20023 @kindex set sigthread
20024 This command tells @value{GDBN} which thread is the @code{libc} signal
20025 thread. That thread is run when a signal is delivered to a running
20026 process. @code{set sigthread} is the shorthand alias of @code{set
20029 @item show signal-thread
20030 @itemx show sigthread
20031 @kindex show signal-thread
20032 @kindex show sigthread
20033 These two commands show which thread will run when the inferior is
20034 delivered a signal.
20037 @kindex set stopped@r{, Hurd command}
20038 This commands tells @value{GDBN} that the inferior process is stopped,
20039 as with the @code{SIGSTOP} signal. The stopped process can be
20040 continued by delivering a signal to it.
20043 @kindex show stopped@r{, Hurd command}
20044 This command shows whether @value{GDBN} thinks the debuggee is
20047 @item set exceptions
20048 @kindex set exceptions@r{, Hurd command}
20049 Use this command to turn off trapping of exceptions in the inferior.
20050 When exception trapping is off, neither breakpoints nor
20051 single-stepping will work. To restore the default, set exception
20054 @item show exceptions
20055 @kindex show exceptions@r{, Hurd command}
20056 Show the current state of trapping exceptions in the inferior.
20058 @item set task pause
20059 @kindex set task@r{, Hurd commands}
20060 @cindex task attributes (@sc{gnu} Hurd)
20061 @cindex pause current task (@sc{gnu} Hurd)
20062 This command toggles task suspension when @value{GDBN} has control.
20063 Setting it to on takes effect immediately, and the task is suspended
20064 whenever @value{GDBN} gets control. Setting it to off will take
20065 effect the next time the inferior is continued. If this option is set
20066 to off, you can use @code{set thread default pause on} or @code{set
20067 thread pause on} (see below) to pause individual threads.
20069 @item show task pause
20070 @kindex show task@r{, Hurd commands}
20071 Show the current state of task suspension.
20073 @item set task detach-suspend-count
20074 @cindex task suspend count
20075 @cindex detach from task, @sc{gnu} Hurd
20076 This command sets the suspend count the task will be left with when
20077 @value{GDBN} detaches from it.
20079 @item show task detach-suspend-count
20080 Show the suspend count the task will be left with when detaching.
20082 @item set task exception-port
20083 @itemx set task excp
20084 @cindex task exception port, @sc{gnu} Hurd
20085 This command sets the task exception port to which @value{GDBN} will
20086 forward exceptions. The argument should be the value of the @dfn{send
20087 rights} of the task. @code{set task excp} is a shorthand alias.
20089 @item set noninvasive
20090 @cindex noninvasive task options
20091 This command switches @value{GDBN} to a mode that is the least
20092 invasive as far as interfering with the inferior is concerned. This
20093 is the same as using @code{set task pause}, @code{set exceptions}, and
20094 @code{set signals} to values opposite to the defaults.
20096 @item info send-rights
20097 @itemx info receive-rights
20098 @itemx info port-rights
20099 @itemx info port-sets
20100 @itemx info dead-names
20103 @cindex send rights, @sc{gnu} Hurd
20104 @cindex receive rights, @sc{gnu} Hurd
20105 @cindex port rights, @sc{gnu} Hurd
20106 @cindex port sets, @sc{gnu} Hurd
20107 @cindex dead names, @sc{gnu} Hurd
20108 These commands display information about, respectively, send rights,
20109 receive rights, port rights, port sets, and dead names of a task.
20110 There are also shorthand aliases: @code{info ports} for @code{info
20111 port-rights} and @code{info psets} for @code{info port-sets}.
20113 @item set thread pause
20114 @kindex set thread@r{, Hurd command}
20115 @cindex thread properties, @sc{gnu} Hurd
20116 @cindex pause current thread (@sc{gnu} Hurd)
20117 This command toggles current thread suspension when @value{GDBN} has
20118 control. Setting it to on takes effect immediately, and the current
20119 thread is suspended whenever @value{GDBN} gets control. Setting it to
20120 off will take effect the next time the inferior is continued.
20121 Normally, this command has no effect, since when @value{GDBN} has
20122 control, the whole task is suspended. However, if you used @code{set
20123 task pause off} (see above), this command comes in handy to suspend
20124 only the current thread.
20126 @item show thread pause
20127 @kindex show thread@r{, Hurd command}
20128 This command shows the state of current thread suspension.
20130 @item set thread run
20131 This command sets whether the current thread is allowed to run.
20133 @item show thread run
20134 Show whether the current thread is allowed to run.
20136 @item set thread detach-suspend-count
20137 @cindex thread suspend count, @sc{gnu} Hurd
20138 @cindex detach from thread, @sc{gnu} Hurd
20139 This command sets the suspend count @value{GDBN} will leave on a
20140 thread when detaching. This number is relative to the suspend count
20141 found by @value{GDBN} when it notices the thread; use @code{set thread
20142 takeover-suspend-count} to force it to an absolute value.
20144 @item show thread detach-suspend-count
20145 Show the suspend count @value{GDBN} will leave on the thread when
20148 @item set thread exception-port
20149 @itemx set thread excp
20150 Set the thread exception port to which to forward exceptions. This
20151 overrides the port set by @code{set task exception-port} (see above).
20152 @code{set thread excp} is the shorthand alias.
20154 @item set thread takeover-suspend-count
20155 Normally, @value{GDBN}'s thread suspend counts are relative to the
20156 value @value{GDBN} finds when it notices each thread. This command
20157 changes the suspend counts to be absolute instead.
20159 @item set thread default
20160 @itemx show thread default
20161 @cindex thread default settings, @sc{gnu} Hurd
20162 Each of the above @code{set thread} commands has a @code{set thread
20163 default} counterpart (e.g., @code{set thread default pause}, @code{set
20164 thread default exception-port}, etc.). The @code{thread default}
20165 variety of commands sets the default thread properties for all
20166 threads; you can then change the properties of individual threads with
20167 the non-default commands.
20174 @value{GDBN} provides the following commands specific to the Darwin target:
20177 @item set debug darwin @var{num}
20178 @kindex set debug darwin
20179 When set to a non zero value, enables debugging messages specific to
20180 the Darwin support. Higher values produce more verbose output.
20182 @item show debug darwin
20183 @kindex show debug darwin
20184 Show the current state of Darwin messages.
20186 @item set debug mach-o @var{num}
20187 @kindex set debug mach-o
20188 When set to a non zero value, enables debugging messages while
20189 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20190 file format used on Darwin for object and executable files.) Higher
20191 values produce more verbose output. This is a command to diagnose
20192 problems internal to @value{GDBN} and should not be needed in normal
20195 @item show debug mach-o
20196 @kindex show debug mach-o
20197 Show the current state of Mach-O file messages.
20199 @item set mach-exceptions on
20200 @itemx set mach-exceptions off
20201 @kindex set mach-exceptions
20202 On Darwin, faults are first reported as a Mach exception and are then
20203 mapped to a Posix signal. Use this command to turn on trapping of
20204 Mach exceptions in the inferior. This might be sometimes useful to
20205 better understand the cause of a fault. The default is off.
20207 @item show mach-exceptions
20208 @kindex show mach-exceptions
20209 Show the current state of exceptions trapping.
20214 @section Embedded Operating Systems
20216 This section describes configurations involving the debugging of
20217 embedded operating systems that are available for several different
20221 * VxWorks:: Using @value{GDBN} with VxWorks
20224 @value{GDBN} includes the ability to debug programs running on
20225 various real-time operating systems.
20228 @subsection Using @value{GDBN} with VxWorks
20234 @kindex target vxworks
20235 @item target vxworks @var{machinename}
20236 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20237 is the target system's machine name or IP address.
20241 On VxWorks, @code{load} links @var{filename} dynamically on the
20242 current target system as well as adding its symbols in @value{GDBN}.
20244 @value{GDBN} enables developers to spawn and debug tasks running on networked
20245 VxWorks targets from a Unix host. Already-running tasks spawned from
20246 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20247 both the Unix host and on the VxWorks target. The program
20248 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20249 installed with the name @code{vxgdb}, to distinguish it from a
20250 @value{GDBN} for debugging programs on the host itself.)
20253 @item VxWorks-timeout @var{args}
20254 @kindex vxworks-timeout
20255 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20256 This option is set by the user, and @var{args} represents the number of
20257 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20258 your VxWorks target is a slow software simulator or is on the far side
20259 of a thin network line.
20262 The following information on connecting to VxWorks was current when
20263 this manual was produced; newer releases of VxWorks may use revised
20266 @findex INCLUDE_RDB
20267 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20268 to include the remote debugging interface routines in the VxWorks
20269 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20270 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20271 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20272 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20273 information on configuring and remaking VxWorks, see the manufacturer's
20275 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20277 Once you have included @file{rdb.a} in your VxWorks system image and set
20278 your Unix execution search path to find @value{GDBN}, you are ready to
20279 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20280 @code{vxgdb}, depending on your installation).
20282 @value{GDBN} comes up showing the prompt:
20289 * VxWorks Connection:: Connecting to VxWorks
20290 * VxWorks Download:: VxWorks download
20291 * VxWorks Attach:: Running tasks
20294 @node VxWorks Connection
20295 @subsubsection Connecting to VxWorks
20297 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20298 network. To connect to a target whose host name is ``@code{tt}'', type:
20301 (vxgdb) target vxworks tt
20305 @value{GDBN} displays messages like these:
20308 Attaching remote machine across net...
20313 @value{GDBN} then attempts to read the symbol tables of any object modules
20314 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20315 these files by searching the directories listed in the command search
20316 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20317 to find an object file, it displays a message such as:
20320 prog.o: No such file or directory.
20323 When this happens, add the appropriate directory to the search path with
20324 the @value{GDBN} command @code{path}, and execute the @code{target}
20327 @node VxWorks Download
20328 @subsubsection VxWorks Download
20330 @cindex download to VxWorks
20331 If you have connected to the VxWorks target and you want to debug an
20332 object that has not yet been loaded, you can use the @value{GDBN}
20333 @code{load} command to download a file from Unix to VxWorks
20334 incrementally. The object file given as an argument to the @code{load}
20335 command is actually opened twice: first by the VxWorks target in order
20336 to download the code, then by @value{GDBN} in order to read the symbol
20337 table. This can lead to problems if the current working directories on
20338 the two systems differ. If both systems have NFS mounted the same
20339 filesystems, you can avoid these problems by using absolute paths.
20340 Otherwise, it is simplest to set the working directory on both systems
20341 to the directory in which the object file resides, and then to reference
20342 the file by its name, without any path. For instance, a program
20343 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20344 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20345 program, type this on VxWorks:
20348 -> cd "@var{vxpath}/vw/demo/rdb"
20352 Then, in @value{GDBN}, type:
20355 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20356 (vxgdb) load prog.o
20359 @value{GDBN} displays a response similar to this:
20362 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20365 You can also use the @code{load} command to reload an object module
20366 after editing and recompiling the corresponding source file. Note that
20367 this makes @value{GDBN} delete all currently-defined breakpoints,
20368 auto-displays, and convenience variables, and to clear the value
20369 history. (This is necessary in order to preserve the integrity of
20370 debugger's data structures that reference the target system's symbol
20373 @node VxWorks Attach
20374 @subsubsection Running Tasks
20376 @cindex running VxWorks tasks
20377 You can also attach to an existing task using the @code{attach} command as
20381 (vxgdb) attach @var{task}
20385 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20386 or suspended when you attach to it. Running tasks are suspended at
20387 the time of attachment.
20389 @node Embedded Processors
20390 @section Embedded Processors
20392 This section goes into details specific to particular embedded
20395 @cindex send command to simulator
20396 Whenever a specific embedded processor has a simulator, @value{GDBN}
20397 allows to send an arbitrary command to the simulator.
20400 @item sim @var{command}
20401 @kindex sim@r{, a command}
20402 Send an arbitrary @var{command} string to the simulator. Consult the
20403 documentation for the specific simulator in use for information about
20404 acceptable commands.
20410 * M32R/D:: Renesas M32R/D
20411 * M68K:: Motorola M68K
20412 * MicroBlaze:: Xilinx MicroBlaze
20413 * MIPS Embedded:: MIPS Embedded
20414 * PowerPC Embedded:: PowerPC Embedded
20415 * PA:: HP PA Embedded
20416 * Sparclet:: Tsqware Sparclet
20417 * Sparclite:: Fujitsu Sparclite
20418 * Z8000:: Zilog Z8000
20421 * Super-H:: Renesas Super-H
20430 @item target rdi @var{dev}
20431 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20432 use this target to communicate with both boards running the Angel
20433 monitor, or with the EmbeddedICE JTAG debug device.
20436 @item target rdp @var{dev}
20441 @value{GDBN} provides the following ARM-specific commands:
20444 @item set arm disassembler
20446 This commands selects from a list of disassembly styles. The
20447 @code{"std"} style is the standard style.
20449 @item show arm disassembler
20451 Show the current disassembly style.
20453 @item set arm apcs32
20454 @cindex ARM 32-bit mode
20455 This command toggles ARM operation mode between 32-bit and 26-bit.
20457 @item show arm apcs32
20458 Display the current usage of the ARM 32-bit mode.
20460 @item set arm fpu @var{fputype}
20461 This command sets the ARM floating-point unit (FPU) type. The
20462 argument @var{fputype} can be one of these:
20466 Determine the FPU type by querying the OS ABI.
20468 Software FPU, with mixed-endian doubles on little-endian ARM
20471 GCC-compiled FPA co-processor.
20473 Software FPU with pure-endian doubles.
20479 Show the current type of the FPU.
20482 This command forces @value{GDBN} to use the specified ABI.
20485 Show the currently used ABI.
20487 @item set arm fallback-mode (arm|thumb|auto)
20488 @value{GDBN} uses the symbol table, when available, to determine
20489 whether instructions are ARM or Thumb. This command controls
20490 @value{GDBN}'s default behavior when the symbol table is not
20491 available. The default is @samp{auto}, which causes @value{GDBN} to
20492 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20495 @item show arm fallback-mode
20496 Show the current fallback instruction mode.
20498 @item set arm force-mode (arm|thumb|auto)
20499 This command overrides use of the symbol table to determine whether
20500 instructions are ARM or Thumb. The default is @samp{auto}, which
20501 causes @value{GDBN} to use the symbol table and then the setting
20502 of @samp{set arm fallback-mode}.
20504 @item show arm force-mode
20505 Show the current forced instruction mode.
20507 @item set debug arm
20508 Toggle whether to display ARM-specific debugging messages from the ARM
20509 target support subsystem.
20511 @item show debug arm
20512 Show whether ARM-specific debugging messages are enabled.
20515 The following commands are available when an ARM target is debugged
20516 using the RDI interface:
20519 @item rdilogfile @r{[}@var{file}@r{]}
20521 @cindex ADP (Angel Debugger Protocol) logging
20522 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20523 With an argument, sets the log file to the specified @var{file}. With
20524 no argument, show the current log file name. The default log file is
20527 @item rdilogenable @r{[}@var{arg}@r{]}
20528 @kindex rdilogenable
20529 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20530 enables logging, with an argument 0 or @code{"no"} disables it. With
20531 no arguments displays the current setting. When logging is enabled,
20532 ADP packets exchanged between @value{GDBN} and the RDI target device
20533 are logged to a file.
20535 @item set rdiromatzero
20536 @kindex set rdiromatzero
20537 @cindex ROM at zero address, RDI
20538 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20539 vector catching is disabled, so that zero address can be used. If off
20540 (the default), vector catching is enabled. For this command to take
20541 effect, it needs to be invoked prior to the @code{target rdi} command.
20543 @item show rdiromatzero
20544 @kindex show rdiromatzero
20545 Show the current setting of ROM at zero address.
20547 @item set rdiheartbeat
20548 @kindex set rdiheartbeat
20549 @cindex RDI heartbeat
20550 Enable or disable RDI heartbeat packets. It is not recommended to
20551 turn on this option, since it confuses ARM and EPI JTAG interface, as
20552 well as the Angel monitor.
20554 @item show rdiheartbeat
20555 @kindex show rdiheartbeat
20556 Show the setting of RDI heartbeat packets.
20560 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20561 The @value{GDBN} ARM simulator accepts the following optional arguments.
20564 @item --swi-support=@var{type}
20565 Tell the simulator which SWI interfaces to support.
20566 @var{type} may be a comma separated list of the following values.
20567 The default value is @code{all}.
20580 @subsection Renesas M32R/D and M32R/SDI
20583 @kindex target m32r
20584 @item target m32r @var{dev}
20585 Renesas M32R/D ROM monitor.
20587 @kindex target m32rsdi
20588 @item target m32rsdi @var{dev}
20589 Renesas M32R SDI server, connected via parallel port to the board.
20592 The following @value{GDBN} commands are specific to the M32R monitor:
20595 @item set download-path @var{path}
20596 @kindex set download-path
20597 @cindex find downloadable @sc{srec} files (M32R)
20598 Set the default path for finding downloadable @sc{srec} files.
20600 @item show download-path
20601 @kindex show download-path
20602 Show the default path for downloadable @sc{srec} files.
20604 @item set board-address @var{addr}
20605 @kindex set board-address
20606 @cindex M32-EVA target board address
20607 Set the IP address for the M32R-EVA target board.
20609 @item show board-address
20610 @kindex show board-address
20611 Show the current IP address of the target board.
20613 @item set server-address @var{addr}
20614 @kindex set server-address
20615 @cindex download server address (M32R)
20616 Set the IP address for the download server, which is the @value{GDBN}'s
20619 @item show server-address
20620 @kindex show server-address
20621 Display the IP address of the download server.
20623 @item upload @r{[}@var{file}@r{]}
20624 @kindex upload@r{, M32R}
20625 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20626 upload capability. If no @var{file} argument is given, the current
20627 executable file is uploaded.
20629 @item tload @r{[}@var{file}@r{]}
20630 @kindex tload@r{, M32R}
20631 Test the @code{upload} command.
20634 The following commands are available for M32R/SDI:
20639 @cindex reset SDI connection, M32R
20640 This command resets the SDI connection.
20644 This command shows the SDI connection status.
20647 @kindex debug_chaos
20648 @cindex M32R/Chaos debugging
20649 Instructs the remote that M32R/Chaos debugging is to be used.
20651 @item use_debug_dma
20652 @kindex use_debug_dma
20653 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20656 @kindex use_mon_code
20657 Instructs the remote to use the MON_CODE method of accessing memory.
20660 @kindex use_ib_break
20661 Instructs the remote to set breakpoints by IB break.
20663 @item use_dbt_break
20664 @kindex use_dbt_break
20665 Instructs the remote to set breakpoints by DBT.
20671 The Motorola m68k configuration includes ColdFire support, and a
20672 target command for the following ROM monitor.
20676 @kindex target dbug
20677 @item target dbug @var{dev}
20678 dBUG ROM monitor for Motorola ColdFire.
20683 @subsection MicroBlaze
20684 @cindex Xilinx MicroBlaze
20685 @cindex XMD, Xilinx Microprocessor Debugger
20687 The MicroBlaze is a soft-core processor supported on various Xilinx
20688 FPGAs, such as Spartan or Virtex series. Boards with these processors
20689 usually have JTAG ports which connect to a host system running the Xilinx
20690 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20691 This host system is used to download the configuration bitstream to
20692 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20693 communicates with the target board using the JTAG interface and
20694 presents a @code{gdbserver} interface to the board. By default
20695 @code{xmd} uses port @code{1234}. (While it is possible to change
20696 this default port, it requires the use of undocumented @code{xmd}
20697 commands. Contact Xilinx support if you need to do this.)
20699 Use these GDB commands to connect to the MicroBlaze target processor.
20702 @item target remote :1234
20703 Use this command to connect to the target if you are running @value{GDBN}
20704 on the same system as @code{xmd}.
20706 @item target remote @var{xmd-host}:1234
20707 Use this command to connect to the target if it is connected to @code{xmd}
20708 running on a different system named @var{xmd-host}.
20711 Use this command to download a program to the MicroBlaze target.
20713 @item set debug microblaze @var{n}
20714 Enable MicroBlaze-specific debugging messages if non-zero.
20716 @item show debug microblaze @var{n}
20717 Show MicroBlaze-specific debugging level.
20720 @node MIPS Embedded
20721 @subsection @acronym{MIPS} Embedded
20723 @cindex @acronym{MIPS} boards
20724 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20725 @acronym{MIPS} board attached to a serial line. This is available when
20726 you configure @value{GDBN} with @samp{--target=mips-elf}.
20729 Use these @value{GDBN} commands to specify the connection to your target board:
20732 @item target mips @var{port}
20733 @kindex target mips @var{port}
20734 To run a program on the board, start up @code{@value{GDBP}} with the
20735 name of your program as the argument. To connect to the board, use the
20736 command @samp{target mips @var{port}}, where @var{port} is the name of
20737 the serial port connected to the board. If the program has not already
20738 been downloaded to the board, you may use the @code{load} command to
20739 download it. You can then use all the usual @value{GDBN} commands.
20741 For example, this sequence connects to the target board through a serial
20742 port, and loads and runs a program called @var{prog} through the
20746 host$ @value{GDBP} @var{prog}
20747 @value{GDBN} is free software and @dots{}
20748 (@value{GDBP}) target mips /dev/ttyb
20749 (@value{GDBP}) load @var{prog}
20753 @item target mips @var{hostname}:@var{portnumber}
20754 On some @value{GDBN} host configurations, you can specify a TCP
20755 connection (for instance, to a serial line managed by a terminal
20756 concentrator) instead of a serial port, using the syntax
20757 @samp{@var{hostname}:@var{portnumber}}.
20759 @item target pmon @var{port}
20760 @kindex target pmon @var{port}
20763 @item target ddb @var{port}
20764 @kindex target ddb @var{port}
20765 NEC's DDB variant of PMON for Vr4300.
20767 @item target lsi @var{port}
20768 @kindex target lsi @var{port}
20769 LSI variant of PMON.
20771 @kindex target r3900
20772 @item target r3900 @var{dev}
20773 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20775 @kindex target array
20776 @item target array @var{dev}
20777 Array Tech LSI33K RAID controller board.
20783 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20786 @item set mipsfpu double
20787 @itemx set mipsfpu single
20788 @itemx set mipsfpu none
20789 @itemx set mipsfpu auto
20790 @itemx show mipsfpu
20791 @kindex set mipsfpu
20792 @kindex show mipsfpu
20793 @cindex @acronym{MIPS} remote floating point
20794 @cindex floating point, @acronym{MIPS} remote
20795 If your target board does not support the @acronym{MIPS} floating point
20796 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20797 need this, you may wish to put the command in your @value{GDBN} init
20798 file). This tells @value{GDBN} how to find the return value of
20799 functions which return floating point values. It also allows
20800 @value{GDBN} to avoid saving the floating point registers when calling
20801 functions on the board. If you are using a floating point coprocessor
20802 with only single precision floating point support, as on the @sc{r4650}
20803 processor, use the command @samp{set mipsfpu single}. The default
20804 double precision floating point coprocessor may be selected using
20805 @samp{set mipsfpu double}.
20807 In previous versions the only choices were double precision or no
20808 floating point, so @samp{set mipsfpu on} will select double precision
20809 and @samp{set mipsfpu off} will select no floating point.
20811 As usual, you can inquire about the @code{mipsfpu} variable with
20812 @samp{show mipsfpu}.
20814 @item set timeout @var{seconds}
20815 @itemx set retransmit-timeout @var{seconds}
20816 @itemx show timeout
20817 @itemx show retransmit-timeout
20818 @cindex @code{timeout}, @acronym{MIPS} protocol
20819 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20820 @kindex set timeout
20821 @kindex show timeout
20822 @kindex set retransmit-timeout
20823 @kindex show retransmit-timeout
20824 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20825 remote protocol, with the @code{set timeout @var{seconds}} command. The
20826 default is 5 seconds. Similarly, you can control the timeout used while
20827 waiting for an acknowledgment of a packet with the @code{set
20828 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20829 You can inspect both values with @code{show timeout} and @code{show
20830 retransmit-timeout}. (These commands are @emph{only} available when
20831 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20833 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20834 is waiting for your program to stop. In that case, @value{GDBN} waits
20835 forever because it has no way of knowing how long the program is going
20836 to run before stopping.
20838 @item set syn-garbage-limit @var{num}
20839 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20840 @cindex synchronize with remote @acronym{MIPS} target
20841 Limit the maximum number of characters @value{GDBN} should ignore when
20842 it tries to synchronize with the remote target. The default is 10
20843 characters. Setting the limit to -1 means there's no limit.
20845 @item show syn-garbage-limit
20846 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20847 Show the current limit on the number of characters to ignore when
20848 trying to synchronize with the remote system.
20850 @item set monitor-prompt @var{prompt}
20851 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20852 @cindex remote monitor prompt
20853 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20854 remote monitor. The default depends on the target:
20864 @item show monitor-prompt
20865 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20866 Show the current strings @value{GDBN} expects as the prompt from the
20869 @item set monitor-warnings
20870 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20871 Enable or disable monitor warnings about hardware breakpoints. This
20872 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20873 display warning messages whose codes are returned by the @code{lsi}
20874 PMON monitor for breakpoint commands.
20876 @item show monitor-warnings
20877 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20878 Show the current setting of printing monitor warnings.
20880 @item pmon @var{command}
20881 @kindex pmon@r{, @acronym{MIPS} remote}
20882 @cindex send PMON command
20883 This command allows sending an arbitrary @var{command} string to the
20884 monitor. The monitor must be in debug mode for this to work.
20887 @node PowerPC Embedded
20888 @subsection PowerPC Embedded
20890 @cindex DVC register
20891 @value{GDBN} supports using the DVC (Data Value Compare) register to
20892 implement in hardware simple hardware watchpoint conditions of the form:
20895 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20896 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20899 The DVC register will be automatically used when @value{GDBN} detects
20900 such pattern in a condition expression, and the created watchpoint uses one
20901 debug register (either the @code{exact-watchpoints} option is on and the
20902 variable is scalar, or the variable has a length of one byte). This feature
20903 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20906 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20907 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20908 in which case watchpoints using only one debug register are created when
20909 watching variables of scalar types.
20911 You can create an artificial array to watch an arbitrary memory
20912 region using one of the following commands (@pxref{Expressions}):
20915 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20916 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20919 PowerPC embedded processors support masked watchpoints. See the discussion
20920 about the @code{mask} argument in @ref{Set Watchpoints}.
20922 @cindex ranged breakpoint
20923 PowerPC embedded processors support hardware accelerated
20924 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20925 the inferior whenever it executes an instruction at any address within
20926 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20927 use the @code{break-range} command.
20929 @value{GDBN} provides the following PowerPC-specific commands:
20932 @kindex break-range
20933 @item break-range @var{start-location}, @var{end-location}
20934 Set a breakpoint for an address range.
20935 @var{start-location} and @var{end-location} can specify a function name,
20936 a line number, an offset of lines from the current line or from the start
20937 location, or an address of an instruction (see @ref{Specify Location},
20938 for a list of all the possible ways to specify a @var{location}.)
20939 The breakpoint will stop execution of the inferior whenever it
20940 executes an instruction at any address within the specified range,
20941 (including @var{start-location} and @var{end-location}.)
20943 @kindex set powerpc
20944 @item set powerpc soft-float
20945 @itemx show powerpc soft-float
20946 Force @value{GDBN} to use (or not use) a software floating point calling
20947 convention. By default, @value{GDBN} selects the calling convention based
20948 on the selected architecture and the provided executable file.
20950 @item set powerpc vector-abi
20951 @itemx show powerpc vector-abi
20952 Force @value{GDBN} to use the specified calling convention for vector
20953 arguments and return values. The valid options are @samp{auto};
20954 @samp{generic}, to avoid vector registers even if they are present;
20955 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20956 registers. By default, @value{GDBN} selects the calling convention
20957 based on the selected architecture and the provided executable file.
20959 @item set powerpc exact-watchpoints
20960 @itemx show powerpc exact-watchpoints
20961 Allow @value{GDBN} to use only one debug register when watching a variable
20962 of scalar type, thus assuming that the variable is accessed through the
20963 address of its first byte.
20965 @kindex target dink32
20966 @item target dink32 @var{dev}
20967 DINK32 ROM monitor.
20969 @kindex target ppcbug
20970 @item target ppcbug @var{dev}
20971 @kindex target ppcbug1
20972 @item target ppcbug1 @var{dev}
20973 PPCBUG ROM monitor for PowerPC.
20976 @item target sds @var{dev}
20977 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20980 @cindex SDS protocol
20981 The following commands specific to the SDS protocol are supported
20985 @item set sdstimeout @var{nsec}
20986 @kindex set sdstimeout
20987 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20988 default is 2 seconds.
20990 @item show sdstimeout
20991 @kindex show sdstimeout
20992 Show the current value of the SDS timeout.
20994 @item sds @var{command}
20995 @kindex sds@r{, a command}
20996 Send the specified @var{command} string to the SDS monitor.
21001 @subsection HP PA Embedded
21005 @kindex target op50n
21006 @item target op50n @var{dev}
21007 OP50N monitor, running on an OKI HPPA board.
21009 @kindex target w89k
21010 @item target w89k @var{dev}
21011 W89K monitor, running on a Winbond HPPA board.
21016 @subsection Tsqware Sparclet
21020 @value{GDBN} enables developers to debug tasks running on
21021 Sparclet targets from a Unix host.
21022 @value{GDBN} uses code that runs on
21023 both the Unix host and on the Sparclet target. The program
21024 @code{@value{GDBP}} is installed and executed on the Unix host.
21027 @item remotetimeout @var{args}
21028 @kindex remotetimeout
21029 @value{GDBN} supports the option @code{remotetimeout}.
21030 This option is set by the user, and @var{args} represents the number of
21031 seconds @value{GDBN} waits for responses.
21034 @cindex compiling, on Sparclet
21035 When compiling for debugging, include the options @samp{-g} to get debug
21036 information and @samp{-Ttext} to relocate the program to where you wish to
21037 load it on the target. You may also want to add the options @samp{-n} or
21038 @samp{-N} in order to reduce the size of the sections. Example:
21041 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21044 You can use @code{objdump} to verify that the addresses are what you intended:
21047 sparclet-aout-objdump --headers --syms prog
21050 @cindex running, on Sparclet
21052 your Unix execution search path to find @value{GDBN}, you are ready to
21053 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21054 (or @code{sparclet-aout-gdb}, depending on your installation).
21056 @value{GDBN} comes up showing the prompt:
21063 * Sparclet File:: Setting the file to debug
21064 * Sparclet Connection:: Connecting to Sparclet
21065 * Sparclet Download:: Sparclet download
21066 * Sparclet Execution:: Running and debugging
21069 @node Sparclet File
21070 @subsubsection Setting File to Debug
21072 The @value{GDBN} command @code{file} lets you choose with program to debug.
21075 (gdbslet) file prog
21079 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21080 @value{GDBN} locates
21081 the file by searching the directories listed in the command search
21083 If the file was compiled with debug information (option @samp{-g}), source
21084 files will be searched as well.
21085 @value{GDBN} locates
21086 the source files by searching the directories listed in the directory search
21087 path (@pxref{Environment, ,Your Program's Environment}).
21089 to find a file, it displays a message such as:
21092 prog: No such file or directory.
21095 When this happens, add the appropriate directories to the search paths with
21096 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21097 @code{target} command again.
21099 @node Sparclet Connection
21100 @subsubsection Connecting to Sparclet
21102 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21103 To connect to a target on serial port ``@code{ttya}'', type:
21106 (gdbslet) target sparclet /dev/ttya
21107 Remote target sparclet connected to /dev/ttya
21108 main () at ../prog.c:3
21112 @value{GDBN} displays messages like these:
21118 @node Sparclet Download
21119 @subsubsection Sparclet Download
21121 @cindex download to Sparclet
21122 Once connected to the Sparclet target,
21123 you can use the @value{GDBN}
21124 @code{load} command to download the file from the host to the target.
21125 The file name and load offset should be given as arguments to the @code{load}
21127 Since the file format is aout, the program must be loaded to the starting
21128 address. You can use @code{objdump} to find out what this value is. The load
21129 offset is an offset which is added to the VMA (virtual memory address)
21130 of each of the file's sections.
21131 For instance, if the program
21132 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21133 and bss at 0x12010170, in @value{GDBN}, type:
21136 (gdbslet) load prog 0x12010000
21137 Loading section .text, size 0xdb0 vma 0x12010000
21140 If the code is loaded at a different address then what the program was linked
21141 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21142 to tell @value{GDBN} where to map the symbol table.
21144 @node Sparclet Execution
21145 @subsubsection Running and Debugging
21147 @cindex running and debugging Sparclet programs
21148 You can now begin debugging the task using @value{GDBN}'s execution control
21149 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21150 manual for the list of commands.
21154 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21156 Starting program: prog
21157 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21158 3 char *symarg = 0;
21160 4 char *execarg = "hello!";
21165 @subsection Fujitsu Sparclite
21169 @kindex target sparclite
21170 @item target sparclite @var{dev}
21171 Fujitsu sparclite boards, used only for the purpose of loading.
21172 You must use an additional command to debug the program.
21173 For example: target remote @var{dev} using @value{GDBN} standard
21179 @subsection Zilog Z8000
21182 @cindex simulator, Z8000
21183 @cindex Zilog Z8000 simulator
21185 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21188 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21189 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21190 segmented variant). The simulator recognizes which architecture is
21191 appropriate by inspecting the object code.
21194 @item target sim @var{args}
21196 @kindex target sim@r{, with Z8000}
21197 Debug programs on a simulated CPU. If the simulator supports setup
21198 options, specify them via @var{args}.
21202 After specifying this target, you can debug programs for the simulated
21203 CPU in the same style as programs for your host computer; use the
21204 @code{file} command to load a new program image, the @code{run} command
21205 to run your program, and so on.
21207 As well as making available all the usual machine registers
21208 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21209 additional items of information as specially named registers:
21214 Counts clock-ticks in the simulator.
21217 Counts instructions run in the simulator.
21220 Execution time in 60ths of a second.
21224 You can refer to these values in @value{GDBN} expressions with the usual
21225 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21226 conditional breakpoint that suspends only after at least 5000
21227 simulated clock ticks.
21230 @subsection Atmel AVR
21233 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21234 following AVR-specific commands:
21237 @item info io_registers
21238 @kindex info io_registers@r{, AVR}
21239 @cindex I/O registers (Atmel AVR)
21240 This command displays information about the AVR I/O registers. For
21241 each register, @value{GDBN} prints its number and value.
21248 When configured for debugging CRIS, @value{GDBN} provides the
21249 following CRIS-specific commands:
21252 @item set cris-version @var{ver}
21253 @cindex CRIS version
21254 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21255 The CRIS version affects register names and sizes. This command is useful in
21256 case autodetection of the CRIS version fails.
21258 @item show cris-version
21259 Show the current CRIS version.
21261 @item set cris-dwarf2-cfi
21262 @cindex DWARF-2 CFI and CRIS
21263 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21264 Change to @samp{off} when using @code{gcc-cris} whose version is below
21267 @item show cris-dwarf2-cfi
21268 Show the current state of using DWARF-2 CFI.
21270 @item set cris-mode @var{mode}
21272 Set the current CRIS mode to @var{mode}. It should only be changed when
21273 debugging in guru mode, in which case it should be set to
21274 @samp{guru} (the default is @samp{normal}).
21276 @item show cris-mode
21277 Show the current CRIS mode.
21281 @subsection Renesas Super-H
21284 For the Renesas Super-H processor, @value{GDBN} provides these
21288 @item set sh calling-convention @var{convention}
21289 @kindex set sh calling-convention
21290 Set the calling-convention used when calling functions from @value{GDBN}.
21291 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21292 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21293 convention. If the DWARF-2 information of the called function specifies
21294 that the function follows the Renesas calling convention, the function
21295 is called using the Renesas calling convention. If the calling convention
21296 is set to @samp{renesas}, the Renesas calling convention is always used,
21297 regardless of the DWARF-2 information. This can be used to override the
21298 default of @samp{gcc} if debug information is missing, or the compiler
21299 does not emit the DWARF-2 calling convention entry for a function.
21301 @item show sh calling-convention
21302 @kindex show sh calling-convention
21303 Show the current calling convention setting.
21308 @node Architectures
21309 @section Architectures
21311 This section describes characteristics of architectures that affect
21312 all uses of @value{GDBN} with the architecture, both native and cross.
21319 * HPPA:: HP PA architecture
21320 * SPU:: Cell Broadband Engine SPU architecture
21326 @subsection AArch64
21327 @cindex AArch64 support
21329 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21330 following special commands:
21333 @item set debug aarch64
21334 @kindex set debug aarch64
21335 This command determines whether AArch64 architecture-specific debugging
21336 messages are to be displayed.
21338 @item show debug aarch64
21339 Show whether AArch64 debugging messages are displayed.
21344 @subsection x86 Architecture-specific Issues
21347 @item set struct-convention @var{mode}
21348 @kindex set struct-convention
21349 @cindex struct return convention
21350 @cindex struct/union returned in registers
21351 Set the convention used by the inferior to return @code{struct}s and
21352 @code{union}s from functions to @var{mode}. Possible values of
21353 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21354 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21355 are returned on the stack, while @code{"reg"} means that a
21356 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21357 be returned in a register.
21359 @item show struct-convention
21360 @kindex show struct-convention
21361 Show the current setting of the convention to return @code{struct}s
21368 See the following section.
21371 @subsection @acronym{MIPS}
21373 @cindex stack on Alpha
21374 @cindex stack on @acronym{MIPS}
21375 @cindex Alpha stack
21376 @cindex @acronym{MIPS} stack
21377 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21378 sometimes requires @value{GDBN} to search backward in the object code to
21379 find the beginning of a function.
21381 @cindex response time, @acronym{MIPS} debugging
21382 To improve response time (especially for embedded applications, where
21383 @value{GDBN} may be restricted to a slow serial line for this search)
21384 you may want to limit the size of this search, using one of these
21388 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21389 @item set heuristic-fence-post @var{limit}
21390 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21391 search for the beginning of a function. A value of @var{0} (the
21392 default) means there is no limit. However, except for @var{0}, the
21393 larger the limit the more bytes @code{heuristic-fence-post} must search
21394 and therefore the longer it takes to run. You should only need to use
21395 this command when debugging a stripped executable.
21397 @item show heuristic-fence-post
21398 Display the current limit.
21402 These commands are available @emph{only} when @value{GDBN} is configured
21403 for debugging programs on Alpha or @acronym{MIPS} processors.
21405 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21409 @item set mips abi @var{arg}
21410 @kindex set mips abi
21411 @cindex set ABI for @acronym{MIPS}
21412 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21413 values of @var{arg} are:
21417 The default ABI associated with the current binary (this is the
21427 @item show mips abi
21428 @kindex show mips abi
21429 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21431 @item set mips compression @var{arg}
21432 @kindex set mips compression
21433 @cindex code compression, @acronym{MIPS}
21434 Tell @value{GDBN} which @acronym{MIPS} compressed
21435 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21436 inferior. @value{GDBN} uses this for code disassembly and other
21437 internal interpretation purposes. This setting is only referred to
21438 when no executable has been associated with the debugging session or
21439 the executable does not provide information about the encoding it uses.
21440 Otherwise this setting is automatically updated from information
21441 provided by the executable.
21443 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21444 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21445 executables containing @acronym{MIPS16} code frequently are not
21446 identified as such.
21448 This setting is ``sticky''; that is, it retains its value across
21449 debugging sessions until reset either explicitly with this command or
21450 implicitly from an executable.
21452 The compiler and/or assembler typically add symbol table annotations to
21453 identify functions compiled for the @acronym{MIPS16} or
21454 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21455 are present, @value{GDBN} uses them in preference to the global
21456 compressed @acronym{ISA} encoding setting.
21458 @item show mips compression
21459 @kindex show mips compression
21460 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21461 @value{GDBN} to debug the inferior.
21464 @itemx show mipsfpu
21465 @xref{MIPS Embedded, set mipsfpu}.
21467 @item set mips mask-address @var{arg}
21468 @kindex set mips mask-address
21469 @cindex @acronym{MIPS} addresses, masking
21470 This command determines whether the most-significant 32 bits of 64-bit
21471 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21472 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21473 setting, which lets @value{GDBN} determine the correct value.
21475 @item show mips mask-address
21476 @kindex show mips mask-address
21477 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21480 @item set remote-mips64-transfers-32bit-regs
21481 @kindex set remote-mips64-transfers-32bit-regs
21482 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21483 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21484 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21485 and 64 bits for other registers, set this option to @samp{on}.
21487 @item show remote-mips64-transfers-32bit-regs
21488 @kindex show remote-mips64-transfers-32bit-regs
21489 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21491 @item set debug mips
21492 @kindex set debug mips
21493 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21494 target code in @value{GDBN}.
21496 @item show debug mips
21497 @kindex show debug mips
21498 Show the current setting of @acronym{MIPS} debugging messages.
21504 @cindex HPPA support
21506 When @value{GDBN} is debugging the HP PA architecture, it provides the
21507 following special commands:
21510 @item set debug hppa
21511 @kindex set debug hppa
21512 This command determines whether HPPA architecture-specific debugging
21513 messages are to be displayed.
21515 @item show debug hppa
21516 Show whether HPPA debugging messages are displayed.
21518 @item maint print unwind @var{address}
21519 @kindex maint print unwind@r{, HPPA}
21520 This command displays the contents of the unwind table entry at the
21521 given @var{address}.
21527 @subsection Cell Broadband Engine SPU architecture
21528 @cindex Cell Broadband Engine
21531 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21532 it provides the following special commands:
21535 @item info spu event
21537 Display SPU event facility status. Shows current event mask
21538 and pending event status.
21540 @item info spu signal
21541 Display SPU signal notification facility status. Shows pending
21542 signal-control word and signal notification mode of both signal
21543 notification channels.
21545 @item info spu mailbox
21546 Display SPU mailbox facility status. Shows all pending entries,
21547 in order of processing, in each of the SPU Write Outbound,
21548 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21551 Display MFC DMA status. Shows all pending commands in the MFC
21552 DMA queue. For each entry, opcode, tag, class IDs, effective
21553 and local store addresses and transfer size are shown.
21555 @item info spu proxydma
21556 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21557 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21558 and local store addresses and transfer size are shown.
21562 When @value{GDBN} is debugging a combined PowerPC/SPU application
21563 on the Cell Broadband Engine, it provides in addition the following
21567 @item set spu stop-on-load @var{arg}
21569 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21570 will give control to the user when a new SPE thread enters its @code{main}
21571 function. The default is @code{off}.
21573 @item show spu stop-on-load
21575 Show whether to stop for new SPE threads.
21577 @item set spu auto-flush-cache @var{arg}
21578 Set whether to automatically flush the software-managed cache. When set to
21579 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21580 cache to be flushed whenever SPE execution stops. This provides a consistent
21581 view of PowerPC memory that is accessed via the cache. If an application
21582 does not use the software-managed cache, this option has no effect.
21584 @item show spu auto-flush-cache
21585 Show whether to automatically flush the software-managed cache.
21590 @subsection PowerPC
21591 @cindex PowerPC architecture
21593 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21594 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21595 numbers stored in the floating point registers. These values must be stored
21596 in two consecutive registers, always starting at an even register like
21597 @code{f0} or @code{f2}.
21599 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21600 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21601 @code{f2} and @code{f3} for @code{$dl1} and so on.
21603 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21604 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21607 @subsection Nios II
21608 @cindex Nios II architecture
21610 When @value{GDBN} is debugging the Nios II architecture,
21611 it provides the following special commands:
21615 @item set debug nios2
21616 @kindex set debug nios2
21617 This command turns on and off debugging messages for the Nios II
21618 target code in @value{GDBN}.
21620 @item show debug nios2
21621 @kindex show debug nios2
21622 Show the current setting of Nios II debugging messages.
21625 @node Controlling GDB
21626 @chapter Controlling @value{GDBN}
21628 You can alter the way @value{GDBN} interacts with you by using the
21629 @code{set} command. For commands controlling how @value{GDBN} displays
21630 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21635 * Editing:: Command editing
21636 * Command History:: Command history
21637 * Screen Size:: Screen size
21638 * Numbers:: Numbers
21639 * ABI:: Configuring the current ABI
21640 * Auto-loading:: Automatically loading associated files
21641 * Messages/Warnings:: Optional warnings and messages
21642 * Debugging Output:: Optional messages about internal happenings
21643 * Other Misc Settings:: Other Miscellaneous Settings
21651 @value{GDBN} indicates its readiness to read a command by printing a string
21652 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21653 can change the prompt string with the @code{set prompt} command. For
21654 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21655 the prompt in one of the @value{GDBN} sessions so that you can always tell
21656 which one you are talking to.
21658 @emph{Note:} @code{set prompt} does not add a space for you after the
21659 prompt you set. This allows you to set a prompt which ends in a space
21660 or a prompt that does not.
21664 @item set prompt @var{newprompt}
21665 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21667 @kindex show prompt
21669 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21672 Versions of @value{GDBN} that ship with Python scripting enabled have
21673 prompt extensions. The commands for interacting with these extensions
21677 @kindex set extended-prompt
21678 @item set extended-prompt @var{prompt}
21679 Set an extended prompt that allows for substitutions.
21680 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21681 substitution. Any escape sequences specified as part of the prompt
21682 string are replaced with the corresponding strings each time the prompt
21688 set extended-prompt Current working directory: \w (gdb)
21691 Note that when an extended-prompt is set, it takes control of the
21692 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21694 @kindex show extended-prompt
21695 @item show extended-prompt
21696 Prints the extended prompt. Any escape sequences specified as part of
21697 the prompt string with @code{set extended-prompt}, are replaced with the
21698 corresponding strings each time the prompt is displayed.
21702 @section Command Editing
21704 @cindex command line editing
21706 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21707 @sc{gnu} library provides consistent behavior for programs which provide a
21708 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21709 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21710 substitution, and a storage and recall of command history across
21711 debugging sessions.
21713 You may control the behavior of command line editing in @value{GDBN} with the
21714 command @code{set}.
21717 @kindex set editing
21720 @itemx set editing on
21721 Enable command line editing (enabled by default).
21723 @item set editing off
21724 Disable command line editing.
21726 @kindex show editing
21728 Show whether command line editing is enabled.
21731 @ifset SYSTEM_READLINE
21732 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21734 @ifclear SYSTEM_READLINE
21735 @xref{Command Line Editing},
21737 for more details about the Readline
21738 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21739 encouraged to read that chapter.
21741 @node Command History
21742 @section Command History
21743 @cindex command history
21745 @value{GDBN} can keep track of the commands you type during your
21746 debugging sessions, so that you can be certain of precisely what
21747 happened. Use these commands to manage the @value{GDBN} command
21750 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21751 package, to provide the history facility.
21752 @ifset SYSTEM_READLINE
21753 @xref{Using History Interactively, , , history, GNU History Library},
21755 @ifclear SYSTEM_READLINE
21756 @xref{Using History Interactively},
21758 for the detailed description of the History library.
21760 To issue a command to @value{GDBN} without affecting certain aspects of
21761 the state which is seen by users, prefix it with @samp{server }
21762 (@pxref{Server Prefix}). This
21763 means that this command will not affect the command history, nor will it
21764 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21765 pressed on a line by itself.
21767 @cindex @code{server}, command prefix
21768 The server prefix does not affect the recording of values into the value
21769 history; to print a value without recording it into the value history,
21770 use the @code{output} command instead of the @code{print} command.
21772 Here is the description of @value{GDBN} commands related to command
21776 @cindex history substitution
21777 @cindex history file
21778 @kindex set history filename
21779 @cindex @env{GDBHISTFILE}, environment variable
21780 @item set history filename @var{fname}
21781 Set the name of the @value{GDBN} command history file to @var{fname}.
21782 This is the file where @value{GDBN} reads an initial command history
21783 list, and where it writes the command history from this session when it
21784 exits. You can access this list through history expansion or through
21785 the history command editing characters listed below. This file defaults
21786 to the value of the environment variable @code{GDBHISTFILE}, or to
21787 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21790 @cindex save command history
21791 @kindex set history save
21792 @item set history save
21793 @itemx set history save on
21794 Record command history in a file, whose name may be specified with the
21795 @code{set history filename} command. By default, this option is disabled.
21797 @item set history save off
21798 Stop recording command history in a file.
21800 @cindex history size
21801 @kindex set history size
21802 @cindex @env{HISTSIZE}, environment variable
21803 @item set history size @var{size}
21804 @itemx set history size unlimited
21805 Set the number of commands which @value{GDBN} keeps in its history list.
21806 This defaults to the value of the environment variable
21807 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21808 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21809 history list is unlimited.
21812 History expansion assigns special meaning to the character @kbd{!}.
21813 @ifset SYSTEM_READLINE
21814 @xref{Event Designators, , , history, GNU History Library},
21816 @ifclear SYSTEM_READLINE
21817 @xref{Event Designators},
21821 @cindex history expansion, turn on/off
21822 Since @kbd{!} is also the logical not operator in C, history expansion
21823 is off by default. If you decide to enable history expansion with the
21824 @code{set history expansion on} command, you may sometimes need to
21825 follow @kbd{!} (when it is used as logical not, in an expression) with
21826 a space or a tab to prevent it from being expanded. The readline
21827 history facilities do not attempt substitution on the strings
21828 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21830 The commands to control history expansion are:
21833 @item set history expansion on
21834 @itemx set history expansion
21835 @kindex set history expansion
21836 Enable history expansion. History expansion is off by default.
21838 @item set history expansion off
21839 Disable history expansion.
21842 @kindex show history
21844 @itemx show history filename
21845 @itemx show history save
21846 @itemx show history size
21847 @itemx show history expansion
21848 These commands display the state of the @value{GDBN} history parameters.
21849 @code{show history} by itself displays all four states.
21854 @kindex show commands
21855 @cindex show last commands
21856 @cindex display command history
21857 @item show commands
21858 Display the last ten commands in the command history.
21860 @item show commands @var{n}
21861 Print ten commands centered on command number @var{n}.
21863 @item show commands +
21864 Print ten commands just after the commands last printed.
21868 @section Screen Size
21869 @cindex size of screen
21870 @cindex pauses in output
21872 Certain commands to @value{GDBN} may produce large amounts of
21873 information output to the screen. To help you read all of it,
21874 @value{GDBN} pauses and asks you for input at the end of each page of
21875 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21876 to discard the remaining output. Also, the screen width setting
21877 determines when to wrap lines of output. Depending on what is being
21878 printed, @value{GDBN} tries to break the line at a readable place,
21879 rather than simply letting it overflow onto the following line.
21881 Normally @value{GDBN} knows the size of the screen from the terminal
21882 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21883 together with the value of the @code{TERM} environment variable and the
21884 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21885 you can override it with the @code{set height} and @code{set
21892 @kindex show height
21893 @item set height @var{lpp}
21894 @itemx set height unlimited
21896 @itemx set width @var{cpl}
21897 @itemx set width unlimited
21899 These @code{set} commands specify a screen height of @var{lpp} lines and
21900 a screen width of @var{cpl} characters. The associated @code{show}
21901 commands display the current settings.
21903 If you specify a height of either @code{unlimited} or zero lines,
21904 @value{GDBN} does not pause during output no matter how long the
21905 output is. This is useful if output is to a file or to an editor
21908 Likewise, you can specify @samp{set width unlimited} or @samp{set
21909 width 0} to prevent @value{GDBN} from wrapping its output.
21911 @item set pagination on
21912 @itemx set pagination off
21913 @kindex set pagination
21914 Turn the output pagination on or off; the default is on. Turning
21915 pagination off is the alternative to @code{set height unlimited}. Note that
21916 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21917 Options, -batch}) also automatically disables pagination.
21919 @item show pagination
21920 @kindex show pagination
21921 Show the current pagination mode.
21926 @cindex number representation
21927 @cindex entering numbers
21929 You can always enter numbers in octal, decimal, or hexadecimal in
21930 @value{GDBN} by the usual conventions: octal numbers begin with
21931 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21932 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21933 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21934 10; likewise, the default display for numbers---when no particular
21935 format is specified---is base 10. You can change the default base for
21936 both input and output with the commands described below.
21939 @kindex set input-radix
21940 @item set input-radix @var{base}
21941 Set the default base for numeric input. Supported choices
21942 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21943 specified either unambiguously or using the current input radix; for
21947 set input-radix 012
21948 set input-radix 10.
21949 set input-radix 0xa
21953 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21954 leaves the input radix unchanged, no matter what it was, since
21955 @samp{10}, being without any leading or trailing signs of its base, is
21956 interpreted in the current radix. Thus, if the current radix is 16,
21957 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21960 @kindex set output-radix
21961 @item set output-radix @var{base}
21962 Set the default base for numeric display. Supported choices
21963 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21964 specified either unambiguously or using the current input radix.
21966 @kindex show input-radix
21967 @item show input-radix
21968 Display the current default base for numeric input.
21970 @kindex show output-radix
21971 @item show output-radix
21972 Display the current default base for numeric display.
21974 @item set radix @r{[}@var{base}@r{]}
21978 These commands set and show the default base for both input and output
21979 of numbers. @code{set radix} sets the radix of input and output to
21980 the same base; without an argument, it resets the radix back to its
21981 default value of 10.
21986 @section Configuring the Current ABI
21988 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21989 application automatically. However, sometimes you need to override its
21990 conclusions. Use these commands to manage @value{GDBN}'s view of the
21996 @cindex Newlib OS ABI and its influence on the longjmp handling
21998 One @value{GDBN} configuration can debug binaries for multiple operating
21999 system targets, either via remote debugging or native emulation.
22000 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22001 but you can override its conclusion using the @code{set osabi} command.
22002 One example where this is useful is in debugging of binaries which use
22003 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22004 not have the same identifying marks that the standard C library for your
22007 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22008 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22009 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22010 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22014 Show the OS ABI currently in use.
22017 With no argument, show the list of registered available OS ABI's.
22019 @item set osabi @var{abi}
22020 Set the current OS ABI to @var{abi}.
22023 @cindex float promotion
22025 Generally, the way that an argument of type @code{float} is passed to a
22026 function depends on whether the function is prototyped. For a prototyped
22027 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22028 according to the architecture's convention for @code{float}. For unprototyped
22029 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22030 @code{double} and then passed.
22032 Unfortunately, some forms of debug information do not reliably indicate whether
22033 a function is prototyped. If @value{GDBN} calls a function that is not marked
22034 as prototyped, it consults @kbd{set coerce-float-to-double}.
22037 @kindex set coerce-float-to-double
22038 @item set coerce-float-to-double
22039 @itemx set coerce-float-to-double on
22040 Arguments of type @code{float} will be promoted to @code{double} when passed
22041 to an unprototyped function. This is the default setting.
22043 @item set coerce-float-to-double off
22044 Arguments of type @code{float} will be passed directly to unprototyped
22047 @kindex show coerce-float-to-double
22048 @item show coerce-float-to-double
22049 Show the current setting of promoting @code{float} to @code{double}.
22053 @kindex show cp-abi
22054 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22055 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22056 used to build your application. @value{GDBN} only fully supports
22057 programs with a single C@t{++} ABI; if your program contains code using
22058 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22059 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22060 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22061 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22062 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22063 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22068 Show the C@t{++} ABI currently in use.
22071 With no argument, show the list of supported C@t{++} ABI's.
22073 @item set cp-abi @var{abi}
22074 @itemx set cp-abi auto
22075 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22079 @section Automatically loading associated files
22080 @cindex auto-loading
22082 @value{GDBN} sometimes reads files with commands and settings automatically,
22083 without being explicitly told so by the user. We call this feature
22084 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22085 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22086 results or introduce security risks (e.g., if the file comes from untrusted
22089 Note that loading of these associated files (including the local @file{.gdbinit}
22090 file) requires accordingly configured @code{auto-load safe-path}
22091 (@pxref{Auto-loading safe path}).
22093 For these reasons, @value{GDBN} includes commands and options to let you
22094 control when to auto-load files and which files should be auto-loaded.
22097 @anchor{set auto-load off}
22098 @kindex set auto-load off
22099 @item set auto-load off
22100 Globally disable loading of all auto-loaded files.
22101 You may want to use this command with the @samp{-iex} option
22102 (@pxref{Option -init-eval-command}) such as:
22104 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22107 Be aware that system init file (@pxref{System-wide configuration})
22108 and init files from your home directory (@pxref{Home Directory Init File})
22109 still get read (as they come from generally trusted directories).
22110 To prevent @value{GDBN} from auto-loading even those init files, use the
22111 @option{-nx} option (@pxref{Mode Options}), in addition to
22112 @code{set auto-load no}.
22114 @anchor{show auto-load}
22115 @kindex show auto-load
22116 @item show auto-load
22117 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22121 (gdb) show auto-load
22122 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22123 libthread-db: Auto-loading of inferior specific libthread_db is on.
22124 local-gdbinit: Auto-loading of .gdbinit script from current directory
22126 python-scripts: Auto-loading of Python scripts is on.
22127 safe-path: List of directories from which it is safe to auto-load files
22128 is $debugdir:$datadir/auto-load.
22129 scripts-directory: List of directories from which to load auto-loaded scripts
22130 is $debugdir:$datadir/auto-load.
22133 @anchor{info auto-load}
22134 @kindex info auto-load
22135 @item info auto-load
22136 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22140 (gdb) info auto-load
22143 Yes /home/user/gdb/gdb-gdb.gdb
22144 libthread-db: No auto-loaded libthread-db.
22145 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22149 Yes /home/user/gdb/gdb-gdb.py
22153 These are various kinds of files @value{GDBN} can automatically load:
22157 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22159 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22161 @xref{dotdebug_gdb_scripts section},
22162 controlled by @ref{set auto-load python-scripts}.
22164 @xref{Init File in the Current Directory},
22165 controlled by @ref{set auto-load local-gdbinit}.
22167 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22170 These are @value{GDBN} control commands for the auto-loading:
22172 @multitable @columnfractions .5 .5
22173 @item @xref{set auto-load off}.
22174 @tab Disable auto-loading globally.
22175 @item @xref{show auto-load}.
22176 @tab Show setting of all kinds of files.
22177 @item @xref{info auto-load}.
22178 @tab Show state of all kinds of files.
22179 @item @xref{set auto-load gdb-scripts}.
22180 @tab Control for @value{GDBN} command scripts.
22181 @item @xref{show auto-load gdb-scripts}.
22182 @tab Show setting of @value{GDBN} command scripts.
22183 @item @xref{info auto-load gdb-scripts}.
22184 @tab Show state of @value{GDBN} command scripts.
22185 @item @xref{set auto-load python-scripts}.
22186 @tab Control for @value{GDBN} Python scripts.
22187 @item @xref{show auto-load python-scripts}.
22188 @tab Show setting of @value{GDBN} Python scripts.
22189 @item @xref{info auto-load python-scripts}.
22190 @tab Show state of @value{GDBN} Python scripts.
22191 @item @xref{set auto-load scripts-directory}.
22192 @tab Control for @value{GDBN} auto-loaded scripts location.
22193 @item @xref{show auto-load scripts-directory}.
22194 @tab Show @value{GDBN} auto-loaded scripts location.
22195 @item @xref{set auto-load local-gdbinit}.
22196 @tab Control for init file in the current directory.
22197 @item @xref{show auto-load local-gdbinit}.
22198 @tab Show setting of init file in the current directory.
22199 @item @xref{info auto-load local-gdbinit}.
22200 @tab Show state of init file in the current directory.
22201 @item @xref{set auto-load libthread-db}.
22202 @tab Control for thread debugging library.
22203 @item @xref{show auto-load libthread-db}.
22204 @tab Show setting of thread debugging library.
22205 @item @xref{info auto-load libthread-db}.
22206 @tab Show state of thread debugging library.
22207 @item @xref{set auto-load safe-path}.
22208 @tab Control directories trusted for automatic loading.
22209 @item @xref{show auto-load safe-path}.
22210 @tab Show directories trusted for automatic loading.
22211 @item @xref{add-auto-load-safe-path}.
22212 @tab Add directory trusted for automatic loading.
22216 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22217 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22218 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22219 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22220 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22221 @xref{Python Auto-loading}.
22224 @node Init File in the Current Directory
22225 @subsection Automatically loading init file in the current directory
22226 @cindex auto-loading init file in the current directory
22228 By default, @value{GDBN} reads and executes the canned sequences of commands
22229 from init file (if any) in the current working directory,
22230 see @ref{Init File in the Current Directory during Startup}.
22232 Note that loading of this local @file{.gdbinit} file also requires accordingly
22233 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22236 @anchor{set auto-load local-gdbinit}
22237 @kindex set auto-load local-gdbinit
22238 @item set auto-load local-gdbinit [on|off]
22239 Enable or disable the auto-loading of canned sequences of commands
22240 (@pxref{Sequences}) found in init file in the current directory.
22242 @anchor{show auto-load local-gdbinit}
22243 @kindex show auto-load local-gdbinit
22244 @item show auto-load local-gdbinit
22245 Show whether auto-loading of canned sequences of commands from init file in the
22246 current directory is enabled or disabled.
22248 @anchor{info auto-load local-gdbinit}
22249 @kindex info auto-load local-gdbinit
22250 @item info auto-load local-gdbinit
22251 Print whether canned sequences of commands from init file in the
22252 current directory have been auto-loaded.
22255 @node libthread_db.so.1 file
22256 @subsection Automatically loading thread debugging library
22257 @cindex auto-loading libthread_db.so.1
22259 This feature is currently present only on @sc{gnu}/Linux native hosts.
22261 @value{GDBN} reads in some cases thread debugging library from places specific
22262 to the inferior (@pxref{set libthread-db-search-path}).
22264 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22265 without checking this @samp{set auto-load libthread-db} switch as system
22266 libraries have to be trusted in general. In all other cases of
22267 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22268 auto-load libthread-db} is enabled before trying to open such thread debugging
22271 Note that loading of this debugging library also requires accordingly configured
22272 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22275 @anchor{set auto-load libthread-db}
22276 @kindex set auto-load libthread-db
22277 @item set auto-load libthread-db [on|off]
22278 Enable or disable the auto-loading of inferior specific thread debugging library.
22280 @anchor{show auto-load libthread-db}
22281 @kindex show auto-load libthread-db
22282 @item show auto-load libthread-db
22283 Show whether auto-loading of inferior specific thread debugging library is
22284 enabled or disabled.
22286 @anchor{info auto-load libthread-db}
22287 @kindex info auto-load libthread-db
22288 @item info auto-load libthread-db
22289 Print the list of all loaded inferior specific thread debugging libraries and
22290 for each such library print list of inferior @var{pid}s using it.
22293 @node objfile-gdb.gdb file
22294 @subsection The @file{@var{objfile}-gdb.gdb} file
22295 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22297 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22298 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22299 auto-load gdb-scripts} is set to @samp{on}.
22301 Note that loading of this script file also requires accordingly configured
22302 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22304 For more background refer to the similar Python scripts auto-loading
22305 description (@pxref{objfile-gdb.py file}).
22308 @anchor{set auto-load gdb-scripts}
22309 @kindex set auto-load gdb-scripts
22310 @item set auto-load gdb-scripts [on|off]
22311 Enable or disable the auto-loading of canned sequences of commands scripts.
22313 @anchor{show auto-load gdb-scripts}
22314 @kindex show auto-load gdb-scripts
22315 @item show auto-load gdb-scripts
22316 Show whether auto-loading of canned sequences of commands scripts is enabled or
22319 @anchor{info auto-load gdb-scripts}
22320 @kindex info auto-load gdb-scripts
22321 @cindex print list of auto-loaded canned sequences of commands scripts
22322 @item info auto-load gdb-scripts [@var{regexp}]
22323 Print the list of all canned sequences of commands scripts that @value{GDBN}
22327 If @var{regexp} is supplied only canned sequences of commands scripts with
22328 matching names are printed.
22330 @node Auto-loading safe path
22331 @subsection Security restriction for auto-loading
22332 @cindex auto-loading safe-path
22334 As the files of inferior can come from untrusted source (such as submitted by
22335 an application user) @value{GDBN} does not always load any files automatically.
22336 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22337 directories trusted for loading files not explicitly requested by user.
22338 Each directory can also be a shell wildcard pattern.
22340 If the path is not set properly you will see a warning and the file will not
22345 Reading symbols from /home/user/gdb/gdb...done.
22346 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22347 declined by your `auto-load safe-path' set
22348 to "$debugdir:$datadir/auto-load".
22349 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22350 declined by your `auto-load safe-path' set
22351 to "$debugdir:$datadir/auto-load".
22355 To instruct @value{GDBN} to go ahead and use the init files anyway,
22356 invoke @value{GDBN} like this:
22359 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22362 The list of trusted directories is controlled by the following commands:
22365 @anchor{set auto-load safe-path}
22366 @kindex set auto-load safe-path
22367 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22368 Set the list of directories (and their subdirectories) trusted for automatic
22369 loading and execution of scripts. You can also enter a specific trusted file.
22370 Each directory can also be a shell wildcard pattern; wildcards do not match
22371 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22372 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22373 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22374 its default value as specified during @value{GDBN} compilation.
22376 The list of directories uses path separator (@samp{:} on GNU and Unix
22377 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22378 to the @env{PATH} environment variable.
22380 @anchor{show auto-load safe-path}
22381 @kindex show auto-load safe-path
22382 @item show auto-load safe-path
22383 Show the list of directories trusted for automatic loading and execution of
22386 @anchor{add-auto-load-safe-path}
22387 @kindex add-auto-load-safe-path
22388 @item add-auto-load-safe-path
22389 Add an entry (or list of entries) the list of directories trusted for automatic
22390 loading and execution of scripts. Multiple entries may be delimited by the
22391 host platform path separator in use.
22394 This variable defaults to what @code{--with-auto-load-dir} has been configured
22395 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22396 substitution applies the same as for @ref{set auto-load scripts-directory}.
22397 The default @code{set auto-load safe-path} value can be also overriden by
22398 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22400 Setting this variable to @file{/} disables this security protection,
22401 corresponding @value{GDBN} configuration option is
22402 @option{--without-auto-load-safe-path}.
22403 This variable is supposed to be set to the system directories writable by the
22404 system superuser only. Users can add their source directories in init files in
22405 their home directories (@pxref{Home Directory Init File}). See also deprecated
22406 init file in the current directory
22407 (@pxref{Init File in the Current Directory during Startup}).
22409 To force @value{GDBN} to load the files it declined to load in the previous
22410 example, you could use one of the following ways:
22413 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22414 Specify this trusted directory (or a file) as additional component of the list.
22415 You have to specify also any existing directories displayed by
22416 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22418 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22419 Specify this directory as in the previous case but just for a single
22420 @value{GDBN} session.
22422 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22423 Disable auto-loading safety for a single @value{GDBN} session.
22424 This assumes all the files you debug during this @value{GDBN} session will come
22425 from trusted sources.
22427 @item @kbd{./configure --without-auto-load-safe-path}
22428 During compilation of @value{GDBN} you may disable any auto-loading safety.
22429 This assumes all the files you will ever debug with this @value{GDBN} come from
22433 On the other hand you can also explicitly forbid automatic files loading which
22434 also suppresses any such warning messages:
22437 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22438 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22440 @item @file{~/.gdbinit}: @samp{set auto-load no}
22441 Disable auto-loading globally for the user
22442 (@pxref{Home Directory Init File}). While it is improbable, you could also
22443 use system init file instead (@pxref{System-wide configuration}).
22446 This setting applies to the file names as entered by user. If no entry matches
22447 @value{GDBN} tries as a last resort to also resolve all the file names into
22448 their canonical form (typically resolving symbolic links) and compare the
22449 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22450 own before starting the comparison so a canonical form of directories is
22451 recommended to be entered.
22453 @node Auto-loading verbose mode
22454 @subsection Displaying files tried for auto-load
22455 @cindex auto-loading verbose mode
22457 For better visibility of all the file locations where you can place scripts to
22458 be auto-loaded with inferior --- or to protect yourself against accidental
22459 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22460 all the files attempted to be loaded. Both existing and non-existing files may
22463 For example the list of directories from which it is safe to auto-load files
22464 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22465 may not be too obvious while setting it up.
22468 (gdb) set debug auto-load on
22469 (gdb) file ~/src/t/true
22470 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22471 for objfile "/tmp/true".
22472 auto-load: Updating directories of "/usr:/opt".
22473 auto-load: Using directory "/usr".
22474 auto-load: Using directory "/opt".
22475 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22476 by your `auto-load safe-path' set to "/usr:/opt".
22480 @anchor{set debug auto-load}
22481 @kindex set debug auto-load
22482 @item set debug auto-load [on|off]
22483 Set whether to print the filenames attempted to be auto-loaded.
22485 @anchor{show debug auto-load}
22486 @kindex show debug auto-load
22487 @item show debug auto-load
22488 Show whether printing of the filenames attempted to be auto-loaded is turned
22492 @node Messages/Warnings
22493 @section Optional Warnings and Messages
22495 @cindex verbose operation
22496 @cindex optional warnings
22497 By default, @value{GDBN} is silent about its inner workings. If you are
22498 running on a slow machine, you may want to use the @code{set verbose}
22499 command. This makes @value{GDBN} tell you when it does a lengthy
22500 internal operation, so you will not think it has crashed.
22502 Currently, the messages controlled by @code{set verbose} are those
22503 which announce that the symbol table for a source file is being read;
22504 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22507 @kindex set verbose
22508 @item set verbose on
22509 Enables @value{GDBN} output of certain informational messages.
22511 @item set verbose off
22512 Disables @value{GDBN} output of certain informational messages.
22514 @kindex show verbose
22516 Displays whether @code{set verbose} is on or off.
22519 By default, if @value{GDBN} encounters bugs in the symbol table of an
22520 object file, it is silent; but if you are debugging a compiler, you may
22521 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22526 @kindex set complaints
22527 @item set complaints @var{limit}
22528 Permits @value{GDBN} to output @var{limit} complaints about each type of
22529 unusual symbols before becoming silent about the problem. Set
22530 @var{limit} to zero to suppress all complaints; set it to a large number
22531 to prevent complaints from being suppressed.
22533 @kindex show complaints
22534 @item show complaints
22535 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22539 @anchor{confirmation requests}
22540 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22541 lot of stupid questions to confirm certain commands. For example, if
22542 you try to run a program which is already running:
22546 The program being debugged has been started already.
22547 Start it from the beginning? (y or n)
22550 If you are willing to unflinchingly face the consequences of your own
22551 commands, you can disable this ``feature'':
22555 @kindex set confirm
22557 @cindex confirmation
22558 @cindex stupid questions
22559 @item set confirm off
22560 Disables confirmation requests. Note that running @value{GDBN} with
22561 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22562 automatically disables confirmation requests.
22564 @item set confirm on
22565 Enables confirmation requests (the default).
22567 @kindex show confirm
22569 Displays state of confirmation requests.
22573 @cindex command tracing
22574 If you need to debug user-defined commands or sourced files you may find it
22575 useful to enable @dfn{command tracing}. In this mode each command will be
22576 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22577 quantity denoting the call depth of each command.
22580 @kindex set trace-commands
22581 @cindex command scripts, debugging
22582 @item set trace-commands on
22583 Enable command tracing.
22584 @item set trace-commands off
22585 Disable command tracing.
22586 @item show trace-commands
22587 Display the current state of command tracing.
22590 @node Debugging Output
22591 @section Optional Messages about Internal Happenings
22592 @cindex optional debugging messages
22594 @value{GDBN} has commands that enable optional debugging messages from
22595 various @value{GDBN} subsystems; normally these commands are of
22596 interest to @value{GDBN} maintainers, or when reporting a bug. This
22597 section documents those commands.
22600 @kindex set exec-done-display
22601 @item set exec-done-display
22602 Turns on or off the notification of asynchronous commands'
22603 completion. When on, @value{GDBN} will print a message when an
22604 asynchronous command finishes its execution. The default is off.
22605 @kindex show exec-done-display
22606 @item show exec-done-display
22607 Displays the current setting of asynchronous command completion
22610 @cindex ARM AArch64
22611 @item set debug aarch64
22612 Turns on or off display of debugging messages related to ARM AArch64.
22613 The default is off.
22615 @item show debug aarch64
22616 Displays the current state of displaying debugging messages related to
22618 @cindex gdbarch debugging info
22619 @cindex architecture debugging info
22620 @item set debug arch
22621 Turns on or off display of gdbarch debugging info. The default is off
22622 @item show debug arch
22623 Displays the current state of displaying gdbarch debugging info.
22624 @item set debug aix-solib
22625 @cindex AIX shared library debugging
22626 Control display of debugging messages from the AIX shared library
22627 support module. The default is off.
22628 @item show debug aix-thread
22629 Show the current state of displaying AIX shared library debugging messages.
22630 @item set debug aix-thread
22631 @cindex AIX threads
22632 Display debugging messages about inner workings of the AIX thread
22634 @item show debug aix-thread
22635 Show the current state of AIX thread debugging info display.
22636 @item set debug check-physname
22638 Check the results of the ``physname'' computation. When reading DWARF
22639 debugging information for C@t{++}, @value{GDBN} attempts to compute
22640 each entity's name. @value{GDBN} can do this computation in two
22641 different ways, depending on exactly what information is present.
22642 When enabled, this setting causes @value{GDBN} to compute the names
22643 both ways and display any discrepancies.
22644 @item show debug check-physname
22645 Show the current state of ``physname'' checking.
22646 @item set debug coff-pe-read
22647 @cindex COFF/PE exported symbols
22648 Control display of debugging messages related to reading of COFF/PE
22649 exported symbols. The default is off.
22650 @item show debug coff-pe-read
22651 Displays the current state of displaying debugging messages related to
22652 reading of COFF/PE exported symbols.
22653 @item set debug dwarf2-die
22654 @cindex DWARF2 DIEs
22655 Dump DWARF2 DIEs after they are read in.
22656 The value is the number of nesting levels to print.
22657 A value of zero turns off the display.
22658 @item show debug dwarf2-die
22659 Show the current state of DWARF2 DIE debugging.
22660 @item set debug dwarf2-read
22661 @cindex DWARF2 Reading
22662 Turns on or off display of debugging messages related to reading
22663 DWARF debug info. The default is 0 (off).
22664 A value of 1 provides basic information.
22665 A value greater than 1 provides more verbose information.
22666 @item show debug dwarf2-read
22667 Show the current state of DWARF2 reader debugging.
22668 @item set debug displaced
22669 @cindex displaced stepping debugging info
22670 Turns on or off display of @value{GDBN} debugging info for the
22671 displaced stepping support. The default is off.
22672 @item show debug displaced
22673 Displays the current state of displaying @value{GDBN} debugging info
22674 related to displaced stepping.
22675 @item set debug event
22676 @cindex event debugging info
22677 Turns on or off display of @value{GDBN} event debugging info. The
22679 @item show debug event
22680 Displays the current state of displaying @value{GDBN} event debugging
22682 @item set debug expression
22683 @cindex expression debugging info
22684 Turns on or off display of debugging info about @value{GDBN}
22685 expression parsing. The default is off.
22686 @item show debug expression
22687 Displays the current state of displaying debugging info about
22688 @value{GDBN} expression parsing.
22689 @item set debug frame
22690 @cindex frame debugging info
22691 Turns on or off display of @value{GDBN} frame debugging info. The
22693 @item show debug frame
22694 Displays the current state of displaying @value{GDBN} frame debugging
22696 @item set debug gnu-nat
22697 @cindex @sc{gnu}/Hurd debug messages
22698 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22699 @item show debug gnu-nat
22700 Show the current state of @sc{gnu}/Hurd debugging messages.
22701 @item set debug infrun
22702 @cindex inferior debugging info
22703 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22704 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22705 for implementing operations such as single-stepping the inferior.
22706 @item show debug infrun
22707 Displays the current state of @value{GDBN} inferior debugging.
22708 @item set debug jit
22709 @cindex just-in-time compilation, debugging messages
22710 Turns on or off debugging messages from JIT debug support.
22711 @item show debug jit
22712 Displays the current state of @value{GDBN} JIT debugging.
22713 @item set debug lin-lwp
22714 @cindex @sc{gnu}/Linux LWP debug messages
22715 @cindex Linux lightweight processes
22716 Turns on or off debugging messages from the Linux LWP debug support.
22717 @item show debug lin-lwp
22718 Show the current state of Linux LWP debugging messages.
22719 @item set debug mach-o
22720 @cindex Mach-O symbols processing
22721 Control display of debugging messages related to Mach-O symbols
22722 processing. The default is off.
22723 @item show debug mach-o
22724 Displays the current state of displaying debugging messages related to
22725 reading of COFF/PE exported symbols.
22726 @item set debug notification
22727 @cindex remote async notification debugging info
22728 Turns on or off debugging messages about remote async notification.
22729 The default is off.
22730 @item show debug notification
22731 Displays the current state of remote async notification debugging messages.
22732 @item set debug observer
22733 @cindex observer debugging info
22734 Turns on or off display of @value{GDBN} observer debugging. This
22735 includes info such as the notification of observable events.
22736 @item show debug observer
22737 Displays the current state of observer debugging.
22738 @item set debug overload
22739 @cindex C@t{++} overload debugging info
22740 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22741 info. This includes info such as ranking of functions, etc. The default
22743 @item show debug overload
22744 Displays the current state of displaying @value{GDBN} C@t{++} overload
22746 @cindex expression parser, debugging info
22747 @cindex debug expression parser
22748 @item set debug parser
22749 Turns on or off the display of expression parser debugging output.
22750 Internally, this sets the @code{yydebug} variable in the expression
22751 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22752 details. The default is off.
22753 @item show debug parser
22754 Show the current state of expression parser debugging.
22755 @cindex packets, reporting on stdout
22756 @cindex serial connections, debugging
22757 @cindex debug remote protocol
22758 @cindex remote protocol debugging
22759 @cindex display remote packets
22760 @item set debug remote
22761 Turns on or off display of reports on all packets sent back and forth across
22762 the serial line to the remote machine. The info is printed on the
22763 @value{GDBN} standard output stream. The default is off.
22764 @item show debug remote
22765 Displays the state of display of remote packets.
22766 @item set debug serial
22767 Turns on or off display of @value{GDBN} serial debugging info. The
22769 @item show debug serial
22770 Displays the current state of displaying @value{GDBN} serial debugging
22772 @item set debug solib-frv
22773 @cindex FR-V shared-library debugging
22774 Turns on or off debugging messages for FR-V shared-library code.
22775 @item show debug solib-frv
22776 Display the current state of FR-V shared-library code debugging
22778 @item set debug symfile
22779 @cindex symbol file functions
22780 Turns on or off display of debugging messages related to symbol file functions.
22781 The default is off. @xref{Files}.
22782 @item show debug symfile
22783 Show the current state of symbol file debugging messages.
22784 @item set debug symtab-create
22785 @cindex symbol table creation
22786 Turns on or off display of debugging messages related to symbol table creation.
22787 The default is 0 (off).
22788 A value of 1 provides basic information.
22789 A value greater than 1 provides more verbose information.
22790 @item show debug symtab-create
22791 Show the current state of symbol table creation debugging.
22792 @item set debug target
22793 @cindex target debugging info
22794 Turns on or off display of @value{GDBN} target debugging info. This info
22795 includes what is going on at the target level of GDB, as it happens. The
22796 default is 0. Set it to 1 to track events, and to 2 to also track the
22797 value of large memory transfers. Changes to this flag do not take effect
22798 until the next time you connect to a target or use the @code{run} command.
22799 @item show debug target
22800 Displays the current state of displaying @value{GDBN} target debugging
22802 @item set debug timestamp
22803 @cindex timestampping debugging info
22804 Turns on or off display of timestamps with @value{GDBN} debugging info.
22805 When enabled, seconds and microseconds are displayed before each debugging
22807 @item show debug timestamp
22808 Displays the current state of displaying timestamps with @value{GDBN}
22810 @item set debugvarobj
22811 @cindex variable object debugging info
22812 Turns on or off display of @value{GDBN} variable object debugging
22813 info. The default is off.
22814 @item show debugvarobj
22815 Displays the current state of displaying @value{GDBN} variable object
22817 @item set debug xml
22818 @cindex XML parser debugging
22819 Turns on or off debugging messages for built-in XML parsers.
22820 @item show debug xml
22821 Displays the current state of XML debugging messages.
22824 @node Other Misc Settings
22825 @section Other Miscellaneous Settings
22826 @cindex miscellaneous settings
22829 @kindex set interactive-mode
22830 @item set interactive-mode
22831 If @code{on}, forces @value{GDBN} to assume that GDB was started
22832 in a terminal. In practice, this means that @value{GDBN} should wait
22833 for the user to answer queries generated by commands entered at
22834 the command prompt. If @code{off}, forces @value{GDBN} to operate
22835 in the opposite mode, and it uses the default answers to all queries.
22836 If @code{auto} (the default), @value{GDBN} tries to determine whether
22837 its standard input is a terminal, and works in interactive-mode if it
22838 is, non-interactively otherwise.
22840 In the vast majority of cases, the debugger should be able to guess
22841 correctly which mode should be used. But this setting can be useful
22842 in certain specific cases, such as running a MinGW @value{GDBN}
22843 inside a cygwin window.
22845 @kindex show interactive-mode
22846 @item show interactive-mode
22847 Displays whether the debugger is operating in interactive mode or not.
22850 @node Extending GDB
22851 @chapter Extending @value{GDBN}
22852 @cindex extending GDB
22854 @value{GDBN} provides three mechanisms for extension. The first is based
22855 on composition of @value{GDBN} commands, the second is based on the
22856 Python scripting language, and the third is for defining new aliases of
22859 To facilitate the use of the first two extensions, @value{GDBN} is capable
22860 of evaluating the contents of a file. When doing so, @value{GDBN}
22861 can recognize which scripting language is being used by looking at
22862 the filename extension. Files with an unrecognized filename extension
22863 are always treated as a @value{GDBN} Command Files.
22864 @xref{Command Files,, Command files}.
22866 You can control how @value{GDBN} evaluates these files with the following
22870 @kindex set script-extension
22871 @kindex show script-extension
22872 @item set script-extension off
22873 All scripts are always evaluated as @value{GDBN} Command Files.
22875 @item set script-extension soft
22876 The debugger determines the scripting language based on filename
22877 extension. If this scripting language is supported, @value{GDBN}
22878 evaluates the script using that language. Otherwise, it evaluates
22879 the file as a @value{GDBN} Command File.
22881 @item set script-extension strict
22882 The debugger determines the scripting language based on filename
22883 extension, and evaluates the script using that language. If the
22884 language is not supported, then the evaluation fails.
22886 @item show script-extension
22887 Display the current value of the @code{script-extension} option.
22892 * Sequences:: Canned Sequences of Commands
22893 * Python:: Scripting @value{GDBN} using Python
22894 * Aliases:: Creating new spellings of existing commands
22898 @section Canned Sequences of Commands
22900 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22901 Command Lists}), @value{GDBN} provides two ways to store sequences of
22902 commands for execution as a unit: user-defined commands and command
22906 * Define:: How to define your own commands
22907 * Hooks:: Hooks for user-defined commands
22908 * Command Files:: How to write scripts of commands to be stored in a file
22909 * Output:: Commands for controlled output
22913 @subsection User-defined Commands
22915 @cindex user-defined command
22916 @cindex arguments, to user-defined commands
22917 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22918 which you assign a new name as a command. This is done with the
22919 @code{define} command. User commands may accept up to 10 arguments
22920 separated by whitespace. Arguments are accessed within the user command
22921 via @code{$arg0@dots{}$arg9}. A trivial example:
22925 print $arg0 + $arg1 + $arg2
22930 To execute the command use:
22937 This defines the command @code{adder}, which prints the sum of
22938 its three arguments. Note the arguments are text substitutions, so they may
22939 reference variables, use complex expressions, or even perform inferior
22942 @cindex argument count in user-defined commands
22943 @cindex how many arguments (user-defined commands)
22944 In addition, @code{$argc} may be used to find out how many arguments have
22945 been passed. This expands to a number in the range 0@dots{}10.
22950 print $arg0 + $arg1
22953 print $arg0 + $arg1 + $arg2
22961 @item define @var{commandname}
22962 Define a command named @var{commandname}. If there is already a command
22963 by that name, you are asked to confirm that you want to redefine it.
22964 @var{commandname} may be a bare command name consisting of letters,
22965 numbers, dashes, and underscores. It may also start with any predefined
22966 prefix command. For example, @samp{define target my-target} creates
22967 a user-defined @samp{target my-target} command.
22969 The definition of the command is made up of other @value{GDBN} command lines,
22970 which are given following the @code{define} command. The end of these
22971 commands is marked by a line containing @code{end}.
22974 @kindex end@r{ (user-defined commands)}
22975 @item document @var{commandname}
22976 Document the user-defined command @var{commandname}, so that it can be
22977 accessed by @code{help}. The command @var{commandname} must already be
22978 defined. This command reads lines of documentation just as @code{define}
22979 reads the lines of the command definition, ending with @code{end}.
22980 After the @code{document} command is finished, @code{help} on command
22981 @var{commandname} displays the documentation you have written.
22983 You may use the @code{document} command again to change the
22984 documentation of a command. Redefining the command with @code{define}
22985 does not change the documentation.
22987 @kindex dont-repeat
22988 @cindex don't repeat command
22990 Used inside a user-defined command, this tells @value{GDBN} that this
22991 command should not be repeated when the user hits @key{RET}
22992 (@pxref{Command Syntax, repeat last command}).
22994 @kindex help user-defined
22995 @item help user-defined
22996 List all user-defined commands and all python commands defined in class
22997 COMAND_USER. The first line of the documentation or docstring is
23002 @itemx show user @var{commandname}
23003 Display the @value{GDBN} commands used to define @var{commandname} (but
23004 not its documentation). If no @var{commandname} is given, display the
23005 definitions for all user-defined commands.
23006 This does not work for user-defined python commands.
23008 @cindex infinite recursion in user-defined commands
23009 @kindex show max-user-call-depth
23010 @kindex set max-user-call-depth
23011 @item show max-user-call-depth
23012 @itemx set max-user-call-depth
23013 The value of @code{max-user-call-depth} controls how many recursion
23014 levels are allowed in user-defined commands before @value{GDBN} suspects an
23015 infinite recursion and aborts the command.
23016 This does not apply to user-defined python commands.
23019 In addition to the above commands, user-defined commands frequently
23020 use control flow commands, described in @ref{Command Files}.
23022 When user-defined commands are executed, the
23023 commands of the definition are not printed. An error in any command
23024 stops execution of the user-defined command.
23026 If used interactively, commands that would ask for confirmation proceed
23027 without asking when used inside a user-defined command. Many @value{GDBN}
23028 commands that normally print messages to say what they are doing omit the
23029 messages when used in a user-defined command.
23032 @subsection User-defined Command Hooks
23033 @cindex command hooks
23034 @cindex hooks, for commands
23035 @cindex hooks, pre-command
23038 You may define @dfn{hooks}, which are a special kind of user-defined
23039 command. Whenever you run the command @samp{foo}, if the user-defined
23040 command @samp{hook-foo} exists, it is executed (with no arguments)
23041 before that command.
23043 @cindex hooks, post-command
23045 A hook may also be defined which is run after the command you executed.
23046 Whenever you run the command @samp{foo}, if the user-defined command
23047 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23048 that command. Post-execution hooks may exist simultaneously with
23049 pre-execution hooks, for the same command.
23051 It is valid for a hook to call the command which it hooks. If this
23052 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23054 @c It would be nice if hookpost could be passed a parameter indicating
23055 @c if the command it hooks executed properly or not. FIXME!
23057 @kindex stop@r{, a pseudo-command}
23058 In addition, a pseudo-command, @samp{stop} exists. Defining
23059 (@samp{hook-stop}) makes the associated commands execute every time
23060 execution stops in your program: before breakpoint commands are run,
23061 displays are printed, or the stack frame is printed.
23063 For example, to ignore @code{SIGALRM} signals while
23064 single-stepping, but treat them normally during normal execution,
23069 handle SIGALRM nopass
23073 handle SIGALRM pass
23076 define hook-continue
23077 handle SIGALRM pass
23081 As a further example, to hook at the beginning and end of the @code{echo}
23082 command, and to add extra text to the beginning and end of the message,
23090 define hookpost-echo
23094 (@value{GDBP}) echo Hello World
23095 <<<---Hello World--->>>
23100 You can define a hook for any single-word command in @value{GDBN}, but
23101 not for command aliases; you should define a hook for the basic command
23102 name, e.g.@: @code{backtrace} rather than @code{bt}.
23103 @c FIXME! So how does Joe User discover whether a command is an alias
23105 You can hook a multi-word command by adding @code{hook-} or
23106 @code{hookpost-} to the last word of the command, e.g.@:
23107 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23109 If an error occurs during the execution of your hook, execution of
23110 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23111 (before the command that you actually typed had a chance to run).
23113 If you try to define a hook which does not match any known command, you
23114 get a warning from the @code{define} command.
23116 @node Command Files
23117 @subsection Command Files
23119 @cindex command files
23120 @cindex scripting commands
23121 A command file for @value{GDBN} is a text file made of lines that are
23122 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23123 also be included. An empty line in a command file does nothing; it
23124 does not mean to repeat the last command, as it would from the
23127 You can request the execution of a command file with the @code{source}
23128 command. Note that the @code{source} command is also used to evaluate
23129 scripts that are not Command Files. The exact behavior can be configured
23130 using the @code{script-extension} setting.
23131 @xref{Extending GDB,, Extending GDB}.
23135 @cindex execute commands from a file
23136 @item source [-s] [-v] @var{filename}
23137 Execute the command file @var{filename}.
23140 The lines in a command file are generally executed sequentially,
23141 unless the order of execution is changed by one of the
23142 @emph{flow-control commands} described below. The commands are not
23143 printed as they are executed. An error in any command terminates
23144 execution of the command file and control is returned to the console.
23146 @value{GDBN} first searches for @var{filename} in the current directory.
23147 If the file is not found there, and @var{filename} does not specify a
23148 directory, then @value{GDBN} also looks for the file on the source search path
23149 (specified with the @samp{directory} command);
23150 except that @file{$cdir} is not searched because the compilation directory
23151 is not relevant to scripts.
23153 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23154 on the search path even if @var{filename} specifies a directory.
23155 The search is done by appending @var{filename} to each element of the
23156 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23157 and the search path contains @file{/home/user} then @value{GDBN} will
23158 look for the script @file{/home/user/mylib/myscript}.
23159 The search is also done if @var{filename} is an absolute path.
23160 For example, if @var{filename} is @file{/tmp/myscript} and
23161 the search path contains @file{/home/user} then @value{GDBN} will
23162 look for the script @file{/home/user/tmp/myscript}.
23163 For DOS-like systems, if @var{filename} contains a drive specification,
23164 it is stripped before concatenation. For example, if @var{filename} is
23165 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23166 will look for the script @file{c:/tmp/myscript}.
23168 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23169 each command as it is executed. The option must be given before
23170 @var{filename}, and is interpreted as part of the filename anywhere else.
23172 Commands that would ask for confirmation if used interactively proceed
23173 without asking when used in a command file. Many @value{GDBN} commands that
23174 normally print messages to say what they are doing omit the messages
23175 when called from command files.
23177 @value{GDBN} also accepts command input from standard input. In this
23178 mode, normal output goes to standard output and error output goes to
23179 standard error. Errors in a command file supplied on standard input do
23180 not terminate execution of the command file---execution continues with
23184 gdb < cmds > log 2>&1
23187 (The syntax above will vary depending on the shell used.) This example
23188 will execute commands from the file @file{cmds}. All output and errors
23189 would be directed to @file{log}.
23191 Since commands stored on command files tend to be more general than
23192 commands typed interactively, they frequently need to deal with
23193 complicated situations, such as different or unexpected values of
23194 variables and symbols, changes in how the program being debugged is
23195 built, etc. @value{GDBN} provides a set of flow-control commands to
23196 deal with these complexities. Using these commands, you can write
23197 complex scripts that loop over data structures, execute commands
23198 conditionally, etc.
23205 This command allows to include in your script conditionally executed
23206 commands. The @code{if} command takes a single argument, which is an
23207 expression to evaluate. It is followed by a series of commands that
23208 are executed only if the expression is true (its value is nonzero).
23209 There can then optionally be an @code{else} line, followed by a series
23210 of commands that are only executed if the expression was false. The
23211 end of the list is marked by a line containing @code{end}.
23215 This command allows to write loops. Its syntax is similar to
23216 @code{if}: the command takes a single argument, which is an expression
23217 to evaluate, and must be followed by the commands to execute, one per
23218 line, terminated by an @code{end}. These commands are called the
23219 @dfn{body} of the loop. The commands in the body of @code{while} are
23220 executed repeatedly as long as the expression evaluates to true.
23224 This command exits the @code{while} loop in whose body it is included.
23225 Execution of the script continues after that @code{while}s @code{end}
23228 @kindex loop_continue
23229 @item loop_continue
23230 This command skips the execution of the rest of the body of commands
23231 in the @code{while} loop in whose body it is included. Execution
23232 branches to the beginning of the @code{while} loop, where it evaluates
23233 the controlling expression.
23235 @kindex end@r{ (if/else/while commands)}
23237 Terminate the block of commands that are the body of @code{if},
23238 @code{else}, or @code{while} flow-control commands.
23243 @subsection Commands for Controlled Output
23245 During the execution of a command file or a user-defined command, normal
23246 @value{GDBN} output is suppressed; the only output that appears is what is
23247 explicitly printed by the commands in the definition. This section
23248 describes three commands useful for generating exactly the output you
23253 @item echo @var{text}
23254 @c I do not consider backslash-space a standard C escape sequence
23255 @c because it is not in ANSI.
23256 Print @var{text}. Nonprinting characters can be included in
23257 @var{text} using C escape sequences, such as @samp{\n} to print a
23258 newline. @strong{No newline is printed unless you specify one.}
23259 In addition to the standard C escape sequences, a backslash followed
23260 by a space stands for a space. This is useful for displaying a
23261 string with spaces at the beginning or the end, since leading and
23262 trailing spaces are otherwise trimmed from all arguments.
23263 To print @samp{@w{ }and foo =@w{ }}, use the command
23264 @samp{echo \@w{ }and foo = \@w{ }}.
23266 A backslash at the end of @var{text} can be used, as in C, to continue
23267 the command onto subsequent lines. For example,
23270 echo This is some text\n\
23271 which is continued\n\
23272 onto several lines.\n
23275 produces the same output as
23278 echo This is some text\n
23279 echo which is continued\n
23280 echo onto several lines.\n
23284 @item output @var{expression}
23285 Print the value of @var{expression} and nothing but that value: no
23286 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23287 value history either. @xref{Expressions, ,Expressions}, for more information
23290 @item output/@var{fmt} @var{expression}
23291 Print the value of @var{expression} in format @var{fmt}. You can use
23292 the same formats as for @code{print}. @xref{Output Formats,,Output
23293 Formats}, for more information.
23296 @item printf @var{template}, @var{expressions}@dots{}
23297 Print the values of one or more @var{expressions} under the control of
23298 the string @var{template}. To print several values, make
23299 @var{expressions} be a comma-separated list of individual expressions,
23300 which may be either numbers or pointers. Their values are printed as
23301 specified by @var{template}, exactly as a C program would do by
23302 executing the code below:
23305 printf (@var{template}, @var{expressions}@dots{});
23308 As in @code{C} @code{printf}, ordinary characters in @var{template}
23309 are printed verbatim, while @dfn{conversion specification} introduced
23310 by the @samp{%} character cause subsequent @var{expressions} to be
23311 evaluated, their values converted and formatted according to type and
23312 style information encoded in the conversion specifications, and then
23315 For example, you can print two values in hex like this:
23318 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23321 @code{printf} supports all the standard @code{C} conversion
23322 specifications, including the flags and modifiers between the @samp{%}
23323 character and the conversion letter, with the following exceptions:
23327 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23330 The modifier @samp{*} is not supported for specifying precision or
23334 The @samp{'} flag (for separation of digits into groups according to
23335 @code{LC_NUMERIC'}) is not supported.
23338 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23342 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23345 The conversion letters @samp{a} and @samp{A} are not supported.
23349 Note that the @samp{ll} type modifier is supported only if the
23350 underlying @code{C} implementation used to build @value{GDBN} supports
23351 the @code{long long int} type, and the @samp{L} type modifier is
23352 supported only if @code{long double} type is available.
23354 As in @code{C}, @code{printf} supports simple backslash-escape
23355 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23356 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23357 single character. Octal and hexadecimal escape sequences are not
23360 Additionally, @code{printf} supports conversion specifications for DFP
23361 (@dfn{Decimal Floating Point}) types using the following length modifiers
23362 together with a floating point specifier.
23367 @samp{H} for printing @code{Decimal32} types.
23370 @samp{D} for printing @code{Decimal64} types.
23373 @samp{DD} for printing @code{Decimal128} types.
23376 If the underlying @code{C} implementation used to build @value{GDBN} has
23377 support for the three length modifiers for DFP types, other modifiers
23378 such as width and precision will also be available for @value{GDBN} to use.
23380 In case there is no such @code{C} support, no additional modifiers will be
23381 available and the value will be printed in the standard way.
23383 Here's an example of printing DFP types using the above conversion letters:
23385 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23389 @item eval @var{template}, @var{expressions}@dots{}
23390 Convert the values of one or more @var{expressions} under the control of
23391 the string @var{template} to a command line, and call it.
23396 @section Scripting @value{GDBN} using Python
23397 @cindex python scripting
23398 @cindex scripting with python
23400 You can script @value{GDBN} using the @uref{http://www.python.org/,
23401 Python programming language}. This feature is available only if
23402 @value{GDBN} was configured using @option{--with-python}.
23404 @cindex python directory
23405 Python scripts used by @value{GDBN} should be installed in
23406 @file{@var{data-directory}/python}, where @var{data-directory} is
23407 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23408 This directory, known as the @dfn{python directory},
23409 is automatically added to the Python Search Path in order to allow
23410 the Python interpreter to locate all scripts installed at this location.
23412 Additionally, @value{GDBN} commands and convenience functions which
23413 are written in Python and are located in the
23414 @file{@var{data-directory}/python/gdb/command} or
23415 @file{@var{data-directory}/python/gdb/function} directories are
23416 automatically imported when @value{GDBN} starts.
23419 * Python Commands:: Accessing Python from @value{GDBN}.
23420 * Python API:: Accessing @value{GDBN} from Python.
23421 * Python Auto-loading:: Automatically loading Python code.
23422 * Python modules:: Python modules provided by @value{GDBN}.
23425 @node Python Commands
23426 @subsection Python Commands
23427 @cindex python commands
23428 @cindex commands to access python
23430 @value{GDBN} provides two commands for accessing the Python interpreter,
23431 and one related setting:
23434 @kindex python-interactive
23436 @item python-interactive @r{[}@var{command}@r{]}
23437 @itemx pi @r{[}@var{command}@r{]}
23438 Without an argument, the @code{python-interactive} command can be used
23439 to start an interactive Python prompt. To return to @value{GDBN},
23440 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23442 Alternatively, a single-line Python command can be given as an
23443 argument and evaluated. If the command is an expression, the result
23444 will be printed; otherwise, nothing will be printed. For example:
23447 (@value{GDBP}) python-interactive 2 + 3
23453 @item python @r{[}@var{command}@r{]}
23454 @itemx py @r{[}@var{command}@r{]}
23455 The @code{python} command can be used to evaluate Python code.
23457 If given an argument, the @code{python} command will evaluate the
23458 argument as a Python command. For example:
23461 (@value{GDBP}) python print 23
23465 If you do not provide an argument to @code{python}, it will act as a
23466 multi-line command, like @code{define}. In this case, the Python
23467 script is made up of subsequent command lines, given after the
23468 @code{python} command. This command list is terminated using a line
23469 containing @code{end}. For example:
23472 (@value{GDBP}) python
23474 End with a line saying just "end".
23480 @kindex set python print-stack
23481 @item set python print-stack
23482 By default, @value{GDBN} will print only the message component of a
23483 Python exception when an error occurs in a Python script. This can be
23484 controlled using @code{set python print-stack}: if @code{full}, then
23485 full Python stack printing is enabled; if @code{none}, then Python stack
23486 and message printing is disabled; if @code{message}, the default, only
23487 the message component of the error is printed.
23490 It is also possible to execute a Python script from the @value{GDBN}
23494 @item source @file{script-name}
23495 The script name must end with @samp{.py} and @value{GDBN} must be configured
23496 to recognize the script language based on filename extension using
23497 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23499 @item python execfile ("script-name")
23500 This method is based on the @code{execfile} Python built-in function,
23501 and thus is always available.
23505 @subsection Python API
23507 @cindex programming in python
23509 You can get quick online help for @value{GDBN}'s Python API by issuing
23510 the command @w{@kbd{python help (gdb)}}.
23512 Functions and methods which have two or more optional arguments allow
23513 them to be specified using keyword syntax. This allows passing some
23514 optional arguments while skipping others. Example:
23515 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23518 * Basic Python:: Basic Python Functions.
23519 * Exception Handling:: How Python exceptions are translated.
23520 * Values From Inferior:: Python representation of values.
23521 * Types In Python:: Python representation of types.
23522 * Pretty Printing API:: Pretty-printing values.
23523 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23524 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23525 * Type Printing API:: Pretty-printing types.
23526 * Frame Filter API:: Filtering Frames.
23527 * Frame Decorator API:: Decorating Frames.
23528 * Writing a Frame Filter:: Writing a Frame Filter.
23529 * Inferiors In Python:: Python representation of inferiors (processes)
23530 * Events In Python:: Listening for events from @value{GDBN}.
23531 * Threads In Python:: Accessing inferior threads from Python.
23532 * Commands In Python:: Implementing new commands in Python.
23533 * Parameters In Python:: Adding new @value{GDBN} parameters.
23534 * Functions In Python:: Writing new convenience functions.
23535 * Progspaces In Python:: Program spaces.
23536 * Objfiles In Python:: Object files.
23537 * Frames In Python:: Accessing inferior stack frames from Python.
23538 * Blocks In Python:: Accessing blocks from Python.
23539 * Symbols In Python:: Python representation of symbols.
23540 * Symbol Tables In Python:: Python representation of symbol tables.
23541 * Line Tables In Python:: Python representation of line tables.
23542 * Breakpoints In Python:: Manipulating breakpoints using Python.
23543 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23545 * Lazy Strings In Python:: Python representation of lazy strings.
23546 * Architectures In Python:: Python representation of architectures.
23550 @subsubsection Basic Python
23552 @cindex python stdout
23553 @cindex python pagination
23554 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23555 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23556 A Python program which outputs to one of these streams may have its
23557 output interrupted by the user (@pxref{Screen Size}). In this
23558 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23560 Some care must be taken when writing Python code to run in
23561 @value{GDBN}. Two things worth noting in particular:
23565 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23566 Python code must not override these, or even change the options using
23567 @code{sigaction}. If your program changes the handling of these
23568 signals, @value{GDBN} will most likely stop working correctly. Note
23569 that it is unfortunately common for GUI toolkits to install a
23570 @code{SIGCHLD} handler.
23573 @value{GDBN} takes care to mark its internal file descriptors as
23574 close-on-exec. However, this cannot be done in a thread-safe way on
23575 all platforms. Your Python programs should be aware of this and
23576 should both create new file descriptors with the close-on-exec flag
23577 set and arrange to close unneeded file descriptors before starting a
23581 @cindex python functions
23582 @cindex python module
23584 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23585 methods and classes added by @value{GDBN} are placed in this module.
23586 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23587 use in all scripts evaluated by the @code{python} command.
23589 @findex gdb.PYTHONDIR
23590 @defvar gdb.PYTHONDIR
23591 A string containing the python directory (@pxref{Python}).
23594 @findex gdb.execute
23595 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23596 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23597 If a GDB exception happens while @var{command} runs, it is
23598 translated as described in @ref{Exception Handling,,Exception Handling}.
23600 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23601 command as having originated from the user invoking it interactively.
23602 It must be a boolean value. If omitted, it defaults to @code{False}.
23604 By default, any output produced by @var{command} is sent to
23605 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23606 @code{True}, then output will be collected by @code{gdb.execute} and
23607 returned as a string. The default is @code{False}, in which case the
23608 return value is @code{None}. If @var{to_string} is @code{True}, the
23609 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23610 and height, and its pagination will be disabled; @pxref{Screen Size}.
23613 @findex gdb.breakpoints
23614 @defun gdb.breakpoints ()
23615 Return a sequence holding all of @value{GDBN}'s breakpoints.
23616 @xref{Breakpoints In Python}, for more information.
23619 @findex gdb.parameter
23620 @defun gdb.parameter (parameter)
23621 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23622 string naming the parameter to look up; @var{parameter} may contain
23623 spaces if the parameter has a multi-part name. For example,
23624 @samp{print object} is a valid parameter name.
23626 If the named parameter does not exist, this function throws a
23627 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23628 parameter's value is converted to a Python value of the appropriate
23629 type, and returned.
23632 @findex gdb.history
23633 @defun gdb.history (number)
23634 Return a value from @value{GDBN}'s value history (@pxref{Value
23635 History}). @var{number} indicates which history element to return.
23636 If @var{number} is negative, then @value{GDBN} will take its absolute value
23637 and count backward from the last element (i.e., the most recent element) to
23638 find the value to return. If @var{number} is zero, then @value{GDBN} will
23639 return the most recent element. If the element specified by @var{number}
23640 doesn't exist in the value history, a @code{gdb.error} exception will be
23643 If no exception is raised, the return value is always an instance of
23644 @code{gdb.Value} (@pxref{Values From Inferior}).
23647 @findex gdb.parse_and_eval
23648 @defun gdb.parse_and_eval (expression)
23649 Parse @var{expression} as an expression in the current language,
23650 evaluate it, and return the result as a @code{gdb.Value}.
23651 @var{expression} must be a string.
23653 This function can be useful when implementing a new command
23654 (@pxref{Commands In Python}), as it provides a way to parse the
23655 command's argument as an expression. It is also useful simply to
23656 compute values, for example, it is the only way to get the value of a
23657 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23660 @findex gdb.find_pc_line
23661 @defun gdb.find_pc_line (pc)
23662 Return the @code{gdb.Symtab_and_line} object corresponding to the
23663 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23664 value of @var{pc} is passed as an argument, then the @code{symtab} and
23665 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23666 will be @code{None} and 0 respectively.
23669 @findex gdb.post_event
23670 @defun gdb.post_event (event)
23671 Put @var{event}, a callable object taking no arguments, into
23672 @value{GDBN}'s internal event queue. This callable will be invoked at
23673 some later point, during @value{GDBN}'s event processing. Events
23674 posted using @code{post_event} will be run in the order in which they
23675 were posted; however, there is no way to know when they will be
23676 processed relative to other events inside @value{GDBN}.
23678 @value{GDBN} is not thread-safe. If your Python program uses multiple
23679 threads, you must be careful to only call @value{GDBN}-specific
23680 functions in the main @value{GDBN} thread. @code{post_event} ensures
23684 (@value{GDBP}) python
23688 > def __init__(self, message):
23689 > self.message = message;
23690 > def __call__(self):
23691 > gdb.write(self.message)
23693 >class MyThread1 (threading.Thread):
23695 > gdb.post_event(Writer("Hello "))
23697 >class MyThread2 (threading.Thread):
23699 > gdb.post_event(Writer("World\n"))
23701 >MyThread1().start()
23702 >MyThread2().start()
23704 (@value{GDBP}) Hello World
23709 @defun gdb.write (string @r{[}, stream{]})
23710 Print a string to @value{GDBN}'s paginated output stream. The
23711 optional @var{stream} determines the stream to print to. The default
23712 stream is @value{GDBN}'s standard output stream. Possible stream
23719 @value{GDBN}'s standard output stream.
23724 @value{GDBN}'s standard error stream.
23729 @value{GDBN}'s log stream (@pxref{Logging Output}).
23732 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23733 call this function and will automatically direct the output to the
23738 @defun gdb.flush ()
23739 Flush the buffer of a @value{GDBN} paginated stream so that the
23740 contents are displayed immediately. @value{GDBN} will flush the
23741 contents of a stream automatically when it encounters a newline in the
23742 buffer. The optional @var{stream} determines the stream to flush. The
23743 default stream is @value{GDBN}'s standard output stream. Possible
23750 @value{GDBN}'s standard output stream.
23755 @value{GDBN}'s standard error stream.
23760 @value{GDBN}'s log stream (@pxref{Logging Output}).
23764 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23765 call this function for the relevant stream.
23768 @findex gdb.target_charset
23769 @defun gdb.target_charset ()
23770 Return the name of the current target character set (@pxref{Character
23771 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23772 that @samp{auto} is never returned.
23775 @findex gdb.target_wide_charset
23776 @defun gdb.target_wide_charset ()
23777 Return the name of the current target wide character set
23778 (@pxref{Character Sets}). This differs from
23779 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23783 @findex gdb.solib_name
23784 @defun gdb.solib_name (address)
23785 Return the name of the shared library holding the given @var{address}
23786 as a string, or @code{None}.
23789 @findex gdb.decode_line
23790 @defun gdb.decode_line @r{[}expression@r{]}
23791 Return locations of the line specified by @var{expression}, or of the
23792 current line if no argument was given. This function returns a Python
23793 tuple containing two elements. The first element contains a string
23794 holding any unparsed section of @var{expression} (or @code{None} if
23795 the expression has been fully parsed). The second element contains
23796 either @code{None} or another tuple that contains all the locations
23797 that match the expression represented as @code{gdb.Symtab_and_line}
23798 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23799 provided, it is decoded the way that @value{GDBN}'s inbuilt
23800 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23803 @defun gdb.prompt_hook (current_prompt)
23804 @anchor{prompt_hook}
23806 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23807 assigned to this operation before a prompt is displayed by
23810 The parameter @code{current_prompt} contains the current @value{GDBN}
23811 prompt. This method must return a Python string, or @code{None}. If
23812 a string is returned, the @value{GDBN} prompt will be set to that
23813 string. If @code{None} is returned, @value{GDBN} will continue to use
23814 the current prompt.
23816 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23817 such as those used by readline for command input, and annotation
23818 related prompts are prohibited from being changed.
23821 @node Exception Handling
23822 @subsubsection Exception Handling
23823 @cindex python exceptions
23824 @cindex exceptions, python
23826 When executing the @code{python} command, Python exceptions
23827 uncaught within the Python code are translated to calls to
23828 @value{GDBN} error-reporting mechanism. If the command that called
23829 @code{python} does not handle the error, @value{GDBN} will
23830 terminate it and print an error message containing the Python
23831 exception name, the associated value, and the Python call stack
23832 backtrace at the point where the exception was raised. Example:
23835 (@value{GDBP}) python print foo
23836 Traceback (most recent call last):
23837 File "<string>", line 1, in <module>
23838 NameError: name 'foo' is not defined
23841 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23842 Python code are converted to Python exceptions. The type of the
23843 Python exception depends on the error.
23847 This is the base class for most exceptions generated by @value{GDBN}.
23848 It is derived from @code{RuntimeError}, for compatibility with earlier
23849 versions of @value{GDBN}.
23851 If an error occurring in @value{GDBN} does not fit into some more
23852 specific category, then the generated exception will have this type.
23854 @item gdb.MemoryError
23855 This is a subclass of @code{gdb.error} which is thrown when an
23856 operation tried to access invalid memory in the inferior.
23858 @item KeyboardInterrupt
23859 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23860 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23863 In all cases, your exception handler will see the @value{GDBN} error
23864 message as its value and the Python call stack backtrace at the Python
23865 statement closest to where the @value{GDBN} error occured as the
23868 @findex gdb.GdbError
23869 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23870 it is useful to be able to throw an exception that doesn't cause a
23871 traceback to be printed. For example, the user may have invoked the
23872 command incorrectly. Use the @code{gdb.GdbError} exception
23873 to handle this case. Example:
23877 >class HelloWorld (gdb.Command):
23878 > """Greet the whole world."""
23879 > def __init__ (self):
23880 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23881 > def invoke (self, args, from_tty):
23882 > argv = gdb.string_to_argv (args)
23883 > if len (argv) != 0:
23884 > raise gdb.GdbError ("hello-world takes no arguments")
23885 > print "Hello, World!"
23888 (gdb) hello-world 42
23889 hello-world takes no arguments
23892 @node Values From Inferior
23893 @subsubsection Values From Inferior
23894 @cindex values from inferior, with Python
23895 @cindex python, working with values from inferior
23897 @cindex @code{gdb.Value}
23898 @value{GDBN} provides values it obtains from the inferior program in
23899 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23900 for its internal bookkeeping of the inferior's values, and for
23901 fetching values when necessary.
23903 Inferior values that are simple scalars can be used directly in
23904 Python expressions that are valid for the value's data type. Here's
23905 an example for an integer or floating-point value @code{some_val}:
23912 As result of this, @code{bar} will also be a @code{gdb.Value} object
23913 whose values are of the same type as those of @code{some_val}.
23915 Inferior values that are structures or instances of some class can
23916 be accessed using the Python @dfn{dictionary syntax}. For example, if
23917 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23918 can access its @code{foo} element with:
23921 bar = some_val['foo']
23924 Again, @code{bar} will also be a @code{gdb.Value} object.
23926 A @code{gdb.Value} that represents a function can be executed via
23927 inferior function call. Any arguments provided to the call must match
23928 the function's prototype, and must be provided in the order specified
23931 For example, @code{some_val} is a @code{gdb.Value} instance
23932 representing a function that takes two integers as arguments. To
23933 execute this function, call it like so:
23936 result = some_val (10,20)
23939 Any values returned from a function call will be stored as a
23942 The following attributes are provided:
23944 @defvar Value.address
23945 If this object is addressable, this read-only attribute holds a
23946 @code{gdb.Value} object representing the address. Otherwise,
23947 this attribute holds @code{None}.
23950 @cindex optimized out value in Python
23951 @defvar Value.is_optimized_out
23952 This read-only boolean attribute is true if the compiler optimized out
23953 this value, thus it is not available for fetching from the inferior.
23957 The type of this @code{gdb.Value}. The value of this attribute is a
23958 @code{gdb.Type} object (@pxref{Types In Python}).
23961 @defvar Value.dynamic_type
23962 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23963 type information (@acronym{RTTI}) to determine the dynamic type of the
23964 value. If this value is of class type, it will return the class in
23965 which the value is embedded, if any. If this value is of pointer or
23966 reference to a class type, it will compute the dynamic type of the
23967 referenced object, and return a pointer or reference to that type,
23968 respectively. In all other cases, it will return the value's static
23971 Note that this feature will only work when debugging a C@t{++} program
23972 that includes @acronym{RTTI} for the object in question. Otherwise,
23973 it will just return the static type of the value as in @kbd{ptype foo}
23974 (@pxref{Symbols, ptype}).
23977 @defvar Value.is_lazy
23978 The value of this read-only boolean attribute is @code{True} if this
23979 @code{gdb.Value} has not yet been fetched from the inferior.
23980 @value{GDBN} does not fetch values until necessary, for efficiency.
23984 myval = gdb.parse_and_eval ('somevar')
23987 The value of @code{somevar} is not fetched at this time. It will be
23988 fetched when the value is needed, or when the @code{fetch_lazy}
23992 The following methods are provided:
23994 @defun Value.__init__ (@var{val})
23995 Many Python values can be converted directly to a @code{gdb.Value} via
23996 this object initializer. Specifically:
23999 @item Python boolean
24000 A Python boolean is converted to the boolean type from the current
24003 @item Python integer
24004 A Python integer is converted to the C @code{long} type for the
24005 current architecture.
24008 A Python long is converted to the C @code{long long} type for the
24009 current architecture.
24012 A Python float is converted to the C @code{double} type for the
24013 current architecture.
24015 @item Python string
24016 A Python string is converted to a target string, using the current
24019 @item @code{gdb.Value}
24020 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24022 @item @code{gdb.LazyString}
24023 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24024 Python}), then the lazy string's @code{value} method is called, and
24025 its result is used.
24029 @defun Value.cast (type)
24030 Return a new instance of @code{gdb.Value} that is the result of
24031 casting this instance to the type described by @var{type}, which must
24032 be a @code{gdb.Type} object. If the cast cannot be performed for some
24033 reason, this method throws an exception.
24036 @defun Value.dereference ()
24037 For pointer data types, this method returns a new @code{gdb.Value} object
24038 whose contents is the object pointed to by the pointer. For example, if
24039 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24046 then you can use the corresponding @code{gdb.Value} to access what
24047 @code{foo} points to like this:
24050 bar = foo.dereference ()
24053 The result @code{bar} will be a @code{gdb.Value} object holding the
24054 value pointed to by @code{foo}.
24056 A similar function @code{Value.referenced_value} exists which also
24057 returns @code{gdb.Value} objects corresonding to the values pointed to
24058 by pointer values (and additionally, values referenced by reference
24059 values). However, the behavior of @code{Value.dereference}
24060 differs from @code{Value.referenced_value} by the fact that the
24061 behavior of @code{Value.dereference} is identical to applying the C
24062 unary operator @code{*} on a given value. For example, consider a
24063 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24067 typedef int *intptr;
24071 intptr &ptrref = ptr;
24074 Though @code{ptrref} is a reference value, one can apply the method
24075 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24076 to it and obtain a @code{gdb.Value} which is identical to that
24077 corresponding to @code{val}. However, if you apply the method
24078 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24079 object identical to that corresponding to @code{ptr}.
24082 py_ptrref = gdb.parse_and_eval ("ptrref")
24083 py_val = py_ptrref.dereference ()
24084 py_ptr = py_ptrref.referenced_value ()
24087 The @code{gdb.Value} object @code{py_val} is identical to that
24088 corresponding to @code{val}, and @code{py_ptr} is identical to that
24089 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24090 be applied whenever the C unary operator @code{*} can be applied
24091 to the corresponding C value. For those cases where applying both
24092 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24093 the results obtained need not be identical (as we have seen in the above
24094 example). The results are however identical when applied on
24095 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24096 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24099 @defun Value.referenced_value ()
24100 For pointer or reference data types, this method returns a new
24101 @code{gdb.Value} object corresponding to the value referenced by the
24102 pointer/reference value. For pointer data types,
24103 @code{Value.dereference} and @code{Value.referenced_value} produce
24104 identical results. The difference between these methods is that
24105 @code{Value.dereference} cannot get the values referenced by reference
24106 values. For example, consider a reference to an @code{int}, declared
24107 in your C@t{++} program as
24115 then applying @code{Value.dereference} to the @code{gdb.Value} object
24116 corresponding to @code{ref} will result in an error, while applying
24117 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24118 identical to that corresponding to @code{val}.
24121 py_ref = gdb.parse_and_eval ("ref")
24122 er_ref = py_ref.dereference () # Results in error
24123 py_val = py_ref.referenced_value () # Returns the referenced value
24126 The @code{gdb.Value} object @code{py_val} is identical to that
24127 corresponding to @code{val}.
24130 @defun Value.dynamic_cast (type)
24131 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24132 operator were used. Consult a C@t{++} reference for details.
24135 @defun Value.reinterpret_cast (type)
24136 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24137 operator were used. Consult a C@t{++} reference for details.
24140 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24141 If this @code{gdb.Value} represents a string, then this method
24142 converts the contents to a Python string. Otherwise, this method will
24143 throw an exception.
24145 Strings are recognized in a language-specific way; whether a given
24146 @code{gdb.Value} represents a string is determined by the current
24149 For C-like languages, a value is a string if it is a pointer to or an
24150 array of characters or ints. The string is assumed to be terminated
24151 by a zero of the appropriate width. However if the optional length
24152 argument is given, the string will be converted to that given length,
24153 ignoring any embedded zeros that the string may contain.
24155 If the optional @var{encoding} argument is given, it must be a string
24156 naming the encoding of the string in the @code{gdb.Value}, such as
24157 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24158 the same encodings as the corresponding argument to Python's
24159 @code{string.decode} method, and the Python codec machinery will be used
24160 to convert the string. If @var{encoding} is not given, or if
24161 @var{encoding} is the empty string, then either the @code{target-charset}
24162 (@pxref{Character Sets}) will be used, or a language-specific encoding
24163 will be used, if the current language is able to supply one.
24165 The optional @var{errors} argument is the same as the corresponding
24166 argument to Python's @code{string.decode} method.
24168 If the optional @var{length} argument is given, the string will be
24169 fetched and converted to the given length.
24172 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24173 If this @code{gdb.Value} represents a string, then this method
24174 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24175 In Python}). Otherwise, this method will throw an exception.
24177 If the optional @var{encoding} argument is given, it must be a string
24178 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24179 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24180 @var{encoding} argument is an encoding that @value{GDBN} does
24181 recognize, @value{GDBN} will raise an error.
24183 When a lazy string is printed, the @value{GDBN} encoding machinery is
24184 used to convert the string during printing. If the optional
24185 @var{encoding} argument is not provided, or is an empty string,
24186 @value{GDBN} will automatically select the encoding most suitable for
24187 the string type. For further information on encoding in @value{GDBN}
24188 please see @ref{Character Sets}.
24190 If the optional @var{length} argument is given, the string will be
24191 fetched and encoded to the length of characters specified. If
24192 the @var{length} argument is not provided, the string will be fetched
24193 and encoded until a null of appropriate width is found.
24196 @defun Value.fetch_lazy ()
24197 If the @code{gdb.Value} object is currently a lazy value
24198 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24199 fetched from the inferior. Any errors that occur in the process
24200 will produce a Python exception.
24202 If the @code{gdb.Value} object is not a lazy value, this method
24205 This method does not return a value.
24209 @node Types In Python
24210 @subsubsection Types In Python
24211 @cindex types in Python
24212 @cindex Python, working with types
24215 @value{GDBN} represents types from the inferior using the class
24218 The following type-related functions are available in the @code{gdb}
24221 @findex gdb.lookup_type
24222 @defun gdb.lookup_type (name @r{[}, block@r{]})
24223 This function looks up a type by name. @var{name} is the name of the
24224 type to look up. It must be a string.
24226 If @var{block} is given, then @var{name} is looked up in that scope.
24227 Otherwise, it is searched for globally.
24229 Ordinarily, this function will return an instance of @code{gdb.Type}.
24230 If the named type cannot be found, it will throw an exception.
24233 If the type is a structure or class type, or an enum type, the fields
24234 of that type can be accessed using the Python @dfn{dictionary syntax}.
24235 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24236 a structure type, you can access its @code{foo} field with:
24239 bar = some_type['foo']
24242 @code{bar} will be a @code{gdb.Field} object; see below under the
24243 description of the @code{Type.fields} method for a description of the
24244 @code{gdb.Field} class.
24246 An instance of @code{Type} has the following attributes:
24249 The type code for this type. The type code will be one of the
24250 @code{TYPE_CODE_} constants defined below.
24253 @defvar Type.sizeof
24254 The size of this type, in target @code{char} units. Usually, a
24255 target's @code{char} type will be an 8-bit byte. However, on some
24256 unusual platforms, this type may have a different size.
24260 The tag name for this type. The tag name is the name after
24261 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24262 languages have this concept. If this type has no tag name, then
24263 @code{None} is returned.
24266 The following methods are provided:
24268 @defun Type.fields ()
24269 For structure and union types, this method returns the fields. Range
24270 types have two fields, the minimum and maximum values. Enum types
24271 have one field per enum constant. Function and method types have one
24272 field per parameter. The base types of C@t{++} classes are also
24273 represented as fields. If the type has no fields, or does not fit
24274 into one of these categories, an empty sequence will be returned.
24276 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24279 This attribute is not available for @code{static} fields (as in
24280 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24281 position of the field. For @code{enum} fields, the value is the
24282 enumeration member's integer representation.
24285 The name of the field, or @code{None} for anonymous fields.
24288 This is @code{True} if the field is artificial, usually meaning that
24289 it was provided by the compiler and not the user. This attribute is
24290 always provided, and is @code{False} if the field is not artificial.
24292 @item is_base_class
24293 This is @code{True} if the field represents a base class of a C@t{++}
24294 structure. This attribute is always provided, and is @code{False}
24295 if the field is not a base class of the type that is the argument of
24296 @code{fields}, or if that type was not a C@t{++} class.
24299 If the field is packed, or is a bitfield, then this will have a
24300 non-zero value, which is the size of the field in bits. Otherwise,
24301 this will be zero; in this case the field's size is given by its type.
24304 The type of the field. This is usually an instance of @code{Type},
24305 but it can be @code{None} in some situations.
24309 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24310 Return a new @code{gdb.Type} object which represents an array of this
24311 type. If one argument is given, it is the inclusive upper bound of
24312 the array; in this case the lower bound is zero. If two arguments are
24313 given, the first argument is the lower bound of the array, and the
24314 second argument is the upper bound of the array. An array's length
24315 must not be negative, but the bounds can be.
24318 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24319 Return a new @code{gdb.Type} object which represents a vector of this
24320 type. If one argument is given, it is the inclusive upper bound of
24321 the vector; in this case the lower bound is zero. If two arguments are
24322 given, the first argument is the lower bound of the vector, and the
24323 second argument is the upper bound of the vector. A vector's length
24324 must not be negative, but the bounds can be.
24326 The difference between an @code{array} and a @code{vector} is that
24327 arrays behave like in C: when used in expressions they decay to a pointer
24328 to the first element whereas vectors are treated as first class values.
24331 @defun Type.const ()
24332 Return a new @code{gdb.Type} object which represents a
24333 @code{const}-qualified variant of this type.
24336 @defun Type.volatile ()
24337 Return a new @code{gdb.Type} object which represents a
24338 @code{volatile}-qualified variant of this type.
24341 @defun Type.unqualified ()
24342 Return a new @code{gdb.Type} object which represents an unqualified
24343 variant of this type. That is, the result is neither @code{const} nor
24347 @defun Type.range ()
24348 Return a Python @code{Tuple} object that contains two elements: the
24349 low bound of the argument type and the high bound of that type. If
24350 the type does not have a range, @value{GDBN} will raise a
24351 @code{gdb.error} exception (@pxref{Exception Handling}).
24354 @defun Type.reference ()
24355 Return a new @code{gdb.Type} object which represents a reference to this
24359 @defun Type.pointer ()
24360 Return a new @code{gdb.Type} object which represents a pointer to this
24364 @defun Type.strip_typedefs ()
24365 Return a new @code{gdb.Type} that represents the real type,
24366 after removing all layers of typedefs.
24369 @defun Type.target ()
24370 Return a new @code{gdb.Type} object which represents the target type
24373 For a pointer type, the target type is the type of the pointed-to
24374 object. For an array type (meaning C-like arrays), the target type is
24375 the type of the elements of the array. For a function or method type,
24376 the target type is the type of the return value. For a complex type,
24377 the target type is the type of the elements. For a typedef, the
24378 target type is the aliased type.
24380 If the type does not have a target, this method will throw an
24384 @defun Type.template_argument (n @r{[}, block@r{]})
24385 If this @code{gdb.Type} is an instantiation of a template, this will
24386 return a new @code{gdb.Type} which represents the type of the
24387 @var{n}th template argument.
24389 If this @code{gdb.Type} is not a template type, this will throw an
24390 exception. Ordinarily, only C@t{++} code will have template types.
24392 If @var{block} is given, then @var{name} is looked up in that scope.
24393 Otherwise, it is searched for globally.
24397 Each type has a code, which indicates what category this type falls
24398 into. The available type categories are represented by constants
24399 defined in the @code{gdb} module:
24402 @findex TYPE_CODE_PTR
24403 @findex gdb.TYPE_CODE_PTR
24404 @item gdb.TYPE_CODE_PTR
24405 The type is a pointer.
24407 @findex TYPE_CODE_ARRAY
24408 @findex gdb.TYPE_CODE_ARRAY
24409 @item gdb.TYPE_CODE_ARRAY
24410 The type is an array.
24412 @findex TYPE_CODE_STRUCT
24413 @findex gdb.TYPE_CODE_STRUCT
24414 @item gdb.TYPE_CODE_STRUCT
24415 The type is a structure.
24417 @findex TYPE_CODE_UNION
24418 @findex gdb.TYPE_CODE_UNION
24419 @item gdb.TYPE_CODE_UNION
24420 The type is a union.
24422 @findex TYPE_CODE_ENUM
24423 @findex gdb.TYPE_CODE_ENUM
24424 @item gdb.TYPE_CODE_ENUM
24425 The type is an enum.
24427 @findex TYPE_CODE_FLAGS
24428 @findex gdb.TYPE_CODE_FLAGS
24429 @item gdb.TYPE_CODE_FLAGS
24430 A bit flags type, used for things such as status registers.
24432 @findex TYPE_CODE_FUNC
24433 @findex gdb.TYPE_CODE_FUNC
24434 @item gdb.TYPE_CODE_FUNC
24435 The type is a function.
24437 @findex TYPE_CODE_INT
24438 @findex gdb.TYPE_CODE_INT
24439 @item gdb.TYPE_CODE_INT
24440 The type is an integer type.
24442 @findex TYPE_CODE_FLT
24443 @findex gdb.TYPE_CODE_FLT
24444 @item gdb.TYPE_CODE_FLT
24445 A floating point type.
24447 @findex TYPE_CODE_VOID
24448 @findex gdb.TYPE_CODE_VOID
24449 @item gdb.TYPE_CODE_VOID
24450 The special type @code{void}.
24452 @findex TYPE_CODE_SET
24453 @findex gdb.TYPE_CODE_SET
24454 @item gdb.TYPE_CODE_SET
24457 @findex TYPE_CODE_RANGE
24458 @findex gdb.TYPE_CODE_RANGE
24459 @item gdb.TYPE_CODE_RANGE
24460 A range type, that is, an integer type with bounds.
24462 @findex TYPE_CODE_STRING
24463 @findex gdb.TYPE_CODE_STRING
24464 @item gdb.TYPE_CODE_STRING
24465 A string type. Note that this is only used for certain languages with
24466 language-defined string types; C strings are not represented this way.
24468 @findex TYPE_CODE_BITSTRING
24469 @findex gdb.TYPE_CODE_BITSTRING
24470 @item gdb.TYPE_CODE_BITSTRING
24471 A string of bits. It is deprecated.
24473 @findex TYPE_CODE_ERROR
24474 @findex gdb.TYPE_CODE_ERROR
24475 @item gdb.TYPE_CODE_ERROR
24476 An unknown or erroneous type.
24478 @findex TYPE_CODE_METHOD
24479 @findex gdb.TYPE_CODE_METHOD
24480 @item gdb.TYPE_CODE_METHOD
24481 A method type, as found in C@t{++} or Java.
24483 @findex TYPE_CODE_METHODPTR
24484 @findex gdb.TYPE_CODE_METHODPTR
24485 @item gdb.TYPE_CODE_METHODPTR
24486 A pointer-to-member-function.
24488 @findex TYPE_CODE_MEMBERPTR
24489 @findex gdb.TYPE_CODE_MEMBERPTR
24490 @item gdb.TYPE_CODE_MEMBERPTR
24491 A pointer-to-member.
24493 @findex TYPE_CODE_REF
24494 @findex gdb.TYPE_CODE_REF
24495 @item gdb.TYPE_CODE_REF
24498 @findex TYPE_CODE_CHAR
24499 @findex gdb.TYPE_CODE_CHAR
24500 @item gdb.TYPE_CODE_CHAR
24503 @findex TYPE_CODE_BOOL
24504 @findex gdb.TYPE_CODE_BOOL
24505 @item gdb.TYPE_CODE_BOOL
24508 @findex TYPE_CODE_COMPLEX
24509 @findex gdb.TYPE_CODE_COMPLEX
24510 @item gdb.TYPE_CODE_COMPLEX
24511 A complex float type.
24513 @findex TYPE_CODE_TYPEDEF
24514 @findex gdb.TYPE_CODE_TYPEDEF
24515 @item gdb.TYPE_CODE_TYPEDEF
24516 A typedef to some other type.
24518 @findex TYPE_CODE_NAMESPACE
24519 @findex gdb.TYPE_CODE_NAMESPACE
24520 @item gdb.TYPE_CODE_NAMESPACE
24521 A C@t{++} namespace.
24523 @findex TYPE_CODE_DECFLOAT
24524 @findex gdb.TYPE_CODE_DECFLOAT
24525 @item gdb.TYPE_CODE_DECFLOAT
24526 A decimal floating point type.
24528 @findex TYPE_CODE_INTERNAL_FUNCTION
24529 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24530 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24531 A function internal to @value{GDBN}. This is the type used to represent
24532 convenience functions.
24535 Further support for types is provided in the @code{gdb.types}
24536 Python module (@pxref{gdb.types}).
24538 @node Pretty Printing API
24539 @subsubsection Pretty Printing API
24541 An example output is provided (@pxref{Pretty Printing}).
24543 A pretty-printer is just an object that holds a value and implements a
24544 specific interface, defined here.
24546 @defun pretty_printer.children (self)
24547 @value{GDBN} will call this method on a pretty-printer to compute the
24548 children of the pretty-printer's value.
24550 This method must return an object conforming to the Python iterator
24551 protocol. Each item returned by the iterator must be a tuple holding
24552 two elements. The first element is the ``name'' of the child; the
24553 second element is the child's value. The value can be any Python
24554 object which is convertible to a @value{GDBN} value.
24556 This method is optional. If it does not exist, @value{GDBN} will act
24557 as though the value has no children.
24560 @defun pretty_printer.display_hint (self)
24561 The CLI may call this method and use its result to change the
24562 formatting of a value. The result will also be supplied to an MI
24563 consumer as a @samp{displayhint} attribute of the variable being
24566 This method is optional. If it does exist, this method must return a
24569 Some display hints are predefined by @value{GDBN}:
24573 Indicate that the object being printed is ``array-like''. The CLI
24574 uses this to respect parameters such as @code{set print elements} and
24575 @code{set print array}.
24578 Indicate that the object being printed is ``map-like'', and that the
24579 children of this value can be assumed to alternate between keys and
24583 Indicate that the object being printed is ``string-like''. If the
24584 printer's @code{to_string} method returns a Python string of some
24585 kind, then @value{GDBN} will call its internal language-specific
24586 string-printing function to format the string. For the CLI this means
24587 adding quotation marks, possibly escaping some characters, respecting
24588 @code{set print elements}, and the like.
24592 @defun pretty_printer.to_string (self)
24593 @value{GDBN} will call this method to display the string
24594 representation of the value passed to the object's constructor.
24596 When printing from the CLI, if the @code{to_string} method exists,
24597 then @value{GDBN} will prepend its result to the values returned by
24598 @code{children}. Exactly how this formatting is done is dependent on
24599 the display hint, and may change as more hints are added. Also,
24600 depending on the print settings (@pxref{Print Settings}), the CLI may
24601 print just the result of @code{to_string} in a stack trace, omitting
24602 the result of @code{children}.
24604 If this method returns a string, it is printed verbatim.
24606 Otherwise, if this method returns an instance of @code{gdb.Value},
24607 then @value{GDBN} prints this value. This may result in a call to
24608 another pretty-printer.
24610 If instead the method returns a Python value which is convertible to a
24611 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24612 the resulting value. Again, this may result in a call to another
24613 pretty-printer. Python scalars (integers, floats, and booleans) and
24614 strings are convertible to @code{gdb.Value}; other types are not.
24616 Finally, if this method returns @code{None} then no further operations
24617 are peformed in this method and nothing is printed.
24619 If the result is not one of these types, an exception is raised.
24622 @value{GDBN} provides a function which can be used to look up the
24623 default pretty-printer for a @code{gdb.Value}:
24625 @findex gdb.default_visualizer
24626 @defun gdb.default_visualizer (value)
24627 This function takes a @code{gdb.Value} object as an argument. If a
24628 pretty-printer for this value exists, then it is returned. If no such
24629 printer exists, then this returns @code{None}.
24632 @node Selecting Pretty-Printers
24633 @subsubsection Selecting Pretty-Printers
24635 The Python list @code{gdb.pretty_printers} contains an array of
24636 functions or callable objects that have been registered via addition
24637 as a pretty-printer. Printers in this list are called @code{global}
24638 printers, they're available when debugging all inferiors.
24639 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24640 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24643 Each function on these lists is passed a single @code{gdb.Value}
24644 argument and should return a pretty-printer object conforming to the
24645 interface definition above (@pxref{Pretty Printing API}). If a function
24646 cannot create a pretty-printer for the value, it should return
24649 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24650 @code{gdb.Objfile} in the current program space and iteratively calls
24651 each enabled lookup routine in the list for that @code{gdb.Objfile}
24652 until it receives a pretty-printer object.
24653 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24654 searches the pretty-printer list of the current program space,
24655 calling each enabled function until an object is returned.
24656 After these lists have been exhausted, it tries the global
24657 @code{gdb.pretty_printers} list, again calling each enabled function until an
24658 object is returned.
24660 The order in which the objfiles are searched is not specified. For a
24661 given list, functions are always invoked from the head of the list,
24662 and iterated over sequentially until the end of the list, or a printer
24663 object is returned.
24665 For various reasons a pretty-printer may not work.
24666 For example, the underlying data structure may have changed and
24667 the pretty-printer is out of date.
24669 The consequences of a broken pretty-printer are severe enough that
24670 @value{GDBN} provides support for enabling and disabling individual
24671 printers. For example, if @code{print frame-arguments} is on,
24672 a backtrace can become highly illegible if any argument is printed
24673 with a broken printer.
24675 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24676 attribute to the registered function or callable object. If this attribute
24677 is present and its value is @code{False}, the printer is disabled, otherwise
24678 the printer is enabled.
24680 @node Writing a Pretty-Printer
24681 @subsubsection Writing a Pretty-Printer
24682 @cindex writing a pretty-printer
24684 A pretty-printer consists of two parts: a lookup function to detect
24685 if the type is supported, and the printer itself.
24687 Here is an example showing how a @code{std::string} printer might be
24688 written. @xref{Pretty Printing API}, for details on the API this class
24692 class StdStringPrinter(object):
24693 "Print a std::string"
24695 def __init__(self, val):
24698 def to_string(self):
24699 return self.val['_M_dataplus']['_M_p']
24701 def display_hint(self):
24705 And here is an example showing how a lookup function for the printer
24706 example above might be written.
24709 def str_lookup_function(val):
24710 lookup_tag = val.type.tag
24711 if lookup_tag == None:
24713 regex = re.compile("^std::basic_string<char,.*>$")
24714 if regex.match(lookup_tag):
24715 return StdStringPrinter(val)
24719 The example lookup function extracts the value's type, and attempts to
24720 match it to a type that it can pretty-print. If it is a type the
24721 printer can pretty-print, it will return a printer object. If not, it
24722 returns @code{None}.
24724 We recommend that you put your core pretty-printers into a Python
24725 package. If your pretty-printers are for use with a library, we
24726 further recommend embedding a version number into the package name.
24727 This practice will enable @value{GDBN} to load multiple versions of
24728 your pretty-printers at the same time, because they will have
24731 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24732 can be evaluated multiple times without changing its meaning. An
24733 ideal auto-load file will consist solely of @code{import}s of your
24734 printer modules, followed by a call to a register pretty-printers with
24735 the current objfile.
24737 Taken as a whole, this approach will scale nicely to multiple
24738 inferiors, each potentially using a different library version.
24739 Embedding a version number in the Python package name will ensure that
24740 @value{GDBN} is able to load both sets of printers simultaneously.
24741 Then, because the search for pretty-printers is done by objfile, and
24742 because your auto-loaded code took care to register your library's
24743 printers with a specific objfile, @value{GDBN} will find the correct
24744 printers for the specific version of the library used by each
24747 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24748 this code might appear in @code{gdb.libstdcxx.v6}:
24751 def register_printers(objfile):
24752 objfile.pretty_printers.append(str_lookup_function)
24756 And then the corresponding contents of the auto-load file would be:
24759 import gdb.libstdcxx.v6
24760 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24763 The previous example illustrates a basic pretty-printer.
24764 There are a few things that can be improved on.
24765 The printer doesn't have a name, making it hard to identify in a
24766 list of installed printers. The lookup function has a name, but
24767 lookup functions can have arbitrary, even identical, names.
24769 Second, the printer only handles one type, whereas a library typically has
24770 several types. One could install a lookup function for each desired type
24771 in the library, but one could also have a single lookup function recognize
24772 several types. The latter is the conventional way this is handled.
24773 If a pretty-printer can handle multiple data types, then its
24774 @dfn{subprinters} are the printers for the individual data types.
24776 The @code{gdb.printing} module provides a formal way of solving these
24777 problems (@pxref{gdb.printing}).
24778 Here is another example that handles multiple types.
24780 These are the types we are going to pretty-print:
24783 struct foo @{ int a, b; @};
24784 struct bar @{ struct foo x, y; @};
24787 Here are the printers:
24791 """Print a foo object."""
24793 def __init__(self, val):
24796 def to_string(self):
24797 return ("a=<" + str(self.val["a"]) +
24798 "> b=<" + str(self.val["b"]) + ">")
24801 """Print a bar object."""
24803 def __init__(self, val):
24806 def to_string(self):
24807 return ("x=<" + str(self.val["x"]) +
24808 "> y=<" + str(self.val["y"]) + ">")
24811 This example doesn't need a lookup function, that is handled by the
24812 @code{gdb.printing} module. Instead a function is provided to build up
24813 the object that handles the lookup.
24816 import gdb.printing
24818 def build_pretty_printer():
24819 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24821 pp.add_printer('foo', '^foo$', fooPrinter)
24822 pp.add_printer('bar', '^bar$', barPrinter)
24826 And here is the autoload support:
24829 import gdb.printing
24831 gdb.printing.register_pretty_printer(
24832 gdb.current_objfile(),
24833 my_library.build_pretty_printer())
24836 Finally, when this printer is loaded into @value{GDBN}, here is the
24837 corresponding output of @samp{info pretty-printer}:
24840 (gdb) info pretty-printer
24847 @node Type Printing API
24848 @subsubsection Type Printing API
24849 @cindex type printing API for Python
24851 @value{GDBN} provides a way for Python code to customize type display.
24852 This is mainly useful for substituting canonical typedef names for
24855 @cindex type printer
24856 A @dfn{type printer} is just a Python object conforming to a certain
24857 protocol. A simple base class implementing the protocol is provided;
24858 see @ref{gdb.types}. A type printer must supply at least:
24860 @defivar type_printer enabled
24861 A boolean which is True if the printer is enabled, and False
24862 otherwise. This is manipulated by the @code{enable type-printer}
24863 and @code{disable type-printer} commands.
24866 @defivar type_printer name
24867 The name of the type printer. This must be a string. This is used by
24868 the @code{enable type-printer} and @code{disable type-printer}
24872 @defmethod type_printer instantiate (self)
24873 This is called by @value{GDBN} at the start of type-printing. It is
24874 only called if the type printer is enabled. This method must return a
24875 new object that supplies a @code{recognize} method, as described below.
24879 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24880 will compute a list of type recognizers. This is done by iterating
24881 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24882 followed by the per-progspace type printers (@pxref{Progspaces In
24883 Python}), and finally the global type printers.
24885 @value{GDBN} will call the @code{instantiate} method of each enabled
24886 type printer. If this method returns @code{None}, then the result is
24887 ignored; otherwise, it is appended to the list of recognizers.
24889 Then, when @value{GDBN} is going to display a type name, it iterates
24890 over the list of recognizers. For each one, it calls the recognition
24891 function, stopping if the function returns a non-@code{None} value.
24892 The recognition function is defined as:
24894 @defmethod type_recognizer recognize (self, type)
24895 If @var{type} is not recognized, return @code{None}. Otherwise,
24896 return a string which is to be printed as the name of @var{type}.
24897 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24901 @value{GDBN} uses this two-pass approach so that type printers can
24902 efficiently cache information without holding on to it too long. For
24903 example, it can be convenient to look up type information in a type
24904 printer and hold it for a recognizer's lifetime; if a single pass were
24905 done then type printers would have to make use of the event system in
24906 order to avoid holding information that could become stale as the
24909 @node Frame Filter API
24910 @subsubsection Filtering Frames.
24911 @cindex frame filters api
24913 Frame filters are Python objects that manipulate the visibility of a
24914 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24917 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24918 commands (@pxref{GDB/MI}), those that return a collection of frames
24919 are affected. The commands that work with frame filters are:
24921 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24922 @code{-stack-list-frames}
24923 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24924 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24925 -stack-list-variables command}), @code{-stack-list-arguments}
24926 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24927 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24928 -stack-list-locals command}).
24930 A frame filter works by taking an iterator as an argument, applying
24931 actions to the contents of that iterator, and returning another
24932 iterator (or, possibly, the same iterator it was provided in the case
24933 where the filter does not perform any operations). Typically, frame
24934 filters utilize tools such as the Python's @code{itertools} module to
24935 work with and create new iterators from the source iterator.
24936 Regardless of how a filter chooses to apply actions, it must not alter
24937 the underlying @value{GDBN} frame or frames, or attempt to alter the
24938 call-stack within @value{GDBN}. This preserves data integrity within
24939 @value{GDBN}. Frame filters are executed on a priority basis and care
24940 should be taken that some frame filters may have been executed before,
24941 and that some frame filters will be executed after.
24943 An important consideration when designing frame filters, and well
24944 worth reflecting upon, is that frame filters should avoid unwinding
24945 the call stack if possible. Some stacks can run very deep, into the
24946 tens of thousands in some cases. To search every frame when a frame
24947 filter executes may be too expensive at that step. The frame filter
24948 cannot know how many frames it has to iterate over, and it may have to
24949 iterate through them all. This ends up duplicating effort as
24950 @value{GDBN} performs this iteration when it prints the frames. If
24951 the filter can defer unwinding frames until frame decorators are
24952 executed, after the last filter has executed, it should. @xref{Frame
24953 Decorator API}, for more information on decorators. Also, there are
24954 examples for both frame decorators and filters in later chapters.
24955 @xref{Writing a Frame Filter}, for more information.
24957 The Python dictionary @code{gdb.frame_filters} contains key/object
24958 pairings that comprise a frame filter. Frame filters in this
24959 dictionary are called @code{global} frame filters, and they are
24960 available when debugging all inferiors. These frame filters must
24961 register with the dictionary directly. In addition to the
24962 @code{global} dictionary, there are other dictionaries that are loaded
24963 with different inferiors via auto-loading (@pxref{Python
24964 Auto-loading}). The two other areas where frame filter dictionaries
24965 can be found are: @code{gdb.Progspace} which contains a
24966 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24967 object which also contains a @code{frame_filters} dictionary
24970 When a command is executed from @value{GDBN} that is compatible with
24971 frame filters, @value{GDBN} combines the @code{global},
24972 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24973 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24974 several frames, and thus several object files, might be in use.
24975 @value{GDBN} then prunes any frame filter whose @code{enabled}
24976 attribute is @code{False}. This pruned list is then sorted according
24977 to the @code{priority} attribute in each filter.
24979 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24980 creates an iterator which wraps each frame in the call stack in a
24981 @code{FrameDecorator} object, and calls each filter in order. The
24982 output from the previous filter will always be the input to the next
24985 Frame filters have a mandatory interface which each frame filter must
24986 implement, defined here:
24988 @defun FrameFilter.filter (iterator)
24989 @value{GDBN} will call this method on a frame filter when it has
24990 reached the order in the priority list for that filter.
24992 For example, if there are four frame filters:
25003 The order that the frame filters will be called is:
25006 Filter3 -> Filter2 -> Filter1 -> Filter4
25009 Note that the output from @code{Filter3} is passed to the input of
25010 @code{Filter2}, and so on.
25012 This @code{filter} method is passed a Python iterator. This iterator
25013 contains a sequence of frame decorators that wrap each
25014 @code{gdb.Frame}, or a frame decorator that wraps another frame
25015 decorator. The first filter that is executed in the sequence of frame
25016 filters will receive an iterator entirely comprised of default
25017 @code{FrameDecorator} objects. However, after each frame filter is
25018 executed, the previous frame filter may have wrapped some or all of
25019 the frame decorators with their own frame decorator. As frame
25020 decorators must also conform to a mandatory interface, these
25021 decorators can be assumed to act in a uniform manner (@pxref{Frame
25024 This method must return an object conforming to the Python iterator
25025 protocol. Each item in the iterator must be an object conforming to
25026 the frame decorator interface. If a frame filter does not wish to
25027 perform any operations on this iterator, it should return that
25028 iterator untouched.
25030 This method is not optional. If it does not exist, @value{GDBN} will
25031 raise and print an error.
25034 @defvar FrameFilter.name
25035 The @code{name} attribute must be Python string which contains the
25036 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25037 Management}). This attribute may contain any combination of letters
25038 or numbers. Care should be taken to ensure that it is unique. This
25039 attribute is mandatory.
25042 @defvar FrameFilter.enabled
25043 The @code{enabled} attribute must be Python boolean. This attribute
25044 indicates to @value{GDBN} whether the frame filter is enabled, and
25045 should be considered when frame filters are executed. If
25046 @code{enabled} is @code{True}, then the frame filter will be executed
25047 when any of the backtrace commands detailed earlier in this chapter
25048 are executed. If @code{enabled} is @code{False}, then the frame
25049 filter will not be executed. This attribute is mandatory.
25052 @defvar FrameFilter.priority
25053 The @code{priority} attribute must be Python integer. This attribute
25054 controls the order of execution in relation to other frame filters.
25055 There are no imposed limits on the range of @code{priority} other than
25056 it must be a valid integer. The higher the @code{priority} attribute,
25057 the sooner the frame filter will be executed in relation to other
25058 frame filters. Although @code{priority} can be negative, it is
25059 recommended practice to assume zero is the lowest priority that a
25060 frame filter can be assigned. Frame filters that have the same
25061 priority are executed in unsorted order in that priority slot. This
25062 attribute is mandatory.
25065 @node Frame Decorator API
25066 @subsubsection Decorating Frames.
25067 @cindex frame decorator api
25069 Frame decorators are sister objects to frame filters (@pxref{Frame
25070 Filter API}). Frame decorators are applied by a frame filter and can
25071 only be used in conjunction with frame filters.
25073 The purpose of a frame decorator is to customize the printed content
25074 of each @code{gdb.Frame} in commands where frame filters are executed.
25075 This concept is called decorating a frame. Frame decorators decorate
25076 a @code{gdb.Frame} with Python code contained within each API call.
25077 This separates the actual data contained in a @code{gdb.Frame} from
25078 the decorated data produced by a frame decorator. This abstraction is
25079 necessary to maintain integrity of the data contained in each
25082 Frame decorators have a mandatory interface, defined below.
25084 @value{GDBN} already contains a frame decorator called
25085 @code{FrameDecorator}. This contains substantial amounts of
25086 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25087 recommended that other frame decorators inherit and extend this
25088 object, and only to override the methods needed.
25090 @defun FrameDecorator.elided (self)
25092 The @code{elided} method groups frames together in a hierarchical
25093 system. An example would be an interpreter, where multiple low-level
25094 frames make up a single call in the interpreted language. In this
25095 example, the frame filter would elide the low-level frames and present
25096 a single high-level frame, representing the call in the interpreted
25097 language, to the user.
25099 The @code{elided} function must return an iterable and this iterable
25100 must contain the frames that are being elided wrapped in a suitable
25101 frame decorator. If no frames are being elided this function may
25102 return an empty iterable, or @code{None}. Elided frames are indented
25103 from normal frames in a @code{CLI} backtrace, or in the case of
25104 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25107 It is the frame filter's task to also filter out the elided frames from
25108 the source iterator. This will avoid printing the frame twice.
25111 @defun FrameDecorator.function (self)
25113 This method returns the name of the function in the frame that is to
25116 This method must return a Python string describing the function, or
25119 If this function returns @code{None}, @value{GDBN} will not print any
25120 data for this field.
25123 @defun FrameDecorator.address (self)
25125 This method returns the address of the frame that is to be printed.
25127 This method must return a Python numeric integer type of sufficient
25128 size to describe the address of the frame, or @code{None}.
25130 If this function returns a @code{None}, @value{GDBN} will not print
25131 any data for this field.
25134 @defun FrameDecorator.filename (self)
25136 This method returns the filename and path associated with this frame.
25138 This method must return a Python string containing the filename and
25139 the path to the object file backing the frame, or @code{None}.
25141 If this function returns a @code{None}, @value{GDBN} will not print
25142 any data for this field.
25145 @defun FrameDecorator.line (self):
25147 This method returns the line number associated with the current
25148 position within the function addressed by this frame.
25150 This method must return a Python integer type, or @code{None}.
25152 If this function returns a @code{None}, @value{GDBN} will not print
25153 any data for this field.
25156 @defun FrameDecorator.frame_args (self)
25157 @anchor{frame_args}
25159 This method must return an iterable, or @code{None}. Returning an
25160 empty iterable, or @code{None} means frame arguments will not be
25161 printed for this frame. This iterable must contain objects that
25162 implement two methods, described here.
25164 This object must implement a @code{argument} method which takes a
25165 single @code{self} parameter and must return a @code{gdb.Symbol}
25166 (@pxref{Symbols In Python}), or a Python string. The object must also
25167 implement a @code{value} method which takes a single @code{self}
25168 parameter and must return a @code{gdb.Value} (@pxref{Values From
25169 Inferior}), a Python value, or @code{None}. If the @code{value}
25170 method returns @code{None}, and the @code{argument} method returns a
25171 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25172 the @code{gdb.Symbol} automatically.
25177 class SymValueWrapper():
25179 def __init__(self, symbol, value):
25189 class SomeFrameDecorator()
25192 def frame_args(self):
25195 block = self.inferior_frame.block()
25199 # Iterate over all symbols in a block. Only add
25200 # symbols that are arguments.
25202 if not sym.is_argument:
25204 args.append(SymValueWrapper(sym,None))
25206 # Add example synthetic argument.
25207 args.append(SymValueWrapper(``foo'', 42))
25213 @defun FrameDecorator.frame_locals (self)
25215 This method must return an iterable or @code{None}. Returning an
25216 empty iterable, or @code{None} means frame local arguments will not be
25217 printed for this frame.
25219 The object interface, the description of the various strategies for
25220 reading frame locals, and the example are largely similar to those
25221 described in the @code{frame_args} function, (@pxref{frame_args,,The
25222 frame filter frame_args function}). Below is a modified example:
25225 class SomeFrameDecorator()
25228 def frame_locals(self):
25231 block = self.inferior_frame.block()
25235 # Iterate over all symbols in a block. Add all
25236 # symbols, except arguments.
25238 if sym.is_argument:
25240 vars.append(SymValueWrapper(sym,None))
25242 # Add an example of a synthetic local variable.
25243 vars.append(SymValueWrapper(``bar'', 99))
25249 @defun FrameDecorator.inferior_frame (self):
25251 This method must return the underlying @code{gdb.Frame} that this
25252 frame decorator is decorating. @value{GDBN} requires the underlying
25253 frame for internal frame information to determine how to print certain
25254 values when printing a frame.
25257 @node Writing a Frame Filter
25258 @subsubsection Writing a Frame Filter
25259 @cindex writing a frame filter
25261 There are three basic elements that a frame filter must implement: it
25262 must correctly implement the documented interface (@pxref{Frame Filter
25263 API}), it must register itself with @value{GDBN}, and finally, it must
25264 decide if it is to work on the data provided by @value{GDBN}. In all
25265 cases, whether it works on the iterator or not, each frame filter must
25266 return an iterator. A bare-bones frame filter follows the pattern in
25267 the following example.
25272 class FrameFilter():
25274 def __init__(self):
25275 # Frame filter attribute creation.
25277 # 'name' is the name of the filter that GDB will display.
25279 # 'priority' is the priority of the filter relative to other
25282 # 'enabled' is a boolean that indicates whether this filter is
25283 # enabled and should be executed.
25286 self.priority = 100
25287 self.enabled = True
25289 # Register this frame filter with the global frame_filters
25291 gdb.frame_filters[self.name] = self
25293 def filter(self, frame_iter):
25294 # Just return the iterator.
25298 The frame filter in the example above implements the three
25299 requirements for all frame filters. It implements the API, self
25300 registers, and makes a decision on the iterator (in this case, it just
25301 returns the iterator untouched).
25303 The first step is attribute creation and assignment, and as shown in
25304 the comments the filter assigns the following attributes: @code{name},
25305 @code{priority} and whether the filter should be enabled with the
25306 @code{enabled} attribute.
25308 The second step is registering the frame filter with the dictionary or
25309 dictionaries that the frame filter has interest in. As shown in the
25310 comments, this filter just registers itself with the global dictionary
25311 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25312 is a dictionary that is initialized in the @code{gdb} module when
25313 @value{GDBN} starts. What dictionary a filter registers with is an
25314 important consideration. Generally, if a filter is specific to a set
25315 of code, it should be registered either in the @code{objfile} or
25316 @code{progspace} dictionaries as they are specific to the program
25317 currently loaded in @value{GDBN}. The global dictionary is always
25318 present in @value{GDBN} and is never unloaded. Any filters registered
25319 with the global dictionary will exist until @value{GDBN} exits. To
25320 avoid filters that may conflict, it is generally better to register
25321 frame filters against the dictionaries that more closely align with
25322 the usage of the filter currently in question. @xref{Python
25323 Auto-loading}, for further information on auto-loading Python scripts.
25325 @value{GDBN} takes a hands-off approach to frame filter registration,
25326 therefore it is the frame filter's responsibility to ensure
25327 registration has occurred, and that any exceptions are handled
25328 appropriately. In particular, you may wish to handle exceptions
25329 relating to Python dictionary key uniqueness. It is mandatory that
25330 the dictionary key is the same as frame filter's @code{name}
25331 attribute. When a user manages frame filters (@pxref{Frame Filter
25332 Management}), the names @value{GDBN} will display are those contained
25333 in the @code{name} attribute.
25335 The final step of this example is the implementation of the
25336 @code{filter} method. As shown in the example comments, we define the
25337 @code{filter} method and note that the method must take an iterator,
25338 and also must return an iterator. In this bare-bones example, the
25339 frame filter is not very useful as it just returns the iterator
25340 untouched. However this is a valid operation for frame filters that
25341 have the @code{enabled} attribute set, but decide not to operate on
25344 In the next example, the frame filter operates on all frames and
25345 utilizes a frame decorator to perform some work on the frames.
25346 @xref{Frame Decorator API}, for further information on the frame
25347 decorator interface.
25349 This example works on inlined frames. It highlights frames which are
25350 inlined by tagging them with an ``[inlined]'' tag. By applying a
25351 frame decorator to all frames with the Python @code{itertools imap}
25352 method, the example defers actions to the frame decorator. Frame
25353 decorators are only processed when @value{GDBN} prints the backtrace.
25355 This introduces a new decision making topic: whether to perform
25356 decision making operations at the filtering step, or at the printing
25357 step. In this example's approach, it does not perform any filtering
25358 decisions at the filtering step beyond mapping a frame decorator to
25359 each frame. This allows the actual decision making to be performed
25360 when each frame is printed. This is an important consideration, and
25361 well worth reflecting upon when designing a frame filter. An issue
25362 that frame filters should avoid is unwinding the stack if possible.
25363 Some stacks can run very deep, into the tens of thousands in some
25364 cases. To search every frame to determine if it is inlined ahead of
25365 time may be too expensive at the filtering step. The frame filter
25366 cannot know how many frames it has to iterate over, and it would have
25367 to iterate through them all. This ends up duplicating effort as
25368 @value{GDBN} performs this iteration when it prints the frames.
25370 In this example decision making can be deferred to the printing step.
25371 As each frame is printed, the frame decorator can examine each frame
25372 in turn when @value{GDBN} iterates. From a performance viewpoint,
25373 this is the most appropriate decision to make as it avoids duplicating
25374 the effort that the printing step would undertake anyway. Also, if
25375 there are many frame filters unwinding the stack during filtering, it
25376 can substantially delay the printing of the backtrace which will
25377 result in large memory usage, and a poor user experience.
25380 class InlineFilter():
25382 def __init__(self):
25383 self.name = "InlinedFrameFilter"
25384 self.priority = 100
25385 self.enabled = True
25386 gdb.frame_filters[self.name] = self
25388 def filter(self, frame_iter):
25389 frame_iter = itertools.imap(InlinedFrameDecorator,
25394 This frame filter is somewhat similar to the earlier example, except
25395 that the @code{filter} method applies a frame decorator object called
25396 @code{InlinedFrameDecorator} to each element in the iterator. The
25397 @code{imap} Python method is light-weight. It does not proactively
25398 iterate over the iterator, but rather creates a new iterator which
25399 wraps the existing one.
25401 Below is the frame decorator for this example.
25404 class InlinedFrameDecorator(FrameDecorator):
25406 def __init__(self, fobj):
25407 super(InlinedFrameDecorator, self).__init__(fobj)
25409 def function(self):
25410 frame = fobj.inferior_frame()
25411 name = str(frame.name())
25413 if frame.type() == gdb.INLINE_FRAME:
25414 name = name + " [inlined]"
25419 This frame decorator only defines and overrides the @code{function}
25420 method. It lets the supplied @code{FrameDecorator}, which is shipped
25421 with @value{GDBN}, perform the other work associated with printing
25424 The combination of these two objects create this output from a
25428 #0 0x004004e0 in bar () at inline.c:11
25429 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25430 #2 0x00400566 in main () at inline.c:31
25433 So in the case of this example, a frame decorator is applied to all
25434 frames, regardless of whether they may be inlined or not. As
25435 @value{GDBN} iterates over the iterator produced by the frame filters,
25436 @value{GDBN} executes each frame decorator which then makes a decision
25437 on what to print in the @code{function} callback. Using a strategy
25438 like this is a way to defer decisions on the frame content to printing
25441 @subheading Eliding Frames
25443 It might be that the above example is not desirable for representing
25444 inlined frames, and a hierarchical approach may be preferred. If we
25445 want to hierarchically represent frames, the @code{elided} frame
25446 decorator interface might be preferable.
25448 This example approaches the issue with the @code{elided} method. This
25449 example is quite long, but very simplistic. It is out-of-scope for
25450 this section to write a complete example that comprehensively covers
25451 all approaches of finding and printing inlined frames. However, this
25452 example illustrates the approach an author might use.
25454 This example comprises of three sections.
25457 class InlineFrameFilter():
25459 def __init__(self):
25460 self.name = "InlinedFrameFilter"
25461 self.priority = 100
25462 self.enabled = True
25463 gdb.frame_filters[self.name] = self
25465 def filter(self, frame_iter):
25466 return ElidingInlineIterator(frame_iter)
25469 This frame filter is very similar to the other examples. The only
25470 difference is this frame filter is wrapping the iterator provided to
25471 it (@code{frame_iter}) with a custom iterator called
25472 @code{ElidingInlineIterator}. This again defers actions to when
25473 @value{GDBN} prints the backtrace, as the iterator is not traversed
25476 The iterator for this example is as follows. It is in this section of
25477 the example where decisions are made on the content of the backtrace.
25480 class ElidingInlineIterator:
25481 def __init__(self, ii):
25482 self.input_iterator = ii
25484 def __iter__(self):
25488 frame = next(self.input_iterator)
25490 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25494 eliding_frame = next(self.input_iterator)
25495 except StopIteration:
25497 return ElidingFrameDecorator(eliding_frame, [frame])
25500 This iterator implements the Python iterator protocol. When the
25501 @code{next} function is called (when @value{GDBN} prints each frame),
25502 the iterator checks if this frame decorator, @code{frame}, is wrapping
25503 an inlined frame. If it is not, it returns the existing frame decorator
25504 untouched. If it is wrapping an inlined frame, it assumes that the
25505 inlined frame was contained within the next oldest frame,
25506 @code{eliding_frame}, which it fetches. It then creates and returns a
25507 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25508 elided frame, and the eliding frame.
25511 class ElidingInlineDecorator(FrameDecorator):
25513 def __init__(self, frame, elided_frames):
25514 super(ElidingInlineDecorator, self).__init__(frame)
25516 self.elided_frames = elided_frames
25519 return iter(self.elided_frames)
25522 This frame decorator overrides one function and returns the inlined
25523 frame in the @code{elided} method. As before it lets
25524 @code{FrameDecorator} do the rest of the work involved in printing
25525 this frame. This produces the following output.
25528 #0 0x004004e0 in bar () at inline.c:11
25529 #2 0x00400529 in main () at inline.c:25
25530 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25533 In that output, @code{max} which has been inlined into @code{main} is
25534 printed hierarchically. Another approach would be to combine the
25535 @code{function} method, and the @code{elided} method to both print a
25536 marker in the inlined frame, and also show the hierarchical
25539 @node Inferiors In Python
25540 @subsubsection Inferiors In Python
25541 @cindex inferiors in Python
25543 @findex gdb.Inferior
25544 Programs which are being run under @value{GDBN} are called inferiors
25545 (@pxref{Inferiors and Programs}). Python scripts can access
25546 information about and manipulate inferiors controlled by @value{GDBN}
25547 via objects of the @code{gdb.Inferior} class.
25549 The following inferior-related functions are available in the @code{gdb}
25552 @defun gdb.inferiors ()
25553 Return a tuple containing all inferior objects.
25556 @defun gdb.selected_inferior ()
25557 Return an object representing the current inferior.
25560 A @code{gdb.Inferior} object has the following attributes:
25562 @defvar Inferior.num
25563 ID of inferior, as assigned by GDB.
25566 @defvar Inferior.pid
25567 Process ID of the inferior, as assigned by the underlying operating
25571 @defvar Inferior.was_attached
25572 Boolean signaling whether the inferior was created using `attach', or
25573 started by @value{GDBN} itself.
25576 A @code{gdb.Inferior} object has the following methods:
25578 @defun Inferior.is_valid ()
25579 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25580 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25581 if the inferior no longer exists within @value{GDBN}. All other
25582 @code{gdb.Inferior} methods will throw an exception if it is invalid
25583 at the time the method is called.
25586 @defun Inferior.threads ()
25587 This method returns a tuple holding all the threads which are valid
25588 when it is called. If there are no valid threads, the method will
25589 return an empty tuple.
25592 @findex Inferior.read_memory
25593 @defun Inferior.read_memory (address, length)
25594 Read @var{length} bytes of memory from the inferior, starting at
25595 @var{address}. Returns a buffer object, which behaves much like an array
25596 or a string. It can be modified and given to the
25597 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25598 value is a @code{memoryview} object.
25601 @findex Inferior.write_memory
25602 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25603 Write the contents of @var{buffer} to the inferior, starting at
25604 @var{address}. The @var{buffer} parameter must be a Python object
25605 which supports the buffer protocol, i.e., a string, an array or the
25606 object returned from @code{Inferior.read_memory}. If given, @var{length}
25607 determines the number of bytes from @var{buffer} to be written.
25610 @findex gdb.search_memory
25611 @defun Inferior.search_memory (address, length, pattern)
25612 Search a region of the inferior memory starting at @var{address} with
25613 the given @var{length} using the search pattern supplied in
25614 @var{pattern}. The @var{pattern} parameter must be a Python object
25615 which supports the buffer protocol, i.e., a string, an array or the
25616 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25617 containing the address where the pattern was found, or @code{None} if
25618 the pattern could not be found.
25621 @node Events In Python
25622 @subsubsection Events In Python
25623 @cindex inferior events in Python
25625 @value{GDBN} provides a general event facility so that Python code can be
25626 notified of various state changes, particularly changes that occur in
25629 An @dfn{event} is just an object that describes some state change. The
25630 type of the object and its attributes will vary depending on the details
25631 of the change. All the existing events are described below.
25633 In order to be notified of an event, you must register an event handler
25634 with an @dfn{event registry}. An event registry is an object in the
25635 @code{gdb.events} module which dispatches particular events. A registry
25636 provides methods to register and unregister event handlers:
25638 @defun EventRegistry.connect (object)
25639 Add the given callable @var{object} to the registry. This object will be
25640 called when an event corresponding to this registry occurs.
25643 @defun EventRegistry.disconnect (object)
25644 Remove the given @var{object} from the registry. Once removed, the object
25645 will no longer receive notifications of events.
25648 Here is an example:
25651 def exit_handler (event):
25652 print "event type: exit"
25653 print "exit code: %d" % (event.exit_code)
25655 gdb.events.exited.connect (exit_handler)
25658 In the above example we connect our handler @code{exit_handler} to the
25659 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25660 called when the inferior exits. The argument @dfn{event} in this example is
25661 of type @code{gdb.ExitedEvent}. As you can see in the example the
25662 @code{ExitedEvent} object has an attribute which indicates the exit code of
25665 The following is a listing of the event registries that are available and
25666 details of the events they emit:
25671 Emits @code{gdb.ThreadEvent}.
25673 Some events can be thread specific when @value{GDBN} is running in non-stop
25674 mode. When represented in Python, these events all extend
25675 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25676 events which are emitted by this or other modules might extend this event.
25677 Examples of these events are @code{gdb.BreakpointEvent} and
25678 @code{gdb.ContinueEvent}.
25680 @defvar ThreadEvent.inferior_thread
25681 In non-stop mode this attribute will be set to the specific thread which was
25682 involved in the emitted event. Otherwise, it will be set to @code{None}.
25685 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25687 This event indicates that the inferior has been continued after a stop. For
25688 inherited attribute refer to @code{gdb.ThreadEvent} above.
25690 @item events.exited
25691 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25692 @code{events.ExitedEvent} has two attributes:
25693 @defvar ExitedEvent.exit_code
25694 An integer representing the exit code, if available, which the inferior
25695 has returned. (The exit code could be unavailable if, for example,
25696 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25697 the attribute does not exist.
25699 @defvar ExitedEvent inferior
25700 A reference to the inferior which triggered the @code{exited} event.
25704 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25706 Indicates that the inferior has stopped. All events emitted by this registry
25707 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25708 will indicate the stopped thread when @value{GDBN} is running in non-stop
25709 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25711 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25713 This event indicates that the inferior or one of its threads has received as
25714 signal. @code{gdb.SignalEvent} has the following attributes:
25716 @defvar SignalEvent.stop_signal
25717 A string representing the signal received by the inferior. A list of possible
25718 signal values can be obtained by running the command @code{info signals} in
25719 the @value{GDBN} command prompt.
25722 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25724 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25725 been hit, and has the following attributes:
25727 @defvar BreakpointEvent.breakpoints
25728 A sequence containing references to all the breakpoints (type
25729 @code{gdb.Breakpoint}) that were hit.
25730 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25732 @defvar BreakpointEvent.breakpoint
25733 A reference to the first breakpoint that was hit.
25734 This function is maintained for backward compatibility and is now deprecated
25735 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25738 @item events.new_objfile
25739 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25740 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25742 @defvar NewObjFileEvent.new_objfile
25743 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25744 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25749 @node Threads In Python
25750 @subsubsection Threads In Python
25751 @cindex threads in python
25753 @findex gdb.InferiorThread
25754 Python scripts can access information about, and manipulate inferior threads
25755 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25757 The following thread-related functions are available in the @code{gdb}
25760 @findex gdb.selected_thread
25761 @defun gdb.selected_thread ()
25762 This function returns the thread object for the selected thread. If there
25763 is no selected thread, this will return @code{None}.
25766 A @code{gdb.InferiorThread} object has the following attributes:
25768 @defvar InferiorThread.name
25769 The name of the thread. If the user specified a name using
25770 @code{thread name}, then this returns that name. Otherwise, if an
25771 OS-supplied name is available, then it is returned. Otherwise, this
25772 returns @code{None}.
25774 This attribute can be assigned to. The new value must be a string
25775 object, which sets the new name, or @code{None}, which removes any
25776 user-specified thread name.
25779 @defvar InferiorThread.num
25780 ID of the thread, as assigned by GDB.
25783 @defvar InferiorThread.ptid
25784 ID of the thread, as assigned by the operating system. This attribute is a
25785 tuple containing three integers. The first is the Process ID (PID); the second
25786 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25787 Either the LWPID or TID may be 0, which indicates that the operating system
25788 does not use that identifier.
25791 A @code{gdb.InferiorThread} object has the following methods:
25793 @defun InferiorThread.is_valid ()
25794 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25795 @code{False} if not. A @code{gdb.InferiorThread} object will become
25796 invalid if the thread exits, or the inferior that the thread belongs
25797 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25798 exception if it is invalid at the time the method is called.
25801 @defun InferiorThread.switch ()
25802 This changes @value{GDBN}'s currently selected thread to the one represented
25806 @defun InferiorThread.is_stopped ()
25807 Return a Boolean indicating whether the thread is stopped.
25810 @defun InferiorThread.is_running ()
25811 Return a Boolean indicating whether the thread is running.
25814 @defun InferiorThread.is_exited ()
25815 Return a Boolean indicating whether the thread is exited.
25818 @node Commands In Python
25819 @subsubsection Commands In Python
25821 @cindex commands in python
25822 @cindex python commands
25823 You can implement new @value{GDBN} CLI commands in Python. A CLI
25824 command is implemented using an instance of the @code{gdb.Command}
25825 class, most commonly using a subclass.
25827 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25828 The object initializer for @code{Command} registers the new command
25829 with @value{GDBN}. This initializer is normally invoked from the
25830 subclass' own @code{__init__} method.
25832 @var{name} is the name of the command. If @var{name} consists of
25833 multiple words, then the initial words are looked for as prefix
25834 commands. In this case, if one of the prefix commands does not exist,
25835 an exception is raised.
25837 There is no support for multi-line commands.
25839 @var{command_class} should be one of the @samp{COMMAND_} constants
25840 defined below. This argument tells @value{GDBN} how to categorize the
25841 new command in the help system.
25843 @var{completer_class} is an optional argument. If given, it should be
25844 one of the @samp{COMPLETE_} constants defined below. This argument
25845 tells @value{GDBN} how to perform completion for this command. If not
25846 given, @value{GDBN} will attempt to complete using the object's
25847 @code{complete} method (see below); if no such method is found, an
25848 error will occur when completion is attempted.
25850 @var{prefix} is an optional argument. If @code{True}, then the new
25851 command is a prefix command; sub-commands of this command may be
25854 The help text for the new command is taken from the Python
25855 documentation string for the command's class, if there is one. If no
25856 documentation string is provided, the default value ``This command is
25857 not documented.'' is used.
25860 @cindex don't repeat Python command
25861 @defun Command.dont_repeat ()
25862 By default, a @value{GDBN} command is repeated when the user enters a
25863 blank line at the command prompt. A command can suppress this
25864 behavior by invoking the @code{dont_repeat} method. This is similar
25865 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25868 @defun Command.invoke (argument, from_tty)
25869 This method is called by @value{GDBN} when this command is invoked.
25871 @var{argument} is a string. It is the argument to the command, after
25872 leading and trailing whitespace has been stripped.
25874 @var{from_tty} is a boolean argument. When true, this means that the
25875 command was entered by the user at the terminal; when false it means
25876 that the command came from elsewhere.
25878 If this method throws an exception, it is turned into a @value{GDBN}
25879 @code{error} call. Otherwise, the return value is ignored.
25881 @findex gdb.string_to_argv
25882 To break @var{argument} up into an argv-like string use
25883 @code{gdb.string_to_argv}. This function behaves identically to
25884 @value{GDBN}'s internal argument lexer @code{buildargv}.
25885 It is recommended to use this for consistency.
25886 Arguments are separated by spaces and may be quoted.
25890 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25891 ['1', '2 "3', '4 "5', "6 '7"]
25896 @cindex completion of Python commands
25897 @defun Command.complete (text, word)
25898 This method is called by @value{GDBN} when the user attempts
25899 completion on this command. All forms of completion are handled by
25900 this method, that is, the @key{TAB} and @key{M-?} key bindings
25901 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25904 The arguments @var{text} and @var{word} are both strings. @var{text}
25905 holds the complete command line up to the cursor's location.
25906 @var{word} holds the last word of the command line; this is computed
25907 using a word-breaking heuristic.
25909 The @code{complete} method can return several values:
25912 If the return value is a sequence, the contents of the sequence are
25913 used as the completions. It is up to @code{complete} to ensure that the
25914 contents actually do complete the word. A zero-length sequence is
25915 allowed, it means that there were no completions available. Only
25916 string elements of the sequence are used; other elements in the
25917 sequence are ignored.
25920 If the return value is one of the @samp{COMPLETE_} constants defined
25921 below, then the corresponding @value{GDBN}-internal completion
25922 function is invoked, and its result is used.
25925 All other results are treated as though there were no available
25930 When a new command is registered, it must be declared as a member of
25931 some general class of commands. This is used to classify top-level
25932 commands in the on-line help system; note that prefix commands are not
25933 listed under their own category but rather that of their top-level
25934 command. The available classifications are represented by constants
25935 defined in the @code{gdb} module:
25938 @findex COMMAND_NONE
25939 @findex gdb.COMMAND_NONE
25940 @item gdb.COMMAND_NONE
25941 The command does not belong to any particular class. A command in
25942 this category will not be displayed in any of the help categories.
25944 @findex COMMAND_RUNNING
25945 @findex gdb.COMMAND_RUNNING
25946 @item gdb.COMMAND_RUNNING
25947 The command is related to running the inferior. For example,
25948 @code{start}, @code{step}, and @code{continue} are in this category.
25949 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25950 commands in this category.
25952 @findex COMMAND_DATA
25953 @findex gdb.COMMAND_DATA
25954 @item gdb.COMMAND_DATA
25955 The command is related to data or variables. For example,
25956 @code{call}, @code{find}, and @code{print} are in this category. Type
25957 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25960 @findex COMMAND_STACK
25961 @findex gdb.COMMAND_STACK
25962 @item gdb.COMMAND_STACK
25963 The command has to do with manipulation of the stack. For example,
25964 @code{backtrace}, @code{frame}, and @code{return} are in this
25965 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25966 list of commands in this category.
25968 @findex COMMAND_FILES
25969 @findex gdb.COMMAND_FILES
25970 @item gdb.COMMAND_FILES
25971 This class is used for file-related commands. For example,
25972 @code{file}, @code{list} and @code{section} are in this category.
25973 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25974 commands in this category.
25976 @findex COMMAND_SUPPORT
25977 @findex gdb.COMMAND_SUPPORT
25978 @item gdb.COMMAND_SUPPORT
25979 This should be used for ``support facilities'', generally meaning
25980 things that are useful to the user when interacting with @value{GDBN},
25981 but not related to the state of the inferior. For example,
25982 @code{help}, @code{make}, and @code{shell} are in this category. Type
25983 @kbd{help support} at the @value{GDBN} prompt to see a list of
25984 commands in this category.
25986 @findex COMMAND_STATUS
25987 @findex gdb.COMMAND_STATUS
25988 @item gdb.COMMAND_STATUS
25989 The command is an @samp{info}-related command, that is, related to the
25990 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25991 and @code{show} are in this category. Type @kbd{help status} at the
25992 @value{GDBN} prompt to see a list of commands in this category.
25994 @findex COMMAND_BREAKPOINTS
25995 @findex gdb.COMMAND_BREAKPOINTS
25996 @item gdb.COMMAND_BREAKPOINTS
25997 The command has to do with breakpoints. For example, @code{break},
25998 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25999 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26002 @findex COMMAND_TRACEPOINTS
26003 @findex gdb.COMMAND_TRACEPOINTS
26004 @item gdb.COMMAND_TRACEPOINTS
26005 The command has to do with tracepoints. For example, @code{trace},
26006 @code{actions}, and @code{tfind} are in this category. Type
26007 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26008 commands in this category.
26010 @findex COMMAND_USER
26011 @findex gdb.COMMAND_USER
26012 @item gdb.COMMAND_USER
26013 The command is a general purpose command for the user, and typically
26014 does not fit in one of the other categories.
26015 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26016 a list of commands in this category, as well as the list of gdb macros
26017 (@pxref{Sequences}).
26019 @findex COMMAND_OBSCURE
26020 @findex gdb.COMMAND_OBSCURE
26021 @item gdb.COMMAND_OBSCURE
26022 The command is only used in unusual circumstances, or is not of
26023 general interest to users. For example, @code{checkpoint},
26024 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26025 obscure} at the @value{GDBN} prompt to see a list of commands in this
26028 @findex COMMAND_MAINTENANCE
26029 @findex gdb.COMMAND_MAINTENANCE
26030 @item gdb.COMMAND_MAINTENANCE
26031 The command is only useful to @value{GDBN} maintainers. The
26032 @code{maintenance} and @code{flushregs} commands are in this category.
26033 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26034 commands in this category.
26037 A new command can use a predefined completion function, either by
26038 specifying it via an argument at initialization, or by returning it
26039 from the @code{complete} method. These predefined completion
26040 constants are all defined in the @code{gdb} module:
26043 @findex COMPLETE_NONE
26044 @findex gdb.COMPLETE_NONE
26045 @item gdb.COMPLETE_NONE
26046 This constant means that no completion should be done.
26048 @findex COMPLETE_FILENAME
26049 @findex gdb.COMPLETE_FILENAME
26050 @item gdb.COMPLETE_FILENAME
26051 This constant means that filename completion should be performed.
26053 @findex COMPLETE_LOCATION
26054 @findex gdb.COMPLETE_LOCATION
26055 @item gdb.COMPLETE_LOCATION
26056 This constant means that location completion should be done.
26057 @xref{Specify Location}.
26059 @findex COMPLETE_COMMAND
26060 @findex gdb.COMPLETE_COMMAND
26061 @item gdb.COMPLETE_COMMAND
26062 This constant means that completion should examine @value{GDBN}
26065 @findex COMPLETE_SYMBOL
26066 @findex gdb.COMPLETE_SYMBOL
26067 @item gdb.COMPLETE_SYMBOL
26068 This constant means that completion should be done using symbol names
26071 @findex COMPLETE_EXPRESSION
26072 @findex gdb.COMPLETE_EXPRESSION
26073 @item gdb.COMPLETE_EXPRESSION
26074 This constant means that completion should be done on expressions.
26075 Often this means completing on symbol names, but some language
26076 parsers also have support for completing on field names.
26079 The following code snippet shows how a trivial CLI command can be
26080 implemented in Python:
26083 class HelloWorld (gdb.Command):
26084 """Greet the whole world."""
26086 def __init__ (self):
26087 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26089 def invoke (self, arg, from_tty):
26090 print "Hello, World!"
26095 The last line instantiates the class, and is necessary to trigger the
26096 registration of the command with @value{GDBN}. Depending on how the
26097 Python code is read into @value{GDBN}, you may need to import the
26098 @code{gdb} module explicitly.
26100 @node Parameters In Python
26101 @subsubsection Parameters In Python
26103 @cindex parameters in python
26104 @cindex python parameters
26105 @tindex gdb.Parameter
26107 You can implement new @value{GDBN} parameters using Python. A new
26108 parameter is implemented as an instance of the @code{gdb.Parameter}
26111 Parameters are exposed to the user via the @code{set} and
26112 @code{show} commands. @xref{Help}.
26114 There are many parameters that already exist and can be set in
26115 @value{GDBN}. Two examples are: @code{set follow fork} and
26116 @code{set charset}. Setting these parameters influences certain
26117 behavior in @value{GDBN}. Similarly, you can define parameters that
26118 can be used to influence behavior in custom Python scripts and commands.
26120 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26121 The object initializer for @code{Parameter} registers the new
26122 parameter with @value{GDBN}. This initializer is normally invoked
26123 from the subclass' own @code{__init__} method.
26125 @var{name} is the name of the new parameter. If @var{name} consists
26126 of multiple words, then the initial words are looked for as prefix
26127 parameters. An example of this can be illustrated with the
26128 @code{set print} set of parameters. If @var{name} is
26129 @code{print foo}, then @code{print} will be searched as the prefix
26130 parameter. In this case the parameter can subsequently be accessed in
26131 @value{GDBN} as @code{set print foo}.
26133 If @var{name} consists of multiple words, and no prefix parameter group
26134 can be found, an exception is raised.
26136 @var{command-class} should be one of the @samp{COMMAND_} constants
26137 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26138 categorize the new parameter in the help system.
26140 @var{parameter-class} should be one of the @samp{PARAM_} constants
26141 defined below. This argument tells @value{GDBN} the type of the new
26142 parameter; this information is used for input validation and
26145 If @var{parameter-class} is @code{PARAM_ENUM}, then
26146 @var{enum-sequence} must be a sequence of strings. These strings
26147 represent the possible values for the parameter.
26149 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26150 of a fourth argument will cause an exception to be thrown.
26152 The help text for the new parameter is taken from the Python
26153 documentation string for the parameter's class, if there is one. If
26154 there is no documentation string, a default value is used.
26157 @defvar Parameter.set_doc
26158 If this attribute exists, and is a string, then its value is used as
26159 the help text for this parameter's @code{set} command. The value is
26160 examined when @code{Parameter.__init__} is invoked; subsequent changes
26164 @defvar Parameter.show_doc
26165 If this attribute exists, and is a string, then its value is used as
26166 the help text for this parameter's @code{show} command. The value is
26167 examined when @code{Parameter.__init__} is invoked; subsequent changes
26171 @defvar Parameter.value
26172 The @code{value} attribute holds the underlying value of the
26173 parameter. It can be read and assigned to just as any other
26174 attribute. @value{GDBN} does validation when assignments are made.
26177 There are two methods that should be implemented in any
26178 @code{Parameter} class. These are:
26180 @defun Parameter.get_set_string (self)
26181 @value{GDBN} will call this method when a @var{parameter}'s value has
26182 been changed via the @code{set} API (for example, @kbd{set foo off}).
26183 The @code{value} attribute has already been populated with the new
26184 value and may be used in output. This method must return a string.
26187 @defun Parameter.get_show_string (self, svalue)
26188 @value{GDBN} will call this method when a @var{parameter}'s
26189 @code{show} API has been invoked (for example, @kbd{show foo}). The
26190 argument @code{svalue} receives the string representation of the
26191 current value. This method must return a string.
26194 When a new parameter is defined, its type must be specified. The
26195 available types are represented by constants defined in the @code{gdb}
26199 @findex PARAM_BOOLEAN
26200 @findex gdb.PARAM_BOOLEAN
26201 @item gdb.PARAM_BOOLEAN
26202 The value is a plain boolean. The Python boolean values, @code{True}
26203 and @code{False} are the only valid values.
26205 @findex PARAM_AUTO_BOOLEAN
26206 @findex gdb.PARAM_AUTO_BOOLEAN
26207 @item gdb.PARAM_AUTO_BOOLEAN
26208 The value has three possible states: true, false, and @samp{auto}. In
26209 Python, true and false are represented using boolean constants, and
26210 @samp{auto} is represented using @code{None}.
26212 @findex PARAM_UINTEGER
26213 @findex gdb.PARAM_UINTEGER
26214 @item gdb.PARAM_UINTEGER
26215 The value is an unsigned integer. The value of 0 should be
26216 interpreted to mean ``unlimited''.
26218 @findex PARAM_INTEGER
26219 @findex gdb.PARAM_INTEGER
26220 @item gdb.PARAM_INTEGER
26221 The value is a signed integer. The value of 0 should be interpreted
26222 to mean ``unlimited''.
26224 @findex PARAM_STRING
26225 @findex gdb.PARAM_STRING
26226 @item gdb.PARAM_STRING
26227 The value is a string. When the user modifies the string, any escape
26228 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26229 translated into corresponding characters and encoded into the current
26232 @findex PARAM_STRING_NOESCAPE
26233 @findex gdb.PARAM_STRING_NOESCAPE
26234 @item gdb.PARAM_STRING_NOESCAPE
26235 The value is a string. When the user modifies the string, escapes are
26236 passed through untranslated.
26238 @findex PARAM_OPTIONAL_FILENAME
26239 @findex gdb.PARAM_OPTIONAL_FILENAME
26240 @item gdb.PARAM_OPTIONAL_FILENAME
26241 The value is a either a filename (a string), or @code{None}.
26243 @findex PARAM_FILENAME
26244 @findex gdb.PARAM_FILENAME
26245 @item gdb.PARAM_FILENAME
26246 The value is a filename. This is just like
26247 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26249 @findex PARAM_ZINTEGER
26250 @findex gdb.PARAM_ZINTEGER
26251 @item gdb.PARAM_ZINTEGER
26252 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26253 is interpreted as itself.
26256 @findex gdb.PARAM_ENUM
26257 @item gdb.PARAM_ENUM
26258 The value is a string, which must be one of a collection string
26259 constants provided when the parameter is created.
26262 @node Functions In Python
26263 @subsubsection Writing new convenience functions
26265 @cindex writing convenience functions
26266 @cindex convenience functions in python
26267 @cindex python convenience functions
26268 @tindex gdb.Function
26270 You can implement new convenience functions (@pxref{Convenience Vars})
26271 in Python. A convenience function is an instance of a subclass of the
26272 class @code{gdb.Function}.
26274 @defun Function.__init__ (name)
26275 The initializer for @code{Function} registers the new function with
26276 @value{GDBN}. The argument @var{name} is the name of the function,
26277 a string. The function will be visible to the user as a convenience
26278 variable of type @code{internal function}, whose name is the same as
26279 the given @var{name}.
26281 The documentation for the new function is taken from the documentation
26282 string for the new class.
26285 @defun Function.invoke (@var{*args})
26286 When a convenience function is evaluated, its arguments are converted
26287 to instances of @code{gdb.Value}, and then the function's
26288 @code{invoke} method is called. Note that @value{GDBN} does not
26289 predetermine the arity of convenience functions. Instead, all
26290 available arguments are passed to @code{invoke}, following the
26291 standard Python calling convention. In particular, a convenience
26292 function can have default values for parameters without ill effect.
26294 The return value of this method is used as its value in the enclosing
26295 expression. If an ordinary Python value is returned, it is converted
26296 to a @code{gdb.Value} following the usual rules.
26299 The following code snippet shows how a trivial convenience function can
26300 be implemented in Python:
26303 class Greet (gdb.Function):
26304 """Return string to greet someone.
26305 Takes a name as argument."""
26307 def __init__ (self):
26308 super (Greet, self).__init__ ("greet")
26310 def invoke (self, name):
26311 return "Hello, %s!" % name.string ()
26316 The last line instantiates the class, and is necessary to trigger the
26317 registration of the function with @value{GDBN}. Depending on how the
26318 Python code is read into @value{GDBN}, you may need to import the
26319 @code{gdb} module explicitly.
26321 Now you can use the function in an expression:
26324 (gdb) print $greet("Bob")
26328 @node Progspaces In Python
26329 @subsubsection Program Spaces In Python
26331 @cindex progspaces in python
26332 @tindex gdb.Progspace
26334 A program space, or @dfn{progspace}, represents a symbolic view
26335 of an address space.
26336 It consists of all of the objfiles of the program.
26337 @xref{Objfiles In Python}.
26338 @xref{Inferiors and Programs, program spaces}, for more details
26339 about program spaces.
26341 The following progspace-related functions are available in the
26344 @findex gdb.current_progspace
26345 @defun gdb.current_progspace ()
26346 This function returns the program space of the currently selected inferior.
26347 @xref{Inferiors and Programs}.
26350 @findex gdb.progspaces
26351 @defun gdb.progspaces ()
26352 Return a sequence of all the progspaces currently known to @value{GDBN}.
26355 Each progspace is represented by an instance of the @code{gdb.Progspace}
26358 @defvar Progspace.filename
26359 The file name of the progspace as a string.
26362 @defvar Progspace.pretty_printers
26363 The @code{pretty_printers} attribute is a list of functions. It is
26364 used to look up pretty-printers. A @code{Value} is passed to each
26365 function in order; if the function returns @code{None}, then the
26366 search continues. Otherwise, the return value should be an object
26367 which is used to format the value. @xref{Pretty Printing API}, for more
26371 @defvar Progspace.type_printers
26372 The @code{type_printers} attribute is a list of type printer objects.
26373 @xref{Type Printing API}, for more information.
26376 @defvar Progspace.frame_filters
26377 The @code{frame_filters} attribute is a dictionary of frame filter
26378 objects. @xref{Frame Filter API}, for more information.
26381 @node Objfiles In Python
26382 @subsubsection Objfiles In Python
26384 @cindex objfiles in python
26385 @tindex gdb.Objfile
26387 @value{GDBN} loads symbols for an inferior from various
26388 symbol-containing files (@pxref{Files}). These include the primary
26389 executable file, any shared libraries used by the inferior, and any
26390 separate debug info files (@pxref{Separate Debug Files}).
26391 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26393 The following objfile-related functions are available in the
26396 @findex gdb.current_objfile
26397 @defun gdb.current_objfile ()
26398 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26399 sets the ``current objfile'' to the corresponding objfile. This
26400 function returns the current objfile. If there is no current objfile,
26401 this function returns @code{None}.
26404 @findex gdb.objfiles
26405 @defun gdb.objfiles ()
26406 Return a sequence of all the objfiles current known to @value{GDBN}.
26407 @xref{Objfiles In Python}.
26410 Each objfile is represented by an instance of the @code{gdb.Objfile}
26413 @defvar Objfile.filename
26414 The file name of the objfile as a string.
26417 @defvar Objfile.pretty_printers
26418 The @code{pretty_printers} attribute is a list of functions. It is
26419 used to look up pretty-printers. A @code{Value} is passed to each
26420 function in order; if the function returns @code{None}, then the
26421 search continues. Otherwise, the return value should be an object
26422 which is used to format the value. @xref{Pretty Printing API}, for more
26426 @defvar Objfile.type_printers
26427 The @code{type_printers} attribute is a list of type printer objects.
26428 @xref{Type Printing API}, for more information.
26431 @defvar Objfile.frame_filters
26432 The @code{frame_filters} attribute is a dictionary of frame filter
26433 objects. @xref{Frame Filter API}, for more information.
26436 A @code{gdb.Objfile} object has the following methods:
26438 @defun Objfile.is_valid ()
26439 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26440 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26441 if the object file it refers to is not loaded in @value{GDBN} any
26442 longer. All other @code{gdb.Objfile} methods will throw an exception
26443 if it is invalid at the time the method is called.
26446 @node Frames In Python
26447 @subsubsection Accessing inferior stack frames from Python.
26449 @cindex frames in python
26450 When the debugged program stops, @value{GDBN} is able to analyze its call
26451 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26452 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26453 while its corresponding frame exists in the inferior's stack. If you try
26454 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26455 exception (@pxref{Exception Handling}).
26457 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26461 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26465 The following frame-related functions are available in the @code{gdb} module:
26467 @findex gdb.selected_frame
26468 @defun gdb.selected_frame ()
26469 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26472 @findex gdb.newest_frame
26473 @defun gdb.newest_frame ()
26474 Return the newest frame object for the selected thread.
26477 @defun gdb.frame_stop_reason_string (reason)
26478 Return a string explaining the reason why @value{GDBN} stopped unwinding
26479 frames, as expressed by the given @var{reason} code (an integer, see the
26480 @code{unwind_stop_reason} method further down in this section).
26483 A @code{gdb.Frame} object has the following methods:
26485 @defun Frame.is_valid ()
26486 Returns true if the @code{gdb.Frame} object is valid, false if not.
26487 A frame object can become invalid if the frame it refers to doesn't
26488 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26489 an exception if it is invalid at the time the method is called.
26492 @defun Frame.name ()
26493 Returns the function name of the frame, or @code{None} if it can't be
26497 @defun Frame.architecture ()
26498 Returns the @code{gdb.Architecture} object corresponding to the frame's
26499 architecture. @xref{Architectures In Python}.
26502 @defun Frame.type ()
26503 Returns the type of the frame. The value can be one of:
26505 @item gdb.NORMAL_FRAME
26506 An ordinary stack frame.
26508 @item gdb.DUMMY_FRAME
26509 A fake stack frame that was created by @value{GDBN} when performing an
26510 inferior function call.
26512 @item gdb.INLINE_FRAME
26513 A frame representing an inlined function. The function was inlined
26514 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26516 @item gdb.TAILCALL_FRAME
26517 A frame representing a tail call. @xref{Tail Call Frames}.
26519 @item gdb.SIGTRAMP_FRAME
26520 A signal trampoline frame. This is the frame created by the OS when
26521 it calls into a signal handler.
26523 @item gdb.ARCH_FRAME
26524 A fake stack frame representing a cross-architecture call.
26526 @item gdb.SENTINEL_FRAME
26527 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26532 @defun Frame.unwind_stop_reason ()
26533 Return an integer representing the reason why it's not possible to find
26534 more frames toward the outermost frame. Use
26535 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26536 function to a string. The value can be one of:
26539 @item gdb.FRAME_UNWIND_NO_REASON
26540 No particular reason (older frames should be available).
26542 @item gdb.FRAME_UNWIND_NULL_ID
26543 The previous frame's analyzer returns an invalid result.
26545 @item gdb.FRAME_UNWIND_OUTERMOST
26546 This frame is the outermost.
26548 @item gdb.FRAME_UNWIND_UNAVAILABLE
26549 Cannot unwind further, because that would require knowing the
26550 values of registers or memory that have not been collected.
26552 @item gdb.FRAME_UNWIND_INNER_ID
26553 This frame ID looks like it ought to belong to a NEXT frame,
26554 but we got it for a PREV frame. Normally, this is a sign of
26555 unwinder failure. It could also indicate stack corruption.
26557 @item gdb.FRAME_UNWIND_SAME_ID
26558 This frame has the same ID as the previous one. That means
26559 that unwinding further would almost certainly give us another
26560 frame with exactly the same ID, so break the chain. Normally,
26561 this is a sign of unwinder failure. It could also indicate
26564 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26565 The frame unwinder did not find any saved PC, but we needed
26566 one to unwind further.
26568 @item gdb.FRAME_UNWIND_FIRST_ERROR
26569 Any stop reason greater or equal to this value indicates some kind
26570 of error. This special value facilitates writing code that tests
26571 for errors in unwinding in a way that will work correctly even if
26572 the list of the other values is modified in future @value{GDBN}
26573 versions. Using it, you could write:
26575 reason = gdb.selected_frame().unwind_stop_reason ()
26576 reason_str = gdb.frame_stop_reason_string (reason)
26577 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26578 print "An error occured: %s" % reason_str
26585 Returns the frame's resume address.
26588 @defun Frame.block ()
26589 Return the frame's code block. @xref{Blocks In Python}.
26592 @defun Frame.function ()
26593 Return the symbol for the function corresponding to this frame.
26594 @xref{Symbols In Python}.
26597 @defun Frame.older ()
26598 Return the frame that called this frame.
26601 @defun Frame.newer ()
26602 Return the frame called by this frame.
26605 @defun Frame.find_sal ()
26606 Return the frame's symtab and line object.
26607 @xref{Symbol Tables In Python}.
26610 @defun Frame.read_var (variable @r{[}, block@r{]})
26611 Return the value of @var{variable} in this frame. If the optional
26612 argument @var{block} is provided, search for the variable from that
26613 block; otherwise start at the frame's current block (which is
26614 determined by the frame's current program counter). @var{variable}
26615 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26616 @code{gdb.Block} object.
26619 @defun Frame.select ()
26620 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26624 @node Blocks In Python
26625 @subsubsection Accessing blocks from Python.
26627 @cindex blocks in python
26630 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26631 roughly to a scope in the source code. Blocks are organized
26632 hierarchically, and are represented individually in Python as a
26633 @code{gdb.Block}. Blocks rely on debugging information being
26636 A frame has a block. Please see @ref{Frames In Python}, for a more
26637 in-depth discussion of frames.
26639 The outermost block is known as the @dfn{global block}. The global
26640 block typically holds public global variables and functions.
26642 The block nested just inside the global block is the @dfn{static
26643 block}. The static block typically holds file-scoped variables and
26646 @value{GDBN} provides a method to get a block's superblock, but there
26647 is currently no way to examine the sub-blocks of a block, or to
26648 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26651 Here is a short example that should help explain blocks:
26654 /* This is in the global block. */
26657 /* This is in the static block. */
26658 static int file_scope;
26660 /* 'function' is in the global block, and 'argument' is
26661 in a block nested inside of 'function'. */
26662 int function (int argument)
26664 /* 'local' is in a block inside 'function'. It may or may
26665 not be in the same block as 'argument'. */
26669 /* 'inner' is in a block whose superblock is the one holding
26673 /* If this call is expanded by the compiler, you may see
26674 a nested block here whose function is 'inline_function'
26675 and whose superblock is the one holding 'inner'. */
26676 inline_function ();
26681 A @code{gdb.Block} is iterable. The iterator returns the symbols
26682 (@pxref{Symbols In Python}) local to the block. Python programs
26683 should not assume that a specific block object will always contain a
26684 given symbol, since changes in @value{GDBN} features and
26685 infrastructure may cause symbols move across blocks in a symbol
26688 The following block-related functions are available in the @code{gdb}
26691 @findex gdb.block_for_pc
26692 @defun gdb.block_for_pc (pc)
26693 Return the innermost @code{gdb.Block} containing the given @var{pc}
26694 value. If the block cannot be found for the @var{pc} value specified,
26695 the function will return @code{None}.
26698 A @code{gdb.Block} object has the following methods:
26700 @defun Block.is_valid ()
26701 Returns @code{True} if the @code{gdb.Block} object is valid,
26702 @code{False} if not. A block object can become invalid if the block it
26703 refers to doesn't exist anymore in the inferior. All other
26704 @code{gdb.Block} methods will throw an exception if it is invalid at
26705 the time the method is called. The block's validity is also checked
26706 during iteration over symbols of the block.
26709 A @code{gdb.Block} object has the following attributes:
26711 @defvar Block.start
26712 The start address of the block. This attribute is not writable.
26716 The end address of the block. This attribute is not writable.
26719 @defvar Block.function
26720 The name of the block represented as a @code{gdb.Symbol}. If the
26721 block is not named, then this attribute holds @code{None}. This
26722 attribute is not writable.
26724 For ordinary function blocks, the superblock is the static block.
26725 However, you should note that it is possible for a function block to
26726 have a superblock that is not the static block -- for instance this
26727 happens for an inlined function.
26730 @defvar Block.superblock
26731 The block containing this block. If this parent block does not exist,
26732 this attribute holds @code{None}. This attribute is not writable.
26735 @defvar Block.global_block
26736 The global block associated with this block. This attribute is not
26740 @defvar Block.static_block
26741 The static block associated with this block. This attribute is not
26745 @defvar Block.is_global
26746 @code{True} if the @code{gdb.Block} object is a global block,
26747 @code{False} if not. This attribute is not
26751 @defvar Block.is_static
26752 @code{True} if the @code{gdb.Block} object is a static block,
26753 @code{False} if not. This attribute is not writable.
26756 @node Symbols In Python
26757 @subsubsection Python representation of Symbols.
26759 @cindex symbols in python
26762 @value{GDBN} represents every variable, function and type as an
26763 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26764 Similarly, Python represents these symbols in @value{GDBN} with the
26765 @code{gdb.Symbol} object.
26767 The following symbol-related functions are available in the @code{gdb}
26770 @findex gdb.lookup_symbol
26771 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26772 This function searches for a symbol by name. The search scope can be
26773 restricted to the parameters defined in the optional domain and block
26776 @var{name} is the name of the symbol. It must be a string. The
26777 optional @var{block} argument restricts the search to symbols visible
26778 in that @var{block}. The @var{block} argument must be a
26779 @code{gdb.Block} object. If omitted, the block for the current frame
26780 is used. The optional @var{domain} argument restricts
26781 the search to the domain type. The @var{domain} argument must be a
26782 domain constant defined in the @code{gdb} module and described later
26785 The result is a tuple of two elements.
26786 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26788 If the symbol is found, the second element is @code{True} if the symbol
26789 is a field of a method's object (e.g., @code{this} in C@t{++}),
26790 otherwise it is @code{False}.
26791 If the symbol is not found, the second element is @code{False}.
26794 @findex gdb.lookup_global_symbol
26795 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26796 This function searches for a global symbol by name.
26797 The search scope can be restricted to by the domain argument.
26799 @var{name} is the name of the symbol. It must be a string.
26800 The optional @var{domain} argument restricts the search to the domain type.
26801 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26802 module and described later in this chapter.
26804 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26808 A @code{gdb.Symbol} object has the following attributes:
26810 @defvar Symbol.type
26811 The type of the symbol or @code{None} if no type is recorded.
26812 This attribute is represented as a @code{gdb.Type} object.
26813 @xref{Types In Python}. This attribute is not writable.
26816 @defvar Symbol.symtab
26817 The symbol table in which the symbol appears. This attribute is
26818 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26819 Python}. This attribute is not writable.
26822 @defvar Symbol.line
26823 The line number in the source code at which the symbol was defined.
26824 This is an integer.
26827 @defvar Symbol.name
26828 The name of the symbol as a string. This attribute is not writable.
26831 @defvar Symbol.linkage_name
26832 The name of the symbol, as used by the linker (i.e., may be mangled).
26833 This attribute is not writable.
26836 @defvar Symbol.print_name
26837 The name of the symbol in a form suitable for output. This is either
26838 @code{name} or @code{linkage_name}, depending on whether the user
26839 asked @value{GDBN} to display demangled or mangled names.
26842 @defvar Symbol.addr_class
26843 The address class of the symbol. This classifies how to find the value
26844 of a symbol. Each address class is a constant defined in the
26845 @code{gdb} module and described later in this chapter.
26848 @defvar Symbol.needs_frame
26849 This is @code{True} if evaluating this symbol's value requires a frame
26850 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26851 local variables will require a frame, but other symbols will not.
26854 @defvar Symbol.is_argument
26855 @code{True} if the symbol is an argument of a function.
26858 @defvar Symbol.is_constant
26859 @code{True} if the symbol is a constant.
26862 @defvar Symbol.is_function
26863 @code{True} if the symbol is a function or a method.
26866 @defvar Symbol.is_variable
26867 @code{True} if the symbol is a variable.
26870 A @code{gdb.Symbol} object has the following methods:
26872 @defun Symbol.is_valid ()
26873 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26874 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26875 the symbol it refers to does not exist in @value{GDBN} any longer.
26876 All other @code{gdb.Symbol} methods will throw an exception if it is
26877 invalid at the time the method is called.
26880 @defun Symbol.value (@r{[}frame@r{]})
26881 Compute the value of the symbol, as a @code{gdb.Value}. For
26882 functions, this computes the address of the function, cast to the
26883 appropriate type. If the symbol requires a frame in order to compute
26884 its value, then @var{frame} must be given. If @var{frame} is not
26885 given, or if @var{frame} is invalid, then this method will throw an
26889 The available domain categories in @code{gdb.Symbol} are represented
26890 as constants in the @code{gdb} module:
26893 @findex SYMBOL_UNDEF_DOMAIN
26894 @findex gdb.SYMBOL_UNDEF_DOMAIN
26895 @item gdb.SYMBOL_UNDEF_DOMAIN
26896 This is used when a domain has not been discovered or none of the
26897 following domains apply. This usually indicates an error either
26898 in the symbol information or in @value{GDBN}'s handling of symbols.
26899 @findex SYMBOL_VAR_DOMAIN
26900 @findex gdb.SYMBOL_VAR_DOMAIN
26901 @item gdb.SYMBOL_VAR_DOMAIN
26902 This domain contains variables, function names, typedef names and enum
26904 @findex SYMBOL_STRUCT_DOMAIN
26905 @findex gdb.SYMBOL_STRUCT_DOMAIN
26906 @item gdb.SYMBOL_STRUCT_DOMAIN
26907 This domain holds struct, union and enum type names.
26908 @findex SYMBOL_LABEL_DOMAIN
26909 @findex gdb.SYMBOL_LABEL_DOMAIN
26910 @item gdb.SYMBOL_LABEL_DOMAIN
26911 This domain contains names of labels (for gotos).
26912 @findex SYMBOL_VARIABLES_DOMAIN
26913 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26914 @item gdb.SYMBOL_VARIABLES_DOMAIN
26915 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26916 contains everything minus functions and types.
26917 @findex SYMBOL_FUNCTIONS_DOMAIN
26918 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26919 @item gdb.SYMBOL_FUNCTION_DOMAIN
26920 This domain contains all functions.
26921 @findex SYMBOL_TYPES_DOMAIN
26922 @findex gdb.SYMBOL_TYPES_DOMAIN
26923 @item gdb.SYMBOL_TYPES_DOMAIN
26924 This domain contains all types.
26927 The available address class categories in @code{gdb.Symbol} are represented
26928 as constants in the @code{gdb} module:
26931 @findex SYMBOL_LOC_UNDEF
26932 @findex gdb.SYMBOL_LOC_UNDEF
26933 @item gdb.SYMBOL_LOC_UNDEF
26934 If this is returned by address class, it indicates an error either in
26935 the symbol information or in @value{GDBN}'s handling of symbols.
26936 @findex SYMBOL_LOC_CONST
26937 @findex gdb.SYMBOL_LOC_CONST
26938 @item gdb.SYMBOL_LOC_CONST
26939 Value is constant int.
26940 @findex SYMBOL_LOC_STATIC
26941 @findex gdb.SYMBOL_LOC_STATIC
26942 @item gdb.SYMBOL_LOC_STATIC
26943 Value is at a fixed address.
26944 @findex SYMBOL_LOC_REGISTER
26945 @findex gdb.SYMBOL_LOC_REGISTER
26946 @item gdb.SYMBOL_LOC_REGISTER
26947 Value is in a register.
26948 @findex SYMBOL_LOC_ARG
26949 @findex gdb.SYMBOL_LOC_ARG
26950 @item gdb.SYMBOL_LOC_ARG
26951 Value is an argument. This value is at the offset stored within the
26952 symbol inside the frame's argument list.
26953 @findex SYMBOL_LOC_REF_ARG
26954 @findex gdb.SYMBOL_LOC_REF_ARG
26955 @item gdb.SYMBOL_LOC_REF_ARG
26956 Value address is stored in the frame's argument list. Just like
26957 @code{LOC_ARG} except that the value's address is stored at the
26958 offset, not the value itself.
26959 @findex SYMBOL_LOC_REGPARM_ADDR
26960 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26961 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26962 Value is a specified register. Just like @code{LOC_REGISTER} except
26963 the register holds the address of the argument instead of the argument
26965 @findex SYMBOL_LOC_LOCAL
26966 @findex gdb.SYMBOL_LOC_LOCAL
26967 @item gdb.SYMBOL_LOC_LOCAL
26968 Value is a local variable.
26969 @findex SYMBOL_LOC_TYPEDEF
26970 @findex gdb.SYMBOL_LOC_TYPEDEF
26971 @item gdb.SYMBOL_LOC_TYPEDEF
26972 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26974 @findex SYMBOL_LOC_BLOCK
26975 @findex gdb.SYMBOL_LOC_BLOCK
26976 @item gdb.SYMBOL_LOC_BLOCK
26978 @findex SYMBOL_LOC_CONST_BYTES
26979 @findex gdb.SYMBOL_LOC_CONST_BYTES
26980 @item gdb.SYMBOL_LOC_CONST_BYTES
26981 Value is a byte-sequence.
26982 @findex SYMBOL_LOC_UNRESOLVED
26983 @findex gdb.SYMBOL_LOC_UNRESOLVED
26984 @item gdb.SYMBOL_LOC_UNRESOLVED
26985 Value is at a fixed address, but the address of the variable has to be
26986 determined from the minimal symbol table whenever the variable is
26988 @findex SYMBOL_LOC_OPTIMIZED_OUT
26989 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26990 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26991 The value does not actually exist in the program.
26992 @findex SYMBOL_LOC_COMPUTED
26993 @findex gdb.SYMBOL_LOC_COMPUTED
26994 @item gdb.SYMBOL_LOC_COMPUTED
26995 The value's address is a computed location.
26998 @node Symbol Tables In Python
26999 @subsubsection Symbol table representation in Python.
27001 @cindex symbol tables in python
27003 @tindex gdb.Symtab_and_line
27005 Access to symbol table data maintained by @value{GDBN} on the inferior
27006 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27007 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27008 from the @code{find_sal} method in @code{gdb.Frame} object.
27009 @xref{Frames In Python}.
27011 For more information on @value{GDBN}'s symbol table management, see
27012 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27014 A @code{gdb.Symtab_and_line} object has the following attributes:
27016 @defvar Symtab_and_line.symtab
27017 The symbol table object (@code{gdb.Symtab}) for this frame.
27018 This attribute is not writable.
27021 @defvar Symtab_and_line.pc
27022 Indicates the start of the address range occupied by code for the
27023 current source line. This attribute is not writable.
27026 @defvar Symtab_and_line.last
27027 Indicates the end of the address range occupied by code for the current
27028 source line. This attribute is not writable.
27031 @defvar Symtab_and_line.line
27032 Indicates the current line number for this object. This
27033 attribute is not writable.
27036 A @code{gdb.Symtab_and_line} object has the following methods:
27038 @defun Symtab_and_line.is_valid ()
27039 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27040 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27041 invalid if the Symbol table and line object it refers to does not
27042 exist in @value{GDBN} any longer. All other
27043 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27044 invalid at the time the method is called.
27047 A @code{gdb.Symtab} object has the following attributes:
27049 @defvar Symtab.filename
27050 The symbol table's source filename. This attribute is not writable.
27053 @defvar Symtab.objfile
27054 The symbol table's backing object file. @xref{Objfiles In Python}.
27055 This attribute is not writable.
27058 A @code{gdb.Symtab} object has the following methods:
27060 @defun Symtab.is_valid ()
27061 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27062 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27063 the symbol table it refers to does not exist in @value{GDBN} any
27064 longer. All other @code{gdb.Symtab} methods will throw an exception
27065 if it is invalid at the time the method is called.
27068 @defun Symtab.fullname ()
27069 Return the symbol table's source absolute file name.
27072 @defun Symtab.global_block ()
27073 Return the global block of the underlying symbol table.
27074 @xref{Blocks In Python}.
27077 @defun Symtab.static_block ()
27078 Return the static block of the underlying symbol table.
27079 @xref{Blocks In Python}.
27082 @defun Symtab.linetable ()
27083 Return the line table associated with the symbol table.
27084 @xref{Line Tables In Python}.
27087 @node Line Tables In Python
27088 @subsubsection Manipulating line tables using Python
27090 @cindex line tables in python
27091 @tindex gdb.LineTable
27093 Python code can request and inspect line table information from a
27094 symbol table that is loaded in @value{GDBN}. A line table is a
27095 mapping of source lines to their executable locations in memory. To
27096 acquire the line table information for a particular symbol table, use
27097 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27099 A @code{gdb.LineTable} is iterable. The iterator returns
27100 @code{LineTableEntry} objects that correspond to the source line and
27101 address for each line table entry. @code{LineTableEntry} objects have
27102 the following attributes:
27104 @defvar LineTableEntry.line
27105 The source line number for this line table entry. This number
27106 corresponds to the actual line of source. This attribute is not
27110 @defvar LineTableEntry.pc
27111 The address that is associated with the line table entry where the
27112 executable code for that source line resides in memory. This
27113 attribute is not writable.
27116 As there can be multiple addresses for a single source line, you may
27117 receive multiple @code{LineTableEntry} objects with matching
27118 @code{line} attributes, but with different @code{pc} attributes. The
27119 iterator is sorted in ascending @code{pc} order. Here is a small
27120 example illustrating iterating over a line table.
27123 symtab = gdb.selected_frame().find_sal().symtab
27124 linetable = symtab.linetable()
27125 for line in linetable:
27126 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27129 This will have the following output:
27132 Line: 33 Address: 0x4005c8L
27133 Line: 37 Address: 0x4005caL
27134 Line: 39 Address: 0x4005d2L
27135 Line: 40 Address: 0x4005f8L
27136 Line: 42 Address: 0x4005ffL
27137 Line: 44 Address: 0x400608L
27138 Line: 42 Address: 0x40060cL
27139 Line: 45 Address: 0x400615L
27142 In addition to being able to iterate over a @code{LineTable}, it also
27143 has the following direct access methods:
27145 @defun LineTable.line (line)
27146 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27147 entries in the line table for the given @var{line}. @var{line} refers
27148 to the source code line. If there are no entries for that source code
27149 @var{line}, the Python @code{None} is returned.
27152 @defun LineTable.has_line (line)
27153 Return a Python @code{Boolean} indicating whether there is an entry in
27154 the line table for this source line. Return @code{True} if an entry
27155 is found, or @code{False} if not.
27158 @defun LineTable.source_lines ()
27159 Return a Python @code{List} of the source line numbers in the symbol
27160 table. Only lines with executable code locations are returned. The
27161 contents of the @code{List} will just be the source line entries
27162 represented as Python @code{Long} values.
27165 @node Breakpoints In Python
27166 @subsubsection Manipulating breakpoints using Python
27168 @cindex breakpoints in python
27169 @tindex gdb.Breakpoint
27171 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27174 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27175 Create a new breakpoint. @var{spec} is a string naming the location
27176 of the breakpoint, or an expression that defines a watchpoint. The
27177 contents can be any location recognized by the @code{break} command,
27178 or in the case of a watchpoint, by the @code{watch} command. The
27179 optional @var{type} denotes the breakpoint to create from the types
27180 defined later in this chapter. This argument can be either:
27181 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27182 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27183 argument allows the breakpoint to become invisible to the user. The
27184 breakpoint will neither be reported when created, nor will it be
27185 listed in the output from @code{info breakpoints} (but will be listed
27186 with the @code{maint info breakpoints} command). The optional
27187 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27188 Temporary breakpoints are deleted after they have been hit. Any
27189 further access to the Python breakpoint after it has been hit will
27190 result in a runtime error (as that breakpoint has now been
27191 automatically deleted). The optional @var{wp_class} argument defines
27192 the class of watchpoint to create, if @var{type} is
27193 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27194 is assumed to be a @code{gdb.WP_WRITE} class.
27197 @defun Breakpoint.stop (self)
27198 The @code{gdb.Breakpoint} class can be sub-classed and, in
27199 particular, you may choose to implement the @code{stop} method.
27200 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27201 it will be called when the inferior reaches any location of a
27202 breakpoint which instantiates that sub-class. If the method returns
27203 @code{True}, the inferior will be stopped at the location of the
27204 breakpoint, otherwise the inferior will continue.
27206 If there are multiple breakpoints at the same location with a
27207 @code{stop} method, each one will be called regardless of the
27208 return status of the previous. This ensures that all @code{stop}
27209 methods have a chance to execute at that location. In this scenario
27210 if one of the methods returns @code{True} but the others return
27211 @code{False}, the inferior will still be stopped.
27213 You should not alter the execution state of the inferior (i.e.@:, step,
27214 next, etc.), alter the current frame context (i.e.@:, change the current
27215 active frame), or alter, add or delete any breakpoint. As a general
27216 rule, you should not alter any data within @value{GDBN} or the inferior
27219 Example @code{stop} implementation:
27222 class MyBreakpoint (gdb.Breakpoint):
27224 inf_val = gdb.parse_and_eval("foo")
27231 The available watchpoint types represented by constants are defined in the
27236 @findex gdb.WP_READ
27238 Read only watchpoint.
27241 @findex gdb.WP_WRITE
27243 Write only watchpoint.
27246 @findex gdb.WP_ACCESS
27247 @item gdb.WP_ACCESS
27248 Read/Write watchpoint.
27251 @defun Breakpoint.is_valid ()
27252 Return @code{True} if this @code{Breakpoint} object is valid,
27253 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27254 if the user deletes the breakpoint. In this case, the object still
27255 exists, but the underlying breakpoint does not. In the cases of
27256 watchpoint scope, the watchpoint remains valid even if execution of the
27257 inferior leaves the scope of that watchpoint.
27260 @defun Breakpoint.delete
27261 Permanently deletes the @value{GDBN} breakpoint. This also
27262 invalidates the Python @code{Breakpoint} object. Any further access
27263 to this object's attributes or methods will raise an error.
27266 @defvar Breakpoint.enabled
27267 This attribute is @code{True} if the breakpoint is enabled, and
27268 @code{False} otherwise. This attribute is writable.
27271 @defvar Breakpoint.silent
27272 This attribute is @code{True} if the breakpoint is silent, and
27273 @code{False} otherwise. This attribute is writable.
27275 Note that a breakpoint can also be silent if it has commands and the
27276 first command is @code{silent}. This is not reported by the
27277 @code{silent} attribute.
27280 @defvar Breakpoint.thread
27281 If the breakpoint is thread-specific, this attribute holds the thread
27282 id. If the breakpoint is not thread-specific, this attribute is
27283 @code{None}. This attribute is writable.
27286 @defvar Breakpoint.task
27287 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27288 id. If the breakpoint is not task-specific (or the underlying
27289 language is not Ada), this attribute is @code{None}. This attribute
27293 @defvar Breakpoint.ignore_count
27294 This attribute holds the ignore count for the breakpoint, an integer.
27295 This attribute is writable.
27298 @defvar Breakpoint.number
27299 This attribute holds the breakpoint's number --- the identifier used by
27300 the user to manipulate the breakpoint. This attribute is not writable.
27303 @defvar Breakpoint.type
27304 This attribute holds the breakpoint's type --- the identifier used to
27305 determine the actual breakpoint type or use-case. This attribute is not
27309 @defvar Breakpoint.visible
27310 This attribute tells whether the breakpoint is visible to the user
27311 when set, or when the @samp{info breakpoints} command is run. This
27312 attribute is not writable.
27315 @defvar Breakpoint.temporary
27316 This attribute indicates whether the breakpoint was created as a
27317 temporary breakpoint. Temporary breakpoints are automatically deleted
27318 after that breakpoint has been hit. Access to this attribute, and all
27319 other attributes and functions other than the @code{is_valid}
27320 function, will result in an error after the breakpoint has been hit
27321 (as it has been automatically deleted). This attribute is not
27325 The available types are represented by constants defined in the @code{gdb}
27329 @findex BP_BREAKPOINT
27330 @findex gdb.BP_BREAKPOINT
27331 @item gdb.BP_BREAKPOINT
27332 Normal code breakpoint.
27334 @findex BP_WATCHPOINT
27335 @findex gdb.BP_WATCHPOINT
27336 @item gdb.BP_WATCHPOINT
27337 Watchpoint breakpoint.
27339 @findex BP_HARDWARE_WATCHPOINT
27340 @findex gdb.BP_HARDWARE_WATCHPOINT
27341 @item gdb.BP_HARDWARE_WATCHPOINT
27342 Hardware assisted watchpoint.
27344 @findex BP_READ_WATCHPOINT
27345 @findex gdb.BP_READ_WATCHPOINT
27346 @item gdb.BP_READ_WATCHPOINT
27347 Hardware assisted read watchpoint.
27349 @findex BP_ACCESS_WATCHPOINT
27350 @findex gdb.BP_ACCESS_WATCHPOINT
27351 @item gdb.BP_ACCESS_WATCHPOINT
27352 Hardware assisted access watchpoint.
27355 @defvar Breakpoint.hit_count
27356 This attribute holds the hit count for the breakpoint, an integer.
27357 This attribute is writable, but currently it can only be set to zero.
27360 @defvar Breakpoint.location
27361 This attribute holds the location of the breakpoint, as specified by
27362 the user. It is a string. If the breakpoint does not have a location
27363 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27364 attribute is not writable.
27367 @defvar Breakpoint.expression
27368 This attribute holds a breakpoint expression, as specified by
27369 the user. It is a string. If the breakpoint does not have an
27370 expression (the breakpoint is not a watchpoint) the attribute's value
27371 is @code{None}. This attribute is not writable.
27374 @defvar Breakpoint.condition
27375 This attribute holds the condition of the breakpoint, as specified by
27376 the user. It is a string. If there is no condition, this attribute's
27377 value is @code{None}. This attribute is writable.
27380 @defvar Breakpoint.commands
27381 This attribute holds the commands attached to the breakpoint. If
27382 there are commands, this attribute's value is a string holding all the
27383 commands, separated by newlines. If there are no commands, this
27384 attribute is @code{None}. This attribute is not writable.
27387 @node Finish Breakpoints in Python
27388 @subsubsection Finish Breakpoints
27390 @cindex python finish breakpoints
27391 @tindex gdb.FinishBreakpoint
27393 A finish breakpoint is a temporary breakpoint set at the return address of
27394 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27395 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27396 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27397 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27398 Finish breakpoints are thread specific and must be create with the right
27401 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27402 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27403 object @var{frame}. If @var{frame} is not provided, this defaults to the
27404 newest frame. The optional @var{internal} argument allows the breakpoint to
27405 become invisible to the user. @xref{Breakpoints In Python}, for further
27406 details about this argument.
27409 @defun FinishBreakpoint.out_of_scope (self)
27410 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27411 @code{return} command, @dots{}), a function may not properly terminate, and
27412 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27413 situation, the @code{out_of_scope} callback will be triggered.
27415 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27419 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27421 print "normal finish"
27424 def out_of_scope ():
27425 print "abnormal finish"
27429 @defvar FinishBreakpoint.return_value
27430 When @value{GDBN} is stopped at a finish breakpoint and the frame
27431 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27432 attribute will contain a @code{gdb.Value} object corresponding to the return
27433 value of the function. The value will be @code{None} if the function return
27434 type is @code{void} or if the return value was not computable. This attribute
27438 @node Lazy Strings In Python
27439 @subsubsection Python representation of lazy strings.
27441 @cindex lazy strings in python
27442 @tindex gdb.LazyString
27444 A @dfn{lazy string} is a string whose contents is not retrieved or
27445 encoded until it is needed.
27447 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27448 @code{address} that points to a region of memory, an @code{encoding}
27449 that will be used to encode that region of memory, and a @code{length}
27450 to delimit the region of memory that represents the string. The
27451 difference between a @code{gdb.LazyString} and a string wrapped within
27452 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27453 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27454 retrieved and encoded during printing, while a @code{gdb.Value}
27455 wrapping a string is immediately retrieved and encoded on creation.
27457 A @code{gdb.LazyString} object has the following functions:
27459 @defun LazyString.value ()
27460 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27461 will point to the string in memory, but will lose all the delayed
27462 retrieval, encoding and handling that @value{GDBN} applies to a
27463 @code{gdb.LazyString}.
27466 @defvar LazyString.address
27467 This attribute holds the address of the string. This attribute is not
27471 @defvar LazyString.length
27472 This attribute holds the length of the string in characters. If the
27473 length is -1, then the string will be fetched and encoded up to the
27474 first null of appropriate width. This attribute is not writable.
27477 @defvar LazyString.encoding
27478 This attribute holds the encoding that will be applied to the string
27479 when the string is printed by @value{GDBN}. If the encoding is not
27480 set, or contains an empty string, then @value{GDBN} will select the
27481 most appropriate encoding when the string is printed. This attribute
27485 @defvar LazyString.type
27486 This attribute holds the type that is represented by the lazy string's
27487 type. For a lazy string this will always be a pointer type. To
27488 resolve this to the lazy string's character type, use the type's
27489 @code{target} method. @xref{Types In Python}. This attribute is not
27493 @node Architectures In Python
27494 @subsubsection Python representation of architectures
27495 @cindex Python architectures
27497 @value{GDBN} uses architecture specific parameters and artifacts in a
27498 number of its various computations. An architecture is represented
27499 by an instance of the @code{gdb.Architecture} class.
27501 A @code{gdb.Architecture} class has the following methods:
27503 @defun Architecture.name ()
27504 Return the name (string value) of the architecture.
27507 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27508 Return a list of disassembled instructions starting from the memory
27509 address @var{start_pc}. The optional arguments @var{end_pc} and
27510 @var{count} determine the number of instructions in the returned list.
27511 If both the optional arguments @var{end_pc} and @var{count} are
27512 specified, then a list of at most @var{count} disassembled instructions
27513 whose start address falls in the closed memory address interval from
27514 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27515 specified, but @var{count} is specified, then @var{count} number of
27516 instructions starting from the address @var{start_pc} are returned. If
27517 @var{count} is not specified but @var{end_pc} is specified, then all
27518 instructions whose start address falls in the closed memory address
27519 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27520 @var{end_pc} nor @var{count} are specified, then a single instruction at
27521 @var{start_pc} is returned. For all of these cases, each element of the
27522 returned list is a Python @code{dict} with the following string keys:
27527 The value corresponding to this key is a Python long integer capturing
27528 the memory address of the instruction.
27531 The value corresponding to this key is a string value which represents
27532 the instruction with assembly language mnemonics. The assembly
27533 language flavor used is the same as that specified by the current CLI
27534 variable @code{disassembly-flavor}. @xref{Machine Code}.
27537 The value corresponding to this key is the length (integer value) of the
27538 instruction in bytes.
27543 @node Python Auto-loading
27544 @subsection Python Auto-loading
27545 @cindex Python auto-loading
27547 When a new object file is read (for example, due to the @code{file}
27548 command, or because the inferior has loaded a shared library),
27549 @value{GDBN} will look for Python support scripts in several ways:
27550 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27551 and @code{.debug_gdb_scripts} section
27552 (@pxref{dotdebug_gdb_scripts section}).
27554 The auto-loading feature is useful for supplying application-specific
27555 debugging commands and scripts.
27557 Auto-loading can be enabled or disabled,
27558 and the list of auto-loaded scripts can be printed.
27561 @anchor{set auto-load python-scripts}
27562 @kindex set auto-load python-scripts
27563 @item set auto-load python-scripts [on|off]
27564 Enable or disable the auto-loading of Python scripts.
27566 @anchor{show auto-load python-scripts}
27567 @kindex show auto-load python-scripts
27568 @item show auto-load python-scripts
27569 Show whether auto-loading of Python scripts is enabled or disabled.
27571 @anchor{info auto-load python-scripts}
27572 @kindex info auto-load python-scripts
27573 @cindex print list of auto-loaded Python scripts
27574 @item info auto-load python-scripts [@var{regexp}]
27575 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27577 Also printed is the list of Python scripts that were mentioned in
27578 the @code{.debug_gdb_scripts} section and were not found
27579 (@pxref{dotdebug_gdb_scripts section}).
27580 This is useful because their names are not printed when @value{GDBN}
27581 tries to load them and fails. There may be many of them, and printing
27582 an error message for each one is problematic.
27584 If @var{regexp} is supplied only Python scripts with matching names are printed.
27589 (gdb) info auto-load python-scripts
27591 Yes py-section-script.py
27592 full name: /tmp/py-section-script.py
27593 No my-foo-pretty-printers.py
27597 When reading an auto-loaded file, @value{GDBN} sets the
27598 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27599 function (@pxref{Objfiles In Python}). This can be useful for
27600 registering objfile-specific pretty-printers and frame-filters.
27603 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27604 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27605 * Which flavor to choose?::
27608 @node objfile-gdb.py file
27609 @subsubsection The @file{@var{objfile}-gdb.py} file
27610 @cindex @file{@var{objfile}-gdb.py}
27612 When a new object file is read, @value{GDBN} looks for
27613 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27614 where @var{objfile} is the object file's real name, formed by ensuring
27615 that the file name is absolute, following all symlinks, and resolving
27616 @code{.} and @code{..} components. If this file exists and is
27617 readable, @value{GDBN} will evaluate it as a Python script.
27619 If this file does not exist, then @value{GDBN} will look for
27620 @var{script-name} file in all of the directories as specified below.
27622 Note that loading of this script file also requires accordingly configured
27623 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27625 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27626 scripts normally according to its @file{.exe} filename. But if no scripts are
27627 found @value{GDBN} also tries script filenames matching the object file without
27628 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27629 is attempted on any platform. This makes the script filenames compatible
27630 between Unix and MS-Windows hosts.
27633 @anchor{set auto-load scripts-directory}
27634 @kindex set auto-load scripts-directory
27635 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27636 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27637 may be delimited by the host platform path separator in use
27638 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27640 Each entry here needs to be covered also by the security setting
27641 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27643 @anchor{with-auto-load-dir}
27644 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27645 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27646 configuration option @option{--with-auto-load-dir}.
27648 Any reference to @file{$debugdir} will get replaced by
27649 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27650 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27651 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27652 @file{$datadir} must be placed as a directory component --- either alone or
27653 delimited by @file{/} or @file{\} directory separators, depending on the host
27656 The list of directories uses path separator (@samp{:} on GNU and Unix
27657 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27658 to the @env{PATH} environment variable.
27660 @anchor{show auto-load scripts-directory}
27661 @kindex show auto-load scripts-directory
27662 @item show auto-load scripts-directory
27663 Show @value{GDBN} auto-loaded scripts location.
27666 @value{GDBN} does not track which files it has already auto-loaded this way.
27667 @value{GDBN} will load the associated script every time the corresponding
27668 @var{objfile} is opened.
27669 So your @file{-gdb.py} file should be careful to avoid errors if it
27670 is evaluated more than once.
27672 @node dotdebug_gdb_scripts section
27673 @subsubsection The @code{.debug_gdb_scripts} section
27674 @cindex @code{.debug_gdb_scripts} section
27676 For systems using file formats like ELF and COFF,
27677 when @value{GDBN} loads a new object file
27678 it will look for a special section named @samp{.debug_gdb_scripts}.
27679 If this section exists, its contents is a list of names of scripts to load.
27681 @value{GDBN} will look for each specified script file first in the
27682 current directory and then along the source search path
27683 (@pxref{Source Path, ,Specifying Source Directories}),
27684 except that @file{$cdir} is not searched, since the compilation
27685 directory is not relevant to scripts.
27687 Entries can be placed in section @code{.debug_gdb_scripts} with,
27688 for example, this GCC macro:
27691 /* Note: The "MS" section flags are to remove duplicates. */
27692 #define DEFINE_GDB_SCRIPT(script_name) \
27694 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27696 .asciz \"" script_name "\"\n\
27702 Then one can reference the macro in a header or source file like this:
27705 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27708 The script name may include directories if desired.
27710 Note that loading of this script file also requires accordingly configured
27711 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27713 If the macro is put in a header, any application or library
27714 using this header will get a reference to the specified script.
27716 @node Which flavor to choose?
27717 @subsubsection Which flavor to choose?
27719 Given the multiple ways of auto-loading Python scripts, it might not always
27720 be clear which one to choose. This section provides some guidance.
27722 Benefits of the @file{-gdb.py} way:
27726 Can be used with file formats that don't support multiple sections.
27729 Ease of finding scripts for public libraries.
27731 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27732 in the source search path.
27733 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27734 isn't a source directory in which to find the script.
27737 Doesn't require source code additions.
27740 Benefits of the @code{.debug_gdb_scripts} way:
27744 Works with static linking.
27746 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27747 trigger their loading. When an application is statically linked the only
27748 objfile available is the executable, and it is cumbersome to attach all the
27749 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27752 Works with classes that are entirely inlined.
27754 Some classes can be entirely inlined, and thus there may not be an associated
27755 shared library to attach a @file{-gdb.py} script to.
27758 Scripts needn't be copied out of the source tree.
27760 In some circumstances, apps can be built out of large collections of internal
27761 libraries, and the build infrastructure necessary to install the
27762 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27763 cumbersome. It may be easier to specify the scripts in the
27764 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27765 top of the source tree to the source search path.
27768 @node Python modules
27769 @subsection Python modules
27770 @cindex python modules
27772 @value{GDBN} comes with several modules to assist writing Python code.
27775 * gdb.printing:: Building and registering pretty-printers.
27776 * gdb.types:: Utilities for working with types.
27777 * gdb.prompt:: Utilities for prompt value substitution.
27781 @subsubsection gdb.printing
27782 @cindex gdb.printing
27784 This module provides a collection of utilities for working with
27788 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27789 This class specifies the API that makes @samp{info pretty-printer},
27790 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27791 Pretty-printers should generally inherit from this class.
27793 @item SubPrettyPrinter (@var{name})
27794 For printers that handle multiple types, this class specifies the
27795 corresponding API for the subprinters.
27797 @item RegexpCollectionPrettyPrinter (@var{name})
27798 Utility class for handling multiple printers, all recognized via
27799 regular expressions.
27800 @xref{Writing a Pretty-Printer}, for an example.
27802 @item FlagEnumerationPrinter (@var{name})
27803 A pretty-printer which handles printing of @code{enum} values. Unlike
27804 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27805 work properly when there is some overlap between the enumeration
27806 constants. @var{name} is the name of the printer and also the name of
27807 the @code{enum} type to look up.
27809 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27810 Register @var{printer} with the pretty-printer list of @var{obj}.
27811 If @var{replace} is @code{True} then any existing copy of the printer
27812 is replaced. Otherwise a @code{RuntimeError} exception is raised
27813 if a printer with the same name already exists.
27817 @subsubsection gdb.types
27820 This module provides a collection of utilities for working with
27821 @code{gdb.Type} objects.
27824 @item get_basic_type (@var{type})
27825 Return @var{type} with const and volatile qualifiers stripped,
27826 and with typedefs and C@t{++} references converted to the underlying type.
27831 typedef const int const_int;
27833 const_int& foo_ref (foo);
27834 int main () @{ return 0; @}
27841 (gdb) python import gdb.types
27842 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27843 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27847 @item has_field (@var{type}, @var{field})
27848 Return @code{True} if @var{type}, assumed to be a type with fields
27849 (e.g., a structure or union), has field @var{field}.
27851 @item make_enum_dict (@var{enum_type})
27852 Return a Python @code{dictionary} type produced from @var{enum_type}.
27854 @item deep_items (@var{type})
27855 Returns a Python iterator similar to the standard
27856 @code{gdb.Type.iteritems} method, except that the iterator returned
27857 by @code{deep_items} will recursively traverse anonymous struct or
27858 union fields. For example:
27872 Then in @value{GDBN}:
27874 (@value{GDBP}) python import gdb.types
27875 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27876 (@value{GDBP}) python print struct_a.keys ()
27878 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27879 @{['a', 'b0', 'b1']@}
27882 @item get_type_recognizers ()
27883 Return a list of the enabled type recognizers for the current context.
27884 This is called by @value{GDBN} during the type-printing process
27885 (@pxref{Type Printing API}).
27887 @item apply_type_recognizers (recognizers, type_obj)
27888 Apply the type recognizers, @var{recognizers}, to the type object
27889 @var{type_obj}. If any recognizer returns a string, return that
27890 string. Otherwise, return @code{None}. This is called by
27891 @value{GDBN} during the type-printing process (@pxref{Type Printing
27894 @item register_type_printer (locus, printer)
27895 This is a convenience function to register a type printer.
27896 @var{printer} is the type printer to register. It must implement the
27897 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27898 which case the printer is registered with that objfile; a
27899 @code{gdb.Progspace}, in which case the printer is registered with
27900 that progspace; or @code{None}, in which case the printer is
27901 registered globally.
27904 This is a base class that implements the type printer protocol. Type
27905 printers are encouraged, but not required, to derive from this class.
27906 It defines a constructor:
27908 @defmethod TypePrinter __init__ (self, name)
27909 Initialize the type printer with the given name. The new printer
27910 starts in the enabled state.
27916 @subsubsection gdb.prompt
27919 This module provides a method for prompt value-substitution.
27922 @item substitute_prompt (@var{string})
27923 Return @var{string} with escape sequences substituted by values. Some
27924 escape sequences take arguments. You can specify arguments inside
27925 ``@{@}'' immediately following the escape sequence.
27927 The escape sequences you can pass to this function are:
27931 Substitute a backslash.
27933 Substitute an ESC character.
27935 Substitute the selected frame; an argument names a frame parameter.
27937 Substitute a newline.
27939 Substitute a parameter's value; the argument names the parameter.
27941 Substitute a carriage return.
27943 Substitute the selected thread; an argument names a thread parameter.
27945 Substitute the version of GDB.
27947 Substitute the current working directory.
27949 Begin a sequence of non-printing characters. These sequences are
27950 typically used with the ESC character, and are not counted in the string
27951 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27952 blue-colored ``(gdb)'' prompt where the length is five.
27954 End a sequence of non-printing characters.
27960 substitute_prompt (``frame: \f,
27961 print arguments: \p@{print frame-arguments@}'')
27964 @exdent will return the string:
27967 "frame: main, print arguments: scalars"
27972 @section Creating new spellings of existing commands
27973 @cindex aliases for commands
27975 It is often useful to define alternate spellings of existing commands.
27976 For example, if a new @value{GDBN} command defined in Python has
27977 a long name to type, it is handy to have an abbreviated version of it
27978 that involves less typing.
27980 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27981 of the @samp{step} command even though it is otherwise an ambiguous
27982 abbreviation of other commands like @samp{set} and @samp{show}.
27984 Aliases are also used to provide shortened or more common versions
27985 of multi-word commands. For example, @value{GDBN} provides the
27986 @samp{tty} alias of the @samp{set inferior-tty} command.
27988 You can define a new alias with the @samp{alias} command.
27993 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27997 @var{ALIAS} specifies the name of the new alias.
27998 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28001 @var{COMMAND} specifies the name of an existing command
28002 that is being aliased.
28004 The @samp{-a} option specifies that the new alias is an abbreviation
28005 of the command. Abbreviations are not shown in command
28006 lists displayed by the @samp{help} command.
28008 The @samp{--} option specifies the end of options,
28009 and is useful when @var{ALIAS} begins with a dash.
28011 Here is a simple example showing how to make an abbreviation
28012 of a command so that there is less to type.
28013 Suppose you were tired of typing @samp{disas}, the current
28014 shortest unambiguous abbreviation of the @samp{disassemble} command
28015 and you wanted an even shorter version named @samp{di}.
28016 The following will accomplish this.
28019 (gdb) alias -a di = disas
28022 Note that aliases are different from user-defined commands.
28023 With a user-defined command, you also need to write documentation
28024 for it with the @samp{document} command.
28025 An alias automatically picks up the documentation of the existing command.
28027 Here is an example where we make @samp{elms} an abbreviation of
28028 @samp{elements} in the @samp{set print elements} command.
28029 This is to show that you can make an abbreviation of any part
28033 (gdb) alias -a set print elms = set print elements
28034 (gdb) alias -a show print elms = show print elements
28035 (gdb) set p elms 20
28037 Limit on string chars or array elements to print is 200.
28040 Note that if you are defining an alias of a @samp{set} command,
28041 and you want to have an alias for the corresponding @samp{show}
28042 command, then you need to define the latter separately.
28044 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28045 @var{ALIAS}, just as they are normally.
28048 (gdb) alias -a set pr elms = set p ele
28051 Finally, here is an example showing the creation of a one word
28052 alias for a more complex command.
28053 This creates alias @samp{spe} of the command @samp{set print elements}.
28056 (gdb) alias spe = set print elements
28061 @chapter Command Interpreters
28062 @cindex command interpreters
28064 @value{GDBN} supports multiple command interpreters, and some command
28065 infrastructure to allow users or user interface writers to switch
28066 between interpreters or run commands in other interpreters.
28068 @value{GDBN} currently supports two command interpreters, the console
28069 interpreter (sometimes called the command-line interpreter or @sc{cli})
28070 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28071 describes both of these interfaces in great detail.
28073 By default, @value{GDBN} will start with the console interpreter.
28074 However, the user may choose to start @value{GDBN} with another
28075 interpreter by specifying the @option{-i} or @option{--interpreter}
28076 startup options. Defined interpreters include:
28080 @cindex console interpreter
28081 The traditional console or command-line interpreter. This is the most often
28082 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28083 @value{GDBN} will use this interpreter.
28086 @cindex mi interpreter
28087 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28088 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28089 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28093 @cindex mi2 interpreter
28094 The current @sc{gdb/mi} interface.
28097 @cindex mi1 interpreter
28098 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28102 @cindex invoke another interpreter
28103 The interpreter being used by @value{GDBN} may not be dynamically
28104 switched at runtime. Although possible, this could lead to a very
28105 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28106 enters the command "interpreter-set console" in a console view,
28107 @value{GDBN} would switch to using the console interpreter, rendering
28108 the IDE inoperable!
28110 @kindex interpreter-exec
28111 Although you may only choose a single interpreter at startup, you may execute
28112 commands in any interpreter from the current interpreter using the appropriate
28113 command. If you are running the console interpreter, simply use the
28114 @code{interpreter-exec} command:
28117 interpreter-exec mi "-data-list-register-names"
28120 @sc{gdb/mi} has a similar command, although it is only available in versions of
28121 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28124 @chapter @value{GDBN} Text User Interface
28126 @cindex Text User Interface
28129 * TUI Overview:: TUI overview
28130 * TUI Keys:: TUI key bindings
28131 * TUI Single Key Mode:: TUI single key mode
28132 * TUI Commands:: TUI-specific commands
28133 * TUI Configuration:: TUI configuration variables
28136 The @value{GDBN} Text User Interface (TUI) is a terminal
28137 interface which uses the @code{curses} library to show the source
28138 file, the assembly output, the program registers and @value{GDBN}
28139 commands in separate text windows. The TUI mode is supported only
28140 on platforms where a suitable version of the @code{curses} library
28143 The TUI mode is enabled by default when you invoke @value{GDBN} as
28144 @samp{@value{GDBP} -tui}.
28145 You can also switch in and out of TUI mode while @value{GDBN} runs by
28146 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28147 @xref{TUI Keys, ,TUI Key Bindings}.
28150 @section TUI Overview
28152 In TUI mode, @value{GDBN} can display several text windows:
28156 This window is the @value{GDBN} command window with the @value{GDBN}
28157 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28158 managed using readline.
28161 The source window shows the source file of the program. The current
28162 line and active breakpoints are displayed in this window.
28165 The assembly window shows the disassembly output of the program.
28168 This window shows the processor registers. Registers are highlighted
28169 when their values change.
28172 The source and assembly windows show the current program position
28173 by highlighting the current line and marking it with a @samp{>} marker.
28174 Breakpoints are indicated with two markers. The first marker
28175 indicates the breakpoint type:
28179 Breakpoint which was hit at least once.
28182 Breakpoint which was never hit.
28185 Hardware breakpoint which was hit at least once.
28188 Hardware breakpoint which was never hit.
28191 The second marker indicates whether the breakpoint is enabled or not:
28195 Breakpoint is enabled.
28198 Breakpoint is disabled.
28201 The source, assembly and register windows are updated when the current
28202 thread changes, when the frame changes, or when the program counter
28205 These windows are not all visible at the same time. The command
28206 window is always visible. The others can be arranged in several
28217 source and assembly,
28220 source and registers, or
28223 assembly and registers.
28226 A status line above the command window shows the following information:
28230 Indicates the current @value{GDBN} target.
28231 (@pxref{Targets, ,Specifying a Debugging Target}).
28234 Gives the current process or thread number.
28235 When no process is being debugged, this field is set to @code{No process}.
28238 Gives the current function name for the selected frame.
28239 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28240 When there is no symbol corresponding to the current program counter,
28241 the string @code{??} is displayed.
28244 Indicates the current line number for the selected frame.
28245 When the current line number is not known, the string @code{??} is displayed.
28248 Indicates the current program counter address.
28252 @section TUI Key Bindings
28253 @cindex TUI key bindings
28255 The TUI installs several key bindings in the readline keymaps
28256 @ifset SYSTEM_READLINE
28257 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28259 @ifclear SYSTEM_READLINE
28260 (@pxref{Command Line Editing}).
28262 The following key bindings are installed for both TUI mode and the
28263 @value{GDBN} standard mode.
28272 Enter or leave the TUI mode. When leaving the TUI mode,
28273 the curses window management stops and @value{GDBN} operates using
28274 its standard mode, writing on the terminal directly. When reentering
28275 the TUI mode, control is given back to the curses windows.
28276 The screen is then refreshed.
28280 Use a TUI layout with only one window. The layout will
28281 either be @samp{source} or @samp{assembly}. When the TUI mode
28282 is not active, it will switch to the TUI mode.
28284 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28288 Use a TUI layout with at least two windows. When the current
28289 layout already has two windows, the next layout with two windows is used.
28290 When a new layout is chosen, one window will always be common to the
28291 previous layout and the new one.
28293 Think of it as the Emacs @kbd{C-x 2} binding.
28297 Change the active window. The TUI associates several key bindings
28298 (like scrolling and arrow keys) with the active window. This command
28299 gives the focus to the next TUI window.
28301 Think of it as the Emacs @kbd{C-x o} binding.
28305 Switch in and out of the TUI SingleKey mode that binds single
28306 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28309 The following key bindings only work in the TUI mode:
28314 Scroll the active window one page up.
28318 Scroll the active window one page down.
28322 Scroll the active window one line up.
28326 Scroll the active window one line down.
28330 Scroll the active window one column left.
28334 Scroll the active window one column right.
28338 Refresh the screen.
28341 Because the arrow keys scroll the active window in the TUI mode, they
28342 are not available for their normal use by readline unless the command
28343 window has the focus. When another window is active, you must use
28344 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28345 and @kbd{C-f} to control the command window.
28347 @node TUI Single Key Mode
28348 @section TUI Single Key Mode
28349 @cindex TUI single key mode
28351 The TUI also provides a @dfn{SingleKey} mode, which binds several
28352 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28353 switch into this mode, where the following key bindings are used:
28356 @kindex c @r{(SingleKey TUI key)}
28360 @kindex d @r{(SingleKey TUI key)}
28364 @kindex f @r{(SingleKey TUI key)}
28368 @kindex n @r{(SingleKey TUI key)}
28372 @kindex q @r{(SingleKey TUI key)}
28374 exit the SingleKey mode.
28376 @kindex r @r{(SingleKey TUI key)}
28380 @kindex s @r{(SingleKey TUI key)}
28384 @kindex u @r{(SingleKey TUI key)}
28388 @kindex v @r{(SingleKey TUI key)}
28392 @kindex w @r{(SingleKey TUI key)}
28397 Other keys temporarily switch to the @value{GDBN} command prompt.
28398 The key that was pressed is inserted in the editing buffer so that
28399 it is possible to type most @value{GDBN} commands without interaction
28400 with the TUI SingleKey mode. Once the command is entered the TUI
28401 SingleKey mode is restored. The only way to permanently leave
28402 this mode is by typing @kbd{q} or @kbd{C-x s}.
28406 @section TUI-specific Commands
28407 @cindex TUI commands
28409 The TUI has specific commands to control the text windows.
28410 These commands are always available, even when @value{GDBN} is not in
28411 the TUI mode. When @value{GDBN} is in the standard mode, most
28412 of these commands will automatically switch to the TUI mode.
28414 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28415 terminal, or @value{GDBN} has been started with the machine interface
28416 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28417 these commands will fail with an error, because it would not be
28418 possible or desirable to enable curses window management.
28423 List and give the size of all displayed windows.
28427 Display the next layout.
28430 Display the previous layout.
28433 Display the source window only.
28436 Display the assembly window only.
28439 Display the source and assembly window.
28442 Display the register window together with the source or assembly window.
28446 Make the next window active for scrolling.
28449 Make the previous window active for scrolling.
28452 Make the source window active for scrolling.
28455 Make the assembly window active for scrolling.
28458 Make the register window active for scrolling.
28461 Make the command window active for scrolling.
28465 Refresh the screen. This is similar to typing @kbd{C-L}.
28467 @item tui reg float
28469 Show the floating point registers in the register window.
28471 @item tui reg general
28472 Show the general registers in the register window.
28475 Show the next register group. The list of register groups as well as
28476 their order is target specific. The predefined register groups are the
28477 following: @code{general}, @code{float}, @code{system}, @code{vector},
28478 @code{all}, @code{save}, @code{restore}.
28480 @item tui reg system
28481 Show the system registers in the register window.
28485 Update the source window and the current execution point.
28487 @item winheight @var{name} +@var{count}
28488 @itemx winheight @var{name} -@var{count}
28490 Change the height of the window @var{name} by @var{count}
28491 lines. Positive counts increase the height, while negative counts
28494 @item tabset @var{nchars}
28496 Set the width of tab stops to be @var{nchars} characters.
28499 @node TUI Configuration
28500 @section TUI Configuration Variables
28501 @cindex TUI configuration variables
28503 Several configuration variables control the appearance of TUI windows.
28506 @item set tui border-kind @var{kind}
28507 @kindex set tui border-kind
28508 Select the border appearance for the source, assembly and register windows.
28509 The possible values are the following:
28512 Use a space character to draw the border.
28515 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28518 Use the Alternate Character Set to draw the border. The border is
28519 drawn using character line graphics if the terminal supports them.
28522 @item set tui border-mode @var{mode}
28523 @kindex set tui border-mode
28524 @itemx set tui active-border-mode @var{mode}
28525 @kindex set tui active-border-mode
28526 Select the display attributes for the borders of the inactive windows
28527 or the active window. The @var{mode} can be one of the following:
28530 Use normal attributes to display the border.
28536 Use reverse video mode.
28539 Use half bright mode.
28541 @item half-standout
28542 Use half bright and standout mode.
28545 Use extra bright or bold mode.
28547 @item bold-standout
28548 Use extra bright or bold and standout mode.
28553 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28556 @cindex @sc{gnu} Emacs
28557 A special interface allows you to use @sc{gnu} Emacs to view (and
28558 edit) the source files for the program you are debugging with
28561 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28562 executable file you want to debug as an argument. This command starts
28563 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28564 created Emacs buffer.
28565 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28567 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28572 All ``terminal'' input and output goes through an Emacs buffer, called
28575 This applies both to @value{GDBN} commands and their output, and to the input
28576 and output done by the program you are debugging.
28578 This is useful because it means that you can copy the text of previous
28579 commands and input them again; you can even use parts of the output
28582 All the facilities of Emacs' Shell mode are available for interacting
28583 with your program. In particular, you can send signals the usual
28584 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28588 @value{GDBN} displays source code through Emacs.
28590 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28591 source file for that frame and puts an arrow (@samp{=>}) at the
28592 left margin of the current line. Emacs uses a separate buffer for
28593 source display, and splits the screen to show both your @value{GDBN} session
28596 Explicit @value{GDBN} @code{list} or search commands still produce output as
28597 usual, but you probably have no reason to use them from Emacs.
28600 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28601 a graphical mode, enabled by default, which provides further buffers
28602 that can control the execution and describe the state of your program.
28603 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28605 If you specify an absolute file name when prompted for the @kbd{M-x
28606 gdb} argument, then Emacs sets your current working directory to where
28607 your program resides. If you only specify the file name, then Emacs
28608 sets your current working directory to the directory associated
28609 with the previous buffer. In this case, @value{GDBN} may find your
28610 program by searching your environment's @code{PATH} variable, but on
28611 some operating systems it might not find the source. So, although the
28612 @value{GDBN} input and output session proceeds normally, the auxiliary
28613 buffer does not display the current source and line of execution.
28615 The initial working directory of @value{GDBN} is printed on the top
28616 line of the GUD buffer and this serves as a default for the commands
28617 that specify files for @value{GDBN} to operate on. @xref{Files,
28618 ,Commands to Specify Files}.
28620 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28621 need to call @value{GDBN} by a different name (for example, if you
28622 keep several configurations around, with different names) you can
28623 customize the Emacs variable @code{gud-gdb-command-name} to run the
28626 In the GUD buffer, you can use these special Emacs commands in
28627 addition to the standard Shell mode commands:
28631 Describe the features of Emacs' GUD Mode.
28634 Execute to another source line, like the @value{GDBN} @code{step} command; also
28635 update the display window to show the current file and location.
28638 Execute to next source line in this function, skipping all function
28639 calls, like the @value{GDBN} @code{next} command. Then update the display window
28640 to show the current file and location.
28643 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28644 display window accordingly.
28647 Execute until exit from the selected stack frame, like the @value{GDBN}
28648 @code{finish} command.
28651 Continue execution of your program, like the @value{GDBN} @code{continue}
28655 Go up the number of frames indicated by the numeric argument
28656 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28657 like the @value{GDBN} @code{up} command.
28660 Go down the number of frames indicated by the numeric argument, like the
28661 @value{GDBN} @code{down} command.
28664 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28665 tells @value{GDBN} to set a breakpoint on the source line point is on.
28667 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28668 separate frame which shows a backtrace when the GUD buffer is current.
28669 Move point to any frame in the stack and type @key{RET} to make it
28670 become the current frame and display the associated source in the
28671 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28672 selected frame become the current one. In graphical mode, the
28673 speedbar displays watch expressions.
28675 If you accidentally delete the source-display buffer, an easy way to get
28676 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28677 request a frame display; when you run under Emacs, this recreates
28678 the source buffer if necessary to show you the context of the current
28681 The source files displayed in Emacs are in ordinary Emacs buffers
28682 which are visiting the source files in the usual way. You can edit
28683 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28684 communicates with Emacs in terms of line numbers. If you add or
28685 delete lines from the text, the line numbers that @value{GDBN} knows cease
28686 to correspond properly with the code.
28688 A more detailed description of Emacs' interaction with @value{GDBN} is
28689 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28693 @chapter The @sc{gdb/mi} Interface
28695 @unnumberedsec Function and Purpose
28697 @cindex @sc{gdb/mi}, its purpose
28698 @sc{gdb/mi} is a line based machine oriented text interface to
28699 @value{GDBN} and is activated by specifying using the
28700 @option{--interpreter} command line option (@pxref{Mode Options}). It
28701 is specifically intended to support the development of systems which
28702 use the debugger as just one small component of a larger system.
28704 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28705 in the form of a reference manual.
28707 Note that @sc{gdb/mi} is still under construction, so some of the
28708 features described below are incomplete and subject to change
28709 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28711 @unnumberedsec Notation and Terminology
28713 @cindex notational conventions, for @sc{gdb/mi}
28714 This chapter uses the following notation:
28718 @code{|} separates two alternatives.
28721 @code{[ @var{something} ]} indicates that @var{something} is optional:
28722 it may or may not be given.
28725 @code{( @var{group} )*} means that @var{group} inside the parentheses
28726 may repeat zero or more times.
28729 @code{( @var{group} )+} means that @var{group} inside the parentheses
28730 may repeat one or more times.
28733 @code{"@var{string}"} means a literal @var{string}.
28737 @heading Dependencies
28741 * GDB/MI General Design::
28742 * GDB/MI Command Syntax::
28743 * GDB/MI Compatibility with CLI::
28744 * GDB/MI Development and Front Ends::
28745 * GDB/MI Output Records::
28746 * GDB/MI Simple Examples::
28747 * GDB/MI Command Description Format::
28748 * GDB/MI Breakpoint Commands::
28749 * GDB/MI Catchpoint Commands::
28750 * GDB/MI Program Context::
28751 * GDB/MI Thread Commands::
28752 * GDB/MI Ada Tasking Commands::
28753 * GDB/MI Program Execution::
28754 * GDB/MI Stack Manipulation::
28755 * GDB/MI Variable Objects::
28756 * GDB/MI Data Manipulation::
28757 * GDB/MI Tracepoint Commands::
28758 * GDB/MI Symbol Query::
28759 * GDB/MI File Commands::
28761 * GDB/MI Kod Commands::
28762 * GDB/MI Memory Overlay Commands::
28763 * GDB/MI Signal Handling Commands::
28765 * GDB/MI Target Manipulation::
28766 * GDB/MI File Transfer Commands::
28767 * GDB/MI Ada Exceptions Commands::
28768 * GDB/MI Miscellaneous Commands::
28771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28772 @node GDB/MI General Design
28773 @section @sc{gdb/mi} General Design
28774 @cindex GDB/MI General Design
28776 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28777 parts---commands sent to @value{GDBN}, responses to those commands
28778 and notifications. Each command results in exactly one response,
28779 indicating either successful completion of the command, or an error.
28780 For the commands that do not resume the target, the response contains the
28781 requested information. For the commands that resume the target, the
28782 response only indicates whether the target was successfully resumed.
28783 Notifications is the mechanism for reporting changes in the state of the
28784 target, or in @value{GDBN} state, that cannot conveniently be associated with
28785 a command and reported as part of that command response.
28787 The important examples of notifications are:
28791 Exec notifications. These are used to report changes in
28792 target state---when a target is resumed, or stopped. It would not
28793 be feasible to include this information in response of resuming
28794 commands, because one resume commands can result in multiple events in
28795 different threads. Also, quite some time may pass before any event
28796 happens in the target, while a frontend needs to know whether the resuming
28797 command itself was successfully executed.
28800 Console output, and status notifications. Console output
28801 notifications are used to report output of CLI commands, as well as
28802 diagnostics for other commands. Status notifications are used to
28803 report the progress of a long-running operation. Naturally, including
28804 this information in command response would mean no output is produced
28805 until the command is finished, which is undesirable.
28808 General notifications. Commands may have various side effects on
28809 the @value{GDBN} or target state beyond their official purpose. For example,
28810 a command may change the selected thread. Although such changes can
28811 be included in command response, using notification allows for more
28812 orthogonal frontend design.
28816 There's no guarantee that whenever an MI command reports an error,
28817 @value{GDBN} or the target are in any specific state, and especially,
28818 the state is not reverted to the state before the MI command was
28819 processed. Therefore, whenever an MI command results in an error,
28820 we recommend that the frontend refreshes all the information shown in
28821 the user interface.
28825 * Context management::
28826 * Asynchronous and non-stop modes::
28830 @node Context management
28831 @subsection Context management
28833 @subsubsection Threads and Frames
28835 In most cases when @value{GDBN} accesses the target, this access is
28836 done in context of a specific thread and frame (@pxref{Frames}).
28837 Often, even when accessing global data, the target requires that a thread
28838 be specified. The CLI interface maintains the selected thread and frame,
28839 and supplies them to target on each command. This is convenient,
28840 because a command line user would not want to specify that information
28841 explicitly on each command, and because user interacts with
28842 @value{GDBN} via a single terminal, so no confusion is possible as
28843 to what thread and frame are the current ones.
28845 In the case of MI, the concept of selected thread and frame is less
28846 useful. First, a frontend can easily remember this information
28847 itself. Second, a graphical frontend can have more than one window,
28848 each one used for debugging a different thread, and the frontend might
28849 want to access additional threads for internal purposes. This
28850 increases the risk that by relying on implicitly selected thread, the
28851 frontend may be operating on a wrong one. Therefore, each MI command
28852 should explicitly specify which thread and frame to operate on. To
28853 make it possible, each MI command accepts the @samp{--thread} and
28854 @samp{--frame} options, the value to each is @value{GDBN} identifier
28855 for thread and frame to operate on.
28857 Usually, each top-level window in a frontend allows the user to select
28858 a thread and a frame, and remembers the user selection for further
28859 operations. However, in some cases @value{GDBN} may suggest that the
28860 current thread be changed. For example, when stopping on a breakpoint
28861 it is reasonable to switch to the thread where breakpoint is hit. For
28862 another example, if the user issues the CLI @samp{thread} command via
28863 the frontend, it is desirable to change the frontend's selected thread to the
28864 one specified by user. @value{GDBN} communicates the suggestion to
28865 change current thread using the @samp{=thread-selected} notification.
28866 No such notification is available for the selected frame at the moment.
28868 Note that historically, MI shares the selected thread with CLI, so
28869 frontends used the @code{-thread-select} to execute commands in the
28870 right context. However, getting this to work right is cumbersome. The
28871 simplest way is for frontend to emit @code{-thread-select} command
28872 before every command. This doubles the number of commands that need
28873 to be sent. The alternative approach is to suppress @code{-thread-select}
28874 if the selected thread in @value{GDBN} is supposed to be identical to the
28875 thread the frontend wants to operate on. However, getting this
28876 optimization right can be tricky. In particular, if the frontend
28877 sends several commands to @value{GDBN}, and one of the commands changes the
28878 selected thread, then the behaviour of subsequent commands will
28879 change. So, a frontend should either wait for response from such
28880 problematic commands, or explicitly add @code{-thread-select} for
28881 all subsequent commands. No frontend is known to do this exactly
28882 right, so it is suggested to just always pass the @samp{--thread} and
28883 @samp{--frame} options.
28885 @subsubsection Language
28887 The execution of several commands depends on which language is selected.
28888 By default, the current language (@pxref{show language}) is used.
28889 But for commands known to be language-sensitive, it is recommended
28890 to use the @samp{--language} option. This option takes one argument,
28891 which is the name of the language to use while executing the command.
28895 -data-evaluate-expression --language c "sizeof (void*)"
28900 The valid language names are the same names accepted by the
28901 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28902 @samp{local} or @samp{unknown}.
28904 @node Asynchronous and non-stop modes
28905 @subsection Asynchronous command execution and non-stop mode
28907 On some targets, @value{GDBN} is capable of processing MI commands
28908 even while the target is running. This is called @dfn{asynchronous
28909 command execution} (@pxref{Background Execution}). The frontend may
28910 specify a preferrence for asynchronous execution using the
28911 @code{-gdb-set target-async 1} command, which should be emitted before
28912 either running the executable or attaching to the target. After the
28913 frontend has started the executable or attached to the target, it can
28914 find if asynchronous execution is enabled using the
28915 @code{-list-target-features} command.
28917 Even if @value{GDBN} can accept a command while target is running,
28918 many commands that access the target do not work when the target is
28919 running. Therefore, asynchronous command execution is most useful
28920 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28921 it is possible to examine the state of one thread, while other threads
28924 When a given thread is running, MI commands that try to access the
28925 target in the context of that thread may not work, or may work only on
28926 some targets. In particular, commands that try to operate on thread's
28927 stack will not work, on any target. Commands that read memory, or
28928 modify breakpoints, may work or not work, depending on the target. Note
28929 that even commands that operate on global state, such as @code{print},
28930 @code{set}, and breakpoint commands, still access the target in the
28931 context of a specific thread, so frontend should try to find a
28932 stopped thread and perform the operation on that thread (using the
28933 @samp{--thread} option).
28935 Which commands will work in the context of a running thread is
28936 highly target dependent. However, the two commands
28937 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28938 to find the state of a thread, will always work.
28940 @node Thread groups
28941 @subsection Thread groups
28942 @value{GDBN} may be used to debug several processes at the same time.
28943 On some platfroms, @value{GDBN} may support debugging of several
28944 hardware systems, each one having several cores with several different
28945 processes running on each core. This section describes the MI
28946 mechanism to support such debugging scenarios.
28948 The key observation is that regardless of the structure of the
28949 target, MI can have a global list of threads, because most commands that
28950 accept the @samp{--thread} option do not need to know what process that
28951 thread belongs to. Therefore, it is not necessary to introduce
28952 neither additional @samp{--process} option, nor an notion of the
28953 current process in the MI interface. The only strictly new feature
28954 that is required is the ability to find how the threads are grouped
28957 To allow the user to discover such grouping, and to support arbitrary
28958 hierarchy of machines/cores/processes, MI introduces the concept of a
28959 @dfn{thread group}. Thread group is a collection of threads and other
28960 thread groups. A thread group always has a string identifier, a type,
28961 and may have additional attributes specific to the type. A new
28962 command, @code{-list-thread-groups}, returns the list of top-level
28963 thread groups, which correspond to processes that @value{GDBN} is
28964 debugging at the moment. By passing an identifier of a thread group
28965 to the @code{-list-thread-groups} command, it is possible to obtain
28966 the members of specific thread group.
28968 To allow the user to easily discover processes, and other objects, he
28969 wishes to debug, a concept of @dfn{available thread group} is
28970 introduced. Available thread group is an thread group that
28971 @value{GDBN} is not debugging, but that can be attached to, using the
28972 @code{-target-attach} command. The list of available top-level thread
28973 groups can be obtained using @samp{-list-thread-groups --available}.
28974 In general, the content of a thread group may be only retrieved only
28975 after attaching to that thread group.
28977 Thread groups are related to inferiors (@pxref{Inferiors and
28978 Programs}). Each inferior corresponds to a thread group of a special
28979 type @samp{process}, and some additional operations are permitted on
28980 such thread groups.
28982 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28983 @node GDB/MI Command Syntax
28984 @section @sc{gdb/mi} Command Syntax
28987 * GDB/MI Input Syntax::
28988 * GDB/MI Output Syntax::
28991 @node GDB/MI Input Syntax
28992 @subsection @sc{gdb/mi} Input Syntax
28994 @cindex input syntax for @sc{gdb/mi}
28995 @cindex @sc{gdb/mi}, input syntax
28997 @item @var{command} @expansion{}
28998 @code{@var{cli-command} | @var{mi-command}}
29000 @item @var{cli-command} @expansion{}
29001 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29002 @var{cli-command} is any existing @value{GDBN} CLI command.
29004 @item @var{mi-command} @expansion{}
29005 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29006 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29008 @item @var{token} @expansion{}
29009 "any sequence of digits"
29011 @item @var{option} @expansion{}
29012 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29014 @item @var{parameter} @expansion{}
29015 @code{@var{non-blank-sequence} | @var{c-string}}
29017 @item @var{operation} @expansion{}
29018 @emph{any of the operations described in this chapter}
29020 @item @var{non-blank-sequence} @expansion{}
29021 @emph{anything, provided it doesn't contain special characters such as
29022 "-", @var{nl}, """ and of course " "}
29024 @item @var{c-string} @expansion{}
29025 @code{""" @var{seven-bit-iso-c-string-content} """}
29027 @item @var{nl} @expansion{}
29036 The CLI commands are still handled by the @sc{mi} interpreter; their
29037 output is described below.
29040 The @code{@var{token}}, when present, is passed back when the command
29044 Some @sc{mi} commands accept optional arguments as part of the parameter
29045 list. Each option is identified by a leading @samp{-} (dash) and may be
29046 followed by an optional argument parameter. Options occur first in the
29047 parameter list and can be delimited from normal parameters using
29048 @samp{--} (this is useful when some parameters begin with a dash).
29055 We want easy access to the existing CLI syntax (for debugging).
29058 We want it to be easy to spot a @sc{mi} operation.
29061 @node GDB/MI Output Syntax
29062 @subsection @sc{gdb/mi} Output Syntax
29064 @cindex output syntax of @sc{gdb/mi}
29065 @cindex @sc{gdb/mi}, output syntax
29066 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29067 followed, optionally, by a single result record. This result record
29068 is for the most recent command. The sequence of output records is
29069 terminated by @samp{(gdb)}.
29071 If an input command was prefixed with a @code{@var{token}} then the
29072 corresponding output for that command will also be prefixed by that same
29076 @item @var{output} @expansion{}
29077 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29079 @item @var{result-record} @expansion{}
29080 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29082 @item @var{out-of-band-record} @expansion{}
29083 @code{@var{async-record} | @var{stream-record}}
29085 @item @var{async-record} @expansion{}
29086 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29088 @item @var{exec-async-output} @expansion{}
29089 @code{[ @var{token} ] "*" @var{async-output}}
29091 @item @var{status-async-output} @expansion{}
29092 @code{[ @var{token} ] "+" @var{async-output}}
29094 @item @var{notify-async-output} @expansion{}
29095 @code{[ @var{token} ] "=" @var{async-output}}
29097 @item @var{async-output} @expansion{}
29098 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29100 @item @var{result-class} @expansion{}
29101 @code{"done" | "running" | "connected" | "error" | "exit"}
29103 @item @var{async-class} @expansion{}
29104 @code{"stopped" | @var{others}} (where @var{others} will be added
29105 depending on the needs---this is still in development).
29107 @item @var{result} @expansion{}
29108 @code{ @var{variable} "=" @var{value}}
29110 @item @var{variable} @expansion{}
29111 @code{ @var{string} }
29113 @item @var{value} @expansion{}
29114 @code{ @var{const} | @var{tuple} | @var{list} }
29116 @item @var{const} @expansion{}
29117 @code{@var{c-string}}
29119 @item @var{tuple} @expansion{}
29120 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29122 @item @var{list} @expansion{}
29123 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29124 @var{result} ( "," @var{result} )* "]" }
29126 @item @var{stream-record} @expansion{}
29127 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29129 @item @var{console-stream-output} @expansion{}
29130 @code{"~" @var{c-string}}
29132 @item @var{target-stream-output} @expansion{}
29133 @code{"@@" @var{c-string}}
29135 @item @var{log-stream-output} @expansion{}
29136 @code{"&" @var{c-string}}
29138 @item @var{nl} @expansion{}
29141 @item @var{token} @expansion{}
29142 @emph{any sequence of digits}.
29150 All output sequences end in a single line containing a period.
29153 The @code{@var{token}} is from the corresponding request. Note that
29154 for all async output, while the token is allowed by the grammar and
29155 may be output by future versions of @value{GDBN} for select async
29156 output messages, it is generally omitted. Frontends should treat
29157 all async output as reporting general changes in the state of the
29158 target and there should be no need to associate async output to any
29162 @cindex status output in @sc{gdb/mi}
29163 @var{status-async-output} contains on-going status information about the
29164 progress of a slow operation. It can be discarded. All status output is
29165 prefixed by @samp{+}.
29168 @cindex async output in @sc{gdb/mi}
29169 @var{exec-async-output} contains asynchronous state change on the target
29170 (stopped, started, disappeared). All async output is prefixed by
29174 @cindex notify output in @sc{gdb/mi}
29175 @var{notify-async-output} contains supplementary information that the
29176 client should handle (e.g., a new breakpoint information). All notify
29177 output is prefixed by @samp{=}.
29180 @cindex console output in @sc{gdb/mi}
29181 @var{console-stream-output} is output that should be displayed as is in the
29182 console. It is the textual response to a CLI command. All the console
29183 output is prefixed by @samp{~}.
29186 @cindex target output in @sc{gdb/mi}
29187 @var{target-stream-output} is the output produced by the target program.
29188 All the target output is prefixed by @samp{@@}.
29191 @cindex log output in @sc{gdb/mi}
29192 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29193 instance messages that should be displayed as part of an error log. All
29194 the log output is prefixed by @samp{&}.
29197 @cindex list output in @sc{gdb/mi}
29198 New @sc{gdb/mi} commands should only output @var{lists} containing
29204 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29205 details about the various output records.
29207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29208 @node GDB/MI Compatibility with CLI
29209 @section @sc{gdb/mi} Compatibility with CLI
29211 @cindex compatibility, @sc{gdb/mi} and CLI
29212 @cindex @sc{gdb/mi}, compatibility with CLI
29214 For the developers convenience CLI commands can be entered directly,
29215 but there may be some unexpected behaviour. For example, commands
29216 that query the user will behave as if the user replied yes, breakpoint
29217 command lists are not executed and some CLI commands, such as
29218 @code{if}, @code{when} and @code{define}, prompt for further input with
29219 @samp{>}, which is not valid MI output.
29221 This feature may be removed at some stage in the future and it is
29222 recommended that front ends use the @code{-interpreter-exec} command
29223 (@pxref{-interpreter-exec}).
29225 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29226 @node GDB/MI Development and Front Ends
29227 @section @sc{gdb/mi} Development and Front Ends
29228 @cindex @sc{gdb/mi} development
29230 The application which takes the MI output and presents the state of the
29231 program being debugged to the user is called a @dfn{front end}.
29233 Although @sc{gdb/mi} is still incomplete, it is currently being used
29234 by a variety of front ends to @value{GDBN}. This makes it difficult
29235 to introduce new functionality without breaking existing usage. This
29236 section tries to minimize the problems by describing how the protocol
29239 Some changes in MI need not break a carefully designed front end, and
29240 for these the MI version will remain unchanged. The following is a
29241 list of changes that may occur within one level, so front ends should
29242 parse MI output in a way that can handle them:
29246 New MI commands may be added.
29249 New fields may be added to the output of any MI command.
29252 The range of values for fields with specified values, e.g.,
29253 @code{in_scope} (@pxref{-var-update}) may be extended.
29255 @c The format of field's content e.g type prefix, may change so parse it
29256 @c at your own risk. Yes, in general?
29258 @c The order of fields may change? Shouldn't really matter but it might
29259 @c resolve inconsistencies.
29262 If the changes are likely to break front ends, the MI version level
29263 will be increased by one. This will allow the front end to parse the
29264 output according to the MI version. Apart from mi0, new versions of
29265 @value{GDBN} will not support old versions of MI and it will be the
29266 responsibility of the front end to work with the new one.
29268 @c Starting with mi3, add a new command -mi-version that prints the MI
29271 The best way to avoid unexpected changes in MI that might break your front
29272 end is to make your project known to @value{GDBN} developers and
29273 follow development on @email{gdb@@sourceware.org} and
29274 @email{gdb-patches@@sourceware.org}.
29275 @cindex mailing lists
29277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29278 @node GDB/MI Output Records
29279 @section @sc{gdb/mi} Output Records
29282 * GDB/MI Result Records::
29283 * GDB/MI Stream Records::
29284 * GDB/MI Async Records::
29285 * GDB/MI Breakpoint Information::
29286 * GDB/MI Frame Information::
29287 * GDB/MI Thread Information::
29288 * GDB/MI Ada Exception Information::
29291 @node GDB/MI Result Records
29292 @subsection @sc{gdb/mi} Result Records
29294 @cindex result records in @sc{gdb/mi}
29295 @cindex @sc{gdb/mi}, result records
29296 In addition to a number of out-of-band notifications, the response to a
29297 @sc{gdb/mi} command includes one of the following result indications:
29301 @item "^done" [ "," @var{results} ]
29302 The synchronous operation was successful, @code{@var{results}} are the return
29307 This result record is equivalent to @samp{^done}. Historically, it
29308 was output instead of @samp{^done} if the command has resumed the
29309 target. This behaviour is maintained for backward compatibility, but
29310 all frontends should treat @samp{^done} and @samp{^running}
29311 identically and rely on the @samp{*running} output record to determine
29312 which threads are resumed.
29316 @value{GDBN} has connected to a remote target.
29318 @item "^error" "," @var{c-string}
29320 The operation failed. The @code{@var{c-string}} contains the corresponding
29325 @value{GDBN} has terminated.
29329 @node GDB/MI Stream Records
29330 @subsection @sc{gdb/mi} Stream Records
29332 @cindex @sc{gdb/mi}, stream records
29333 @cindex stream records in @sc{gdb/mi}
29334 @value{GDBN} internally maintains a number of output streams: the console, the
29335 target, and the log. The output intended for each of these streams is
29336 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29338 Each stream record begins with a unique @dfn{prefix character} which
29339 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29340 Syntax}). In addition to the prefix, each stream record contains a
29341 @code{@var{string-output}}. This is either raw text (with an implicit new
29342 line) or a quoted C string (which does not contain an implicit newline).
29345 @item "~" @var{string-output}
29346 The console output stream contains text that should be displayed in the
29347 CLI console window. It contains the textual responses to CLI commands.
29349 @item "@@" @var{string-output}
29350 The target output stream contains any textual output from the running
29351 target. This is only present when GDB's event loop is truly
29352 asynchronous, which is currently only the case for remote targets.
29354 @item "&" @var{string-output}
29355 The log stream contains debugging messages being produced by @value{GDBN}'s
29359 @node GDB/MI Async Records
29360 @subsection @sc{gdb/mi} Async Records
29362 @cindex async records in @sc{gdb/mi}
29363 @cindex @sc{gdb/mi}, async records
29364 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29365 additional changes that have occurred. Those changes can either be a
29366 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29367 target activity (e.g., target stopped).
29369 The following is the list of possible async records:
29373 @item *running,thread-id="@var{thread}"
29374 The target is now running. The @var{thread} field tells which
29375 specific thread is now running, and can be @samp{all} if all threads
29376 are running. The frontend should assume that no interaction with a
29377 running thread is possible after this notification is produced.
29378 The frontend should not assume that this notification is output
29379 only once for any command. @value{GDBN} may emit this notification
29380 several times, either for different threads, because it cannot resume
29381 all threads together, or even for a single thread, if the thread must
29382 be stepped though some code before letting it run freely.
29384 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29385 The target has stopped. The @var{reason} field can have one of the
29389 @item breakpoint-hit
29390 A breakpoint was reached.
29391 @item watchpoint-trigger
29392 A watchpoint was triggered.
29393 @item read-watchpoint-trigger
29394 A read watchpoint was triggered.
29395 @item access-watchpoint-trigger
29396 An access watchpoint was triggered.
29397 @item function-finished
29398 An -exec-finish or similar CLI command was accomplished.
29399 @item location-reached
29400 An -exec-until or similar CLI command was accomplished.
29401 @item watchpoint-scope
29402 A watchpoint has gone out of scope.
29403 @item end-stepping-range
29404 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29405 similar CLI command was accomplished.
29406 @item exited-signalled
29407 The inferior exited because of a signal.
29409 The inferior exited.
29410 @item exited-normally
29411 The inferior exited normally.
29412 @item signal-received
29413 A signal was received by the inferior.
29415 The inferior has stopped due to a library being loaded or unloaded.
29416 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29417 set or when a @code{catch load} or @code{catch unload} catchpoint is
29418 in use (@pxref{Set Catchpoints}).
29420 The inferior has forked. This is reported when @code{catch fork}
29421 (@pxref{Set Catchpoints}) has been used.
29423 The inferior has vforked. This is reported in when @code{catch vfork}
29424 (@pxref{Set Catchpoints}) has been used.
29425 @item syscall-entry
29426 The inferior entered a system call. This is reported when @code{catch
29427 syscall} (@pxref{Set Catchpoints}) has been used.
29428 @item syscall-entry
29429 The inferior returned from a system call. This is reported when
29430 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29432 The inferior called @code{exec}. This is reported when @code{catch exec}
29433 (@pxref{Set Catchpoints}) has been used.
29436 The @var{id} field identifies the thread that directly caused the stop
29437 -- for example by hitting a breakpoint. Depending on whether all-stop
29438 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29439 stop all threads, or only the thread that directly triggered the stop.
29440 If all threads are stopped, the @var{stopped} field will have the
29441 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29442 field will be a list of thread identifiers. Presently, this list will
29443 always include a single thread, but frontend should be prepared to see
29444 several threads in the list. The @var{core} field reports the
29445 processor core on which the stop event has happened. This field may be absent
29446 if such information is not available.
29448 @item =thread-group-added,id="@var{id}"
29449 @itemx =thread-group-removed,id="@var{id}"
29450 A thread group was either added or removed. The @var{id} field
29451 contains the @value{GDBN} identifier of the thread group. When a thread
29452 group is added, it generally might not be associated with a running
29453 process. When a thread group is removed, its id becomes invalid and
29454 cannot be used in any way.
29456 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29457 A thread group became associated with a running program,
29458 either because the program was just started or the thread group
29459 was attached to a program. The @var{id} field contains the
29460 @value{GDBN} identifier of the thread group. The @var{pid} field
29461 contains process identifier, specific to the operating system.
29463 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29464 A thread group is no longer associated with a running program,
29465 either because the program has exited, or because it was detached
29466 from. The @var{id} field contains the @value{GDBN} identifier of the
29467 thread group. @var{code} is the exit code of the inferior; it exists
29468 only when the inferior exited with some code.
29470 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29471 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29472 A thread either was created, or has exited. The @var{id} field
29473 contains the @value{GDBN} identifier of the thread. The @var{gid}
29474 field identifies the thread group this thread belongs to.
29476 @item =thread-selected,id="@var{id}"
29477 Informs that the selected thread was changed as result of the last
29478 command. This notification is not emitted as result of @code{-thread-select}
29479 command but is emitted whenever an MI command that is not documented
29480 to change the selected thread actually changes it. In particular,
29481 invoking, directly or indirectly (via user-defined command), the CLI
29482 @code{thread} command, will generate this notification.
29484 We suggest that in response to this notification, front ends
29485 highlight the selected thread and cause subsequent commands to apply to
29488 @item =library-loaded,...
29489 Reports that a new library file was loaded by the program. This
29490 notification has 4 fields---@var{id}, @var{target-name},
29491 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29492 opaque identifier of the library. For remote debugging case,
29493 @var{target-name} and @var{host-name} fields give the name of the
29494 library file on the target, and on the host respectively. For native
29495 debugging, both those fields have the same value. The
29496 @var{symbols-loaded} field is emitted only for backward compatibility
29497 and should not be relied on to convey any useful information. The
29498 @var{thread-group} field, if present, specifies the id of the thread
29499 group in whose context the library was loaded. If the field is
29500 absent, it means the library was loaded in the context of all present
29503 @item =library-unloaded,...
29504 Reports that a library was unloaded by the program. This notification
29505 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29506 the same meaning as for the @code{=library-loaded} notification.
29507 The @var{thread-group} field, if present, specifies the id of the
29508 thread group in whose context the library was unloaded. If the field is
29509 absent, it means the library was unloaded in the context of all present
29512 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29513 @itemx =traceframe-changed,end
29514 Reports that the trace frame was changed and its new number is
29515 @var{tfnum}. The number of the tracepoint associated with this trace
29516 frame is @var{tpnum}.
29518 @item =tsv-created,name=@var{name},initial=@var{initial}
29519 Reports that the new trace state variable @var{name} is created with
29520 initial value @var{initial}.
29522 @item =tsv-deleted,name=@var{name}
29523 @itemx =tsv-deleted
29524 Reports that the trace state variable @var{name} is deleted or all
29525 trace state variables are deleted.
29527 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29528 Reports that the trace state variable @var{name} is modified with
29529 the initial value @var{initial}. The current value @var{current} of
29530 trace state variable is optional and is reported if the current
29531 value of trace state variable is known.
29533 @item =breakpoint-created,bkpt=@{...@}
29534 @itemx =breakpoint-modified,bkpt=@{...@}
29535 @itemx =breakpoint-deleted,id=@var{number}
29536 Reports that a breakpoint was created, modified, or deleted,
29537 respectively. Only user-visible breakpoints are reported to the MI
29540 The @var{bkpt} argument is of the same form as returned by the various
29541 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29542 @var{number} is the ordinal number of the breakpoint.
29544 Note that if a breakpoint is emitted in the result record of a
29545 command, then it will not also be emitted in an async record.
29547 @item =record-started,thread-group="@var{id}"
29548 @itemx =record-stopped,thread-group="@var{id}"
29549 Execution log recording was either started or stopped on an
29550 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29551 group corresponding to the affected inferior.
29553 @item =cmd-param-changed,param=@var{param},value=@var{value}
29554 Reports that a parameter of the command @code{set @var{param}} is
29555 changed to @var{value}. In the multi-word @code{set} command,
29556 the @var{param} is the whole parameter list to @code{set} command.
29557 For example, In command @code{set check type on}, @var{param}
29558 is @code{check type} and @var{value} is @code{on}.
29560 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29561 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29562 written in an inferior. The @var{id} is the identifier of the
29563 thread group corresponding to the affected inferior. The optional
29564 @code{type="code"} part is reported if the memory written to holds
29568 @node GDB/MI Breakpoint Information
29569 @subsection @sc{gdb/mi} Breakpoint Information
29571 When @value{GDBN} reports information about a breakpoint, a
29572 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29577 The breakpoint number. For a breakpoint that represents one location
29578 of a multi-location breakpoint, this will be a dotted pair, like
29582 The type of the breakpoint. For ordinary breakpoints this will be
29583 @samp{breakpoint}, but many values are possible.
29586 If the type of the breakpoint is @samp{catchpoint}, then this
29587 indicates the exact type of catchpoint.
29590 This is the breakpoint disposition---either @samp{del}, meaning that
29591 the breakpoint will be deleted at the next stop, or @samp{keep},
29592 meaning that the breakpoint will not be deleted.
29595 This indicates whether the breakpoint is enabled, in which case the
29596 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29597 Note that this is not the same as the field @code{enable}.
29600 The address of the breakpoint. This may be a hexidecimal number,
29601 giving the address; or the string @samp{<PENDING>}, for a pending
29602 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29603 multiple locations. This field will not be present if no address can
29604 be determined. For example, a watchpoint does not have an address.
29607 If known, the function in which the breakpoint appears.
29608 If not known, this field is not present.
29611 The name of the source file which contains this function, if known.
29612 If not known, this field is not present.
29615 The full file name of the source file which contains this function, if
29616 known. If not known, this field is not present.
29619 The line number at which this breakpoint appears, if known.
29620 If not known, this field is not present.
29623 If the source file is not known, this field may be provided. If
29624 provided, this holds the address of the breakpoint, possibly followed
29628 If this breakpoint is pending, this field is present and holds the
29629 text used to set the breakpoint, as entered by the user.
29632 Where this breakpoint's condition is evaluated, either @samp{host} or
29636 If this is a thread-specific breakpoint, then this identifies the
29637 thread in which the breakpoint can trigger.
29640 If this breakpoint is restricted to a particular Ada task, then this
29641 field will hold the task identifier.
29644 If the breakpoint is conditional, this is the condition expression.
29647 The ignore count of the breakpoint.
29650 The enable count of the breakpoint.
29652 @item traceframe-usage
29655 @item static-tracepoint-marker-string-id
29656 For a static tracepoint, the name of the static tracepoint marker.
29659 For a masked watchpoint, this is the mask.
29662 A tracepoint's pass count.
29664 @item original-location
29665 The location of the breakpoint as originally specified by the user.
29666 This field is optional.
29669 The number of times the breakpoint has been hit.
29672 This field is only given for tracepoints. This is either @samp{y},
29673 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29677 Some extra data, the exact contents of which are type-dependent.
29681 For example, here is what the output of @code{-break-insert}
29682 (@pxref{GDB/MI Breakpoint Commands}) might be:
29685 -> -break-insert main
29686 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29687 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29688 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29693 @node GDB/MI Frame Information
29694 @subsection @sc{gdb/mi} Frame Information
29696 Response from many MI commands includes an information about stack
29697 frame. This information is a tuple that may have the following
29702 The level of the stack frame. The innermost frame has the level of
29703 zero. This field is always present.
29706 The name of the function corresponding to the frame. This field may
29707 be absent if @value{GDBN} is unable to determine the function name.
29710 The code address for the frame. This field is always present.
29713 The name of the source files that correspond to the frame's code
29714 address. This field may be absent.
29717 The source line corresponding to the frames' code address. This field
29721 The name of the binary file (either executable or shared library) the
29722 corresponds to the frame's code address. This field may be absent.
29726 @node GDB/MI Thread Information
29727 @subsection @sc{gdb/mi} Thread Information
29729 Whenever @value{GDBN} has to report an information about a thread, it
29730 uses a tuple with the following fields:
29734 The numeric id assigned to the thread by @value{GDBN}. This field is
29738 Target-specific string identifying the thread. This field is always present.
29741 Additional information about the thread provided by the target.
29742 It is supposed to be human-readable and not interpreted by the
29743 frontend. This field is optional.
29746 Either @samp{stopped} or @samp{running}, depending on whether the
29747 thread is presently running. This field is always present.
29750 The value of this field is an integer number of the processor core the
29751 thread was last seen on. This field is optional.
29754 @node GDB/MI Ada Exception Information
29755 @subsection @sc{gdb/mi} Ada Exception Information
29757 Whenever a @code{*stopped} record is emitted because the program
29758 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29759 @value{GDBN} provides the name of the exception that was raised via
29760 the @code{exception-name} field.
29762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29763 @node GDB/MI Simple Examples
29764 @section Simple Examples of @sc{gdb/mi} Interaction
29765 @cindex @sc{gdb/mi}, simple examples
29767 This subsection presents several simple examples of interaction using
29768 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29769 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29770 the output received from @sc{gdb/mi}.
29772 Note the line breaks shown in the examples are here only for
29773 readability, they don't appear in the real output.
29775 @subheading Setting a Breakpoint
29777 Setting a breakpoint generates synchronous output which contains detailed
29778 information of the breakpoint.
29781 -> -break-insert main
29782 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29783 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29784 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29789 @subheading Program Execution
29791 Program execution generates asynchronous records and MI gives the
29792 reason that execution stopped.
29798 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29799 frame=@{addr="0x08048564",func="main",
29800 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29801 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29806 <- *stopped,reason="exited-normally"
29810 @subheading Quitting @value{GDBN}
29812 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29820 Please note that @samp{^exit} is printed immediately, but it might
29821 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29822 performs necessary cleanups, including killing programs being debugged
29823 or disconnecting from debug hardware, so the frontend should wait till
29824 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29825 fails to exit in reasonable time.
29827 @subheading A Bad Command
29829 Here's what happens if you pass a non-existent command:
29833 <- ^error,msg="Undefined MI command: rubbish"
29838 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29839 @node GDB/MI Command Description Format
29840 @section @sc{gdb/mi} Command Description Format
29842 The remaining sections describe blocks of commands. Each block of
29843 commands is laid out in a fashion similar to this section.
29845 @subheading Motivation
29847 The motivation for this collection of commands.
29849 @subheading Introduction
29851 A brief introduction to this collection of commands as a whole.
29853 @subheading Commands
29855 For each command in the block, the following is described:
29857 @subsubheading Synopsis
29860 -command @var{args}@dots{}
29863 @subsubheading Result
29865 @subsubheading @value{GDBN} Command
29867 The corresponding @value{GDBN} CLI command(s), if any.
29869 @subsubheading Example
29871 Example(s) formatted for readability. Some of the described commands have
29872 not been implemented yet and these are labeled N.A.@: (not available).
29875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29876 @node GDB/MI Breakpoint Commands
29877 @section @sc{gdb/mi} Breakpoint Commands
29879 @cindex breakpoint commands for @sc{gdb/mi}
29880 @cindex @sc{gdb/mi}, breakpoint commands
29881 This section documents @sc{gdb/mi} commands for manipulating
29884 @subheading The @code{-break-after} Command
29885 @findex -break-after
29887 @subsubheading Synopsis
29890 -break-after @var{number} @var{count}
29893 The breakpoint number @var{number} is not in effect until it has been
29894 hit @var{count} times. To see how this is reflected in the output of
29895 the @samp{-break-list} command, see the description of the
29896 @samp{-break-list} command below.
29898 @subsubheading @value{GDBN} Command
29900 The corresponding @value{GDBN} command is @samp{ignore}.
29902 @subsubheading Example
29907 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29908 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29909 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29917 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29918 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29919 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29920 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29921 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29922 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29923 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29924 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29925 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29926 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29931 @subheading The @code{-break-catch} Command
29932 @findex -break-catch
29935 @subheading The @code{-break-commands} Command
29936 @findex -break-commands
29938 @subsubheading Synopsis
29941 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29944 Specifies the CLI commands that should be executed when breakpoint
29945 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29946 are the commands. If no command is specified, any previously-set
29947 commands are cleared. @xref{Break Commands}. Typical use of this
29948 functionality is tracing a program, that is, printing of values of
29949 some variables whenever breakpoint is hit and then continuing.
29951 @subsubheading @value{GDBN} Command
29953 The corresponding @value{GDBN} command is @samp{commands}.
29955 @subsubheading Example
29960 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29961 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29962 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29965 -break-commands 1 "print v" "continue"
29970 @subheading The @code{-break-condition} Command
29971 @findex -break-condition
29973 @subsubheading Synopsis
29976 -break-condition @var{number} @var{expr}
29979 Breakpoint @var{number} will stop the program only if the condition in
29980 @var{expr} is true. The condition becomes part of the
29981 @samp{-break-list} output (see the description of the @samp{-break-list}
29984 @subsubheading @value{GDBN} Command
29986 The corresponding @value{GDBN} command is @samp{condition}.
29988 @subsubheading Example
29992 -break-condition 1 1
29996 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29997 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29998 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29999 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30000 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30001 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30002 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30003 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30004 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30005 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30009 @subheading The @code{-break-delete} Command
30010 @findex -break-delete
30012 @subsubheading Synopsis
30015 -break-delete ( @var{breakpoint} )+
30018 Delete the breakpoint(s) whose number(s) are specified in the argument
30019 list. This is obviously reflected in the breakpoint list.
30021 @subsubheading @value{GDBN} Command
30023 The corresponding @value{GDBN} command is @samp{delete}.
30025 @subsubheading Example
30033 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30034 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30035 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30036 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30037 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30038 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30039 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30044 @subheading The @code{-break-disable} Command
30045 @findex -break-disable
30047 @subsubheading Synopsis
30050 -break-disable ( @var{breakpoint} )+
30053 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30054 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30056 @subsubheading @value{GDBN} Command
30058 The corresponding @value{GDBN} command is @samp{disable}.
30060 @subsubheading Example
30068 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30069 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30070 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30071 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30072 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30073 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30074 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30075 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30076 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30077 line="5",thread-groups=["i1"],times="0"@}]@}
30081 @subheading The @code{-break-enable} Command
30082 @findex -break-enable
30084 @subsubheading Synopsis
30087 -break-enable ( @var{breakpoint} )+
30090 Enable (previously disabled) @var{breakpoint}(s).
30092 @subsubheading @value{GDBN} Command
30094 The corresponding @value{GDBN} command is @samp{enable}.
30096 @subsubheading Example
30104 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30105 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30106 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30107 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30108 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30109 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30110 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30111 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30112 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30113 line="5",thread-groups=["i1"],times="0"@}]@}
30117 @subheading The @code{-break-info} Command
30118 @findex -break-info
30120 @subsubheading Synopsis
30123 -break-info @var{breakpoint}
30127 Get information about a single breakpoint.
30129 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30130 Information}, for details on the format of each breakpoint in the
30133 @subsubheading @value{GDBN} Command
30135 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30137 @subsubheading Example
30140 @subheading The @code{-break-insert} Command
30141 @findex -break-insert
30143 @subsubheading Synopsis
30146 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30147 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30148 [ -p @var{thread-id} ] [ @var{location} ]
30152 If specified, @var{location}, can be one of:
30159 @item filename:linenum
30160 @item filename:function
30164 The possible optional parameters of this command are:
30168 Insert a temporary breakpoint.
30170 Insert a hardware breakpoint.
30172 If @var{location} cannot be parsed (for example if it
30173 refers to unknown files or functions), create a pending
30174 breakpoint. Without this flag, @value{GDBN} will report
30175 an error, and won't create a breakpoint, if @var{location}
30178 Create a disabled breakpoint.
30180 Create a tracepoint. @xref{Tracepoints}. When this parameter
30181 is used together with @samp{-h}, a fast tracepoint is created.
30182 @item -c @var{condition}
30183 Make the breakpoint conditional on @var{condition}.
30184 @item -i @var{ignore-count}
30185 Initialize the @var{ignore-count}.
30186 @item -p @var{thread-id}
30187 Restrict the breakpoint to the specified @var{thread-id}.
30190 @subsubheading Result
30192 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30193 resulting breakpoint.
30195 Note: this format is open to change.
30196 @c An out-of-band breakpoint instead of part of the result?
30198 @subsubheading @value{GDBN} Command
30200 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30201 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30203 @subsubheading Example
30208 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30209 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30212 -break-insert -t foo
30213 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30214 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30218 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30219 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30220 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30221 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30222 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30223 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30224 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30225 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30226 addr="0x0001072c", func="main",file="recursive2.c",
30227 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30229 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30230 addr="0x00010774",func="foo",file="recursive2.c",
30231 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30234 @c -break-insert -r foo.*
30235 @c ~int foo(int, int);
30236 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30237 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30242 @subheading The @code{-dprintf-insert} Command
30243 @findex -dprintf-insert
30245 @subsubheading Synopsis
30248 -dprintf-insert [ -t ] [ -f ] [ -d ]
30249 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30250 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30255 If specified, @var{location}, can be one of:
30258 @item @var{function}
30261 @c @item @var{linenum}
30262 @item @var{filename}:@var{linenum}
30263 @item @var{filename}:function
30264 @item *@var{address}
30267 The possible optional parameters of this command are:
30271 Insert a temporary breakpoint.
30273 If @var{location} cannot be parsed (for example, if it
30274 refers to unknown files or functions), create a pending
30275 breakpoint. Without this flag, @value{GDBN} will report
30276 an error, and won't create a breakpoint, if @var{location}
30279 Create a disabled breakpoint.
30280 @item -c @var{condition}
30281 Make the breakpoint conditional on @var{condition}.
30282 @item -i @var{ignore-count}
30283 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30284 to @var{ignore-count}.
30285 @item -p @var{thread-id}
30286 Restrict the breakpoint to the specified @var{thread-id}.
30289 @subsubheading Result
30291 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30292 resulting breakpoint.
30294 @c An out-of-band breakpoint instead of part of the result?
30296 @subsubheading @value{GDBN} Command
30298 The corresponding @value{GDBN} command is @samp{dprintf}.
30300 @subsubheading Example
30304 4-dprintf-insert foo "At foo entry\n"
30305 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30306 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30307 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30308 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30309 original-location="foo"@}
30311 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30312 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30313 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30314 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30315 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30316 original-location="mi-dprintf.c:26"@}
30320 @subheading The @code{-break-list} Command
30321 @findex -break-list
30323 @subsubheading Synopsis
30329 Displays the list of inserted breakpoints, showing the following fields:
30333 number of the breakpoint
30335 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30337 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30340 is the breakpoint enabled or no: @samp{y} or @samp{n}
30342 memory location at which the breakpoint is set
30344 logical location of the breakpoint, expressed by function name, file
30346 @item Thread-groups
30347 list of thread groups to which this breakpoint applies
30349 number of times the breakpoint has been hit
30352 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30353 @code{body} field is an empty list.
30355 @subsubheading @value{GDBN} Command
30357 The corresponding @value{GDBN} command is @samp{info break}.
30359 @subsubheading Example
30364 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30365 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30366 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30367 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30368 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30369 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30370 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30371 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30372 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30374 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30375 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30376 line="13",thread-groups=["i1"],times="0"@}]@}
30380 Here's an example of the result when there are no breakpoints:
30385 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30386 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30387 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30388 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30389 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30390 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30391 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30396 @subheading The @code{-break-passcount} Command
30397 @findex -break-passcount
30399 @subsubheading Synopsis
30402 -break-passcount @var{tracepoint-number} @var{passcount}
30405 Set the passcount for tracepoint @var{tracepoint-number} to
30406 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30407 is not a tracepoint, error is emitted. This corresponds to CLI
30408 command @samp{passcount}.
30410 @subheading The @code{-break-watch} Command
30411 @findex -break-watch
30413 @subsubheading Synopsis
30416 -break-watch [ -a | -r ]
30419 Create a watchpoint. With the @samp{-a} option it will create an
30420 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30421 read from or on a write to the memory location. With the @samp{-r}
30422 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30423 trigger only when the memory location is accessed for reading. Without
30424 either of the options, the watchpoint created is a regular watchpoint,
30425 i.e., it will trigger when the memory location is accessed for writing.
30426 @xref{Set Watchpoints, , Setting Watchpoints}.
30428 Note that @samp{-break-list} will report a single list of watchpoints and
30429 breakpoints inserted.
30431 @subsubheading @value{GDBN} Command
30433 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30436 @subsubheading Example
30438 Setting a watchpoint on a variable in the @code{main} function:
30443 ^done,wpt=@{number="2",exp="x"@}
30448 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30449 value=@{old="-268439212",new="55"@},
30450 frame=@{func="main",args=[],file="recursive2.c",
30451 fullname="/home/foo/bar/recursive2.c",line="5"@}
30455 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30456 the program execution twice: first for the variable changing value, then
30457 for the watchpoint going out of scope.
30462 ^done,wpt=@{number="5",exp="C"@}
30467 *stopped,reason="watchpoint-trigger",
30468 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30469 frame=@{func="callee4",args=[],
30470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30471 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30476 *stopped,reason="watchpoint-scope",wpnum="5",
30477 frame=@{func="callee3",args=[@{name="strarg",
30478 value="0x11940 \"A string argument.\""@}],
30479 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30480 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30484 Listing breakpoints and watchpoints, at different points in the program
30485 execution. Note that once the watchpoint goes out of scope, it is
30491 ^done,wpt=@{number="2",exp="C"@}
30494 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30495 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30496 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30497 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30498 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30499 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30500 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30501 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30502 addr="0x00010734",func="callee4",
30503 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30504 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30506 bkpt=@{number="2",type="watchpoint",disp="keep",
30507 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30512 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30513 value=@{old="-276895068",new="3"@},
30514 frame=@{func="callee4",args=[],
30515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30516 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30519 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30520 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30521 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30522 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30523 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30524 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30525 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30526 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30527 addr="0x00010734",func="callee4",
30528 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30529 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30531 bkpt=@{number="2",type="watchpoint",disp="keep",
30532 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30536 ^done,reason="watchpoint-scope",wpnum="2",
30537 frame=@{func="callee3",args=[@{name="strarg",
30538 value="0x11940 \"A string argument.\""@}],
30539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30540 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30543 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30544 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30545 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30546 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30547 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30548 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30549 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30550 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30551 addr="0x00010734",func="callee4",
30552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30553 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30554 thread-groups=["i1"],times="1"@}]@}
30559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30560 @node GDB/MI Catchpoint Commands
30561 @section @sc{gdb/mi} Catchpoint Commands
30563 This section documents @sc{gdb/mi} commands for manipulating
30567 * Shared Library GDB/MI Catchpoint Commands::
30568 * Ada Exception GDB/MI Catchpoint Commands::
30571 @node Shared Library GDB/MI Catchpoint Commands
30572 @subsection Shared Library @sc{gdb/mi} Catchpoints
30574 @subheading The @code{-catch-load} Command
30575 @findex -catch-load
30577 @subsubheading Synopsis
30580 -catch-load [ -t ] [ -d ] @var{regexp}
30583 Add a catchpoint for library load events. If the @samp{-t} option is used,
30584 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30585 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30586 in a disabled state. The @samp{regexp} argument is a regular
30587 expression used to match the name of the loaded library.
30590 @subsubheading @value{GDBN} Command
30592 The corresponding @value{GDBN} command is @samp{catch load}.
30594 @subsubheading Example
30597 -catch-load -t foo.so
30598 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30599 what="load of library matching foo.so",catch-type="load",times="0"@}
30604 @subheading The @code{-catch-unload} Command
30605 @findex -catch-unload
30607 @subsubheading Synopsis
30610 -catch-unload [ -t ] [ -d ] @var{regexp}
30613 Add a catchpoint for library unload events. If the @samp{-t} option is
30614 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30615 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30616 created in a disabled state. The @samp{regexp} argument is a regular
30617 expression used to match the name of the unloaded library.
30619 @subsubheading @value{GDBN} Command
30621 The corresponding @value{GDBN} command is @samp{catch unload}.
30623 @subsubheading Example
30626 -catch-unload -d bar.so
30627 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30628 what="load of library matching bar.so",catch-type="unload",times="0"@}
30632 @node Ada Exception GDB/MI Catchpoint Commands
30633 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30635 The following @sc{gdb/mi} commands can be used to create catchpoints
30636 that stop the execution when Ada exceptions are being raised.
30638 @subheading The @code{-catch-assert} Command
30639 @findex -catch-assert
30641 @subsubheading Synopsis
30644 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30647 Add a catchpoint for failed Ada assertions.
30649 The possible optional parameters for this command are:
30652 @item -c @var{condition}
30653 Make the catchpoint conditional on @var{condition}.
30655 Create a disabled catchpoint.
30657 Create a temporary catchpoint.
30660 @subsubheading @value{GDBN} Command
30662 The corresponding @value{GDBN} command is @samp{catch assert}.
30664 @subsubheading Example
30668 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30669 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30670 thread-groups=["i1"],times="0",
30671 original-location="__gnat_debug_raise_assert_failure"@}
30675 @subheading The @code{-catch-exception} Command
30676 @findex -catch-exception
30678 @subsubheading Synopsis
30681 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30685 Add a catchpoint stopping when Ada exceptions are raised.
30686 By default, the command stops the program when any Ada exception
30687 gets raised. But it is also possible, by using some of the
30688 optional parameters described below, to create more selective
30691 The possible optional parameters for this command are:
30694 @item -c @var{condition}
30695 Make the catchpoint conditional on @var{condition}.
30697 Create a disabled catchpoint.
30698 @item -e @var{exception-name}
30699 Only stop when @var{exception-name} is raised. This option cannot
30700 be used combined with @samp{-u}.
30702 Create a temporary catchpoint.
30704 Stop only when an unhandled exception gets raised. This option
30705 cannot be used combined with @samp{-e}.
30708 @subsubheading @value{GDBN} Command
30710 The corresponding @value{GDBN} commands are @samp{catch exception}
30711 and @samp{catch exception unhandled}.
30713 @subsubheading Example
30716 -catch-exception -e Program_Error
30717 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30718 enabled="y",addr="0x0000000000404874",
30719 what="`Program_Error' Ada exception", thread-groups=["i1"],
30720 times="0",original-location="__gnat_debug_raise_exception"@}
30724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30725 @node GDB/MI Program Context
30726 @section @sc{gdb/mi} Program Context
30728 @subheading The @code{-exec-arguments} Command
30729 @findex -exec-arguments
30732 @subsubheading Synopsis
30735 -exec-arguments @var{args}
30738 Set the inferior program arguments, to be used in the next
30741 @subsubheading @value{GDBN} Command
30743 The corresponding @value{GDBN} command is @samp{set args}.
30745 @subsubheading Example
30749 -exec-arguments -v word
30756 @subheading The @code{-exec-show-arguments} Command
30757 @findex -exec-show-arguments
30759 @subsubheading Synopsis
30762 -exec-show-arguments
30765 Print the arguments of the program.
30767 @subsubheading @value{GDBN} Command
30769 The corresponding @value{GDBN} command is @samp{show args}.
30771 @subsubheading Example
30776 @subheading The @code{-environment-cd} Command
30777 @findex -environment-cd
30779 @subsubheading Synopsis
30782 -environment-cd @var{pathdir}
30785 Set @value{GDBN}'s working directory.
30787 @subsubheading @value{GDBN} Command
30789 The corresponding @value{GDBN} command is @samp{cd}.
30791 @subsubheading Example
30795 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30801 @subheading The @code{-environment-directory} Command
30802 @findex -environment-directory
30804 @subsubheading Synopsis
30807 -environment-directory [ -r ] [ @var{pathdir} ]+
30810 Add directories @var{pathdir} to beginning of search path for source files.
30811 If the @samp{-r} option is used, the search path is reset to the default
30812 search path. If directories @var{pathdir} are supplied in addition to the
30813 @samp{-r} option, the search path is first reset and then addition
30815 Multiple directories may be specified, separated by blanks. Specifying
30816 multiple directories in a single command
30817 results in the directories added to the beginning of the
30818 search path in the same order they were presented in the command.
30819 If blanks are needed as
30820 part of a directory name, double-quotes should be used around
30821 the name. In the command output, the path will show up separated
30822 by the system directory-separator character. The directory-separator
30823 character must not be used
30824 in any directory name.
30825 If no directories are specified, the current search path is displayed.
30827 @subsubheading @value{GDBN} Command
30829 The corresponding @value{GDBN} command is @samp{dir}.
30831 @subsubheading Example
30835 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30836 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30838 -environment-directory ""
30839 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30841 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30842 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30844 -environment-directory -r
30845 ^done,source-path="$cdir:$cwd"
30850 @subheading The @code{-environment-path} Command
30851 @findex -environment-path
30853 @subsubheading Synopsis
30856 -environment-path [ -r ] [ @var{pathdir} ]+
30859 Add directories @var{pathdir} to beginning of search path for object files.
30860 If the @samp{-r} option is used, the search path is reset to the original
30861 search path that existed at gdb start-up. If directories @var{pathdir} are
30862 supplied in addition to the
30863 @samp{-r} option, the search path is first reset and then addition
30865 Multiple directories may be specified, separated by blanks. Specifying
30866 multiple directories in a single command
30867 results in the directories added to the beginning of the
30868 search path in the same order they were presented in the command.
30869 If blanks are needed as
30870 part of a directory name, double-quotes should be used around
30871 the name. In the command output, the path will show up separated
30872 by the system directory-separator character. The directory-separator
30873 character must not be used
30874 in any directory name.
30875 If no directories are specified, the current path is displayed.
30878 @subsubheading @value{GDBN} Command
30880 The corresponding @value{GDBN} command is @samp{path}.
30882 @subsubheading Example
30887 ^done,path="/usr/bin"
30889 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30890 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30892 -environment-path -r /usr/local/bin
30893 ^done,path="/usr/local/bin:/usr/bin"
30898 @subheading The @code{-environment-pwd} Command
30899 @findex -environment-pwd
30901 @subsubheading Synopsis
30907 Show the current working directory.
30909 @subsubheading @value{GDBN} Command
30911 The corresponding @value{GDBN} command is @samp{pwd}.
30913 @subsubheading Example
30918 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30923 @node GDB/MI Thread Commands
30924 @section @sc{gdb/mi} Thread Commands
30927 @subheading The @code{-thread-info} Command
30928 @findex -thread-info
30930 @subsubheading Synopsis
30933 -thread-info [ @var{thread-id} ]
30936 Reports information about either a specific thread, if
30937 the @var{thread-id} parameter is present, or about all
30938 threads. When printing information about all threads,
30939 also reports the current thread.
30941 @subsubheading @value{GDBN} Command
30943 The @samp{info thread} command prints the same information
30946 @subsubheading Result
30948 The result is a list of threads. The following attributes are
30949 defined for a given thread:
30953 This field exists only for the current thread. It has the value @samp{*}.
30956 The identifier that @value{GDBN} uses to refer to the thread.
30959 The identifier that the target uses to refer to the thread.
30962 Extra information about the thread, in a target-specific format. This
30966 The name of the thread. If the user specified a name using the
30967 @code{thread name} command, then this name is given. Otherwise, if
30968 @value{GDBN} can extract the thread name from the target, then that
30969 name is given. If @value{GDBN} cannot find the thread name, then this
30973 The stack frame currently executing in the thread.
30976 The thread's state. The @samp{state} field may have the following
30981 The thread is stopped. Frame information is available for stopped
30985 The thread is running. There's no frame information for running
30991 If @value{GDBN} can find the CPU core on which this thread is running,
30992 then this field is the core identifier. This field is optional.
30996 @subsubheading Example
31001 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31002 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31003 args=[]@},state="running"@},
31004 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31005 frame=@{level="0",addr="0x0804891f",func="foo",
31006 args=[@{name="i",value="10"@}],
31007 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31008 state="running"@}],
31009 current-thread-id="1"
31013 @subheading The @code{-thread-list-ids} Command
31014 @findex -thread-list-ids
31016 @subsubheading Synopsis
31022 Produces a list of the currently known @value{GDBN} thread ids. At the
31023 end of the list it also prints the total number of such threads.
31025 This command is retained for historical reasons, the
31026 @code{-thread-info} command should be used instead.
31028 @subsubheading @value{GDBN} Command
31030 Part of @samp{info threads} supplies the same information.
31032 @subsubheading Example
31037 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31038 current-thread-id="1",number-of-threads="3"
31043 @subheading The @code{-thread-select} Command
31044 @findex -thread-select
31046 @subsubheading Synopsis
31049 -thread-select @var{threadnum}
31052 Make @var{threadnum} the current thread. It prints the number of the new
31053 current thread, and the topmost frame for that thread.
31055 This command is deprecated in favor of explicitly using the
31056 @samp{--thread} option to each command.
31058 @subsubheading @value{GDBN} Command
31060 The corresponding @value{GDBN} command is @samp{thread}.
31062 @subsubheading Example
31069 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31070 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31074 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31075 number-of-threads="3"
31078 ^done,new-thread-id="3",
31079 frame=@{level="0",func="vprintf",
31080 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31081 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31085 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31086 @node GDB/MI Ada Tasking Commands
31087 @section @sc{gdb/mi} Ada Tasking Commands
31089 @subheading The @code{-ada-task-info} Command
31090 @findex -ada-task-info
31092 @subsubheading Synopsis
31095 -ada-task-info [ @var{task-id} ]
31098 Reports information about either a specific Ada task, if the
31099 @var{task-id} parameter is present, or about all Ada tasks.
31101 @subsubheading @value{GDBN} Command
31103 The @samp{info tasks} command prints the same information
31104 about all Ada tasks (@pxref{Ada Tasks}).
31106 @subsubheading Result
31108 The result is a table of Ada tasks. The following columns are
31109 defined for each Ada task:
31113 This field exists only for the current thread. It has the value @samp{*}.
31116 The identifier that @value{GDBN} uses to refer to the Ada task.
31119 The identifier that the target uses to refer to the Ada task.
31122 The identifier of the thread corresponding to the Ada task.
31124 This field should always exist, as Ada tasks are always implemented
31125 on top of a thread. But if @value{GDBN} cannot find this corresponding
31126 thread for any reason, the field is omitted.
31129 This field exists only when the task was created by another task.
31130 In this case, it provides the ID of the parent task.
31133 The base priority of the task.
31136 The current state of the task. For a detailed description of the
31137 possible states, see @ref{Ada Tasks}.
31140 The name of the task.
31144 @subsubheading Example
31148 ^done,tasks=@{nr_rows="3",nr_cols="8",
31149 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31150 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31151 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31152 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31153 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31154 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31155 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31156 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31157 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31158 state="Child Termination Wait",name="main_task"@}]@}
31162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31163 @node GDB/MI Program Execution
31164 @section @sc{gdb/mi} Program Execution
31166 These are the asynchronous commands which generate the out-of-band
31167 record @samp{*stopped}. Currently @value{GDBN} only really executes
31168 asynchronously with remote targets and this interaction is mimicked in
31171 @subheading The @code{-exec-continue} Command
31172 @findex -exec-continue
31174 @subsubheading Synopsis
31177 -exec-continue [--reverse] [--all|--thread-group N]
31180 Resumes the execution of the inferior program, which will continue
31181 to execute until it reaches a debugger stop event. If the
31182 @samp{--reverse} option is specified, execution resumes in reverse until
31183 it reaches a stop event. Stop events may include
31186 breakpoints or watchpoints
31188 signals or exceptions
31190 the end of the process (or its beginning under @samp{--reverse})
31192 the end or beginning of a replay log if one is being used.
31194 In all-stop mode (@pxref{All-Stop
31195 Mode}), may resume only one thread, or all threads, depending on the
31196 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31197 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31198 ignored in all-stop mode. If the @samp{--thread-group} options is
31199 specified, then all threads in that thread group are resumed.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} corresponding is @samp{continue}.
31205 @subsubheading Example
31212 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31213 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31219 @subheading The @code{-exec-finish} Command
31220 @findex -exec-finish
31222 @subsubheading Synopsis
31225 -exec-finish [--reverse]
31228 Resumes the execution of the inferior program until the current
31229 function is exited. Displays the results returned by the function.
31230 If the @samp{--reverse} option is specified, resumes the reverse
31231 execution of the inferior program until the point where current
31232 function was called.
31234 @subsubheading @value{GDBN} Command
31236 The corresponding @value{GDBN} command is @samp{finish}.
31238 @subsubheading Example
31240 Function returning @code{void}.
31247 *stopped,reason="function-finished",frame=@{func="main",args=[],
31248 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31252 Function returning other than @code{void}. The name of the internal
31253 @value{GDBN} variable storing the result is printed, together with the
31260 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31261 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31262 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31263 gdb-result-var="$1",return-value="0"
31268 @subheading The @code{-exec-interrupt} Command
31269 @findex -exec-interrupt
31271 @subsubheading Synopsis
31274 -exec-interrupt [--all|--thread-group N]
31277 Interrupts the background execution of the target. Note how the token
31278 associated with the stop message is the one for the execution command
31279 that has been interrupted. The token for the interrupt itself only
31280 appears in the @samp{^done} output. If the user is trying to
31281 interrupt a non-running program, an error message will be printed.
31283 Note that when asynchronous execution is enabled, this command is
31284 asynchronous just like other execution commands. That is, first the
31285 @samp{^done} response will be printed, and the target stop will be
31286 reported after that using the @samp{*stopped} notification.
31288 In non-stop mode, only the context thread is interrupted by default.
31289 All threads (in all inferiors) will be interrupted if the
31290 @samp{--all} option is specified. If the @samp{--thread-group}
31291 option is specified, all threads in that group will be interrupted.
31293 @subsubheading @value{GDBN} Command
31295 The corresponding @value{GDBN} command is @samp{interrupt}.
31297 @subsubheading Example
31308 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31309 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31310 fullname="/home/foo/bar/try.c",line="13"@}
31315 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31319 @subheading The @code{-exec-jump} Command
31322 @subsubheading Synopsis
31325 -exec-jump @var{location}
31328 Resumes execution of the inferior program at the location specified by
31329 parameter. @xref{Specify Location}, for a description of the
31330 different forms of @var{location}.
31332 @subsubheading @value{GDBN} Command
31334 The corresponding @value{GDBN} command is @samp{jump}.
31336 @subsubheading Example
31339 -exec-jump foo.c:10
31340 *running,thread-id="all"
31345 @subheading The @code{-exec-next} Command
31348 @subsubheading Synopsis
31351 -exec-next [--reverse]
31354 Resumes execution of the inferior program, stopping when the beginning
31355 of the next source line is reached.
31357 If the @samp{--reverse} option is specified, resumes reverse execution
31358 of the inferior program, stopping at the beginning of the previous
31359 source line. If you issue this command on the first line of a
31360 function, it will take you back to the caller of that function, to the
31361 source line where the function was called.
31364 @subsubheading @value{GDBN} Command
31366 The corresponding @value{GDBN} command is @samp{next}.
31368 @subsubheading Example
31374 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31379 @subheading The @code{-exec-next-instruction} Command
31380 @findex -exec-next-instruction
31382 @subsubheading Synopsis
31385 -exec-next-instruction [--reverse]
31388 Executes one machine instruction. If the instruction is a function
31389 call, continues until the function returns. If the program stops at an
31390 instruction in the middle of a source line, the address will be
31393 If the @samp{--reverse} option is specified, resumes reverse execution
31394 of the inferior program, stopping at the previous instruction. If the
31395 previously executed instruction was a return from another function,
31396 it will continue to execute in reverse until the call to that function
31397 (from the current stack frame) is reached.
31399 @subsubheading @value{GDBN} Command
31401 The corresponding @value{GDBN} command is @samp{nexti}.
31403 @subsubheading Example
31407 -exec-next-instruction
31411 *stopped,reason="end-stepping-range",
31412 addr="0x000100d4",line="5",file="hello.c"
31417 @subheading The @code{-exec-return} Command
31418 @findex -exec-return
31420 @subsubheading Synopsis
31426 Makes current function return immediately. Doesn't execute the inferior.
31427 Displays the new current frame.
31429 @subsubheading @value{GDBN} Command
31431 The corresponding @value{GDBN} command is @samp{return}.
31433 @subsubheading Example
31437 200-break-insert callee4
31438 200^done,bkpt=@{number="1",addr="0x00010734",
31439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31444 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31445 frame=@{func="callee4",args=[],
31446 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31447 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31453 111^done,frame=@{level="0",func="callee3",
31454 args=[@{name="strarg",
31455 value="0x11940 \"A string argument.\""@}],
31456 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31457 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31462 @subheading The @code{-exec-run} Command
31465 @subsubheading Synopsis
31468 -exec-run [ --all | --thread-group N ] [ --start ]
31471 Starts execution of the inferior from the beginning. The inferior
31472 executes until either a breakpoint is encountered or the program
31473 exits. In the latter case the output will include an exit code, if
31474 the program has exited exceptionally.
31476 When neither the @samp{--all} nor the @samp{--thread-group} option
31477 is specified, the current inferior is started. If the
31478 @samp{--thread-group} option is specified, it should refer to a thread
31479 group of type @samp{process}, and that thread group will be started.
31480 If the @samp{--all} option is specified, then all inferiors will be started.
31482 Using the @samp{--start} option instructs the debugger to stop
31483 the execution at the start of the inferior's main subprogram,
31484 following the same behavior as the @code{start} command
31485 (@pxref{Starting}).
31487 @subsubheading @value{GDBN} Command
31489 The corresponding @value{GDBN} command is @samp{run}.
31491 @subsubheading Examples
31496 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31501 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31502 frame=@{func="main",args=[],file="recursive2.c",
31503 fullname="/home/foo/bar/recursive2.c",line="4"@}
31508 Program exited normally:
31516 *stopped,reason="exited-normally"
31521 Program exited exceptionally:
31529 *stopped,reason="exited",exit-code="01"
31533 Another way the program can terminate is if it receives a signal such as
31534 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31538 *stopped,reason="exited-signalled",signal-name="SIGINT",
31539 signal-meaning="Interrupt"
31543 @c @subheading -exec-signal
31546 @subheading The @code{-exec-step} Command
31549 @subsubheading Synopsis
31552 -exec-step [--reverse]
31555 Resumes execution of the inferior program, stopping when the beginning
31556 of the next source line is reached, if the next source line is not a
31557 function call. If it is, stop at the first instruction of the called
31558 function. If the @samp{--reverse} option is specified, resumes reverse
31559 execution of the inferior program, stopping at the beginning of the
31560 previously executed source line.
31562 @subsubheading @value{GDBN} Command
31564 The corresponding @value{GDBN} command is @samp{step}.
31566 @subsubheading Example
31568 Stepping into a function:
31574 *stopped,reason="end-stepping-range",
31575 frame=@{func="foo",args=[@{name="a",value="10"@},
31576 @{name="b",value="0"@}],file="recursive2.c",
31577 fullname="/home/foo/bar/recursive2.c",line="11"@}
31587 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31592 @subheading The @code{-exec-step-instruction} Command
31593 @findex -exec-step-instruction
31595 @subsubheading Synopsis
31598 -exec-step-instruction [--reverse]
31601 Resumes the inferior which executes one machine instruction. If the
31602 @samp{--reverse} option is specified, resumes reverse execution of the
31603 inferior program, stopping at the previously executed instruction.
31604 The output, once @value{GDBN} has stopped, will vary depending on
31605 whether we have stopped in the middle of a source line or not. In the
31606 former case, the address at which the program stopped will be printed
31609 @subsubheading @value{GDBN} Command
31611 The corresponding @value{GDBN} command is @samp{stepi}.
31613 @subsubheading Example
31617 -exec-step-instruction
31621 *stopped,reason="end-stepping-range",
31622 frame=@{func="foo",args=[],file="try.c",
31623 fullname="/home/foo/bar/try.c",line="10"@}
31625 -exec-step-instruction
31629 *stopped,reason="end-stepping-range",
31630 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31631 fullname="/home/foo/bar/try.c",line="10"@}
31636 @subheading The @code{-exec-until} Command
31637 @findex -exec-until
31639 @subsubheading Synopsis
31642 -exec-until [ @var{location} ]
31645 Executes the inferior until the @var{location} specified in the
31646 argument is reached. If there is no argument, the inferior executes
31647 until a source line greater than the current one is reached. The
31648 reason for stopping in this case will be @samp{location-reached}.
31650 @subsubheading @value{GDBN} Command
31652 The corresponding @value{GDBN} command is @samp{until}.
31654 @subsubheading Example
31658 -exec-until recursive2.c:6
31662 *stopped,reason="location-reached",frame=@{func="main",args=[],
31663 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31668 @subheading -file-clear
31669 Is this going away????
31672 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31673 @node GDB/MI Stack Manipulation
31674 @section @sc{gdb/mi} Stack Manipulation Commands
31676 @subheading The @code{-enable-frame-filters} Command
31677 @findex -enable-frame-filters
31680 -enable-frame-filters
31683 @value{GDBN} allows Python-based frame filters to affect the output of
31684 the MI commands relating to stack traces. As there is no way to
31685 implement this in a fully backward-compatible way, a front end must
31686 request that this functionality be enabled.
31688 Once enabled, this feature cannot be disabled.
31690 Note that if Python support has not been compiled into @value{GDBN},
31691 this command will still succeed (and do nothing).
31693 @subheading The @code{-stack-info-frame} Command
31694 @findex -stack-info-frame
31696 @subsubheading Synopsis
31702 Get info on the selected frame.
31704 @subsubheading @value{GDBN} Command
31706 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31707 (without arguments).
31709 @subsubheading Example
31714 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31715 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31716 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31720 @subheading The @code{-stack-info-depth} Command
31721 @findex -stack-info-depth
31723 @subsubheading Synopsis
31726 -stack-info-depth [ @var{max-depth} ]
31729 Return the depth of the stack. If the integer argument @var{max-depth}
31730 is specified, do not count beyond @var{max-depth} frames.
31732 @subsubheading @value{GDBN} Command
31734 There's no equivalent @value{GDBN} command.
31736 @subsubheading Example
31738 For a stack with frame levels 0 through 11:
31745 -stack-info-depth 4
31748 -stack-info-depth 12
31751 -stack-info-depth 11
31754 -stack-info-depth 13
31759 @anchor{-stack-list-arguments}
31760 @subheading The @code{-stack-list-arguments} Command
31761 @findex -stack-list-arguments
31763 @subsubheading Synopsis
31766 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31767 [ @var{low-frame} @var{high-frame} ]
31770 Display a list of the arguments for the frames between @var{low-frame}
31771 and @var{high-frame} (inclusive). If @var{low-frame} and
31772 @var{high-frame} are not provided, list the arguments for the whole
31773 call stack. If the two arguments are equal, show the single frame
31774 at the corresponding level. It is an error if @var{low-frame} is
31775 larger than the actual number of frames. On the other hand,
31776 @var{high-frame} may be larger than the actual number of frames, in
31777 which case only existing frames will be returned.
31779 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31780 the variables; if it is 1 or @code{--all-values}, print also their
31781 values; and if it is 2 or @code{--simple-values}, print the name,
31782 type and value for simple data types, and the name and type for arrays,
31783 structures and unions. If the option @code{--no-frame-filters} is
31784 supplied, then Python frame filters will not be executed.
31786 If the @code{--skip-unavailable} option is specified, arguments that
31787 are not available are not listed. Partially available arguments
31788 are still displayed, however.
31790 Use of this command to obtain arguments in a single frame is
31791 deprecated in favor of the @samp{-stack-list-variables} command.
31793 @subsubheading @value{GDBN} Command
31795 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31796 @samp{gdb_get_args} command which partially overlaps with the
31797 functionality of @samp{-stack-list-arguments}.
31799 @subsubheading Example
31806 frame=@{level="0",addr="0x00010734",func="callee4",
31807 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31808 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31809 frame=@{level="1",addr="0x0001076c",func="callee3",
31810 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31811 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31812 frame=@{level="2",addr="0x0001078c",func="callee2",
31813 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31814 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31815 frame=@{level="3",addr="0x000107b4",func="callee1",
31816 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31817 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31818 frame=@{level="4",addr="0x000107e0",func="main",
31819 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31820 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31822 -stack-list-arguments 0
31825 frame=@{level="0",args=[]@},
31826 frame=@{level="1",args=[name="strarg"]@},
31827 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31828 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31829 frame=@{level="4",args=[]@}]
31831 -stack-list-arguments 1
31834 frame=@{level="0",args=[]@},
31836 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31837 frame=@{level="2",args=[
31838 @{name="intarg",value="2"@},
31839 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31840 @{frame=@{level="3",args=[
31841 @{name="intarg",value="2"@},
31842 @{name="strarg",value="0x11940 \"A string argument.\""@},
31843 @{name="fltarg",value="3.5"@}]@},
31844 frame=@{level="4",args=[]@}]
31846 -stack-list-arguments 0 2 2
31847 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31849 -stack-list-arguments 1 2 2
31850 ^done,stack-args=[frame=@{level="2",
31851 args=[@{name="intarg",value="2"@},
31852 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31856 @c @subheading -stack-list-exception-handlers
31859 @anchor{-stack-list-frames}
31860 @subheading The @code{-stack-list-frames} Command
31861 @findex -stack-list-frames
31863 @subsubheading Synopsis
31866 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31869 List the frames currently on the stack. For each frame it displays the
31874 The frame number, 0 being the topmost frame, i.e., the innermost function.
31876 The @code{$pc} value for that frame.
31880 File name of the source file where the function lives.
31881 @item @var{fullname}
31882 The full file name of the source file where the function lives.
31884 Line number corresponding to the @code{$pc}.
31886 The shared library where this function is defined. This is only given
31887 if the frame's function is not known.
31890 If invoked without arguments, this command prints a backtrace for the
31891 whole stack. If given two integer arguments, it shows the frames whose
31892 levels are between the two arguments (inclusive). If the two arguments
31893 are equal, it shows the single frame at the corresponding level. It is
31894 an error if @var{low-frame} is larger than the actual number of
31895 frames. On the other hand, @var{high-frame} may be larger than the
31896 actual number of frames, in which case only existing frames will be
31897 returned. If the option @code{--no-frame-filters} is supplied, then
31898 Python frame filters will not be executed.
31900 @subsubheading @value{GDBN} Command
31902 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31904 @subsubheading Example
31906 Full stack backtrace:
31912 [frame=@{level="0",addr="0x0001076c",func="foo",
31913 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31914 frame=@{level="1",addr="0x000107a4",func="foo",
31915 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31916 frame=@{level="2",addr="0x000107a4",func="foo",
31917 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31918 frame=@{level="3",addr="0x000107a4",func="foo",
31919 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31920 frame=@{level="4",addr="0x000107a4",func="foo",
31921 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31922 frame=@{level="5",addr="0x000107a4",func="foo",
31923 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31924 frame=@{level="6",addr="0x000107a4",func="foo",
31925 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31926 frame=@{level="7",addr="0x000107a4",func="foo",
31927 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31928 frame=@{level="8",addr="0x000107a4",func="foo",
31929 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31930 frame=@{level="9",addr="0x000107a4",func="foo",
31931 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31932 frame=@{level="10",addr="0x000107a4",func="foo",
31933 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31934 frame=@{level="11",addr="0x00010738",func="main",
31935 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31939 Show frames between @var{low_frame} and @var{high_frame}:
31943 -stack-list-frames 3 5
31945 [frame=@{level="3",addr="0x000107a4",func="foo",
31946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31947 frame=@{level="4",addr="0x000107a4",func="foo",
31948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31949 frame=@{level="5",addr="0x000107a4",func="foo",
31950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31954 Show a single frame:
31958 -stack-list-frames 3 3
31960 [frame=@{level="3",addr="0x000107a4",func="foo",
31961 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31966 @subheading The @code{-stack-list-locals} Command
31967 @findex -stack-list-locals
31968 @anchor{-stack-list-locals}
31970 @subsubheading Synopsis
31973 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31976 Display the local variable names for the selected frame. If
31977 @var{print-values} is 0 or @code{--no-values}, print only the names of
31978 the variables; if it is 1 or @code{--all-values}, print also their
31979 values; and if it is 2 or @code{--simple-values}, print the name,
31980 type and value for simple data types, and the name and type for arrays,
31981 structures and unions. In this last case, a frontend can immediately
31982 display the value of simple data types and create variable objects for
31983 other data types when the user wishes to explore their values in
31984 more detail. If the option @code{--no-frame-filters} is supplied, then
31985 Python frame filters will not be executed.
31987 If the @code{--skip-unavailable} option is specified, local variables
31988 that are not available are not listed. Partially available local
31989 variables are still displayed, however.
31991 This command is deprecated in favor of the
31992 @samp{-stack-list-variables} command.
31994 @subsubheading @value{GDBN} Command
31996 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31998 @subsubheading Example
32002 -stack-list-locals 0
32003 ^done,locals=[name="A",name="B",name="C"]
32005 -stack-list-locals --all-values
32006 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32007 @{name="C",value="@{1, 2, 3@}"@}]
32008 -stack-list-locals --simple-values
32009 ^done,locals=[@{name="A",type="int",value="1"@},
32010 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32014 @anchor{-stack-list-variables}
32015 @subheading The @code{-stack-list-variables} Command
32016 @findex -stack-list-variables
32018 @subsubheading Synopsis
32021 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32024 Display the names of local variables and function arguments for the selected frame. If
32025 @var{print-values} is 0 or @code{--no-values}, print only the names of
32026 the variables; if it is 1 or @code{--all-values}, print also their
32027 values; and if it is 2 or @code{--simple-values}, print the name,
32028 type and value for simple data types, and the name and type for arrays,
32029 structures and unions. If the option @code{--no-frame-filters} is
32030 supplied, then Python frame filters will not be executed.
32032 If the @code{--skip-unavailable} option is specified, local variables
32033 and arguments that are not available are not listed. Partially
32034 available arguments and local variables are still displayed, however.
32036 @subsubheading Example
32040 -stack-list-variables --thread 1 --frame 0 --all-values
32041 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32046 @subheading The @code{-stack-select-frame} Command
32047 @findex -stack-select-frame
32049 @subsubheading Synopsis
32052 -stack-select-frame @var{framenum}
32055 Change the selected frame. Select a different frame @var{framenum} on
32058 This command in deprecated in favor of passing the @samp{--frame}
32059 option to every command.
32061 @subsubheading @value{GDBN} Command
32063 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32064 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32066 @subsubheading Example
32070 -stack-select-frame 2
32075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32076 @node GDB/MI Variable Objects
32077 @section @sc{gdb/mi} Variable Objects
32081 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32083 For the implementation of a variable debugger window (locals, watched
32084 expressions, etc.), we are proposing the adaptation of the existing code
32085 used by @code{Insight}.
32087 The two main reasons for that are:
32091 It has been proven in practice (it is already on its second generation).
32094 It will shorten development time (needless to say how important it is
32098 The original interface was designed to be used by Tcl code, so it was
32099 slightly changed so it could be used through @sc{gdb/mi}. This section
32100 describes the @sc{gdb/mi} operations that will be available and gives some
32101 hints about their use.
32103 @emph{Note}: In addition to the set of operations described here, we
32104 expect the @sc{gui} implementation of a variable window to require, at
32105 least, the following operations:
32108 @item @code{-gdb-show} @code{output-radix}
32109 @item @code{-stack-list-arguments}
32110 @item @code{-stack-list-locals}
32111 @item @code{-stack-select-frame}
32116 @subheading Introduction to Variable Objects
32118 @cindex variable objects in @sc{gdb/mi}
32120 Variable objects are "object-oriented" MI interface for examining and
32121 changing values of expressions. Unlike some other MI interfaces that
32122 work with expressions, variable objects are specifically designed for
32123 simple and efficient presentation in the frontend. A variable object
32124 is identified by string name. When a variable object is created, the
32125 frontend specifies the expression for that variable object. The
32126 expression can be a simple variable, or it can be an arbitrary complex
32127 expression, and can even involve CPU registers. After creating a
32128 variable object, the frontend can invoke other variable object
32129 operations---for example to obtain or change the value of a variable
32130 object, or to change display format.
32132 Variable objects have hierarchical tree structure. Any variable object
32133 that corresponds to a composite type, such as structure in C, has
32134 a number of child variable objects, for example corresponding to each
32135 element of a structure. A child variable object can itself have
32136 children, recursively. Recursion ends when we reach
32137 leaf variable objects, which always have built-in types. Child variable
32138 objects are created only by explicit request, so if a frontend
32139 is not interested in the children of a particular variable object, no
32140 child will be created.
32142 For a leaf variable object it is possible to obtain its value as a
32143 string, or set the value from a string. String value can be also
32144 obtained for a non-leaf variable object, but it's generally a string
32145 that only indicates the type of the object, and does not list its
32146 contents. Assignment to a non-leaf variable object is not allowed.
32148 A frontend does not need to read the values of all variable objects each time
32149 the program stops. Instead, MI provides an update command that lists all
32150 variable objects whose values has changed since the last update
32151 operation. This considerably reduces the amount of data that must
32152 be transferred to the frontend. As noted above, children variable
32153 objects are created on demand, and only leaf variable objects have a
32154 real value. As result, gdb will read target memory only for leaf
32155 variables that frontend has created.
32157 The automatic update is not always desirable. For example, a frontend
32158 might want to keep a value of some expression for future reference,
32159 and never update it. For another example, fetching memory is
32160 relatively slow for embedded targets, so a frontend might want
32161 to disable automatic update for the variables that are either not
32162 visible on the screen, or ``closed''. This is possible using so
32163 called ``frozen variable objects''. Such variable objects are never
32164 implicitly updated.
32166 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32167 fixed variable object, the expression is parsed when the variable
32168 object is created, including associating identifiers to specific
32169 variables. The meaning of expression never changes. For a floating
32170 variable object the values of variables whose names appear in the
32171 expressions are re-evaluated every time in the context of the current
32172 frame. Consider this example:
32177 struct work_state state;
32184 If a fixed variable object for the @code{state} variable is created in
32185 this function, and we enter the recursive call, the variable
32186 object will report the value of @code{state} in the top-level
32187 @code{do_work} invocation. On the other hand, a floating variable
32188 object will report the value of @code{state} in the current frame.
32190 If an expression specified when creating a fixed variable object
32191 refers to a local variable, the variable object becomes bound to the
32192 thread and frame in which the variable object is created. When such
32193 variable object is updated, @value{GDBN} makes sure that the
32194 thread/frame combination the variable object is bound to still exists,
32195 and re-evaluates the variable object in context of that thread/frame.
32197 The following is the complete set of @sc{gdb/mi} operations defined to
32198 access this functionality:
32200 @multitable @columnfractions .4 .6
32201 @item @strong{Operation}
32202 @tab @strong{Description}
32204 @item @code{-enable-pretty-printing}
32205 @tab enable Python-based pretty-printing
32206 @item @code{-var-create}
32207 @tab create a variable object
32208 @item @code{-var-delete}
32209 @tab delete the variable object and/or its children
32210 @item @code{-var-set-format}
32211 @tab set the display format of this variable
32212 @item @code{-var-show-format}
32213 @tab show the display format of this variable
32214 @item @code{-var-info-num-children}
32215 @tab tells how many children this object has
32216 @item @code{-var-list-children}
32217 @tab return a list of the object's children
32218 @item @code{-var-info-type}
32219 @tab show the type of this variable object
32220 @item @code{-var-info-expression}
32221 @tab print parent-relative expression that this variable object represents
32222 @item @code{-var-info-path-expression}
32223 @tab print full expression that this variable object represents
32224 @item @code{-var-show-attributes}
32225 @tab is this variable editable? does it exist here?
32226 @item @code{-var-evaluate-expression}
32227 @tab get the value of this variable
32228 @item @code{-var-assign}
32229 @tab set the value of this variable
32230 @item @code{-var-update}
32231 @tab update the variable and its children
32232 @item @code{-var-set-frozen}
32233 @tab set frozeness attribute
32234 @item @code{-var-set-update-range}
32235 @tab set range of children to display on update
32238 In the next subsection we describe each operation in detail and suggest
32239 how it can be used.
32241 @subheading Description And Use of Operations on Variable Objects
32243 @subheading The @code{-enable-pretty-printing} Command
32244 @findex -enable-pretty-printing
32247 -enable-pretty-printing
32250 @value{GDBN} allows Python-based visualizers to affect the output of the
32251 MI variable object commands. However, because there was no way to
32252 implement this in a fully backward-compatible way, a front end must
32253 request that this functionality be enabled.
32255 Once enabled, this feature cannot be disabled.
32257 Note that if Python support has not been compiled into @value{GDBN},
32258 this command will still succeed (and do nothing).
32260 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32261 may work differently in future versions of @value{GDBN}.
32263 @subheading The @code{-var-create} Command
32264 @findex -var-create
32266 @subsubheading Synopsis
32269 -var-create @{@var{name} | "-"@}
32270 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32273 This operation creates a variable object, which allows the monitoring of
32274 a variable, the result of an expression, a memory cell or a CPU
32277 The @var{name} parameter is the string by which the object can be
32278 referenced. It must be unique. If @samp{-} is specified, the varobj
32279 system will generate a string ``varNNNNNN'' automatically. It will be
32280 unique provided that one does not specify @var{name} of that format.
32281 The command fails if a duplicate name is found.
32283 The frame under which the expression should be evaluated can be
32284 specified by @var{frame-addr}. A @samp{*} indicates that the current
32285 frame should be used. A @samp{@@} indicates that a floating variable
32286 object must be created.
32288 @var{expression} is any expression valid on the current language set (must not
32289 begin with a @samp{*}), or one of the following:
32293 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32296 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32299 @samp{$@var{regname}} --- a CPU register name
32302 @cindex dynamic varobj
32303 A varobj's contents may be provided by a Python-based pretty-printer. In this
32304 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32305 have slightly different semantics in some cases. If the
32306 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32307 will never create a dynamic varobj. This ensures backward
32308 compatibility for existing clients.
32310 @subsubheading Result
32312 This operation returns attributes of the newly-created varobj. These
32317 The name of the varobj.
32320 The number of children of the varobj. This number is not necessarily
32321 reliable for a dynamic varobj. Instead, you must examine the
32322 @samp{has_more} attribute.
32325 The varobj's scalar value. For a varobj whose type is some sort of
32326 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32327 will not be interesting.
32330 The varobj's type. This is a string representation of the type, as
32331 would be printed by the @value{GDBN} CLI. If @samp{print object}
32332 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32333 @emph{actual} (derived) type of the object is shown rather than the
32334 @emph{declared} one.
32337 If a variable object is bound to a specific thread, then this is the
32338 thread's identifier.
32341 For a dynamic varobj, this indicates whether there appear to be any
32342 children available. For a non-dynamic varobj, this will be 0.
32345 This attribute will be present and have the value @samp{1} if the
32346 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32347 then this attribute will not be present.
32350 A dynamic varobj can supply a display hint to the front end. The
32351 value comes directly from the Python pretty-printer object's
32352 @code{display_hint} method. @xref{Pretty Printing API}.
32355 Typical output will look like this:
32358 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32359 has_more="@var{has_more}"
32363 @subheading The @code{-var-delete} Command
32364 @findex -var-delete
32366 @subsubheading Synopsis
32369 -var-delete [ -c ] @var{name}
32372 Deletes a previously created variable object and all of its children.
32373 With the @samp{-c} option, just deletes the children.
32375 Returns an error if the object @var{name} is not found.
32378 @subheading The @code{-var-set-format} Command
32379 @findex -var-set-format
32381 @subsubheading Synopsis
32384 -var-set-format @var{name} @var{format-spec}
32387 Sets the output format for the value of the object @var{name} to be
32390 @anchor{-var-set-format}
32391 The syntax for the @var{format-spec} is as follows:
32394 @var{format-spec} @expansion{}
32395 @{binary | decimal | hexadecimal | octal | natural@}
32398 The natural format is the default format choosen automatically
32399 based on the variable type (like decimal for an @code{int}, hex
32400 for pointers, etc.).
32402 For a variable with children, the format is set only on the
32403 variable itself, and the children are not affected.
32405 @subheading The @code{-var-show-format} Command
32406 @findex -var-show-format
32408 @subsubheading Synopsis
32411 -var-show-format @var{name}
32414 Returns the format used to display the value of the object @var{name}.
32417 @var{format} @expansion{}
32422 @subheading The @code{-var-info-num-children} Command
32423 @findex -var-info-num-children
32425 @subsubheading Synopsis
32428 -var-info-num-children @var{name}
32431 Returns the number of children of a variable object @var{name}:
32437 Note that this number is not completely reliable for a dynamic varobj.
32438 It will return the current number of children, but more children may
32442 @subheading The @code{-var-list-children} Command
32443 @findex -var-list-children
32445 @subsubheading Synopsis
32448 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32450 @anchor{-var-list-children}
32452 Return a list of the children of the specified variable object and
32453 create variable objects for them, if they do not already exist. With
32454 a single argument or if @var{print-values} has a value of 0 or
32455 @code{--no-values}, print only the names of the variables; if
32456 @var{print-values} is 1 or @code{--all-values}, also print their
32457 values; and if it is 2 or @code{--simple-values} print the name and
32458 value for simple data types and just the name for arrays, structures
32461 @var{from} and @var{to}, if specified, indicate the range of children
32462 to report. If @var{from} or @var{to} is less than zero, the range is
32463 reset and all children will be reported. Otherwise, children starting
32464 at @var{from} (zero-based) and up to and excluding @var{to} will be
32467 If a child range is requested, it will only affect the current call to
32468 @code{-var-list-children}, but not future calls to @code{-var-update}.
32469 For this, you must instead use @code{-var-set-update-range}. The
32470 intent of this approach is to enable a front end to implement any
32471 update approach it likes; for example, scrolling a view may cause the
32472 front end to request more children with @code{-var-list-children}, and
32473 then the front end could call @code{-var-set-update-range} with a
32474 different range to ensure that future updates are restricted to just
32477 For each child the following results are returned:
32482 Name of the variable object created for this child.
32485 The expression to be shown to the user by the front end to designate this child.
32486 For example this may be the name of a structure member.
32488 For a dynamic varobj, this value cannot be used to form an
32489 expression. There is no way to do this at all with a dynamic varobj.
32491 For C/C@t{++} structures there are several pseudo children returned to
32492 designate access qualifiers. For these pseudo children @var{exp} is
32493 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32494 type and value are not present.
32496 A dynamic varobj will not report the access qualifying
32497 pseudo-children, regardless of the language. This information is not
32498 available at all with a dynamic varobj.
32501 Number of children this child has. For a dynamic varobj, this will be
32505 The type of the child. If @samp{print object}
32506 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32507 @emph{actual} (derived) type of the object is shown rather than the
32508 @emph{declared} one.
32511 If values were requested, this is the value.
32514 If this variable object is associated with a thread, this is the thread id.
32515 Otherwise this result is not present.
32518 If the variable object is frozen, this variable will be present with a value of 1.
32521 The result may have its own attributes:
32525 A dynamic varobj can supply a display hint to the front end. The
32526 value comes directly from the Python pretty-printer object's
32527 @code{display_hint} method. @xref{Pretty Printing API}.
32530 This is an integer attribute which is nonzero if there are children
32531 remaining after the end of the selected range.
32534 @subsubheading Example
32538 -var-list-children n
32539 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32540 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32542 -var-list-children --all-values n
32543 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32544 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32548 @subheading The @code{-var-info-type} Command
32549 @findex -var-info-type
32551 @subsubheading Synopsis
32554 -var-info-type @var{name}
32557 Returns the type of the specified variable @var{name}. The type is
32558 returned as a string in the same format as it is output by the
32562 type=@var{typename}
32566 @subheading The @code{-var-info-expression} Command
32567 @findex -var-info-expression
32569 @subsubheading Synopsis
32572 -var-info-expression @var{name}
32575 Returns a string that is suitable for presenting this
32576 variable object in user interface. The string is generally
32577 not valid expression in the current language, and cannot be evaluated.
32579 For example, if @code{a} is an array, and variable object
32580 @code{A} was created for @code{a}, then we'll get this output:
32583 (gdb) -var-info-expression A.1
32584 ^done,lang="C",exp="1"
32588 Here, the value of @code{lang} is the language name, which can be
32589 found in @ref{Supported Languages}.
32591 Note that the output of the @code{-var-list-children} command also
32592 includes those expressions, so the @code{-var-info-expression} command
32595 @subheading The @code{-var-info-path-expression} Command
32596 @findex -var-info-path-expression
32598 @subsubheading Synopsis
32601 -var-info-path-expression @var{name}
32604 Returns an expression that can be evaluated in the current
32605 context and will yield the same value that a variable object has.
32606 Compare this with the @code{-var-info-expression} command, which
32607 result can be used only for UI presentation. Typical use of
32608 the @code{-var-info-path-expression} command is creating a
32609 watchpoint from a variable object.
32611 This command is currently not valid for children of a dynamic varobj,
32612 and will give an error when invoked on one.
32614 For example, suppose @code{C} is a C@t{++} class, derived from class
32615 @code{Base}, and that the @code{Base} class has a member called
32616 @code{m_size}. Assume a variable @code{c} is has the type of
32617 @code{C} and a variable object @code{C} was created for variable
32618 @code{c}. Then, we'll get this output:
32620 (gdb) -var-info-path-expression C.Base.public.m_size
32621 ^done,path_expr=((Base)c).m_size)
32624 @subheading The @code{-var-show-attributes} Command
32625 @findex -var-show-attributes
32627 @subsubheading Synopsis
32630 -var-show-attributes @var{name}
32633 List attributes of the specified variable object @var{name}:
32636 status=@var{attr} [ ( ,@var{attr} )* ]
32640 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32642 @subheading The @code{-var-evaluate-expression} Command
32643 @findex -var-evaluate-expression
32645 @subsubheading Synopsis
32648 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32651 Evaluates the expression that is represented by the specified variable
32652 object and returns its value as a string. The format of the string
32653 can be specified with the @samp{-f} option. The possible values of
32654 this option are the same as for @code{-var-set-format}
32655 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32656 the current display format will be used. The current display format
32657 can be changed using the @code{-var-set-format} command.
32663 Note that one must invoke @code{-var-list-children} for a variable
32664 before the value of a child variable can be evaluated.
32666 @subheading The @code{-var-assign} Command
32667 @findex -var-assign
32669 @subsubheading Synopsis
32672 -var-assign @var{name} @var{expression}
32675 Assigns the value of @var{expression} to the variable object specified
32676 by @var{name}. The object must be @samp{editable}. If the variable's
32677 value is altered by the assign, the variable will show up in any
32678 subsequent @code{-var-update} list.
32680 @subsubheading Example
32688 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32692 @subheading The @code{-var-update} Command
32693 @findex -var-update
32695 @subsubheading Synopsis
32698 -var-update [@var{print-values}] @{@var{name} | "*"@}
32701 Reevaluate the expressions corresponding to the variable object
32702 @var{name} and all its direct and indirect children, and return the
32703 list of variable objects whose values have changed; @var{name} must
32704 be a root variable object. Here, ``changed'' means that the result of
32705 @code{-var-evaluate-expression} before and after the
32706 @code{-var-update} is different. If @samp{*} is used as the variable
32707 object names, all existing variable objects are updated, except
32708 for frozen ones (@pxref{-var-set-frozen}). The option
32709 @var{print-values} determines whether both names and values, or just
32710 names are printed. The possible values of this option are the same
32711 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32712 recommended to use the @samp{--all-values} option, to reduce the
32713 number of MI commands needed on each program stop.
32715 With the @samp{*} parameter, if a variable object is bound to a
32716 currently running thread, it will not be updated, without any
32719 If @code{-var-set-update-range} was previously used on a varobj, then
32720 only the selected range of children will be reported.
32722 @code{-var-update} reports all the changed varobjs in a tuple named
32725 Each item in the change list is itself a tuple holding:
32729 The name of the varobj.
32732 If values were requested for this update, then this field will be
32733 present and will hold the value of the varobj.
32736 @anchor{-var-update}
32737 This field is a string which may take one of three values:
32741 The variable object's current value is valid.
32744 The variable object does not currently hold a valid value but it may
32745 hold one in the future if its associated expression comes back into
32749 The variable object no longer holds a valid value.
32750 This can occur when the executable file being debugged has changed,
32751 either through recompilation or by using the @value{GDBN} @code{file}
32752 command. The front end should normally choose to delete these variable
32756 In the future new values may be added to this list so the front should
32757 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32760 This is only present if the varobj is still valid. If the type
32761 changed, then this will be the string @samp{true}; otherwise it will
32764 When a varobj's type changes, its children are also likely to have
32765 become incorrect. Therefore, the varobj's children are automatically
32766 deleted when this attribute is @samp{true}. Also, the varobj's update
32767 range, when set using the @code{-var-set-update-range} command, is
32771 If the varobj's type changed, then this field will be present and will
32774 @item new_num_children
32775 For a dynamic varobj, if the number of children changed, or if the
32776 type changed, this will be the new number of children.
32778 The @samp{numchild} field in other varobj responses is generally not
32779 valid for a dynamic varobj -- it will show the number of children that
32780 @value{GDBN} knows about, but because dynamic varobjs lazily
32781 instantiate their children, this will not reflect the number of
32782 children which may be available.
32784 The @samp{new_num_children} attribute only reports changes to the
32785 number of children known by @value{GDBN}. This is the only way to
32786 detect whether an update has removed children (which necessarily can
32787 only happen at the end of the update range).
32790 The display hint, if any.
32793 This is an integer value, which will be 1 if there are more children
32794 available outside the varobj's update range.
32797 This attribute will be present and have the value @samp{1} if the
32798 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32799 then this attribute will not be present.
32802 If new children were added to a dynamic varobj within the selected
32803 update range (as set by @code{-var-set-update-range}), then they will
32804 be listed in this attribute.
32807 @subsubheading Example
32814 -var-update --all-values var1
32815 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32816 type_changed="false"@}]
32820 @subheading The @code{-var-set-frozen} Command
32821 @findex -var-set-frozen
32822 @anchor{-var-set-frozen}
32824 @subsubheading Synopsis
32827 -var-set-frozen @var{name} @var{flag}
32830 Set the frozenness flag on the variable object @var{name}. The
32831 @var{flag} parameter should be either @samp{1} to make the variable
32832 frozen or @samp{0} to make it unfrozen. If a variable object is
32833 frozen, then neither itself, nor any of its children, are
32834 implicitly updated by @code{-var-update} of
32835 a parent variable or by @code{-var-update *}. Only
32836 @code{-var-update} of the variable itself will update its value and
32837 values of its children. After a variable object is unfrozen, it is
32838 implicitly updated by all subsequent @code{-var-update} operations.
32839 Unfreezing a variable does not update it, only subsequent
32840 @code{-var-update} does.
32842 @subsubheading Example
32846 -var-set-frozen V 1
32851 @subheading The @code{-var-set-update-range} command
32852 @findex -var-set-update-range
32853 @anchor{-var-set-update-range}
32855 @subsubheading Synopsis
32858 -var-set-update-range @var{name} @var{from} @var{to}
32861 Set the range of children to be returned by future invocations of
32862 @code{-var-update}.
32864 @var{from} and @var{to} indicate the range of children to report. If
32865 @var{from} or @var{to} is less than zero, the range is reset and all
32866 children will be reported. Otherwise, children starting at @var{from}
32867 (zero-based) and up to and excluding @var{to} will be reported.
32869 @subsubheading Example
32873 -var-set-update-range V 1 2
32877 @subheading The @code{-var-set-visualizer} command
32878 @findex -var-set-visualizer
32879 @anchor{-var-set-visualizer}
32881 @subsubheading Synopsis
32884 -var-set-visualizer @var{name} @var{visualizer}
32887 Set a visualizer for the variable object @var{name}.
32889 @var{visualizer} is the visualizer to use. The special value
32890 @samp{None} means to disable any visualizer in use.
32892 If not @samp{None}, @var{visualizer} must be a Python expression.
32893 This expression must evaluate to a callable object which accepts a
32894 single argument. @value{GDBN} will call this object with the value of
32895 the varobj @var{name} as an argument (this is done so that the same
32896 Python pretty-printing code can be used for both the CLI and MI).
32897 When called, this object must return an object which conforms to the
32898 pretty-printing interface (@pxref{Pretty Printing API}).
32900 The pre-defined function @code{gdb.default_visualizer} may be used to
32901 select a visualizer by following the built-in process
32902 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32903 a varobj is created, and so ordinarily is not needed.
32905 This feature is only available if Python support is enabled. The MI
32906 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32907 can be used to check this.
32909 @subsubheading Example
32911 Resetting the visualizer:
32915 -var-set-visualizer V None
32919 Reselecting the default (type-based) visualizer:
32923 -var-set-visualizer V gdb.default_visualizer
32927 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32928 can be used to instantiate this class for a varobj:
32932 -var-set-visualizer V "lambda val: SomeClass()"
32936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32937 @node GDB/MI Data Manipulation
32938 @section @sc{gdb/mi} Data Manipulation
32940 @cindex data manipulation, in @sc{gdb/mi}
32941 @cindex @sc{gdb/mi}, data manipulation
32942 This section describes the @sc{gdb/mi} commands that manipulate data:
32943 examine memory and registers, evaluate expressions, etc.
32945 @c REMOVED FROM THE INTERFACE.
32946 @c @subheading -data-assign
32947 @c Change the value of a program variable. Plenty of side effects.
32948 @c @subsubheading GDB Command
32950 @c @subsubheading Example
32953 @subheading The @code{-data-disassemble} Command
32954 @findex -data-disassemble
32956 @subsubheading Synopsis
32960 [ -s @var{start-addr} -e @var{end-addr} ]
32961 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32969 @item @var{start-addr}
32970 is the beginning address (or @code{$pc})
32971 @item @var{end-addr}
32973 @item @var{filename}
32974 is the name of the file to disassemble
32975 @item @var{linenum}
32976 is the line number to disassemble around
32978 is the number of disassembly lines to be produced. If it is -1,
32979 the whole function will be disassembled, in case no @var{end-addr} is
32980 specified. If @var{end-addr} is specified as a non-zero value, and
32981 @var{lines} is lower than the number of disassembly lines between
32982 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32983 displayed; if @var{lines} is higher than the number of lines between
32984 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32987 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32988 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32989 mixed source and disassembly with raw opcodes).
32992 @subsubheading Result
32994 The result of the @code{-data-disassemble} command will be a list named
32995 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32996 used with the @code{-data-disassemble} command.
32998 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33003 The address at which this instruction was disassembled.
33006 The name of the function this instruction is within.
33009 The decimal offset in bytes from the start of @samp{func-name}.
33012 The text disassembly for this @samp{address}.
33015 This field is only present for mode 2. This contains the raw opcode
33016 bytes for the @samp{inst} field.
33020 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33021 @samp{src_and_asm_line}, each of which has the following fields:
33025 The line number within @samp{file}.
33028 The file name from the compilation unit. This might be an absolute
33029 file name or a relative file name depending on the compile command
33033 Absolute file name of @samp{file}. It is converted to a canonical form
33034 using the source file search path
33035 (@pxref{Source Path, ,Specifying Source Directories})
33036 and after resolving all the symbolic links.
33038 If the source file is not found this field will contain the path as
33039 present in the debug information.
33041 @item line_asm_insn
33042 This is a list of tuples containing the disassembly for @samp{line} in
33043 @samp{file}. The fields of each tuple are the same as for
33044 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33045 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33050 Note that whatever included in the @samp{inst} field, is not
33051 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33054 @subsubheading @value{GDBN} Command
33056 The corresponding @value{GDBN} command is @samp{disassemble}.
33058 @subsubheading Example
33060 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33064 -data-disassemble -s $pc -e "$pc + 20" -- 0
33067 @{address="0x000107c0",func-name="main",offset="4",
33068 inst="mov 2, %o0"@},
33069 @{address="0x000107c4",func-name="main",offset="8",
33070 inst="sethi %hi(0x11800), %o2"@},
33071 @{address="0x000107c8",func-name="main",offset="12",
33072 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33073 @{address="0x000107cc",func-name="main",offset="16",
33074 inst="sethi %hi(0x11800), %o2"@},
33075 @{address="0x000107d0",func-name="main",offset="20",
33076 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33080 Disassemble the whole @code{main} function. Line 32 is part of
33084 -data-disassemble -f basics.c -l 32 -- 0
33086 @{address="0x000107bc",func-name="main",offset="0",
33087 inst="save %sp, -112, %sp"@},
33088 @{address="0x000107c0",func-name="main",offset="4",
33089 inst="mov 2, %o0"@},
33090 @{address="0x000107c4",func-name="main",offset="8",
33091 inst="sethi %hi(0x11800), %o2"@},
33093 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33094 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33098 Disassemble 3 instructions from the start of @code{main}:
33102 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33104 @{address="0x000107bc",func-name="main",offset="0",
33105 inst="save %sp, -112, %sp"@},
33106 @{address="0x000107c0",func-name="main",offset="4",
33107 inst="mov 2, %o0"@},
33108 @{address="0x000107c4",func-name="main",offset="8",
33109 inst="sethi %hi(0x11800), %o2"@}]
33113 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33117 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33119 src_and_asm_line=@{line="31",
33120 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33121 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33122 line_asm_insn=[@{address="0x000107bc",
33123 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33124 src_and_asm_line=@{line="32",
33125 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33126 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33127 line_asm_insn=[@{address="0x000107c0",
33128 func-name="main",offset="4",inst="mov 2, %o0"@},
33129 @{address="0x000107c4",func-name="main",offset="8",
33130 inst="sethi %hi(0x11800), %o2"@}]@}]
33135 @subheading The @code{-data-evaluate-expression} Command
33136 @findex -data-evaluate-expression
33138 @subsubheading Synopsis
33141 -data-evaluate-expression @var{expr}
33144 Evaluate @var{expr} as an expression. The expression could contain an
33145 inferior function call. The function call will execute synchronously.
33146 If the expression contains spaces, it must be enclosed in double quotes.
33148 @subsubheading @value{GDBN} Command
33150 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33151 @samp{call}. In @code{gdbtk} only, there's a corresponding
33152 @samp{gdb_eval} command.
33154 @subsubheading Example
33156 In the following example, the numbers that precede the commands are the
33157 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33158 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33162 211-data-evaluate-expression A
33165 311-data-evaluate-expression &A
33166 311^done,value="0xefffeb7c"
33168 411-data-evaluate-expression A+3
33171 511-data-evaluate-expression "A + 3"
33177 @subheading The @code{-data-list-changed-registers} Command
33178 @findex -data-list-changed-registers
33180 @subsubheading Synopsis
33183 -data-list-changed-registers
33186 Display a list of the registers that have changed.
33188 @subsubheading @value{GDBN} Command
33190 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33191 has the corresponding command @samp{gdb_changed_register_list}.
33193 @subsubheading Example
33195 On a PPC MBX board:
33203 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33204 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33207 -data-list-changed-registers
33208 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33209 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33210 "24","25","26","27","28","30","31","64","65","66","67","69"]
33215 @subheading The @code{-data-list-register-names} Command
33216 @findex -data-list-register-names
33218 @subsubheading Synopsis
33221 -data-list-register-names [ ( @var{regno} )+ ]
33224 Show a list of register names for the current target. If no arguments
33225 are given, it shows a list of the names of all the registers. If
33226 integer numbers are given as arguments, it will print a list of the
33227 names of the registers corresponding to the arguments. To ensure
33228 consistency between a register name and its number, the output list may
33229 include empty register names.
33231 @subsubheading @value{GDBN} Command
33233 @value{GDBN} does not have a command which corresponds to
33234 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33235 corresponding command @samp{gdb_regnames}.
33237 @subsubheading Example
33239 For the PPC MBX board:
33242 -data-list-register-names
33243 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33244 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33245 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33246 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33247 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33248 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33249 "", "pc","ps","cr","lr","ctr","xer"]
33251 -data-list-register-names 1 2 3
33252 ^done,register-names=["r1","r2","r3"]
33256 @subheading The @code{-data-list-register-values} Command
33257 @findex -data-list-register-values
33259 @subsubheading Synopsis
33262 -data-list-register-values
33263 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33266 Display the registers' contents. @var{fmt} is the format according to
33267 which the registers' contents are to be returned, followed by an optional
33268 list of numbers specifying the registers to display. A missing list of
33269 numbers indicates that the contents of all the registers must be
33270 returned. The @code{--skip-unavailable} option indicates that only
33271 the available registers are to be returned.
33273 Allowed formats for @var{fmt} are:
33290 @subsubheading @value{GDBN} Command
33292 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33293 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33295 @subsubheading Example
33297 For a PPC MBX board (note: line breaks are for readability only, they
33298 don't appear in the actual output):
33302 -data-list-register-values r 64 65
33303 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33304 @{number="65",value="0x00029002"@}]
33306 -data-list-register-values x
33307 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33308 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33309 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33310 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33311 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33312 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33313 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33314 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33315 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33316 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33317 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33318 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33319 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33320 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33321 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33322 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33323 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33324 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33325 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33326 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33327 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33328 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33329 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33330 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33331 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33332 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33333 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33334 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33335 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33336 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33337 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33338 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33339 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33340 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33341 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33342 @{number="69",value="0x20002b03"@}]
33347 @subheading The @code{-data-read-memory} Command
33348 @findex -data-read-memory
33350 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33352 @subsubheading Synopsis
33355 -data-read-memory [ -o @var{byte-offset} ]
33356 @var{address} @var{word-format} @var{word-size}
33357 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33364 @item @var{address}
33365 An expression specifying the address of the first memory word to be
33366 read. Complex expressions containing embedded white space should be
33367 quoted using the C convention.
33369 @item @var{word-format}
33370 The format to be used to print the memory words. The notation is the
33371 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33374 @item @var{word-size}
33375 The size of each memory word in bytes.
33377 @item @var{nr-rows}
33378 The number of rows in the output table.
33380 @item @var{nr-cols}
33381 The number of columns in the output table.
33384 If present, indicates that each row should include an @sc{ascii} dump. The
33385 value of @var{aschar} is used as a padding character when a byte is not a
33386 member of the printable @sc{ascii} character set (printable @sc{ascii}
33387 characters are those whose code is between 32 and 126, inclusively).
33389 @item @var{byte-offset}
33390 An offset to add to the @var{address} before fetching memory.
33393 This command displays memory contents as a table of @var{nr-rows} by
33394 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33395 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33396 (returned as @samp{total-bytes}). Should less than the requested number
33397 of bytes be returned by the target, the missing words are identified
33398 using @samp{N/A}. The number of bytes read from the target is returned
33399 in @samp{nr-bytes} and the starting address used to read memory in
33402 The address of the next/previous row or page is available in
33403 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33406 @subsubheading @value{GDBN} Command
33408 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33409 @samp{gdb_get_mem} memory read command.
33411 @subsubheading Example
33413 Read six bytes of memory starting at @code{bytes+6} but then offset by
33414 @code{-6} bytes. Format as three rows of two columns. One byte per
33415 word. Display each word in hex.
33419 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33420 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33421 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33422 prev-page="0x0000138a",memory=[
33423 @{addr="0x00001390",data=["0x00","0x01"]@},
33424 @{addr="0x00001392",data=["0x02","0x03"]@},
33425 @{addr="0x00001394",data=["0x04","0x05"]@}]
33429 Read two bytes of memory starting at address @code{shorts + 64} and
33430 display as a single word formatted in decimal.
33434 5-data-read-memory shorts+64 d 2 1 1
33435 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33436 next-row="0x00001512",prev-row="0x0000150e",
33437 next-page="0x00001512",prev-page="0x0000150e",memory=[
33438 @{addr="0x00001510",data=["128"]@}]
33442 Read thirty two bytes of memory starting at @code{bytes+16} and format
33443 as eight rows of four columns. Include a string encoding with @samp{x}
33444 used as the non-printable character.
33448 4-data-read-memory bytes+16 x 1 8 4 x
33449 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33450 next-row="0x000013c0",prev-row="0x0000139c",
33451 next-page="0x000013c0",prev-page="0x00001380",memory=[
33452 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33453 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33454 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33455 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33456 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33457 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33458 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33459 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33463 @subheading The @code{-data-read-memory-bytes} Command
33464 @findex -data-read-memory-bytes
33466 @subsubheading Synopsis
33469 -data-read-memory-bytes [ -o @var{byte-offset} ]
33470 @var{address} @var{count}
33477 @item @var{address}
33478 An expression specifying the address of the first memory word to be
33479 read. Complex expressions containing embedded white space should be
33480 quoted using the C convention.
33483 The number of bytes to read. This should be an integer literal.
33485 @item @var{byte-offset}
33486 The offsets in bytes relative to @var{address} at which to start
33487 reading. This should be an integer literal. This option is provided
33488 so that a frontend is not required to first evaluate address and then
33489 perform address arithmetics itself.
33493 This command attempts to read all accessible memory regions in the
33494 specified range. First, all regions marked as unreadable in the memory
33495 map (if one is defined) will be skipped. @xref{Memory Region
33496 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33497 regions. For each one, if reading full region results in an errors,
33498 @value{GDBN} will try to read a subset of the region.
33500 In general, every single byte in the region may be readable or not,
33501 and the only way to read every readable byte is to try a read at
33502 every address, which is not practical. Therefore, @value{GDBN} will
33503 attempt to read all accessible bytes at either beginning or the end
33504 of the region, using a binary division scheme. This heuristic works
33505 well for reading accross a memory map boundary. Note that if a region
33506 has a readable range that is neither at the beginning or the end,
33507 @value{GDBN} will not read it.
33509 The result record (@pxref{GDB/MI Result Records}) that is output of
33510 the command includes a field named @samp{memory} whose content is a
33511 list of tuples. Each tuple represent a successfully read memory block
33512 and has the following fields:
33516 The start address of the memory block, as hexadecimal literal.
33519 The end address of the memory block, as hexadecimal literal.
33522 The offset of the memory block, as hexadecimal literal, relative to
33523 the start address passed to @code{-data-read-memory-bytes}.
33526 The contents of the memory block, in hex.
33532 @subsubheading @value{GDBN} Command
33534 The corresponding @value{GDBN} command is @samp{x}.
33536 @subsubheading Example
33540 -data-read-memory-bytes &a 10
33541 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33543 contents="01000000020000000300"@}]
33548 @subheading The @code{-data-write-memory-bytes} Command
33549 @findex -data-write-memory-bytes
33551 @subsubheading Synopsis
33554 -data-write-memory-bytes @var{address} @var{contents}
33555 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33562 @item @var{address}
33563 An expression specifying the address of the first memory word to be
33564 read. Complex expressions containing embedded white space should be
33565 quoted using the C convention.
33567 @item @var{contents}
33568 The hex-encoded bytes to write.
33571 Optional argument indicating the number of bytes to be written. If @var{count}
33572 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33573 write @var{contents} until it fills @var{count} bytes.
33577 @subsubheading @value{GDBN} Command
33579 There's no corresponding @value{GDBN} command.
33581 @subsubheading Example
33585 -data-write-memory-bytes &a "aabbccdd"
33592 -data-write-memory-bytes &a "aabbccdd" 16e
33597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33598 @node GDB/MI Tracepoint Commands
33599 @section @sc{gdb/mi} Tracepoint Commands
33601 The commands defined in this section implement MI support for
33602 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33604 @subheading The @code{-trace-find} Command
33605 @findex -trace-find
33607 @subsubheading Synopsis
33610 -trace-find @var{mode} [@var{parameters}@dots{}]
33613 Find a trace frame using criteria defined by @var{mode} and
33614 @var{parameters}. The following table lists permissible
33615 modes and their parameters. For details of operation, see @ref{tfind}.
33620 No parameters are required. Stops examining trace frames.
33623 An integer is required as parameter. Selects tracepoint frame with
33626 @item tracepoint-number
33627 An integer is required as parameter. Finds next
33628 trace frame that corresponds to tracepoint with the specified number.
33631 An address is required as parameter. Finds
33632 next trace frame that corresponds to any tracepoint at the specified
33635 @item pc-inside-range
33636 Two addresses are required as parameters. Finds next trace
33637 frame that corresponds to a tracepoint at an address inside the
33638 specified range. Both bounds are considered to be inside the range.
33640 @item pc-outside-range
33641 Two addresses are required as parameters. Finds
33642 next trace frame that corresponds to a tracepoint at an address outside
33643 the specified range. Both bounds are considered to be inside the range.
33646 Line specification is required as parameter. @xref{Specify Location}.
33647 Finds next trace frame that corresponds to a tracepoint at
33648 the specified location.
33652 If @samp{none} was passed as @var{mode}, the response does not
33653 have fields. Otherwise, the response may have the following fields:
33657 This field has either @samp{0} or @samp{1} as the value, depending
33658 on whether a matching tracepoint was found.
33661 The index of the found traceframe. This field is present iff
33662 the @samp{found} field has value of @samp{1}.
33665 The index of the found tracepoint. This field is present iff
33666 the @samp{found} field has value of @samp{1}.
33669 The information about the frame corresponding to the found trace
33670 frame. This field is present only if a trace frame was found.
33671 @xref{GDB/MI Frame Information}, for description of this field.
33675 @subsubheading @value{GDBN} Command
33677 The corresponding @value{GDBN} command is @samp{tfind}.
33679 @subheading -trace-define-variable
33680 @findex -trace-define-variable
33682 @subsubheading Synopsis
33685 -trace-define-variable @var{name} [ @var{value} ]
33688 Create trace variable @var{name} if it does not exist. If
33689 @var{value} is specified, sets the initial value of the specified
33690 trace variable to that value. Note that the @var{name} should start
33691 with the @samp{$} character.
33693 @subsubheading @value{GDBN} Command
33695 The corresponding @value{GDBN} command is @samp{tvariable}.
33697 @subheading The @code{-trace-frame-collected} Command
33698 @findex -trace-frame-collected
33700 @subsubheading Synopsis
33703 -trace-frame-collected
33704 [--var-print-values @var{var_pval}]
33705 [--comp-print-values @var{comp_pval}]
33706 [--registers-format @var{regformat}]
33707 [--memory-contents]
33710 This command returns the set of collected objects, register names,
33711 trace state variable names, memory ranges and computed expressions
33712 that have been collected at a particular trace frame. The optional
33713 parameters to the command affect the output format in different ways.
33714 See the output description table below for more details.
33716 The reported names can be used in the normal manner to create
33717 varobjs and inspect the objects themselves. The items returned by
33718 this command are categorized so that it is clear which is a variable,
33719 which is a register, which is a trace state variable, which is a
33720 memory range and which is a computed expression.
33722 For instance, if the actions were
33724 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33725 collect *(int*)0xaf02bef0@@40
33729 the object collected in its entirety would be @code{myVar}. The
33730 object @code{myArray} would be partially collected, because only the
33731 element at index @code{myIndex} would be collected. The remaining
33732 objects would be computed expressions.
33734 An example output would be:
33738 -trace-frame-collected
33740 explicit-variables=[@{name="myVar",value="1"@}],
33741 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33742 @{name="myObj.field",value="0"@},
33743 @{name="myPtr->field",value="1"@},
33744 @{name="myCount + 2",value="3"@},
33745 @{name="$tvar1 + 1",value="43970027"@}],
33746 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33747 @{number="1",value="0x0"@},
33748 @{number="2",value="0x4"@},
33750 @{number="125",value="0x0"@}],
33751 tvars=[@{name="$tvar1",current="43970026"@}],
33752 memory=[@{address="0x0000000000602264",length="4"@},
33753 @{address="0x0000000000615bc0",length="4"@}]
33760 @item explicit-variables
33761 The set of objects that have been collected in their entirety (as
33762 opposed to collecting just a few elements of an array or a few struct
33763 members). For each object, its name and value are printed.
33764 The @code{--var-print-values} option affects how or whether the value
33765 field is output. If @var{var_pval} is 0, then print only the names;
33766 if it is 1, print also their values; and if it is 2, print the name,
33767 type and value for simple data types, and the name and type for
33768 arrays, structures and unions.
33770 @item computed-expressions
33771 The set of computed expressions that have been collected at the
33772 current trace frame. The @code{--comp-print-values} option affects
33773 this set like the @code{--var-print-values} option affects the
33774 @code{explicit-variables} set. See above.
33777 The registers that have been collected at the current trace frame.
33778 For each register collected, the name and current value are returned.
33779 The value is formatted according to the @code{--registers-format}
33780 option. See the @command{-data-list-register-values} command for a
33781 list of the allowed formats. The default is @samp{x}.
33784 The trace state variables that have been collected at the current
33785 trace frame. For each trace state variable collected, the name and
33786 current value are returned.
33789 The set of memory ranges that have been collected at the current trace
33790 frame. Its content is a list of tuples. Each tuple represents a
33791 collected memory range and has the following fields:
33795 The start address of the memory range, as hexadecimal literal.
33798 The length of the memory range, as decimal literal.
33801 The contents of the memory block, in hex. This field is only present
33802 if the @code{--memory-contents} option is specified.
33808 @subsubheading @value{GDBN} Command
33810 There is no corresponding @value{GDBN} command.
33812 @subsubheading Example
33814 @subheading -trace-list-variables
33815 @findex -trace-list-variables
33817 @subsubheading Synopsis
33820 -trace-list-variables
33823 Return a table of all defined trace variables. Each element of the
33824 table has the following fields:
33828 The name of the trace variable. This field is always present.
33831 The initial value. This is a 64-bit signed integer. This
33832 field is always present.
33835 The value the trace variable has at the moment. This is a 64-bit
33836 signed integer. This field is absent iff current value is
33837 not defined, for example if the trace was never run, or is
33842 @subsubheading @value{GDBN} Command
33844 The corresponding @value{GDBN} command is @samp{tvariables}.
33846 @subsubheading Example
33850 -trace-list-variables
33851 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33852 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33853 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33854 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33855 body=[variable=@{name="$trace_timestamp",initial="0"@}
33856 variable=@{name="$foo",initial="10",current="15"@}]@}
33860 @subheading -trace-save
33861 @findex -trace-save
33863 @subsubheading Synopsis
33866 -trace-save [-r ] @var{filename}
33869 Saves the collected trace data to @var{filename}. Without the
33870 @samp{-r} option, the data is downloaded from the target and saved
33871 in a local file. With the @samp{-r} option the target is asked
33872 to perform the save.
33874 @subsubheading @value{GDBN} Command
33876 The corresponding @value{GDBN} command is @samp{tsave}.
33879 @subheading -trace-start
33880 @findex -trace-start
33882 @subsubheading Synopsis
33888 Starts a tracing experiments. The result of this command does not
33891 @subsubheading @value{GDBN} Command
33893 The corresponding @value{GDBN} command is @samp{tstart}.
33895 @subheading -trace-status
33896 @findex -trace-status
33898 @subsubheading Synopsis
33904 Obtains the status of a tracing experiment. The result may include
33905 the following fields:
33910 May have a value of either @samp{0}, when no tracing operations are
33911 supported, @samp{1}, when all tracing operations are supported, or
33912 @samp{file} when examining trace file. In the latter case, examining
33913 of trace frame is possible but new tracing experiement cannot be
33914 started. This field is always present.
33917 May have a value of either @samp{0} or @samp{1} depending on whether
33918 tracing experiement is in progress on target. This field is present
33919 if @samp{supported} field is not @samp{0}.
33922 Report the reason why the tracing was stopped last time. This field
33923 may be absent iff tracing was never stopped on target yet. The
33924 value of @samp{request} means the tracing was stopped as result of
33925 the @code{-trace-stop} command. The value of @samp{overflow} means
33926 the tracing buffer is full. The value of @samp{disconnection} means
33927 tracing was automatically stopped when @value{GDBN} has disconnected.
33928 The value of @samp{passcount} means tracing was stopped when a
33929 tracepoint was passed a maximal number of times for that tracepoint.
33930 This field is present if @samp{supported} field is not @samp{0}.
33932 @item stopping-tracepoint
33933 The number of tracepoint whose passcount as exceeded. This field is
33934 present iff the @samp{stop-reason} field has the value of
33938 @itemx frames-created
33939 The @samp{frames} field is a count of the total number of trace frames
33940 in the trace buffer, while @samp{frames-created} is the total created
33941 during the run, including ones that were discarded, such as when a
33942 circular trace buffer filled up. Both fields are optional.
33946 These fields tell the current size of the tracing buffer and the
33947 remaining space. These fields are optional.
33950 The value of the circular trace buffer flag. @code{1} means that the
33951 trace buffer is circular and old trace frames will be discarded if
33952 necessary to make room, @code{0} means that the trace buffer is linear
33956 The value of the disconnected tracing flag. @code{1} means that
33957 tracing will continue after @value{GDBN} disconnects, @code{0} means
33958 that the trace run will stop.
33961 The filename of the trace file being examined. This field is
33962 optional, and only present when examining a trace file.
33966 @subsubheading @value{GDBN} Command
33968 The corresponding @value{GDBN} command is @samp{tstatus}.
33970 @subheading -trace-stop
33971 @findex -trace-stop
33973 @subsubheading Synopsis
33979 Stops a tracing experiment. The result of this command has the same
33980 fields as @code{-trace-status}, except that the @samp{supported} and
33981 @samp{running} fields are not output.
33983 @subsubheading @value{GDBN} Command
33985 The corresponding @value{GDBN} command is @samp{tstop}.
33988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33989 @node GDB/MI Symbol Query
33990 @section @sc{gdb/mi} Symbol Query Commands
33994 @subheading The @code{-symbol-info-address} Command
33995 @findex -symbol-info-address
33997 @subsubheading Synopsis
34000 -symbol-info-address @var{symbol}
34003 Describe where @var{symbol} is stored.
34005 @subsubheading @value{GDBN} Command
34007 The corresponding @value{GDBN} command is @samp{info address}.
34009 @subsubheading Example
34013 @subheading The @code{-symbol-info-file} Command
34014 @findex -symbol-info-file
34016 @subsubheading Synopsis
34022 Show the file for the symbol.
34024 @subsubheading @value{GDBN} Command
34026 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34027 @samp{gdb_find_file}.
34029 @subsubheading Example
34033 @subheading The @code{-symbol-info-function} Command
34034 @findex -symbol-info-function
34036 @subsubheading Synopsis
34039 -symbol-info-function
34042 Show which function the symbol lives in.
34044 @subsubheading @value{GDBN} Command
34046 @samp{gdb_get_function} in @code{gdbtk}.
34048 @subsubheading Example
34052 @subheading The @code{-symbol-info-line} Command
34053 @findex -symbol-info-line
34055 @subsubheading Synopsis
34061 Show the core addresses of the code for a source line.
34063 @subsubheading @value{GDBN} Command
34065 The corresponding @value{GDBN} command is @samp{info line}.
34066 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34068 @subsubheading Example
34072 @subheading The @code{-symbol-info-symbol} Command
34073 @findex -symbol-info-symbol
34075 @subsubheading Synopsis
34078 -symbol-info-symbol @var{addr}
34081 Describe what symbol is at location @var{addr}.
34083 @subsubheading @value{GDBN} Command
34085 The corresponding @value{GDBN} command is @samp{info symbol}.
34087 @subsubheading Example
34091 @subheading The @code{-symbol-list-functions} Command
34092 @findex -symbol-list-functions
34094 @subsubheading Synopsis
34097 -symbol-list-functions
34100 List the functions in the executable.
34102 @subsubheading @value{GDBN} Command
34104 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34105 @samp{gdb_search} in @code{gdbtk}.
34107 @subsubheading Example
34112 @subheading The @code{-symbol-list-lines} Command
34113 @findex -symbol-list-lines
34115 @subsubheading Synopsis
34118 -symbol-list-lines @var{filename}
34121 Print the list of lines that contain code and their associated program
34122 addresses for the given source filename. The entries are sorted in
34123 ascending PC order.
34125 @subsubheading @value{GDBN} Command
34127 There is no corresponding @value{GDBN} command.
34129 @subsubheading Example
34132 -symbol-list-lines basics.c
34133 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34139 @subheading The @code{-symbol-list-types} Command
34140 @findex -symbol-list-types
34142 @subsubheading Synopsis
34148 List all the type names.
34150 @subsubheading @value{GDBN} Command
34152 The corresponding commands are @samp{info types} in @value{GDBN},
34153 @samp{gdb_search} in @code{gdbtk}.
34155 @subsubheading Example
34159 @subheading The @code{-symbol-list-variables} Command
34160 @findex -symbol-list-variables
34162 @subsubheading Synopsis
34165 -symbol-list-variables
34168 List all the global and static variable names.
34170 @subsubheading @value{GDBN} Command
34172 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34174 @subsubheading Example
34178 @subheading The @code{-symbol-locate} Command
34179 @findex -symbol-locate
34181 @subsubheading Synopsis
34187 @subsubheading @value{GDBN} Command
34189 @samp{gdb_loc} in @code{gdbtk}.
34191 @subsubheading Example
34195 @subheading The @code{-symbol-type} Command
34196 @findex -symbol-type
34198 @subsubheading Synopsis
34201 -symbol-type @var{variable}
34204 Show type of @var{variable}.
34206 @subsubheading @value{GDBN} Command
34208 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34209 @samp{gdb_obj_variable}.
34211 @subsubheading Example
34216 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34217 @node GDB/MI File Commands
34218 @section @sc{gdb/mi} File Commands
34220 This section describes the GDB/MI commands to specify executable file names
34221 and to read in and obtain symbol table information.
34223 @subheading The @code{-file-exec-and-symbols} Command
34224 @findex -file-exec-and-symbols
34226 @subsubheading Synopsis
34229 -file-exec-and-symbols @var{file}
34232 Specify the executable file to be debugged. This file is the one from
34233 which the symbol table is also read. If no file is specified, the
34234 command clears the executable and symbol information. If breakpoints
34235 are set when using this command with no arguments, @value{GDBN} will produce
34236 error messages. Otherwise, no output is produced, except a completion
34239 @subsubheading @value{GDBN} Command
34241 The corresponding @value{GDBN} command is @samp{file}.
34243 @subsubheading Example
34247 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34253 @subheading The @code{-file-exec-file} Command
34254 @findex -file-exec-file
34256 @subsubheading Synopsis
34259 -file-exec-file @var{file}
34262 Specify the executable file to be debugged. Unlike
34263 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34264 from this file. If used without argument, @value{GDBN} clears the information
34265 about the executable file. No output is produced, except a completion
34268 @subsubheading @value{GDBN} Command
34270 The corresponding @value{GDBN} command is @samp{exec-file}.
34272 @subsubheading Example
34276 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34283 @subheading The @code{-file-list-exec-sections} Command
34284 @findex -file-list-exec-sections
34286 @subsubheading Synopsis
34289 -file-list-exec-sections
34292 List the sections of the current executable file.
34294 @subsubheading @value{GDBN} Command
34296 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34297 information as this command. @code{gdbtk} has a corresponding command
34298 @samp{gdb_load_info}.
34300 @subsubheading Example
34305 @subheading The @code{-file-list-exec-source-file} Command
34306 @findex -file-list-exec-source-file
34308 @subsubheading Synopsis
34311 -file-list-exec-source-file
34314 List the line number, the current source file, and the absolute path
34315 to the current source file for the current executable. The macro
34316 information field has a value of @samp{1} or @samp{0} depending on
34317 whether or not the file includes preprocessor macro information.
34319 @subsubheading @value{GDBN} Command
34321 The @value{GDBN} equivalent is @samp{info source}
34323 @subsubheading Example
34327 123-file-list-exec-source-file
34328 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34333 @subheading The @code{-file-list-exec-source-files} Command
34334 @findex -file-list-exec-source-files
34336 @subsubheading Synopsis
34339 -file-list-exec-source-files
34342 List the source files for the current executable.
34344 It will always output both the filename and fullname (absolute file
34345 name) of a source file.
34347 @subsubheading @value{GDBN} Command
34349 The @value{GDBN} equivalent is @samp{info sources}.
34350 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34352 @subsubheading Example
34355 -file-list-exec-source-files
34357 @{file=foo.c,fullname=/home/foo.c@},
34358 @{file=/home/bar.c,fullname=/home/bar.c@},
34359 @{file=gdb_could_not_find_fullpath.c@}]
34364 @subheading The @code{-file-list-shared-libraries} Command
34365 @findex -file-list-shared-libraries
34367 @subsubheading Synopsis
34370 -file-list-shared-libraries
34373 List the shared libraries in the program.
34375 @subsubheading @value{GDBN} Command
34377 The corresponding @value{GDBN} command is @samp{info shared}.
34379 @subsubheading Example
34383 @subheading The @code{-file-list-symbol-files} Command
34384 @findex -file-list-symbol-files
34386 @subsubheading Synopsis
34389 -file-list-symbol-files
34394 @subsubheading @value{GDBN} Command
34396 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34398 @subsubheading Example
34403 @subheading The @code{-file-symbol-file} Command
34404 @findex -file-symbol-file
34406 @subsubheading Synopsis
34409 -file-symbol-file @var{file}
34412 Read symbol table info from the specified @var{file} argument. When
34413 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34414 produced, except for a completion notification.
34416 @subsubheading @value{GDBN} Command
34418 The corresponding @value{GDBN} command is @samp{symbol-file}.
34420 @subsubheading Example
34424 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34431 @node GDB/MI Memory Overlay Commands
34432 @section @sc{gdb/mi} Memory Overlay Commands
34434 The memory overlay commands are not implemented.
34436 @c @subheading -overlay-auto
34438 @c @subheading -overlay-list-mapping-state
34440 @c @subheading -overlay-list-overlays
34442 @c @subheading -overlay-map
34444 @c @subheading -overlay-off
34446 @c @subheading -overlay-on
34448 @c @subheading -overlay-unmap
34450 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34451 @node GDB/MI Signal Handling Commands
34452 @section @sc{gdb/mi} Signal Handling Commands
34454 Signal handling commands are not implemented.
34456 @c @subheading -signal-handle
34458 @c @subheading -signal-list-handle-actions
34460 @c @subheading -signal-list-signal-types
34464 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34465 @node GDB/MI Target Manipulation
34466 @section @sc{gdb/mi} Target Manipulation Commands
34469 @subheading The @code{-target-attach} Command
34470 @findex -target-attach
34472 @subsubheading Synopsis
34475 -target-attach @var{pid} | @var{gid} | @var{file}
34478 Attach to a process @var{pid} or a file @var{file} outside of
34479 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34480 group, the id previously returned by
34481 @samp{-list-thread-groups --available} must be used.
34483 @subsubheading @value{GDBN} Command
34485 The corresponding @value{GDBN} command is @samp{attach}.
34487 @subsubheading Example
34491 =thread-created,id="1"
34492 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34498 @subheading The @code{-target-compare-sections} Command
34499 @findex -target-compare-sections
34501 @subsubheading Synopsis
34504 -target-compare-sections [ @var{section} ]
34507 Compare data of section @var{section} on target to the exec file.
34508 Without the argument, all sections are compared.
34510 @subsubheading @value{GDBN} Command
34512 The @value{GDBN} equivalent is @samp{compare-sections}.
34514 @subsubheading Example
34519 @subheading The @code{-target-detach} Command
34520 @findex -target-detach
34522 @subsubheading Synopsis
34525 -target-detach [ @var{pid} | @var{gid} ]
34528 Detach from the remote target which normally resumes its execution.
34529 If either @var{pid} or @var{gid} is specified, detaches from either
34530 the specified process, or specified thread group. There's no output.
34532 @subsubheading @value{GDBN} Command
34534 The corresponding @value{GDBN} command is @samp{detach}.
34536 @subsubheading Example
34546 @subheading The @code{-target-disconnect} Command
34547 @findex -target-disconnect
34549 @subsubheading Synopsis
34555 Disconnect from the remote target. There's no output and the target is
34556 generally not resumed.
34558 @subsubheading @value{GDBN} Command
34560 The corresponding @value{GDBN} command is @samp{disconnect}.
34562 @subsubheading Example
34572 @subheading The @code{-target-download} Command
34573 @findex -target-download
34575 @subsubheading Synopsis
34581 Loads the executable onto the remote target.
34582 It prints out an update message every half second, which includes the fields:
34586 The name of the section.
34588 The size of what has been sent so far for that section.
34590 The size of the section.
34592 The total size of what was sent so far (the current and the previous sections).
34594 The size of the overall executable to download.
34598 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34599 @sc{gdb/mi} Output Syntax}).
34601 In addition, it prints the name and size of the sections, as they are
34602 downloaded. These messages include the following fields:
34606 The name of the section.
34608 The size of the section.
34610 The size of the overall executable to download.
34614 At the end, a summary is printed.
34616 @subsubheading @value{GDBN} Command
34618 The corresponding @value{GDBN} command is @samp{load}.
34620 @subsubheading Example
34622 Note: each status message appears on a single line. Here the messages
34623 have been broken down so that they can fit onto a page.
34628 +download,@{section=".text",section-size="6668",total-size="9880"@}
34629 +download,@{section=".text",section-sent="512",section-size="6668",
34630 total-sent="512",total-size="9880"@}
34631 +download,@{section=".text",section-sent="1024",section-size="6668",
34632 total-sent="1024",total-size="9880"@}
34633 +download,@{section=".text",section-sent="1536",section-size="6668",
34634 total-sent="1536",total-size="9880"@}
34635 +download,@{section=".text",section-sent="2048",section-size="6668",
34636 total-sent="2048",total-size="9880"@}
34637 +download,@{section=".text",section-sent="2560",section-size="6668",
34638 total-sent="2560",total-size="9880"@}
34639 +download,@{section=".text",section-sent="3072",section-size="6668",
34640 total-sent="3072",total-size="9880"@}
34641 +download,@{section=".text",section-sent="3584",section-size="6668",
34642 total-sent="3584",total-size="9880"@}
34643 +download,@{section=".text",section-sent="4096",section-size="6668",
34644 total-sent="4096",total-size="9880"@}
34645 +download,@{section=".text",section-sent="4608",section-size="6668",
34646 total-sent="4608",total-size="9880"@}
34647 +download,@{section=".text",section-sent="5120",section-size="6668",
34648 total-sent="5120",total-size="9880"@}
34649 +download,@{section=".text",section-sent="5632",section-size="6668",
34650 total-sent="5632",total-size="9880"@}
34651 +download,@{section=".text",section-sent="6144",section-size="6668",
34652 total-sent="6144",total-size="9880"@}
34653 +download,@{section=".text",section-sent="6656",section-size="6668",
34654 total-sent="6656",total-size="9880"@}
34655 +download,@{section=".init",section-size="28",total-size="9880"@}
34656 +download,@{section=".fini",section-size="28",total-size="9880"@}
34657 +download,@{section=".data",section-size="3156",total-size="9880"@}
34658 +download,@{section=".data",section-sent="512",section-size="3156",
34659 total-sent="7236",total-size="9880"@}
34660 +download,@{section=".data",section-sent="1024",section-size="3156",
34661 total-sent="7748",total-size="9880"@}
34662 +download,@{section=".data",section-sent="1536",section-size="3156",
34663 total-sent="8260",total-size="9880"@}
34664 +download,@{section=".data",section-sent="2048",section-size="3156",
34665 total-sent="8772",total-size="9880"@}
34666 +download,@{section=".data",section-sent="2560",section-size="3156",
34667 total-sent="9284",total-size="9880"@}
34668 +download,@{section=".data",section-sent="3072",section-size="3156",
34669 total-sent="9796",total-size="9880"@}
34670 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34677 @subheading The @code{-target-exec-status} Command
34678 @findex -target-exec-status
34680 @subsubheading Synopsis
34683 -target-exec-status
34686 Provide information on the state of the target (whether it is running or
34687 not, for instance).
34689 @subsubheading @value{GDBN} Command
34691 There's no equivalent @value{GDBN} command.
34693 @subsubheading Example
34697 @subheading The @code{-target-list-available-targets} Command
34698 @findex -target-list-available-targets
34700 @subsubheading Synopsis
34703 -target-list-available-targets
34706 List the possible targets to connect to.
34708 @subsubheading @value{GDBN} Command
34710 The corresponding @value{GDBN} command is @samp{help target}.
34712 @subsubheading Example
34716 @subheading The @code{-target-list-current-targets} Command
34717 @findex -target-list-current-targets
34719 @subsubheading Synopsis
34722 -target-list-current-targets
34725 Describe the current target.
34727 @subsubheading @value{GDBN} Command
34729 The corresponding information is printed by @samp{info file} (among
34732 @subsubheading Example
34736 @subheading The @code{-target-list-parameters} Command
34737 @findex -target-list-parameters
34739 @subsubheading Synopsis
34742 -target-list-parameters
34748 @subsubheading @value{GDBN} Command
34752 @subsubheading Example
34756 @subheading The @code{-target-select} Command
34757 @findex -target-select
34759 @subsubheading Synopsis
34762 -target-select @var{type} @var{parameters @dots{}}
34765 Connect @value{GDBN} to the remote target. This command takes two args:
34769 The type of target, for instance @samp{remote}, etc.
34770 @item @var{parameters}
34771 Device names, host names and the like. @xref{Target Commands, ,
34772 Commands for Managing Targets}, for more details.
34775 The output is a connection notification, followed by the address at
34776 which the target program is, in the following form:
34779 ^connected,addr="@var{address}",func="@var{function name}",
34780 args=[@var{arg list}]
34783 @subsubheading @value{GDBN} Command
34785 The corresponding @value{GDBN} command is @samp{target}.
34787 @subsubheading Example
34791 -target-select remote /dev/ttya
34792 ^connected,addr="0xfe00a300",func="??",args=[]
34796 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34797 @node GDB/MI File Transfer Commands
34798 @section @sc{gdb/mi} File Transfer Commands
34801 @subheading The @code{-target-file-put} Command
34802 @findex -target-file-put
34804 @subsubheading Synopsis
34807 -target-file-put @var{hostfile} @var{targetfile}
34810 Copy file @var{hostfile} from the host system (the machine running
34811 @value{GDBN}) to @var{targetfile} on the target system.
34813 @subsubheading @value{GDBN} Command
34815 The corresponding @value{GDBN} command is @samp{remote put}.
34817 @subsubheading Example
34821 -target-file-put localfile remotefile
34827 @subheading The @code{-target-file-get} Command
34828 @findex -target-file-get
34830 @subsubheading Synopsis
34833 -target-file-get @var{targetfile} @var{hostfile}
34836 Copy file @var{targetfile} from the target system to @var{hostfile}
34837 on the host system.
34839 @subsubheading @value{GDBN} Command
34841 The corresponding @value{GDBN} command is @samp{remote get}.
34843 @subsubheading Example
34847 -target-file-get remotefile localfile
34853 @subheading The @code{-target-file-delete} Command
34854 @findex -target-file-delete
34856 @subsubheading Synopsis
34859 -target-file-delete @var{targetfile}
34862 Delete @var{targetfile} from the target system.
34864 @subsubheading @value{GDBN} Command
34866 The corresponding @value{GDBN} command is @samp{remote delete}.
34868 @subsubheading Example
34872 -target-file-delete remotefile
34878 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34879 @node GDB/MI Ada Exceptions Commands
34880 @section Ada Exceptions @sc{gdb/mi} Commands
34882 @subheading The @code{-info-ada-exceptions} Command
34883 @findex -info-ada-exceptions
34885 @subsubheading Synopsis
34888 -info-ada-exceptions [ @var{regexp}]
34891 List all Ada exceptions defined within the program being debugged.
34892 With a regular expression @var{regexp}, only those exceptions whose
34893 names match @var{regexp} are listed.
34895 @subsubheading @value{GDBN} Command
34897 The corresponding @value{GDBN} command is @samp{info exceptions}.
34899 @subsubheading Result
34901 The result is a table of Ada exceptions. The following columns are
34902 defined for each exception:
34906 The name of the exception.
34909 The address of the exception.
34913 @subsubheading Example
34916 -info-ada-exceptions aint
34917 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34918 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34919 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34920 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34921 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34924 @subheading Catching Ada Exceptions
34926 The commands describing how to ask @value{GDBN} to stop when a program
34927 raises an exception are described at @ref{Ada Exception GDB/MI
34928 Catchpoint Commands}.
34931 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34932 @node GDB/MI Miscellaneous Commands
34933 @section Miscellaneous @sc{gdb/mi} Commands
34935 @c @subheading -gdb-complete
34937 @subheading The @code{-gdb-exit} Command
34940 @subsubheading Synopsis
34946 Exit @value{GDBN} immediately.
34948 @subsubheading @value{GDBN} Command
34950 Approximately corresponds to @samp{quit}.
34952 @subsubheading Example
34962 @subheading The @code{-exec-abort} Command
34963 @findex -exec-abort
34965 @subsubheading Synopsis
34971 Kill the inferior running program.
34973 @subsubheading @value{GDBN} Command
34975 The corresponding @value{GDBN} command is @samp{kill}.
34977 @subsubheading Example
34982 @subheading The @code{-gdb-set} Command
34985 @subsubheading Synopsis
34991 Set an internal @value{GDBN} variable.
34992 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34994 @subsubheading @value{GDBN} Command
34996 The corresponding @value{GDBN} command is @samp{set}.
34998 @subsubheading Example
35008 @subheading The @code{-gdb-show} Command
35011 @subsubheading Synopsis
35017 Show the current value of a @value{GDBN} variable.
35019 @subsubheading @value{GDBN} Command
35021 The corresponding @value{GDBN} command is @samp{show}.
35023 @subsubheading Example
35032 @c @subheading -gdb-source
35035 @subheading The @code{-gdb-version} Command
35036 @findex -gdb-version
35038 @subsubheading Synopsis
35044 Show version information for @value{GDBN}. Used mostly in testing.
35046 @subsubheading @value{GDBN} Command
35048 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35049 default shows this information when you start an interactive session.
35051 @subsubheading Example
35053 @c This example modifies the actual output from GDB to avoid overfull
35059 ~Copyright 2000 Free Software Foundation, Inc.
35060 ~GDB is free software, covered by the GNU General Public License, and
35061 ~you are welcome to change it and/or distribute copies of it under
35062 ~ certain conditions.
35063 ~Type "show copying" to see the conditions.
35064 ~There is absolutely no warranty for GDB. Type "show warranty" for
35066 ~This GDB was configured as
35067 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35072 @subheading The @code{-list-features} Command
35073 @findex -list-features
35075 Returns a list of particular features of the MI protocol that
35076 this version of gdb implements. A feature can be a command,
35077 or a new field in an output of some command, or even an
35078 important bugfix. While a frontend can sometimes detect presence
35079 of a feature at runtime, it is easier to perform detection at debugger
35082 The command returns a list of strings, with each string naming an
35083 available feature. Each returned string is just a name, it does not
35084 have any internal structure. The list of possible feature names
35090 (gdb) -list-features
35091 ^done,result=["feature1","feature2"]
35094 The current list of features is:
35097 @item frozen-varobjs
35098 Indicates support for the @code{-var-set-frozen} command, as well
35099 as possible presense of the @code{frozen} field in the output
35100 of @code{-varobj-create}.
35101 @item pending-breakpoints
35102 Indicates support for the @option{-f} option to the @code{-break-insert}
35105 Indicates Python scripting support, Python-based
35106 pretty-printing commands, and possible presence of the
35107 @samp{display_hint} field in the output of @code{-var-list-children}
35109 Indicates support for the @code{-thread-info} command.
35110 @item data-read-memory-bytes
35111 Indicates support for the @code{-data-read-memory-bytes} and the
35112 @code{-data-write-memory-bytes} commands.
35113 @item breakpoint-notifications
35114 Indicates that changes to breakpoints and breakpoints created via the
35115 CLI will be announced via async records.
35116 @item ada-task-info
35117 Indicates support for the @code{-ada-task-info} command.
35118 @item ada-exceptions
35119 Indicates support for the following commands, all of them related to Ada
35120 exceptions: @code{-info-ada-exceptions}, @code{-catch-assert} and
35121 @code{-catch-exception}.
35124 @subheading The @code{-list-target-features} Command
35125 @findex -list-target-features
35127 Returns a list of particular features that are supported by the
35128 target. Those features affect the permitted MI commands, but
35129 unlike the features reported by the @code{-list-features} command, the
35130 features depend on which target GDB is using at the moment. Whenever
35131 a target can change, due to commands such as @code{-target-select},
35132 @code{-target-attach} or @code{-exec-run}, the list of target features
35133 may change, and the frontend should obtain it again.
35137 (gdb) -list-target-features
35138 ^done,result=["async"]
35141 The current list of features is:
35145 Indicates that the target is capable of asynchronous command
35146 execution, which means that @value{GDBN} will accept further commands
35147 while the target is running.
35150 Indicates that the target is capable of reverse execution.
35151 @xref{Reverse Execution}, for more information.
35155 @subheading The @code{-list-thread-groups} Command
35156 @findex -list-thread-groups
35158 @subheading Synopsis
35161 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35164 Lists thread groups (@pxref{Thread groups}). When a single thread
35165 group is passed as the argument, lists the children of that group.
35166 When several thread group are passed, lists information about those
35167 thread groups. Without any parameters, lists information about all
35168 top-level thread groups.
35170 Normally, thread groups that are being debugged are reported.
35171 With the @samp{--available} option, @value{GDBN} reports thread groups
35172 available on the target.
35174 The output of this command may have either a @samp{threads} result or
35175 a @samp{groups} result. The @samp{thread} result has a list of tuples
35176 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35177 Information}). The @samp{groups} result has a list of tuples as value,
35178 each tuple describing a thread group. If top-level groups are
35179 requested (that is, no parameter is passed), or when several groups
35180 are passed, the output always has a @samp{groups} result. The format
35181 of the @samp{group} result is described below.
35183 To reduce the number of roundtrips it's possible to list thread groups
35184 together with their children, by passing the @samp{--recurse} option
35185 and the recursion depth. Presently, only recursion depth of 1 is
35186 permitted. If this option is present, then every reported thread group
35187 will also include its children, either as @samp{group} or
35188 @samp{threads} field.
35190 In general, any combination of option and parameters is permitted, with
35191 the following caveats:
35195 When a single thread group is passed, the output will typically
35196 be the @samp{threads} result. Because threads may not contain
35197 anything, the @samp{recurse} option will be ignored.
35200 When the @samp{--available} option is passed, limited information may
35201 be available. In particular, the list of threads of a process might
35202 be inaccessible. Further, specifying specific thread groups might
35203 not give any performance advantage over listing all thread groups.
35204 The frontend should assume that @samp{-list-thread-groups --available}
35205 is always an expensive operation and cache the results.
35209 The @samp{groups} result is a list of tuples, where each tuple may
35210 have the following fields:
35214 Identifier of the thread group. This field is always present.
35215 The identifier is an opaque string; frontends should not try to
35216 convert it to an integer, even though it might look like one.
35219 The type of the thread group. At present, only @samp{process} is a
35223 The target-specific process identifier. This field is only present
35224 for thread groups of type @samp{process} and only if the process exists.
35227 The number of children this thread group has. This field may be
35228 absent for an available thread group.
35231 This field has a list of tuples as value, each tuple describing a
35232 thread. It may be present if the @samp{--recurse} option is
35233 specified, and it's actually possible to obtain the threads.
35236 This field is a list of integers, each identifying a core that one
35237 thread of the group is running on. This field may be absent if
35238 such information is not available.
35241 The name of the executable file that corresponds to this thread group.
35242 The field is only present for thread groups of type @samp{process},
35243 and only if there is a corresponding executable file.
35247 @subheading Example
35251 -list-thread-groups
35252 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35253 -list-thread-groups 17
35254 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35255 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35256 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35257 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35258 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35259 -list-thread-groups --available
35260 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35261 -list-thread-groups --available --recurse 1
35262 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35263 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35264 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35265 -list-thread-groups --available --recurse 1 17 18
35266 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35267 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35268 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35271 @subheading The @code{-info-os} Command
35274 @subsubheading Synopsis
35277 -info-os [ @var{type} ]
35280 If no argument is supplied, the command returns a table of available
35281 operating-system-specific information types. If one of these types is
35282 supplied as an argument @var{type}, then the command returns a table
35283 of data of that type.
35285 The types of information available depend on the target operating
35288 @subsubheading @value{GDBN} Command
35290 The corresponding @value{GDBN} command is @samp{info os}.
35292 @subsubheading Example
35294 When run on a @sc{gnu}/Linux system, the output will look something
35300 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35301 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35302 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35303 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35304 body=[item=@{col0="processes",col1="Listing of all processes",
35305 col2="Processes"@},
35306 item=@{col0="procgroups",col1="Listing of all process groups",
35307 col2="Process groups"@},
35308 item=@{col0="threads",col1="Listing of all threads",
35310 item=@{col0="files",col1="Listing of all file descriptors",
35311 col2="File descriptors"@},
35312 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35314 item=@{col0="shm",col1="Listing of all shared-memory regions",
35315 col2="Shared-memory regions"@},
35316 item=@{col0="semaphores",col1="Listing of all semaphores",
35317 col2="Semaphores"@},
35318 item=@{col0="msg",col1="Listing of all message queues",
35319 col2="Message queues"@},
35320 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35321 col2="Kernel modules"@}]@}
35324 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35325 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35326 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35327 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35328 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35329 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35330 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35331 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35333 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35334 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35338 (Note that the MI output here includes a @code{"Title"} column that
35339 does not appear in command-line @code{info os}; this column is useful
35340 for MI clients that want to enumerate the types of data, such as in a
35341 popup menu, but is needless clutter on the command line, and
35342 @code{info os} omits it.)
35344 @subheading The @code{-add-inferior} Command
35345 @findex -add-inferior
35347 @subheading Synopsis
35353 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35354 inferior is not associated with any executable. Such association may
35355 be established with the @samp{-file-exec-and-symbols} command
35356 (@pxref{GDB/MI File Commands}). The command response has a single
35357 field, @samp{inferior}, whose value is the identifier of the
35358 thread group corresponding to the new inferior.
35360 @subheading Example
35365 ^done,inferior="i3"
35368 @subheading The @code{-interpreter-exec} Command
35369 @findex -interpreter-exec
35371 @subheading Synopsis
35374 -interpreter-exec @var{interpreter} @var{command}
35376 @anchor{-interpreter-exec}
35378 Execute the specified @var{command} in the given @var{interpreter}.
35380 @subheading @value{GDBN} Command
35382 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35384 @subheading Example
35388 -interpreter-exec console "break main"
35389 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35390 &"During symbol reading, bad structure-type format.\n"
35391 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35396 @subheading The @code{-inferior-tty-set} Command
35397 @findex -inferior-tty-set
35399 @subheading Synopsis
35402 -inferior-tty-set /dev/pts/1
35405 Set terminal for future runs of the program being debugged.
35407 @subheading @value{GDBN} Command
35409 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35411 @subheading Example
35415 -inferior-tty-set /dev/pts/1
35420 @subheading The @code{-inferior-tty-show} Command
35421 @findex -inferior-tty-show
35423 @subheading Synopsis
35429 Show terminal for future runs of program being debugged.
35431 @subheading @value{GDBN} Command
35433 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35435 @subheading Example
35439 -inferior-tty-set /dev/pts/1
35443 ^done,inferior_tty_terminal="/dev/pts/1"
35447 @subheading The @code{-enable-timings} Command
35448 @findex -enable-timings
35450 @subheading Synopsis
35453 -enable-timings [yes | no]
35456 Toggle the printing of the wallclock, user and system times for an MI
35457 command as a field in its output. This command is to help frontend
35458 developers optimize the performance of their code. No argument is
35459 equivalent to @samp{yes}.
35461 @subheading @value{GDBN} Command
35465 @subheading Example
35473 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35474 addr="0x080484ed",func="main",file="myprog.c",
35475 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35477 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35485 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35486 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35487 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35488 fullname="/home/nickrob/myprog.c",line="73"@}
35493 @chapter @value{GDBN} Annotations
35495 This chapter describes annotations in @value{GDBN}. Annotations were
35496 designed to interface @value{GDBN} to graphical user interfaces or other
35497 similar programs which want to interact with @value{GDBN} at a
35498 relatively high level.
35500 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35504 This is Edition @value{EDITION}, @value{DATE}.
35508 * Annotations Overview:: What annotations are; the general syntax.
35509 * Server Prefix:: Issuing a command without affecting user state.
35510 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35511 * Errors:: Annotations for error messages.
35512 * Invalidation:: Some annotations describe things now invalid.
35513 * Annotations for Running::
35514 Whether the program is running, how it stopped, etc.
35515 * Source Annotations:: Annotations describing source code.
35518 @node Annotations Overview
35519 @section What is an Annotation?
35520 @cindex annotations
35522 Annotations start with a newline character, two @samp{control-z}
35523 characters, and the name of the annotation. If there is no additional
35524 information associated with this annotation, the name of the annotation
35525 is followed immediately by a newline. If there is additional
35526 information, the name of the annotation is followed by a space, the
35527 additional information, and a newline. The additional information
35528 cannot contain newline characters.
35530 Any output not beginning with a newline and two @samp{control-z}
35531 characters denotes literal output from @value{GDBN}. Currently there is
35532 no need for @value{GDBN} to output a newline followed by two
35533 @samp{control-z} characters, but if there was such a need, the
35534 annotations could be extended with an @samp{escape} annotation which
35535 means those three characters as output.
35537 The annotation @var{level}, which is specified using the
35538 @option{--annotate} command line option (@pxref{Mode Options}), controls
35539 how much information @value{GDBN} prints together with its prompt,
35540 values of expressions, source lines, and other types of output. Level 0
35541 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35542 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35543 for programs that control @value{GDBN}, and level 2 annotations have
35544 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35545 Interface, annotate, GDB's Obsolete Annotations}).
35548 @kindex set annotate
35549 @item set annotate @var{level}
35550 The @value{GDBN} command @code{set annotate} sets the level of
35551 annotations to the specified @var{level}.
35553 @item show annotate
35554 @kindex show annotate
35555 Show the current annotation level.
35558 This chapter describes level 3 annotations.
35560 A simple example of starting up @value{GDBN} with annotations is:
35563 $ @kbd{gdb --annotate=3}
35565 Copyright 2003 Free Software Foundation, Inc.
35566 GDB is free software, covered by the GNU General Public License,
35567 and you are welcome to change it and/or distribute copies of it
35568 under certain conditions.
35569 Type "show copying" to see the conditions.
35570 There is absolutely no warranty for GDB. Type "show warranty"
35572 This GDB was configured as "i386-pc-linux-gnu"
35583 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35584 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35585 denotes a @samp{control-z} character) are annotations; the rest is
35586 output from @value{GDBN}.
35588 @node Server Prefix
35589 @section The Server Prefix
35590 @cindex server prefix
35592 If you prefix a command with @samp{server } then it will not affect
35593 the command history, nor will it affect @value{GDBN}'s notion of which
35594 command to repeat if @key{RET} is pressed on a line by itself. This
35595 means that commands can be run behind a user's back by a front-end in
35596 a transparent manner.
35598 The @code{server } prefix does not affect the recording of values into
35599 the value history; to print a value without recording it into the
35600 value history, use the @code{output} command instead of the
35601 @code{print} command.
35603 Using this prefix also disables confirmation requests
35604 (@pxref{confirmation requests}).
35607 @section Annotation for @value{GDBN} Input
35609 @cindex annotations for prompts
35610 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35611 to know when to send output, when the output from a given command is
35614 Different kinds of input each have a different @dfn{input type}. Each
35615 input type has three annotations: a @code{pre-} annotation, which
35616 denotes the beginning of any prompt which is being output, a plain
35617 annotation, which denotes the end of the prompt, and then a @code{post-}
35618 annotation which denotes the end of any echo which may (or may not) be
35619 associated with the input. For example, the @code{prompt} input type
35620 features the following annotations:
35628 The input types are
35631 @findex pre-prompt annotation
35632 @findex prompt annotation
35633 @findex post-prompt annotation
35635 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35637 @findex pre-commands annotation
35638 @findex commands annotation
35639 @findex post-commands annotation
35641 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35642 command. The annotations are repeated for each command which is input.
35644 @findex pre-overload-choice annotation
35645 @findex overload-choice annotation
35646 @findex post-overload-choice annotation
35647 @item overload-choice
35648 When @value{GDBN} wants the user to select between various overloaded functions.
35650 @findex pre-query annotation
35651 @findex query annotation
35652 @findex post-query annotation
35654 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35656 @findex pre-prompt-for-continue annotation
35657 @findex prompt-for-continue annotation
35658 @findex post-prompt-for-continue annotation
35659 @item prompt-for-continue
35660 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35661 expect this to work well; instead use @code{set height 0} to disable
35662 prompting. This is because the counting of lines is buggy in the
35663 presence of annotations.
35668 @cindex annotations for errors, warnings and interrupts
35670 @findex quit annotation
35675 This annotation occurs right before @value{GDBN} responds to an interrupt.
35677 @findex error annotation
35682 This annotation occurs right before @value{GDBN} responds to an error.
35684 Quit and error annotations indicate that any annotations which @value{GDBN} was
35685 in the middle of may end abruptly. For example, if a
35686 @code{value-history-begin} annotation is followed by a @code{error}, one
35687 cannot expect to receive the matching @code{value-history-end}. One
35688 cannot expect not to receive it either, however; an error annotation
35689 does not necessarily mean that @value{GDBN} is immediately returning all the way
35692 @findex error-begin annotation
35693 A quit or error annotation may be preceded by
35699 Any output between that and the quit or error annotation is the error
35702 Warning messages are not yet annotated.
35703 @c If we want to change that, need to fix warning(), type_error(),
35704 @c range_error(), and possibly other places.
35707 @section Invalidation Notices
35709 @cindex annotations for invalidation messages
35710 The following annotations say that certain pieces of state may have
35714 @findex frames-invalid annotation
35715 @item ^Z^Zframes-invalid
35717 The frames (for example, output from the @code{backtrace} command) may
35720 @findex breakpoints-invalid annotation
35721 @item ^Z^Zbreakpoints-invalid
35723 The breakpoints may have changed. For example, the user just added or
35724 deleted a breakpoint.
35727 @node Annotations for Running
35728 @section Running the Program
35729 @cindex annotations for running programs
35731 @findex starting annotation
35732 @findex stopping annotation
35733 When the program starts executing due to a @value{GDBN} command such as
35734 @code{step} or @code{continue},
35740 is output. When the program stops,
35746 is output. Before the @code{stopped} annotation, a variety of
35747 annotations describe how the program stopped.
35750 @findex exited annotation
35751 @item ^Z^Zexited @var{exit-status}
35752 The program exited, and @var{exit-status} is the exit status (zero for
35753 successful exit, otherwise nonzero).
35755 @findex signalled annotation
35756 @findex signal-name annotation
35757 @findex signal-name-end annotation
35758 @findex signal-string annotation
35759 @findex signal-string-end annotation
35760 @item ^Z^Zsignalled
35761 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35762 annotation continues:
35768 ^Z^Zsignal-name-end
35772 ^Z^Zsignal-string-end
35777 where @var{name} is the name of the signal, such as @code{SIGILL} or
35778 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35779 as @code{Illegal Instruction} or @code{Segmentation fault}.
35780 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35781 user's benefit and have no particular format.
35783 @findex signal annotation
35785 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35786 just saying that the program received the signal, not that it was
35787 terminated with it.
35789 @findex breakpoint annotation
35790 @item ^Z^Zbreakpoint @var{number}
35791 The program hit breakpoint number @var{number}.
35793 @findex watchpoint annotation
35794 @item ^Z^Zwatchpoint @var{number}
35795 The program hit watchpoint number @var{number}.
35798 @node Source Annotations
35799 @section Displaying Source
35800 @cindex annotations for source display
35802 @findex source annotation
35803 The following annotation is used instead of displaying source code:
35806 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35809 where @var{filename} is an absolute file name indicating which source
35810 file, @var{line} is the line number within that file (where 1 is the
35811 first line in the file), @var{character} is the character position
35812 within the file (where 0 is the first character in the file) (for most
35813 debug formats this will necessarily point to the beginning of a line),
35814 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35815 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35816 @var{addr} is the address in the target program associated with the
35817 source which is being displayed. @var{addr} is in the form @samp{0x}
35818 followed by one or more lowercase hex digits (note that this does not
35819 depend on the language).
35821 @node JIT Interface
35822 @chapter JIT Compilation Interface
35823 @cindex just-in-time compilation
35824 @cindex JIT compilation interface
35826 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35827 interface. A JIT compiler is a program or library that generates native
35828 executable code at runtime and executes it, usually in order to achieve good
35829 performance while maintaining platform independence.
35831 Programs that use JIT compilation are normally difficult to debug because
35832 portions of their code are generated at runtime, instead of being loaded from
35833 object files, which is where @value{GDBN} normally finds the program's symbols
35834 and debug information. In order to debug programs that use JIT compilation,
35835 @value{GDBN} has an interface that allows the program to register in-memory
35836 symbol files with @value{GDBN} at runtime.
35838 If you are using @value{GDBN} to debug a program that uses this interface, then
35839 it should work transparently so long as you have not stripped the binary. If
35840 you are developing a JIT compiler, then the interface is documented in the rest
35841 of this chapter. At this time, the only known client of this interface is the
35844 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35845 JIT compiler communicates with @value{GDBN} by writing data into a global
35846 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35847 attaches, it reads a linked list of symbol files from the global variable to
35848 find existing code, and puts a breakpoint in the function so that it can find
35849 out about additional code.
35852 * Declarations:: Relevant C struct declarations
35853 * Registering Code:: Steps to register code
35854 * Unregistering Code:: Steps to unregister code
35855 * Custom Debug Info:: Emit debug information in a custom format
35859 @section JIT Declarations
35861 These are the relevant struct declarations that a C program should include to
35862 implement the interface:
35872 struct jit_code_entry
35874 struct jit_code_entry *next_entry;
35875 struct jit_code_entry *prev_entry;
35876 const char *symfile_addr;
35877 uint64_t symfile_size;
35880 struct jit_descriptor
35883 /* This type should be jit_actions_t, but we use uint32_t
35884 to be explicit about the bitwidth. */
35885 uint32_t action_flag;
35886 struct jit_code_entry *relevant_entry;
35887 struct jit_code_entry *first_entry;
35890 /* GDB puts a breakpoint in this function. */
35891 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35893 /* Make sure to specify the version statically, because the
35894 debugger may check the version before we can set it. */
35895 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35898 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35899 modifications to this global data properly, which can easily be done by putting
35900 a global mutex around modifications to these structures.
35902 @node Registering Code
35903 @section Registering Code
35905 To register code with @value{GDBN}, the JIT should follow this protocol:
35909 Generate an object file in memory with symbols and other desired debug
35910 information. The file must include the virtual addresses of the sections.
35913 Create a code entry for the file, which gives the start and size of the symbol
35917 Add it to the linked list in the JIT descriptor.
35920 Point the relevant_entry field of the descriptor at the entry.
35923 Set @code{action_flag} to @code{JIT_REGISTER} and call
35924 @code{__jit_debug_register_code}.
35927 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35928 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35929 new code. However, the linked list must still be maintained in order to allow
35930 @value{GDBN} to attach to a running process and still find the symbol files.
35932 @node Unregistering Code
35933 @section Unregistering Code
35935 If code is freed, then the JIT should use the following protocol:
35939 Remove the code entry corresponding to the code from the linked list.
35942 Point the @code{relevant_entry} field of the descriptor at the code entry.
35945 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35946 @code{__jit_debug_register_code}.
35949 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35950 and the JIT will leak the memory used for the associated symbol files.
35952 @node Custom Debug Info
35953 @section Custom Debug Info
35954 @cindex custom JIT debug info
35955 @cindex JIT debug info reader
35957 Generating debug information in platform-native file formats (like ELF
35958 or COFF) may be an overkill for JIT compilers; especially if all the
35959 debug info is used for is displaying a meaningful backtrace. The
35960 issue can be resolved by having the JIT writers decide on a debug info
35961 format and also provide a reader that parses the debug info generated
35962 by the JIT compiler. This section gives a brief overview on writing
35963 such a parser. More specific details can be found in the source file
35964 @file{gdb/jit-reader.in}, which is also installed as a header at
35965 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35967 The reader is implemented as a shared object (so this functionality is
35968 not available on platforms which don't allow loading shared objects at
35969 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35970 @code{jit-reader-unload} are provided, to be used to load and unload
35971 the readers from a preconfigured directory. Once loaded, the shared
35972 object is used the parse the debug information emitted by the JIT
35976 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35977 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35980 @node Using JIT Debug Info Readers
35981 @subsection Using JIT Debug Info Readers
35982 @kindex jit-reader-load
35983 @kindex jit-reader-unload
35985 Readers can be loaded and unloaded using the @code{jit-reader-load}
35986 and @code{jit-reader-unload} commands.
35989 @item jit-reader-load @var{reader}
35990 Load the JIT reader named @var{reader}. @var{reader} is a shared
35991 object specified as either an absolute or a relative file name. In
35992 the latter case, @value{GDBN} will try to load the reader from a
35993 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35994 system (here @var{libdir} is the system library directory, often
35995 @file{/usr/local/lib}).
35997 Only one reader can be active at a time; trying to load a second
35998 reader when one is already loaded will result in @value{GDBN}
35999 reporting an error. A new JIT reader can be loaded by first unloading
36000 the current one using @code{jit-reader-unload} and then invoking
36001 @code{jit-reader-load}.
36003 @item jit-reader-unload
36004 Unload the currently loaded JIT reader.
36008 @node Writing JIT Debug Info Readers
36009 @subsection Writing JIT Debug Info Readers
36010 @cindex writing JIT debug info readers
36012 As mentioned, a reader is essentially a shared object conforming to a
36013 certain ABI. This ABI is described in @file{jit-reader.h}.
36015 @file{jit-reader.h} defines the structures, macros and functions
36016 required to write a reader. It is installed (along with
36017 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36018 the system include directory.
36020 Readers need to be released under a GPL compatible license. A reader
36021 can be declared as released under such a license by placing the macro
36022 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36024 The entry point for readers is the symbol @code{gdb_init_reader},
36025 which is expected to be a function with the prototype
36027 @findex gdb_init_reader
36029 extern struct gdb_reader_funcs *gdb_init_reader (void);
36032 @cindex @code{struct gdb_reader_funcs}
36034 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36035 functions. These functions are executed to read the debug info
36036 generated by the JIT compiler (@code{read}), to unwind stack frames
36037 (@code{unwind}) and to create canonical frame IDs
36038 (@code{get_Frame_id}). It also has a callback that is called when the
36039 reader is being unloaded (@code{destroy}). The struct looks like this
36042 struct gdb_reader_funcs
36044 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36045 int reader_version;
36047 /* For use by the reader. */
36050 gdb_read_debug_info *read;
36051 gdb_unwind_frame *unwind;
36052 gdb_get_frame_id *get_frame_id;
36053 gdb_destroy_reader *destroy;
36057 @cindex @code{struct gdb_symbol_callbacks}
36058 @cindex @code{struct gdb_unwind_callbacks}
36060 The callbacks are provided with another set of callbacks by
36061 @value{GDBN} to do their job. For @code{read}, these callbacks are
36062 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36063 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36064 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36065 files and new symbol tables inside those object files. @code{struct
36066 gdb_unwind_callbacks} has callbacks to read registers off the current
36067 frame and to write out the values of the registers in the previous
36068 frame. Both have a callback (@code{target_read}) to read bytes off the
36069 target's address space.
36071 @node In-Process Agent
36072 @chapter In-Process Agent
36073 @cindex debugging agent
36074 The traditional debugging model is conceptually low-speed, but works fine,
36075 because most bugs can be reproduced in debugging-mode execution. However,
36076 as multi-core or many-core processors are becoming mainstream, and
36077 multi-threaded programs become more and more popular, there should be more
36078 and more bugs that only manifest themselves at normal-mode execution, for
36079 example, thread races, because debugger's interference with the program's
36080 timing may conceal the bugs. On the other hand, in some applications,
36081 it is not feasible for the debugger to interrupt the program's execution
36082 long enough for the developer to learn anything helpful about its behavior.
36083 If the program's correctness depends on its real-time behavior, delays
36084 introduced by a debugger might cause the program to fail, even when the
36085 code itself is correct. It is useful to be able to observe the program's
36086 behavior without interrupting it.
36088 Therefore, traditional debugging model is too intrusive to reproduce
36089 some bugs. In order to reduce the interference with the program, we can
36090 reduce the number of operations performed by debugger. The
36091 @dfn{In-Process Agent}, a shared library, is running within the same
36092 process with inferior, and is able to perform some debugging operations
36093 itself. As a result, debugger is only involved when necessary, and
36094 performance of debugging can be improved accordingly. Note that
36095 interference with program can be reduced but can't be removed completely,
36096 because the in-process agent will still stop or slow down the program.
36098 The in-process agent can interpret and execute Agent Expressions
36099 (@pxref{Agent Expressions}) during performing debugging operations. The
36100 agent expressions can be used for different purposes, such as collecting
36101 data in tracepoints, and condition evaluation in breakpoints.
36103 @anchor{Control Agent}
36104 You can control whether the in-process agent is used as an aid for
36105 debugging with the following commands:
36108 @kindex set agent on
36110 Causes the in-process agent to perform some operations on behalf of the
36111 debugger. Just which operations requested by the user will be done
36112 by the in-process agent depends on the its capabilities. For example,
36113 if you request to evaluate breakpoint conditions in the in-process agent,
36114 and the in-process agent has such capability as well, then breakpoint
36115 conditions will be evaluated in the in-process agent.
36117 @kindex set agent off
36118 @item set agent off
36119 Disables execution of debugging operations by the in-process agent. All
36120 of the operations will be performed by @value{GDBN}.
36124 Display the current setting of execution of debugging operations by
36125 the in-process agent.
36129 * In-Process Agent Protocol::
36132 @node In-Process Agent Protocol
36133 @section In-Process Agent Protocol
36134 @cindex in-process agent protocol
36136 The in-process agent is able to communicate with both @value{GDBN} and
36137 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36138 used for communications between @value{GDBN} or GDBserver and the IPA.
36139 In general, @value{GDBN} or GDBserver sends commands
36140 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36141 in-process agent replies back with the return result of the command, or
36142 some other information. The data sent to in-process agent is composed
36143 of primitive data types, such as 4-byte or 8-byte type, and composite
36144 types, which are called objects (@pxref{IPA Protocol Objects}).
36147 * IPA Protocol Objects::
36148 * IPA Protocol Commands::
36151 @node IPA Protocol Objects
36152 @subsection IPA Protocol Objects
36153 @cindex ipa protocol objects
36155 The commands sent to and results received from agent may contain some
36156 complex data types called @dfn{objects}.
36158 The in-process agent is running on the same machine with @value{GDBN}
36159 or GDBserver, so it doesn't have to handle as much differences between
36160 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36161 However, there are still some differences of two ends in two processes:
36165 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36166 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36168 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36169 GDBserver is compiled with one, and in-process agent is compiled with
36173 Here are the IPA Protocol Objects:
36177 agent expression object. It represents an agent expression
36178 (@pxref{Agent Expressions}).
36179 @anchor{agent expression object}
36181 tracepoint action object. It represents a tracepoint action
36182 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36183 memory, static trace data and to evaluate expression.
36184 @anchor{tracepoint action object}
36186 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36187 @anchor{tracepoint object}
36191 The following table describes important attributes of each IPA protocol
36194 @multitable @columnfractions .30 .20 .50
36195 @headitem Name @tab Size @tab Description
36196 @item @emph{agent expression object} @tab @tab
36197 @item length @tab 4 @tab length of bytes code
36198 @item byte code @tab @var{length} @tab contents of byte code
36199 @item @emph{tracepoint action for collecting memory} @tab @tab
36200 @item 'M' @tab 1 @tab type of tracepoint action
36201 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36202 address of the lowest byte to collect, otherwise @var{addr} is the offset
36203 of @var{basereg} for memory collecting.
36204 @item len @tab 8 @tab length of memory for collecting
36205 @item basereg @tab 4 @tab the register number containing the starting
36206 memory address for collecting.
36207 @item @emph{tracepoint action for collecting registers} @tab @tab
36208 @item 'R' @tab 1 @tab type of tracepoint action
36209 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36210 @item 'L' @tab 1 @tab type of tracepoint action
36211 @item @emph{tracepoint action for expression evaluation} @tab @tab
36212 @item 'X' @tab 1 @tab type of tracepoint action
36213 @item agent expression @tab length of @tab @ref{agent expression object}
36214 @item @emph{tracepoint object} @tab @tab
36215 @item number @tab 4 @tab number of tracepoint
36216 @item address @tab 8 @tab address of tracepoint inserted on
36217 @item type @tab 4 @tab type of tracepoint
36218 @item enabled @tab 1 @tab enable or disable of tracepoint
36219 @item step_count @tab 8 @tab step
36220 @item pass_count @tab 8 @tab pass
36221 @item numactions @tab 4 @tab number of tracepoint actions
36222 @item hit count @tab 8 @tab hit count
36223 @item trace frame usage @tab 8 @tab trace frame usage
36224 @item compiled_cond @tab 8 @tab compiled condition
36225 @item orig_size @tab 8 @tab orig size
36226 @item condition @tab 4 if condition is NULL otherwise length of
36227 @ref{agent expression object}
36228 @tab zero if condition is NULL, otherwise is
36229 @ref{agent expression object}
36230 @item actions @tab variable
36231 @tab numactions number of @ref{tracepoint action object}
36234 @node IPA Protocol Commands
36235 @subsection IPA Protocol Commands
36236 @cindex ipa protocol commands
36238 The spaces in each command are delimiters to ease reading this commands
36239 specification. They don't exist in real commands.
36243 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36244 Installs a new fast tracepoint described by @var{tracepoint_object}
36245 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36246 head of @dfn{jumppad}, which is used to jump to data collection routine
36251 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36252 @var{target_address} is address of tracepoint in the inferior.
36253 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36254 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36255 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36256 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36263 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36264 is about to kill inferiors.
36272 @item probe_marker_at:@var{address}
36273 Asks in-process agent to probe the marker at @var{address}.
36280 @item unprobe_marker_at:@var{address}
36281 Asks in-process agent to unprobe the marker at @var{address}.
36285 @chapter Reporting Bugs in @value{GDBN}
36286 @cindex bugs in @value{GDBN}
36287 @cindex reporting bugs in @value{GDBN}
36289 Your bug reports play an essential role in making @value{GDBN} reliable.
36291 Reporting a bug may help you by bringing a solution to your problem, or it
36292 may not. But in any case the principal function of a bug report is to help
36293 the entire community by making the next version of @value{GDBN} work better. Bug
36294 reports are your contribution to the maintenance of @value{GDBN}.
36296 In order for a bug report to serve its purpose, you must include the
36297 information that enables us to fix the bug.
36300 * Bug Criteria:: Have you found a bug?
36301 * Bug Reporting:: How to report bugs
36305 @section Have You Found a Bug?
36306 @cindex bug criteria
36308 If you are not sure whether you have found a bug, here are some guidelines:
36311 @cindex fatal signal
36312 @cindex debugger crash
36313 @cindex crash of debugger
36315 If the debugger gets a fatal signal, for any input whatever, that is a
36316 @value{GDBN} bug. Reliable debuggers never crash.
36318 @cindex error on valid input
36320 If @value{GDBN} produces an error message for valid input, that is a
36321 bug. (Note that if you're cross debugging, the problem may also be
36322 somewhere in the connection to the target.)
36324 @cindex invalid input
36326 If @value{GDBN} does not produce an error message for invalid input,
36327 that is a bug. However, you should note that your idea of
36328 ``invalid input'' might be our idea of ``an extension'' or ``support
36329 for traditional practice''.
36332 If you are an experienced user of debugging tools, your suggestions
36333 for improvement of @value{GDBN} are welcome in any case.
36336 @node Bug Reporting
36337 @section How to Report Bugs
36338 @cindex bug reports
36339 @cindex @value{GDBN} bugs, reporting
36341 A number of companies and individuals offer support for @sc{gnu} products.
36342 If you obtained @value{GDBN} from a support organization, we recommend you
36343 contact that organization first.
36345 You can find contact information for many support companies and
36346 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36348 @c should add a web page ref...
36351 @ifset BUGURL_DEFAULT
36352 In any event, we also recommend that you submit bug reports for
36353 @value{GDBN}. The preferred method is to submit them directly using
36354 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36355 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36358 @strong{Do not send bug reports to @samp{info-gdb}, or to
36359 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36360 not want to receive bug reports. Those that do have arranged to receive
36363 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36364 serves as a repeater. The mailing list and the newsgroup carry exactly
36365 the same messages. Often people think of posting bug reports to the
36366 newsgroup instead of mailing them. This appears to work, but it has one
36367 problem which can be crucial: a newsgroup posting often lacks a mail
36368 path back to the sender. Thus, if we need to ask for more information,
36369 we may be unable to reach you. For this reason, it is better to send
36370 bug reports to the mailing list.
36372 @ifclear BUGURL_DEFAULT
36373 In any event, we also recommend that you submit bug reports for
36374 @value{GDBN} to @value{BUGURL}.
36378 The fundamental principle of reporting bugs usefully is this:
36379 @strong{report all the facts}. If you are not sure whether to state a
36380 fact or leave it out, state it!
36382 Often people omit facts because they think they know what causes the
36383 problem and assume that some details do not matter. Thus, you might
36384 assume that the name of the variable you use in an example does not matter.
36385 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36386 stray memory reference which happens to fetch from the location where that
36387 name is stored in memory; perhaps, if the name were different, the contents
36388 of that location would fool the debugger into doing the right thing despite
36389 the bug. Play it safe and give a specific, complete example. That is the
36390 easiest thing for you to do, and the most helpful.
36392 Keep in mind that the purpose of a bug report is to enable us to fix the
36393 bug. It may be that the bug has been reported previously, but neither
36394 you nor we can know that unless your bug report is complete and
36397 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36398 bell?'' Those bug reports are useless, and we urge everyone to
36399 @emph{refuse to respond to them} except to chide the sender to report
36402 To enable us to fix the bug, you should include all these things:
36406 The version of @value{GDBN}. @value{GDBN} announces it if you start
36407 with no arguments; you can also print it at any time using @code{show
36410 Without this, we will not know whether there is any point in looking for
36411 the bug in the current version of @value{GDBN}.
36414 The type of machine you are using, and the operating system name and
36418 The details of the @value{GDBN} build-time configuration.
36419 @value{GDBN} shows these details if you invoke it with the
36420 @option{--configuration} command-line option, or if you type
36421 @code{show configuration} at @value{GDBN}'s prompt.
36424 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36425 ``@value{GCC}--2.8.1''.
36428 What compiler (and its version) was used to compile the program you are
36429 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36430 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36431 to get this information; for other compilers, see the documentation for
36435 The command arguments you gave the compiler to compile your example and
36436 observe the bug. For example, did you use @samp{-O}? To guarantee
36437 you will not omit something important, list them all. A copy of the
36438 Makefile (or the output from make) is sufficient.
36440 If we were to try to guess the arguments, we would probably guess wrong
36441 and then we might not encounter the bug.
36444 A complete input script, and all necessary source files, that will
36448 A description of what behavior you observe that you believe is
36449 incorrect. For example, ``It gets a fatal signal.''
36451 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36452 will certainly notice it. But if the bug is incorrect output, we might
36453 not notice unless it is glaringly wrong. You might as well not give us
36454 a chance to make a mistake.
36456 Even if the problem you experience is a fatal signal, you should still
36457 say so explicitly. Suppose something strange is going on, such as, your
36458 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36459 the C library on your system. (This has happened!) Your copy might
36460 crash and ours would not. If you told us to expect a crash, then when
36461 ours fails to crash, we would know that the bug was not happening for
36462 us. If you had not told us to expect a crash, then we would not be able
36463 to draw any conclusion from our observations.
36466 @cindex recording a session script
36467 To collect all this information, you can use a session recording program
36468 such as @command{script}, which is available on many Unix systems.
36469 Just run your @value{GDBN} session inside @command{script} and then
36470 include the @file{typescript} file with your bug report.
36472 Another way to record a @value{GDBN} session is to run @value{GDBN}
36473 inside Emacs and then save the entire buffer to a file.
36476 If you wish to suggest changes to the @value{GDBN} source, send us context
36477 diffs. If you even discuss something in the @value{GDBN} source, refer to
36478 it by context, not by line number.
36480 The line numbers in our development sources will not match those in your
36481 sources. Your line numbers would convey no useful information to us.
36485 Here are some things that are not necessary:
36489 A description of the envelope of the bug.
36491 Often people who encounter a bug spend a lot of time investigating
36492 which changes to the input file will make the bug go away and which
36493 changes will not affect it.
36495 This is often time consuming and not very useful, because the way we
36496 will find the bug is by running a single example under the debugger
36497 with breakpoints, not by pure deduction from a series of examples.
36498 We recommend that you save your time for something else.
36500 Of course, if you can find a simpler example to report @emph{instead}
36501 of the original one, that is a convenience for us. Errors in the
36502 output will be easier to spot, running under the debugger will take
36503 less time, and so on.
36505 However, simplification is not vital; if you do not want to do this,
36506 report the bug anyway and send us the entire test case you used.
36509 A patch for the bug.
36511 A patch for the bug does help us if it is a good one. But do not omit
36512 the necessary information, such as the test case, on the assumption that
36513 a patch is all we need. We might see problems with your patch and decide
36514 to fix the problem another way, or we might not understand it at all.
36516 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36517 construct an example that will make the program follow a certain path
36518 through the code. If you do not send us the example, we will not be able
36519 to construct one, so we will not be able to verify that the bug is fixed.
36521 And if we cannot understand what bug you are trying to fix, or why your
36522 patch should be an improvement, we will not install it. A test case will
36523 help us to understand.
36526 A guess about what the bug is or what it depends on.
36528 Such guesses are usually wrong. Even we cannot guess right about such
36529 things without first using the debugger to find the facts.
36532 @c The readline documentation is distributed with the readline code
36533 @c and consists of the two following files:
36536 @c Use -I with makeinfo to point to the appropriate directory,
36537 @c environment var TEXINPUTS with TeX.
36538 @ifclear SYSTEM_READLINE
36539 @include rluser.texi
36540 @include hsuser.texi
36544 @appendix In Memoriam
36546 The @value{GDBN} project mourns the loss of the following long-time
36551 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36552 to Free Software in general. Outside of @value{GDBN}, he was known in
36553 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36555 @item Michael Snyder
36556 Michael was one of the Global Maintainers of the @value{GDBN} project,
36557 with contributions recorded as early as 1996, until 2011. In addition
36558 to his day to day participation, he was a large driving force behind
36559 adding Reverse Debugging to @value{GDBN}.
36562 Beyond their technical contributions to the project, they were also
36563 enjoyable members of the Free Software Community. We will miss them.
36565 @node Formatting Documentation
36566 @appendix Formatting Documentation
36568 @cindex @value{GDBN} reference card
36569 @cindex reference card
36570 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36571 for printing with PostScript or Ghostscript, in the @file{gdb}
36572 subdirectory of the main source directory@footnote{In
36573 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36574 release.}. If you can use PostScript or Ghostscript with your printer,
36575 you can print the reference card immediately with @file{refcard.ps}.
36577 The release also includes the source for the reference card. You
36578 can format it, using @TeX{}, by typing:
36584 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36585 mode on US ``letter'' size paper;
36586 that is, on a sheet 11 inches wide by 8.5 inches
36587 high. You will need to specify this form of printing as an option to
36588 your @sc{dvi} output program.
36590 @cindex documentation
36592 All the documentation for @value{GDBN} comes as part of the machine-readable
36593 distribution. The documentation is written in Texinfo format, which is
36594 a documentation system that uses a single source file to produce both
36595 on-line information and a printed manual. You can use one of the Info
36596 formatting commands to create the on-line version of the documentation
36597 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36599 @value{GDBN} includes an already formatted copy of the on-line Info
36600 version of this manual in the @file{gdb} subdirectory. The main Info
36601 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36602 subordinate files matching @samp{gdb.info*} in the same directory. If
36603 necessary, you can print out these files, or read them with any editor;
36604 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36605 Emacs or the standalone @code{info} program, available as part of the
36606 @sc{gnu} Texinfo distribution.
36608 If you want to format these Info files yourself, you need one of the
36609 Info formatting programs, such as @code{texinfo-format-buffer} or
36612 If you have @code{makeinfo} installed, and are in the top level
36613 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36614 version @value{GDBVN}), you can make the Info file by typing:
36621 If you want to typeset and print copies of this manual, you need @TeX{},
36622 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36623 Texinfo definitions file.
36625 @TeX{} is a typesetting program; it does not print files directly, but
36626 produces output files called @sc{dvi} files. To print a typeset
36627 document, you need a program to print @sc{dvi} files. If your system
36628 has @TeX{} installed, chances are it has such a program. The precise
36629 command to use depends on your system; @kbd{lpr -d} is common; another
36630 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36631 require a file name without any extension or a @samp{.dvi} extension.
36633 @TeX{} also requires a macro definitions file called
36634 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36635 written in Texinfo format. On its own, @TeX{} cannot either read or
36636 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36637 and is located in the @file{gdb-@var{version-number}/texinfo}
36640 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36641 typeset and print this manual. First switch to the @file{gdb}
36642 subdirectory of the main source directory (for example, to
36643 @file{gdb-@value{GDBVN}/gdb}) and type:
36649 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36651 @node Installing GDB
36652 @appendix Installing @value{GDBN}
36653 @cindex installation
36656 * Requirements:: Requirements for building @value{GDBN}
36657 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36658 * Separate Objdir:: Compiling @value{GDBN} in another directory
36659 * Config Names:: Specifying names for hosts and targets
36660 * Configure Options:: Summary of options for configure
36661 * System-wide configuration:: Having a system-wide init file
36665 @section Requirements for Building @value{GDBN}
36666 @cindex building @value{GDBN}, requirements for
36668 Building @value{GDBN} requires various tools and packages to be available.
36669 Other packages will be used only if they are found.
36671 @heading Tools/Packages Necessary for Building @value{GDBN}
36673 @item ISO C90 compiler
36674 @value{GDBN} is written in ISO C90. It should be buildable with any
36675 working C90 compiler, e.g.@: GCC.
36679 @heading Tools/Packages Optional for Building @value{GDBN}
36683 @value{GDBN} can use the Expat XML parsing library. This library may be
36684 included with your operating system distribution; if it is not, you
36685 can get the latest version from @url{http://expat.sourceforge.net}.
36686 The @file{configure} script will search for this library in several
36687 standard locations; if it is installed in an unusual path, you can
36688 use the @option{--with-libexpat-prefix} option to specify its location.
36694 Remote protocol memory maps (@pxref{Memory Map Format})
36696 Target descriptions (@pxref{Target Descriptions})
36698 Remote shared library lists (@xref{Library List Format},
36699 or alternatively @pxref{Library List Format for SVR4 Targets})
36701 MS-Windows shared libraries (@pxref{Shared Libraries})
36703 Traceframe info (@pxref{Traceframe Info Format})
36705 Branch trace (@pxref{Branch Trace Format})
36709 @cindex compressed debug sections
36710 @value{GDBN} will use the @samp{zlib} library, if available, to read
36711 compressed debug sections. Some linkers, such as GNU gold, are capable
36712 of producing binaries with compressed debug sections. If @value{GDBN}
36713 is compiled with @samp{zlib}, it will be able to read the debug
36714 information in such binaries.
36716 The @samp{zlib} library is likely included with your operating system
36717 distribution; if it is not, you can get the latest version from
36718 @url{http://zlib.net}.
36721 @value{GDBN}'s features related to character sets (@pxref{Character
36722 Sets}) require a functioning @code{iconv} implementation. If you are
36723 on a GNU system, then this is provided by the GNU C Library. Some
36724 other systems also provide a working @code{iconv}.
36726 If @value{GDBN} is using the @code{iconv} program which is installed
36727 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36728 This is done with @option{--with-iconv-bin} which specifies the
36729 directory that contains the @code{iconv} program.
36731 On systems without @code{iconv}, you can install GNU Libiconv. If you
36732 have previously installed Libiconv, you can use the
36733 @option{--with-libiconv-prefix} option to configure.
36735 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36736 arrange to build Libiconv if a directory named @file{libiconv} appears
36737 in the top-most source directory. If Libiconv is built this way, and
36738 if the operating system does not provide a suitable @code{iconv}
36739 implementation, then the just-built library will automatically be used
36740 by @value{GDBN}. One easy way to set this up is to download GNU
36741 Libiconv, unpack it, and then rename the directory holding the
36742 Libiconv source code to @samp{libiconv}.
36745 @node Running Configure
36746 @section Invoking the @value{GDBN} @file{configure} Script
36747 @cindex configuring @value{GDBN}
36748 @value{GDBN} comes with a @file{configure} script that automates the process
36749 of preparing @value{GDBN} for installation; you can then use @code{make} to
36750 build the @code{gdb} program.
36752 @c irrelevant in info file; it's as current as the code it lives with.
36753 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36754 look at the @file{README} file in the sources; we may have improved the
36755 installation procedures since publishing this manual.}
36758 The @value{GDBN} distribution includes all the source code you need for
36759 @value{GDBN} in a single directory, whose name is usually composed by
36760 appending the version number to @samp{gdb}.
36762 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36763 @file{gdb-@value{GDBVN}} directory. That directory contains:
36766 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36767 script for configuring @value{GDBN} and all its supporting libraries
36769 @item gdb-@value{GDBVN}/gdb
36770 the source specific to @value{GDBN} itself
36772 @item gdb-@value{GDBVN}/bfd
36773 source for the Binary File Descriptor library
36775 @item gdb-@value{GDBVN}/include
36776 @sc{gnu} include files
36778 @item gdb-@value{GDBVN}/libiberty
36779 source for the @samp{-liberty} free software library
36781 @item gdb-@value{GDBVN}/opcodes
36782 source for the library of opcode tables and disassemblers
36784 @item gdb-@value{GDBVN}/readline
36785 source for the @sc{gnu} command-line interface
36787 @item gdb-@value{GDBVN}/glob
36788 source for the @sc{gnu} filename pattern-matching subroutine
36790 @item gdb-@value{GDBVN}/mmalloc
36791 source for the @sc{gnu} memory-mapped malloc package
36794 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36795 from the @file{gdb-@var{version-number}} source directory, which in
36796 this example is the @file{gdb-@value{GDBVN}} directory.
36798 First switch to the @file{gdb-@var{version-number}} source directory
36799 if you are not already in it; then run @file{configure}. Pass the
36800 identifier for the platform on which @value{GDBN} will run as an
36806 cd gdb-@value{GDBVN}
36807 ./configure @var{host}
36812 where @var{host} is an identifier such as @samp{sun4} or
36813 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36814 (You can often leave off @var{host}; @file{configure} tries to guess the
36815 correct value by examining your system.)
36817 Running @samp{configure @var{host}} and then running @code{make} builds the
36818 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36819 libraries, then @code{gdb} itself. The configured source files, and the
36820 binaries, are left in the corresponding source directories.
36823 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36824 system does not recognize this automatically when you run a different
36825 shell, you may need to run @code{sh} on it explicitly:
36828 sh configure @var{host}
36831 If you run @file{configure} from a directory that contains source
36832 directories for multiple libraries or programs, such as the
36833 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36835 creates configuration files for every directory level underneath (unless
36836 you tell it not to, with the @samp{--norecursion} option).
36838 You should run the @file{configure} script from the top directory in the
36839 source tree, the @file{gdb-@var{version-number}} directory. If you run
36840 @file{configure} from one of the subdirectories, you will configure only
36841 that subdirectory. That is usually not what you want. In particular,
36842 if you run the first @file{configure} from the @file{gdb} subdirectory
36843 of the @file{gdb-@var{version-number}} directory, you will omit the
36844 configuration of @file{bfd}, @file{readline}, and other sibling
36845 directories of the @file{gdb} subdirectory. This leads to build errors
36846 about missing include files such as @file{bfd/bfd.h}.
36848 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36849 However, you should make sure that the shell on your path (named by
36850 the @samp{SHELL} environment variable) is publicly readable. Remember
36851 that @value{GDBN} uses the shell to start your program---some systems refuse to
36852 let @value{GDBN} debug child processes whose programs are not readable.
36854 @node Separate Objdir
36855 @section Compiling @value{GDBN} in Another Directory
36857 If you want to run @value{GDBN} versions for several host or target machines,
36858 you need a different @code{gdb} compiled for each combination of
36859 host and target. @file{configure} is designed to make this easy by
36860 allowing you to generate each configuration in a separate subdirectory,
36861 rather than in the source directory. If your @code{make} program
36862 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36863 @code{make} in each of these directories builds the @code{gdb}
36864 program specified there.
36866 To build @code{gdb} in a separate directory, run @file{configure}
36867 with the @samp{--srcdir} option to specify where to find the source.
36868 (You also need to specify a path to find @file{configure}
36869 itself from your working directory. If the path to @file{configure}
36870 would be the same as the argument to @samp{--srcdir}, you can leave out
36871 the @samp{--srcdir} option; it is assumed.)
36873 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36874 separate directory for a Sun 4 like this:
36878 cd gdb-@value{GDBVN}
36881 ../gdb-@value{GDBVN}/configure sun4
36886 When @file{configure} builds a configuration using a remote source
36887 directory, it creates a tree for the binaries with the same structure
36888 (and using the same names) as the tree under the source directory. In
36889 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36890 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36891 @file{gdb-sun4/gdb}.
36893 Make sure that your path to the @file{configure} script has just one
36894 instance of @file{gdb} in it. If your path to @file{configure} looks
36895 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36896 one subdirectory of @value{GDBN}, not the whole package. This leads to
36897 build errors about missing include files such as @file{bfd/bfd.h}.
36899 One popular reason to build several @value{GDBN} configurations in separate
36900 directories is to configure @value{GDBN} for cross-compiling (where
36901 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36902 programs that run on another machine---the @dfn{target}).
36903 You specify a cross-debugging target by
36904 giving the @samp{--target=@var{target}} option to @file{configure}.
36906 When you run @code{make} to build a program or library, you must run
36907 it in a configured directory---whatever directory you were in when you
36908 called @file{configure} (or one of its subdirectories).
36910 The @code{Makefile} that @file{configure} generates in each source
36911 directory also runs recursively. If you type @code{make} in a source
36912 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36913 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36914 will build all the required libraries, and then build GDB.
36916 When you have multiple hosts or targets configured in separate
36917 directories, you can run @code{make} on them in parallel (for example,
36918 if they are NFS-mounted on each of the hosts); they will not interfere
36922 @section Specifying Names for Hosts and Targets
36924 The specifications used for hosts and targets in the @file{configure}
36925 script are based on a three-part naming scheme, but some short predefined
36926 aliases are also supported. The full naming scheme encodes three pieces
36927 of information in the following pattern:
36930 @var{architecture}-@var{vendor}-@var{os}
36933 For example, you can use the alias @code{sun4} as a @var{host} argument,
36934 or as the value for @var{target} in a @code{--target=@var{target}}
36935 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36937 The @file{configure} script accompanying @value{GDBN} does not provide
36938 any query facility to list all supported host and target names or
36939 aliases. @file{configure} calls the Bourne shell script
36940 @code{config.sub} to map abbreviations to full names; you can read the
36941 script, if you wish, or you can use it to test your guesses on
36942 abbreviations---for example:
36945 % sh config.sub i386-linux
36947 % sh config.sub alpha-linux
36948 alpha-unknown-linux-gnu
36949 % sh config.sub hp9k700
36951 % sh config.sub sun4
36952 sparc-sun-sunos4.1.1
36953 % sh config.sub sun3
36954 m68k-sun-sunos4.1.1
36955 % sh config.sub i986v
36956 Invalid configuration `i986v': machine `i986v' not recognized
36960 @code{config.sub} is also distributed in the @value{GDBN} source
36961 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36963 @node Configure Options
36964 @section @file{configure} Options
36966 Here is a summary of the @file{configure} options and arguments that
36967 are most often useful for building @value{GDBN}. @file{configure} also has
36968 several other options not listed here. @inforef{What Configure
36969 Does,,configure.info}, for a full explanation of @file{configure}.
36972 configure @r{[}--help@r{]}
36973 @r{[}--prefix=@var{dir}@r{]}
36974 @r{[}--exec-prefix=@var{dir}@r{]}
36975 @r{[}--srcdir=@var{dirname}@r{]}
36976 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36977 @r{[}--target=@var{target}@r{]}
36982 You may introduce options with a single @samp{-} rather than
36983 @samp{--} if you prefer; but you may abbreviate option names if you use
36988 Display a quick summary of how to invoke @file{configure}.
36990 @item --prefix=@var{dir}
36991 Configure the source to install programs and files under directory
36994 @item --exec-prefix=@var{dir}
36995 Configure the source to install programs under directory
36998 @c avoid splitting the warning from the explanation:
37000 @item --srcdir=@var{dirname}
37001 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37002 @code{make} that implements the @code{VPATH} feature.}@*
37003 Use this option to make configurations in directories separate from the
37004 @value{GDBN} source directories. Among other things, you can use this to
37005 build (or maintain) several configurations simultaneously, in separate
37006 directories. @file{configure} writes configuration-specific files in
37007 the current directory, but arranges for them to use the source in the
37008 directory @var{dirname}. @file{configure} creates directories under
37009 the working directory in parallel to the source directories below
37012 @item --norecursion
37013 Configure only the directory level where @file{configure} is executed; do not
37014 propagate configuration to subdirectories.
37016 @item --target=@var{target}
37017 Configure @value{GDBN} for cross-debugging programs running on the specified
37018 @var{target}. Without this option, @value{GDBN} is configured to debug
37019 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37021 There is no convenient way to generate a list of all available targets.
37023 @item @var{host} @dots{}
37024 Configure @value{GDBN} to run on the specified @var{host}.
37026 There is no convenient way to generate a list of all available hosts.
37029 There are many other options available as well, but they are generally
37030 needed for special purposes only.
37032 @node System-wide configuration
37033 @section System-wide configuration and settings
37034 @cindex system-wide init file
37036 @value{GDBN} can be configured to have a system-wide init file;
37037 this file will be read and executed at startup (@pxref{Startup, , What
37038 @value{GDBN} does during startup}).
37040 Here is the corresponding configure option:
37043 @item --with-system-gdbinit=@var{file}
37044 Specify that the default location of the system-wide init file is
37048 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37049 it may be subject to relocation. Two possible cases:
37053 If the default location of this init file contains @file{$prefix},
37054 it will be subject to relocation. Suppose that the configure options
37055 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37056 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37057 init file is looked for as @file{$install/etc/gdbinit} instead of
37058 @file{$prefix/etc/gdbinit}.
37061 By contrast, if the default location does not contain the prefix,
37062 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37063 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37064 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37065 wherever @value{GDBN} is installed.
37068 If the configured location of the system-wide init file (as given by the
37069 @option{--with-system-gdbinit} option at configure time) is in the
37070 data-directory (as specified by @option{--with-gdb-datadir} at configure
37071 time) or in one of its subdirectories, then @value{GDBN} will look for the
37072 system-wide init file in the directory specified by the
37073 @option{--data-directory} command-line option.
37074 Note that the system-wide init file is only read once, during @value{GDBN}
37075 initialization. If the data-directory is changed after @value{GDBN} has
37076 started with the @code{set data-directory} command, the file will not be
37080 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37083 @node System-wide Configuration Scripts
37084 @subsection Installed System-wide Configuration Scripts
37085 @cindex system-wide configuration scripts
37087 The @file{system-gdbinit} directory, located inside the data-directory
37088 (as specified by @option{--with-gdb-datadir} at configure time) contains
37089 a number of scripts which can be used as system-wide init files. To
37090 automatically source those scripts at startup, @value{GDBN} should be
37091 configured with @option{--with-system-gdbinit}. Otherwise, any user
37092 should be able to source them by hand as needed.
37094 The following scripts are currently available:
37097 @item @file{elinos.py}
37099 @cindex ELinOS system-wide configuration script
37100 This script is useful when debugging a program on an ELinOS target.
37101 It takes advantage of the environment variables defined in a standard
37102 ELinOS environment in order to determine the location of the system
37103 shared libraries, and then sets the @samp{solib-absolute-prefix}
37104 and @samp{solib-search-path} variables appropriately.
37106 @item @file{wrs-linux.py}
37107 @pindex wrs-linux.py
37108 @cindex Wind River Linux system-wide configuration script
37109 This script is useful when debugging a program on a target running
37110 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37111 the host-side sysroot used by the target system.
37115 @node Maintenance Commands
37116 @appendix Maintenance Commands
37117 @cindex maintenance commands
37118 @cindex internal commands
37120 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37121 includes a number of commands intended for @value{GDBN} developers,
37122 that are not documented elsewhere in this manual. These commands are
37123 provided here for reference. (For commands that turn on debugging
37124 messages, see @ref{Debugging Output}.)
37127 @kindex maint agent
37128 @kindex maint agent-eval
37129 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37130 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37131 Translate the given @var{expression} into remote agent bytecodes.
37132 This command is useful for debugging the Agent Expression mechanism
37133 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37134 expression useful for data collection, such as by tracepoints, while
37135 @samp{maint agent-eval} produces an expression that evaluates directly
37136 to a result. For instance, a collection expression for @code{globa +
37137 globb} will include bytecodes to record four bytes of memory at each
37138 of the addresses of @code{globa} and @code{globb}, while discarding
37139 the result of the addition, while an evaluation expression will do the
37140 addition and return the sum.
37141 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37142 If not, generate remote agent bytecode for current frame PC address.
37144 @kindex maint agent-printf
37145 @item maint agent-printf @var{format},@var{expr},...
37146 Translate the given format string and list of argument expressions
37147 into remote agent bytecodes and display them as a disassembled list.
37148 This command is useful for debugging the agent version of dynamic
37149 printf (@pxref{Dynamic Printf}).
37151 @kindex maint info breakpoints
37152 @item @anchor{maint info breakpoints}maint info breakpoints
37153 Using the same format as @samp{info breakpoints}, display both the
37154 breakpoints you've set explicitly, and those @value{GDBN} is using for
37155 internal purposes. Internal breakpoints are shown with negative
37156 breakpoint numbers. The type column identifies what kind of breakpoint
37161 Normal, explicitly set breakpoint.
37164 Normal, explicitly set watchpoint.
37167 Internal breakpoint, used to handle correctly stepping through
37168 @code{longjmp} calls.
37170 @item longjmp resume
37171 Internal breakpoint at the target of a @code{longjmp}.
37174 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37177 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37180 Shared library events.
37184 @kindex maint info bfds
37185 @item maint info bfds
37186 This prints information about each @code{bfd} object that is known to
37187 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37189 @kindex set displaced-stepping
37190 @kindex show displaced-stepping
37191 @cindex displaced stepping support
37192 @cindex out-of-line single-stepping
37193 @item set displaced-stepping
37194 @itemx show displaced-stepping
37195 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37196 if the target supports it. Displaced stepping is a way to single-step
37197 over breakpoints without removing them from the inferior, by executing
37198 an out-of-line copy of the instruction that was originally at the
37199 breakpoint location. It is also known as out-of-line single-stepping.
37202 @item set displaced-stepping on
37203 If the target architecture supports it, @value{GDBN} will use
37204 displaced stepping to step over breakpoints.
37206 @item set displaced-stepping off
37207 @value{GDBN} will not use displaced stepping to step over breakpoints,
37208 even if such is supported by the target architecture.
37210 @cindex non-stop mode, and @samp{set displaced-stepping}
37211 @item set displaced-stepping auto
37212 This is the default mode. @value{GDBN} will use displaced stepping
37213 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37214 architecture supports displaced stepping.
37217 @kindex maint check-psymtabs
37218 @item maint check-psymtabs
37219 Check the consistency of currently expanded psymtabs versus symtabs.
37220 Use this to check, for example, whether a symbol is in one but not the other.
37222 @kindex maint check-symtabs
37223 @item maint check-symtabs
37224 Check the consistency of currently expanded symtabs.
37226 @kindex maint expand-symtabs
37227 @item maint expand-symtabs [@var{regexp}]
37228 Expand symbol tables.
37229 If @var{regexp} is specified, only expand symbol tables for file
37230 names matching @var{regexp}.
37232 @kindex maint cplus first_component
37233 @item maint cplus first_component @var{name}
37234 Print the first C@t{++} class/namespace component of @var{name}.
37236 @kindex maint cplus namespace
37237 @item maint cplus namespace
37238 Print the list of possible C@t{++} namespaces.
37240 @kindex maint demangle
37241 @item maint demangle @var{name}
37242 Demangle a C@t{++} or Objective-C mangled @var{name}.
37244 @kindex maint deprecate
37245 @kindex maint undeprecate
37246 @cindex deprecated commands
37247 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37248 @itemx maint undeprecate @var{command}
37249 Deprecate or undeprecate the named @var{command}. Deprecated commands
37250 cause @value{GDBN} to issue a warning when you use them. The optional
37251 argument @var{replacement} says which newer command should be used in
37252 favor of the deprecated one; if it is given, @value{GDBN} will mention
37253 the replacement as part of the warning.
37255 @kindex maint dump-me
37256 @item maint dump-me
37257 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37258 Cause a fatal signal in the debugger and force it to dump its core.
37259 This is supported only on systems which support aborting a program
37260 with the @code{SIGQUIT} signal.
37262 @kindex maint internal-error
37263 @kindex maint internal-warning
37264 @item maint internal-error @r{[}@var{message-text}@r{]}
37265 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37266 Cause @value{GDBN} to call the internal function @code{internal_error}
37267 or @code{internal_warning} and hence behave as though an internal error
37268 or internal warning has been detected. In addition to reporting the
37269 internal problem, these functions give the user the opportunity to
37270 either quit @value{GDBN} or create a core file of the current
37271 @value{GDBN} session.
37273 These commands take an optional parameter @var{message-text} that is
37274 used as the text of the error or warning message.
37276 Here's an example of using @code{internal-error}:
37279 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37280 @dots{}/maint.c:121: internal-error: testing, 1, 2
37281 A problem internal to GDB has been detected. Further
37282 debugging may prove unreliable.
37283 Quit this debugging session? (y or n) @kbd{n}
37284 Create a core file? (y or n) @kbd{n}
37288 @cindex @value{GDBN} internal error
37289 @cindex internal errors, control of @value{GDBN} behavior
37291 @kindex maint set internal-error
37292 @kindex maint show internal-error
37293 @kindex maint set internal-warning
37294 @kindex maint show internal-warning
37295 @item maint set internal-error @var{action} [ask|yes|no]
37296 @itemx maint show internal-error @var{action}
37297 @itemx maint set internal-warning @var{action} [ask|yes|no]
37298 @itemx maint show internal-warning @var{action}
37299 When @value{GDBN} reports an internal problem (error or warning) it
37300 gives the user the opportunity to both quit @value{GDBN} and create a
37301 core file of the current @value{GDBN} session. These commands let you
37302 override the default behaviour for each particular @var{action},
37303 described in the table below.
37307 You can specify that @value{GDBN} should always (yes) or never (no)
37308 quit. The default is to ask the user what to do.
37311 You can specify that @value{GDBN} should always (yes) or never (no)
37312 create a core file. The default is to ask the user what to do.
37315 @kindex maint packet
37316 @item maint packet @var{text}
37317 If @value{GDBN} is talking to an inferior via the serial protocol,
37318 then this command sends the string @var{text} to the inferior, and
37319 displays the response packet. @value{GDBN} supplies the initial
37320 @samp{$} character, the terminating @samp{#} character, and the
37323 @kindex maint print architecture
37324 @item maint print architecture @r{[}@var{file}@r{]}
37325 Print the entire architecture configuration. The optional argument
37326 @var{file} names the file where the output goes.
37328 @kindex maint print c-tdesc
37329 @item maint print c-tdesc
37330 Print the current target description (@pxref{Target Descriptions}) as
37331 a C source file. The created source file can be used in @value{GDBN}
37332 when an XML parser is not available to parse the description.
37334 @kindex maint print dummy-frames
37335 @item maint print dummy-frames
37336 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37339 (@value{GDBP}) @kbd{b add}
37341 (@value{GDBP}) @kbd{print add(2,3)}
37342 Breakpoint 2, add (a=2, b=3) at @dots{}
37344 The program being debugged stopped while in a function called from GDB.
37346 (@value{GDBP}) @kbd{maint print dummy-frames}
37347 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37348 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37349 call_lo=0x01014000 call_hi=0x01014001
37353 Takes an optional file parameter.
37355 @kindex maint print registers
37356 @kindex maint print raw-registers
37357 @kindex maint print cooked-registers
37358 @kindex maint print register-groups
37359 @kindex maint print remote-registers
37360 @item maint print registers @r{[}@var{file}@r{]}
37361 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37362 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37363 @itemx maint print register-groups @r{[}@var{file}@r{]}
37364 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37365 Print @value{GDBN}'s internal register data structures.
37367 The command @code{maint print raw-registers} includes the contents of
37368 the raw register cache; the command @code{maint print
37369 cooked-registers} includes the (cooked) value of all registers,
37370 including registers which aren't available on the target nor visible
37371 to user; the command @code{maint print register-groups} includes the
37372 groups that each register is a member of; and the command @code{maint
37373 print remote-registers} includes the remote target's register numbers
37374 and offsets in the `G' packets.
37376 These commands take an optional parameter, a file name to which to
37377 write the information.
37379 @kindex maint print reggroups
37380 @item maint print reggroups @r{[}@var{file}@r{]}
37381 Print @value{GDBN}'s internal register group data structures. The
37382 optional argument @var{file} tells to what file to write the
37385 The register groups info looks like this:
37388 (@value{GDBP}) @kbd{maint print reggroups}
37401 This command forces @value{GDBN} to flush its internal register cache.
37403 @kindex maint print objfiles
37404 @cindex info for known object files
37405 @item maint print objfiles @r{[}@var{regexp}@r{]}
37406 Print a dump of all known object files.
37407 If @var{regexp} is specified, only print object files whose names
37408 match @var{regexp}. For each object file, this command prints its name,
37409 address in memory, and all of its psymtabs and symtabs.
37411 @kindex maint print section-scripts
37412 @cindex info for known .debug_gdb_scripts-loaded scripts
37413 @item maint print section-scripts [@var{regexp}]
37414 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37415 If @var{regexp} is specified, only print scripts loaded by object files
37416 matching @var{regexp}.
37417 For each script, this command prints its name as specified in the objfile,
37418 and the full path if known.
37419 @xref{dotdebug_gdb_scripts section}.
37421 @kindex maint print statistics
37422 @cindex bcache statistics
37423 @item maint print statistics
37424 This command prints, for each object file in the program, various data
37425 about that object file followed by the byte cache (@dfn{bcache})
37426 statistics for the object file. The objfile data includes the number
37427 of minimal, partial, full, and stabs symbols, the number of types
37428 defined by the objfile, the number of as yet unexpanded psym tables,
37429 the number of line tables and string tables, and the amount of memory
37430 used by the various tables. The bcache statistics include the counts,
37431 sizes, and counts of duplicates of all and unique objects, max,
37432 average, and median entry size, total memory used and its overhead and
37433 savings, and various measures of the hash table size and chain
37436 @kindex maint print target-stack
37437 @cindex target stack description
37438 @item maint print target-stack
37439 A @dfn{target} is an interface between the debugger and a particular
37440 kind of file or process. Targets can be stacked in @dfn{strata},
37441 so that more than one target can potentially respond to a request.
37442 In particular, memory accesses will walk down the stack of targets
37443 until they find a target that is interested in handling that particular
37446 This command prints a short description of each layer that was pushed on
37447 the @dfn{target stack}, starting from the top layer down to the bottom one.
37449 @kindex maint print type
37450 @cindex type chain of a data type
37451 @item maint print type @var{expr}
37452 Print the type chain for a type specified by @var{expr}. The argument
37453 can be either a type name or a symbol. If it is a symbol, the type of
37454 that symbol is described. The type chain produced by this command is
37455 a recursive definition of the data type as stored in @value{GDBN}'s
37456 data structures, including its flags and contained types.
37458 @kindex maint set dwarf2 always-disassemble
37459 @kindex maint show dwarf2 always-disassemble
37460 @item maint set dwarf2 always-disassemble
37461 @item maint show dwarf2 always-disassemble
37462 Control the behavior of @code{info address} when using DWARF debugging
37465 The default is @code{off}, which means that @value{GDBN} should try to
37466 describe a variable's location in an easily readable format. When
37467 @code{on}, @value{GDBN} will instead display the DWARF location
37468 expression in an assembly-like format. Note that some locations are
37469 too complex for @value{GDBN} to describe simply; in this case you will
37470 always see the disassembly form.
37472 Here is an example of the resulting disassembly:
37475 (gdb) info addr argc
37476 Symbol "argc" is a complex DWARF expression:
37480 For more information on these expressions, see
37481 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37483 @kindex maint set dwarf2 max-cache-age
37484 @kindex maint show dwarf2 max-cache-age
37485 @item maint set dwarf2 max-cache-age
37486 @itemx maint show dwarf2 max-cache-age
37487 Control the DWARF 2 compilation unit cache.
37489 @cindex DWARF 2 compilation units cache
37490 In object files with inter-compilation-unit references, such as those
37491 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37492 reader needs to frequently refer to previously read compilation units.
37493 This setting controls how long a compilation unit will remain in the
37494 cache if it is not referenced. A higher limit means that cached
37495 compilation units will be stored in memory longer, and more total
37496 memory will be used. Setting it to zero disables caching, which will
37497 slow down @value{GDBN} startup, but reduce memory consumption.
37499 @kindex maint set profile
37500 @kindex maint show profile
37501 @cindex profiling GDB
37502 @item maint set profile
37503 @itemx maint show profile
37504 Control profiling of @value{GDBN}.
37506 Profiling will be disabled until you use the @samp{maint set profile}
37507 command to enable it. When you enable profiling, the system will begin
37508 collecting timing and execution count data; when you disable profiling or
37509 exit @value{GDBN}, the results will be written to a log file. Remember that
37510 if you use profiling, @value{GDBN} will overwrite the profiling log file
37511 (often called @file{gmon.out}). If you have a record of important profiling
37512 data in a @file{gmon.out} file, be sure to move it to a safe location.
37514 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37515 compiled with the @samp{-pg} compiler option.
37517 @kindex maint set show-debug-regs
37518 @kindex maint show show-debug-regs
37519 @cindex hardware debug registers
37520 @item maint set show-debug-regs
37521 @itemx maint show show-debug-regs
37522 Control whether to show variables that mirror the hardware debug
37523 registers. Use @code{ON} to enable, @code{OFF} to disable. If
37524 enabled, the debug registers values are shown when @value{GDBN} inserts or
37525 removes a hardware breakpoint or watchpoint, and when the inferior
37526 triggers a hardware-assisted breakpoint or watchpoint.
37528 @kindex maint set show-all-tib
37529 @kindex maint show show-all-tib
37530 @item maint set show-all-tib
37531 @itemx maint show show-all-tib
37532 Control whether to show all non zero areas within a 1k block starting
37533 at thread local base, when using the @samp{info w32 thread-information-block}
37536 @kindex maint set per-command
37537 @kindex maint show per-command
37538 @item maint set per-command
37539 @itemx maint show per-command
37540 @cindex resources used by commands
37542 @value{GDBN} can display the resources used by each command.
37543 This is useful in debugging performance problems.
37546 @item maint set per-command space [on|off]
37547 @itemx maint show per-command space
37548 Enable or disable the printing of the memory used by GDB for each command.
37549 If enabled, @value{GDBN} will display how much memory each command
37550 took, following the command's own output.
37551 This can also be requested by invoking @value{GDBN} with the
37552 @option{--statistics} command-line switch (@pxref{Mode Options}).
37554 @item maint set per-command time [on|off]
37555 @itemx maint show per-command time
37556 Enable or disable the printing of the execution time of @value{GDBN}
37558 If enabled, @value{GDBN} will display how much time it
37559 took to execute each command, following the command's own output.
37560 Both CPU time and wallclock time are printed.
37561 Printing both is useful when trying to determine whether the cost is
37562 CPU or, e.g., disk/network latency.
37563 Note that the CPU time printed is for @value{GDBN} only, it does not include
37564 the execution time of the inferior because there's no mechanism currently
37565 to compute how much time was spent by @value{GDBN} and how much time was
37566 spent by the program been debugged.
37567 This can also be requested by invoking @value{GDBN} with the
37568 @option{--statistics} command-line switch (@pxref{Mode Options}).
37570 @item maint set per-command symtab [on|off]
37571 @itemx maint show per-command symtab
37572 Enable or disable the printing of basic symbol table statistics
37574 If enabled, @value{GDBN} will display the following information:
37578 number of symbol tables
37580 number of primary symbol tables
37582 number of blocks in the blockvector
37586 @kindex maint space
37587 @cindex memory used by commands
37588 @item maint space @var{value}
37589 An alias for @code{maint set per-command space}.
37590 A non-zero value enables it, zero disables it.
37593 @cindex time of command execution
37594 @item maint time @var{value}
37595 An alias for @code{maint set per-command time}.
37596 A non-zero value enables it, zero disables it.
37598 @kindex maint translate-address
37599 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37600 Find the symbol stored at the location specified by the address
37601 @var{addr} and an optional section name @var{section}. If found,
37602 @value{GDBN} prints the name of the closest symbol and an offset from
37603 the symbol's location to the specified address. This is similar to
37604 the @code{info address} command (@pxref{Symbols}), except that this
37605 command also allows to find symbols in other sections.
37607 If section was not specified, the section in which the symbol was found
37608 is also printed. For dynamically linked executables, the name of
37609 executable or shared library containing the symbol is printed as well.
37613 The following command is useful for non-interactive invocations of
37614 @value{GDBN}, such as in the test suite.
37617 @item set watchdog @var{nsec}
37618 @kindex set watchdog
37619 @cindex watchdog timer
37620 @cindex timeout for commands
37621 Set the maximum number of seconds @value{GDBN} will wait for the
37622 target operation to finish. If this time expires, @value{GDBN}
37623 reports and error and the command is aborted.
37625 @item show watchdog
37626 Show the current setting of the target wait timeout.
37629 @node Remote Protocol
37630 @appendix @value{GDBN} Remote Serial Protocol
37635 * Stop Reply Packets::
37636 * General Query Packets::
37637 * Architecture-Specific Protocol Details::
37638 * Tracepoint Packets::
37639 * Host I/O Packets::
37641 * Notification Packets::
37642 * Remote Non-Stop::
37643 * Packet Acknowledgment::
37645 * File-I/O Remote Protocol Extension::
37646 * Library List Format::
37647 * Library List Format for SVR4 Targets::
37648 * Memory Map Format::
37649 * Thread List Format::
37650 * Traceframe Info Format::
37651 * Branch Trace Format::
37657 There may be occasions when you need to know something about the
37658 protocol---for example, if there is only one serial port to your target
37659 machine, you might want your program to do something special if it
37660 recognizes a packet meant for @value{GDBN}.
37662 In the examples below, @samp{->} and @samp{<-} are used to indicate
37663 transmitted and received data, respectively.
37665 @cindex protocol, @value{GDBN} remote serial
37666 @cindex serial protocol, @value{GDBN} remote
37667 @cindex remote serial protocol
37668 All @value{GDBN} commands and responses (other than acknowledgments
37669 and notifications, see @ref{Notification Packets}) are sent as a
37670 @var{packet}. A @var{packet} is introduced with the character
37671 @samp{$}, the actual @var{packet-data}, and the terminating character
37672 @samp{#} followed by a two-digit @var{checksum}:
37675 @code{$}@var{packet-data}@code{#}@var{checksum}
37679 @cindex checksum, for @value{GDBN} remote
37681 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37682 characters between the leading @samp{$} and the trailing @samp{#} (an
37683 eight bit unsigned checksum).
37685 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37686 specification also included an optional two-digit @var{sequence-id}:
37689 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37692 @cindex sequence-id, for @value{GDBN} remote
37694 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37695 has never output @var{sequence-id}s. Stubs that handle packets added
37696 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37698 When either the host or the target machine receives a packet, the first
37699 response expected is an acknowledgment: either @samp{+} (to indicate
37700 the package was received correctly) or @samp{-} (to request
37704 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37709 The @samp{+}/@samp{-} acknowledgments can be disabled
37710 once a connection is established.
37711 @xref{Packet Acknowledgment}, for details.
37713 The host (@value{GDBN}) sends @var{command}s, and the target (the
37714 debugging stub incorporated in your program) sends a @var{response}. In
37715 the case of step and continue @var{command}s, the response is only sent
37716 when the operation has completed, and the target has again stopped all
37717 threads in all attached processes. This is the default all-stop mode
37718 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37719 execution mode; see @ref{Remote Non-Stop}, for details.
37721 @var{packet-data} consists of a sequence of characters with the
37722 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37725 @cindex remote protocol, field separator
37726 Fields within the packet should be separated using @samp{,} @samp{;} or
37727 @samp{:}. Except where otherwise noted all numbers are represented in
37728 @sc{hex} with leading zeros suppressed.
37730 Implementors should note that prior to @value{GDBN} 5.0, the character
37731 @samp{:} could not appear as the third character in a packet (as it
37732 would potentially conflict with the @var{sequence-id}).
37734 @cindex remote protocol, binary data
37735 @anchor{Binary Data}
37736 Binary data in most packets is encoded either as two hexadecimal
37737 digits per byte of binary data. This allowed the traditional remote
37738 protocol to work over connections which were only seven-bit clean.
37739 Some packets designed more recently assume an eight-bit clean
37740 connection, and use a more efficient encoding to send and receive
37743 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37744 as an escape character. Any escaped byte is transmitted as the escape
37745 character followed by the original character XORed with @code{0x20}.
37746 For example, the byte @code{0x7d} would be transmitted as the two
37747 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37748 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37749 @samp{@}}) must always be escaped. Responses sent by the stub
37750 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37751 is not interpreted as the start of a run-length encoded sequence
37754 Response @var{data} can be run-length encoded to save space.
37755 Run-length encoding replaces runs of identical characters with one
37756 instance of the repeated character, followed by a @samp{*} and a
37757 repeat count. The repeat count is itself sent encoded, to avoid
37758 binary characters in @var{data}: a value of @var{n} is sent as
37759 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37760 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37761 code 32) for a repeat count of 3. (This is because run-length
37762 encoding starts to win for counts 3 or more.) Thus, for example,
37763 @samp{0* } is a run-length encoding of ``0000'': the space character
37764 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37767 The printable characters @samp{#} and @samp{$} or with a numeric value
37768 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37769 seven repeats (@samp{$}) can be expanded using a repeat count of only
37770 five (@samp{"}). For example, @samp{00000000} can be encoded as
37773 The error response returned for some packets includes a two character
37774 error number. That number is not well defined.
37776 @cindex empty response, for unsupported packets
37777 For any @var{command} not supported by the stub, an empty response
37778 (@samp{$#00}) should be returned. That way it is possible to extend the
37779 protocol. A newer @value{GDBN} can tell if a packet is supported based
37782 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37783 commands for register access, and the @samp{m} and @samp{M} commands
37784 for memory access. Stubs that only control single-threaded targets
37785 can implement run control with the @samp{c} (continue), and @samp{s}
37786 (step) commands. Stubs that support multi-threading targets should
37787 support the @samp{vCont} command. All other commands are optional.
37792 The following table provides a complete list of all currently defined
37793 @var{command}s and their corresponding response @var{data}.
37794 @xref{File-I/O Remote Protocol Extension}, for details about the File
37795 I/O extension of the remote protocol.
37797 Each packet's description has a template showing the packet's overall
37798 syntax, followed by an explanation of the packet's meaning. We
37799 include spaces in some of the templates for clarity; these are not
37800 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37801 separate its components. For example, a template like @samp{foo
37802 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37803 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37804 @var{baz}. @value{GDBN} does not transmit a space character between the
37805 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37808 @cindex @var{thread-id}, in remote protocol
37809 @anchor{thread-id syntax}
37810 Several packets and replies include a @var{thread-id} field to identify
37811 a thread. Normally these are positive numbers with a target-specific
37812 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37813 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37816 In addition, the remote protocol supports a multiprocess feature in
37817 which the @var{thread-id} syntax is extended to optionally include both
37818 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37819 The @var{pid} (process) and @var{tid} (thread) components each have the
37820 format described above: a positive number with target-specific
37821 interpretation formatted as a big-endian hex string, literal @samp{-1}
37822 to indicate all processes or threads (respectively), or @samp{0} to
37823 indicate an arbitrary process or thread. Specifying just a process, as
37824 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37825 error to specify all processes but a specific thread, such as
37826 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37827 for those packets and replies explicitly documented to include a process
37828 ID, rather than a @var{thread-id}.
37830 The multiprocess @var{thread-id} syntax extensions are only used if both
37831 @value{GDBN} and the stub report support for the @samp{multiprocess}
37832 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37835 Note that all packet forms beginning with an upper- or lower-case
37836 letter, other than those described here, are reserved for future use.
37838 Here are the packet descriptions.
37843 @cindex @samp{!} packet
37844 @anchor{extended mode}
37845 Enable extended mode. In extended mode, the remote server is made
37846 persistent. The @samp{R} packet is used to restart the program being
37852 The remote target both supports and has enabled extended mode.
37856 @cindex @samp{?} packet
37857 Indicate the reason the target halted. The reply is the same as for
37858 step and continue. This packet has a special interpretation when the
37859 target is in non-stop mode; see @ref{Remote Non-Stop}.
37862 @xref{Stop Reply Packets}, for the reply specifications.
37864 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37865 @cindex @samp{A} packet
37866 Initialized @code{argv[]} array passed into program. @var{arglen}
37867 specifies the number of bytes in the hex encoded byte stream
37868 @var{arg}. See @code{gdbserver} for more details.
37873 The arguments were set.
37879 @cindex @samp{b} packet
37880 (Don't use this packet; its behavior is not well-defined.)
37881 Change the serial line speed to @var{baud}.
37883 JTC: @emph{When does the transport layer state change? When it's
37884 received, or after the ACK is transmitted. In either case, there are
37885 problems if the command or the acknowledgment packet is dropped.}
37887 Stan: @emph{If people really wanted to add something like this, and get
37888 it working for the first time, they ought to modify ser-unix.c to send
37889 some kind of out-of-band message to a specially-setup stub and have the
37890 switch happen "in between" packets, so that from remote protocol's point
37891 of view, nothing actually happened.}
37893 @item B @var{addr},@var{mode}
37894 @cindex @samp{B} packet
37895 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37896 breakpoint at @var{addr}.
37898 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37899 (@pxref{insert breakpoint or watchpoint packet}).
37901 @cindex @samp{bc} packet
37904 Backward continue. Execute the target system in reverse. No parameter.
37905 @xref{Reverse Execution}, for more information.
37908 @xref{Stop Reply Packets}, for the reply specifications.
37910 @cindex @samp{bs} packet
37913 Backward single step. Execute one instruction in reverse. No parameter.
37914 @xref{Reverse Execution}, for more information.
37917 @xref{Stop Reply Packets}, for the reply specifications.
37919 @item c @r{[}@var{addr}@r{]}
37920 @cindex @samp{c} packet
37921 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37922 resume at current address.
37924 This packet is deprecated for multi-threading support. @xref{vCont
37928 @xref{Stop Reply Packets}, for the reply specifications.
37930 @item C @var{sig}@r{[};@var{addr}@r{]}
37931 @cindex @samp{C} packet
37932 Continue with signal @var{sig} (hex signal number). If
37933 @samp{;@var{addr}} is omitted, resume at same address.
37935 This packet is deprecated for multi-threading support. @xref{vCont
37939 @xref{Stop Reply Packets}, for the reply specifications.
37942 @cindex @samp{d} packet
37945 Don't use this packet; instead, define a general set packet
37946 (@pxref{General Query Packets}).
37950 @cindex @samp{D} packet
37951 The first form of the packet is used to detach @value{GDBN} from the
37952 remote system. It is sent to the remote target
37953 before @value{GDBN} disconnects via the @code{detach} command.
37955 The second form, including a process ID, is used when multiprocess
37956 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37957 detach only a specific process. The @var{pid} is specified as a
37958 big-endian hex string.
37968 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37969 @cindex @samp{F} packet
37970 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37971 This is part of the File-I/O protocol extension. @xref{File-I/O
37972 Remote Protocol Extension}, for the specification.
37975 @anchor{read registers packet}
37976 @cindex @samp{g} packet
37977 Read general registers.
37981 @item @var{XX@dots{}}
37982 Each byte of register data is described by two hex digits. The bytes
37983 with the register are transmitted in target byte order. The size of
37984 each register and their position within the @samp{g} packet are
37985 determined by the @value{GDBN} internal gdbarch functions
37986 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37987 specification of several standard @samp{g} packets is specified below.
37989 When reading registers from a trace frame (@pxref{Analyze Collected
37990 Data,,Using the Collected Data}), the stub may also return a string of
37991 literal @samp{x}'s in place of the register data digits, to indicate
37992 that the corresponding register has not been collected, thus its value
37993 is unavailable. For example, for an architecture with 4 registers of
37994 4 bytes each, the following reply indicates to @value{GDBN} that
37995 registers 0 and 2 have not been collected, while registers 1 and 3
37996 have been collected, and both have zero value:
38000 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38007 @item G @var{XX@dots{}}
38008 @cindex @samp{G} packet
38009 Write general registers. @xref{read registers packet}, for a
38010 description of the @var{XX@dots{}} data.
38020 @item H @var{op} @var{thread-id}
38021 @cindex @samp{H} packet
38022 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38023 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38024 it should be @samp{c} for step and continue operations (note that this
38025 is deprecated, supporting the @samp{vCont} command is a better
38026 option), @samp{g} for other operations. The thread designator
38027 @var{thread-id} has the format and interpretation described in
38028 @ref{thread-id syntax}.
38039 @c 'H': How restrictive (or permissive) is the thread model. If a
38040 @c thread is selected and stopped, are other threads allowed
38041 @c to continue to execute? As I mentioned above, I think the
38042 @c semantics of each command when a thread is selected must be
38043 @c described. For example:
38045 @c 'g': If the stub supports threads and a specific thread is
38046 @c selected, returns the register block from that thread;
38047 @c otherwise returns current registers.
38049 @c 'G' If the stub supports threads and a specific thread is
38050 @c selected, sets the registers of the register block of
38051 @c that thread; otherwise sets current registers.
38053 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38054 @anchor{cycle step packet}
38055 @cindex @samp{i} packet
38056 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38057 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38058 step starting at that address.
38061 @cindex @samp{I} packet
38062 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38066 @cindex @samp{k} packet
38069 FIXME: @emph{There is no description of how to operate when a specific
38070 thread context has been selected (i.e.@: does 'k' kill only that
38073 @item m @var{addr},@var{length}
38074 @cindex @samp{m} packet
38075 Read @var{length} bytes of memory starting at address @var{addr}.
38076 Note that @var{addr} may not be aligned to any particular boundary.
38078 The stub need not use any particular size or alignment when gathering
38079 data from memory for the response; even if @var{addr} is word-aligned
38080 and @var{length} is a multiple of the word size, the stub is free to
38081 use byte accesses, or not. For this reason, this packet may not be
38082 suitable for accessing memory-mapped I/O devices.
38083 @cindex alignment of remote memory accesses
38084 @cindex size of remote memory accesses
38085 @cindex memory, alignment and size of remote accesses
38089 @item @var{XX@dots{}}
38090 Memory contents; each byte is transmitted as a two-digit hexadecimal
38091 number. The reply may contain fewer bytes than requested if the
38092 server was able to read only part of the region of memory.
38097 @item M @var{addr},@var{length}:@var{XX@dots{}}
38098 @cindex @samp{M} packet
38099 Write @var{length} bytes of memory starting at address @var{addr}.
38100 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38101 hexadecimal number.
38108 for an error (this includes the case where only part of the data was
38113 @cindex @samp{p} packet
38114 Read the value of register @var{n}; @var{n} is in hex.
38115 @xref{read registers packet}, for a description of how the returned
38116 register value is encoded.
38120 @item @var{XX@dots{}}
38121 the register's value
38125 Indicating an unrecognized @var{query}.
38128 @item P @var{n@dots{}}=@var{r@dots{}}
38129 @anchor{write register packet}
38130 @cindex @samp{P} packet
38131 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38132 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38133 digits for each byte in the register (target byte order).
38143 @item q @var{name} @var{params}@dots{}
38144 @itemx Q @var{name} @var{params}@dots{}
38145 @cindex @samp{q} packet
38146 @cindex @samp{Q} packet
38147 General query (@samp{q}) and set (@samp{Q}). These packets are
38148 described fully in @ref{General Query Packets}.
38151 @cindex @samp{r} packet
38152 Reset the entire system.
38154 Don't use this packet; use the @samp{R} packet instead.
38157 @cindex @samp{R} packet
38158 Restart the program being debugged. @var{XX}, while needed, is ignored.
38159 This packet is only available in extended mode (@pxref{extended mode}).
38161 The @samp{R} packet has no reply.
38163 @item s @r{[}@var{addr}@r{]}
38164 @cindex @samp{s} packet
38165 Single step. @var{addr} is the address at which to resume. If
38166 @var{addr} is omitted, resume at same address.
38168 This packet is deprecated for multi-threading support. @xref{vCont
38172 @xref{Stop Reply Packets}, for the reply specifications.
38174 @item S @var{sig}@r{[};@var{addr}@r{]}
38175 @anchor{step with signal packet}
38176 @cindex @samp{S} packet
38177 Step with signal. This is analogous to the @samp{C} packet, but
38178 requests a single-step, rather than a normal resumption of execution.
38180 This packet is deprecated for multi-threading support. @xref{vCont
38184 @xref{Stop Reply Packets}, for the reply specifications.
38186 @item t @var{addr}:@var{PP},@var{MM}
38187 @cindex @samp{t} packet
38188 Search backwards starting at address @var{addr} for a match with pattern
38189 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38190 @var{addr} must be at least 3 digits.
38192 @item T @var{thread-id}
38193 @cindex @samp{T} packet
38194 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38199 thread is still alive
38205 Packets starting with @samp{v} are identified by a multi-letter name,
38206 up to the first @samp{;} or @samp{?} (or the end of the packet).
38208 @item vAttach;@var{pid}
38209 @cindex @samp{vAttach} packet
38210 Attach to a new process with the specified process ID @var{pid}.
38211 The process ID is a
38212 hexadecimal integer identifying the process. In all-stop mode, all
38213 threads in the attached process are stopped; in non-stop mode, it may be
38214 attached without being stopped if that is supported by the target.
38216 @c In non-stop mode, on a successful vAttach, the stub should set the
38217 @c current thread to a thread of the newly-attached process. After
38218 @c attaching, GDB queries for the attached process's thread ID with qC.
38219 @c Also note that, from a user perspective, whether or not the
38220 @c target is stopped on attach in non-stop mode depends on whether you
38221 @c use the foreground or background version of the attach command, not
38222 @c on what vAttach does; GDB does the right thing with respect to either
38223 @c stopping or restarting threads.
38225 This packet is only available in extended mode (@pxref{extended mode}).
38231 @item @r{Any stop packet}
38232 for success in all-stop mode (@pxref{Stop Reply Packets})
38234 for success in non-stop mode (@pxref{Remote Non-Stop})
38237 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38238 @cindex @samp{vCont} packet
38239 @anchor{vCont packet}
38240 Resume the inferior, specifying different actions for each thread.
38241 If an action is specified with no @var{thread-id}, then it is applied to any
38242 threads that don't have a specific action specified; if no default action is
38243 specified then other threads should remain stopped in all-stop mode and
38244 in their current state in non-stop mode.
38245 Specifying multiple
38246 default actions is an error; specifying no actions is also an error.
38247 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38249 Currently supported actions are:
38255 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38259 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38262 @item r @var{start},@var{end}
38263 Step once, and then keep stepping as long as the thread stops at
38264 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38265 The remote stub reports a stop reply when either the thread goes out
38266 of the range or is stopped due to an unrelated reason, such as hitting
38267 a breakpoint. @xref{range stepping}.
38269 If the range is empty (@var{start} == @var{end}), then the action
38270 becomes equivalent to the @samp{s} action. In other words,
38271 single-step once, and report the stop (even if the stepped instruction
38272 jumps to @var{start}).
38274 (A stop reply may be sent at any point even if the PC is still within
38275 the stepping range; for example, it is valid to implement this packet
38276 in a degenerate way as a single instruction step operation.)
38280 The optional argument @var{addr} normally associated with the
38281 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38282 not supported in @samp{vCont}.
38284 The @samp{t} action is only relevant in non-stop mode
38285 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38286 A stop reply should be generated for any affected thread not already stopped.
38287 When a thread is stopped by means of a @samp{t} action,
38288 the corresponding stop reply should indicate that the thread has stopped with
38289 signal @samp{0}, regardless of whether the target uses some other signal
38290 as an implementation detail.
38292 The stub must support @samp{vCont} if it reports support for
38293 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38294 this case @samp{vCont} actions can be specified to apply to all threads
38295 in a process by using the @samp{p@var{pid}.-1} form of the
38299 @xref{Stop Reply Packets}, for the reply specifications.
38302 @cindex @samp{vCont?} packet
38303 Request a list of actions supported by the @samp{vCont} packet.
38307 @item vCont@r{[};@var{action}@dots{}@r{]}
38308 The @samp{vCont} packet is supported. Each @var{action} is a supported
38309 command in the @samp{vCont} packet.
38311 The @samp{vCont} packet is not supported.
38314 @item vFile:@var{operation}:@var{parameter}@dots{}
38315 @cindex @samp{vFile} packet
38316 Perform a file operation on the target system. For details,
38317 see @ref{Host I/O Packets}.
38319 @item vFlashErase:@var{addr},@var{length}
38320 @cindex @samp{vFlashErase} packet
38321 Direct the stub to erase @var{length} bytes of flash starting at
38322 @var{addr}. The region may enclose any number of flash blocks, but
38323 its start and end must fall on block boundaries, as indicated by the
38324 flash block size appearing in the memory map (@pxref{Memory Map
38325 Format}). @value{GDBN} groups flash memory programming operations
38326 together, and sends a @samp{vFlashDone} request after each group; the
38327 stub is allowed to delay erase operation until the @samp{vFlashDone}
38328 packet is received.
38338 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38339 @cindex @samp{vFlashWrite} packet
38340 Direct the stub to write data to flash address @var{addr}. The data
38341 is passed in binary form using the same encoding as for the @samp{X}
38342 packet (@pxref{Binary Data}). The memory ranges specified by
38343 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38344 not overlap, and must appear in order of increasing addresses
38345 (although @samp{vFlashErase} packets for higher addresses may already
38346 have been received; the ordering is guaranteed only between
38347 @samp{vFlashWrite} packets). If a packet writes to an address that was
38348 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38349 target-specific method, the results are unpredictable.
38357 for vFlashWrite addressing non-flash memory
38363 @cindex @samp{vFlashDone} packet
38364 Indicate to the stub that flash programming operation is finished.
38365 The stub is permitted to delay or batch the effects of a group of
38366 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38367 @samp{vFlashDone} packet is received. The contents of the affected
38368 regions of flash memory are unpredictable until the @samp{vFlashDone}
38369 request is completed.
38371 @item vKill;@var{pid}
38372 @cindex @samp{vKill} packet
38373 Kill the process with the specified process ID. @var{pid} is a
38374 hexadecimal integer identifying the process. This packet is used in
38375 preference to @samp{k} when multiprocess protocol extensions are
38376 supported; see @ref{multiprocess extensions}.
38386 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38387 @cindex @samp{vRun} packet
38388 Run the program @var{filename}, passing it each @var{argument} on its
38389 command line. The file and arguments are hex-encoded strings. If
38390 @var{filename} is an empty string, the stub may use a default program
38391 (e.g.@: the last program run). The program is created in the stopped
38394 @c FIXME: What about non-stop mode?
38396 This packet is only available in extended mode (@pxref{extended mode}).
38402 @item @r{Any stop packet}
38403 for success (@pxref{Stop Reply Packets})
38407 @cindex @samp{vStopped} packet
38408 @xref{Notification Packets}.
38410 @item X @var{addr},@var{length}:@var{XX@dots{}}
38412 @cindex @samp{X} packet
38413 Write data to memory, where the data is transmitted in binary.
38414 @var{addr} is address, @var{length} is number of bytes,
38415 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38425 @item z @var{type},@var{addr},@var{kind}
38426 @itemx Z @var{type},@var{addr},@var{kind}
38427 @anchor{insert breakpoint or watchpoint packet}
38428 @cindex @samp{z} packet
38429 @cindex @samp{Z} packets
38430 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38431 watchpoint starting at address @var{address} of kind @var{kind}.
38433 Each breakpoint and watchpoint packet @var{type} is documented
38436 @emph{Implementation notes: A remote target shall return an empty string
38437 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38438 remote target shall support either both or neither of a given
38439 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38440 avoid potential problems with duplicate packets, the operations should
38441 be implemented in an idempotent way.}
38443 @item z0,@var{addr},@var{kind}
38444 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38445 @cindex @samp{z0} packet
38446 @cindex @samp{Z0} packet
38447 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38448 @var{addr} of type @var{kind}.
38450 A memory breakpoint is implemented by replacing the instruction at
38451 @var{addr} with a software breakpoint or trap instruction. The
38452 @var{kind} is target-specific and typically indicates the size of
38453 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38454 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38455 architectures have additional meanings for @var{kind};
38456 @var{cond_list} is an optional list of conditional expressions in bytecode
38457 form that should be evaluated on the target's side. These are the
38458 conditions that should be taken into consideration when deciding if
38459 the breakpoint trigger should be reported back to @var{GDBN}.
38461 The @var{cond_list} parameter is comprised of a series of expressions,
38462 concatenated without separators. Each expression has the following form:
38466 @item X @var{len},@var{expr}
38467 @var{len} is the length of the bytecode expression and @var{expr} is the
38468 actual conditional expression in bytecode form.
38472 The optional @var{cmd_list} parameter introduces commands that may be
38473 run on the target, rather than being reported back to @value{GDBN}.
38474 The parameter starts with a numeric flag @var{persist}; if the flag is
38475 nonzero, then the breakpoint may remain active and the commands
38476 continue to be run even when @value{GDBN} disconnects from the target.
38477 Following this flag is a series of expressions concatenated with no
38478 separators. Each expression has the following form:
38482 @item X @var{len},@var{expr}
38483 @var{len} is the length of the bytecode expression and @var{expr} is the
38484 actual conditional expression in bytecode form.
38488 see @ref{Architecture-Specific Protocol Details}.
38490 @emph{Implementation note: It is possible for a target to copy or move
38491 code that contains memory breakpoints (e.g., when implementing
38492 overlays). The behavior of this packet, in the presence of such a
38493 target, is not defined.}
38505 @item z1,@var{addr},@var{kind}
38506 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38507 @cindex @samp{z1} packet
38508 @cindex @samp{Z1} packet
38509 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38510 address @var{addr}.
38512 A hardware breakpoint is implemented using a mechanism that is not
38513 dependant on being able to modify the target's memory. @var{kind}
38514 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38516 @emph{Implementation note: A hardware breakpoint is not affected by code
38529 @item z2,@var{addr},@var{kind}
38530 @itemx Z2,@var{addr},@var{kind}
38531 @cindex @samp{z2} packet
38532 @cindex @samp{Z2} packet
38533 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38534 @var{kind} is interpreted as the number of bytes to watch.
38546 @item z3,@var{addr},@var{kind}
38547 @itemx Z3,@var{addr},@var{kind}
38548 @cindex @samp{z3} packet
38549 @cindex @samp{Z3} packet
38550 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38551 @var{kind} is interpreted as the number of bytes to watch.
38563 @item z4,@var{addr},@var{kind}
38564 @itemx Z4,@var{addr},@var{kind}
38565 @cindex @samp{z4} packet
38566 @cindex @samp{Z4} packet
38567 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38568 @var{kind} is interpreted as the number of bytes to watch.
38582 @node Stop Reply Packets
38583 @section Stop Reply Packets
38584 @cindex stop reply packets
38586 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38587 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38588 receive any of the below as a reply. Except for @samp{?}
38589 and @samp{vStopped}, that reply is only returned
38590 when the target halts. In the below the exact meaning of @dfn{signal
38591 number} is defined by the header @file{include/gdb/signals.h} in the
38592 @value{GDBN} source code.
38594 As in the description of request packets, we include spaces in the
38595 reply templates for clarity; these are not part of the reply packet's
38596 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38602 The program received signal number @var{AA} (a two-digit hexadecimal
38603 number). This is equivalent to a @samp{T} response with no
38604 @var{n}:@var{r} pairs.
38606 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38607 @cindex @samp{T} packet reply
38608 The program received signal number @var{AA} (a two-digit hexadecimal
38609 number). This is equivalent to an @samp{S} response, except that the
38610 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38611 and other information directly in the stop reply packet, reducing
38612 round-trip latency. Single-step and breakpoint traps are reported
38613 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38617 If @var{n} is a hexadecimal number, it is a register number, and the
38618 corresponding @var{r} gives that register's value. @var{r} is a
38619 series of bytes in target byte order, with each byte given by a
38620 two-digit hex number.
38623 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38624 the stopped thread, as specified in @ref{thread-id syntax}.
38627 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38628 the core on which the stop event was detected.
38631 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38632 specific event that stopped the target. The currently defined stop
38633 reasons are listed below. @var{aa} should be @samp{05}, the trap
38634 signal. At most one stop reason should be present.
38637 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38638 and go on to the next; this allows us to extend the protocol in the
38642 The currently defined stop reasons are:
38648 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38651 @cindex shared library events, remote reply
38653 The packet indicates that the loaded libraries have changed.
38654 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38655 list of loaded libraries. @var{r} is ignored.
38657 @cindex replay log events, remote reply
38659 The packet indicates that the target cannot continue replaying
38660 logged execution events, because it has reached the end (or the
38661 beginning when executing backward) of the log. The value of @var{r}
38662 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38663 for more information.
38667 @itemx W @var{AA} ; process:@var{pid}
38668 The process exited, and @var{AA} is the exit status. This is only
38669 applicable to certain targets.
38671 The second form of the response, including the process ID of the exited
38672 process, can be used only when @value{GDBN} has reported support for
38673 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38674 The @var{pid} is formatted as a big-endian hex string.
38677 @itemx X @var{AA} ; process:@var{pid}
38678 The process terminated with signal @var{AA}.
38680 The second form of the response, including the process ID of the
38681 terminated process, can be used only when @value{GDBN} has reported
38682 support for multiprocess protocol extensions; see @ref{multiprocess
38683 extensions}. The @var{pid} is formatted as a big-endian hex string.
38685 @item O @var{XX}@dots{}
38686 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38687 written as the program's console output. This can happen at any time
38688 while the program is running and the debugger should continue to wait
38689 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38691 @item F @var{call-id},@var{parameter}@dots{}
38692 @var{call-id} is the identifier which says which host system call should
38693 be called. This is just the name of the function. Translation into the
38694 correct system call is only applicable as it's defined in @value{GDBN}.
38695 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38698 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38699 this very system call.
38701 The target replies with this packet when it expects @value{GDBN} to
38702 call a host system call on behalf of the target. @value{GDBN} replies
38703 with an appropriate @samp{F} packet and keeps up waiting for the next
38704 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38705 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38706 Protocol Extension}, for more details.
38710 @node General Query Packets
38711 @section General Query Packets
38712 @cindex remote query requests
38714 Packets starting with @samp{q} are @dfn{general query packets};
38715 packets starting with @samp{Q} are @dfn{general set packets}. General
38716 query and set packets are a semi-unified form for retrieving and
38717 sending information to and from the stub.
38719 The initial letter of a query or set packet is followed by a name
38720 indicating what sort of thing the packet applies to. For example,
38721 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38722 definitions with the stub. These packet names follow some
38727 The name must not contain commas, colons or semicolons.
38729 Most @value{GDBN} query and set packets have a leading upper case
38732 The names of custom vendor packets should use a company prefix, in
38733 lower case, followed by a period. For example, packets designed at
38734 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38735 foos) or @samp{Qacme.bar} (for setting bars).
38738 The name of a query or set packet should be separated from any
38739 parameters by a @samp{:}; the parameters themselves should be
38740 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38741 full packet name, and check for a separator or the end of the packet,
38742 in case two packet names share a common prefix. New packets should not begin
38743 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38744 packets predate these conventions, and have arguments without any terminator
38745 for the packet name; we suspect they are in widespread use in places that
38746 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38747 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38750 Like the descriptions of the other packets, each description here
38751 has a template showing the packet's overall syntax, followed by an
38752 explanation of the packet's meaning. We include spaces in some of the
38753 templates for clarity; these are not part of the packet's syntax. No
38754 @value{GDBN} packet uses spaces to separate its components.
38756 Here are the currently defined query and set packets:
38762 Turn on or off the agent as a helper to perform some debugging operations
38763 delegated from @value{GDBN} (@pxref{Control Agent}).
38765 @item QAllow:@var{op}:@var{val}@dots{}
38766 @cindex @samp{QAllow} packet
38767 Specify which operations @value{GDBN} expects to request of the
38768 target, as a semicolon-separated list of operation name and value
38769 pairs. Possible values for @var{op} include @samp{WriteReg},
38770 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38771 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38772 indicating that @value{GDBN} will not request the operation, or 1,
38773 indicating that it may. (The target can then use this to set up its
38774 own internals optimally, for instance if the debugger never expects to
38775 insert breakpoints, it may not need to install its own trap handler.)
38778 @cindex current thread, remote request
38779 @cindex @samp{qC} packet
38780 Return the current thread ID.
38784 @item QC @var{thread-id}
38785 Where @var{thread-id} is a thread ID as documented in
38786 @ref{thread-id syntax}.
38787 @item @r{(anything else)}
38788 Any other reply implies the old thread ID.
38791 @item qCRC:@var{addr},@var{length}
38792 @cindex CRC of memory block, remote request
38793 @cindex @samp{qCRC} packet
38794 Compute the CRC checksum of a block of memory using CRC-32 defined in
38795 IEEE 802.3. The CRC is computed byte at a time, taking the most
38796 significant bit of each byte first. The initial pattern code
38797 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38799 @emph{Note:} This is the same CRC used in validating separate debug
38800 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38801 Files}). However the algorithm is slightly different. When validating
38802 separate debug files, the CRC is computed taking the @emph{least}
38803 significant bit of each byte first, and the final result is inverted to
38804 detect trailing zeros.
38809 An error (such as memory fault)
38810 @item C @var{crc32}
38811 The specified memory region's checksum is @var{crc32}.
38814 @item QDisableRandomization:@var{value}
38815 @cindex disable address space randomization, remote request
38816 @cindex @samp{QDisableRandomization} packet
38817 Some target operating systems will randomize the virtual address space
38818 of the inferior process as a security feature, but provide a feature
38819 to disable such randomization, e.g.@: to allow for a more deterministic
38820 debugging experience. On such systems, this packet with a @var{value}
38821 of 1 directs the target to disable address space randomization for
38822 processes subsequently started via @samp{vRun} packets, while a packet
38823 with a @var{value} of 0 tells the target to enable address space
38826 This packet is only available in extended mode (@pxref{extended mode}).
38831 The request succeeded.
38834 An error occurred. @var{nn} are hex digits.
38837 An empty reply indicates that @samp{QDisableRandomization} is not supported
38841 This packet is not probed by default; the remote stub must request it,
38842 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38843 This should only be done on targets that actually support disabling
38844 address space randomization.
38847 @itemx qsThreadInfo
38848 @cindex list active threads, remote request
38849 @cindex @samp{qfThreadInfo} packet
38850 @cindex @samp{qsThreadInfo} packet
38851 Obtain a list of all active thread IDs from the target (OS). Since there
38852 may be too many active threads to fit into one reply packet, this query
38853 works iteratively: it may require more than one query/reply sequence to
38854 obtain the entire list of threads. The first query of the sequence will
38855 be the @samp{qfThreadInfo} query; subsequent queries in the
38856 sequence will be the @samp{qsThreadInfo} query.
38858 NOTE: This packet replaces the @samp{qL} query (see below).
38862 @item m @var{thread-id}
38864 @item m @var{thread-id},@var{thread-id}@dots{}
38865 a comma-separated list of thread IDs
38867 (lower case letter @samp{L}) denotes end of list.
38870 In response to each query, the target will reply with a list of one or
38871 more thread IDs, separated by commas.
38872 @value{GDBN} will respond to each reply with a request for more thread
38873 ids (using the @samp{qs} form of the query), until the target responds
38874 with @samp{l} (lower-case ell, for @dfn{last}).
38875 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38878 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38879 @cindex get thread-local storage address, remote request
38880 @cindex @samp{qGetTLSAddr} packet
38881 Fetch the address associated with thread local storage specified
38882 by @var{thread-id}, @var{offset}, and @var{lm}.
38884 @var{thread-id} is the thread ID associated with the
38885 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38887 @var{offset} is the (big endian, hex encoded) offset associated with the
38888 thread local variable. (This offset is obtained from the debug
38889 information associated with the variable.)
38891 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38892 load module associated with the thread local storage. For example,
38893 a @sc{gnu}/Linux system will pass the link map address of the shared
38894 object associated with the thread local storage under consideration.
38895 Other operating environments may choose to represent the load module
38896 differently, so the precise meaning of this parameter will vary.
38900 @item @var{XX}@dots{}
38901 Hex encoded (big endian) bytes representing the address of the thread
38902 local storage requested.
38905 An error occurred. @var{nn} are hex digits.
38908 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38911 @item qGetTIBAddr:@var{thread-id}
38912 @cindex get thread information block address
38913 @cindex @samp{qGetTIBAddr} packet
38914 Fetch address of the Windows OS specific Thread Information Block.
38916 @var{thread-id} is the thread ID associated with the thread.
38920 @item @var{XX}@dots{}
38921 Hex encoded (big endian) bytes representing the linear address of the
38922 thread information block.
38925 An error occured. This means that either the thread was not found, or the
38926 address could not be retrieved.
38929 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38932 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38933 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38934 digit) is one to indicate the first query and zero to indicate a
38935 subsequent query; @var{threadcount} (two hex digits) is the maximum
38936 number of threads the response packet can contain; and @var{nextthread}
38937 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38938 returned in the response as @var{argthread}.
38940 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38944 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38945 Where: @var{count} (two hex digits) is the number of threads being
38946 returned; @var{done} (one hex digit) is zero to indicate more threads
38947 and one indicates no further threads; @var{argthreadid} (eight hex
38948 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38949 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38950 digits). See @code{remote.c:parse_threadlist_response()}.
38954 @cindex section offsets, remote request
38955 @cindex @samp{qOffsets} packet
38956 Get section offsets that the target used when relocating the downloaded
38961 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38962 Relocate the @code{Text} section by @var{xxx} from its original address.
38963 Relocate the @code{Data} section by @var{yyy} from its original address.
38964 If the object file format provides segment information (e.g.@: @sc{elf}
38965 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38966 segments by the supplied offsets.
38968 @emph{Note: while a @code{Bss} offset may be included in the response,
38969 @value{GDBN} ignores this and instead applies the @code{Data} offset
38970 to the @code{Bss} section.}
38972 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38973 Relocate the first segment of the object file, which conventionally
38974 contains program code, to a starting address of @var{xxx}. If
38975 @samp{DataSeg} is specified, relocate the second segment, which
38976 conventionally contains modifiable data, to a starting address of
38977 @var{yyy}. @value{GDBN} will report an error if the object file
38978 does not contain segment information, or does not contain at least
38979 as many segments as mentioned in the reply. Extra segments are
38980 kept at fixed offsets relative to the last relocated segment.
38983 @item qP @var{mode} @var{thread-id}
38984 @cindex thread information, remote request
38985 @cindex @samp{qP} packet
38986 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38987 encoded 32 bit mode; @var{thread-id} is a thread ID
38988 (@pxref{thread-id syntax}).
38990 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38993 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38997 @cindex non-stop mode, remote request
38998 @cindex @samp{QNonStop} packet
39000 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39001 @xref{Remote Non-Stop}, for more information.
39006 The request succeeded.
39009 An error occurred. @var{nn} are hex digits.
39012 An empty reply indicates that @samp{QNonStop} is not supported by
39016 This packet is not probed by default; the remote stub must request it,
39017 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39018 Use of this packet is controlled by the @code{set non-stop} command;
39019 @pxref{Non-Stop Mode}.
39021 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39022 @cindex pass signals to inferior, remote request
39023 @cindex @samp{QPassSignals} packet
39024 @anchor{QPassSignals}
39025 Each listed @var{signal} should be passed directly to the inferior process.
39026 Signals are numbered identically to continue packets and stop replies
39027 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39028 strictly greater than the previous item. These signals do not need to stop
39029 the inferior, or be reported to @value{GDBN}. All other signals should be
39030 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39031 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39032 new list. This packet improves performance when using @samp{handle
39033 @var{signal} nostop noprint pass}.
39038 The request succeeded.
39041 An error occurred. @var{nn} are hex digits.
39044 An empty reply indicates that @samp{QPassSignals} is not supported by
39048 Use of this packet is controlled by the @code{set remote pass-signals}
39049 command (@pxref{Remote Configuration, set remote pass-signals}).
39050 This packet is not probed by default; the remote stub must request it,
39051 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39053 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39054 @cindex signals the inferior may see, remote request
39055 @cindex @samp{QProgramSignals} packet
39056 @anchor{QProgramSignals}
39057 Each listed @var{signal} may be delivered to the inferior process.
39058 Others should be silently discarded.
39060 In some cases, the remote stub may need to decide whether to deliver a
39061 signal to the program or not without @value{GDBN} involvement. One
39062 example of that is while detaching --- the program's threads may have
39063 stopped for signals that haven't yet had a chance of being reported to
39064 @value{GDBN}, and so the remote stub can use the signal list specified
39065 by this packet to know whether to deliver or ignore those pending
39068 This does not influence whether to deliver a signal as requested by a
39069 resumption packet (@pxref{vCont packet}).
39071 Signals are numbered identically to continue packets and stop replies
39072 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39073 strictly greater than the previous item. Multiple
39074 @samp{QProgramSignals} packets do not combine; any earlier
39075 @samp{QProgramSignals} list is completely replaced by the new list.
39080 The request succeeded.
39083 An error occurred. @var{nn} are hex digits.
39086 An empty reply indicates that @samp{QProgramSignals} is not supported
39090 Use of this packet is controlled by the @code{set remote program-signals}
39091 command (@pxref{Remote Configuration, set remote program-signals}).
39092 This packet is not probed by default; the remote stub must request it,
39093 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39095 @item qRcmd,@var{command}
39096 @cindex execute remote command, remote request
39097 @cindex @samp{qRcmd} packet
39098 @var{command} (hex encoded) is passed to the local interpreter for
39099 execution. Invalid commands should be reported using the output
39100 string. Before the final result packet, the target may also respond
39101 with a number of intermediate @samp{O@var{output}} console output
39102 packets. @emph{Implementors should note that providing access to a
39103 stubs's interpreter may have security implications}.
39108 A command response with no output.
39110 A command response with the hex encoded output string @var{OUTPUT}.
39112 Indicate a badly formed request.
39114 An empty reply indicates that @samp{qRcmd} is not recognized.
39117 (Note that the @code{qRcmd} packet's name is separated from the
39118 command by a @samp{,}, not a @samp{:}, contrary to the naming
39119 conventions above. Please don't use this packet as a model for new
39122 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39123 @cindex searching memory, in remote debugging
39125 @cindex @samp{qSearch:memory} packet
39127 @cindex @samp{qSearch memory} packet
39128 @anchor{qSearch memory}
39129 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39130 @var{address} and @var{length} are encoded in hex.
39131 @var{search-pattern} is a sequence of bytes, hex encoded.
39136 The pattern was not found.
39138 The pattern was found at @var{address}.
39140 A badly formed request or an error was encountered while searching memory.
39142 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39145 @item QStartNoAckMode
39146 @cindex @samp{QStartNoAckMode} packet
39147 @anchor{QStartNoAckMode}
39148 Request that the remote stub disable the normal @samp{+}/@samp{-}
39149 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39154 The stub has switched to no-acknowledgment mode.
39155 @value{GDBN} acknowledges this reponse,
39156 but neither the stub nor @value{GDBN} shall send or expect further
39157 @samp{+}/@samp{-} acknowledgments in the current connection.
39159 An empty reply indicates that the stub does not support no-acknowledgment mode.
39162 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39163 @cindex supported packets, remote query
39164 @cindex features of the remote protocol
39165 @cindex @samp{qSupported} packet
39166 @anchor{qSupported}
39167 Tell the remote stub about features supported by @value{GDBN}, and
39168 query the stub for features it supports. This packet allows
39169 @value{GDBN} and the remote stub to take advantage of each others'
39170 features. @samp{qSupported} also consolidates multiple feature probes
39171 at startup, to improve @value{GDBN} performance---a single larger
39172 packet performs better than multiple smaller probe packets on
39173 high-latency links. Some features may enable behavior which must not
39174 be on by default, e.g.@: because it would confuse older clients or
39175 stubs. Other features may describe packets which could be
39176 automatically probed for, but are not. These features must be
39177 reported before @value{GDBN} will use them. This ``default
39178 unsupported'' behavior is not appropriate for all packets, but it
39179 helps to keep the initial connection time under control with new
39180 versions of @value{GDBN} which support increasing numbers of packets.
39184 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39185 The stub supports or does not support each returned @var{stubfeature},
39186 depending on the form of each @var{stubfeature} (see below for the
39189 An empty reply indicates that @samp{qSupported} is not recognized,
39190 or that no features needed to be reported to @value{GDBN}.
39193 The allowed forms for each feature (either a @var{gdbfeature} in the
39194 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39198 @item @var{name}=@var{value}
39199 The remote protocol feature @var{name} is supported, and associated
39200 with the specified @var{value}. The format of @var{value} depends
39201 on the feature, but it must not include a semicolon.
39203 The remote protocol feature @var{name} is supported, and does not
39204 need an associated value.
39206 The remote protocol feature @var{name} is not supported.
39208 The remote protocol feature @var{name} may be supported, and
39209 @value{GDBN} should auto-detect support in some other way when it is
39210 needed. This form will not be used for @var{gdbfeature} notifications,
39211 but may be used for @var{stubfeature} responses.
39214 Whenever the stub receives a @samp{qSupported} request, the
39215 supplied set of @value{GDBN} features should override any previous
39216 request. This allows @value{GDBN} to put the stub in a known
39217 state, even if the stub had previously been communicating with
39218 a different version of @value{GDBN}.
39220 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39225 This feature indicates whether @value{GDBN} supports multiprocess
39226 extensions to the remote protocol. @value{GDBN} does not use such
39227 extensions unless the stub also reports that it supports them by
39228 including @samp{multiprocess+} in its @samp{qSupported} reply.
39229 @xref{multiprocess extensions}, for details.
39232 This feature indicates that @value{GDBN} supports the XML target
39233 description. If the stub sees @samp{xmlRegisters=} with target
39234 specific strings separated by a comma, it will report register
39238 This feature indicates whether @value{GDBN} supports the
39239 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39240 instruction reply packet}).
39243 Stubs should ignore any unknown values for
39244 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39245 packet supports receiving packets of unlimited length (earlier
39246 versions of @value{GDBN} may reject overly long responses). Additional values
39247 for @var{gdbfeature} may be defined in the future to let the stub take
39248 advantage of new features in @value{GDBN}, e.g.@: incompatible
39249 improvements in the remote protocol---the @samp{multiprocess} feature is
39250 an example of such a feature. The stub's reply should be independent
39251 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39252 describes all the features it supports, and then the stub replies with
39253 all the features it supports.
39255 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39256 responses, as long as each response uses one of the standard forms.
39258 Some features are flags. A stub which supports a flag feature
39259 should respond with a @samp{+} form response. Other features
39260 require values, and the stub should respond with an @samp{=}
39263 Each feature has a default value, which @value{GDBN} will use if
39264 @samp{qSupported} is not available or if the feature is not mentioned
39265 in the @samp{qSupported} response. The default values are fixed; a
39266 stub is free to omit any feature responses that match the defaults.
39268 Not all features can be probed, but for those which can, the probing
39269 mechanism is useful: in some cases, a stub's internal
39270 architecture may not allow the protocol layer to know some information
39271 about the underlying target in advance. This is especially common in
39272 stubs which may be configured for multiple targets.
39274 These are the currently defined stub features and their properties:
39276 @multitable @columnfractions 0.35 0.2 0.12 0.2
39277 @c NOTE: The first row should be @headitem, but we do not yet require
39278 @c a new enough version of Texinfo (4.7) to use @headitem.
39280 @tab Value Required
39284 @item @samp{PacketSize}
39289 @item @samp{qXfer:auxv:read}
39294 @item @samp{qXfer:btrace:read}
39299 @item @samp{qXfer:features:read}
39304 @item @samp{qXfer:libraries:read}
39309 @item @samp{qXfer:libraries-svr4:read}
39314 @item @samp{augmented-libraries-svr4-read}
39319 @item @samp{qXfer:memory-map:read}
39324 @item @samp{qXfer:sdata:read}
39329 @item @samp{qXfer:spu:read}
39334 @item @samp{qXfer:spu:write}
39339 @item @samp{qXfer:siginfo:read}
39344 @item @samp{qXfer:siginfo:write}
39349 @item @samp{qXfer:threads:read}
39354 @item @samp{qXfer:traceframe-info:read}
39359 @item @samp{qXfer:uib:read}
39364 @item @samp{qXfer:fdpic:read}
39369 @item @samp{Qbtrace:off}
39374 @item @samp{Qbtrace:bts}
39379 @item @samp{QNonStop}
39384 @item @samp{QPassSignals}
39389 @item @samp{QStartNoAckMode}
39394 @item @samp{multiprocess}
39399 @item @samp{ConditionalBreakpoints}
39404 @item @samp{ConditionalTracepoints}
39409 @item @samp{ReverseContinue}
39414 @item @samp{ReverseStep}
39419 @item @samp{TracepointSource}
39424 @item @samp{QAgent}
39429 @item @samp{QAllow}
39434 @item @samp{QDisableRandomization}
39439 @item @samp{EnableDisableTracepoints}
39444 @item @samp{QTBuffer:size}
39449 @item @samp{tracenz}
39454 @item @samp{BreakpointCommands}
39461 These are the currently defined stub features, in more detail:
39464 @cindex packet size, remote protocol
39465 @item PacketSize=@var{bytes}
39466 The remote stub can accept packets up to at least @var{bytes} in
39467 length. @value{GDBN} will send packets up to this size for bulk
39468 transfers, and will never send larger packets. This is a limit on the
39469 data characters in the packet, including the frame and checksum.
39470 There is no trailing NUL byte in a remote protocol packet; if the stub
39471 stores packets in a NUL-terminated format, it should allow an extra
39472 byte in its buffer for the NUL. If this stub feature is not supported,
39473 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39475 @item qXfer:auxv:read
39476 The remote stub understands the @samp{qXfer:auxv:read} packet
39477 (@pxref{qXfer auxiliary vector read}).
39479 @item qXfer:btrace:read
39480 The remote stub understands the @samp{qXfer:btrace:read}
39481 packet (@pxref{qXfer btrace read}).
39483 @item qXfer:features:read
39484 The remote stub understands the @samp{qXfer:features:read} packet
39485 (@pxref{qXfer target description read}).
39487 @item qXfer:libraries:read
39488 The remote stub understands the @samp{qXfer:libraries:read} packet
39489 (@pxref{qXfer library list read}).
39491 @item qXfer:libraries-svr4:read
39492 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39493 (@pxref{qXfer svr4 library list read}).
39495 @item augmented-libraries-svr4-read
39496 The remote stub understands the augmented form of the
39497 @samp{qXfer:libraries-svr4:read} packet
39498 (@pxref{qXfer svr4 library list read}).
39500 @item qXfer:memory-map:read
39501 The remote stub understands the @samp{qXfer:memory-map:read} packet
39502 (@pxref{qXfer memory map read}).
39504 @item qXfer:sdata:read
39505 The remote stub understands the @samp{qXfer:sdata:read} packet
39506 (@pxref{qXfer sdata read}).
39508 @item qXfer:spu:read
39509 The remote stub understands the @samp{qXfer:spu:read} packet
39510 (@pxref{qXfer spu read}).
39512 @item qXfer:spu:write
39513 The remote stub understands the @samp{qXfer:spu:write} packet
39514 (@pxref{qXfer spu write}).
39516 @item qXfer:siginfo:read
39517 The remote stub understands the @samp{qXfer:siginfo:read} packet
39518 (@pxref{qXfer siginfo read}).
39520 @item qXfer:siginfo:write
39521 The remote stub understands the @samp{qXfer:siginfo:write} packet
39522 (@pxref{qXfer siginfo write}).
39524 @item qXfer:threads:read
39525 The remote stub understands the @samp{qXfer:threads:read} packet
39526 (@pxref{qXfer threads read}).
39528 @item qXfer:traceframe-info:read
39529 The remote stub understands the @samp{qXfer:traceframe-info:read}
39530 packet (@pxref{qXfer traceframe info read}).
39532 @item qXfer:uib:read
39533 The remote stub understands the @samp{qXfer:uib:read}
39534 packet (@pxref{qXfer unwind info block}).
39536 @item qXfer:fdpic:read
39537 The remote stub understands the @samp{qXfer:fdpic:read}
39538 packet (@pxref{qXfer fdpic loadmap read}).
39541 The remote stub understands the @samp{QNonStop} packet
39542 (@pxref{QNonStop}).
39545 The remote stub understands the @samp{QPassSignals} packet
39546 (@pxref{QPassSignals}).
39548 @item QStartNoAckMode
39549 The remote stub understands the @samp{QStartNoAckMode} packet and
39550 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39553 @anchor{multiprocess extensions}
39554 @cindex multiprocess extensions, in remote protocol
39555 The remote stub understands the multiprocess extensions to the remote
39556 protocol syntax. The multiprocess extensions affect the syntax of
39557 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39558 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39559 replies. Note that reporting this feature indicates support for the
39560 syntactic extensions only, not that the stub necessarily supports
39561 debugging of more than one process at a time. The stub must not use
39562 multiprocess extensions in packet replies unless @value{GDBN} has also
39563 indicated it supports them in its @samp{qSupported} request.
39565 @item qXfer:osdata:read
39566 The remote stub understands the @samp{qXfer:osdata:read} packet
39567 ((@pxref{qXfer osdata read}).
39569 @item ConditionalBreakpoints
39570 The target accepts and implements evaluation of conditional expressions
39571 defined for breakpoints. The target will only report breakpoint triggers
39572 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39574 @item ConditionalTracepoints
39575 The remote stub accepts and implements conditional expressions defined
39576 for tracepoints (@pxref{Tracepoint Conditions}).
39578 @item ReverseContinue
39579 The remote stub accepts and implements the reverse continue packet
39583 The remote stub accepts and implements the reverse step packet
39586 @item TracepointSource
39587 The remote stub understands the @samp{QTDPsrc} packet that supplies
39588 the source form of tracepoint definitions.
39591 The remote stub understands the @samp{QAgent} packet.
39594 The remote stub understands the @samp{QAllow} packet.
39596 @item QDisableRandomization
39597 The remote stub understands the @samp{QDisableRandomization} packet.
39599 @item StaticTracepoint
39600 @cindex static tracepoints, in remote protocol
39601 The remote stub supports static tracepoints.
39603 @item InstallInTrace
39604 @anchor{install tracepoint in tracing}
39605 The remote stub supports installing tracepoint in tracing.
39607 @item EnableDisableTracepoints
39608 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39609 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39610 to be enabled and disabled while a trace experiment is running.
39612 @item QTBuffer:size
39613 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39614 packet that allows to change the size of the trace buffer.
39617 @cindex string tracing, in remote protocol
39618 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39619 See @ref{Bytecode Descriptions} for details about the bytecode.
39621 @item BreakpointCommands
39622 @cindex breakpoint commands, in remote protocol
39623 The remote stub supports running a breakpoint's command list itself,
39624 rather than reporting the hit to @value{GDBN}.
39627 The remote stub understands the @samp{Qbtrace:off} packet.
39630 The remote stub understands the @samp{Qbtrace:bts} packet.
39635 @cindex symbol lookup, remote request
39636 @cindex @samp{qSymbol} packet
39637 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39638 requests. Accept requests from the target for the values of symbols.
39643 The target does not need to look up any (more) symbols.
39644 @item qSymbol:@var{sym_name}
39645 The target requests the value of symbol @var{sym_name} (hex encoded).
39646 @value{GDBN} may provide the value by using the
39647 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39651 @item qSymbol:@var{sym_value}:@var{sym_name}
39652 Set the value of @var{sym_name} to @var{sym_value}.
39654 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39655 target has previously requested.
39657 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39658 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39664 The target does not need to look up any (more) symbols.
39665 @item qSymbol:@var{sym_name}
39666 The target requests the value of a new symbol @var{sym_name} (hex
39667 encoded). @value{GDBN} will continue to supply the values of symbols
39668 (if available), until the target ceases to request them.
39673 @itemx QTDisconnected
39680 @itemx qTMinFTPILen
39682 @xref{Tracepoint Packets}.
39684 @item qThreadExtraInfo,@var{thread-id}
39685 @cindex thread attributes info, remote request
39686 @cindex @samp{qThreadExtraInfo} packet
39687 Obtain a printable string description of a thread's attributes from
39688 the target OS. @var{thread-id} is a thread ID;
39689 see @ref{thread-id syntax}. This
39690 string may contain anything that the target OS thinks is interesting
39691 for @value{GDBN} to tell the user about the thread. The string is
39692 displayed in @value{GDBN}'s @code{info threads} display. Some
39693 examples of possible thread extra info strings are @samp{Runnable}, or
39694 @samp{Blocked on Mutex}.
39698 @item @var{XX}@dots{}
39699 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39700 comprising the printable string containing the extra information about
39701 the thread's attributes.
39704 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39705 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39706 conventions above. Please don't use this packet as a model for new
39725 @xref{Tracepoint Packets}.
39727 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39728 @cindex read special object, remote request
39729 @cindex @samp{qXfer} packet
39730 @anchor{qXfer read}
39731 Read uninterpreted bytes from the target's special data area
39732 identified by the keyword @var{object}. Request @var{length} bytes
39733 starting at @var{offset} bytes into the data. The content and
39734 encoding of @var{annex} is specific to @var{object}; it can supply
39735 additional details about what data to access.
39737 Here are the specific requests of this form defined so far. All
39738 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39739 formats, listed below.
39742 @item qXfer:auxv:read::@var{offset},@var{length}
39743 @anchor{qXfer auxiliary vector read}
39744 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39745 auxiliary vector}. Note @var{annex} must be empty.
39747 This packet is not probed by default; the remote stub must request it,
39748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39750 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39751 @anchor{qXfer btrace read}
39753 Return a description of the current branch trace.
39754 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39755 packet may have one of the following values:
39759 Returns all available branch trace.
39762 Returns all available branch trace if the branch trace changed since
39763 the last read request.
39766 This packet is not probed by default; the remote stub must request it
39767 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39769 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39770 @anchor{qXfer target description read}
39771 Access the @dfn{target description}. @xref{Target Descriptions}. The
39772 annex specifies which XML document to access. The main description is
39773 always loaded from the @samp{target.xml} annex.
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:read:@var{annex}:@var{offset},@var{length}
39779 @anchor{qXfer library list read}
39780 Access the target's list of loaded libraries. @xref{Library List Format}.
39781 The annex part of the generic @samp{qXfer} packet must be empty
39782 (@pxref{qXfer read}).
39784 Targets which maintain a list of libraries in the program's memory do
39785 not need to implement this packet; it is designed for platforms where
39786 the operating system manages the list of loaded libraries.
39788 This packet is not probed by default; the remote stub must request it,
39789 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39791 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39792 @anchor{qXfer svr4 library list read}
39793 Access the target's list of loaded libraries when the target is an SVR4
39794 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39795 of the generic @samp{qXfer} packet must be empty unless the remote
39796 stub indicated it supports the augmented form of this packet
39797 by supplying an appropriate @samp{qSupported} response
39798 (@pxref{qXfer read}, @ref{qSupported}).
39800 This packet is optional for better performance on SVR4 targets.
39801 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39803 This packet is not probed by default; the remote stub must request it,
39804 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39806 If the remote stub indicates it supports the augmented form of this
39807 packet then the annex part of the generic @samp{qXfer} packet may
39808 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39809 arguments. The currently supported arguments are:
39812 @item start=@var{address}
39813 A hexadecimal number specifying the address of the @samp{struct
39814 link_map} to start reading the library list from. If unset or zero
39815 then the first @samp{struct link_map} in the library list will be
39816 chosen as the starting point.
39818 @item prev=@var{address}
39819 A hexadecimal number specifying the address of the @samp{struct
39820 link_map} immediately preceding the @samp{struct link_map}
39821 specified by the @samp{start} argument. If unset or zero then
39822 the remote stub will expect that no @samp{struct link_map}
39823 exists prior to the starting point.
39827 Arguments that are not understood by the remote stub will be silently
39830 @item qXfer:memory-map:read::@var{offset},@var{length}
39831 @anchor{qXfer memory map read}
39832 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39833 annex part of the generic @samp{qXfer} packet must be empty
39834 (@pxref{qXfer read}).
39836 This packet is not probed by default; the remote stub must request it,
39837 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39839 @item qXfer:sdata:read::@var{offset},@var{length}
39840 @anchor{qXfer sdata read}
39842 Read contents of the extra collected static tracepoint marker
39843 information. The annex part of the generic @samp{qXfer} packet must
39844 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39847 This packet is not probed by default; the remote stub must request it,
39848 by supplying an appropriate @samp{qSupported} response
39849 (@pxref{qSupported}).
39851 @item qXfer:siginfo:read::@var{offset},@var{length}
39852 @anchor{qXfer siginfo read}
39853 Read contents of the extra signal information on the target
39854 system. The annex part of the generic @samp{qXfer} packet must be
39855 empty (@pxref{qXfer read}).
39857 This packet is not probed by default; the remote stub must request it,
39858 by supplying an appropriate @samp{qSupported} response
39859 (@pxref{qSupported}).
39861 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39862 @anchor{qXfer spu read}
39863 Read contents of an @code{spufs} file on the target system. The
39864 annex specifies which file to read; it must be of the form
39865 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39866 in the target process, and @var{name} identifes the @code{spufs} file
39867 in that context to be accessed.
39869 This packet is not probed by default; the remote stub must request it,
39870 by supplying an appropriate @samp{qSupported} response
39871 (@pxref{qSupported}).
39873 @item qXfer:threads:read::@var{offset},@var{length}
39874 @anchor{qXfer threads read}
39875 Access the list of threads on target. @xref{Thread List Format}. The
39876 annex part of the generic @samp{qXfer} packet must be empty
39877 (@pxref{qXfer read}).
39879 This packet is not probed by default; the remote stub must request it,
39880 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39882 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39883 @anchor{qXfer traceframe info read}
39885 Return a description of the current traceframe's contents.
39886 @xref{Traceframe Info Format}. The annex part of the generic
39887 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39889 This packet is not probed by default; the remote stub must request it,
39890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39892 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39893 @anchor{qXfer unwind info block}
39895 Return the unwind information block for @var{pc}. This packet is used
39896 on OpenVMS/ia64 to ask the kernel unwind information.
39898 This packet is not probed by default.
39900 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39901 @anchor{qXfer fdpic loadmap read}
39902 Read contents of @code{loadmap}s on the target system. The
39903 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39904 executable @code{loadmap} or interpreter @code{loadmap} to read.
39906 This packet is not probed by default; the remote stub must request it,
39907 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39909 @item qXfer:osdata:read::@var{offset},@var{length}
39910 @anchor{qXfer osdata read}
39911 Access the target's @dfn{operating system information}.
39912 @xref{Operating System Information}.
39919 Data @var{data} (@pxref{Binary Data}) has been read from the
39920 target. There may be more data at a higher address (although
39921 it is permitted to return @samp{m} even for the last valid
39922 block of data, as long as at least one byte of data was read).
39923 @var{data} may have fewer bytes than the @var{length} in the
39927 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39928 There is no more data to be read. @var{data} may have fewer bytes
39929 than the @var{length} in the request.
39932 The @var{offset} in the request is at the end of the data.
39933 There is no more data to be read.
39936 The request was malformed, or @var{annex} was invalid.
39939 The offset was invalid, or there was an error encountered reading the data.
39940 @var{nn} is a hex-encoded @code{errno} value.
39943 An empty reply indicates the @var{object} string was not recognized by
39944 the stub, or that the object does not support reading.
39947 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39948 @cindex write data into object, remote request
39949 @anchor{qXfer write}
39950 Write uninterpreted bytes into the target's special data area
39951 identified by the keyword @var{object}, starting at @var{offset} bytes
39952 into the data. @var{data}@dots{} is the binary-encoded data
39953 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39954 is specific to @var{object}; it can supply additional details about what data
39957 Here are the specific requests of this form defined so far. All
39958 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39959 formats, listed below.
39962 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39963 @anchor{qXfer siginfo write}
39964 Write @var{data} to the extra signal information on the target system.
39965 The annex part of the generic @samp{qXfer} packet must be
39966 empty (@pxref{qXfer write}).
39968 This packet is not probed by default; the remote stub must request it,
39969 by supplying an appropriate @samp{qSupported} response
39970 (@pxref{qSupported}).
39972 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39973 @anchor{qXfer spu write}
39974 Write @var{data} to an @code{spufs} file on the target system. The
39975 annex specifies which file to write; it must be of the form
39976 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39977 in the target process, and @var{name} identifes the @code{spufs} file
39978 in that context to be accessed.
39980 This packet is not probed by default; the remote stub must request it,
39981 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39987 @var{nn} (hex encoded) is the number of bytes written.
39988 This may be fewer bytes than supplied in the request.
39991 The request was malformed, or @var{annex} was invalid.
39994 The offset was invalid, or there was an error encountered writing the data.
39995 @var{nn} is a hex-encoded @code{errno} value.
39998 An empty reply indicates the @var{object} string was not
39999 recognized by the stub, or that the object does not support writing.
40002 @item qXfer:@var{object}:@var{operation}:@dots{}
40003 Requests of this form may be added in the future. When a stub does
40004 not recognize the @var{object} keyword, or its support for
40005 @var{object} does not recognize the @var{operation} keyword, the stub
40006 must respond with an empty packet.
40008 @item qAttached:@var{pid}
40009 @cindex query attached, remote request
40010 @cindex @samp{qAttached} packet
40011 Return an indication of whether the remote server attached to an
40012 existing process or created a new process. When the multiprocess
40013 protocol extensions are supported (@pxref{multiprocess extensions}),
40014 @var{pid} is an integer in hexadecimal format identifying the target
40015 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40016 the query packet will be simplified as @samp{qAttached}.
40018 This query is used, for example, to know whether the remote process
40019 should be detached or killed when a @value{GDBN} session is ended with
40020 the @code{quit} command.
40025 The remote server attached to an existing process.
40027 The remote server created a new process.
40029 A badly formed request or an error was encountered.
40033 Enable branch tracing for the current thread using bts tracing.
40038 Branch tracing has been enabled.
40040 A badly formed request or an error was encountered.
40044 Disable branch tracing for the current thread.
40049 Branch tracing has been disabled.
40051 A badly formed request or an error was encountered.
40056 @node Architecture-Specific Protocol Details
40057 @section Architecture-Specific Protocol Details
40059 This section describes how the remote protocol is applied to specific
40060 target architectures. Also see @ref{Standard Target Features}, for
40061 details of XML target descriptions for each architecture.
40064 * ARM-Specific Protocol Details::
40065 * MIPS-Specific Protocol Details::
40068 @node ARM-Specific Protocol Details
40069 @subsection @acronym{ARM}-specific Protocol Details
40072 * ARM Breakpoint Kinds::
40075 @node ARM Breakpoint Kinds
40076 @subsubsection @acronym{ARM} Breakpoint Kinds
40077 @cindex breakpoint kinds, @acronym{ARM}
40079 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40084 16-bit Thumb mode breakpoint.
40087 32-bit Thumb mode (Thumb-2) breakpoint.
40090 32-bit @acronym{ARM} mode breakpoint.
40094 @node MIPS-Specific Protocol Details
40095 @subsection @acronym{MIPS}-specific Protocol Details
40098 * MIPS Register packet Format::
40099 * MIPS Breakpoint Kinds::
40102 @node MIPS Register packet Format
40103 @subsubsection @acronym{MIPS} Register Packet Format
40104 @cindex register packet format, @acronym{MIPS}
40106 The following @code{g}/@code{G} packets have previously been defined.
40107 In the below, some thirty-two bit registers are transferred as
40108 sixty-four bits. Those registers should be zero/sign extended (which?)
40109 to fill the space allocated. Register bytes are transferred in target
40110 byte order. The two nibbles within a register byte are transferred
40111 most-significant -- least-significant.
40116 All registers are transferred as thirty-two bit quantities in the order:
40117 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40118 registers; fsr; fir; fp.
40121 All registers are transferred as sixty-four bit quantities (including
40122 thirty-two bit registers such as @code{sr}). The ordering is the same
40127 @node MIPS Breakpoint Kinds
40128 @subsubsection @acronym{MIPS} Breakpoint Kinds
40129 @cindex breakpoint kinds, @acronym{MIPS}
40131 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40136 16-bit @acronym{MIPS16} mode breakpoint.
40139 16-bit @acronym{microMIPS} mode breakpoint.
40142 32-bit standard @acronym{MIPS} mode breakpoint.
40145 32-bit @acronym{microMIPS} mode breakpoint.
40149 @node Tracepoint Packets
40150 @section Tracepoint Packets
40151 @cindex tracepoint packets
40152 @cindex packets, tracepoint
40154 Here we describe the packets @value{GDBN} uses to implement
40155 tracepoints (@pxref{Tracepoints}).
40159 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40160 @cindex @samp{QTDP} packet
40161 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40162 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40163 the tracepoint is disabled. @var{step} is the tracepoint's step
40164 count, and @var{pass} is its pass count. If an @samp{F} is present,
40165 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40166 the number of bytes that the target should copy elsewhere to make room
40167 for the tracepoint. If an @samp{X} is present, it introduces a
40168 tracepoint condition, which consists of a hexadecimal length, followed
40169 by a comma and hex-encoded bytes, in a manner similar to action
40170 encodings as described below. If the trailing @samp{-} is present,
40171 further @samp{QTDP} packets will follow to specify this tracepoint's
40177 The packet was understood and carried out.
40179 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40181 The packet was not recognized.
40184 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40185 Define actions to be taken when a tracepoint is hit. @var{n} and
40186 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40187 this tracepoint. This packet may only be sent immediately after
40188 another @samp{QTDP} packet that ended with a @samp{-}. If the
40189 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40190 specifying more actions for this tracepoint.
40192 In the series of action packets for a given tracepoint, at most one
40193 can have an @samp{S} before its first @var{action}. If such a packet
40194 is sent, it and the following packets define ``while-stepping''
40195 actions. Any prior packets define ordinary actions --- that is, those
40196 taken when the tracepoint is first hit. If no action packet has an
40197 @samp{S}, then all the packets in the series specify ordinary
40198 tracepoint actions.
40200 The @samp{@var{action}@dots{}} portion of the packet is a series of
40201 actions, concatenated without separators. Each action has one of the
40207 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40208 a hexadecimal number whose @var{i}'th bit is set if register number
40209 @var{i} should be collected. (The least significant bit is numbered
40210 zero.) Note that @var{mask} may be any number of digits long; it may
40211 not fit in a 32-bit word.
40213 @item M @var{basereg},@var{offset},@var{len}
40214 Collect @var{len} bytes of memory starting at the address in register
40215 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40216 @samp{-1}, then the range has a fixed address: @var{offset} is the
40217 address of the lowest byte to collect. The @var{basereg},
40218 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40219 values (the @samp{-1} value for @var{basereg} is a special case).
40221 @item X @var{len},@var{expr}
40222 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40223 it directs. @var{expr} is an agent expression, as described in
40224 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40225 two-digit hex number in the packet; @var{len} is the number of bytes
40226 in the expression (and thus one-half the number of hex digits in the
40231 Any number of actions may be packed together in a single @samp{QTDP}
40232 packet, as long as the packet does not exceed the maximum packet
40233 length (400 bytes, for many stubs). There may be only one @samp{R}
40234 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40235 actions. Any registers referred to by @samp{M} and @samp{X} actions
40236 must be collected by a preceding @samp{R} action. (The
40237 ``while-stepping'' actions are treated as if they were attached to a
40238 separate tracepoint, as far as these restrictions are concerned.)
40243 The packet was understood and carried out.
40245 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40247 The packet was not recognized.
40250 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40251 @cindex @samp{QTDPsrc} packet
40252 Specify a source string of tracepoint @var{n} at address @var{addr}.
40253 This is useful to get accurate reproduction of the tracepoints
40254 originally downloaded at the beginning of the trace run. @var{type}
40255 is the name of the tracepoint part, such as @samp{cond} for the
40256 tracepoint's conditional expression (see below for a list of types), while
40257 @var{bytes} is the string, encoded in hexadecimal.
40259 @var{start} is the offset of the @var{bytes} within the overall source
40260 string, while @var{slen} is the total length of the source string.
40261 This is intended for handling source strings that are longer than will
40262 fit in a single packet.
40263 @c Add detailed example when this info is moved into a dedicated
40264 @c tracepoint descriptions section.
40266 The available string types are @samp{at} for the location,
40267 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40268 @value{GDBN} sends a separate packet for each command in the action
40269 list, in the same order in which the commands are stored in the list.
40271 The target does not need to do anything with source strings except
40272 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40275 Although this packet is optional, and @value{GDBN} will only send it
40276 if the target replies with @samp{TracepointSource} @xref{General
40277 Query Packets}, it makes both disconnected tracing and trace files
40278 much easier to use. Otherwise the user must be careful that the
40279 tracepoints in effect while looking at trace frames are identical to
40280 the ones in effect during the trace run; even a small discrepancy
40281 could cause @samp{tdump} not to work, or a particular trace frame not
40284 @item QTDV:@var{n}:@var{value}
40285 @cindex define trace state variable, remote request
40286 @cindex @samp{QTDV} packet
40287 Create a new trace state variable, number @var{n}, with an initial
40288 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40289 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40290 the option of not using this packet for initial values of zero; the
40291 target should simply create the trace state variables as they are
40292 mentioned in expressions.
40294 @item QTFrame:@var{n}
40295 @cindex @samp{QTFrame} packet
40296 Select the @var{n}'th tracepoint frame from the buffer, and use the
40297 register and memory contents recorded there to answer subsequent
40298 request packets from @value{GDBN}.
40300 A successful reply from the stub indicates that the stub has found the
40301 requested frame. The response is a series of parts, concatenated
40302 without separators, describing the frame we selected. Each part has
40303 one of the following forms:
40307 The selected frame is number @var{n} in the trace frame buffer;
40308 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40309 was no frame matching the criteria in the request packet.
40312 The selected trace frame records a hit of tracepoint number @var{t};
40313 @var{t} is a hexadecimal number.
40317 @item QTFrame:pc:@var{addr}
40318 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40319 currently selected frame whose PC is @var{addr};
40320 @var{addr} is a hexadecimal number.
40322 @item QTFrame:tdp:@var{t}
40323 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40324 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40325 is a hexadecimal number.
40327 @item QTFrame:range:@var{start}:@var{end}
40328 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40329 currently selected frame whose PC is between @var{start} (inclusive)
40330 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40333 @item QTFrame:outside:@var{start}:@var{end}
40334 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40335 frame @emph{outside} the given range of addresses (exclusive).
40338 @cindex @samp{qTMinFTPILen} packet
40339 This packet requests the minimum length of instruction at which a fast
40340 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40341 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40342 it depends on the target system being able to create trampolines in
40343 the first 64K of memory, which might or might not be possible for that
40344 system. So the reply to this packet will be 4 if it is able to
40351 The minimum instruction length is currently unknown.
40353 The minimum instruction length is @var{length}, where @var{length} is greater
40354 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40355 that a fast tracepoint may be placed on any instruction regardless of size.
40357 An error has occurred.
40359 An empty reply indicates that the request is not supported by the stub.
40363 @cindex @samp{QTStart} packet
40364 Begin the tracepoint experiment. Begin collecting data from
40365 tracepoint hits in the trace frame buffer. This packet supports the
40366 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40367 instruction reply packet}).
40370 @cindex @samp{QTStop} packet
40371 End the tracepoint experiment. Stop collecting trace frames.
40373 @item QTEnable:@var{n}:@var{addr}
40375 @cindex @samp{QTEnable} packet
40376 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40377 experiment. If the tracepoint was previously disabled, then collection
40378 of data from it will resume.
40380 @item QTDisable:@var{n}:@var{addr}
40382 @cindex @samp{QTDisable} packet
40383 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40384 experiment. No more data will be collected from the tracepoint unless
40385 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40388 @cindex @samp{QTinit} packet
40389 Clear the table of tracepoints, and empty the trace frame buffer.
40391 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40392 @cindex @samp{QTro} packet
40393 Establish the given ranges of memory as ``transparent''. The stub
40394 will answer requests for these ranges from memory's current contents,
40395 if they were not collected as part of the tracepoint hit.
40397 @value{GDBN} uses this to mark read-only regions of memory, like those
40398 containing program code. Since these areas never change, they should
40399 still have the same contents they did when the tracepoint was hit, so
40400 there's no reason for the stub to refuse to provide their contents.
40402 @item QTDisconnected:@var{value}
40403 @cindex @samp{QTDisconnected} packet
40404 Set the choice to what to do with the tracing run when @value{GDBN}
40405 disconnects from the target. A @var{value} of 1 directs the target to
40406 continue the tracing run, while 0 tells the target to stop tracing if
40407 @value{GDBN} is no longer in the picture.
40410 @cindex @samp{qTStatus} packet
40411 Ask the stub if there is a trace experiment running right now.
40413 The reply has the form:
40417 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40418 @var{running} is a single digit @code{1} if the trace is presently
40419 running, or @code{0} if not. It is followed by semicolon-separated
40420 optional fields that an agent may use to report additional status.
40424 If the trace is not running, the agent may report any of several
40425 explanations as one of the optional fields:
40430 No trace has been run yet.
40432 @item tstop[:@var{text}]:0
40433 The trace was stopped by a user-originated stop command. The optional
40434 @var{text} field is a user-supplied string supplied as part of the
40435 stop command (for instance, an explanation of why the trace was
40436 stopped manually). It is hex-encoded.
40439 The trace stopped because the trace buffer filled up.
40441 @item tdisconnected:0
40442 The trace stopped because @value{GDBN} disconnected from the target.
40444 @item tpasscount:@var{tpnum}
40445 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40447 @item terror:@var{text}:@var{tpnum}
40448 The trace stopped because tracepoint @var{tpnum} had an error. The
40449 string @var{text} is available to describe the nature of the error
40450 (for instance, a divide by zero in the condition expression).
40451 @var{text} is hex encoded.
40454 The trace stopped for some other reason.
40458 Additional optional fields supply statistical and other information.
40459 Although not required, they are extremely useful for users monitoring
40460 the progress of a trace run. If a trace has stopped, and these
40461 numbers are reported, they must reflect the state of the just-stopped
40466 @item tframes:@var{n}
40467 The number of trace frames in the buffer.
40469 @item tcreated:@var{n}
40470 The total number of trace frames created during the run. This may
40471 be larger than the trace frame count, if the buffer is circular.
40473 @item tsize:@var{n}
40474 The total size of the trace buffer, in bytes.
40476 @item tfree:@var{n}
40477 The number of bytes still unused in the buffer.
40479 @item circular:@var{n}
40480 The value of the circular trace buffer flag. @code{1} means that the
40481 trace buffer is circular and old trace frames will be discarded if
40482 necessary to make room, @code{0} means that the trace buffer is linear
40485 @item disconn:@var{n}
40486 The value of the disconnected tracing flag. @code{1} means that
40487 tracing will continue after @value{GDBN} disconnects, @code{0} means
40488 that the trace run will stop.
40492 @item qTP:@var{tp}:@var{addr}
40493 @cindex tracepoint status, remote request
40494 @cindex @samp{qTP} packet
40495 Ask the stub for the current state of tracepoint number @var{tp} at
40496 address @var{addr}.
40500 @item V@var{hits}:@var{usage}
40501 The tracepoint has been hit @var{hits} times so far during the trace
40502 run, and accounts for @var{usage} in the trace buffer. Note that
40503 @code{while-stepping} steps are not counted as separate hits, but the
40504 steps' space consumption is added into the usage number.
40508 @item qTV:@var{var}
40509 @cindex trace state variable value, remote request
40510 @cindex @samp{qTV} packet
40511 Ask the stub for the value of the trace state variable number @var{var}.
40516 The value of the variable is @var{value}. This will be the current
40517 value of the variable if the user is examining a running target, or a
40518 saved value if the variable was collected in the trace frame that the
40519 user is looking at. Note that multiple requests may result in
40520 different reply values, such as when requesting values while the
40521 program is running.
40524 The value of the variable is unknown. This would occur, for example,
40525 if the user is examining a trace frame in which the requested variable
40530 @cindex @samp{qTfP} packet
40532 @cindex @samp{qTsP} packet
40533 These packets request data about tracepoints that are being used by
40534 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40535 of data, and multiple @code{qTsP} to get additional pieces. Replies
40536 to these packets generally take the form of the @code{QTDP} packets
40537 that define tracepoints. (FIXME add detailed syntax)
40540 @cindex @samp{qTfV} packet
40542 @cindex @samp{qTsV} packet
40543 These packets request data about trace state variables that are on the
40544 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40545 and multiple @code{qTsV} to get additional variables. Replies to
40546 these packets follow the syntax of the @code{QTDV} packets that define
40547 trace state variables.
40553 @cindex @samp{qTfSTM} packet
40554 @cindex @samp{qTsSTM} packet
40555 These packets request data about static tracepoint markers that exist
40556 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40557 first piece of data, and multiple @code{qTsSTM} to get additional
40558 pieces. Replies to these packets take the following form:
40562 @item m @var{address}:@var{id}:@var{extra}
40564 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40565 a comma-separated list of markers
40567 (lower case letter @samp{L}) denotes end of list.
40569 An error occurred. @var{nn} are hex digits.
40571 An empty reply indicates that the request is not supported by the
40575 @var{address} is encoded in hex.
40576 @var{id} and @var{extra} are strings encoded in hex.
40578 In response to each query, the target will reply with a list of one or
40579 more markers, separated by commas. @value{GDBN} will respond to each
40580 reply with a request for more markers (using the @samp{qs} form of the
40581 query), until the target responds with @samp{l} (lower-case ell, for
40584 @item qTSTMat:@var{address}
40586 @cindex @samp{qTSTMat} packet
40587 This packets requests data about static tracepoint markers in the
40588 target program at @var{address}. Replies to this packet follow the
40589 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40590 tracepoint markers.
40592 @item QTSave:@var{filename}
40593 @cindex @samp{QTSave} packet
40594 This packet directs the target to save trace data to the file name
40595 @var{filename} in the target's filesystem. @var{filename} is encoded
40596 as a hex string; the interpretation of the file name (relative vs
40597 absolute, wild cards, etc) is up to the target.
40599 @item qTBuffer:@var{offset},@var{len}
40600 @cindex @samp{qTBuffer} packet
40601 Return up to @var{len} bytes of the current contents of trace buffer,
40602 starting at @var{offset}. The trace buffer is treated as if it were
40603 a contiguous collection of traceframes, as per the trace file format.
40604 The reply consists as many hex-encoded bytes as the target can deliver
40605 in a packet; it is not an error to return fewer than were asked for.
40606 A reply consisting of just @code{l} indicates that no bytes are
40609 @item QTBuffer:circular:@var{value}
40610 This packet directs the target to use a circular trace buffer if
40611 @var{value} is 1, or a linear buffer if the value is 0.
40613 @item QTBuffer:size:@var{size}
40614 @anchor{QTBuffer-size}
40615 @cindex @samp{QTBuffer size} packet
40616 This packet directs the target to make the trace buffer be of size
40617 @var{size} if possible. A value of @code{-1} tells the target to
40618 use whatever size it prefers.
40620 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40621 @cindex @samp{QTNotes} packet
40622 This packet adds optional textual notes to the trace run. Allowable
40623 types include @code{user}, @code{notes}, and @code{tstop}, the
40624 @var{text} fields are arbitrary strings, hex-encoded.
40628 @subsection Relocate instruction reply packet
40629 When installing fast tracepoints in memory, the target may need to
40630 relocate the instruction currently at the tracepoint address to a
40631 different address in memory. For most instructions, a simple copy is
40632 enough, but, for example, call instructions that implicitly push the
40633 return address on the stack, and relative branches or other
40634 PC-relative instructions require offset adjustment, so that the effect
40635 of executing the instruction at a different address is the same as if
40636 it had executed in the original location.
40638 In response to several of the tracepoint packets, the target may also
40639 respond with a number of intermediate @samp{qRelocInsn} request
40640 packets before the final result packet, to have @value{GDBN} handle
40641 this relocation operation. If a packet supports this mechanism, its
40642 documentation will explicitly say so. See for example the above
40643 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40644 format of the request is:
40647 @item qRelocInsn:@var{from};@var{to}
40649 This requests @value{GDBN} to copy instruction at address @var{from}
40650 to address @var{to}, possibly adjusted so that executing the
40651 instruction at @var{to} has the same effect as executing it at
40652 @var{from}. @value{GDBN} writes the adjusted instruction to target
40653 memory starting at @var{to}.
40658 @item qRelocInsn:@var{adjusted_size}
40659 Informs the stub the relocation is complete. @var{adjusted_size} is
40660 the length in bytes of resulting relocated instruction sequence.
40662 A badly formed request was detected, or an error was encountered while
40663 relocating the instruction.
40666 @node Host I/O Packets
40667 @section Host I/O Packets
40668 @cindex Host I/O, remote protocol
40669 @cindex file transfer, remote protocol
40671 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40672 operations on the far side of a remote link. For example, Host I/O is
40673 used to upload and download files to a remote target with its own
40674 filesystem. Host I/O uses the same constant values and data structure
40675 layout as the target-initiated File-I/O protocol. However, the
40676 Host I/O packets are structured differently. The target-initiated
40677 protocol relies on target memory to store parameters and buffers.
40678 Host I/O requests are initiated by @value{GDBN}, and the
40679 target's memory is not involved. @xref{File-I/O Remote Protocol
40680 Extension}, for more details on the target-initiated protocol.
40682 The Host I/O request packets all encode a single operation along with
40683 its arguments. They have this format:
40687 @item vFile:@var{operation}: @var{parameter}@dots{}
40688 @var{operation} is the name of the particular request; the target
40689 should compare the entire packet name up to the second colon when checking
40690 for a supported operation. The format of @var{parameter} depends on
40691 the operation. Numbers are always passed in hexadecimal. Negative
40692 numbers have an explicit minus sign (i.e.@: two's complement is not
40693 used). Strings (e.g.@: filenames) are encoded as a series of
40694 hexadecimal bytes. The last argument to a system call may be a
40695 buffer of escaped binary data (@pxref{Binary Data}).
40699 The valid responses to Host I/O packets are:
40703 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40704 @var{result} is the integer value returned by this operation, usually
40705 non-negative for success and -1 for errors. If an error has occured,
40706 @var{errno} will be included in the result. @var{errno} will have a
40707 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40708 operations which return data, @var{attachment} supplies the data as a
40709 binary buffer. Binary buffers in response packets are escaped in the
40710 normal way (@pxref{Binary Data}). See the individual packet
40711 documentation for the interpretation of @var{result} and
40715 An empty response indicates that this operation is not recognized.
40719 These are the supported Host I/O operations:
40722 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40723 Open a file at @var{pathname} and return a file descriptor for it, or
40724 return -1 if an error occurs. @var{pathname} is a string,
40725 @var{flags} is an integer indicating a mask of open flags
40726 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40727 of mode bits to use if the file is created (@pxref{mode_t Values}).
40728 @xref{open}, for details of the open flags and mode values.
40730 @item vFile:close: @var{fd}
40731 Close the open file corresponding to @var{fd} and return 0, or
40732 -1 if an error occurs.
40734 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40735 Read data from the open file corresponding to @var{fd}. Up to
40736 @var{count} bytes will be read from the file, starting at @var{offset}
40737 relative to the start of the file. The target may read fewer bytes;
40738 common reasons include packet size limits and an end-of-file
40739 condition. The number of bytes read is returned. Zero should only be
40740 returned for a successful read at the end of the file, or if
40741 @var{count} was zero.
40743 The data read should be returned as a binary attachment on success.
40744 If zero bytes were read, the response should include an empty binary
40745 attachment (i.e.@: a trailing semicolon). The return value is the
40746 number of target bytes read; the binary attachment may be longer if
40747 some characters were escaped.
40749 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40750 Write @var{data} (a binary buffer) to the open file corresponding
40751 to @var{fd}. Start the write at @var{offset} from the start of the
40752 file. Unlike many @code{write} system calls, there is no
40753 separate @var{count} argument; the length of @var{data} in the
40754 packet is used. @samp{vFile:write} returns the number of bytes written,
40755 which may be shorter than the length of @var{data}, or -1 if an
40758 @item vFile:unlink: @var{pathname}
40759 Delete the file at @var{pathname} on the target. Return 0,
40760 or -1 if an error occurs. @var{pathname} is a string.
40762 @item vFile:readlink: @var{filename}
40763 Read value of symbolic link @var{filename} on the target. Return
40764 the number of bytes read, or -1 if an error occurs.
40766 The data read should be returned as a binary attachment on success.
40767 If zero bytes were read, the response should include an empty binary
40768 attachment (i.e.@: a trailing semicolon). The return value is the
40769 number of target bytes read; the binary attachment may be longer if
40770 some characters were escaped.
40775 @section Interrupts
40776 @cindex interrupts (remote protocol)
40778 When a program on the remote target is running, @value{GDBN} may
40779 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40780 a @code{BREAK} followed by @code{g},
40781 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40783 The precise meaning of @code{BREAK} is defined by the transport
40784 mechanism and may, in fact, be undefined. @value{GDBN} does not
40785 currently define a @code{BREAK} mechanism for any of the network
40786 interfaces except for TCP, in which case @value{GDBN} sends the
40787 @code{telnet} BREAK sequence.
40789 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40790 transport mechanisms. It is represented by sending the single byte
40791 @code{0x03} without any of the usual packet overhead described in
40792 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40793 transmitted as part of a packet, it is considered to be packet data
40794 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40795 (@pxref{X packet}), used for binary downloads, may include an unescaped
40796 @code{0x03} as part of its packet.
40798 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40799 When Linux kernel receives this sequence from serial port,
40800 it stops execution and connects to gdb.
40802 Stubs are not required to recognize these interrupt mechanisms and the
40803 precise meaning associated with receipt of the interrupt is
40804 implementation defined. If the target supports debugging of multiple
40805 threads and/or processes, it should attempt to interrupt all
40806 currently-executing threads and processes.
40807 If the stub is successful at interrupting the
40808 running program, it should send one of the stop
40809 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40810 of successfully stopping the program in all-stop mode, and a stop reply
40811 for each stopped thread in non-stop mode.
40812 Interrupts received while the
40813 program is stopped are discarded.
40815 @node Notification Packets
40816 @section Notification Packets
40817 @cindex notification packets
40818 @cindex packets, notification
40820 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40821 packets that require no acknowledgment. Both the GDB and the stub
40822 may send notifications (although the only notifications defined at
40823 present are sent by the stub). Notifications carry information
40824 without incurring the round-trip latency of an acknowledgment, and so
40825 are useful for low-impact communications where occasional packet loss
40828 A notification packet has the form @samp{% @var{data} #
40829 @var{checksum}}, where @var{data} is the content of the notification,
40830 and @var{checksum} is a checksum of @var{data}, computed and formatted
40831 as for ordinary @value{GDBN} packets. A notification's @var{data}
40832 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40833 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40834 to acknowledge the notification's receipt or to report its corruption.
40836 Every notification's @var{data} begins with a name, which contains no
40837 colon characters, followed by a colon character.
40839 Recipients should silently ignore corrupted notifications and
40840 notifications they do not understand. Recipients should restart
40841 timeout periods on receipt of a well-formed notification, whether or
40842 not they understand it.
40844 Senders should only send the notifications described here when this
40845 protocol description specifies that they are permitted. In the
40846 future, we may extend the protocol to permit existing notifications in
40847 new contexts; this rule helps older senders avoid confusing newer
40850 (Older versions of @value{GDBN} ignore bytes received until they see
40851 the @samp{$} byte that begins an ordinary packet, so new stubs may
40852 transmit notifications without fear of confusing older clients. There
40853 are no notifications defined for @value{GDBN} to send at the moment, but we
40854 assume that most older stubs would ignore them, as well.)
40856 Each notification is comprised of three parts:
40858 @item @var{name}:@var{event}
40859 The notification packet is sent by the side that initiates the
40860 exchange (currently, only the stub does that), with @var{event}
40861 carrying the specific information about the notification.
40862 @var{name} is the name of the notification.
40864 The acknowledge sent by the other side, usually @value{GDBN}, to
40865 acknowledge the exchange and request the event.
40868 The purpose of an asynchronous notification mechanism is to report to
40869 @value{GDBN} that something interesting happened in the remote stub.
40871 The remote stub may send notification @var{name}:@var{event}
40872 at any time, but @value{GDBN} acknowledges the notification when
40873 appropriate. The notification event is pending before @value{GDBN}
40874 acknowledges. Only one notification at a time may be pending; if
40875 additional events occur before @value{GDBN} has acknowledged the
40876 previous notification, they must be queued by the stub for later
40877 synchronous transmission in response to @var{ack} packets from
40878 @value{GDBN}. Because the notification mechanism is unreliable,
40879 the stub is permitted to resend a notification if it believes
40880 @value{GDBN} may not have received it.
40882 Specifically, notifications may appear when @value{GDBN} is not
40883 otherwise reading input from the stub, or when @value{GDBN} is
40884 expecting to read a normal synchronous response or a
40885 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40886 Notification packets are distinct from any other communication from
40887 the stub so there is no ambiguity.
40889 After receiving a notification, @value{GDBN} shall acknowledge it by
40890 sending a @var{ack} packet as a regular, synchronous request to the
40891 stub. Such acknowledgment is not required to happen immediately, as
40892 @value{GDBN} is permitted to send other, unrelated packets to the
40893 stub first, which the stub should process normally.
40895 Upon receiving a @var{ack} packet, if the stub has other queued
40896 events to report to @value{GDBN}, it shall respond by sending a
40897 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40898 packet to solicit further responses; again, it is permitted to send
40899 other, unrelated packets as well which the stub should process
40902 If the stub receives a @var{ack} packet and there are no additional
40903 @var{event} to report, the stub shall return an @samp{OK} response.
40904 At this point, @value{GDBN} has finished processing a notification
40905 and the stub has completed sending any queued events. @value{GDBN}
40906 won't accept any new notifications until the final @samp{OK} is
40907 received . If further notification events occur, the stub shall send
40908 a new notification, @value{GDBN} shall accept the notification, and
40909 the process shall be repeated.
40911 The process of asynchronous notification can be illustrated by the
40914 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40917 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40919 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40924 The following notifications are defined:
40925 @multitable @columnfractions 0.12 0.12 0.38 0.38
40934 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40935 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40936 for information on how these notifications are acknowledged by
40938 @tab Report an asynchronous stop event in non-stop mode.
40942 @node Remote Non-Stop
40943 @section Remote Protocol Support for Non-Stop Mode
40945 @value{GDBN}'s remote protocol supports non-stop debugging of
40946 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40947 supports non-stop mode, it should report that to @value{GDBN} by including
40948 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40950 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40951 establishing a new connection with the stub. Entering non-stop mode
40952 does not alter the state of any currently-running threads, but targets
40953 must stop all threads in any already-attached processes when entering
40954 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40955 probe the target state after a mode change.
40957 In non-stop mode, when an attached process encounters an event that
40958 would otherwise be reported with a stop reply, it uses the
40959 asynchronous notification mechanism (@pxref{Notification Packets}) to
40960 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40961 in all processes are stopped when a stop reply is sent, in non-stop
40962 mode only the thread reporting the stop event is stopped. That is,
40963 when reporting a @samp{S} or @samp{T} response to indicate completion
40964 of a step operation, hitting a breakpoint, or a fault, only the
40965 affected thread is stopped; any other still-running threads continue
40966 to run. When reporting a @samp{W} or @samp{X} response, all running
40967 threads belonging to other attached processes continue to run.
40969 In non-stop mode, the target shall respond to the @samp{?} packet as
40970 follows. First, any incomplete stop reply notification/@samp{vStopped}
40971 sequence in progress is abandoned. The target must begin a new
40972 sequence reporting stop events for all stopped threads, whether or not
40973 it has previously reported those events to @value{GDBN}. The first
40974 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40975 subsequent stop replies are sent as responses to @samp{vStopped} packets
40976 using the mechanism described above. The target must not send
40977 asynchronous stop reply notifications until the sequence is complete.
40978 If all threads are running when the target receives the @samp{?} packet,
40979 or if the target is not attached to any process, it shall respond
40982 @node Packet Acknowledgment
40983 @section Packet Acknowledgment
40985 @cindex acknowledgment, for @value{GDBN} remote
40986 @cindex packet acknowledgment, for @value{GDBN} remote
40987 By default, when either the host or the target machine receives a packet,
40988 the first response expected is an acknowledgment: either @samp{+} (to indicate
40989 the package was received correctly) or @samp{-} (to request retransmission).
40990 This mechanism allows the @value{GDBN} remote protocol to operate over
40991 unreliable transport mechanisms, such as a serial line.
40993 In cases where the transport mechanism is itself reliable (such as a pipe or
40994 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40995 It may be desirable to disable them in that case to reduce communication
40996 overhead, or for other reasons. This can be accomplished by means of the
40997 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40999 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41000 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41001 and response format still includes the normal checksum, as described in
41002 @ref{Overview}, but the checksum may be ignored by the receiver.
41004 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41005 no-acknowledgment mode, it should report that to @value{GDBN}
41006 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41007 @pxref{qSupported}.
41008 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41009 disabled via the @code{set remote noack-packet off} command
41010 (@pxref{Remote Configuration}),
41011 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41012 Only then may the stub actually turn off packet acknowledgments.
41013 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41014 response, which can be safely ignored by the stub.
41016 Note that @code{set remote noack-packet} command only affects negotiation
41017 between @value{GDBN} and the stub when subsequent connections are made;
41018 it does not affect the protocol acknowledgment state for any current
41020 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41021 new connection is established,
41022 there is also no protocol request to re-enable the acknowledgments
41023 for the current connection, once disabled.
41028 Example sequence of a target being re-started. Notice how the restart
41029 does not get any direct output:
41034 @emph{target restarts}
41037 <- @code{T001:1234123412341234}
41041 Example sequence of a target being stepped by a single instruction:
41044 -> @code{G1445@dots{}}
41049 <- @code{T001:1234123412341234}
41053 <- @code{1455@dots{}}
41057 @node File-I/O Remote Protocol Extension
41058 @section File-I/O Remote Protocol Extension
41059 @cindex File-I/O remote protocol extension
41062 * File-I/O Overview::
41063 * Protocol Basics::
41064 * The F Request Packet::
41065 * The F Reply Packet::
41066 * The Ctrl-C Message::
41068 * List of Supported Calls::
41069 * Protocol-specific Representation of Datatypes::
41071 * File-I/O Examples::
41074 @node File-I/O Overview
41075 @subsection File-I/O Overview
41076 @cindex file-i/o overview
41078 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41079 target to use the host's file system and console I/O to perform various
41080 system calls. System calls on the target system are translated into a
41081 remote protocol packet to the host system, which then performs the needed
41082 actions and returns a response packet to the target system.
41083 This simulates file system operations even on targets that lack file systems.
41085 The protocol is defined to be independent of both the host and target systems.
41086 It uses its own internal representation of datatypes and values. Both
41087 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41088 translating the system-dependent value representations into the internal
41089 protocol representations when data is transmitted.
41091 The communication is synchronous. A system call is possible only when
41092 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41093 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41094 the target is stopped to allow deterministic access to the target's
41095 memory. Therefore File-I/O is not interruptible by target signals. On
41096 the other hand, it is possible to interrupt File-I/O by a user interrupt
41097 (@samp{Ctrl-C}) within @value{GDBN}.
41099 The target's request to perform a host system call does not finish
41100 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41101 after finishing the system call, the target returns to continuing the
41102 previous activity (continue, step). No additional continue or step
41103 request from @value{GDBN} is required.
41106 (@value{GDBP}) continue
41107 <- target requests 'system call X'
41108 target is stopped, @value{GDBN} executes system call
41109 -> @value{GDBN} returns result
41110 ... target continues, @value{GDBN} returns to wait for the target
41111 <- target hits breakpoint and sends a Txx packet
41114 The protocol only supports I/O on the console and to regular files on
41115 the host file system. Character or block special devices, pipes,
41116 named pipes, sockets or any other communication method on the host
41117 system are not supported by this protocol.
41119 File I/O is not supported in non-stop mode.
41121 @node Protocol Basics
41122 @subsection Protocol Basics
41123 @cindex protocol basics, file-i/o
41125 The File-I/O protocol uses the @code{F} packet as the request as well
41126 as reply packet. Since a File-I/O system call can only occur when
41127 @value{GDBN} is waiting for a response from the continuing or stepping target,
41128 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41129 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41130 This @code{F} packet contains all information needed to allow @value{GDBN}
41131 to call the appropriate host system call:
41135 A unique identifier for the requested system call.
41138 All parameters to the system call. Pointers are given as addresses
41139 in the target memory address space. Pointers to strings are given as
41140 pointer/length pair. Numerical values are given as they are.
41141 Numerical control flags are given in a protocol-specific representation.
41145 At this point, @value{GDBN} has to perform the following actions.
41149 If the parameters include pointer values to data needed as input to a
41150 system call, @value{GDBN} requests this data from the target with a
41151 standard @code{m} packet request. This additional communication has to be
41152 expected by the target implementation and is handled as any other @code{m}
41156 @value{GDBN} translates all value from protocol representation to host
41157 representation as needed. Datatypes are coerced into the host types.
41160 @value{GDBN} calls the system call.
41163 It then coerces datatypes back to protocol representation.
41166 If the system call is expected to return data in buffer space specified
41167 by pointer parameters to the call, the data is transmitted to the
41168 target using a @code{M} or @code{X} packet. This packet has to be expected
41169 by the target implementation and is handled as any other @code{M} or @code{X}
41174 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41175 necessary information for the target to continue. This at least contains
41182 @code{errno}, if has been changed by the system call.
41189 After having done the needed type and value coercion, the target continues
41190 the latest continue or step action.
41192 @node The F Request Packet
41193 @subsection The @code{F} Request Packet
41194 @cindex file-i/o request packet
41195 @cindex @code{F} request packet
41197 The @code{F} request packet has the following format:
41200 @item F@var{call-id},@var{parameter@dots{}}
41202 @var{call-id} is the identifier to indicate the host system call to be called.
41203 This is just the name of the function.
41205 @var{parameter@dots{}} are the parameters to the system call.
41206 Parameters are hexadecimal integer values, either the actual values in case
41207 of scalar datatypes, pointers to target buffer space in case of compound
41208 datatypes and unspecified memory areas, or pointer/length pairs in case
41209 of string parameters. These are appended to the @var{call-id} as a
41210 comma-delimited list. All values are transmitted in ASCII
41211 string representation, pointer/length pairs separated by a slash.
41217 @node The F Reply Packet
41218 @subsection The @code{F} Reply Packet
41219 @cindex file-i/o reply packet
41220 @cindex @code{F} reply packet
41222 The @code{F} reply packet has the following format:
41226 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41228 @var{retcode} is the return code of the system call as hexadecimal value.
41230 @var{errno} is the @code{errno} set by the call, in protocol-specific
41232 This parameter can be omitted if the call was successful.
41234 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41235 case, @var{errno} must be sent as well, even if the call was successful.
41236 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41243 or, if the call was interrupted before the host call has been performed:
41250 assuming 4 is the protocol-specific representation of @code{EINTR}.
41255 @node The Ctrl-C Message
41256 @subsection The @samp{Ctrl-C} Message
41257 @cindex ctrl-c message, in file-i/o protocol
41259 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41260 reply packet (@pxref{The F Reply Packet}),
41261 the target should behave as if it had
41262 gotten a break message. The meaning for the target is ``system call
41263 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41264 (as with a break message) and return to @value{GDBN} with a @code{T02}
41267 It's important for the target to know in which
41268 state the system call was interrupted. There are two possible cases:
41272 The system call hasn't been performed on the host yet.
41275 The system call on the host has been finished.
41279 These two states can be distinguished by the target by the value of the
41280 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41281 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41282 on POSIX systems. In any other case, the target may presume that the
41283 system call has been finished --- successfully or not --- and should behave
41284 as if the break message arrived right after the system call.
41286 @value{GDBN} must behave reliably. If the system call has not been called
41287 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41288 @code{errno} in the packet. If the system call on the host has been finished
41289 before the user requests a break, the full action must be finished by
41290 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41291 The @code{F} packet may only be sent when either nothing has happened
41292 or the full action has been completed.
41295 @subsection Console I/O
41296 @cindex console i/o as part of file-i/o
41298 By default and if not explicitly closed by the target system, the file
41299 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41300 on the @value{GDBN} console is handled as any other file output operation
41301 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41302 by @value{GDBN} so that after the target read request from file descriptor
41303 0 all following typing is buffered until either one of the following
41308 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41310 system call is treated as finished.
41313 The user presses @key{RET}. This is treated as end of input with a trailing
41317 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41318 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41322 If the user has typed more characters than fit in the buffer given to
41323 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41324 either another @code{read(0, @dots{})} is requested by the target, or debugging
41325 is stopped at the user's request.
41328 @node List of Supported Calls
41329 @subsection List of Supported Calls
41330 @cindex list of supported file-i/o calls
41347 @unnumberedsubsubsec open
41348 @cindex open, file-i/o system call
41353 int open(const char *pathname, int flags);
41354 int open(const char *pathname, int flags, mode_t mode);
41358 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41361 @var{flags} is the bitwise @code{OR} of the following values:
41365 If the file does not exist it will be created. The host
41366 rules apply as far as file ownership and time stamps
41370 When used with @code{O_CREAT}, if the file already exists it is
41371 an error and open() fails.
41374 If the file already exists and the open mode allows
41375 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41376 truncated to zero length.
41379 The file is opened in append mode.
41382 The file is opened for reading only.
41385 The file is opened for writing only.
41388 The file is opened for reading and writing.
41392 Other bits are silently ignored.
41396 @var{mode} is the bitwise @code{OR} of the following values:
41400 User has read permission.
41403 User has write permission.
41406 Group has read permission.
41409 Group has write permission.
41412 Others have read permission.
41415 Others have write permission.
41419 Other bits are silently ignored.
41422 @item Return value:
41423 @code{open} returns the new file descriptor or -1 if an error
41430 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41433 @var{pathname} refers to a directory.
41436 The requested access is not allowed.
41439 @var{pathname} was too long.
41442 A directory component in @var{pathname} does not exist.
41445 @var{pathname} refers to a device, pipe, named pipe or socket.
41448 @var{pathname} refers to a file on a read-only filesystem and
41449 write access was requested.
41452 @var{pathname} is an invalid pointer value.
41455 No space on device to create the file.
41458 The process already has the maximum number of files open.
41461 The limit on the total number of files open on the system
41465 The call was interrupted by the user.
41471 @unnumberedsubsubsec close
41472 @cindex close, file-i/o system call
41481 @samp{Fclose,@var{fd}}
41483 @item Return value:
41484 @code{close} returns zero on success, or -1 if an error occurred.
41490 @var{fd} isn't a valid open file descriptor.
41493 The call was interrupted by the user.
41499 @unnumberedsubsubsec read
41500 @cindex read, file-i/o system call
41505 int read(int fd, void *buf, unsigned int count);
41509 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41511 @item Return value:
41512 On success, the number of bytes read is returned.
41513 Zero indicates end of file. If count is zero, read
41514 returns zero as well. On error, -1 is returned.
41520 @var{fd} is not a valid file descriptor or is not open for
41524 @var{bufptr} is an invalid pointer value.
41527 The call was interrupted by the user.
41533 @unnumberedsubsubsec write
41534 @cindex write, file-i/o system call
41539 int write(int fd, const void *buf, unsigned int count);
41543 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41545 @item Return value:
41546 On success, the number of bytes written are returned.
41547 Zero indicates nothing was written. On error, -1
41554 @var{fd} is not a valid file descriptor or is not open for
41558 @var{bufptr} is an invalid pointer value.
41561 An attempt was made to write a file that exceeds the
41562 host-specific maximum file size allowed.
41565 No space on device to write the data.
41568 The call was interrupted by the user.
41574 @unnumberedsubsubsec lseek
41575 @cindex lseek, file-i/o system call
41580 long lseek (int fd, long offset, int flag);
41584 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41586 @var{flag} is one of:
41590 The offset is set to @var{offset} bytes.
41593 The offset is set to its current location plus @var{offset}
41597 The offset is set to the size of the file plus @var{offset}
41601 @item Return value:
41602 On success, the resulting unsigned offset in bytes from
41603 the beginning of the file is returned. Otherwise, a
41604 value of -1 is returned.
41610 @var{fd} is not a valid open file descriptor.
41613 @var{fd} is associated with the @value{GDBN} console.
41616 @var{flag} is not a proper value.
41619 The call was interrupted by the user.
41625 @unnumberedsubsubsec rename
41626 @cindex rename, file-i/o system call
41631 int rename(const char *oldpath, const char *newpath);
41635 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41637 @item Return value:
41638 On success, zero is returned. On error, -1 is returned.
41644 @var{newpath} is an existing directory, but @var{oldpath} is not a
41648 @var{newpath} is a non-empty directory.
41651 @var{oldpath} or @var{newpath} is a directory that is in use by some
41655 An attempt was made to make a directory a subdirectory
41659 A component used as a directory in @var{oldpath} or new
41660 path is not a directory. Or @var{oldpath} is a directory
41661 and @var{newpath} exists but is not a directory.
41664 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41667 No access to the file or the path of the file.
41671 @var{oldpath} or @var{newpath} was too long.
41674 A directory component in @var{oldpath} or @var{newpath} does not exist.
41677 The file is on a read-only filesystem.
41680 The device containing the file has no room for the new
41684 The call was interrupted by the user.
41690 @unnumberedsubsubsec unlink
41691 @cindex unlink, file-i/o system call
41696 int unlink(const char *pathname);
41700 @samp{Funlink,@var{pathnameptr}/@var{len}}
41702 @item Return value:
41703 On success, zero is returned. On error, -1 is returned.
41709 No access to the file or the path of the file.
41712 The system does not allow unlinking of directories.
41715 The file @var{pathname} cannot be unlinked because it's
41716 being used by another process.
41719 @var{pathnameptr} is an invalid pointer value.
41722 @var{pathname} was too long.
41725 A directory component in @var{pathname} does not exist.
41728 A component of the path is not a directory.
41731 The file is on a read-only filesystem.
41734 The call was interrupted by the user.
41740 @unnumberedsubsubsec stat/fstat
41741 @cindex fstat, file-i/o system call
41742 @cindex stat, file-i/o system call
41747 int stat(const char *pathname, struct stat *buf);
41748 int fstat(int fd, struct stat *buf);
41752 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41753 @samp{Ffstat,@var{fd},@var{bufptr}}
41755 @item Return value:
41756 On success, zero is returned. On error, -1 is returned.
41762 @var{fd} is not a valid open file.
41765 A directory component in @var{pathname} does not exist or the
41766 path is an empty string.
41769 A component of the path is not a directory.
41772 @var{pathnameptr} is an invalid pointer value.
41775 No access to the file or the path of the file.
41778 @var{pathname} was too long.
41781 The call was interrupted by the user.
41787 @unnumberedsubsubsec gettimeofday
41788 @cindex gettimeofday, file-i/o system call
41793 int gettimeofday(struct timeval *tv, void *tz);
41797 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41799 @item Return value:
41800 On success, 0 is returned, -1 otherwise.
41806 @var{tz} is a non-NULL pointer.
41809 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41815 @unnumberedsubsubsec isatty
41816 @cindex isatty, file-i/o system call
41821 int isatty(int fd);
41825 @samp{Fisatty,@var{fd}}
41827 @item Return value:
41828 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41834 The call was interrupted by the user.
41839 Note that the @code{isatty} call is treated as a special case: it returns
41840 1 to the target if the file descriptor is attached
41841 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41842 would require implementing @code{ioctl} and would be more complex than
41847 @unnumberedsubsubsec system
41848 @cindex system, file-i/o system call
41853 int system(const char *command);
41857 @samp{Fsystem,@var{commandptr}/@var{len}}
41859 @item Return value:
41860 If @var{len} is zero, the return value indicates whether a shell is
41861 available. A zero return value indicates a shell is not available.
41862 For non-zero @var{len}, the value returned is -1 on error and the
41863 return status of the command otherwise. Only the exit status of the
41864 command is returned, which is extracted from the host's @code{system}
41865 return value by calling @code{WEXITSTATUS(retval)}. In case
41866 @file{/bin/sh} could not be executed, 127 is returned.
41872 The call was interrupted by the user.
41877 @value{GDBN} takes over the full task of calling the necessary host calls
41878 to perform the @code{system} call. The return value of @code{system} on
41879 the host is simplified before it's returned
41880 to the target. Any termination signal information from the child process
41881 is discarded, and the return value consists
41882 entirely of the exit status of the called command.
41884 Due to security concerns, the @code{system} call is by default refused
41885 by @value{GDBN}. The user has to allow this call explicitly with the
41886 @code{set remote system-call-allowed 1} command.
41889 @item set remote system-call-allowed
41890 @kindex set remote system-call-allowed
41891 Control whether to allow the @code{system} calls in the File I/O
41892 protocol for the remote target. The default is zero (disabled).
41894 @item show remote system-call-allowed
41895 @kindex show remote system-call-allowed
41896 Show whether the @code{system} calls are allowed in the File I/O
41900 @node Protocol-specific Representation of Datatypes
41901 @subsection Protocol-specific Representation of Datatypes
41902 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41905 * Integral Datatypes::
41907 * Memory Transfer::
41912 @node Integral Datatypes
41913 @unnumberedsubsubsec Integral Datatypes
41914 @cindex integral datatypes, in file-i/o protocol
41916 The integral datatypes used in the system calls are @code{int},
41917 @code{unsigned int}, @code{long}, @code{unsigned long},
41918 @code{mode_t}, and @code{time_t}.
41920 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41921 implemented as 32 bit values in this protocol.
41923 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41925 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41926 in @file{limits.h}) to allow range checking on host and target.
41928 @code{time_t} datatypes are defined as seconds since the Epoch.
41930 All integral datatypes transferred as part of a memory read or write of a
41931 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41934 @node Pointer Values
41935 @unnumberedsubsubsec Pointer Values
41936 @cindex pointer values, in file-i/o protocol
41938 Pointers to target data are transmitted as they are. An exception
41939 is made for pointers to buffers for which the length isn't
41940 transmitted as part of the function call, namely strings. Strings
41941 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41948 which is a pointer to data of length 18 bytes at position 0x1aaf.
41949 The length is defined as the full string length in bytes, including
41950 the trailing null byte. For example, the string @code{"hello world"}
41951 at address 0x123456 is transmitted as
41957 @node Memory Transfer
41958 @unnumberedsubsubsec Memory Transfer
41959 @cindex memory transfer, in file-i/o protocol
41961 Structured data which is transferred using a memory read or write (for
41962 example, a @code{struct stat}) is expected to be in a protocol-specific format
41963 with all scalar multibyte datatypes being big endian. Translation to
41964 this representation needs to be done both by the target before the @code{F}
41965 packet is sent, and by @value{GDBN} before
41966 it transfers memory to the target. Transferred pointers to structured
41967 data should point to the already-coerced data at any time.
41971 @unnumberedsubsubsec struct stat
41972 @cindex struct stat, in file-i/o protocol
41974 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41975 is defined as follows:
41979 unsigned int st_dev; /* device */
41980 unsigned int st_ino; /* inode */
41981 mode_t st_mode; /* protection */
41982 unsigned int st_nlink; /* number of hard links */
41983 unsigned int st_uid; /* user ID of owner */
41984 unsigned int st_gid; /* group ID of owner */
41985 unsigned int st_rdev; /* device type (if inode device) */
41986 unsigned long st_size; /* total size, in bytes */
41987 unsigned long st_blksize; /* blocksize for filesystem I/O */
41988 unsigned long st_blocks; /* number of blocks allocated */
41989 time_t st_atime; /* time of last access */
41990 time_t st_mtime; /* time of last modification */
41991 time_t st_ctime; /* time of last change */
41995 The integral datatypes conform to the definitions given in the
41996 appropriate section (see @ref{Integral Datatypes}, for details) so this
41997 structure is of size 64 bytes.
41999 The values of several fields have a restricted meaning and/or
42005 A value of 0 represents a file, 1 the console.
42008 No valid meaning for the target. Transmitted unchanged.
42011 Valid mode bits are described in @ref{Constants}. Any other
42012 bits have currently no meaning for the target.
42017 No valid meaning for the target. Transmitted unchanged.
42022 These values have a host and file system dependent
42023 accuracy. Especially on Windows hosts, the file system may not
42024 support exact timing values.
42027 The target gets a @code{struct stat} of the above representation and is
42028 responsible for coercing it to the target representation before
42031 Note that due to size differences between the host, target, and protocol
42032 representations of @code{struct stat} members, these members could eventually
42033 get truncated on the target.
42035 @node struct timeval
42036 @unnumberedsubsubsec struct timeval
42037 @cindex struct timeval, in file-i/o protocol
42039 The buffer of type @code{struct timeval} used by the File-I/O protocol
42040 is defined as follows:
42044 time_t tv_sec; /* second */
42045 long tv_usec; /* microsecond */
42049 The integral datatypes conform to the definitions given in the
42050 appropriate section (see @ref{Integral Datatypes}, for details) so this
42051 structure is of size 8 bytes.
42054 @subsection Constants
42055 @cindex constants, in file-i/o protocol
42057 The following values are used for the constants inside of the
42058 protocol. @value{GDBN} and target are responsible for translating these
42059 values before and after the call as needed.
42070 @unnumberedsubsubsec Open Flags
42071 @cindex open flags, in file-i/o protocol
42073 All values are given in hexadecimal representation.
42085 @node mode_t Values
42086 @unnumberedsubsubsec mode_t Values
42087 @cindex mode_t values, in file-i/o protocol
42089 All values are given in octal representation.
42106 @unnumberedsubsubsec Errno Values
42107 @cindex errno values, in file-i/o protocol
42109 All values are given in decimal representation.
42134 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42135 any error value not in the list of supported error numbers.
42138 @unnumberedsubsubsec Lseek Flags
42139 @cindex lseek flags, in file-i/o protocol
42148 @unnumberedsubsubsec Limits
42149 @cindex limits, in file-i/o protocol
42151 All values are given in decimal representation.
42154 INT_MIN -2147483648
42156 UINT_MAX 4294967295
42157 LONG_MIN -9223372036854775808
42158 LONG_MAX 9223372036854775807
42159 ULONG_MAX 18446744073709551615
42162 @node File-I/O Examples
42163 @subsection File-I/O Examples
42164 @cindex file-i/o examples
42166 Example sequence of a write call, file descriptor 3, buffer is at target
42167 address 0x1234, 6 bytes should be written:
42170 <- @code{Fwrite,3,1234,6}
42171 @emph{request memory read from target}
42174 @emph{return "6 bytes written"}
42178 Example sequence of a read call, file descriptor 3, buffer is at target
42179 address 0x1234, 6 bytes should be read:
42182 <- @code{Fread,3,1234,6}
42183 @emph{request memory write to target}
42184 -> @code{X1234,6:XXXXXX}
42185 @emph{return "6 bytes read"}
42189 Example sequence of a read call, call fails on the host due to invalid
42190 file descriptor (@code{EBADF}):
42193 <- @code{Fread,3,1234,6}
42197 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42201 <- @code{Fread,3,1234,6}
42206 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42210 <- @code{Fread,3,1234,6}
42211 -> @code{X1234,6:XXXXXX}
42215 @node Library List Format
42216 @section Library List Format
42217 @cindex library list format, remote protocol
42219 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42220 same process as your application to manage libraries. In this case,
42221 @value{GDBN} can use the loader's symbol table and normal memory
42222 operations to maintain a list of shared libraries. On other
42223 platforms, the operating system manages loaded libraries.
42224 @value{GDBN} can not retrieve the list of currently loaded libraries
42225 through memory operations, so it uses the @samp{qXfer:libraries:read}
42226 packet (@pxref{qXfer library list read}) instead. The remote stub
42227 queries the target's operating system and reports which libraries
42230 The @samp{qXfer:libraries:read} packet returns an XML document which
42231 lists loaded libraries and their offsets. Each library has an
42232 associated name and one or more segment or section base addresses,
42233 which report where the library was loaded in memory.
42235 For the common case of libraries that are fully linked binaries, the
42236 library should have a list of segments. If the target supports
42237 dynamic linking of a relocatable object file, its library XML element
42238 should instead include a list of allocated sections. The segment or
42239 section bases are start addresses, not relocation offsets; they do not
42240 depend on the library's link-time base addresses.
42242 @value{GDBN} must be linked with the Expat library to support XML
42243 library lists. @xref{Expat}.
42245 A simple memory map, with one loaded library relocated by a single
42246 offset, looks like this:
42250 <library name="/lib/libc.so.6">
42251 <segment address="0x10000000"/>
42256 Another simple memory map, with one loaded library with three
42257 allocated sections (.text, .data, .bss), looks like this:
42261 <library name="sharedlib.o">
42262 <section address="0x10000000"/>
42263 <section address="0x20000000"/>
42264 <section address="0x30000000"/>
42269 The format of a library list is described by this DTD:
42272 <!-- library-list: Root element with versioning -->
42273 <!ELEMENT library-list (library)*>
42274 <!ATTLIST library-list version CDATA #FIXED "1.0">
42275 <!ELEMENT library (segment*, section*)>
42276 <!ATTLIST library name CDATA #REQUIRED>
42277 <!ELEMENT segment EMPTY>
42278 <!ATTLIST segment address CDATA #REQUIRED>
42279 <!ELEMENT section EMPTY>
42280 <!ATTLIST section address CDATA #REQUIRED>
42283 In addition, segments and section descriptors cannot be mixed within a
42284 single library element, and you must supply at least one segment or
42285 section for each library.
42287 @node Library List Format for SVR4 Targets
42288 @section Library List Format for SVR4 Targets
42289 @cindex library list format, remote protocol
42291 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42292 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42293 shared libraries. Still a special library list provided by this packet is
42294 more efficient for the @value{GDBN} remote protocol.
42296 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42297 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42298 target, the following parameters are reported:
42302 @code{name}, the absolute file name from the @code{l_name} field of
42303 @code{struct link_map}.
42305 @code{lm} with address of @code{struct link_map} used for TLS
42306 (Thread Local Storage) access.
42308 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42309 @code{struct link_map}. For prelinked libraries this is not an absolute
42310 memory address. It is a displacement of absolute memory address against
42311 address the file was prelinked to during the library load.
42313 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42316 Additionally the single @code{main-lm} attribute specifies address of
42317 @code{struct link_map} used for the main executable. This parameter is used
42318 for TLS access and its presence is optional.
42320 @value{GDBN} must be linked with the Expat library to support XML
42321 SVR4 library lists. @xref{Expat}.
42323 A simple memory map, with two loaded libraries (which do not use prelink),
42327 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42328 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42330 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42332 </library-list-svr>
42335 The format of an SVR4 library list is described by this DTD:
42338 <!-- library-list-svr4: Root element with versioning -->
42339 <!ELEMENT library-list-svr4 (library)*>
42340 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42341 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42342 <!ELEMENT library EMPTY>
42343 <!ATTLIST library name CDATA #REQUIRED>
42344 <!ATTLIST library lm CDATA #REQUIRED>
42345 <!ATTLIST library l_addr CDATA #REQUIRED>
42346 <!ATTLIST library l_ld CDATA #REQUIRED>
42349 @node Memory Map Format
42350 @section Memory Map Format
42351 @cindex memory map format
42353 To be able to write into flash memory, @value{GDBN} needs to obtain a
42354 memory map from the target. This section describes the format of the
42357 The memory map is obtained using the @samp{qXfer:memory-map:read}
42358 (@pxref{qXfer memory map read}) packet and is an XML document that
42359 lists memory regions.
42361 @value{GDBN} must be linked with the Expat library to support XML
42362 memory maps. @xref{Expat}.
42364 The top-level structure of the document is shown below:
42367 <?xml version="1.0"?>
42368 <!DOCTYPE memory-map
42369 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42370 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42376 Each region can be either:
42381 A region of RAM starting at @var{addr} and extending for @var{length}
42385 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42390 A region of read-only memory:
42393 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42398 A region of flash memory, with erasure blocks @var{blocksize}
42402 <memory type="flash" start="@var{addr}" length="@var{length}">
42403 <property name="blocksize">@var{blocksize}</property>
42409 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42410 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42411 packets to write to addresses in such ranges.
42413 The formal DTD for memory map format is given below:
42416 <!-- ................................................... -->
42417 <!-- Memory Map XML DTD ................................ -->
42418 <!-- File: memory-map.dtd .............................. -->
42419 <!-- .................................... .............. -->
42420 <!-- memory-map.dtd -->
42421 <!-- memory-map: Root element with versioning -->
42422 <!ELEMENT memory-map (memory | property)>
42423 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42424 <!ELEMENT memory (property)>
42425 <!-- memory: Specifies a memory region,
42426 and its type, or device. -->
42427 <!ATTLIST memory type CDATA #REQUIRED
42428 start CDATA #REQUIRED
42429 length CDATA #REQUIRED
42430 device CDATA #IMPLIED>
42431 <!-- property: Generic attribute tag -->
42432 <!ELEMENT property (#PCDATA | property)*>
42433 <!ATTLIST property name CDATA #REQUIRED>
42436 @node Thread List Format
42437 @section Thread List Format
42438 @cindex thread list format
42440 To efficiently update the list of threads and their attributes,
42441 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42442 (@pxref{qXfer threads read}) and obtains the XML document with
42443 the following structure:
42446 <?xml version="1.0"?>
42448 <thread id="id" core="0">
42449 ... description ...
42454 Each @samp{thread} element must have the @samp{id} attribute that
42455 identifies the thread (@pxref{thread-id syntax}). The
42456 @samp{core} attribute, if present, specifies which processor core
42457 the thread was last executing on. The content of the of @samp{thread}
42458 element is interpreted as human-readable auxilliary information.
42460 @node Traceframe Info Format
42461 @section Traceframe Info Format
42462 @cindex traceframe info format
42464 To be able to know which objects in the inferior can be examined when
42465 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42466 memory ranges, registers and trace state variables that have been
42467 collected in a traceframe.
42469 This list is obtained using the @samp{qXfer:traceframe-info:read}
42470 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42472 @value{GDBN} must be linked with the Expat library to support XML
42473 traceframe info discovery. @xref{Expat}.
42475 The top-level structure of the document is shown below:
42478 <?xml version="1.0"?>
42479 <!DOCTYPE traceframe-info
42480 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42481 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42487 Each traceframe block can be either:
42492 A region of collected memory starting at @var{addr} and extending for
42493 @var{length} bytes from there:
42496 <memory start="@var{addr}" length="@var{length}"/>
42500 A block indicating trace state variable numbered @var{number} has been
42504 <tvar id="@var{number}"/>
42509 The formal DTD for the traceframe info format is given below:
42512 <!ELEMENT traceframe-info (memory | tvar)* >
42513 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42515 <!ELEMENT memory EMPTY>
42516 <!ATTLIST memory start CDATA #REQUIRED
42517 length CDATA #REQUIRED>
42519 <!ATTLIST tvar id CDATA #REQUIRED>
42522 @node Branch Trace Format
42523 @section Branch Trace Format
42524 @cindex branch trace format
42526 In order to display the branch trace of an inferior thread,
42527 @value{GDBN} needs to obtain the list of branches. This list is
42528 represented as list of sequential code blocks that are connected via
42529 branches. The code in each block has been executed sequentially.
42531 This list is obtained using the @samp{qXfer:btrace:read}
42532 (@pxref{qXfer btrace read}) packet and is an XML document.
42534 @value{GDBN} must be linked with the Expat library to support XML
42535 traceframe info discovery. @xref{Expat}.
42537 The top-level structure of the document is shown below:
42540 <?xml version="1.0"?>
42542 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42543 "http://sourceware.org/gdb/gdb-btrace.dtd">
42552 A block of sequentially executed instructions starting at @var{begin}
42553 and ending at @var{end}:
42556 <block begin="@var{begin}" end="@var{end}"/>
42561 The formal DTD for the branch trace format is given below:
42564 <!ELEMENT btrace (block)* >
42565 <!ATTLIST btrace version CDATA #FIXED "1.0">
42567 <!ELEMENT block EMPTY>
42568 <!ATTLIST block begin CDATA #REQUIRED
42569 end CDATA #REQUIRED>
42572 @include agentexpr.texi
42574 @node Target Descriptions
42575 @appendix Target Descriptions
42576 @cindex target descriptions
42578 One of the challenges of using @value{GDBN} to debug embedded systems
42579 is that there are so many minor variants of each processor
42580 architecture in use. It is common practice for vendors to start with
42581 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42582 and then make changes to adapt it to a particular market niche. Some
42583 architectures have hundreds of variants, available from dozens of
42584 vendors. This leads to a number of problems:
42588 With so many different customized processors, it is difficult for
42589 the @value{GDBN} maintainers to keep up with the changes.
42591 Since individual variants may have short lifetimes or limited
42592 audiences, it may not be worthwhile to carry information about every
42593 variant in the @value{GDBN} source tree.
42595 When @value{GDBN} does support the architecture of the embedded system
42596 at hand, the task of finding the correct architecture name to give the
42597 @command{set architecture} command can be error-prone.
42600 To address these problems, the @value{GDBN} remote protocol allows a
42601 target system to not only identify itself to @value{GDBN}, but to
42602 actually describe its own features. This lets @value{GDBN} support
42603 processor variants it has never seen before --- to the extent that the
42604 descriptions are accurate, and that @value{GDBN} understands them.
42606 @value{GDBN} must be linked with the Expat library to support XML
42607 target descriptions. @xref{Expat}.
42610 * Retrieving Descriptions:: How descriptions are fetched from a target.
42611 * Target Description Format:: The contents of a target description.
42612 * Predefined Target Types:: Standard types available for target
42614 * Standard Target Features:: Features @value{GDBN} knows about.
42617 @node Retrieving Descriptions
42618 @section Retrieving Descriptions
42620 Target descriptions can be read from the target automatically, or
42621 specified by the user manually. The default behavior is to read the
42622 description from the target. @value{GDBN} retrieves it via the remote
42623 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42624 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42625 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42626 XML document, of the form described in @ref{Target Description
42629 Alternatively, you can specify a file to read for the target description.
42630 If a file is set, the target will not be queried. The commands to
42631 specify a file are:
42634 @cindex set tdesc filename
42635 @item set tdesc filename @var{path}
42636 Read the target description from @var{path}.
42638 @cindex unset tdesc filename
42639 @item unset tdesc filename
42640 Do not read the XML target description from a file. @value{GDBN}
42641 will use the description supplied by the current target.
42643 @cindex show tdesc filename
42644 @item show tdesc filename
42645 Show the filename to read for a target description, if any.
42649 @node Target Description Format
42650 @section Target Description Format
42651 @cindex target descriptions, XML format
42653 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42654 document which complies with the Document Type Definition provided in
42655 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42656 means you can use generally available tools like @command{xmllint} to
42657 check that your feature descriptions are well-formed and valid.
42658 However, to help people unfamiliar with XML write descriptions for
42659 their targets, we also describe the grammar here.
42661 Target descriptions can identify the architecture of the remote target
42662 and (for some architectures) provide information about custom register
42663 sets. They can also identify the OS ABI of the remote target.
42664 @value{GDBN} can use this information to autoconfigure for your
42665 target, or to warn you if you connect to an unsupported target.
42667 Here is a simple target description:
42670 <target version="1.0">
42671 <architecture>i386:x86-64</architecture>
42676 This minimal description only says that the target uses
42677 the x86-64 architecture.
42679 A target description has the following overall form, with [ ] marking
42680 optional elements and @dots{} marking repeatable elements. The elements
42681 are explained further below.
42684 <?xml version="1.0"?>
42685 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42686 <target version="1.0">
42687 @r{[}@var{architecture}@r{]}
42688 @r{[}@var{osabi}@r{]}
42689 @r{[}@var{compatible}@r{]}
42690 @r{[}@var{feature}@dots{}@r{]}
42695 The description is generally insensitive to whitespace and line
42696 breaks, under the usual common-sense rules. The XML version
42697 declaration and document type declaration can generally be omitted
42698 (@value{GDBN} does not require them), but specifying them may be
42699 useful for XML validation tools. The @samp{version} attribute for
42700 @samp{<target>} may also be omitted, but we recommend
42701 including it; if future versions of @value{GDBN} use an incompatible
42702 revision of @file{gdb-target.dtd}, they will detect and report
42703 the version mismatch.
42705 @subsection Inclusion
42706 @cindex target descriptions, inclusion
42709 @cindex <xi:include>
42712 It can sometimes be valuable to split a target description up into
42713 several different annexes, either for organizational purposes, or to
42714 share files between different possible target descriptions. You can
42715 divide a description into multiple files by replacing any element of
42716 the target description with an inclusion directive of the form:
42719 <xi:include href="@var{document}"/>
42723 When @value{GDBN} encounters an element of this form, it will retrieve
42724 the named XML @var{document}, and replace the inclusion directive with
42725 the contents of that document. If the current description was read
42726 using @samp{qXfer}, then so will be the included document;
42727 @var{document} will be interpreted as the name of an annex. If the
42728 current description was read from a file, @value{GDBN} will look for
42729 @var{document} as a file in the same directory where it found the
42730 original description.
42732 @subsection Architecture
42733 @cindex <architecture>
42735 An @samp{<architecture>} element has this form:
42738 <architecture>@var{arch}</architecture>
42741 @var{arch} is one of the architectures from the set accepted by
42742 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42745 @cindex @code{<osabi>}
42747 This optional field was introduced in @value{GDBN} version 7.0.
42748 Previous versions of @value{GDBN} ignore it.
42750 An @samp{<osabi>} element has this form:
42753 <osabi>@var{abi-name}</osabi>
42756 @var{abi-name} is an OS ABI name from the same selection accepted by
42757 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42759 @subsection Compatible Architecture
42760 @cindex @code{<compatible>}
42762 This optional field was introduced in @value{GDBN} version 7.0.
42763 Previous versions of @value{GDBN} ignore it.
42765 A @samp{<compatible>} element has this form:
42768 <compatible>@var{arch}</compatible>
42771 @var{arch} is one of the architectures from the set accepted by
42772 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42774 A @samp{<compatible>} element is used to specify that the target
42775 is able to run binaries in some other than the main target architecture
42776 given by the @samp{<architecture>} element. For example, on the
42777 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42778 or @code{powerpc:common64}, but the system is able to run binaries
42779 in the @code{spu} architecture as well. The way to describe this
42780 capability with @samp{<compatible>} is as follows:
42783 <architecture>powerpc:common</architecture>
42784 <compatible>spu</compatible>
42787 @subsection Features
42790 Each @samp{<feature>} describes some logical portion of the target
42791 system. Features are currently used to describe available CPU
42792 registers and the types of their contents. A @samp{<feature>} element
42796 <feature name="@var{name}">
42797 @r{[}@var{type}@dots{}@r{]}
42803 Each feature's name should be unique within the description. The name
42804 of a feature does not matter unless @value{GDBN} has some special
42805 knowledge of the contents of that feature; if it does, the feature
42806 should have its standard name. @xref{Standard Target Features}.
42810 Any register's value is a collection of bits which @value{GDBN} must
42811 interpret. The default interpretation is a two's complement integer,
42812 but other types can be requested by name in the register description.
42813 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42814 Target Types}), and the description can define additional composite types.
42816 Each type element must have an @samp{id} attribute, which gives
42817 a unique (within the containing @samp{<feature>}) name to the type.
42818 Types must be defined before they are used.
42821 Some targets offer vector registers, which can be treated as arrays
42822 of scalar elements. These types are written as @samp{<vector>} elements,
42823 specifying the array element type, @var{type}, and the number of elements,
42827 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42831 If a register's value is usefully viewed in multiple ways, define it
42832 with a union type containing the useful representations. The
42833 @samp{<union>} element contains one or more @samp{<field>} elements,
42834 each of which has a @var{name} and a @var{type}:
42837 <union id="@var{id}">
42838 <field name="@var{name}" type="@var{type}"/>
42844 If a register's value is composed from several separate values, define
42845 it with a structure type. There are two forms of the @samp{<struct>}
42846 element; a @samp{<struct>} element must either contain only bitfields
42847 or contain no bitfields. If the structure contains only bitfields,
42848 its total size in bytes must be specified, each bitfield must have an
42849 explicit start and end, and bitfields are automatically assigned an
42850 integer type. The field's @var{start} should be less than or
42851 equal to its @var{end}, and zero represents the least significant bit.
42854 <struct id="@var{id}" size="@var{size}">
42855 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42860 If the structure contains no bitfields, then each field has an
42861 explicit type, and no implicit padding is added.
42864 <struct id="@var{id}">
42865 <field name="@var{name}" type="@var{type}"/>
42871 If a register's value is a series of single-bit flags, define it with
42872 a flags type. The @samp{<flags>} element has an explicit @var{size}
42873 and contains one or more @samp{<field>} elements. Each field has a
42874 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42878 <flags id="@var{id}" size="@var{size}">
42879 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42884 @subsection Registers
42887 Each register is represented as an element with this form:
42890 <reg name="@var{name}"
42891 bitsize="@var{size}"
42892 @r{[}regnum="@var{num}"@r{]}
42893 @r{[}save-restore="@var{save-restore}"@r{]}
42894 @r{[}type="@var{type}"@r{]}
42895 @r{[}group="@var{group}"@r{]}/>
42899 The components are as follows:
42904 The register's name; it must be unique within the target description.
42907 The register's size, in bits.
42910 The register's number. If omitted, a register's number is one greater
42911 than that of the previous register (either in the current feature or in
42912 a preceding feature); the first register in the target description
42913 defaults to zero. This register number is used to read or write
42914 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42915 packets, and registers appear in the @code{g} and @code{G} packets
42916 in order of increasing register number.
42919 Whether the register should be preserved across inferior function
42920 calls; this must be either @code{yes} or @code{no}. The default is
42921 @code{yes}, which is appropriate for most registers except for
42922 some system control registers; this is not related to the target's
42926 The type of the register. @var{type} may be a predefined type, a type
42927 defined in the current feature, or one of the special types @code{int}
42928 and @code{float}. @code{int} is an integer type of the correct size
42929 for @var{bitsize}, and @code{float} is a floating point type (in the
42930 architecture's normal floating point format) of the correct size for
42931 @var{bitsize}. The default is @code{int}.
42934 The register group to which this register belongs. @var{group} must
42935 be either @code{general}, @code{float}, or @code{vector}. If no
42936 @var{group} is specified, @value{GDBN} will not display the register
42937 in @code{info registers}.
42941 @node Predefined Target Types
42942 @section Predefined Target Types
42943 @cindex target descriptions, predefined types
42945 Type definitions in the self-description can build up composite types
42946 from basic building blocks, but can not define fundamental types. Instead,
42947 standard identifiers are provided by @value{GDBN} for the fundamental
42948 types. The currently supported types are:
42957 Signed integer types holding the specified number of bits.
42964 Unsigned integer types holding the specified number of bits.
42968 Pointers to unspecified code and data. The program counter and
42969 any dedicated return address register may be marked as code
42970 pointers; printing a code pointer converts it into a symbolic
42971 address. The stack pointer and any dedicated address registers
42972 may be marked as data pointers.
42975 Single precision IEEE floating point.
42978 Double precision IEEE floating point.
42981 The 12-byte extended precision format used by ARM FPA registers.
42984 The 10-byte extended precision format used by x87 registers.
42987 32bit @sc{eflags} register used by x86.
42990 32bit @sc{mxcsr} register used by x86.
42994 @node Standard Target Features
42995 @section Standard Target Features
42996 @cindex target descriptions, standard features
42998 A target description must contain either no registers or all the
42999 target's registers. If the description contains no registers, then
43000 @value{GDBN} will assume a default register layout, selected based on
43001 the architecture. If the description contains any registers, the
43002 default layout will not be used; the standard registers must be
43003 described in the target description, in such a way that @value{GDBN}
43004 can recognize them.
43006 This is accomplished by giving specific names to feature elements
43007 which contain standard registers. @value{GDBN} will look for features
43008 with those names and verify that they contain the expected registers;
43009 if any known feature is missing required registers, or if any required
43010 feature is missing, @value{GDBN} will reject the target
43011 description. You can add additional registers to any of the
43012 standard features --- @value{GDBN} will display them just as if
43013 they were added to an unrecognized feature.
43015 This section lists the known features and their expected contents.
43016 Sample XML documents for these features are included in the
43017 @value{GDBN} source tree, in the directory @file{gdb/features}.
43019 Names recognized by @value{GDBN} should include the name of the
43020 company or organization which selected the name, and the overall
43021 architecture to which the feature applies; so e.g.@: the feature
43022 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43024 The names of registers are not case sensitive for the purpose
43025 of recognizing standard features, but @value{GDBN} will only display
43026 registers using the capitalization used in the description.
43029 * AArch64 Features::
43034 * Nios II Features::
43035 * PowerPC Features::
43036 * S/390 and System z Features::
43041 @node AArch64 Features
43042 @subsection AArch64 Features
43043 @cindex target descriptions, AArch64 features
43045 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43046 targets. It should contain registers @samp{x0} through @samp{x30},
43047 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43049 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43050 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43054 @subsection ARM Features
43055 @cindex target descriptions, ARM features
43057 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43059 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43060 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43062 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43063 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43064 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43067 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43068 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43070 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43071 it should contain at least registers @samp{wR0} through @samp{wR15} and
43072 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43073 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43075 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43076 should contain at least registers @samp{d0} through @samp{d15}. If
43077 they are present, @samp{d16} through @samp{d31} should also be included.
43078 @value{GDBN} will synthesize the single-precision registers from
43079 halves of the double-precision registers.
43081 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43082 need to contain registers; it instructs @value{GDBN} to display the
43083 VFP double-precision registers as vectors and to synthesize the
43084 quad-precision registers from pairs of double-precision registers.
43085 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43086 be present and include 32 double-precision registers.
43088 @node i386 Features
43089 @subsection i386 Features
43090 @cindex target descriptions, i386 features
43092 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43093 targets. It should describe the following registers:
43097 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43099 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43101 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43102 @samp{fs}, @samp{gs}
43104 @samp{st0} through @samp{st7}
43106 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43107 @samp{foseg}, @samp{fooff} and @samp{fop}
43110 The register sets may be different, depending on the target.
43112 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43113 describe registers:
43117 @samp{xmm0} through @samp{xmm7} for i386
43119 @samp{xmm0} through @samp{xmm15} for amd64
43124 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43125 @samp{org.gnu.gdb.i386.sse} feature. It should
43126 describe the upper 128 bits of @sc{ymm} registers:
43130 @samp{ymm0h} through @samp{ymm7h} for i386
43132 @samp{ymm0h} through @samp{ymm15h} for amd64
43135 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43136 describe a single register, @samp{orig_eax}.
43138 @node MIPS Features
43139 @subsection @acronym{MIPS} Features
43140 @cindex target descriptions, @acronym{MIPS} features
43142 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43143 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43144 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43147 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43148 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43149 registers. They may be 32-bit or 64-bit depending on the target.
43151 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43152 it may be optional in a future version of @value{GDBN}. It should
43153 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43154 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43156 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43157 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43158 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43159 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43161 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43162 contain a single register, @samp{restart}, which is used by the
43163 Linux kernel to control restartable syscalls.
43165 @node M68K Features
43166 @subsection M68K Features
43167 @cindex target descriptions, M68K features
43170 @item @samp{org.gnu.gdb.m68k.core}
43171 @itemx @samp{org.gnu.gdb.coldfire.core}
43172 @itemx @samp{org.gnu.gdb.fido.core}
43173 One of those features must be always present.
43174 The feature that is present determines which flavor of m68k is
43175 used. The feature that is present should contain registers
43176 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43177 @samp{sp}, @samp{ps} and @samp{pc}.
43179 @item @samp{org.gnu.gdb.coldfire.fp}
43180 This feature is optional. If present, it should contain registers
43181 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43185 @node Nios II Features
43186 @subsection Nios II Features
43187 @cindex target descriptions, Nios II features
43189 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43190 targets. It should contain the 32 core registers (@samp{zero},
43191 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43192 @samp{pc}, and the 16 control registers (@samp{status} through
43195 @node PowerPC Features
43196 @subsection PowerPC Features
43197 @cindex target descriptions, PowerPC features
43199 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43200 targets. It should contain registers @samp{r0} through @samp{r31},
43201 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43202 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43204 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43205 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43207 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43208 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43211 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43212 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43213 will combine these registers with the floating point registers
43214 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43215 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43216 through @samp{vs63}, the set of vector registers for POWER7.
43218 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43219 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43220 @samp{spefscr}. SPE targets should provide 32-bit registers in
43221 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43222 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43223 these to present registers @samp{ev0} through @samp{ev31} to the
43226 @node S/390 and System z Features
43227 @subsection S/390 and System z Features
43228 @cindex target descriptions, S/390 features
43229 @cindex target descriptions, System z features
43231 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43232 System z targets. It should contain the PSW and the 16 general
43233 registers. In particular, System z targets should provide the 64-bit
43234 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43235 S/390 targets should provide the 32-bit versions of these registers.
43236 A System z target that runs in 31-bit addressing mode should provide
43237 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43238 register's upper halves @samp{r0h} through @samp{r15h}, and their
43239 lower halves @samp{r0l} through @samp{r15l}.
43241 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43242 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43245 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43246 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43248 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43249 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43250 targets and 32-bit otherwise. In addition, the feature may contain
43251 the @samp{last_break} register, whose width depends on the addressing
43252 mode, as well as the @samp{system_call} register, which is always
43255 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43256 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43257 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43259 @node TIC6x Features
43260 @subsection TMS320C6x Features
43261 @cindex target descriptions, TIC6x features
43262 @cindex target descriptions, TMS320C6x features
43263 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43264 targets. It should contain registers @samp{A0} through @samp{A15},
43265 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43267 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43268 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43269 through @samp{B31}.
43271 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43272 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43274 @node Operating System Information
43275 @appendix Operating System Information
43276 @cindex operating system information
43282 Users of @value{GDBN} often wish to obtain information about the state of
43283 the operating system running on the target---for example the list of
43284 processes, or the list of open files. This section describes the
43285 mechanism that makes it possible. This mechanism is similar to the
43286 target features mechanism (@pxref{Target Descriptions}), but focuses
43287 on a different aspect of target.
43289 Operating system information is retrived from the target via the
43290 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43291 read}). The object name in the request should be @samp{osdata}, and
43292 the @var{annex} identifies the data to be fetched.
43295 @appendixsection Process list
43296 @cindex operating system information, process list
43298 When requesting the process list, the @var{annex} field in the
43299 @samp{qXfer} request should be @samp{processes}. The returned data is
43300 an XML document. The formal syntax of this document is defined in
43301 @file{gdb/features/osdata.dtd}.
43303 An example document is:
43306 <?xml version="1.0"?>
43307 <!DOCTYPE target SYSTEM "osdata.dtd">
43308 <osdata type="processes">
43310 <column name="pid">1</column>
43311 <column name="user">root</column>
43312 <column name="command">/sbin/init</column>
43313 <column name="cores">1,2,3</column>
43318 Each item should include a column whose name is @samp{pid}. The value
43319 of that column should identify the process on the target. The
43320 @samp{user} and @samp{command} columns are optional, and will be
43321 displayed by @value{GDBN}. The @samp{cores} column, if present,
43322 should contain a comma-separated list of cores that this process
43323 is running on. Target may provide additional columns,
43324 which @value{GDBN} currently ignores.
43326 @node Trace File Format
43327 @appendix Trace File Format
43328 @cindex trace file format
43330 The trace file comes in three parts: a header, a textual description
43331 section, and a trace frame section with binary data.
43333 The header has the form @code{\x7fTRACE0\n}. The first byte is
43334 @code{0x7f} so as to indicate that the file contains binary data,
43335 while the @code{0} is a version number that may have different values
43338 The description section consists of multiple lines of @sc{ascii} text
43339 separated by newline characters (@code{0xa}). The lines may include a
43340 variety of optional descriptive or context-setting information, such
43341 as tracepoint definitions or register set size. @value{GDBN} will
43342 ignore any line that it does not recognize. An empty line marks the end
43345 @c FIXME add some specific types of data
43347 The trace frame section consists of a number of consecutive frames.
43348 Each frame begins with a two-byte tracepoint number, followed by a
43349 four-byte size giving the amount of data in the frame. The data in
43350 the frame consists of a number of blocks, each introduced by a
43351 character indicating its type (at least register, memory, and trace
43352 state variable). The data in this section is raw binary, not a
43353 hexadecimal or other encoding; its endianness matches the target's
43356 @c FIXME bi-arch may require endianness/arch info in description section
43359 @item R @var{bytes}
43360 Register block. The number and ordering of bytes matches that of a
43361 @code{g} packet in the remote protocol. Note that these are the
43362 actual bytes, in target order and @value{GDBN} register order, not a
43363 hexadecimal encoding.
43365 @item M @var{address} @var{length} @var{bytes}...
43366 Memory block. This is a contiguous block of memory, at the 8-byte
43367 address @var{address}, with a 2-byte length @var{length}, followed by
43368 @var{length} bytes.
43370 @item V @var{number} @var{value}
43371 Trace state variable block. This records the 8-byte signed value
43372 @var{value} of trace state variable numbered @var{number}.
43376 Future enhancements of the trace file format may include additional types
43379 @node Index Section Format
43380 @appendix @code{.gdb_index} section format
43381 @cindex .gdb_index section format
43382 @cindex index section format
43384 This section documents the index section that is created by @code{save
43385 gdb-index} (@pxref{Index Files}). The index section is
43386 DWARF-specific; some knowledge of DWARF is assumed in this
43389 The mapped index file format is designed to be directly
43390 @code{mmap}able on any architecture. In most cases, a datum is
43391 represented using a little-endian 32-bit integer value, called an
43392 @code{offset_type}. Big endian machines must byte-swap the values
43393 before using them. Exceptions to this rule are noted. The data is
43394 laid out such that alignment is always respected.
43396 A mapped index consists of several areas, laid out in order.
43400 The file header. This is a sequence of values, of @code{offset_type}
43401 unless otherwise noted:
43405 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43406 Version 4 uses a different hashing function from versions 5 and 6.
43407 Version 6 includes symbols for inlined functions, whereas versions 4
43408 and 5 do not. Version 7 adds attributes to the CU indices in the
43409 symbol table. Version 8 specifies that symbols from DWARF type units
43410 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43411 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43413 @value{GDBN} will only read version 4, 5, or 6 indices
43414 by specifying @code{set use-deprecated-index-sections on}.
43415 GDB has a workaround for potentially broken version 7 indices so it is
43416 currently not flagged as deprecated.
43419 The offset, from the start of the file, of the CU list.
43422 The offset, from the start of the file, of the types CU list. Note
43423 that this area can be empty, in which case this offset will be equal
43424 to the next offset.
43427 The offset, from the start of the file, of the address area.
43430 The offset, from the start of the file, of the symbol table.
43433 The offset, from the start of the file, of the constant pool.
43437 The CU list. This is a sequence of pairs of 64-bit little-endian
43438 values, sorted by the CU offset. The first element in each pair is
43439 the offset of a CU in the @code{.debug_info} section. The second
43440 element in each pair is the length of that CU. References to a CU
43441 elsewhere in the map are done using a CU index, which is just the
43442 0-based index into this table. Note that if there are type CUs, then
43443 conceptually CUs and type CUs form a single list for the purposes of
43447 The types CU list. This is a sequence of triplets of 64-bit
43448 little-endian values. In a triplet, the first value is the CU offset,
43449 the second value is the type offset in the CU, and the third value is
43450 the type signature. The types CU list is not sorted.
43453 The address area. The address area consists of a sequence of address
43454 entries. Each address entry has three elements:
43458 The low address. This is a 64-bit little-endian value.
43461 The high address. This is a 64-bit little-endian value. Like
43462 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43465 The CU index. This is an @code{offset_type} value.
43469 The symbol table. This is an open-addressed hash table. The size of
43470 the hash table is always a power of 2.
43472 Each slot in the hash table consists of a pair of @code{offset_type}
43473 values. The first value is the offset of the symbol's name in the
43474 constant pool. The second value is the offset of the CU vector in the
43477 If both values are 0, then this slot in the hash table is empty. This
43478 is ok because while 0 is a valid constant pool index, it cannot be a
43479 valid index for both a string and a CU vector.
43481 The hash value for a table entry is computed by applying an
43482 iterative hash function to the symbol's name. Starting with an
43483 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43484 the string is incorporated into the hash using the formula depending on the
43489 The formula is @code{r = r * 67 + c - 113}.
43491 @item Versions 5 to 7
43492 The formula is @code{r = r * 67 + tolower (c) - 113}.
43495 The terminating @samp{\0} is not incorporated into the hash.
43497 The step size used in the hash table is computed via
43498 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43499 value, and @samp{size} is the size of the hash table. The step size
43500 is used to find the next candidate slot when handling a hash
43503 The names of C@t{++} symbols in the hash table are canonicalized. We
43504 don't currently have a simple description of the canonicalization
43505 algorithm; if you intend to create new index sections, you must read
43509 The constant pool. This is simply a bunch of bytes. It is organized
43510 so that alignment is correct: CU vectors are stored first, followed by
43513 A CU vector in the constant pool is a sequence of @code{offset_type}
43514 values. The first value is the number of CU indices in the vector.
43515 Each subsequent value is the index and symbol attributes of a CU in
43516 the CU list. This element in the hash table is used to indicate which
43517 CUs define the symbol and how the symbol is used.
43518 See below for the format of each CU index+attributes entry.
43520 A string in the constant pool is zero-terminated.
43523 Attributes were added to CU index values in @code{.gdb_index} version 7.
43524 If a symbol has multiple uses within a CU then there is one
43525 CU index+attributes value for each use.
43527 The format of each CU index+attributes entry is as follows
43533 This is the index of the CU in the CU list.
43535 These bits are reserved for future purposes and must be zero.
43537 The kind of the symbol in the CU.
43541 This value is reserved and should not be used.
43542 By reserving zero the full @code{offset_type} value is backwards compatible
43543 with previous versions of the index.
43545 The symbol is a type.
43547 The symbol is a variable or an enum value.
43549 The symbol is a function.
43551 Any other kind of symbol.
43553 These values are reserved.
43557 This bit is zero if the value is global and one if it is static.
43559 The determination of whether a symbol is global or static is complicated.
43560 The authorative reference is the file @file{dwarf2read.c} in
43561 @value{GDBN} sources.
43565 This pseudo-code describes the computation of a symbol's kind and
43566 global/static attributes in the index.
43569 is_external = get_attribute (die, DW_AT_external);
43570 language = get_attribute (cu_die, DW_AT_language);
43573 case DW_TAG_typedef:
43574 case DW_TAG_base_type:
43575 case DW_TAG_subrange_type:
43579 case DW_TAG_enumerator:
43581 is_static = (language != CPLUS && language != JAVA);
43583 case DW_TAG_subprogram:
43585 is_static = ! (is_external || language == ADA);
43587 case DW_TAG_constant:
43589 is_static = ! is_external;
43591 case DW_TAG_variable:
43593 is_static = ! is_external;
43595 case DW_TAG_namespace:
43599 case DW_TAG_class_type:
43600 case DW_TAG_interface_type:
43601 case DW_TAG_structure_type:
43602 case DW_TAG_union_type:
43603 case DW_TAG_enumeration_type:
43605 is_static = (language != CPLUS && language != JAVA);
43613 @appendix Manual pages
43617 * gdb man:: The GNU Debugger man page
43618 * gdbserver man:: Remote Server for the GNU Debugger man page
43619 * gcore man:: Generate a core file of a running program
43620 * gdbinit man:: gdbinit scripts
43626 @c man title gdb The GNU Debugger
43628 @c man begin SYNOPSIS gdb
43629 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43630 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43631 [@option{-b}@w{ }@var{bps}]
43632 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43633 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43634 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43635 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43636 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43639 @c man begin DESCRIPTION gdb
43640 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43641 going on ``inside'' another program while it executes -- or what another
43642 program was doing at the moment it crashed.
43644 @value{GDBN} can do four main kinds of things (plus other things in support of
43645 these) to help you catch bugs in the act:
43649 Start your program, specifying anything that might affect its behavior.
43652 Make your program stop on specified conditions.
43655 Examine what has happened, when your program has stopped.
43658 Change things in your program, so you can experiment with correcting the
43659 effects of one bug and go on to learn about another.
43662 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43665 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43666 commands from the terminal until you tell it to exit with the @value{GDBN}
43667 command @code{quit}. You can get online help from @value{GDBN} itself
43668 by using the command @code{help}.
43670 You can run @code{gdb} with no arguments or options; but the most
43671 usual way to start @value{GDBN} is with one argument or two, specifying an
43672 executable program as the argument:
43678 You can also start with both an executable program and a core file specified:
43684 You can, instead, specify a process ID as a second argument, if you want
43685 to debug a running process:
43693 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43694 named @file{1234}; @value{GDBN} does check for a core file first).
43695 With option @option{-p} you can omit the @var{program} filename.
43697 Here are some of the most frequently needed @value{GDBN} commands:
43699 @c pod2man highlights the right hand side of the @item lines.
43701 @item break [@var{file}:]@var{functiop}
43702 Set a breakpoint at @var{function} (in @var{file}).
43704 @item run [@var{arglist}]
43705 Start your program (with @var{arglist}, if specified).
43708 Backtrace: display the program stack.
43710 @item print @var{expr}
43711 Display the value of an expression.
43714 Continue running your program (after stopping, e.g. at a breakpoint).
43717 Execute next program line (after stopping); step @emph{over} any
43718 function calls in the line.
43720 @item edit [@var{file}:]@var{function}
43721 look at the program line where it is presently stopped.
43723 @item list [@var{file}:]@var{function}
43724 type the text of the program in the vicinity of where it is presently stopped.
43727 Execute next program line (after stopping); step @emph{into} any
43728 function calls in the line.
43730 @item help [@var{name}]
43731 Show information about @value{GDBN} command @var{name}, or general information
43732 about using @value{GDBN}.
43735 Exit from @value{GDBN}.
43739 For full details on @value{GDBN},
43740 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43741 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43742 as the @code{gdb} entry in the @code{info} program.
43746 @c man begin OPTIONS gdb
43747 Any arguments other than options specify an executable
43748 file and core file (or process ID); that is, the first argument
43749 encountered with no
43750 associated option flag is equivalent to a @option{-se} option, and the second,
43751 if any, is equivalent to a @option{-c} option if it's the name of a file.
43753 both long and short forms; both are shown here. The long forms are also
43754 recognized if you truncate them, so long as enough of the option is
43755 present to be unambiguous. (If you prefer, you can flag option
43756 arguments with @option{+} rather than @option{-}, though we illustrate the
43757 more usual convention.)
43759 All the options and command line arguments you give are processed
43760 in sequential order. The order makes a difference when the @option{-x}
43766 List all options, with brief explanations.
43768 @item -symbols=@var{file}
43769 @itemx -s @var{file}
43770 Read symbol table from file @var{file}.
43773 Enable writing into executable and core files.
43775 @item -exec=@var{file}
43776 @itemx -e @var{file}
43777 Use file @var{file} as the executable file to execute when
43778 appropriate, and for examining pure data in conjunction with a core
43781 @item -se=@var{file}
43782 Read symbol table from file @var{file} and use it as the executable
43785 @item -core=@var{file}
43786 @itemx -c @var{file}
43787 Use file @var{file} as a core dump to examine.
43789 @item -command=@var{file}
43790 @itemx -x @var{file}
43791 Execute @value{GDBN} commands from file @var{file}.
43793 @item -ex @var{command}
43794 Execute given @value{GDBN} @var{command}.
43796 @item -directory=@var{directory}
43797 @itemx -d @var{directory}
43798 Add @var{directory} to the path to search for source files.
43801 Do not execute commands from @file{~/.gdbinit}.
43805 Do not execute commands from any @file{.gdbinit} initialization files.
43809 ``Quiet''. Do not print the introductory and copyright messages. These
43810 messages are also suppressed in batch mode.
43813 Run in batch mode. Exit with status @code{0} after processing all the command
43814 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43815 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43816 commands in the command files.
43818 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43819 download and run a program on another computer; in order to make this
43820 more useful, the message
43823 Program exited normally.
43827 (which is ordinarily issued whenever a program running under @value{GDBN} control
43828 terminates) is not issued when running in batch mode.
43830 @item -cd=@var{directory}
43831 Run @value{GDBN} using @var{directory} as its working directory,
43832 instead of the current directory.
43836 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43837 @value{GDBN} to output the full file name and line number in a standard,
43838 recognizable fashion each time a stack frame is displayed (which
43839 includes each time the program stops). This recognizable format looks
43840 like two @samp{\032} characters, followed by the file name, line number
43841 and character position separated by colons, and a newline. The
43842 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43843 characters as a signal to display the source code for the frame.
43846 Set the line speed (baud rate or bits per second) of any serial
43847 interface used by @value{GDBN} for remote debugging.
43849 @item -tty=@var{device}
43850 Run using @var{device} for your program's standard input and output.
43854 @c man begin SEEALSO gdb
43856 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43857 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43858 documentation are properly installed at your site, the command
43865 should give you access to the complete manual.
43867 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43868 Richard M. Stallman and Roland H. Pesch, July 1991.
43872 @node gdbserver man
43873 @heading gdbserver man
43875 @c man title gdbserver Remote Server for the GNU Debugger
43877 @c man begin SYNOPSIS gdbserver
43878 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43880 gdbserver --attach @var{comm} @var{pid}
43882 gdbserver --multi @var{comm}
43886 @c man begin DESCRIPTION gdbserver
43887 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43888 than the one which is running the program being debugged.
43891 @subheading Usage (server (target) side)
43894 Usage (server (target) side):
43897 First, you need to have a copy of the program you want to debug put onto
43898 the target system. The program can be stripped to save space if needed, as
43899 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43900 the @value{GDBN} running on the host system.
43902 To use the server, you log on to the target system, and run the @command{gdbserver}
43903 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43904 your program, and (c) its arguments. The general syntax is:
43907 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43910 For example, using a serial port, you might say:
43914 @c @file would wrap it as F</dev/com1>.
43915 target> gdbserver /dev/com1 emacs foo.txt
43918 target> gdbserver @file{/dev/com1} emacs foo.txt
43922 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43923 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43924 waits patiently for the host @value{GDBN} to communicate with it.
43926 To use a TCP connection, you could say:
43929 target> gdbserver host:2345 emacs foo.txt
43932 This says pretty much the same thing as the last example, except that we are
43933 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43934 that we are expecting to see a TCP connection from @code{host} to local TCP port
43935 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43936 want for the port number as long as it does not conflict with any existing TCP
43937 ports on the target system. This same port number must be used in the host
43938 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43939 you chose a port number that conflicts with another service, @command{gdbserver} will
43940 print an error message and exit.
43942 @command{gdbserver} can also attach to running programs.
43943 This is accomplished via the @option{--attach} argument. The syntax is:
43946 target> gdbserver --attach @var{comm} @var{pid}
43949 @var{pid} is the process ID of a currently running process. It isn't
43950 necessary to point @command{gdbserver} at a binary for the running process.
43952 To start @code{gdbserver} without supplying an initial command to run
43953 or process ID to attach, use the @option{--multi} command line option.
43954 In such case you should connect using @kbd{target extended-remote} to start
43955 the program you want to debug.
43958 target> gdbserver --multi @var{comm}
43962 @subheading Usage (host side)
43968 You need an unstripped copy of the target program on your host system, since
43969 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43970 would, with the target program as the first argument. (You may need to use the
43971 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43972 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43973 new command you need to know about is @code{target remote}
43974 (or @code{target extended-remote}). Its argument is either
43975 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43976 descriptor. For example:
43980 @c @file would wrap it as F</dev/ttyb>.
43981 (gdb) target remote /dev/ttyb
43984 (gdb) target remote @file{/dev/ttyb}
43989 communicates with the server via serial line @file{/dev/ttyb}, and:
43992 (gdb) target remote the-target:2345
43996 communicates via a TCP connection to port 2345 on host `the-target', where
43997 you previously started up @command{gdbserver} with the same port number. Note that for
43998 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43999 command, otherwise you may get an error that looks something like
44000 `Connection refused'.
44002 @command{gdbserver} can also debug multiple inferiors at once,
44005 the @value{GDBN} manual in node @code{Inferiors and Programs}
44006 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44009 @ref{Inferiors and Programs}.
44011 In such case use the @code{extended-remote} @value{GDBN} command variant:
44014 (gdb) target extended-remote the-target:2345
44017 The @command{gdbserver} option @option{--multi} may or may not be used in such
44021 @c man begin OPTIONS gdbserver
44022 There are three different modes for invoking @command{gdbserver}:
44027 Debug a specific program specified by its program name:
44030 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44033 The @var{comm} parameter specifies how should the server communicate
44034 with @value{GDBN}; it is either a device name (to use a serial line),
44035 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44036 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44037 debug in @var{prog}. Any remaining arguments will be passed to the
44038 program verbatim. When the program exits, @value{GDBN} will close the
44039 connection, and @code{gdbserver} will exit.
44042 Debug a specific program by specifying the process ID of a running
44046 gdbserver --attach @var{comm} @var{pid}
44049 The @var{comm} parameter is as described above. Supply the process ID
44050 of a running program in @var{pid}; @value{GDBN} will do everything
44051 else. Like with the previous mode, when the process @var{pid} exits,
44052 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44055 Multi-process mode -- debug more than one program/process:
44058 gdbserver --multi @var{comm}
44061 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44062 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44063 close the connection when a process being debugged exits, so you can
44064 debug several processes in the same session.
44067 In each of the modes you may specify these options:
44072 List all options, with brief explanations.
44075 This option causes @command{gdbserver} to print its version number and exit.
44078 @command{gdbserver} will attach to a running program. The syntax is:
44081 target> gdbserver --attach @var{comm} @var{pid}
44084 @var{pid} is the process ID of a currently running process. It isn't
44085 necessary to point @command{gdbserver} at a binary for the running process.
44088 To start @code{gdbserver} without supplying an initial command to run
44089 or process ID to attach, use this command line option.
44090 Then you can connect using @kbd{target extended-remote} and start
44091 the program you want to debug. The syntax is:
44094 target> gdbserver --multi @var{comm}
44098 Instruct @code{gdbserver} to display extra status information about the debugging
44100 This option is intended for @code{gdbserver} development and for bug reports to
44103 @item --remote-debug
44104 Instruct @code{gdbserver} to display remote protocol debug output.
44105 This option is intended for @code{gdbserver} development and for bug reports to
44109 Specify a wrapper to launch programs
44110 for debugging. The option should be followed by the name of the
44111 wrapper, then any command-line arguments to pass to the wrapper, then
44112 @kbd{--} indicating the end of the wrapper arguments.
44115 By default, @command{gdbserver} keeps the listening TCP port open, so that
44116 additional connections are possible. However, if you start @code{gdbserver}
44117 with the @option{--once} option, it will stop listening for any further
44118 connection attempts after connecting to the first @value{GDBN} session.
44120 @c --disable-packet is not documented for users.
44122 @c --disable-randomization and --no-disable-randomization are superseded by
44123 @c QDisableRandomization.
44128 @c man begin SEEALSO gdbserver
44130 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44131 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44132 documentation are properly installed at your site, the command
44138 should give you access to the complete manual.
44140 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44141 Richard M. Stallman and Roland H. Pesch, July 1991.
44148 @c man title gcore Generate a core file of a running program
44151 @c man begin SYNOPSIS gcore
44152 gcore [-o @var{filename}] @var{pid}
44156 @c man begin DESCRIPTION gcore
44157 Generate a core dump of a running program with process ID @var{pid}.
44158 Produced file is equivalent to a kernel produced core file as if the process
44159 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44160 limit). Unlike after a crash, after @command{gcore} the program remains
44161 running without any change.
44164 @c man begin OPTIONS gcore
44166 @item -o @var{filename}
44167 The optional argument
44168 @var{filename} specifies the file name where to put the core dump.
44169 If not specified, the file name defaults to @file{core.@var{pid}},
44170 where @var{pid} is the running program process ID.
44174 @c man begin SEEALSO gcore
44176 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44177 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44178 documentation are properly installed at your site, the command
44185 should give you access to the complete manual.
44187 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44188 Richard M. Stallman and Roland H. Pesch, July 1991.
44195 @c man title gdbinit GDB initialization scripts
44198 @c man begin SYNOPSIS gdbinit
44199 @ifset SYSTEM_GDBINIT
44200 @value{SYSTEM_GDBINIT}
44209 @c man begin DESCRIPTION gdbinit
44210 These files contain @value{GDBN} commands to automatically execute during
44211 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44214 the @value{GDBN} manual in node @code{Sequences}
44215 -- shell command @code{info -f gdb -n Sequences}.
44221 Please read more in
44223 the @value{GDBN} manual in node @code{Startup}
44224 -- shell command @code{info -f gdb -n Startup}.
44231 @ifset SYSTEM_GDBINIT
44232 @item @value{SYSTEM_GDBINIT}
44234 @ifclear SYSTEM_GDBINIT
44235 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44237 System-wide initialization file. It is executed unless user specified
44238 @value{GDBN} option @code{-nx} or @code{-n}.
44241 the @value{GDBN} manual in node @code{System-wide configuration}
44242 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44245 @ref{System-wide configuration}.
44249 User initialization file. It is executed unless user specified
44250 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44253 Initialization file for current directory. It may need to be enabled with
44254 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44257 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44258 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44261 @ref{Init File in the Current Directory}.
44266 @c man begin SEEALSO gdbinit
44268 gdb(1), @code{info -f gdb -n Startup}
44270 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44271 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44272 documentation are properly installed at your site, the command
44278 should give you access to the complete manual.
44280 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44281 Richard M. Stallman and Roland H. Pesch, July 1991.
44287 @node GNU Free Documentation License
44288 @appendix GNU Free Documentation License
44291 @node Concept Index
44292 @unnumbered Concept Index
44296 @node Command and Variable Index
44297 @unnumbered Command, Variable, and Function Index
44302 % I think something like @@colophon should be in texinfo. In the
44304 \long\def\colophon{\hbox to0pt{}\vfill
44305 \centerline{The body of this manual is set in}
44306 \centerline{\fontname\tenrm,}
44307 \centerline{with headings in {\bf\fontname\tenbf}}
44308 \centerline{and examples in {\tt\fontname\tentt}.}
44309 \centerline{{\it\fontname\tenit\/},}
44310 \centerline{{\bf\fontname\tenbf}, and}
44311 \centerline{{\sl\fontname\tensl\/}}
44312 \centerline{are used for emphasis.}\vfill}
44314 % Blame: doc@@cygnus.com, 1991.